Hard Coal Mining Research Articles

Remote detection and monitoring of post-mining heat island

Underground hard coal mining activity in southern Poland has lasted more than 200 years. Among many factors related to mining and influencing the natural environment, the longest-active are coal waste heaps and tailings ponds. Several hundred objects are inventoried in Lower and Upper Silesia, of which 109 are located in the Lower Silesian Coal Basin (LSCB). These remnants of mining activity are built of gangue, waste coal, and coal silt (post-mining wastes). They cause environmental hazards, i.e., soil, air, groundwater, and surface water pollution in the storage area. They also tend to combust spontaneously, emitting enormous amounts of greenhouse gases into the atmosphere and increasing their neighborhood’s air, soil, and water temperature. Indigenous fires occur more than 20 years after the end of the waste disposal phase. The post-mining heat island (PMHI) phenomena, related to thermal activity development of the post-coal mining heaps and tailings ponds, is still under-recognition and research. Therefore, our study aims to improve and develop a methodology for remote detection and monitoring of heat islands resulting from coal mining operations to track the thermal activity of heaps and tailings ponds in LSCB from mines closure to 2023. The study used open satellite data from the Landsat program to identify and track post-mining heat islands over 23 years within the former mining area and verify the results within the borders of the inventoried heaps and tailings ponds. As a result, geospatial analysis on a time scale was carried out to identify post-mining hot spots. The self-heating intensity index (SHII) and the air temperature thermal indicator (ATTI) were calculated for identified and confirmed objects. SHII ranged between 0.00 and 10.07, and ATTI, on the other hand, varied from −12.68 to 25.18. Moreover, maps of the thermal activity of selected heaps were developed, the characteristics of the self-combustion phenomena were identified, and the remote detection of PMHI and its monitoring methodology was developed. The provided method can be used in the future to regularly monitor coal mining areas to prevent and identify hazardous hot spots and verify the maturity stage of the self-combustion processes.

Post-mining deformations in the area affected by the former “Siersza” Hard Coal Mine in Trzebinia (southern Poland)

Post-mining deformations in the area affected by the former “Siersza” Hard Coal Mine in Trzebinia (southern Poland)

Operation Optimization of a Bucket Conveyor Transporting Wastes in the Processing Plant of a Hard Coal Mine

This study presents the structure and principles of operation of the control system for a bucket conveyor operating in a jig preparation plant. The idea of controlling the conveyor speed is to maintain constant, nominal filling of the buckets, and thus achieve a constant mass of material on the conveyor. As part of the completed task, a new control algorithm was developed and implemented to increase transport efficiency. Simulation and industrial test results were analyzed, in which the traditional PID controller was replaced with a fuzzy controller, which enabled control error reduction, thus achieving better control quality.

Identification of strong tremor causes for appropriate rock burst prevention in a hard coal mine

Identification of strong tremor causes for appropriate rock burst prevention in a hard coal mine

The Optimal Transportation Option in an Underground Hard Coal Mine: A Multi-Criteria Cost Analysis

The issue of transport in underground hard coal mines is very rarely described in the literature. The financial aspects of this issue are even less often analyzed. Publications in this area focus on technical issues and the safety of mining crews. More attention is paid to transport in open-pit mines. The above premises and practical needs imply the need to conduct economic analyses of transport systems in underground hard coal mines. This paper is a scientific communication, which presents the concept of a multi-criteria cost analysis as a tool to support the selection of the optimal transportation option in an underground hard coal mine. Considerations in this area have not been carried out in the relevant literature, and the problem of selecting a transportation option is a complex and necessary issue in the practice of underground mines with extensive mine workings. The methodology presented includes five cost criteria (costs of carrying out the transportation task; route expansion costs; rolling stock maintenance costs; depreciation costs; and additional personnel costs). The simultaneous application of criteria relating to utility properties in addition to cost criteria makes it possible to adopt a specific technical and organizational model of the transportation system based on the indication of the optimal solution, resulting from the mathematical construction of functions of objectives relating to utility and cost. The optimal variant of the designed system and configuration of the material transportation system in underground workings takes into consideration the following: (1) seven utility criteria (KU1—transportation task completion time; KU2—compatibility of transportation systems; KU3—continuous connectivity; KU4—co-use with other transportation tasks; KU5—safety; KU6—inconvenience; KU7—operation under overplanning conditions) and (2) five cost criteria (KK1—costs of implementing the transportation task; KK2—costs of route expansion; KK3—rolling stock maintenance costs; KK4—depreciation costs; KK5—additional personnel costs). Based on the aforementioned criteria, two objective functions are built for each option: utility and cost. They present divergent goals; therefore, they are non-cooperative functions. Both utility and costs strive for the maximum. In the developed methodology, an ideal point is usually a fictitious solution representing a set of maximum values among all the achievable values in a set of solutions, but it is impossible to achieve this simultaneously based on all the criteria. This point illustrates the maximum utility and lowest cost among the alternatives considered, which is obviously impossible for any of the variants to meet at the same time, although it indicates the possibilities of the technique and the range of costs. For the developed method, a so-called “PND” nadir point is also determined, representing the least-preferred level of achievement of all goals simultaneously, determined from the set of optimal points in the Pareto sense. The originality of the conceptual considerations undertaken stems from: filling the gap in the economic methodology of complex transportation systems evaluation; embedding considerations in the trend concerning complex transportation systems of underground mines; and focusing considerations on the pre-investment phase, making it possible to optimize costs before expenditures are incurred.

Demonstrating the need for a just transition: Socioeconomic diagnosis of polish cities living on hard coal mining

Under the increasing pressure of decarbonization, the issue of further development of post-mining regions and economies based on the extraction of fossil fuels is becoming a priority and urgent issue, especially in the European Union, where a complete departure from coal production is planned in the coming years. For these reasons, this article seeks effective ways to prevent the negative effects of mine closures. This goal is implemented in the context of a long-term socioeconomic diagnosis of 12 Polish cities located in the Upper Silesian Coal Basin. These are cities where the coal industry has been completely liquidated, only some of the mines have been closed or all mining plants have been maintained. In the course of research, which is a multiple case study, the following are used: descriptive statistics, cluster analysis and multi-criteria analysis. The obtained results indicate a negative socioeconomic situation of cities where all mines have been closed (Zabrze, Bytom, Sosnowiec). The condition of cities where hard coal is still mined is much better. Nevertheless, the development of the entire region is slower than the development of the country, which implies the need for central management and economic support. Research results indicate a significant isolation and exclusion of cities that use a homogeneous development strategy based solely on the mining industry. In the future – when all mining plants are liquidated – this problem may intensify and lead to the collapse of the entire Upper Silesian Coal Basin and other regions of the European Union where coal is still mined. Bearing in mind the results of the above analyzes, it should be stated that the EU just transition program is essential in the process of transforming and supporting post-mining regions.

Main objectives of the strategy, as well as motivations for the transformation of hard coal mining in Poland

Purpose: in the cognitive space, the article focuses on the issue of dynamically growing social awareness of the impact of hard coal on climate change - which determines the need to implement a strategy to abandon this raw material. The authors of the article also point out that in connection with this process - as the world strives for sustainable and more ecological development - the transformation of the hard coal mining sector becomes an inevitable challenge. Methodology: the theses presented in the article were verified using the following methods: literature review, critical analysis of literature, analysis and comparison of documents and an example of good practices. Resultat: properly managing the transformation of the hard coal mining sector is key to ensuring that it delivers long-term social and economic benefits - while minimizing the negative impact of the transformation on mining communities and workers in the hard coal mining sector. Therefore, a holistic approach is important in this space, taking into account the ecological, economic, political and social context of transformation. Originality: the transformation of mining is necessary due to the sustainable development goals, environmental protection and the fight against climate change. It is also a political challenge that requires well-thought-out investments, policies and regulations to minimize the negative socio-economic effects of the transformation and to use the development potential of the transformed areas in all their dimensions. Keywords: mining, strategy, transforming.

Examples of using laser scanning as a support for traditional measuring methods in hard coal mining

In recent years, the growing interest in new techniques for spatial data acquisition, processing and analysis has also found applications in surveying and geological departments, where it is used in the process of developing documentation. In the conditions of mining operations, surveying measurements must be carried out quickly, safely and with sufficient accuracy. The use of laser scanning allows the collection of a significant amount of data, which requires time-consuming processing, but is necessary for accurate modelling of objects in 3D. The legal basis for the use of laser scanning in mining is the acts that regulate activities in the field of surveying, geological survey documentation and technical standards for surveying. The process of implementing laser scanning in underground mining requires compliance with occupational safety regulations and technical standards, as well as proper training of personnel. The laser scanners used in practice are equipped with the SLAM algorithm, enabling precise measurement and point cloud generation. Appropriate software is crucial for processing and analysing the collected data. The use of laser scanning makes it possible to efficiently perform non-standard measurements, which contributes to streamlining work at mining facilities. However, to realize its full potential, it is necessary to train personnel and raise the level of use of this technology.

Optimal geometry of the powered roof support’s operation

Monitoring the working parameters of powered roof support is an area for improvement in hard coal mining. The phenomena occurring during the operation generate many risks from difficult geological and mining conditions, leading to undesirable events. In addition, improper use of machinery and equipment results in a high accident rate in mining. Thus, monitoring the operation of machines in mining reduces accidents and losses resulting from stops and prevents unforeseen failures caused by operational and external factors. The paper presents the research results on the optimal geometry of the powered roof support operation in the mining wall. The research included the powered roof support’s essential elements’ operation. Sensors constituting the measuring system were installed on these elements. The measurements made by the sensors made it possible to determine the working height at a given stage of the section’s operation. The research was carried out in three sections, which were part of the powered roof support. The measurements were taken during actual changes occurring in the coal mining process.

The Impact of Atmospheric Pressure Changes on Methane Emission from Goafs to Coal Mine Workings

Increased effectiveness of methane drainage from sealed post-mining goaves in hard coal mines contributes to reduced methane emission from goaves into the mine ventilation system. This paper focuses on issues concerning the assessment of the additional amount of methane released from the goaf into mine workings during periods of atmospheric pressure drops, which can be captured with a methane drainage system. Thanks to the solutions presented in the paper, it is possible to control the efficiency of the goaf drainage system, which in turn leads to the reduction of methane emission from the mine ventilation air into Earth’s atmosphere. These solutions are of great added value for both the environment and coal mines as they reduce the costs arising from greenhouse gas emissions that are incurred by mining companies, increasing the efficiency of methane capture and its use in gas engines or district heating systems. The paper uses relationships relating to the influence of atmospheric pressure changes on the process of gas release from the goaf according to the hysteresis loop of methane release during atmospheric pressure changes, which was developed based on conducted research. The analysis and conclusions presented in this paper may facilitate the development of strategies aimed at reducing methane emissions from a mine’s ventilated air into Earth’s atmosphere.

Competitiveness of the Polish hard coal mining sector as a fuel supplier for heat and power generation

Competitiveness of the Polish hard coal mining sector as a fuel supplier for heat and power generation

Forecast of the Maximum Methane Concentration in the Longwall Outlet and in the Ventilation Roadway. Case Study

Abstract The mining process of the coal seam wall is accompanied by the release of methane into the mine atmosphere. This process is highly variable and depends on the methane content in the seam and the methane saturation of the rocks surrounding the seam. This is the specificity of the Polish hard coal mining industry. In the article, prognostic formulas for the maximum methane concentration at the outlet of the longwall ventilation gallery were developed. In the presented article, these formulas were used to predict methane concentration at the longwall outlet and in the ventilation gallery at a distance of up to 10 m in front of the longwall. In order to assess the accuracy of the forecasts, their results were compared with the forecast at the exit of the ventilation roadway. The obtained results are so accurate that it is worth repeating this type of check also using measurements in other longwalls. It will allow to reduce the risk of methane explosion during operation.

An Economic Evaluation of the Functioning of Hard Coal Mining in Poland in the Years 2016-2018

An Economic Evaluation of the Functioning of Hard Coal Mining in Poland in the Years 2016-2018

Criteria for Assessing the Longevity of Hard Coal Mines

Criteria for Assessing the Longevity of Hard Coal Mines

Assessment of the Impact of a Municipal Landfill on Microbiological Quality of Air in the Revitalized Area of “Brzeszcze Wschód” Hard Coal Mine

Assessment of the Impact of a Municipal Landfill on Microbiological Quality of Air in the Revitalized Area of “Brzeszcze Wschód” Hard Coal Mine

Study on the Usefulness of Lean Management Tools and Techniques in Coal Mines in Poland

The article presents research on the possibilities of utilising the Lean Management method to increase the profitability of coal mining operations through cost rationalisation and production optimisation. The Lean Management method has its roots in the automotive industry, but its significant benefits can allow it to be transferred to other industries. Based on the analysis of global literature describing examples of its application in general mining, as well as the authors’ own observations related to Polish hard coal mining, it was determined that the Lean Management method is not being utilised in this field. This article outlines the course and results of an original expert-mathematical study to assess the usefulness of specific Lean Management tools and techniques in hard coal mining. The study drew on knowledge obtained from selected, competent experts who demonstrated high levels of agreement in their assessments. Five core production areas were identified, and twelve widely used Lean Management tools and techniques were selected. The obtained assessments of the usefulness of Lean tools could serve as valuable guidance for mining management in the selection of methods for improving mining production in coal mines.

Treatment of radium-bearing brine using various zeolites: NaP1, NaX, clinoptilolite, 3A, 5A, 13X, ZSM-5, SAPO-11, SAPO-34

This paper investigates the possibility of radium removal from brines using zeolites. Radium concentration in collected from hard coal mine water was as follows: 226Ra 3.3 ± 0.2 Bq/L, 228Ra 5.5 ± 0.5 Bq/L. Ten types of zeolites were selected for treatment: clinoptilolite, NaP1, NaX, 3A, 5A, 13X, Y, ZSM-5, SAPO-11, and SAPO-34. Sequential batch purification tests were performed. High efficiencies of radium removal from mine brine achieved with NaP1 and NaX, synthesized from fly ahes, are promising for the further application of obtained zeolitic materials, especially for water treatment. Furthermore, the use of zeolites derived from waste fly ash is an ecological and sustainable solution for environmental protection and remediation.

An attempt to use machine learning algorithms to predict strong tremors during longwall mining of a coal seam

Strong tremors during longwall mining are usually associated with the fracturing of thick sandstone layers. The prediction of such tremors is important and can be treated as a form of rockburst prevention. The article presents the possibility of predicting the occurrence of strong tremors based on the random forest algorithm in the 48-h forecast horizon. The study concerns a longwall panel in coal seam No. 506 in one of the hard coal mines in the Upper Silesian Coal Basin, Poland. The extraction of this longwall panel was carried out at a great depth, surrounded by thick layers of sandstone and with the occurrence of edges in the previously mined seams. Therefore, seismic activity was high and strong tremors occurred. Based on the seismic catalogue and data related to the longwall face advance, 12 parameters were selected that were most significantly positively or negatively correlated with the occurrence of strong tremors. Based on 10 randomly selected datasets, models of the random forest algorithm were trained and then tested. Due to the much smaller number of cases of strong tremors compared to days when there were no strong tremors, the set of training data was balanced using the ADASYN algorithm. The obtained models had an average recall value of 0.79, and average accuracy equalled 0.912. The trained models showed high efficiency in predicting minority cases of days with strong tremors for up to 48 h and a relatively low percentage of misclassifications.

Numerical simulation of hydraulic fracture extension patterns at the interface of coal-measure composite rock mass with Cohesive Zone Model

This study presents the development of a numerical computational model for hydraulic fracturing of coal-measure rock mass. The model is based on the B-K hybrid fracture energy criterion and is implemented using the extended finite element method (XFEM) and cohesive zone model (CZM) in the ABAQUS software. The study took into account the elastic-plastic damage properties of the coal-measure rock mass, as well as the combined effects of tensile and shear damage during the start and expansion of hydraulic fractures. The expansion trajectories and fracture morphology of hydraulic fractures at the interface of coal-measure rock mass under different lithological combinations (lithological strength differences) and ground stress conditions are revealed, and the main controlling factors affecting the expansion across the bedding are clarified. The study provides valuable insights into the management of hydraulic fracturing in the challenging context of hard roof coal mines, the stimulation of coal-measure gas co-production reservoirs, and the development of effective fracturing stimulation strategies for shale oil reservoirs interlayered with thin sandstone, and it can promote the development of industrial production technology for coal-measure gas and shale oil and gas resources, and is beneficial to increase the proportion of clean energy in China's energy consumption structure, and thus promoting a further reduction in the carbon emissions from energy consumption.

Wind Power Plants and Selected Technical and Economic Aspects of Their Construction on Mine Heaps

As a result of energy transformation and decarbonization, the production of hard coal and lignite mining plants is gradually being phased out. Mine heaps, i.e., mine waste heaps, created as a result of the operation of these plants, are not attractive as land for housing, for the construction of production plants, or for agriculture. One of the most advantageous ways of recultivating these areas is using them as a place for the installation of renewable energy sources. In the case of post-mining heaps, it seems natural to use photovoltaics and wind turbines due to the artificial elevation of the terrain. This issue was analysed within the RFCS project SUMAD (Sustainable Use of Mining Waste Heaps). Experts from various countries and scientific disciplines analysed possible scenarios for the mine heaps’ management, with a special attention to geotechnical, environmental and socio-economic challenges. This article discusses one of the variants, namely the possibility of constructing the wind turbines on mining heaps.