Compositions – Dust suppressants for bulk materials – or processes of...
Reexamination Certificate
2002-06-21
2004-04-27
Boyer, Charles (Department: 1751)
Compositions
Dust suppressants for bulk materials, or processes of...
Reexamination Certificate
active
06726849
ABSTRACT:
BACKGROUND OF THE INVENTION
In underground coal mines, stone dusting of exposed rock surfaces is used to prevent and suppress fires caused by the ignition of coal dust and methane gas produced during the mining process. Stone dusting involves coating the surfaces of the mine with a fine-ground limestone dust. The dust adheres to the walls of the mine and prevents propagation of fires along exposed surfaces of unmined coal in the mine. In the event of the ignition of coal dust and gas within the mine, the concussion of an explosion and fire will cause the loosely adhering dust to fall from the surfaces of the mine to produce a limestone dust-air suspension that suppresses the propagation of flame and stops the fire.
In traditional stone dusting, a loose, poorly cohesive, dusty inert material is applied to the surfaces of walls and ceiling of the mine. In the event of a coal dust explosion, that the material is easily suspended into the air of the mine by the concussion. The traditional process of stone dusting is generally dusty and wasteful. Working personnel in the ventilation area have to be evacuated while the stone dusting procedure is performed because of the excessive amount of, respirable dust produced in the air of the mine during the stone dust application. The evacuation reduces the amount of time the mine can operate. In traditional practice, dust is applied by “flingers”. With this method, a substantial portion of the dust does not adhere to the surfaces of the mine and typically falls to the floor becoming wet and therefore inactive, leaving only a limited amount of material remaining usefully positioned on the walls and ceiling.
Kritchevsky, U.S. Pat. No. 2,195,573 discloses a method of laying dust which comprises contacting it with an aqueous solution of a condensation product of alkylolamine and a higher organic acid substance, preferably the higher fatty acids. This results in absorption of the aqueous material by the dust particles to a relatively substantial depth, with the result that the dust is prevented from becoming airborne when the surface is agitated.
Burns et al., U.S. Pat. No. 4,316,811 discloses a dust suppressant composition comprising polyethylene oxide crystalline thermoplastic, water soluble polymer, and the balance water. The dust suppressant composition can be applied by a variety of methods, such as spraying, immersion, painting, slurry and rinsing.
Kittle, U.S. Pat. No. 4,561,905 discloses a method of suppressing coal dust comprising the steps of diluting with water an emulsion comprising water, a surfactant, and oil which exhibits a tacky characteristic when in the form of a film in the absence of water. This mixture which is in the form of an emulsion is diluted and foamed. The foam is then sprayed into a mass of coal.
Roe, U.S. Pat. Nos. 4,971,720 and 5,143,645 disclose a foam formed from a solution of demineralized make-down water and foaming agent, wherein the foam is contacted with solid materials to suppress process dust emissions.
What is needed in the industry is a method of dusting coal mine surfaces to prevent and suppress fires and explosions in underground coal mines without the detrimental side effect of wasteful excess airborne dust production.
SUMMARY OF THE INVENTION
The present invention utilizes the cohesive property of foamed material composed of a small amount of water, with a fine grained mineral dust such as that obtained from limestone, dolomite, magnesite, Class F fly ash, silica fume, gypsum, anhydrite, non-expansive clays, or fine ground mine tailings, and mixtures thereof; suspended in a foam. Dry mineral dust is blended with foam to produce a mass of material that is highly vesicular but that is cohesive and fluid enough to be pumped and sprayed as a foamed mass against mine wall surfaces and ceilings. The foamed material is applied with a spraying device that allows the foamed mass to adhere to the surfaces. Because of the low density of the material, the material can be built up to any thickness suitable for the application.
A significant advantage of the present invention is that no excessive airborne dust is produced during application, thus eliminating the need to evacuate the personnel in the area during application. The process is much cleaner and far less wasteful than normal stone dusting. After application, the low water content of the material permits evaporation of the water in the foamed mass, resulting in a dry mass of fine, poorly cohesive, vesicular material that dusts readily and has similar properties to that of the dry dust used in traditional stone dusting practice.
In one embodiment, the present invention includes a foamed material comprising limestone dust, a foaming agent and water.
In another embodiment, the present invention includes a foamed material comprising dust of at least one material selected from the group consisting of dolomite, magnesite, Class F fly ash, silica fume, gypsum, anhydrite, non-expansive clays, fine ground mine tailings, and mixtures thereof; a foaming agent and water.
In another embodiment, the present invention includes a dry powder formulation comprising limestone dust, a dry powder foaming agent and an additive that promotes the production of gas upon contact with water.
In another embodiment, the present invention includes a dry powder formulation comprising dust of at least one material selected from the group consisting of dolomite, magnesite, Class F fly ash, silica fume, gypsum, anhydrite, non-expansive clays, fine ground mine tailings, and mixtures thereof; a dry powder foaming agent and an additive that promotes the production of gas upon contact with water.
In another embodiment, the present invention includes a method of dusting coal mine surfaces comprising the steps of: providing a foam mixture comprising a foaming agent and water; incorporating air into the foam mixture to produce a foam; combining the foam and limestone dust to form a foamed material; and applying the foamed material to a mine surface.
In another embodiment, the present invention includes a method of dusting coal mine surfaces comprising the steps of: providing a foam mixture comprising a foaming agent and water; incorporating air into the foam mixture to produce a foam; combining the foam and dust of at least one material selected from the group consisting of dolomite, magnesite, Class F fly ash, silica fume, gypsum, anhydrite, non-expansive clays, fine ground mine tailings, and mixtures thereof, to form a foamed material; and applying the foamed material to a mine surface.
In another embodiment, the present invention includes a method of dusting coal mine surfaces comprising: providing a dry powder formulation comprising limestone dust, dry powder foaming agent, and an additive that promotes the production of gas upon contact with water; mixing the dry powder formulation with water to generate a foamed material; and applying the foamed material to a mine surface.
In another embodiment, the present invention includes a method of dusting coal mine surfaces comprising: providing a dry powder formulation comprising dust of at least one material selected from the group consisting of dolomite, magnesite, Class F fly ash, silica fume, gypsum, anhydrite, non-expansive clays, fine ground mine tailings, and mixtures thereof; dry powder foaming agent; and, an additive that promotes the production of gas upon contact with water; mixing the dry powder formulation with water to generate a foamed material; and applying the foamed material to a mine surface.
In a further embodiment, the present invention includes a method of dusting coal mine surfaces comprising: providing a dry powder formulation comprising limestone dust, dry powder foaming agent, and an additive that promotes the production of gas upon contact with water; and, applying the dry powder formulation to a wet surface.
In a further embodiment, the present invention includes a method of dusting coal mine surfaces comprising: providing a dry powder formulation comprising dust of at least one material selected from the group consis
Champa Jeffrey T.
Cowsette Dontave D.
Gay Frank T.
Hulvey Bradley S.
Boyer Charles
Construction Research & Technology GmbH
Renner Kenner Greive Bobak Taylor & Weber
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