Innovative management of hard coal resources in line with rational deposit management

Reasons of problems of the polish hard coal mining in connection with restructuring changes in the period 1988–2014

Economic and social aspects of restructuring Polish coal mining: Focusing on Poland and the EU

Consolidation as a risk management method in the lifecycle of a mining company: A novel methodological approach and evidence from the coal industry in Poland

Methane drainage is used in Polish coal mines in order to reduce mine methane emissions as well as to keep methane concentration in mine workings at safe levels. This article describes methods of methane drainage during mining used in Polish coal mines. The first method involves drilling boreholes from tailgate roadway to an unstressed zone in roof or floor layers of a mined seam. It is the main method used in Polish mining, where both the location of drilled boreholes as well as their parameters are dependent on mining and ventilation systems of longwalls. The second method is based on drilling overlying drainage galleries in seams situated under or over the mined seam. This article compares these methods with regard to their effectiveness under mining conditions in Polish mines. High effectiveness of methane drainage of longwalls with different ventilation and methane drainage systems has been proven. The highest effectiveness of methane drainage has been observed for the system with overlying drainage gallery and with the parallel tailgate roadways. In case of classic U ventilation system of longwall panel, boreholes drilled from the tailgate roadway behind the longwall front are lost.

Economic transitions have the potential to displace workers and cause social unrest. Coal mine closures in the eastern United States due to the changing electricity system and the resulting employment losses in rural areas have become salient issues for all levels of government. Previous research has not distinguished among the potential causes of recent mine closures, such as rising production costs and decreasing coal demand from the electricity sector. This analysis utilizes unique data on coal mine and power plant operation to estimate the impact of supply and demand factors on mine closure. We model closure as a function of expected profits, which allows us to compare the effects on mine closure of specific demand and supply shocks to expected mine profits. Our results suggest that each shock substantially affected coal mine employment. Increasing costs of producing Appalachian coal have had the largest impact on closures with lower natural gas prices and lower electricity demand each accounting for a substantial number of closures additionally.

The Discourse of Regret or Relief? Wałbrzych Twenty Years After the Closure of the Mines
 The paper presents the results of field research carried out in 2015 in Wałbrzych, focused on as well memory as arising postmemory of citizens, clustered around the closure of all coal mines in the 1990s. For citizens of Wałbrzych their failure was liminal situation and memory about it is still alive and constitutes significant element of identity. Memory of this social trauma and civilizational collapse is passed down from one generation to the next and also has impact on those whowere not personally affected by it. The narratives established around the liquidation of the coal mines are split and often contrary. On the one hand the work in the mine was considered positively (primarily because of the financial benefitsand social respect), but on the other hand poor working conditions were emphasized. Respondents remembered about dangerousness of the work in mine (therefore relief discourse), but at the same time they criticized decision about the closure of coal mines (therefore resentment discourse).

During the extraction of hard coal in Polish conditions, methane is emitted, which is referred to as ‘mine gas’. As a result of the desorption of methane, a greenhouse gas is released from coal seams. In order to reduce atmospheric emissions, methane from coal seams is captured by a methane drainage system. On the other hand, methane, which has been separated into underground mining excavations, is discharged into the atmosphere with a stream of ventilation air. For many years, Polish hard coal mines have been capturing methane to ensure the safety of the crew and the continuity of mining operations. As a greenhouse gas, methane has a significant potential, as it is more effective at absorbing and re-emitting radiation than carbon dioxide. The increase in the amount of methane in the atmosphere is a significant factor influencing global warming, however, it is not as strong as the increase in carbon dioxide. Therefore, in Polish mines, the methane–air mixture captured in the methane drainage system is not emitted to the atmosphere, but burned as fuel in systems, including cogeneration systems, to generate electricity, heat and cold. However, in order for such use to be possible, the methane–air mixture must meet appropriate quality and quantity requirements. The article presents an analysis of changes in selected parameters of the captured methane–air mixture from one of the hard coal mines in the Upper Silesian Coal Basin in Poland. The paper analyses the changes in concentration and size of the captured methane stream through the methane capturing system. The gas captured by the methane drainage system, as an energy source, can be used in cogeneration, when the methane concentration is greater than 40%. Considering the variability of CH4 concentration in the captured mixture, it was also indicated which pure methane stream must be added to the gas mixture in order for this gas to be used as a fuel for gas engines. The balance of power of produced electric energy in gas engines is presented. Possible solutions ensuring constant concentration of the captured methane–air mixture are also presented.

Streszczenie W latach 2001-2010 produkcja oraz liczba funkcjonujących kopalń węgla kamiennego w polskim gór­nictwie węgla kamiennego uległa znacznemu zmniejszeniu. Wydobycie węgla ze 102,78 · 106 Mg ograniczono do 76,15 · 106 Mg. Eksploatacja pokładów realizowana w 43 zakładach górniczych w roku 2001, na skutek likwidacji oraz połączenia kopalń, w roku 2010 dotyczyła 29 kopalń. Liczba 30 kopalń metanowych w roku 2001, w których wydobywano węgiel na poziomie 72,37 · 106 Mg, wroku2010 wynosiła21 kopalń, produkujących 52,18 · 106Mg węgla. Pomimo spadku produkcji węgla oraz malejącej liczby kopalń w Polsce wentylacyjna emisja metanu z pro­cesów eksploatacji węgla kopalń metanowych od roku 2001 wzrosła o około 50 m3/Mg. W miarę upływu lat, wysiłki na rzecz odmetanowania niosą jednak pozytywny skutek. Pomimo wzrostu „strat" metanu w procesie odmetanowania, z roku na rok zwiększa się ilość metanu ujętego systemami odmetanowania. Z rozeznania i przeglądu literaturowego dotyczącego zagadnień związanych z emisją metanu w Polsce wynika, że w 2009 roku opublikowano Raport Krajowej Inwentaryzacji Emisji i Pochłaniania gazów ciep­larnianych za rok 2007. Z Raportu Krajowej Inwentaryzacji... wynika, że brak jest danych szczegółowych dotyczących wskaźników emisji metanu z kopalń węgla kamiennego dla polskiego górnictwa. W związku z tym, przygotowano i obliczono szczegółowo emisje metanu z kopalń metanowych w Polsce. Zastosowana metodyka szacowania metanu wykonana została dla dwóch podstawowych źródeł jego emisji. Obliczono emisję metanu w trakcie procesu eksploatacji węgla jako emisję wentylacyjną oraz emisję z układów odgazowania. Takie podejście wynikało z wytycznych IPCC z roku 2006. Aktualizacja proponowanych metod IPCC (2006) szacowania emisji metanu z układów wentylacyjnych i z układów odmetanowania kopalń węgla kamiennego (czynnych i zlikwidowanych) w Polsce polega na za­łożeniu, że wskaźnik emisji metanu (EF) obliczamy, opierając się na wydobyciu z koplań metanowych oraz rzeczywistych wielkościach metanowości bezwzględnej. Rezultat modyfikacji metody szacowania emisji metanu z procesów górniczych dla polskich metanowych koplań węgla kamiennego to równanie wskaźnika emisji metanu. W górnictwie polskim, od roku 2008 średni wskaźnik emisji z systemu węgla kamiennego utrzymuje się na stałym poziomie około 10 m3 C^/Mg. Uzyskane wyniki obliczeń emisji metanu w całym analizowanym okresie lat 2001-2010, mieszczą się w granicach 402-462 Gg (śr. 441,45 Gg).

Poland is a big user of fossil fuels for electricity and heat production. The most important fossil fuel is hard, brown coal and the Polish energy system is based on this source. However, the world has begun to decarbonize the climate and reduce the carbon dioxide and methane which are the main gasses impacting climate change. The main aim of this paper was to recognize changes in Polish coal sector. We focused our attention to the economic situation and employment in coal sector in Poland. The time rage included 1989–2020 and the prognosis 2021–2025. The Polish coal sector faced dramatic changes. The number of hard coal mines decreased from 70 in 1990 to 21 in 2020. In the same timeframe, the prices for hard coal increased from 12.37 PLN/dt to 313.27 PLN/dt. The employment decreased from more than 350 thousand to less than 100 thousand people in hard coal mines. The decrease changes are the effect of strict policies of the European Union. The economic situation of Polish hard coal mines is rather poor. Polish mines achieved negative economic results due to the effect of poor management. We used advanced statistics, including the Augmented Dickey–Fuller test (ADF), to measure the stationarity of analyzed time series. We also used Generalized AutoRegressive Conditional Heteroskedasticity (GARCH) models and conducted a prognosis. Our research proved that the time series describing the hard coal economic situation were not stationary. The Generalized AutoRegressive Conditional Heteroskedasticity (GARCH) models confirmed big changes in Polish coal sector economic results. The elaborated prognosis of variables proved that the price of hard coal will increase in 2021–2025. Moreover, the economic situation will be worse. Our analysis confirmed that global trends of the hard coal sector were influenced by the European Union (EU) energy policy and closing down the mines. The economic situation of Polish hard coal sector worsened.

In Polish coal mines as the extraction descents to the increasing depth, the risk of methane and spontaneous fire is observed. The coexistence of these two hazards enforces at the design phase and during extraction, the assessment in terms of the selection of a prevention scope for their eradication. Based on a set of indicators and parameters describing the level of co-occurrence of both threats on a set of 75 longwalls extracted in Polish hard coal mines, their classification and systematization was performed with the use of statistical methods. Adoption of the methods described in the publication made it possible to split the set of 75 longwalls into statistically homogeneous subsets, characterizing similar longwalls, and the development of a synthetic evaluation instrument, with the coexistence of hazards allowed to calculate for each longwall its dimensionless value that is a reflection of the level of associated risk. The calculation results reflect with high probability the actual level of associated hazards when mining these longwalls.

The article analyzes the world experience in assessment of the methane emissions from closed mines and the possibilities of its utilization for the country's economy by natural gas producers. Government regulators, the oil and gas sector, the agencies for development and policymakers should consider methane resources by identifying potential hazards associated with the methane release after mine closure and decommissioning and improving the controllability of emission reduction measures. Important concomitant benefits of methane from closed mines extraction and utilization are a significant reduction in the risk of uncontrolled surface emissions, the exploitation of gaseous resources that would otherwise become waste, and a reduction in greenhouse gas emissions. According to the researchers, 103 billion m3 of methane was emitted from existing underground and open deposits in 2010, and another 22 billion m3 from closed mines. The total amount of 125 billion m3 for 2010 is 50% higher than the estimate of 83 billion m3 obtained by the Emissions Data System of the American Geophysical Union. This is stated in a new study by the Pacific Northwest National Laboratory of the US Department of Energy. The closure of coal mines and, consequently, methane emissions from closed mines will continue to be a pressing and important issue in the foreseeable future as countries continue to exploit and deplete their coal reserves at an ever-increasing rate. This is the case in many developed countries, where coal production is declining and mines are closing. However, this also applies to some developed and developing countries, where coal mining will continue to play a significant role in the structure of the energy balance, and closed mines will be replaced by new ones. Thus, the total emissions from closed and closed mines can be significant and are likely to be increasingly significant. In 2010, the Ministry of Foreign Affairs accounted for 17% of global emissions of mine methane and, according to forecasts, in 2050 this share may increase to 24%. Coal is paramount in ensuring the energy security of many countries and plays a significant role in mitigating energy shortages around the world. As coal reserves deplete or due to changes in the energy sector of the economy, mines are inevitably closed and decommissioned. Closure of mines can provide a small but important opportunity to use such an environmentally friendly source of energy as methane from closed mines (MSS), which can be extracted and disposed of using existing technologies. There is an urgent need to develop projects that will be implemented after the cessation of mining activities and aimed at reducing overall emissions from the life cycle of coal mining, by optimizing the extraction and utilization of methane that would otherwise enter the atmosphere. World experience and theoretical studies of methane emissions to the surface during conservation (closure) of mines are important for understanding the processes of methane release and the corresponding degree of its further involvement in the economy of Ukraine. Keywords: methane emissions, utilization projects, closed mines, methane flow, potential danger

Studies on the competitive sorption of CO2 and CH4 on hard coal

Roof bolting is the most popular type of support for underground mines’ workings. However, in Polish coal mines it is used only as a supplementary support. To raise the effectiveness and economic score of horizontal development works, JSW (Jastrzębska Spółka Węglowa) started a project to introduce the independent rock bolting support in its mines. The key element of the project is the monitoring of mine workings supported with roof bolting, as appropriate control allows one to ensure a proper level of safety. The following work presents a monitoring system for mine working supported with roof bolting applied in the project, as well as results of the measurements obtained using this system. The aim of the monitoring was to prove that independent roof bolting provides a proper level of safety and thus is applicable in conditions of Polish underground coal mines, particularly Budryk mine. It was to be proved by the evaluation of data obtained from instrumented bolts, extensometers of different type and convergence measurements. These results allowed us to verify the validity and reliability of the roof bolting in geological and mining conditions of Silesian Coal Basin.

Deepening of active mine shaft comprises number of specific an very difficult operations, because it calls for use of untypical devices securing hoist operation in the shaft, as well as special technology tailored to actual technology of the deepened shaft face. The Leon IV shaft at the Rydułtowy mine is one of the last mining shafts deepened in Polish coal mining from the surface, and then deepened and finally equipped with mine shaft hoist installation. This investment will allow for the construction of the exploitation level of 1150 m and the availability of further coal extraction up to a depth of 1200 m. It will guarantee the possibility of exploitation of over 65 million tons of coal and continuous operation of the mine until 2040. At the same time, for the first time in the Polish hard coal mining industry, a flexible guiding of the mining cage and skips was used, which in comparison with rigid guiding is a much cheaper solution and has many other advantages. The chapter presents most important problems and technical solution implemented during construction and deepening of the Leon IV Shaft at Rydułtowy Coal Mine in Poland.

The following criteria for selection of doublets at Polish coal mines were accepted: the difference in magnitude (based on seismic moment) of two events not larger than 0.15, the distance between their hypocenters not greater than 150 m, and the time interval between their occurrence not longer than 10 days. Similarly, the criteria for seismic events at copper mines are: the difference in magnitude not exceeding 0.15, the distance not greater than 200 m, and the time interval not longer than 20 days. Seismic events from the Wujek and Ziemowit coal mines that occurred between 1993 and 1995, and seismic events from the Polkowice copper mine that occurred between 1994 and 1996 and from the Rudna copper mine that occurred between 1994 and 2004 were considered. Their source parameters and focal mechanisms were known in most cases from previous studies. Altogether 108 seismic pairs from coal mines and 118 pairs from copper mines were found, forming doublets, triplets and quadruplets, within the magnitude range from 0.7 to 3.5. The distance and time intervals between two events forming pairs are not dependent on magnitude of these events. The focal mechanism of seismic events forming pairs is similar in over 60 percent of pairs at coal mines and in about one third of pairs at copper mines. Spatial distributions of doublets in particular sections of coal and copper mines display dominant linear trends, characteristic for a given area, which are often in conformity with the direction of nodal planes determined by fault plane solution of one or both the events forming a doublet. In such cases, the rupture plane can be discriminated among the nodal planes.