The paper presents a model for calculations of the temperature field in electric mine motors with a water cooled frame. That model was worked out with use of modified and improved thermal networks developed by the author for determining the temperature distributions in different types of ac machines. Thermal calculations for a selected type of 400 kW mining motor were performed with use of an original computer program. Their results were compared with those obtained from measurements. On the basis of the verified simulation results there was determined the influence of value changes of parameters characterising the work environment condition (ambient temperature, inlet temperature and cooling water discharge, degree of covering the casing with coal dust) on the mining motor thermal state.

The article presents current state of the structure of hard coal enrichment plants in Poland, taking the capacity, the range of grain enrichment and the type of equipment used into account. This data were presented in a tabular format for each Polish Coal Company operating on the Polish market. The article was also present simplified: flow sheet of the steam and coking coal enrichment system. Based on the presented data, the planned needs and trends were described in terms of increasing production efficiency, minimizing water consumption and safety of work. A list of research and development works which must be undertaken were also presented as well as factors determining the technological development of the processing plants.

In the processes of coal mining, preparation and combustion, the rejects and by-products are generated. These are, among others, the rejects from the coal washing and dry deshaling processes as well as the coal combustion by-products (fly ash and slag). Current legal and industry regulations recommend determining the content of mercury in them. The regulations also define the acceptable content of mercury. The aim of the paper was to determine the mercury content in the rejects derived from the coal cleaning processes as well as in the combustion by-products in respect of their utilization. The mercury content in the representative samples of the rejects derived from the coal washing and dry deshaling processes as well as in the coal combustion by products derived from 8 coal-fired boilers was determined. The mercury content in the rejects from the coal washing process varied from 54 to 245 μg/kg, (the average of 98 μg/kg) and in the rejects from the dry deshaling process it varied from 76 to 310 μg/kg (the average of 148 μg/kg). The mercury content in the fly ash varied from 70 to 1420 μg/kg, (the average of 567 μg/kg) and in the slag it varied from 8 to 58 μg/kg (the average of 21 μg/kg). At the moment, in light of the regulations from the point of view of mercury content in the rejects from the coal preparation processes and in the coal combustion by-products, there are no significant barriers determining the way of their utilization. Nevertheless, in the future, regulations limiting the maximum content of mercury as well as the acceptable amount of leachable mercury may be introduced. Therefore, preparing for this situation by developing other alternative methods of using the rejects and by-products is recommended.

In recent years, the Budryk Coal Mine (KWK Budryk) reached the mining depth of 1300 m, where there is about 160 million tons of coal, including 120 million tons of coking coal (type 35). The task of the Coal Processing Plant complex modernization was undertaken. The article presents the modernization of coal screening, classification and dewatering systems at the KWK Budryk Processing Plant and the implementation of screening of PROGRESS ECO sp. z o.o. SK. The modernization project defined the following technical requirements for all screens in the KWK Budryk Coal Processing Plant extension project:

- Vibrating screens with a linear type drive with a drive unit placed on the drive beam of the trommel screen in the form of vibration generators;

- Screen drives equipped with a starting-braking device;

- The use of main screen drive bearings with a nominal service life of at least 40,000 man-hours;

- All work surfaces made of materials with a strength of up to 80 mm grain and abrasion resistance; side strips and sieves fixed in a way ensuring trouble-free operation, and at the same time quick and easy replacement;

- Sheets made of stainless steel;

- Side walls, beams and other elements attached to them connected with screws using a system protecting against corrosion and elements separation;

- The use of a work parameters monitoring and visualization system, i.e.

- pitch of the riddle,

- bearing operating temperatures and the condition of their wear.

Three types of screens were provided:

- PWP1-1Z-2,8x6,0 screeners that alternatively perform sieving or desliming processes,

- PWP1-2.4x6.0 screening machines performing desliming processes,

- PWP1-2.0x6.0 screens performing the classification process.

Coal reserves in the Czech Republic are estimated to be 10 billion tons – hard coal about 37%, brown coal about 60% and lignite 3%. Hard coal is produced in Northern Moravia. In 2017 the production of hard coal was 5.5 million tons. Brown coal is mined in North-Western Bohemia − the production of brown coal in 2017 was 38.1 million tons. Significant quantities of hard coal are exported to: Slovakia, Austria, Germany and Hungary. In accordance with the National Energy Policy, coal will remain the main source of energy in the country in the future, despite the increased use of nuclear energy and natural gas. The government expects that in 2030 energy from coal will account for 30.5% of energy produced. There are five coal companies in the Czech Republic: OKD, a.s., the only hard coal producer and four brown coal mining companies: Severočeské Doly a.s., owned by ČEZ, the largest producer of brown coal, Vršanská uhelná a.s., with coal resources until 2055, Severní energetická a.s. with the largest brown coal reserves in the Czech Republic and Sokolovska uhelná a.s., the smallest mining company extracting lignite. OKD operates coal in two mines Kopalnia Důlní závod 1 – (consists of three mines: ČSA Mine, Lazy Mine, Darkov Mine) and Mine Důlní závod 2 (ttwo mines Sever, Jih). The article also presents a pro-ecological solution for the management of waste heaps after coal enrichment – a plant for the enrichment of coal waste from the Hermanice heap.

The aim of the paper was to estimate how the value of 1 GJ of energy in coal with a calorific value of 5500 kcal/kg varies on the international coal market compared to 1 GJ of energy in coal with a calorific value of 6000 kcal/kg. The analysis of data from different ports was intended to answer the question of whether the pricing of coals of different producers according to their calorific value is convergent. The best-known price standard for thermal coal is 25.1 MJ/kg coal (6000 kcal/kg) and, until recently, coals with such quality parameters dominated international trade. Currently, coals with parameters other than considered to be standard parameters are traded on the coal market, hence it is necessary to price a unit of energy (e.g. 1 GJ) contained in these coals. The indices have been selected of the largest exporters of thermal coal for which data was available and referred to the same coal types (grades) determined on the same basis (FOB). Theoretically, the price differential between 6000 kcal/kg and 5000 kcal/kg coal (in USD/ton) should be (at least) as much as the difference in calorific value, i.e. about 9% per USD/ton. In reality, the price differential between these types of coal is greater, though. The overall conclusion of the analysis is that the price calculated per 1 GJ of energy fluctuated on average by 5.9% over the entire period considered. The analytical results obtained for coal from four countries are quite convergent, so it can be assumed that the calculated relationship between the prices of coal with different calorific values (6000 and 5000 kcal/kg) is a good approximation of the observed relationships in the international trade. The calculation results provide a simple formula allowing to estimate the price of coal with a calorific value other than the standard 25.1 MJ/kg (6000 kcal/kg) using the relationships from the international market.

The quality of coal has been analyzed basing on the data from geological exploration and chemical – geological analyses of coal carried out on the samples obtained from the boreholes and mining pits. The operated coal seams indexed as 382 and 385/2 reveals the changeable morphology due to the thickness of carbon shoals and stent intergrowths. The other parameters, such as the ash content or the calorific value are strongly linked with the non-coal rock interlayers, which presence causes the decrease in the calorific value and increase in the amount of after-burning ash. These parameters are less dependable on the sedimentation environment of the coal formation material. The content of total sulfur in the analyzed seams does not show any link with the values of the parameters analyzed before. The total sulfur is made up from sulphide gathered in coal and sulphates deriving from the decomposition of plants and supplied by deposit waters in different phases of coal seam formation. The obtained results could be useful in the reconnaissance of the prospective seams lying below the currently exploited ones (e.g. 389) and the seams in the neighboring areas.

The paper presents an analysis of hard coal prices offered at the coal depots in Poland. Coal depots are one of the most popular forms of purchasing coal by Polish households. Prices refer to price offers for cobble coal (grain size: 60–120 mm) and their analysis is performed based on the regions rather than on all Polish provinces. From January 2010 to May 2019, there were two regions that were distinguished in terms of price spread: the S-W region and the N-E region. In the case of the S-W region, the difference between the province with the minimum price (Śląskie Province) and with the maximum price (Dolnośląskie Province since September 2017) ranged from PLN 53–83/ton, and in the N-E region the difference ranged PLN 64–130/ton. In the case of the remaining two regions, prices varied from a few to approximately PLN 80/ton for the N-W region, and from a few to about PLN 40 /ton for the S-E region. In order to determine how the origin of the coal affects its prices (domestic coal, imported coal), the analysis also included cobble coal price offers that are part of the Author’s own database created for several years. In the case of cobble coal from domestic producers, price offers varied betwwen PLN 14–33/GJ, and price offers for imported cobble coal stood varied between PLN 12–32/GJ. The N-E region attracted particular attention as the price offers for imported cobble coal reached a level similar to the offers from the S-W region, i.e. the region closest to Silesian coal mines. Price differentials within provinces belonging to a given region were influenced by the geographical rent. The paper also analyses average selling prices offered by domestic producers for various size grades of steam coal as well as selling prices for imported coal (free-at-frontier price).

Volatility is one of the most characteristic features in the all market types. In the raw material market, including the bituminous coal market, volatility is visible in the supply and demand variations, in consequence in the prices fluctuations. Market actors usually having opposite interests, for example buy low, sell high, are vitally interested in identifying the causes of these fluctuations.

Some of the factors causing the market fluctuations are quite common, others are more complicated because of circumstances complexity. This article attempts to examine the relationships between bituminous coal fines prices and the economic situation. Given the complexity of the issue, the research area has been narrowed down – territorially to Poland and temporarily – to the present decade.

The average prices of coal fines in Poland are presented by the Industrial Development Agency (Agencję Rozwoju Przemysłu SA) in the form of two indices: PSCMI 1 and PSCMI 2. Both indices are calculated based on the prices of pattern bituminous coal, produced by domestic manufacturers and sold on domestic markets, the energy and heat market respectively.

Statistical methods, because of their quantitative nature, are important in identifying the correlations between the coal fines prices and economic conditions. Therefore, the article presents examples of relatively strong linear correlations between the PSCMI 1 and/or PSCMI 2 and some indicators of the economic situation.

The possibility of the application of nontraditional method of greenhouse gas utilization by the injection of CO2 (sequestration) into porous geological deposits, treated as unconventional gas collectors, requires the fulfillment of basic criteria such as the impact on the environment and long term storage. The important issue is the physical behavior of the deposit during the porous structure saturation phase by carbon dioxide. What should be mentioned first and foremost is: the availability of CO2 transport along the porous structure and adsorption capacity. The work presents the results of water vapor sorption on coal samples from selected Hard Coal Mines of a differentiated carbon content. The received results were presented in the form of sorption and desorption isotherms performed in a temperature of 303 K. It was additionally described with a BET adsorption isotherm. Based on sorption data, a specific surface area was calculated, in accordance with BET theory. The amount of the adsorbed water vapor molecules for the analyzed coal samples was dependent on the degree of metamorphism. The obtained isotherms can be described as type II according to the BET classification. Volumetric type apparatus -adsorption- microburette liquid was used for the sorption experiments. Water vapor sorption in relation to coals allows for the quantitative determination of primary adsorption centers as a measure of adsorbed molecule interconnections with the adsorbent surface. Based on the BET adsorption equation, out of water vapor isotherms, the amount of adsorption active centers, which potentially may take part in CO2 adsorption in coal seams during injection of this gas, was determined. The sorption capacity of coals is determined by the degree of metamorphism, which also has very large impact on the sorption capacity of the deposit.

The annexation of Crimea and military operations that began in eastern Ukraine in April 2014 were the cause of the growing threat to Ukraine’s energy security. In terms of coal supplies, Donbass is of key importance for the country’s economy. Despite military operations on the east, illegal trade with the occupied territories was flourishing. This situation led to an increase in dissatisfaction amid certain social strata, as well as among volunteer battalions participants who took part in the military operations in Donbass and were the initiators of the Donbass blockade. The main purpose of the study to analyse the specific of the development of coal industry in Ukraine and the main reasons of the blockade of Donbass and its consequences.

This article presents values of porosity and compression strength of hard coals from the area of the Upper Silesian Coal Basin. The change of the stage of carbonification, which results from conversion of coal substance in the process of coalification, is a source of many changes in the structure of coal. These changes exert influence on values of physical parameters, including the values of porosity and strength. Porosity and compression strength change with the degree of carbonification, a result of the depth of deposition. This study determined the values of effective porosity of coals and their strength considering the age chronology of coal seams and the depth of their occurrence. It examined coals of the Cracow Sandstone Series, the Mudstone Series, the Upper Silesian Sandstone Series, and the Paralic Series from depths ranging from about 350 m to 1200 m. The authors have shown that effective porosity of the Upper Silesian coals changes for particular stratigraphic groups and assumes values from a few to a dozen or so per cent, while compression strength from several to several dozen megapascals. It has been observed, from a chronostratigraphic perspective, that there is a shifting of the upper and lower limits of intervals of porosity variations towards higher values for younger coals. With the increase in compression strength, value of porosity in particular stratigraphic groups generally decreases. However, no regular changes were observed in mean, uniaxial compressive strength with the increase in the age of subsequent stratigraphic groups. On the other hand, for bright coal and semi-bright coal, a visible decrease in compression strength with the depth of deposition of strata was observed.

Applying new technologies basing on coal utilization demands precise identification of coal-bed composition. It is suggested, that such possibility is enabled by coal-bed logging with use of - adjusted to this aim - microlithotype analysis. Modification of this research method relies on ten-fold augmentation of 20 point grid size dimensions - up to 500 x 500 [...]. Maceral associations - as identified duringmicroscope observations - are placed in computer database according to their localization in logging. This allows for later graphic interpretation - microlithotype profile drawing. 13 associations has been educed in description, in majority being consistent with commonly used microlithotypes. However, a few changes has been introduced: in description of vitrite, telovitrite, macroscopically recognized in logging as vitrine layers, has been distinguished, as well as detro-gelo-vitrite, macroscopically recognized in logging as durain, while within bimaceralic microlithotypes there has been distinguished: vitrinertite (W), vitrinertite (I), clarite (W), clarite (I), durite (L), durite (I), all on the basis of dominant ingredient named in parenthesis. Accepted research methodology enables precise characteristics of petrographic variation within coal-bed logging. This allows especially to describe variation within dull coal (durain). Basing on research results, it is suggested that the biggest share in seam composition belongs to duroclarite - 23.8%, then vitrite - 18.7% and clarodurite - 17.6%, lower share of few percent belongs to: vitrinertite (I), vitrinertite (W), inertite, clarite (W), vitrinertoliptite, durite (I), durite (L), while both liptite and clarite (L) are less than one percent . Sequence of following microlithotypes also illustrate facies variation, what allows interpretation of environments of peat deposition in paleo-peat bog 116/2. Dominating percentage in log belongs to Forest Moor facies - 33.5%, while the lowest is Forest Terrestial Moor - 12.5%.

Thin coal seams found in the Lions Cove Formation, Polonia Glacier Group (Middle Eocene, upper part) at King George Bay, King George Island (South Shetland Islands, West Antarctica), represent lustrous (vitrine) brown-coal metaphase. The coal from the lower seam represents carbonized wood, probably angiosperm, that from the upper ones originated due to accumulation of branches or larger wood fragments and leaf remains. These coals are slightly older than metaxylite brown coal previously described from Admiralty Bay on King George Island, and dated at Eocene-Oligocene boundary. Both coal occurrences are evidences for a warm climate which prevailed in the Antarctic Peninsula sector during the Arctowski Interglacial (ca 50—32 Ma).

Coal production in 2018 increased by 3.3% and amounted to 7.81 million tons. Compared to 2010, it increased by 620 million tons. The structure of coal production in the world is very stable in the analyzed period of 2010–2018. Steam coal dominates in production with a share of 77%. Since 1990, the share of coal in the consumption of primary energy carriers has fallen by 3% in the global economy. In the EU, the share of coal in the consumption of primary energy carriers is more than twice lower than in the world, and in 2018 amounted to 13%. BP estimates the sufficiency of coal proven reserves based on 2018 data for the next 132 years. For oil and gas, they are estimated at 51 years. The decline in hard coal production in the European U nion can be dated almost continuously since 1990, which has decreased by 74%. In 2018, 74 million tons of coal were produced in the EU. In 2018, hard coal consumption in EU countries dropped to 226 million tons, i.e. by 20.6%.

In 2018, global trade in steam coal amounted to 1.14 billion tons. The situation in China is crucial for the international coal market. The slight change in the import policy of this country significantly affects the situation in international trade in steam coal. In 2019, coal prices (at Newcastle, Richards Bay, ARA ports) dropped by an average of 23 U SD/ton. The average decreases for these three indices were 33%. The prices of steam coal in the forecasts presented in the paper are under pressure of the falling demand.

The analysis of leaching behavior of harmful substances, such as arsenic, is one of the parameters of risk assessment resulting from the storage or economic use of coal waste. The leachability depends both on the environmental conditions of the storage area as well as on the properties of the waste material itself. There are a number of leaching tests that allow to model specific conditions or measure the specific properties of the leaching process. The conducted research aimed at comparing two methods with different application assumptions. The study of arsenic leaching from waste from the hard coal enrichment process was carried out in accordance with the Polish PN-EN 12457 standard and the US TCLP procedure. The leaching results obtained with both methods did not exceed the limit values of this parameter, defined in the Polish law. Both methods were also characterized by the good repeatability of the results. The use of an acetic acid solution (TCLP method) resulted in three times higher arsenic leaching from the examined waste compared to the use of deionized water as a leaching fluid (method PN-EN 12457). Therefore, the use of organic acid tests for mining waste intended for storage with municipal waste should be considered, as the results of the basic test based on clean water leaching may be inadequate to the actual leaching of arsenic under such environmental conditions.

The paper presents selected issues related to the development of international coal markets. World consumption of coal dropped for the second year in a row in 2016, primarily due to lower demand from China and the U S. The share of coal in global primary energy consumption decreased to 28%. World coal production accounted to 3.66 billion toe and it was lower by 6.2% when compared to the previous year. More than 60% of this decline took place in China. The decline in global production was more than four times higher than the decrease in consumption. The sufficiency of world resources of coal are estimated at 153 years – that is three times more than the sufficiency of oil and gas resources. After several years of decline, coal prices increased by 77% in 2016. The current spot prices are at the level of $80/t and are close to the 2014 prices. In the European market, after the first half of the year, coal prices reached the level of around 66% higher than in the same period of the last year. The average price in the first half amounted to PLN 12.6/GJ, which is close to the 2012 prices. The share of spot trade in the total purchase amount accounted to approx. 20%. Prices in futures contracts can be estimated on the basis of the Japan-Australia contracts prices and prices in supplies to power plants located in Germany. On average, the prices in supplies to these power plants were higher by approximately 9% in the years 2010–2016 and prices in Australia – Japan contracts were 12% higher than CIF ARA prices in 2017. Global energy coal trade reached about 1.012 billion tonnes in 2016. In 2019, a decline by 4.8% is expected primarily due to the expected reduction in the demand in major importing countries in Asia.

Control of the technological processes of coal enrichment takes place in the presence of wide disturbances. Thus, one of the basic tasks of the coal enrichment process control systems is the stabilization of coal quality parameters at a preset level. An important problem is the choice of the controller which is robust for a variety of disturbances. The tuning of the controller parameters is no less important in the control process . Many methods of tuning the controller use the dynamic characteristics of the controlled process (dynamic model of the controlled object). Based on many studies it was found that the dynamics of many processes of coal enrichment can be represented by a dynamic model with properties of the inertial element with a time delay. The identification of object parameters (including the time constant) in industrial conditions is usually performed during normal operation (with the influence of disturbances) from this reason, determined parameters of the dynamic model may differ from the parameters of the actual process. The control system with controller parameters tuned on the basis of such a model may not satisfy the assumed control quality requirements.

In the paper, the analysis of the influence of changes in object model parameters in the course of the controlled value has been carried out. Research on the controller settings calculated according to parameters T and τ were carried out on objects with other parameter values. In the studies, a sensitivity analysis method was used. The sensitivity analysis for the three methods of tuning the PI controller for the coal enrichment processes control systems characterized by dynamic properties of the inertial element with time delay has been presented. Considerations are performed at various parameters of the object on the basis of the response of the control system for a constant value of set point. The assessment of considered tuning methods based on selected indices of control quality have been implemented.

Petřvald is a typical mining town in the Czech part of the Upper Silesian Basin. Since the Petřvald sub-basin is limited by significant tectonic structures, its development was to a great extent independent from other areas of the basin and can serve as an example of the influence of the geological structure on the development of mining and residential communities. In the first phase of mining development (ca 1830 to 1844) first claims begin to occur in the area. Thick coal seams were available in shallow depths. Due to missing railway connection, the demand for coal was not very large and the village economy was focused on agriculture. In the second phase (1844 to 1871), the first underground mines start to operate in the area. They were situated in favorable areas with thin overburden. Also, the connection to the railway improved the sale opportunities and a significant share of the local population worked in the mines. The third phase of mining (1871 to 1963) brought still increasing demand for coal, which resulted in establishing new coal mines in geologically less favorable areas (thicker overburden, water-bearing horizons). From the 1930s to the end of the 1950s the extraction peaked, which coincided with the urbanistic and cultural climax. New housing was provided for miners and their families by the companies. The final stage of mining development (1963 to 1998) is connected with the steady decline of production and phase-out of mining. The reason was a lack of economically recoverable coal reserves connected to unfavorable geological conditions. We conclude that the results of studies concerning specific geological parameters of coal deposits can be used for more detailed analyses regarding the development of urbanism, or to explain its causes.

There was done an inventarization of 41 coal mining dumping grounds, gathering waste material from 27 mines. Considering the fact, that five mines belong to multi-motion plants the research comprised 32 hard coal deposits. Source data with localization of particular dumps have been obtained from archival materials from the mines and municipalities, in the boundaries where the dumps occur as well as free accessible published materials (books, scientific papers). The data have been verified, in the beginning on the basis of topographical maps, orthophotomaps and aerial photographs and then, after vision done during field works they have been drawn on the topographic base, what resulted in creating the map of post-mining dumping grounds. Valorisation of coal mining waste dumps, using already repeatedly presented method, included defining of: name of the dump, coal mine from where the wastes come from, state of the dump, surface of the dump, type of technical and biological reclamation, accessibility of the object, possibilities of recovery of coal and the results have been drawn on the map. On the basis of collected and elaborated data there was done an attempt of defining of potential possibilities of recovery of coal from the dumps and connecting of coal quality in exploited deposits and coal content in waste material. The results showed that in spite of initial information that the majority of the dumps comprise potential objects of coal recovery of coal from waste material, eventually only in some cases (thirteen objects) the recovery seems to be economically justified.