SOLID FUEL

The present invention relates to the field of underground coal combustion, in particular to the combustion of coal and other organic materials contained in suspended or abandoned underground mine workings, in order to generate thermal energy.

This proposal relates, in the first place, to regions whose activities have been underground coal mining for many years. Infrastructure, business activity and social life of the population of these regions were due to the main direction of their activities - coal mining, coal delivery to the consumer, ensuring the required quality of this product. The termination of the activities of these regions led to a sharp decline in the employment of the population and a decline in its well-being. At the state level, there appeared a threat of hopelessness of life in such regions and the growth of social tension in them. It is possible to improve the situation radically in previously successful coal-producing regions if their population is provided with heat in the broadest sense of the term. For example, by constantly providing the thermal energy obtained from burning the remaining coal reserves

4 in the bowels, which are usually about half of the coal mined before and delivered to the surface.

Of course, it is essential to provide such regions with energy at the expense of coal from their own resources for the time sufficient to reorient their population to new areas of activity. Thus, conditions can be created to improve the living conditions of the population for decades of years to come.

The presence of a large number of patents and patent applications, as well as scientific articles and other publications in the field of obtaining and using energy from the burning of in-situ underground coal, either attests to the social importance of this direction of use of thermal energy.

One of such publication is the patent application of China CN1186897 (A) in where the inventors WANG RULIN et al. describe coal underground gasifying technology according to which at the bottom of the coal bed a gasified channel with cross section of 0.21-1.23 sg.m. and 20-56m length is built. Through the initiator nearby well entrance of the admission intake pipe, the coal bed is ignited to form the combustion surface. The stage of semi-water gas is obtained through blowing in air containing 5-38% (volume percent) of water vapor, and controlling the wind pressure and blowing rate. When the well outlet of the gas outlet pipe is 800-900 deg. C, the gas outlet pipe is used as admission intake pipe.

The inventions of Yanko Stanislav Vasyliovich et all. are also known. In their Ukrainian patent application, UA68703 (A) they describe a method for production of thermal energy consisting in laying crosscuts, which open coal layers, a burning out of the coal layer and tapping hot gases to the surface. At that air input crosscut is laid on the bottom horizon and gas intake crosscut is laid on the top horizon on each layer. Between the top and the bottom crosscuts there is made the cross. In the crosses, heat exchangers are placed, and in parallel to each heat exchanger, the pipe is placed which on the one end is connected to an external pipe of the heat exchanger.

In another Ukrainian patent application UA68702 (A) Yanko Stanislav Vasyliovich et all. describe a method for production of thermal energy at burning of coal layers. The method consists in drilling from the surface to the coal layer, air input through gas intake holes, delineation of coal areas by linkages, firing of coal through air input holes and tapping of hot gases on the surface through the gas intake holes. Those linkages on the delineated area are made between air input holes and are located on outline of a polygon with leaving of a coal virgin between the end air input and the gas intake holes. The gas intake hole is joined from one or several air input holes located between the end holes in a contour of the polygon, and that air is forced simultaneously through all air input holes.

In his US and Canadian patents US 4,387,655, US 5,368,105 and CA1155301 Chaiken Robert F. describes a method for recovering energy from wasted coal. The method is provided by the steps of creating at least one channel through the wasted coal, igniting the wasted coal in this channel, subjecting said wasted coal, at least at said channel, to a negative pressure applied at a preselected point, connecting said wasted coal, at least at said channel, to a source of air remote from said preselected zone whereby air is induced through said ignited coal to burn said coal to produce hot gaseous products of combustion, and the hot gaseous products of combustion are drawn from said zone, and utilizing said hot gaseous products of combustion in a heat exchange relationship to recover the heat energy therefrom.

Finally, there is known an invention according to the USSR Authors Certificate (patent) SU1475146, in which I, Michael Kipnis and others inventors, describe a method for underground coal combustion. The method includes drilling the air intake shaft and gas product outtake shaft, connecting them with a channel, blowing air into the air intake shaft, igniting the coal seam from the side facing the air intake shaft, maintaining the combustion of the coal, moving the firewall in the direction of blasting and pumping out the products incineration from the gas outtake shaft.

In order to increase the stability and completeness of working out the shallow seams while simultaneously increasing the length of the coal barrel between the air intake shaft and gas outtake shaft, a coal block is first divided into some blocks between the air intake shaft and gas outtake shaft, and the ignition of the formation from the side facing the air supply shaft. The maintenance of blocks combustion are in the direction of the flow of blasting is carried out in blocks, and the processing of blocks is carried out sequentially, starting from the block adjacent to the gas outtake shaft barrel and up to the block, adjacent to the air intake shaft. In addition, in order to ensure the stability of the process of burning coal with a high yield of volatile substances, and the mouth of the gas outtake shaft is cased with a heat-resistant material.

With all the variety of methods for underground coal combustion, there is practically no intelligible estimate of the required amount of energy for a long- term constant supply of heat to regions previously occupied by traditional coal mining.

In addition, in all these considered patents and applications, there are no economic calculations for the implementation of the process of underground coal combustion, including financial losses of states, associated with maintaining the vital activity of these regions for several decades and beyond for an indefinite period of time. The only exception is Canada's application CA2770811A1, in which the authors compare financial losses for extinguishing fires from spontaneous combustion of coal in abandoned mines with the costs of burning coal in them in order to obtain energy.

From the abovementioned, it can be concluded that to solve the above problem it is necessary not only to monitor the burning of coal and to register the state of the process, but also to be able to influence it and maintain a long projected flow. In addition, in order to ensure the required stoichiometry of the process, an oxidizer (air) must be supplied to the area of the basic treatment of the coal bed in sufficient quantities.

It is impossible to overestimate the significance of aforementioned factor, which actually corresponds to similar judgments of the majority of patent authors in this field. They contain references to the peculiarities of fire testing of various coals in the real conditions of their occurrence. Most authors note the influence on the process of underground coal combustion of geological features of the occurrence of coal, such as the presence of subsurface water in the bowels, rock cracks in the roof of the reservoir, rock composition and the presence of voids in it, geotectonic features of the occurrence of coal, soil and roof rocks of specific mine workings.

Many of published inventions are devoted to methods of controlling the combustion process or the effect to its course, and the ultimate goal of which is to deliver air to the zone of fire treatment. A common drawback of the claimed methods is their instability, primarily due to the lack of a real time location of the combustion area and more than the difficult delivery of the oxidizer there, which is usually carried out from the surface.

Essential, in my opinion, the lack of most inventions for utilization from the combustion of underground coal is the lack of strategy in setting a task for determining the consumer of underground thermal energy, after which tactical decisions can be made - how to burn coal in the bowels, how to ensure its long burning and constant delivery to necessary amount of heat to a consumer.

In my understanding, the main consumer of heat should recognize the regions that previously produced coal in mines. Currently, many of these regions, because of the long absence of directed activities, are destructive, unpromising and generally unprofitable for the states of their location. The above contains a definition of who the consumer is.

The reply to the question of how to provide heat to such regions is much more difficult, because it requires knowledge, in each case, of the operational management of the processes of coal firing in the formation directly in the zone of its occurrence.

The basis for the proposed method are the results of research works, carried out by me in 1983-1988. These works were resulted in a successful large-scale experiment of underground coal seam burning in a designated canned mine area near the city of Selidovo, Donetsk region, Ukraine, in which earlier, for decades, coal was mined. I carried out this a large-scale experiment on burning of remaining coal reserves in real conditions on a dedicated section of a mothballed mine. The process of burning lasted continuously for several months and was stopped with the interruption of the flow of air into the combustion zone in order to summarize the results of the experiment. Based on the results of the research, I concluded that it is possible to influence "manually" the underground combustion process in a subterranean space at a distance and under conditions that guarantee the safety of life and health and / or by means of mechanisms controlled such as outside, from the surface of the earth, and underground, at the same level as the combustion zone. The latter option is preferable, proceeding from the modern development of technics and technology.

SUMMARY OF THE INVENTION

According to the first embodiment of the present invention, there is proposed a method for energy recovery through combustion in-situ of solid fuel in canned mines with the preserved system of drifts and their ventilation. Group of successive steps provides this method.

First of all, it is creation in the mine, at least one air intake channel from the surface up to a burning area of a coal seam. The next step is to create at least one up to three or more channels to ensure that the gas from the burned coal seam can be diverted by another shaft barrel to the surface. Further at least one air intake channel and at least one gas outtake channel are connected with a connective channel along the coal seam towards from the at least one air intake channel up to the at least one gas outtake channel and air incoming into said at least one air intake channel.

The next step is delineation of a combustible coal seam on several separate blocks with leaving of the coal virgins between the air input channel and the gas intake channel.

Then, there is implemented an igniting of the coal seam from the side facing at least one or more gas outtake channel (coal fired gases) and maintaining the combustion of the coal by air, incoming into the at least one air intake channel and the connective channel.

Finally, there is being implemented the protection of at least one coal burning block by mobile firewalls made in the form of shields produced of fireproof material. The firewalls are remotely movable on the rails or along the rails of the corresponding drift of the canned mine. By this, air is inducted to the combustion zone directly through said combustion coal. Gaseous combustion products (firing gases) are discharged through at least one or more gas outtake channel and used in heat exchange to extract thermal energy from them.

According to the next embodiment of the present method, the igniting of the coal seam is carried out from the facing of at least one or more gas outtake channel in preselected place at the distance from 5- 50 up to 500 meters from at least one or more gas outtake channel. i According to the next embodiment of the present method, the maintaining of the coal combustion is carried out from block to block at the distance of 500 - 1000 meters along the prepared coal seam in the direction from the at least one or more gas outtake channel to at least one air intake channel.

According to the next embodiment of the present method, each of at least one or more coal fire gases outtake channel is supplied with at least 3-4 heat exchangers for utilizing of hot gaseous products of combustion and to recover the heat energy therefrom.

The mentioned mobile firewalls, which are made in the form of shields, made of fireproof material, are remotely movable on the rails or. along the rails of the corresponding drift of the canned mine by unmanned vehicles, remotely controllable such as from the surface or inside of the mine.

According to the next embodiment of the present method, the mobile firewalls, which are remotely movable on the rails or along the rails by unmanned vehicles, are remotely controllable such as from the surface or inside of the mine, provide air supply to the combustion area, while the movement of these firewalls itself is provide creating a temperature of at least near 60 ° C behind the combustion front of the corresponding coal block.

Finally, by means of the mobile firewalls, remotely movable on the rails or along rails by unmanned vehicles, which are remotely controlled such from the surface or inside of the mine, there is created a hollow space corresponding to the dimensions of the trolleys traveling on the rails or along the rails of the given drift and its length is from about 500 meters to about 2000 meters in the direction of burning coal.

3 BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a canned mine and a proposed coal combustion zone, according to an embodiment of the present invention.

FIG. 2 is an enlarged cross sectional view of a coal ignition zone and the supply system shown in FIG. 1.

FIG. 3 is an enlarged cross sectional view of coal combustion zone and air supply system shown in FIG. 1.

FIG. 4 illustrate the possible composition of the gaseous products of coal combustion and the scheme of their separation in a surface plant

FIG. 5 is an enlarged view of the coal combustion zone at the end of this process, and

FIG. 6 is a possible schematic view of the system for monitoring underground coal combustion.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is susceptible of embodiment in various forms, as shown in the drawings, hereinafter will be described in the presently preferred embodiments of the invention with the understanding that the present disclosure

/o is to be considered as an exemplification of the invention, and it is not intended to limit the invention to the specific embodiments illustrated. Embodiments of the present invention will be described hereinafter with reference to the drawings. It is noted that the drawings are schematic.

Underground coal combustion (UCC) is a technological process by which the extracted gas comes from a coal seam as a result of combustion and possibly concomitant partial gasification of coal in-situ in the presence of an oxidant. The resulting gas, in some sources called "synthesis gas" or "syngas", can be used, according to these sources, as raw materials for various applications, for example, the production of clean fuels, chemical production, power generation, etc. In our case, we consider the gas formed as a result of underground combustion of coal gas, as a source of thermal energy. The gaseous product formed by UCC, as a rule, includes "synthesis gas". It may contain other components, the percentage and composition of which depends on various factors, including the amount of oxidant used for the UCC, such as, for example, air, the composition of the organic matter of the coal being burnt, the operating temperature, the amount and the presence of moisture in the combustion zone, and etc.

UCC produced gas will contain (see FIG. 4): a) main syngas components (e.g., CO, H ₂ , C0 ₂ , N _2; and CH ₄ ); b) micro particles, for example soot and ash and coal particles; c) moisture; d) components of hydrocarbons, such as C ₂ - C ₆ hydrocarbons, oxygen, argon, sulfur-containing components (for example, H ₂ S, COS), nitrogen (e.g. HCN), traces of heavy metals (arsenic and mercury) and also chlorides.

The invention is explained by the drawings of FIG. 1 - 6. FIG. 1 illustrates an example of an underground coal combustion in a combustion and gasification chamber 10. The chamber 10 is supplied with an air intake channel such as well 12, and gas outtake channel or channels such as production well 14. Further, an air intake channel such as well 12 and a gas outtake channel or channels such as production well 14, can be connected, for example, by connective channel 16 (see FIG. 1) along the coal seam 18 towards from air intake channel 12 up to gas outtake channel or channels 14 and is supplied with a means for air incoming into air intake channel 12.

During the UCC process, well 12 is used to incoming an oxidizing gas (such as air), into the zone of ignition and coal combustion of reactor cavity 20 (in other sources referred to as the combustion and gasification chamber 10) that is a cavity in coal seam 18 created initially by explosion, drilling, etc. and subsequently expanded by combustion and gasification of the coal. Cavity 16 forms between the place of air injection and the roof of coal seam 18 and laterally grows up to known limit during the coal combustion and gasification process.

During the UCC process, production wells 14 are used to extract the coal fire gases formed during the UCC process as shown by the yellow or orange arrow (see FIGS. 1 - 3). In total, during the claimed process, at least three gas- discharging wells 14 are used made in the form of pipes of a material, corresponding to the mine roof rock, resistant to an aggressive environment and high temperature of the outgoing gas. The initiation channel of UCC process (not shown in the drawings) may be used to initiate the gasification process in coal seam 18, as which is shown by the red in FIG. 1 - 3.

II Since, according to the proposed method, coal combustion is predominantly carried out in a canned mine, said injection cannel or well 12 and gas outlet channels or wells 14 can be pipes housed within existing mine shafts or specially drilled wells. The diameter of said pipes can be near 250mm and more.

During the UCC process, the coal is combusted and cavity 20 moves away from the gas outtake channels or wells 14 into direction of air injection channel or well 12. In the examples in FIGS. 1 and 3, a direction of the combustion process is changing from right to left as shown. A key aspect of the UCC process is the ability to move the oxidant (air) entry place in accordance with the movement of the coal combustion surface.

FIG. 2 illustrates a close up view of reactor cavity 20, in which the combustion zone # 1 smoothly passes into the combustion zone # 2, etc.

Before the combustion of coal, there is provided the delineation of a combustible coal seam 18 on, several separate blocks with leaving of the coal virgins (not shown in the drawings) between air inputs channel 12 and the gas intake channels 14.

Then, there is implemented an igniting of the coal seam 18 from the side facing gas outtake channels 14 and maintaining the combustion of the coal by air, blowing into air intake channel 12 and the connective channel 16 (see FIGS. 2, 3).

The protecting of at least one coal-burning block is provided by mobile firewalls made in the form of shields produced of fireproof material (not shown in the drawings). The firewalls are remotely movable on the rails or along the rails of the corresponding drift of the canned mine, whereby air is induced through this burned coal to produce hot gaseous products of combustion, which are drawn from mentioned area and utilized in a heat exchange relationship to recover the heat energy therefrom.

The igniting of the coal seam 18 is carried out from the facing of gas outtake channels 14 in preselected place at distance from 5 - 50 up to 500 meters from this gas outtake channel 14 (see FIG.l).

According to the most preferred embodiment of the present method, the maintaining of the coal combustion is carried out from block to block at a distance of 500 -1000 meters along the prepared coal seam 18 in the direction from gas outtake channel 14 to air intake channel 12. Wherein each of gas outtake channels 14 are supplied with at least 3-4 heat exchangers for the sustainable extraction of thermal energy from the gaseous combustion products of coal.

The mentioned mobile firewalls (not shown in the drawings), which are made in the form of shields made of fireproof material, are remotely movable on the rails or along the rails of the corresponding drift of the canned mine by unmanned vehicles, remotely controllable such as from the surface or underground. These mobile firewalls provide temperature at least near 60 °C behind the combustion front of the corresponding coal block.

Finally, by means of the mentioned mobile firewalls, remotely movable on rails or along the rails of the drift by unmanned vehicles or by another accessible method, an empty space is created corresponding to the volume formed by these firewalls and its length is from 500 meters to 2000 meters in direction of coal combustion (see FIG. 1).

The possible composition of UCC gaseous products and the process of their utilization is shown in FIG. 4. In addition to the installation of mobile firewalls, unmanned vehicles that are remotely controlled such from the surface or inside of the mine by means of a computer automatic system, place the temperature sensors, gas analyzers, video cameras and any other necessary equipment remotely connected with this automatic system in the corresponding mine drifts (see FIG. 6). These same unmanned vehicles can also remotely change the location of said equipment.

The present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, and it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be constructed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended below claims.

IS