An analysis of the impact of mining with caving on the surface shows that a type of rock mass strata seems to be one of the critical factors affecting the process. Correlating the values of mining-induced surface deformation with the rock mass structure and the state of its disturbance is of crucial importance. Therefore, if other mining conditions are left unaffected, then those factors exert the key influence on a course and distribution of subsidence and rock mass deformation. A proper description of rock mass type and properties also seems rational for a proper determination of prediction parameters, especially in the case of a multi-seam coal mining, and/or the exploitation carried out at considerable depths. A general outcome of the study discussed in this paper is the development of the methodology and model practices for determining the rock mass type and, as a result, for selecting the optimal values of parameters for predicting the values of surface subsidence in relation to particular geological and mining conditions. The study proves that the type of rock mass may be described by such factors as the influence of overburden strata, the influence of Carboniferous layers, the disturbance of rock mass and the depth of exploitation.
In recent years, more and more attention has been paid to the quality of produced coal size categories for energy purposes. This is important from the perspective of promoting clean coal technologies which aim at changing the perception of coal as a fuel friendly for the environment. This is specifically because hard coal resources in Poland allow the national energy security to be guaranteed on the basis of energy production based on hard coal. Fine coals upgraded at coal processing facilities in the separation process in fine coal jigs are mainly used in energy production from coal. In the article, an analysis of hard coal upgrading in a jig regarding the optimum recovery of a useful fraction in the concentrate (combustible and volatile matter) and non-useful fraction in tailings (ash and sulfur) was conducted. Based on the industrial testing of a fine coal jig, the granulometric and densimetric analysis of the taken samples of concentrate, middlings and tailings of coal was conducted in laboratory conditions. Yields of products were calculated in separated size-fractions of separation products, and ash content and total sulfur content were determined in them. Based on the results of granulometric, densimetric and chemical analyses of the obtained size-fractions, the balance of separation products and appropriate calculations, Fuerstenau upgrading curves which allowed the process to be evaluated and a comparison of the results of hard coal upgrading regarding the optimum recovery of the organic phase in the concentrate and mineral components in tailings to be drawn. The obtained results were evaluated on the basis of different criteria for changing the device’s hydrodynamic operational conditions. The ash content and total sulfur content were analyzed as non-useful substances.
The research was aimed at examining the impact of the petrographic composition of coal from the Janina mine on the gasification process and petrographic composition of the resulting char. The coal was subjected to fluidized bed gasification at a temperature below 1000°C in oxygen and CO2 atmosphere. The rank of coal is borderline subbituminous to bituminous coal. The petrographic composition is as follows: macerals from the vitrinite (61.0% vol.); liptinite (4.8% vol.) and inertinite groups (29.0% vol.). The petrofactor in coal from the Janina deposit is 6.9. The high content of macerals of the inertinite group, which can be considered inert during the gasification, naturally affects the process. The content of non-reactive macerals is around 27% vol. The petrographic analysis of char was carried out based on the classification of International Committee for Coal and Organic Petrology. Both inertoid (34.7% vol.) and crassinetwork (25.1% vol.) have a dominant share in chars resulting from the above-mentioned process. In addition, the examined char contained 3.1% vol. of mineroids and 4.3% vol. of fusinoids and solids. The calculated aromaticity factor increases from 0.75 in coal to 0.98 in char. The carbon conversion is 30.3%. Approximately 40% vol. of the low porosity components in the residues after the gasification process indicate a low degree of carbon conversion. The ash content in coal amounted to 13.8% and increased to 24.10% in char. Based on the petrographic composition of the starting coal and the degree of conversion of macerals in the char, it can be stated that the coal from the Janina deposit is moderately suitable for the gasification process.
A significant part of hard coal production (15–19% in the years 2010–2017, i.e. 1.0–1.3 billion tons per year) is traded on the international market. The majority of coal trade takes place by sea, accounting for 91–94% of the total coal trade. The article discusses the share of coal in international seaborne trade and the largest coal ports. Coal is one the five major bulk commodities (in addition to iron ore, grain, bauxite, alumina, and phosphate rock). In the years 2010–2016, the share of coal in international seaborne trade and major bulk commodities was 36–41% and 11–12%, respectively. Based on the analysis of coal throughput in different ports worldwide, the ports with the largest throughput include the ports of Qinhuangdao (China), Newcastle (Australia), and Richards Bay (South Africa). For 2013–2017, their throughput amounted to a total of 411–476 million tons of coal. The largest coal exporting countries were: Australia, Indonesia, Russia, Colombia, South Africa, and the US (a total of 85% share in global coal exports), while the largest importers are Asian countries: China, India, Japan, South Korea and Taiwan (a 64% share in global imports). In Europe, Germany is the largest importer of coal (54 million tons imported in 2016). The article also discusses the freight costs and the bulk carrier fleet. Taking the price of coal at the recipient’s (i.e. at the importer’s port) into account, the share of freight costs in the CIF price of steam coal (the price of a good delivered at the frontier of the importing country) was at the level of 10–14%. In the years 2010–2016, the share of bulk carriers in the world fleet was in the range of 11–15%. In terms of tonnage, bulk carriers accounted for 31–35% of the total tonnage of all types of ships in the world. The share of new (1–4 years) bulk carriers in the total number of ships on a global scale in the years 2010–2016 was 29–46%.
Several surface measurement methods for determining the volume of deep or layered stone exist. One of the key indicators of coal extraction efficiency in open cast mining is to determine the volume of excavated rock. Procedures for determining the volume have been used for many centuries. Determining the extracted volume or layered material has been a periodically recurring role of mine -surveying practice, and mine surveyors apply different methods for its determination. The incorrect determination of the rock volume may result in large economic losses of the mining enterprise. The choice of the method for determining the volume depends on the deadline by which the determined volume has to be submitted to the superior components or the mining enterprise management, as well as on the requirements for accuracy of the volume determination, and a financial limit beyond which this volume determination has to be done. Secondary conditions for determining the volumes include the level of personnel training in the individual procedures and methods of measuring and calculating volumes, the technical standards of the enterprise, the applied instrumentation, hardware and software. The article compares the values of the accurately defined mathematical solid (a cylindrical segment) to the methods of calculating the volume normally used in mining and surveying practice and programs commonly used to calculate volumes in order to determine the threshold value of the systematic deviation in input measurements to determine the volume. The mathematical model is the basis for determining the correct volumes of the extracted material. The surface of the drawn or layered material does not form a smooth surface as a mathematical model. The process of determining volume errors on the mathematical model has been verified on the real body of coal deposition. The comparison of the determination of the errors between the digital terrain model on the mathematical body and the real homogenization coal stock is presented at the Conclusion of the article.
Paper deals with the new localizer GLOP2 designed for detection of the miners trapped in underground hard coal mines. The results of a field test conducted in coal mine BOBREK show that the presented localizer allows for efficient measurement of the distance between a trapped miner and the rescuer in the range of up to 15 m.
The paper describes the results of various actions and industrial tests conducted in order to decrease the content of unburned carbon in the fly ash of a circulating fluidised bed combustor (CFBC). Several attempts to improve the situation were made and the effects of several parameters on the unburned carbon content in the fly ash were investigated (e.g. bed temperature, cyclone separation efficiency, fuel particle size distribution, boiler hydrodynamics, grid design, and fuel data). Unfortunately, no satisfactory solution to these problems was found. Probably, apart from attrition and char fragmentation, additional factors also contributed to the formation of unburned carbon in the CFBC fly ash.
The study investigates chemical modifications of coal fly ash (FA) treated with HCl or NH4HCO3 or NaOH or Na2edta, based on the research conducted to examine the behaviour of Cd(II) and Pb(II) ions adsorbed from water solution on treated fly ash. In laboratory tests, the equilibrium and kinetics were examined applying various temperatures (293 - 333 K) and pH (2 - 11) values. The maximum Cd(II) and Pb(II) ions adsorption capacity obtained at 293 K, pH 9 and mixing time 2 h from the Langmuir model can be grouped in the following order: FA-NaOH > FA-NH4HCO3 > FA > FA-Na2edta > FA-HCl. The morphology of fly ash grains was examined via small-angle X-ray scattering (SAXS) and images of scanning electron microscope (SEM). The adsorption kinetics data were well fitted by a pseudo-second-order rate model but showed a very poor fit for the pseudofirst order model. The intra-particle model also revealed that there are two separate stages in the sorption process, i.e. the external diffusion and the inter-particle diffusion. Thermodynamics parameters such as free energy, enthalpy and entropy were also determined. A laboratory test demonstrated that the modified coal fly ash worked well for the Cd(II) and Pb(II) ion uptake from polluted waters.
A modified approach to equilibrium modelling of coal gasification is presented, based on global thermodynamic analysis of both homogeneous and heterogeneous reactions occurring during a gasification process conducted in a circulating fluid bed reactor. The model is based on large-scale experiments (ca. 200 kg/h) with air used as a gasification agent and introduces empirical modifications governing the quasi-equilibrium state of two reactions: water-gas shift and Boudouard reaction. The model predicts the formation of the eight key gaseous species: CO, CO2, H2O, H2, H2S, N2, COS and CH4, volatile hydrocarbons represented by propane and benzene, tar represented by naphthalene, and char containing the five elements C, H, O, N, S and inorganic matter.
Any complete CFD model of pulverised coal-fired boiler needs to consider ash deposition phenomena. Wall boundary conditions (temperature and emissivity) should be temporally corrected to account for the effects of deposit growth on the combustion conditions. At present voluminous publications concerning ash related problems are available. The current paper presents development of an engineering tool integrating deposit formation models with the CFD code. It was then applied to two tangentially-fired boilers. The developed numerical tool was validated by comparing it with boiler evaporator power variation based on the on-line diagnostic system with the results from the full CFD simulation.
The most important and the most frequently used plastics are polyethylene (PE) and polypropylene (PP). They are characterised with high heating values (approximately 40 MJ/kg). Moreover, their chemical composition, based mainly on carbon and hydrogen, allows to use them in industrial processes. One of the methods of utilisation of plastic waste can be its use in the metallurgical industry. This paper presents results of thermal decomposition of waste PE/PP. Chemical and thermal analysis (TG) of studied wastes was carried out. Evolved gaseous products from the decomposition of wastes were indentified using mass spectrometry (TG-MS). This paper also presents an application of plastic wastes as supplemental fuel in blast furnace processes (as a substitute for coke) and as an addition in processes of coking coal.
This article presents the use of a multi-criterion Analytic Hierarchy Process (AHP) method to assess geological and mining condition nuisance in longwall mining operations in selected coal mines in Poland. For this purpose, a methodology has been developed which was used to calculate the operational nuisance indicator (WUe) in relation to the cost of mining coal in individual longwalls. Components of the aggregate operational nuisance indicator include four sub-indicators: the natural hazards indicator (UZN), an indicator describing the seam parameters (UPZ), an indicator describing the technical parameters (UT) and an environmental impact indicator (UŚ). In total, the impact of 28 different criteria, which formed particular components of the nuisance indicators were analysed. In total 471 longwalls in 11 coal mines were analysed, including 277 longwalls that were mined in the period of 2011 to 2016 and 194 longwalls scheduled for exploitation in the years 2017 to 2021. Correlation analysis was used to evaluate the relationships between nuisance and the operating costs of longwalls. The analysis revealed a strong correlation between the level of nuisance and the operating costs of the longwalls under study. The design of the longwall schedule should therefore also take into account the nuisance arising from the geological and mining conditions of the operations. Selective operations management allows for the optimization of costs for mining in underground mines using the longwall system. This knowledge can also be used to reduce the total operating costs of mines as a result of abandoning the mining operations in entire longwalls or portions of longwalls that may be permanently unprofitable. Currently, underground mines do not employ this optimization method, which even more emphasizes the need for popularizing this approach.
The environment is the greatest good for the people. Everyone wants to breath air of the best possible quality, whether living in the city center of a metropolis or in a rural area. Air polluted with very fine particles contribute to the negative effect on people’s health and the whole environment. A significant part of air dust pollution comes from the so-called low emissions sources which include: non-standard furnaces, fireplaces, low-efficiency outdated boilers and local heat sources. Since the beginning of Polish Mining Group’s existence, the company actively participates and supports many activities, the aim of which is to improve the air quality by producing and supplying high quality coal for the residential sector. The company has undertaken pro-ecological activities towards creating a new, pro-ecological strategy as well as product offer. The production of an ecological coal assortment is systematically developing but new coal products are also being launched on the market. One of the company’s priorities is the production of thermal coal for the residential sector. Many organizational and technological changes have been made In that area (e.g. the establishmsnt of the Eco-Fuels Production Plant) to ensure a suitable level of production of the highest quality thermal coal.
The petrographic composition of coal has a significant impact on its technological and sorption properties. That composition is most frequently determined by means of microscope quantitative analyses. Thus, aside from the purely scientific aspect, such measurements have an important practical application in the industrial usage of coal, as well as in issues related to the safety in underground mining facilities. The article discusses research aiming at analyzing the usefulness of selected parameters of a digital image description in the process of automatic identification of macerals of the inertinite group using neural networks. The description of the investigated images was based on statistical parameters determined on the basis of a histogram and co-occurrence matrix (Haralick parameters). Each of the studied macerals was described by means of a 20-element feature vector. An analysis of its principal components (PCA) was conducted, along with establishing the relationship between the number of the applied components and the effectiveness of the MLP network. Based on that, the optimum number of input variables for the investigated classification task was chosen, which resulted in reduction of the size of the network’s hidden layer. As part of the discussed research, the authors also analyzed the process of classification of macerals of the inertinite group using an algorithm based on a group of MLP networks, where each network possessed one output. As a result, average recognition effectiveness of 80.9% was obtained for a single MLP network, and of 93.6% for a group of neural networks. The obtained results indicate that it is possible to use the proposed methodology as a tool supporting microscopic analyses of coal.
The article compares the management of energy resources in Poland and Ukraine over the period 2000–2017. The analysis took changes in the volume of coal, oil and natural gas resources into consideration. The indicators of supplies of these fuels for Poland and Ukraine have additionally been compared with selected EU countries. In order to assess energy security of Poland and Ukraine, the changes in the primary energy consumption have been analyzed in general in first order, then the possibilities of meeting the demand for natural gas, coal and oil have been determined based on the domestic extraction of individual energy resources. Such a comparison indicates the dominant role of coal in Poland while the extraction of oil and natural gas meets the domestic demand to a greater extent in Ukraine. Over the period 2000-2017, trends in primary energy consumption were different; a 17% increase was noted in Poland, while a nearly 40% decline was noted in Ukraine. The main factors responsible for radical changes in fuel and energy management in Ukraine have been identified: military operations in the east of the country and the annexation of Crimea, demographic changes. These events had a negative impact especially on the volume of hard coal mining in Ukraine; the significant increase in imports from 5.36 to 19.14 million tons in 2011-2017 was necessary for balancing. The balance of foreign exchange for electricity was also compared. Over the past years, this comparison has been favorable for Ukraine, where the dominance of electricity exports over imports is noticeable, which generated revenues of over USD 200 million in 2017.
To investigate the effect of different proximate index on minimum ignition temperature(MIT) of coal dust cloud, 30 types of coal specimens with different characteristics were chosen. A two-furnace automatic coal proximate analyzer was employed to determine the indexes for moisture content, ash content, volatile matter, fixed carbon and MIT of different types of coal specimens. As the calculated results showed that these indexes exhibited high correlation, a principal component analysis (PCA) was adopted to extract principal components for multiple factors affecting MIT of coal dust, and then, the effect of the indexes for each type of coal on MIT of coal dust was analyzed. Based on experimental data, support vector machine (SVM) regression model was constructed to predicate the MIT of coal dust, having a predicating error below 10%. This method can be applied in the predication of the MIT for coal dust, which is beneficial to the assessment of the risk induced by coal dust explosion (CDE).
A laboratory study was performed to study the effects of various operating factors, viz. adsorbent dose, contact time, solution pH, stirring speed, initial concentration and temperature on the adsorption of triphenyltin chloride (TPT) onto coal fly ash supported nZnO (CFAZ). The adsorption capacity increases with increase in the adsorbent amount, contact time, pH, stirring speed and initial TPT concentration, and decrease with increase in the solution temperature. The adsorption data have been analyzed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) adsorption models to determine the mechanistic parameters associated with the adsorption process while the kinetic data were analyzed by pseudo first-order, pseudo second-order, Elovich, fractional power and intraparticle diffusivity kinetic models. The thermodynamic parameters of the process were also determined. The results of this study show that 0.5 g of CFAZ was able to remove up to 99.60% of TPT from contaminated natural seawater at 60 min contact time, stirring speed of 200 rpm and at a pH of 8. It was also found that the equilibrium and kinetic data fitted better to Freundlich and pseudo second-order models, respectively. It can therefore be concluded that CFAZ can be effectively used for shipyard process wastewater treatment
The technology for gob-side entry retaining in steep coal seams is still in the development stage. The analysis results of the caving structure of main roof, low influence of gateway’s stability because of long filling distance and weak dynamic effect of the gateway, and the low stress redistribution environment indicate that using this technology in steep coal seams has significant advantages. Moreover, to reinforce the waste rock and the soft floor and to better guard against the impact of the waste rock during natural filling, a rock blocking device and grouting reinforcement method were invented, and theoretical calculations result show that the blocking device has high safety factor. In addition, we also developed a set of hydraulic support devices for use in the strengthening support zone. Furthermore, because the retaining gateway was a systematic project, the selection of the size and shape of the gateway cross section and its support method during the initial driving stage is a key step. Thus, first, a section the size of bottom width and roof height of a new gateway was determined to meet any related requirements. Then, according to the cross sections of 75 statistical gateways and the support technique, it chosen a trapezoidal cross section when the dip of the coal seam is 35° < α ≤ 45°, a special and an inclined arch cross section when 45° < α ≤ 55°. Eventually, a support system of bolts and cables combined with steel mesh and steel belts was provided. The support system used optimized material and improved parameters, can enhanced the self-bearing ability of the surrounding coal and rock masses.
Geodesic measurements of mining area deformations indicate that their description fails to be regular, as opposed to what the predictions based on the relationships of the geometric-integral theory suggest. The Knothe theory, most commonly applied in that case, considers such parameters as the exploitation coefficient a and the angle of the main influences range tgβ, describing the geomechanical properties of the medium, as well as the mining conditions. The study shows that the values of the parameters a = 0.8 and tgβ = 2.0, most commonly adopted for the prediction of surface deformation, are not entirely adequate in describing each and every mining situation in the analysed rock mass. Therefore, the paper aims to propose methodology for determining the value of exploitation coefficient a, which allows to predict the values of surface subsidence caused by underground coal mining with roof caving, depending on geological and mining conditions. The characteristics of the analysed areas show that the following factors affect surface subsidence: thickness of overburden, type of overburden strata, type of Carboniferous strata, rock mass disturbance and depth of exploitation. These factors may allow to determine the exploitation coefficient a, used in the Knothe theory for surface deformation prediction.
Samples of steam coal used in heat and power plants as well as densimetric fractions obtained on a laboratory scale by dense organic liquid separation have been examined. The contents of ash, mercury, chromium, cadmium, copper, nickel and lead have been determined in coal, in the light and medium fraction as well as in the refuse. The degree of removal of mineral matter and the examined heavy metals as well as the coal combustible parts yield have been determined. Examination of 5 coals revealed that it is possible to remove 41% of mercury and more than 35% of other heavy metals bound to mineral matter in coal.
In this study, non-sintered ceramsite was prepared using coal gasiﬁcation coarse slag obtained from a methanol plant. The basic performance and heavy metal leaching toxicity were analyzed. The results showed that seven out of nine non-sintered ceramsite groups were in accordance with the national standard of compressive strength (5 MPa), while only three groups met the national standard of water absorption index of less than 22%. The heavy metal concentrations in these three groups were found to be lower than that speciﬁed in National Class IV of surface water environment standards. The concentration of Cr was found to be 16.45 μg/L, which represents only 1% of the IV standard. The optimum mixing ratio, which showed high compressive strength (6.76 MPa) and low water absorption (20.12%), was found to be 73% coal gasiﬁcation coarse slag, 15% cement, and 12% quartz sand. The characterization using Fourier transform infrared spectroscopy showed that the formation of gelatin in ceramsite enhances the performance of the ceramsite base and increases the immobilization of heavy metal. The study proved that the preparation of non-sintered ceramsite using coal gasiﬁcation coarse slag reduces its environmental risk and achieves efﬁcient utilization of the slag. Therefore, it can be concluded that it is a feasible and environmental friendly method for the disposal of coal slag.
In this work problems associated with requirements related to pollution emissions in compliance with more restrictive standards, low-emission combustion technology, technical realization of the monitoring system as well as algorithms allowing combustion process diagnostics are discussed. Results of semi-industrial laboratory facility and industrial (power station) research are presented as well as the possibility of application of information obtained from the optical fibre monitoring system for combustion process control. Moreover, directions of further research aimed to limit combustion process environmental negative effects are presented.
As part of the presented work, tests were carried out to check the possibility of replacing of conventional reducers used in the lead pyrometallurgical processes by cheaper, but equally effective substitutes. For research of lead oxide reduction, the following fine-grained carbonaceous materials were used, ie anthracite dust and coal flotation concentrate, as well as traditional used coke breeze for comparison. The obtained test results indicate a similar ability to reduce the lead oxide of all studied carbonaceous materials.