Experimental study of negative pressure gas drainage influences on coal moisture content

Abstract

In the light of water loss phenomena of coal by negative pressure gas extraction, the relationship between time and coal moisture content, rate of water loss in special condition of temperature and negative pressure were studied in laboratory, and the water lose mechanism of coal was analyzed. Results show that the moisture content of Three coals decreased as the negative pressure reaction time increases. In the initial phase, the moisture content of coals descends quickly, afterwards, the decrease trend slows, and finally the moisture content of coals tends to a constant value. The maximum saturated water loss rate reaches 82.19%, and the water loss of coals in experimental conditions is larger. The negative pressure by gas extraction reduces the coal pore gas pressure, and the boiling point and the saturated vapor pressure of water decrease; it increases the free water vaporization (no boiling) rate of coals. Adsorption water and liquid water can change from a liquid to a gas, and it was extracted by negative pressure, and this action would reduce the coal moisture content. The moisture of coal has great affected on dust quantity by mining. A long and continuous gas extraction will result in water loss of coal, and it is of great disservice to the coal mine dust prevention, so it is necessary to take water injection into coal seams or enhanced dust prevention measures after gas extraction.