EQUILIBRIUM MODELING OF A DOWNDRAFT GASIFIER II—FLAMING-PYROLYSIS ZONE

Abstract

An equilibrium model has been applied to the flaming-pyrolysis (FP) zone, the most important and active zone, in a downdraft biomass gasifier. The model predicts the temperature, gas composition and char yield at the exit of the FP zone for a set of specified fuel material, heat loss and input condition. Based on the model, a parametric study has been conducted to simulate the influences of the air/feed mass ratio (A/F), moisture/feed mass ratio (W/F), heat loss rate, and the volatility of the biomass fuel over feasible ranges of these parameters. It has been found: a) the A/F has a tremendous influence on the performance of the FP zone, and the minimum A/F required to completely pyrolyze the biomass fuel in the FP zone is approximately 1.2; b) high W/F and high heat loss rate result in a low temperature in the FP zone, which in turn may prevent the biomass fuel from being completely pyrolyzed in the FP zone, and c) biomass fuel with very low volatile content may result in an excessively high temperature ...