Experimental study on temporal variation of high temperature region and index gas of coal spontaneous combustion

Spontaneous combustion of coal is one of main mine hazards which may result in gas explosion disaster in coal mining operation. In order to study the dynamic variation of the high temperature region of coal spontaneous com- bustion,this paper used a laboratory furnace to simulate the whole process of coal spontaneous combustion from room temperature to the ignition point of coal samples,and analyzed the dynamic rules of the temperature region and index gases comprehensively. The study obtained the following conclusions:in the process of spontaneous combustion of coal,(1) hot spots firstly appeared in the area with low oxygen concentration,and gradually shifted to the area with high ox- ygen concentration,namely hot spots gradually moved from the upper far away from air intake to air intake. At the cry- ogenic stage,hot spots moved down slowly,while,in high-temperature phase,hot spots moved down quickly. Finally hot spots remained in about 3 / 10 height of coal pile;and (2) in the laboratory furnace,the temperatures of various regions are different,so at the same time,the generation rate of index gas showed big differences at different heights. The self- activation reaction stage (130 ℃ ) was determined experimentally. When the temperature reached about 130 ℃ ,hot spots were located at approximately 127 cm (about 6 / 10 height of the coal pile),the generation rates v of all kinds of index gases increased sharply,so 127 cm could be used for the dividing line of generation rates. Above the dividing line,v increased slowly,the production of index gas accounted for a very small proportion of the total;under the divid- ing line,v increased rapidly,the production of index gas accounted for a very large proportion of the total.