(624e) Systematic Performance Optimization of Hydrogen Production / Power Generation System Based On CO2 Sorption Enhanced Coal/Biomass Gasification

This paper proposes one kind of hydrogen production / power generation system and the performance from the point of view of chemical energy conversion and green house gas (GHG) emissions is investigated. This system has the advantage of nearly zero emission. It is based on CO2 sorption enhanced carbonate materials(coal, biomass, etc.) gasification technique and advanced power generation cycle(gas turbine combined cycle, fuel cell hybrid cycle, etc). The gasification process is divided into two reactors: a fluidized bed gasifier(carbonate materials gasifciaiton/CO2 acceptor) and an absorb regeneration, which are connected by recycling absorbent/heat carrier. In the first reactor, carbon is converted to syngas and meanwhile, CO2 released from this process is absorbed by absorbent. Syngas is mainly composed of 60-90% hydrogen and 10-40% methane. Contents of CO2 and CO can be lower than 1%. In second reactor, used absorbent is calcined. The regenerated absorbent is recycled to the gasifier to absorb CO2 and to provide heat of endothermic reactions. Thus CO2 can be released during calcination process and separated at nearly pure state. Due to lower operation temperature(600°C-1000°C), gasification process is far beyond chemical equilibrium. A gasification kinetics unit model is developed based on main char-gas, gas-gas, absorbent-CO2 reaction kinetics. This model can predict the gas composition, syngas yield, solid(unconverted char, ash, unconverted absorbent, limestone) content in bed materials. Gasification operation conditions (temperature, pressure, calcium to carbon ratio, steam to carbon ratio) will determine carbon conversion ratio, gases qualities and quantity of gasification process. Syngas yield and gas content will then determine performance(thermal efficiency, CO2 emissions) of power generation process. Furthermore, there is complicated mass and heat transfer between different parts. Systematic study is done by way of flowsheet simulation and parameters sensitive studies. Influence of key operation conditions on units and system is analyzed. Results provide ways to system optimization.