Pre-evalution research of using coal seam water injection to control strong pressure in Zhaozhuang Coal Mine

In order to assess effect of using coal seam water injection to control strong pressure of No.3 coal seam of Zhaozhuang Coal Mine, pre-evaluation research of using coal seam water injection to control strong pressure was carried out. Water injection parameters including moisture content, water absorption, firmness coefficient of coal sample and so on were tested to analyze feasibility of water injection of No.3 coal seam. Absolute variation and change rate of compressive strength of test sample before and after soaking were test to analyze expected pressure-relief effect of water injection and propose injection project. The analysis result shows that No.3 coal seam can meet the conditions of water injection, and after soaking, physical properties of coal and rock samples are changed, compressive strength is reduced greatly, which indicates water injection has desired expected pressure-relief effect

Analysis of combustion duration and residual gas in secondary explosion of coal dust

Secondary explosion experiments of coal dust were carried out by use of 20 L spherical explosion device under the conditions of different coal dust concentration, particle size and ignition energy separately, and influence of coal dust concentration, particle size and ignition energy on combustion duration and residual gas was analyzed. The results show that under the same conditions, the secondary explosion combustion duration(T2) of coal dust is greater than the first explosion combustion duration(T1). Ignition energy has the greatest influence on T2, and coal dust particle size has the least influence. With increase of coal dust concentration, T2 first decreases and then increases. With decrease of coal dust particle size or increase of ignition energy, T2 decreases continually. For the same kind of gas under the same conditions, volume fraction of residual gas after the secondary explosion of coal dust is smaller than that after the first explosion. In a certain range, with decreases of coal dust particle size, volume fraction of residual CO continuously decreases after the secondary explosion, ratio of volume fraction of CO to the one of CO2 decreases, and volume fraction of CH4 increases. With increase of ignition energy, volume fraction of residual CO or CH4 after the secondary explosion continuously increases, and ratio of volume fraction of CO to the one of CO2 shows an increasing trend

Research on secondary explosion characteristic of coal dust

Influence of concentration, particle size and ignition energy of coal dust on secondary explosion characteristic of coal dust were studied by use of 20 L spherical explosion device, and the secondary explosion characteristic of coal dust was compared with the first explosion characteristic of coal dust. The results show that with the increase of coal dust concentration, the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust increase firstly and then decrease, the maximum pressure difference between the first explosion and secondary explosion decreases firstly and then increases, and the maximum rising rate difference of pressure between the first explosion and secondary explosion decreases firstly, then increases and decreases lastly; with the decrease of coal dust particle size, the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust gradually increase, the maximum pressure difference and the maximum rising rate difference of pressure between the first explosion and secondary explosion increase firstly and then decrease; with the increase of ignition energy, the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust, and the maximum pressure difference and the maximum rising rate difference of pressure between the first explosion and secondary explosion increase; the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust is smaller than that of the first explosion; coal dust concentration is the main influence factor on the characteristic difference between secondary explosion and the first explosion of coal dust