Method for producing refractory mortar from waste corundum precast blocks

Abstract

The invention discloses a method for producing refractory mortar by using waste corundum precast blocks. The method comprises the following steps: sorting, crushing, deironing, rolling, screening and grinding waste corundum precast blocks to prepare regenerated corundum micro powder; mixing the regenerated corundum micro powder, the alpha alumina powder, the high-activity alumina powder micro powder, the clay powder and a small amount of the regenerated aggregate by using the water reducing agent and the carboxymethyl cellulose in proportion, and adding water and stirring to obtain the refractory mortar. According to the present invention, the high value-added recovery of the waste refractory material is achieved, the prepared slurry has characteristics of high Al2O3 content, high refractoriness, and large normal temperature and high temperature bonding strength, the cost is reduced by more than 80%, and the method is suitable for high temperature kiln masonry, and has significant economic benefits and significant environmental protection benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refractory materials, and particularly relates to a method for producing refractory mortar by using waste corundum precast blocks. BACKGROUND

[0002] The waste corundum precast blocks used in the present application are mainly waste precast blocks recovered after being used as the inner lining of a ladle, and the main use of the precast blocks is the lining construction of the ladle, and the material is mainly aluminum oxide.

[0003] Refractory mortar is a key stitching material for lining industrial kilns with refractory bricks, and its performance directly affects the overall structural strength, air tightness and service life of the kiln. In particular, for high-temperature kilns such as ladles and hot blast stoves, the refractory mortar is required to not only have good construction performance, but also have high refractoriness, high bonding strength and excellent high-temperature volume stability.

[0004] At present, high-performance corundum refractory mortar is mostly prepared from new raw materials such as white corundum and tabular corundum, resulting in high raw material cost and limiting its wide application. For example, the invention patent CN201410836277.8 discloses a high-aluminum mortar which uses high-alumina bauxite clinker and alumina micro powder as new materials. Although the problem of mortar fullness is solved, the mortar has defects such as large shrinkage at high temperature and insufficient load softening temperature, and the raw material cost is high.

[0005] In order to reduce the cost, there are also attempts to use waste materials in the prior art, but there are often problems of performance sacrifice or limited application scenarios. The invention patent CN112250311A discloses a method for producing refractory mortar by using waste refractory materials, but it focuses on the recycling of low-grade materials, and the Al2O3 content of the obtained product is usually less than 80%, and the refractory performance is limited, which is difficult to meet the use requirements in harsh environments of high-temperature kilns. The common practice is to simply crush the waste materials and use them as aggregates, which fails to realize the high-value-added transformation of waste materials, and the high-temperature strength and erosion resistance of the product are often unsatisfactory.

[0006] Therefore, there is an urgent need in the field for a solution that can realize the efficient and high-value-added recycling of waste refractory materials, especially high-alumina waste refractory materials, without sacrificing performance, and prepare high-end refractory mortar with low cost and excellent performance, which can be comparable to new material products. SUMMARY

[0007] The present application aims to provide a method for producing refractory mortar by using waste corundum precast blocks, which realizes the high-value-added resource utilization of waste materials, significantly reduces the cost of the obtained mortar product, and has excellent bonding strength and significantly improved high-temperature performance indicators.

[0008] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions: A method for producing refractory slurry using waste corundum precast blocks specifically includes the following steps: Step 1: Remove surface impurities from the recycled waste corundum precast blocks, then crush the waste corundum precast blocks, remove iron during the crushing process, and screen them through a primary screen to select recycled corundum aggregate with a particle size of ≤3mm. Step 2: Remove false particles from the ≤3mm recycled corundum aggregate using a roller mill, and then screen it through a secondary screen to obtain recycled corundum granules with a particle size of ≤0.5mm. Step 3: Process the recycled corundum particles with a particle size of ≤0.5mm into recycled corundum micro powder with a particle size of ≤74μm using a grinding equipment; Step 4: Add the processed recycled corundum powder, α-alumina powder, activated alumina powder, clay powder, carboxymethyl cellulose, and recycled aggregate concrete water-reducing agent to a powder mixer according to the proportion, and stir for 10-15 minutes to obtain refractory powder. The above proportions are as follows, by weight percentage: Regenerated corundum micro powder: 70-80%, α-alumina powder: 10-20%, Activated alumina powder: 5-10%, Clay powder: 5-8%; Water-reducing agent for concrete with added recycled aggregate: 0.1-0.3%; Added carboxymethyl cellulose: 0.3-0.6%; Step 5: Put the refractory powder into a mixer and mix for 1-2 minutes. Add water and mix for 3-5 minutes to obtain refractory slurry.

[0009] Furthermore, in step 3, the composition of the recycled corundum micro powder, by mass percentage, is: Al2O3 content of 90% or more; and the composition of the clay powder, by mass percentage, is: Al2O3 content of 30% or more.

[0010] Furthermore, the grinding equipment in step 3 is a Raymond mill, and the powder mixer in step 4 is a cone mixer.

[0011] Furthermore, in step 4, the α-alumina powder added has a particle size of 3-5 μm, the activated alumina powder has a particle size of 1-5 μm, and the clay powder has a particle size ≤74 μm.

[0012] Furthermore, the plasticity index of the clay powder in step 4 is 15-25%.

[0013] Furthermore, in step 5, the amount of water added accounts for 20-25% of the mass of the refractory powder.

[0014] This invention also provides a refractory mortar, prepared by the above method. After the refractory mortar is laid and naturally dried to form a finished product, the product, by mass percentage, has an Al2O3 content of 90%-95%, a SiO2 content of 3-5%, and the remainder being impurities, with a bulk density of 2.7-2.9 g / cm³. 3 Refractoriness ≥1700℃, bond strength ≥2MPa at 200℃×24h, bond strength ≥4MPa at 1450℃×3h. Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: 1. Resource recycling and cost advantages: Using waste corundum precast blocks as the main raw material, the high-value utilization of solid waste is realized, which reduces the raw material cost compared with the same performance mud prepared using new materials, resulting in significant economic benefits.

[0015] 2. Superior performance: Utilizing recycled corundum material with a more stable crystal structure after high-temperature use, and combining it with the hydration bonding and high-temperature ceramic bonding mechanism of highly active alumina powder micropowder, the product avoids the problem of impurities introduced by traditional binders forming low-melting-point phases. The product exhibits high high-temperature strength and strong erosion resistance, eliminating the "weakest link effect" in kiln lining joints.

[0016] 3. Environmentally friendly: The entire process produces no secondary pollution.

[0017] Good construction performance: By adding carboxymethyl cellulose, clay and special recycled aggregate concrete water-reducing agent, the adhesion, water retention and fluidity of the mud are optimized, making construction convenient and the initial setting time moderate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] This invention provides a method for producing refractory slurry using waste corundum precast blocks, specifically including the following steps: Step 1: Remove the sintered layer and slag from the surface of the recycled and stored waste corundum precast blocks, then crush the waste corundum precast blocks, remove iron during the crushing process, and select recycled corundum aggregate with a particle size of ≤3mm through a primary screen. Step 2: Remove the false particles attached to the surface of the recycled corundum aggregate with a particle size ≤3mm through a roller mill. If the false particles are not opened and dispersed during dry powder mixing, it will be difficult to mix the dry powder evenly, which will affect the mixing effect and thus the quality of the final product. Then, it is screened through a two-stage sieve to obtain recycled corundum particles with a particle size ≤0.5mm. Step 3: Recycled corundum particles with a particle size ≤0.5mm are processed by Raymond mill to obtain recycled corundum micro powder with a particle size ≤74μm. Because the particle size of recycled corundum micro powder is small, Raymond mill, which produces less dust and causes no environmental pollution, is used. The content of Al2O3 in the recycled corundum micro powder is greater than 90% by mass percentage. Step 4: Add the processed recycled corundum powder, α-alumina powder, activated alumina powder, clay powder, carboxymethyl cellulose, and recycled aggregate concrete water-reducing agent to a cone mixer according to the formula. The mixing of materials with different specific gravities and particle sizes will not produce chip segregation. After stirring for 10-15 minutes, refractory powder is obtained. The above proportions are as follows, by weight percentage: Regenerated corundum micro powder: 70-80%, particle size ≤74μm, α-alumina powder: 10-20%, particle size 3-5μm, Activated alumina powder: 5-10%, particle size 1-5μm. Clay powder: 5-8%, particle size ≤74μm, Al2O3 content in the clay powder is above 30% by mass, and the plasticity index of the clay powder is 15-25%. Water-reducing agent for concrete with added recycled aggregate: 0.1-0.3%, Added carboxymethyl cellulose: 0.3-0.6%; Alpha alumina powder and activated alumina powder are commercially available products, both with an Al2O3 content of over 99%.

[0020] Step 5: Put the refractory powder into a cement slurry mixer and mix for 1-2 minutes. Add water and mix for 3-5 minutes. The amount of water added should be 20-25% of the mass of the refractory powder to obtain refractory slurry.

[0021] After the refractory mortar is completed, the content of Al2O3 in the formed mortar is 90%-95% by mass, the content of SiO2 is 3%-5%, and the balance is impurities, with a bulk density of 2.7-2.9 g / cm³. 3 Fire resistance ≥1700℃, bond strength ≥2MPa at 200℃×24h, bond strength ≥4MPa at 1450℃×3h.

[0022] Example 1 Step 1: Remove the sintered layer and slag from the surface of the recycled and stored waste corundum precast blocks, then crush the waste corundum precast blocks, remove iron during the crushing process, and select recycled corundum aggregate with a particle size of ≤3mm through a primary screen. Step 2: Remove the false particles and impurities attached to the surface of the recycled corundum aggregate smaller than 3mm by using a roller mill, and then screen it through a two-stage sieve to obtain recycled corundum particles ≤0.5mm. Step 3: Process the ≤0.5mm recycled corundum particles using a Raymond mill or other grinding equipment to obtain ≤74μm recycled corundum micro powder. The Al2O3 content of the recycled corundum micro powder is 93.9% by mass percentage. Step 4: Add the processed recycled corundum powder, α-alumina powder, activated alumina powder, clay powder, carboxymethyl cellulose, and recycled aggregate concrete water-reducing agent to a cone mixer according to the formula, and stir for 10-15 minutes to obtain refractory powder. The above proportions are as follows, by weight percentage: Regenerated corundum micro powder: 72.2%, particle size ≤74μm. α-alumina powder: 14%, particle size 3-5μm. Activated alumina powder: 7%, particle size 1-5μm. Clay powder: 6%, particle size ≤74μm, plasticity index of clay powder is 23.2%. Water-reducing agent for concrete with added recycled aggregate: 0.3%, Added carboxymethyl cellulose: 0.5%; Step 5: Put the refractory powder into a cement slurry mixer and mix for 1-2 minutes. Add water and mix for 3-5 minutes. The amount of water added should be 20-25% of the mass of the refractory powder to obtain refractory slurry.

[0023] According to the masonry construction standards, refractory mortar should be used to coat the brick joints, with a coating thickness of 1-2 mm. The on-site construction temperature should be between 10-30℃, and the mortar should be kept at this temperature for 3 minutes to achieve its strength. Tests on samples showed that the newly produced environmentally friendly high-refractory mortar product, by weight percentage, contains 91.42% Al2O3, 4.2% SiO2, and the remainder is impurities, with a bulk density of 2.76 g / cm³. 3 Fire resistance ≥1700℃. Bond strength at 200℃×24h: 2.67MPa; Bond strength at 1450℃×3h: 4.92MPa.

[0024] Example 2 Step 1: Remove the sintered layer and slag from the surface of the recycled and stored waste corundum precast blocks, then crush the waste corundum precast blocks, remove iron during the crushing process, and select recycled corundum aggregate with a particle size of ≤3mm through a primary screen. Step 2: Remove the false particles and impurities attached to the surface of the ≤3mm recycled corundum aggregate by a roller mill, and then screen it through a two-stage sieve to obtain ≤0.5mm recycled corundum particles. Step 3: Process the ≤0.5mm recycled corundum particles using a Raymond mill or other grinding equipment to obtain ≤74μm recycled corundum micro powder. The recycled corundum micro powder has an Al2O3 content of 94.2% by mass percentage. Step 4: Add the processed recycled corundum powder, α-alumina powder, activated alumina powder, clay powder, carboxymethyl cellulose, and recycled aggregate concrete water-reducing agent to a cone mixer according to the formula, and stir for 10-15 minutes to obtain refractory powder. The above proportions are as follows, by weight percentage: Regenerated corundum micro powder: 77.2%, particle size ≤74μm. α-alumina powder: 11%, particle size 3-5μm, Activated alumina powder: 6%, particle size 1-5μm. Clay powder: 5%, particle size ≤74μm, plasticity index of clay powder is 24.5%. Water-reducing agent for concrete with added recycled aggregate: 0.3%, Added carboxymethyl cellulose: 0.5%; Step 5: Put the refractory powder into a cement slurry mixer and mix for 1-2 minutes. Add water and mix for 3-5 minutes. The amount of water added should be 20-25% of the mass of the refractory powder to obtain refractory slurry.

[0025] According to the masonry construction standards, refractory mortar should be used to coat the brick joints, with a coating thickness of 1-2 mm. The on-site construction temperature should be between 10-30℃, and the mortar should be kept at this temperature for 3 minutes to achieve its strength. Tests on samples showed that the newly produced environmentally friendly high-refractory mortar product, by weight percentage, contains 92.10% Al2O3, 3.76% SiO2, with the remainder being impurities, and has a bulk density of 2.81 g / cm³. 3 Fire resistance ≥1700℃. Bond strength at 200℃×24h: 2.45MPa; Bond strength at 1450℃×3h: 5.14MPa.

[0026] Example 3 Step 1: Remove the sintered layer and slag from the surface of the recycled and stored waste corundum precast blocks, then crush the waste corundum precast blocks, remove iron during the crushing process, and select recycled corundum aggregate with a particle size of ≤3mm through a primary screen. Step 2: Remove the false particles and impurities attached to the surface of the ≤3mm recycled corundum aggregate by a roller mill, and then screen it through a two-stage sieve to obtain ≤0.5mm recycled corundum particles. Step 3: Process the ≤0.5mm recycled corundum particles using a Raymond mill or other grinding equipment to obtain ≤74μm recycled corundum micro powder. The recycled corundum micro powder has an Al2O3 content of 93.4% by mass percentage. Step 4: Add the processed recycled corundum powder, α-alumina powder, activated alumina powder, clay powder, carboxymethyl cellulose, and recycled aggregate concrete water-reducing agent to a cone mixer according to the formula, and stir for 10-15 minutes to obtain refractory powder. The above proportions are as follows, by weight percentage: Regenerated corundum micro powder: 74.2%, particle size ≤74μm. α-alumina powder: 10%, particle size 3-5μm. Activated alumina powder: 8%, particle size 1-5μm. Clay powder: 7%, particle size ≤74μm, plasticity index of clay powder is 24.3%. Water-reducing agent for concrete with added recycled aggregate: 0.3%, Added carboxymethyl cellulose: 0.5%; Step 5: Put the refractory powder into a cement slurry mixer and mix for 1-2 minutes. Add water and mix for 3-5 minutes. The amount of water added should be 20-25% of the mass of the refractory powder to obtain refractory slurry.

[0027] According to the masonry construction standards, refractory mortar should be used to coat the brick joints, with a coating thickness of 1-2 mm. The on-site construction temperature should be between 10-30℃, and the mortar should be kept at this temperature for 3 minutes to achieve its strength. Tests on samples show that the newly produced environmentally friendly high-refractory mortar product, by weight percentage, contains 90.3% Al2O3, 4.85% SiO2, with the remainder being impurities. Its bulk density is 2.72 g / cm³, and its refractoriness is ≥1700℃. The bond strength at 200℃ for 24 hours is 2.71 MPa, and at 1450℃ for 3 hours is 4.56 MPa.

[0028] This invention improves the workability and adhesion of the product by rationally adjusting the proportions of carboxymethyl cellulose, clay, etc. At the same time, by introducing α-alumina and recycled aggregate concrete water-reducing agents, it enhances the material's good flowability and adhesion while preventing excessive water from affecting the material's high-temperature performance, thus improving the material's workability and high-temperature performance.

[0029] This invention utilizes high-quality corundum precast blocks through processing and recycling, along with a suitable proportioning system combining activated alumina powder and α-alumina powder. Leveraging the strength generated by the hydration of activated alumina powder, it achieves excellent bonding strength at room temperature. Simultaneously, it reduces the introduction of low-melting-point components from traditional fire mortar, and the high-temperature chemical reaction generates a high-melting-point phase, significantly improving high-temperature performance. This results in mortar properties equal to or better than the bricks themselves, eliminating the shortcomings of high-temperature or ultra-high-temperature kiln lining joints and extending the overall service life of high-temperature kilns. This invention also achieves efficient recycling and reuse of waste materials, reducing raw material costs by over 80%, resulting in significant economic benefits.

Claims

1. A method for producing a refractory slurry using waste corundum precast blocks, characterized by, Specifically comprising the following steps: Step 1, the recycled waste corundum prefabricated block, remove surface impurities, and then crush the waste corundum prefabricated block, remove iron during the crushing process, and screen through a first screen, select the particle size of the recycled corundum aggregate ≤3mm; Step 2, the recycled corundum aggregate ≤3mm is passed through a wheel grinder to eliminate false particles, and then screened through a second screen to obtain recycled corundum particle material with a particle size of ≤0.5mm; Step 3, the recycled corundum particles with a particle size of ≤0.5mm are processed by a grinding equipment to obtain recycled corundum micropowder ≤74μm; Step 4, the processed recycled corundum micropowder, α-alumina powder, active alumina powder, clay powder, carboxymethyl cellulose, and recycled aggregate concrete are added into a powder mixer according to the proportion, and stirred for 10-15min to obtain refractory powder; The above proportion is as follows according to weight percentage: Recycled corundum micropowder: 70-80%, α-alumina powder: 10-20%, Active alumina powder: 5-10%, Clay powder: 5-8%; Additional recycled aggregate concrete water reducing agent: 0.1-0.3%; Additional carboxymethyl cellulose: 0.3-0.6%; Step 5, the refractory powder is placed into a mixer and stirred for 1-2min, and then stirred for 3-5min after adding water to obtain refractory slurry.

2. The method for producing refractory mortar by using waste corundum precast block according to claim 1, characterized in that, The composition of the recycled corundum micropowder in step 3 is Al2O3 content of 90% or more according to mass percentage; the composition of the clay powder is Al2O3 content of 30% or more according to mass percentage.

3. The method for producing refractory mortar by using waste corundum precast block according to claim 1, characterized in that, The grinding equipment in step 3 is a Raymond mill, and the powder mixer in step 4 is a conical mixer.

4. The method for producing refractory mortar by using waste corundum precast block according to claim 1, characterized in that, The particle size of the α-alumina powder added in step 4 is 3-5μm, the particle size of the active alumina powder is 1-5μm, and the particle size of the clay powder is ≤74μm.

5. The method for producing refractory mortar by using waste corundum precast block according to claim 1, characterized in that, The plasticity index of the clay powder in step 4 is 15-25%.

6. The method for producing refractory mortar by using waste corundum precast block according to claim 1, characterized in that, The amount of water added in step 5 accounts for 20-25% of the mass of the refractory powder.

7. A refractory slurry, characterized by, The formed product prepared by the method of any one of claims 1-7, after naturally air-drying and forming, has an Al2O3 content of 90-95% by mass, a SiO2 content of 3-5% by mass, and the balance being impurities, a bulk density of 2.7-2.9 g / cm 3 , a refractoriness of ≥1700℃, a 200℃×24h bonding strength of ≥2Mpa, and a 1450℃×3h bonding strength of ≥4Mpa.