Study on coal bed gas displacement by flue gas in coal-fired power plants under different gas injection factors

doi:10.16265/j.cnki.issn1003-3033.2025.11.2963

Abstract

Abstract:

In order to improve the efficiency of gas extraction, numerical simulation methods were employed to analyze the characteristics of changes in gas volume fraction, gas breakthrough time, coal permeability, CH₄ extraction rate, and extraction quantity under different gas injection pressures. The results show that after flue gas injection, the volume fraction of CH₄ shows a downward trend, while the volume fractions of CO₂, N₂ and O₂ show an upward trend. The increase in injection pressure will shorten the breakthrough time of each gas in the flue gas, reduce the permeability of the coal seam and increase the gas extraction volume. At 180 days of extraction, the gas injection pressure increased from 0.5 MPa to 2.5 MPa, the coal seam permeability decreased from 8.722 7×10^-17 m² to 8.711 5×10^-17 m², and the extraction volume increased from 449.01 m³ to 715.30 m³. The gas drainage rate shows the variation characteristics of rising - falling - rising - falling. From the perspective of the influence of gas injection pressure on drainage, the gas injection pressure has a relatively small impact on the drainage in the first two stages.

Key words: injection pressure, power plant flue gas, CH₄ extraction, coalbed methane, gas pressure, gas drainage volume

CLC Number:

X936

BAI Gang, WANG Xuepeng, SU Jun, LIU Zhengdong, LI Jinyu, FAN Chaojun. Study on coal bed gas displacement by flue gas in coal-fired power plants under different gas injection factors[J]. China Safety Science Journal, 2025, 35(11): 65-71.

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条件	固体变形	流体边界	温度边界
边界EF	15 MPa	零通量	零通量
边界EG	辊支撑	零通量	零通量
边界FH	辊支撑	零通量	零通量
边界GH	固定约束	零通量	零通量
抽采孔	自由边界	86kPa	自由边界
注气孔	自由边界	狄式条件	狄式条件

组	注气压力/MPa	注气温度/K
1	0.5	300
2	1.0	300
3	1.5	300
4	2.0	300
5	2.5	300

压力/ MPa	抽采总量/ m³(60 d)	抽采总量/ m³(120 d)	抽采总量/ m³(180 d)
0.5	123.37	300.55	449.01
1.0	134.08	336.93	509.98
1.5	155.97	390.28	586.47
2.0	168	429.11	650.46
2.5	177.67	464.76	715.30