Modeling of Gasification Reaction in Pressurized Entrained-Flow Gasifier

Abstract

IGCC is one of the most promising technologies to reduce the environmental impact of coal power generation, and gasification is a key process for IGCC system. Since entrained-flow gasifiers are operated at high temperature and elevated pressure, it is important to clarify coal reactivity in such high-temperature and elevated-pressure conditions. Coal is pyrolyzed rapidly in a gasifier and devolatilization is suppressed by furnace pressure. The changes in char structure because of elevated pressure have been found in a pressurized drop tube reactor (PDTF), and an extended chemical percolation model has been proposed as a useful devolatilization model which is applicable to elevated pressure. Several mechanisms and kinetic models of char gasification with carbon dioxide and/or steam have been proposed, and L-H type reaction rate equations and a random pore model are also useful for char gasification. These kinetic models are applicable to char gasification in Zone II where pore diffusion controlles the observed reaction rate of char gasificaiton. The gasification reaction models discussed in this paper would be useful to evaluate gasification performances in pressurized entrained-flow gasifiers.