Analysis of an updraft biomass gasifier with high temperature steam using a numerical model

Abstract

High temperature steam gasification (HTSG) is a gasification technology which utilizes super-heated steam at a temperature above 1273 K. This paper addresses the performance analysis of an updraft HTSG gasifier using a numerical model. The experimental data obtained from a demonstration-scale gasifier was successfully simulated by the developed model. The calculation results showed 150–300 K temperature difference between gas phase and solid phase throughout the bed. Among a number of reactions, char gasification and water–gas shift reaction at char gasification zone played a major role to determine the syn-gas composition. Steam temperature, the ratio of steam to biomass and biomass feed rate affected the syn-gas composition while biomass particle diameter showed no significant effect. For the steam temperature and the ratio of steam to biomass, the difference of solid temperature at the bottom of gasifier determined the syn-gas composition. For biomass feed rate, the ratio of unreacted char extracted from the bottom of gasifier to supplied biomass determined the syn-gas composition.