فهرست مطالب

Chemical Engineering - Volume:8 Issue: 2, Spring 2011

Iranian journal of chemical engineering
Volume:8 Issue: 2, Spring 2011

  • تاریخ انتشار: 1390/07/03
  • تعداد عناوین: 8
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  • M. Pirdashti, M. Omidi, H. Pirdashti, M. H. Hassim Pages 3-17
    Today, the advantage of biotechnology, especially from an environmental aspect, is undeniable compared to other technologies. Kimia Gharb Gostar Industries Company (KGGICO) - the largest producer of citric acid in the Middle East, is one of the companies that applies biotechnology. Citrogypsum is a by–product of citric acid production and is considered a valid residuum of this company. In this paper, acid citric production and condition of citrogypsum production in the company were introduced besides the definition of citrogypsum production and its applications around the world. Based on this information and the evaluation of present conditions regarding Iran’s demands for citrogypsum, the best priority was introduced, and strategy selection and proper programming emphasized for self-sufficiency. The Delphi technique was used to elicit expert opinions about the criteria for evaluating the usages. The criteria identified by the experts were profitability, capacity of production, the degree of investment, marketable, production ease, and time of production. The Analytical Hierarchy Process (AHP) and Expert Choice software were used to compare the alternatives based on the criteria derived from the Delphi process.
  • B. Vaferi, A. Jahanmiri Pages 18-28
    Differential Evolution algorithm (DE), one of the evolutionary algorithms, is a new optimization technique capable of handling non-differentiable, non-linear and multimodal objective functions. DE needs a large run time for optimizing the complex objective function. Thus, an attempt to speed up DE is necessary. This paper introduces a modification on original DE that enhances the convergence rate by reducing vector dispersal at any iteration. Our Adaptive Differential Evolution algorithm (ADE) utilizes variable scaling parameter (F) against constant scaling parameter in original DE at any iteration. The proposed ADE is applied to optimize three non-linear chemical engineering problems. The obtained results have been compared with those results obtained using DE. The considered comparison criteria are the vectors dispersal, convergence history (run time and number of iterations that led to reach to global optimum) and error in any iteration. As compared to DE, ADE is found to perform better in locating the global optimal solution, reduces the memory and computational efforts by reducing the number of iterations required to reach the global optimal solution for all the considered problems.
  • G. Sheibani, F. Naeimpoor, P. Hejazi Pages 29-40
    Soil contamination with TNT is a serious environmental hazard due to the toxic and mutagenic effects of TNT. Bioremediation is an environmentally safe method in the treatment of explosive-contaminated sites. In the present research, after selection of superior bacteria in the aqueous phase, bioremediation of TNT contaminated clay soil at 1000mg/kg was performed in slurry phase, which resulted in a maximum TNT removal of 89% after 15 days. Afterwards, the effects of operational and environmental factors were examined via the two-level fractional factorial design method () for seven factors, i.e., glucose (2, 8g/l), yeast extract (0, 0.2g/l), (NH4)2SO4 (0.1, 0.5g/l), Tween80 (1, 5g/l) and slurry concentrations (20, 40%w/v) as well as inoculum size (5, 10%v/v) and temperature (20, 35˚C). Among these factors, significant factors were found to be slurry, surfactant and glucose concentrations as well as inoculum size. In addition, considerable interactions were observed between glucose and the other significant factors.
  • A. Khosravan, B. Lashkari Pages 41-56
    The biosorption of Cd(II) ions from aqueous solutions by dried activated sludge was investigated as a function of initial pH, initial cadmium ion concentration, adsorbent mass, adsorbent particle size and temperature. Biosorption experiments were performed using activated sludge of the systems of wastewater refining of milk factory. The results showed that increasing the initial pH from 2 to 5.5 and the adsorbent mass from 0.5g to 2g increased the removal efficiency from 11% to 68% and 68% to 79% respectively. Increasing the adsorbent particle sizes from smaller than 0.063mm to greater than 0.5mm and the initial cadmium ion concentration from 15ppm to 120ppm decreased the removal efficiency from 77% to 67% and 80% to 54% respectively. The equilibrium data fitted both the Langmuir and Freundlich adsorption models, but the Freundlich isotherm was found to fit the experimental data slightly better than the Langmuir isotherm. The characteristic parameters for each isotherm have been determined. Maximum adsorption capacity (q0) was calculated at different temperatures (303, 318, and 333 K) 1.283, 1.581 and 1.726 mg/g, respectively. The dimensionless separation factor (RL) showed that the activated sludge of milk factory can be used for the removal of cadmium ions from aqueous solutions. The results (n, RL) represented good and favorable adsorption. Therefore, the activated sludge could remove Cd(II) ions effectively from aqueous solution.
  • P. Pirie, F. Naeimpoor, P. Hejazi Pages 57-68
    Contamination of soils with nitroaromatic hydrocarbons, due to their toxic effects, is one of the environmental issues. Therefore, the purpose of this study is to examine para-nitrophenol (PNP) biodegradation in a microcosm consisting of kaolan clayey soil by A. faecalis, the superior bacterium among the four examined bacterial species. Preliminary experiments were performed in slurry phase to investigate biodegradation of PNP by A. faecalis in shaking flasks at initial concentrations of 25 and 50mgkg-1 which resulted in 72 and 57% PNP removals after 20 days, respectively. To identify the effective factors on PNP biodegradation, experiments were carried out in shake flasks at various levels of eight factors, i.e. PNP, glucose and yeast concentrations, temperature, soil-water ratio, initial pH, inoculum size as well as PNP concentration in pre-exposure based on Plackett-Burman design method. Results showed 20.9 up to 75.5% PNP removal in soil slurry after 12 days within the design space. Analysis of variance revealed that temperature, inoculum size, yeast extract concentration, pH and soil-water ratio are the most effective factors on PNP biodegradation, respectively.
  • M. Bayat, F. Rahmani, T. Ghiyami, M. R. Rahimpour Pages 69-80
    In this paper, a heterogeneous one-dimensional model for simulation of cascade methanol reactor has been developed, while the various percent of CO was injected to these reactors. In the cascade reactor configuration, a system with two-catalyst bed instead of one single catalyst bed is applied for methanol synthesis. In the first catalyst bed, the synthesis gas is partly converted to methanol in a water-cooled reactor. In the second bed, which is a gas-cooled reactor, the reaction heat is used to preheat the feed gas to the first bed. In this study, the various percent CO injections of feed entrance (1% and 2%) to different reactors (first and second reactor) of conventional dual type methanol reactor have been considered. The simulation results represent 5.127% and 4.158% enhancement in the yield of methanol production in comparison with conventional dual type methanol reactor (CDMR) and membrane dual type methanol reactor (MDMR) respectively, while 2% CO was injected to the first reactor. Also, by CO injection to the feed, water produced during methanol synthesis via CO2 hydrogenation which accelerates the catalyst deactivation and reduces methanol production rate, is reduced greatly.
  • E. Ebrahimnia-Bajestan, H. Niazmand Pages 81-97
    In the current study, numerical simulation of laminar flow and heat transfer of water mixture with carbon nanotubes (CNT) as nanofluids in a 90 degree curved pipe are considered. The incompressible Navier-Stokes and energy equations are solved numerically in a body fitted coordinates system using a control volume technique. An interfacial layer-based model is applied to predict the thermal conductivity of nanofluid. The axial velocity contours, secondary flow patterns and temperature fields for different values of the particles concentrations are examined in detail. Furthermore, the effects of nanoparticles concentration on the heat transfer are studied. The results indicate that due to the secondary flows induced by curvature effects, the heat transfer rate is improved, and enhanced remarkably further using nanofluids. Furthermore, the nanoparticles, especially at higher concentration levels, generate more uniform cross sectional temperature distributions.
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