Gasification of pulverized coal in a counterflow moving bed filtration combustion reactor: In search of the optimum

Abstract

Air-steam gasification of pulverized coal in filtration combustion mode in a moving bed updraft reactor with a counterflow of solid granular heat carrier is considered theoretically. The pulverized coal is supplied to the middle part of the reactor to be mixed and react with the oxidant gas preheated via heat exchange with the solid heat carrier. The parametric domain for major control parameters, which are the air, steam, and the heat carrier supply rates referred to coal flowrate, providing highly efficient gasification conversion with no char in the products is determined using the approximation of thermodynamic equilibrium of products. The procedure for optimization is proposed for a given composition of coal. The excess heat accumulated with the heat carrier provides an opportunity to evaporate water within the reactor; thus, the steam supply can be replaced with a supply of liquid water improving the overall energy efficiency of gasification. This process, as it secures extended residence of gaseous products in a hot reducing environment and an efficient heat recuperation with the solid heat carrier promises a way to combine the merits of entrained-flow gasification (high throughput and tar-free syngas) with the high energy efficiency of counterflow updraft gasification.