doi:10.16186/j.cnki.1673-9787.2023020065

Received:2023/02/22

Revised:2023/04/06

Published:2024/05/15

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

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

1. School 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， Jiaozuo  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:  Objectives To investigate the coupling mechanism between pyrite and coal gasification under different CO₂ pressures. Methods Anaerobic fermentation experiments for gas production were conducted using high-pressure tanks at pressures of 1, 3 and 5 MPa with coal and pyrite. Results (1) Gas production was optimal at 1 MPa, yielding a final gas output of 1.26 mmol/g. As the pressure increased, gas production decreased, with only 0.02 mmol/g at 5 MPa. (2) As pressure increased, the concentration of HCO₃^- and the redox potential (Eh) in the solution rose gradually, while the pH decreased, reaching a minimum of 4.02 at the end of the 5 MPa experiment. Total Fe levels in the 1 MPa tank fluctuated and showed depletion, while the total Fe concentration in the 3 and 5 MPa tanks increased continuously in the early stages, indicating greater pyrite dissolution at higher pressures. (3) Under high-pressure conditions, significant reductions in chemical oxygen demand (COD) and short-chain fatty acid levels reflected a decrease in anaerobic fermentation and increased acidification of pyrite. (4) With rising pressure, the abundance and diversity of functional microbial species declined, with Thiobacillus spp. becoming predominant, leading to near cessation of anaerobic fermentation. Conclusions Optimal CO₂ pressure conditions can promote microbial growth and metabolism in coal reservoirs, while the oxidation of added pyrite generates iron ions that enhance enzymatic activity within microbial communities, supporting effective biogenic gas production from coal. The findings provide theoretical support for studying gas production mechanisms following nutrient injection in situ conditions.

Key words:CO₂ pressure; coal biogenic gas production;pyrite; total Fe; acidification degree