03/02098 Effect of acid treatment on thermal extraction for ‘hypercoal’ production: Li, C. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry 2003, 48, (1), 455–456

Abstract

Introduction Thermal extraction using an organic solvent was carried out to produce ashless coal (HyperCoal). HyperCoal is expected to be fired directly in a gas turbine to achieve higher net power output and minimize CO2 emission. The required extraction yield is higher than 60%, and ash content in the HyperCoal is less than 200 ppm, in addition to less than 0.5 ppm sodium and potassium. In our previous work, the extraction yields of higher than 60% were obtained for several bituminous coals using a flow-type extractor at 360C, with nonpolar solvents of 1-methylnaphthalene (1-MN) and Light Cycle Oil (LCO). While, in the case of polar solvents N-methyl-2pyrrolidinone (NMP) and Crude Methylnaphthalene Oil (CMNO) the extraction yields of higher than 80% were attained.The high extraction yields were considered to be mainly due to the heat-induced relaxation of coal aggregates in the case of 1-MN, while in NMP, not only due to the heat-induced relaxation but also solvent-induced one. However, what kinds of coal aggregations were released during the thermal extraction was not clear yet. In addition, these solvents give relatively low extraction yields for some low-rank coals. In the present work, different ranks of coals were acid-treated in organic acids. Effects of acid treatment on the thermal extraction yields and the changes of coal structure were investigated. Furthermore, mechanisms for thermal extraction and acid treatment are discussed.