Coal char particles were successfully burnt in a fluidized bed of silica sand particles whenever both particles were mixed well and char particles were gasified by steam in a sand-free bed without agglomerate formation under conditions of low oxygen concentration.
A horizontal perforated plate was used to devide the fluidized bed into two stages. When the mixture of char and silica sand particles was fluidized in the two-stage fluidized bed, only a small amount of char particles was fluidized within the sand bed while larger amount in the upper stage.
The two-stage gasifier, therefore, was composed of combuster where the char was burnt by air in the bed of silica sand particles, providing the process heat, and a gasifier where char was gasified by steam, producing low-heating-value gas. Coal char particles were fed continuously to the lower stage of the bed and ash particles were discharged from the upper stage.
Experimental data were reported on the carbon gasified, heat conversion and exit gas composition. Results of continuous ash removal tests were also examined briefly for a three-stage fluidized bed gasifier.