Low temperature drying of low rank coal by supercritical carbon dioxide with methanol as entrainer

Abstract

Berau coal as lignite was dried with supercritical carbon dioxide. When methanol was added in supercritical carbon dioxide as an entrainer, the extraction rate of water remarkably increased. Methanol added as an entrainer can reduce water contents to half of those of the coal dried with supercritical carbon dioxide and thermally dried coal. The surface area and pore volume of coal slightly decreased with increase in the mole fraction of methanol added in supercritical carbon dioxide. Flash pyrolysis was carried out at 740 °C for 5 s. The tar yield was significantly larger and the char yield was smaller for the coal dried with supercritical carbon dioxide+methanol compared with those dried with supercritical carbon dioxide only and dried thermally.