Changes on Methane Concentration after CO₂ Injection in a Longwall Gob: A Case Study

Abstract

Large areas of gob containing a considerable amount of methane in China are produced annually. The practice of injecting CO2 into gobs to extract methane could not only reduce the greenhouse gas emission, but also exploit clean methane resource. In this paper, an experimental apparatus was built to conduct the simulation of injecting CO2 into gob. The results show that the gob volume can be orderly divided into three zones from bottom to top: the residual coal zone (RCZ), the gas transitive zone (GTZ) and the methane enrichment zone (MEZ). The gob methane concentration exhibits an increasing trend before and after CO2 injection, and the methane concentration in the MEZ is obviously higher than that in the RCZ and GTZ. After CO2 injection, the methane concentration in RCZ decreases, while the methane concentration in the MEZ significantly increases. Meanwhile, the methane concentration in the RCZ would decrease as the total amount of CO2 injected increases and that the methane concentration in the MEZ would increase as the methane concentration in the RCZ increases. Based on the simulation results, a new in-situ technology was proposed and applied in a gob of Yiyuan mine in China to improve its methane extraction concentration by arranging a highly-located roadway in the MEZ and injecting CO2 into the GTZ. The field testing shows that this technology can increase the gob methane concentration by 22% for the highly-located roadway with an original low methane concentration of 20%-25%.

Department(s)

Mining Engineering

Comments

This research was supported by the National Natural Science Foundation of China (51504160), the Key Scientific and Technological Coal Projects of Shanxi Province (MQ2014-12), the Coalbed Methane Joint Research Foundation of Shanxi Province (2015012008), and the Team Foundation of Taiyuan University of Technology (No. 2014TD001). This work is also a project funded by the Open Projects of State Key Laboratory of Coal Resources and Safe Mining , CUMT (14KF03).

Keywords and Phrases

Atmospheric composition; Carbon dioxide; Coal mines; Greenhouse gases; Methanation; Experimental apparatus; Experimental study; Field testing; Longwalls; Methane concentrations; Methane enrichments; Methane extraction; Situ technology; Methane; CO2 injection; Coal mine; Experimental study; Longwall gob; Methane concentration

International Standard Serial Number (ISSN)

1875-5100

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2016 Elsevier, All rights reserved.

Publication Date

01 Feb 2016

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