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CN-121181342-B - Composite castable for coal injection duct of cement kiln, preparation method and application

CN121181342BCN 121181342 BCN121181342 BCN 121181342BCN-121181342-B

Abstract

The invention belongs to the technical field of refractory materials, and in particular relates to a composite castable and a preparation method for a cement kiln coal injection pipe, and the composite castable comprises, by weight, 45-55% of zirconium mullite aggregate; 15-20% of silicon carbide particles, 8-12% of dispersible alumina micro powder, 4-6% of calcium aluminate cement, 3-5% of rare earth modified silica fume, wherein the content of SiO 2 in the rare earth modified silica fume is more than or equal to 94%, 3-5% of Y 2 O 3 ;ZrO 2 -TiO 2 -Al 2 O 3 precursor powder accounting for 0.5-1.5% by weight, 0.1-0.3% of water reducer, 0.05-0.1% of retarder and the balance of water. According to the casting material, the ZrO 2 -TiO 2 -Al 2 O 3 precursor powder is added, and the casting material is subjected to in-situ reaction at 1100-1300 ℃, so that micro-expansion and sintering shrinkage are dynamically matched, cracking is avoided, the thermal stability is remarkably improved due to the doping of Zr 4+ , once the casting material is formed, the Zr doped aluminum titanate crystal phase is not decomposed or reversed in a high-temperature environment in a subsequent service, and the structural stability can be kept.

Inventors

  • XU GAO
  • WANG QIANG
  • WANG DAOJUN
  • CHANG ZHAO
  • WANG SHAOJIAN

Assignees

  • 长兴兴鹰新型耐火建材有限公司

Dates

Publication Date
20260512
Application Date
20250909

Claims (8)

  1. 1. The composite castable for the coal injection duct of the cement kiln is characterized by comprising the following components in percentage by weight: 45-55% of zirconium mullite aggregate; 15-20% of silicon carbide particles; 8-12% of dispersible alumina micropowder; 4-6% of calcium aluminate cement; 3-5% of rare earth modified silica fume, wherein the content of SiO 2 in the rare earth modified silica fume is more than or equal to 94%, and 0.5-1.5 wt% of Y 2 O 3 is doped; 3-5% of ZrO 2 -TiO 2 -Al 2 O 3 precursor powder; 0.1-0.3% of water reducer; 0.05-0.1% of retarder and the balance of water; the preparation method of the ZrO 2 -TiO 2 -Al 2 O 3 precursor powder comprises the following steps: (1) 1 (1.8-1.9) dissolving a zirconium source, a titanium source and an aluminum source in a solvent according to the mol ratio of ZrO 2 ：TiO 2 ：Al 2 O 3 of (0.1-0.2), and adding deionized water to carry out hydrolysis-polycondensation reaction to obtain sol; (2) Drying and crushing the sol, heating to 600-800 ℃ at 2-3 ℃ per min under the air atmosphere, preserving heat for 2-3 hours, and cooling to obtain the precursor powder.
  2. 2. The composite castable for the coal injection duct of the cement kiln according to claim 1, wherein the rare earth modified silica fume is silica fume modified by Y 2 O 3 .
  3. 3. The composite castable for the coal injection duct of the cement kiln, according to claim 1, is characterized in that the content of Y 2 O 3 in the rare earth modified silica fume is 0.8-1.2 wt%.
  4. 4. The composite castable for the coal injection duct of the cement kiln, according to claim 1, is characterized in that the grain size grading of the zirconium mullite aggregate is that, based on the proportion of the zirconium mullite aggregate in the composite castable, 5-8 mm accounts for 30-40%, and 0.5-1 mm accounts for 15-20%.
  5. 5. A method for preparing a composite castable for a coal-injection duct of a cement kiln according to any one of claims 1 to 4, comprising the steps of: (1) Carrying out dry mixing on zirconium mullite aggregate and silicon carbide particles to obtain a particle mixture; (2) Adding the dispersible alumina micropowder, the calcium aluminate cement, the rare earth modified silica fume and the ZrO 2 -TiO 2 -Al 2 O 3 precursor powder, and continuously dry-mixing for 3-5 minutes; (3) Dissolving a water reducing agent and a retarder in water, adding the water reducing agent and the retarder into the mixture obtained in the step (2), and wet mixing for 4-6 minutes to obtain castable; (4) Pouring the castable into a mould for vibration molding, curing for 12-24 hours at 15-25 ℃, and demoulding; (5) And (3) drying the demoulded sample at 100-110 ℃ for 24 hours, and then carrying out heat treatment at 980-1100 ℃ for 3 hours to obtain the finished castable.
  6. 6. The preparation method according to claim 5, wherein the heat treatment process is performed in an air atmosphere at a temperature rising rate of 3-5 ℃ per minute.
  7. 7. Use of a composite castable for a cement kiln coal-injection duct according to any one of claims 1-4, for a cement kiln coal-injection duct liner.
  8. 8. The application of claim 7, wherein the composite castable is applied to the inner wall of the coal injection pipe, and the heating rate is controlled to be 3-5 ℃ per minute in the ignition heating process of the kiln system.

Description

Composite castable for coal injection duct of cement kiln, preparation method and application Technical Field The invention belongs to the technical field of refractory materials, and particularly relates to a composite castable for a coal injection pipe of a cement kiln, a preparation method and technical application thereof, in particular to a zirconium mullite-silicon carbide-based castable with high thermal shock resistance, alkali erosion resistance and controllable micro-expansion characteristic, and a preparation method and application thereof in a coal injection pipe lining. Background The coal injection pipe of the cement kiln is a key thermal component in a rotary kiln system, has extremely bad working environment, is at high temperature of 1100-1400 ℃ for a long time, bears severe scouring of high-speed coal dust airflow, is exposed to corrosive atmospheres such as alkali metal (K 2O、Na2 O) and the like, and is subjected to thermal shock impact caused by frequent start and stop. Therefore, the coal injection pipe lining material must have excellent high temperature strength, thermal shock resistance, anti-scour properties and chemical resistance. At present, corundum-mullite, silicon carbide or corundum-spinel systems are mostly adopted as castable for the coal injection pipes. For example, CN104108941A discloses a castable for a coal-injection duct prefabricated brick, which comprises, by weight, 50-60% of white corundum, 10-15% of mullite, 10-15% of corundum fine powder, 4-6% of fused spinel, 4-6% of silicon carbide and 8-10% of an additive. The special castable for the coal injection pipe disclosed by CN102584295A consists of silicon carbide, andalusite, corundum, spinel powder, zirconium mullite powder, alumina micro powder and other materials, is a micro-expansion irreversible castable, and is beneficial to reducing the internal stress of the material at high temperature. CN113773058A discloses an erosion-resistant corundum-zirconium mullite coal injection pipe castable, which comprises 100 parts of corundum powder, 10-20 parts of 5-10 mm zirconium mullite coarse aggregate, 20-30 parts of 0.1-1 mm zirconium mullite fine aggregate, 5-10 parts of simple substance powder, 5-15 parts of boron modified polysilsesquioxane, 15-30 parts of alumina powder and 20-30 parts of heat-resistant steel fiber, wherein the zirconium mullite aggregate is introduced on the basis of the ultralow cement corundum castable, and the composition of a matrix is adjusted by optimizing the grain composition, so that a mullite crystal phase is generated at a high temperature, and the mullite crystal phase is columnar crystal, and has small thermal expansion coefficient, good thermal shock property and high strength. The castable comprises, by weight, 50-75 parts of calcium titanate aluminate, 5-10 parts of high titanium slag, 6-10 parts of alumina powder, 4-8 parts of titanium dioxide, 5-8 parts of pure calcium aluminate cement, 0.01-0.03 part of explosion-proof fiber, 0.01-0.03 part of a water reducer and 6-10 parts of titanium dioxide sol. Because the main crystal phase in the calcium titanate aluminate is calcium hexaluminate and calcium titanate aluminate, the secondary crystal phase consists of a small amount of high-temperature phases such as calcium dialuminate, aluminum titanate, calcium titanate and the like, the volume expansion effect can not be generated when the secondary crystal phase reacts with alkaline substances, and the strength and compactness of the castable can be further improved when the glass phase is generated in the matrix. However, the prior art still has the following problems: The thermal shock stability is insufficient, the traditional material is easy to crack under the thermal cycle, and the structure is peeled off; Alkali corrosion resistance is weak, alkali metal vapor permeates and reacts with the matrix to generate nepheline (NaAlSiO 4) or kalioplast (KAlSiO 4), and volume expansion and structural damage are caused; High temperature performance decay, namely phase change decomposition (such as easy decomposition of pure aluminum titanate at 750-1280 ℃) occurs at long-term high temperature, so that performance is reduced. Disclosure of Invention The invention aims to provide a composite castable for a coal injection pipe of a cement kiln, a preparation method and application thereof, and the composite castable has the characteristics of high thermal shock resistance and alkali corrosion resistance, solves the problems of thermal shock cracking, alkali corrosion damage, high-temperature performance attenuation and the like in the prior art, and prolongs the service life of the coal injection pipe. In order to achieve the aim, the invention provides a composite castable taking zirconium mullite, silicon carbide and aluminum oxide as main raw materials, zrO 2-TiO2-Al2O3 precursor powder is introduced as a controllable micro-expansion component, and Y 2O3 modified silica fume is matched, so