A two-dimensional non-isothermal mathematical model has been developed for the ethane dehydrogenation reaction in a fixed-bed catalytic membrane reactor. Since ethane dehydrogenation is an equilibrium reaction,removal...A two-dimensional non-isothermal mathematical model has been developed for the ethane dehydrogenation reaction in a fixed-bed catalytic membrane reactor. Since ethane dehydrogenation is an equilibrium reaction,removal of produced hydrogen by the membrane shifts the thermodynamic equilibrium to ethylene production.For further displacement of the dehydrogenation reaction, oxidative dehydrogenation method has been used.Since ethane dehydrogenation is an endothermic reaction, the energy produced by the oxidative dehydrogenation method is consumed by the dehydrogenation reaction. The results show that the oxidative dehydrogenation method generated a substantial improvement in the reactor performance in terms of high conversions and signi ficant energy saving. It was also established that the sweep gas velocity in the shell side of the reactor is one of the most important factors in the effectiveness of the reactor.展开更多
A successful design, previously adapted for treatment of complex wastewaters in a microbial fuel cell(MFC),was used to fabricate two MFCs, with a few changes for cost reduction and ease of construction. Performance an...A successful design, previously adapted for treatment of complex wastewaters in a microbial fuel cell(MFC),was used to fabricate two MFCs, with a few changes for cost reduction and ease of construction. Performance and electrochemical characteristics of MFCs were evaluated in different environmental conditions(in complete darkness and presence of light), and different flow patterns of batch and continuous in four hydraulic retention times from 8 to 30 h. Changes in chemical oxygen demand, and nitrate and phosphate concentrations were evaluated. In contrast to the microbial fuel cell operated in darkness(D-MFC) with a stable open circuit voltage of 700 mV, presence of light led to growth of other species, and consecutively low and unsteady open circuit voltage. Although the performance of the MFC subjected to light(L-MFC) was quite low and unsteady in dynamic state(internal resistance = 100 Ω, power density = 5.15 W·m^(-3)), it reached power density of 9.2 W·m^(-3) which was close to performance of D-MFC(internal resistance = 50 Ω, power density = 10.3 W·m^(-3)).Evaluated only for D-MFC, the coulombic efficiency observed in batch mode(30%) was quite higher than the maximum acquired in continuous mode(9.6%) even at the highest hydraulic retention time. In this study,changes in phosphate and different types of nitrogen existing in dairy wastewater were investigated for the first time. At hydraulic retention time of 8 h, the orthophosphate concentration in effluent was 84% higher compared to influent. Total nitrogen and total Kjeldahl nitrogen were reduced 70% and 99% respectively at hydraulic retention time of 30 h, while nitrate and nitrite concentrations increased. The microbial electrolysis cell(MEC), revamped from D-MFC, showed the maximum gas production of 0.2 m^3 H_2·m^(-3)·d^(-1) at 700 mV applied voltage.展开更多
文摘A two-dimensional non-isothermal mathematical model has been developed for the ethane dehydrogenation reaction in a fixed-bed catalytic membrane reactor. Since ethane dehydrogenation is an equilibrium reaction,removal of produced hydrogen by the membrane shifts the thermodynamic equilibrium to ethylene production.For further displacement of the dehydrogenation reaction, oxidative dehydrogenation method has been used.Since ethane dehydrogenation is an endothermic reaction, the energy produced by the oxidative dehydrogenation method is consumed by the dehydrogenation reaction. The results show that the oxidative dehydrogenation method generated a substantial improvement in the reactor performance in terms of high conversions and signi ficant energy saving. It was also established that the sweep gas velocity in the shell side of the reactor is one of the most important factors in the effectiveness of the reactor.
基金supported by Sharif University of Technology,Vice President for Research Grant G930111
文摘A successful design, previously adapted for treatment of complex wastewaters in a microbial fuel cell(MFC),was used to fabricate two MFCs, with a few changes for cost reduction and ease of construction. Performance and electrochemical characteristics of MFCs were evaluated in different environmental conditions(in complete darkness and presence of light), and different flow patterns of batch and continuous in four hydraulic retention times from 8 to 30 h. Changes in chemical oxygen demand, and nitrate and phosphate concentrations were evaluated. In contrast to the microbial fuel cell operated in darkness(D-MFC) with a stable open circuit voltage of 700 mV, presence of light led to growth of other species, and consecutively low and unsteady open circuit voltage. Although the performance of the MFC subjected to light(L-MFC) was quite low and unsteady in dynamic state(internal resistance = 100 Ω, power density = 5.15 W·m^(-3)), it reached power density of 9.2 W·m^(-3) which was close to performance of D-MFC(internal resistance = 50 Ω, power density = 10.3 W·m^(-3)).Evaluated only for D-MFC, the coulombic efficiency observed in batch mode(30%) was quite higher than the maximum acquired in continuous mode(9.6%) even at the highest hydraulic retention time. In this study,changes in phosphate and different types of nitrogen existing in dairy wastewater were investigated for the first time. At hydraulic retention time of 8 h, the orthophosphate concentration in effluent was 84% higher compared to influent. Total nitrogen and total Kjeldahl nitrogen were reduced 70% and 99% respectively at hydraulic retention time of 30 h, while nitrate and nitrite concentrations increased. The microbial electrolysis cell(MEC), revamped from D-MFC, showed the maximum gas production of 0.2 m^3 H_2·m^(-3)·d^(-1) at 700 mV applied voltage.
