【摘要】：礦井瓦斯災(zāi)害的防治和煤層氣的開發(fā)利用與煤體的微觀結(jié)構(gòu)特征及瓦斯吸附規(guī)律密切相關(guān),研究低階煤的孔隙結(jié)構(gòu)對其瓦斯吸附特性影響有利于準(zhǔn)確評價低階煤的儲層特征。選取新疆準(zhǔn)南煤田10個典型實驗礦井的低階煤煤樣,結(jié)合煤體孔隙結(jié)構(gòu)特征從熱力學(xué)角度分析其對煤體瓦斯吸附特性影響。(1)利用低溫氮吸附實驗分析準(zhǔn)南低階煤孔隙結(jié)構(gòu),結(jié)果表明準(zhǔn)南低階煤的孔隙較為發(fā)育,孔隙結(jié)構(gòu)復(fù)雜,相同孔徑段比表面積和孔容大小及占比存在不同程度的差異,比表面積以過渡孔和微孔為主,孔容則以過渡孔和中孔為主,微孔較小,相同孔徑段比表面積和孔容隨孔隙直徑變化規(guī)律相似。(2)基于PCT-C80吸附量熱實驗系統(tǒng)測定實驗低階煤的瓦斯吸附熱數(shù)據(jù),通過四種吸附模型的擬合對比表明D-A吸附理論模型更適合描述實驗低階煤的瓦斯吸附特性。通過(Clausius-Clapeyron)和(Gibb-Helmholtz)方程計算瓦斯等量吸附熱及吸附摘變,建立考慮標(biāo)準(zhǔn)平衡壓力常數(shù)的吸附自由能方程計算瓦斯吸附自由能變。表明理論方程計算值與實驗實測吸附熱值存在差別,溫度升高煤體瓦斯等量吸附熱及煤體吸附熱均減小,瓦斯吸附自由能變增大,吸附熵變減小,從熱力學(xué)角度證實升溫不利于煤體瓦斯吸附,其瓦斯吸附熱力學(xué)參數(shù)適用于表述煤體瓦斯吸附特性。(3)通過分析孔隙結(jié)構(gòu)對其瓦斯吸附熱力學(xué)特性影響,得到低階煤孔隙結(jié)構(gòu)與煤體瓦斯吸附熱關(guān)系,表明除實驗煤樣過渡孔比表面積以外,隨著BET比表面積及其余各孔徑段比表面積增大,瓦斯吸附熱Q、吸附自由能變AG、吸附熵變△S均線性增大,其中微孔比表面積對Q的影響起主要作用,隨著BJH孔體積及微孔孔體積增大,Q、AG、△S均線性增大,微孔體積對Q的影響起主要作用。本文為新疆準(zhǔn)南煤田低階煤的瓦斯抽采工作提供一定的實驗數(shù)據(jù)基礎(chǔ)和理論依據(jù)。
[Abstract]:The prevention and cure of mine gas disaster and the exploitation and utilization of coalbed methane are closely related to the microstructure of coal body and the law of gas adsorption. It is helpful to accurately evaluate the reservoir characteristics of low rank coal by studying the influence of pore structure of low rank coal on its gas adsorption characteristics. The low-rank coal samples from 10 typical experimental coal mines in the quasi-southern coal field of Xinjiang are selected. According to the pore structure characteristics of coal body, the influence of coal pore structure on gas adsorption characteristics of coal body is analyzed from the point of view of thermodynamics. (1) the pore structure of low rank coal is analyzed by nitrogen adsorption experiment at low temperature. The results show that the pore structure of low rank coal is relatively developed. The pore structure is complex, the specific surface area and pore volume size and proportion of the same pore size are different, the specific surface area is mainly transition pore and micropore, the pore volume is mainly transition pore and mesopore, and the micropore is small. The specific surface area and pore volume of the same pore size vary with the pore diameter. (2) based on the PCT-C80 adsorption calorimetry experimental system, the gas adsorption heat data of experimental low-rank coal are measured. The comparison of four adsorption models shows that the D-A adsorption model is more suitable to describe the gas adsorption characteristics of experimental low-rank coal. Through (Clausius-Clapeyron) and (Gibb-Helmholtz) equations to calculate the gas adsorption heat and adsorption variation, the adsorption free energy equation considering the standard equilibrium pressure constant was established to calculate the gas adsorption free energy variation. The results show that there is a difference between the calculated values of the theoretical equation and the experimental measured adsorption calorific values. When the temperature rises, the adsorption heat of coal body gas and the adsorption heat of coal body decrease, the free energy of gas adsorption increases and the adsorption entropy decreases. From the thermodynamics point of view, it is proved that heating temperature is unfavorable to gas adsorption of coal body, and the thermodynamic parameters of gas adsorption are suitable for describing the gas adsorption characteristics of coal body. (3) the influence of pore structure on the thermodynamic characteristics of gas adsorption is analyzed. The relationship between pore structure of low-rank coal and gas adsorption heat of coal body is obtained. The results show that with the increase of BET specific surface area and other pore specific surface area, the gas adsorption heat Q and adsorption free energy change AG, with the exception of experimental coal sample transition pore specific surface area. The adsorption entropy is increasing with the increase of S mean linearity, and the specific surface area of micropore plays a major role in the influence of Q. With the increase of BJH pore volume and micropore volume, QG and S mean linearity increase, and the micropore volume plays a major role in the influence of Q. This paper provides some experimental data and theoretical basis for the gas extraction of low rank coal in Zhongnan coalfield, Xinjiang.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TD712

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