煤自燃预测气体及活化能变化研究

为了研究煤在低温阶段的自燃活化能及气体产生规律,基于耗氧量与煤温间的计算模型,利用煤氧化动力学测试系统,分析了3种不同自燃性煤的低温氧化表征。结果表明:1)随着煤自燃倾向性增强,煤的耗氧量和耗氧速率逐渐增大,且其耗氧速率急剧增大的拐点温度逐渐升高;2)不同自燃性煤活化能变化规律存在显著差异,利用阶段耗氧量拐点计算出铜川和大同煤样温度分别为203℃、228℃时,活化能快速减小,开始进入自发氧化阶段;晋城煤样活化能经历先减小后增大的过程,其中过渡温度段91~135℃时,活化能最小;同时拟合出活化能(E)与指前因子(A)关系式满足动力补偿效应,验证了机理函数的合理性;3)依据复合气体CO_2/CO、CH_4/C_2H_6、C_2H_4/C_2H_6、C_3H_8/C_2H_6随温度的变化趋势,结合煤低温氧化特性,可预测煤样的氧化进程和煤体温度。

Forecast of the coal gas spontaneous combustion and changing regularity of the activation energy

This article is dedicated to a study of how to predict the liability of the coal gas spontaneous combustion and the changing regularity of the activation energy.For the above said purpose,the paper has investigated and analyzed the activation energy and the gas-generating laws at the coal low temperature oxidation stage based on the calculation model of the oxygen consumption and the coal temperature change,the low-temperature oxidation characteristics of the three coal samples with different spontaneous combustion tendencies by testing the coal oxidation kinetics system.The results of our testing and investigation show that,(1) at the low temperature oxidation stage,the oxygen consumption and its consumption rate for the three kinds of coal tend to increase gradually with the intensification of the spontaneous combustion trend,and,so does the inflection temperature at which the oxygen consumption rate may increase very quickly.(2)In the spontaneous combustion oxidation process of different coal samples,the activation energy variation tendencies may turn to be significantly varous.Therefore,with the temperature rising,the coal from Tongchuan mine tends to increase first and later reduce quickly,whereas the activation energy of the coal produced in Datong mine tends to decrease gradually and progressively.Thus,in terms of the inflection point of the stage oxygen consumption and coal temperature change,the spontaneous combustion points of the coal samples gaianed from Tongchuan and Datong prove to be 203 ℃ and 228 ℃,respectively,whereas the activation energy of the two kinds of coal samples tend to be reduced rapidly,and soon they both turn to come to the self-accelerating spontaneous reaction stage.However,the activation energy of the coal samples from Jincheng mine tend to decrease first and then quickly increase.And,even in the temperature transition period (91-135 ℃),the activation energy can still keep its minimum extent.Therefore,the fitted formula of the three coal samples in terms of the activation energy (E) and pre-exponential factor (A) can all meet the dynamic compensatior.effect,which prove to be consistent with the mechanical function.(3)Furthermore,when we compared and analyzed the gas generation regularities of the three kinds of coal,we have traced the changing regularies of the single gas and composite gas.Thus,finally,it can be concluded that it is possible to divide the low temperature oxidation into fotir stages according to the variation tendencies of the composite gas,that is,(ψ) (CO2) /(ψ)(CO),(ψ)(CH4)/(C2H6),(ψ)(C2H4)/(ψ)(CEH6),(ψ)(C3H8)/(ψ)(C2H6),which could be employed to forecast the oxidation process and the coal combustion temperatures,when combined with the low-temperature oxidation characteristics of the different kinds of coal.