Band 10, Heft 1

For successful design and operation of Liquid-Solid (LS) and Gas-Liquid-Solid (GLS) stirred tank reactors engineers and scientists must define geometrical and operating conditions for a specific medium (specified physical properties) in such a way that provides the optimum level of solid suspension. Failure to design the stirred tank reactor to achieve optimum conditions and maintain the system at these conditions during operation may be detrimental to product quality (selectivity and yield) and cost. Successful design and operation require comprehensive knowledge about how the state of solid suspension may be affected by changing physical, operational, and geometrical parameters. Also, accurate correlations are necessary to fulfill that objective. This article intends to provide that background for scientists and engineers. It critically surveys the published work in this field and makes specific recommendations for the appropriate conditions that provide the successful operation of agitated vessels.

The literature on the use of Fenton oxidation in wastewater treatment has established the method as one of the most effective and suitable methods for recalcitrant wastewater treatment. It is an advanced oxidation process (AOP) that utilises the highly reactive hydroxyl radical (•OH) to aggressively and non-selectively destroy organic contaminants. The Fenton oxidation possesses environmental and economic benefits coupled with effective mineralisation of most wastewater organics. Broadly, the Fenton oxidation encompasses three types of oxidation routes for the production of •OH: (i) through the use of Fenton reagents alone, termed classical Fenton oxidation (CFO), (ii) assisted by means of UV (photo-Fenton), or (iii) electron beams (electro-Fenton). However, this review is limited to CFO, which involves the catalytic decomposition of hydrogen peroxide (H2O2) by suitable transition metals to generate •OH. Despite the many advantages of the CFO process, there are issues related to operational parameters and the final treated wastewater, the most notable being pH modulation, the presence of the catalyst and the cost of the oxidant (H2O2). Furthermore, sludge generation constitutes an apparent drawback to the utilisation of this technology. This paper attempts to review the highlighted limitations and presents researches and advances reported in the literature addressing these issues.

The work is dedicated to the study on the external and internal mass transfers of glucose for alcoholic fermentation under glucose inhibition limitation using a bioreactor with stationary basket beds of immobilized Saccharomyces cerevisiae cells. By means of the substrate mass balance for a single particle of biocatalysts, considering the kinetic model adapted for the inhibitory effect of glucose, specific mathematical models have been developed for describing the profiles of the substrate concentration in the outer and inner regions of biocatalysts and, implicitly, for estimating its mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of the mass flows are significantly influenced by the internal diffusion velocity of substrate and rate of the biochemical reaction of substrate consumption, but also by the position inside the basket bed. These influences cumulated led to the appearance of biological inactive region near the particle centre, its magnitude varying from 0.34 to 31% from the overall volume of particles. The presented results are the first unitary approach of the aspects of substrate mass transfer in a basket bed of immobilized biocatalysts, the proposed models being original and complex.

Optimization of process variables in the oxidative coupling of methane (OCM) over Mn/Na2WO4/SiO2 catalyst in a fluidized bed reactor was carried out. Effects of operating temperature, distribution pattern of oxygen injected to the reactor and the number of injections on the reactor performance on C2 (ethane + ethylene) yield were investigated. Process variables for one, two and three secondary oxygen injections were investigated to obtain the maximum C2 yield by genetic algorithm optimization method. The maximum C2 selectivity and yield of 47.1% and 22.87%, respectively, were achieved for three secondary oxygen injections at operating temperature of 746.05°C. The C2 yield achieved in this study is approximately 4% better than previous works reported in literature while the optimum temperature is lower.

Thermodynamic restrictions and simultaneous effects of operational conditions on the homogeneous rhodium-catalyzed carbonylation of methanol are studied in this line of research. It is shown that the general NRTL-Virial model can be appropriated to study thermodynamics of the carbonylation. It is obtained that the reaction is kinetically and thermodynamically reasonable at temperatures above 420K and below 520K, respectively. Moreover, at carbon monoxide partial pressures above 10 bar, the reaction rate is independent of the partial pressure. These results are in full accord with those reported in the literature. In addition, PCO > 2 bar is necessary for initializing the reaction. The parameters involved in the rate expression, equilibrium constants, CO solubility, and rate constant, are determined. The equilibrium constants are calculated with B3LYP/SDD ab initio method, and the value of Henry’s coefficient for CO (HCO) is determined as a function of temperature and methyl acetate conversion. The results predicted by this function agree well with those proposed by the general NRTL-Virial model with the errors below 11%. The Variation of CO solubility with acetic acid and methyl acetate concentrations is in good agreement with that obtained by others. It is found that the determined parameters give satisfactory predictions in modeling and simulation of the reaction.

The influence of selected parameters on the effectiveness factor of catalyst particles for the synthesis reaction of methyl tert-butyl ether (MTBE) from methanol and isobutene is analyzed. The catalyst is the sulfonated ion-exchange resin Bayer K2631. To this aim, the mass and heat balance equations that are presented as a system of differential equations, has been solved by means of the commercial mathematical software MathCad, for which a tailor - made program has been created. Four chosen parameters (tortuosity, particle radius, methanol to isobutene molar ratio and temperature) have been considered to carry out the calculations. The obtained results have been analyzed and presented in a graphical form. They show that the effectiveness factor can be equal, lower or higher than unity depending on the value of the considered parameters. The effectiveness factor is mainly dependent on mass and heat diffusional limitations at certain reaction conditions.

The effects of K, Ce, Zn, Cs, and Rb promoters on the structure and catalytic behavior of precipitated 50%Fe/50%Mn catalyst in Fischer–Tropsch synthesis (FTS) were investigated in a fixed-bed reactor. The effects of promoter on Fischer-Tropsch iron catalysts caused an increased growth probability of hydrocarbon chains from 0.67 to 0.75 for K to Rb promoter, and the olefin/paraffin ratios increased from 0.99 to 1.36 for Rb to K-promoted catalyst. The effect on the olefin selectivity was certainly due to increased adsorption strength of CO causing an enhanced displacement of olefin. The catalysts were assessed in terms of their FTS activity and product selectivity using Anderson–Schulz–Flory (ASF) models. The effects of various reaction conditions such as flow rates, temperatures, and H2/CO feed ratios were studied and process synthesis concepts were used to investigate interactions between the optimum regions for reactor operation and the experimental results.

Experiments on commercial FCC equilibrium catalysts with different hydrogen transfer properties and content of Ni and V contaminant metals were performed in a CREC Riser Simulator reactor to study the behavior of thiophenic compounds in the gasoline boiling range. Thiophene and alkylthiophenes were used as test reactants dissolved in aromatic and paraffinic solvents in usual concentrations of the process, from about 150 to 400 ppm of each compound. The experiments were performed under conditions similar to those of the industrial operation (510 º C, contact time 5 to 20 s). The reaction effluents were analyzed by on-line gas chromatography using two detectors simultaneously: FID (hydrocarbons) and PFPD (sulfur). The results showed that a higher hydrogen transfer capacity in a catalyst favors the decrease of the concentration of sulfur compounds in gasoline by adsorption and / or coke formation. These results were more pronounced as the molecular weight of the alkylthiophene increased. Reductions in total sulfur concentration in the gas phase as high as 65 % were observed. Among contaminant metals, Ni seemed to have an important contribution to this effect.

This paper discusses the hydromagnetic boundary layer flow of an Oldroyd-B fluid in a porous channel. Both suction and injection (blowing) cases are considered. Appropriate similarity transformations are invoked to convert the partial differential equations into ordinary ones. Homotopy analysis method (HAM) is used for the presentation of analytic solution of the nonlinear differential system. Graphical results provide the salient features of the embedded flow parameters which include the Reynolds number, the Deborah numbers, and the Hartman number. Comparison between the existing numerical solution in a Maxwell fluid and present deduced series solution in a limiting sense is excellent.

In the last few years, multiobjective evolutionary algorithms (MOEAs) have gained significant interest as a reliable option to optimize problems with conflicting objectives in science and engineering. These algorithms generate an optimal set of trade-off solutions referred to as the Pareto domain. In this investigation, a MOEA was used to optimize simultaneously conflicting design variables of an industrial styrene reactor. The dual population evolutionary algorithm (DPEA) was implemented to optimize the productivity, yield, and selectivity of styrene. To evaluate the robustness and versatility of the algorithm, two and three objective optimization case studies were conducted for three different configurations of the reactor: adiabatic, steam-injected, and isothermal.Results indicated that DPEA is a robust optimization strategy to generate a well-defined Pareto domain with a wide range of solutions. In addition, the Pareto-optimal solutions of the steam-injected configuration were superior to the adiabatic reactor and to a portion of the isothermal configuration. The optimal operating conditions corresponding to the Pareto domains were also slightly better in terms of profit when compared with previously published studies. The Pareto domains were then ranked using the Net Flow Method (NFM), a ranking algorithm that incorporates the knowledge and preferences of an expert into the optimization routine.

In this work the epoxidation of methallyl alcohol (MAA) with 30 wt% H2O2 over the Ti-MWW catalyst has been studied. The significant parameters for the MAA epoxidation were established as temperature (20-120°C), the molar ratio of MAA/H2O2 (1:1-5:1), methanol (solvent) concentration (5-90 wt%), Ti-MWW catalyst concentration (0-5.0 wt%), reaction time (5-300 min) and intensity of stirring (0-500 rpm). The process of MAA epoxidation was carried out the most effective at temperature of 100°C, the molar ratio of MAA/H2O2=1:1, methanol concentration of 40 wt%, the catalyst concentration of 2 wt%, the reaction time of 15 min and with the stirring intensity over 350 rpm. These the best technological parameters (mild and relatively safe) allow to obtain the selectivity of transformation to 2MG 37 mol%, the MAA conversion 52 mol%, and the selectivity of transformation to organic compounds in relation to H2O2 consumed 48 mol%.

The transport behavior of Pb(II) through a novel disphase supplying supported liquid membrane (DSSLM) with 2-ethyl hexyl phosphonic acid-mono-2-ethyl hexyl ester (PC-88A) as the carrier in kerosene, polyvinylidene fluoride membrane(PVDF) as the support and HCl as the stripping agent, has been studied. The effects of organic-to-feed volume ratio (O:F), pH, initial concentration of Pb(II) and ionic strength in the feed solution, organic-to-strip volume ratio (O:S), concentration of HCl solution and PC-88A concentration in the supplying strip phase on transport of Pb(II) have also been investigated. The advantages of DSSLM campared to the traditional SLM were investigated. The system stability, the reuse of membrane solution and the retention of membrane phase were also studied. When initial Pb(II) concentration was 2.00 × 10-4 mol/L, the transport percentage of Pb(II) was up to 92.9% under the optimun conditions in 175 min. The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry. The results were in good agreement with experimental results.

This investigation reports on the experimental and theoretical investigation carried out to evaluate the bubble diameter and effective interfacial area in a novel Hybrid Rotating and Reciprocating Perforated Plate Bubble Column. Air-water system is used in this investigation. Countercurrent mode is employed. The effects of agitation level, superficial gas velocity and superficial liquid velocity on the bubble size distribution are studied. The mean bubble diameter is predicted using photographic technique. A simple correlation is developed for the determination of mean bubble diameter. It is found that the mean bubble diameter values for hybrid column are 1.8 to 2.5 times smaller when compared with conventional reciprocating plate column. The interfacial area is calculated based on the experimental results of the gas holdup and bubble diameter. Effects of agitation level, superficial gas velocity, superficial liquid velocity and plate free area on the interfacial area have been investigated. Correlations are developed for the determination of interfacial area for both mixer-settler and emulsion regions. It could be noted that the interfacial area for the hybrid column is 3 to 6 times higher in both mixer-settler region and emulsion region than that of conventional reciprocating plate column which is quite large.

A trickle fixed-bed reactor model for the Fischer-Tropsch synthesis applicable to both cobalt and iron catalysts which accounts for gas and liquid recycle is described. A selection of kinetic models for both iron and cobalt catalysts (4 each) is included in the reactor model and their effect on model predictions is compared. While the model is 1-D and reaction rates are determined for quasi-average radial bed temperatures, a correlation is used to account for radial thermal conductivity and radial convective heat transfer. Traditional pressure drop calculations for a packed column were modified with a correlation to account for trickle-flow conditions. In addition to describing the model in detail and showing validation results, this paper presents results of varying fundamental, theoretically-based parameters (i.e. effective diffusivity, Prandtl number, friction factor, etc.). For example, the model predicts that decreasing effective diffusivity from 7.1E-09 to 2.8E-09 m2/s results in a lower maximum temperature (518 K vs. 523 K) and a longer required bed length to achieve 60% conversion of CO (8.5 m vs. 5.7 m). Using molar averages of properties to calculate the Prandtl number for the gas phase (recommended by the authors) results in average bed temperatures up to 10 K higher and reactor lengths 17-45% shorter than assuming a Prandtl number of 0.7. Using the Tallmadge equation to estimate friction losses, as recommended by the authors, results in a pressure drop 40% smaller than using the Ergun equation. Validation of the model was accomplished by matching published full-scale plant data from the SASOL Arge reactors.

This study deals with purification and characterization of lignin peroxidase (LiP) isolated from Agaricus bitorqus A66 during decolorization of NOVASOL Direct Black dye. A laboratory scale experiment was conducted for maximum LiP production under optimal conditions. Purification & fractionation of LiP was performed on DEAE-Sepharose ion exchange chromatography followed by Sephadex G-50 gel filtration. The purified LiP has a specific activity of 519 U/mg with 6.73% activity recover. The optimum pH and temperature of purified LiP for the oxidation of veratryl alcohol were 6.8 and 45 °C, respectively. Michaelis-Menten kinetic constants (Vmax and Km) were determined using different concentrations of veratryl alcohol (1-35 mM). The Km and Vmax were 16.67 mM and 179.2 U/mL respectively, for veratryl alcohol oxidation as determined from the Lineweaver-Burk plot. Thermal inactivation studies were carried out at different temperatures to check the thermal stability of the enzyme. Enthalpy of activation decreased where Free energy of activation for thermal denaturation increased at higher temperatures. A possible explanation for the thermal inactivation of LiP at higher temperatures is also discussed.

Torrefaction is a thermal treatment without air or oxygen in the temperature range of 473-573 K. The pyrolysis kinetics of three chemical components (cellulose, hemicelluloses, and lignin) and wood at low temperatures of relevance to torrefaction conditions have been reviewed. A series of thermogravimetric (TG) experiments have been carried out to study the intrinsic torrefaction kinetics of major chemical components and British Columbia (BC) softwoods. The weight loss during BC softwood torrefaction was found to be mainly associated with the decomposition of hemicelluloses, although there was also certain degree of decomposition of cellulose and lignin. The weight loss of the BC softwoods during torrefaction could be approximately estimated from the chemical composition of wood species and the weight loss data for torrefaction of pure cellulose, hemicelluloses, and lignin, respectively. Based on the fitting of the TG curves of BC softwoods and three chemical components, two different torrefaciton models were proposed. The simple one-step (single-stage) kinetic model with the first order reaction can predict the reaction data reasonably well over the long residence time, with the final sample weight being strongly related to the torrefaction temperature. A two-component and one-step first order reaction kinetic model, on the other hand, gave improved agreement with data over short residence time, and can be used to guide the design and optimization of torrefaction reactors over the weight loss range of 0 to 40% at the temperature range of 533-573 K, which covers the typical range of industrially relevant operations.

In an industrial hydrocracking plant, except to the reactor, the separation section can affect the accuracy of the developed mathematical model. In this study, two combined-bed six and seven-lump kinetic models for the hydrocracking of vacuum gas oil in a real refinery are developed and their accuracies for the prediction of product yields are compared. In the six-lump model, the engaged components are selected according to the actual products of the plant, but the seven-lump one is included of lumps which are partitioned based on the specified initial and final boiling points.For both approaches, a complete kinetic network with the catalyst-decay functions is considered. It is found that over a 17-month period of operation from the start of run, the average absolute deviation (AAD%) of the six-lump and the seven-lump models for the yield prediction are 20.51% and 5.21%, respectively for all products. Additionally, the sum of residuals for the seven-lump model has been appreciably decreased in comparison to the six-lump one. Therefore, it is confirmed that partitioning of the products to the lumps with specific boiling points can acceptably decrease the deviation of the prediction. So it is conclusive that including the operation of the separation section in commercial models can effectively increase the accuracy of the model and smooth the prediction error.

Liquid phase hydrodynamics in an aerated tank (ID = 0.19 m) stirred by a half elliptical blade disk turbine (HEDT) have been investigated using particle image velocimetry (PIV) under both aerated and unaerated conditions. The effect of the gas flow rate on the aerated mean velocity of the liquid phase, turbulent kinetic energy and turbulent kinetic energy dissipation are discussed, and their comparisons with those under unaerated conditions are also carried out. Under aerated conditions, the presence of gas does not remarkably change the velocity pattern of the liquid phase. When the direction of the liquid flow is the same as the buoyancy, the liquid is accelerated up to 10.4% by bubbles at position of z/T=0.8 and r/T=0.45; while the liquid flow reversely, the liquid is decelerated about 37.5% under the gas flow rate of 0.2 vvm at the position of z/T=0.25 and r/T=0.45. The turbulent kinetic energy in the bulk flow increases after introducing gas phase, and the average turbulent kinetic energy of the upper, middle and lower regions at 0.2 vvm are increased by 37.3%, 37.8% and 142.7%, respectively. Large-eddy PIV approach is carried out to estimate the distribution of the turbulence kinetic energy dissipation. The result shows that the distribution of the turbulent kinetic energy dissipation is similar as those of turbulent kinetic energy.

In this study, Fenton-like degradation of Orange II in water was investigated over an FeZSM-5 zeolite catalyst prepared by ion exchange. A color removal of 99.99 % and a COD elimination of 55.0 % were achieved after a reaction time of 2h at 266.7 mM H2O2 at 323 K for 0.05 g/dm3 of Orange II solution at a pH around 7. Initial decolorization rate was described by an equation of -rAo = 6.4x103 e-30.7/RT COII,o CH2O2,o0.3 where R is in kJ/mol. No significant decay in decolorization efficiency of the used catalyst was observed.

Previous research has demonstrated that supercritical phase Fischer Tropsch Synthesis (SC-FTS) using hexanes as the solvent medium offers superior activity maintenance to traditional fixed-bed (gas phase) Fischer Tropsch Synthesis (GP-FTS) (Elbashir et al., 2005). This has prompted an investigation into whether supercritical media can reactivate a catalyst used in GP-FTS. To that end, a study was conducted in which a series of GP-FTS experiments of approximately 2 days each were performed, separated by in situ periods of catalyst reactivation using supercritical hexanes as well as SC-FTS.It was found that the supercritical hexanes media and SC-FTS reactivation periods were effective in partially restoring lost catalyst activity and selectivity. GP-FTS was demonstrated to have detrimental effects on subsequent SC-FTS operation while SC-FTS operation showed beneficial effects on subsequent GP-FTS operation. Specifically, SC-FTS reactivations reduced the methane selectivity in subsequent GP-FTS periods. The CO2 selectivity in SC-FTS is consistently lower than that in GP-FTS, while the olefin selectivity into the diesel range is higher in SC-FTS. While the propagation probability was initially higher in SC-FTS than GP-FTS, the propagation probability values converged as the experiment progressed.

The kinetics for the esterification of acetic acid with methanol was studied systemically in the presence of low-corrosive Brønsted acidic ionic liquids (BAILs) as catalysts. The effect of various parameters such as catalyst type, agitation speed, temperature, catalyst loading, and molar ratio of the reactants on the conversion of acidic acid was studied in detail to obtain the optimal reaction conditions. Moreover, the pseudo-homogeneous (PH) kinetic model was utilized successfully to correlate the experimental data in the temperature range from 323.15 to 343.15 K. Thus, a complete kinetic equation for describing this esterification system was developed that provides to obtain the kinetic information for the simulation and design of catalytic distillation column in the synthesis of methyl acetate.

A novel hybrid rotating and reciprocating perforated plate bubble column is designed indigenously. The novelty lies in combining the effects of stirred tank reactors, bubble columns and reciprocating plate columns using bevel gear arrangement. Box-Behnken experimental design in response surface methodology is chosen to predict the relationship between experimental variables and desired response of gas holdup. Agitation level, superficial gas velocity, superficial liquid velocity, perforation diameter and plate spacing are used as experimental variables. Air-water system is used in this investigation. The linear, square and interactive effects of experimental variables on gas holdup are studied. The F-test and P values were used to identify the experimental variables that significantly impact gas holdup.

Commercial HZSM-5 was modified by treating with phosphoric acid and boric acid for the selective methylation of benzene. The study of the performance with respect to the selectivity of the major products, toluene and xylene is the interest of the work. Catalysts were characterized based on BET surface area and XRD, SEM and NH3-TPD analysis to observe the change in properties due to their modification. Although benzene conversion is the highest with HZSM-5 catalyst, but in terms of selectivity, BZSM-5 and PZSM-5 are found to be the suitable catalyst for toluene and xylenes respectively. Xylene selectivity declines for HZSM-5 with the increase in temperature where as the PZSM-5 and BZSM-5 show slightly increasing tendency.

In this work, computational fluid dynamics (CFD) has been employed to compute local convection heat transfer coefficient (h) that is the key parameter in calculation of heat transfer rate between the particle and fluids in packed bed reactors. In addition, the relation between Reynolds number and Nusselt number for spherical and trilobe catalyst particles have been investigated. Moreover, the parameters of Ranz-Marshall (R-M) correlation have been estimated in order to use it for trilobe catalyst particle. The heat transfer coefficients of the spherical and trilobe particles were compared and the effect of particle shape and configuration on heat transfer rate has been investigated. Eulerian-Eulerian approach was employed in order to investigate gas-liquid hydrodynamic especially liquid film formation around trilobe particles. The effects of liquid film around a trilobe particle and liquid volume fraction on heat transfer coefficient have also been studied. The CFD simulation results indicate that increasing inlet liquid volume fraction raises the liquid film thickness around the particles leading to reduction of heat transfer coefficient. In addition, the results revealed that flow field and temperature profiles around the particles became more complicated as a result of liquid film formation and gas-liquid interactions.

In this work, a design equation has been presented for a reactor composed of an annular photoreactor and a continuous stirred tank reactor (CSTR) with a batch-recirculated current. In this reactor the removal of a contaminant namely C.I. Acid Red 17 (AR17) that is a monoazo acidic dye by means of UV/H2O2 process has been investigated. AR17 kinetics in all cases follows pseudo-first-order kinetics. The effects of the operational parameters such as liquid volume inside the CSTR, volumetric flow rate and initial concentration of H2O2 in the removal efficiency have been surveyed. The results indicate that the increase in volumetric liquid rate increases the removal rate; also, the increase in the experimental liquid volume inside the CSTR decreases the removal efficiency. H2O2 concentration has a critical effect in the removal efficiency. A rate equation for removal of AR17 was achieved by kinetic modeling. Resulted equation was combined with mole balance equation for achieving final equation. The presented final design equation is thoroughly able to predict the reaction rate constant (kap1) under various conditions so that calculated and experimental results are in good agreement.

The importance of projection and splashing of bubbling bed particles on the heat transfer rate towards a membrane wall heat exchanger placed above the bed was studied.To characterize the heat transferred from a bubbling fluidized bed to a membrane wall heat exchanger placed above the freeboard, a laboratory scale fluidized bed reactor, heated by a 2 kW electric resistance, was used. The reactor, with an internal diameter of 54.5 mm, had two 0.83 m height double pipe heat exchangers placed one above the other. Only the heat exchanger close to the bed surface participated in the heat exchange process. Tests were done without and with combustion.For experiments without combustion the bed was fluidized with air at superficial velocities of 0.2 to 0.5 m/s in the 400-700 °C temperature range. For experiments with combustion, the fluidizing gas was obtained through propane combustion in the bed in 700-720 °C temperature range, for superficial velocities of 0.2 to 0.3 m/s. Five different bed particle sizes were considered: 107.5, 142.5, 180, 282.5 and 357.5 µm.Particle convective heat transfer coefficients were obtained in the range of 2 to 16 W/m²/K and a correlation for the corresponding Nusselt number as a function of the fluidization characteristics and the combustion equivalence ratio is proposed.For the three smaller bed particle sizes, the particle entrainment ratio had a strong influence on the heat transferred towards the membrane wall and the corresponding bed particle entrainment rate was determined and correlated with the fluidization characteristics and the combustion equivalence ratio.

The fuel cell based heat and power co-generation is considered to be well qualified for a distributed energy system for residential and small commercial applications. A kW-scale system is under development in the New Energy Group in South China University of Technology. Natural gas is selected as fuel for hydrogen production. The system mainly consists of a fuel processing unit, a power generation unit and an auxiliary unit. The fuel processing unit includes a reformer (integrated with steam generation), two high and low temperature shift reactors, and a preferential oxidation reactor. The reformer integrated with steam generation is designed to produce hydrogen-rich syngas from natural gas and water. It can be operated under steam methane reforming or oxidative steam reforming modes. 800 grams of commercial nickel catalyst supported on gamma alumina are loaded in the reformer. The reactor performances under typical steam reforming and oxidative reforming modes are tested. Influences of reaction temperature, steam-to-carbon ratio and methane space velocity on reactor performance under steam reforming mode are experimentally investigated. Influences of oxygen-to-carbon ratio, steam-to-carbon ratio and methane space velocity on reactor performance under oxidative reforming mode are also studied. The reformer will be integrated with the other parts of the system to build a complete system.

In this work a mathematical model for a flow-by electrochemical reactor operating galvanostatically for the Cu and Cd electrodeposition and hydrogen evolution reaction (HER) has been proposed. X-ray computed tomography was used to measure experimental metallic distributions. Good agreement was found between the experimental measurements and model predictions for conversion, current efficiencies, electrode potential and metallic deposit distributions. Differences were observed between experimental results and model predictions and were attributed to a change in Cd electrodeposition and HER kinetics.

For the first time, the catalytic activities of sulfated zirconia and sulfated tin oxide have been directly compared for esterification of free fatty acids (FFA) in crude palm oil to produce fatty acid methyl esters (FAME). Both sulfated zirconia and sulfated tin oxide catalysts were prepared by hydroxide precipitation, followed with impregnation using sulfuric acid as the source of sulfate. The concentrations of sulfuric acid were varied. The sulfated zirconia and sulfated tin oxide catalysts were characterized by XRD, nitrogen adsorption, elemental analysis, FTIR and potentiometric titration. Esterification of FFA in crude palm oil was carried out in a stirred-tank reactor equipped with a reflux condenser. The influences of the amount of methanol and catalysts were investigated. The results have revealed that both sulfated zirconia and sulfated tin oxide well catalyze the esterification of FFA to produce FAME. Sulfated tin oxide is, on average, 2 times more active than sulfated zirconia. Increasing the concentration of sulfuric acid used in the preparation of both catalysts results in higher sulfur contents and greater acidities of the catalysts. As a result, the conversions of FFA increase. Moreover, the conversions of FFA have been found to increase with the amounts of methanol and catalysts up to certain values and then level off.

Biogas produced by the anaerobic digestion of waste contains approximately 1000-1200 ppmv H2S, which is toxic and corrosive. It is necessary to remove H2S before using the biogas in further application. Biotrickling filters containing immobilized Thiobacillus sp. on inert packings are used extensively in the industries. The design equations for biotrickling filter are complex in nature. A simplified simulation model has been proposed where the complexity of solving the diffusion equation forming a boundary value problem has been avoided by utilizing an approximate general solution available in the literature for this class of problems. The simplified simulation model has been validated with the experimental data, with the analytical solutions available for limiting cases, and with the numerical solution. The results have been found in good agreement for air-H2S system. Further, the performance of an industrial biotrickling filter, designed to treat 10000 m3.day-1 biogas to reduce H2S concentration from 1200 ppmv to 100 ppmv, has been analyzed by studying the effect of packed bed height, inlet concentration of H2S, empty bed residence time of gas, biofilm thickness and packing size on its removal efficiency by using proposed simplified model.

The power consumption and mixing performance of a coaxial mixer with different rotating speeds consisting of a helical ribbon (HR) agitator and four dispersion impellers (45° pitched blade impeller, Rushton turbine, 2-blade hydrofoil, and Pfaudler) in syrup solutions of different concentrations were evaluated in an elliptical dished-base cylindrical stirred vessel with a diameter of T=0.48 m and a filled aspect ratio H/T=1. The results show that stagnant zone is effectively eliminated and mixing time is significantly shortened with a coaxial mixer. The power consumption of HR is not affected by the inner dispersion impeller as greatly as the Anchor is, but the effect of the dispersion impeller increases with the increase of its diameter. On the other hand, the inner dispersion impeller is less affected by HR if the speed ratio RN between the high- and low-speed impellers increases. The power curves with different speed ratios fit well with each other when the modified definitions of generalized Reynolds number Re* and power number Np* are used considering the influence of the speed ratio. On the basis of the mixing time at a given power consumption, a Pfaudler-HR presents a better mixing performance than an Anchor as the outer agitator for a coaxial mixer.

Two numerical methods in the family of weighted residual methods; the orthogonal collocation and least squares methods, are used within the spectral framework to solve a linear reaction-diffusion pellet problem with slab and spherical geometries. The node points are in this work taken as the roots of orthogonal polynomials in the Jacobi family. Two Jacobi polynomial parameters, alpha and beta, can be used to tune the distribution of the roots within the domain. Further, the internal points and the boundary points of the boundary-value problem can be given according to: i) Gauss-Lobatto-Jacobi points, or ii) Gauss-Jacobi points plus the boundary points. The objective of this paper is thus to investigate the influence of the distribution of the node points within the domain adopting the orthogonal collocation and least squares methods. Moreover, the results of the two numerical methods are compared to examine whether the methods show the same sensitivity and accuracy to the node point distribution. The notifying findings are as follows: i) The Legendre polynomial, i.e., alpha=beta=0, is a very robust Jacobi polynomial giving the better condition number of the coefficient matrix and the polynomial also give good behavior of the error as a function of polynomial order. This polynomial gives good results for small and large gradients within both slab and spherical pellet geometries. This trend is observed for both of the weighted residual methods applied. ii) Applying the least squares method the error decreases faster with increasing polynomial order than observed with the orthogonal collocation method. However, the orthogonal collocation method is not so sensitive to the choice of Jacobi polynomial and the method also obtains lower error values than the least squares method due to favorable lower condition numbers of the coefficient matrices. Thus, for this particular problem, the orthogonal collocation method is recommended above the least squares method. iii) The orthogonal collocation method show minor differences between Gauss-Lobatto-Jacobi points and Gauss-Jacobi plus boundary points.

Sweet potato medium containing 230.0 g•kg-1 liquefied starch was used for simultaneous saccharification and fermentation (SSF) for fuel ethanol production. Glucose releasing rate was controlled by the initial addition of incremental glucoamylase. The increasing rates of glucose concentration display a positive relationship when glucoamylase is added in early stage (0 to 8 hours (h)). Serious cells growth inhibition occurred in the early stage when 1.0 g•kg-1 glucoamylase is added, whereas glucose providing limitation occurred in the batch with 0.2 g•kg-1 glucoamylase added in later stage (64 to 80 h). The optimum dosage of glucoamylase was 0.8 g•kg-1, where a final ethanol concentration of 118.2 g•kg-1 was attained within 72 h. The results of our study suggest cell growth inhibition and substrate providing limitation can be avoided simultaneously by adding a proper dosage of glucoamylase. It is indicated further that cells growth inhibition in early stage in the batch with 1.0 g•kg-1 glucoamylase added was due to the high increasing rate of initial glucose concentration, but not the high overall glucose concentration.

Reactive simulations of gas-solid flows occurring in fluidized beds with horizontal membrane insertion were carried out using computational fluid dynamics based on the kinetic theory of granular flows. The effect of altering the membrane arrangement on the overall reactor performance (degree of conversion achieved) was investigated by means of fractional factorial designs. When membranes served only as hydrodynamic modifiers to the flow, it was found that significant improvements could be obtained by optimising the membrane arrangement. A slightly larger improvement could be attained by injecting some of the reacting gas through the membranes. When compared to the improvements that can be attained by simply scaling up the reactor height and especially the reactor width, however, these improvements were of less significance. The use of membranes solely for altering reactor hydrodynamics by serving as obstructions and gas injection points can therefore not be merited. Further optimisation studies into membrane arrangement are therefore only recommended for specific processes in which the membranes play a central role by extracting some of the process gasses.

Kinetics of chemical vapor deposition (CVD) of silicon-rich tungsten silicide films from WF6/Si2H6 mixtures was investigated as a function of the configuration of a hot-wall tubular reactor. The step coverage within micron-sized trenches was analyzed to determine the overall sticking probability, which is the ratio between the film-forming species deposited on a surface and the flux of that species to the surface. The overall sticking probability was found in the range 0.01 - 0.30 as the deposition temperature was varied from 120 to 360°C. The activation energy was 25 kJ/mol. These sticking probabilities were lower than those for CVD of tungsten silicide film from WF6/SiH4 mixtures, which yielded better step-coverage profiles. The extinction temperature, Tex, below which no deposition was observed, ranged from 70 ‹ Tex ‹ 80°C. Tex = 70°C corresponded to an inner reactor diameter, d, of 22 mm, and Tex = 80°C corresponded to d = 11 mm. The dependence of Tex on d strongly suggests that radical chain reactions are involved in the CVD process. The reaction producing active intermediate species occurs in the gas phase and these active species are consumed on the surface of the reactor wall. Therefore, the volume to surface ratio of the reactor may be the key factor to control Tex, and an increase in d leads to a decrease in Tex. For Tex = 80°C, pre-heating of the gas phase can be used to induce the chain reaction and increase the silicon content in the tungsten silicide films.

The kinetics of nitrate hydrogenation in water over niobia- and alumina-supported Pd-Cu catalysts were examined. A Langmuir-Hinshelwood kinetic model fitted concentration data, providing consistent kinetic and thermodynamic parameters. The kinetic model assumed a bimolecular surface reaction as the rate-determining step, with two types of sites. Pd-Cu/gamma-Al2O3 was active and selective under the reaction conditions. However, Pd-Cu/Nb2O5 deactivated during time on stream, and a deactivation function was added to the kinetic model to best fit the experimental data.

Adipic acid was synthesized by the oxidation of cyclohexene using 30% hydrogen peroxide in a microemulsion in the presence of sodium tungstate as catalyst. The proposed green process is environmentally friendly since catalyst and surfactant are recycled and pure adipic acid is produced in high yield (70% to 79%). Microemulsions are used as a “green solvent” and give a better contact between the phases. Alkyldimethylbenzylammonium chloride (C12-C14) was used as a surfactant for the generation of the microemulsion since it enables the use of harmful organic solvents and phase-transfer catalysts to be avoided. Optimised operating conditions (temperature, reaction time, separation process) have been defined and applied to evaluate the industrial practicability. The main interest of the present work is the easy recovery of pure adipic acid and the reuse of the reaction media (surfactant and catalyst). This shows promise for developing a future green industrial process that will enable greenhouse gas emissions (N2O), among others, to be reduced.

A three-dimensional Eulerian multiphase based computational model was developed to simulate the black liquor gasification processes in a fluidized bed gasifier (FBG) at low temperature. The standard k-e model and kinetic theory of granular model were used to simulate the gas phase and solid phase, respectively. Black liquor pyrolysis, homogeneous reactions and heterogeneous reactions were taken into account in chemical model. The reaction rates of homogeneous and heterogeneous reaction were determined by Arrhenius–Eddy dissipation reaction rate and kinetic reaction rate. Simulations were carried out at four different operating conditions, i.e. reactor temperature was kept at 550 degree centigrade or 600 degree centigrade, and nitrogen or air was used as fluidizing medium. The calculated results were in well agreement with the experiment used as calibration. Base on the simulation, gas-sold flow patterns and gas species molar fraction distributions were obtained, the relationship of gas composition profiles with the temperature and the fluidizing media were discussed.

The influence of the catalytic site deposition on Fischer-Tropsch synthesis was investigated on cobalt catalysts supported on carbon nanotubes. The catalysts were prepared using incipient wetness impregnation by controlling the deposition of catalytic sites on either the inner or the outer surfaces of nanotubes. The catalysts were characterized extensively and the reaction was performed at similar operating conditions. The in-10Co/CNT catalyst showed better CO conversion compared to the out-10Co/CNT catalyst at all reaction temperatures. An improvement on the catalyst performance was demonstrated in the case of particle deposition inside the pores of the nanotubes with higher C5+ and C2-C4 selectivity.

Volumetric liquid-phase mass transfer coefficient (kLa) is one of the most important parameters for the evaluation of the performance of a gas-inducing agitated tank (GIAT). In this paper, two equations in terms of power input per unit liquid volume (P/VL) and relative gas dispersion parameter (NI/Ncd), respectively, are developed according to data in literature. They can correlate existing kLa values within ±20% of measured ones for bladed impellers with different impeller submergence to tank diameter ratios in the range of 0.5 -1.23. In order to validate these equations, the liquid phase mass transfer coefficients in a continuous GIAT equipped with a 4-blade straight impeller were measured by removal of oxygen from water. It was found that the equation in P/VL criterion could correlate kLa values within ±12% of the experimental data, and the equation in NI/Ncd criterion could correlate kLa values within ±15.6% with an exception of 26.8% for NI = 16.7 Hz.

The aim of this work is to identify the optimum process parameters of sonication, manosonication and thermosonication for deactivating E. coli ATCC 25922 in water-based suspension. The influence of ultrasonic intensity, frequency, pressure, temperature and treatment time on the efficiency of ultrasonic treatments was investigated in this study theoretically and experimentally. The theoretical part of this study involved solving the Rayleigh-Plesset equation with different parameters and evaluating their effects on the collapse pressure of a bubble with initial radius of 0.01mm. The experimental part of the work was conducted using ultrasonic horn reactor at three levels of intensities; low (17.56 W/cm2), intermediate (21.49 W/cm2) and high (24.17 W/cm2) with fixed frequency. Thermosonication and manosonication experiments were conducted at the sub-lethal temperatures of E. coli; 45, 50, 55 and 60°C and pressures of 2, 3 and 4 bars. The optimum treatment conditions of sonication, manosonication and thermosonication were evaluated through calculating the specific energy required to obtain 5 log reduction of E. coli in each treatment. Thermosonication treatment at 21.49W/cm2 and 45°C for 4 minutes was found to be the optimum treatment conditions to deactivate E. coli in water-based suspension.

In the present study Schiff’s bases are synthesized by the conventional as well as by microwave irradiation. Excellent yield within short reaction time is obtained using microwave irradiation along with other advantages like mild reaction condition, non-hazardous and safer environmental conditions. The effects of temperature, reactant molar ratio, and microwave power variation on yield are observed. Mathematical model has been developed using matlab software to obtain the yield as a function of microwave power. Kinetic study of the reaction has also been attempted. Schiff’s bases structures are confirmed by IR, 1HNMR, Mass Spectra and elemental analysis.

Among the different processes for elimination of volatile organic compounds (VOCs) from gaseous effluents (mainly air streams), the frequently employed catalytic oxidation is undertaken in this contribution. With the purpose of reducing the amount of catalyst needed for incineration and the surface of recuperative heat exchangers, thermal swing adsorption can be use as a previous step for VOC concentration.By means of simulating the behavior of a conventional packed bed reactor and using kinetic expressions recently developed for the incineration of mixtures of ethyl acetate and ethanol on a laboratory catalyst based on Mn/Cu oxides, it is shown in this paper that the reduction in catalyst volume is significantly larger than the concentration factor, due to the combined effect of the lower flow rate and temperature rise.A second aspect dealt with in this contribution concern the simulation of the packed bed reactor. The intraparticle mass-transfer limitations turn out to be very strong and, consequently, the mass conservation balances of three species inside the particles should be solved numerically and iteratively at each position inside the bed. A precise approximation to circumvent such procedure is developed and shown to reduce computing time in more than one order of magnitude and to avoid convergence troubles otherwise found with the numerical procedure.

Using a self-established laboratory scale continuous-flow reactor, the experimental research on continuous hydrothermal conversion of glycerin into lactic acid was made, to lay a foundation for quantity production of lactic acid from glycerin. The optimal operation condition for producing lactic acid in the continuous-flow reactor, and a ~60% lactic acid yield was achieved. Bad mixing of the reactants as well as a large surface area of the inner wall of the reactor tube decreased significantly the lactic acid yields, especially with a long residence time under a high concentration of alkali. The continuous-flow reactor was modified by substituting the 1/8’’ tube with a 1/4’’ tube and equipping a mixing device, and was tested to perform as well as the one with a 1/8’’ tube. The research results would help design and establish a more high-efficient continuous-flow reactor for hydrothermal conversion of glycerin into lactic acid.

Ammonia has become an important source for hydrogen especially for fuel cell applications that require COx free hydrogen. In this study, high surface area Pt incorporated mesoporous siliceous materials were prepared for ammonia decomposition reaction to produce clean hydrogen. The results of a fixed bed flow reactor tests, conducted using pure ammonia showed that Pt-SiO2 type catalysts which were prepared by a one-pot hydrothermal synthesis procedure were very active in ammonia decomposition, such as 72% conversion was reached at 500°C at a gas hourly space velocity of 5,100 ml/h.gcat over the catalyst prepared at Pt/Si mol ratio of 0.03. Activity of the synthesized catalysts increased with an increase in Pt loading. Platinum incorporated siliceous materials prepared by impregnation procedures were also tested in ammonia decomposition and highly promising results were obtained.

The effects of selected variables in the production of laccase by Pycnoporus sanguineus using 2 L stirred tank reactor were investigated. Three operating variables namely agitation rate, aeration rate and pH were studied and optimized for maximum enzyme production. Screening experiments of the three variables were done using 2 level full factorial design (FFD). Analysis on factorial screening indicated laccase production was significantly influenced by agitation rate and pH and not aeration rate. The effect of agitation and pH were further optimized using face centered central composite (FCCCD) with fixed aeration rate. The initial factorial screening was augmented with new experiments in order to produce face-centered design for the optimization. Statistical analysis indicated the experimental data fitted well a quadratic model. Model validation was done through residual analysis. Maximum laccase production of 67.1 U L-1 was predicted and experimentally validated under the proposed optimum conditions.

A kinetic modeling of longitudinal and depth profiles of multiwall carbon nanotubes (MWCNTs) synthesis using xylene and ferrocene in a floating catalyst (FC) reactor is hereby reported. Both amorphous and arrays of carbon nanotubes (CNTs) are formed, whose ratio sharply increases along a growth window and from the bottom to top of the arrays. A model is presented for the rate of CNTs synthesis as well as the rate of amorphous carbon formation which undesirably forms on the nanotube walls and reduces nanotubes quality and synthesis efficiency. Based on the amounts of amorphous carbons and CNTs formed in the reactor, kinetic parameters of formation of these species from xylene were estimated. It is shown that, as the temperature increases, the weight ratio of amorphous carbon to CNTs shows minimum at 970 K. The ratio increases with decreasing the amount of deposited iron. Increasing pressure and carrier gas is found to have marginal effects on producing CNTs with lower amounts of amorphous carbon. Higher surface density of CNTs (number of CNTs per surface area) and their diameter, result in a significantly higher amount of amorphous carbon deposition.

In this work, we report the catalytic performance of the first generation Hoveyda-Grubbs precatalyst for the metathesis reaction of 1-octene. The reaction temperature (30 to 100°C) and catalyst load (1-octene/Ru molar ratio 5,000 to 10,000) were varied and quantities such as product distribution, activity and selectivity were evaluated. Reaction temperature showed a significant effect and turn over numbers as high as 4458 were observed for this system. Two competing mechanisms were observed for temperatures above 60°C, namely metathesis and isomerisation. The experimental product-time distribution data for the complex parallel reaction system was fairly accurately described by three elementary pseudo-first order reaction rates. The effects of temperature (Arrhenius Equation) and catalyst load were incorporated in the observed rate constant. The observed activation energies were around 10 kcal/mol.

This work investigated a micro-scale catalytic plate reactor designed for thermal coupling of an exothermic reaction (combustion) to endothermic reforming reactions. The system was studied through both experiments and modelling. A 3D model, previously developed by the authors, was employed and adapted to simulate the real reactor geometry. The aim of the work was to study the influence of different kinetic sub-models for the reforming reactions on the model results. Multi-component mass transport was modelled using a Fick-like law. Operating conditions utilized in the experiments and for the modelling were those typical of reforming reactions. The kinetics sub-models of the methane reforming and combustion reactions were taken from the literature. In particular, for the combustion process a power-law kinetic expression was used with a linear dependence on methane concentration and zero dependence on oxygen concentration. Instead, for the reforming reactions two different kinetics, suggested, respectively, by Xu and Froment and by Hou and Hughes, were employed. The comparison between model results and experimental findings was performed to discriminate which of the two reforming kinetics was more suitable to describe the experiments. It was found that when using the reforming proposed by kinetics Hou and Hughes was employed, the agreement between model results and experiments was elevated while it resulted poor when the other kinetic sub-model was used. An analysis of the features and of the origins of the two sub-models was performed and the comparisons with the characteristics of our experiments was carried out in order to find the reasons for the different agreement.

Pectin is a widespread complex heteropolysaccharide contained in plants cell wall. The hydrolysis of this natural-occurring polymer is an important process both in food industry and pectin-rich wastewater treatment. Although pectin-degrading enzymes have been produced classically by microbial mold strains, production kinetics of the involved endo- and exo- pectinolytic enzymes is still a challenge in industrial microbiology. In order to assess the pectinases production kinetics, the strain Aspergillus flavipes FP-500 was grown in batch cultures using pectin, glucose or galacturonic acid as limiting substrates. Unstructured models were useful for describing the experimental behavior, and for estimating the kinetic parameters associated to the Logistic, Monod and Luedeking-Piret models. Our results pointed out that the exopolygalacturonases production is basically non-growth associated, suggesting an inducible nature for some exo- isoenzymes and endopolygalacturonases, even if some constitutive activity is postulated. Besides, to identify the combined effect of carbon source and pH on polygalacturonases production, several experiments were developed at different pH culture conditions. Exopectinases produced on glucose were inhibited by culture media acidification, while on galacturonic acid these enzymes are produced mainly at pH values of 5.0 or higher. Exopectinases production on pectin was not importantly affected by the established pH values during the culture. Endopectinases were produced basically at acidic conditions on pectin, but growth on galacturonic acid showed a strong inducing effect on endopectinases at pH 5.0

Oxidative decomposition of chlorobenzene diluted in air was carried out in a dielectric barrier discharge reactor. In order to understand the role of the ground electrode, various reactor configurations were tested. Among silver paste, copper wire and aluminum foil tested as the outer electrodes, typical results indicated the best performance of silver paste, probably due to uniform distribution of microdischarges. Likewise, low flow rates gave better conversion and selectivity to gaseous products.

The transient catalytic activity of vanadyl pyrophosphate (VPP) catalyst was studied at ambient and elevated pressure (4.1 bar) and a wide range of operating conditions. The range included the commercial operating conditions typical of fixed bed, fluidized bed and circulating fluidized beds (CFB) for the partial oxidation of n-butane to maleic anhydride (MA). The maleic anhydride yield improved by increasing the feed oxygen molar fraction, temperature and pressure. When the catalyst was cycled between an oxidizing (synthetic air) and a reducing environment; yield increased with an increase in the catalyst residence time in the oxidizing environment. This effect was more pronounced at higher pressure. At ambient pressure, MA selectivity varied between 50-73 % while it decreased to about 48-54 % at a pressure of 4.1 bar. A strong MA selectivity dependency on feed composition was observed when the oxidation time was in the range of actual industrial reactors (< 1 minute). Selectivity data suggested that different oxygen species might be responsible for CO formation compared to other products such as CO2 and MA. Under oxidizing feed conditions (oxygen/n-butane ≥ than 3.7), an increase in n butane conversion was the main contributor to improved MA yield: n-butane conversion increased by about 70 % when the catalyst oxidation time extended from 0.3 to 10 minute. While, under fuel rich feed conditions, typical of industrial CFB operations, both MA selectivity and n-butane conversion contributed to enhancement in MA yield. Depending on the feed composition, MA selectivity increases by about 16-30 % and n butane conversion increases by about 32-55 % by extending the catalyst oxidation time. These results show the critical importance of catalyst oxidation time on reaction yield improvement especially when operating under fuel rich feed conditions. The surface adsorbed or surface lattice oxygen species were suggested to be the main responsible for n butane activation. While, the contribution of catalyst’s sub-surface lattice oxygen was believed to be very limited at fuel rich feed conditions. Under these conditions, catalyst over-reduction cannot be effectively compensated even after excessive catalyst regeneration and presence of gas phase oxygen is critical to maintain a high catalytic activity. As the reactor pressure increased to 4.1 bar, up to 60 % increase in n butane conversion accompanied by 100 % increase in oxygen conversion was observed. MA selectivity decreased by about 20 % on average but the increase in n-butane conversion resulted in an overall yield improvement of up to 30 %. Data show that the catalytic performance could be enhanced at certain combination of reactor pressure and temperature.

In this work, the absorption of pure carbon dioxide by aqueous triethanolamine solutions (TEA) was studied in terms of the kinetic process. The process was made in a stirred tank reactor with a flat and known interfacial area, the operating variables being temperature (288 to 313 K) and concentration in the range 0.1-2.0 M. From the results, it was deduced that the absorption of pure carbon dioxide by aqueous triethanolamine takes place under isothermal conditions in which there is an instantaneous reaction regime at low concentrations, while at higher concentrations it takes place in a moderately fast reaction regime, following a first-order kinetic with respect to alkanolamine. In these conditions of concentrations and temperatures essayed, an expression for the constant kinetic was deduced.

A simple co-precipitation method was utilized to synthesize γ-Al 2 O 3 catalysts using aluminum nitrate nonahydrate as the source of aluminum cations for methanol dehydration to dimethyl ether (DME). Different precipitating agents comprising ammonium carbonate, ammonium bicarbonate and ammonia solutions were used for preparation of the samples. The catalysts were characterized by XRD, FTIR, SEM, NH 3 -TPD and N 2 adsorption-desorption techniques. The sample prepared by ammonia solution had the highest acidity among the synthesized catalysts. Also, N 2 adsorption-desorption results showed suitable textural properties for all of the synthesized samples. Vapor phase dehydration of methanol to DME was performed in the fixed bed micro reactor over the synthesized catalysts and commercial one for comparison purposes. The effects of different characteristics of catalysts such as surface area, acidity, sintering factor and temperature as an operating parameter on performance of catalysts were investigated. The catalyst prepared by ammonia solution showed best catalytic activity due to the suitable textural properties and high amount of acidic sites. Also, the results showed that only high acid strength can’t result high yield of DME for a solid acid catalyst.

The continuous operation of a stirred tank reactor for styrene polymerization was modeled. The proposed approach consists of an iterative procedure between two modules that considers the fluid-dynamics and kinetics respectively. The kinetic module considers a complex kinetic mechanism and is used to predict the time evolution of global variables, such as conversion and species concentrations, physicochemical properties and molecular structure characteristics of the final product. In order to obtain a 3D representation of the flow field, the simulation of the hydrodynamics of the reactor was carried out with the aid of a commercial computational fluid dynamics (CFD) software package. Because CFD is capable to predict the complete velocity distribution in a tank, it provided a good alternative to carry out residence time distribution (RTD) studies. It was found that the stimulus-response tracer method is reasonably accurate to obtain a complete RTD compared to the particle tracking method. The obtained RTD results showed a good agreement when validated with experimental data and literature information.From the estimates of the kinetic module and the RTD predictions, a statistical calculus allows the determination of the average properties at the reactor outlet. The convergence of the iterative procedure was tested and reasonable predictions were achieved for an industrial reactor.

In this present investigation, textiles samples of non-polymeric nature, e.g, cotton, silk etc. of Indian origin were pyrolysed in a 50 mm diameter and 640 mm long packed bed pyrolyser placed in a tubular furnace from 573K to 1173K in a nitrogen atmosphere. Experiments were designed to investigate the effects of temperature of pyrolysis on yields of char, pyro-oil and gas and their characteristics. A kinetic scheme has been proposed where two parallel reactions occur simultaneously to produce volatiles and char. The kinetic rate constants of both the reactions have been determined in the temperature range under study. The activation energies and pre-exponential factors of all products (solid reactant, volatile and char) have been determined. A mathematical model for the pyrolysis of textile waste has been developed using the kinetic parameters determined under the present study. Calorific values of pyro-oil and char obtained at different temperature have been determined. The structural characteristics of char at different temperatures of 573, 873 and 1173K has also been analysed using SEM.

A generalized radiative heat transfer law is introduced into an irreversible light-driven engine with a working fluid composed of the bimolecular reacting system [A]=[B], and the effects of heat transfer laws on the optimal paths of the engine are investigated in this paper. Piston paths for maximizing work output and minimizing entropy generation are determined for such an engine with rate-dependent loss mechanisms of friction and heat leakage by applying the optimal control theory. Numerical examples for the optimal configurations with three special heat transfer laws ( n=-1, n=1 and n=4 ) are provided, and the obtained results are compared with each other. The research on the optimal paths of a light-driven engine from Newton’s heat transfer law to the generalized radiative heat transfer law enriches the finite time thermodynamics. The results presented herein can provide some guidelines for optimal design and operation of real light-driven engines.

A mixture of post-commercial polyolefin waste (PE/PP/PS) was pyrolyzed over various micro- and mesoporous catalysts using a fluidized-bed reactor operating isothermally at ambient pressure. The yield of volatile hydrocarbons with zeolitic nano-catalysts (n-ZSM-5 > n-MOR > n-USY) were higher than with non-zeolitic catalysts (MCM-41 > ASA). MCM-41 with large mesopores and ASA with weaker acid sites resulted in a highly olefinic product mixture with a wide carbon number distribution, whereas n-USY yielded a saturate-rich product mixture with a wide carbon number distribution and substantial coke levels. A novel developed model based on kinetic and mechanistic considerations which take into account chemical reactions and catalyst deactivation for the catalytic degradation of commingled polyolefin waste has been investigated. This model represents the benefits of product selectivity for the chemical composition such as alkanes, alkenes, aromatics and coke in relation to the performance and the particle size selection of the catalyst used as well as the effect of the fluidizing gas and reaction temperature.

Response surface methodology (RSM) was used to model and optimize the immobilized Candida antarctica lipase B catalysed synthesis of butyl-4-methyl-3-oxopentanoate. To determine optimum conditions of the transesterification, a four-factor and five-level central composite rotatable design (CCRD) was used. The factors studied were enzyme load (A), reaction temperature (B), methyl-4-methyl-3-oxopentanoate concentration (C) and n-butanol concentration (D). A quadratic polynomial regression model was used to analyze the experimental data at a 95% confidence level (p < 0.05). The results indicated that the RSM approach gave reasonable results for the optimization of the reaction parameters in the range of tested parameters. The optimal conditions for the enzymatic reaction were obtained at 0.01 mol of methyl-4-methyl-3-oxopentanoate and 0.03 mol of n-butanol using 104 mg of Novozym 435 at 55 °C and 300 rpm for 6 h. Under these conditions, the transesterification percentage was 87 %. Further, kinetic modelling of the enzymatic synthesis was illustrated. Initial rate data and progress curve data were used to arrive at a suitable model. The kinetics was found to obey the ternary complex ordered bi-bi model with inhibition by the substrate methyl-4-methyl-3-oxopentanoate. The values of kinetic parameters obtained from nonlinear regression analysis were found to be Vmax of 0.04 mol/L.min; Km(A) 0.11 mol/L; Km(B) 2 mol/L and Ki(A) 2.2 mol/L.

A series of supported NiMo catalysts were prepared by impregnating ammonium heptamolybdate and nickel nitrate (at 12 and 3 wt% of Mo and Ni, respectively) over chitosan (Chi) modified Al2O3 carrier. Alumina substrate was first impregnated with the organic additive (in acidic aqueous HNO3 solution, given the insolubility of chitosan at neutral pH) at concentrations corresponding to Chi/Ni mol ratios of 0.5, 1 and 2. Lower Mo dispersion in materials prepared over Chi-modified alumina was observed by Raman spectroscopy. Also, in those samples formation of hardly reducible aluminum molybdates (due to acidic conditions used during chitosan deposition) was evidenced by thermal analysis. Sulfided (under H2S/H2 flow, at 400 °C) catalysts were tested in dibenzothiophene hydrodesulfurization (HDS, at 72.4 kg/cm2, 320 °C, batch reactor, n-hexadecane as solvent) where no improved activity (in pseudo first order kinetic constant basis) was registered for chitosan-modified samples. However, increased selectivity to the product from direct desulfurization route (biphenyl) suggested enhanced promotion of MoS2 phase (by Ni) in catalysts prepared with organic additive. CO adsorption at -173 °C (followed by infrared spectroscopy) showed lower concentration of NiMoS active sites over catalysts prepared over chitosan-impregnated alumina carrier pointing out to the existence of highly efficient sites, in spite of their lower surface concentration. The present investigation opens the possibility of using chitosan, a sub-product from seafood industry, as efficient HDS catalyst additive.

This article presents the analysis of gas holdup, pressure drop and bubble size of gas-liquid-solid flow in a modified downflow slurry bubble column. The analysis is done based on the Lockhart-Martinelli principle. The Lockhart-Martinelli model is modified and incorporate to predict the frictional pressure drop and gas holdup of three-phase flow in the modified bubble column. The effects of operating variables such as slurry flow rate, gas flow rate, slurry concentration and particle diameter on frictional pressure drop and gas holdup are investigated. To predict the gas holdup, Sauter mean bubble diameter and pressure drop, correlations have also been developed as function of different dimensionless groups by introducing the operating variables and physical properties. The studies of the pressure drop in the downflow slurry bubble column may give insight into a further understanding and modeling of the three-phase flow characteristics in industrial applications.

Particulate Matter (PM) emissions from either on-road or off-road diesel engines are subject to federal and/or state standards. Recently, Diesel Particulate Filters (DPF) have been shown to be the most efficient way to reduce the PM emissions. However, DPFs need to be regenerated periodically. In order to predict when to regenerate the DPF under real-time driving conditions, a regeneration model for the DPF is needed. In this study, a transient one-dimensional model is used to track gas and solid temperatures and the particulate deposit thickness, and is studied under the Urban Dynamometer Driving Schedule (UDDS) which has variable exhaust flow rate, exhaust temperature, and PM concentration. In order to determine the best conditions, the thermal regeneration is initiated at different time points during the UDDS cycle. Moreover, we also calculate the transient temperature profile and the deposit thickness for each case. We found that the regeneration efficiency is the highest when the regeneration is initiated at 180 seconds into the UDDS cycle which corresponds to a period of extended city driving without stopping.

Algal biomass is a potentially inexpensive source of energy which has high lipid content. As India is the Asia’s largest milk producing country (104.8 million tons in the year 2008), the milk production terminates with an effluent production of 5.24% of the total milk produced i.e., 20 million tons of dairy waste is produced. This effluent can be broken down in many ways, but a more economical way is broken down by the growth of the algal species Chlorella vulgaris which results in the tremendous reduction in various toxic salts concentration and other complex chemicals. As the dairy effluent is hostile to the natural environment, the algae is used not only to break down the toxic substances but also to produce Biomass, which is produced at a rate of 17g/l, which contains a lipid content of 30% ( from 1:1 ratio of effluent and water). Also the treated effluent has low chemical oxygen demand [COD], hence this can be used for irrigation of farms mainly those which are heavily fed with chemical fertilizers. The biosynthesis of organics salts, alkanoates [PHAs] and other phenolic compounds, involves algal species the process is secured by using i) large inoculums ii) tolerant strain (pure strain or GM, if available). This research work uses the pure strain of Chlorella vulgaris which involves the treatment of effluent with three different dilutions and analyzing them.

PSA (pressure swing adsorption) has been a well known commercialized process in the petroleum refining engineering. With the consideration that the volatiles, odorants or essential oils in a variety of plants and herbs may be separated taking the advantage of PSA, we present in this article a newly designed process: PSA plus TSA (thermal swing adsorption). As the odorants or essential oils are unlike the volatile components in the petroleum, being characteristic with higher boiling points and able to become liquefied during the PSA treatment, thereby a TSA technique is necessarily incorporated, so that the whole process can be operated in an entirely gaseous phase to facilitate the separation.

The biofilter packed with pressmud and inoculated with activated sludge obtained from pharmaceutical industry wastewater treatment plant was employed for the removal of ethyl acetate and xylene in this study. The effect of process variables like gas flow rates (0.03, 0.06, 0.09 and 0.12 m3 h-1), inlet concentration of ethyl acetate (1.75, 3.0, 7.0 and 10.5 g.m-3) and xylene (0.2, 0.4, 0.6 and 1.2. g.m-3) on the performance of biofilters was validated. The removal efficiency exceeded 97% for ethyl acetate at inlet concentrations up to 3.0 g.m-3 and 95% for xylene at inlet concentrations up to 0.4 g m-3. The maximum elimination capacity of 165 g m-3 h-1 and 66 g m-3 h-1 for the mixture of ethyl acetate and xylene were obtained. A steady state mathematical model was tested and proved to adequately describe the experimental results at the two operating regimes for both ethyl acetate and xylene.

The Two-Fluid Model (TFM) using the Kinetic Theory of Granular Flow (KTGF) was applied to simulate 3-D dense fluidized beds with different complex internals. The slugging fluidization was found in the simulated results. When the internals were placed into the reactors, the simulated results showed that the slugs were broken up and bubbling fluidization was formed instead of slugging fluidization. The formation, growth, size, and shape of bubbles were validated to ensure a reasonable prediction. Furthermore, the simulated pressure drop was compared with the corresponding experimental data from the dense fluidized beds with different complex internals, and good agreements were observed. Finally, the flow nonuniformity in the dense fluidized beds was evaluated by a developed method. This method extended Radial Nonuniformity Index (RNI) to Face Nonuniformity Index (FNI) and Volume Nonuniformity Index (VNI). From the calculated FNI and VNI, the fluidization quality of the fluidized beds was quantitatively judged as follows: No.3 > No.1> No.2 > No.4 > Without Internal.

The unsteady state temperature of the reactive mixture along a tubular reactor presents a maximum value resulting from the exothermicity of the chemical reaction.The knowledge of the maximum temperature, (position and value) is an important indicator for safety and quality of reactors in which a highly exothermic reaction takes place. This paper deals with experimental and theoretical estimation and localization of this maximum temperature along a chemical tubular reactor at unsteady state. This reactor is equipped with a jacket in which the refrigerating fluid flows in counter current configuration.The reaction undertaken in the inner tube of the reactor is oxidation of sodium thiosulfate by hydrogen peroxide.The unsteady state is described from the resolution of the model equations, obtained from mass and energy balances, with the numerical method of McCormack.The influences of hydrodynamic, thermal and chemical parameters on the value and position of the maximum temperature are studied.

A thermodynamic analysis of glycerol steam reforming in the presence of a CO2 adsorbent (CaO) and solid oxygen transfer material (Fe2O3) for high-purity hydrogen production was performed using the Gibbs free energy minimization method. CO in reformate gas was reduced via CO oxidation by Fe2O3 into CO2 coupled with in situ CO2 capture by CaO. The high-purity hydrogen produced without using a downstream reactor has potential application in proton exchange membrane fuel cells (PEMFCs). The influence of temperature (300–1000 °C), pressure (0.1–1.0 MPa), and mole ratios of H2O/glycerol (1–10), CaO/glycerol (0–6), and Fe2O3/glycerol (0–6) on equilibrium gas compositions and carbon formation was evaluated. The produced gas (99.8 mol% H2 and 12.8 ppm CO) was obtained without carbon formation under the optimal conditions (450 °C, 0.1 MPa, CaO/glycerol mole ratio of 3, Fe2O3/glycerol mole ratio of 3 and H2O/glycerol mole ratio of 10), and can be directly used in PEMFCs. However, further optimizations are needed.

Particle dispersion in a spout-fluid bed was investigated using time series of particle trajectory by evaluation of dispersion coefficient based on Einstein’s expression. A series of experiments were performed in a lab-scale spout-fluid bed using microwave heating and infrared thermal imaging (MH-ITI) technique for recording the position of a tracer. The influence of gas velocity on the particle dispersion in different flow regimes has been taken into account. The results show that the particle dispersion behavior depends on the flow regime. In the flow regime of internal jet, the increase of gas velocity improves the axial dispersion. In the case of jet in fluidized bed with bubbling, increasing fluidizing gas velocity promotes the radial dispersion at the lower part of bed and the axial dispersion at the upper part of bed. In the flow regime of jet in fluidized bed with slugging, the effect of fluidizing gas is related to the slug pattern. The result also indicates that the transition of flow regime can be evaluated from the particle trajectory.

In this study, the recovery of boron from the clay waste of boron industry by leaching with sulfuric acid solution was studied in a batch reactor and the subsequent production of boric acid (H3BO3) was investigated. The effects of acid concentration, solid-to-liquid ratio and reaction temperature on the leaching process were examined. Experimental studies were carried out in the ranges of 0.1-1.0 M for acid concentration, 1-10 g/120 mL for solid-to-liquid ratio and 25-75°C for reaction temperature. The analysis of the experimental data showed that the kinetics of the leaching process fitted the Avrami model in the form of X = 1 – exp (–k t n). For the production of boric acid, the optimum leaching conditions were determined as follows: acid concentration, 0.1 M; solid-to-liquid ratio, 6 g/120 mL; reaction temperature, 50°C and reaction time, 60 min. Finally, boric acid was produced in the purity of more than 95% by crystallization of the leach solution.

Direct dimethyl ether (DME) synthesis from syngas has been increasingly attracted attentions. Relationship between the synergistic effect and the deactivation behavior of hybrid catalysts was studied in this paper. Two kinds of catalysts with different synergistic effect were tested in a fixed bed reactor and the catalysts before and after stability testing were characterized by XRD, N2-adsorption and TGA. Results show that the deactivation behavior of the catalyst is mainly caused by the deactivation of the methanol synthesis catalyst. Sintering of Cu particles is the main reason of the catalyst deactivation. In addition, coking during synthesis is another reason for the catalyst deactivation. Both the two reasons are deeply affected by the synergistic effect.

Laboratory research in the photo-catalytic degradation of dyes in aqueous slurry of TiO2 under UV light radiation has been shown to be potentially applicable in the treatment of wastewater effluents from textile plants. Therefore, reliable kinetic data that are free from mass transfer limitations are required for the design and scale-up of the photo reactor. In this study, batch experiments were designed to measure the mass transfer coefficient, adsorption equilibrium constant and chemical reaction rate constant for the dye reactive orange 16. The mass transfer coefficient was determined for mixing speeds of 240 - 660 rpm with corresponding values of 3.0x10-5 to 2.8 x10-4 1/s, respectively. The mass transfer coefficient became constant for mixing speeds at or greater than 600 rpm. The adsorption equilibrium constant was determined using the Langmuir Isotherm model, and a value of 1.09x10-4 l/mg was determined. The integrated form of the Langmuir-Hinshelwood model was used to describe the photo-oxidation kinetics. The rate constant was determined at different UV light intensities of 8.8 - 26.4 mW/cm2 and the corresponding values were 146.38 - 381.20 mg/l.min, respectively. The relation between the rate constant and UV light intensity can be described by the formula: 1/kr=a/I^0.5 +b .

In this work the water-gas shift (WGS) process was addressed, with particular emphasis in the development of phenomenological models that can reproduce experimental results in a WGS reactor operating at low temperatures. It was simulated the conversion obtained in a fixed-bed reactor (PBR) packed with a Cu-based catalyst making use of a composed kinetic equation in which the Langmuir-Hinshelwood rate model was used for the lowest temperature range (up to 215 ºC), while for temperatures in the range 215 – 300 ºC a redox model was employed. Several packed-bed reactor models were then proposed, all of them without any fitting parameters. After comparing the simulations against experimental CO conversion data for different temperatures and space time values, it was concluded that the heterogeneous model comprising axial dispersion and mass transfer resistances shows the best fitting. This model revealed also good adherence to other experiments employing different feed compositions (CO and H2O contents); it predicts also the overall trend of increasing CO conversion with the total pressure. This modeling work is particularly important for small scale applications related with hydrogen production/purification for fuel cells.

The particle concentration profiles were investigated using an optical fiber probe in a fluidized bed with acoustic assistance. The effects of sound frequency, sound pressure level, and sound wave forms on the particle concentration profiles were researched. Experimental results indicated that the application of an acoustic field could remarkably influence the particle concentration profiles in a fluidized bed. The particle concentration increased with increasing sound pressure level. However, the particle concentration was highest at sound frequency of 150 Hz, and decreased towards both low and high frequency. Compared with Square wave, both Sine wave and Triangle wave can enhance particle concentration in radial and axial profiles.

This work presents the studies on the optimization of the process of phenol hydroxylation over the Ti-MWW catalyst. The medium of the reaction was only water introduced into the rector with the 30 wt% hydrogen peroxide (oxidizing agent) and formed during the reaction from the hydrogen peroxide. For the mathematical optimization the rotatable-uniform design was used. The main investigated technological parameters were: the temperature, the molar ratio of phenol/hydrogen peroxide, the catalyst content and the reaction time. The course of the main functions describing the process were presented in the form of layer drawings. The analysis of the layer drawings allowed to establish the most beneficial parameters for this process. Studies have shown that in water solution it is best to conduct phenol hydroxylation process at: the temperature of 93-100oC, phenol/hydrogen peroxide molar ratio 0.9-1, catalyst concentration 3-3.5 wt% and during the reaction time of 55-60 minutes. Under these conditions, it is possible to achieve phenol conversion of 85 mol%, selectivity of transformation to organic compounds in relation to phenol consumed 50 mol% and the yield of hydroquinone about 19 mol%. The phenol hydroxylation method, presented in this article, is a preferred alternative to conventional solutions, as it is more environmentally and cost-effective, taking into account consumption of raw materials and energy.

Evidence of the control of yield and different morphological features of polyaniline (PANI), along with their higher thermal stability is reported. The syntheses were performed by varying the reaction time from 2 to 6 hours for three different methods using three different oxidizing agents. The freshly prepared PANI was investigated by means of fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The polymer yield was increased with the increasing of reaction time from 2 to 6 h for all oxidants in the synthesis approaches; while the reverse trend was observed for KPS in rapid mixing polymerization and mechanical stirring methods. The highest yield was obtained for 6 h reaction time using APS through mechanical stirring method. FESEM analysis showed the growth of regular and uniform PANI nanoparticles, along with the prevention of secondary growth and agglomeration of primary nanofibers using all three oxidizing agents for sonochemistry and rapid mixing polymerization method, except H2O2 in the case of later technique. However, irregular and agglomerated PANI was found for all oxidants in mechanical stirring method. TGA data showed that PANI synthesized by mechanical stirring method is thermally more stable than those prepared by sonochemistry and rapid mixing polymerization.

In this study, the spent activated carbon (AC) saturated with caramel was regenerated using solvent assisted with microwave radiation. The efficiency of regeneration was evaluated under parameters such as power and time of microwave radiation, and concentrations and pH of an activator. The quality of regenerated AC (RAC) was assessed by methylene blue (MB) and iodine adsorption. The optimum condition for AC regeneration was under a microwave power of 680 W and 10 min radiation, with 20% ethyl alcohol in the activator and pH of 9–10. Under this condition, the adsorption of iodine and MB on RAC was 878 and 218 mg/g, respectively. The micro structure of RAC was characterized by SEM observation. The surface area of RAC was determined under N2 sorption. The pore size distributions of virgin and RAC determined by Horvath–Kawazoe (HK) and DFT methods resulted in a mean pore diameter of 1.2 nm and a pore volume of 1 cm3/g. A regeneration efficiency of more than 85% could be achieved by microwave assisted solvent regeneration.

Landfill leachate was treated using non-powdered activated carbon sequencing batch reactor (NPAC-SBR) and powdered activated carbon (PAC) augmented SBR (PAC-SBR) processesto examine Langmuir and Freundlichadsorption isothermsin the SBR technique.Response surface methodology (RSM) was used for the experimental design and statistical analysis.Based on the obtained results, the maximum adsorption capacitiesof ammonia nitrogen (NH3-N), color, and chemical oxygen demand (COD) for the Langmuir adsorption isotherm were 5.63 mg/g, 25.30 Pt.Co/g, and 13.21 mg/g,respectively, whereas for the Freundlichadsorption isotherm, thesewere 6 mg/g, 46.29Pt.Co/g, and 15.41 mg/g, respectively.Generally, Freundlich isotherm values for NH3-N, color, and COD were higher than Langmuir isotherm values.The NH3-N adsorption on PAC was lower than the color and COD adsorptions because a great part of NH3-Nwas biologically removed in the SBR process.Increasing aeration rate and contact times in the SBR processes increased the adsorption isotherms of NH3-N, color, and COD on PAC

To study the effects of La modifier on Ni/γ-Al2O3 catalysts for the hydrotreating of crude 2-ethylhexanol, four samples with various La contents were prepared by the hydrothermal deposition method and characterized by ICP–AES, XRD, XPS, TPR, and H2 chemisorption. It was found that the number of catalytic active sites of the four samples with a similar Ni loading follows the order: Ni/La0/Al (13.2μmol gcat-1) < Ni/La0.5/Al (15.1μmol gcat-1) < Ni/La2.0/Al (15.8μmol gcat-1) < Ni/La1.0/Al (17.1μmol gcat-1). The results indicate that the catalyst modified by an appropriate La can obtain more active centers and higher hydrogenation performance because it possesses a higher surface Ni content and an appropriate Ni dispersion degree.

Phase equilibrium calculations in systems subject to chemical reactions play a major role in the design of reactive separation schemes including chemical reaction engineering. Basically, these calculations involve the global minimization of Gibbs free energy constrained by the material balances and chemical equilibrium restrictions. However, Gibbs free energy function is non-convex, highly non-linear with many decision variables, and may have several local minimums including trivial and nonphysical solutions. In these conditions, conventional numerical methods are not suitable for solving reactive phase equilibrium problems. Recently, there has been a significant and increasing interest in the development of global strategies for reliably solving reactive phase equilibrium problems subject. Harmony search (HS) is a global stochastic optimization method, which has been conceptualized using the musical process of searching for a perfect state of harmony. Until now, HS has been successfully applied to solve various engineering and optimization problems. However, there are few studies concerning the application of this optimization method for chemical engineering calculations. To the best of our knowledge, the performance of HS for solving reactive phase equilibrium problems has not yet been reported. Therefore, this paper introduces the application of HS-based algorithms to the constrained global minimization of Gibbs free energy in reactive systems. Specifically, we have studied the performance of three variants of HS in reactive phase equilibrium calculations. Our results are useful to identify the capabilities and relative strengths of HS with respect to other stochastic optimization methods for the simultaneous calculation of physical and chemical equilibrium.

In current work, Radioactive Particle Tracking (RPT) experiment has been performed in a rectangular bubble column having dimensions reported by Pfleger et al. (1999). As has been reported in recent decades, RPT has come to be accepted now as a reliable and versatile non-invasive flow measurement technique for mapping the flow fields in multiphase reactors.In this work, the objective has been to benchmark RPT (which is a very versatile technique) against reported data (Pfleger et al. 1999) with Laser Doppler Anemometry (LDA) (which is claimed to be a very accurate technique at low volume fractions of the dispersed phase). We show that RPT does remarkably well both in terms of versatility and accuracy. Overall, this work helps to establish the accuracy standards of the RPT technique.

A novel dual-bed reactor comprising of the upper-layer Na2WO4-Mn/SiO2 particle catalysts and the under-layer Na3PO4-Mn/SiO2/cordierite monolithic catalysts with beds-interspace supplementary oxygen was constructed for oxidative coupling of methane (OCM). The catalytic performance of OCM in the dual-bed reactor was remarkably improved compared with that in the previously reported chemical reactor for OCM.

We present an experimental study on the stabilization of bubbling gas-fluidized beds of magnetic powders by interparticle forces induced by an externally applied magnetic field in the cross-flow configuration. The samples tested consist of magnetite and steel powders in a range of particle size dp between 35 and 110 microns, allowing us to investigate the effect of particle size and material properties on magnetic stabilization. According to our observations, the stabilization physical mechanism is ruled by the jamming of particle chains created due to attractive forces induced between the magnetized particles. Even in the case of the horizontally applied field, these chains are mechanically stable at orientations close to the gas flow direction in agreement with the prediction of a chain model based on the balance between gas flow shear and interparticle magnetic force fm. Since fm is increased as dp is increased, the critical gas velocity at marginal stability vc for a fixed field strength B is seen to increase with dp. The yield stress of the stabilized bed s increases steadily as the gas velocity v0 is decreased below vc. Thus, s is increased with dp for fixed v0 and B. It is inferred also from our results that natural aggregation of fine particles due to the universal van der Waals interaction enhances the yield stress of the magnetically stabilized bed. A main conclusion is that interparticle short ranged attractive forces play an essential role on magnetic stabilization of fluidized beds.

The bubbling behaviour of fluidized beds has been thoroughly investigated in the last decades by means of several techniques, e.g. X-ray, Inductance, Resistance and Impedance based techniques, PIV. In recent years, Digital Image Analysis Techniques have shown their potential for accurate and cost effectively measurements.Most of the work related to bubble behaviour analysis deals with single-sized particles, while almost all industrial equipment operates with multi-sized particles. Although considerable work has been done in the past with focus on the analysis of the mixing-segregation behaviour and predictions of fluid dynamics regime transitions, a lack of knowledge still exists in the analysis of bubbles properties measurements for the case of polydispersed systems.In this work, digital image analysis has been adopted to accurately measure fundamental global parameters such as bubble hold up and bed expansion as well as average bubble hold-up distribution maps or bubble size distributions in bubbling fluidized beds of binary mixtures of particles. The experiments have been carried out at steady state conditions with binary mixtures of corundum particles, at various inlet gas velocities. This preliminary study has been performed with the aim to collect valuable data for future development of predictive models and validation of CFD codes.

In the present paper the segregating behaviour of solids of different size and density in gas-fluidized beds is studied. In particular, the attention is focussed on pairs composed of a bigger/less dense species and a smaller/denser species. Typical industrial examples of such combinations are encountered in fluidized beds of biomass/sand mixtures. Their behaviour is not easily predictable, as the segregation tendency promoted by the difference in density is counteracted by the difference in size. While typically the denser component is expected to appear predominantly at the bottom of the fluidized bed, experiments on mixtures exhibiting the reverse behaviour have been reported (e.g. Chiba et al., 1980).A simple model to predict the segregation direction of the components, i.e. which species will segregate to the top of the bed (the flotsam), depending upon their difference in properties (size, density) and the mixture composition, is discussed. The predicted behaviour is compared with experimental data available in the literature and agreement is found for the majority of them. For one mixture, experiments are conducted as well as computational simulations based on the combined Discrete Element Method and Computational Fluid Dynamics (DEM-CFD) approach. This allows investigating how an initially mixed bed upon suspension evolves as a result of the segregation prevalence in the bed.

Gas-liquid stirred vessels are widely employed to carry out chemical reactions involving a gas reagent and a liquid phase. The usual way for introducing the gas stream into the liquid phase is through suitable distributors placed below the impeller. An interesting alternative is that of using “self ingesting” vessels where the headspace gas phase is injected and dispersed into the vessel through suitable surface vortices. In this work the performance of a Long Draft Tube Self-ingesting Reactor (LDTSR) dealing with three-phase (gas-liquid-solid) systems, is investigated. Preliminary experimental results on the effectiveness of this contactor for particle suspension and gas-liquid mass transfer performance in the three-phase system, are presented. Mass-transfer parameter kLa was measured by the recently introduced Simplified Dynamic Pressure Method (SDPM). It is found that the presence of low particle fractions causes a significant increase of the minimum speed required for vortex ingestion of the gas. Impeller pumping capacity and gas-liquid mass transfer coefficient are found to be affected by the presence of solid particles.

This work investigates on the effect of air humidity on the flow properties of powders. The moisture of a powder sample (50 µm glass beads) was conditioned by fluidization with humid air. Air humidity was kept between 0 and 70% at ambient temperature. A Schulze shear cell was used to measure the bulk flow properties of the moisturized samples. A Couette fluidized bed rheometer was used to measure the torque necessary for the rotation of the inner cylinder when the fluidized powder had been moisturized with the same procedure. These experiments show a certain continuity of the results below and above the minimum fluidization velocity, suggesting a similar continuity of the role that interparticle interactions play in the fixed and in the fluidized bed. Experiments below the minimum fluidization velocity were interpreted with a rheological model in which the variable load along the vertical direction in the Couette was calculated with a modified Janssen equation. In this approach the apparent weight of the powder is given by the difference between the gravity and the upward body force determined by the rising gas flow. The agreement between the model and the experiments supports the proposed approach.

The drag force on a particle in a multiparticle suspension is a function of the particle-fluid relative velocity and of the particle volume concentration. Its determination heavily relies on experimental observations, as theoretical support is still limited to viscous flow regime and dilute solid concentrations. When uniform particle suspensions are considered, there is a certain abundance of experimental data available which has permitted the proposition of simple and reliable relationships for the determination of the drag force: these relationships are normally expressed through the use of the so-called “voidage function”, i.e. a function by which the drag force on an isolated particle has to be multiplied in order to obtain the drag force on a particle in a multiparticle suspension. The extension of the approach mentioned above to suspensions made up of particles differing in size and density has been attempted here and new simple relationships are presented for the case of binary-solid systems. The basic idea draws an analogy between binary-solid suspension and single-particle suspensions thereby making possible the use of well established results. The simple relationships obtained for the estimation of the drag force on a particle in a binary-solid suspension have been tested, with satisfactory success, against experimental data available in literature.

A single bubble of typical volume 20 mm³ ≤ VB ≤ 400 mm³ was placed in downward conically diverging flow of low and moderate viscous liquids (aqueous solutions of glycerine and of electrolytes (NaCl, Na3PO4, MgSO4), and butanol). Experiments were performed over a range of Reynolds number 60≤Re≤2200, Weber number 1≤We≤14, Tadaki number 1≤Ta≤10, Eötvös number 1≤Eo≤22, and bubble aspect ratio 0.4≤b/a≤0.9. The bubble shape, bubble position and motion were investigated by direct observation of two plane projection of bubble by high speed camera. Typical sampling frequency was 150 fps. Relatively long records, (approximately 9000 frames per one bubble observation) allow us to get relevant statistics of treated data. Bubble aspect ratio has been determined from both projection planes. Dimensionless front area of observed bubble has been introduced as suitable parameter for correlation with Eötvös number. Model of static bubble and classical Wellek correlation were employed as asymptotes. Bubble rising velocity has been determined and tested for each single bubble with respect to liquid properties. Velocity data are plotted within the frame given by several theoretical predictions for pure and contaminated liquids. Dimensional analysis is used considering viscosity and surface tension effect. New simple correlation of bubble rising velocity separating the effects of viscosity and surface tension is presented.

The use of the core-annular flow pattern, where a thin fluid surrounds a very viscous one, has been suggested as an attractive artificial-lift method for heavy oils in the current Brazilian ultra-deepwater production scenario. This paper reports the pressure drop measurements and the core-annular flow observed in a 2 7/8-inch and 300 meter deep pilot-scale well conveying a mixture of heavy crude oil (2000 mPa.s and 950 kg/m3 at 35 C) and water at several combinations of the individual flow rates. The two-phase pressure drop data are compared with those of single-phase oil flow to assess the gains due to water injection. Another issue is the handling of the core-annular flow once it has been established. High-frequency pressure-gradient signals were collected and a treatment based on the Gabor transform together with neural networks is proposed as a promising solution for monitoring and control. The preliminary results are encouraging. The pilot-scale tests, including long-term experiments, were conducted in order to investigate the applicability of using water to transport heavy oils in actual wells. It represents an important step towards the full scale application of the proposed artificial-lift technology. The registered improvements in terms of oil production rate and pressure drop reductions are remarkable.

An inline oil/water separator based on an axial cyclone is studied numerically and experimentally. Single phase measurements were done with LDA and compared with numerical data, obtained with Reynolds avaraged Navier-Stokes equations with the Reynolds-stress model SSG. Results show an annular region with reversed axial flow and declining rotation due to friction at the wall, giving a qualitative agreement between numerical and experimental data. A method is introduced to determine the phase distribution inside a liquid-liquid axial cyclone, based on electric conductivity. Preliminary results indicate a time-dependent oil-rich kernel. Presented results for the separation efficiency of the tested axial cyclone indicate the need for better understanding of swirling flow.

In the industrial processes that employ the fluidized bed technology (gasification of coal or biomasses, polymerization, etc.), solids of various kinds are simultaneously subjected to fluidization. Due to the fact that solids that differ in density and/or size differently react to the frictional force exerted by the gas stream, mixtures of two solids tend to form, when fluidized, segregated layers rich in either of their components. A peculiar case, in this frame, is that of homogeneous mixtures whose denser component is also the smaller one and achieves the fluidized state at the bottom of the column, while the other solid, bigger and lighter, forms a packed layer on top of it.With reference to this special type of binary systems, several series of experiments are presented that provide their initial and final fluidization velocities at varying composition. Following what done in a recent study on beds of two solids differing in density or size, it is shown that the theoretical equations for calculating uif and uff keep their validity even when applied to mixtures that exhibit an unusual fluidization pattern. Calculated values of the initial and final fluidization velocities are characterized by a low error level, fully comparable with that encountered with other types of binary beds.

Typical flow problems, like arching or bridging, of ultrafine cohesive powders are caused by undesired particle adhesion, poor flowability and large compressibility and intensified by poor permeability. Thus, the physical understanding of micromechanics of ultrafine particle flow and permeation is very essential to design properly the product quality and to improve the process performance in particle technology.A force balance at a homogenously assumed, dynamic bridge is formulated at the hopper outlet that includes the dead weight, inertia, wall and drag forces. The permeation resistance is calculated as sum of a microscopic flow-around resistance of single particles plus the macroscopic bed resistance of the moving cohesive powder bridge. The resulting differential equation is shown for turbulent flow-through conditions of air. The first integration gives analytical discharge velocity-time function, steady-state discharge velocity and the characteristic discharge time of incipient (accelerated) flow. The second integration results in analytical height-time and velocity-height functions, discharge and residence times. This method results in physically consistent, analytical models that are comfortable to handle and easy to prove. The steady-state discharge velocity is compared with measurements of full-scale silos at Coperion and Zeppelin companies. This publication describes the results of a closed collaboration between university and industry. The practical objective of the project was to solve the serious discharge problems of ultrafine, compressible, hardly permeable, cohesive powders by applying mechanical vibrations during their gravitational flow.

The 40 MW Strongoli power plant, located in the Calabria region of Italy, produces power from 100% biomass sources. The combustion of wood biomass, exhausted olive residues and palm kernel shells, occurs in a sand-filled, Circulating Fluidized Bed (CFB) combustor. Operational experience with the unit dates back to 2003. This paper describes the optimization of the boiler in order to minimize erosion on internal surfaces and structures. Detailed three-dimensional, transient, multiphase gas-solid flow fields were computed and are presented. Details of the complex geometry include the combustion chamber, cyclone, cyclone dipleg, seal pot, fluidized bed heat exchanger and cyclone outlet structures including suspension tubes. The gas-solid flow was computed using the commercially-available software package Barracuda, a CFD software based on a unique Eulerian-Lagrangian formulation that was essential to the success of the subject work. Both instantaneous and time-averaged results were obtained. Results were validated against operational erosion experience. The validated model, in turn, was utilized to redesign various components of the boiler, optimizing both erosion characteristics and performance behaviour of the system. The redesigned unit was commissioned in early 2012.