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  • Author: Magdalena Tutak x
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Abstract

One of the most common and most dangerous hazards in underground coal mines is fire hazard. Mine fires can be exogenous or endogenous in nature. In the case of the former, a particular hazard is posed by methane fires that occur in dog headings and longwalls. Endogenous and exogenous fires are large hazard for working crew in mining headings and cause economics losses for mining plants. Mine fires result in emission of harmful chemical products and have a crucial impact on the physical parameters of the airflow. The subject of the article concerns the analysis of the consequences of methane fires in dog headings. These consequences were identified by means of model-based tests. For this purpose, a model was developed and boundary conditions were adopted to reflect the actual layout of the headings and the condition of the atmosphere in the area under analysis. The objective of the test was to determine the effects of methane fires on the chemical composition of the atmosphere and the physical parameters of the gas mixture generated in the process. The results obtained clearly indicate that fires have a significant impact on the above-mentioned values. The paper presents the distributions for the physical parameters of the resulting gas mixture and the concentration of fire gases. Moreover, it shows the distributions of temperature and oxygen concentration levels in the headings under analysis. The methodology developed for the application of model-based tests to analyse fire events in mine headings represents a new approach to the problem of investigating the consequences of such fires. It is also suitable for variant analyses of the processes related to the ventilation of underground mine workings as well as for analyses of emergency states. Model-based tests should support the assessment of the methane hazard levels and, subsequently, lead to an improvement of work safety in mines.

Abstract

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.

Abstract

Hard coal mines and mining enterprises involved in hard coal exploitation in the area of the Upper Silesian Coal Basin (Górnośląskie Zagłębie Węglowe) are characterised by the presence of natural hazards typical of this type of exploitation. These hazards include the risks related to methane, coal dust explosion, endogenous fires, as well as rock burst and caving of roof rocks. The article presents the results of a taxonomic analysis aimed at determining the similarity of hard coal mines and mining enterprises in Poland in terms of the dangerous incidents caused by the risks related to methane, coal dust explosion, endogenous fires, as well as rock burst and caving of roof rocks. The analysis was carried out for the 2008-2018 data and encompassed a total of 26 hard coal mines and mining enterprises located in the Upper Silesian Coal Basin. The analysis was performed using the k-means method of non-hierarchical clustering. The main objective of the article was to determine homogenous groups (clusters) of mines exhibiting the greatest similarity in terms of dangerous incidents caused by the activation of natural hazards in the years 2008-2018. These data can be successfully used for the development of preventive measures and risk analyses for these enterprises.

Abstract

Dustiness of the mine atmosphere during carrying out exploitation is one of the most hazardous factors threaten to health and life of employees. Also it is large hazard for all type of mechanical and electrical devices operating in mining headings. Coal dust is also very dangerous due to its possibility of explosion. Currently applied technologies of rock mass mining process, entire transport process of output and applied ventilation system cause that rock and coal dust is presented practically in each of the mining heading. Practically, is impossible to eliminate dust from mining headings. However, one can determine its parameters and potential ways its displacement. In the paper there is presented modeling research methodology of dustiness state in a driven dog heading. Developed model is the basis for this methodology, including the diphase flow of mixture of air and dust in the mining heading. Analysis was performed for real driven dog heading. Based on performed analyses, distributions of particular fraction and movement trajectories of selected dust grains were determined. Developed methodology gives a lot of opportunities for analysis of dustiness state in mining headings and in other compartments. It enables to determine parameters of particular grains and their impact on ventilation parameters of the air stream in the tested headings. Obtained results can also be used to reduce dust hazard.

Abstract

One of the most dangerous and most commonly present risks in hard coal mines is methane hazard. During exploitation by longwall system with caving, methane is emitted to mine heading from the mined coal and coal left in a pile. A large amount of methane also flows from neighboring seams through cracks and fissures formed in rock mass. In a case of accumulation of explosive methane concentration in goaf zone and with appropriate oxygen concentration and occurrence of initials (e.g. spark or endogenous fire), it may come to the explosion of this gas. In the paper there are presented results of numerical analysis of mixture of air and methane streams flow through the real heading system of a mine, characterized by high methane hazard. The aim of the studies was to analyze the ventilation system of considered heading system and determination of braking zones in goaf zone, in which dangerous and explosive concertation of methane can occur with sufficient oxygen concentration equal to at least 12%. Determination of position of these zones is necessary for the selection of appropriate parameters of the ventilation system to ensure safety of the crew. Analysis of the scale of methane hazard allows to select such a ventilation system of exploitation and neighboring headings that ensures chemical composition of mining atmosphere required by regulation, and required efficiency of methane drainage. The obtained results clearly show that numerical methods, combined with the results of tests in real conditions can be successfully used for the analysis of variants of processes related to ventilation of underground mining, and also in the analysis of emergency states.