Terminating Expansion Of Underground Coal Fires And Protecting The Environment

Abstract

Method and apparatus for environment protection (climate change) from toxic elements and subsidence by existing underground coal seam fires by expansion termination of these fires. The method is based on creating, on the path of or around a burning coal seam fire, a subterranean void-barrier, with non-combustible gases (or fluids) and absence of oxidiser. The void-barrier may be substantially free from combustible material. The void-barrier will prevent further expansion of the existing coal seam fire, and may be created by known methods of coal extraction in gasified form, such as Underground Coal Gasification (USG). By-products from void-barrier creation can be utilized to reduce environmental pollution and for production of useful commercial entities such as gas or liquid fuels like: petrol, diesel, jet fuel, avgas, paraffin or electrical power generation and/or chemicals like CO.sub.2 for enrichment of coal or which may be sold.

Claims

1. A method of terminating expansion of any type of coal fire in an underground seam by creating an underground void-barrier without combustible materials, comprising the steps of: conducting and analysing geotechnical, thermal and geological investigation of the coal seam and existing fire properties; selecting a configuration of the void-barrier to be created ahead of or around the existing fire; engineering and designing safe and reliable void-barrier in coal seam impenetrable by coal fire with protection against subsidence and coal re-ignition based on UCG methodology and materials available at the time of design and place of implementation.

2. The method of claim 1, wherein creating the void-barrier comprises: evacuating coal from a space ahead of or around the fire.

3. The method of claim 2, wherein evacuating coal from the space comprises: using an Underground Coal Gasification (UCG) process.

4. (canceled)

5. The method claim 3, further comprising of: utilizing by-products of the UCG process.

6. The method of claim 3, further comprising: covering a surface created by the UCG process with non-combustible and gas penetration resistant material in case of engineering request.

7. The method of claim 3, further comprising: preventing subsidence by leaving some coal behind to support overburden, for as long as required and wear required according to design.

8.-15. (canceled)

16. A method for environment and climate change protection from toxic elements generated by existing underground coal seam fires comprising: terminating expansion of the fires by creating in the coal seam a void-barrier substantially without fuel and oxidiser on the path of the burning fire, thereby isolating remaining coal in the seam from the fire and preventing its ignition.

17. The method of claim 16, wherein: the void-barrier is created by evacuating surrounding coal from a space in the coal seam ahead of or around the fire.

18. The method of claim 16, wherein: the void-barrier is created by a process of underground coal gasification.

19. The method of claim 16, further comprising: utilizing by-products from void-barrier creation.

20. The method of claim 19, wherein: the by-products comprise syngas and land rehabilitation.

21. The method of claim 2, further comprising preventing subsidence and air excess to the void by creating an overburden support structures in the void designed according to engineering sines at time of design and from materials available in area of implementation.

22. The method of claim 1, wherein expansion of the coal fire is permanently terminated by using an available quality assurance methodology.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments of the invention. These drawings are provided to facilitate the reader's understanding of the invention and shall not be considered limiting of the breadth, scope, or applicability of the invention. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale.

[0037] FIG. 1 is a schematic presentation of underground void-barrier creation in coal seam method, example.

[0038] FIG. 2 is a schematic presentation of an underground void-barrier created in coal seam, and terminating expansion of a subterranean coal seam fire.

[0039] FIG. 3 is a diagram illustrating some steps of an exemplary method of terminating expansion of a subterranean coal seam fire.

[0040] The figures are not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the invention be limited only by the claims and the equivalents thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0041] The present invention may be described herein in terms of exemplary environments. Description in terms of these environments is provided to allow the various features and embodiments of the invention to be portrayed in the context of an exemplary application. After reading this description, it may become apparent to one of ordinary skill in the art how the invention can be implemented in different and alternative environments.

[0042] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention pertains. All patents, applications, published applications and other publications referred to herein are incorporated by reference in their entirety. If a definition set forth herein is contrary to or otherwise inconsistent with a definition set forth in applications, published applications and other publications that are herein incorporated by reference, the definition set forth in this document prevails over the definition that is incorporated herein by reference.

[0043] Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term including should be read as meaning including, without limitation or the like; the term example is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms a or an should be read as meaning at least one, one or more or the like; and adjectives such as conventional, traditional, normal, standard, known and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.

[0044] A group of items linked with the conjunction and should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as and/or unless expressly stated otherwise. Similarly, a group of items linked with the conjunction or should not be read as requiring mutual exclusivity among that group, but rather should also be read as and/or unless expressly stated otherwise. Furthermore, although items, elements or components of the invention may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated.

[0045] The presence of broadening words and phrases such as one or more, at least, but not limited to or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term module does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed across multiple locations.

[0046] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.

[0047] Coal burns. A coal seam fire, as the name infers, propagates along a subterranean coal seam which follows a path between an overlying layer of material referred to as overburden and an underlying layer of material referred to as underburden. A related term is interburden, meaning material that lies between two areas of economic interest, such as the material separating coal seams within strata. The overburden and underburden limit the vertical extent (thickness) of the coal seam. The coal seam may also have a limited lateral (horizontal) extent. The subterranean coal seam is thus bounded by other, presumably non-flammable material.

[0048] The present invention relates to methods and apparatus for terminating expansion of existing underground coal fires, and for protecting the environment from pollution by toxic gases, heavy metals and dust particles resulting from expansion of such fires. The method is based on the creation, on the path of burning coal seam fire expansion, a subterranean void-barrier, with non-combustible materials and without oxidiser (such as oxygen) to prevent further expansion of existing seam fire. In other words, the method is based on the creation of a void, which may be referred to as a void barrier in coal seam, ahead of the fire, by removing a volume of coal required to prevent ignition of coal remaining in seam coal by the existing fire or by spontaneous ignition from high temperatures created by the existing fire.

[0049] To ensure controlled coal removal to form the void-barrier, the removal may be performed by well-known underground coal gasification (UCG) processes. UCG involves creating entrances (accesses) to the coal seam, which are essentially wells extending from ground level, through any topsoil and overburden, into the coal seam. These entrances may include access holes for providing air/oxygen and temperature control agent (such as steam) to the coal seam, an access hole for extracting syngas from the coal seam, and another access hole for initiating ignition of coal in the seam or via extracting access.

[0050] Upon completion of coal removal from the seam, all entrances (accesses) to the void will be hermetically sealed by means (such as a valve) or materials suitable for existing on site conditions. Before sealing the accesses, a non-flammable material, or a gas such as nitrogen which will not support combustion may be introduced into the void-barrier to ensure that there is no oxidiser in the void-barrier and to prevent the coal fire from propagating past the void-barrier. In this manner, when the coal fire reaches the void barrier, it will be denied of oxygen and will extinguish itself. Subsequently, access to the coal seam for resuming mining operations may be re-established.

[0051] Syngas generated during void-barrier creation can be collected and sold, and may be (i) used for the production of liquid fuels, such as petrol, diesel, jet fuel, avgas and paraffin (ii) used for electrical power generation, and (iii) used (CO.sub.2, for example) for enrichment of healthy coal or sold.

[0052] FIG. 1 is a schematic presentation, illustration, or diagram (in cross-sectional view) of an exemplary subterranean coal field 100. The coal field may comprise a coal seam 102 extending generally horizontally beneath overburden material 104 and above underburden material 106. Topsoil 108 may cover the overburden material.

[0053] A coal seam fire (not shown) is to the right of the figure (as viewed). A direction of a subterranean coal seam fire extension (or propagation of the fire) is indicated by the arrow 110, extending from right-to-left in the figure. The progress (or front) of the coal seam fire is indicated by the dashed line 112.

[0054] In order to terminate further propagation of the coal seam fire, an underground void-barrier 120 may be created, ahead of or around (to the left of, as viewed) the fire. As discussed in greater detail hereinbelow, the void-barrier may be devoid of oxidiser (such as oxygen), so that the environment in the void-barrier will not sustain further propagation of the coal seam fire. The void-barrier may also be substantially devoid of coal, the primary flammable material involved in the fire. An exemplary technique for creating the void-barrier will now be discussed.

[0055] An underground coal gasification (UCG) system 130 may be used to create the void-barrier 120, as follows.

[0056] Air or oxygen (O.sub.2) may be provided by a pump 132 through a line 134 which extends into a subterranean area for creating the void-barrier, such as in the coal seam ahead of or adjacent to (or around) the fire. (For purposes of this discussion, the area for creating the void-barrier and the resulting void-barrier which is created may both be represented by the dashed line 120.) A control and/or non-return valve 136 may be disposed in the line 154, such as above-ground, for regulating (including shutting off) the flow of air or oxygen and preventing back flow in case of air or oxygen pressure will drop below pressure existing in the void.

[0057] When underground coal gasification (UCG) is performed, a by-product is syngas. The syngas may be collected in a collection (holding) tank 142 via a line 144 extending from the subterranean area for the void-barrier to above-ground. A control or non-return valve 146 may be disposed in the line 144, such as above-ground, for regulating (including shutting off) the flow of syngas. Ignition may be combined with Syngas outlet because syngas production will start at outlet pipe. An ignition source (not shown) may be provided. A subterranean portion of the line 144 may be considered to be an ignition well.

[0058] Steam may be provided by a source 152 (such as a boileror water pump, or gravity feed) through a line 154 which extends into the subterranean area for creating the void-barrier. A control and/or non-return valve 156 may be disposed in the line 154, such as above-ground, for regulating (including shutting off) the flow of steam and preventing back flow in the case of steam pressure dropping below the pressure in the void.

[0059] In summary, a coal seam fire may be terminated by creating a void-barrier ahead of or around a coal seam fire. The void-barrier may be created by gasification (controlled burning) of coal in the coal seam. Gasification may be controlled by regulating the amount of oxygen available to the fire and temperature. The gasification process may be cooled with steam.

[0060] FIG. 2 is a schematic presentation, illustration, or diagram (in cross-sectional view) of the exemplary coal mine (or coal field) 100, after the void-barrier has been created. This figure illustrates that, after underground coal gasification (UCG) is performed, holes through the topsoil for the lines 136, 140 and 144 may be plugged, such as hermetically sealed. In this manner, a void-barrier 120 with no combustible materials and without oxygen has been created (formed) so that extension/expansion/propagation of the coal fire may be terminated. Ash remaining from the underground coal gasification (UCG) process may be disposed (deposited) on the bottom of the void-barrier. This ash may be used for sealing of underground surfaces and entrances (accesses) to the void-barrier.

[0061] The structural design of the void-barrier may be determined on a case-by-case basis, depending on the characteristics of the coal seam, as may be determined by various surveys and investigations.

[0062] FIG. 3 shows an exemplary method 300 of terminating expansion of a subterranean coal seam fire. The following steps may be performed to implement the method. [0063] (step 302) Conduct geotechnical, thermal and geological investigation of the coal seam. [0064] (step 304) Select a configuration and size for a void-barrier, based on the results of the investigations. [0065] (step 306) Develop UCG implementation strategy and cost recovery options. [0066] (step 308) Implement UCG process according to strategy and options. This involves creating accesses (entrances) to the coal seam, ahead of the fire, in an area that will become a void-barrier. [0067] (step 310) Conduct gasified coal extraction operation (and sell by-products). [0068] (step 312) Seal all entrances (accesses) to the void-barrier upon completion of the UCG operation.

[0069] In the process of creating the void-barrier, an overburden support structure may be formed, such as by leaving some of the coal behind, to prevent subsidence.

[0070] Optionally, the void-barrier or portions thereof may be filled, via the entrances, with non-combustible filler as well as binder, and inert gas if required, the object being to deprive the void of oxidizer and prevent exit of combustible gases generated by coal to the void so that the fire will extinguish itself upon reaching the void-barrier. (Binder is a substance (like glue) holding filler (like ash) and surface together.) Filling may be performed during creation of the void-barrier, or after completing creation of the void-barrier. After the void barrier is created and filled, the entrances to the void-barrier may be sealed to prevent oxidizer from getting into the void-barrier.

[0071] There have thus been shown some techniques for terminating expansion of underground coal by creating in the coal seam a void-barrier substantially without fuel (coal) and without oxidiser on the path of the burning fire, thereby separating (isolating) remaining coal in the seam from the fire and preventing its ignition. In this manner, substantially all of the fuel (coal) may be removed from the area/volume of the void-barrier(s).

[0072] If desired, access may then be gained to the mine, including the void-barrier, to ensure that all vestiges of the fire are appropriately dealt with, and give the all clear for resuming mining operations.

[0073] There has thus been described a cost-effective, safe way of fighting subterranean coal seam fires by terminating expansion of the fire.

[0074] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example architectural or other configuration for the invention, which is done to aid in understanding the features and functionality that can be included in the invention. The invention is not restricted to the illustrated example architectures or configurations, but the desired features can be implemented using a variety of alternative architectures and configurations. Indeed, it will be apparent to one of skill in the art how alternative functional, logical or physical partitioning and configurations can be implemented to implement the desired features of the present invention. Also, a multitude of different constituent module names other than those depicted herein can be applied to the various partitions. Additionally, with regard to flow diagrams, operational descriptions and method claims, the order in which the steps are presented herein shall not mandate that various embodiments be implemented to perform the recited functionality in the same order unless the context dictates otherwise.

[0075] Although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments.