索特平均直径对煤粉及其在瓦斯气氛下爆炸特性的影响

Effect of Sauter mean diameter of coal dust on its explosibility with and without methane gas

为了研究索特平均直径(D_(3,2))对煤粉及其在瓦斯气氛中爆炸特性的影响,利用20-L球形爆炸装置,测量了煤粉初始样和混合样及其在瓦斯气氛中的爆炸特性参数,研究了粒径分散度σ_(D)对煤尘爆炸威力的影响,对比分析了粒径特征参数d_(50),D_(4,3),D_(3,2)值与煤粉粉尘爆炸威力的相关性;同时收集了煤粉粉尘爆炸的固体残渣,并通过扫描电镜对其微观结构进行了表征;最后,结合煤粉粉尘爆炸实验数据和产物微观结构分析结果,探讨了煤粉粉尘及其在瓦斯气氛中爆炸的机理。实验结果表明:当d_(50)值相同时,σ_(D)值最大(2.31)时煤粉粉尘的压力最大值P_(max)和(d P/d t)_(max)值较σ_(D)值最小(1.49)时分别增加了14.71%和68.05%,说明煤粉粉尘的粒径分散度σ_(D)会显著影响其爆炸性能;相对于d_(50)值和D_(4,3)值,D_(3,2)值可以更好的阐述煤粉粉尘的爆炸特性,D_(3,2)值最大(120μm)时的粉尘爆炸压力P_(ex)和(d P/d t)_(ex)值较D_(3,2)值最小(2.5μm)时分别降低了33.33%和83.33%,说明D_(3,2)值对(d P/d t)_(ex)值的影响大于对P_(ex)值的影响;在瓦斯气氛中,随着D_(3,2)值的增加,煤粉粉尘的(d P/d t)_(ex)值逐渐减小,低瓦斯体积分数时,D_(3,2)值对P_(ex)值影响较小,但高瓦斯体积分数时,D_(3,2)值越大则P_(ex)值越小,而煤粉颗粒的D_(3,2)值越小,挥发分燃烧速率更快,爆炸更剧烈,其残渣表面的孔洞越多,破碎程度也越大。

In order to study the influence of sauter mean diameter(D_(3,2))on the explosibility of coal dust with and without methane gas,a 20-L spherical vessel is used to measure the explosive characteristics parameters,the influence of particle size dispersionσ_(D)on the explosion power of coal dust is studied,and the correlations between the values of d_(50),D_(4,3)and D_(3,2)and the explosibility coal dust are analyzed.Also,the solid residues of coal dust explosion is collected and characterized by a scanning electron microscope.Finally,the mechanism of coal dust explosion with and without methane gas is discussed on the basis of dust explosion experimental results and the microstructure analysis results of the explosion solid products.The experimental results show that P_(max)and(d P/d t)_(max)values of coal dust with the maximumσ_(D)(2.31)increased by 14.71%and 68.05%respectively compared to those with the minimumσ_(D)(1.49),which shows that particle size dispersionσ_(D)of coal dust can significantly affect its explosion performance.Compared with d_(50)and D_(4,3)values,the D_(3,2)can better illustrate the explosion characteristics of coal dust.The P_(ex)and(d P/d t)_(ex)values of coal dust with the maximum D_(3,2)(120μm)increased by 33.33%and 83.33%respectively compared to those with the minimum D_(3,2)(2.5μm),therefore,the influence of D_(3,2)on(d P/d t)_(ex)are higher than that of P_(ex).In the methane gas atmosphere,with the increase of D_(3,2),the(d P/d t)_(ex)value of coal dust explosion decreases gradually.When the methane gas concentration is low,the D_(3,2)had little influence on P_(ex)values,but when the methane gas concentration is high,the larger D_(3,2)results in smaller P_(ex)values.Smaller D_(3,2)of coal particles leads to a faster combustion rate of coal particles and higher explosibility,and the residues of coal dust has greater breakage and more holes in their surfaces.The results illustrate the importance ofσ_(D)and D_(3,2)values on evaluating the explosion hazard characterization of coal dust or combustible dust,which is of great significance to the prevention of gas and dust explosion in coal mines.