Simulation Of SOFC-GT Hybrid System With CO₂Capture

The Solid Oxide Fuel Cell (SOFC) is a promising technology for electricity generation. It converts the chemical energy of the fuel gas directly to electricity energy and therefore, very high electrical efficiencies can be achieved. The high operating temperature of the SOFC also provides excellent possibilities for cogeneration applications. The exhaust temperature of SOFC compatibility turbine inlet temperature of the gas turbine(GT), they are composed of hybrid systems, can further improve the overall system efficiency. For the hybrid system, the ideal fuel is natural gas, exhaust gas contains a certain amount of CO2. With the development of computer technology, computer simulation study is an effective method of SOFC-GT hybrid system. With the help of the Aspen Plus process simulation software, mainly inseach in the following aspects:(1) In order to make full use of the existing features of the Aspen Plus, introduct the SOFC cell stack model and the direct oxidation of dry methane cell stack model which based on natural gas feed tubular internal reforming. The simulation results show that compared with the SOFC of reforming unit, the SOFC of dry methane direct oxidation not only simplify the device, also improve the battery performance and the efficiency of the battery. The efficiency of dry methane direct oxidation battery can reach75.39%while the the fuel efficiency is85%, it is only49.18%of the pre-restructuring battery, the efficiency is improved by about26.21%;(2)Depending on the working pressure of SOFC,established compression model and atmospheric model of SOFC-GT hybrid systems. The two models is also divided into the SOFC of a reforming unit and the SOFC of dry methane direct oxidation. The results showed that the SOFC-GT hybrid device can improve the efficiency of the system, fully use the energy. The atmospheric model system efficiency higher than the pressure model;(3)Depending on the exhaust CO2capture technology, combined with the hydrogen selectivity and oxygen selective semi-permeable membrane, builded the establishment of Water Gas Shift Membrane Reactor model and Oxygen Conducting Membrane model. Each model is divided into a pressurized model and atmospheric model, and were done with a reforming unit and dry methane direct oxidation in these two areas. The simulation results show that efficiency of Water Gas Shift Membrane Reactor model and the Oxygen Conducting Membrane model higher than traditional chemical absorption method. But the difference between the two models depended on the fuel cell operating temperature, pressure, fuel utilization and compressor pressure ratio. Pressure model in the range of800to1000℃, WGSMR system efficiency has been higher than OCM model. The fuel utilization rate is low, system efficient of WGSMR model high more the OCM model. The system efficient of OCM model more higher when high fuel efficiency. Atmospheric model, in the temperature range of800to1000℃, WGSMR model and system efficiency of the OCM model difference is not obvious. Both system efficiency reaches its maximum when the air compressor pressure ratio is4.Simulation results show that not only in solid oxide fuel cell power generation efficiency, but also in CO2capture also has a bright future.