Syngas production from co-gasification of coal and biomass

Abstract

In this work, the co-pyrolysis and co-gasification of Indonesian coal (sub-bituminous) and two types of biomass (rice straw and Leucaena leucocepha) were studied using a drop-tube fixed bed reactor. The synergetic effect in co-processing was manifested by the higher gas yield and lower tar yield compared to the predicted values from the experiments which used either coal or biomass alone. Results showed that the synergetic effect was found especially at a biomass and coal ratio of 1:1 and became more apparent when reaction temperature was increased. In addition, interaction between coal char and volatile derived from biomass was examined in a rapid heating thermobalance reactor. Three types of coal char were prepared i.e. slow pyrolyzed-coal char (Ex-char), fast pyrolyzed-coal char (In char) and acid washed-coal char (Ac-char) and three types of volatile sources were used (cellulose, xylan and rice straw). The results indicated that the steam gasification rate of Ex-char and In-char were significantly diminished by contacting with volatiles derived from all sources, especially from rice straw. However, in the case of Ac-char, the reduction of steam gasification rate with the appearance of volatiles was less dominant. It was due to the destruction of coal char structure and the loss of minerals on coal char surfaces. Moreover, the effect of coal char on the decomposition of biomass derived tar was also investigated in a two-stage fixed bed reactor. It was found that coal char exhibited the catalytic effect both on tar thermal cracking and tar steam reforming. Nevertheless, the catalytic role of char which was prepared under high pyrolysis temperature was less significant due to the loss of active structure on char. The obtained results will be useful for the effective design and operation of co-processing of coal and biomass.