Hard Coal Deposits Research Articles

Restructuring substantial increase in natural gas reserves by coalbed methane (CBM) recovery

Coal deposits, especially hard coal deposits, contain in their structure large amounts of methane, which during exploitation is diluted through industrial ventilation and degassing technologies down to non-hazardous concentrations, reducing the major risk factor for the safety of workers and resources minerals. The amount of methane released and exhausted into the atmosphere by the degassing and ventilation stations of the mining units, in addition to being wasted instead of being used, is also a factor of environmental pollution, as a potential greenhouse gas (GHG). The environmental issues and the climate crisis faced by humanity compel the establishment of an Action Program on the methane issue, which includes the capture, recovery and exploitation of gas from active coal mines, or from virgin strata, from unexploited mining fields, with the help of currently available technologies and practices, which represent the chance to obtain clean energy and substantial climate benefits, in the short and long term. The solution to the use of methane gas from coal at active mining operations in Jiu a Valley - Romania, by burning it to obtain the thermal agent, brought important economic benefits by reducing energy costs and environmental protection by reducing methane emissions in the atmosphere. The present paper proposes an analysis of the benefits obtained as well as the development possibilities of methane usage for obtaining a clean fuel.

Modelling of a multi-seam hard coal deposit using IT tools

With the rising demand for mineral resources, efficient deposit management has become a critical challenge in modern mining. This article underscores the significance of geological modeling in coal deposit management, emphasizing the essential role that digital deposit models play across various mine departments. It outlines the methodology for creating geological models, detailing steps such as data digitization, validation, model construction, calibration, and continuous updates. The article examines three specific deposit modelling software programs (Minex, MineScape, and Carlson) highlighting their unique features and suitability for multi-seam coal deposits. The findings include the development of contour maps, structural and qualitative models, and conducting economic analyses. Additionally, the article discusses the importance of modelling tectonic disturbances and creating qualitative maps for effective deposit exploitation planning. It concludes by emphasizing that the integration of information technology with geological expertise is crucial for precise planning and optimization of mining operations, leading to more efficient and sustainable resource management.

Potentially Harmful Elements Content in Soil and Stream Sediments in Southwestern Districts of Katowice (Southern Poland) – Geochemical Record of Historical Industrial Plants’ Activity

Abstract The aim of the research was to assess the quality of topsoils and stream sediments in the districts of the Katowice City of southern Poland in the Upper Silesian Industrial Agglomeration, influenced primarily by the exploitation of hard coal deposits and metallurgy. The task was carried out using indicators used to assess anthropogenic soil contamination (contamination factor CF and the Igeo geoaccumulation index), as well as ecotoxicological indicators used to determine the quality of stream sediments (Threshold Effect Concentration TEC and Probable Effect Concentration PEC). In order to indicate the most polluted areas, geochemical maps of selected elements in soil and stream sediments were developed. The material comes from the top layer of soil (0.0–0.3 m) and stream sediments located in the districts of the Katowice City. The work took into account selected potentially harmful elements (PHEs). The concentrations of elements were measured using the ICP-AES method, except for Hg (the CV-AAS method). The values of the CF and Igeo indicators allowed for the indication of high concentrations of most metals, arsenic, and sulfur in the topsoil layer, significantly exceeding the geochemical background values caused by the historical exploitation of Zn-Pb and zinc ores and ferrous metallurgy. The values of the TEC and PEC indicators classify the sediments into categories that may threaten the environment and living organisms.

Groundwater vulnerability to pollution in degraded coal mining areas: modifying the DRASTIC method using the factor of exploitation impact on land surface

Mining activities such as underground exploitation of hard coal deposits and open cast mining are strong factors on groundwater depending on mine life cycle phases. The impact of coal mining activities on groundwater have been reported from many countries. In this case, a vulnerability assessment was conducted base on standard DRASTIC method and its modification DRASTIC MINE (DRASTICM) method. In order to take into account, the impact of mining activities, a new parameter was added which defined the impact of coal seams on the rock mass above, including the degree of its drainage and the range of its impact. In the standard DRASTIC method, the results indicate that groundwater vulnerability with high (38.6%) and very high occurrence classes (16.9% of the area), mostly covers the central part of the cast mine. In contrast, the reclaimed area of the excavation is a low-class area. The DRASTICM method increased the vulnerability index from 3 to 24 on 95% of the area, so a new vulnerability class of extremely high was delineated, which occurred in 1.6% of the area. This indicates areas that should be treated as a priority in order to avoid pollution, and in the final stage to plan activities in the field of the reclamation of mining areas. The results showed that groundwater vulnerability assessment in coal mining areas can be significantly improved.

Mobility of the Major and Trace Elements in the Coal Mining Wastes

Domestic and foreign static tests are considered to assess the impact of mineral waste from coal mining and processing on water objects when waste is placed in dumps or used for reclamation purposes. The results of static tests according to GOST R 58914–2020 for three samples of mineral waste taken from hard and brown coal deposits are presented. The wastes differ significantly in mineral and chemical composition, including sulfur content. It is shown that the high content of sulfur in the waste, including it in a water-soluble form, determines the low pH value of the aqueous extract. This, in turn, leads to an increase in the yield of water-soluble substances and to an increase in the mobility of major and trace elements.

Time variability of methane extraction from hard coal deposits in the Upper Silesian Coal Basin (Poland) in relation to geological and mining conditions

Time variability of methane extraction from hard coal deposits in the Upper Silesian Coal Basin (Poland) in relation to geological and mining conditions

Environmental hazard quantification toolkit based on modular numerical simulations

Abstract. Quantifying impacts on the environment and human health is a critical requirement for geological subsurface utilisation projects. In practice, an easily accessible interface for operators and regulators is needed so that risks can be monitored, managed, and mitigated. The primary goal of this work was to create an environmental hazards quantification toolkit as part of a risk assessment for in-situ coal conversion at two European study areas: the Kardia lignite mine in Greece and the Máza-Váralja hard coal deposit in Hungary, with complex geological settings. A substantial rock volume is extracted during this operation, and a contaminant pool is potentially left behind, which may put the freshwater aquifers and existing infrastructure at the surface at risk. The data-driven, predictive tool is outlined exemplary in this paper for the Kardia contaminant transport model. Three input parameters were varied in a previous scenario analysis: the hydraulic conductivity, as well as the solute dispersivity and retardation coefficient. Numerical models are computationally intensive, so the number of simulations that can be performed for scenario analyses is limited. The presented approach overcomes these limitations by instead using surrogate models to determine the probability and severity of each hazard. Different surrogates based on look-up tables or machine learning algorithms were tested for their simplicity, goodness of fit, and efficiency. The best performing surrogate was then used to develop an interactive dashboard for visualising the hazard probability distributions. The machine learning surrogates performed best on the data with coefficients of determination R2>0.98, and were able to make the predictions quasi-instantaneously. The retardation coefficient was identified as the most influential parameter, which was also visualised using the toolkit dashboard. It showed that the median values for the contaminant concentrations in the nearby aquifer varied by five orders of magnitude depending on whether the lower or upper retardation range was chosen. The flexibility of this approach to update parameter uncertainties as needed can significantly increase the quality of predictions and the value of risk assessments. In principle, this newly developed tool can be used as a basis for similar hazard quantification activities.

The Effect of Mining Remnants on Elastic Strain Energy Arising in the Tremor-Inducing Layer

A vast majority of hard coal deposits in Poland have a multi-seam structure, hence the presence of mining remnants left from previous operations. The impact of those remnants (exploitation edges or residual pillars) can further intensify geomechanical phenomena occurring in the rock mass, leading to changes in the original state of stress. This applies to all layers within the rock strata, including thick and coherent ones (referred to as tremor-inducing layers) where the impacts of mining remnants are likely to trigger tremors, thus enhancing the rock bursts hazard. In the light of the geomechanical model of rock strata recalled in the study, it is assumed that homogeneous and isotropic elastic layers are found between the considered mining remnant (which is revealed as the stress distribution), and the rock medium modelled as a homogeneous and isotropic half-plane. Development of the state of stress in the bedded medium was brought down to the analysis of interacting elastic layers, where the biharmonic equation is satisfied for each layer and for each respective half-plane. This equation can be solved by the integral Fourrier transform method. The impacts of the exploitation edge and the residual pillar on the elastic strain energy in the tremor-inducing layer is illustrated by recalling the Burzyński’s stress criterion. Strain energy in the tremor-inducing layer was analysed for various deformation properties of the surrounding strata and for various methods of coal extraction from the seam underneath the tremor-inducing layer. The results of the study evidence that a change in deformation properties of strata in the vicinity of the tremor-inducing layer may affect the state of stress and strain energy, which impacts on the tremor hazard levels in the vicinity of mining remnants areas.

Selecting the optimal exploitation option using a digital deposit model and the AHP

The prime objective of the study was to identify and evaluate options for development and exploitation of a prospective hard coal deposit using a digital geological model and a multi-criteria decision-making approach allowed, in elaborated research process, to identify investment alternatives and outline the one that maximizes the benefits for the potential investor. The developed research methodology was based on decision criteria including: economic, technical, geological, social, and environmental aspects. The combination of the above criteria made it possible to create six options for the development of the deposit named as: 1.2 MAX and 1.2 EKO, 1.5 MAX and 1.5 EKO, and 1.8 MAX and 1.8 EKO. The Analytic Hierarchy Process (AHP) was used as a method to select the optimum investment option. The research process consisted in taking into account the positive and negative impacts of individual exploitation options by building four separate hierarchical models (BOCR analysis), i.e. Benefits (B), Opportunities (O), Costs (C) and Risks (R).Digital geological model of the existing and prospective deposit was a key source of information for AHP assessment process. The structural model of 15 seams of economic importance and a qualitative model of coal quality parameters were elaborated. The structural and quality models were prepared on the basis of lithostratigraphic profiles from 55 surface boreholes, 16 underground boreholes and 250 geological profiles of mine workings in the area of the existing coal deposit. These models constituted input for the assessment of economic efficiency of the above mentioned options. The digital model served as the basis for the creation of access, development and mining work schedules, and the developed simulations of mining exploitation were used to build a model of surface deformation considered as one of the most significant decision-making factor.The result of the work was formulated as a ranking of the analyzed scenarios, indicating the most attractive ones. In this case, and in terms of the adopted AHP methodology, the dynamic strategy scenarios is represented by ‘No additional shafts' scenario, 1.8 EKO, 1.8 MAX and 1.5 EKO scenarios. Their implementation fulfils the policy of sustainable depletion of the reserves of a prospective deposit, while maintaining environmental standards and high economic efficiency. The ‘No additional shafts' scenario represents the idea of rapid decommissioning of the mining industry, while scenarios 1.8 EKO, 1.8 MAX and 1.5 EKO are in turn scenarios of rational resources management allowing for gradual depletion of the deposit reserves in a long-term perspective.

The environmental fate of metals from zinc and lead mining area in surface water (Przemsza River, southern Poland)

The chemical composition of surface waters of the Przemsza River flowing through Upper Silesia (in southern Poland) is strongly affected by Zn and Pb ore, and less by Carboniferous hard coal deposits. The chemical type of surface water is Ca-HCO3. In the waters, three groups of metals and metalloids were found that directly interfere with the mineralization of the deposit. Although genetically related to the same deposit, each group exhibits a different fate in the environment. A typical deposit association is Pb-Zn-Ag-As-Sb-Hg. The first group of metals in surface waters is consistent with the typical association of the ore Zn-Pb-Cd-(Tl), the second includes Ag-Sb-Hg, and the third includes the additives in the zinc and lead ore Co-Ni-Mo-Mn:[(Ca↔Na)+(HCO3↔Cl)]+[(Zn-Pb-Cd-(Tl))+(Ag-Sb-Hg)+Co-Ni-Mo-Mn)].Depending on the pH-Eh conditions, metals and metalloids precipitate out of the solution or sorb on solid particles. The concentrations of individual groups of metals are interdependent but show different environmental fates along the river course. The natural process of the enrichment of surface waters with Zn-Pb-Cd-(Tl) is by water circulation in a rock matrix naturally rich in the metals and draining groundwaters by the river. Under oxidizing and slightly alkaline conditions, Ag-Sb-Hg incorporated into the soluted chemical compounds, may, when the physicochemical parameters of the waters change, be adsorbed and/or precipitated. The presence and ratio of concentrations of Co-Ni-Mo-Mn with respect to zinc are almost identical, differing only in concentration.

Possibilities of Capturing Methane from Hard Coal Deposits Lying at Great Depths

Methane present in coal seams is a natural hazard present during the exploitation of underground mining plants. It is an explosive and flammable gas that is released into mining excavations, and it is necessary to reduce its concentration. Capturing methane while preparing extraction is virtually impossible due to the low permeability of coal resulting from its deposition depth. After the beginning of exploitation and disrupting the seam’s structure, methane is released into mine air. The most common method of minimizing gas released into ventilation air is draining the rock mass. This method allows achieving the desired ventilation parameters but requires appropriate mining techniques in hazardous areas. The article presents the example of methane capture during the operation in the longwall B-15 with an overlying drainage gallery. The authors have highlighted an example of the longwall B-15 that when using this particular drainage method, allowed capturing twice the amount of methane forecasted, thus increasing the efficiency of methane drainage. At the preliminary stage of longwall development, the amount of methane charged by the drainage system had relatively low values, reaching 15 m3/min. In the next few months, these parameters increased and varied between 35 to 55 m3/min. A significant difference in methane capture appeared in the second stage of exploitation, where the highest value of captured methane reached 82 m3/min. This particular longwall example shows that it is crucial to properly design the drainage system for seams with high forecasted methane release. It is worth remembering that using a drainage gallery provides an increase in the methane capture from the desorption zone areas, thus increasing total methane capture in comparison to forecasts.

3D representation of geological observations in underground mine workings of the Upper Silesian Coal Basin

The purpose of the paper is to present the possibilities of the three-dimensional representation of geological strata in underground (access) workings in a hard coal deposit in the SW part of the Upper Silesian Coal Basin, using CAD software and its flagship program AutoCAD. The 3D visualization of the results of underground workings’ mapping is presented and illustrated on two opening out workings (descending galleries). The criteria for choosing these workings were based on their length and the complexity of geological settings observed while they were driven. The described method may be applied in spatial visualization of geological structures observed in other deposits, mines and existing workings (it is not applicable for designing mine workings), also beyond the area of the Upper Silesian Coal Basin (USCB). The method presented describes the problem of the visualization of underground mine workings in a typical geological aspect, considering (aimed at) detailed visualization of geological settings revealed on the side walls of workings cutting the deposit.

Occurrence consequences of mining terrain surface discontinuous linear deformations in a residential building

In the article a case study of consequences of underground mining exploitation of hard coal deposit on terrain surface and in a residential building has been presented. It was realized an exploitation of two hard coal seams (in three layers) in Poland, in the Upper Silesian Coal Basin, in 2013 – 2019. Operation was conducted at relatively small depth and by use of five longwalls with significant height and large decline. There were observed exploitation influences of fifth longwall on terrain surface and in the building by use of geodetic surveys. Measurements were carried out on the ground and wall points located in two perpendicular directions. Heights differences and distances between next points before and after the end of exploitation of last longwall have been measured. There the inclinations changes of particular sections have been determined. Analysis of surveys results shown that processes of the terrain and buildings deformations take place differently and terrain inclinations and building deviations have other values. Moreover, next to the building four discontinuous linear deformations of terrain surface (one in front of the building, one under the building, two behind the building) have been occurred. The ground steps location was detected by use of profile leveling of road located on the east of the building. A ground step with height of 15 cm under the building caused its crack. Example of the building with a partial basement proved that a consolidation type of building in the ground has a significant influence on values of its deviations.

Mining terrain curvatures approximation using the polynomials and a subsidence trough profile fragmentation

In an article a method of average course obtaining of measured mining terrain curvatures has been presented. Terrain curvatures values are very important for building objects located on mining areas and which have a considerable length or/and a great cubature. Curvatures observed graph has an irregular course and that’s why there is a need of their average course determination in order to obtain the most probable value. Measured curvatures approximation by use of the polynomial various orders has been done. Additionally, a whole profile of subsidence trough into the parts has been divided. Subsidence trough fragmentation allowed for a better fit of the curvatures average values to the observed values. A right polynomial order and a trough segments proper number taking into account value of variability coefficient of curvatures random dispersion have been chosen. Geodesic surveys, based on which a graph of measured curvatures has been obtained, in the Upper Silesian Coal Basin (Poland) have been done. There was conducted a mining exploitation of hard coal deposits by use of the longwall system with a roof rocks cave-in.

Evaluation of undeveloped hard coal deposits and estimation of hard coal reserves in the Upper Silesian Coal Basin, Poland

The article presents the results of works concerning evaluation of undeveloped deposits in the Upper Silesian Coal Basin and an estimation of hard coal reserves which can be developed by 2050. Evaluation of hard coal deposits was established on criterions choice and their score determination. On the basis of obtained the final score and after consultations with experts in the field of hard coal mining, there were selected three areas of undeveloped deposits with the amount of about 1.99 Gt (billion metric tons) of anticipated economic resources which can extend the coal reserve base located in the direct vicinity of operating hard coal mines. Additionally, one undeveloped coal deposit with estimated resources amounts to about 1.15 Gt was selected as a potential deposit whose resources could be included in the reserves of operating mines, up to the depth of 1,500 metres. Deposit areas were selected and hard coal reserves were estimated with a view to building new coal mines. For Oświęcim-Polanka deposit, there was built a 3D geological model with estimated the amount of 924 Mt (million metric tons) of anticipated economic resources of coal. An example of a deposit development with ventilation, extraction and transport/haulage underground roadways connecting coal seams with the surface are presented. The designed mine working was placed in the 3D geological deposit model which is a useful tool for designing spatial deposit management.

A Multiscale Structural Analysis of Soft and Hard Coal Deposits in Deep High‐Gas Coal Seams

In recent years, with the increases in coal mining depths, the risk of coal seam outburst occurrences has increased. Therefore, it is of major significance to study the multiscale structures of soft and hard coal deposits in order to prevent and control the coal and gas outbursts. In this research investigation, soft and hard coal multiscale structures were comprehensively examined using various laboratory methods. The results revealed the following: (1) From a macrostructural aspect, the physical and mechanical properties of the soft coal were weaker than those of the hard coal. It was found that the majority of the examined specimens were characterized by scaly structures without blocks larger than 50 mm. The hard coal was observed to be mainly massive with only a small part being clastic. Therefore, the structural characteristics were considered to be stable. (2) From a microstructural perspective, the surfaces of the soft coal specimens were observed to be rough. The pores were found to be more developed, with the edge of pores being mainly hackly. At the same time, fractures were also relatively developed, showing good connectivity. (3) From a micropore structural perspective, it was found that the BET‐specific surface areas and BJH‐specific surface areas of the soft coal specimens were higher than those of the hard coal specimens, which indicated that the gas adsorption and diffusion migration abilities of the soft coal were greater than those of the hard coal. (4) It was suggested from the study results that the ventilation and gas extraction processes should be strengthened in the mining activities of coal seams with high, soft stratification content. At the same time, the methods used for water injection modification should be enhanced in order to improve the mechanical stability of soft coal. Consequently, the instantaneous released gases will be decelerated, and the occurrences of coal and gas outburst events in mine working faces can be prevented.

A New Look at the Geological Structure of the Knurów Hard Coal Deposit in Light of Model Tests

Abstract The Knurów hard coal deposit is characterized by rich fold and fault tectonics and diverse morphology of the overburden. The deposit contains a fold zone called Knurów anticline and four complex of faults with the total amplitudes reaching up to several dozen meters. While making a 3D model of the deposit, a range of complications related to the correct interpretation of the running and development of the aforementioned tectonic structures were encountered. Additional data were begun to be introduced during the detailed analysis of the 3D model being made in stages, thereby forcing the software to perform the modeling according to preset assumptions. This process covered such areas of the deposit that were poorly explored or documented to an extent requiring an intervention from a geologist.

Linear discontinuous deformations created on the surface as an effect of underground mining and local geological conditions-case study

Underground mining negatively impacts the rock mass and land surface, as well as the objects located on it. One of the forms of such impact are linear discontinuous deformations, which presently in Polish Upper Silesian Basin conditions are more and more often accompanied by underground mining. Discontinuous deformations of mining origin not always arise on the surface, resulting from the occurrence of unfavorable geological and mining factors, and create different forms, mainly ground steps, cracks, and fissures. Presented in this article results of the research concern the problem of the occurrence of linear discontinuous deformations in the area of the greatest Polish hard coal deposit, Upper Silesian Basin, where several unfavorable factors triggered the system of linear discontinuous deformations in the shape of ground steps. Ground steps caused several damages to building objects, small architecture elements, and roads in surrounding area. One of the most important objects exposed to damage threat here is an old historic church. Ground steps occurred as a joined effect of underground mining influences together with impact of fault zones located close to the church and probably activated by mining works. In the paper, mining and geological conditions have been discussed, that led to arising of discontinuous deformations on the surface. Apart from description of mentioned factors, detailed calculations were carried out aimed at recognition of probable distribution on the surface of subsidence, horizontal displacement, and horizontal strain around the church. Their contribution to ground steps creation process has been discussed as well.

INFLUENCE OF A TURBULENT ENVIRONMENT ON THE MANAGING OF A MINING ENTERPRISE

Motivation: It should be taken into consideration that classical planning methods that worked well at the end of the 20th century are often not effective in a turbulent environment. The article presents planning methods that can be applied in such conditions.
 Problem statement: The article presents methods of planning of the future in a variable environment. There are constant changes in the macro-environment of mining enterprises in Poland. Therefore, it is extremely difficult to create an appropriate plan for the company's core business i.e. extracting hard coal deposits.
 Approach and results: The scenario-based planning and SARIMA mathematical model and the forecasts for the demand for hard coal based on them have been presented. The scenarios are used to verify the potential company strategy.
 Conclusions: It should be noted that the strategy must be created in several variants which finally will enable the company to choose the one that will let it gain a competitive advantage. Only then will the mining company be able to stay ahead of its competitors. In order to allow decision-makers in companies to make the right decisions, appropriate methods and tools for managing the company should be used.

Economic valuation of coal deposits – The value of geological information in the resource recognition process

Resource and economic assessment under uncertainty and risk is quite a difficult process. Many geological, mining, technical and economic aspects should be taken in to consideration simultaneously. The assessment process is also subject to errors, including measurement and interpretation errors and errors resulting from lack of knowledge or over-optimism. Uncertainty about the true value of the geological parameters is reduced as the recognition process and the knowledge about deposits improve. Especially at the first stages of mine development, the information available is insufficient and can lead to incorrect interpretation.In this paper, the impact of geological information on key economic parameters was examined, using the example of a hard coal deposit in mine X in Poland. A scenario analysis was performed, based on a Monte Carlo simulation. The simulation was conducted using ogive distributions and copulas (empirical copulas) binding six geological parameters (coal and waste rock thickness, coal density, coal calorific value (LHV) and sulfur and ash content). To achieve the research purposes, the most popular economic measures (indicators), i.e., IRR, NPV and EBITDA, were used. Finally, differential distributions of these parameters were built and commented upon.The three analyzed scenarios were elaborated considering the data from the geological 3D model of coal deposit X. A polygon (testing) area was defined in the coal field, where complete geological information was available. The first data set (scenario 1) incorporated only information from deep surface boreholes (drillings), the second included data from surface drillings and channel samples and the third used only channel sampling. To interpolate the geological data between boreholes, the inverse distance interpolator was applied.Significant differences in the values of selected economic parameters were obtained; the largest in scenario 1. The average value of the IRR difference distribution (overestimation) was 6.4%; for NPV it was up to 213.7 million PLN and for EBITDA up to 678.6 million PLN in comparison to the reference scenario, or possibly even more. The results achieved are influenced by optimistic estimates of the thickness of coal partings, the amount of coal impurities and finally, lower costs of waste rock handling and coal production, despite the unfavorable values of the coal-quality parameters. The total cost of waste rock management underground and coal processing should be of special interest in the assessment process. These observations led to the general conclusion that interpretation of the geological information at the early stages of the exploration based only on surface boreholes, can lead to overestimating the potential value of the coal reserves and hence to significant errors.It is worth mentioning that the aspects of geological appraisals presented above are commented upon in the professional literature, but elaborations regarding the influence of geological information in the resource economic evaluation are very limited. To strengthen the results achieved, there is a need to continue the research and verify the results obtained on other examples of coal mines.