Abstract
The combustion of ash-free coal, called "Hyper-coal", prepared by a solvent de-ashing technique leads to a novel coal power generation system with the high thermal efficiency of 48% via a direct firing gas turbine. The coal solvent extraction yield attained about 70% and the ash content decreased below several hundred ppm using a large-scale sample manufacturing equipment. Some trace elements in the ash-free coals made from four kinds of bituminous coals, namely three Australian coals with the low mercury contents of 14-33 ppb and one Chinese coal with the relatively high content of 107 ppb, were quantitatively analyzed using cold vapor AAS for mercury, and ICP-AES or ICP-MS for the other object elements. The mercury content was drastically decreased from 107 to 32 ppb for the Chinese coal, while no apparent difference in the mercury content between the raw and produced ash-free coals was observed for the Australian coals. The residue coal and solvent used for the Hyper-coal manufacturing process were also analyzed for the restricted kinds of coals, but the material balance of mercury hardly attained 100% in the Chinese coal. Possibly, part of the vaporized mercury disappeared by condensation on the wall or other places in the autoclave extractor. The contents of the other trace metals in the ash-free coal were low compared with the corresponding raw coal.
