粒径对煤粉云最低着火温度特性的影响

为了研究粒径对煤粉云最低着火温度特性的影响，采用粉尘云最低着火温度测试装置测试了不同粒径下煤粉云的最低着火温度，并结合ReaxFF分子动力学对其反应机理进行了微观层面的探讨。结果表明:当煤粉中位径在34 μm时，煤粉云的最佳着火质量浓度为750 g/m³，最低着火温度为550 ℃；随着煤粉粒径的增加，煤粉云最低着火温度逐渐增大，当煤粉中位径达到124 μm，煤粉云最低着火温度上升至650 ℃。通过ReaxFF分子动力学对煤粉热解过程的计算结果表明:随着反应的进行，大分子煤结构逐步分解，芳香环、C—C键、C—O键和C—H键等断裂，产生更小的分子结构，其中，H₂、H₂O、CO₂和CH₂O等小分子产生的数量逐渐增多；H·自由基和OH·自由基在反应初期有明显的数量变化，且其含量对于最终稳定产物有重要影响。

Influence of Particle Size on Minimum Ignition Temperature Characteristics of Coal Dust Cloud

To explore the influence of particle size on the minimum ignition temperature characteristics of coal dust cloud, the minimum ignition temperature of coal dust cloud with different particle sizes was tested by using the minimum ignition temperature test device of dust cloud. The reaction mechanism was discussed at micro scopic level using ReaxFF molecular dynamics research method. The results show that when the median diameter of coal particle is 34 μm, the optimum ignition mass concentration and minimum ignition temperature of coal dust cloud are 750 g/m³ and 550 ℃, respectively. The minimum ignition temperature of coal dust cloud gradually increases with the increase of coal particle size. When the median diameter of coal particle reaches 124 μm, the minimum ignition temperature of coal dust cloud rises to 650 ℃. In addition, the pyrolysis result of coal dust calculated by ReaxFF molecular dynamics shows that, with the reaction proceeding, the structure of macro-molecular coal is decomposed step by step, and the aromatic rings, C—C bonds, C—O bonds, and C—H bonds fractures to form the smaller molecular structure. Among them, the numbers of small molecules such as H₂, H₂O, CO₂, and CH₂O gradually increase. H· radicals and OH· radicals have obvious quantity changes at the initial stage of the reaction, and its content has an important influence on the final stable product.