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Fuel Processing Technology, Vol.46, No.2, 143-155, 1996
Supercritical desulfurization of high rank coal with alcohol/water and alcohol/KOH
A high rank coal with total sulfur of 4.90% was extracted employing alcohol/KOH and alcohol/water under supercritical conditions both in a semi-continuous reactor and in a batch reactor. In the semi-continuous reactor it was found that supercritical desulphurization is mainly taking place within about one hour at 400 degrees C. Pretreatment of coal with KOH up to 5% concentration was favourable for sulfur removal, but greater KOH concentration and longer soaking time brought about the opposite results. When the ethanol concentration was 95 vol% the organosulfur removal achieved the maximum. Ethanol/KOH solution as supercritical solvent enhanced the desulfurization process, in which the inorganic sulfur was removed preferentially. In the batch reactor it was found that there was reincorporation of both organic sulfur and inorganic sulfur. KOH addition can improve the sulphur removal greatly. When KOH/coal ratio was greater than 0.5, the tendency for sulfur removal was gradually slow.
Keywords:EXTRACTION