煤矿乏风瓦斯热逆流氧化床的阻力特性研究

Resistance characteristics of thermal reverse-flow oxidation bed for coal mine ventilation air methane

热逆流氧化是实现煤矿乏风低浓度瓦斯减排和有效利用的主要技术之一。为了掌握热逆流氧化床的阻力特性,更好地为其设计提供理论参考依据,借助Fluent计算流体力学软件,对热逆流氧化床阻力特性开展了相关的数值研究,得出以下主要结论:①伴随气体温度和流速在氧化床内变化,氧化床的压强梯度也发生剧烈变化。在预热段,压强梯度的绝对值沿气体流动方向增加;而在反应段内,压强梯度基本保持不变;反应产生的气体进入蓄热段后,温度不断下降,压强梯度的绝对值也随之下降。②氧化床阻力在前半周期内随时间增加而不断降低;进入后半周期,氧化床阻力开始回升,到后半周期结束时恢复到该周期开始时的阻力值;随着气流方向的周期改变,氧化床阻力以V型波的形式呈现周期性变化。③氧化床的压强损失随着乏风量的增加几乎呈线性增加、随着乏风瓦斯中甲烷浓度的升高而增加、随着蜂窝陶瓷孔隙率的增大而降低,而换向半周期对氧化床的压强损失几乎没影响。

Thermal reverse-flow oxidation is one of the main technologies to realize the mitigation and effective utilization of coal mine ventilation air methane(VAM).For finding out the resistance characteristics of the thermal reverse-flow oxidation bed and providing a better theoretical reference for its overall design,a numerical study on resistance characteristics of the thermal reverse-flow oxidation bed is carried out with the CFD software,the following conclusions are obtained.First,with the changes of gas temperature and flow rate in the oxidation bed,the pressure gradient changes dramatically.At the preheated section,the absolute value of the pressure gradient increases along the direction in which the gas flows.At the reaction section,the pressure gradient remains unchanged.When the gas gets into the regenerative section,the temperature keeps going down,the absolute value of the pressure gradient begins to slide down.Second,the resistance of oxidation bed decreases continuously within the first half period.In the second half period,the resistance begins to pick up and rises to the original value at the end of the second half period.With the periodic changes of the air flow direction,the resistance of oxidation bed changes in V-type waves.Third,the pressure loss of the oxidation bed increases linearly with the growth of VAM volume,rises with the increase of the methane concentration of VAM,and decreases with the growth of the porosity of ceramic honeycomb,whereas it is hardly influenced by the half period.