Method for Suppressing and Extinguishing a Coal Seam Fire

Abstract

A method for the suppression of coal seam fires provides for the location and determination of the boundaries of a coal seam fire, directing access to the coal seam, preparation of the coal seam prior to suppression and the suppression of the fire within the coal seam using a foam mixture, the method providing minimal impact and disruption to the surface above the coal seam fire.

Claims

1. An improved method and process for the suppression of coal seam fires consisting of the steps of: locating the nature and extent of the coal seam fire using topical and diagnostic testing, including aerial observation using thermal deviation and observed geological indicators known to be associated with underground thermal issues; pinpointing and identifying the outer perimeter or coal seam fire area, including the upper boundary or geological ceiling and lower boundary or geological floor of said active coal seam fire area; determining the minimal number of least environmentally detrimental surface locations for the application of directional boring equipment to a plurality of fire perimeter points from a minimal number of surface locations to conduct directional boring; drilling a plurality of directional bore holes from said minimal number of surface locations to completely surround said active coal seam fire area providing said multiple bore holes from said surface locations into said outer perimeter, said upper boundary and said lower boundary of said coal seam fire area; applying by forcible injection large quantities of a foam mixture comprising soap, water and an inert gas into each of said plurality of bore holes contemporaneously to wet and cool said fire within said coal seam fire area into a central core of said coal seam from said outer perimeter to said central core, forcible displacing combustion air sources for said coal seam fire until such time said entire coal seam has been saturated with said foam mixture to extinguish said coal seam fire; confirming said extinction of said coal seam fire and any reignition of said coal seam fire; filling said plurality of said bore holes with cement or a dense slurry of materials removed during said boring process to seal said plurality of said bore holes to eliminate any intrusion of combustion air into said plurality of said bore holes to prevent subsequent reignition of any further coal seam fire; and restoring said minimal number of said surface locations to a pre-suppression condition prior to application of said method and process.

2. The method and process of claim 1, further comprising the step including: destabilizing said coal seam prior to the forcible injection of said foam mixture using pressurized expansion injection to open said coal seam to allow for lessened impedance of said foam mixture into said coal seam, said pressurized expansion injection using pressurized steam or non-toxic environmental chemicals to separate substrate layers within said coal seam and dissolve minerals within said coal seam layers.

3. The method and process of claim 1, further comprising the steps including: destabilizing said coal seam prior to the forcible injection of said foam mixture using pressurized expansion injection to open and expand said coal seam to allow for lessened impedance of said foam mixture into said coal seam, said pressurized expansion injection using pressurized steam or non-toxic environmental chemicals to separate substrate layers within said coal seam and dissolve minerals within said coal seam layers; and introducing a granular material, including sand, fine gravel, silica or other know porous granular materials into said newly formed open and expanded said coal seam to maintain said coal seam layer separation, allowing said foam mixture to penetrate said coal seam and perpetuate flow throughout said coal seam for enhanced saturation.

4. The method and process of claim 1, further comprising any other process or step disclosed within the specification, drawings or within the known art of fire suppression which may be adapted or included within the defined method or process.

Description

III. DESCRIPTION OF THE DRAWINGS

[0019] The following illustrations and drawings are included and attached to this application. These drawings descriptions are as indicated below:

[0020] FIG. 1 is a cross sectional perspective view of an underground coal seam.

[0021] FIG. 2 is a topical surface representation of the area above the coal seam indicating preferred drill site for conducting the boring.

[0022] FIG. 3 is an illustration showing a plurality of bore holes entering the coal seam fire.

[0023] FIG. 4 is an illustration of a boring pathway using a directional boring apparatus.

[0024] FIG. 5 is a representative view of the coal seam fire being extinguished from its perimeter into a central core.

[0025] FIG. 6 is an illustration showing the surface restorative procedures upon complete extinguishment of the coal seam fire.

IV. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] A method and process for the suppression and extinguishment of a coal seam fire 10 to minimize surface interruption and damage to the surface above the coal seam fire 10, the method and process a indicated in FIGS. 1-6 of the drawings including the steps of locating the nature and extent of the coal seam fire 10 which is active using topical and diagnostic testing, including initial aerial observation of thermal deviation and geological indicators consistent with underground fire, pinpointing the outer perimeter 20 (a/k/a coal seam fire area 20), upper boundary 22 (a/k/a geological ceiling 22) and lower boundary 24 (a/k/a geological floor 24) of the active coal seam fire area, FIG. 2, determining the minimal number of least environmentally detrimental surface locations 30 for the application of directional boring equipment to a plurality of fire perimeter 20 points from as few surface locations 30 to conduct drilling, suppression, extinguishment and restoration procedures, FIG. 3, drilling a plurality of directional bore holes 40 from the determined least environmentally detrimental surface locations 30 completely surrounding the active coal seam fire 10 providing multiple passages from the surface locations 30 into the outer perimeter 20, geological ceiling 22 and geological floor 24 of the coal seam fire 10, FIGS. 3-4, applying large quantities of a foam mixture 50 of soap, water and an inert gas through forcible injection into each of the plurality of bore holes 40 contemporaneously to wet and cool the fire into the coal seam fire perimeter 20, ceiling 22 and floor 24 to ultimately into the central core of the coal seam A from the outside of the fire to its core, FIG. 5, the foam forcibly displacing the combustion air source from the coal seam fire 10 until such time as the entire coal seam A has been saturated with the foam mixture 50 to extinguish the coal seam fire 10, confirming the extinction of the coal seam fire 10 and the absence of any reignition of the coal seam fire 10, filling the bore holes 40 and sealing them to eliminate any intrusion of new combustion air to reduce the chance of subsequent reignition, FIG. 6, and restoring the surface locations 30 to a pre-suppression condition, or as close as possible to the condition of the surface prior to the method application, FIGS. 1 and 6.

[0027] It is contemplated that since coal seams A are known to vary in several factors, that other additional steps may be required to gain access to the coal seam A and for the preparation of the coal seam A to maximize the extinguishment method. There are several different types of coal which vary in combustion character, ignition temperature, density and layering thickness. Coal originates from peat, or plant matter, and is classified and ranked from lignite, which is a soft, immature brown coal, sub-bituminous, which is darker and harder than the lignite, bituminous, which is the next phase and is the state at which the coal becomes hard and black, and the final stage anthracite, which is black and shiny and very hard. It is this final state that is most desired for use in modern industry as it is the rank of coal having the most potential energy. Because each coal seam A is formed by layers of these differently ranked coals, as the coal matures, the layers become more difficult to separate and likely more densely compacted. It is also recognized that burning coal produces ash, which can cool and compact to a hardness more dense than the coal itself.

[0028] In the more compact coal seams A, especially those which have been on fire for longer periods, it may be necessary to introduce steps to include the destabilization of the coal seam substrate layers within the hot coal seam fire 10 prior to the injection of the soap, water and inert gas foam mixture 50 using pressurized expansion injection to open the coal seam A to allow for a less impeded injection of the foam mixture 50 throughout the coal seam A. This may include pressurized steam or introduction of some type of least environmentally detrimental or non-toxic chemicals to separate the substrate layers and dissolve minerals within the coal seam layers. Further, where the separated layers appear to be potentially destabilized during injection of the foam mixture 50, it may also be necessary to introduce a granular material, including sand or other know porous granular material into the newly formed and expanded seams to maintain the coal seam layer separation, allowing the foam mixture 50 to penetrate the coal seam A and perpetuate flow throughout the coal seam A for complete saturation.

[0029] Coal seams A may vary in depth from a few feet below the surface to several hundred feet below the surfaceeven within a common and contiguous coal seam A, justifying the use of directional and horizontal boring techniques. As previously mentioned, using the directional boring technique, the number of surface locations 30 are drastically reduced and each bore is cleaned to allow for the unimpeded flow of the foam mixture 50 into the coal seam A from numerous locations contemporaneously from the top ceiling 22, the floor 24 of the coal seam A and surrounding the entire perimeter 20. The inert gas included in the soap, water and inert gas foam mixture 50 is preferably a nitrogen gas which has been demonstrated to produce no toxic gas emission when used in the suppression of an underground fire and displace oxygen from the fire source, starving the fire of its fuel source for continued combustion. Filling the bore holes 40, a cement slurry, or a dense slurry mixture of the materials removed during the boring process, is pumped into each bore hole into the extinguished coal seam A for the permanent sealing of the formation for stability purposes and to eliminate combustion air back into the coals seam which could potentially lead to reignition.

[0030] Although the embodiments of the invention have been described and shown above, it will be appreciated by those skilled in the art that numerous modifications may be made therein without departing from the scope of the invention as herein described.