Artificial Coalification of the Low-Rank Coal in Hokkaido Coals under High Pressure

The present report deals with the artificial coalification of Hokkaido coals such as Tokachi lignite, Tsuchiya lignite and Tenpoku coal under high pressure in order to make crear the mechanism of natural coalification.About 20g of powdered sample of those coals was placed in the stainless steel autoclave of shaking type with 350-380ml of water and the air in the autoclave was replaced with methane. Then the powdered sample in the autoclave was heated at the constant temperature (300°C) and time (24hrs) under different pressure at about 300, 600 and 800kg/cm2.As the results of proximate analyses, structural analyses according to van Krevelen's densimetric method, determination of oxygen containing groups and Lc (002) by X-ray diffraction, it could generally be concluded that those products were hardly affected by pressure at the range of 300-800kg/cm2, but the products prepared from Tokachi lignite, the lowest-rank coal, were affected a little and it seemed that variation during artificial coalification under lower pressure was rather larger than under higher pressure.