Low-density porous refractory material and preparation method thereof

Abstract

The invention discloses a low-density porous refractory material and a preparation method thereof, and belongs to the field of refractory materials, the refractory material comprises the following main chemical components: 70wt%-80wt% of Al2O3 and 20wt%-30wt% of SiO2, and the content of other impurities is less than 1wt%; main crystal phases after sintering are mullite phases and corundum phases; the volume density is 200 to 400kg / m; the preparation method comprises the following steps: taking aluminum oxide powder, silicon dioxide powder, silica sol and polycrystalline mullite fiber as main raw materials, taking ammonium polyacrylate as a dispersing agent, taking AOS, SDBS and the like as foaming agents, taking stearic acid, xanthan gum and the like as foam stabilizers, taking starch as a coagulating agent, and taking walnut powder, polystyrene particles and the like as pore-foaming agents; the low-density porous refractory material is prepared through the steps of burdening, stirring and foaming, adding of a pore-foaming agent, injection molding and solidification forming, drying and high-temperature sintering. The prepared refractory material is low in density and porous on the premise of meeting the use requirements.

Description

Technical Field

[0001] The invention relates to the field of refractory materials, in particular to a low-density porous refractory material and a preparation method thereof. Background Art

[0002] With the development of science and technology, high-energy consumption industries are expanding rapidly, and high-temperature thermal equipment is constantly emerging. As the operating temperature of thermal equipment increases, the requirements for the refractory insulation of the lining refractory materials of thermal equipment are also higher. Traditional kilns use heavy refractory materials. Although the refractoriness can meet the requirements, they also have problems such as large heat capacity, low heating rate, high energy consumption, and poor insulation. The use of fiber-type insulation refractory materials has problems such as low strength, short service life, and high price.

[0003] Traditional porous thermal insulation refractory materials are prepared by the burnout addition method, that is, wood chips, polymers, carbon particles and other completely combustible materials are added during the material preparation process. After high-temperature sintering, less ash remains and pores are formed in situ. However, the density of thermal insulation refractory materials prepared by this method is generally 1200kg / m 3 above.

[0004] The foaming method can be used to prepare thermal insulation refractory materials with relatively low density. The density of thermal insulation refractory materials prepared by the foaming method is 400-600kg / m 3 If the density is lower, defoaming and mold collapse will occur due to excessively high porosity and reduced bubble support, making it impossible to produce insulating refractory materials with lower density and better thermal insulation performance. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a low-density porous refractory material and a preparation method thereof, which combines the stirring foaming method with the burnout method to further reduce the density of the insulating refractory material, increase the porosity of the material, and prepare a porous refractory material with a lower density. The density of the material is 200-400kg / m 3 , and at the same time has better high temperature thermal insulation performance and excellent mechanical properties.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A low-density porous refractory material comprises the following raw materials in weight percentage: 10wt%-15wt% water, 20wt%-30wt% silica sol, 25wt%-35wt% alumina powder, 5wt%-10wt% silica powder, 8wt%-14wt% polycrystalline mullite fiber, 0.3wt%-0.5wt% dispersant, 1wt%-2wt% foaming agent, 0.4wt%-1wt% foam stabilizer, 2wt%-6wt% coagulant and 15wt%-20wt% pore-forming agent.

[0008] The further improvement of the technical solution of the present invention lies in that: the solid content of the silica sol is 30wt%; the particle size of the alumina powder is 2-15μm; the particle size of the silicon dioxide powder is 2-15μm; the length of the polycrystalline mullite fiber is 3-5mm; the dispersant is ammonium polyacrylate; the foaming agent is any one of AOS, SDBS and SDS; the foam stabilizer is any one of PEG, stearic acid, xanthan gum and carrageenan; the coagulant is starch; the pore-forming agent is any one of walnut shell powder, polystyrene particles and sawdust; and the particle size of the pore-forming agent is 0.3mm-0.4mm.

[0009] The further improvement of the technical solution of the present invention is that: the particle size of the aluminum oxide powder is 7-8 μm; the particle size of the silicon dioxide powder is 7-8 μm; the foaming agent is SDBS; the foam stabilizer is xanthan gum; and the pore-forming agent is walnut shell powder.

[0010] A method for preparing a low-density porous refractory material comprises the following steps:

[0011] Step 1, mixing water, silica sol, dispersant, alumina powder and silica powder to form a slurry; adding a foam stabilizer and a foaming agent to the slurry and stirring to foam; after foaming, adding a porogen to the slurry and stirring to form a slurry; then adding polycrystalline mullite fiber and starch and stirring to form a slurry;

[0012] Step 2, pouring the slurry stirred in step 1 into a mold to solidify and shape, demolding after leaving it at room temperature for a period of time, and then drying it under heating conditions, the temperature gradually increases as the moisture in the green body decreases until the green body is completely dry;

[0013] Step 3, placing the completely dried green body in a high temperature furnace for sintering;

[0014] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0015] The further improvement of the technical solution of the present invention is that: in step 2, the room temperature placement time is 24-48 hours; the heating temperature is 30-100° C., and the drying time is 5-7 days.

[0016] A further improvement of the technical solution of the present invention is that in step 3, the sintering temperature is 1400° C.-1500° C.; and the heat preservation time is 6-10 hours.

[0017] The further improvement of the technical solution of the present invention is that the low-density porous refractory material prepared in step 4 has a chemical composition mainly composed of 70wt%-80wt% Al2O3 and 20wt%-30wt% SiO2, and the content of other impurities is less than 1wt%; the crystalline phase after sintering is mainly mullite phase and corundum phase; the volume density is 200-400kg / m 3 .

[0018] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0019] The innovation of the present invention lies in that the density of the insulating refractory material is further reduced and the porosity of the material is increased by combining the stirring foaming method with the burnout method, thereby preparing a porous refractory material with a lower density. The material has a higher porosity and a volume density of only 200-400kg / m 3 At the same time, the main crystal phases of the material are mullite phase and corundum phase. It has better high-temperature thermal insulation performance and excellent mechanical properties, providing a low-density porous refractory material for high-temperature kiln linings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative labor.

[0021] Figure 1 This is a microstructure diagram of a low-density porous refractory material prepared by a method for preparing a low-density porous refractory material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0023] The present invention is further described in detail below with reference to the accompanying drawings and embodiments:

[0024] A low-density porous refractory material is prepared from the following raw materials in parts by weight: 10wt%-15wt% water, 20wt%-30wt% silica sol, 25wt%-35wt% alumina powder, 5wt%-10wt% silicon dioxide powder, 8wt%-14wt% polycrystalline mullite fiber, 0.3wt%-0.5wt% dispersant, 1wt%-2wt% foaming agent, 0.4wt%-1wt% foam stabilizer, 2wt%-6wt% coagulant, and 15wt%-20wt% porogen.

[0025] The solid content of silica sol is 30wt%;

[0026] The particle size of the alumina powder is 2-15 μm, preferably 7-8 μm;

[0027] The particle size of the silicon dioxide powder is 2-15 μm, preferably 7-8 μm;

[0028] The length of polycrystalline mullite fiber is 3-5mm;

[0029] The dispersant is ammonium polyacrylate;

[0030] The foaming agent is any one of AOS, SDBS and SDS, preferably SDBS;

[0031] Among them, the full name of AOS is: Sodium Alpha-olefin Sulfonate, and its Chinese name is: Sodium α-olefin sulfonate; the full name of SDBS is: Sodium Dodecylbenzene Sulfonate, and its Chinese name is: Sodium Dodecylbenzene Sulfonate; the full name of SDS is: Sodium Dodecyl Sulfate, and its Chinese name is: Sodium Dodecyl Sulfate;

[0032] The foam stabilizer is any one of PEG, stearic acid, xanthan gum and carrageenan, preferably xanthan gum;

[0033] Among them, the full English name of PEG is: Polyethylene Glycol, and the Chinese name is: Polyethylene Glycol;

[0034] The coagulant is starch;

[0035] The porogen is any one of walnut shell powder, polystyrene particles and sawdust, etc., with a particle size of 0.3mm-0.4mm, and is preferably walnut shell powder.

[0036] A method for preparing a low-density porous refractory material comprises the following steps:

[0037] Step 1, according to the weight ratio, using a disperser to stir, first, under the condition of slow stirring, add 20wt%-30wt% of silica sol and 0.3wt%-0.5wt% of ammonium polyacrylate dispersant to 10wt%-15wt% of water and stir evenly to prepare a mixed solution; then take 5wt%-10wt% of silicon dioxide powder and 25wt%-35wt% of aluminum oxide powder and add them to the above mixed solution while stirring to form a slurry with uniform dispersion and good suspension; then increase the speed of the disperser to fast stirring, take 0.4wt%-1wt% of the foam stabilizer and slowly sprinkle it into the above slurry in batches; take 1wt%-2wt% of the foaming agent and add it to the above slurry and stir and foam to a preset volume; after the slurry reaches the preset volume, add 15wt%-20wt% of the porogen and stir evenly; finally, add 8wt%-14wt% of polycrystalline mullite fiber and 2wt%-6wt% of starch and stir for 20 minutes;

[0038] Step 2, pour the stirred slurry into a mold to solidify and form, place it at room temperature for 24-48 hours, then demould it, and then dry it at 30-100°C for 5-7 days, and the temperature is gradually increased as the moisture in the green body decreases until the green body is completely dry;

[0039] Step 3, placing the completely dried green body in a high temperature furnace for sintering at a sintering temperature of 1400°C-1500°C for a holding time of 6-10 hours;

[0040] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0041] like Figure 1 As shown in the figure, the microstructure of the prepared low-density porous refractory material is mainly composed of 70wt%-80wt% Al2O3 and 20wt%-30wt% SiO2, and the content of other impurities is less than 1wt%; the main crystal phases after sintering are mullite phase and corundum phase; the volume density is 200-400kg / m 3 .

[0042] Example 1

[0043] A low-density porous refractory material comprises the following raw materials in weight percentage: 10wt% water; 25wt% silica sol; 30wt% alumina powder, median particle size D50=8μm; 7wt% silica powder, median particle size D50=8μm; 8wt% polycrystalline mullite fiber, fiber length is 3-5mm; 0.5wt% ammonium polyacrylate dispersant; 2wt% SDBS foaming agent; 0.5wt% xanthan gum foam stabilizer; 2wt% starch coagulant; 15wt% walnut shell powder pore-forming agent, particle size is 0.3mm-0.4mm. The preparation method comprises the following steps:

[0044] Step 1, according to the weight ratio, using a disperser to stir, first, under the condition of slow stirring, add 25wt% of silica sol and 0.5wt% of ammonium polyacrylate dispersant to 10wt% of water and stir evenly to prepare a mixed solution; then take 7wt% of silicon dioxide powder and 30wt% of aluminum oxide powder and add them to the mixed solution while stirring to form a slurry with uniform dispersion and good suspension; then increase the speed of the disperser to rapid stirring, take 0.5wt% of xanthan gum foam stabilizer and slowly sprinkle it into the slurry in batches; take 2wt% of SDBS foaming agent and add it to the slurry and stir and foam to a preset volume; after the slurry reaches the preset volume, add 15wt% of walnut shell powder and stir evenly; finally, add 8wt% of polycrystalline mullite fiber and 2wt% of starch and stir for 20 minutes.

[0045] Step 2: pour the stirred slurry into a mold to solidify and form, place it at room temperature for 48 hours, and then demould it. Then dry it at 30°C for 7 days, and then increase the temperature to 100°C and dry it until the green body is completely dry.

[0046] Step 3, place the completely dried green body in a high-temperature furnace for sintering. When the temperature is increased from room temperature to 500°C, the heating rate is 2°C / min, and it is kept at 500°C for 3 hours; when the temperature is increased from 500°C to 1500°C, the heating rate is 3°C / min, the sintering temperature is 1500°C, and it is kept at this temperature for 6 hours.

[0047] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0048] The main crystal phases of the prepared low-density porous refractory material are mullite phase and corundum phase, the porosity is 88wt%, and the volume density is 350kg / m 3 , thermal conductivity is 0.32w / m*k, maximum operating temperature is 1600℃, compressive strength is 3.6MPa, and flexural strength is 1.8MPa.

[0049] Example 2

[0050] A low-density porous refractory material comprises the following raw materials in weight percentage: 15wt% water; 20wt% silica sol; 25wt% alumina powder, D50=8μm; 10wt% silica powder, D50=8μm; 10wt% polycrystalline mullite fiber, fiber length is 3-5mm; 0.5wt% ammonium polyacrylate dispersant; 2wt% SDBS foaming agent; 0.5wt% xanthan gum foam stabilizer; 2wt% starch coagulant; 15wt% walnut shell powder pore-forming agent, particle size is 0.3mm-0.4mm. The preparation method comprises the following steps:

[0051] Step 1, according to the weight ratio, using a disperser to stir, first, under the condition of slow stirring, add 20wt% of silica sol and 0.5wt% of ammonium polyacrylate dispersant to 15wt% of water and stir evenly to prepare a mixed solution; then take 10wt% of silicon dioxide powder and 25wt% of aluminum oxide powder and add them to the above mixed solution while stirring to form a slurry with uniform dispersion and good suspension; then increase the speed of the disperser to fast stirring, take 0.5wt% of xanthan gum foam stabilizer and slowly sprinkle it into the above slurry in batches; take 2wt% of SDBS foaming agent and add it to the above slurry and stir and foam to a preset volume; after the slurry reaches the preset volume, add 15wt% of porogen walnut shell powder and stir evenly; finally, add 10wt% of polycrystalline mullite fiber and 2wt% of coagulant starch and stir for 20 minutes.

[0052] Step 2: pour the stirred slurry into a mold to solidify and form, place it at room temperature for 48 hours, and then demould it. Then dry it at 30°C for 7 days, and then increase the temperature to 100°C and dry it until the green body is completely dry.

[0053] Step 3, place the completely dried green body in a high-temperature furnace for sintering. When heating from room temperature to 500°C, the heating rate is 2°C / min, and it is kept at 500°C for 3 hours; when heating from 500°C to 1500°C, the heating rate is 3°C / min, the sintering temperature is 1500°C, and it is kept at this temperature for 6 hours.

[0054] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0055] The main crystal phases of the prepared low-density porous refractory material are mullite phase and corundum phase, the porosity is 92wt%, and the volume density is 300kg / m 3 , thermal conductivity is 0.3w / m*k, maximum operating temperature is 1600℃, compressive strength is 3.2MPa, and flexural strength is 1.2MPa.

[0056] Example 3

[0057] A low-density porous refractory material comprises the following raw materials in weight percentage: 13wt% water; 27wt% silica sol; 25wt% alumina powder, D50=8μm; 5wt% silica powder, D50=8μm; 8wt% polycrystalline mullite fiber, fiber length is 3-5mm; 0.5wt% ammonium polyacrylate dispersant; 2wt% SDBS foaming agent; 1wt% xanthan gum foam stabilizer; 3.5wt% starch coagulant; 15wt% walnut shell powder pore-forming agent, particle size is 0.3mm-0.4mm. The preparation method comprises the following steps:

[0058] Step 1, according to the weight ratio, using a disperser to stir, first, under the condition of slow stirring, add 27wt% of silica sol and 0.5wt% of ammonium polyacrylate dispersant to 13wt% of water and stir evenly to prepare a mixed solution; then take 5wt% of silicon dioxide powder and 25wt% of aluminum oxide powder and add them to the mixed solution while stirring to form a slurry with uniform dispersion and good suspension; then increase the speed of the disperser to fast stirring, take 1wt% of xanthan gum foam stabilizer and slowly sprinkle it into the slurry in batches; take 2wt% of SDBS foaming agent and add it to the slurry and stir and foam to a preset volume; after the slurry reaches the preset volume, add 15wt% of porogen walnut shell powder and stir evenly; finally, add 8wt% of polycrystalline mullite fiber and 3.5wt% of coagulant starch and stir for 20 minutes.

[0059] Step 2: pour the stirred slurry into a mold to solidify and form, place it at room temperature for 48 hours, and then demould it. Then dry it at 30°C for 7 days, and then increase the temperature to 100°C and dry it until the green body is completely dry.

[0060] Step 3, place the completely dried green body in a high-temperature furnace for sintering. When heating from room temperature to 500°C, the heating rate is 2°C / min, and it is kept at 500°C for 3 hours; when heating from 500°C to 1500°C, the heating rate is 3°C / min, the sintering temperature is 1500°C, and it is kept at this temperature for 6 hours.

[0061] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0062] The main crystal phases of the prepared low-density porous refractory material are mullite phase and corundum phase, with a porosity of 90wt% and a volume density of 330kg / m 3 , thermal conductivity 0.31w / m*k, maximum operating temperature 1600℃, compressive strength 3.4MPa, flexural strength 1.6MPa.

[0063] Example 4

[0064] A low-density porous refractory material comprises the following raw materials in weight percentage: 11wt% water; 30wt% silica sol; 20wt% alumina powder, D50=8μm; 5wt% silica powder, D50=8μm; 9wt% polycrystalline mullite fiber, fiber length is 3-5mm; 0.4wt% ammonium polyacrylate dispersant; 1wt% SDBS foaming agent; 0.6wt% xanthan gum foam stabilizer; 3wt% starch coagulant; 20wt% walnut shell powder pore-forming agent, particle size is 0.3mm-0.4mm. The preparation method comprises the following steps:

[0065] Step 1, according to the weight ratio, using a disperser to stir, first, under the condition of slow stirring, add 30wt% of silica sol and 0.4wt% of ammonium polyacrylate dispersant to 11wt% of water and stir evenly to prepare a mixed solution; then take 5wt% of silicon dioxide powder and 20wt% of aluminum oxide powder and add them to the above mixed solution while stirring to form a slurry with uniform dispersion and good suspension; then increase the speed of the disperser to fast stirring, take 0.6wt% of xanthan gum foam stabilizer and slowly sprinkle it into the above slurry in batches; take 1wt% of SDBS foaming agent and add it to the above slurry and stir and foam to a preset volume; after the slurry reaches the preset volume, add 20wt% of walnut shell powder and stir evenly; finally, add 9wt% of polycrystalline mullite fiber and 3wt% of starch and stir for 20 minutes.

[0066] Step 2: pour the stirred slurry into a mold to solidify and form, place it at room temperature for 48 hours, and then demould it. Then dry it at 30°C for 7 days, and then increase the temperature to 100°C and dry it until the green body is completely dry.

[0067] Step 3, place the completely dried green body in a high-temperature furnace for sintering. When heating from room temperature to 500°C, the heating rate is 2°C / min, and it is kept at 500°C for 3 hours; when heating from 500°C to 1500°C, the heating rate is 3°C / min, the sintering temperature is 1500°C, and it is kept at this temperature for 6 hours.

[0068] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0069] The main crystal phases of the prepared low-density porous refractory material are mullite phase and corundum phase, with a porosity of 92wt% and a volume density of 300kg / m 3 , thermal conductivity 0.31w / m*k, maximum operating temperature 1600℃, compressive strength 3MPa, flexural strength 1.1MPa.

[0070] Example 5

[0071] A low-density porous refractory material comprises the following raw materials in weight percentage: 10wt% water; 20wt% silica sol; 35wt% alumina powder, D50=8μm; 6wt% silica powder, D50=8μm; 8wt% polycrystalline mullite fiber, fiber length is 3-5mm; 0.5wt% ammonium polyacrylate dispersant; 1wt% SDBS foaming agent; 0.5wt% xanthan gum foam stabilizer; 2wt% starch coagulant; 17wt% walnut shell powder pore-forming agent, particle size is 0.3mm-0.4mm. The preparation method comprises the following steps:

[0072] Step 1, according to the weight ratio, using a disperser to stir, first, under the condition of slow stirring, add 20wt% of silica sol and 0.5wt% of ammonium polyacrylate dispersant to 10wt% of water and stir evenly to prepare a mixed solution; then take 6wt% of silicon dioxide powder and 35wt% of aluminum oxide powder and add them to the above mixed solution while stirring to form a slurry with uniform dispersion and good suspension; then increase the speed of the disperser to fast stirring, take 0.5wt% of xanthan gum foam stabilizer and slowly sprinkle it into the above slurry in batches; take 1wt% of SDBS foaming agent and add it to the above slurry and stir and foam to a preset volume; after the slurry reaches the preset volume, add 17wt% of walnut shell powder and stir evenly; finally, add 8wt% of polycrystalline mullite fiber and 2wt% of starch and stir for 20 minutes.

[0073] Step 2: pour the stirred slurry into a mold to solidify and form, place it at room temperature for 48 hours, and then demould it. Then dry it at 30°C for 7 days, and then increase the temperature to 100°C and dry it until the green body is completely dry.

[0074] Step 3, place the completely dried green body in a high-temperature furnace for sintering. When heating from room temperature to 500°C, the heating rate is 2°C / min, and it is kept at 500°C for 3 hours; when heating from 500°C to 1500°C, the heating rate is 3°C / min, the sintering temperature is 1500°C, and it is kept at this temperature for 6 hours.

[0075] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0076] The main crystal phases of the prepared low-density porous refractory material are mullite phase and corundum phase, with a porosity of 83wt% and a volume density of 400kg / m 3 , thermal conductivity 0.36w / m*k, maximum operating temperature 1600℃, compressive strength 3.9MPa, flexural strength 2MPa.

[0077] Example 6

[0078] A low-density porous refractory material comprises the following raw materials in weight percentage: 10wt% water; 23wt% silica sol; 25wt% alumina powder, D50=8μm; 5wt% silica powder, D50=8μm; 14wt% polycrystalline mullite fiber, fiber length is 3-5mm; 0.3wt% ammonium polyacrylate dispersant; 1.3wt% SDBS foaming agent; 0.4wt% xanthan gum foam stabilizer; 6wt% starch coagulant; 15wt% walnut shell powder pore-forming agent, particle size is 0.3mm-0.4mm. The preparation method comprises the following steps:

[0079] Step 1, according to the weight ratio, using a disperser to stir, first, under the condition of slow stirring, add 23wt% of silica sol and 0.3wt% of ammonium polyacrylate dispersant to 10wt% of water and stir evenly to prepare a mixed solution; then take 5wt% of silicon dioxide powder and 25wt% of aluminum oxide powder and add them to the above mixed solution while stirring to form a slurry with uniform dispersion and good suspension; then increase the speed of the disperser to fast stirring, take 0.4wt% of xanthan gum foam stabilizer and slowly sprinkle it into the above slurry in batches; take 1.3wt% of SDBS foaming agent and add it to the above slurry and stir and foam to a preset volume; after the slurry reaches the preset volume, add 15wt% of walnut shell powder and stir evenly; finally, add 14wt% of polycrystalline mullite fiber and 6wt% of starch and stir for 20 minutes.

[0080] Step 2: pour the stirred slurry into a mold to solidify and form, place it at room temperature for 48 hours, and then demould it. Then dry it at 30°C for 7 days, and then increase the temperature to 100°C and dry it until the green body is completely dry.

[0081] Step 3, place the completely dried green body in a high-temperature furnace for sintering. When heating from room temperature to 500°C, the heating rate is 2°C / min, and it is kept at 500°C for 3 hours; when heating from 500°C to 1500°C, the heating rate is 3°C / min, the sintering temperature is 1500°C, and it is kept at this temperature for 6 hours.

[0082] Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

[0083] The main crystal phases of the prepared low-density porous refractory material are mullite phase and corundum phase, with a porosity of 85wt% and a volume density of 380kg / m 3 , thermal conductivity 0.35w / m*k, maximum operating temperature 1600℃, compressive strength 3.7MPa, flexural strength 1.9MPa.

[0084] In addition, the upper and lower limits and interval values ​​of the process parameters (such as weight percentage, time, temperature, etc.) of the present invention can all achieve the present invention, and the embodiments are not listed one by one here.

[0085] Comparative Example 1:

[0086] When the stirring and foaming method is used alone to prepare porous refractory materials, a slurry is first prepared, and then a foaming agent and a foam stabilizer are added under stirring conditions, bubbles are introduced into the slurry by stirring, and finally a coagulant is added and the slurry is solidified by injection molding (the difference between the present invention and this method is that on the basis of stirring and foaming, a large amount of combustible particles are introduced into the slurry. With high-temperature sintering, the combustible particles burn, leaving pores, which can further reduce the density of the green body).

[0087] The porous refractory material prepared by the stirring and foaming method alone has a porosity of 60-75wt% and a bulk density of 500-600kg / m 3 , thermal conductivity is 0.43w / m*k, compressive strength is 4.3MPa, flexural strength is 2.2MPa, when the foaming volume density is lower than 400kg / m 3 Finally, defoaming and mold collapse occur after injection molding, and the pores are too large, which has a great impact on product quality.

[0088] Comparative Example 2:

[0089] The porous refractory material is prepared by the burnout method alone. This method is to mix the combustible particles with ceramic powder, dry press or add water to form a mud blank, and then sinter the combustible particles at high temperature to burn and leave holes. The volume density of the refractory material prepared by this method is 1000kg / m 3 Above, the porosity is 30%-50%, which is not conducive to kiln energy saving.

[0090] The performance test results of Examples 1-6 and Comparative Examples 1-2 are shown in Table 1 below:

[0091] Table 1 Comparison table of performance test results of embodiments and comparative examples

[0092]

[0093]

[0094] As shown in Table 1, the low-density porous refractory materials prepared by the present invention have a bulk density of less than 400 kg / m 3 The porosity is greater than 80%, and the compressive strength, flexural strength and thermal conductivity can meet the use requirements. Therefore, the low-density porous refractory material prepared by the present invention has a high porosity and a bulk density of 200-400kg / m 3 At the same time, the main crystal phases of the material are mullite phase and corundum phase, which have excellent high temperature resistance and mechanical properties, providing a low-density porous refractory material for high-temperature kiln linings.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-density porous refractory material, characterized in that: The invention comprises the following raw materials in weight percentage: 10wt%-15wt% water, 20wt%-30wt% silica sol, 25wt%-35wt% alumina powder, 5wt%-10wt% silicon dioxide powder, 8wt%-14wt% polycrystalline mullite fiber, 0.3wt%-0.5wt% dispersant, 1wt%-2wt% foaming agent, 0.4wt%-1wt% foam stabilizer, 2wt%-6wt% coagulant and 15wt%-20wt% pore-forming agent.

2. A low-density porous refractory material according to claim 1, characterized in that: The solid content of the silica sol is 30wt%; The particle size of the alumina powder is 2-15 μm; The particle size of the silicon dioxide powder is 2-15 μm; The length of the polycrystalline mullite fiber is 3-5 mm; The dispersant is ammonium polyacrylate; The foaming agent is any one of AOS, SDBS and SDS; The foam stabilizer is any one of PEG, stearic acid, xanthan gum and carrageenan; The coagulant is starch; The porogen is any one of walnut shell powder, polystyrene particles and sawdust; The particle size of the porogen is 0.3 mm to 0.4 mm.

3. A low-density porous refractory material according to claim 2, characterized in that: The particle size of the alumina powder is 7-8 μm; The particle size of the silicon dioxide powder is 7-8 μm; The foaming agent is SDBS; The foam stabilizer is xanthan gum; The porogen is walnut shell powder.

4. A method for preparing a low-density porous refractory material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1, mixing water, silica sol, dispersant, alumina powder and silica powder to form a slurry; adding a foam stabilizer and a foaming agent to the slurry and stirring to foam; after foaming, adding a porogen to the slurry and stirring to form a slurry; then adding polycrystalline mullite fiber and starch and stirring to form a slurry; Step 2, pouring the slurry stirred in step 1 into a mold to solidify and shape, demolding after leaving it at room temperature for a period of time, and then drying it under heating conditions, the temperature gradually increases as the moisture in the green body decreases until the green body is completely dry; Step 3, placing the completely dried green body in a high temperature furnace for sintering; Step 4: After the green body is cooled, the green body is processed into a desired size using processing equipment to obtain a low-density porous refractory material.

5. The method for preparing a low-density porous refractory material according to claim 4, characterized in that: In step 2, the room temperature storage time is 24-48 hours; the heating temperature is 30-100° C., and the drying time is 5-7 days.

6. The method for preparing a low-density porous refractory material according to claim 4, characterized in that: In step 3, the sintering temperature is 1400° C.-1500° C.; the holding time is 6-10 hours.

7. The method for preparing a low-density porous refractory material according to claim 4, characterized in that: The low-density porous refractory material prepared in step 4 has a chemical composition mainly composed of 70wt%-80wt% Al2O3 and 20wt%-30wt% SiO2, and the content of other impurities is less than 1wt%; the crystalline phase after sintering is mainly mullite phase and corundum phase; the volume density is 200-400kg / m³.

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