DonNTU   Masters' portal

Viacheslav Moiseienko

Institute of Mining and Geology

Department of environmental activities

Speciality Integrated use of subsoil

Improving ecologo-economic activity of coal mines by increasing the extraction of methane from the enclosing rock layers

Scientific adviser: Ph. D., Helen Zavyalova

Resume Abstract

Abstract

Table of Contents

• Introduction
• Theme urgency
• Goal and tasks of the research
• An approach to the unification of synthesis of Moore FSM on FPGA
• Conclusion
• References

The Donetsk basin is the largest industrial region of Ukraine with a high concentration of the coal, metallurgical and chemical industries, making it one of the most dangerous regions of Ukraine and Europe from the point of view of environmental pollution. The main contribution of the emissions of methane into the atmosphere, makes the coal industry [1]. The estimated reserves of methane in coal deposits range from 12 to 25 trillion м³.

Every year millions of cubic meters of methane goes into the atmosphere from coal mines of Donbass. Methane is present in large quantities in the porous structure of coal is released as a result of mining operations, accumulated in the workings and then emitted into the atmosphere that it contributes to global warming, methane is the second leading greenhouse gas regulated by the Kyoto Protocol.

In world practice the following types of underground coal deposits: preliminary manufactured at prospective sites to the design and construction of the mines, it allows you to extract up to 15…25% of the gas released during the mining of the mine field; a pre – construction period of the mine is 10…20%; concomitant, – in the operation of the mine, – 5…25% (in addition, during this period, ventilation removes 20% to 50% is contained in coal–bearing strata of methane; next, from abandoned mines – 15…45%. According to these data, the percentage of gas extracted from fields during their development and after mine closure.

The interaction of mine with the environment presented in (Fig.1).

In master's degree work was carried out the selection of technical solutions aimed at the reduction of carbon emissions from mining and consumption of traditional fuels or replacing them with alternative forms of energy, the application of which will improve the environmental situation in areas adjacent to the mine site and reduce greenhouse risks.

The aim of the study is the choice of technical solutions aimed at the reduction of carbon emissions from mining and consumption of traditional fuels or replacing them with alternative forms of energy, the application of which will improve the environmental situation in areas adjacent to the mine site and reduce greenhouse risks.

On the basis of generalization of the obtained data and the results of other authors, was clarified the mechanism of the transition in the mountain range of hydrocarbon compounds linked to a gaseous state under the influence of the treatment works. The presence of mine workings (shafts, wells, horizontal and inclined preparatory, treatment and adjacent goaf) facilitates entry of these gaseous compounds in the atmosphere intensifies the greenhouse effect. The most rational current strategy of reducing the greenhouse effect from released gases from the bowels is to capture and recycle different ways of mining of hydrocarbons into carbon dioxide, which is 21 times less harmful than methane. Thus there is a transformation of chemical energy of hydrocarbons into heat, the latter is converted into mechanical and electrical, and then use in the workplace and in everyday life. Currently intensively investigated the possibility of disposal or recycling of carbon dioxide in a liquid or solid compounds, including organic.

At the present stage of development of process for extraction of coal seams is most acceptable, in our opinion, and perhaps the only correct one, is a comprehensive approach to addressing the issue of environmental security in developing coal and gas deposits. It involves the combination of all of the ways and means of degassing to maximize the capture and utilization of coal mine gases. Only the rational use of technical means of extracting methane makes it possible to utilize its maximum amount and drastically reduce emissions. For the successful implementation of this approach requires more than just information about the technical characteristics of the used equipment, but especially important information about the parameters of the areas of accumulation of gases, to know how to direct gases to degassing and recycling installations.

The allocation of major Sources of gas flows are determined by the geological structure of the strata where they are in their natural (random) manner, as by gas and by mutual situation. The estimate of the number released from the developed array gases is a geological and geochemical task, defined by existing regulations for any sextoplist.

Based On the results of the conducted research, taking into account peculiarities of desorption and filtration SHG of undermined coal–bearing strata, the proposed technology increase the efficiency of capture of methane degasification wells drilled from preparing workings.

Method of degassing of gas–and–coal deposits (Fig. 2A), characterized in that by measuring the deformation of the massif sets the parameters for local area unloading of the array ahead of the zone of bearing pressure and force exerted on the productive section of the wellbore (fracking) is carried out in the period of finding it in the local area of discharge at a distance Lвл+20m.

According to another method (Fig. 2B), the force on the productive section of the wellbore with simultaneous application of a dispersed filler is carried out in the period of finding it at the unloading area of the array ahead of the stope Lр-Lмр.

These processing methods allow to increase the size of the areas destroyed rock around the wells and increase the efficiency of degasification wells compared to conventional technologies by 20…40%. Technical solutions aimed at the reduction of carbon emissions from mining and consumption of traditional fuels or replacing them with alternative forms of energy will improve the environmental situation in areas adjacent to the mine site and reduce greenhouse risks. Additionally, the utilization of SHG will provide additional income.

Currently, the mines of Ukraine prevails associated degassing thickness weal through drilled from underground wells. To improve the efficiency of the degassing methods for the use of the techniques of artificial unloading and increasing the fracture and, consequently, gas recovery array, such as hydro pneumonectomies coal seams and rock strata and other ways of getrowsdata.

Some other Known methods such as proposed by the specialists of the National mining University the special workings of the ventilation horizon [2] that can be considered as a technical equivalent of the complex groundwater and surface wells. However, due to the complexity of systems development and relatively high costs on this method and some others are not yet widely spread.

Released from the rock mass gas can contain up to 100% methane, but in a ventilated bottom spaces of the mine workings it is diluted with air to a content of not more than 1.0 to 0.75 percent, the air-gas mixture is directed to the ventilation shaft. That part of the gas which is released in unventilated the goaf, or mixed with air leaks and, at the expense of mine depression, migrates in the vent stream, or stored in mined-out space, where it can be removed by using the gas exhaust units.

From the smitten rock mass and pumped water on the way transportation is also desorbed gases [3], which are mixed with the air of the mine workings and goes into the atmosphere. Not allocated gas shall be issued to the surface in the composition of the coal, rock and water. It should be noted that the solubility of methane in water is very low, and at atmospheric pressure it evaporates pretty quickly.

located over and under-developed layer of gas-bearing layers of rocks and formations of satellites–the production of methane, which accumulates in porous and fractured reservoirs primarily developed space.

Education collector cavities occurs as you move the line stope, with the largest cracks occur intermittently (discontinuously), as immediate collapse and precipitation of the main roof. A significant amount of gas from these reservoirs is recovered via underground degasification wells drilled from development workings, transport it by degassing pipelines, using as precursors flow vacuum pumps. The disadvantage of this method of degassing is a significant aspiration of air through cracks in the array and leaks in pipelines, worsening energy potential degassing of the medium. The quality of the mixture in the pipes should not be less than 30% (in some cases allow 25% methane) for security reasons.

A Significant drawback of this most common in the mines of this method of degassing is limited to the duration of operation of the groundwater wells. Beginning intensive gas recovery from the array in the borehole, as already noted, due to the deformation of the rock environment and the development of the fracture under the influence of mining operations. The area of influence of underground mining has almost a dimensionally stable, determined mainly by the geometry of the mine workings and the depth of the location. Ending the exploitation of groundwater wells is determined by their stability in the undermined thicker and duration of degassing pipeline until its destruction in the rapidly settling of the roof behind the stope. Thus, efficient operation of wells possible in some segments of the distances are approximately constant in front of and behind stope, and the duration of their work in these stretches – speed heading stope. Formed mobile phase degassed array (Fig. 3, the positions 11, 12) approximately constant length. The greater the intensity of plevyak (speed of heading stope), the smaller the length of the well and therefore, lower overall productivity.

Thus, on the basis of these studies we can identify the following cell parts degassing of the array. There is one located in the bottom part of the excavation, it includes space development and adjacent to the goaf. Its size is determined by the width of lava and step caving of the immediate roof. The movement in space is determined by the width of excavation equipment and the number of cycles of coal mining.

Another area includes an area in which the formation of cracks in the roof and the soil layer is adjacent to longwall development. Its dimensions are determined by the power taken out of the formation, deformation-strength properties composing the roof and soil rocks a step of precipitation of the main roof, the depth of mining and a number of other factors.

Fixed areas are characterized by the presence of a deconsolidated environment, they are near the borders of developed space, such as near furnaces installation [4]. In the rocks of the main roof cavity formed between the roof and settled hovering rocks–bridges, which can also be attributed to stationary sites. To extract from these cavities methane advisable through drilled from the surface of the well. In addition, they are formed along the structures erected for the protection of preparatory workings from the action of rock pressure [5]. Capture of methane from these sites is carried out using a so-called barrier wells, installations of gas suction or through left in the goaf processes of degassing pipelines.

With the participation of the author proposes a method to capture methane released from transported by mining of rock mass [6]. The basis of his supposed creation of a stand-alone transport channel using belt conveyors tubular type and the suction of methane from sealed bunkers. A detailed study of this method was not part of the scope of this work.

Analysis of the above data shows that, by intensive coal seams to increase the volume of recoverable groundwater wells methane these possible approaches. Acceleration of diffusion of gas from the rocks can be achieved by reducing the blockiness of rocks, for example by combining natural or artificial their destruction, which leads to reducing the size and increasing the shape factor of the blocks. It is also necessary to improve the filtration characteristics of the environment by strengthening their microresonator, in particular by disclosing and fixing the width of cracks [7]. In addition, you should look at measures to increase the length of areas of coal-bearing rock strata, in which there is an intensive gas transition from a bound to a free state.

1. Considering in the previous sections of the paper studies the ways of emissions into the atmosphere and approximate numerical indicators of consumption of methane during intensive mining of longwalls at the seams with high gas content.

2. The analysis of the current most common methods associated degassing of the developed array of coal–gas, identified areas of their application and the directions of integrated degassing intensively working on gas-bearing layers, ensuring the capture of 60…80% mining of hydrocarbons and the corresponding reduction in their emissions.

3. It is established that increase of the load at the coalface leads to shortening of the functioning of the underground degasification wells and reduce the quantity and quality of the captured methane. Proposed new technical solutions without additional capital and operating costs to increase by 20 to 40% percent increase in the rate of degassing wells.

4. On the basis of the analysis of eco-efficiency integrated degassing of the massif is established that it is not dependent on the performance of the mine, as determined by the amount of captured methane released and the duration of implementation of its utilization.

5. Additional environmental effects are obtained by using the captured mine methane as an energy feedstock. In this case, you can opt out of spending the limited traditional fuels, such as natural gas, coal, oil, uranium, biofuels, and others.

6. The implementation developed in the paper to increase the flow rate of underground degasification wells allows for the period of their existence is to increase the amount recoverable from solid methane by 20…40%. The use of the proposed technology during the year, provided that the work is always one "Bush" wells, will provide a high economic effect.

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