Structure and Gasification Property of Coals Extracted with Supercritical CO2/NMP Mixed Solvent

Two coal samples were extracted with supercritical carbon dioxide(SCCO2)/N methyl 2 pyrrolidinone(NMP) mixed solvent. A high extraction yield of 14%(daf) was obtained for Qujing coal while 4%(daf) for Nanlutian coal. The results of characterization of raw and residue coals indicated that the mixed solvent showed high selectivity for hydroxy rich and aliphatic components. The extraction reduced the average stacking height of coal crystallite as well as the swelling ratio of residue coals. After extraction, the BET surface area of Nanlutian lignite decreased while slight increased for Qujing coal. The surface of coal particles was corroded by the mixed solvent. The gasification reactivity was enhanced by extraction for both coals while the change of Qujing coal was more remarkable.