Copyright (c) 2009 Berkeley Electronic Press All rights reserved. http://www.bepress.com/ijcre Recent documents in International Journal of Chemical Reactor Engineering en-us Wed, 18 Nov 2009 23:28:43 PST 3600 http://www.bepress.com/ijcre/vol7/A64 http://www.bepress.com/ijcre/vol7/A64 Tue, 17 Nov 2009 04:48:27 PST This paper is concerned with the experimental investigation of stability and emission in a LPG-air premixed coaxial jet burner. By varying the fuel-air ratio in the core flow stream, the flame stability of this coaxial jet flame burner is carried out experimentally, extensively over a wide range of core velocity at 4-16 m/sec. The overall equivalence ratios for all cases are enhanced with the increase in core velocity. An improvement in stability limits are observed with the increase in coflow velocity. However, the NO level for two coflow velocities increases with the increase in core flow velocity which is attributed to the fact that the flame gets stabilized at a higher core equivalence ratio. The flue gas CO2 level is enhanced with the increase in core velocity for three different coflow velocities. The increase in CO2 is mainly due to the combustion of fuel and the subsequent conversion of CO to CO2 in the higher combustion gas temperature. In order to reduce the emission level, the coflow stream is premixed by injecting fuel into the coflow stream with an equivalence ratio even below flammability limits. The stability limit is found to be improved marginally, when the premixed mixture is used in the coflow stream. Interestingly, by using premixed fuel-air mixture in the coflow stream, there is a decrease in NO emission levels. Of course, the use of fuel-air mixtures in the coflow stream enhances the CO2 level. D. P. Mishra combustion http://www.bepress.com/ijcre/vol7/A63 http://www.bepress.com/ijcre/vol7/A63 Tue, 17 Nov 2009 04:48:23 PST The activity of a V-MCM-41 catalyst with a V/Si molar ratio of 0.04 was compared with the activity of a pure MCM-41 catalyst and some DRIFTS studies were performed in order to understand the mechanism of selective oxidation of ethanol. V-MCM-41 was found to be much more active than pure MCM-41, favouring the formation of high amounts of ethylene over 300°C. MCM-41, on the other hand, was found to favour the formation of acetaldehyde over ethylene at all studied temperatures. It was shown by reaction findings that over V-MCM-41, ethylene was produced mainly in the presence of gas phase oxygen whereas acetaldehyde was produced using the lattice oxygen even in the absence of gas phase oxygen. DRIFTS studies indicated the formation of acetaldehyde molecules from acetate-like surface species which were formed by the removal of a hydrogen atom from the α-carbon of chemisorbed ethoxy species by the help of the lattice oxygen. On the other hand, removal of a hydrogen atom from the β-carbon of the ethoxy species, in the presence of gas phase oxygen, resulted in the formation of vinyl-like surface species which then yielded ethylene molecules. Yesim Gucbilmez Reaction Kinetics Catalytic Applications http://www.bepress.com/ijcre/vol7/A62 http://www.bepress.com/ijcre/vol7/A62 Mon, 16 Nov 2009 12:51:07 PST In this work, electrophoretic deposition (EPD) was applied to obtain novel hydroxyapatite (HAP)/lignin (Lig) biocomposite coatings on titanium substrate. Nanosized hydroxyapatite powder, prepared by using the modified chemical precipitation method, was used for the fabrication of HAP/Lig composite coatings. EPD was performed at different values of constant voltage and constant deposition time. It was confirmed that control over deposited mass can be achieved by applied voltage and time. The uniform and compact coatings were successfully deposited at applied voltage of 60 V in various deposition times lower than 1 minute. The effect of lignin as natural non-toxic polymer on microstructure, morphology and thermal behavior of biocomposite HAP/Lig coatings was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The electrophoretically deposited HAP/Lig coating has been successfully sintered at lower sintering temperature of 900°C, producing non-fractured coating and indicating that lignin may exhibit adhesive role, strengthening the bonding between HAP particles and substrate surface. Sanja Erakovic Biocomposite materials http://www.bepress.com/ijcre/vol7/A61 http://www.bepress.com/ijcre/vol7/A61 Wed, 11 Nov 2009 22:45:52 PST The performance of an anaerobic downflow stationary fixed film bioreactor has been simulated mathematically and a software package developed. Each flow channel of the reactor is assumed equivalent to a tubular reactor with a specific degree of axial dispersion. The variation of axial dispersion coefficient along the length of the flow channel (due to the change in gas velocity ) is accounted for and so is resistance to substrate transfer into biofilm which is taken into account by incorporating effectiveness factor into performance equations. Effectiveness factor is computed by numerically integrating the expression for intrinsic rate and the package is applicable to all forms of kinetic equations. Experimental data from pilot plants exhibit encouraging agreement with results predicted by the developed simulation package. Narayanan C.M. Bioprocess Engineering Reactor design Process Analysis and Simulation http://www.bepress.com/ijcre/vol7/A60 http://www.bepress.com/ijcre/vol7/A60 Wed, 11 Nov 2009 22:45:49 PST The hydrodynamics of gas-particle conical fluidized bed containing dried TiO2 micro-size particles were studied experimentally and computationally. The pressure drop was studied by pressure measurements and mean solid velocity in the different axial and radial positions and their experimental values were measured by a parallel 3-fiber optical probe. The Eulerian-Eulerian multiphase model, including kinetic theory of granular flow using Gidaspow (1994) drag function was used in the computational fluid dynamics (CFD) simulation. The frictional viscosity of solids is predicted from the equation proposed by Schaeffer (1987), whereas semi-empirical boundary equations developed by Johnson and Jackson (1987) were applied for the tangential velocity and granular temperature of the solids at the wall. Three different types of boundary conditions (BC), consisting in free-slip/no-friction, no-slip/friction and high-slip/small-friction, were used in this work to compare the results of the model with the experimental data. The numerical predictions using free-slip/no-friction BC agreed reasonably well with the experimental pressure drop measurements, especially at superficial gas velocities higher than the minimum fluidization velocity, Umf. The results for simulated mean axial solid velocity show that the free-slip BC was in better agreement with the experimental data compared with the other boundary conditions. The model also provides reasonable predictions for particle circulation and formation of fountain zone, gulf-effect and air velocity. Alireza Bahramian CFD modeling http://www.bepress.com/ijcre/vol7/A59 http://www.bepress.com/ijcre/vol7/A59 Wed, 11 Nov 2009 22:45:46 PST The optimum design, modeling and simulation of a fixed bed multi-tube reformer for the renewable hydrogen production are carried out in the present paper. The analogies between plug flow model and a fixed bed reactor are used as design patterns. The steam reformer is designed to produce enough hydrogen to feed a 200kW fuel cell system (>2.19molH/s) and considering 85% of fuel utilization in the cell electrodes. The reactor prototype is optimized and then analyzed using a multiphysics and axisymmetric model, implemented on FEMLABM(R) where the differential mass balance by convection-diffusion and the energy balance for convection-conduction are solved. The temperature profile is controlled to maximize hydrogen production. The catalyst bed internal profiles and the effect of temperature on ethanol conversion and carbon monoxide production are discussed as well. Luis E. Arteaga Catalyst Fuel Cells Hydrogen Energy http://www.bepress.com/ijcre/vol7/A58 http://www.bepress.com/ijcre/vol7/A58 Wed, 11 Nov 2009 22:45:41 PST During the last years there has been an increasing interest in using ethanol as a substitute for fossil fuels. The bioethanol used today is mainly produced from sugar cane and cereals, but reducing the production costs of ethanol is still crucial for a viable economic process. Cellulose from vegetable biomass will be the next cheap raw material for second generation fuel ethanol production and agricultural by-products with a low commercial value, as corn stover, corn fiber and cane bagasses would become an attractive feedstock for bioethanol production.In this study, different strains of Saccharomyces cerevisiae have been screened for the ability of bioethanol production. Yeasts were grown in a synthetic liquid medium containing sucrose in batch regime and the growth rates, ethanol and biomass productions were determined as well as their growth ability in cane molasses. The results indicate that a flocculent yeast, isolated in our lab and designated by strain F, was the most promising yeast strain among those tested for continuous ethanol production. This strain was isolated from corn hydrolysates, obtained from a Portuguese distillery facility (DVT, Torres Novas, Portugal) showing highest growth rate (0.49h-1), highest ethanol yield (0.35g/g) and high flocculation capacity. <P> The study on ethanol production in continuous reactor process with the selected yeast strain (strain F) was made on sucrose and cane molasses at different dilution rates (0.05-0.42 h-1). A steady flocculating yeast fluidized bed reactor system was established allowing the functioning of the reactor for 1000 h. Data shows that when the dilution rate rose to 0.42h-1, the highest productivity (20g/Lh) was obtained attaining an ethanol concentration in the reactor of 47g/L for sucrose and molasses media. José Duarte Biochemical Engineering http://www.bepress.com/ijcre/vol7/A57 http://www.bepress.com/ijcre/vol7/A57 Wed, 11 Nov 2009 13:36:48 PST Typical models to estimate effectiveness factors include sphere, cylinder, slab and strong internal diffusion limitations models. However, a reliable model for complex-irregular catalyst shapes is still lacking. Therefore in this work a new approach is proposed which makes simultaneous use of the 1D and GC models to approximate a 3D problem in order to determine the effectiveness factor of a tri-lobular catalytic on a HDS reaction involving diesel. The restrictive internal diffusion phenomena were examined at the cross-section of the catalyst including the effects of its shape. Simulation for the HDS reaction involved the consideration of a small scale reactor using industrial operating conditions. Effects of the intrinsic kinetic, considering strong internal diffusion effects, were calculated through well established computational algorithms. Mathematical simulations of the reaction effectiveness using a given feed-stock of diesel are described completely for a tri-lobular particle considering organic sulfur compound for molecular diffusion, pore size, shape and radial transport across the section of the catalyst and results were validated with models and data published in the literature of typical analysis. M. J. Macías Hernández Catalylsis http://www.bepress.com/ijcre/vol7/A56 http://www.bepress.com/ijcre/vol7/A56 Sun, 08 Nov 2009 18:23:59 PST Particulate matter emissions from diesel-fueled cars, trucks, and buses are regulated by state and federal government agencies. Although improvements in engine performance have taken place, aftertreatment is necessary to meet the existing emissions standards. In order for a particulate emissions control system to function under real driving conditions, real-time model predictive control is needed.As a first step towards this goal, we perform a parametric study to compare two existing models of diesel particulate trap regeneration: a one-dimensional plus time model that tracks gas and solid temperatures and the particulate deposit thickness developed by Bissett (Chemical Engineering Science, 1984, 39, 1233-1244) and a one-dimensional plus time model that uses averaging theory to focus solely on the thermal evolution in the diesel particulate trap developed by Zheng and Keith (AIChE Journal, 2007, 53, 1316-1324). We use both models to predict the ignition time and ignition location within the diesel particulate trap. In this parametric study, three operating parameters are varied: the initial deposit thickness, the exhaust gas flowrate, and the exhaust gas temperature. It was found that the Zheng and Keith model agrees very well with the Bissett model under most operating conditions except when the initial deposit thickness and exhaust gas temperatures are low and the gas flow rate is high. These studies suggest the Zheng and Keith model may be appropriate for real time control of diesel particulate filter regeneration.We then perform a sensitivity analysis of the ignition time and ignition length to changes in the initial deposit thickness and gas flowrate under various conditions using the averaged model. We have found that the ignition time and ignition length are most sensitive to changes in deposit thickness when the deposit thickness and exhaust temperature is low. Also, the ignition time is relatively insensitive to changes in gas flow rate, but the ignition length is most sensitive to changes in gas flow rate at low exhaust temperatures. These studies are useful towards the ultimate development of a predictive particulate emissions control system for diesel-fueled vehicles. Di Huang reactor modeling http://www.bepress.com/ijcre/vol7/A55 http://www.bepress.com/ijcre/vol7/A55 Sun, 08 Nov 2009 18:23:56 PST The aim of this work was to assess the influence of various formulation parameters on the incorporation of Curcumin into nanoparticles. For this purpose, the influence of the aqueous monomer (ethylene diamine, hexamethylene diamine, and 1,4-diaminobutane), as well as the effect of the stirring rate and the influence of the nanoencapsulation method on the encapsulation efficiency were investigated. It was found that variation in the amount of ingredients had profound effects on the curcuminoid loading capacity, the mean particle size, and size distribution. Furthermore, from the thermal results, it is concluded that the reactivity of diamine and the length of flexible methylene chain in diamine determine the thermal properties of resultant polymer wall membrane. The encapsulation yield depends not only on the encapsulation process but also on the chemical structure of the diamine. Whereas, the size and its distribution vary according to the process choice and the emulsification stirring rate. Fabien Salaün