Volume 7, Issue 1

Fischer-Tropsch synthesis (FTS), an exothermic reaction where hydrogen and carbon monoxide synthesis gas are converted to hydrocarbon products, has been under development since the 1930's. The interest in FTS depends on current and perceived future prices of crude oil but is increasingly viewed as an option for exploiting stranded natural gas. Other advantages of FTS hydrocarbons include the absence of sulphur, nitrogen, heavy metal contaminants, low aromatic content and the ability to produce high value middle distillates/fuels. Current interest is directed towards slurry bubble processes – comprising gas, liquid, and solid phases. Industrial slurry phase FTS reactors may range in size from 6 – 10 m in diameter and upwards of 30 m in height and include multiple internal heat transfer tubes. Such systems offer numerous advantages including high heat transfer rates, good mixing, and ease of online catalyst addition and withdrawal. However, one disadvantage is the complex hydrodynamics associated with slurry bubble columns, which make scale-up difficult. A literature review on heat transfer studies and correlations has been completed focusing on previous experimental setups, the synthesis of the key findings/parameters, and the identification of the necessary criteria required for reactor design and scale-up.The parameters having the most pronounced impact on heat transfer in slurry bubble columns and three-phase fluidized beds are the superficial gas velocity and liquid properties such as viscosity and surface tension, which significantly alter the bubble properties and the column hydrodynamics. The effect of particles is poorly understood and is a complex function of particle diameter and concentration. The experimental results and correlations reported here from the majority of studies are dependent upon the equipment and properties of the three phases studied – resulting in very limited applicability to other systems or for scale-up. Other concerns include the use of relatively low gas velocities, ambient temperature and pressure, relatively large particles, and relatively small columns employed in most studies, which are not relevant to industrial operating conditions. Furthermore, studies involving multiple internals were relatively few. Most columns were only equipped with a single tube or small heat flux probe thereby measuring only the local heat transfer and not taking into account the effect on column hydrodynamics of multiple internals. Of these studies only a few tubes were equipped with heaters (that did not run the entire tube length) and heat flux probes while the remaining probes were inactive.

In this paper, different phenomena affecting laboratory trickle-bed reactors are carefully reviewed. Before focusing on laboratory scale, some general considerations about trickle-bed reactors are discussed: regimes, industrial uses, etc. The main factors a laboratory trickle bed reactors are presented and detailed. The greatest six factors include: homogeneity of the catalyst bed, catalyst wetting, axial dispersion, channeling, isothermicity and mass transfer. These factors are reviewed and different criteria, suggested in the literature, are given in order to minimize the influence of these six factors; for each criterion, a simple application is presented. Finally, the application of all the criteria given in the paper is based on a hypothetical example (hydrodesulfurization).

Supercritical water possesses a number of important characteristics that make it suitable for oxidation, synthesis and gasification reactions. It is especially advantageous for very wet biomass whose gasification in this medium avoids the large expense of energy required for drying. Although the process is in laboratory scale it has a great potential for production of hydrogen and other gases from biomass. This paper reviews the present state of the art and summarizes major observations arrived at in small scale laboratory flow and batch reactors. Effects of operating parameters like, pressure, temperature, etc., on the yield and conversion are discussed. Catalysts appear to play an important role in increasing the conversion rate and decreasing the reaction temperature for gasification. Heat recovery from the product stream holds key to making the gasification process auto-thermal. Heat exchanger efficiency, therefore, plays an important role in this process. Several investigators have used the equilibrium model and exergy analysis for thermodynamic analysis of supercritical gasification plants. Energy efficiency of such a plant could be around 50%.

There has been tremendous development within mixing operations in industry. Incomplete knowledge of this process caused serious economic losses to process industries. For optimum yields and the economic potential that goes with better understanding of mixing, research in this field continues to grow. The major forms of mixing in industry are either by mechanical or pneumatic agitation. Airlift bioreactors achieve mixing through pneumatic agitation and have gained attention over two decades for their fluid dynamic characteristics and low power consumption. It has been widely applied in bioprocess industries for production of biochemicals, to wastewater treatment in which the performance of this reactor has been overwhelming with respect to its production levels as compared to the conventional mechanical agitation.In this review, mixing through mechanical and pneumatic agitation is compared. An extensive literature is distilled from various investigators on the hydrodynamics and mixing characteristics of airlift bioreactors. This review has emphasis on factors that affect mixing such as the geometrical parameters of the vessel, gas flow rate, properties of the liquid medium, sparger design and measuring techniques employed. In an attempt to understand process related issues, sophisticated advances in the measuring techniques provides more insight into mixing in this reactor. Thus extensive correlations have been proposed by various investigators to predict the hydrodynamic and mixing parameters. Some design modifications proposed by several scholars have also been reviewed.

In the present study, a model for the fast pyrolysis of a spherical biomass particle has been developed. The model admits the generation of data which are not accessible experimentally such as the intra-particle temperature and concentration distribution. Simulations have been carried using data from the reactor as well as from literature and the effects of the heating rate and the particle size have been examined. The kinetic model is coupled with a heat transfer model. The reaction kinetic constants have been chosen in order to match the theory to the data taken from experiments carried out in a laboratory wire mesh reactor, for a temperature range from 573 K to 873 K and a heating rate of 200 K/s. Pyrolysis temperature and product distribution profiles in both spatial and temporal directions throughout the particle are presented. The effects of the particle size and the reactor's heating rate in the final pyrolysis products and temperature are shown and discussed. Simulations were carried out using Matlab and the model has been validated against the experimental results. The heating rate, which is an important operating condition in thermal processes, seems to have a positive effect on the biomass conversion to gaseous and liquid products, an increase of the first resulting to an increase of the second. Particle size was found to have a negative effect on pyrolysis conversion as larger particles tend to give higher char yields. For the particular experimental system analyzed here, it seems that the radial non-uniformity is not very large and acceptable results can also be taken using a lumped particle model. Validation of the model with experimental data showed great accordance, thus the model could be used for the prediction of final pyrolysis yields and temperatures.

Chromatographic reactor is an attractive mode of operation that combines chemical reaction and product separation in the same unit. In this work, esterification of butyl cellosolve with acetic acid using cation exchange resin Amberlyst-15 is investigated in a chromatographic reactor. The study involves determining the appropriate kinetic model for the reaction by performing experiments at different temperatures, mole ratios of the reactants, catalyst loadings and stirring speeds. Characterization of the adsorption capacity of the resin for different components involved in the reaction is performed through adsorption experiments for the nonreactive binaries. The combined separation-reaction process is experimentally investigated using a fixed bed chromatographic column. A mathematical model is developed and the experimental data is compared with the model predictions. It is shown that the experimental and predicted data closely follow each other and that the high conversion can be obtained with a relatively high purity of the product.

An external liquid circulation is introduced into a traditional internal loop reactor in order to improve liquid circulation and increase the interface between gas and liquid phases. The effects of superficial gas velocity and external liquid circulation velocity on local and overall gas holdups are explored experimentally and numerically in the loop section of a combined gas-liquid contactor, which consists of a liquid spray, sieve plates and an internal loop with external liquid circulation. Local gas holdup is measured experimentally by a double-sensor conductivity probe. Numerical simulations are conducted in the platform of a commercial software package, ANSYS CFX 10.0. Gas holdup and other information are obtained by solving the governing equations of mass and momentum balances for gas and liquid phases in a hybrid mesh system. Both measured and simulated results indicate that local, section-averaged, and overall gas holdups increase with an increase of the superficial gas velocity. The downcomer tube for circulating external liquid has a significant influence in the gas-distributor and the downcomer-tube action regions rather than in the upper draft-tube and the gas-liquid separation regions. Good agreement between measured and predicted data suggests that CFD simulation together with experimental investigation can be employed to develop novel gas-liquid contactors with a complex geometrical configuration.

We study a hybrid adsorption heat pump water heater for domestic use that comprises a water heater with dual heat sources. This water heater combines the advantages of an adsorption heat pump and a conventional gas boiler. An experimental study on the output and coefficient of performance (COP) of the system was performed under various environmental conditions, and some important conclusions and suggestions that improved the hybrid water heater system are presented. In addition, a numerical analysis for experimental results was presented by process simulation, and then the COP of the system was examined.

High concentrations of N-containing compounds in drinking water cause health problems such as cyanosis among children and cancer of the alimentary canal. Therefore, removal of nitrate from water samples is of significant importance from the health and environmental point of view. In this work, the effective parameters on removal of nitrate by adsorption process, which included the amount of granular activated carbon (m), initial concentration (C0), contact time, pH and temperature (T), were investigated. The removal process was monitored using an on-line spectrophotometric analysis system. It was found that the content of adsorption followed decreasing order: m= 10>5>2>1g, C0= 20>15>25>10 ppm, pH=4>7>10>1 and T=25>35>45>55 0C. The three-layered feed forward back propagation neural network was used for modeling of nitrate adsorption on granular activated carbon. The comparison between the predicted results of the designed ANN model and the experimental data proved that modeling of nitrate adsorption process using artificial neuron network was a good and precise method to predict the extent of adsorption of nitrate on GAC under different conditions.

In the present study, the photocatalytic degradation of 2,4-DCP has been investigated in a batch reactor under UV light in slurry mode using titania P-25 (surface area 50 m2/g) as a photocatalyst and sodium hypochlorite as an oxidant. Variables studied include catalyst dose, pH and oxidant concentration. The rate of degradation was studied in terms of changes in concentration of the pollutant and reduction in chemical oxygen demand. The optimal values of operational parameters leading to 2,4-DCP abatement were obtained by using response surface methodology.

Inactivation of Bacillus subtilis spores was carried out using solar-driven Advanced Oxidation Processes (AOPs) alone and coupled with free chlorine in sequential processes. Experimental results showed that Fenton-like processes are more efficient under the tested conditions than heterogeneous photocatalytic processes using suspended titanium dioxide. Experimental data were fitted using modified Chick-Watson kinetics and the accumulated energy as the radiation dose needed for spore deactivation. It was demonstrated that the deactivation of B. subtilis spores using chlorine can be enhanced by primary treatment with photocatalysis. This study also suggests that AOPs could be an effective alternative to control the occurrence of highly resistant waterborne pathogens.

The present work aims to employ genetic algorithm (GA) to optimize a HDS process, which is difficult to optimize by conventional methods. The considered chemical process is the three phase catalytic trickle-bed reactor in which hydrodesulphurization reaction occurs. Non-linear kinetics coupled with the transitional mathematical model of the gas, liquid and solid phases are used to describe the dynamic behavior of the multivariable process. The model, based on a two-film theory, was tested with regards to hydrodesulphurization of vacuum gas oil in a high-pressure pilot plant operated under isothermal conditions. Due to the high dimensionality and non-linearity of the model, a rigorous one, the solution of the optimization problem through conventional algorithms does not always lead to the convergence. This fact justifies the use of an evolutionary method, based on the GAs, to deal with this process. In this way, in order to optimize the process, the GA code is coupled with the rigorous model of the reactor. The aim of the optimization through GAs was to search for the optimal conditions that minimize the gas make and sulfur content of the outlet oil. Many simulations are conducted in order to find the maximization of the objective function without violating the constraints. The results show that the GA is used successfully in the process optimization.

The aim of this work was to study the production of diethyldichlorosilane [(C2H5)2SiCl2]. The catalytic reaction of silicon (Si) of purity 99.9% with ethylchloride (C2H5Cl) was investigated in a fluidized bed reactor. Cuprous chloride (CuCl) of purity 99.9% was used as a catalyst of the reaction. Gas chromatography was used on-line for analysis of the reaction products. The experimental work was carried out using a stainless steel column of 5cm internal diameter and 50cm height as the fluidized bed reactor.The experiments start with different bed temperatures between 200 and 300 C to identify the optimum reaction temperature. This temperature was found to be at 250 C, which resulted in the maximum of ethylchloride (EtCl) conversion and diethyldichlorosilane yield. In fifteen runs, the variables considered were sieve-analysis average particle size dp (50,100, and 150 µm), contact mass weight wt (100 – 200 gm) and reacted gas velocity Ug (1.41 – 2.83 cm/s). It was found that the conversion of EtCl increases with decreasing reacted gas velocity, increasing bed contact mass and particle diameter. The yield of Et2SiCl2 was not affected by these variables, but bed temperature was found to have a significant affect.Two mathematical models, the Orcut model and the continuous CSTR model were used to predict theoretical data for the conversion of EtCl. The comparison between the experimental and the theoretical data showed good agreement with an absolute error of less than 9%.

Acetylene was pyrolyzed in a thermogravimetric reactor system under the vacuum carburizing conditions of steel. The products of pyrolysis were collected and analyzed by gas chromatography. The reactor was numerically simulated by using a detailed reaction mechanism. Sensitivity analysis and reaction flow analysis was performed under the investigated conditions to identify important reaction steps. The comparison of experimental and modeling results is discussed in this paper.

This paper presents how vapor deposited coating of carbon (partially diamond) on stainless steel 304 substrate was affected by temperature, pressure and duration of deposition in conjunction with sound vibration. To do so a hot filament chemical vapor deposition apparatus was designed and fabricated. The experiments were carried out under different frequency of vibration (ranging from sonic and ultra sonic). Results show that deposition rate varies with temperature, pressure and duration under vibrating and non-vibrating conditions. It was found that the deposition rate was higher for vibrating condition than that of non-vibrating condition. In this study, the higher the temperature, pressure and duration, the higher the effectiveness of frequency of vibration on the deposition rate was obtained. During thermal CVD process, activation of reactive species was enhanced by chemical activity with the increase of temperature and pressure. By adding extra energy of sound, kinetic energy was increased more due to increase of the adsorption and diffusion rate, which causes the increase of deposition rate.A coating of carbon (partially diamond) has been deposited on the substrate, and the characterization of the coating has been done by SEM including EDX and XRD. The coating of carbon was identified by EDX, and the allotropic forms of graphite and diamond peaks of carbon are found by XRD analysis. SEM analysis shown that the microstructures of deposited coatings were more compact and smoother under higher temperature and pressure than that of lower temperature and pressure.The experimental results are compared with those available in the literature and physical explanations are provided.

Alkylation of mesitylene with tert-butyl alcohol in the presence of novel mesoporous superacidic catalysts, namely, UDCaT-4, UDCaT-5 and UDCaT-6 was investigated. The catalysts are modified versions of zirconia showing high catalytic activity, stability and reusability in the presence of water as compared to conventional sulfated zirconia. The catalytic activity is in the order: UDCaT-5 (most active) > UDCaT-6 > UDCaT-4 > sulfated zirconia (S-ZrO2) (least active). The synergistic effect of the very high sulfur content present (9% w/w S) and the preservation of the tetragonal phase in UDCaT-5, in comparison with sulfated zirconia (4% w/w S), were responsible for higher catalytic activity. A catalyst ensuring the production of 2-tert-butyl-mesitylene (2-TBMT) with 98% selectivity and 94% conversion of tert-butanol (TBA) was developed under optimum reaction conditions. The formation of products is correlated with the acidity of the catalyst. The reactions were conducted in liquid phase at relatively low reaction temperatures (120–150 °C). A systematic investigation of the effects of various operating parameters was accomplished and a mathematical model is developed to describe the reaction pathway and validated with experimental results. The reaction was carried out without using any solvent in order to make the process cleaner and greener. An overall second order kinetic equation was used to fit the experimental data, under the assumption that both mesitylene and tert-butanol are weakly adsorbed. An independent dehydration study of tert-butanol (TBA) was also done.

A mathematical model is presented to investigate the performance of tubular catalytic membrane reactor for dehydrogenation of cyclohexane using a FAU type zeolite membrane. The empirical correlations for the permeance of cyclohexane, benzene and hydrogen through FAU type zeolite membrane as a function of temperature have been developed. Three reactor configurations have been considered: conventional fixed bed, full length membrane reactor and hybrid reactor. The reactor performance has been studied in terms of conversion of cyclohexane to produce hydrogen. The observed conversions are ranked in the order: full length membrane reactor > hybrid reactor > fixed bed reactor. The simulation studies have been carried out for two feed conditions: one with hydrogen and another without hydrogen. The effect of cofeeding of hydrogen, sweep gas flow rate variation, and dilution ratio on the conversion of cyclohexane has been investigated in detail. The maximum percent increase in conversion of cyclohexane has been obtained at 473 K in hybrid as well as in membrane reactor. This temperature is also found to be optimum for sweep gas flow rate of 4.5 x 10-5 mol s-1. The conversion is observed to be suppressed by cofeeding of hydrogen and percent reduction is lowest at high temperature of 490 K in membrane reactor. The enhancement in the conversion is observed as a consequence of dilution of the feed with inert gas. The results reveal that hybrid reactor is not necessarily a better choice than the full length membrane reactor. However, at the expense of loss of reactant, hybrid reactor is better than full length membrane reactor.

The objective of this work was to utilize ossein waste (degelatinised bones) from gelatin industry as an innovative substrate for protease enzyme production and to optimize the process parameters of protease production in a batch reactor. Production of protease enzyme was carried out using ossein waste as nitrogen and carbon source. The waste residue was cleaned, ground and sieved to powder. The powder was used as nutrient a for protease production by Bacillus brevis. The fermentation conditions were optimized by studying the effect of various parameters, namely substrate concentration, innoculam size, pH, rpm, and temperature in batch cultivation technique. The maximum production of protease enzyme using ossein waste was found to be 366.3U/ml at 72h for a substrate concentration of 3.5%, 7pH and 130rpm at 350C.

Three–dimensional numerical simulations of an isothermal swirl fluidised bed (SFB) system with no chemical reactions were performed to study the swirl decay process and its effects on bed performance, i.e. particle concentration in the freeboard. The commercial CFD code package ANSYS 11.0 was chosen to carry out our simulation. We used 200?m glass beads with property similar to Geldart group A particles as the particulate phase with assumption that they are cohesionless and mono-dispersed, and air at 25°C as the gas phase in our simulation. Different initial swirl intensities were controlled by varying the secondary gas velocities. The solids volume fraction of solids suspension layers in the freeboard agreed generally well with literature description, which showed an annular shape with high values near the wall side. For the first time, swirl intensity and its decay process were predicted numerically by incorporating a swirl number function into ANSYS 11.0 and its effects on the bed fluid dynamics were also discussed in a qualitative or semi-quantitative manner.

In this study, an artificial neural network (ANN) modeling of a delayed coking unit (DCU) is proposed. Different data from various DCU have been collected. Feed API and Cat Cracker (CCR) weight percent have been considered as network inputs. Coke, output CCR, light gases, gasoline, gas-oil and C5+ weight percents are the network outputs. 70 percent of the data have been used for training of ANN. Among the Multi Layer Perceptron (MLP) architectures a network with 31 hidden neurons has been found as best MLP predictor. Radial Basis Function (RBF) also has been implemented for identification of the plant. An RBF network with 20 spread was found as best estimator of the DCU. Best RBF network and best MLP network performance in prediction of 30 percent of unseen data were compared. It was found that RBF method has the best generalization capability and was used in DCU modeling.

Different agricultural residue was evaluated as a biofilter material for the removal of Hydrogen sulfide (H2S) using Thiobacillus sp. A Combination of four different agricultural residues, viz., sugarcane bagasse, coconut coir pith, rice husk and saw dust were evaluated as biofilter material. From results, it was observed that filter material having composition of 2:4:2:2, 4:4:2:2 and 4:2:2:4 has resulted in retaining 70% moisture content at the end of 10 days. The biofilter was operated for 128 days in three phases by varying inlet H2S concentration from 321 to 2020 ppmv. Biofilter exhibited 100% removal efficiency (RE) at an inlet concentration of 570 ppmv, 99% RE at an inlet concentration of 1416 ppmv and 66% RE at a maximum inlet concentration of 2020 ppmv. The filter performance in terms of RE, dropped to 48% when the air was not humidified before sending to the filter, which has direct relation with the MC of the filter material. The RE recovered to 66% with recovery of moisture content (MC) to 57% upon subsequent re-introduction of the humidifier in to the circuit. The pH has dropped from 7.8 to 4.8 during the course of operation of the filter. H2S was effectively removed under different operating conditions using mixed agricultural residue as filter material. However humidification was most essential to maintain the required moisture content in the biofilter. SEM analysis has shown the good growth of Thiobacillus sp. in the filter bed and hence the new material proved to be good support for the immobilization of Thiobacillus sp.

The substitution reaction of benzyl chloride and sodium butyrate to form benzyl butyrate, using tetrabutyl ammonium bromide as the phase transfer catalyst (PTC) in a solid-liquid phase condition was studied. Benzyl chloride in solvent toluene forms the organic phase whereas sodium butyrate remains in solid form. A kinetic study of the system had been performed by varying different process variables. Different phase transfer catalysts were employed to find out the most effective catalyst. No conversion was found without catalyst.Homogeneous solubilisation mechanism was followed to explain the kinetic model and to interpret the experimental data.

To concentrate CO2 in combustion processes by efficient and energy-saving ways is a first and very important step for its sequestration. Chemical looping combustion (CLC) could easily achieve this goal. A chemical-looping combustion system consists of a fuel reactor and an air reactor. Two reactors in the form of interconnected fluidized beds are used in the process: (1) a fuel reactor where the oxygen carrier is reduced by reaction with the fuel, and (2) an air reactor where the reduced oxygen carrier from the fuel reactor is oxidized with air. The outlet gas from the fuel reactor consists of CO2 and H2O, while the outlet gas stream from the air reactor contains only N2 and some unused O2. The water in combustion products can be easily removed by condensation and pure carbon dioxide is obtained without any loss of energy for separation.Until now, there is little literature about mathematical modeling of chemical-looping combustion using the computational fluid dynamics (CFD) approach. In this work, the reaction kinetic model of the fuel reactor (CaSO4+ H2) is developed by means of the commercial code FLUENT and the effects of partial pressure of H2 (concentration of H2) on chemical looping combustion performance are also studied. The results show that the concentration of H2 could enhance the CLC performance.

The isobaric lean catalytic combustion in a high-pressure recuperative reactor in view of gas turbine technologies is examined. A new type of the T/P bifurcation diagram is revealed and elucidated. It is found that the reactor thermally stabilizes at higher pressures. The elevated P to 0.5 MPa extends bifurcation isola for mfin, i.e. each fold is improved by approximately 15%. The thermal and concentration hysteresis bifurcation diagrams are also improved, i.e. the ignition temperature was decreased from 490 to 475 K and the extinction concentration from 177 to 157 ppmv, respectively. The pressure drops are alleviated by the factor of P/P0 slightly corrected for the gas thermal expansion effect. It is also revealed, that the intra-phase mass transfer resistances are reduced at elevated pressures. The fuel conversion pressure dependences are provided for some types of high-pressure reactors.

We investigated, experimentally and theoretically, the formation of slopping in a 1:5 scaled water model of a copper converter. The gas injected through submerged tuyeres in the copper converters results in slopping; the formation of standing waves. The high amplitude of the standing waves contributes to the premature wearing down of the converter's refractory lining. We present a methodology for controlling slopping by using two submerged tuyere lines. The combined lateral and bottom gas injection reduces the amplitude of the slopping by interfering with the oscillation modes of the surface wave. For a Froude number of 10 for both sets of tuyeres, the experimental results showed a 50% reduction in the amplitude of the surface wave in the water model.

Fluidized bed processes are widely used in the refining industry, mostly for conversion applications (e.g. fluid catalytic cracking, fluid coking, residue hydroconversion, Fischer-Tropsch Synthesis, etc.). These are large scale processes operating under severe conditions. Fluidized bed processes involve many complex phenomena that need to be considered in order to ensure proper design, operation and reliability. There have been thousands of publications over many years in the field of fluidization, but some of the fundamentals of fluid-particle flows still remain to be clarified. As a consequence, scale-up and industrialization of new technologies or processes remain a difficult, challenging and risky task.IFP is deeply involved with fluidized bed processes used in the refining industry. Over the last twenty years, industrial developments and PhD studies were conducted to explore new concepts, to develop new technologies, to scale-up hydrodynamics, to understand and quantify key phenomena. This paper discusses R&D practices in the field and current challenges encountered, mostly based on IFP experience. It does not intend, however, to provide an extensive literature review of all topics addressed in this paper.Interactions between particles, multiphase flow and reactor geometries are complex issues in fluidized beds. Therefore, experimentation is required to study new concepts such as downflow systems, complex phenomena such as vaporization of droplets in contact with gas-particle systems. The design of the experiment and the development of appropriate instrumentation are never simple and in the absence of simple similarities, anticipation of the main flow features is unavoidable. Modeling of results is then mandatory in order to translate results to industrial perspectives. Over the last 15 years, CFD has appeared as a promising tool to describe multiphase flow phenomena in complex geometries. Unfortunately, the lack of theoretical models to describe gas particle flow, at least for Group A powders, still leads researchers to conduct experiments to validate simulations or to adjust the gas-particle closure equations to validate results. Furthermore, observation in industrial units, during start-up or under steady conditions, when possible, greatly aids in validating research efforts and methodology.Despite its maturity, our industry is moving forward. There are ongoing developments in the energy and fuels market as well as in environmental fields, but also in the scientific background available to describe multiphase flow. Therefore, evolutionary R&D in the field is still needed to progress in the description of complex phenomena in order to optimize reactors and technologies and to face the changes of our industry.

The increase in society's need for fuels and decrease in crude oil resources are important reasons to make more interest for both academic and industry in converting gas to liquids. Fischer-Tropsch synthesis is one of the most attractive methods of Gas-to-Liquids (GTL) processes and the reactor in which, this reaction occurs, is the heart of this process. This work deals with modeling of a commercial size slurry bubble column reactor by two different models, i.e. single bubble class model (SBCM) and double bubble class model (DBCM). The reactor is assumed to work in a churn-turbulent flow regime and the reaction kinetic is a Langmuir-Hinshelwood type. Cobalt-based catalyst is used for this study as it plays an important role in preparing heavy cuts and the higher yield of the liquid products. Parameter sensitivity analysis was carried out for different conditions such as catalyst concentration, superficial gas velocity, H2 over CO ratio, and column diameter. The results of the SBCM and DBCM revealed that there is no significant difference between single and double bubble class models in terms of temperature, concentration and conversion profiles in the reactor, so the simpler SBCM with less number of model parameters can be a good and reliable model of choice for analyzing the slurry bubble column reactors.

Numerous continuous intensified reactors are now accessible on the market that offer enhanced thermal performances in a continuous reactor. Such reactors are then particularly suited to fast and highly exothermic reactions. In this paper, the ability to also manage a slow and equilibrated system, the methyl acetate esterification reaction, on condition of intensification in terms of design and operating conditions is presented. To achieve this purpose, a new kinetics model has been developed and validated from experiments carried out in a lab scale batch reactor. Implemented in a simulation framework, this model leads to an intensified design of the reactor and the associated operating conditions. All this intensification methodology has been supported and validated by experimental studies.

The effective parameters on p-Xylene yield in the nonselective disproportionation reaction over unmodified ZSM-5 catalyst were investigated using the validated model developed in this study. The results of this study indicate that toluene conversion and benzene/xylene ratio is increased by increasing feed temperature and reactor residence time. Even though an adiabatic operation is applied, an almost isothermal reactor temperature profile is predicted by the model due to the low heat of reaction. At different feed operating temperatures, different maximum para-Xylene yields are reached at different weight hourly space velocities (WHSV)-1. Since the model numerical predictions demonstrate that the lower feed temperature requires larger reactor to obtain the maximum p-Xylene yield, therefore, selection of optimum conditions is a function of two independent variables, feed temperature, and (WHSV)-1, and should be selected in order to minimize the objective function of total manufacturing and operating costs.

The transformation of methanol into olefins (MTO) is gaining interest in view of the strong demand for light olefins by the petrochemical industry. Modeling of MTO process is required for both reactor design and process control. In this paper, a three layer perceptron neural network model is used to predict main product yields in methanol to olefins conversion. The network is fed with three inputs, i.e. the reactor temperature, water/methanol ratios in feed, and space-time to predict the weight fraction of unconverted methanol, ethylene, propylene and butanes. The optimum structure of neural network (NN) is determined by a trial and error method. The performance of basic backpropagation (BBP) training algorithm is compared with backpropagation with declining learning-rate factor algorithm (BDLRF). It is found that BDLRF has a better performance in both training and test phases. The network with optimum topology learns the input-output mappings with enough accuracy for interpolation cases. By using NN model in MTO process developing complex reaction kinetic in both global and hybrid model can be avoided.

The preparation of mesocarbon microbeads (MCMB) has been studied by heating coal tar pitch with different phenyl silicone oil content at 350°C for 2h.The spheres with diameters ranging from 0.54 to 11.4?m were obtained. The as-extracted MCMB when the silicone oil/coal pitch value was 3 had a very homogeneous size, a small diameter and also an excellent sphericity. The yield of MCMB was 8.3%, and microcrystalline structure was better. After stabilization, the spheres carbonized at 900°C still kept spherical, but broken into small particles during the graphitization. The stabilization destroyed the microcrystalline structure of as-extracted MCMB, but the microcrystalline structure became better after carbonization. The structure of graphitized MCMB at 2300°C was close to the graphite structure, and clear graphitization fringes were observable.

Orthogonal array designs (OAD), OA25 (56), were applied for the first time to optimize cyclo-dehydration of 1,4-butanediol (BD) to tetrahydrofuran (THF)- assisted with additives in near-critical water (NCW) in which the interactions between the variables were temporarily neglected. Six parameters at five levels such as reaction time (t, min), reaction temperature (T,°C), reactant/water ratio (R/W, wt./ wt.), additive/reactant ratio (A/R, wt./wt.), sort of additives and reaction pressure (P, MPa) were investigated. The effects of these parameters were studied by using analysis of variance (ANOVA) to determine the relationship between experimental conditions and levels of yield of THF and conversion of BD. The results showed that the additives had the most significant influence on the yield of THF and conversion of BD, and the other five factors had some advantageous effects on the yield of THF and conversion of BD, however, those effects were much smaller than that of the additives. Finally, the optimal experimental conditions were proposed which could provide the highest yield with respect to the considered factors. Base on these results, a possible reaction mechanism was proposed.

A mathematical model was developed for the filtration process and the influence of aeration on Submerged Membrane Bioreactors. The dynamics of sludge attachment to and detachment from the membrane, in relation to the filtration and a strong intermittent aeration, were included in the model. The influence on the membrane fouling of intermittent aeration injected on the membrane surface, and its synchronization with intermittent filtration, were studied numerically and experimentally. For the evaluation of filtration cake development, the assumption of the presence of two cake layers (one dynamic and the other stable) was considered. The model development and simulation focused on the description of existing relationships among important system variables like mixed liquor suspended solids concentration, aeration, temperature of the sludge suspension, transmembrane pressure, and the fouling increase during the filtration process. The model obtained offers the possibility of improving the design configuration and operation strategies of Submerged Membrane Bioreactors in wastewater treatment, and it allows the of aeration-filtration cycles to be optimized.

Numerical simulations of cyclones with various vortex finder dimensions and inlet section angles were performed to study the gas shortcut flow rate. The numerical solutions were carried out using commercial computational fluid dynamics (CFD) code Fluent 6.1. A prediction model of the gas shortcut flow rate was obtained based on response surface methodology by means of the statistical software program (Minitab V14). The results show that the length of the vortex finder insertion, the vortex finder diameter and the inlet section angle play an important role in influencing the gas shortcut flow rate. The gas shortcut flow rate decreases when increasing the inlet section angle, and increases when increasing the vortex finder diameter and decreasing the length of the vortex finder insertion. Compared with the effect of the length of the vortex finder insertion on the shortcut flow rate, the effect of the vortex finder diameter on the gas shortcut flow rate seems more pronounced. The effect of the vortex finder dimension on the gas shortcut flow rate is changed with the different inlet section angles, i.e., the effects of the vortex finder dimension of the conventional cyclone (the inlet section angle is 0º) on the gas shortcut flow rate is stronger than the cyclone with 30º and 45º inlet section angles.

The main objectives of the further downstream operations (product upgrading) of Fischer-Tropsch products are to i) improve yields and selectivities of the desired fractions, and ii) improve fuel properties to meet the fuel product specifications. The present study addresses the combination of low-temperature Fischer-Tropsch (FT) synthesis (with Co or Fe catalysts) and hydrocarbon modification reactions (hydroprocessing) in one reactor.In addition to earlier results with Pt/ZSM-5 in a dual-layer configuration in a fixed-bed reactor (Mena et al. 2007), the objective of the present investigation was to study the influence of CO during hydroprocessing and oligomerisation reactions of hydrocarbon model compounds (1-octene, ethene/propene) on two different bifunctional catalysts (Pt/ZSM-5, Pt/Beta). In addition, the influence of the catalyst-bed configuration for the combination FT synthesis and hydrocarbon reactions was investigated (dual layer/physical mixture).The achieved results indicate a potential of combining FT and hydrocarbons reactions in one reactor. Hydrogenation, isomerisation, cracking and oligomerisation reactions take place on a Pt/zeolite catalyst at FTS temperatures and in the presence of CO and H2O. The most critical point of this combination seems to be the deleterious effect of CO on the cracking reactions of isomers. For that reason, the wax fraction (C21+) was only partially cracked. The experimental results also indicate that the type of zeolite and the catalyst-bed configuration have an influence on the diesel/gasoline ratio obtained. It seems that the final fuel products will be a mixture of gasoline and diesel fuel and C1 to C5 compounds, as long as no diesel-selective hydroprocessing catalyst is found.

This work is focused on the modelling, analysis and optimization of industrial ethylene oxide production in a packed bed reactor. The aim is to identify the critical variables that maximize the reactor productivity in an existing facility without compromising personnel safety and equipment integrity. The chemical reactions involved are highly exothermic making the internal temperature control of this unit a challenging task. Temperature excursions at dangerous levels have been experienced due to variations in composition and temperature of fresh feed to the reactor. Therefore, the prediction of dynamic temperature and composition profiles in the reactor are important for its safe operation. The model we developed incorporates catalyst deactivation and the effect of an inhibitory agent: 1,2-dichloroethene. The model predictions were found to be in good agreement with the plant data. Our model-based optimization studies show that the optimal set point for the inlet coolant temperature is suitable for preventing reactor hot spots and maximizing ethylene oxide selectivity. The heat integration aspects of the process were addressed.

Biosorption of Reactive Red 2 and Reactive Blue 81 dye from an aqueous solution using soya bean meal in a batch system was evaluated. The potential of the meal to act as an adsorbent was determined using Scanning Electron Micrograph and Fourier Transform Infrared Analysis. The effect of sorbent dosage (0.2 to 1.2 g/100 mL), pH (1 to 7) and initial dye concentration (20 to 120 mg/L) on the biosorption process was studied. The equilibrium dye uptake capacity was found to be more at 0.2 g/100 mL of sorbent dosage when compared to all other sorbent dosage studied in the present investigation with the initial dye concentration of 30 mg/L and pH value of 6. The equilibrium dye uptake capacity was found to be more at pH value of 2.0 when compared to all other pH levels studied in the present investigation with the sorbent dosage of 2.0 g/L at 30 mg/L initial dye concentration. The equilibrium uptake value was found to be higher for Reactive Red 2 when compared with Reactive Blue 81 dye. The rate of sorption was investigated using pseudo first and pseudo second order rate equations. The pseudo second order rate expression fit the experimental data well. The equilibrium data was analysed using Langmuir and Freundlich adsorption isotherm model. The equilibrium data for both dyes followed the Freundlich adsorption isotherm at 30°C. Intra particle diffusion model was used to determine the mechanism of the biosorption process. In this present investigation, the maximum uptake capacity of Reactive Red 2 dye was observed as 49.04 mg/g using Soya Bean Meal at 120 mg/L initial dye concentration. The adsorption capacity of Soya Bean Meal was found to be comparable with other low cost adsorbents.

Recovery of propionic acid from different sources, like aqueous streams or from fermentation broth, is important in view of its wide usage in food, chemical and pharmaceutical industries. Reactive extraction is an emerging separation technique having numerous advantages like high selectivity and recovery. Effect of acid concentration, extractant concentration, pH, temperature and kinetics are the important steps in the reactive extraction. Equilibrium of propionic acid extraction using tri-n-butyl phosphate (TBP) and Aliquat 336 in n-hexanol respectively was carried out to find the better extractant out of the two for extraction of propionic acid. Aliquat 336 was found to be better than TBP with Ks = 2.2119 m3/kmol, thus indicating good complexation between it and the acid. The kinetics of extraction of the acid using Aliquat 336 in a stirred cell was investigated. The reaction was found to be first order in acid concentration and zero order in Aliquat 336 concentration. The reaction was found to be fast pseudo first order reaction occurring in the diffusion film and was found to be independent of hydrodynamics conditions. Rate constant was evaluated to be 163.398 1/s.

In this study we report the effects of support and pretreatment conditions on growth of carbon nanotubes (CNTs) by chemical vapor deposition of methane on iron catalyst supported on MgO, silica or alumina. The iron was impregnated onto the supports, and then the samples were dried, calcined at 550°C and pretreated in either helium or hydrogen up to 1000°C before exposure to methane as a carbon source for CNTs growth. Temperature programmed reduction (TPR) of the fresh catalysts and the ones pre-treated in He and in H2 shows various interactions of the iron with supports at pretreatment conditions. The CNTs are characterized by SEM, Raman, FTIR, and TEM. The IG/ID of Raman spectroscopy are 6.2, 3.8 and 0.7 for the CNTs grown on the MgO, alumina, and silica-supported iron catalysts pretreated in helium, respectively. When the Fe/MgO catalyst is pretreated in hydrogen the IG/ID ratio dramatically reduces to 0.8. A less significant effect of pretreating of the catalysts in hydrogen is observed for silica- and alumina-supported catalysts. RBM peaks of Raman spectra along with TEM results indicate the formation of bundles of 0.8-1.2 nm single-wall as well as multiwall carbon nanotubes on the Fe/MgO catalyst pre-treated in He.

The direct electro oxidation of dimethylsulphoxide (DMSO) to dimethylsulphone (DMSO2) at a Pb/PbO2 anode and electro reduction of maleic acid (MA) to succinic acid (SA) at stainless steel cathode have been has been carried out in methane sulphonic acid (MSA) medium in a batch divided cell. It is to be noted that, as methane sulphonic acid medium (MAS) is biodegradable, it is a preferred medium for the electrochemical reactions.The process parameters such as concentration of MSA, DMSO and current density have been critically examined and the comparative performances of Pb/PbO2 with TSIA electrode as well as the reusing of electrolyte under optimum conditions have been investigated. The reaction parameters such as acid concentration, current density, the use of divided and undivided cells, etc. have been studied on electrochemical reduction of MA to SA.In the case of direct electro oxidation of dimethylsulphoxide to dimethylsulphone, the current efficiency on TSIA anode has been around 60- 65% while that with Pb/PbO2 has been more than 90%. The electro reduction of MA to SA has given current efficiency around 65 – 70%. Based on the result obtained on trials, the optimum parameters of the reaction found to be 1.0 M acid concentration and 5.0 A dm-2 current density. Divided cell has given good results when compared to undivided cell.

Glycerol in aqueous solutions was reacted with acetaldehyde and acetone to form glycerol acetals. The formed acetal was extracted using a solvent and the glycerol is recovered by hydrolysis of the extractant. The reaction equilibrium constants ranged from 1-35 for glycerol-acetaldehyde system and 2.2-5.5 for glycerol-acetone system, respectively. Phase equilibrium measurements showed that the distribution coefficient was from 1.5-8.5 for glycerol-acetaldehyde system and 2-6.5 for glycerol-acetone system. The extraction efficiency of the solvent increased with increase in temperature. Maximum efficiency achieved was 94% at the refluxing temperature of toluene. The reactive extraction route to obtain glycerol is more economical than the distillation route in pure form. The maximum conversion obtained during the acetalization reaction was 87% and the extraction efficiency achieved was 94%. The hydrolysis of the acetal recorded complete recovery of high purity glycerol. The reported study has an application for the recovery of pure glycerol from aqueous solutions generated during biodiesel processing.

Coal power stations as well as waste incinerators produce humid acid gases which may condense in industrial chimneys. These condensates can cause corrosion of chimney internal cladding which is made of stainless steel, nickel base alloys or non metallic materials. In the aim of polluting emission reduction and material optimal choice, it is necessary to determine and characterize all the phenomena which occur throughout the chimney and more especially condensation and dissolution of acid gases (in this particular case, sulfur dioxide SO2).

In the present work, the fungal species Aspergillus terreus MTCC 1782 was used for the production of L-asparaginase using natural substrates like groundnut oil cake, cottonseed oil cake and corn flour in modified Czepak-Dox media and compared the L-asparaginase production using synthetic L-proline. The modified Czepak-Dox media with 2% L-proline, supplemented with 1% sodium nitrate and 1% L-asparagine has shown maximum L-asparaginase activity of 34.98 IU/mL on the third day of production. The modified Czepak-Dox media with 2% groundnut oil cake, 1% sodium nitrate and 1.2% L-asparagine showed maximum L-asparaginase activity of 30.35 IU/mL on the fourth day. These results are comparatively higher than the maximum L-asparaginase production reported in the literature (19.5 U/mL), by isolated Aspergillus sp. using Czepak-Dox media containing 2% (w/v) L-asparagine as the sole substrate along with 1% (w/v) ammonium sulfate as an additional nitrogen source. It is observed that the addition of L-proline or ground nut oil cake increases the L-asparaginase production. The groundnut oil cake is found as the potential natural and cheaper substrate for L-asparaginase production by Aspergillus terreus MTCC1782.

Perlite was utilized as an adsorbent for the removal of malachite green from their aqueous solution. The effects of the initial dye concentration, contact time, adsorbent dose, pH, and temperature were studied for the adsorption of malachite green in batch mode. The dye adsorption equilibrium was rapidly attained after 40 min of contact time. Adsorbent was characterized by FTIR, XRD and SEM. The Langmuir and Freundlich isotherm described the adsorption data over the concentration range (20 – 100 mg/L). The rate parameters of the intra particle diffusion were calculated and compared to identify the adsorption mechanisms. The thermodynamic parameters such as entropy change, enthalpy change, and energy of adsorption were calculated to know the nature of adsorption. The negative values of energy of adsorption and the positive values of enthalpy change suggested that the adsorption process is spontaneous and exothermic. Kinetic studies showed that the adsorption process obeyed the pseudo first-order kinetic model.

This article presents ultrasound assisted carbonization method for the synthesis of calcium carbonate nanoparticles (nano calcite). The effect of different surfactants, such as polyacrylic acid, steric acid, sodium tripolyphosphate and myristic acid, on the synthesis of nano CaCO3 was investigated. Concentration of surfactants ranged from 0.2-1.0g/L. X-ray diffraction patterns (XRD) confirmed cubic structure of nano CaCO3 showing characteristic reflection of calcite phase. Transmission electron microscopy (TEM) images showed that the particles are cubical in nature. The use of an ultrasound probe during synthesis leads to narrow distribution of particles. The conductivity and pH value of reaction mixture was measured during the reaction. The time required for the completion of reaction changes with different surfactants was also found. The crystallite size was found to be dependent on surfactant concentration. The minimum time was noted for sodium tripolyphosphate which was 40 min. The crystallite size was found to increase as per the trail sequence of the surfactant, sodium tripolyphosphate, steric acid and polyacrylic acid, myristic acid. The myristic acid shows the biggest crystallite size due to its hydrophobic nature, while sodium tripolyphosphate plays an important role in crystal growth inhibition giving lower crystallite size. Finally, the results presented here demonstrate that nano-calcite crystals can be synthesized, for high potential industrial applications such as filler in the paper and polymer industry.

Hydrogen sulphide (H2S) is one of the main odor causing, toxic, and corrosive chemicals found in wastewater treatment, pulp and paper and several other industries. One of the main challenges of winter operation of biofilters for H2S removal is to deal with the heat effects of biofiltration process. During winter lower air temperature, snow fall on biofilter vessels and moisture condensation in air ducts decrease percent removal of H2S significantly. In this work, laboratory and field data that are collected during winter operation of biofilters are analyzed and presented. The results demonstrate that temperature within the biofilter should be maintained at a minimum of 15°C to avoid lower percent removal or odor breakthrough resulting from untreated H2S emissions in the air. It was found that heat input to the incoming air by steam addition easily remedy the problem.

It is well known that the catalytic characteristics of perovskites for various redox reactions depend primarily on the preparation procedure. The conventional method for perovskite preparation, the so-called "ceramic method," involves a calcination step with a temperature of at least 800 oC, resulting in large grain size and low specific surface area (usually several m2/g). Recently, a new method for perovskite preparation designated as reactive grinding has been proposed by our group, generating a large variety of perovskites at room temperature with extraordinarily high specific surface areas on the order of 100 m2/g when grinding additives are used. Additionally, this novel technology is favorable to yield perovskites with an abundant deficiency structure simultaneously with a nanosized crystallite domain.Series of La(Co, Mn)1-x(Cu)xO3 perovskites were prepared by reactive grinding and characterized by XRD, O2-TPD, and H2-TPR showing anion deficiency (O2 vacancy) in lanthanum cobaltites and cation deficiency (O2 excess) in lanthanum manganites. These samples were thereafter used for catalytic purification of NO, CO and soot pollutants coming from an automobile. For NO reduction by CO, a better catalytic performance was found over LaCoO3 compared to LaMnO3. The deNOx activity of LaCoO3 can be considerably improved via 20% Cu substitution, leading to a 97% N2 yield and nearly complete CO conversion at 450 oC. This improvement was ascribed to the ease of generation of anion deficiencies after Cu incorporation, which plays a crucial role in NO adsorption and dissociation. A mechanism was proposed with dissociation of chemisorbed NO upon oxygen vacancies forming N2 and/or N2O, and oxidized perovskite surface, with continuous reduction by CO with the production of CO2. For soot combustion, the better activity was observed again in the case of LaCoO3 with respect to LaMnO3. A mechanism was proposed with an attack of soot by O- species which immigrates from the perovskite surface. Cation deficiency of lanthanum manganites associates with overstoichiometric oxygen from the perovskite lattice, which can be only utilized for an oxidation process but less active compared to molecular oxygen formed upon anion vacancies. In summary, the anion deficiency of perovskite-typed oxides seems to make more contribution for both NO reduction and soot oxidation in comparison with cation deficiency.

In this work, modeling of a catalyst pellet (uniform, non-uniform) for Fischer-Tropsch Synthesis (FTS) is studied. Under FTS conditions the pores of catalyst pellet are filled with heavy hydrocarbons leading to transport restrictions through the pellet. On the other hand, the active materials used as catalysts are often expensive metals dispersed on large-surface area supports. In order to understand the catalyst behavior aiming to improve its performance parameters such as effectiveness factor and yield modeling of a catalyst pellet with various types of non-uniform activity distributions are examined. The models were solved by OCFE method at non-isothermal conditions. Moreover, a parametric sensitivity analysis has been carried out to compare the effects of various non-uniform activity distributions, the pellet size, the feed composition and the temperature on the performance of the catalyst.

A series of high surface area (~700 m2/g) nanostructured coupled semiconductor photocatalysts (NCSP) based on transition metals (M = Cr, V) doped titania-silica aerogel of various molar ratios of Ti:Si (1:25, 1:33 and 1:50) were synthesized via direct synthesis and wet impregnation methods. All samples reveal well-dispersed TiO2 with three different types of Ti coordination namely isolated Ti, non-isolated Ti and octahedrally coordinated Ti species. Cr and V (5 wt%)-titania silica aerogel under visible light irradiation reduced the bandgap energy of T25 to 2.9 eV. The photocatalytic activity of NCSP is 3 fold more active than photocatalyst supported on amorphous silica. Cr (5 wt%)-titania silica aerogel photocatalyst gives the highest conversion of styrene under both UV and visible light irradiation (55% and 47% respectively).

Particulate matter emissions from diesel-fueled cars, trucks, and buses are regulated by state and federal government agencies. Although improvements in engine performance have taken place, aftertreatment is necessary to meet the existing emissions standards. In order for a particulate emissions control system to function under real driving conditions, real-time model predictive control is needed.As a first step towards this goal, we perform a parametric study to compare two existing models of diesel particulate trap regeneration: a one-dimensional plus time model that tracks gas and solid temperatures and the particulate deposit thickness developed by Bissett (Chemical Engineering Science, 1984, 39, 1233-1244) and a one-dimensional plus time model that uses averaging theory to focus solely on the thermal evolution in the diesel particulate trap developed by Zheng and Keith (AIChE Journal, 2007, 53, 1316-1324). We use both models to predict the ignition time and ignition location within the diesel particulate trap. In this parametric study, three operating parameters are varied: the initial deposit thickness, the exhaust gas flowrate, and the exhaust gas temperature. It was found that the Zheng and Keith model agrees very well with the Bissett model under most operating conditions except when the initial deposit thickness and exhaust gas temperatures are low and the gas flow rate is high. These studies suggest the Zheng and Keith model may be appropriate for real time control of diesel particulate filter regeneration.We then perform a sensitivity analysis of the ignition time and ignition length to changes in the initial deposit thickness and gas flowrate under various conditions using the averaged model. We have found that the ignition time and ignition length are most sensitive to changes in deposit thickness when the deposit thickness and exhaust temperature is low. Also, the ignition time is relatively insensitive to changes in gas flow rate, but the ignition length is most sensitive to changes in gas flow rate at low exhaust temperatures. These studies are useful towards the ultimate development of a predictive particulate emissions control system for diesel-fueled vehicles.

Typical models to estimate effectiveness factors include sphere, cylinder, slab and strong internal diffusion limitations models. However, a reliable model for complex-irregular catalyst shapes is still lacking. Therefore in this work a new approach is proposed which makes simultaneous use of the 1D and GC models to approximate a 3D problem in order to determine the effectiveness factor of a tri-lobular catalytic on a HDS reaction involving diesel. The restrictive internal diffusion phenomena were examined at the cross-section of the catalyst including the effects of its shape. Simulation for the HDS reaction involved the consideration of a small scale reactor using industrial operating conditions. Effects of the intrinsic kinetic, considering strong internal diffusion effects, were calculated through well established computational algorithms. Mathematical simulations of the reaction effectiveness using a given feed-stock of diesel are described completely for a tri-lobular particle considering organic sulfur compound for molecular diffusion, pore size, shape and radial transport across the section of the catalyst and results were validated with models and data published in the literature of typical analysis.

The optimum design, modeling and simulation of a fixed bed multi-tube reformer for the renewable hydrogen production are carried out in the present paper. The analogies between plug flow model and a fixed bed reactor are used as design patterns. The steam reformer is designed to produce enough hydrogen to feed a 200kW fuel cell system (>2.19molH/s) and considering 85% of fuel utilization in the cell electrodes. The reactor prototype is optimized and then analyzed using a multiphysics and axisymmetric model, implemented on FEMLABM(R) where the differential mass balance by convection-diffusion and the energy balance for convection-conduction are solved. The temperature profile is controlled to maximize hydrogen production. The catalyst bed internal profiles and the effect of temperature on ethanol conversion and carbon monoxide production are discussed as well.

The hydrodynamics of gas-particle conical fluidized bed containing dried TiO2 micro-size particles were studied experimentally and computationally. The pressure drop was studied by pressure measurements and mean solid velocity in the different axial and radial positions and their experimental values were measured by a parallel 3-fiber optical probe. The Eulerian-Eulerian multiphase model, including kinetic theory of granular flow using Gidaspow (1994) drag function was used in the computational fluid dynamics (CFD) simulation. The frictional viscosity of solids is predicted from the equation proposed by Schaeffer (1987), whereas semi-empirical boundary equations developed by Johnson and Jackson (1987) were applied for the tangential velocity and granular temperature of the solids at the wall. Three different types of boundary conditions (BC), consisting in free-slip/no-friction, no-slip/friction and high-slip/small-friction, were used in this work to compare the results of the model with the experimental data. The numerical predictions using free-slip/no-friction BC agreed reasonably well with the experimental pressure drop measurements, especially at superficial gas velocities higher than the minimum fluidization velocity, Umf. The results for simulated mean axial solid velocity show that the free-slip BC was in better agreement with the experimental data compared with the other boundary conditions. The model also provides reasonable predictions for particle circulation and formation of fountain zone, gulf-effect and air velocity.

The performance of an anaerobic downflow stationary fixed film bioreactor has been simulated mathematically and a software package developed. Each flow channel of the reactor is assumed equivalent to a tubular reactor with a specific degree of axial dispersion. The variation of axial dispersion coefficient along the length of the flow channel (due to the change in gas velocity ) is accounted for and so is resistance to substrate transfer into biofilm which is taken into account by incorporating effectiveness factor into performance equations. Effectiveness factor is computed by numerically integrating the expression for intrinsic rate and the package is applicable to all forms of kinetic equations. Experimental data from pilot plants exhibit encouraging agreement with results predicted by the developed simulation package.

In this work, electrophoretic deposition (EPD) was applied to obtain novel hydroxyapatite (HAP)/lignin (Lig) biocomposite coatings on titanium substrate. Nanosized hydroxyapatite powder, prepared by using the modified chemical precipitation method, was used for the fabrication of HAP/Lig composite coatings. EPD was performed at different values of constant voltage and constant deposition time. It was confirmed that control over deposited mass can be achieved by applied voltage and time. The uniform and compact coatings were successfully deposited at applied voltage of 60 V in various deposition times lower than 1 minute. The effect of lignin as natural non-toxic polymer on microstructure, morphology and thermal behavior of biocomposite HAP/Lig coatings was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The electrophoretically deposited HAP/Lig coating has been successfully sintered at lower sintering temperature of 900°C, producing non-fractured coating and indicating that lignin may exhibit adhesive role, strengthening the bonding between HAP particles and substrate surface.

The activity of a V-MCM-41 catalyst with a V/Si molar ratio of 0.04 was compared with the activity of a pure MCM-41 catalyst and some DRIFTS studies were performed in order to understand the mechanism of selective oxidation of ethanol. V-MCM-41 was found to be much more active than pure MCM-41, favouring the formation of high amounts of ethylene over 300°C. MCM-41, on the other hand, was found to favour the formation of acetaldehyde over ethylene at all studied temperatures. It was shown by reaction findings that over V-MCM-41, ethylene was produced mainly in the presence of gas phase oxygen whereas acetaldehyde was produced using the lattice oxygen even in the absence of gas phase oxygen. DRIFTS studies indicated the formation of acetaldehyde molecules from acetate-like surface species which were formed by the removal of a hydrogen atom from the ?-carbon of chemisorbed ethoxy species by the help of the lattice oxygen. On the other hand, removal of a hydrogen atom from the ?-carbon of the ethoxy species, in the presence of gas phase oxygen, resulted in the formation of vinyl-like surface species which then yielded ethylene molecules.

This paper is concerned with the experimental investigation of stability and emission in a LPG-air premixed coaxial jet burner. By varying the fuel-air ratio in the core flow stream, the flame stability of this coaxial jet flame burner is carried out experimentally, extensively over a wide range of core velocity at 4-16 m/sec. The overall equivalence ratios for all cases are enhanced with the increase in core velocity. An improvement in stability limits are observed with the increase in coflow velocity. However, the NO level for two coflow velocities increases with the increase in core flow velocity which is attributed to the fact that the flame gets stabilized at a higher core equivalence ratio. The flue gas CO2 level is enhanced with the increase in core velocity for three different coflow velocities. The increase in CO2 is mainly due to the combustion of fuel and the subsequent conversion of CO to CO2 in the higher combustion gas temperature. In order to reduce the emission level, the coflow stream is premixed by injecting fuel into the coflow stream with an equivalence ratio even below flammability limits. The stability limit is found to be improved marginally, when the premixed mixture is used in the coflow stream. Interestingly, by using premixed fuel-air mixture in the coflow stream, there is a decrease in NO emission levels. Of course, the use of fuel-air mixtures in the coflow stream enhances the CO2 level.

This paper presents a CFD comparative investigation of two types of hydrocyclone: uni-flow and reverse flow hydrocyclones. The study is conducted by means of a Reynolds Averaged Navier-Stockes (RANS) simulation using the finite volume code Fluent. The fluid flow is described by the use of the Reynolds Stress Model, while the determination of particles flow and the air core formation are modeled by the mean of two multiphase models which are respectively the Stochastic Lagrangian model (DPM) and the Volume of Fluid Model (VOF). The flow features are examined in terms of pressure drop and separation efficiency in order to contribute to better performance. The validity of the proposed approach is verified by the good agreement between the predicted and the measured results which are given by the Company of Phosphate of Gafsa (CPG-Tunisia). This study proves that uniflow hydrocyclone is more energy efficient because of its lower pressure drop and its higher removal efficiency for small particles from their carrying fluid.

Experimental investigation of heat transfer characteristics of circular tube fitted with straight half twist insert has been presented. The heat transfer coefficient increases with Reynolds number and decreases with spacer distance for both the single direction and left-right twist inserts. Also, there is no appreciable increase in heat transfer enhancement in straight half twist insert with 2-inch spacer distance. Experiments were carried out in turbulent flow using straight half twist insert with 4-inch spacer and similar trend of increasing Nusselt number with Reynolds number was observed. CFD simulation for the heat transfer augmentation in the plain tube and the tube fitted with half twist inserts has also been explained using Fluent version 6.3.26. The data obtained by simulation are matching with the experimental value with the discrepancy of less than ±10% for the plain tube and the tube fitted with straight-half twist inserts for Nusselt number and friction factor.

Microneedle arrays have been shown to increase skin permeability for the transdermal delivery of drugs with high molecular weights. Various theoretical studies have been proposed to predict the drug transport behaviour after drug injection using microneedles. However it is important for the optimal design of microneedle systems to consider the effects of biological factors such as skin metabolism and variations in pharmacokinetic parameters as well as to improve the enhancement of skin permeability. A mathematical model for microneedle systems is introduced and applied to simulate the verapamil transport with metabolism in the skin. A comparative analysis for a transdermal delivery of verapamil from microneedles is presented in this paper. The results indicate that the skin metabolism does not markedly affect the skin permeation after verapamil injection using microneedles.

In the first part of the present study, Discrete Element Method (DEM) is adopted as a numerical simulation technique for studying gravity packing of randomly distributed monodispersed particles in a box of a rectangular cross section (can be thought as a fluidized bed). Packing density, coordination number distribution and radial distribution function (RDF) are calculated. Stability of the packing, spatial and temporal effects of the wall on packings are analyzed. Qualitatively and quantitatively, the results agree well with the existing literatures. Since this model uses structural reconstruction, many of the features of random packing like clear second peak split in the RDF plot have been observed. From experiments, it is well known that the confining walls impart some order in the near-wall regions. However to the best of the author's knowledge, the actual symmetries of these orderings (of walls) have never been analyzed and these have been the focus of the second part of this study. Taking a cue from structural analysis of amorphous (glassy) atomic systems, the Honeycutt-Andersen (HA) index and Bond Order Orientation (BOO) order have been employed to study the local symmetries of both near wall and core regions. It shows that the 1551 HA index, signifying icosahedral order, is more predominate in the core part than the wall. There is also some good amount of cubic symmetries both in the wall and core regions. However the most predominate structure is distorted icosahedra, which is probably appearing because of a competing effect between the icosahedral order and cubic symmetries.

Jatropha curcas (JTC) oil, an inedible vegetable oil, can be a substitute feedstock for traditional food crops in the production of environment friendly and renewable fuel (biodiesel). In the present study, unsupported potassium carbonate was used as a catalyst to provide an understanding of the catalytic activity in the transesterification reaction. Researching the potential and the behavior of potassium carbonate is very important because every biomass ash contains this compound in a significant amount. It can be extracted by using classical extraction or leaching technologies. During the biodiesel production reaction, the formation of soap as a byproduct was also monitored using the FTIR-ATR method. From this study it was observed that the transesterification of JTC oil to JTC biodiesel appeared to be complete within 15 minutes when a 5 wt% (based on the wt. of the oil) potassium carbonate, 6:1 methanol to oil molar ratio, 60°C or a 4 wt% potassium carbonate, 9:1 methanol to oil molar ratio and 60°C reaction temperature were used.

Two chars prepared from parent coals of a high volatile bituminous coal and an anthracite coal were subjected to isothermal combustion tests in a thermogravimetric analyser (TGA). The chars were burned in mixtures of O2/CO2 and O2/N2 with O2 concentrations of 3%, 6%, 10%, 21% and 30% and combustion temperature ranging from 723 K to 1163 K. Experimental results show that replacing the inert nitrogen gas in the oxidizer with CO2 has little influence on the measured reactivity of coal chars under conditions of the experiments. The measured reactivity of each char was found to be approximately first order (0.88 – 0.90) to the concentration of O2 in the O2/CO2 mixtures. As char combustion tests were conducted under relatively high temperatures conditions, internal and external effectiveness factors were estimated in order to derive combustion kinetics of both chars. The values of activation energy for both chars, obtained by taking account of both the internal and external effectiveness factors (i.e. with correction), were very much in line with the literature data. The activation energy of the bituminous coal char combustion in O2/CO2 was found to be 96323 (without correction) – 108893 (with correction) kJ/kmol within the temperature range of 723 – 873 K, whereas the activation energy of the anthracite char was found to be 125716 (without correction) – 140486 (with correction) kJ/kmol within the temperature range of 773 – 973 K.

In the present paper, a new simple chemical vapor deposition (CVD) method was investigated for synthesis of carbon nanotube (CNT) films on macroporous kaolin substrates (in mullite phase) using cyclohexanol and ferrocene as carbon source and catalyst, respectively. Effect of growth temperature on structure of the CNT films was also investigated by SEM images. Growth of a novel structure of the CNTs at 600°C on the macroporous kaolin substrate was succeeded. The novelty of these CNTs lies in their heart-like caps. At 650°C, CNTs were grown perpendicular on the macroporous surface of kaolin substrate. At higher temperatures (700, 750, 800°C), a quite different structure of CNT films was obtained. This interesting structure is composed of a continuous mat like thin film of long CNTs grown horizontally over the entire surface of macroporous kaolin substrate, and some casually overgrown humps. Various structures such as carbon fibers, helical CNTs and Y junction CNTs were observed in the overgrown humps. The results demonstrate ability of the proposed CVD method to perform growing of the CNT films with interesting structures on the macroporous kaolin substrates. We then perform a sensitivity analysis of the ignition time and ignition length to changes in the initial deposit thickness and gas flowrate under various conditions using the averaged model. We have found that the ignition time and ignition length are most sensitive to changes in deposit thickness when the deposit thickness and exhaust temperature is low. Also, the ignition time is relatively insensitive to changes in gas flow rate, but the ignition length is most sensitive to changes in gas flow rate at low exhaust temperatures. These studies are useful towards the ultimate development of a predictive particulate emissions control system for diesel-fueled vehicles.

The scale-up of an uneven type of dielectric barrier discharge (DBD) reactor driven by a positive–negative pulse power supply for the removal of particulate matter (PM) from a diesel engine has been carried out. The scale of the uneven DBD reactor was changed by using three kinds of reactors consisting of 20, 30, or 50 pairs of uneven alumina and stainless steel plates. In this study, relations of energy injection into the above DBD reactors, PM removals, PM removal efficiencies with pair numbers have been investigated. The parameters in the kinetic model used to describe the PM removal are given.

In this work, thermal activation of pistachio shell was studied in a fluidized bed reactor. The effects of operating conditions on the pore development within the char particles were studied experimentally. The results showed that activation temperature, residence time, oxidizing gas type and concentration have main effects on the Iodine adsorption capacity of the product. The highest surface area was obtained using steam activation at temperature 850°C for 45 min. The synthesis process was also simulated using artificial neural networks (ANNs) to estimate the Iodine number of the product. The present work applied a Tan-sigmoid transfer function in three layers in the feed forward neural network with back propagation algorithm. The results of the network are in good agreement with the experimental data with a maximum relative deviation of 0.015%.

Bed segregation is inevitable in biomass-sand fluidized beds because of density and size differences, but segregation pattern can be significantly different under various operational conditions. In the present work, the combination of image processing technology and pressure fluctuations analysis is used to investigate the fluidization and segregation. Experiments have been carried out in a 3D fluidized bed. The biomass material studied is cotton stalk. Two groups of binary systems are considered, obtained by mixing sand with biomass particles of different sizes and/or concentrations. In addition, the bed-frozen method is also adopted to examine the segregation degree. It is found that the transition velocity from bubbling to turbulent fluidization regime decreases with the increase of biomass size and concentration. The results also show that the biomass concentration has little influence on the segregation degree, and the biomass size significantly affects the rate of segregation, which increases with the size. The pressure gradient and standard deviation of pressure fluctuation are demonstrated to be useful for indicating the bed segregation, which are validated by the result by the bed-frozen method.

This contribution is focused on the analysis of the structure of packed beds of spherical particles at relatively low aspect ratios (i.e., particle to tube diameter ratio) as those arising in multitubular fixed bed reactors. On one hand, the computed tomography (CT) technique is employed to evaluate the position of each particle in the packing and from this information local properties such as particle center distribution and radial porosity profile were obtained. On the other hand, results from a previously developed algorithm to simulate packings were compared with those from our CT data and from literature sources. The agreement was very satisfactory.

This investigation attempts to study electrocoagulation of Acid Blue 113 textile effluent in a batch electrochemical reactor covering wide range in the operating conditions. Experiments were designed using statistical tool of Response Surface Method (RSM) to analyze the combined effect of operating parameters on the efficiency of electro coagulation process. The level of importance of the experimental parameters on the percentage COD removal has been determined by using analysis of variance (ANOVA). Further, the percentage COD removal was also modeled using artificial neural network (ANN).

The effects of boundary slip on the stability of viscosity-stratified microchannel flow are investigated. In this approach, the boundary slip is considered by Navier slip assumption and the stability of the flow is studied by the small disturbance theory. Numerical results indicate that the stability of stratified microchannel flow is enhanced by boundary slip and it is controlled by boundary slip, the ratio of viscosity, surface tension and interface location.

The models to prevent accidents from occurring in process industry, or to minimize the harm if an accident does take place, always revolve around forecasting the likely accidents and their impacts. Based on the several effects of an accident on the environment, the approach used in this study involves a qualitative analysis by the Environmental Effects Analysis (EEA) combined to Quantitative Risk Assessment approach (QRA). In fact, the EEA, under its current formalism, emphasizes environmental effects in normal operations solely. It does not consider abnormal situations (accidental aspects). In order to overcome this lack, the authors propose an extension of the current formalism of the EEA through the inclusion of accidental events that may occur in each phase of the product’s life cycle, where from the EEA – Accidental Aspect method. Impacts associated with abnormal situations are identified and assessed in accordance with risk assessment practices. Risk assessment can be both qualitative and quantitative. Nevertheless, whenever possible, we adopt a Quantitative Risk Assessment approach (QRA). The evaluation criteria used in the classical EEA, i.e. Environmental Priority Number (EPN), is redefined to take into account the impacts due to accidental aspects. By doing so, we establish an effective link between methods for assessing environmental impacts and approaches to risk management. The validation of the proposed methodology is made on a storage system with a high potential of fire risk.

In the present work, a kinetic model has been developed for the batch fermentation of glucose for the production of L-glutamic acid (LGA) by Corynebacterium glutamicum. Parameters of the kinetic model have been determined by using the experimental data available in literature and the results have been compared by carrying out computer simulation. The kinetic model proposed in the present study provides better predictions for the growth of biomass, substrate consumption and LGA production as compared to the prediction reported by Bona and Moser (Bioprocess Engineering 17(2) (1997b) 121-125). The present model also fits the experimental data given by Zhang et al. (Enzyme and Microbial Technology, 22, 205-209, 1998) and Khan et al. (Biochemical Engineering Journal, 25, 173–178, 2005), respectively. Sensitivity analysis was carried out to assess the validity of the developed model, and to reveal the kinetic parameter that has maximum impact on LGA production. It is found that an increase in the non-growth associated product formation coefficient caused highest negative impact on LGA production.

Copper supported on inverse opal titania generated in-situ by sol-gel technology on optical fibers is effective in improving the photon utilization rate in a photocatalytic reactor. Inverse opal titania allows the slow-down of photons and improves the quantum efficiency for the photoreduction of gaseous CO2 to CH3OH in the presence of water vapor and UV light. Methanol production rates (0.0364 ±0.0014 µ mol.g-cat-1.h-1) were comparable to those of a conventional fiber optic reactor using Cu supported on unstructured titania, but required much lower light intensities. The production rate was independent of the feed rate indicating that the reaction is not mass-transfer controlled. The production rate increased with UV radiation intensity as I0.74 in contrast to I0.20 for unstructured titania. The inverse opal titania was predominantly anatase (101 crystalline phase), had a stop band gap of 307-397 nm and therefore capable of trapping UV light in the opal. Copper supported on inverse opal titania showed features similar to those of pure titania and Copper was present mostly as Cu0. XPS data showed that Cu was mostly dispersed on the surface.

The paper presents the dispersion of the concentration y(t, s) on the length (s) with respect to time (t), corresponding to the adsorption process of a phenothiazine derivative on graphite electrodes. The numerical simulation by equations with partial derivatives of the second order with two independent variables (t and s) (PDE II.2), based on (Mpdx) which associates with Taylor series was performed. Also, the adsorption process defined by PDE II.2 was included in a regulation scheme of concentration y(t, s) with multiple freedom levels. It insures good performances and a remarkable flexibility for extending the method in similar categories of applications.

Biomass is characterized by a high oxygen content (typically ? 40 % w/w). Its conversion into feedstocks that can directly be used in existing petrochemical feed streams will therefore require an efficient and selective deoxygenation chemistry. Ruthenium or iron-based water/acid-tolerant and high-temperature stable metal complexes that are active ionic hydrogenation and hydrogenolysis catalysts maybe ideally suited for this purpose.

Temperature effect on the performance of Pd-Ru/Nb2O5-TiO2 (PRNT) catalyst on hydrogen production from reactions between ethanol and steam was evaluated. Parallel reactions occurred in all conditions studied according to what was observed by the presence of H2, CO2, CH4, CO, C2H4, C2H6, C2H4O and (C2H5)2O. While at 300 °C the process seems to be dominated by ethanol dehydrogenation and decomposition, at 375 °C dehydration it seems to compete for active sites with ethanol dehydrogenation and decomposition reactions. At 450 °C there is a dehydration reaction to ethane, basically competing at the same level with ethanol dehydrogenation decomposition reactions. Hydrogen production on PRNT catalyst is maximized at 300 °C.

Acidic lanthanum and aluminum diphosphates were prepared and characterized (surface area, XRD, FT-IR, 31P-NMR and 27Al-NMR). These materials were used as catalyst for the esterification of oleic acid and transesterification of soybean oil. Under optimized conditions the methyl and ethyl ester yields were above 95%. Although the catalysts are recyclable, they slowly lost their catalytic activities, due to leaching of the phosphate.

Results of a research activity aiming at investigating the feasibility of the acetone-butanol-ethanol (ABE) production by Clostridium acetobutylicum ATCC824 are reported. The kinetics of the ABE production process by free C. acetobutylicum in batch reactors has been assessed. A CSTR equipped with a microfiltration unit has been set-up and operated to assess the kinetics in the solventogenic phase. Solutions of lactose—concentration ranging between 10 and 100 g/L—were adopted as medium with the aim of emulating cheese whey. The conversion process was characterized in terms of cells, acids, solvents, pH and total organic compounds as a function of time. Tests carried out under batch conditions show that: i) cells growth is constant for lactose concentration (CL) smaller than 100 g/L; ii) the butanol specific production rate - estimated at the onset of the solventogenic phase - as a function of CL may be represented by a Monod-like kinetics; iii) the lactose conversion—measured at the end of the solventogenesis phase—decreases with CL; iv) the selectivity of butanol with respect to total solvents increases with CL and stabilizes at about 72%W for CL larger than 30 g/L. Preliminary tests carried out under continuous conditions show that the process takes advantage from the steady state operation under solventogenic conditions. In particular, the butanol conversion rate is larger in the CSTR than in the STR, despite the lower final lactose concentration experienced in the CSTR.

The need for green renewable sources is adamant because of the adverse effects of the increasing use of fossil fuels on our society. Biomass has been considered as a very attractive candidate for green energy carriers, chemicals and materials. The development of cheap and efficient fractionation technology to separate biomass into its main constituents is highly desirable. It enables treatment of each constituent separately, using dedicated conversion technologies to get specific target chemicals. The synergistic combination of aquathermolysis (hot pressurised water treatment) and pyrolysis (thermal degradation in the absence of oxygen) is a promising thermolysis option, integrating fractionation of biomass with production of valuable chemicals. Batch aquathermolysis in an autoclave and subsequent pyrolysis using bubbling fluidised bed reactor technology with beech, poplar, spruce and straw indicate the potential of this hybrid concept to valorise lignocellulosic biomass. Hemicellulose-derived furfural was obtained in yields that ranged from 2 wt% for spruce to 8 wt% for straw. Hydroxymethylfurfural from hemicellulose was obtained in yields from 0.3 wt% for poplar to 3 wt% for spruce. Pyrolysis of the aquathermolised biomass types resulted in 8 wt% (straw) to 11 wt% (spruce) of cellulose-derived levoglucosan. Next to the furfurals and levoglucosan, appreciable amounts of acetic acid were obtained as well from the aquathermolysis step, ranging from 1 wt% for spruce to 5 wt% for straw. To elucidate relations between the chemical changes occurring in the biomass during the integrated process and type and amount of the chemical products formed, a 13C-solid state NMR study has been conducted. Main conclusions are that aquathermolysis results in hemicellulose degradation to lower molecular weight components. Lignin ether bonds are broken, but apart from that, lignin is hardly affected by the aquathermolysis. Cellulose is also retained, although it seems to become more crystalline, probably due to a higher ordering of amorphous cellulose when the samples are cooled down after aquathermolysis. These NMR results are in agreement with thermogravimetric analyses results.

The production of Substitute Natural Gas from biomass (Bio-SNG) is an attractive option to reduce CO2 emissions and replace declining fossil natural gas reserves. The Energy research Center of the Netherlands (ECN) is working on the development of a technology to convert a wide range of biomass into Bio-SNG.The ECN Bio-SNG technology is based on indirect gasification of biomass. The MILENA indirect gasifier is developed to produce a gas, which can be upgraded into SNG with a high efficiency. Because of the indirect heating of the gasification process, no air separation is required. Char and tar are removed from the producer gas and are used as fuel to produce the required heat for the gasification process. The OLGA tar removal technology is used to remove tar and dust from the gas. After gas cleaning, the gas is catalytically converted into a mixture of CH4, CO2 and H2O. After compression and removal of CO2 and H2O, the remaining methane can be used as Bio-SNG.ECN produced the first Bio-SNG in 2004, using a conventional fluidized bed gasifier. The lab-scale MILENA gasifier was built in 2004. The installation is capable of producing approximately 8 Nm3/h methane-rich medium calorific gas with high efficiency. The lab-scale installation has been in operation for more than 1000 hours now and is working fine. Several biomass fuels were tested. Woody biomass appears to be the most suited fuel. The lab-scale gasifier is coupled to lab-scale gas cleaning installations (including OLGA) and a methanation unit. The integrated system was tested during several duration tests.The 30 kWth lab-scale gasifier was scaled up to 800 kWth biomass input. ECN has recently finished the construction of this pilot-scale gasifier, which has been taken into operation in the summer of 2008. First results, using wood as a fuel, show that the gas composition is similar to gas from the lab-scale installation.The pilot scale gasifier will be coupled to the existing pilot scale OLGA gas cleaning unit in 2009. Tests with the pilot-scale MILENA and OLGA will form the basis of a 10 MW MILENA – OLGA – gas engine demonstration plant. This demonstration will be taken into operation in 2012 and will be followed by a large SNG demonstration. 10 MW biomass input is seen as an attractive commercial scale for combined heat and power production from biomass. The scale foreseen for a commercial single-train Bio-SNG production facility is between 50 and 500 MWth. The expected net overall efficiency from wood to Bio-SNG is 70%.

During the last years there has been an increasing interest in using ethanol as a substitute for fossil fuels. The bioethanol used today is mainly produced from sugar cane and cereals, but reducing the production costs of ethanol is still crucial for a viable economic process. Cellulose from vegetable biomass will be the next cheap raw material for second generation fuel ethanol production and agricultural by-products with a low commercial value, as corn stover, corn fiber and cane bagasses would become an attractive feedstock for bioethanol production.In this study, different strains of Saccharomyces cerevisiae have been screened for the ability of bioethanol production. Yeasts were grown in a synthetic liquid medium containing sucrose in batch regime and the growth rates, ethanol and biomass productions were determined as well as their growth ability in cane molasses.The results indicate that a flocculent yeast, isolated in our lab and designated by strain F, was the most promising yeast strain among those tested for continuous ethanol production. This strain was isolated from corn hydrolysates, obtained from a Portuguese distillery facility (DVT, Torres Novas, Portugal) showing highest growth rate (0.49h-1), highest ethanol yield (0.35g/g) and high flocculation capacity.The study on ethanol production in continuous reactor process with the selected yeast strain (strain F) was made on sucrose and cane molasses at different dilution rates (0.05-0.42 h-1). A steady flocculating yeast fluidized bed reactor system was established allowing the functioning of the reactor for 1000 h. Data shows that when the dilution rate rose to 0.42h-1, the highest productivity (20g/Lh) was obtained attaining an ethanol concentration in the reactor of 47g/L for sucrose and molasses media.

The interest for furfural has increased in the last years due to its potential for competing with oil derivatives as platform chemical. In addition, furfural, derived from C5 sugars, can play a key role in the valorization of the hemicellulose contained in biomass when considering the development of a modern biorefinery concept. The development of such new and competitive biorefinery processes must be based on accurate kinetic data for the reactions involving furfural in the conditions used for its production.This work addresses the determination of furfural destruction kinetics in aqueous acidic environment, using sulphuric acid as catalyst, in the temperature range 150 - 200°C, acid concentration range 36.4 - 145.5 mM and furfural initial concentration between 60.4 and 72.5 mM. These studies were carried out using a recently built lab-scale titanium reactor that enables liquid phase reactions in a relatively broad range of conditions.The obtained results show that destruction of furfural follows first-order reaction kinetics within the range of temperature and acid concentration evaluated. Moreover, the proposed kinetic model takes into account the effects of temperature and acid dilution on the ions activity, and thus H3O+, by using the electrolyte Non-Random Two-Liquid (eNRTL) model. By using this approach, the rate constant dependence on temperature could be described by the Arrhenius law and thus the activation energy could be estimated as being 125.1 [kJ/mol] and the pre-exponential factor 3.71•1011[s-1]. Separation of different reaction products was achieved by means of HPLC, these products were not yet completely identified. Contrarily to what is reported in previous works, formic acid formation from furfural under the tested conditions can be regarded as playing a far less pronounced role than suggested before.

Jatropha oil has good potential as the renewable energy as well as lubricant feedstock. Production of Jatropha oil based lubricant was performed via a two-step process; (i) the transesterification of Jatropha oil to produce Jatropha Methyl Ester (JME) and, (ii) transesterification of JME with trimethylolpropane (TMP) under the presence of alkaline based catalyst. Transesterification of Jatropha oil was carried out at 65°C for 1 hour by using 1-2% NaOH as catalyst. While, the transesterification of JME was carried out at 150°C with pressure kept at 10mbar. The conversion of JME to jatropha biolubricant was found to be more than 80%. However, to maintain forward reaction, the amount of JME was maintained at about 4:1 ratios to TMP. The basic properties of jatropha biolubricant are found comparable to other plant based biolubricant.

In order to evaluate new strategies for the production of renewable energy within sustainable organic agriculture, a process-simulation model for a 100 ha organic farm was developed. Data used for the model was obtained from laboratory trials, literature data, consultancy with experts, and results from the BioConcens project (http://www.bioconcens.elr.dk). Different design approaches were evaluated in order to establish the most suitable configuration. Rye grains, clover grass silage, maize silage, whey and cattle manure were selected as raw materials for co-production of fuels, feed and fertilizer at the organic farm, based on the fact that crops grown in organic agriculture act as key carbon sources whereas manure and whey were applied primarily as the nutrient and water supply for the fermentations within the process (anaerobic digestion and simultaneous saccharification and fermentation, respectively). Results from batch and lab-scale fermentation trials provided basic input for the model. To cover the direct energy requirements on the farm, it was calculated that it requires approximately 16.2 ha of rye and 14 milking cows or 5.7 ha of clover grass, 2.5 ha of maize and 13 cows to supply a 100 ha organic farm with ethanol or biogas, respectively. This calculation was based on the assumption that the electrical efficiency of CHP (combined heat and power) unit was 38%. A variety of different scenarios can be simulated to mirror the farmer's needs.

This study is focused on the effect of the application of biological pretreatment of Eucalyptus globulus Labill wood pieces on the cellulose digestibility by depolymerizing enzymes. Wood chips were incubated with five different white-rot fungi (WRF) for 30, 45 and 60 days at 25°C. The effect of the fungal action was determined as weight losses, changes in chemical composition and released sugars in the wood chips. Enzymatic hydrolysis was conducted in a discontinuous reactor at 37°C, using a commercial cellulase preparation from Trichoderma reesei. The enzyme/substrate ratio was 0.04 g/g. The highest weight losses were obtained using Stereum hirsutum and Lentinus edodes for all the incubation times, reaching 27.2% and 25.8% at 60 days, respectively. The lowest weight losses were produced by Coriolus versicolor and Pleurotus ostreatus, reaching 6.0 and 9.1%, respectively after 60 days. For all the tested fungi, the yield of reducing sugars and glucose increased significantly over the untreated controls, with Stereum hirsutum producing after 30 days pretreatment the best values (140 mM reducing sugars and 53 mM glucose); after this time no additional increments were observed. Pre-treated wood pieces showed changes in chemical composition in comparison to control samples. Total extractable substances contents are higher in wood pieces subjected to fungal action. However, lignin and alpha-cellulose values are lower in comparison to control samples. Some net holocellulose consumption could be observed, mainly during pretreatment with S. hirsutum by 45 and 60 days. Altogether these results support the potential of Eucalyptus globulus pre-treatment with S. hirsutum and L. edodes by periods not longer than 30 days, as a tool to increase the wood accessibility to depolymerizing action of hydrolytic enzymes. This preliminary study contributes to the identification of fungal pretreatment conditions for more effective cellulose degradation, a vital step in the utilization of monomer sugars process from cellulose to produce ethanol. Additional analysis of the solid and liquid fractions after saccharification is necessary to complement this information.

This paper investigates the feasibility of using municipal solid waste (MSW) as biomass substrates for bioethanol production. MSW are categorised into three types: paper and card, kitchen organics, and green organics. MSW data are collected from UK Department of Environment, food and rural affairs (DEFRA). Characterisations of cellulose, hemicellulose, and lignin contents have shown that MSW has high potential as biomass source. Experimental work on waste characterisation and MSW-to-ethanol conversion has been carried out in laboratory. The experimental results have shown that more than 85% of the cellulose from the waste can be converted to glucose which can be easily fermented to ethanol production. This MSW-to-ethanol process provides an alternative solution for both biomass resources for cost reduction and preventing organic fraction of municipal solid waste going into landfill.Projected estimates of waste to ethanol bases on London (UK) as a case study are made. Recommendation on both sustainable waste management and biofuel production are developed based on the result findings.

This work aimed to study the recovery of three types of waste by the process of pyrolysis: biomass, plastics and used tyres. The effects of experimental conditions in products yield and composition were studied. The increase of reaction time increased alkane content both in gas phase from 53% to 70% v/v and in liquid fraction from 48% to 60% w/w. The rise of reaction temperature led to a decrease of liquid yield (from 82% to 73% w/w), which was followed by the increase of solids and gases. The increase of reaction temperature also allowed the increase of the alkane content in gas phase from 39% to 70% v/v. The increase of initial pressure did not lead to appreciable variations in product yields or composition. The parameter that most affected products yield and composition was plastics content on the wastes initial mixture. The enhancement of this parameter increased liquids yield from 33% to 92% w/w, at the expenses of solids and gases contents and also decreased aromatics contents from 52% to 28% w/w.

This article deals with the use of ASPEN PLUS to model the thermo chemical processes occurring in wood biomass gasifiers. An original equilibrium gasification model using ASPEN PLUS was first built and validate based on existing data of a downdraft gasifier (DDG). The thermo chemical models assume that reactants reach chemical equilibrium. The simulations enabled to predict the composition of the flaming pyrolysis gas as well as the final composition of the producer gas. A parametric study based on air/fuel ratio variation was then conducted. The model was finally adapted to the operating conditions of a staged gasifier developed at the Technical University of Denmark (DTU). Parametric studies were conducted to observe the effect of humidity with a low air injection. ASPEN PLUS was shown to be well adapted to model the gasification process (equilibrium), and it was possible to simulate both a DDG and a DTU using the same model. Data about the composition of flaming pyrolysis and the exit gas were obtained.

This work is focused on the development of new characterization techniques of physical and thermodynamic properties. These techniques have been validated using the binary system DMSO-CO2 for which several studies of characterization have been well documented. We focused on the DMSO-rich phase and we carried out measurements of volumetric expansion, density, viscosity and CO2 solubility at 298.15, 308.15 and 313.15 K and pressures up to 9 MPa. The experimental procedures were compared and validated with the available literature data on SC-CO2-DMSO system. We made density and CO2 solubility measurements, using respectively the vibrating tube technology and two static analytical methods. Lastly, we developed an innovative falling body viscosimeter for high pressure measurements. All the measurements made are in good agreement with the already published data in spite of very different experimental techniques. This work is a contribution to the understanding of the DMSO-CO2 binary as it implements new viscosity data. Moreover, it opens new perspectives about the determination of the properties of other systems such as polymers-CO2 and fats-CO2, which are essential for supercritical process design such as extraction, crystallization, chromatography and synthesis reaction.

The aim of this work was to assess the influence of various formulation parameters on the incorporation of Curcumin into nanoparticles. For this purpose, the influence of the aqueous monomer (ethylene diamine, hexamethylene diamine, and 1,4-diaminobutane), as well as the effect of the stirring rate and the influence of the nanoencapsulation method on the encapsulation efficiency were investigated. It was found that variation in the amount of ingredients had profound effects on the curcuminoid loading capacity, the mean particle size, and size distribution. Furthermore, from the thermal results, it is concluded that the reactivity of diamine and the length of flexible methylene chain in diamine determine the thermal properties of resultant polymer wall membrane. The encapsulation yield depends not only on the encapsulation process but also on the chemical structure of the diamine. Whereas, the size and its distribution vary according to the process choice and the emulsification stirring rate.

The efficiency of liquid/liquid dispersion is an important sake in numerous sectors, such as the chemical, food, cosmetic and environmental industries. In the present study, dispersion is achieved in an open-loop reactor consisting of simple curved pipes, either helically coiled or chaotically twisted. In both configurations, we investigate the drop breakup process of two immiscible fluids (W/O) and especially investigate the effect of the continuous phase viscosity, which is varied by the addition of different fractions of butanol in the native sunflower oil. The global Reynolds numbers vary between 40 and 240, so that the flow remains laminar while the Dean roll-cells in the bends develop significantly. Different fractions of butanol are added to the oil in each case to examine the influence of the continuous phase viscosity on the drop size distribution of the dispersed phase (water). When the butanol fraction is decreased, the dispersion process is intensified and smaller drops are created. The Sauter mean diameters obtained in the chaotic twisted pipe are compared with those in a helically coiled pipe flow. The results show that chaotic advection intensifies the droplet breakup until there is a 25% reduction in droplet size.

Recycling the stillage condensates to dilute worts in the fermentation stage would be an effective way to decrease wastewater production and ground water consumption. However, condensates contain fermentation inhibiting solutes, such as volatile acids, alcohols and aromatic compounds that should be removed. Reverse osmosis was investigated as a clean process for such a purpose. Pilot scale experiments were carried out with industrial condensates and using Hydranautics ESPA2 membrane. The influence of transmembrane pressure (TMP), volume reduction factor (VRF) and pH on permeate flow rate and rejection rates of inhibitory compounds were investigated. The optimal operating conditions were TMP=10 bar to get the maximal admissible permeate flow, a low VRF to produce the less concentrated permeate and a pH ? 6 to obtain the highest rejection rates of the acids. Results were confirmed by trials at pre-industrial scale in a distillery. However, the permeate produced at pH 6 proved to be less fermentable than the permeate produced at natural pH because of an increase in the osmotic pressure. Natural pH permeate displayed a fermentation activity almost equivalent to tap water chosen as the blank. The remaining inhibitory acids did not seem to significantly hinder yeast growth nor yeast physiology.

Supercritical fluids and ionic liquids are neoteric solvents that can be used as non-conventional reaction media for enzymatic catalysis under optimised conditions. These solvents exhibit many different physical and chemical properties, but have two cross-points: they are not-miscible and can be easily separated from substrates and products, and they can be reused. As supercritical carbon dioxide (scCO2) can dissolve in the ionic liquid (IL) phase (up to 0.7 mole fraction), a new concept of biphasic bioreactors for Fine Chemicals syntheses may be developed by using both enzyme and chemical catalysts "immobilized" into the IL phase, and substrates transported by the scCO2 phase. The system was tested for the continuous chemoenzymatic dynamic kinetic resolution (DKR) of rac-1-phenylethanol in IL/scCO2 by using simultaneously immobilized lipase (Novozym 435) and acid zeolites catalysts at 50°C and 100 bars, providing good yields (up 98.0 %) for R-phenylethyl propionate ester with excellent enantioselectivity (up to 97.3 %), and without any activity loss after 14 days of operation.

Among many other potential applications, intermittent solid slug feeders can be used to effectively inject biomass materials into fluidized bed reactors for pyrolysis. In particular, these feeders can be used to convey biomass materials that are highly cohesive to prevent plugging or undesirable reaction in the feeding tube. Although feeders of this design have been shown to work very effectively, they have not been studied in detail or optimized for the pyrolysis process. In addition, the operating conditions required to obtain predictable and consistent mass flow rates and slugs of desirable characteristics need to be established.The purpose of this work was to design, build and demonstrate the operation of a horizontal intermittent solid slug feeder and to test it with sawdust as the feed material. Sawdust is an extremely cohesive and difficult biomass to inject, but one that holds great potential as an important renewable feedstock for pyrolysis.The intermittent feeder designed for this work consisted of a pressurized vertical solids storage silo leading to a pneumatic pinch valve. The pinch valve, controlled by solenoid valves connected to a relay timer, released the feed into a horizontal feeding tube at a ninety degree angle. Within the silo, a rotating mixer prevented the bridging of solids. Intermittent pulses of gas from a control volume were fed into the horizontal feeding tube, as well as, in some cases, a continuous gas flow. The timing of the pulses was controlled by solenoid valves with a relay timer. While the pinch valve is opened, solids fall into the horizontal feeding tube forming a plug, which is then propelled by the pulsating gas into the reactor. The solid mass flow rate was experimentally measured by collecting the solids and continuously measuring the mass using a digital balance.Several variables were tested in order to optimize the performance of the feeder and the consistency of the feeding rate. They included the silo pressure, mixing rate, gas pulse pressure and volume, continuous gas mass flow rate, and the open pinch-valve time interval. The goals of this optimization were (a) to maximize the solid-to-gas ratio of mass flow rates, since the gas mass flux must be minimized to avoid wasting energy, and (b) to define operating conditions required to inject consistent biomass mass flow rates suitable for a laboratory scale pyrolysis reactor, and (c) to propose initial design criteria and a calibration procedure for intermittent solid slug feeders.The results demonstrated that the intermittent solid slug feeder system successfully achieved the desired objectives and showed how to efficiently select its optimum operating conditions.

Methyl esters of fatty acids (also known as biodiesel) made from transesterification of vegetable oils and animal fats with methanol, have shown a lot of promise as alternative diesel fuels. Glycerol is the inevitable byproduct of transesterification process. While there are existing markets for glycerol, a significant increase in availability of glycerol, resulting from the expanded use of vegetable oils and animal fats, would destabilize the glycerol market. In this study, the synthesis of glycerol carbonate from glycerol and dimethyl carbonate was investigated. Glycerol carbonate is a key multifunctional compound employed as a solvent, additive, monomer and chemical intermediate. The resulting glycerol carbonate was obtained in almost quantitative yield. According to measured data a well-elaborated mathematical model of the reactor was used for experiments can be adequate to assign parameters of kinetic equations of the assumed reaction mechanism. Component mass balances were built into the reactor model and order of reactions was fixed.

The main issue of this paper is the synthesis of a robust control law for regulation purposes, which is applied to a class of chemical reactor which exhibits highly nonlinear and oscillatory behavior. The considered methodology employs the typical structure of Proportional-Integral controllers, where the corresponding integral term is now proposed as an integral high order sliding-mode compensator, which deals with the intrinsic nonlinearities of the system to be regulated. A theoretical frame is provided to demonstrate that the proposed controller produces semi-global practical stability; performance of the proposed methodology is assessed via comparison with other controllers.

Surfactants can increase the low rate of heterogeneous liquid-liquid reactions involving partially miscible substrates through formation of micelles. This is a direct consequence of higher solubilization of substrates by micelles in reaction zones. In this case, rate enhancement of NaOH (base) catalyzed hydrolysis of ethyl acetate was studied. Micelles by cationic surfactant tetradecyl trimethyl ammonium bromide (TTAB) made the rate enhancement. In the presence of NaOH, CMC (critical micellar concentration) of TTAB decreases from its original value and attains the value of 2.97 × 10-4 M. In the absence of TTAB, the second order rate constant increases linearly with temperature. The hydrolysis reaction follows second order kinetics at different temperatures in the presence of different concentrations of TTAB. For a particular temperature, on addition of TTAB beyond CMC, rate constant first increases sharply and then becomes almost constant. At TTAB concentration of 1.485 × 10-3 M, rate constant attains maximum value (2.65 times of rate constant without TTAB) and then it becomes almost constant. The applied model successfully explains change in rate constant due to incorporation of micelles by the addition of TTAB. This model involves certain assumptions like one substrate molecule is solubilized in one micelle; substrate molecule doesn't form a complex with monomer of surfactant; and no competitive inhibition occurs during reaction. Correlations between bulk phase rate constant (k0), micellar phase rate constant (km) and temperature (T) are incorporated into the model for this particular system.

Hexagon-shaped Zn oxide nano-pole films with terraces and steps have been successfully fabricated by means of a combined approach involving sol-gel process, high-temperature heat treatment, and the hydrothermal method. The surface chemistry and morphological features of the films were characterized by means of x-ray photoelectron spectroscopy and scanning electron microcopy. All the diffraction peaks in x-ray diffraction pattern match with those of the hexagonal wurtzite phase of Zn oxide. Transmittance measurements show that the optical transmittance of the sample synthesized at 520°C on quartz glass substrate is the highest, reaching about 65% in the visible-light region. Based on the detailed structural characterization and the nucleation-growth kinetics, we find that the whole crystallization process of wurtzite Zn oxide nano-poles includes nanocatalysis and layer-by-layer growth mechanism. The present study provides an important understanding of the growth mechanism for nano-pole synthesis of Zn oxide and related materials.