Mineralogical examination of the entrained-flow coal gasification residues and the feed coals from northwest China

Abstract

Minerals are the dominant impurities in coal and their changes in gasifiers could cause many problems such as fouling, slagging, and ash deposition. The mineralogy of the coal gasification residues derived from two commercial entrained-flow coal gasification plants from the Ningdong Energy and Chemical Industry Base were determined. A range of minerals were detected by the analyses of X-ray diffraction and scanning electron microscope with associated energy-dispersive X-ray spectrometer (SEM–EDS). The mineral species formed in General Electric (GE) gasification were more abundant than that in the Gaskombinat Schwarze Pumpe (GSP) gasification. The neoformed minerals such as grossular and hedenbergite detected in the residues indicated that the gasification processes share some similarities with magmatism in geological system. The existence of wustite in the GE coal gasification residues indicated the reductive environment in the GE gasifier. Compared to the GSP feed coals, the higher proportions of calcite, pyrite, and siderite and the higher Na contents in the GE feed coals indicated that the ash problems probably happen in the coal-water slurry gasification. Reducing the proportions of those Na-, Ca-, and Fe-containing mineral from the feed coal is necessary for the improvement of the coal gasification process.