Design of Coal Seam Exploitation in Methane Hazard Conditions: A Case Study

Abstract

Carrying out exploitation in coal mines with a methane hazard imposes the use of special procedures and the analyses of numerous parameters in order to secure mining teams working underground. The article presents a method of coal seam exploitation design under conditions of a methane hazard for the newly prepared coal seams 404/1 and 403/1 in the years 2022 to 2030 in a coal mine in southern Poland as a case study. It primarily focuses on the preparation of the methane hazard prognosis. When adequately prepared, this is key to correctly designing the mining system in the newly opened parts of the deposit. Based on the obtained results, the appropriate methane drainage system and detection systems can be selected. The calculations led to the definition in which the longwall panel emissions of methane would be the highest. The estimates showed that, from 2022 to the beginning of 2028, even methane emissions between approximately 30 m3/min and 45 m3/min are forecast, with a significant increase for half of 2028 to a value between 57.58 m3/min and 100.00 m3/min. The highest value of methane emission was forecast for the A4 and A5 longwall panels in the 403/1 coal seam at 13.53 and 49.67 m3/min, respectively, and for the A2 and B1 longwall panels in the 404/1 seam at 41.85 m3/min and 25.46 m3/min, all with advance equal 7 m/d. Therefore, a drainage system will be required in all designed longwall panels. Considering the methane emission into the longwalls and the designed U-type ventilation, the calculated drainage effectiveness will vary between 38.3 and 40.6%. Higher effectiveness values require the application of a U-type ventilation with drainage, which allows obtaining effectiveness reaching 60.2%, with the methane emission between 20 and 30 m3/min, or even up to 62.6%, with the methane emission at the level of 30–40 m3/min. Another critical design stage is utilizing the gathered methane; the proposition is to use it in the cogeneration system. The heat generated by gas-powered engines should be used in the absorbent coolers that are used for chilling the water for the central air-conditioning system of the mine.