Distribution and Catalytic Activity of Eutectic Salts in Steam Gasification of Coal

Abstract

The reactivity of coal char in steam is enhanced by the addition of binary and ternary eutectic alkali salts due to their reduced melting points. The catalytic steam gasification of Illinois No. 6 coal was carried out using binary (Na2CO3−K2CO3) and ternary (Li2CO3−Na2CO3−K2CO3) eutectic salt mixtures in a fixed bed reactor at different catalyst loadings. For the same catalyst loading, the ternary catalyst showed higher carbon conversions compared to the binary catalyst. The physical distribution of both catalyst systems on the coal char surface was examined using a scanning electron microscope (SEM). Both catalysts showed uniform dispersion on the ungasified coal matrix indicating homogeneous physical mixing. An attempt has been made to establish a qualitative correlation between the type of catalyst, its distribution, and effect on the overall carbon conversions. Gasified chars were highly porous in nature and coalesce in the case of the binary catalyst whereas the ternary catalyst showed highly porous and crystalline morphology. X-ray diffraction spectra showed the formation of potassium polysulfides (KxSy) in the gasified chars of the eutectic catalyst systems.