瓦斯压力对瓦斯在煤中扩散影响的实验研究
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摘要
为了研究瓦斯压力对瓦斯在不同变质程度煤中扩散的影响,采集了我国典型矿区的煤样,采用低温氮吸附法和压汞法对煤样进行了孔隙特征分析,开展了不同压力下煤粒瓦斯吸附-解吸扩散动力学实验,分别采用单孔扩散模型和双孔扩散模型对扩散实验结果进行拟合.结果表明,双孔扩散模型比单孔扩散模型能更准确地描述煤粒瓦斯吸附-解吸扩散全过程.基于双孔扩散模型反演计算大孔和微孔有效扩散系数D_(ae),D_(ie),分析认为:二次多项式函数能很好地描述D_(ae)与压力的关系,在吸附过程中,当瓦斯压力小于某一临界压力时,D_(ae)随着压力的增大而减小,当瓦斯压力大于某一临界压力时,D_(ae)随着压力的增大而增大;在解吸过程中,当瓦斯压力大于某一临界压力值时,D_(ae)随着压力的减小而减小,当瓦斯压力小于某一临界压力值时,D_(ae)随着压力的减小而增大;大孔有效扩散系数均值Symbol`A@D_(ae)越大,临界瓦斯压力值就越大.而微孔有效扩散系数D_(ie)与压力则较好地符合一元线性关系:在吸附过程中D_(ie)随着压力的增大而增大,在解吸过程中D_(ie)随着压力的减小而减小.各煤样在吸附-解吸过程中的扩散特征参数β基本保持不变.
Coal samples from typical mining areas in China were collected to investigate the impact of gas pressure on the gas diffusion in coals with different metamorphic degrees. The pore characteristics of coal samples were analyzed using the low-temperature nitrogen sorption and mercury pressure methods, the adsorption-desorption diffusion kinetics experiments of coal particles were made under different pressure. The diffusion experiments results were fitted by applying the unipore diffusion model and the bidisperse diffusion model. The results show that the bidisperse diffusion model more accurately describes the whole process of gas adsorption-desorption of coal particles relatively to the unipore diffusion model. The macropore effective diffusion coefficients D_(ae) and micropore effective diffusion coefficients D_(ie) were calculated using the bidisperse diffusion model. The analysis shows that the relationship between D_(ae) and pressure is better described by the quadratic polynomial model. In the adsorption process, D_(ae) decreases with the increase of pressure when the gas pressure is smaller than a threshold value, and D_(ae) increases with the increase of pressure when the gas pressure is greater than another threshold point. In the desorption process, D_(ae) reduces with the decrease of the pressure when the gas pressure is larger than a threshold value, and D_(ae) increases with the decrease of the pressure when the gas pressure is smaller than another threshold point. The average macropore diffusion effective coefficientSymbol`A@D_(ae) is larger if the critical value of gas pressure is higher. The micropore effective diffusion coefficient D_(ie) and pressure are well consistent with the linear relationship. D_(ie) increases with the increase of pressure during the adsorption process, and D_(ie) decreases with the decrease of pressure during the desorption process. The diffusion characteristic parameter β remains the same in the adsorption-desorption process of coal samples.
Coal samples from typical mining areas in China were collected to investigate the impact of gas pressure on the gas diffusion in coals with different metamorphic degrees. The pore characteristics of coal samples were analyzed using the low-temperature nitrogen sorption and mercury pressure methods, the adsorption-desorption diffusion kinetics experiments of coal particles were made under different pressure. The diffusion experiments results were fitted by applying the unipore diffusion model and the bidisperse diffusion model. The results show that the bidisperse diffusion model more accurately describes the whole process of gas adsorption-desorption of coal particles relatively to the unipore diffusion model. The macropore effective diffusion coefficients D_(ae) and micropore effective diffusion coefficients D_(ie) were calculated using the bidisperse diffusion model. The analysis shows that the relationship between D_(ae) and pressure is better described by the quadratic polynomial model. In the adsorption process, D_(ae) decreases with the increase of pressure when the gas pressure is smaller than a threshold value, and D_(ae) increases with the increase of pressure when the gas pressure is greater than another threshold point. In the desorption process, D_(ae) reduces with the decrease of the pressure when the gas pressure is larger than a threshold value, and D_(ae) increases with the decrease of the pressure when the gas pressure is smaller than another threshold point. The average macropore diffusion effective coefficientSymbol`A@D_(ae) is larger if the critical value of gas pressure is higher. The micropore effective diffusion coefficient D_(ie) and pressure are well consistent with the linear relationship. D_(ie) increases with the increase of pressure during the adsorption process, and D_(ie) decreases with the decrease of pressure during the desorption process. The diffusion characteristic parameter β remains the same in the adsorption-desorption process of coal samples.
引文
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[14] STAIB G,SAKUROVS R,GRAY E M A,A pressure and concentration dependence of CO2 diffusion in two Australian bituminous coals[J].International Journal of Coal Geology,2013,116:106-116.
[15] NANDI S P,WALKER P L.Activated diffusion of methane from coals at elevated pressures[J].Fuel,1975,54(2):81-86.
[16] CRANK J.The mathematics of diffusion[M].London:Oxford University Press,1975:135-136.
[17] CLARKSON C R,BUSTIN R M.The effect of pore structure and gas pressure upon the transport properties of coal:Alaboratory and modelling study:2.Adsorption rate modelling[J].Fuel,1999,78:1345-1362.
[18] RUCKENSTEIN E,VAIDYANATHAN A S,YOUNGQUIST G R.Sorption by solids with bidisperse pore structures[J].Chem Eng Sci,1971,26(9):1305-1318.
[19] BUSCH A,GENSTERBLUM Y.CBM and CO2-ECBM related sorption processes in coal:A review[J].International Journal of Coal Geology,2011,87(2):49-71.
[20] WANG G D,REN T,QI Q,et al.Determining the diffusion coefficient of gas diffusion in coal:Development of numerical solution[J].Fuel,2017,196:47-58.
[21] GOODMAN A L,BUSCH A,DUFFY G J,et al.An inter-laboratory comparison of CO2 isotherms measured on argonne premium coal samples[J].Energy & Fuels,2004,18(4):1175-1182.
[22] 王公达.煤层瓦斯吸附解吸迟滞规律及其对渗流特性影响研究[D].北京:中国矿业大学(北京),2015:5-6.WANG Gongda.Adsorption and desorption hysteresis of coal seam gas and its influence on gas permeability[D].Beijing:China University of Mining & Technology(Beijing),2015:5-6.
[23] LIU H H,MOU J H,CHENG Y P.Impact of pore structure on gas adsorption and diffusion dynamics for long-flame coal[J].Nat Gas Sci Eng,2015,22:203-221.
[2] 张飞燕,韩颖.煤屑瓦斯扩散规律研究[J].煤炭学报,2013,38(9):1589-1596.ZHANG Feiyan,HAN Ying.Research on the law of gas diffusion from drill cuttings[J].Journal of China Coal Society,2013,38(9):1589-1596.
[3] 张登峰,崔永君,李松庚,等.甲烷及二氧化碳在不同煤阶煤内部的吸附扩散行为[J].煤炭学报,2011,36(10):1693-1698.ZHANG Dengfeng,CUI Yongjun,LI Songgeng et al.Adsorption and diffusion behaviors of methane and carbon dioxide on various rank coals[J].Journal of China Coal Society,2011,36(10):1693-1698.
[4] 韩颖,张飞燕,余伟凡,等.煤屑瓦斯全程扩散规律的实验研究[J].煤炭学报,2011,36(10):1699-1703.HAN Ying,ZHANG Feiyan,YU Weifan,et al.Experimental study on gas diffusion law from drill cuttings during the whole desorption process[J].Journal of China Coal Society,2011,36(10):1699-1703.
[5] 马东民,张遂安,蔺亚兵.煤的等温吸附-解吸实验及其精确拟合[J].煤炭学报,2011,36(3):477-480.MA Dongmin,ZHANG Suian,LIN Yabing.Isothermal adsorption and desorption experiment of coal and experimental results accuracy fitting[J].Journal of China Coal Society,2011,36(3):477-480.
[6] 聂百胜,郭勇义,吴世跃,等.煤粒瓦斯扩散的理论模型及其解析解[J].中国矿业大学学报,2001,30(1):19-22.NIE Baisheng,GUO Yongyi,WU Shiyue,et al.Theoretical model of gas diffusion through coal particles and its analytical solution[J].Journal of China University of Mining & Technology,2001,30(1):19-22.
[7] 魏建平,王洪磊,王登科,等.考虑渗流-扩散的煤层瓦斯流动修正模型[J].中国矿业大学学报,2016,45(5):873-878.WEI Jianping,WAND Honglei,WAND Dengke,et al.An improved model of gas flow in coal based on the effect of penetration and diffusion[J].Journal of China University of Mining & Technology,2016,45(5):873-878.
[8] 李志强,成墙,刘彦伟,等.柱状煤芯瓦斯扩散模型与扩散特征实验研究[J].中国矿业大学学报,2017,46(5):1033-1040.LI Zhiqiang,CHENG Qiang,LIU Yanwei,et al.Research on gas diffusion model and experimental diffusion characteristic of cylindrical coal[J].Journal of China University of Mining & Technology,2017,46(5):1033-1040.
[9] 聂百胜,杨涛,李祥春,等.煤粒瓦斯解吸扩散规律实验[J].中国矿业大学学报,2013,42(6):975-981.NIE Baisheng,YANG Tao,LI Xiangchun,et al.Research on diffusion of methane in coal particles[J].Journal of China University of Mining & Technology,2013,42(6):975-981.
[10] 李志强,王登科,宋党育.新扩散模型下温度对煤粒瓦斯动态扩散系数的影响[J].煤炭学报,2015,40(5):1055-1064.LI Zhiqiang,WANG Dengke,SONG Dangyu.Influence of temperature on dynamic diffusion coefficient of CH4 into coal particles by new diffusion model[J].Journal of China Coal Society,2015,40(5):1055-1064.
[11] CHARRIèRE D,POKRYSZKA Z,BEHRA P.Effect of pressure and temperature on diffusion of CO2 and CH4 into coal from the Lorraine basin (France)[J].International Journal of Coal Geology,2010,81(4):373-380.
[12] PAN Z J,CONNELL L D,CAMILLERI M,et al.Effects of matrix moisture on gas diffusion and flow in coal[J].Fuel,2010,89(11):3207-3217.
[13] CUI X J,BUSTIN R M,DIPPLE G.Selective transport of CO2,CH4,and N2 in coals:Insights from modeling of experimental gas adsorption data[J].Fuel,2004,83(3):293-303.
[14] STAIB G,SAKUROVS R,GRAY E M A,A pressure and concentration dependence of CO2 diffusion in two Australian bituminous coals[J].International Journal of Coal Geology,2013,116:106-116.
[15] NANDI S P,WALKER P L.Activated diffusion of methane from coals at elevated pressures[J].Fuel,1975,54(2):81-86.
[16] CRANK J.The mathematics of diffusion[M].London:Oxford University Press,1975:135-136.
[17] CLARKSON C R,BUSTIN R M.The effect of pore structure and gas pressure upon the transport properties of coal:Alaboratory and modelling study:2.Adsorption rate modelling[J].Fuel,1999,78:1345-1362.
[18] RUCKENSTEIN E,VAIDYANATHAN A S,YOUNGQUIST G R.Sorption by solids with bidisperse pore structures[J].Chem Eng Sci,1971,26(9):1305-1318.
[19] BUSCH A,GENSTERBLUM Y.CBM and CO2-ECBM related sorption processes in coal:A review[J].International Journal of Coal Geology,2011,87(2):49-71.
[20] WANG G D,REN T,QI Q,et al.Determining the diffusion coefficient of gas diffusion in coal:Development of numerical solution[J].Fuel,2017,196:47-58.
[21] GOODMAN A L,BUSCH A,DUFFY G J,et al.An inter-laboratory comparison of CO2 isotherms measured on argonne premium coal samples[J].Energy & Fuels,2004,18(4):1175-1182.
[22] 王公达.煤层瓦斯吸附解吸迟滞规律及其对渗流特性影响研究[D].北京:中国矿业大学(北京),2015:5-6.WANG Gongda.Adsorption and desorption hysteresis of coal seam gas and its influence on gas permeability[D].Beijing:China University of Mining & Technology(Beijing),2015:5-6.
[23] LIU H H,MOU J H,CHENG Y P.Impact of pore structure on gas adsorption and diffusion dynamics for long-flame coal[J].Nat Gas Sci Eng,2015,22:203-221.
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