doi:10.16186/j.cnki.1673-9787.2023020065

Received:2023-02-22

Revised:2023-04-06

Online Date: 2023-06-25

Study on the coupling mechanism between pyrite and coal to gas under different CO₂ pressure conditions(Online)

XIA Daping1,2,3, LIAO Jiajia1, WANG Xinyi1,2,3, LI Saisai4, GU Pengtao4, YUAN Xiaoying1, JIAN Kuo5

1.Institute of Resources & Environment，Henan Polytechnic University，Jiaozuo  454000，Henan，China;2.Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization，Jiaozuo  454000，Henan，China;3.Mining Research Institute，Henan Polytechnic University，Ji- aozuo  454000，Henan，China;4.School of Energy Science and Engineering，Henan Polytechnic University，Jiaozuo  454000，Henan，China;5.College of Energy and Materials Engineering，Taiyuan University of Science and Technology，Jincheng  048011，Shanxi，China

Abstract:The in situ biogasification utilisation of coal can be affected by a variety of factors. Pyrite, as a common mineral fraction in coal seams and top and bottom plates, is likely to be involved in the anaerobic fermentation process when enriched bacterial solution is injected, and there is a lot of free gas in the coal seams. In order to study the effect of anaerobic fermentation of coal involving pyrite under different CO₂ pressure conditions, anaerobic fermentation gas production experiments of coal and pyrite were designed for three pressure autoclaves at 1, 3 and 5 MPa, and the results showed that: (1) the gas production was better at the pressure of 1 MPa, which was 1.26 mmol/L,with the increase of CO₂ pressure, the gas production decreased faster, and the gas production at 5 MPa was only 0.02 mmol/L, basically no output. (2) With the increase of pressure, the  concentration gradually increased, and the total iron was consumed in 1MPa with large fluctuations, while the total iron concentration kept increasing in 3 MPa  and 5 MPa, indicating that the dissolved amount of pyrite increased more in the latter two, and was positively correlated with the  concentration. (3) As the reaction progressed, the pH value kept decreasing, with the lowest value appearing at the end of the reaction at 5 MPa at 4.02, while the Eh value gradually increased; the COD value and short-chain fatty acid content also gradually decreased with the increase in pressure, which also reflected the decrease in the degree of anaerobic fermentation and the increase in the intensity of pyrite acidification. The study of anaerobic fermentation of coal under pyrite and different CO₂ pressure conditions can provide good theoretical support for an in-depth understanding of the gas production mechanism during nutrient enrichment injection under in situ conditions.

Key words:pressure;coal biogenic gas production;pyrite;total iron;degree of acidification

CLC: P618.11