• Energy Research

Underground coal gasification is an alternative method for mining coal from thin and ultra-thin seams, which enables conversion of solid fossil fuels into combustible gases at the site of coal occurrence. At the same time, in the case when the coal seam thickness is critically small for the effective course of thermochemical reactions, it is necessary to intensify the gasification process. This paper studies one of the possible methods to intensify the process of underground coal gasification due to the influence of magnetic fields on the injected blast supplied into the gas generator gasification channel. Research tests conducted on a bench setup confirm the effectiveness of injected blast activation in a magnetic field by creating magnetic field inhomogeneity by placing permanent magnets and a discrete solid magnetized phase in a special device. For the first time, the dependence of changing growth of carbon participation during the solid fuel gasification process on changing magnetic field strength in the range of 0-600 E has been determined. It has been proven that the injected blast magnetization can significantly intensify the underground gasification process by increasing the carbon participation share in the fuel, which may be of practical importance for increasing the yield of combustible components.

Ukraine is an energy-dependent country, with less that 50% of its energy consumption fulfilled by its own resources. Natural gas is of paramount importance, especially for industry and society. Therefore, there is an urgent need to search for alternative and potential energy sources, such as gas hydrate deposits in the Black Sea, which can reduce the consumption of imported gas. It is necessary to refine the process parameters of the dissociation of gas hydrate deposits with a heterogeneous structure. The analyzed known geological–geophysical data devoted to the study of the offshore area and the seabed give grounds to assert the existence of a significant amount of hydrate deposits in the Black Sea. An integrated methodological approach is applied, which consists of the development of algorithms for analytical and laboratory studies of gas volumes obtained during the dissociation of deposits with a heterogeneous structure. These data are used for the computer modelling of the dissociation zone in the Surfer-8.0 software package based on the data interpolation method, which uses three methods for calculating the volumes of modelling bodies. A 3D grid-visualization of the studied part of the gas hydrate deposit has been developed. The dissociation zone parameters of gas hydrate deposits with different shares of rock intercalation, that is, the minimum and maximum diameters, have been determined, and the potentially recoverable gas volumes have been assessed. The effective time of the process of gas hydrate deposit dissociation has been substantiated. The obtained research results of the dissociation process of gas hydrate deposits can be used in the development of new technological schemes for gas recovery from the deep-water Black Sea area.

The authors of the paper consider the concept of further prospective development of mining enterprises. The basis of this concept are scientific results obtained during the study of physical and chemical processes of solids conversion into the gaseous state: coal → gaseous fuels. It was established that the main base of development of mining regions is a mining power-chemical complex. The basic segment of which is a well underground coal gasification station. It is established that increase of indicators of efficient operation of the station from gasification is possible by synthesis of technical and technological decisions on the use of coal seam energy. When coal gasification is over, the gasifier passes into a mode of thermal generator with the use of alothermal technique to remove heat and thermic decomposition products from the degassed space of the gasifier. Generator gas at its initial temperature (1100 – 1300oС) around an underground gasifier creates a powerful heat boiler with a temperature regime of 200 – 300oС. It was established that at work of six gasifiers on a coal seam with thickness of 1.0 m with geometrical parameters each at a width of 30 m and at the length of 450 m energy-thermal power will be 237.8 MW. At the same time, additional energy resources can be obtained by involving segments of alternative forms of energy supply to the life cycle of the mining enterprise.

Topical issues concerning the possibilities of effective energy generation on the basis of Ukrainian mining enterprises have been highlighted. Attention is drawn to one of the most challenging tendencies of nontraditional energy sources development in the process of wind-driven powerplant use. The plants consume energy of technogenic air flows. Operation schemes and engineering solutions as for the possibilities to involve nontraditional sources of energy resulting from operation of technogenic objects and industrial structures of enterprises (i.e. stopes, mine dumps, industrial facilities etc.) in power balance of a mining enterprise have been demonstrated. Energy efficiency of the wind-driven powerplants in the context of different operation schemes aimed at utilization of energy of technogenic air flows has been analyzed. Output of a wind-driven system as a component of technological segment of a mining enterprise making it possible to meet 20 to 44% of its power demand has been determined. The objective of the paper is to substantiate process solutions as well as technical and engineering ones as for the obtaining nontraditional energy sources basing upon introduction of wind-driven power plants.

This paper contains the research conducted within the grant No. 0120U102084 (financed by the Ministry of Education and Science of Ukraine), and Dubrovnik International ESEE Mining School (project in the framework of EIT Raw Materials).

This research is aimed to substantiate the optimally safe direction for mining operations developing in the conditions of shear processes under hydrostatic pressure influence when mining the Zavalivskyi Graphite Deposit. Using a graphical–analytical method, the slope stability index of the Pivdenno–Skhidnyi open-pit walls in the Zavalivskyi deposit and the safe distance for placing mining equipment have been determined. This method involves constructing a calculation scheme for each studied open-pit wall area based on the determined parameters by algebraically adding forces along a curvilinear shear surface, taking into account hydrostatic pressure within a possible collapse prism. During the research, factors have been identified that influence the optimal direction for stripping and mining operations developing under conditions of shear processes caused by flooding of lower horizons at the Zavalivskyi Graphite Plant. It has been revealed that the determining factor when choosing the direction for the development of mining operations is the safety factor of the open-pit working wall, ranging from 0.9 to 2.71 in the studied areas. Moreover, according to current normative documents, this indicator should not be less than 1.3. It has been determined that a promising direction for the development of mining operations in the Pivdenno–Skhidnyi open-pit mine is its south-western, western, and north-eastern areas, with a length of 556 m and a safe size for placing mining equipment of 27.12–32.54 m. Recommendations and measures for conducting mining operations have been developed to ensure the stable condition of the open-pit walls.

This work was supported by the Ministry of Education and Science of Ukraine, grants No.0116U008041 and No.0117U001127.

The present paper considers aspects of underground iron ore mining in Ukraine, in particular the level of mine production and reserves of basic ore fields. It analyzes and generalizes the practice of using cemented rockfill under difficult mining and hydrogeological conditions of the Pivdenno-Bilozerske high-grade iron ore field. The Belozersky iron ore district is the only one in Ukraine that, without any technological cycle of beneficiation, can provide both domestic and foreign consumers with high-quality raw iron ore as required by world markets. The PJSC Zaporizhzhia iron ore plant extracts iron ore from the Pivdenno-Bilozerske field with an iron content of more than 60% using the low-waste, environmentally friendly technology of backfilling the mined-out area with a hardening mixture. The peculiarities of the technology for steep deposit mining and the main processes of backfilling operations in terms of preparation, transportation, and construction of the backfill mass with its stability assessment are explained in detail in this paper. As a result of using cemented rockfill, rock mass stability is provided, a considerable part of industrial waste is disposed of in the mined-out area, and the earth’s surface subsidence within the area is prevented (in comparison with mining enterprises in other fields).