Abstract
In under-developing countries as China, coal is mainly used as an energy source, considerable amount of which is for daily living use. However it is very difficult to equip a desulphurizer to each personal furnace. The air pollution problem there is now serious and is becoming an environmental problem on earth. If clean coal can be obtained at a coal field, the air pollution problem can be cleared. Recently, column floatation has been paid much attention as a prospective technique to remove minerals including inorganic sulphur from coal at a coal field. In this article, the prospective aspects of the column floatation as a coal cleaning process at a coal field is described putting special emphasis on the possible application in under developing countries. The floatation mechanisms are also illustrated on the basis of recent data of column floatation. It was shown that the coal recovery and ash rejection strongly depend on hydrophobicity of coal particles and that a surrounding flow of each bubble plays a roll in catching particles regardless of its hydrophobicity for the case of high gas feed.
