Methodology for preparing coal seams with high methane content by complex impact method
1 Hanoi University of Mining and Geology, Hanoi, Vietnam 2 Vietnam Mining Science and Technology Asscociation, Hanoi, Vietnam 3 Dong Bac Corporation – Ministry of National Defence, Quang Ninh, Vietnam 4 Vietnam National Coal – Mineral Industries Holding Corporation Limited, Hanoi, Vietnam
- Keywords: Gas emission, High methane content, Impact vibration, Low permeability, Preparation of coal seams.
- Received: 12th-Apr-2021
- Revised: 10th-July-2021
- Accepted: 8th-Aug-2021
- Online: 1st-Dec-2021
- Section: Mining Engineering
Safety is always a top priority in underground coal mining, especially when mining at great depths, which is accompanied by an increase in methane content of the coal seams. The high concentration of methane in mine airstream is cause of many negative effects on various underground works. In some cases, when the methane content in underground areas reaches the limit value, mine fires can occur with great loss of people and equipment. In many countries, where the coal mining industry is developed, practical experience in deep mining has shown that current popular methods of coal seams preparation can not always bring absolute safety in working faces, especially when extracting and recovering coal seams with high methane content. The purpose of this study is to develop an appropriate coal seam preparation method that can minimize the risk of methane emissions, which is one of the causes of unsafety in the underground coal mining. In this paper, the authors propose to use a combination of different impact methods through boreholes to control the intensity of methane release from high methane content coal seams. The combined use of hydraulic and vibration methods will greatly increase the network of man-made cracks in the coal mass, which allows methane to escape more easily and reduce the gas content of coal block before extracting. The research and testing of the complex impact method in real conditions has yielded positive results: the ability to release gas increased by at least 3÷5 times and the degassing efficiency reached over 60% for coal seams, which has low permeability. After research and analysis, the authors conclude that the complex effect method is a promising new direction to support the control of methane emissions and contribute to the improvement of technical – safety effects when extracting coal seams with high methane content.