The electromotive force （e.m.f.） of solid oxide fuel cells using biomass produced gas （BPG） as the fuels is calculated at 700-1,200 K using an in-house computer program, based on thermodynamic equilibrium analysis...The electromotive force （e.m.f.） of solid oxide fuel cells using biomass produced gas （BPG） as the fuels is calculated at 700-1,200 K using an in-house computer program, based on thermodynamic equilibrium analysis. Tour program also predicts the concentration of oxygen in the fuel chamber as well as the concentration of equilibrium species such as H2, CO, CO2 and CH4. Compared with using hydrogen as a fuel, the e.m.f. for cells using BPG as the fuels is relative low and strongly influenced by carbon deposition. To remove carbon deposition, the optimum amount of H2O to add is determined at various operating temperatures. Further the e.m.f, for cells based on yttria stabilized zirconia and doped ceria as electrolytes are compared. The study reveals that when using BPG as fuel, the depression of e.m.f, for a SOFC using doped ceria as electrolyte is relatively small when compared with that using Yttria stabilized zirconia.展开更多
An experimental study of the treatment of plastic-contained Japanese MSW （municipal solid waste） employing 1 ton capacity hydrothermal reactor to produce chlorine-free solid fuel has been performed. The system appli...An experimental study of the treatment of plastic-contained Japanese MSW （municipal solid waste） employing 1 ton capacity hydrothermal reactor to produce chlorine-free solid fuel has been performed. The system applies medium-pressure saturated steam at about 2 MPa in a stirred reactor for certain holding period. It was shown that the products exhibited organic chlorine conversion into inorganic chlorine, which can then be water washed. To obtain an optimal operating condition, the temperature and holding period was integrated into one parameter called RS （reaction severity）. It was found that to convert 75% organic chlorine in the MSW, the optimum RS number correlates to an operating temperature of about 225℃ and holding period of 90 min, or 235 ℃ for 60 min. Since hydrothermal treatment is a batch process, a shorter holding period is preferable to increase the number of batches and indirectly increase its processing capacity.展开更多
Thermodynamic analyses in the literature have shown that solid oxide fuel cells(SOFCs) with proton conducting electrolyte(H-SOFC) exhibited higher performance than SOFC with oxygen ion conducting electrolyte(O-SOFC).H...Thermodynamic analyses in the literature have shown that solid oxide fuel cells(SOFCs) with proton conducting electrolyte(H-SOFC) exhibited higher performance than SOFC with oxygen ion conducting electrolyte(O-SOFC).However, these studies only consider H2 electrochemical oxidation and totally neglect the contribution of CO electrochemical oxidation in O-SOFC. In this short communication, a thermodynamic model is developed to compare the theoretically maximum efficiencies of H-SOFC and O-SOFC, considering the electrochemical oxidation of CO in O-SOFC anode. It is found that O-SOFC exhibits a higher maximum efficiency than H-SOFC due to the contribution from CO electrochemical oxidation, which is contrary to the common understanding of electrolyte effect on SOFC performance. The effects of operating temperature and fuel utilization factor on the theoretical efficiency of SOFC are also analyzed and discussed.展开更多
Steady-state model of a high-temperature solid oxide fuel cell （SOFC） is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversi...Steady-state model of a high-temperature solid oxide fuel cell （SOFC） is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversible value is attributed to polarizations and imperfect conversions of reactions. An imperfect power formula summarizes the effect of transport laws, irreversible polarizations and efficiency of power yield. Reversible electrochemical theory is extended to the case with dissipative chemical reactions; this case includes systems with incomplete conversions, characterized by ＂reduced affinities＂ and an idle run voltage. Efficiency drop is linked with thermodynamic and electrochemical irreversibilities expressed in terms of polarizations （activation, concentration and ohmic）. Effect of incomplete conversions is modeled by assuming that substrates can be remained after the reaction and that side reactions may occur. Optimum and feasibility conditions are discussed for basic input parameters of the cell. Calculations of maximum power show that the data differ for power generated and consumed and depend on current intensity, number of mass transfer units, polarizations, electrode surface area, average chemical rate, etc.. These data provide bounds for SOFC energy generators, which are more exact and informative than reversible bounds for electrochemical transformation.展开更多
Biomass in the form of nutshell, hay of catkin, wheat straw and linseed residue in particles have been pyrolyzed in laboratory scale fixed bed reactor which yielded liquid oil, solid char and gas. The variation of oil...Biomass in the form of nutshell, hay of catkin, wheat straw and linseed residue in particles have been pyrolyzed in laboratory scale fixed bed reactor which yielded liquid oil, solid char and gas. The variation of oil yield for different biomass feedstock with reactor bed temperature and feed size is presented in this paper. A maximum liquid yield of 55 wt% of dry feedstock is obtained at an optimum temperature of 500℃ for a feed size of 300-600μm with a running time of 55 min for nutshell as the feedstock while the minimum liquid oil yield is found to be 30 wt% of feedstock at an optimum temperature of 400℃ for a feed size of 2.36 mm with a running time of 65 min for linseed residue as the feedstock. A comparison on the product yields is highlighted in this study. The pyrolysis liquid products are characterized and compared for some of the fuel properties like HHV （higher heating value）, viscosity, density and specific gravity.展开更多
基金V. ACKN0WLEDGMENT This work was supported by the National Natural Science Foundation of China （No.50372066 and No.50332040）.
文摘The electromotive force （e.m.f.） of solid oxide fuel cells using biomass produced gas （BPG） as the fuels is calculated at 700-1,200 K using an in-house computer program, based on thermodynamic equilibrium analysis. Tour program also predicts the concentration of oxygen in the fuel chamber as well as the concentration of equilibrium species such as H2, CO, CO2 and CH4. Compared with using hydrogen as a fuel, the e.m.f. for cells using BPG as the fuels is relative low and strongly influenced by carbon deposition. To remove carbon deposition, the optimum amount of H2O to add is determined at various operating temperatures. Further the e.m.f, for cells based on yttria stabilized zirconia and doped ceria as electrolytes are compared. The study reveals that when using BPG as fuel, the depression of e.m.f, for a SOFC using doped ceria as electrolyte is relatively small when compared with that using Yttria stabilized zirconia.
文摘An experimental study of the treatment of plastic-contained Japanese MSW （municipal solid waste） employing 1 ton capacity hydrothermal reactor to produce chlorine-free solid fuel has been performed. The system applies medium-pressure saturated steam at about 2 MPa in a stirred reactor for certain holding period. It was shown that the products exhibited organic chlorine conversion into inorganic chlorine, which can then be water washed. To obtain an optimal operating condition, the temperature and holding period was integrated into one parameter called RS （reaction severity）. It was found that to convert 75% organic chlorine in the MSW, the optimum RS number correlates to an operating temperature of about 225℃ and holding period of 90 min, or 235 ℃ for 60 min. Since hydrothermal treatment is a batch process, a shorter holding period is preferable to increase the number of batches and indirectly increase its processing capacity.
基金Supported by Hong Kong Research Grant Council(PolyU 5238/11E)
文摘Thermodynamic analyses in the literature have shown that solid oxide fuel cells(SOFCs) with proton conducting electrolyte(H-SOFC) exhibited higher performance than SOFC with oxygen ion conducting electrolyte(O-SOFC).However, these studies only consider H2 electrochemical oxidation and totally neglect the contribution of CO electrochemical oxidation in O-SOFC. In this short communication, a thermodynamic model is developed to compare the theoretically maximum efficiencies of H-SOFC and O-SOFC, considering the electrochemical oxidation of CO in O-SOFC anode. It is found that O-SOFC exhibits a higher maximum efficiency than H-SOFC due to the contribution from CO electrochemical oxidation, which is contrary to the common understanding of electrolyte effect on SOFC performance. The effects of operating temperature and fuel utilization factor on the theoretical efficiency of SOFC are also analyzed and discussed.
文摘Steady-state model of a high-temperature solid oxide fuel cell （SOFC） is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversible value is attributed to polarizations and imperfect conversions of reactions. An imperfect power formula summarizes the effect of transport laws, irreversible polarizations and efficiency of power yield. Reversible electrochemical theory is extended to the case with dissipative chemical reactions; this case includes systems with incomplete conversions, characterized by ＂reduced affinities＂ and an idle run voltage. Efficiency drop is linked with thermodynamic and electrochemical irreversibilities expressed in terms of polarizations （activation, concentration and ohmic）. Effect of incomplete conversions is modeled by assuming that substrates can be remained after the reaction and that side reactions may occur. Optimum and feasibility conditions are discussed for basic input parameters of the cell. Calculations of maximum power show that the data differ for power generated and consumed and depend on current intensity, number of mass transfer units, polarizations, electrode surface area, average chemical rate, etc.. These data provide bounds for SOFC energy generators, which are more exact and informative than reversible bounds for electrochemical transformation.
文摘Biomass in the form of nutshell, hay of catkin, wheat straw and linseed residue in particles have been pyrolyzed in laboratory scale fixed bed reactor which yielded liquid oil, solid char and gas. The variation of oil yield for different biomass feedstock with reactor bed temperature and feed size is presented in this paper. A maximum liquid yield of 55 wt% of dry feedstock is obtained at an optimum temperature of 500℃ for a feed size of 300-600μm with a running time of 55 min for nutshell as the feedstock while the minimum liquid oil yield is found to be 30 wt% of feedstock at an optimum temperature of 400℃ for a feed size of 2.36 mm with a running time of 65 min for linseed residue as the feedstock. A comparison on the product yields is highlighted in this study. The pyrolysis liquid products are characterized and compared for some of the fuel properties like HHV （higher heating value）, viscosity, density and specific gravity.
