粒度对煤吸附/解吸一氧化碳的影响

Effect of particle size on adsorption and desorption of carbon monoxide by coal

CO常作为有效标志气体用于煤自燃预报预警,采空区自燃封闭后CO迅速降低甚至消失的致因尚不明晰,影响煤自燃程度的精准判定。为深入研究煤体对CO气体的吸附/解吸特征,采用压汞和液态氮气吸附实验,测试研究煤样孔隙结构;利用自主研发的气体吸附/解吸装置,在303.15~333.15 K与0.15~0.50 MPa条件下,探索不同粒度煤样对CO气体吸附/解吸特性的影响,并深入分析CO的吸附速率和解吸滞后效应。结果表明:灵新矿不黏煤煤样的孔容以大孔和过渡孔为主,分别占33.02%和38.26%;孔比表面积以微孔和过渡孔为主,共占97.73%。粒径减小,微孔孔容与孔比表面积所占比例增加,过渡孔和中孔的孔容与孔比表面积所占比例减小,不同粒径煤样对CO气体吸附量与压力成正比;压力一定时,CO吸附量与温度成反比;同温同压条件下,煤样粒径越小,CO吸附量越大;相同温度下,煤对CO饱和吸附量与粒径呈正相关关系,CO解析过程中,粒径减小,饱和吸附量a值增大;煤样对CO吸附速率可划分为3个阶段:0~750 s为快速上升期、750~2 250 s为缓慢上升期、2 250~3 600 s为饱和平衡期;不同粒径煤样CO解吸滞后性随温度的升高而降低;温度相同时煤样粒径越小,CO解吸滞后性越小,达到吸附/解吸的平衡点越容易。

CO gas is often used as an effective indicator gas for the prediction and early warning of coal spontaneous combustion,but the causes for the rapid decrease or even disappearance of CO after the closing of spontaneous combustion in goaf are not clear,which affects the accurate determination of the coal spontaneous combustion degree.In order to study the adsorption/desorption characteristics of CO gas in coal,the pore structure of coal samples was determined by pressured-mercury testing and liquid N2 adsorption experiment.The effects of coal samples with different particle sizes on CO gas adsorption/desorption characteristics were investigated at 303.15-333.15 K and 0.15-0.50 MPa by using a self-developed gas adsorption/desorption device,and the adsorption rate and desorption hysteresis effect of CO gas were analyzed in depth.The results showed that the pore volume of non-cohesive coal sample from Lingxin Mine was mainly large pores and transition pores,accounting for 33.02%and 38.26%,respectively.The pore specific surface area was mainly micropores and transition pores,accounting for 97.73%.With the diminishment of particle size,the proportion of micropore volume increased,and the proportion of transition pore and mesopore decreased.The adsorption amount of CO gas on coal samples with varing particle sizes increased with the rising of pressure.When the pressure was constant,the adsorption amount of CO gas decreased with the rising of temperature.Under the identical temperature and pressure conditions,the smaller the sample particle size was,the larger the CO gas adsorption amount was;at the same temperature,the saturated adsorption capacity of coal for CO was positively correlated with particle size.In the process of CO desorption,the saturated adsorption capacity increased with decreasing particle size.The CO adsorption rate of coal samples could be divided into three stages:rapid rising period(0-750 s),slow rising period(750-2250 s),and saturated equilibrium period(2250-3600 s).The CO gas desorption hysteresis with varing sample particle sizes decreased with the rising of temperature.At the identical temperature,the smaller the sample particle size was,the smaller the desorption hysteresis of CO gas was,and the easier it was to reach the equilibrium state of adsorption/desorption.