分散度对煤粉爆炸特性的影响

煤矿工作面煤尘呈多分散性,因此采用单一粒径的煤样评估煤尘爆炸风险存在缺陷。为了研究分散度对煤尘爆炸特性的影响规律,找出合适的平均粒径表示方式来评估分散度对爆炸风险的影响,以5种粒径分布范围相同但分散度不同的煤样为研究对象,采用20 L爆炸球实验装置,测量样品的最大爆炸压力P_ex、最大爆炸压力上升速率(dp/dt)_ex、开始点火至最大爆炸压力的时间段t_1和开始点火至最大爆炸压力上升速率的时间段t_2四个参数。后续采用热值分析、扫描电镜试验方法探究不同分散度煤尘的反应程度。借助方差分析和斯皮尔曼相关性分析研究测量结果组间的差异性、不同粒径表示方式与爆炸特性参数的相关性。实验结果表明:对于具有相同粒径分布的煤粉,分散度对煤粉爆炸反应速率影响较大。小粒径煤尘颗粒的质量分数越大,反应速率越快,反应越充分,释放的能量越大。当小粒径煤尘质量分数达到30%时,最大爆炸压力上升速率显著增大,t_1和t_2明显减小。粒径最小的原始样品3的爆炸产物热值最低,且爆炸产物表面形成了较为丰富的孔洞结构,说明小粒径煤尘较快的脱挥发速率能增加爆炸的反应程度。D₁₀,D₂₅(为投影面积的10%和25%的颗粒直径)、D_3,2(索特尔直径)与最大爆炸压力上升速率、t_1和t_2三个参数的斯皮尔曼相关系数均落在高度相关和显著相关的区间,呈现出较好的相关性。对于多分散性的煤尘,D₁₀,D₂₅和D_3,2可以较好的评估分散度对煤尘爆炸特性的影响。

Effect of dispersity on explosion characteristics of coal dust

The coal dust is polydisperse in the coalface of longwall mining.Thus,the evaluation of the explosion risk of coal dust by single particle size is defective.In order to investigate the effect of dispersion on the characteristics of coal dust explosions and find the appropriate expressive ways of average particle size to estimate the explosion risk,five coal samples with the same particle size distribution range whereas with different dispersions were investigated.The 20 L explosion sphere vessels experimental device was used to measure four parameters of the sample,including the maximum explosion pressure (Pex),the maximum explosion pressure rise rate ((dp/dt)ex),the period from the ignition to the maximum explosion pressure (t1),and the period from the ignition to the maximum explosion pressure rise rate (t2).Calorific value analysis and scanning electron microscopy were used to investigate the degree of reaction of coal dust with different dispersions.The diversities between the measurement results of different groups were investigated by the analysis of variance.The correlation between various particle size representation methods and the explosion characteristics parameters were investigated by Spearman correlation analysis.The experimental results showed that the dispersity had a great significant influence on the explosion reaction rate of coal dust with the same particle size span.The larger the mass fraction of small coal dust particle size is,the faster the reaction rate,the more complete the reaction and released energy.When the small particles accounted for 30%,the (dp/dt)ex increased significantly,t1 and t2 decreased significantly.The explosive products of the original sample 3 with small particle size had the lowest calorific value and rich pore structures on the particles surfaces,which could proved that the explosion reaction degree of the finer coal dust can be increased due to the accelerating devolatilization rate.The Spearman correlation coefficients between D10,D25 (the particle size for which 10% and 25% of the particles by the projection area),D3,2 (Sauter mean diameter) and (dp/dt)ex,t1,t2 fall within highly correlated and significantly correlated intervals.It showed a good correlation.D10,D25 and D3,2 are the appropriate methods to describe the dispersion of polydisperse coal dust for investigating the explosions.