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Reaction Engineering, Kinetics and Catalysts,
Volume 1, Issue 2 , Summer 2004, Pages 3-10
Abstract
This paper presents the results of an investigation into the treatment of Tehran Refinery effluents in UASB reactors. Four pilot-scale UASB reactors were built with similar dimensions, each with a volume of 45.78 1, and operated in parallel at 37 °C. The sludge seed was prepared from the waste activated ...
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This paper presents the results of an investigation into the treatment of Tehran Refinery effluents in UASB reactors. Four pilot-scale UASB reactors were built with similar dimensions, each with a volume of 45.78 1, and operated in parallel at 37 °C. The sludge seed was prepared from the waste activated sludge of the wastewater treatment unit of the refinery. The organic loading rates were gradually increased from 0.05-0.1 kg COD/m3.d to about 2, 1.5, 0.5 and 1.5 kg COD/m3.d for reactors 1 to 4, respectively, at an influent COD of about 220 mg/l. This is in accordance with hydraulic retention times of 2.5, 4.5 and 8.5 hours for reactors 1 to 3 and 4.5 hours for reactor 4. Methanol was initially added to the reactors in order to increase the microbial activity of the sludge, except for the last one, in order to compare the effect of methanol on start-up. The addition of methanol was stopped after 37 days and the reactors were operated for another 30 days. At this stage, the influent COD was varied between 50-300 mg/l. The results show that the COD removal efficiencies of the reactors are around 30-50%. However, when the influent COD increases above 200 mg/l, the COD removal efficiencies increase up to 70%. It is found that methanol has no significant effect in shortening the start-up period in this case. Scanning Electron Microscopy (SEM) examination and image analysis of the granules of sludge were also performed in order to investigate the structure of granules and the size distribution. Analysis of the biogas shows more than 90% methane content. The results obtained in this research are promising for the anaerobic treatment of refinery wastewaters in UASB reactors.
Full article
Reaction Engineering, Kinetics and Catalysts,
Volume 1, Issue 2 , Summer 2004, Pages 11-18
Abstract
Copper-manganese oxide catalysts are prepared with an atomic ratio of Cu/Mn=2/1 using a coprecipitation procedure under air atmosphere. The time of aging, i.e., the time that precipitate remains in contact with the precipitating medium, has been varied from 0 (for unaged precursor) to 300 minutes and ...
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Copper-manganese oxide catalysts are prepared with an atomic ratio of Cu/Mn=2/1 using a coprecipitation procedure under air atmosphere. The time of aging, i.e., the time that precipitate remains in contact with the precipitating medium, has been varied from 0 (for unaged precursor) to 300 minutes and the effect of precipitate aging time in each atmosphere upon the structure and morphology of different catalysts and their precursors is investigated. The precursors and catalysts were characterized by powder X-ray diffraction (XRD), temperature programmed reduction (TPR) and transmission electron microscopy (TEM). X-ray diffraction and electron microscopy showed that aging of the initial precursor altered the structure of the precursor. The TPR reduction profiles of the copper — manganese mixed oxide catalysts showed a dramatic change of shape on aging. In all catalysts, CuO was completely reduced to metal while the MnO did not reduce under the experimental conditions.
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Transport Phenomena,
Volume 1, Issue 2 , Summer 2004, Pages 19-27
Abstract
The present study attempted deriving and solving the falling- cylinder governing equations for power law model non-Newtonian fluids. Based on this theoretical study, a novel falling- cylinder rheometer (FCR) was designed and constructed to measure the Theological properties of non-Newtonian fluids. Different ...
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The present study attempted deriving and solving the falling- cylinder governing equations for power law model non-Newtonian fluids. Based on this theoretical study, a novel falling- cylinder rheometer (FCR) was designed and constructed to measure the Theological properties of non-Newtonian fluids. Different falling cylinders with predesigned densities were used to determine the apparent viscosity of polyvinyl alcohol (PVA) solutions in water with various concentrations. The results indicate that all PVA solutions obey the power law model with the power law index as well as the consistency index changing linearly with concentration. Increasing concentration of the solution decreases power law index, while enhances consistency index and apparent viscosity.
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Biomedical and Biotechnology,
Volume 1, Issue 2 , Summer 2004, Pages 29-37
Abstract
Immobilization of Lipase produced from Rhizomucor miehei on HDPE fine powder was investigated. As compared to an aqueous system, immobilization in a non-aquous organic medium such as n-hexane was not successful and caused enzyme denaturation. Prewetting the support with ethanol increased the immobilized ...
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Immobilization of Lipase produced from Rhizomucor miehei on HDPE fine powder was investigated. As compared to an aqueous system, immobilization in a non-aquous organic medium such as n-hexane was not successful and caused enzyme denaturation. Prewetting the support with ethanol increased the immobilized protein and enzyme activity as much as 31% and 34%, respectively. The maximum immobilized activity was obtained at the isoelectric pH of 4-5. The enzyme was suspected to have competition and/or interaction with other protein entities on the surface. Immobilization of the enzyme onto the support seems to be via shear sensitive weak physical adsorption. Proper duration of mixing was found to be around 6 minutes. Longer periods of shaking led to enzyme desorption, thereby reducing the immobilized activity. Neither efficiency nor stability was improved using glutaraldehyde as a cross-linking agent despite the fact that in some occasions, protein loading of the support was improved. This suggests the possible effect of glutaraldehyde on enzyme denaturation in these conditions. At optimum conditions, immobilized enzyme activity was enhanced almost 6-folds increasing from 8 units (per 0.5 ml of the enzyme liquor) to about 45.8 units (when 0.5 ml was immobilized on one gram of support).
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Separation Technology,
Volume 1, Issue 2 , Summer 2004, Pages 39-44
Abstract
Recently, use of naturally-occurring low-cost and harmless material for removal of trace contaminants from colored wastewater has attracted extensive attention. In this study, silkworm pupa has been used as a basic dye adsorbent. Adsorption capacity and isotherms have been assessed. Results show that ...
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Recently, use of naturally-occurring low-cost and harmless material for removal of trace contaminants from colored wastewater has attracted extensive attention. In this study, silkworm pupa has been used as a basic dye adsorbent. Adsorption capacity and isotherms have been assessed. Results show that adsorption isotherms can be expressed well by Langmuir equation. The effects of parameters such as pH, temperature, agitation time and speed on the adsorption efficiency were investigated. It was found that among those factors the pH is the most pronounced one. Also the adsorption capacity of pupa towards the various cationic dyes is changed as follows: basic blue >basic yellow >basic red.
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Modeling and Simulation
Volume 1, Issue 2 , Summer 2004, Pages 45-53
Abstract
Arterial stenosis, for example Atherosclerosis, is one of the most serious forms of arterial disease in the formation of which hemodynamic factors play a significant role. In the present study, a 3-D rigid carotid artery with axisymmetric stenosis with 75% reduction in cross-sectional area is considered. ...
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Arterial stenosis, for example Atherosclerosis, is one of the most serious forms of arterial disease in the formation of which hemodynamic factors play a significant role. In the present study, a 3-D rigid carotid artery with axisymmetric stenosis with 75% reduction in cross-sectional area is considered. Laminar blood flow is assumed to have both Newtonian and non-Newtonian behavior (generalized Newtonian fluid), while steady state and pulsatile cases are imposed separately. Governing equations are momentum and continuity. Employing the finite volume technique, flow features such as velocity profiles, flow separation zone and wall shear stress distribution in post stenotic region are calculated. Based on the results of the steady state situation, reverse and circulating flows exist until far from stenosis in Newtonian case. But, in non-Newtonian condition, these regions are limited to smaller areas near the stenosis. As blood flow becomes unsteady, in Newtonian case reverse flows become larger and stronger even far from stenosis while circulating flows weaken. Considering the same assumptions with non-Newtonian behavior, circulating flows become stronger than those of Newtonian model, while reverse flows weaken. Obtained results agree with the analytical results available for Newtonian fluid..
Full article
Modeling and Simulation
Volume 1, Issue 2 , Summer 2004, Pages 55-70
Abstract
SHAHAB is a PC- based simulator developed by Olefin Research Group (ORG), with the simultaneous simulation of the reactor, the firebox, the convection section and the transfer line exchanger in steam Cracking units. The reaction mechanism of thermal cracking of hydrocarbons is generally accepted as free-radical ...
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SHAHAB is a PC- based simulator developed by Olefin Research Group (ORG), with the simultaneous simulation of the reactor, the firebox, the convection section and the transfer line exchanger in steam Cracking units. The reaction mechanism of thermal cracking of hydrocarbons is generally accepted as free-radical chain reactions. Using a rigorous kinetic model, a complete reaction network for representing the decomposition of hydrocarbon feedstocks has been developed and used for simulation of thermal hydrocarbon crackers. Taking into account the kinetics of coke formation, SHAHAB provides a detailed understanding of product, temperature and pressure distribution, coke thickness profile, reactor run length, fuel consumption and the amount of steam generated.