Energy and exergy analyses of power generation via an integrated biomass post-firing combined-cycle

Biomass energy recently has received much attention due to its renewability and relatively low environment impact, both of which suggest it has good prospects as are placement for fossil fuels in the future. Furthermore, biomass gasification reduces problems associated with direct burning of biomass, and the producer gas from the gasification process can be utilised in various power generation systems. In this article, a biomass post-firing combined cycle is proposed and energy and exergy analyses are reported for the cycle. The cycle energy and exergy efficiencies are both determined peak at specific compressor pressure ratio, and increasing the compressor pressure ratio reduces the mass of air per mass of steam in the cycle and, correspondingly, the gas turbine size. With increasing compressor pressure ratio and decreasing gas turbine inlet temperature, the quantity of natural gas required relative to biomass is observed to decrease, while the exergy loss and exergy destruction rates are seen to increase. Furthermore, as the gas inlet temperature to the heat recovery steam generator rises, the exergy destruction rate increases and the exergy loss rate decreases. The highest exergy efficiency is exhibited by the gas turbine and the lowest by the combustor and the condenser.