Energy and exergy analysis of a large scale biomass gasification process

The economic value of energy processing depends on both quality and quantity of energy. In case of all thermodynamic energy conversion processes (such as gasification and pyrolysis), the conservation of energy (first law of thermodynamics) and the quality of energy (second law of thermodynamics) are significant. This paper presents energy and exergy analysis of a large scale biomass gasification process based on chemical equilibrium considerations. The gasification model was developed on the basis of Gibbs free energy minimisation approach, controlled by mass and energy balances for the system using Aspen Plus. Wood was used as solid waste biomass for this study. Energy and exergy (available energy) losses were analysed by using the composition of dry biomass. The analysis was carried out in an adiabatic system at atmospheric pressure, with input of biomass and air at ambient conditions and steam at atmospheric pressure and temperature of 25°C. The study found that the exergy efficiency of wood waste is 23% and corresponding energy efficiency is 78%.