CN113511904A - Light-weight mullite refractory material and preparation method thereof - Google Patents
Light-weight mullite refractory material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a light-weight mullite refractory material and a preparation scheme thereof. The technical scheme is as follows: the light-weight mullite refractory material is prepared from fly ash, three-grade alumina fine powder and alpha-Al2O3Fine powder, aluminum-zirconium composite sol, La2O3Fine powder and magnetite powder. The preparation method of the lightweight mullite refractory material comprises the following steps: firstly, blending fly ash, magnetite powder and aluminum-zirconium composite sol, and then adding three-stage raw bauxite fine powder and alpha-Al2O3Fine powder and La2O3Mixing the fine powders, ageing, shaping, drying, heating to 1000 deg.C at 4-6 deg.C/min under magnetic field, and heating to 1400 deg.C-E at 1.5-2.5 deg.C/minAnd preserving heat at 1600 ℃, cooling, cutting and grinding to obtain the lightweight mullite refractory material. The product prepared by the invention has the characteristics of high utilization rate of the fly ash, higher porosity, small average pore diameter, higher strength and low heat conductivity coefficient; can replace the traditional heavy mullite refractory material and meet the requirement of energy conservation in high-temperature industry.
Description
Technical Field
The invention belongs to the technical field of mullite refractory materials. In particular to a light-weight mullite refractory material and a preparation method thereof.
Background
Fly ash is fine ash captured by various means after coal is combusted, and is main solid waste discharged by a coal-fired power plant. In recent years, fly ash emissions from coal-fired power plants have increased year by year due to rapid developments in the power industry. If the fly ash is not treated, on one hand, the increase of suspended particles in the air can be caused, and the quality of the air is reduced; on the other hand, some toxic substances contained in the fly ash may enter rivers to pollute water sources. Therefore, it is urgent to enhance the utilization of fly ash.
At present, the fly ash is mainly used for producing fly ash cement, fly ash bricks, fly ash silicate building blocks, fly ash aerated concrete and other building materials, and can also be used as agricultural fertilizer and soil conditioner, recycled industrial raw materials and used as environmental materials. The main components of the fly ash are alumina and silica, and the fly ash can also be used as a raw material for preparing an aluminum-silicon refractory material, in particular to a raw material for preparing a mullite refractory material. The fly ash is mainly used for preparing light mullite refractory materials in the field of refractory materials.
The patent technology of the fly ash light high-temperature mullite refractory brick (CN103183517A) comprises the following raw materials in percentage by weight: 40-50% of fly ash, 25-35% of clay, 10-20% of aluminum powder, 7-8% of coal gangue, 1-2% of polystyrene and 0.5-1.5% of sawdust.
The patent technology of 'a preparation method of a low-cost porous mullite heat-insulating material' (CN103253959A) selects fly ash as a main raw material, and the porous mullite heat-insulating material obtained by the technology is subjected to pretreatment, material mixing, foaming, grouting, demoulding, drying and sintering processes has the porosity of 85-93% and the heat conductivity coefficient of 0.05-0.10W/(m.K), but the process is complex and the compressive strength of the porous mullite heat-insulating material is only 1.0-3.0 MPa.
The patent technology of 'a method for preparing mullite light refractory material by using high-alumina fly ash' (CN103964866A) uses high-alumina fly ash as a raw material, the highest using amount reaches 60%, and the mullite light refractory material is prepared by processes of vibration casting molding, maintenance, drying, sintering and the like; although the light refractory material prepared by the technology has high mullite content and thermal conductivity not more than 0.7W/(m.K), the highest compressive strength is only 35.6MPa, and the content of alumina in the fly ash is limited to be not less than 40%.
The patent technology of 'a method for preparing a mullite-phase multiphase material by using high-alumina fly ash' (CN104609842A) is disclosed, wherein the compressive strength range in the embodiment is only 3.25-43.91 MPa, and the content of alumina in the selected fly ash is 45.01 wt%.
The patent of "a high-strength light refractory material and its preparation method" (CN106365655A) is a technology which uses flyash, alumina, calcium carbonate, magnesium carbonate, sodium carbonate, titanium oxide, zirconium oxide, zinc oxide, bismuth oxide and pore-forming agent as raw materials, and the prepared light refractory material has a normal-temperature compressive strength as high as 250MPa, but has a complex phase, and the used titanium oxide, zirconium oxide and bismuth oxide are expensive, and the melting points of sodium carbonate, zinc oxide in the raw materials and vermiculite and alum in the pore-forming agent are not high, so that the high-temperature performance of the light refractory material is probably damaged.
The fly ash is used as a non-main raw material and can also be used for preparing a traditional heavy mullite refractory material, for example, a high-strength mullite refractory brick (CN109400190A) patent technology is disclosed, mullite particles, silicon dioxide powder, kaolin, the fly ash and the like are used as raw materials, and the using amount of the fly ash is converted into 3.8-9.2 wt%; the prepared mullite refractory brick has good corrosion resistance and fire resistance and high strength. However, compared with the light mullite refractory material, the heat conductivity coefficient is much higher, which is not beneficial to energy conservation of high-temperature industry.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for preparing a light-weight mullite refractory material by using a large amount of fly ash, and the prepared light-weight mullite refractory material has low heat conductivity coefficient and high strength, can replace the traditional heavy mullite refractory material and can meet the energy-saving requirement of high-temperature industry.
In order to achieve the purpose, the invention adopts the technical scheme that:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, mixing the raw materials of the lightweight mullite refractory material and the content of the raw materials, blending the fly ash, the magnetite powder and the aluminum-zirconium composite sol, and mixing for 5-15 min to prepare a mixture A. Then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3And adding the fine powder into the mixture A, and continuously mixing for 15-20 min to obtain a mixture B. And ageing the mixture B for 12-24 hours, and performing compression molding under the condition of 60-100 MPa to obtain a biscuit.
Drying the biscuit for 12-24 hours at the temperature of 100-120 ℃; under the condition that the magnetic induction intensity is 1-10 mT, firstly heating from room temperature to 1000 ℃ at the speed of 4-6 ℃/min, then heating to 1400-1600 ℃ at the speed of 1.5-2.5 ℃/min, preserving heat for 3-5 h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
Al of the fly ash2O3The content is more than 30 wt%; the particle size of the fly ash is less than 150 mu m.
Al of the three-stage raw bauxite fine powder2O3The content is more than 56 wt%; the granularity of the third-level raw alumina fine powder is less than 95 mu m.
The alpha-Al2O3The purity of the micro powder is 99.3 wt%; alpha-Al2O3The particle size of the micro powder is less than 10 μm.
In the aluminum zirconium composite sol: ZrO (ZrO)2The content is more than 5 wt%; al (Al)2O3The content is more than 10 wt%.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following positive effects:
(1) the invention can fully exert the characteristics of small specific gravity, fine granularity (less than 150 mu m range), a certain amount of hollow glass beads and the like of the fly ash, and the prepared lightweight mullite refractory material has high porosity, low heat conductivity and average pore diameter of 2-10 mu m.
(2) The fly ash is a product of high-temperature combustion of coal, has poor activity and poor binding property among fly ash particles, and is difficult to obtain high strength when being directly applied to prepare a refractory material in a large amount. According to the invention, 3-12 wt% of three-stage raw bauxite fine powder is introduced, so that the shaping of the biscuit is greatly improved, the high-density biscuit can be obtained, and a good foundation is laid for mass transfer in the subsequent sintering process. Fly ash, three-grade raw bauxite fine powder and alpha-Al2O3The micro powder has almost no magnetism, and the effect is weak even if an external magnetic field is applied; according to the invention, 0.4-1.5 wt% of magnetite powder is uniformly introduced through a premixing process, so that the interaction between a system and a magnetic field is favorably improved; under the action of Lorentz force, mass transfer in the lightweight mullite refractory material is further accelerated, and the proper heating rate is matched to be favorable for forming columnar mullite in the lightweight mullite refractory material, so that the strength of the lightweight mullite refractory material is obviously improved.
(3) The fly ash originally contains a certain amount of glass phase, the glass phase is converted into a liquid phase at high temperature, and the sintering promotion effect of the liquid phase is favorable for improving the strength of the lightweight mullite refractory material; however, excessive liquid phase can negatively impact the high temperature performance of the lightweight mullite refractory. 0.2-1 wt% of La is introduced into the catalyst2O3Fine powder of La in a high temperature sintering process3+By melting into a high-temperature liquid phase, reducing the liquid phase without affecting the sintering promoting effect of the liquid phaseViscosity, thereby ensuring that the lightweight mullite refractory material has good high temperature resistance.
(4) The using amount of the fly ash is 60-72 wt% of the raw material, the pressure of the fly ash on the ecological environment can be greatly reduced, the performance of the prepared light-weight mullite refractory material is excellent, the traditional heavy mullite refractory material can be completely replaced, the requirement of high-temperature industrial energy conservation is met, and the additional value of the fly ash is greatly improved.
The light-weight mullite refractory material prepared by the invention is detected as follows: the bulk density is 1.71-2.09 g/cm3(ii) a The apparent porosity is 27.6 to 41.5%; the average pore diameter is within 2-9 μm; the normal-temperature compressive strength is 101.3-178.5 MPa; the thermal conductivity at 1000 ℃ is 0.450 to 0.732 (W/(m.k)).
Therefore, the light-weight mullite refractory material prepared by the invention has the characteristics of high utilization rate of the fly ash, higher porosity, small average pore diameter, higher strength and low heat conductivity coefficient; can replace the traditional heavy mullite refractory material and meet the requirement of energy conservation in high-temperature industry.
Detailed Description
The invention is further described with reference to specific embodiments, without limiting its scope.
A lightweight mullite refractory material and a preparation method thereof. The preparation method of the embodiment comprises the following steps:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, mixing the raw materials of the lightweight mullite refractory material and the content of the raw materials, blending the fly ash, the magnetite powder and the aluminum-zirconium composite sol, and mixing for 5-15 min to prepare a mixture A. Then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3And adding the fine powder into the mixture A, and continuously mixing for 15-20 min to obtain a mixture B. And ageing the mixture B for 12-24 hours, and performing compression molding under the condition of 60-100 MPa to obtain a biscuit.
Drying the biscuit for 12-24 hours at the temperature of 100-120 ℃; under the condition that the magnetic induction intensity is 1-10 mT, firstly heating from room temperature to 1000 ℃ at the speed of 4-6 ℃/min, then heating to 1400-1600 ℃ at the speed of 1.5-2.5 ℃/min, preserving heat for 3-5 h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
In this embodiment:
al of the fly ash2O3The content is more than 30 wt%; the granularity of the fly ash is less than 150 mu m;
al of the three-stage raw bauxite fine powder2O3The content is more than 56 wt%; the granularity of the third-level raw bauxite fine powder is less than 95 mu m;
the alpha-Al2O3The purity of the micro powder is 99.3 wt%; alpha-Al2O3The granularity of the micro powder is less than 10 mu m;
in the aluminum zirconium composite sol: ZrO (ZrO)2The content is more than 5 wt%; al (Al)2O3The content is more than 10 wt%.
The detailed description is omitted in the embodiments.
Example 1
A lightweight mullite refractory material and a preparation method thereof. The preparation method in this example is:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, the raw materials and the content of the lightweight mullite refractory material are proportioned, and the fly ash, the magnetite powder and the aluminum-zirconium composite sol are blended and mixed for 5min to prepare a mixture A. Then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3Adding the fine powder into the mixture A, and continuously mixing for 15min to obtain a mixture B. And ageing the mixture B for 12 hours, and performing compression molding under the condition of 70MPa to obtain a biscuit.
Drying the biscuit at 100 ℃ for 12 hours; under the condition that the magnetic induction intensity is 1mT, firstly heating from room temperature to 1000 ℃ at the speed of 4 ℃/min, then heating to 1400 ℃ at the speed of 1.5 ℃/min, preserving the heat for 3h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
The lightweight mullite refractory prepared in the embodiment is detected as follows: the bulk density is 1.75g/cm3(ii) a The apparent porosity is 40.1%; the average pore diameter is 4.45 mu m; the normal temperature compressive strength is 121.7 MPa; the thermal conductivity at 1000 ℃ was 0.569 (W/(m.k)).
Example 2
A lightweight mullite refractory material and a preparation method thereof. The preparation method in this example is:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, the raw materials and the content of the lightweight mullite refractory material are proportioned, and the fly ash, the magnetite powder and the aluminum-zirconium composite sol are blended and mixed for 8min to prepare a mixture A. Then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3Adding fine powder into the mixture A, andmixing for 16min to obtain mixture B. And ageing the mixture B for 15 hours, and performing compression molding under the condition of 80MPa to obtain a biscuit.
Drying the biscuit at 110 ℃ for 15 h; under the condition that the magnetic induction intensity is 5mT, firstly heating from room temperature to 1000 ℃ at the speed of 5 ℃/min, then heating to 1500 ℃ at the speed of 2 ℃/min, preserving heat for 4h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
The lightweight mullite refractory prepared in the embodiment is detected as follows: the bulk density is 1.87g/cm3(ii) a The apparent porosity is 38.4%; the average pore diameter is 4.49 mu m; the normal temperature compressive strength is 156.5 MPa; the thermal conductivity at 1000 ℃ was 0.618 (W/(m.k)).
Example 3
A lightweight mullite refractory material and a preparation method thereof. The preparation method in this example is:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, the raw materials and the content of the lightweight mullite refractory material are proportioned, and the fly ash, the magnetite powder and the aluminum-zirconium composite sol are blended and mixed for 10min to prepare a mixture A. Then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3Adding the fine powder into the mixture A, and continuously mixing for 18min to obtain a mixture B. And ageing the mixture B for 19 hours, and performing compression molding under the condition of 100MPa to obtain a biscuit.
Drying the biscuit at 120 ℃ for 18 h; under the condition that the magnetic induction intensity is 10mT, firstly heating from room temperature to 1000 ℃ at the speed of 6 ℃/min, then heating to 1600 ℃ at the speed of 2.5 ℃/min, preserving the temperature for 5h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
The lightweight mullite refractory prepared in the embodiment is detected as follows: the bulk density is 2.09g/cm3(ii) a The apparent porosity is 27.6%; the average pore diameter is 8.24 mu m; the normal temperature compressive strength is 178.5 MPa; the thermal conductivity at 1000 ℃ was 0.732 (W/(m.k)).
Example 4
A lightweight mullite refractory material and a preparation method thereof. The preparation method in this example is:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, the raw materials and the content of the lightweight mullite refractory material are proportioned, and the fly ash, the magnetite powder and the aluminum-zirconium composite sol are blended and mixed for 13min to prepare a mixture A. Then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3Adding the fine powder into the mixture A, and continuously mixing for 19min to obtain a mixture B. And ageing the mixture B for 22 hours, and performing compression molding under the condition of 90MPa to obtain a biscuit.
Drying the biscuit at 110 ℃ for 21 h; under the condition that the magnetic induction intensity is 8mT, firstly heating from room temperature to 1000 ℃ at the speed of 5 ℃/min, then heating to 1500 ℃ at the speed of 2 ℃/min, preserving heat for 4h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
The lightweight mullite refractory prepared in the embodiment is detected as follows: the bulk density is 1.82g/cm3(ii) a The apparent porosity is 35.5%; the average pore diameter is 5.41 mu m; the normal temperature compressive strength is 136.4 MPa; the thermal conductivity at 1000 ℃ was 0.676 (W/(m.k)).
Example 5
A lightweight mullite refractory material and a preparation method thereof. The preparation method in this example is:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, the raw materials and the content of the lightweight mullite refractory material are proportioned, and the fly ash, the magnetite powder and the aluminum-zirconium composite sol are blended and mixed for 15min to prepare a mixture A. Then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3Adding the fine powder into the mixture A, and continuously mixing for 20min to obtain a mixture B. And ageing the mixture B for 24 hours, and performing compression molding under the condition of 60MPa to obtain a biscuit.
Drying the biscuit at 100 ℃ for 24 hours; under the condition that the magnetic induction intensity is 3mT, firstly heating from room temperature to 1000 ℃ at the speed of 4 ℃/min, then heating to 1400 ℃ at the speed of 1.5 ℃/min, preserving the heat for 3h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
The lightweight mullite refractory prepared in the embodiment is detected as follows: the bulk density is 1.71g/cm3(ii) a Apparent porosity was 41.5%; the average pore diameter is 2.04 mu m; the normal temperature compressive strength is 101.3 MPa; the thermal conductivity at 1000 ℃ was 0.450 (W/(m.k)).
Compared with the prior art, the specific implementation mode has the following positive effects:
(1) the specific embodiment can fully utilize the characteristics of small specific gravity, fine particle size (less than 150 mu m range), certain amount of hollow glass beads and the like of the fly ash, and the prepared lightweight mullite refractory material has high porosity, low heat conductivity and average pore diameter of 2-10 mu m.
(2) The fly ash is a product of high-temperature combustion of coal, has poor activity and poor binding property among fly ash particles, and is directly applied to a large amount of fly ashIt is difficult to obtain high strength in the production of refractory materials. According to the embodiment, 3-12 wt% of three-stage raw bauxite fine powder is introduced, so that the shaping of the biscuit is greatly improved, the high-density biscuit can be obtained, and a good foundation is laid for mass transfer in the subsequent sintering process. Fly ash, three-grade raw bauxite fine powder and alpha-Al2O3The micro powder has almost no magnetism, and the effect is weak even if an external magnetic field is applied; according to the embodiment, 0.4-1.5 wt of magnetite powder is uniformly introduced through a premixing process, so that the interaction between a system and a magnetic field is favorably improved; under the action of Lorentz force, mass transfer in the lightweight mullite refractory material is further accelerated, and the proper heating rate is matched to be favorable for forming columnar mullite in the lightweight mullite refractory material, so that the strength of the lightweight mullite refractory material is obviously improved.
(3) The fly ash originally contains a certain amount of glass phase, the glass phase is converted into a liquid phase at high temperature, and the sintering promotion effect of the liquid phase is favorable for improving the strength of the lightweight mullite refractory material; however, excessive liquid phase can negatively impact the high temperature performance of the lightweight mullite refractory. The specific embodiment introduces 0.2-1 wt of La2O3Fine powder of La in a high temperature sintering process3+The high-temperature liquid phase is blended, the viscosity of the liquid phase is reduced while the sintering promotion effect of the liquid phase is not influenced, and therefore the light-weight mullite refractory material is ensured to have good high-temperature resistance.
(4) The using amount of the fly ash in the embodiment is 60-72 wt% of the raw material, so that the pressure of the fly ash on the ecological environment can be greatly reduced, the performance of the prepared light-weight mullite refractory material is excellent, the traditional heavy mullite refractory material can be completely replaced, the energy-saving requirement of the high-temperature industry is met, and the additional value of the fly ash is greatly improved.
The detection results of the lightweight mullite refractory material prepared by the embodiment are as follows: the bulk density is 1.71-2.09 g/cm3(ii) a The apparent porosity is 27.6 to 41.5%; the average pore diameter is within 2-9 μm; the normal-temperature compressive strength is 101.3-178.5 MPa; the thermal conductivity at 1000 ℃ is 0.450 to 0.732 (W/(m.k)).
Therefore, the lightweight mullite refractory material prepared by the embodiment has the characteristics of high utilization rate of the fly ash, higher porosity, small average pore diameter, higher strength and low heat conductivity coefficient; can replace the traditional heavy mullite refractory material and meet the requirement of energy conservation in high-temperature industry.
Claims (6)
1. A preparation method of a light-weight mullite refractory material is characterized by comprising the following steps:
(1) the light-weight mullite refractory material comprises the following raw materials in percentage by weight:
(2) the preparation method of the lightweight mullite refractory material comprises the following steps:
firstly, mixing the raw materials of the lightweight mullite refractory material and the content of the raw materials, blending the fly ash, the magnetite powder and the aluminum-zirconium composite sol, and mixing for 5-15 min to prepare a mixture A; then the three-grade raw bauxite fine powder and the alpha-Al are mixed2O3Fine powder and the La2O3Adding the fine powder into the mixture A, and continuously mixing for 15-20 min to obtain a mixture B; ageing the mixture B for 12-24 hours, and performing compression molding under the condition of 60-100 MPa to obtain a biscuit;
drying the biscuit for 12-24 hours at the temperature of 100-120 ℃; under the condition that the magnetic induction intensity is 1-10 mT, firstly heating from room temperature to 1000 ℃ at the speed of 4-6 ℃/min, then heating to 1400-1600 ℃ at the speed of 1.5-2.5 ℃/min, preserving heat for 3-5 h, naturally cooling, and cutting and grinding to obtain the light-weight mullite refractory material.
2. The method of claim 1, wherein the Al of the fly ash is2O3The content is more than 30 wt%; the particle size of the fly ash is less than 150 mu m.
3. The method of claim 1, wherein the fine, tertiary raw alumina powder is Al2O3The content is more than 56 wt%; the granularity of the third-level raw alumina fine powder is less than 95 mu m.
4. The method of claim 1, wherein the α -Al is selected from the group consisting of2O3The purity of the micro powder is 99.3 wt%; alpha-Al2O3The particle size of the micro powder is less than 10 μm.
5. The method of claim 1, wherein the aluminum zirconium composite sol comprises: ZrO (ZrO)2The content is more than 5 wt%; al (Al)2O3The content is more than 10 wt%.
6. A lightweight mullite refractory, characterized by: the lightweight mullite refractory material is prepared by the preparation method of the lightweight mullite refractory material according to the claim 1-5.
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