Refractory material for lining of rotary kiln and preparation method of refractory material

Abstract

The invention relates to the technical field of refractory materials, and discloses a rotary kiln lining refractory material and a preparation method thereof, the raw materials comprise mullite, boron carbide, calcium hexaluminate, silicon carbide, silica powder, alpha-alumina micro powder, coating powder, modified refractory fiber, and a binder. The mullite and the boron carbide are selected as base materials and have excellent acid corrosion resistance, the titanium dioxide and the aluminum oxide are used for treating the refractory fibers, so that a compact enrichment layer is formed, low-temperature sintering is promoted by adding the yttrium oxide, the titanium dioxide is introduced into the refractory fibers, and the corrosion resistance of the refractory fibers is improved. And micropores in the fiber surface can be blocked, so that the porosity of the refractory material is reduced, and the diffusion path of acid steam is prolonged. The refractory material provided by the invention has excellent high-temperature stability and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory materials, in particular to a rotary kiln lining refractory material and a preparation method thereof. Background Art

[0002] A rotary kiln is a steel cylinder lined with refractory material. It rotates to calcine materials and is widely used in industries such as building materials, metallurgy, chemicals, and environmental protection. During operation, the refractory material in the kiln lining is subjected to stress from the kiln's rotation and the rolling impact of high-temperature materials, which can damage the refractory material.

[0003] Existing lining refractory materials mainly include aggregates, matrices and adhesives. Aggregates include high-alumina bauxite clinker, sintered / fused corundum, mullite, etc. The selection and matching of aggregates can achieve the goals of high strength, high-temperature stability and acid resistance. In addition, a small amount of refractory fiber can be added to the matrix to achieve the purpose of thermal shock resistance, thereby avoiding the problem of damage to the lining caused by huge thermal stress inside the material when the temperature fluctuates drastically due to the start and stop of the rotary kiln and fluctuations in operating conditions. However, we know that the molding method of refractory fiber is the melt blowing method, which is used in lining materials. During the use of the rotary kiln, the refractory fiber has a tendency to transform into recrystallization of mullite and calcite when it is reheated, which leads to the problem of pulverization and aging of the heated surface. Summary of the Invention

[0004] Technical problems solved by the present invention:

[0005] The invention is used to solve the existing problem that the heating surface of the rotary kiln lining added with refractory fiber is prone to powdering and aging during use.

[0006] The technical solution adopted in the present invention is:

[0007] In response to the above technical problems, the present invention aims to provide a rotary kiln lining refractory material and a preparation method thereof. The specific contents are as follows:

[0008] The invention provides a rotary kiln lining refractory material. The raw material components include mullite, boron carbide, calcium hexaaluminate, silicon carbide, silicon micropowder, α-alumina micropowder, coating powder, modified refractory fiber and binder.

[0009] According to some preferred embodiments, the raw material components, by weight, include 10 to 30 parts of mullite, 5 to 15 parts of boron carbide, 5 to 15 parts of calcium hexaaluminate, 3 to 8 parts of silicon carbide, 5 to 10 parts of silicon micropowder, 10 to 20 parts of α-alumina micropowder, 5 to 10 parts of coated powder, 2 to 5 parts of modified refractory fiber, and 2 to 5 parts of binder.

[0010] According to some preferred embodiments, the preparation method of the modified refractory fiber is to immerse the refractory fiber in a slurry, and then dry and calcine it to obtain it. In the aforementioned, the refractory fiber includes aluminum silicate fiber and mullite fiber. In the aforementioned, the components in the slurry include titanium dioxide, zirconium oxide, α-alumina, yttrium oxide, aluminum phosphate sol, carboxymethyl cellulose, defoaming agent, and water, and the mass ratio of the aforementioned components is 25-40:2-6:10-25:2-5:8-12:0.8-1.5:0.1:150-300. In the aforementioned, the refractory fiber needs to be plasma activated before impregnation, specifically: the refractory fiber is ultrasonically treated with anhydrous ethanol and ultrapure water for 5 minutes and then dried, and then immersed in a 68% nitric acid solution for reaction for 30 minutes, and then washed and dried with ultrapure water, and then placed in a plasma equipment for treatment, with argon as the reaction gas, the power is 300W, and the time is 60s. In the aforementioned process, the impregnation step is ultrasonic impregnation at room temperature for 2-4 hours. In the aforementioned process, the drying step is oven drying at 60°C. In the aforementioned process, the calcination step is performed by first heating the material to 600-800°C at a rate of 5°C / min for 1 hour, then heating the material to 900-1000°C at a rate of 3°C / min for 2 hours, and finally heating the material to 1100-1150°C at a rate of 5°C / min for 1.5 hours.

[0011] According to some preferred embodiments, the coated powder is porous mullite-coated lanthanum zirconate. Furthermore, the preparation method of porous mullite-coated lanthanum zirconate is that lanthanum zirconate and precursor sol are spray-coated and then sintered in sections. In the aforementioned, the components of the precursor sol are: aluminum isopropoxide, ethyl orthosilicate, polyethylene glycol PEG-2000, nitric acid, ethanol = 100:25:8:3:200, and its preparation method is that ethyl orthosilicate is treated with 2 / 3 parts of ethanol and nitric acid at 40°C for 1h, and then aluminum isopropoxide and 1 / 3 parts of ethanol are added and refluxed at 80°C for 3h. After the end, PEG-2000 is added to obtain the precursor sol. In the aforementioned, spray coating: inlet air temperature is 250°C, outlet air temperature is 100°C. In the above, the sintering process is as follows: heating to 300°C at 5°C / min for 2h, heating to 800°C at 3°C / min for 2h, heating to 1250°C at 5°C / min for 2h, and heating to 1350°C at 2°C / min for 0.5h.

[0012] According to some preferred embodiments, the binder is silicone resin, phenolic resin and aluminum phosphate, and the mass ratio of the three is 1-3:2-6:1-3.

[0013] Second, the present invention provides a method for preparing the aforementioned rotary kiln lining refractory material, comprising the following steps: blending the various raw material components of the refractory material to obtain the refractory material.

[0014] The technical mechanism and beneficial effects adopted by the present invention are:

[0015] (1) The refractory material provided by the present invention uses mullite and boron carbide as matrix materials. Both of the aforementioned materials have excellent acid corrosion resistance. In addition, mullite and boron carbide have similar thermal expansion coefficients and good compatibility. Therefore, compounding the two will not cause expansion mismatch problems. Therefore, the refractory material prepared in this way can meet the high-temperature volume stability and acid resistance required in its application process. At the same time, silicon carbide and mullite are added to further improve the refractoriness, high-temperature stability and thermal shock resistance of the refractory material.

[0016] (2) The refractory material provided by the present invention is obtained by modifying the refractory fiber, specifically by treating the refractory fiber with titanium dioxide and aluminum oxide to form a dense enriched layer, and promoting low-temperature sintering by adding yttrium oxide. By introducing titanium dioxide into the refractory fiber, titanium dioxide can block the micropores on the fiber surface, thereby reducing the porosity of the refractory material and extending the diffusion path of the acid vapor. Yttrium oxide promotes the formation of aluminum titanate between titanium dioxide and aluminum oxide at high temperatures, thereby enhancing the interfacial connection strength of the refractory fiber. If the refractory fiber is not treated, then when the refractory fiber is distributed in the matrix material, the silicon dioxide in the refractory fiber will react with the acid, thereby causing the pulverization of the refractory fiber, resulting in the failure of the fiber's refractory properties, and the intrusion of the acid will cause the corrosion and expansion of the slag balls in the fiber, thereby causing the generation of stress cracks, and causing pulverization and peeling. After the refractory fiber is modified, titanium dioxide transforms into titanium sulfate in a high-temperature, acidic atmosphere. This dense coating physically blocks the acid diffusion path, thereby resisting acid corrosion. Furthermore, the solid solution formed on the refractory fiber surface buffers thermal stress, reducing pulverization and spalling. The liquid phase generated during sintering penetrates the microcracks of the slag ball, forming a filling phase that matches the thermal expansion, inhibiting acid penetration and slag ball expansion, thereby slowing the corrosion rate.

[0017] (3) The refractory material provided by the present invention can effectively improve the high-temperature stability and corrosion resistance of the refractory material by adding lanthanum zirconate. However, it has the defect of insufficient toughness. Based on this, the lanthanum zirconate is coated and the pores of porous mullite are utilized to eliminate the brittle cracking of lanthanum zirconate. DETAILED DESCRIPTION

[0018] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0019] Example 1

[0020] This embodiment provides a refractory material for a rotary kiln lining. The raw material components, calculated by weight, include 25 parts of mullite, 10 parts of boron carbide, 10 parts of calcium hexaaluminate, 5 parts of silicon carbide, 8 parts of silicon micropowder, 15 parts of α-alumina micropowder, 8 parts of coating powder, 4 parts of modified refractory fiber, and 4 parts of binder.

[0021] In the aforementioned, the preparation method of the modified refractory fiber is:

[0022] (1) Aluminum silicate fiber and mullite fiber were blended in a mass ratio of 1:1. After blending, they were ultrasonically treated with anhydrous ethanol and ultrapure water for 5 minutes, then dried. They were then immersed in a 68% nitric acid solution for 30 minutes, washed with ultrapure water, dried, and set aside. They were then placed in a plasma device for treatment using argon as the reaction gas, a power of 300 W, and a time of 60 seconds to obtain pretreated refractory fibers.

[0023] (2) Immerse the pretreated refractory fiber in a slurry and ultrasonicate for 2 hours. The proportions of the slurry components are titanium dioxide, zirconium oxide, α-alumina, yttrium oxide, aluminum phosphate sol, carboxymethyl cellulose, silicone defoamer, and water = 35:5:20:3:10:1.2:0.1:200.

[0024] (3) After impregnation, the fiber is taken out and dried in an oven, then heated to 750°C at a rate of 5°C / min for 1 hour, then heated to 950°C at a rate of 3°C / min for 2 hours, and finally heated to 1100°C at a rate of 5°C / min for 1.5 hours. After treatment, the fiber is cooled naturally to obtain the modified refractory fiber.

[0025] In the above, the method for preparing the coated powder is:

[0026] (1) The components of the precursor sol are: aluminum isopropoxide, tetraethyl orthosilicate, polyethylene glycol PEG-2000, nitric acid, and ethanol in a ratio of 100:25:8:3:200. The precursor sol is prepared by treating tetraethyl orthosilicate with 2 / 3 parts of ethanol and nitric acid at 40°C for 1 hour, then adding aluminum isopropoxide and 1 / 3 parts of ethanol and refluxing at 80°C for 3 hours. After the reaction, PEG-2000 is added to obtain the precursor sol.

[0027] (2) The obtained precursor sol was mixed with lanthanum zirconate at a ratio of 1 L:20 g, and coated in a spray granulation tower with an inlet air temperature of 250°C and an outlet air temperature of 100°C to obtain an intermediate.

[0028] (3) The intermediate is sintered by heating to 300°C at 5°C / min for 2h, heating to 800°C at 3°C / min for 2h, heating to 1250°C at 5°C / min for 2h, and heating to 1350°C at 2°C / min for 0.5h to obtain porphyry-coated lanthanum zirconate.

[0029] In the above, the binder is silicone resin, phenolic resin, and aluminum phosphate, with a mass ratio of 2:6:2.

[0030] Example 2

[0031] The difference between this embodiment and embodiment 1 is that the components of the refractory material are different, specifically: 28 parts of mullite, 12 parts of boron carbide, 12 parts of calcium hexaaluminate, 6 parts of silicon carbide, 6 parts of silicon micropowder, 12 parts of α-alumina micropowder, 5 parts of coating powder, 3 parts of modified refractory fiber, and 4 parts of binder.

[0032] Comparative Example 1

[0033] The difference between this comparative example and Example 1 is that the modified refractory fiber is replaced by refractory fiber.

[0034] Comparative Example 2

[0035] The difference between this comparative example and Example 1 is that α-alumina is not included in the slurry.

[0036] Comparative Example 3

[0037] The difference between this comparative example and Example 1 is that the slurry does not include aluminum phosphate sol and yttrium oxide.

[0038] Comparative Example 4

[0039] The difference between this comparative example and Example 1 is that the coated powder is replaced with lanthanum zirconate.

[0040] Test example

[0041] Tests were conducted using the refractory materials prepared in Examples 1-2 and Comparative Examples 1-4 (the refractory materials were naturally dried at 38°C for 24 hours, then dried in a 60°C drying room for 48 hours, and then heat treated at 1400°C for 4 hours to obtain the finished product). The apparent porosity (GB / T2997-2015), flexural strength retention (GB / T 7320-2008), high-temperature thermal expansion coefficient (GB / T-7320-2008), and erosion index (GB / T8931-2007) were measured. The results are shown in Table 1.

[0042] Table 1 Measurement results

[0043]

[0044] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A rotary kiln lining refractory material, characterized in that: The raw material components include mullite, boron carbide, calcium hexaaluminate, silicon carbide, silicon micropowder, alpha-alumina micropowder, coated powder, modified refractory fiber and binder.

2. The rotary kiln lining refractory material according to claim 1, characterized in that: The raw material components are calculated by weight and include 10 to 30 parts of mullite, 5 to 15 parts of boron carbide, 5 to 15 parts of calcium hexaaluminate, 3 to 8 parts of silicon carbide, 5 to 10 parts of silicon micropowder, 10 to 20 parts of α-alumina micropowder, 5 to 10 parts of coated powder, 2 to 5 parts of modified refractory fiber, and 2 to 5 parts of binder.

3. The rotary kiln lining refractory material according to claim 1, characterized in that: The binder is organic silicon resin, phenolic resin and aluminum phosphate, and the mass ratio of the three is 1-3:2-6:1-3.

4. The rotary kiln lining refractory material according to any one of claims 1 to 3, characterized in that: The modified refractory fiber is prepared by dipping the refractory fiber into a slurry, and then drying and calcining the slurry.

5. The rotary kiln lining refractory material according to claim 4, characterized in that: The refractory fibers include aluminum silicate fibers and mullite fibers; the refractory fibers are plasma treated.

6. The rotary kiln lining refractory material according to claim 4, characterized in that: The components in the slurry include titanium dioxide, zirconium oxide, α-alumina, yttrium oxide, aluminum phosphate sol, carboxymethyl cellulose, defoaming agent and water, and the mass ratio of the above components is 25-40:2-6:10-25:2-5:8-12:0.8-1.5:0.1:150-300.

7. The rotary kiln lining refractory material according to any one of claims 1 to 3, characterized in that: The coated powder is porous mullite-coated lanthanum zirconate, and the preparation method of the coated powder is that the lanthanum zirconate and the precursor sol are spray-coated and then sintered in sections.

8. The rotary kiln lining refractory material according to claim 7, characterized in that: The precursor sol comprises aluminum isopropoxide, tetraethyl orthosilicate, polyethylene glycol, nitric acid, and ethanol in a ratio of 100:25:8:3:

200. The precursor sol is prepared by treating tetraethyl orthosilicate with 2 / 3 parts of ethanol and nitric acid at 40°C for 1 hour, followed by the addition of aluminum isopropoxide and 1 / 3 parts of ethanol and refluxing at 80°C for 3 hours. After the reaction, polyethylene glycol is added to obtain the precursor sol.

9. A method for preparing a rotary kiln lining refractory material according to any one of claims 1 to 8, characterized in that: The refractory material is obtained by blending the various raw material components of the refractory material.

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