A biomass-based small-scale power generation system with energy/exergy recuperation

Abstract

Small-scale biomass power generation will play an important role in ensuring the regional power supply by using the local biomass resource and protecting the environment in the future. In this study, a small-scale high-efficient combined heat and power generation system with a separated-type biomass gasification process combining the energy/exergy recuperation is proposed for the first time. The spatial subdivision of the processes for the biomass pyrolysis, char combustion, tar reforming and catalyst regeneration is adopted by using a separated-type biomass gasifier design to realize the optimization of each conversion step and improve the whole system performance. To obtain the maximum power generation efficiency, the energy flow and exergy flow in the system are analyzed in details and the operating condition of the gasification system is optimized. The results demonstrate that the relatively low temperature as well as low steam/carbon ratio in the tar reformer should be conducive to the improvement of energy and exergy efficiencies. In the optimum operation condition, the biomass input of 548.86 kW (higher heating value) could generate 263.65 kW of electrical power with the total energy and exergy efficiencies of 37.9% and 43.2%, respectively, in which 153.44 kW of energy could be recuperated back to the gasification process by air and steam with 136.56 kW of energy obtained from gas turbine exhaust to enhance the whole power generation efficiency. It is expected to provide a new design concept for the development of high-efficient small-scale biomass gasification system for the combined heat and power generation.