Thermodynamic Equilibrium Model and Exergy Analysis of a Biomass Gasifier

Abstract

Biomass gasification involves the production of a gaseous fuel by partial oxidation of a solid fuel. Clean synthesis (syn) gas, produced from partial combustion of biomass, can be burnt in a gas turbine combustion chamber to run a biomass based combined cycle power plant. A thermochemical model has been developed to predict the gas composition and performance of a biomass gasifier based on thermodynamic equilibrium concept for different biomass materials. A simplified numerical method is applied to solve the thermochemical equilibrium reactions. The system consists of a pressurized circulating fluidized bed to produce the syn gas from the biomass. The effect of the relative air fuel ratio (RAFR), steam fuel ratio (SFR), and gasifier pressure has been examined on the gas composition, gasifier temperature, lower heating value of syn gas, and exergy efficiency of biomass gasifier to obtain a high yield from the biomass. It has been found that at lower values of RAFR and SFR, the heating value of the syn gas and the exergy efficiency of gasifier is high.