Modeling of KW-Scale Fuel Cell Combined Heat and Power Generation Systems

With the natural gas as feed stock, the KW-scale fuel cell co-generation system combines hydrogen production, fuel cell power generation and waste heat recovery. It achieves the cascade utilization of natural gas and can satisfy the energy need of residential and small business users for power and hot water services. The process flow diagram for such a system was designed, with auto-thermal reforming of natural gas for hydrogen production. The system was modeled and simulated by Aspen Plus¿. The simulation results for input, output and key process parameters of a typical 1 KW co-generation system were showcased. Influences of the steam to carbon ratio, oxygen to carbon ratio, reformer feed temperature on the system performance, represented by the power generation efficiency, fuel processing efficiency, hydrogen production rate, CO concentration in the syngas and hot water production rate, were analyzed. The results indicate that an optimal operational window of feed temperature range from 450~500°C, steam to carbon molar ratio of 1.75, and oxygen to carbon molar ratio of 0.5 is obtained to achieve electrical efficiency of 28.2%, fuel processing efficiency of 73.3%.