多因素对液态CO_(2)冻融致裂煤体的影响试验研究

Experimental study on influence of multiple factors on liquid CO_(2) freeze-thaw cracking coal

为研究多因素耦合对液态CO_(2)冻融致裂煤体的影响,采用自主研发的液态CO_(2)冻融致裂试验装置,利用核磁共振测试技术,测定不同影响因素下液态CO_(2)冻融致裂后煤体的孔隙度,分别研究液态CO_(2)冻结时间(t)、冻融循环次数(n)和煤体含水饱和度(W)对煤体孔隙度(φ)的影响;采用响应曲面法设计试验,构建φ与t、n和W的二次回归响应曲面模型,分析t、n和W单独及耦合作用时对φ的敏感程度及影响特征,并预测优化与验证不同影响因素下的φ。结果表明:随着t的延长和n的增多,φ呈指数函数关系变化,随W的增大,φ呈线性关系增加;影响因素t、n和W均为φ的极显著项(显著性判别值P<0.01),对φ影响的主次关系为:n>W>t。交互项nt交互作用极显著,nW交互作用次之,Wt交互作用不显著,对φ影响的主次关系为:nt>nW>Wt。模型预测当t、n和W分别为57 min、19次、96%时,φ达到最大值(9.47%),4组试验值与模型预测值平均误差为2.98%,所测φ平均值为9.58%,φ较优化之前(8.94%)提高了7.16%。

In order to study the coupling influence of multi-factor on liquid CO_(2) freeze-thaw cracking coal,a liquid CO_(2) freeze-thaw cracking test device was designed.The nuclear magnetic resonance testing technology was used to measure the porosity of coal after liquid CO_(2) freeze-thaw cracking under different influencing factors.The effects of liquid CO_(2) freezing time(t),number of freeze-thaw cycles(n)and water saturation(W)on coal porosity(φ)were studied.The quadratic regression response surface model ofφwith t,n and W was constructed by response surface method.The sensitivity of t,n and W toφsingle and coupled was analyzed,and the influence characteristics were predicted,optimized and verified under different influencing factors.The results show that theφchanges exponentially with the increase of t and n,and linearly with the increase of W.The influencing factors t,n and W are all extremely significant terms ofφ(significant discriminant value P<0.01),and the influence relationship of toφis as follows:n>W>t.The interaction between nt and Wt is very significant,followed by nW and Wt.The primary and secondary effects onφare nt>nW>Wt.When t,n and W are 57 min,19 times and 96%,respectively,the maximum value ofφis 9.47%.The average error between the four test values and the predicted value of the model is 2.98%,and the measured average value ofφis 9.58%,which is 7.16%higher than that before optimization(8.94%).