峰峰矿区煤变质作用对煤层气中氮气含量的影响

Coal Metamorphism's Influence on Coalbed N_2 Concentration in Fengfeng Mining Area

在系统整理46个钻孔煤层气样数据资料的基础上,探讨了峰峰矿区煤变质过程中煤层气中N2含量的变化规律及其原因。结果表明:燕山期岩浆的"烘烤"作用是煤层气中N2含量平均值偏高的重要原因;随煤变质程度增强,煤层气中N2与CH4的比值呈"增—减—增"的变化规律;在焦煤阶段,热氨化作用生成的N2逐渐增多,CH4生成量相对减少,比值增大;在瘦煤阶段,热氨化作用产生的NH3部分以NH+4形式参与铵伊利石矿物的生成,致使N2生成量相对减少,比值减小;在贫煤阶段,含氮有机质又通过热裂解作用生成N2,N2含量相对增多,比值增大。

Based on the systematic analysis of the data of 46 coalbed gas samples, this paper discusses the coal metamorphism＇s influence on coalbed N2 concentration in Fengfeng Mining Area . The results show that：Yanshanian magma＇s ＂baking＂ is the main reason for the high N2 concentration;The coal metamorphic degree enhanced, ratios of N2/CH4 present the changing rule of ＂increase-decrease-increase＂; In coking coal stage,the liberation rate of N2 by thermal ammoniation is faster than the liberation rate of CH4, so the ratio increases;In meager coal stage, NH3 generated by thermal ammoniation participates in the formation of ammonium illite in the form of NH4＋, thus the liberation rate of N2 decreases relatively, the ratio decreases in lean coal stage,organic nitrogen liberates N2 by thermal cracking effect, N2 concentration increases relatively again, so ratios of N2/CH4 increase.