AU2014292751B2

AU2014292751B2 - Coal ash solidification foam material used for prevention and treatment of spontaneous combustion of coal and preparation method therefor

Info

Publication number: AU2014292751B2
Application number: AU2014292751A
Authority: AU
Inventors: Yuwei Jia; Lei Li; Yi Lu; Botao Qin; Leilin Zhang
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2013-07-17
Filing date: 2014-03-26
Publication date: 2016-02-25
Anticipated expiration: 2034-03-26
Also published as: RU2588588C2; CA2879374A1; ZA201408380B; RU2014143658A; CN103387410A; WO2015007104A1; CA2879374C; AU2014292751A1; CN103387410B

Description

1 Coal Ash Solidification Foam Material Used For Prevention And Treatment Of Spontaneous Combustion Of Coal And Preparation Method Therefor Field of the Invention The present invention relates to a solidified foam material and preparation method thereof, in particular to a coal ash solidified foam material for preventing spontaneous combustion of coal and preparation method thereof. Background of the Invention Spontaneous combustion of coal is one of the major natural disasters in coal mines, and severely threatens production safety and life safety in coal mines. The fire disasters in coal fields are mainly incurred by spontaneous combustion of coal owing to air leakage and oxygen supply in surface cracks. Spontaneous combustion of coal in mine underground mainly occur in mined-out spaces, open-off cuts, mining stop lines, geological structure zones, and tunnel top-coal caving region, where air leakage channels exist. To prevent spontaneous combustion of coal, techniques such as grouting, inert gas, inhibitor, gel, and polyurethane foam, etc. are utilized in China and foreign countries. However, all these methods have some drawbacks: the mud grouting technique consumes soil heavily and is unsuitable for use in regions short of soil, and the grout tends to seep downwards and can't seal up small cracks; inert gasses tend to diffuse along with the leaking air, and it is difficult to retain the inert gasses in the injection area; ammonium salt gels release toxic and harmful gasses, and the colloid may crack easily; inhibitors may erode the underground equipment and endanger the physical and mental health of the workers, and the fire prevention and suppression effect is not ideal; organic solidified foam materials can attain a satisfactory result, but the cost and ambient temperature requirement are high. In recent years, a three-phase foam new technique is adopted to prevent and suppress spontaneous combustion of coal in coal mines. It is much superior to conventional fire prevention and suppression techniques and materials, and can meet demands for fire prevention and suppression in a large area. Three-phase foam materials lack of strength and have not been solidified; whereas, in some occasions, solidified foam materials that have a high foam expansion, can be solidified, and have appropriate strength to fill, seal, and prevent spontaneous combustion of coal are required. A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims. Throughout the description and claims of the specification, the word "comprise" and variations of the word, such as "comprising" and "comprises", is not intended to exclude other additives, components, integers or steps.

la Summary of the Invention To address the issues related to prevention of spontaneous combustion of coal in the prior art, the present invention provides a coal ash solidified foam material for preventing spontaneous combustion of coal, which can dilute the oxygen concentration in a residual coal space, has a low heat conductivity coefficient, high heat insulation effect, and is easy to manipulate, safe, and low in cost. The coal ash solidified foam material according to the present invention comprises the following ingredients, in parts by weight (pbw): 40-60pbw of water, 100pbw of coal ash, 25-40pbw of compound powder for chemically self-producing gas, 3-5pbw of accelerator, 2-4pbw of activator, 1-2pbw of water reducer, and 1pbw of compound foam stabilizer; 2 The compound powder for chemically self-producing gas is prepared at the following blending ratio, in parts by weight (pbw): 24-35pbw of semi-hydrated calcium sulfate and 1-5pbw of sodium bicarbonate, which have a chemical reaction with each other and produce an inert gas (i.e., carbon dioxide gas), and thereby create foams in the grout; the accelerator is prepared at the following blending ratio, in pbw: 1-2pbw of alumina clinker, lpbw of sodium carbonate, and 1-2pbw of quick lime, wherein, the alumina clinker is composed of the following ingredients, in weight percentage: 94wt% of sodium aluminate, 4wt% of aluminum oxide, and 2wt% of calcium aluminosilicate; the activator is prepared at the following blending ratio, in pbw: 0.8-1.6pbw of magnesium oxide and 1.2-2.4pbw of magnesium chloride; the water reducer is prepared at the following blending ratio, in pbw: 0.5-lpbw of calcium lignosulphonate and 0.5-lpbw of condensate of naphthalene sulfonate and formaldehyde, wherein, in the condensate of naphthalene sulfonate and formaldehyde, the content of Na 2

SO

4 is <3%; the compound foam stabilizer is prepared at the following blending ratio, in pbw: 0.2pbw of ethylene glycol butyl ether, 0.3pbw of nano-silicon, and 0.5pbw of hydroxyethyl cellulose; the solidification time can be adjusted by adjusting the weight fractions among the accelerator, activator, and water reducer. The preparation process of the coal ash solidified foam material according to the present invention comprises the following steps: step 1: adding 40-60pbw of water, 0.2pbw of ethylene glycol butyl ether, 0.3pbw of nano-silicon, and 0.5pbw of hydroxyethyl cellulose into a special-purpose blending container A, and then stirring the mixed solution at 3,000±100rpm of rotation speed by a stirrer for 2min., to form a uniform foam solution; step 2: adding 100pbw of coal ash, 1-2pbw of alumina clinker, lpbw of sodium carbonate, 1-2pbw of quick lime, 0.8-1.6pbw of magnesium oxide, 1.2-2.4pbw of magnesium chloride, 0.5-lpbw of calcium lignosulphonate, and 0.5-lpbw of condensate of naphthalene sulfonate and formaldehyde into a dry-blending mixer B, and stirring the mixed powder at 3,000+100rpm of rotation speed by a stirrer for 3min., to form blended powder; step 3: adding the blended powder prepared in the dry-blending mixer B into the uniform foam solution in the special-purpose blending container A, and stirring the mixture at 12,000±500rpm of rotation speed by a stirrer in the special-purpose blending container A for 2min., to form blended grout, keeping still the blended grout to produce foams, so as to produce the coal ash solidified foam material for preventing spontaneous combustion of coal. Beneficial effects: with the technical scheme described above, in the present invention, the semi-hydrated calcium sulfate and sodium bicarbonate have a chemical reaction in water and produce an inert gas (i.e., carbon dioxide gas), and thereby create foams in the grout; with the compound foam stabilizer (i.e., compounded by ethylene glycol butyl ether, the nano-silicon and hydroxyethyl cellulose), the solid particles are homogeneously dispersed and suspend in the grout; the solidification time is adjusted by adjusting the weight fractions among the accelerator, activator, and water reducer; thus, the coal ash solidified foam fluid material is produced ultimately, which is lightweight, has a 8-15 foam expansion factor, and the foam fluid can uniformly cover loose coal-rock mass, and has strong crack penetration capability, adjustable solidification time, high compression strength (>1.5Mpa); some inert gas (i.e., carbon dioxide gas) is released in the foaming reaction process and the inert gas can dilute the oxygen concentration in 3 a residual coal space very well; in addition, the coal ash solidified foam material is of low heat conductivity coefficient that can attain a good heat insulation effect, and the coal ash solidified foam material is easy to manipulate, safe, and low in cost. It can cover the coal mass and isolate the coal mass from oxygen quickly, effectively seal air leakage channels and cracks in the coal mass, and prevent oxidation of the coal. This material is of great significance for preventing and suppressing spontaneous combustion of coal. Compared to the prior art, the present invention has the following advantages: (1) The coal ash solidified foam material for preventing spontaneous combustion of coal according to the present invention employs a foam self-producing system in which semi-hydrated calcium sulfate, sodium bicarbonate, and water have a chemical reaction and produce an inert gas. All of the three ingredients are environment-friendly materials and the inert gas (carbon dioxide) produced in the chemical reaction can dilute the oxygen concentration in a residual coal space; (2) The coal ash solidified foam material for preventing spontaneous combustion of coal according to the present invention is prepared from main raw materials including coal ash, semi-hydrated calcium sulfate, and sodium bicarbonate, which are widely available, and the process is simple; (3) In the coal ash solidified foam material for preventing spontaneous combustion of coal according to the present invention, the foam fluid can cover the coal mass very well, and has strong crack penetration capability and adjustable solidification time; (4) The coal ash solidified foam material for preventing spontaneous combustion of coal according to the present invention is lightweight (the foam expansion factor is 8-15), has high compression strength (>1.5Mpa) and low heat conductivity coefficient, can attain a good heat insulation effect, and has high applicability in the field of coal spontaneous combustion prevention. Detailed Description of the Embodiments Embodiment 1: the coal ash solidified foam material comprises the following ingredients, in parts by weight (pbw): 40-60pbw of water, 100pbw of coal ash, 25-40pbw of compound powder for chemically self-producing gas, 3-5pbw of accelerator, 2-4pbw of activator, 1-2pbw of water reducer, and 1pbw of compound foam stabilizer; The compound powder for chemically self-producing gas is composed of semi-hydrated calcium sulfate and sodium bicarbonate, which have a chemical reaction with each other in water and produce carbon dioxide, and thereby create foam in the grout. The two ingredients are blended at the following blending ratio, in parts by weight (pbw): 24-35pbw of semi-hydrated calcium sulfate and 1-5pbw of sodium bicarbonate; the accelerator is composed of alumina clinker, sodium carbonate, and quick lime, and is prepared at the following blending ratio, in pbw: 1-2pbw of alumina clinker, 1pbw of sodium carbonate, and 1-2pbw of quick lime, wherein, the alumina clinker is composed of the following ingredients, in weight percentage: 94wt% of sodium aluminate, 4wt% of aluminum oxide, and 2wt% of calcium aluminosilicate; the activator is a magnesium-based curing agent, composed of magnesium oxide and magnesium chloride, and 4 prepared at the following blending ratio, in pbw: 0.8-1.6pbw of magnesium oxide and 1.2-2.4pbw of magnesium chloride; the water reducer is composed of calcium lignosulphonate and a condensate of naphthalene sulfonate and formaldehyde, and is prepared at the following blending ratio, in pbw: 0.5-lpbw of calcium lignosulphonate and 0.5-lpbw of condensate of naphthalene sulfonate and formaldehyde, wherein, in the condensate of naphthalene sulfonate and formaldehyde, the content of Na 2

SO

4 is <3%; the compound foam stabilizer is compounded from ethylene glycol butyl ether, nano-silicon, and hydroxyethyl cellulose, and is prepared at the following blending ratio, in pbw: 0.2pbw of ethylene glycol butyl ether, 0.3pbw of nano-silicon, and 0.5pbw of hydroxyethyl cellulose; the compound foam stabilizer is helpful for the solid particles in the grout to disperse and suspend homogeneously and can decrease the volumetric density difference among upper, middle, and lower part of the coal ash solidified foam material, so that the pore size distribution is uniform, the pore structure can be improved significantly, and string-pores can be reduced. Embodiment 2: first, add 50pbw of water, 0.2pbw of ethylene glycol butyl ether, 0.3pbw of nano-silicon, and 0.5pbw of hydroxyethyl cellulose into a special-purpose blending container A, stir the mixed solution at 3,000100rpm of rotation speed by a stirrer for 2min., to form a uniform foam solution; then, in a dry-blending mixer B, add 100pbw of coal ash, lpbw of alumina clinker, lpbw of sodium carbonate, lpbw of quick lime, 1.2pbw of magnesium oxide, 1.8pbw of magnesium chloride, 0.5pbw of calcium lignosulphonate, and 0.5pbw of condensate of naphthalene sulfonate and formaldehyde, wherein, the content of Na 2

SO

4 in the condensate of naphthalene sulfonate and formaldehyde is <3%, and the alumina clinker is composed of the following ingredients, in weight percentage: 94 wt% of sodium aluminate, 4 wt% of aluminum oxide, and 2 wt% of calcium aluminosilicate, stir the mixed powder at 3,000±100rpm of rotation speed by a stirrer for 3 min., to form blended powder; finally, add the blended powder in the dry-blending mixer B into the uniform foam solution in the special-purpose blending container A, and stir the mixture at 12,000±500rpm of rotation speed by a stirrer for 2 min., to form blended grout; then, keep still the grout to produce foams, so as to obtain the coal ash solidified foam material for preventing spontaneous combustion of coal. Inject the prepared coal ash solidified foam fluid for preventing spontaneous combustion of coal with a 3MPa ground mobile injection pump through a conveying pipeline into surface cracks to be sealed in a coal field, to cover the coal mass, reduce and control air leakage, so as to prevent spontaneous combustion of the coal. Embodiment 3: first, add 60pbw of water, 0.2pbw of ethylene glycol butyl ether, 0.3pbw of nano-silicon, and 0.5pbw of hydroxyethyl cellulose into a special-purpose blending container A, stir the mixed solution at 3,000+100rpm of rotation speed by a stirrer for 2min., to form a uniform foam solution; then, in a dry-blending mixer B, add 100pbw of coal ash, 2pbw of alumina clinker, lpbw of sodium carbonate, 2pbw of quick lime, 1.6pbw of magnesium oxide, 2.4pbw of magnesium chloride, lpbw of calcium lignosulphonate, and lpbw of condensate of naphthalene sulfonate and formaldehyde, wherein, the content of Na2SO4 in the condensate of naphthalene sulfonate and formaldehyde is <3%, and the alumina clinker is composed of the following ingredients, in weight percentage: 94 wt% of sodium aluminate, 4 wt% of aluminum oxide, and 2 wt% of calcium aluminosilicate, stir the mixed powder at 3,000±100rpm of rotation speed by a stirrer for 3 min., to form blended powder; finally, add the blended powder in the dry-blending mixer B into the uniform foam solution in the special-purpose blending container A, and stir the 5 mixture at 12,000500rpm of rotation speed by a stirrer for 2min., to form blended grout; then, keep still the grout to produce foams, so as to obtain the coal ash solidified foam material for preventing spontaneous combustion of coal. Inject the prepared coal ash solidified foam fluid for preventing spontaneous combustion of coal with a 2MPa underground mobile injection pump through a conveying pipeline into the bore-holes in an underground mined-out area. The coal ash solidified foam fluid will reach to the surface of the loose coal mass and isolate the coal from oxygen, and thereby prevent spontaneous combustion of the coal.

Claims

1. A coal ash solidified foam material for preventing spontaneous combustion of coal, wherein, the coal ash solidified foam material comprising the following ingredients, in parts by weight (pbw): 40-60pbw of water, 100pbw of coal ash, 25-40pbw of compound powder for chemically self-producing gas, 3-5pbw of accelerator, 2-4pbw of activator, 1-2pbw of water reducer, and 1pbw of compound foam stabilizer; the compound powder for chemically self-producing gas is prepared at the following blending ratio, in parts by weight (pbw): 24-35pbw of semi-hydrated calcium sulfate and 1-5pbw of sodium bicarbonate, which have a chemical reaction with each other and produce an inert gas, and thereby create foams in grout; the accelerator is prepared at the following blending ratio, in pbw: 1-2pbw of alumina clinker, 1pbw of sodium carbonate, and 1-2pbw of quick lime, wherein, the alumina clinker is composed of the following ingredients, in weight percentage: 94wt% of sodium aluminate, 4wt% of aluminum oxide, and 2wt% of calcium aluminosilicate; the activator is prepared at the following blending ratio, in pbw: 0.8-1.6pbw of magnesium oxide and 1.2-2.4pbw of magnesium chloride; the water reducer is prepared at the following blending ratio, in pbw: 0.5-lpbw of calcium lignosulphonate and 0.5-lpbw of condensate of naphthalene sulfonate and formaldehyde, wherein, in the condensate of naphthalene sulfonate and formaldehyde, the content of Na 2 SO 4 is <3%; the compound foam stabilizer is prepared at the following blending ratio, in pbw: 0.2pbw of ethylene glycol butyl ether, 0.3pbw of nano-silicon, and 0.5pbw of hydroxyethyl cellulose; the solidification time can be adjusted by adjusting the weight fractions among the accelerator, activator, and water reducer.

2. A method for preparing the coal ash solidified foam material for preventing spontaneous combustion of coal according to claim 1, comprising: step 1: adding 40-60pbw of water, 24-35pbw of semi-hydrated calcium sulfate, 1-5pbw of sodium bicarbonate, 0.2pbw of ethylene glycol butyl ether, 0.3pbw of nano-silicon, and 0.5pbw of hydroxyethyl cellulose into a special-purpose blending container A, and stirring the mixed solution at 3,000+100rpm of rotation speed by a stirrer for 2min., to form a uniform foam solution; step 2: adding 100pbw of coal ash, 1-2pbw of alumina clinker, 1pbw of sodium carbonate, 1-2pbw of quick lime, 0.8-1.6pbw of magnesium oxide, 1.2-2.4pbw of magnesium chloride, 0.5-lpbw of calcium lignosulphonate, and 0.5-lpbw of condensate of naphthalene sulfonate and formaldehyde into a dry-blending mixer B, and stirring the mixed powder at 3,000+100rpm of rotation speed by a stirrer for 3min., to form blended powder; step 3: adding the blended powder prepared in the dry-blending mixer B into the uniform foam solution in the special-purpose blending container A, and stirring the mixture at 12,000+500rpm of rotation speed by a stirrer in the special-purpose blending container A for 2min., to form blended grout, keeping still the blended grout to produce foams, so as to produce the coal ash solidified foam material for preventing spontaneous combustion of coal.

3. A coal ash solidified foam material according to claim 1, wherein the inert gas is carbon dioxide gas.