Analysis of the Scale of Methane Hazard in Polish Hard Coal Mines

In the majority of Polish mines, the exploitation of hard coal is accompanied by the release of considerable amounts of methane. Being flammable and explosive, methane may form an explosive mixture with air once it appears in mine workings. For this reason, the methane hazard is recognised as one of the ventilation risks in the mining industry. This process leads to the formation of air and methane mixture, whose considerable amounts permeate into the atmosphere and the natural environment. This phenomenon is extremely unfavourable because methane is, besides carbon dioxide, yet another gas that exacerbates the greenhouse effect. For this reason, it is increasingly more common to equip mines with methane collection systems in the process of demethylation. These play a vital role for both the natural environment and the safety of work in mines. A reduction of the methane content in headings increases the safety of the working crew and enhances the effectiveness of mining production. The article presents an analysis of the methane-related hazard based on methane emissions during mining exploitation. The analysis was based on the data concerning the amount of methane emitted into the atmosphere and collected by methane extraction systems from 16 coal mines. It led to identification of homogenous mines with similar values of the absolute methane-bearing capacity and ventilation methane-bearing capacity as well as with similar amounts of methane collected by methane extraction systems. The analysis was performed using the non-hierarchical k-average method, which belongs to the group of algorithms for analysing clusters. As a result, the mines were divided into the assumed number of groups. The results obtained made it possible to determine a group of mines in which, in the Author’s opinion, similar systems can be applied for controlling and reducing the methane hazard. These results also open up numerous possibilities for undertaking joint business ventures by the mines in terms of using the collected methane and implementing preventive measures.