Explosions of coal dust are a major safety concern within the coal mining industry. The explosion and

subsequent fires caused by coal dust can result in significant property damage, loss of life in underground

coal mines and damage to coal processing facilities. The United States Bureau of Mines conducted

research on coal dust explosions until 1996 when it was dissolved. In the following years, the American

Society for Testing and Materials (ASTM) developed a test standard, ASTM E1226, to provide a standard

test method characterizing the “explosibility” of particulate solids of combustible materials suspended

in air. The research presented herein investigates the explosive characteristic of Pulverized Pittsburgh

Coal dust using the ASTM E1226-12 test standard. The explosibility characteristics include: maximum

explosion pressure, (Pmax); maximum rate of pressure rise, (dP/dt)max; and explosibility index, (Kst). Nine

Pulverized Pittsburgh Coal dust concentrations, ranging from 30 to 1,500 g/m3, were tested in a 20-Liter

Siwek Sphere. The newly recorded dust explosibility characteristics are then compared to explosibility

characteristics published by the Bureau of Mines in their 20 liter vessel and procedure predating ASTM

E1126-12. The information presented in this paper will allow for structures and devices to be built to

protect people from the effects of coal dust explosions.

The study included bituminous coal seams (30 samples coal from the Bogdanka and Chełm deposits)

of the Lublin Formation, the most coal-bearing strata in the best developed and recognized in

terms of mining parts of the Lublin Coal Basin in Poland. High phosphorus concentrations in coal of

the Lublin Formation were found (1375 g/Mg) as well as P2O5 in coal ash (2.267 wt%). The phosphorus

contents in coal and coal ash from the 385 and 391 coal seams in the area of the Lubelski Coal Bogdanka

Mine and in the area of its SE neighbor is the highest (max. 2.644 wt. % in coal and 6.055 wt. %

of P2O5 in coal ash). It has been shown that mineral matter effectively affects phosphorus contents

in coal and coal ash. At the same time, phosphate minerals (probably apatite and crandallite) present

in kaolinite aggregates of tonsteins contain the most of phosphorus and have the greatest impact on

the average P content in the 382, 385, 387, and 391. The secondary source of phosphorus in these

coal seams and main source of phosphorus in these coal deposits that do not contain mineral matter

of pyroclastic origin (378, 389, 394) may be clay minerals, which absorbed phosphorus compounds

derived from organic matter released during coalification. Phosphorus-rich ash from the combustion

of the Lublin Formation coal tend to be environmentally beneficial to the environment and also useful

for improving the soil quality. Due to the low degree of coalification and high content of phosphorus

in coal, this coals of little use for coking.

The article presents the challenges faced by the hard coal mining sector in Poland. The biggest

challenge results from a decrease in the demand for coal, which was triggered mainly by the climate

policy, including the tightening of environmental standards and an increase in the efficiency of generating

units. The fundamental model of the MRÓWKA domestic coal market has been described.

The model allows for determining the marginal price of a given fuel for a given generating unit in

the system and the optimal mix of fuels to meet the energy demand. The results of the model calculations

for the baseline and alternative scenarios were presented. It has been shown that the optimal

distribution of coal mining capacities promotes the import of the discussed fuel in the north-eastern

part of the country and that the individual customer valuation leads to a decrease in the competitiveness

of the units located in the central-western part of the country. The paper also discusses the

potential impact of the domestic oversupply on the balance sheet and the price of coal. According

to the obtained results and the basic laws of economics, an oversupply of coal leads to a decrease

in prices. For the analyzed variants, the dependence of prices was estimated at PLN 0.0308 / GJ for

every million tons of the oversupply. The fall in prices is largely due to the fuel supply to units located

close to ports or railway border crossings. Based on the presented arguments it can be concluded

that the maximization of financial result from the extraction of coal should be based on an analysis

taking incremental changes in fuel prices into account.

In the paper, on the basis of our studies and the available literature data, a model of changes in the number of active centers corresponding to the structure of the reactive coal particle has been developed. A new distribution function that links the specific surface area of a particle with its porosity and reaction degree has been proposed. An equation for estimation of changes in this parameter during the reaction, on the basis of the initial value, has been presented. In the range of our data and the analysis of the literature data, the model, with satisfactory accuracy, describes internal structural changes of coal and coal char particles. The present results may constitute a basis for complex modelling of coal conversion processes.

Based on the results it was found that the total active centres are related to the internal surface area and porosity of the particle. For a specific coal type, this value depends on the porosity, true density and size of the particle. Changes in total active centres, when these structural properties during thermal conversion of coal are considered, are described in equations.

The evaluation of threats connected with the presence of methane in coal seams is based on our

knowledge of the total content of this gas in coal. The most important parameter determining the potential

of coal seams to accumulate methane is the sorption capacity of coal a. It is heavily influenced by the

degree of coalification of the coal substance, determined by the vitrinite reflectance R0 or the content of

volatile matter V daf. The relationship between the degree of coalification and the sorption capacity in the

area of the Upper Silesian Coal Basin (USCB) has not been thoroughly investigated, which is due to the

zonation of methane accumulation in this area and the considerable changeability of methane content in

various localities of the Basin. Understanding this relationship call for in-depth investigation, especially

since it depends on the analyzed reflectance range. The present work attempts to explain the reasons for

which the sorption capacity changes along with the degree of coalification in the area of Jastrzębie (the

Zofiówka Monocline). The relationship between parameters R0 and V daf was investigated. The authors

also analyzed changes of the maceral composition, real density and the micropore volume. Furthermore,

coalification-dependent changes in the sorption capacity of the investigated coal seams were identified.

The conducted analyses have indicated a significant role of petrographic factors in relation to the accumulation

properties of the seams located in the investigated area of USCB.

Fresh bituminous coal was stored in air-/water-oxidation conditions after 20 and 80 days, respectively. FTIR results show that the Hydrophilicity Index (HI) value of air-oxidized coal is higher than that of water-oxidized coal. SEM results show that the surface roughness of water-oxidized coal is higher than that of air-oxidized coal and water-oxidized coal surface has more holes and chips than air-oxidized coal surface. Flotation results show that the floatability of water-oxidized coal is worse than that of air-oxidized coal. The flotation performance of both air-/water-oxidized coals can be improved at larger collector dosages. The air-oxidation processes changed the HI value of coal greater than the water-oxidation processes while the water-oxidation processes changed the surface morphology of coal greater than the air-oxidation processes. Both the changes in HI value and surface roughness of coal determine the flotation behavior of oxidized coal. The changes in the surface morphology of coal particles after oxidation processes may be the primary factor determining the floatability of coal particles while the changes in the HI value of coal particles may be the inferior factor.

The Bogdanka coal mine, the only currently operating mine in the Lublin Coal Basin (LCB),

extracts coal from the Upper Carboniferous formations of the LCB. The average sulfur content in

the No. 385/2 seam is 0.98%, while in the case of the No. 391 seam it is slightly higher and amounts

to 1.15%. The iron sulfides (pyrite and marcasite) in bituminous coal seams form macroscopically

visible massive, vein, and dispersed forms. A microscopic examination has confirmed their complex

structure. Massive forms contain euhedral crystals and framboids. The sulfide aggregations are often

associated with a halo of dispersed veins and framboids. Pyrite and marcasite often fill the fusinite

cells. Framboids are highly variable when it comes to their size and the degree of compaction within

the carbonaceous matter. Their large aggregations form polyframboids. The cracks are often filled

with crystalline accumulations of iron sulfides (octaedric crystals). The Wavelenth Dispersive Spectrometry

(WDS) microanalysis allowed the chemical composition of sulfides in coal samples from the

examined depoists to be analyzed. It has been shown that they are dominated by iron sulfides FeS2 –

pyrite and marcasite. The examined sulfides contain small admixtures of Pb, Hg, Zn, Cu, Ag, Sb, Co,

Ni, As, and Cd. When it comes to the examined admixtures, the highest concentration of up to 0.24%,

is observed for As. In addition, small amounts of galena, siderite, and barite have also been found in

the examined coal samples. The amounts of the critical elements in the examined samples do not allow

for their economically justified exploitation. Higher concentrations of these elements can be found in

the ashes resulting from the combustion process.

Preliminary lab-scale investigations were conducted on slagging abatement in biomass-firing by fuel mixing. Three agriculture biomass fuels and olive cake were used in the experiments. Polish lignites and bituminous coals were examined as anti-sintering additives. The effects of chlorine release, potassium retention and ash sintering were examined by heating samples of biomass fuels and additives in the muffle oven and, next, firing them in the laboratory down-fired furnace at the temperature in the range of 800-1150ºC. The obtained slag samples were analysed on: chlorine and potassium content, sintering tendency and crystalline components. Among the examined coals lignite from Turów mine and bituminous coal from Bolesław Śmiały mine appeared to be the most effective in potassium retention in aluminosilicate and chlorine release from slag. Possibly the major factor of these coals which reduced ash sintering was relatively high content of kaolinite

The paper presents the results of the mechanical, electrical, CCSEM and XRD measurements of hard coal, conducted in simulated conditions of sintering in atmospheres of O2/CO2,. The changes of the coal ash resistivity are correlated with the content of the oxides and with the sintering temperature determined by the mechanical test and Leitz method. The SEM-EDS analysis was conducted for deposits on the probe. The changes of the measured ash samples, observed during sintering process in O2/CO2 atmosphere, were discussed in the ash microstructure point of view.

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%.