烟煤吸附、解吸过程中热流特征实验初探

Heat flow characteristics of bituminous coal adsorption and desorption process

煤吸附、解吸瓦斯过程中会伴有明显的热效应,其变化规律对煤与瓦斯突出等瓦斯灾害预测技术具有重要的研究价值。利用自行设计搭建的多参量煤吸附、解吸热效应测试实验系统,开展0.5 MPa、0.8 MPa、1.1 MPa 3种压力下,烟煤对于CO_(2)、N_(2)、CH_(4)3种气体吸附、解吸过程中压力、温度和热流测试实验,综合分析了烟煤吸附、解吸过程中热流变化特征。结果表明:(1)烟煤试样吸附、解吸过程中,煤壁上热流密度变化分为5个过程:①抽真空阶段,热流迅速增大,后缓慢减小到0;②充气阶段,热流与充气速率呈正相关;③吸附阶段,热流先快上再快下最后缓慢下降;④放气阶段,热流与泄压速率呈正相关性;⑤解吸阶段,分为快速下降和缓慢上升两阶段。(2)实验中,N_(2)、CH_(4)、CO_(2)3种气体在相同气压下,吸附、解吸最大热流密度值依次增大;相同气体在3种不同压力下,最大热流密度值随气压升高依次增大。(3)推导出的吸附、解吸过程中热量的理论值始终大于实验值,但整体趋势一致。(4)热流密度参量具有流入、流出方向矢量特征,比温度指标优越,热流密度与热量传递变化规律一致,可以很好地表征烟煤吸附、解吸热效应变化规律,为煤与瓦斯突出预测新指标的研究提供参考。

The process of coal adsorption and desorption of gas is accompanied by obvious thermal effects,and its variation pattern is of great value for the research of gas hazard prediction techniques such as coal and gas outburst prediction.Using self-designed multiparameter coal adsorption and desorption heat effect test system,we conducted pressure,temperature and heat flow test experiments for CO_(2),N_(2) and CH_(4) gas adsorption and desorption of bituminous coal at 0.5 MPa,0.8 MPa and 1.1 MPa,and analyzed the characteristics of heat flow changes of bituminous coal during the adsorption and desorption process.The study showed that:(1)during the whole process of adsorption and desorption of bituminous coal specimens,the change of heat flow density on the coal wall is divided into five processes:①in the evacuation stage,the heat flow increases rapidly and then decreases slowly to 0;②in the inflation stage,the heat flow is positively correlated with the inflation rate;③in the adsorption stage,the heat flow is first fast up and then fast down and finally decreases slowly;④in the deflation stage,the heat flow is positively correlated with the pressure relief rate;⑤in the desorption stage,it is divided into two stages:the stage of fast down and slow rise.(2)The maximum heat flux values of N_(2),CH_(4),and CO_(2) three gases increase sequentially;for the same gas,the maximum heat flux values under the three gas pressures will increase with the increase of pressure.(3)The theoretical values of heat in the process of adsorption and desorption are always larger than the experimental values,but the overall trend is consistent.(4)The heat flux parameter has the characteristics of inflow and outflow direction vector,which is superior to the temperature index.The heat flux is consistent with the heat transfer change law,which can well characterize the change law of thermal effect of adsorption and desorption of bituminous coal,and provide reference for the research of new index of coal and gas outburst prediction.