Band 14, Heft 1 -

Membrane reactors are attracting increasing attention for ultrapure hydrogen production from fossil fuel, integrating catalytic reaction and separation processes into one single unit thus can realize the removal of hydrogen or introduction of reactant in situ , which removes the thermodynamic bottleneck and improves hydrogen yield and selectivity. In this review, the state-of-the-art concepts for hydrogen production through membrane reactors are introduced, mainly including fixed bed membrane reactors, fluidized bed membrane reactors, and micro-channel membrane reactors, referring higher hydrocarbons as feedstock, such as ethanol, propane, or heptane; novel heating methods, like solar energy realized through molten salt; new modular designs, including panel and tubular configurations; ultra-compact micro-channel designs; carbon dioxide capture with chemical looping; multifuel processors for liquid and/or solid hydrocarbons; etc. Recent developments and commercialization hurdles for each type of membrane reactor are summarized. Modeling the reactor is fundamental to explore complex hydrodynamics in reactor systems, meaningful to investigate the effects of some important operating factors on reactor performances. Researches for reactor modeling are also discussed. Reaction kinetics for hydrocarbons reforming and reactor hydrodynamics are summarized respectively. Cold model is introduced to investigate physical phenomena in reactors.

An accurate model is required to optimize the propane dehydrogenation reaction carried out in the radial moving bed reactors (RMBR). The present study modeled the RMBR using a plug flow reactor model incorporated with kinetic models expressed in simple power-law model. Catalyst activity and coke formation were also considered. The model was solved numerically by discretizing the RMBR in axial and radial directions. The optimized kinetic parameters were then used to predict the trends of propane conversion, temperature, catalyst activity and coke content in the RMBR along axial and radial directions. It was found that the predicted activation energies of the propane dehydrogenation, propane cracking and ethylene hydrogenation were in reasonable agreement with the experimental values reported in the literature. The model developed has accurately predicted the reaction temperature profile, conversion profile and catalyst coke content. The deviations of these simulated results from the plant data were less than 5%.

This study explores the lab prepared nickel hydroxide catalyzed oxidative degradation of Methylene Blue (MB) in aqueous medium using batch reactor. Nickel hydroxide was prepared by reaction of sodium hypochlorite, sodium hydroxide and nickel sulphate hexahydrate in distilled water. The catalytic oxidative degradation of Methylene Blue was explored in terms of various parameters like effect of time, hydrogen peroxide, temperature, initial concentration of dye, catalyst dosage and effect of speed of agitation on degradation of Methylene Blue. Experimental data was subjected to kinetics analysis using Curve Expert software. Degradation reaction was taking place according to Langmuir-Hinshelwood mechanism. According to this mechanism the reactants adsorb at the surface of catalyst in first step followed by chemical reaction between adsorbed reactants in second step. Catalyst was heterogeneous in nature which was separated by simple filtration easily.

A mass transfer model was developed to capture CO 2 from a gas mixture in hollow fibre membrane contactors under laminar flow conditions. The axial and radial diffusions through membrane and convection in tube and shell sides with chemical reaction were investigated. COMSOL software was used to numerically solve a system of non-linear equations with boundary conditions by use of the finite element method. Three different amine solutions of monoethanolamine (MEA), diethanolamine (DEA) and n -methyldiethanolamine (MDEA) were chosen as absorbent in lumen to consider the mass transfer rate of CO 2 and its removal efficiency. The modelling results were compared with experimental data available in the literature and a good agreement was observed. The CFD results revealed that MEA had the best performance for CO 2 removal as compared to DEA and MDEA under various operating conditions due to the different CO 2 loading factor of absorbents. Furthermore, efficiency of CO 2 removal was highly dependent on the absorbent concentration and flow rate, increasing of the gas flow rate caused a reduction in gas residence time in the shell and consequently declined CO 2 mass transfer. The modelling results showed the effect of absorbent concentration on the CO 2 mass transfer was improved due to availability of absorbent reactants at the gas-liquid interface.

In this study, a steady-state heterogeneous one-dimensional model predicts the performance of a thermally double coupled auto-thermal multi-tubular reactor for simultaneous production of hydrogen, benzene, methanol and dimethyether (DME) in an economical approach for both co- and counter- current modes of operation. Reversed flow of cyclohexane has been considered for the counter-current flow regime. The simulation results for co- and counter-current modes have been investigated and compared with corresponding predictions for conventional methanol reactor and traditional coupled methanol reactor. In addition, various operating parameters along the reactor have been studied. The simulation results present that methanol yield in co- and counter- current modes are reached to 0.3735 and 0.3363 in a thermally double coupled reactor, respectively. Also, results for counter-current mode show a superior performance in hydrogen and benzene production. Finally, the results of simulation illustrate that the coupling of these reactions could be beneficial.

We discuss the three-dimensional boundary layer flow of Maxwell nanofluid in the present article. The flow is caused due to bidirectional stretching surface. An applied magnetic field is taken into account. Heat and mass transfer characteristics are considered in the presence of thermal radiation, Brownian motion, thermophoresis and chemical reaction effects. Mathematical modelling is made under a low magnetic Reynolds number and Rosseland’s approximation. Expressions of series solutions for velocities, temperature and concentration are developed. Impacts of influential parameters on the temperature and concentration are sketched and examined. Numerical values of local Nusselt and Sherwood numbers are computed and analyzed. We found that an increase in thermophoresis and Brownian motion parameters enhanced the temperature field and thermal boundary layer thickness. The concentration field reduced gradually when we enhance the values of Lewis number and chemical reaction parameter. The values of local Nusselt number are higher for a larger radiation parameter.

A mathematical model of a bubbling fluidized-bed reactor for the production of polyolefins is presented. The model is employed to simulate a typical, commercial-scale reactor where the synthesis of polyethylene using supported catalysts is carried out. Results are used to follow the evolution of temperature within the reactor bed to avoid conditions producing polymer degradation. The fluidized bed is modeled as a heterogeneous system with a bubble gas phase and a solid-particle emulsion. The catalyst active sites are considered located within a growing, solid, ever changing particle composed of the support, the catalyst and the polymer being produced. The model sees the reactor as a three phase complex: (a) the bubble phase, transporting most of the gas entering the reactor; (b) the solid-particle phase, where polymerization takes place; and (c) the interstitial-gas phase among solid particles. Both gaseous phases move continuously upward, with different velocities, and are modeled as plug flows. For the solid-particle phase, modeling alternatives are explored, ranging from a descending plug-flow limiting case to the opposite extreme of a perfectly mixed tank related to the particle drag-effect the rising bubble produces in the bed. In the scouting process between these limits instabilities are predicted by the model. The most realistic representation of the bed is that of the two gas phases moving upward in two plug-flow patterns and the solids moving with ascending and descending trajectories due to back-mixing.

Small amount of different nickel precursors (nickel nitrate or nickel molybdate) were incorporated into MoBi-based catalyst to produce a series of modified composite oxides catalysts for the selective oxidation of isobutene (IB) to methacrolein (MAL). Nickel nitrate introduction can effectively improve IB conversion and nickel molybdate introduction can remarkably enhance the selectivity of MAL. The XRD results show that nickel introduction has some influence on the catalyst structure. The catalyst modified with NiMoO 4 showed the highest MAL yield of 87.8%. According to the H 2 -TPR, BET and XPS results, the catalyst modified with NiMoO 4 exhibits lower reduction temperature, higher pore volume and better lattice oxygen mobility, which were confirmed to be responsible for excellent catalytic performance for the title reaction. In the case of an excess of O 2 , an empirical kinetic model was used to evaluate the rate data. The activation energy (Ea) was found to be 172.4 kJ mol −1 .

Transesterification reaction was performed in the presence of soybean oil, methanol, and Demineralized water plant sedimentation catalyst at 60°C for 8 h in this study. Central composite design method was used to study the effect of catalyst concentration and methanol to oil molar ratio on purity and yield of produced biodiesel. The results showed catalyst concentration of 9.08 wt% and methanol to oil molar ratio of 22.49 as the optimum condition in which the values of purity and yield of the produced biodiesel in the second-order models were 99.89% and 81.83%, respectively. Experiments are in good agreement with the mentioned values as corresponded values are 99.95% and 86.68%, respectively. The catalyst was reused five times and XRF analyses showed a reduction in content of available CaO in catalyst after further usages, because of CaO extraction by methanol. Also for kinetics investigation, effects of temperature and time of the reaction on the produced biodiesel conversion at optimal condition were investigated. Rate constant at different temperatures and then activation energy were determined. Results showed high accuracy of first order kinetic model. Mean relative error of experimental data for the presented model was 2.42%.

The main objective of the present study is to investigate the biogas recovery process from meat industry wastewater using continuously stirred tank reactor (CSTR). Plackett–Burman design was used to screen the effective process variables among temperature, alkalinity dose, organic loading rate, agitation speed, nutrients, dilution factor and volatile fatty acid content. Box-Behnken design (BBD) was used to study the individual and interactive of process variables on the biogas recovery process. Optimum conditions for maximizing the biogas recovery was determined using derringer’s desired function methodology as follows; temperature of 45 ° C, organic loading rate of 8 m 3 /COD/day, C:N ratio of 90:10 and dilution factor of 15%. Under these optimal conditions, predicted biogas recovery and COD removal are found to be 0.08 m 3 /L/d and 94%, respectively. This result confirms the effectiveness of CSTR to treat meat industry wastewater in terms of biogas recovery.

CO 2 capture using solid sorbents in fluidized bed reactors is a promising technology. The multiphase CFD model is increasingly developed to study the reactors, but it is difficult to model all the realistic details and it requires significant computational time. In this study, both the multiphase CFD model (i.e., CFD-DEM model coupled with reaction) and the simplified reactor models (i.e., plug flow model and bubbling two-phase model) are developed for modeling a fluidized bed CO 2 capture reactor. The comparisons are made at different gas velocities from fixed bed to fluidized bed. The DEM based model reveals a detailed view of CO 2 adsorption process with particle flow dynamics, based on which the assumptions in the simplified models can be evaluated. The plug flow model predictions generally show similar trends to the DEM model but there are quantitative differences; thus, it can be used to determine the reactor performance limit. The bubbling two-phase model gives better predictions than the plug flow model because the effect of bubbles on the inter-phase mass transfer and reaction is included. In the future, a closer combination of the multiphase CFD simulation and the simplified reactor models will likely be an efficient design method of CO 2 capture fluidized bed reactors.

In this research, the kinetics of platinum extraction from a selective linear paraffin dehydrogenation spent catalyst in cyanide solutions at high pressure and temperature was experimentally studied. Three variables, including reaction temperature, initial sodium cyanide concentration in solution and liquid to solid weight ratio were investigated. Based on the design of experiments via response surface methodology (RSM) by computer simulating software “Minitab 16”, experiments were carried out at operating conditions including five solution temperatures, five initial concentrations of cyanide solution and five liquid/solid weight ratios. The effects of these operating conditions on the reaction kinetics and extraction time were determined. The obtained kinetics data were fitted into an empirical power–law rate equation. The kinetics model parameters were evaluated by using experimental data via non-linear regression analysis. It was found that the platinum extraction from a selective linear paraffin dehydrogenation spent catalyst in cyanide solution at high pressure and temperature can be appropriately modeled by the proposed correlation in the selected range of operating conditions.

Influence of dealumination of zeolite ZSM-22 (Si/Al ratio of 45) by treating it with oxalic acid on its catalytic performance in n-hexadecane hydroisomerization reaction was studied. This reaction is an attempt in the direction of green and sustainable source of diesel via improving the cold-flow properties of deoxygenated vegetable oils. Pt (0.5 wt%) on ZSM-22 treated with 1 M oxalic acid afforded highest yields of the mono-branched paraffins. This improved is attributed to selective removal of active sites on external surface of zeolite crystals (responsible for undesired cracking reactions) using the bulkier dealuminating agent, oxalic acid. Thus, pore-mouth key-lock mechanism was brought to play the role to cause high selectivity to mono-branched isomers. Preferential external site deactivation was inferred from mesitylene cracking results. Effects of operating parameters such as temperature, and space velocity on product distribution also were studied. Also, kinetics of the reactions involved too has been in brief reported.

In this paper, we introduce a theoretical and numerical study for the effects of thermal buoyancy and constant heat flux on the Casson fluid flow and heat transfer over an exponentially stretching sheet taking into account the effects of variable thermal conductivity, heat generation/absorption and viscous dissipation. The governing partial differential equations are transformed into coupled, non-linear ordinary differential equations by using suitable transformations. Numerical solutions to these equations are obtained by using the fourth order Runge-Kutta method with the shooting technique. The effects of various physical parameters which governing the flow and heat treansfer such as the buoyancy parameter, the thermal conductivity parameter, heat generation or absorption parameter and the Prandtl number on velocity and temperature are discussed by using graphical approach. Moreover, numerical results indicate that the local skin-friction coefficient and the local Nusselt number are strongly affected by the constant heat flux.

Statistical design of experiments was used for design and analysis of nickel extraction from hazardous waste. Sulphuric acid leaching of zinc plant residue has been performed for monitoring and evaluating the effects of process factors on the nickel leaching yield. Factorial design was planned first in order to study the effect of six process factors and screen main variables. These factors were reaction time, acid concentration, solid-liquid ratio % (w/v), particle size, stirring speed and reaction temperature. The main factors and their interaction were studied by analysis of variance (ANOVA), and the results showed that the reaction time, acid concentration and solid-liquid ratio were the most significant factors. In the second set of experiments, response surface methodology (RSM) was used for modelling and optimisation of significant factors. Quadratic model was derived for the prediction of nickel extraction. The optimum values for maximum nickel was identified to be a leaching time of 30 min, acid concentration 10% (V/V) and solid liquid ratio of 10%. Using these optimum conditions, more than 94% nickel was extracted. In addition the results of model equation showed a good agreement with the experimental data.

Currently the economics of biodiesel production is the main obstacle to its large-scale industrialization. The high cost is mainly due to the cost of the expensive feedstocks used in the production process. In the past years, researchers have studied several methods to reduce the production cost of biodiesel. One method involved replacing the edible oil feedstock with the non edible one such as Jojoba oil. In this research Jojoba oil was extracted by subcritical water technology to produce jojoba oil-based biodiesel. This represents a promising alternative route for cleaner and sustainable fuel production through transestrification reaction with methanol catalyzed by potassium hydroxide. The transestrification reaction has been optimized in batch reactor with a molar ratio of 6:1 methanol to jojoba oil, using a concentration of 1.35 wt% potassium hydroxide and vigorous stirring of 600 rpm at different temperatures of 25, 40 and 50 °C. The obtained conversions under these conditions were 83, 87, and 95 % after 80, 50, and 25 min, respectively. Based on the obtained data, a complete design for the process was developed and optimized by using ASPEN HYSYS simulation software. The maximum expected yields of methyl jojoboate, jojobyl alcohol, and methanol recovery were found to be 99.14, 93.3 and 99.9 %, respectively.

Two refractory azo dyes- Congo red and Orange G, especially at high concentrations were subjected to coagulation with different conventional coagulants and newer formulations developed from Aluminum sulfate, Iron (III) chloride, Aluminium chloride, Poly diallydimethylammonium chloride (Poly DADMAC) and Poly Aluminium Chloride (PAC). The highest COD reduction of 99 % was obtained with PAC SAB 18 (Powder Grade PAC) for Congo red at pH 4.5 while the color removal of 99 % was achieved with almost all the coagulants in the present study at specific pH within 3–8. The optimum dose for the iron-based coagulant is 200 mg/L while that of aluminum-based coagulants and PAC is 150–200 mg/L. Results showed that Orange G was more difficult to remove with a maximum COD removal of 65 % and 35 % color removal using various formulations. The combinational formulations of inorganic-inorganic and inorganic-organic produced a substantial enhancement in COD and color removal and reduced sludge. PAC-Fe30/70 produces the minimum sludge of 50 mL/g on Congo red. pH in the range 3–9 showed high reductions in COD and color (90–99 %) for Congo red while jerky rise in COD and color reduction was observed in the case of Orange G after pH 9. An attempt to understand the dye coagulation mechanism has been made based on the specific difference in dye structure and cation speciation.

CFD simulation of cylindrical bubble column including air as dispersed phase and water as continuous phase operating in churn-turbulent flow regime with diameter of 0.49 m, height of 3.6 m and gas superficial velocity of 0.14 m/s have been conducted. All simulations have been carried out in a 2D axisymmetric, unsteady and Euler/Euler framework with the aid of commercial software FLUENT v. 14.5. Simulations were validated by our experimental results through residence time distribution (RTD) data. Effect of bubble size distribution at inlet on column hydrodynamic was investigated and results clearly showed that equilibrium bubble size distribution in most parts of column is independent of bubble size distribution at inlet. In addition, liquid axial velocity and gas hold-up profiles results in column center were approximately the same for cases with different inlet distribution and confirmed similarity of their hydrodynamic.

The degradation of phenolic compounds (PC) by Fe(III) aquacomplexes was investigated in homogeneous phase at neutral pH in dark and using monochromatic irradiation lamp (365 nm). The process of degradation depends essentially on the concentration of monomeric species, which is the most reactive species in terms of HO • radicals formation. A dark study of a system containing a mixture of phenolic compounds (3,5-dimethylphenol, 2,6-dimethylphenol, m-methylphenol, phenol) and Fe(III) was performed before starting the photochemical study. In this step only the 2,6-dimethylphenol give a thermal reaction with iron in homogenous solution. Under monochromatic excitation (365 nm), the photodegradation of PC induced by Fe(III) aquacomplexes showed that this process followed pseudo first-order kinetic. We investigate also the effect of initial concentrations of Fe(OH) 2+ , Fe(III) and the substrate. Tertiobutanol, used as scavenger of (HO • ), confirmed that this radical was the main pathway of PC degradation. However the degradation of the 2,6-dimethylphenol in the presence of tertiobutanol, was not slowed completely which confirm that the degradation was a combination of thermal and photochemical reactions.

This paper proposes a predictive mechanistic model to describe the classical pseudo-homogeneous second order kinetic law; the objective of the model is to study the transesterification process of any triglycerides feed stock into the synthetized biodiesel in a batch reactor, which contains a jacket heat exchanger system and a stirrer. The developed model consists of a set of ordinary differential equations which represent the mass and the energy balance for each chemical component in the reactor, accomplished by the temperature’s dynamics in the heat exchanger system, as well as, a reaction kinetic scheme, where the apparent rate and activation energies follow the Arrhenius equation (Noureddini and Zhu 1997, 1457), and the physical-chemical properties of oils, biodiesel and products have been considered. The physical-chemical properties required for products, intermediates and reactants were estimated implementing molecular group contribution methods. The constants in the reactions rates were taken directly from relevant works oriented to experimental study of the kinetic triglycerides methanolysis. The model’s usefulness was verified comparing the produced results against experimental results obtained in the biodiesel synthesis from sunflower (Vicente et al. 2005, 5447), Brassica carinata (Vicente et al. 2005, 899) and soybean (Noureddini and Zhu 1997, 1457) oils. In each case, the model matched the experimental results. Using the proposed model, it is possible to evaluate how the operating conditions and variables like the type of feed, the temperatures of the reactor and the jacket, the heat transfer, the stirrer rate and the changes on thermophysical properties of the species affect the conversion and reactor performance.

Seventeen carbon sources were screened to identify those with the potential to support pGAP-regulated recombinant enzyme production by Pichia pastoris , using phytase as a model product. Of these, four, namely glucose, glycerol, fructose and ethanol, supported cell growth and enzyme production, and the performance of the latter two was analyzed. Ranges of acceptable residual carbon source concentrations, i.e. those at which no substrate-related growth inhibition occurred, were determined and used to design fed-batch bioreactor-based processes. In fed-batch cultures, fructose supported higher biomass concentrations and equivalent extracellular enzyme activities than glucose. The same metrics for the cultures grown on ethanol were comparable to those of the cultures grown on glucose, but with a greater required fermentation time.

This paper presents a computational procedure for producing tailor made polymer resins, satisfying customers’ needs while operating with maximum profit. The case study is an industrial large-scale polymerization reactor. The molecular properties considered are melt index (MI), which measures the molecular weight distribution, and stress exponent (SE), which is related to polydispersity. An economic objective function is associated to a deterministic mathematical model and the resulting optimization problem is solved by genetic algorithm (GA), a stochastic method. The GA parameters for both binary and real codifications are tuned by means of the design of experiments. Attempting to achieve the global optimum, a hybrid method, which introduces process knowledge into GA random initial population, is proposed. The binary codification performs better than the real GA, especially with hybridization. Results show that the GA can satisfactorily predict tailor made polymer resins with profits up to 25% higher than the industrial practice.

This paper deals with the 3D-modeling of the reactive transport within a light photocatalytic textile used to decontaminate industrial effluents. The model consists of the coupling of fluid flow governing equations, species convection diffusion equations and a heterogeneous reaction equation. It is solved numerically on a Representative Volume Element (RVE) of the textile, i.e. at the microscopic scale regarding the industrial photocatalytic reactor using Comsol Multiphysics software. In a preliminary approach, the reactive transport model was first applied in a 2D simple geometry to verify its accuracy in terms of mass balance of the species. Then successive simulations using pseudo-periodic boundary conditions were performed in the RVE and the depollution efficiency along the textile length is analysed in terms of pollutant concentration. A sensitivity analysis was done to reveal the relative importance of the kinetic and hydrodynamic parameters in prediction of pollutant concentration fields in the RVE. It was found that a high adsorption rate associated with a low permeable fabric maximizes the amount of treated fluid. Finally the performances of a typical reactor composed of a stack of textiles were investigated. Results show a significant improvement of depollution efficiency of this particular configuration compared to single textiles in parallel.

The main objective of the present study is to prepare a chitosan based nanofiber and model the electrospinning process using response surface methodology (RSM). The electrospinning parameters such as collector distance, polymer solution concentration and applied voltage were optimized by using three-variable-three-level Box–Behnken design (BBD). Based on RSM analysis, second order polynomial equation was formed and it indicated good correspondence between experimental and predicted values. 3D response surface plots were used to study the individual and interactive effects of process variables on chitosan based nanofiber diameter. The optimum process conditions for the minimum chitosan based nanofiber diameter (0.3 µm) were found to be collector distance of 12 cm, polymer solution concentration of 25% and applied voltage of 6 kV.

The influence of temperature on the sorption of As(III) onto iron oxide coated quartz sand (IOCQS) was studied in the temperature range of 298–318 K. An increase in temperature was found to have positive influence on the adsorption of As(III) ions onto IOCQS surfaces because of increased diffusion of As(III) ions into the pores of IOCQS at higher temperature. The enhanced sorption at higher temperature indicated endothermic adsorption process. Equilibrium isotherms for the adsorption of As(III) on IOCQS were analyzed at different temperatures. Among the conventional isotherms, Freundlich isotherm best predicted specific uptake at different temperatures, followed by Redlich–Peterson, Langmuir and Temkin isotherm models. Various thermodynamic parameters namely heat of adsorption (∆ H 0 ), change in entropy (∆ S 0 ), and Gibbs free energy change (∆ G 0 ) were computed from the equilibrium constant ( K D ) values. The results indicated positive value for heat of adsorption ∆ H 0 , a positive ∆ S 0 and a negative ∆ G 0 . Finally, the isosteric heat of adsorption (Δ H st,a ) values were calculated and quantitatively correlated with the fractional loading of As(III) onto IOCQS. The surface heterogeneity of adsorbents could be quantitatively described with an isosteric enthalpy function of fractional loading based on Do and Do model. The results show that the IOCQS possesses heterogeneous surface with sorption sites having different activities.

Pipeline transportation is the best way to send the coal slime to circulating fluid bed boilers. The pressure loss of coal slime in pipeline transportation should be calculated accurately which has close relationship with the system design. In this paper, the influencing factors of coal slime pressure loss in pipe flow at high pressure were investigated at a designed test facility. The experimental results show that pressure loss is directly proportional to flow rate, but inversely proportional to pipe diameter. It is also found that the pressure loss has a complex exponential relationship with volume concentration. Based on the results above, a new calculation model for pressure loss of coal slime was built up. The coefficients in the calculation model were determined from the experimental data by means of nonlinear curve fitting step by step. The validity of this calculation model was verified by the experiments carried out on the large-scale circular pipeline transportation system which has the same parameters with industrial application.

Acetates of glycerol have been produced in a heterogeneous reaction system using acidic ion-exchange resin catalysts; Amberlyst-15 (A-15), Amberlyst-16 (A-16), Amberlyst-36 (A-36), Amberlite-IR 120 (A-IR 120) and Relite-EXC8D (R-EXC8D). Effect of reaction temperature on glycerol conversion and product (mono, di and tri glycerol acetates) selectivities were investigated via reaction experiments conducted with glycerol to acetic acid initial molar ratio (G/Ac) of 1/6. Increase in glycerol conversion with an increase in temperature was observed for all catalysts. Among the catalysts investigated, R-EXC8D exhibited the highest activity in the temperature range of 95–150°C. Reaction was completed within a 25 minute short time period.

A detailed, comprehensive mathematical model for bulk polymerization of styrene using multifunctional initiators – both linear and cyclic – in a batch reactor was developed. The model is based on a kinetic mechanism that considers thermal initiation and chemical initiation by sequential decomposition of labile groups, propagation, transfer to monomer, termination by combination and re-initiation reactions due to undecomposed labile groups. The model predicts the evolution of global reaction variables (e.g, concentration of reagents, products, radical species and labile groups) as well as the evolution of the detailed complete polymer molecular weight distributions, with polymer species characterized by chain length and number of undecomposed labile groups. The mathematical model was adjusted and validated using experimental data for various peroxide-type multifunctional initiators: diethyl ketone triperoxide (DEKTP, cyclic trifunctional), pinacolone diperoxide (PDP, cyclic bifunctional) and 1,1-bis(tert-butylperoxy)cyclohexane (L331, linear bifunctional). The model very adequately predicts polymerization rates and complete molecular weight distributions. The model is used to theoretically evaluate the influence of initiator structure and functionality as well as reaction conditions.

An approximate analytical expression for estimating the effectiveness factors of non-catalytic gas-solid reactions is proposed. The new expression is derived from the analytical solution for simple first order reactions (Ishida and Wen 1968. Comparison of kinetic and diffusional models for solid-gas reactions. AIChE Journal 14, 311–317. http://dx.doi.org/10.1002/aic.690140218). The scaled Thiele modulus concept is introduced to account for the variations of the reaction rate form that differs from the first order. The validity of the new expression is demonstrated for the reactions of different orders and of different forms via comparisons against a complete particle-reactor model using the collocation method for solving heat and mass fluxes inside the particles. In addition, the proposed approach is applied to redox reactions of ferric oxide where non-isothermal condition, net consumption of gaseous reactant, and parallel reactions are encountered. The results show that the effectiveness factor method compared well with the orthogonal collocation method over a wide range of Thiele moduli, reaction orders and reaction forms. Therefore, the proposed expression can serve as a generic replacement for more complex and computationally expensive combined particle-reactor modelling which is often employed in reactor systems with significant intra-particle diffusion resistances.

Micromixers are the microfluidic devices able to rapidly mix more than two liquids, with low pressure drop and high mixing efficiency (ε mixing ). In this study, the effect of Reynolds number ratio (Re r ) and aspect ratio (AR) of heart-like biometric micromixer applied would be investigated by a numerical simulation and experimental confirmation. Results show that the heart-like biometric micromixer resulting from the coupling effect of the split and recombination (SAR) and biometric design can produce a high mixing efficiency, low pressure drop and short mixing path under a case of low Reynolds number. Two dimensional results also find that a flow mixing efficiency of ε mixing =0.89 and an optimal mixing index of M idx =115 could be achieved at a flow condition of Re r =0.75 and Re 2 =0.1 of the middle-inlet channel I 2 . In additional, the three dimensional results indicate that a high flow mixing efficiency of ε mixing =0.84 and the lowest pressure drop of 164.2 Pa was obtained at the flow conditions of Re r =0.9 and AR=10 when the middle-inlet channel I 2 was Re 2 =0.1. These findings will be useful to improvement the efficiency for micromixcers of biometric design in the future.

In this study, the hydrogen generation from the hydrolysis of NaBH 4 with Cr 0.0125 -Ni-W-B catalyst prepared in the presence of cold plasma was investigated based on Cr content, NaBH 4 concentration, NaOH concentration, temperature, plasma applying time and plasma gases effects. The results of the activity tests indicate that the choice of Cr and the catalyst composition greatly influenced the activity as well as the selectivity for hydrogen generation from the hydrolysis of NaBH 4. The Cr 0.0125 -Ni-W-B catalyst was treated with argon, nitrogen and carbon dioxide plasma at different treatment times. The catalysts were characterized using SEM, BET surface area measurement and XRD.

The principal deficiency of the widely utilized Alfrey – Price (AP) scheme for computing reactivity ratios in the widely used free radical copolymerization is that it ignores important factors, such as the steric effects. This often leads to inaccurate reactivity ratio predictions by AP model. Accordingly, in this study, exclusively data-driven, Q–e parameter-based new models have been developed for the reactivity ratio prediction in free radical copolymerization. In the model development, a novel artificial intelligence formalism known as “ genetic programming (GP)” that performs symbolic regression has been employed. The GP-based models possess a different functional form than AP model. Further, parameters of GP-based models were fine-tuned using Levenberg–Marquardt (LM) nonlinear regression method. A comparison of AP, GP and GP-LM as well as artificial neural network (ANN)-based models indicates that GP and GP-LM models exhibit superior reactivity ratio prediction accuracy and generalization performance (with correlation coefficient magnitudes close to or greater than 0.9) when compared with AP and ANN models. The GP-based reactivity ratio prediction models developed here due to their higher accuracy and generalization capability have the potential of replacing the widely used AP models.

Micro-kinetic modeling of Pt-catalyzed hydrogen oxidation in a monolithic reactor was carried out for various feed temperatures. The monolith behavior was described by a simplified steady-state model that avoids surface species enthalpy evaluation and does not have temperatures as unknowns. A simplified pseudoarch length method was used to obtain the multiple solution branches for this typical exothermic reaction system. Based on parametric sensitivity and surface species distribution analyses of the micro-kinetic modeling results, macro-kinetic models that involve only gas concentrations were derived and were used to explain the composition effects on ignition temperature.

Methanol catalytic combustion in a mini-scale tubular quartz-made combustor is investigated in this study. An alumina sphere was employed as the support for the platinum catalyst. The experimental results showed that the combustion can be self-ignited at room temperature. Using the combustor wall temperature to characterize the combustor performance, it was found that the combustion temperature can reach a high value within a short time. The experimental results indicated that the combustor performance depends greatly on the fuel/air supply. A higher temperature can be obtained with a higher fuel/air flow rate. The insulated and non-insulated combustor experimental results indicated that heat loss to the environment is an important factor in governing the combustion characteristics due to the large surface/volume ratio. A higher temperature can also be obtained when the combustor is insulated. Because most of the combustion took place at the combustor entrance region, the experimental result suggested that the combustor length can be shortened, leading to a more compact design allowing the combustor integration with various applications. A simple numerical model was built to provide a greater understanding of the combustion characteristics and examine the heat loss effect on combustor performance.

This work investigated the performance of isovaleraldehyde (3-methylbutanal) removal from gas streams in photocatalytic reactors at room temperature. The feasibility of pollutant removal using the up-scaled reactor was systematically assessed by monitoring the removal efficiency at different operational parameters, such as geometries of reactor, air flow rate and inlet concentration. A proposal modeling for scaling up the photocatalytic reactors is described and detailed in this present study. In this context, the photocatalytic degradation of isovaleraldehyde (Isoval) in gas phase is studied. In fact, the removal rate has been compared at different continuous flow reactors: a photocatalytic tangential reactor (PTR), planar reactor and P5000 pilot. The effects of the inlet concentration, flow rate, geometries and size of reactors on the removal efficiency are also studied. A kinetic model taking into account the mass transfer step is developed. The modeling is done by introducing an equivalent intermediate (EI) formed by the photo-oxidation of Isoval. This new approach has substantially improved the agreement between modeling and experiments with a satisfactory overall description of the mineralization from lab to pilot scales.

The goal of this work was to design an adaptive nonlinear proportional–integral (PI) controller to regulate the dynamics of an aerobic wastewater bioreactor, providing a mathematical sketch of proof of the convergence of the control scheme. Adequate operating regions were determined and the corresponding steady-state points were studied via phase portrait and bifurcation analysis. The proposed controller was applied to a wastewater treatment plant to regulate dissolved oxygen (DO) concentration and, indirectly, the concentration of chemical oxygen demand (COD) in the bioreactor; the recirculation flow rate was considered as the manipulated variable. The implementation was based on the mathematical bioreactor’s model, which was experimentally verified; it describes COD dynamics, DO, biomass, recirculation biomass concentrations, and temperature. The obtained results, via numerical simulations, showed that the proposed control law is able to control DO concentration; this control exhibited better performance in comparison to a linear one.

The present work deals with modeling and simulation of a pilot-scale bubbling fluidized bed gasifier (BFBG) for the gasification of high ash Indian coal. Taking into account different stages of coal gasification, such as drying, volatilization, gasification and combustion processes, a two-dimensional model with quadrilateral cells is developed using FLUENT 12.0 software. The model incorporates exchange of mass, momentum and energy between gaseous phase (phase 1) and solid phase (phase 2) using Eulerian–Eulerian approach. The solid phase is described by kinetic theory of granular flows. Four heterogeneous and four homogeneous reactions covering six species in gaseous phase (CO, CO 2 , H 2 , N 2 , O 2 and H 2 O) and coal in solid phase are considered for the above process. The kinetics for the homogeneous reactions are described using eddy dissipation model available in FLUENT while that for heterogeneous reactions, a user-defined function (UDF) with Arrhenius kinetics is written in C language. The validation of the above model has been done using experimental data generated in a pilot-scale BFBG at Center Institute of Mining and Fuel Research (CIMFR), Dhanbad, India. The computed exit gas compositions as well as temperature profile inside the gasifier are in good agreement (within an error band of ±10%) with experimental data. The flow behaviors and volume fraction profiles of gas and solid phases in the bed zone and freeboard zone of the gasifier have also been predicted using this model.

The influence of interparticle forces (IPFs) on the hydrodynamics of a gas–solid fluidized bed was experimentally investigated with the help of a polymer coating approach. The results showed that the presence of IPFs in the bed can considerably change the hydrodynamic parameters. The tendency of the fluidizing gas passing through the bed in the emulsion phase increased with IPFs in the bubbling regime. The performance of a fluidized bed reactor was then studied through simulation of a reactive catalytic system using three different hydrodynamic models: (a) a simple two-phase flow model, (b) a dynamic two-phase flow model, and (c) a dynamic two-phase flow model, integrating the effects of superficial gas velocity and IPFs. The simple two-phase flow model was found to underestimate the reactor performance for catalytic reaction most likely due to the oversimplified assumptions involved in this model. Also, the simulation results showed that modification of the bed hydrodynamics due to IPFs resulted in a better performance for a bubbling fluidized bed reactor. This suggests that the hydrodynamic models should take into account the effects of superficial gas velocity and variation in the ratio of the magnitude of IPFs/hydrodynamic forces, due to any operational reason, to yield a more reliable evaluation of the performance of the fluidized bed reactor.

In this study, a new approach is proposed to investigate the kinetics of sunflower oil and rapeseed oil transesterification in the presence of potassium hydroxide. Transesterification is a heterogeneous process which affected by a number of parameters, that are not readily available in the literature, such as mass transfer coefficients, partition coefficients, and specific surface area of the dispersed phase. However, under intense agitation condition, mass transfer restrictions may be neglected, and the two phases are supposed to remain in thermodynamic equilibrium, during the process. Therefore, a model was developed independent of the mass transfer coefficient and specific surface area, which is reliable for the intense agitation condition. According to the results, the model is valid at least for mixing rates over 500 rpm. The results of the model were used to study the effects of temperature, methanol-to-oil ratio, and catalyst concentration on the biodiesel conversion. Biodiesel production rate increases with increasing temperature, although rapeseed oil transesterification is more temperature dependent. The results show that the maximum amount of catalyst concentration is less than 1% (by weight); however, the optimum value depends on the operating temperature. The optimum value of the methanol-to-oil-ratio decreases with increasing temperature. Thus, at higher temperatures, less amount of methanol and catalyst are required, which leads to easier purification of biodiesel.

In this study, the performance of an extended aeration activated sludge reactor (EAASR) was investigated for the removal of nitrobenzene (NB), a commonly used organic chemical in various industries. In a set of experiments, increasing NB concentrations between 1 and 800 mg/L were applied to the EAASR. Synthetic wastewater containing NB was successfully treated up to 92.0 and 100.0% in terms of chemical oxygen demand (COD) and NB removal. The major NB removal mechanism in this EAASR was assessed to be air stripping after kinetic evaluation as compared to somewhat limited bacterial degradation of NB. Although NB is known to be toxic, the removal efficiency of NB was never below 97.4% even at high NB concentrations. Under lower NB concentrations, it was found that the bacterial floc formation was intact with existing Ciliata and Rotifera . However, at higher NB concentrations, free swimming Ciliata and Rotifera specimens disappeared while the flocs became smaller and dispersed.

The algae biomass is one of the potential biomass resources for extracting lipid to produce fuel. The off grade or residuals of dehydrated algae particles can be used in pyrolysis reactions to produce fuel or useful chemicals. Due to higher ash contents of algae biomass, pyrolysis process needs an appropriate design of pyrolysis reactor. The heating rate of algae biomass is a key factor for increasing of bio-oil production rate. Instead of heat transfer from reactor walls to the biomass, heated inert particles are added to the conventional fluidized bed reactor to increase heat transfer rate and yield of the bio-oil as called flash pyrolysis. The introduced pyrolysis reaction in the novel heating method of fluidized bed reactor studied numerically. For this purpose, an Eulerian-Eulerian CFD model utilized for modeling of the dehydrated algae pyrolysis in the fluidized bed reactor. The appropriate reaction rate of the algae pyrolysis is based on the heating rate, temperature sensitive activation energy and the reaction selectivity utilized to the algae pyrolysis. In addition, the segregation and density change of the biomass particles investigated in the CFD modeling to analysis mixing of the particles and corresponding heat transfer between the mixed particles. The validation of the CFD model investigated using results of prepared experimental setup.

This paper presents a state estimation structure for a Continuous Stirred Tank Reactor (CSTR), by means of an Asymptotic Observer jointly with a disturbance high order sliding mode-based estimator. The proposed estimation scheme allows the asymptotic reconstruction of the concentration inside the reactor based on the measures of the temperature inside the reactor and the temperature inside the jacket, in presence of changes in the global coefficient of heat transfer UA$UA$, the Arrhenius constant k0${k_0}$ and the activation energy E . Additionally, the structure is able to estimate UA$UA$ and the kinetics term k0e−ERT${k_0}{e^{- {E \over {RT}}}}$. The properties of the proposed scheme are proved mathematically and verified through numerical simulations.

The catalytic dehydrogenation of iso-butane to iso-butylene is an equilibrium limited endothermic reaction and requires high temperature. The catalyst deactivates quickly, due to deposition of carbonaceous species and countered by periodic regeneration. The reaction-engineering constraints are tied up with operation and/or technology design features. CATOFIN ® is a sophisticated commercialized technology for propane/iso-butane dehydrogenation using multiple adiabatic fixed-bed reactors having Cr 2 O 3 /Al 2 O 3 as catalyst, that undergo cyclic operations (~18–30m); dehydrogenation, regeneration, evacuation, purging and reduction. It is always a concern, how to maintain CATOFIN ® reactor at an optimum production, while overcoming gradual decrease of heat in catalyst bed and deactivation. A homogeneous one-dimensional dynamic reactor model for a commercial CATOFIN ® fixed-bed iso-butane dehydrogenation reactor is developed in an equation oriented (EO) platform Aspen Custom Modeler (ACM), for operational optimization and process intensification. Both reaction and regeneration steps were modeled and results were validated. The model predicts the dynamic behavior and demonstrates the extent of catalyst utilization with operating conditions and time, coke formation and removal, etc. The model computes optimum catalyst bed temperature profiles, feed rate, pre-heating, rates for reaction and regeneration, fuel gas requirement, optimum catalyst amount, overall cycle time optimization, and suggest best operational philosophy.

The aim of this research is to find the correlation between chemical compositions of biomass, including cellulose, hemicelluloses and lignin, and kinetic rates of biomass combustion. The combustion behavior of biomass constituent was studied by thermogravimetric analyzer. The correlations were generated by means of using Response Surface Methodology based on Simplex-Lattice experimental design. The results obtained from statistical analysis can be used to generate mathematical models and also contour plots which exhibited the relationship between biomass composition and its combustion kinetic. From the observation, the models and contour plots indicated the complexity of combustion mechanism. The correlations proposed by this research were expected to be potentially used to predict combustion behavior in case of real biomass.

In gas-solids risers of fast fluidization regime, the gross particle flux determined by integrating the product of the measured average particle concentration and velocity is always found several times or even larger than that measured by direct experimental methods. Based on analysis of the measurement mechanisms and a simple model for two-phase flow structure in gas-solids risers, this big unidirectional deviation is first explained in depth in this study. It is concluded that the unique two-phase flow structure (i.e. the low-velocity dense phase and high-velocity dilute phase in a gas-solids riser) and the bad coupling quality of the measured transient particle concentration and velocity during data processing lead to this big unidirectional deviation. Finally, this explanation is extended to wider multiphase flow systems and advices are proposed in measuring phase fluxes.

Present work analyses the regeneration of aqueous solutions of glucosamine employed in carbon dioxide capture by gas–liquid absorption by using new methodologies. The aim of the development of these methods is to avoid the aggressiveness shown by the most common one: stripping (e.g. corrosion or degradation). This latest produces an important amine loss and also involves a high energetic cost. This research work has checked the behavior of two new regeneration processes when a thermolabile amine is employed in the chemical solvent for carbon dioxide absorption. These methods are based on the removal of bicarbonate ion and amine deprotonation showing suitable results in comparison with thermal treatment.

In this study, oxidative-extractive desulfurization (OEDS) of liquid fuel has been studied using an ionic liquid prepared by coordination of dimethyl sulfoxide (DMSO) with ZnCl 2 . Synthetic model liquid fuel was prepared by dissolving dibenzothiophene (DBT) in iso-octane. In addition, actual diesel was also tested for total sulfur removal. Oxidation in the OEDS process was achieved by adding hydrogen peroxide and acetic acid to the mixture. Different parameters such as oil to ionic liquid ratio, oxidant to sulfur ratio and temperature were optimized. Kinetic study was performed at different temperatures so as to calculate the reaction rate constants. Optimized conditions were also tested for their applicability on actual diesel. At the optimized conditions (oxidant to sulfur ratio = 6, oil to ionic liquid ratio = 3 and temperature = 30°C), 78% sulfur removal was observed from model oil (initial sulfur concentration = 1,000 mg/L) and 65% sulfur removal was observed for actual diesel oil (initial sulfur concentration = 140 mg/L).