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Due to varied flow behavior, the demarcation of hydrodynamic flow regimes is an important task in the design and scale-up of bubble column reactors. This article reviews most hydrodynamic studies performed for flow regime identification in bubble columns. It begins with a brief introduction to various flow regimes. The second section examines experimental methods for measurement of flow regime transition. A few experimental studies are presented in detail, followed by the effect of operating and design conditions on flow regime transition. A table summarizes the reported experimental studies, along with their operating and design conditions and significant conclusions. The next section deals with the current state of transition prediction, and includes purely empirical correlations, semi-empirical models, linear stability theory, and Computational Fluid Dynamics (CFD) based studies.

Chemical oxidation techniques in use for the reduction of malodorous total reduced sulfur (TRS) emissions in the kraft mills atmospheric effluents were reviewed with an emphasis on recent industrial improvements in chlorine dioxide (ClO2) oxidation of TRS as well as on laboratory developments of an iron-based chemistry process. The ClO2 approach was implemented successfully at the industrial scale in two Québec kraft mills. The approach consisted in mixing the non-condensable gases (NCG) containing the TRS with gaseous chlorine dioxide obtained either as a residue from a bleach plant vent stream or through vaporization of fresh solution. Full-scale tests have shown that the amount of chlorine dioxide injected or mixed in the NCG was sufficient to reduce the TRS load below the 10 ppmv-regulated levels in a cost efficient way as compared with incineration. A prospective approach validated in laboratory conditions and using the iron redox chemistry for alkaline oxidative scrubbing of TRS is being investigated at Laval University to reduce the odor pollution and to convert TRS into valuable sulfur. Two configurations were evaluated, one consisting of homogeneous Fe(III) sequestered in trans-1,2-diaminocyclohexanetetraacetic acid (cdta) chelates and another of heterogeneous Fe(III) as Fe/Ce oxides-hydroxides mixtures. The relative performances, advantages and weaknesses of the various chemical oxidation processes were discussed. In addition, the fundamentals of the alkaline oxidative scrubbing of TRS using the iron-based alkaline approach were summarized in terms of the gas-liquid thermodynamic equilibria and of the homogeneous and heterogeneous iron redox reactions.

Catalytic reduction using CO has significant potential for the control of NOx using Pt group catalysts as CO is already present in the exhausts and Pt group catalysts have high durability in the presence of SO2 and H2O. Different reaction mechanisms are given in the literature for this reaction based on NO dissociation, -NCO formation and so on, but the exact reaction mechanism capable of capturing experimentally observed features is as yet unavailable. To determine the kinetics and reaction mechanism, we propose here an elementary reaction mechanism based on NO dissociation applicable to Pt group catalysts and simulated with CHEMKIN 4.0.2 using single and multiple PSR (Perfectly Stirred Reactor) model. The activation energies of the elementary steps are found from the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. Excellent agreement between literature experiments and our simulation results are observed for the NO-CO reaction on Pt and Rh catalysts and for the NO-CO-O2 reaction on Ir catalyst. The effect of temperature on the NO reduction activity is captured well by the model. Additionally the simulations can also point towards importance of particular reactions, selectivity to N2, effects of surface coverage, effects of residence time and catalytic surface area on NO reduction.

One of the main uses given to ferrous sulphate in the pharmaceutical industry is that of iron supplement. The objectives of this work were to recycle a Cuban metallurgical solid waste with high iron concentration in its two oxidation forms, as well as the finding of optimal conditions for the leaching reaction of this solid waste with sulfuric acid. These results will allow defining a technology for the synthesis of iron inorganic salt for the pharmaceutical industry. A complete factorial experimental design was made, which included three Independent variables on three different levels (3^3) in order to optimize extraction of iron (II) and iron (III). These variables were: sulfuric acid concentration, reaction temperature and molar relation between sulfuric acid and both iron species. The goal of multiple optimizations was to maximize conversions of both iron species and their concentrations in the final liquor, favouring the first.

The objective of this work was to investigate the relative contribution of the convective and dispersive mixing mechanisms to the overall solid phase mixing mechanism for three-phase fluidized bed reactors. Noninvasive Radioactive Particle Tracking (RPT) data were obtained at various operating conditions, reactor diameters and particle systems. The structural wake model was updated and consists of three sub-phases: the particle wake and downflow-emulsion phase following the convective mixing mechanism and the vortex-emulsion phase following the dispersive mixing mechanism.The particle velocity mean and STD increased with the superficial liquid and gas velocity as well as the reactor diameter for each particle phase. Therefore, the extent of mixing increased under these operating parameters. The particle phase's holdup and a new Mixing Mechanism Indicator (MMI), however, exhibited a much more complex trend. For the larger reactor (Dc = 0.292 m), the convective mixing mechanism dominated and at low superficial liquid velocity the contribution of the convective mixing mechanism increased with superficial gas velocity. This trend, however, was reversed when the superficial liquid velocity increased. For the smaller reactor (Dc = 0.10 m), the random movement of the solid dominated. Therefore, the extent of mixing and the mixing mechanism did not follow the same trend. The CFD and the mixing model have to follow both those hydrodynamic properties.Relations to estimate mean and STD particle velocity distribution as well as particle phase holdup were developed. Solid in the established region mainly followed the convective mixing mechanism. Random movement of the solid was mostly observed at the top of the bed, but it was also present in the established region and at the bed bottom. The volume of each region depended on the operating conditions, reactor diameter and particle system. Furthermore, the particle wake expulsion frequency range was similar to the wake shedding frequency found in literature. It is, thus, possible to assume that wake shedding was mainly responsible for the solid exchange between particle phases.

This paper focuses on the determination of optimum control trajectories for the operation of a batch polymerisation reactor. Operating policies needed to achieve pre-specified properties in minimum time are obtained. Two models dealing with the polymerisation of styrene using AIBN as initiator in a batch reactor are considered. The first model (Model I), taken from the literature, is derived from the first principles of the polymerisation system while the other (Model II) is more rigorous involving both mass and energy balances to simulate a batch polymerisation reactor operation.A dynamic optimisation problem incorporating Model I is formulated and solved to find the optimal temperature trajectory and initial initiator concentrations that will yield desired levels of monomer conversion and number average molecular weight in minimum time. The total batch time is divided into a finite number of intervals and piecewise constant reactor temperature is assumed in each interval. The reaction temperature and the length of each interval are optimised using Control Vector Parameterisation technique. Significant savings in batch time are obtained when these results are compared with those available in the literature obtained using the Pontryagin's Maximum Principle.Incorporating Model II, a second dynamic optimisation problem is formulated and solved where the coolant flow rates and lengths of the intervals are optimised to minimise the batch time and yield desired levels of monomer conversion and number average chain length. With examples, the results show that although both optimisation problems result in similar product qualities, the optimal operations are significantly different. Batch time is significantly higher for the second optimisation problem. gPROMS modelling software was used to build the process model and perform the dynamic optimisation.

Modeling of an esterification reaction in a batch pervaporation membrane reactor (PVMR), and an analysis of the PVMR performance under different reaction conditions for different membrane characteristics are presented. Esterification of ethyl alcohol with acetic acid was considered as the model reaction. The PVMR performance for this reaction could be represented by a 2-step series model. The PVMR performance was similar to that of the batch reactor when both the reactors were in the kinetic regime. However, the performance of the PVMR was superior to that of the batch reactor when both were in the intermediate/equilibrium regime of the reaction. In these regions, the PVMR performance was influenced/limited by the membrane flux and selectivity. The analysis showed that the membrane flux affected the PVMR performance in the intermediate region and the membrane selectivity affected the performance in the equilibrium regime. Further, the limitations introduced by a low-flux membrane could be overcome by appropriate selection of the membrane area and that due to poor selectivity could be compensated to a certain extent by adjusting the feed ratio.

The pervaporation reactor is, specifically, the new technology for reaction and separation. It is rather difficult to predict the market potential of processes newly introduced on the market. However, in comparing investment costs, environmental aspects of pervaporation systems with those of conventional processes, it can be said that pervaporation reactor will play an important role in the chemical industry for new installations as well as for rehabilitation of existing plants. Techno-economic studies are showing that pervaporation reactors have good market potential. There are many examples where pervaporation reactors can reduce product costs by an important margin. The most common reaction system studied for the application of pervaporation is an esterification reaction between an alcohol and an acid in the presence of a highly acidic catalyst (e.g., concentrated sulfuric acid). In the present paper, modified/improved model for pervaporation reactor for benzyl alcohol acetylation is presented. The parametric sensitivity is studied for the performance of pervaporation reactor. The use of pervaporation coupled to the esterification reaction increases the conversion considerably. The modified model allows the evaluations of the reaction time necessary to achieve a given conversion. The model makes it possible to determine the membrane surface area / operating time ratio for a given conversion. The present model can be extended for the other esterification reactions in pervaporation reactors.

Hydrolysis of two types of cellulose, namely, totally amorphous Carboxymethylcellulose (CMC) and highly crystalline wood shavings, by Aspergillus niger cellulase was studied in a stirred batch reactor at 50oC. Two kinetic models were devised to predict the rate of reducing sugar production assuming competitive and non-competitive product inhibition of the enzyme. The applicability of the models was tested by comparing experimental results with those predicted by the models. Both models followed the experimental data fairly well, giving standard deviation of 13.3 and 7.9 for the competitive and the non-competitive inhibition models, respectively. However the non-competitive inhibition model showed more realistic behaviour than the non-competitive model and represented better the experimental data. The significance of crystallinity was determined by comparing the production of reducing sugar from wood shavings to the production from CMC. At same initial substrate concentration, it was found that the production of reducing sugar ceased at much shorter times for wood shavings in comparison to that for CMC.

A gas heated steam reformer (GHR) which converts natural gas to synthesis gas for methanol or Fischer-Tropsch purposes has been modelled for steady state conditions. The model is in two dimensions and is made up of a fixed bed reactor model, representing one of the reactor tubes in the GHR, and an annulus model, representing the annular space on the shell side of the GHR where hot, fully converted syngas emits heat to the reactor tube. The annulus model is described and evaluated in this article. This is a plug flow model which involves heat transfer in radial direction caused by radiation and by turbulence. The gas radiation is modelled by the use of the discrete ordinates method and the effect on heat transfer from turbulence is modelled as an effective radial thermal conductivity. Both heat transfer mechanisms vary with the radial position. An additional annulus model, made in the commercial CFD code FLUENT and based on the k-? turbulence model and the discrete ordinates radiation model, is used to estimate effective radial thermal conductivities. These were implemented in the annulus model of the GHR model. The reactor and the annulus models were combined and linked by the wall temperature profile and the heat flux profile on the outer reactor tube wall. The simulation results were used to study the heat flux and temperature profiles along the reactor length and the radial temperature profiles in the annulus.

Within the last years renewable energy sources came more and more into the public focus. Steam gasification of solid biomass yields high quality producer gases that can be used for efficient combined heat and power production (CHP) and as a renewable resource for chemical syntheses. The dual fluidized bed steam gasification technology provides the necessary heat for steam gasification by circulating hot bed material that is heated in a second fluidized bed reactor by combustion of residual biomass char. The hydrogen content in producer gas of such gasifiers is about 40vol% (dry basis). Addition of carbonates to the bed material and adequate adjustment of operation conditions in the reactors allow selective transport of CO2 from gasification to combustion zone (Absorption Enhanced Reforming – AER concept). An 8MW (fuel power) CHP plant successfully demonstrates gasification in Guessing, Austria since 2002. A process development unit (100 kW fuel power) has been recently operated to investigate the potential of the selective CO2 transport achieving a H2 content of up to 75vol% (dry basis) in the producer gas. No significant increase in tar formation occurs despite the low gasification temperatures (600-700°C). It can be shown, that the selective transport of CO2 yields high hydrogen contents in the producer gas and the possibility of operating at lower temperatures increases the efficiency of energy conversion.

The present work studies the sunflower oil hydrogenation on supported palladium catalysts, by analyzing the surface kinetics and the mass transfer limitations of products and reactants. Initially, a simplified model was studied. This model took into account only the consecutive hydrogenation of linoleic acid (diene), to reach the production of oleic (monoene) and stearic (saturated) acids. Using the adjusted values of the kinetic constants and the activation energies of the hydrogenation obtained with this model, a new scheme was investigated considering the geometric isomerization reactions (cis-trans). The diene hydrogenation constant was larger than that of the monoene. This fact confirms the higher reaction rate of the diene hydrogenation in comparison with that of the monoene. With respect to the isomerization rates, these have an activation energy superior to that of the monoene hydrogenation, and slightly superior to the diene hydrogenation activation energy. This fact verifies the influence of temperature on the formation of trans-isomers.

A gas-solid fluidized bed bioreactor has been successfully used for the bioremediation of ethanol (a model volatile organic compound, VOC) contaminated air. A key objective of this fluidized bioreactor study was to compare the performance of fluid bed operation to packed bed operation. A fluid bed system increased homogeneity and improved upon operating problems such as plugging and channelling normally associated with packed bed bioreactors. The bioreactor bed was comprised of a mixture of moist sawdust particles and glass spheres. Depending on the superficial velocity of the waste gas stream, the bioreactor could be operated in either packed or fluidized mode. During fluid bed operation, the sawdust and glass sphere mixture was maintained in a bubbling/slugging regime. As expected, fluid bed operation demonstrated significantly higher mass transfer rates but the maximum elimination capacity was 75 g m-3sawdust h-1 as compared to 225 g m-3sawdust h-1 for packed bed operation. In packed bed mode, higher ethanol concentrations were used in order to have comparable ethanol loadings and this may have contributed to faster growth rates and thus faster bioremediation rates.

Enhanced operating performance can be obtained by combining the design characteristics of impellers. The asymmetricity of BT6 impeller blades when combined with symmetric ICI gasfoil blades results in two new diskless impeller designs, one with extension of the upper blade part (PBIUP) and the other with lower blade part (PBIDN). These impellers are experimentally characterized at intense agitation and sparging conditions for power draw, gas holdup and transition regimes. CFD modeling is used to evaluate the performance of impellers based on the pressure distribution and cavity formation on and around the impeller blades. Cavity formation on the new impellers is found to be higher as compared with ICI impeller but lower than BT6. The maximum experimental power drop at intense gas flow and agitation conditions for PBIUP and PBIDN is found to be 14% and 22% as compared to power drop of 10% for ICI gasfoil and 25% for BT6. The coalescence regions, identified from predicted gas holdup profiles, confirmed the experimental observations regarding the formation of larger bubbles in the tank. Overall, PBIUP is found to give uniform gas dispersion as compared to other impellers along with the desired objective of lower power drop.

We revisit the analysis of a reactor network consisting of two coupled continuous stirred tank reactors (CSTRs) arranged in series (Chem. Eng. J. 59 (1995) 169). The main idea proposed in this earlier work is to improve process conversion by generating periodic behaviour in the first reactor (by appropriate choice of design and operational parameters) which then 'forces' the second reactor. The performance of this cascade system was shown to be greatly enhanced using the above strategy. In this paper we show some conceptual errors in the analysis in the original paper. We also show that by employing a systematic bifurcation analysis, including the use of a path following software, greater insights can be gained regarding the system's behaviour. Using these techniques we show that operation and design parameters can be readily identified to ensure that the cascade has a superior performance to a single CSTR.

The optimum operating conditions of a single – step synthesis of dimethyl ether (DME) from synthesis gas has been determined. The bifunctional catalyst has been prepared by physically mixing of a commercial methanol catalyst (KMT Co.) and a dehydration catalyst (H-MF-90) which has been characterized by XRD, XRF and BET techniques. Catalytic synthesis of dimethyl ether from synthesis gas was evaluated in agitated slurry micro reactor in different ranges of operating conditions which were determined by experimental design according to Taguchi algorithm. The range of operating conditions were chosen as follows: H2/CO mole ratio in feed varying from 0.26 to 1.5, the pressure varying from 10 to 50 bar, the temperature varying from 200 to 240 ºC and weight ratio of methanol catalyst to dehydration catalyst from 0.67 to 4. The experiments have been conducted for different operating conditions at fixed impeller speed equal to 1600rpm and space velocity equal to 500 ml/gcat.h. Considering the results of experiments, optimum conditions for direct synthesis of DME were predicted as follows: T=240 ºC, P=33.3 Bar, H2/CO=1.5 and weight ratio of methanol catalyst to dehydration catalyst equal to 3.

The past attempts of Arrhenius plots of carbon nanotube (CNT) yield (or CNT length) to obtain the overall activation energy for CNT formation under changing reaction temperature conditions have created substantial errors. Here we propose an inverse method to accurately account for the effect of temperature on gas-phase reactions and species composition. The overall activation energy of soot formation for a xylene-based CVD reactor was calculated and successfully compared with the measured gas-phase concentration data. Our proposed inverse method is expected to help improve the performance of CVD reactors and optimize its design.

In wastewater treatment, the membrane bioreactor (MBR) holds the potential to become one of the new generation processes, ensuring effluent quality and disinfection of sufficiently high levels to allow water reuse and recycle. Furthermore, the possibility to operate with high biomass concentrations (2 to 5 times higher than in conventional activated sludge process, CAS) allows to impose high solid retention times(SRT) that can be beneficial to a sludge production reduction and so to a reduction of disposal costs. These non-conventional operating conditions (high SRT) can also induce different sludge characteristics and dewatering aptitude, which are essential parameters for the optimization of the sludge post-treatment, like mechanical dewatering. The objective of this work was to study the performances of a complete sludge retention membrane bioreactor, in terms of organic removal efficiency, sludge production and sludge dewaterability. The adaptability of Activated Sludge Model 3 (ASM3) to provide good prediction results of high SRT-MBR was studied. Typical parameters adopted to describe sludge dewaterability were quantified and compared with the conventional activated sludge process (CAS).

A generalized modeling approach is used to develop a systematic algorithm for formulating and solving chemical/biochemical reaction engineering problems. This systematic approach is general enough that it can treat different systems with varying degrees of complexity utilizing the same methodology. The procedure can be used in both introductory and advanced chemical/biochemical reaction engineering courses. This will provide the students with a powerful "toolkit" to tackle a wide range of academic and industrial engineering problems as well as a solid starting point for developing research projects in this field. This may also allow the students to have a better understanding of the multiple phenomena encountered in chemical/biochemical engineering systems and encourage them to prepare models at an optimum level of sophistication for design, optimization, and exploration of novel ideas.

Air gasification of dried sewage sludge (DSS) in a fluidized bed has been studied as an effective alternative for the management of this material in a usable way. Nevertheless, one of the major issues in this technology is to deal with the tar formed during the process. To minimize the tar production, it is very important to optimize the operating conditions. In a previous work (Manyà et al., Energy Fuels, Vol. 19, 629–636, 2005) some unexpected results, in which tar production increases with the equivalence ratio, have been obtained. As it has been mentioned in that work, tar production could present unexpected trends while the bed composition changes from sand to a mixture of char and sand. Ashes contained in char have catalytic active metals which could promote gasification reactions. As the char content in the bed increases, the catalytic activity in the reactor could increase too, until the steady state is achieved. The aim of this work is to characterize the non-stationary period and its influence on the overall results obtained from gasification tests. Experiments have been carried out in a laboratory-scale BFB reactor at atmospheric pressure and at a reactor temperature of 1123 K with an equivalent ratio of 30%. Results show that at the beginning of the experiments the tar production was higher, until the steady state is reached. The gasification study has been enhanced with an analysis of tar composition by means of GC/MS and GC/FID. An effect of the transition period has been observed in tar composition also. The nitrogen aromatics percent increased with time whereas the polycyclic aromatic hydrocarbon decreased.

An industrial steam reformer of a methanol plant was modeled at a dynamic condition in which a one dimensional homogeneous model was coupled with a verified kinetics from the literature. A close agreement was observed between the results of the model and industrial data from a real plant at steady state conditions. The open loop response of the system to switching between two operating conditions was investigated and shown that the produced synthesis gas during the transition period would be unsuitable for the downstream methanol converter. The genetic algorithm was then employed to perform a multi-objective dynamic optimization on the reactor performance in case of switching the feed and operating conditions. Maximization of methane conversion and minimization of a stoichiometric parameter, were considered as the two objectives' functions that were optimized for a fixed feed rate of methane to the existing unit. The results of the dynamic optimization for the specified reformer configuration were achieved after switching the operating condition. Results of the optimization showed that the produced synthesis gas would stay in its acceptable limits in terms of quality of the feed of the methanol converter and also, the final conversion of the reformer would be improved compared to the steady state condition. This procedure could be applied to the advanced process control of the methanol plant.

The current work is a computational simulation, with the geometry of the Parr reactor series 4581, of a multiphase system with two fluids (hydrocarbon and hydrogen) and two domains (tank and impeller) for the kinetics of residue catalytic hydrocracking. The fluid dynamics modeling is based on the SPH process and the fundamental equations of mass balance and momentum quantities in an isothermal system. The turbulence phenomena are considered through the k-? model for the hydrocarbon and ``disperse phase zero equation" for the hydrogen. The chemical reactions are modeled by the means of a reactional net based on the pseudo components concept, with their loads and products separated according to the commercial cuts, schematized with six parallel reactions, three thermal and three catalytic, with pseudo-first order reaction rates. The domains are composed of hydrocarbon as a general fluid (a mixture of pseudo components + catalyst = ``slurry phase") and the hydrogen as an ideal gas.

Amorphous natural silicoaluminates, such as expanded perlite, transform themselves in three-dimensional crystalline species, exhibiting effects of the alkaline solutions with NaCl. In this paper the kinetics and the effect of the reaction conditions over the crystallization process are studied.Na(OH) solutions 15%, 18%, and 20 % w/v, and NaCl solutions from 0 % up to 30 % w/v were used. Temperature range was from 80ºC to 95 ºC. The effect of the solid/liquid relationship and the fluid dynamic conditions were studied. The rate of the zeolite formation process depends on the concentration of Na(OH) / NaCl solutions and on the reaction temperatures.The fluid dynamic conditions and the solid/liquid relationships have no effect over the crystallization process in the studied range. The effect of the NaCl is to increase the reaction rate independently of the kind of obtained zeolite, which is associated with the relationship Si/Al.Powder X – ray diffraction (XRD) analysis and scanning electron microscopic (SEM) were employed to study the zeolite formation process in order to elucidate the mode of zeolite crystallization.The mechanism implies the formation of units of nuclei of growth, and the population of these units is controlled by NaCl concentrations. The nucleation and growth Avrami model properly describes the process of formation of the crystalline species. It is found that the parameters k and n are linked respectively with the conditions and the reaction mechanism.

In this study, the use of a natural material, sawdust, in a fluidised biofiltrer has been considered. The performance of the biofiltration of ethanol and toluene was estimated in the presence of the native microorganisms of the material and also after the addition, and a period of acclimatization, of external microorganisms. Modifications of the physical and biological characteristics of the material were studied in order to better understand the process. The influence of biofilter shutdown periods was also considered to evaluate the effect of a period of inactivity on subsequent performances.This study shows that a significant degradation of the pollutants is obtainable provided that the following steps are performed: seeding with activated sludge, introduction of nutrients, and control of the changes in the material characteristics and the bed moisture.During the operation of the fluidized bed biofilter, the moisture of the bed had an important effect on the biofilter performance, but was rather difficult to control because of its dependence on the ambient and inlet air temperatures, which changed during the day and the seasons. During the tests with the batch of sawdust particles used as delivered without any sludge enrichment, a reduction in abatement performances was measured with time. In the case of ethanol alone, for a concentration of 0.02 g.m-3, abatement decreased from 24% to 18% then to 7%. The partial or complete addition of sawdust particles previously activated with sludge significantly enhanced the performance of the biofilter, both for ethanol and toluene pollution. Abatements of ethanol of 85% and 60% were achieved when the sawdust particles were activated by sludge. In contrast, a 5-week shutdown of the reactor produced a decrease in abatement, either by a loss of microorganism efficiency during their "starvation" or by their destruction.

The influx of noise through inlet streams is often a problem in the operation of large-scale microbial fermentations. It can distort the otherwise smooth performance and, more seriously, displace the fermentation to an undesirable state. Therefore, removal or reduction of the noise content of measured data is important for retrieving the true process variables for bioreactor operation and control. This is done by noise filters, which are soft devices that process noisy data and generate less noisy values with identifiable features. Three types of filters have been compared here by applying them to a continuous fermentation by Saccharomyces cerevisiae under (a) monotonic, (b) oscillating and (c) chaotic operation. Recognising self-similarity as a characteristic feature under the influence of noise, fractal dimensions of the output concentrations are suggested as effective indexes of both noise-affected and noise-filtered performance. On this basis, a hybrid neural filter (HNF) was the best, an auto-associative neural filter (ANF) was somewhat inferior and an extended Kalman filter (EKF) the poorest. While these results and similar observations for other microbial systems favour the use of both fractal dimensions and the HNF, the EKF and other algorithmic filters have some merits, which are discussed.

Various shapes and sizes, including spherical, cubic nanoparticles and hexagonal nanorods with the dimensions of 50-500nm, of TiO2 were prepared through hydrolysis of titanium butoxide in sol-gel method with the introduction of different surfactant composition and concentrations during preparation. Prepared TiO2 nanoparticles were studied for photocatalytic decomposition of methyl orange (MO) in fixed film batch reactors. The results showed that shape, size and photocatalytic activity of TiO2 depend not only on surfactant composition but also on surfactant concentration. Photocatalytic decomposition of MO followed the first order kinetic reaction. The analysis of reaction rate constants showed that the shape is more important than the size in determining the photocatalytic activity of shape- and size-controlled TiO2 nanoparticles. TiO2 nanorods had higher photocatalytic activities than spherical and cubic TiO2 nanoparticles.

The aim of this paper is the regulation of the temperature, at outlet conditions, for a class of plug flow chemical reactors. The considered reactor is modeled by a set of hyperbolic partial differential equations, as related to mass and energy balances, with consideration that the measured output for this kind of systems is the outlet temperature, as is usual with industrial practice. It is proposed that in nonlinear feedback which contains a proportional contribution of the named regulation error plus a high order sliding-mode term-to-tray to compensate for the convective transport, the nonlinear terms and disturbances employing the stabilizing effects of the sliding modes have a satisfactory performance. A theoretical frame for the stabilization properties of the proposed controller is provided and numerical simulations illustrate the corresponding performance, which is compared with a well tuned PI control law.

A novel fluidized bed membrane reactor with internal catalyst circulation is being developed for the production of high-purity H2 from an autothermal reformer. In order to provide guidance to pilot reactor testing, a cold model was built to study the influence of reactor configuration on hydrodynamics and catalyst circulation. It was found that catalyst circulation was reproducible, but that parallel non-communicating flow channels could lead to flow instability. Solids circulation was found to be adequate for design of the autothermal reformer.

Our understanding of gas-liquid–liquid reaction systems is not well developed today despite their widespread use in the process industries. Research work is demanded or inspired in those fields where basic information is either lacking or poorly organized. The field of mixing and agitation in gas-liquid-liquid reaction system is a typical example. Methyl ethyl ketazine formation is a typical case of homogeneous catalyzed gas-liquid-liquid reaction. The parametric study of ketazine formation has been carried out in a semi batch reactor. Agitation effect on methyl ethyl ketazine formation has been studied. Two types of agitators are used - flat paddle stirrer and vaned disk stirrer. The studies show that agitation plays an important role on the reaction. Yield of ketazine improved with degree of agitation, categorizing the reaction as moderately fast. Vaned disk stirrer is found to be more effective compared to flat paddle stirrer. Rate of reaction increases up to 600 rpm indicating diffusion control, beyond 600 rpm there is no appreciable change in the yield, thus favoring kinetics controlled mechanism. This 600 rpm can be thus regarded as "the desired level of agitation."

Decolouration by catalytic oxidation of Acid Red 186 dye solutions was investigated using several manganese-based heterogeneous catalysts, namely MnOx (manganese oxides), Mn-Cu and Mn-Ce composite oxides. Also, catalytic activity of CeO2 and CuOx (copper oxides) were tested. Catalysts were used in slurry conditions, at 130ºC and oxygen partial pressure of 15 bar. Additional uncatalysed run and thermolysis (no catalyst, no oxygen) were studied. The results revealed that MnOx and Mn-Cu were the most active catalysts concerning the reduction of colour. MnCu5 and CuOx led to the highest TOC decreases. From the overall process (colour and TOC reductions) and having in consideration catalyst stability, MnCu5 was considered suitable to AR186 oxidation.

Fruit and vegetable wastes are generated in large quantities around the world. This kind of residue constitutes a source of nuisance in municipal landfills because of its high biodegradability. Another residue that is generated in large quantities around the world and also constitutes a source of nuisance is the sewage sludge. Both residues can be treated together by the anaerobic co-digestion process. In this sense, the aim of the present study was to evaluate the anaerobic co-digestion of fruit and vegetable waste and sewage sludge, in order to monitor the waste stabilization time and the biogas generation, among others. The study was conducted in a 70 litter stainless steel anaerobic reactor, with no mixing system, at room temperature (25±5ºC), during a period of 105 days. The fruit and vegetable wastes were collected in a central distribution market for food, and were shredded and blended before the experiment. The seed inoculum was collected in an anaerobic domestic sewage station of treatment. The parameters analyzed were: chemical oxygen demand, C/N and C/N/P ratios, pH, alkalinity, volatile fatty acids, and biogas generation. The results showed that the chemical oxygen demand was reduced around 20%. The parameters, pH, alkalinity and volatile fatty acids were stabilized, but the C/N wasn’t stabilized. The final value obtained for C/N ratio was around 20/1. The biogas generation was around 331 litters and most of the biogas production occurred during the first month of the experiment. The low chemical oxygen demand removal, the high C/N ratio and the biogas generation almost always in the first few days of the experiment probably indicate that this residue, although being organic, presents difficulties in its degradation, maybe because of the high organic load that was applied to the reactor. The fact of the reactor being disproved by a mixing system can also have contributed to the low residue degradation.

A redox reaction scheme consisting of two steps as an alternate to the partial oxidation of methane (POX) for synthesis gas production is proposed. With the use of a thermodynamic analysis the CoWO4 spinel was introduced as a new oxygen carrier material, capable to be reduced with methane (15% CH4/Ar) and reoxidized with steam (30% H2O/Ar) to produce syngas and hydrogen in each redox step, respectively. H2 production is feasible during the regeneration of CoWO4 by oxidation of reduced species (Co and W) with steam. CoWO4 synthesis was performed using the solid state reaction. Characterization included: XRD, SEM and particle size determination. Redox-cycle performance was followed by TGA. Thermal stability of CoWO4 was tested by exposing the material to ten consecutive reduction/oxidation (H2/Ar, H2O/Ar) cycles at 850°C and after. Results indicate that CoWO4 showed no significant loss of activity. This stable behavior is associated to its crystalline structure, which allows the fixation of the active metals (Co + W) through the spinel structure, thus inhibiting particle nucleation and migration, which are the main causes of sintering after exposure to steam at high temperatures. The addition of Ni to CoWO4 as a POX catalyst produced an enhancement of the reduction step of 20% in metal oxide conversion with respect to CoWO4.

Gasification of biomass is an attractive technology for combined heat and power (CHP) production. A dual fluidized bed steam gasifier is in commercial operation at the biomass CHP plant in Guessing/Austria since 2002. For circulating fluidized bed applications the bed material consumption is economically crucial. Thus, cyclones for circulating fluidized beds need to be designed properly. Some erosion and caking in the cyclone of the gasifier could be observed with increasing hours of operation. The influences of these effects as well as the influence of the solid circulation rate between the two units on the separation efficiency were investigated by fluid-dynamic investigations using a scaled cold model. The results show that due to erosion and caking elutriation rates are increased, especially for smaller particles. However, the cyclone achieves fractional separation efficiencies of more than 99.9%.

Steady-state tracer gas measurements were carried out to study the gas mixing behaviors in a spout-fluid bed with a cross section of 0.3 m x 0.03 m and height of 2 m. Two different tracer gases were simultaneously injected, one was injected into the spouting gas flow and the other was injected into the fluidizing gas flow. Radial tracer gas concentrations at various bed elevations under different flow patterns were measured. The mechanism of gas mixing was discussed based on the racer gas concentrations and the flow patterns recorded by a high-resolution digital CCD camera. It was found that gas mixing in spout-fluid beds was due to both convection and dispersion. A three-region mixing model was developed to describe the gas mixing in the spout-fluid bed. The spout jet region and the boundary region were modeled with a mass transfer model; the annular region was modeled with a dispersion model. Effects of spouting gas and fluidizing gas flow rate on the gas exchange between the spout jet and the annular dense region, and the gas dispersion in the annular dense region were examined with flow patterns. The results showed that increase in spouting gas velocity and fluidizing gas flow rate could both promote the gas mixing in spout-fluid beds. The gas-solid flow pattern transited from internal jet to spouting to spout-fluidizing, and the gases were better mixed. But the gases became poorly mixed when the flow pattern transited from stable flow to instable flow.

Life Cycle Assessment (LCA) is a powerful tool in order to identify sustainable alternatives in process engineering. In this work, the LCA of two fluoride effluent treatment processes in the aluminium trifluoride (AlF3) manufacture has been carried out. Two scenarios have been considered: (i) chemical precipitation for fluoride removal, leading to a water-rich sludge, which has poor dewatering properties and therefore, must be managed in inert waste landfills, and (ii) the recovery of fluoride by crystallization as synthetic fluorite to be reused in the hydrogen fluoride (HF) manufacture. The LCA software SimaPro 7 (PRé Consultants BV) makes it possible to compare in terms of different methodologies like Eco-Indicator 99 and CML 2 Baseline 2000. Environmental metrics developed by IChemE were included in the software. The crystallization process in a Fluidized Bed Reactor allows reductions in the range of 20-40% for most metrics because of the recycled synthetic fluorite to the HF manufacture.

This work deals with the multicriteria cost-environment design of multiproduct batch plants, where the design variables are the equipment item sizes as well as the operating conditions. The case study is a multiproduct batch plant for the production of four recombinant proteins. Given the important combinatorial aspect of the problem, the approach used consists in coupling a stochastic algorithm, indeed a Genetic Algorithm (GA) with a Discrete Event Simulator (DES). To take into account the conflicting situations that may be encountered at the earliest stage of batch plant design, i.e. compromise situations between cost and environmental consideration, a Multicriteria Genetic Algorithm (MUGA) was developed with a Pareto optimal ranking method. The results show how the methodology can be used to find a range of trade-off solutions for optimizing batch plant design.

In this study a mathematical model has been developed to simulate two dimensional fluidized beds with uniform fluidization. The model consists of two sub models for hydrodynamic and thermal behavior of fluidized beds on which a FORTRAN program entitled (NEWFLUIDIZED) is devolved .The program is used to predict the volume fraction of gas and particle phases, the velocity of the two phases, the gas pressure and the temperature distribution for two phases. Also the program calculates the heat transfer coefficient. Besides that, the program predicts the fluidized bed stability and determines the optimum input gas velocity for fluidized beds to achieve the best thermal behavior. The hydrodynamic model is verified by comparing its results with the computational fluid dynamic code MFIX [1]. The thermal model was tested and compared to the available previous experimental correlations. The model results show good agreement with MFIX results and the thermal model of the present work confirms Zenz [2] and Gunn [3] equations.

Catalytic wet air oxidation of oxalic acid in aqueous solution was investigated in a stirred reactor over a Pt (0.7% in wt)/Al2O3 catalyst at atmospheric pressure, in a concentration range of oxalic acid of 500-3000 ppm, and at a temperature range of 313-353 K. The conversions obtained after 5 h were 28.96 %, 45.98 % and 30.74 % for initial concentrations of 500, 1500, 3000 ppm, respectively. A rate equation of oxalic acid oxidation, in mol.h-1.g-1Pt was determined from measurements of initial rates, at different initial concentrations of oxalic acid, temperatures and catalyst mass loads. The activation energy for oxalic acid conversion was found to be 24.6 kJ mol-1.The heterogeneous catalyzed free-radical oxidation of oxalic acid was discussed.

A commercial process simulator was used to develop a detailed simulation of a biodiesel production process, and carry out case studies and optimization. The simulated process produced biodiesel from a feedstock containing 5 wt.% free fatty acids in a fixed-bed reactor with sulfated-zirconia as an acidic catalyst. Sized unit operation blocks, material and energy flows were used to conduct an economic assessment of the process. Total capital investment, total manufacturing cost, after tax rate-of-return and production cost ($/kg) were all determined for the process. The process was then optimized by maximizing the after tax rate-of-return (ATROR). Based on our previous work, the most economical process for transesterification of waste vegetable oil at the scale of 8000 metric tones/yr of biodiesel production among the four processes examined was based on a solid acid catalyst reaction. Our results showed that the process is economically feasible, even without government subsidy, while at the same time, the produced biodiesel met the required ASTM standard for purity.

Gentamicin production by immobilized cells of M. echinospora has been studied in repeated-batch processes using different immobilizing carriers such as calcium-alginate, carrageenan, agar, PVA, celite, polyurethane foam and activated carbon. With ca-alginate, gentamicin production was maximum (1096 mg/l) and the bead stability was good, whereby alginate was selected for further experimentation. The role of alginate concentration, CaCl2 concentration, bead diameter, curing time and bead inoculum quantity were studied. Better gentamicin outputs (1549 mg/l) were attained with alginate 4% (w/v), CaCl2 0.2 M, bead diameter 2.69 mm, curing time 18 h and inoculum quantity 20% v/v for six repeated cycles in shake flask. Productivity of gentamicin was increased to 1.8 fold in a fluidized bed reactor with optimized alginate immobilized beads and increased reusability. The FBR was operated for 30 days in fed batch mode operation.

Effluents from radiographic X-ray film developing processes feature a high contaminant load (COD about 70000 mg/L and total phenols concentration about 16956 mg/L). Photo-Fenton's are potentially useful oxidation processes for destroying toxic organic compounds in water. In these reactions, hydrogen peroxide is combined with ferrous or ferric iron in the presence of light to generate hydroxyl radicals (·OH). The photo-Fenton process was explored as a photochemical treatment to degrade wastewater from radiographic X-ray film developing processes coming from odontologic clinics. A response surface methodology was applied to optimize the photo-Fenton oxidation process conditions using total phenol removal as the target parameter to be optimized, and the reagent concentrations, as related to the initial concentration of organic matter in the effluent, and time and pH as the control factors to be optimized. The best results in terms of maximal total phenol removal and economic process were achieved when wastewater samples were treated at pH 5 in the presence of hydrogen peroxide and iron in the ratios [total phenols]:[H2O2] 1:3 w/w and [Fe2+]:[H2O2] 1:18 w/w and time 1 h.

Stevia rebaudiana is a plant native of South America, and its active constituents are considered, by Food Science researchers, the "sweeteners of the future." Therefore, research on this plant has been increased. Stevia is a source of natural diet sweetening, without calories and safe for health. Its crude extract, however, is foul-smelling, bitter tasting, and dark brown; subsequent purification is essential to obtain a product of commercial quality. In this work, adsorption in modified zeolites associated with the filtration with membranes was applied in order to purify stevia crude extract. For the adsorption process, 40 g of CaX modified zeolites were used. In the ultrafiltration process, membranes with porosities of 0.05, 0.1 and 0.2 ?m were used. The transmembrane pressure was fixed at 2, 4 and 6 bar for each membrane. The best conditions of flux were obtained with the 0.2 ?m membrane and 6 bar, resulting in high clarification and recuperation of stevioside (91.75%). This work shows that the adsorption in modified zeolites associated with the membrane filtration is promising for stevia extract purification.

Steam reforming reaction heat effects were implemented in CFD simulations of different packed tube models of 1-hole and 4-hole cylinders. A computationally less expensive 120° wall segment approach was utilized for the simulations in this study. Heat effects of the reactions were introduced by heat generation/consumption terms in the catalyst particles considering suitable reaction kinetics proposed in the literature. Due to strong diffusion limitations the activity of the catalyst particles is confined to a thin layer at the particle surface. Therefore, the energetic effects of the reactions were restricted to the outer 5% of the particle dimension by a user-defined code. The selection of the correct active region was verified for both the particle external and internal–hole surfaces. Simulation results of the reaction heat effects were qualitatively and quantitatively compared to cold flow cases where there were no heat effects but only tube wall heat transfer. Due to the endothermic nature of the reactions, relatively lower temperature fields were observed when the heat effects were introduced, where the positions of the solid particles play an important role. The implications of introducing the detailed reaction heat effects were emphasized in the development of suitable packed tube models.

The goal of this paper is to develop a nonlinear observer-based control strategy for a jacketed continuous stirred tank reactor (CSTR). The nonlinear adaptive state estimator/observer (ASE/ASO) is designed based on a model structure that mainly consists of an energy balance equation. In this observation approach, reactor concentration is considered as an imprecisely known extra state (augmented state) with no dynamics. Despite significant process/model discrepancy, the proposed state observer estimated adequately the states of the simulated reactor. Mainly due to the design simplicity, negligible computational effort and fast convergence, the observer is recommended for online implementation. The generic model controller (GMC) has also been synthesized for the example reactor. The nonlinear GMC scheme receives the required information about the reactor concentration from the ASE for calculating the controller responses. Simulation experiments have been carried out to investigate the superior performance provided by the proposed GMC-ASE algorithm compared to the conventional proportional integral (PI) controller.

The paper presents a spectroscopic and catalytic study of encapsulated Keggin type heteropoly acid (12-tungstophosphoric acid, HPW) in the mesopores of MCM-41 molecular sieves. Nitrogen physisorption, FTIR, SEM, XRD and catalytic methods have been used to characterize and compare the properties of the samples. Methanol conversion, ?-pinene isomerization and ethyl acetate oxidation have been applied as model reactions for the evaluation of acid site activity. The combined physicochemical and catalytic investigations clearly show that the introduction of 12-tungstophosphoric acid into MCM-41 causes significant changes in the properties of the sample.

A biofilm is an accumulation of microbial cells and inorganic compounds held together in a polymeric matrix and firmly attached to a substratum; its study has been focused to its description as a biological catalysts. Nevertheless, it is known that the presence of biofilms in flow systems is able to change hydrodynamic behaviour. This phenomenon could be associated to the presence of velocity profiles that cause convective flow inside the biofilm. Following this idea, in this work, the description of a biofilm as a permeable fixed bed pseudo-homogeneous chemical reactor is proposed in order to find concentration and velocity profiles inside the biofilm. The model is simplified by considering a constant acceleration field that provokes flow inside the biofilm. Depending on the velocity profile, concentration profiles of the substrate are predicted. This study considers laminar flow inside the biofilm, therefore it is not necessary to consider the possible compactation of the biofilm due to an increase of the resistance against drag by flow outside. It is assumed that the biofilm is thin enough to be represented using rectangular coordinates without regarding the actual geometry. Finally, first order Kinetics is considered for the substrate consumption; literature data is used to adjust the proposed model. Simulation results show that concentration profiles are clearly dispersed by the convective flow, because of the addition of two orthogonal contributions, the one depending on the reaction-diffusion phenomenon and the other depending on the convective flow inside the biofilm.

Supercritical fluid extraction solubility data for monoolein, diolein and triolein in carbon dioxide were measured using a phase equilibrium re-circulation high-pressure type apparatus at 60° C and at various pressures. In order to examine the supercritical fluid extraction operation effects at high-pressures, detailed experimental determination were made on the compositions of the equilibrium vapor and liquid phases in the system (carbon dioxide/monoolein, carbon dioxide/diolein and carbon dioxide/triolein) at various conditions. It was found that weight fractions of up to 1% of monoolein could be obtained in the vapor phase. This might be sufficient to make supercritical fluid extraction using carbon dioxide solvent a possibility for this component. This renders a separation by simple distillation impossible. These systems were modeled based on the Redlich-Kowng equation of state. The experimental data was found to agree well with the data obtained by the model.

The paper reports the inhibition model of the purified polyphenol oxidase (PPO) activity from basil (Ocimum basilicum L.) with L-cysteine, ethylenediaminetetraacetic acid (EDTA), ascorbic acid, gallic acid, D,L-dithiothreitol, tropolone, glutathione, sodium azide, benzoic acid, salicylic acid and 4-aminobenzoic acid inhibitors using 4-methylcatechol, catechol and pyrogallol as substrates. The inhibitors such as salicylic acid, benzoic acid and EDTA did not inhibit Ocimum basilicum L. PPO for all substrates used in this study. Purification was carried out by precipitation of contaminating proteins with (NH4)2O4 dialysis of the supernatant and a Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity chromatography. The enzyme-catalysed browning reaction was significantly inhibited in the presence of L-cysteine, ascorbic acid, gallic acid, D,L-dithiothreitol, tropolone, glutathione, sodium azide and 4-aminobenzoic acid inhibitors. It was found that the inhibition types were (i) competitive inhibition for L-cysteine, ascorbic acid, D,L-dithiothreitol, tropolone and sodium azide inhibitors using 4-methylcatechol as a substrate; for L-cysteine, ascorbic acid, gallic acid, tropolone and glutathione inhibitors using catechol as a substrate; and for ascorbic acid inhibitor using pyrogallol as a substrate, (ii) uncompetitive inhibition for gallic acid inhibitor using 4-methylcatechol as a substrate; for 4-aminobenzoic acid inhibitor using catechol as a substrate; for tropolone and 4-aminobenzoic acid inhibitors using pyrogallol as a substrate, (iii) noncompetitive inhibition for 4-aminobenzoic acid inhibitor using 4-methylcatechol as a substrate; for D,L-dithiothreitol and sodium azide inhibitors using catechol as a substrate; and for L-cysteine, glutathione and sodium azide inhibitors using pyrogallol as a substrate. Furthermore, tropolone was the most effective inhibitor for Ocimum basilicum L. PPO because of its low KI value. Results showed that the type of inhibition depended on the origin of the PPO studied and also on the substrate used.

The demand for green technologies is continually increasing due to the growing consciousness of alimentary, environmental and toxicity risks. Supercritical technologies have beneficed from that interest and have therefore received increased attention as propitious media for elaboration of materials in general and formation of particles in particular, especially for pharmaceutical applications. This work presents the recrystallization of several drugs from liquid organic solutions, using CO2 as the precipitating agent. Three drugs were specially studied: theophylline, tolbutamide and griseofulvin. To select the suitable process among the several potentialities offered by SCF and to further understand and interpret the crystallization behaviour, selected phase behaviour of binary and ternary systems involving solute-solvent-CO2 were investigated and are presented hereby as background. Drugs were further precipitated by compressed CO2 as antisolvent, and experimental data focused mostly on results obtained in the discontinuous stirred version of the process. There was special emphasis on the influence of stirring and CO2 introduction rates upon the crystals characteristics and the production yields. The main difference between the investigated drug-solvent systems was their sensitivity to the stirring. As a first step, macro- and micro-mixing times were estimated; it was shown that mixing times due to circulation and to molecular diffusion were in the same range, with no significant breakthrough as a function of the solvent. Since the large size of particles produced by batch might be detrimental for therapeutic applications and/or administration routes, several precipitations were performed in the semi-continuous mode. Conditions were varied in order to play with phase behaviour, i.e. by setting the pressure below or above the critical locus of the solvent-CO2 system. Morphology of particles suggested that precipitation was confined within the solvent droplets, originating smaller precipitates than particles produced at monophasic conditions. The results obtained for three systems show that size of precipitates can be manipulated by a proper selection of thermodynamics and time or space scales, although the later has to be more accurately investigated to view the two versions of the antisolvent processes as complementary.

Environmentally-conscious design of processes and products is increasingly viewed as an important strategy in the sustainable development of new refining and chemical processes. This paper discusses a new process technology developed by UOP and Eni S.p.A; the UOP/Eni EcofiningTM process to produce green diesel from vegetable oil. This novel process utilizes catalytic saturation, hydrodeoxygenation, decarboxylation and hydroisomerization reactions to produce an isoparaffin-rich diesel fuel from renewable feedstock containing triglycerides and fatty acids. The resultant biofuel product has a high cetane value, a lower gravity, good cold flow properties and excellent storage stability. Green diesel is completely compatible for blending with the standard mix of petroleum-derived diesel fuels, thus providing significant value to the refiner. The process for producing green diesel operates at mild operating conditions and integrates well within existing petroleum refineries. In contrast to fatty acid methyl esters, where fuel properties depend on feed origin and process configuration, green diesel product is independent of feed origin and the fully deoxygenated biofuel is readily blended with conventional diesel fuel. A life cycle assessment (LCA) of this promising new biofuel production technology has been undertaken to quantify the intrinsic benefits of green diesel production over the current practice of converting various forms of lipids to fatty acid methyl esters. This paper will describe the technology, discuss the results of the LCA study and summarize the advantages this new technology can offer over other processing routes.

The forced variation of reaction parameters is a known method to improve the performance of catalytic reactors leading to process intensification. The most often experimentally varied parameters so far were the reactant concentrations or pressure. Due to the high thermal inertia of conventional reactors it was almost impossible to achieve fast periodic reproducible temperature changes. However, it has been proven theoretically that fast periodic temperature variations may increase the reaction rate compared to the stationary temperature conditions.The possibility to thermally cycle microstructured stainless steel reactors in a periodic way with temperature differences of up to 60 K and a frequency as high as 0.06 Hz has been demonstrated. This gives the opportunity to study the influence of fast temperature changes on heterogeneously catalyzed gas phase reactions. The catalytic CO oxidation over Pt supported on Al2O3 was chosen as a test reaction. The concentrations of CO, O2 and CO2 were monitored online at the reactor outlet using FTIR and mass spectrometry. The experimental measurements under non-stationary temperature conditions have shown an increase in the measured CO2 concentration compared with the one under temperature stationary conditions. For a temperature oscillation frequency of 0.048 Hz with an amplitude of 38 K, the mean CO2 concentration is 1.72 times higher than the mean value obtained under quasi-stationary conditions. A possible explanation for this phenomenon is an increase of the reaction rate due to the presence of a transitional reactive species surface coverage resulting from the temperature oscillations.

The influence of temperature on the formation of soot from ethylene pyrolysis has been studied. Pyrolysis experiments were carried out in a quartz reactor in the 1000-1200 °C temperature range, for an inlet C2H4 concentration of 50000 ppmv and a gas residence time of 4552/T(K) seconds. Outlet gases were analyzed by gas chromatography and the amount of soot produced measured. The reactivity of the soot samples obtained towards O2 and NO was also studied. Results show that the higher the formation temperature, the less reactive the soot. The soot samples were further characterized using elemental analysis, scanning electron microscopy and Raman spectroscopy, in order to study their structural properties, and relate them to their reactivity. Additionally, a comparison of the reactivity towards NO between acetylene and ethylene soot samples obtained under similar conditions has been carried out. The soot samples obtained from ethylene pyrolysis present higher reactivity towards NO than the soot samples formed from acetylene.

Preliminary studies highlight the positive effect of coupling photocatalysis and biological processes for the treatment of biorecalcitrant compounds. Before biological treatment, photocatalysis can be used as a pre-treatment process to increase pesticide biodegradability. Kinetics of amitrole biodegradation during cultures of Pseudomonas fluorescens was examined to ensure that the target compound was biorecalcitrant; its inhibitory effect justified a pre-oxidation. The biodegradation of cyanuric acid, one of the by-products resulting from photocatalyis of amitrole was confirmed. Pseudomonas fluorescens could metabolize this compound as a nitrogen source when a supplementary carbon source was added. The addition of supplementary carbon and nitrogen sources favoured growth and accordingly cyanuric acid degradation. Degradation yields (with TiO2 coated on cellulose fibers, 25 g.m-2) in the range 47% to 55% were obtained after 50h of irradiation for solutions of amitrole in the range concentrations between 70 to 6000 ppm. Between 10% and 34% of amitrole was mineralized to carbon dioxide. The production of ammonium and nitrate ions was negligible. An inhibition of TiO2 active sites was assumed to account for the weak mineralization. Identification of some of the intermediate by-products by LC-MS/MS shows negligible quantity of cyanuric acid. This work demonstrates that the hybrid process photocatalysis/bioremediation is a cost-effective promising solution for the treatment of wastewater containing biorecalcitrant compounds.

Removal of SO2 from gas emissions by selective absorption into a liquid is a common method to reduce air pollution and environmental risks. The absorption efficiency is determined by the interaction between the gases and the liquid. A great number of gas desulphurization methods have been developed where aqueous or organic solvents are used as sorbents.N,N-dimethylaniline (DMA) is an organic solvent used in the industry because its affinity with SO2. This absorption is neither too strong nor too weak, thus absorption and desorption can occur leading to a regenerative process where SO2 can be recovered. However, a direct contact between SO2 and DMA leads to several environmental problems caused by solvent evaporation and drops dragging into the gas stream.In order to increase the process efficiency and reduce environmental risks, a non-dispersive absorption process using hollow fibre membrane modules is developed in this work for a solvent zero emission process. The mass transfer into a fibre may be described by three main assumptions: gas-phase laminar flow, gas-phase plug-flow and gas-phase mixing. A numerical calculation was carried out to establish the performance of a hollow fibre membrane contactor for the removal of SO2 when water and N,N-dimethylaniline are used as sorbents in order to compare both, wetted and non-wetted operating modes.

Enzymatic transformations in ionic liquids (ILs)/supercritical carbon dioxide (scCO2) biphasic systems, whereby enzyme molecules are ``immobilized" in the IL phase and substrates/products are transported by the scCO2 phase, are described as a way for carrying out clean synthetic chemical processes to produce pure products. As a model system to study, the ionic liquid butyltrimethyl ammonium (bis(trifluoromethane)sulfonyl imine) ([btma][NTf2]) was assayed for Candida antarctica lipase B (CALB)-catalyzed the kinetic resolution of rac-1-phenylethanol. The suitability of this IL was established from both the activity and stability of the enzyme. A continuous dynamic kinetic resolution (DKR) process in [btma][NTf2])/scCO2 biphasic system was carried out by using simultaneously both immobilized Candida antarctica lipase B in silica gel and silica modified with benzenosulfonic acid groups (SCX) catalysts at 50 ºC and 10 MPa, providing a good yield (78 %) for (R)-1-phenylethyl propionate product with excellent enantioselectivity (ee = 92 %) in continuous operation.

The work focuses on a dual fluidized bed gasification technology that is successfully operated for combined heat and power production at a scale of 8 MWth in Guessing/Austria since 2002. The reactor concept consists of a circulating fluidized bed system with a steam-fluidized bubbling bed integrated into the solids return loop. Accompanying the operation of the commercial scale plant, parameter models have been developed and validated by comparison to measured data. As the models naturally fulfill mass and energy balances, the simulation also allows the validation of measurement data. The behaviour of the plant is studied by carrying out variations of selected parameters. Evaluation of different plant operation cases yields correlations between process variables. The solids circulation rate is shown versus riser exit velocity. Fuel water content and gasification temperature significantly influence global plant performance. Simulation predicts the efficiency of the existing power plant in optimized operation. Finally, part load behaviour is investigated and performance maps of the CHP plant are presented. High fuel water content at high gas engine load results in high gas velocities in the riser (erosion limit) and higher heat ratio in the produced energy. It is concluded that CHP-concepts based on fluidized bed steam gasification can reach high electric efficiencies and high overall fuel utilization rates even at small plant capacities of about 10 MWth.

The interactions between chemical reactions and transport may be divided into direct effects, for example on the molecular level, and indirect effects, for example those arising from the geometrical configuration of the integrated reactor/exchanger. Attention herein is focused on the latter, although in many instances the direct effects must be accounted for as well. Particular attention is given to the identification of behavior that does not arise in chemical reactors not connected to an exchanger or in exchangers not connected to a chemical reactor, as well as to optimal conditions and configurations of combined reactors and exchangers. Generalizations are difficult to formulate for such complex behavior and equipment, necessitating a primary reliance on illustrative examples. However, some general conclusions are drawn concerning the occurrence, identification, and performance of interactive designs.

Organic synthetic dyes are widely produced and used today. Significant losses of organic and inorganic content occurs during the manufacturing and application of dyes and its discharge in the effluent presents a threat to the eco-systems due to general toxicity and resistance to destruction by biological treatment methods. Particularly azo dyes are of special environmental concern due to their degradation products such as aromatic amines, which are considered highly carcinogenic. So, dyes have to be removed from coloured wastewater before discharge. However, traditional treatment methods (adsorption, coagulation/flocculation) mainly transfer the contaminants from wastewater to secondary waste. Therefore, advanced oxidation processes seem to be sustainable and clean technology to decolorize and minimize organic dyes content from wastewater. In this paper, degradation of an azo dye C.I. Direct Orange 39 (DO39) using Fenton type processes (Fe2+/H2O2, Fe3+/H2O2and Fe0/H2O2) has been performed. The molar ratio of Fenton’s type reagents has been varied in the range of 1 : 5 up to 1 : 50 at 0.5 and 1.0 mM concentrations of iron salts and iron powder. Experiments have been conducted for two hours in a batch reactor with magnetic stirring, ambient conditions and pH 3. The process efficiency and formation of degradation by-products have been determined on the basis of results obtained by UV/VIS spectrophotometric, total organic carbon (TOC) and high performance liquid chromatography (HPLC) analyses. The optimal Fenton and Fenton ``like" processes parameters have been applied in the photo reactor, too. It has been observed that simultaneous utilization of UV irradiation with Fenton's and Fenton ``like" reagents increases the degradation of DO39 dye. Degradation of the dye in dilute aqueous solution follows pseudo-first order kinetics. The maximal decolourization of 20 mg L-1 DO39 in water of 93.2% and TOC degradation of 76.9% were obtained using Fe3+/H2O2= 1 : 5 molar ratio. The results indicate that the treatment of DO39 dye wastewater with UV/Fe3 +/H2O2 system was found to be the most efficient.

Photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde was performed in water organic-free solutions by using a fixed bed continuous photoreactor containing Pyrex beads on which a TiO2 home prepared photocatalyst was supported. The influence of liquid flow rate, inlet alcohol concentration and catalyst amount on the photoprocess was studied. The highest selectivity to p-anisaldehyde was about 47% being CO2, the other main oxidation product; traces of 4-methoxybenzoic acid were also detected. The radiation field inside the photoreactor has been modelled by applying the Monte Carlo method thus allowing the determination of the local volumetric rate of photon absorption (LVRPA). It was found that the radiation intensity profile sharply decreases inside the bed so that an important aliquot of the bed is not active for the photoreaction occurrence. This finding indicates that the reactivity results, obtained by measuring the concentration values of reagents and products at the exit of photoreactor, can not be used jointly with the radiation modelling ones for determining the dependence of reaction kinetics on light intensity. The Langmuir-Hinshelwood approach has been satisfactorily applied for modelling the photoreactivity results and the values of all the model parameters have been determined.

Heterogeneous photocatalysis with titanium dioxide TiO2 is an advanced oxidation processes that uses ultraviolet radiation to carry out reactions leading to the degradation of polluting agents in water. For the development and scaling up of efficient photocatalytic processes it is important to model the transport of radiation in the reactor volume, because it affects the photo reaction. In the present work we have used the P1 approximation of radiative transfer theory to evaluate radiation distributions inside a specific annular photocatalytic reactor known as Photo CREC–Water II. The reactor consists of two concentric tubes with a TiO2/water suspension flowing axially in the annular space between them, and a lamp at the center of the inner tube. The theoretical results are compared with experimental data from measurements of radiation transmission through several observation windows in the external reactor wall. In general the model describes the observed experimental results well. Due to the nature of the employed approximation a good quantitative agreement is possible only for suspensions with a large optical depth. For small optical depths the agreement is adequate only for the central portion of the reactor length.

Heterogeneous photocatalysis employing titanium dioxide has emerged as an efficient method to remove a wide range of toxic compounds from polluted waters. In particular, chlorophenols constitute an important group of aquatic contaminants that have been successfully degraded by photocatalysis. In this work, the modeling of a slurry reactor for the photocatalytic degradation of 4-chlorophenol (4-CP) is presented. The experimental reactor is a thin rectangular parallelepiped limited by two parallel windows made of borosilicate glass. It is illuminated from one side by two tubular UV lamps (UV Philips TLK40/09N) located at the focal axis of cylindrical reflectors of a parabolic cross-section. The flat plate reactor is placed inside the loop of an isothermal, batch recycling system. The model describes the degradation of 4-CP as well as the formation and disappearance of the main intermediate products: 4-chlorocatechol (4-CC) and hydroquinone (HQ). Intrinsic kinetic expressions, previously obtained in a laboratory scale reactor, were employed to solve the mass balance for each species. To take account of the radiation effects on the reaction rate, the radiative transfer equation was solved in the flat plate reactor. The radiation model involves two spatial variables and two angular variables in the direction of radiation propagation.To validate the model, experimental runs were conducted by varying the catalyst loading (0.05, 0.1, 0.5, 1.0 x 10-3 g/cm3) and the 4-CP initial concentration (0.7 and 1.4 x 10-7 mol/cm3). Good agreement was found between simulation results and experimental data. Based on the experimental and predicted concentrations of 4-CP and 4-CC, the root mean square error (RMSE) of the model was 9.9 %.

A study has been carried out on the effect of acid catalyst properties and operating conditions (methanol/n-butane ratio in the feed, temperature, space time, time on stream) on the yield of light olefins (C2-C4) in the simultaneous cracking of n-butane and methanol. The operation has been carried out in an isothermal fixed bed reactor in the 400-575 °C range, using catalysts prepared based on HZSM-5 zeolites (with different Si/Al ratio), HY, Ni/HZSM-5 and SAPO-18. The results are evidence of a synergism between the transformation reactions of both reactants, whose consequence is an increase in the yield of olefins that correspond to the transformation of methanol and the cracking of n-butane. Furthermore, catalyst deactivation by coke is significantly attenuated compared to the corresponding transformation of methanol. Based on the effect of operating conditions on product distribution, a kinetic model is proposed by combining the schemes corresponding to the transformation of individual components.

The catalytic behaviour of a commercial HZSM-5 zeolite (Si/Al=30) for the selective transformation of bio-ethanol into olefins (BTO process) has been improved by two alternative methods: a) treatment with 0.2M alkali solution for a short time; and b) impregnation with Ni. By means of experimentation in an isothermal fixed bed reactor connected on-line to a GC for the analysis of the reaction products, it has been proven that moderate alkali treatment (10 min) slightly modifies the superficial structure and acidity of the HZSM-5 zeolite, which provokes a significant increase in the concentration of C2-C4 olefins, whereas deactivation rate and hydrothermal stability are similar. Moreover, 1 wt% nickel content in the catalyst is the optimum in order to obtain the better compromise concerning hydrothermal stability of the catalyst, coke deactivation, total yield of olefins and selectivity to C3-C4 olefins in the 400-500 °C range. In fact, the average production rate of C3-C4 olefins is twice as high as that of the parent zeolite in 8 h time on-stream experiments at 450 °C and 75wt% water content in the feed. Both methods are highly interesting because of the simplicity and reproducibility for obtaining economic and selective catalysts for the BTO process at moderate temperatures (catalysts modified by alkali treatment) and high temperatures (nickel based catalysts).

Wet oxidation of phenol over an Fe/activated carbon catalyst has been studied in a trickle-bed reactor in the following operational window: inlet C phenol=0.5 and 1 g/L, T=100-127 °C, PT=3-8 atm, W=0-4.8 g, QL=0.125-2 mL/min and QO2=91.6 NmL/min. The experiments were carried out in the absence of mass transfer limitations. Oxidation and mineralization reactions of phenol are proven to take place on the catalyst surface through a heterogeneous mechanism. Due to the complexity of the phenol oxidation route, simple reaction schemes have been assumed by lumping the intermediate species and generalized kinetic models for phenol and TOC abatement have been proposed. Two kinetic expressions, a power law rate and a Langmuir-Hinshelwood type rate expression, have been considered but only a convergence with statistically reliable parameters was found for the former model. A power law model with first order for phenol and 0.74 for oxygen and apparent activation energy of 74 kJ/mol described the experimental results in the oxidation of phenol well. Mineralization of phenol (TOC abatement) was described by a similar rate expression and takes into account the presence of refractory species such as the low molecular weight acids formed upon phenol oxidation.

This work focuses on the application of Advanced Oxidation Processes (AOPs) to purify phenolic effluents, which when combined with innovation and effectiveness contribute towards the preservation of natural resources and environmental quality. Phenols are typical pollutants found in wastewaters from different industries such as petrochemical, pharmaceutical, resin manufacturing, olive-oil, pesticides, dyeing production or cosmetic industry. Nevertheless due to their toxicity and harmfulness, they cannot be poured to water systems. Phenol has been chosen as a model compound in this study because it is usually a component of industrial wastewaters. Furthermore phenol-like compounds are generated by intermediate compounds in the oxidation pathway of higher molecular weight aromatic hydrocarbons.Phenol can be effectively removed but this does not imply that the all toxicity levels of the effluent have been diminished, since the oxidation pathway passes through more toxic products. Before each AOP application, the reaction intermediates must be identified in order to determine the influence they have on operating conditions, and subsequently establish the criteria for the complete destruction of toxic compounds. These studies will assist in the cost-effective operation of industrial setups, and also in the design of integrated processes for wastewater treatment.The main objectives of this work are, first to identify and measure toxic intermediates and, second, to develop a kinetic model for phenol degradation based on a mechanism in series. Chemical pathways in the phenol oxidation consider its hydroxylation to catechol, hydroquinone and resorcinol. These dihydroxylated rings are later oxidised to quinone-like compounds. These quinone-like compounds break into short-chain acids, like acetic, formic and oxalic acids. In order to propose a reaction pathway several runs were carried out at room temperature controlling the operational pH throughout the reaction. Experiments were carried out under different operating conditions, and the decay curves of phenol and aromatic intermediates were monitored, using doses of oxidant and catalyst until R=40 mol oxidant/mol phenol and [Fe(II)]=20 mg/L. Kinetic parameters were rightly fitted to the kinetic model, predicting successfully the reaction rates of each toxic compounds.

The microaerial oxidation of an aqueous solution of lactose to lactonionic acid (LBA) over the heterogeneous bimetallic catalyst Bi-Pd supported on mesoporous SBA-15 material was carried out in an agitated semi-batch reactor in alkaline medium within the pH range of 7 to 9.The present work focused on the synthesis and characterization of the bimetallic catalyst as well as optimization of the reaction operating conditions. To this purpose, the effect of both active metals loading on the support, metal/lactose ratio, reaction pH and dissolved oxygen concentration on the oxidation performances was examined at a very mild temperature of 65 oC.The bimetallic catalyst 1.02%Pd, 0.64%Bi/SBA-15, (Bi/Pd molar ratio of 0.3) showed the highest activity (96 % lactose conversion) and 100 % selectivity towards the targeted LBA product. Furthermore, the formulated catalyst proved to be stable in the reaction medium as both metals leaching was insignificant. Based on XRD and XPS analyses, it is suggested that the metals constituting the bimetallic catalyst active sites assemble into an intermetallic alloy having Bi1.75Pd stoichiometry.

Catalytic Wet Air Oxidation (CWAO) has been investigated for the treatment of water contaminated by 4-hydroxybenzoic acid (4HBA) and equimolar mixture of phenol-4HBA. Both batch measurements for kinetics determination and continuous fixed bed operation have been performed on the same Activated Carbon (AC). After a fast initial deactivation AC was proved stable and efficient at moderate temperature and oxygen pressure, like for phenol degradation.The kinetic study in the case of highly adsorbing material as AC may require complex approach to account for the variation of adsorbed reactants during batch oxidation. Adsorption isotherms at reaction temperature and with aged AC have been obtained according to Langmuir equation and used in 4HBA mass balance to derive more significant kinetic parameters. At high catalyst loading and relatively low pollutant concentration, the variation of 4HBA during the batch may be even higher on the solid than in the aqueous phase.

The technological development of catalytic processes under rapid deactivation requires the rigorous calculation of the deactivation kinetic equation in order to be useful in the simulation and optimization of industrial processes. Accordingly, suitable equipment for reaction and product analysis and a rigorous methodology for kinetic data analysis are required. These aspects are approached in this paper using the transformation of methanol into olefins on a SAPO-18 as the model reaction. In this reaction, deactivation is rapid and there is also an initiation period depending on process conditions. The correct use of gas chromatography allows for improving the collection of experimental data of composition with time-on-stream, given that, on the one hand, it minimizes the time required for analysis (4 min), and on the other, a better homogenization of the reaction product sample is achieved, which allows for a more accurate determination of the composition corresponding to a given time-on-stream. Furthermore, the rigorous kinetic modelling of deactivation requires a data analysis methodology that considers the past history of the catalyst and an activity to be defined based on a rigorous physical meaning. Accordingly, the concept of the integrated kinetic model has been used in this paper, whose basis is the calculation of kinetic parameters by simultaneously solving the zero time-on-stream kinetic model and the kinetic equation for deactivation.

The use of agro industrial by-products like cassava starch and sugar cane bagasse show great potential as substrates and support amylases production by solid-substrate fermentation (SSF). The production of amylolytic enzymes by Aspergillus niger LPB 28 increased with forced air using a column fermentation system and optimized conditions in a column bioreactor when it was followed by kinetics of respiratory metabolism. The O2 consumption and CO2 production by A. niger were measured in the top of the columns through the use of a GC system linked to a program for chromatograph control and integration with 2m length, with helium as the carrier gas and a thermal conductivity detector. The kinetic parameters were determined using the program FERSOL.

The performances of a semi-industrial-scale membrane bioreactor to treat dilute swine wastewater were investigated on a 3 month running period. The treated water was directly reused in the piggery for flushing purposes. The pilot was proved to have good performances in terms of ammonium removal (99%), and COD removal (86%), despite an accumulation of heavy metals in the biological tanks (up to 17 mg/L for zinc and up to 115 mg/L for copper). 79% of the total phosphorus was eliminated through the process, 61% via centrifugation and 18% by biological uptake. The pilot showed a good adaptability to the variations of the loading rates of dilute swine wastewater's major components (COD, TN, TP, heavy metals).

A graphite fluid-wall aerosol flow reactor heated with concentrated sunlight has been developed over the past five years for the solar-thermal decarbonization of methane. The fluid-wall is provided by an inert or compatible gas that prevents contact of reactants and products of reaction with a graphite reaction tube. The reactor provides for a low thermal mass that is compatible with intermittent sunlight and the graphite construction allows rapid heating/cooling rates and ultra-high temperatures. The decarbonization of methane has been demonstrated at over 90% for residence times on the order of 10 milliseconds at a reactor wall temperature near 2000 K. The carbon black resulting from the dissociation of methane is nanosized, amorphous, and ash-free and can be used for industrial rubber production. The hydrogen can be supplied to a pipeline and used for chemical processing or to supply fuel cell vehicles.

In order to adjust the redox properties of perovskite-based silver catalysts to satisfy the requirements for their application under overstoichiometric oxygen conditions (lean burn), three mixtures were prepared [Mixture (I): 10% La0.88Ag0.12FeO3 + 90% Al2O3; Mixture (II): 3% Ag/(10% La0.88Ag0.12FeO3 + 90% Al2O3); Mixture (III): 10% La0.88Ag0.12FeO3 + 90% (3%Ag/Al2O3)]. Mixture (I) with only a 10% La0.88Ag0.12FeO3 blend exhibited a NO reduction behavior similar to that of La0.88Ag0.12FeO3 alone at stoichiometric oxygen (1% O2). NO conversion of La0.88Ag0.12FeO3 under an excess of oxygen (10% O2) was however significantly improved by mixing with Al2O3 resulting in a value of ~ 30% at >400 °C in the case of Mixture (I). Ag impregnation facilitated the NO catalytic reduction, leading to a better deNOx performance for Mixture (II) and Mixture (III) than that of Mixture (I). It was also found that those silver atoms associated with Al2O3 are more effective for NO transformation. Therefore, the optimal mixed catalyst was Mixture (III), which shows satisfactory NO reduction and C3H6 oxidation at 500 °C under the whole range of O2 content from 1% to 10%.

An experimental investigation of the combined influence of flow pulsation and modified duct surface on cross-flow transport and convective heat transfer intensification in laminar flow was carried out. The experiments were performed with a fluid with a kinematic viscosity of 1.8x10-6 m2/s and Prandtl number of Pr = 15. The active length L of the channel is 900 mm and lateral extension is W = 90 mm. Pulsation amplitude (A range of 0.28 mm – 0.53 mm) was used together with pulsation frequency (range of 16 Hz ? f ? 54 Hz). A steady flow Reynolds number range of 100 < Re < 600 was studied. All the geometric parameters of the device such as the relative fin spacing and relative fin thickness were constant. The results of the flow visualization showed recirculation eddies formation when flow pulsation and fins are combined. This enhances the mixing of the fluid within the channel. The intensification of the heat transfer coefficient due to pulsation and use of fins becomes more significant with increasing pulsation amplitude. The combined influence of flow pulsation and modified surface geometry on the heat transfer coefficient was found to be significant at moderately low but non-zero net flow rates or Peclet number Pe. Maximum heat transfer intensification of 2.4 was obtained. In general, no significant heat transfer was obtained at very low and very high flow rates.

HDPE has been pyrolysed at 450 °C and 500 °C using HZSM-5 zeolite as a catalyst. Batch runs have been carried out at atmospheric pressure in a conical spouted bed reactor. Product analysis has been carried out by means of a GC, connected on-line with a thermostated line. The degradation rate of the plastic is slightly faster at 500 °C than at 450 °C and much faster than thermal pyrolysis in both cases. Products have been grouped into five lumps: the lump of light olefins, C2-C4; light alkanes, C1-C4; the gasoline fraction, C5-C11 compounds; C11+ hydrocarbons; and the coke deposited on the catalyst. An HZSM-5 catalyst is appropriate to obtain light olefins; about 55 wt% in both cases. The yield of gasoline fraction is also considerable and although its composition is not suitable for commercial gasoline, is interesting for its use in petrochemistry. The catalyst deactivation rate is low.

This work is related to the tracking of sulfate concentration trajectories in a continuous anaerobic bioreactor, where Desulfovibrio alaskensis is considered for different operation purposes. A new design of a class of nonlinear proportional control law with an adaptive gain was proposed. The proposed controller was applied to the mathematical bioreactor's model with the kinetics experimentally corroborated; this describes the dynamics of biomass, sulfate and sulfide concentrations. The open-loop stability conditions of the optimum set points and the corresponding closed-loop performances were analyzed. The proposed control law is able to track trajectories, despite sustained disturbances. An Internal Model Control (IMC) Proportional-Integral Controller was implemented for comparison purposes and the corresponding performances were illustrated via numerical experiments.

Asymptotes, approximations, and generalizations are presented for homogeneous reactions in a round tube. The well-known solutions for plug flow and laminar flow are first reinterpreted as asymptotes for perfect and negligible radial mixing, respectively, for non-energetic reactions. The use of integrated-mean terms to derive asymptotes and approximate solutions for a wide range of behavior, including energetic reactions in adiabatic flow, is then illustrated.Generalized solutions analogous to those for thermal convection in terms of Re and Pr appear to be impossible to formulate for systems involving multiple reaction mechanisms because of the many parameters, including for energetic reactions the frequency factor, energy of activation, and heat of reaction for each mechanism. However, generalization appears to be feasible in terms of differential formulations and numerical methods of solution.

A mathematical model is developed to optimize the performance of the radial flow reactors of styrene production through an oxidative reheat process. The model integrates the hydrodynamic configuration of the reactors with the underlying chemical reactions where the kinetic expressions were found in the literature. The predictions of the model were compared with the actual plant data and satisfactory results were obtained. In order to optimize the performance of the plant, a combination of yield and selectivity styrene was adopted as the objective function. The global criterion multi-objective method using Levenberg-Marquardt algorithm was used in order to search for the optimal solution of the process. Three main process variables, i.e., the flow rate of steam injected to the second and third reactor and the fraction of oxygen injected to the secondary injection port of the second reactor, were determined in the optimization. The results show that the optimal operating conditions may lead to 2.6 % increase in the styrene yield and 1.5% increase in styrene selectivity, which significantly improves the profitability of the whole styrene production process.

Polyphenol oxidase (PPO) from mushrooms (Agaricus bisporus (J.E.Lange) Imbach) was partially purified and characterized. The enzyme exhibited both monophenolase and diphenolase activities that were measured spectrophotometrically using L-tyrosine and pyrogallol as substrates. A two-fold purification in both activities was achieved by ammonium sulfate fractionation. The monophenolase activity was 3.35 EU/ml, and the diphenolase activity was 189.3 EU/ml. PPO was relatively stable at -15°C for 44 days. The enzyme was not very heat stable, and its activity decreased when incubated at the temperatures higher than 35°C. PPO activity showed two pH optima, at 5.3 and 7.0 at 25°C when pyrogallol was used as the substrate.Mono-, di- and triphenols were substrates for PPO. Using Vmax/Km as a specificity constant, pyrocatechol was the better substrate followed by pyrogallol. The kinetic parameters of the enzyme were: Vmax = 78 EU/min/ml, Km = 1.4 mM and KS = 250 mM for pyrogallol and Vmax = 168 EU/min/ml, Km = 0.40 mM and KS = 270 mM for the pyrocatechol. Of the inhibitors tested, competitive-type inhibition was observed with benzoic acid and sodium azide. A mixed-type inhibition was observed with L-cysteine and sodium fluoride.

The concepts of green chemistry and sustainable development are being considered more and more due to the evolution of regulations and mentalities. In this context, the development of supercritical fluid technologies should go on to evolve in the right direction.Since the nineteen fifties, studies and development efforts have been focused on new ways of separating substances using the specific properties of supercritical fluids. In this context, a mention must be made about the use of carbon dioxide as an extracting agent in many industrial processes (decaffeination of coffee and tea, extraction of hops, spice, aromatic substances, fragrances, pharmaceuticals, etc). Processes using these fluids are particularly attractive at the industrial scale in many fields such as impregnation, analytical and preparative separations, organic synthesis, waste management and material recycling. The industrial development of the supercritical fluid technology is accompanied by numerous research activities, in particular, in the field of inorganic Materials Science for the synthesis of multifunctional nanomaterials.Today, supercritical fluid technology allows the production, with a reduction of the environmental impact, of well designed nanomaterials with controlled properties for applications in many interesting fields, such as catalysis, electronics, energy, optics, pharmacology, etc. This paper is focused on the interest of using supercritical fluids to overcome the drawbacks of solution chemistry approaches for designing multifunctional nanomaterials in term of chemical engineering, sustainable chemistry and control of size, morphology, composition and the structure of nanomaterials.

Fischer-Tropsch synthesis (FTS) offers the potential to produce high-value transportation fuels or petrochemicals from biomass (``2nd generation biofuels"). Primary synthesis products contain mainly n-alkanes and n-alkenes, ranging from methane to high molecular weight waxes. Bifunctional catalysts, as used in petroleum refining, are capable of modifying hydrocarbon molecules. They are characterized by the presence of acidic sites, which provide the hydrocracking and isomerization functions, as well as metal sites, which provide hydro-/dehydrogenation functions, and thus avoid the formation of carbon. The present study addresses the combination of FT synthesis (with Co or Fe catalysts) and hydrocarbon modification reactions. Experimental results obtained in a dual layer configuration with Fe and Co catalysts and Pt/ZSM-5 indicate i) an increase of branched hydrocarbons in the gasoline range (C5-C10), ii) a decrease of alkene and alcohol yields, iii) partial hydrocracking of long chain hydrocarbon molecules leading to higher yields of gasoline and distillates, iv) nearly constant methane selectivity in comparison with the FT catalyst alone, and v) no significant catalyst deactivation. In addition, studies with 1-octene as the model compound were carried out, being mixed with synthesis gas H2/CO or with H2/Ar. The presence of CO decreases reaction rates of hydrogenation and hydrocracking, although all reactions still occur to a significant extent. For the conditions used in this study (1 MPa, 200-300 °C, 4000 kg s/m3), a significant change of hydrocarbon product composition with hydroprocessing catalyst functions added can be observed.

In this paper a real-time system for detecting changes in dynamic systems is designed. The cumulative sum (CUSUM) or the Page-Hinkley test is intended to reveal any drift from the normal behavior of the process. The process behavior under its normal operating conditions is established by a reliable model. In order to obtain this reliable model for the process dynamics, the black-box identification by means of a NARMAX (Nonlinear Auto-Regressive Moving Average with eXogenous) model has been chosen in this study. It is based on the neural network approach. This paper will show the choice and the performance of this neural network in the training and the test phases. A study is related to the inputs number, hidden neurons used and their influence on the behavior of the neural predictor. Three statistical criterions are used for the validation of the experimental data. After describing the system architecture and the proposed methodology of the fault detection, we present a realistic application such as a reactor in order to show the technique's potential. The purpose is to detect the change presence and pinpoint the moment it occurred.

Gasification is an attractive technology for waste thermal treatment. The successful design and modelling of a gasifier requires reliable kinetic data. The purpose of this work is to study the steam gasification kinetics of chars produced by municipal wastes pyrolysis. The municipal solid wastes (MSW) are modelled as a mixture of four organic constituents: paper, wood, plastics, and vegetables. The various char samples are obtained by pyrolysis of each waste constituent, in a fixed bed reactor at 1000°C, in order to minimize their volatile content and thus, to eliminate any subsequent devolatilization of the carbonaceous residues. These chars are used as raw materials in steam gasification experiments. The gasification studies are performed on each char separately, in a tubular kiln at various temperatures (900°C, 950°C and 1000°C) and various vapour pressures (0.2 bar, 0.5 bar and 0.7 bar). The gases produced are analysed by gas chromatography in order to determine the gasification kinetics. The kinetics parameters, with respect to H2O, together with the influence of the char's physical properties are experimentally determined. A kinetic expression for the gasification reaction, based on the random pore model is deduced. It is shown that the char resulting from the pyrolysis of MSW constituents, essentially paper, wood and vegetables have the same gasification kinetics. On the contrary, the plastic char steam gasification kinetic appears to be significantly slower.

The present investigation pertains to a theoretical study of simulation of a multicomponent catalytic distillation column. Basically it deals with the development of a mathematical model for esterification of acetic acid with methanol by using a packed column with two different feed setups: a single feed column and a two feed column. The reaction kinetics has been assumed to be heterogeneous. It also includes the solution technique for the solution of the model. An in-house code in C++ has been developed to solve the model equations. Further, the comparison of the model has been done with available experimental data. Finally the effect of design variables namely- reflux ratio, feed tray location, and start of reactive section have been studied.

The specific surface area of ground perovskites is strongly dependent on the synthesis and pretreatment conditions. Calcining the ground LaCo1-xCuxO3-? perovskites at 5000C causes a decrease of their specific surface, but the further reductive pretreatment of the calcined sample in hydrogen leads to only a minor change in the specific surface area.The introduction of extra- and intra-perovskite lattice copper has different effects on the structure stability, reducibility and catalytic properties of LaCoO3 perovskites. Under the same pretreatment conditions the basic structure of both LaCoO3 and Cu2O/LaCoO3 samples is retained at the reduction temperature of 5000C (90 min) while that of Co-Cu based perovskites is completely collapsed producing a high dispersion of bimetallic metals and Co-Cu alloys supported on amorphous La2O3. For a series of LaCo1-xCuxO3 samples, increasing the copper content in the perovskite structure leads to an increase in the metal surface area of the reduced phase. The pretreated catalysts were tested for CO dissociation and for alcohol synthesis from syngas. The results indicated that the copper sites neighboring with cobalt atoms in the reduced perovskites decrease the activity in CO dissociation and increase the rate of higher alcohol synthesis while extra-perovkite lattice copper tends to produce methanol, methane and CO2. The overall activity in syngas conversion and higher alcohol productivity are proportional to the Co-Cu metal surface. The role of dual sites of Co and Cu for the synthesis of higher alcohols is discussed. The catalytic activity and alcohol productivity as well as product distribution depend strongly on reaction temperature and pretreatment conditions. The highest productivity of alcohols in the present study is about 73 mg/gcat/h for sample LaCo0.7Cu0.3O3.

Oxidative dehydrogenation of ethane to ethylene was investigated over Chromia and Cr-V mixed oxide catalysts synthesized following a complexation procedure. With an O2/C2H6 feed ratio of 0.17, Chromia exhibited a total conversion value of about 0.20 at 447°C (at a space time of 0.24 s.g/mL) with an ethylene selectivity of 0.82. Chromia catalyst was more active than Cr-V mixed oxide at temperatures as low as 200°C. Pulse-response experiments carried out with ethane pulses injected into O2-He indicated the presence of at least two different sites for the formation of CO2 and H2O over Chromia catalyst. In the dynamic experiments carried out with the Cr-V mixed oxide catalyst and by injecting O2 pulses into a gas stream containing a mixture of C2H6 and He, formation of CO rather than C2H4 was favored. Results of the dynamic runs carried out without gas phase oxygen strengthened the conclusion of lattice oxygen participation in the selective oxidation of ethane reaction through a redox mechanism.

The world is bound to make a gradual shift from a hydrocarbon economy towards a hydrogen economy. This shift is being facilitated by the technological development in hydrogen energy that is occurring around the world. Gasification of biomass for generating biomass synthesis gas is a promising source for the distributed power generation concept as it is based on the local raw material supply. This concept has to be augmented by hydrogen fuel cell technology for modular, efficient and environmentally benign implementation. This provides the platform for looking at the option of separating hydrogen from biomass synthesis gas which is composed of H2, N2, CO, CO2, CH4, Tar, alkali traces and particulate matter at varying compositions depending on the biomass and operating conditions. This paper makes a critical review of the attempts made to reform and separate hydrogen through a hydrogen permeable membrane reformer reactor as it provides the energy efficient route. The feasibility and various membranes from palladium to ceramic membranes used in the reactor configurations and the engineering problems of the reactor will be analyzed. The inherent problems in providing a one shot modular solution for solving the problem will be discussed in the paper.

In the present investigation, pyrolysis and gasification, two widely used thermochemical processes, are compared as potential chemical recycling methods for MWP and plastic rich MSW in terms of products of high value and their end uses. High temperature pyrolysis results in a wide spectrum of products which also contain monomers of C2-C4 range such as ethylene and 1,3-butadiene. Recovery of monomers from their isomers and other products is difficult and energy-intensive. Gasification breaks solid wastes into simple molecules (mainly CO & H2) which subsequently can be converted to value added liquid chemicals (namely alcohols) by a catalytic synthesis processes. Synthetic alcohol then can be converted to the desired petrochemical precursors. After reviewing different aspects of both pyrolysis and gasification, recycling through gasification is chosen as the preferred route for project SPORT as syngas product can be converted into several key petrochemical products in high yield.

The upgrading of bio-oil by catalytic transformation upon acidic catalysts is aimed at adapting its composition to that of conventional fuel, or at obtaining petrochemical raw materials, such as olefins and aromatics. A further alternative of growing interest for bio-oil upgrading is catalytic reforming for obtaining H2. The viability of any of these alternatives requires minimizing both the plugging problems that arise in the reactor when the bio-oil is fed and the rapid deactivation of the catalyst, which are associated with the thermal degradation of the lignocellulosic components. In this paper, the catalytic transformation of bio-oil (obtained by fast pyrolysis of vegetable biomass) in a fluidized bed reactor upon a Ni-HZSM-5 zeolite catalyst has been studied, and special attention has been paid to the design of the feed preheating zone. Operation in a single-unit (U-shaped steel tube) for the thermal treatment of the bio-oil (in the downward zone of the U-tube) and its catalytic transformation (in a fluidized bed located in the upward zone of the U-tube) has been compared with operation in a two-unit system, where both steps are carried out in separate units connected through a thermostated line (U-shaped tube for thermal treatment, followed by a fluidized bed reactor for catalytic transformation). It has been proven that a separate step of thermal treatment prior to the catalytic transformation notably improves the global process of bio-oil upgrading. Firstly, it contributes to minimizing coke deposition on the acidic catalyst, mainly the deposition of "thermal" coke (which is associated with the thermal degradation of the bio-oil components at high temperatures), leading to an important attenuation of catalyst deactivation. Secondly, the bio-oil components degraded in the thermal treatment can subsequently be subjected to another upgrading treatment (by steam activation or pyrolysis) in order to obtain a high quality char, which involves upgrading the entire bio-oil.

The application of a hybrid framework based on the combination, artificial neural network-genetic algorithm (ANN-GA), for n-thymol synthesis modeling and optimization has been developed. The effects of molar ratio propylene/cresol (X1), catalyst mass (X2) and temperature (X3) on n-thymol selectivity Y1 and m-cresol conversion Y2 were studied. A 3-8-2 ANN model was found to be very suitable for reaction modeling. The multiobjective optimization, led to optimal operating conditions (0.55 ? X1 ? 0.77; 1.773 g ? X2 ? 1.86 g; 289.74 °C ? X3 ? 291.33 °C) representing good solutions for obtaining high n-thymol selectivity and high m-cresol conversion. This optimal zone corresponded to n-thymol selectivity and m-cresol conversion ranging respectively in the interval [79.3; 79.5]% and [13.4 %; 23.7]%. These results were better than those obtained with a sequential method based on experimental design for which, optimum conditions led to n-thymol selectivity and m-cresol conversion values respectively equal to 67% and 11%. The hybrid method ANN-GA showed its ability to solve complex problems with a good fitting.

A tangential flow two colliding streams cyclone reactor (TFTCSCR) was employed as a chemical reactor in the implementation of a solid-liquid reaction. The reaction between barium sulfide particles and a sodium carbonate solution as a typical example of such reactions was considered. Higher conversions of BaS obtained in this reactor may indicate the better performance capability of TFTCSCR relative to those of conventional reaction systems. A stochastic model, based on the Markov chain discrete formulation has been developed for the TFTCSCR, which describes the flow pattern and the residence time distribution (RTD) within the reactor. The predicted values for BaS conversion have been compared with those determined experimentally. The degree of agreement was between 80-85%.

An intrinsic kinetic model based on the reaction mechanism of the photocatalytic oxidation of cyanide with TiO2 has been developed and applied to the results of experiments carried out using different catalyst concentrations, initial concentrations of cyanide and incident radiation fluxes. The results of the kinetic modeling have been compared with the use of an empirical model equation generated following the response surface methodology; a statistical procedure to correlate the influence of several factors on a response variable.The kinetic model reproduces the experimental data with a relative error below 13%, slightly lower than that obtained with the empirical model equation. In contrast with the latter, the kinetic model is based on the intrinsic photocatalytic reaction mechanism and takes into account the radiation profiles inside the photoreactor. Consequently, after validating the model in a broad range of experimental conditions, it could be applied to any other reactor configuration, allowing the simulation and optimization of the radiation and reaction rate fields with scaling-up and photoreactor design purposes.

Results from CFD simulations in a laboratory scale cylindrical bubble column with an internal diameter of 0.44 m under different operation conditions are presented. The effects of the continuous phase viscosity, bubble diameter and drag model were evaluated and the results were compared with experimental data found in the literature in three different gas inlet velocities. It was found that the approach used in this work provided physically consistent results, showing the transient effects in the column and good agreement with experimental data found in the literature for a homogeneous flow regime. Also, a case for a column with internals was simulated and a flow behavior qualitatively different from the column without internals was found.

Microstructured reactors with their benefits especially concerning enhanced mass and heat transfer represent a means for process intensification. A broadly used microstructured lab tool in the area of gas/liquid contacting is the Falling Film Microreactor (FFMR) developed by IMM in which liquid films of a few tens of micrometer thickness and interfacial areas of up to 20,000 m2/m3 combined with an effective heat exchange can be obtained. Now the concept of the Falling Film Microreactor has been developed further with regard to increasing throughput in order to reach pilot production level and as a basis for future production scale throughput. Therefore, two different prototypes with a tenfold larger structured surface area have been developed and realized. The feasibility of a corresponding increase of throughput has been demonstrated for the oxidation of an organic compound using oxygen which is closely linked to an industrial relevant reaction and additionally by the absorption of CO2 in an aqueous sodium hydroxide solution. Naturally, process optimisation itself also contributes to the efforts to increase throughput. Therefore, the oxidation reaction has been optimised in both varying process parameters (temperature, flow rates, pressure) and reactor parameters (microchannel width and depth) in the original, standard Falling Film Microreactor. Conducting experiments at 10 bar instead of ambient pressure and using a reaction plate with 1200 µm x 400 µm channels instead of 600 µm x 200 µm channels lead to an increase in conversion. These investigations also encourage exploring more challenging process conditions and thereby following the concept of "novel chemistry."

A set of TiO2 samples with different anatase/rutile ratios was prepared by calcinations at different temperatures from commercial photocatalyst Degussa P25. The effects of the two crystalline phases of titanium (IV) oxide on the photocatalytic activity in gaseous phase through oxidation of light hydrocarbons were studied. Crystalline phase transformation from anatase to rutile occurred at 700°C for P25. Results indicate that samples with higher anatase/rutile ratios presented higher intrinsic activities for the photodegradation of a propane/isobutane/butane (40/35/25 %V) mixture. However, the activity did not totally disappear after complete crystalline transformation from anatase to rutile, indicating that the pure rutile phase also presents photoactivity. During the photocatalytic reaction of TiO2 samples, a linear dependence was found between the inverse of the intrinsic reaction rate constant (k intrinsic) and the water adsorption capacity in the surface (WAPS) of the synthesized TiO2 catalyst. The thermal treatment used to induce the formation of rutile by calcination would presumably reduce water adsorption capacity and surface area, leading to a decrease in photocatalytic activity.

Producing hydrogen from natural gas for a mini scale fuel cell is a new challenge for researchers. Therefore, modeling of hydrogen production microreactors should be helpful for designing and developing new microreactors. Experimental sensing of velocity, concentration, temperature and reaction rates in numerous points of the microreactor is impracticable. A microreactor in special geometry was considered for hydrogen production and a CFD model was developed in order to incorporate the mechanism of autothermal reforming. This mechanism includes three main reactions and Langmuir-Hinshelwood type kinetic rates. A three dimensional reformer model was developed to simulate the reactive laminar flow model of this microreactor. Effects of styles of feed entrance, air to fuel ratio and adding water to methane were studied. This model shows that there are hot spots near the entrance of the microreactor where the total oxidation of methane occurs and air distribution along the microreactor is a good solution for hot spot problems. The model shows that air distribution is good for fuel cell application because of high hydrogen production and low CO content in the outlet.

Current trends in the chemical process industries indicate the growth of a significant niche for flexible, multi-purpose plants producing relatively small quantities of high-value products. Batch processes are inherently more suited to such applications, and extensive research has been done on process scheduling in such plants using mathematical programming, heuristic or artificial intelligence methods. This work describes an alternative approach based on pinch analysis, which has been used since the 1970s for applications ranging from conservation of industrial utilities in process plants, to management problems in supply chains, financial planning and emissions control. All these applications assume that valuable resources need to be allocated to different demands with both quantity and quality specifications. Pinch analysis is shown here to be applicable to visualizing and analyzing the scheduling and allocation of batch reactors in multi-purpose plants. Two specific types of problems are described. The pinch analysis approach is demonstrated using illustrative case studies. The pinch analysis approach allows for quick identification of processing bottlenecks and provides rules for subsequent detailed scheduling.

With the recent interest in the application of nanoscale metal and metal oxide particles, there is now interest in manufacturing these materials in larger quantities. A number of techniques have evolved for the synthesis of nanopowders. For metal and metal oxide nanoparticles where coalescence is the dominating growth mechanism, concentration and the time–temperature history of the nanoparticles resulting from the reactor design determines the final particle average diameter. In this paper, we present the results of controlled synthesis of alumina nanopowder in a three-jet plasmachemical reactor, where temperature and velocity distributions are controlled by the angle of impingement of the plasma jets. The flow and temperature fields for various impingement angles were measured by an enthalpy probe. The products were characterized by means of electron microscopy, XRD analysis, and BET analysis. The dependences of particle size on the operation parameters (injection velocity of raw material, plasma jet enthalpy, solid/gas mass flow rates ratio, and impingement angle of plasma jets) are discussed. In comparison with the single jet reactor, the novel reactor can increase the production rate several times to manufacture the product with the same required surface area.

Used tyres pose a serious environmental problem and pyrolysis is considered one of the more feasible solutions that may be economically profitable on a large scale. In this study the pyrolysis of tyres has been carried out in a conical spouted bed reactor at 500 °C and the liquid product has been characterized taking into account composition, heat value and simulated distillation. The tyre mass feed in each run was 2 g and the bed was made up of 15 g of sand. Pyrolysis of scrap tyre at the 500 °C gives way to a yield of 3.1% of gases, 37.6% of liquid fraction (C5-C10 range hydrocarbons), 25.6% of tar (C11+) and 33.7% of char. The liquid fraction is of suitable quality for its use as fuel but the char requires activation for its upgrading.

The thermal degradation kinetics of a random copolymer of isobutyl methacrylate / lauryl methacrylate, produced by free-radical solution polymerization is investigated over a temperature range of 350 to 750 K, using dynamic thermogravimetric experiments. Heat treatment of the copolymer affects the main polymer backbone and side chains. The thermal degradation of the copolymer proceeds in three distinct steps of weight loss: the first and easiest step is initiated by scissions of head-to-head linkages representing one type of defect in the polymer backbone; the second and more difficult step is initiated by scissions at the vinylidene chain ends; the third and most energetic step is initiated by random scissions within the polymer chain.The time evolution of molecular weight distribution (MWD) is measured by gel permeation chromatography (GPC). The most pronounced changes in the trend of the average molecular weight are observed during the transition from each degradation step to the subsequent one. A continuous distribution kinetic model based on a population balance is developed to describe the observed degradation behaviour of the copolymer. This comprehensive model conforms to the special mechanisms for random chain-scission and chain-end depolymerization. The pseudo-kinetic rate parameters for each degradation step are estimated to be respectively equal to 1.1 10-8, 5.6 10-8 and 1.08 10-7 mol g-1 min-1. The average calculated activation energies are respectively 89.2, 116.4 and 134.8 kJ/mol.Global kinetic parameters of degradation are also determined using dynamic thermogravimetric (TGA/DTGA) data. The model-fitting and model-free isoconversional methods are used to retrieve the kinetic parameters of the degradation process. The model-free isoconversional method can satisfactorily describe the dependence of the activation energy on the conversion and is recommended over the model-fitting methods for obtaining the reliable and consistent kinetic parameters of polymer degradation.

A model has been developed to investigate the operation of a distillation column with an external side reactor coupled to it (ESR). This system is compared to two more conventional process systems, namely a reactor followed by a single distillation column with recycle (R-D), and a reactor followed by two distillation columns in series with recycle (R-D-D). The toluene disproportionation reaction is used in the comparison. It is found that the reactor followed by a single column is an unattractive system as the overall conversion is low (14%) compared with 56% for the R-D-D system and 40% for the ESR system. An economic comparison of the two attractive processes was performed and the results show that the side reactor system requires similar capital costs, but reduced annual utility costs. The difference is approximately 12.5% which is significant, but below the 25-50% required to make a change in established technology viable. The side reactor system does not necessarily use new technology, but it does use the old technology in a new way. Therefore, it is still worth investigating these systems further and should be a possibility when designing a new plant.

A series of carbon-supported bimetallic catalysts with different metallic loadings was synthesized, using platinum as the principal active phase and molybdenum or tungsten as promoting phases. The materials were prepared by organometallic precursor thermolysis and characterized by direct current electrochemical methods, transmission electron microscopy, scanning electron microscopy and x-ray diffraction. Electrodes were elaborated with each catalyst and their electrochemical performances were studied by cyclic voltammetry. These results show an increased activity of the catalysts with small amounts of Mo or W, towards oxidation of methanol with respect to the catalyst containing only platinum. XRD results reveal the presence of molybdenum or tungsten bronzes (HxMoO3, HxWO3) that are responsible for the increase in activity. It is believed that the bronzes participate in a spillover effect by promoting the removal of protons from the platinum surface. It was found that the presence of molybdenum in this type of catalyst prevents the platinum phase from sintering during the thermal treatment and allows them to keep platinum particles with mean sizes between 2 and 8 nm. The proposed catalysts are adequate for methanol oxidation in liquid-fuel alcohol fuel cell systems, since it was found that oxidation potentials are lower than those observed with platinum catalysts.

There is not much known about the reactivity of hydrocarbon soot to oxygen and NO. According to the chemical and structural properties of one soot obtained from acetylene pyrolysis, SEVACARB MT and CABOT carbon blacks were selected to perform a reactivity study. The properties of the materials were determined through ultimate and proximate analysis as well as SEM, TEM and XRD techniques. A study of the oxidation of the three materials is performed for different oxidation conditions of temperature (1123-1273 K) and oxygen concentration (100-1000 ppmv). The reaction of acetylene soot with NO and SEVACARB MT carbon black is carried out at 1373 K with 1800-3000 ppmv NO. Results are compared to analyze their reactivity similarities and the possibility of using carbon blacks as acetylene soot substitutes in laboratory work.

Doped anatase thin films on glass were deposited by ultra-spinning from titanium isopropoxide-based sol-gels. To test the self-cleaning properties of anatase-coated glass, crystalline fluoranthene, a polycyclic aromatic compound, was sprayed over the glass and then irradiated using a 365 nm UV source. This anthropogenic contaminant was removed until 98 wt.% at 140 h of irradiation time with the 2 wt.% zinc ferrite-doped anatase film. The fluoranthene proportion degraded on anatase-free glass was much lower than with anatase coating giving only 12% for an irradiation time of 140 h. In this form, the coated-glass transparency was recovered almost totally at this irradiation time for the doped anatase film mentioned, which did not occur with anatase-free glass, even after more than 400 h of UV irradiation. A correlation was found between the total weight losses of the solid compound and the intensity of the Raman vibration at 671 cm-1 during photocatalytic degradation. After 140 h of irradiation, while the presence of fluoranthene is not detected by Raman spectroscopy, glass plate presented ultra-thin zones of degradation products. Thus, the removal of these intermediate products deposited on glass was directly measured by means of weight difference. The self-cleaning properties of doped anatase coating on window glass could have a positive influence on outdoor and indoor air quality. In this work, degradation mechanisms and intermediate products were not discussed or identified.

The objective of this research is to show the efficiency of a pilot plant based on sieving and attrition for the treatment of stormwater sediments. Seven sediments from retention/infiltration ponds and street sweeping were chosen for the pilot study. Geotechnical tests were carried out in order to make sure that the treated sediments have the required characteristics to be re-used. The study shows that these sediments can valuably be processed by means of a pilot plant allowing the concentration of pollutants in the fine particles. Our results are encouraging and show that, taking into account environmental, geotechnical and economical requirements, up to 75 % of the bulk sediment can be re-used after the proposed treatment.

A systematic approach to identifying a robust kinetic model fitted on noisy data is presented. The bootstrap coupled with Monte-Carlo simulations and exploratory data analysis techniques are employed to evaluate candidate model formulations to given sets of experimental data. The approach is applied in an industrial case study in determining the most practical rate expression for the water-gas shift reaction over a cobalt Fischer-Tropsch catalyst.

The transesterification reaction is the most utilized process to obtain biodiesel. Fried oil transesterification reactions with methanol have been studied using several zeolites Y and interchanged with CsCl and KOH. The reaction has been carried out both in a slurry reactor and a fixed bed catalytic reactor. The catalytic effects of zeolites have been tested within a temperature range of 60-476°C, 2.5-5% catalyst/waste oil weight ratio, and 6:1 - 100:1 methanol/oil molar ratio. Cosolvents (THF, n-hexane) in the reaction feedstock effect have also been studied as well as catalyst regeneration effects. Viscosity of both the oil and the transesterification reaction products was determined as an initial guide to investigate the degree of conversion to biodiesel as well as FAME content by GC. When interchanged zeolites are used conversions are improved, getting the best yields (98% FAME) for the Y756 zeolite interchanged with KOH. Viscosities of the reaction product obtained reached values next to diesel standard ones.

The oxidation of a blend of model molecules (tetralin plus indane in hexadecane) and two deep hydrotreated LCOs was performed by treating the fuel in the presence of air with a CuCr/P(4-PVP) catalyst. The blend was studied at different operating conditions, and the product composition was determined by elemental analysis, and by GC. The hydrotreated LCO were fractionated in cuts, and the naphtheno-aromatic compounds present were characterized by HPLC, GC-MS, and HNMR techniques, as well as elemental analysis, and ASTM methods. These cuts were oxidized in a continuous stirred tank reactor from which samples of product were taken at different residence times and analyzed. In particular, the acid number, storage stability, and cetane number were followed as a function of the oxidation severity. The oxidized products were tested in a diesel engine. Their emissions were compared with those of a biodiesel, a blend, and a hydrotreated product. The results indicated that the oxidation rate and the type of molecules are different in the light, medium, and heavy part of the hydrotreated products, with a different acid number, cetane number storage stability, and emissions in a diesel engine throughout the distillation range. The paper discusses the mechanism of the oxidation reactions, the effects of severity in the hydrotreating, and the effect of oxygenated molecules contained in the light part of the diesel.

The new concept of a rotating fluidized bed in a static geometry was numerically and experimentally studied. The particle bed can be both tangentially and radially fluidized by injecting the fluidization gas tangentially in the static fluidization chamber via multiple gas inlet slots located in its outer cylindrical wall. The tangential fluidization of the particles induces a rotating motion of the particle bed. As a result of the particle bed rotational motion, the solids experience a radially outwards centrifugal force. A radially inwards gas-solid drag force and radial fluidization of the particle bed can be introduced by forcing the fluidization gas to leave the fluidization chamber via a chimney with one or multiple gas outlet slots, positioned at the axis of the fluidization chamber. The solids can be continuously fed and removed in and out of the fluidization chamber via solids inlet and outlet holes in the front or back ends of the fluidization chamber.The fluidization patterns of low-density polymer particles with a large diameter and of high-density salt particles with a small diameter were experimentally studied in a 24-cm diameter, 13.5-cm long non-optimized static fluidization chamber at different solids loadings. Scale-up to a 36-cm diameter fluidization chamber was also studied. With both types of particles, a rotating fluidized bed and an acceptable gas-solid separation was obtained provided that the solids loading was sufficiently high. Slugging and channeling and a non-uniform distribution of the gas over the gas inlet slots to the fluidization chamber may occur at low solids loadings and can be detected via well-chosen pressure measurements. The fluidization patterns observed in the same fluidization chamber were completely different with the polymer particles and with the salt particles. The polymer particles tend to form a dense and uniform bed, its behavior being mainly characterized by tangential fluidization. The salt particles tend to form a less dense, bubbling fluidized bed that is both tangentially and radially fluidized.Computational fluid dynamics simulations give an improved insight in the gas and solid phase flow pattern.

Steam oxidation of iron metal which is the reverse reaction of the reduction of iron oxides as a hydrogen storage material was conducted under the condition of 673K with varied partial pressures of water vapor. The kinetic model of the steam oxidation of iron metal was expressed as the ordinary shrinking-core model with film diffusion control by experimental data obtained from thermogravimetric measurement. The apparent rate constant of steam oxidation was expressed as the Langmuir type equation against the partial pressure of water vapor. A model of a simulated moving bed-type reactor to solve the problem of over-reduction of materials was made. In our previous work (forthcoming), the kinetic model of the reduction of iron oxide with hydrogen was expressed as a shrinking-core model with reaction control, and the modeling of a simulated moving bed-type reactor was made with an irreversible reaction model. In this work, the modeling of a simulated moving bed-type reactor was achieved with the model of a reversible reaction consisting of reduction rate and oxidation rate.

Fixed-bed columns containing solid catalysts and adsorbents were employed for simultaneous reaction and separation. The models developed for propene metathesis were validated with experimental data for configurations with and without the effect of pressure swing reaction. The models for the mass and momentum transfer in the catalyst bed and adsorber were solved using orthogonal collocation within the method of lines. The reactor/separator performances were tested for beds with varying numbers of layers of catalysts and adsorbents which were arranged sequentially. The pressure reaction columns behaved as reactor/separators in series. As the number of layers increased, a homogeneous distribution of the catalyst and adsorbent was approached in the limit. These configurations with variable catalyst/adsorbent distributions were investigated for propene metathesis reaction, in terms of product purity, selectivity, conversion, recovery, yield and productivity. Improved reactor performance was observed with a pressure swing separation system and in particular with close to well-mixed reactor/separator configurations.

The catalytic wet oxidation of an azo dye was investigated at 180°C and 15 bar of oxygen partial pressure. The effects of different catalysts were examined under operating conditions selected in pre-runs of non-catalytic oxidation and thermolysis (absence of oxygen). Manganese - copper catalysts with different molar ratios were tested and MnCu5 (50% Mn and 50% Cu) was found to be the most effective, giving almost complete dye degradation and 56.8% TOC removal after 60 minutes of reaction. Moreover, this catalyst revealed to be stable regarding metal leaching and catalyst poisoning due to sulphur or carbon depositions.

Theoretically, there are several methods that can be used to remove CO from H2-rich gases. As for the applications of PEM-FCs to vehicles, boats and yachts and residential co-generators, however, the feasible choice may be only between the preferential CO oxidation (CO-PROX) and the selective CO methanation (CO-SMET) because of the limited available spaces and low operating pressures in such application systems. The CO-PROX process has so far been extensively tested since it is somehow reliable to remove CO down to 10 ppmv by raising the O2 consumption unlimitedly. Nonetheless, the technology requires a closely controlled low O2 supply to keep the possibly lowest H2 parallel oxidation and a working temperature window suitably wide for control purposes. This, while making the method costly and complicated, obviously hampers its application to low-power PEM-FCs where very small oxidant flows have to be provided by use of well-refined expensive flow meters, such as mass flow meters. Without any additional reactant required, the CO-SMET can avoid the above-mentioned shortcomings of the CO-PROX application. Furthermore, the CO methanation is less exothermic than the CO and H2 oxidations. Thus, a CO-SMET reactor is inherently more easily controllable than a CO-PROX one. The present work deals with a screening of catalysts for CO abatement via selective methanation. Ru-based catalysts supported on TiO2, ZrO2 and CeO2 were prepared by a conventional impregnation method and CO removal was determined by varying the operating conditions. The obtained results showed good performances of the Ru/ZrO2 and Ru/CeO2 supported catalysts, and also the feasibility and applicability of the CO-SMET process, especially by employing the Ru/CeO2 supported catalyst.

In the present study, Ni incorporated MCM-41 structured mesoporous catalysts with a Ni/Si atomic ratio of 0.036 and 0.15 were prepared by a direct hydrothermal synthesis procedure. These catalysts had surface area values of 860.5 m2/g (Ni-MCM-41 having a Ni/Si ratio of 0.036) and 944.9 m2/g (Ni-MCM-41 having a Ni/Si ratio of 0.15). They also had narrow pore size distributions with average pore diameters of 2.7-2.6 nm respectively. Ni MCM-41 synthesized by the one-pot hydrothermal synthesis procedure showed very high activity and relatively high hydrogen yield in steam reforming of ethanol in a temperature range between 300-550°C. Besides the steam reforming reaction, formation of some formaldehyde and small amounts of ethylene were also observed at low temperatures for the catalyst containing a Ni/Si ratio of 0.036. The disappearance of formaldehyde and the formation of some methane at high temperatures indicated the increased significance of cracking in addition to reforming and dehydration reactions. The increase of the Ni/Si ratio makes the catalyst more active at lower temperatures.

A thorough understanding of fundamental parameters, such as transient and time-averaged gas and solid velocities, is helpful for designing and manipulating the gas-solid jetting fluidized beds. In this study, a new two-fluid model developed in our group is used to investigate numerically the gas and solid velocities in the gas-solid jetting fluidized beds by adding the user-defined Fortran subroutines in the platform of CFX 4.4, a commercial CFD software package. Simulation is carried out in a two-dimensional fluidized bed 2.0 m high and 0.3 m wide equipped with a nozzle in the centre at the inlet. Resin, belonging to Geldart B Group, is selected as the solid material. The numerical results show that the solid movement is predominantly upward in the center of the bed, whilst it is primarily downward in the outer region of the bed. Particles exchange between these two regions across their neighboring boundary. Gas interchange between the jet and the emulsion phase becomes obvious with the jet evolution. The time-averaged distributions of gas and solid velocities in the bed are greatly influenced by jet gas velocity, and the effect of the static bed height can be ignored. These numerical computations provide helpful information for designing and scaling up the jetting fluidized bed.

Fuel Cell (FC) technology promises to be a viable alternative for small scale electric heat and power generation (combined heat and power units, CHP). Moreover, the polymer electrolyte membrane FC (PEM-FC) is currently considered the most suitable technology for vehicles, both for traction and as auxiliary power unit APU; the latter is used on boats and yachts too. The ideal fuel for the PEM-FC is pure H2 gas. However, due to the lack of H2 distribution infrastructures, the current way of producing H2 to feed PEM-FC involves the reforming of hydrocarbon feedstocks and the removing of the catalyst poison CO with a series of catalytic steps. Water Gas Shift (WGS) is an attractive option for CO conversion although, due to its exothermic nature (?H298°C = -41.1 kJ?mol-1), the equilibrium conversion is thermodynamically limited at high temperatures. In contrast, at low temperatures, the reaction rate is constrained by kinetics such that highly performing catalysts are necessary to provide adequate activity. For these reasons two WGS stages are generally employed: a high temperature stage (HT-WGS), which takes place between 400-500°C and reduces the CO concentration to about 2-5%, followed by a second shift at a lower temperature (LT-WGS), with a cooling stage in between, which is carried out over a temperature range of 200-400°C and reduces the CO concentration to about 0.5-1%. In this work, catalysts based on Pt and mixed Pt+Re on different supports were prepared and their catalytic activity was tested; moreover, a comparison with commercial catalysts was also carried out. Very promising results were obtained in the HT-WGS range as the catalytic performances of the prepared catalysts were superior to those reached by the commercial catalyst; therefore they can be considered as possible candidates for FC technology.

Within the context of reducing the green house gas emissions, substituting hydrogen for natural gas could have a great environmental impact, but hydrogen has different combustion characteristics than natural gas. This paper reports results of experimental tests of premixed combustion of natural gas-hydrogen mixtures in a porous burner made of open cell metallic foam. The technology of porous radiant burners shows environmental and economical advantages compared to traditional diffusion flame burners. The tests showed that substituting natural gas for hydrogen in a porous burner reduces the pollutant emissions of CO and NOx and the quantity of CO2 produced. For specific powers below 500 kW/m2, the emissions were below the "Blue Angel" label values. But working conditions are limited by hydrogen addition and the equivalence ratio has to be lowered to prevent flashback. The radiant combustion mode is more difficult to obtain with mixtures containing hydrogen and it disappears completely for mixtures with more than 80% vol. hydrogen.

In this study, the dissolution kinetics of tincal in phosphoric acid solutions was investigated. The effects of reaction temperature, acid concentration, solid to liquid ratio, particle size and stirring speed were determined in the experiments. The results showed that the dissolution rate increased with increasing acid concentration, reaction temperature, stirring speed and increased with decreasing particle size and solid to liquid ratio. The dissolution rate was found to be based on the first order pseudo homogenous reaction model. The activation energy of the tincal in phosphoric acid solution was determined as 42.28 kJ.mol-1.

Hydrogenation of vegetable oils using stable catalysts with satisfactory activity and selectivity as well as very low trans fatty acid (TFA) and saturated fatty acid (SFA) production is a challenging task. It is known that unhealthy TFA formation is the result of positional and conjugative isomerization side-reactions occurring during hydrogenation. From this standpoint, it is possible to formulate active, selective and stable catalysts which would minimize the production of TFA and SFA.Monometallic Pd and bimetallic Pd-Me (Me=Mo, Ni, Co, Ru, and Sr,) highly dispersed on mesostructured SBA-silica material with pore size ranging from 6 to 7 nm, BET-specific surface of 800-900 m²/g, and metal nominal total loading up to 1.0 % w/w, were comparatively investigated as catalysts for lowering the unhealthy trans (TFA) and saturated (SFA) fatty acids and maximizing the highly health-beneficial cis-monoenes production during the hydrogenation of sunflower oil at 110 oC under hydrogen pressure of 5 atm.The Pd-catalyst at nominal metal loading of 0.8 % supported on nanostructured support was active and selective for the hydrogenation of sunflower oil under mild process conditions. It produced less saturated acid and reached a good selectivity towards monoenes. In all cases, the consecutive impregnations of Pd and a second metal on the mesoporous silica support preserved the mesoporous structure of the support with slight modification of the textural characteristics in terms of BET surface area, pore size distribution and total pore volume. The addition of nominal 0.2 % Co, Sr or Ru to 0.8% Pd-catalyst enhanced its activity. However, the addition of nominal 0.2 % Ni or Mo dropped the activity of monometallic Pd-catalyst significantly. It is clearly shown that Ru had some promoting effect to inhibit further the formation of trans fatty acids. The addition of a second metal to Pd-catalyst had no significant effect on the formation of C18:0.High degree of metal-metal, metal-support as well as metal-oil interactions would greatly influence the reaction mechanisms of the vegetable oil hydrogenation.

This paper presents an experimental study on zeolite NaX dehydration under microwave irradiation at a laboratory scale. Dehydration rates vary linearly with the absorbed power and show no influence with the purge gas flowrate. A pulsed mode of irradiation enhances dehydration due to higher temperatures reached and improved mass transport rates. A thermal balance model is developed in order to assess the maximum temperature reached in the adsorbent bed and the use of the dissipated energy inside the solid is discussed. From these results, this paper evaluates the economic interest in a microwave regeneration process and discusses the technical feasibility at an industrial scale.

Various parameters such as type of feedstock, inlet and outlet coil temperature, heat flux and residence time, affect the performance of a thermal cracking reactor. The pyrolysis coil configuration is one of the most important parameters which affects the performance of the reactor.In this research the effect of four different coil configurations, namely single row, millisecond, split and reversed split have been studied on run length, product yields, outside surface temperature of coil, coke deposition as well as temperature and pressure distribution. The reactor under investigation is the thermal cracker of Abadan petrochemical complex which uses propane as feedstock. The results show that millisecond coil configuration has the highest yield of ethylene and lowest coke thickness. However, it exhibits the lowest run length and worst ratio of length to diameter conditions. On the other hand, single row coil configuration has the lowest ethylene yield and highest coke thickness but, the highest run length with the lowest pressure drop also belongs to this coil configuration. It also presents the most even distribution of pressure and a linear temperature profile across the coil length, favoring better selectivity.

This paper highlights our recent work on preparation and characterization of nanostructure transition metal (Me) oxide (Me = Mn, Ti and Zr) ion-sieves. The controlled hydrothermal and Sol-Gel method have been developed in the synthesis of ion-sieves by the acid treatment of Li-Me-O tri-oxide precursors. The structure characteristic and ion-exchange property are studied by XRD, TEM, nitrogen adsorption-desorption analysis, lithium ion adsorptive isotherm and kinetics measurement. The result shows that these transition metal oxide ion-sieves, promising in the lithium extraction from brine or seawater, have good selectivity and remarkable adsorption capacity for lithium ions. The maximum adsorption capacity of manganese dioxide and titania by now is 3.47 and 4.02 mmol/g, respectively. The adsorption capacity of zirconia ion-sieve is only 0.675 mmol/g. To the best of our knowledge there is no other report on zirconia with the lithium adsorption property up-to-date.

In the present paper the observations on the simultaneous adsorption biodegradation (SAB) of resorcinol and phenol from two separate synthetic wastewater samples have been reported. For SAB, immobilization of Pseudomonas putida MTCC 1194 on granular activated carbon (GAC) has been done. The optimum process parameters like adsorbent dose, particle size of GAC, and pH have been determined experimentally by calculating percentage removal. The optimum process parameters have also been verified by the theoretical model of Weber and Morris (1963). Under the experimental conditions at 28 degrees Celsius the optimum process parameters are noted as adsorbent dose = 10 g/l, GAC particle size = 2- 4 mm and pH = 6.24. The isotherm studies of these processes have been done. Adsorption studies have also been done separately for both the compounds for comparing the efficiency of SAB over adsorption.

An explicit method for limiting the volume fraction of the dispersed phase in the CFD simulations of dense gas-solid flows is described and validated both on structured and unstructured computational grids. The procedure is based on the excess solids volume correction method proposed by Lettieri et al. (2003), which has been extended in this work to non-uniform grids made of cells having different shape and size. The method has been implemented in OpenFOAM and validated through the simulation of a fluidised bed in which the superficial gas velocity has been reduced to a value close to zero.

The technical re-conversion of MTBE process to produce ETBE was studied, using a non-equilibrium model in catalytic distillation with an UNIFAC method at steady state. The simulation was carried out in Aspen Plus, analyzing the possibility of using the actual installations of the MTBE plant as it works, to produce ETBE. The study is focused on the reactive and the catalytic distillation sections, which rule the process behavior. The analysis of azeotrope conditions revealed that the ethanol-to-isobutene molar feed ratio is the main factor affecting the equilibrium, by modifying the separation between the ETBE product and the butylenes in the catalytic column. The indirect effect of increasing the operating pressure in the reaction equilibrium, by changing the phase equilibrium temperatures increasing them also, as well as by modifying the ethanol-isobutene feed ratio at the reactive zones at a higher value, are the variables that limit the equilibrium. Consequently, a high isobutene conversion is attained. Finally, doing a comparison between the two processes, it can be confirmed that the ETBE can be produced in the same installations, obtaining an isobutene conversion of 98 weight % and an ETBE product with an overall composition of 98 weight %.

Submerged gas jets issuing into fluidized beds are used in many different industries and it is important to have a fundamental understanding of how the gas and surrounding medium interact – to understand the flow patterns and how the solids behave in the vicinity of the nozzle jet. Following the discussions of Bohnet and Teifke (1985) and Idelchek (1994) it was decided to qualitatively investigate the effects of altering the region surrounding the contact between the jet and the fluidized bed. Alteration of the flow pattern was accomplished using a semi-cylindrical shroud (0.035 m i.d. and 0.043 m long) that formed a physical barrier around the nozzle tip. The nozzle inner diameter was 0.0016 m i.d. and the motive gas flow rate was supersonic. Videos were recorded of the solids and gas flow patterns via a special transparent plate on the wall of the fluidized bed for a half-jet with and without a shroud at a superficial fluidization gas velocity of 0.11 m/s. Presented below are the original videos and observations derived from the two simple experiments in a fluidized bed with a rectangular cross-section (0.10 by 1.20 m and 2.0 m high). There was a significant difference in the flow patterns of the solids in the vicinity of the nozzle tip when the shroud was present. Furthermore, the jet expansion angle and penetration were observed to decrease by approximately 50% and 43%, respectively.

Catalytic graphitisation of carbon was used to explain the synthesis of carbon nanotubes from acetylene using the catalytic chemical vapour deposition method. This was achieved by comparing the kinetics of synthesis of carbon nanotubes at varying acetylene concentrations and different operating temperature ranging from 850 to 1100 deg.C, using the Langmuir-Hinshelwood mechanism to obtain the model kinetics. Optimum production rate of carbon nanotubes and carbon nanofibres of 8.2mg/s was observed at 1000 deg.C and acetylene concentration of 4725 ppm. 4th order kinetics was also proposed and the data fitted the experiments quite well. Comparison of experimental results with the computed values shows appreciable agreement with correlation coefficients ranging from 0.81-0.99.

The yields and selectivities in both the catalyzed and non-catalyzed oxidative dehydrogenation of propane were found to increase with increasing pressure. The results showed that the maximum yields of valuable ODH products could be obtained by adjusting only reactants' partial pressure, while keeping their ratio constant.

Sulphate-reducing bacteria (SRB) are anaerobic bacteria that couple the oxidation of simple organic compounds to the reduction of sulphate to sulphide. SRB have become important components of bioremediation systems. In this work, a natural SRB sludge was collected in the coastal mud flat of Colindres (Cantabria, Spain) and the removal of soluble cadmium as cadmium sulphide from a synthetic feeding was studied. Discontinuous experiments were performed at room temperature, using four 600 ml reactors. In stage 1, a 250 mL biomass solution (18.16 g/L of volatile matter) was introduced in each reactor and was fed with a solution of cadmium sulphate, sodium sulphate and sucrose as carbon and energy source. The Chemical Oxygen Demand (COD) to SO4-2 ratio (this SO4-2 coming from Na2SO4) was 10 in all the stages of the four reactors, and the different cadmium content tested in each reactor varied from 4 to 12 mg/L. Stages 2, 3, 4 and 5 were performed with the same biomass but with higher initial cadmium amount, from 16 to 300 mg/L, in order to determine the amount of metal causing inhibition of the bacterial activity. Soluble cadmium was analyzed by Atomic Absorption Spectrometry. Additionally in stage 4, the evolution of pH and COD was studied. Results indicated that inhibition of biomass was not found up to a Cd concentration of 300 mg/L. Continuous experiments were performed in an UASB reactor of 1 litter of useful capacity, being the hydraulic residence time 0.833 days and 720 mg of COD/day the organic matter in the influent. After a period of acclimation, biomass was fed with increasing amounts of soluble Cadmium and the specific rate of cadmium elimination was determined.

This article examines the propagation of kefir grains in fresh HTP whole fat cows' milk, with some additions (glucose and bakers yeast). The objective of our work was an experimental determination of the various process parameters relative influence on the propagation and daily kefir grain increase mass, using the Taguchi method for experimental design. The effects of medium temperature, glucose mass concentration, bakers yeast mass concentration and the rotational frequency of the stirrer at four levels were studied. Orthogonal array layout of L16 was selected for the proposed experimental design. All experiments were performed in an automated laboratory reaction calorimeter RC1 (Mettler-Toledo) with the same milk (3.5 % fat). The gravimetric method was used to determine daily kefir grain mass increases. Relative contributions of the proposed influencing process parameters on the daily kefir grains increase mass were estimated by analysis of the variance (ANOVA). The highest increase (51.5 %) was found at the rotational frequency of the stirrer 90 (1/min), at glucose mass concentration 20 g/L, and at medium temperature 24 °C. Within the observed range of yeast mass concentration this process parameter was found to be insignificant compared to others. The rotational frequency of the stirrer has the highest relative influence on the daily kefir grains increase mass (37.3 %) while glucose mass concentration and medium temperature have lower ones, 18.8 % and 9.9 %, respectively. The remaining fraction represents error influence. The main reason for its relatively high value (34.0 %) is that kefir grains are bulky and awkward to handle. This fact confirms the importance of optimal kefir grains production management.

Land-filling is widely accepted and used in many waste management strategies, but it can constitute hazard for the environment. A study was conducted to evaluate the environmental hazard of a leachate flowing into surface waters without adequate treatment. The investigated leachate has been formed at an industrial landfill, where non-hazardous wastes from all phases of tanning processes including wastewater treatment were disposed. Collected leachate was characterised in terms of biodegradable (as reflected by its average BOD5 value 420-600 mg?L-1) and recalcitrant fractions (average COD was 1200-3400 mg?L-1). To set up a satisfactory treatment method for removal of pollutants from the leachate different toxicity reduction methods were employed to identify groups of substances most hazardous to the environment. We have used filtration, air stripping, adsorption on activated carbon, coagulation-flocculation processes and advanced oxidation with Fe2+/H2O2. It has been estimated that an effective treatment of the leachate could be achieved by the removal of persistent organic fractions and ammonium to avoid broad contamination of surface and groundwater; and this will minimise its serious risk to ecosystems and human health if the chemicals from the leachate migrate to drinking water catchments areas.

The vertical component of solid velocity has been measured in shallow spouted beds by means of an optical fibre, for different geometric factors of the contactor (angle and inlet diameter) and under different experimental conditions (height of the stagnant bed, particle diameter and air velocity). The study has been carried out with glass beads and materials of lower density (high- and low-density polyethylene, polypropylene and extruded and expanded polystyrene) in the spout zone of shallow spouted beds. The calculation of velocity along the axis has been carried out by solving a force balance rising along the spout and the core of the fountain.