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Separation Technology,
Volume 2, Issue 1 , January 2005, Pages 3-9
Abstract
A case study is presented in which two modifications of activated sludge treatment of complex chemical wastewater are experimentally compared: a combination of common activated sludge with powdered activated carbon treatment (PACT), and bioaugmentation of activated sludge treatment (BAST). Industrial ...
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A case study is presented in which two modifications of activated sludge treatment of complex chemical wastewater are experimentally compared: a combination of common activated sludge with powdered activated carbon treatment (PACT), and bioaugmentation of activated sludge treatment (BAST). Industrial wastewater of Pars Oil Refinery that was passed through an oil recovery stage was used to investigate the effect of furfural on two treatment processes in the range between 100-2000 ppm. Furfural was added manually. For comparison, furfural, COD, MLSS (Mixed Liquor Suspended Solids) concentrations and SVI (Sludge Volume Index) were measured daily. The results show a little higher COD removal efficiency in PACT system and the same furfural removal in both methods. But, it should be mentioned that at low HRT (Hydraulic Retention Time), BAST system showed better results in both furfural and COD removal than PACT system. SVI measurement shows that settability of effluent sludge in BAST system was always better than in PACT system. Because of rapid growth of microbial biomass in BAST system, the MLSS concentration in this modification was higher than in PACT system and in this way, BAST system has a lower requirement to return sludge than PACT system. Finally, it could be concluded that BAST system may be an attractive alternative to existing PACT system and if the former is used, it will result in both high performance and optimum conditions with economical operation.
Full article
Separation Technology,
Volume 2, Issue 1 , January 2005, Pages 10-23
Abstract
The effects and influences of various operational parameters on the efficiency of mixer-settlers are thoroughly studied in this paper. One of the most important factors in designing a mixer-settler is to obtain an optimum operational extraction and overall efficiency. These two factors are dependent ...
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The effects and influences of various operational parameters on the efficiency of mixer-settlers are thoroughly studied in this paper. One of the most important factors in designing a mixer-settler is to obtain an optimum operational extraction and overall efficiency. These two factors are dependent on various parameters such as impeller shape, size and speed of impeller, baffle size, residence time, volumetric flow rates and the ratio of heavy to light phases. In this paper, the effect of impeller speed and volumetric flowrates of two phases on efficiency are studied. Also, the effect of hold-up of each stage upon stage efficiency is studied. According to the above experiments and achieved results, it can be concluded that in general, an increase in impeller speed and solvent amount results in an increase in extraction efficiency. Also, when hold-up of the dispersed phase decreases, the stage efficiency usually increases up to a certain point.
Full article
Modeling and Simulation
Volume 2, Issue 1 , January 2005, Pages 24-33
Abstract
A new model to calculate heat eddy diffusivity in separating and reattaching flows based on modification of constant Prt is proposed. This modification is made using an empirical correlation between maximum Nusselt number and entrance Reynolds number. The model includes both the simplicity of Prt=0.9 ...
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A new model to calculate heat eddy diffusivity in separating and reattaching flows based on modification of constant Prt is proposed. This modification is made using an empirical correlation between maximum Nusselt number and entrance Reynolds number. The model includes both the simplicity of Prt=0.9 assumption and the accuracy of two-equation heat-transfer models. Furthermore, an appropriate low Reynolds number k — e model is adopted for calculation of eddy viscosity. The model is used for prediction of Nusselt number distribution at various ranges of Reynolds number and expansion ratio. The numerical results are compared with available experimental data in the literature and have shown good agreement. The CPU time for the present model is about 33% less than that of two-equation heat-transfer model.
Full article
Modeling and Simulation
Volume 2, Issue 1 , January 2005, Pages 31-54
Abstract
General modeling and optimization of syngas production via noncatalytic autothermal partial oxidation of methane are carried out using our developed scientific software which was based on the minimization of total Gibbs energy. In this work, a novel application of the direct search and Newton-Raphson ...
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General modeling and optimization of syngas production via noncatalytic autothermal partial oxidation of methane are carried out using our developed scientific software which was based on the minimization of total Gibbs energy. In this work, a novel application of the direct search and Newton-Raphson methods was introduced to apply to optimization of a complex chemical reaction. Sensitivity analysis was done to investigate the effect of several parameters on the quality of syngas and the production yield. The acceptable concentrations of CO2 and H2O injected into the methane feed are optimized in the specified temperature and pressure range, while H2/CO ratio in the product stream is set to remain at 1.5 or 2, methane slip in the syngas is less than 1.5% and the non-endothermic conversion area of reaction prevail, simultaneously. This facilitates monetizing CO2 in the petrochemical and steel industries. The output from this software is comparable both with the experimental results, cited in Ref [1] , and with that from ASPEN PLUS in simulating the experiments mentioned in Ref [2]
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Modeling and Simulation
Volume 2, Issue 1 , January 2005, Pages 52-60
Abstract
n this paper, a mathematical model has been derived to predict the granulation time of anaerobic sludge in UASB reactors. In the proposed model, some physical, chemical and biological parameters affecting the granulation phenomena have been considered. To validate the model, 12 pilot-scale experiments ...
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n this paper, a mathematical model has been derived to predict the granulation time of anaerobic sludge in UASB reactors. In the proposed model, some physical, chemical and biological parameters affecting the granulation phenomena have been considered. To validate the model, 12 pilot-scale experiments in 4 UASB reactors are carried out and the results are discussed here. The reactors are started up at different environmental conditions and the granulation time in each experiment is determined. The results show that the model is able to explain different mechanisms involved in the granulation process.
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Environmental Engineering,
Volume 2, Issue 1 , January 2005, Pages 61-70
Abstract
This article presents the research results on production and performance of palladium-only catalytic converters. Monolith is used as the catalyst carrier and gamma alumina as the substrate. Dipping method is used for monolith washcoating. Palladium as the active metal is impregnated on gamma alumina ...
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This article presents the research results on production and performance of palladium-only catalytic converters. Monolith is used as the catalyst carrier and gamma alumina as the substrate. Dipping method is used for monolith washcoating. Palladium as the active metal is impregnated on gamma alumina using wet impregnation to produce catalyst samples. The effects of factors such as percent solids in slurry, milling time, calcination time and temperature, pH and existence of Al(NO3)3 on wash-coat characteristics were studied experimentally. SEM, XRD and BET tests were carried out on the samples. Catalyst performance was tested in an experimental reactor that was designed for this research. The results show that catalytic activity increases as calcination time increases, whereas it declines as calcination temperature increases. Furthermore, as the slurry pH decreases, the catalytic activity also decreases. It was observed that impregnation of Al(NO3)3 does not have any effect on catalytic activity.
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Thermodynamics,
Volume 2, Issue 1 , January 2005, Pages 71-81
Abstract
The present study investigates the use of different GE mixing rules in cubic equations of state for prediction of phase behavior of multicomponent hydrocarbon systems. To predict VLE data in multicomponent symmetric and asymmetric mixtures such as systems that contain light gases (nitrogen, carbon dioxide, ...
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The present study investigates the use of different GE mixing rules in cubic equations of state for prediction of phase behavior of multicomponent hydrocarbon systems. To predict VLE data in multicomponent symmetric and asymmetric mixtures such as systems that contain light gases (nitrogen, carbon dioxide, etc.) and heavy hydrocarbons, the SRK equation of state has been combined with excess Gibbs energy models. In this study, the PSRK method, developed by Holderbuom and Gmehling for VLE data prediction, is re-examined. To visualize the effect of different mixing rules in predicting VLE data, Wong and Sandler mixing rule was applied. New group and molecular interaction parameters in UNIFAC and W-S models were introduced. These parameters were obtained by regressing the available VLE data. The results of comparisons between applied models and experimental data are presented. These indicate that although all suggested models could provide reasonably good VLE information for the systems containing components of similar size in a wide range of temperatures and pressures, but only PSRK method shows minimum absolute and relative errors for both vapor and liquid compositions in asymmetric systems.