Study on the coupling mechanism between pyrite and coal gasification under different CO2 pressure

XIA Daping; LIAO Jiajia; WANG Xinyi; LI Saisai; GU Pengtao; YUAN Xiaoying; JIAN Kuo

doi:10.16186/j.cnki.1673-9787.2023020065

Abstract：Objectives To investigate the coupling mechanism between pyrite and coal gasfication under dif-ferent CO2 pressure,Methods anaerobic fermentation gas production experiments were carried out using high-pressure tanks with third-order pressures of 1,3 and 5 MPa for coal and pyrite,respectively.Results(1)The gas production was better at a pressure of 1 MPa,with a final gas production value of 1.26 mmol/g.As the pressure increased,the gas production in the tank decreased,and it was only 0.02 mmol/g at the 5 MPa.(2)With the increase of pressure,the mass concentration of HCO-3 and Eh in the aqueous solution gradually increased,while the pH kept decreasing,with the lowest value appeared at the end of the reaction in the 5 MPa experimental group,which was 4.02.The total Fe in the 1 MPa tank had a depletion and fluc-tuation,while the total Fe concentration in the 3 MPa and 5 MPa pressure tanks increased continuously in the pre-reaction period,indicating that the amount of dissolved pyrite increased more at the pressure of 3 MPa and 5 MPa.(3)Under high-pressure conditions,the significant decrease in chemical oxygen demand(COD)and short-chain fatty acid concentrations reflects a weakened anaerobic fermentation and an en-hanced degree of pyrite acidification.(4)The high throughput results indicated that the increase in pressure led to a decrease in the abundance and strain diversity of the functional species,with Thiobacillus spp.gradually became dominant,and this brought the anaerobic fermentation process to a basic standstill.Con-clusions Suitable CO2 pressure conditions can promote the growth and metabolism of microorganisms under coal reservoir conditions,while the addition of pyrite undergoes oxidation to produce iron ions,which can promote the enzymatic activity of the bacterial colony and make the biogenic gas production reaction of coal proceed smoothly.The study could provide good theoretical support for an in-depth understanding of the gas production mechanism after nutrient enrichment injection in situ conditions.