Numerical Exergetic Analysis of Different Biomass and Fossil Fuels Gasification

Abstract

In this paper, the effect of fuel composition on gasification exergetic efficiency is investigated with the aid of equilibrium and non-equilibrium models. The work aims at comparing, for different fuels, the second principle theoretical efficiencies of air gasification and oxygen-steam gasification. The study considered several fuels, ranging from coals to biomasses; numerical tests were carried out by an equilibrium model in three gasification conditions: Carbon Deposition Boundary (complete fuel gasification, no solid matter in the products), 1200 K and 1500 K reaction temperature. According to the results obtained, air gasification operated on biomass fuels shows higher exergetic efficiency values compared to oxygen gasification for the Carbon Deposition Boundary and 1200 K conditions tested; this demonstrates the suitability of using air as oxidizer. To provide a complete discussion, a modified equilibrium model able to account for the main non-equilibrium effects was applied to evaluate the exergetic efficiency of biomass fuels under real gasification conditions.