Impermeable wear-resistant brick for hazardous waste rotary kiln and preparation method of impermeable wear-resistant brick

Abstract

The invention discloses an anti-permeation wear-resistant brick for a hazardous waste rotary kiln and a preparation method of the anti-permeation wear-resistant brick. The wear-resistant brick comprises a working layer and a heat insulation layer, the working layer is composed of 60 homogeneous alumina, 75 high-purity mullite, andalusite, alumina powder, silicon carbide powder, metal silicon powder, kaolin powder and silica fume, and a binding agent is added; the heat insulation layer is composed of 65 porous mullite, 60 homogeneous alumina, alumina powder, andalusite powder and clay, and a binding agent is additionally added. Respectively mixing the powder material and the granular material in the working layer, sequentially adding a binding agent and a powder material mixture into the granular material mixture, and carrying out wet mixing, so as to obtain working layer pug; respectively mixing powder and granules in the heat insulation layer, sequentially adding a binding agent and a powder mixture into the granule mixture, and carrying out wet mixing to obtain heat insulation layer pug; and extruding the two pugs to form a green brick, drying the green brick, and sintering to obtain the wear-resistant brick. The wear-resistant brick not only can prolong the service life of the regional refractory brick and reduce the overall thermal conductivity of the refractory brick, but also is convenient to construct and stable in structure.

Description

I. Technical Field:

[0001] This invention belongs to the technical field of refractory bricks for rotary kilns used in hazardous waste incineration, specifically relating to an anti-permeability and wear-resistant brick for rotary kilns used in hazardous waste incineration and its preparation method. II. Background Technology:

[0002] Rotary kilns are key equipment in hazardous waste incineration systems, and their operating efficiency largely depends on the service life of their refractory linings. The service life of these refractory linings is significantly affected by the properties of the incinerated materials, exhibiting considerable variation. In recent years, with the gradual increase in the water and soluble salt content of incinerated materials, the moisture content of these materials is generally around 30%, and in some cases even as high as 50%, posing a more severe challenge to the durability of the lining materials.

[0003] Based on the temperature gradient and the physicochemical changes experienced by the materials, a rotary kiln incinerator can be divided into four main zones: the feeding zone, the drying zone, the combustion zone, and the burnout zone. The feeding and drying zones primarily facilitate the evaporation of moisture from the materials, maintaining the solid material temperature below 700–000℃. Due to the intermittent feeding method of the rotary kiln, the refractory bricks around the feed inlet must withstand frequent and drastic temperature fluctuations. Simultaneously, as the rotary kiln rotates periodically and the materials gradually move forward, at the bottom of the kiln, the surface of the refractory bricks comes into direct contact with materials containing water and soluble salts, allowing moisture and salts to penetrate into the refractory bricks. Outside the bottom zone, as the kiln rotates, the refractory bricks primarily come into contact with high-temperature flue gas, causing the refractory brick temperature to gradually rise. The moisture embedded within the refractory bricks rapidly vaporizes and expands, while soluble salts deposit inside the refractory bricks, generating significant internal stress and easily leading to damage such as spalling and cracking. In this zone, the refractory bricks are primarily subjected to drastic temperature changes, acid and alkali corrosion, and water vapor erosion. Therefore, higher requirements are placed on the thermal shock resistance and impermeability of refractory bricks.

[0004] Currently, chrome corundum and corundum mullite refractory bricks are commonly used in this area. Although these materials have a certain degree of erosion resistance, they are not fully compatible with actual working conditions and are prone to damage such as spalling and cracking, leading to frequent shutdowns of rotary kilns for maintenance and affecting the stable operation of the system. III. Summary of the Invention:

[0005] The technical problem this invention aims to solve is: addressing the issues of existing refractory bricks used in rotary kiln incinerators not being fully compatible with actual operating conditions, being prone to spalling and cracking, leading to frequent kiln shutdowns for maintenance, and affecting the stable operation of the system. This invention provides an anti-permeability and wear-resistant brick for hazardous waste rotary kilns and its preparation method. The technical solution of this invention combines the insulating layer of refractory bricks with an anti-permeability and wear-resistant working layer to create an anti-permeability and wear-resistant brick. This not only improves the service life of the refractory bricks in this area and reduces the overall thermal conductivity of the refractory bricks, but also facilitates construction and provides structural stability.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] This invention provides an anti-permeability and wear-resistant brick for a hazardous waste rotary kiln, the anti-permeability and wear-resistant brick comprising a working layer anti-permeability and wear-resistant brick and a heat insulation layer bonded thereto;

[0008] The raw material composition of the working layer anti-permeability and wear-resistant brick, expressed as a percentage by mass, is as follows: 8-17% homogeneous bauxite (60%), 30-55% high-purity mullite (75%), 15-30% andalusite, 4-10% alumina powder, 5-15% silicon carbide powder, 1-5% metallic silicon powder, 3-10% kaolin powder, and 1-3% silica fume; in addition, a binder accounting for 2-4% of the total weight of all raw materials in the working layer is added.

[0009] The raw material composition of the insulation layer, expressed as a percentage by mass, is as follows: 20-50% porous mullite (65%), 15-38% homogeneous bauxite (60%), 3-10% alumina powder, 6-20% andalusite powder, and 5-12% clay. In addition, a binder accounting for 3-5% of the total weight of the raw materials of the insulation layer is added.

[0010] According to the above-mentioned anti-permeability and wear-resistant bricks for hazardous waste rotary kilns, the raw material composition of the working layer anti-permeability and wear-resistant bricks includes: 60 homogeneous bauxite with a particle size ≤ 5 mm, 75 high-purity mullite with a particle size ≤ 3 mm, andalusite with a particle size ≤ 1 mm, alumina powder with a particle size < 30 μm, silicon carbide powder with a particle size ≤ 1 mm, metallic silicon powder with a particle size < 20 μm, kaolin powder with a particle size < 0.074 mm, and silica fume with a particle size < 2 μm.

[0011] According to the above-mentioned anti-permeability and wear-resistant bricks for hazardous waste rotary kilns, the andalusite with a particle size ≤1mm includes andalusite granules of 0-1mm andalusite powder of 200 mesh, and the ratio between the granules and the powder is 3:1.

[0012] According to the above-mentioned anti-permeability and wear-resistant bricks for hazardous waste rotary kilns, in the raw material composition of the insulation layer, the particle size of 65 porous mullite is ≤5mm, the particle size of 60 homogeneous bauxite is ≤3mm, the particle size of alumina powder is <30μm, the particle size of andalusite powder is <0.074mm, and the particle size of clay is <0.074mm.

[0013] According to the above-mentioned anti-permeability and wear-resistant bricks for hazardous waste rotary kilns, the binder is a dextrin solution with a specific gravity of 1.15 to 1.25 g / mL.

[0014] According to the above-mentioned anti-permeability and wear-resistant bricks for hazardous waste rotary kilns, the thickness of the working layer of the anti-permeability and wear-resistant bricks is 230-250mm, and the thickness of the heat insulation layer is 50-70mm.

[0015] In addition, a method for preparing the above-mentioned anti-permeability and wear-resistant bricks for hazardous waste rotary kilns is provided, the method comprising the following steps:

[0016] a. Weigh out all raw materials according to the above-mentioned raw material composition of the working layer anti-permeability and wear-resistant brick. Mix the weighed raw materials andalusite powder, alumina powder, silicon carbide powder, metallic silicon powder, kaolin powder and silica fume to obtain the first mixed powder. Mix raw materials 60 homogeneous bauxite, 75 high-purity mullite and andalusite granules to obtain the first mixed granules. Add a binder to the first mixed granules and wet mix for 5-7 minutes. Then add the obtained first mixed powder and continue wet grinding for 15-30 minutes to obtain the working layer anti-permeability and wear-resistant brick mortar.

[0017] b. Weigh out various raw materials according to the above-mentioned raw material composition of the insulation layer, mix the weighed raw materials alumina powder, andalusite powder and clay to obtain a second mixed powder; mix the weighed raw materials 65 porous mullite and 60 homogeneous bauxite granules to obtain a second mixed granular material; add a binder to the obtained second mixed granular material and wet mix for 5-7 minutes; then add the obtained second mixed powder and continue wet grinding for 15-30 minutes to obtain the insulation layer mud material;

[0018] c. Add the obtained working layer impermeable and wear-resistant brick mortar and the heat insulation layer mortar to both sides of the partition mold, remove the partition, and press it into brick blanks with a molding pressure of 630 tons.

[0019] d. Dry the obtained brick blanks at 100-120℃ for 10-12 hours; after drying, place them in a tunnel kiln for firing at a temperature of 1350-1450℃, and keep them at the highest temperature for 8 hours; after firing, the product, impermeable and wear-resistant bricks for hazardous waste rotary kilns, is obtained.

[0020] According to the above preparation method of anti-permeability and wear-resistant bricks for hazardous waste rotary kilns, in step c, the two opposite sides of the partition in the partition mold are serrated.

[0021] The positive and beneficial effects of this invention are as follows:

[0022] 1. In the technical solution of this invention, the working layer increases the mullite phase content in the refractory material by rationally proportioning 75% high-purity mullite, andalusite, and kaolin powder, thereby significantly improving the thermal shock stability of the working layer's anti-permeability and wear-resistant bricks. Simultaneously, the addition of andalusite powder and silica fume effectively reduces the porosity of the working layer's anti-permeability and wear-resistant bricks, enhancing their density and anti-permeability.

[0023] 2. In the technical solution of this invention, the insulation layer uses 65 porous mullite as aggregate, which can effectively reduce the thermal conductivity of the insulation layer and improve its insulation performance. By controlling the ratio of alumina powder, andalusite powder, and clay, the thermal expansion coefficient of the insulation layer can be regulated. Precise control of the composition and content of the working layer and the insulation layer matrix can effectively adjust the thermal expansion coefficients of the two layers to achieve optimal matching. This adjustment significantly enhances the bonding strength between the working layer and the insulation layer, thereby preventing crack formation at the interface. Simultaneously, the working layer maintains excellent erosion resistance, while the insulation layer maintains a high porosity, ensuring a significant insulation effect.

[0024] 3. In the method for preparing anti-permeability and wear-resistant bricks of the present invention, the mold partitions used have serrated sides on both sides, which increases the contact area between the working layer and the heat insulation layer, thereby improving the bonding strength.

[0025] 4. The technical solution of this invention improves the impermeability of the working layer refractory bricks by reducing the apparent porosity; and improves the thermal conductivity of the working layer refractory bricks, thereby effectively improving the temperature gradient distribution during temperature changes and slowing down the spalling and cracking of the refractory bricks.

[0026] 5. In the raw material composition of this invention, the appropriate addition of andalusite, metallic silicon, and silica fume can reduce the apparent porosity of the anti-permeability and wear-resistant bricks. The addition of 75% high-purity mullite, andalusite, and kaolin can improve the thermal shock resistance of the anti-permeability and wear-resistant bricks. By controlling the composition and content of the insulation layer raw materials, the thermal expansion coefficient of the insulation layer material is matched with the expansion coefficient of the working layer material, which improves the bonding strength of the interface between the two materials. No cracks will appear at the joint. At the same time, the working layer can maintain excellent high-temperature performance, and the insulation layer can still maintain a high porosity, which has excellent heat insulation effect.

[0027] 6. The anti-permeability and wear-resistant bricks prepared using the technical solution of this invention reduce the apparent porosity of the bricks by 3%, thus reducing liquid permeation. Furthermore, it lowers the internal temperature gradient of the special refractory bricks, effectively alleviating internal stress concentration during drastic temperature changes and preventing spalling and cracking. Simultaneously, by adjusting the thermal expansion coefficient of the insulation layer material to match that of the special wear-resistant bricks, the bonding strength at the interface between the two materials is significantly improved. The anti-permeability and wear-resistant composite bricks prepared by this invention not only possess excellent anti-spalling and anti-cracking properties but also have good thermal insulation effects, effectively reducing heat loss. This solves the problem of refractory brick spalling and cracking in the feeding and drying zones of hazardous waste rotary kilns, extending the average service life by 6 months. In addition, the construction is simple, the structure is stable, significantly extending the service life of the refractory bricks and improving equipment operating efficiency.

[0028] 7. The relevant performance parameters of the anti-permeability and wear-resistant bricks prepared by this invention are detailed in Table 1. IV. Description of the attached drawings:

[0029] Figure 1 A schematic diagram of the structure of the anti-permeability and wear-resistant brick prepared by this invention;

[0030] Figure 1 In the middle, 1 is the working layer of anti-permeability and wear-resistant bricks with a thickness of 230-250mm; 2 is the heat insulation layer with a thickness of 50-70mm. V. Detailed Implementation Methods:

[0031] The present invention will be further illustrated below with reference to the embodiments, but this does not limit the scope of protection of the technical solutions of the present invention.

[0032] In the following embodiments, the raw material composition of the working layer anti-permeability and wear-resistant bricks includes: 60 homogeneous bauxite with a particle size ≤ 5 mm, 75 high-purity mullite with a particle size ≤ 3 mm, andalusite with a particle size ≤ 1 mm, alumina powder with a particle size < 30 μm, silicon carbide powder with a particle size ≤ 1 mm, metallic silicon powder with a particle size < 20 μm, kaolin powder with a particle size < 0.074 mm, and silica fume with a particle size < 2 μm; the andalusite with a particle size ≤ 1 mm includes 0-1 mm andalusite granules and 200 mesh andalusite powder, with a particle size to powder ratio of 3:1. The raw material composition of the insulation layer includes: 65 porous mullite with a particle size ≤ 5 mm, 60 homogeneous bauxite with a particle size ≤ 3 mm, alumina powder with a particle size < 30 μm, andalusite powder with a particle size < 0.074 mm, and clay with a particle size < 0.074 mm. The binder used was a dextrin solution with a specific gravity of 1.15–1.25 g / mL.

[0033] Example 1:

[0034] The present invention relates to an anti-permeability and wear-resistant brick for a hazardous waste rotary kiln, comprising an anti-permeability and wear-resistant working layer and an insulation layer bonded thereto, wherein the working layer has a thickness of 230 mm and the insulation layer has a thickness of 70 mm.

[0035] Expressed as a percentage by mass, the raw material composition of the working layer anti-permeability and wear-resistant brick is as follows: 10% homogeneous bauxite of grade 60, 47% high-purity mullite of grade 75, 15% andalusite (andalusite with a particle size ≤1mm, including andalusite granules of 0-1mm andalusite powder of 200 mesh, with a ratio of granules to powder of 3:1), 6% alumina powder, 12% silicon carbide powder, 3% metallic silicon powder, 5% kaolin powder, and 2% silica fume; in addition, a binder dextrin solution (the specific gravity of the dextrin solution is 1.18g / mL) is added, accounting for 2.8% of the total weight of the raw materials of the working layer.

[0036] The raw material composition of the insulation layer, expressed as a percentage by mass, is as follows: 43% porous mullite (65%), 26% homogeneous bauxite (60%), 6% calcined alumina powder, 17% andalusite powder, and 8% binding clay; in addition, a binder dextrin solution (with a specific gravity of 1.18 g / mL) is added, accounting for 3.5% of the total weight of the raw materials of the insulation layer.

[0037] Example 2:

[0038] The present invention relates to an anti-permeability and wear-resistant brick for a hazardous waste rotary kiln, comprising a working layer of anti-permeability and wear-resistant brick and a heat insulation layer bonded thereto, wherein the working layer has a thickness of 250 mm and the heat insulation layer has a thickness of 50 mm.

[0039] Expressed as a percentage by mass, the raw material composition of the working layer anti-permeability and wear-resistant brick is as follows: 15% homogeneous bauxite of grade 60, 42% high-purity mullite of grade 75, 20% andalusite (andalusite with a particle size ≤1mm, including andalusite granules of 0-1mm andalusite powder of 200 mesh, with a ratio of granules to powder of 3:1), 5% alumina powder, 11% silicon carbide powder, 1% metallic silicon powder, 5% kaolin powder, and 1% silica fume; in addition, a binder dextrin solution (the specific gravity of the dextrin solution is 1.18g / mL) is added, accounting for 2.8% of the total weight of the raw materials of the working layer.

[0040] The raw material composition of the insulation layer, expressed as a percentage by mass, is as follows: 41% porous mullite (65%), 33% homogeneous bauxite (60%), 10% calcined alumina powder, 10% andalusite powder, and 6% binding clay; in addition, a binder dextrin solution (the specific gravity of the dextrin solution is 1.18 g / mL) is added, accounting for 3.5% of the total weight of the raw materials of the insulation layer.

[0041] Example 3:

[0042] The present invention relates to an anti-permeability and wear-resistant brick for a hazardous waste rotary kiln, comprising an anti-permeability and wear-resistant working layer and an insulation layer bonded thereto, wherein the working layer has a thickness of 230 mm and the insulation layer has a thickness of 70 mm.

[0043] Expressed as a percentage by mass, the raw material composition of the working layer anti-permeability and wear-resistant brick is as follows: 16% homogeneous bauxite of 60, 39% high-purity mullite of 75, 22% andalusite (andalusite with a particle size ≤1mm includes andalusite granules of 0-1mm and andalusite powder of 200 mesh, with a ratio of granules to powder of 3:1), 8% alumina powder, 8% silicon carbide powder, 1% metallic silicon powder, 5% kaolin powder and 1% silica fume; in addition, a binder dextrin solution (the specific gravity of the dextrin solution is 1.18g / mL) is added, accounting for 2.8% of the total weight of the raw materials of the working layer.

[0044] The raw material composition of the insulation layer, expressed as a percentage by mass, is as follows: 50% porous mullite (65%), 23% homogeneous bauxite (60%), 9% calcined alumina powder, 11% andalusite powder, and 7% binding clay; in addition, a binder dextrin solution (the specific gravity of the dextrin solution is 1.18 g / mL) is added, accounting for 3.5% of the total weight of the raw materials of the insulation layer.

[0045] Example 4:

[0046] The detailed steps of the preparation method of the anti-permeability and wear-resistant bricks for hazardous waste rotary kilns described in any of Embodiments 1 to 3 of the present invention are as follows:

[0047] a. Weigh various raw materials according to the raw material composition of the working layer anti-permeability and wear-resistant brick as described in any of Examples 1 to 3. Mix the weighed raw materials andalusite powder, alumina powder, silicon carbide powder, metallic silicon powder, kaolin powder and silica fume to obtain a first mixed powder. Mix the raw materials 60 homogeneous bauxite, 75 high-purity mullite and andalusite granules to obtain a first mixed granular material. Add the binder dextrin solution to the first mixed granular material and wet mix for 6 minutes. Then add the obtained first mixed powder and continue wet grinding for 20 minutes to obtain the working layer anti-permeability and wear-resistant brick slurry.

[0048] b. Weigh various raw materials according to the raw material composition of the insulation layer described in any of Examples 1 to 3, mix the weighed raw materials alumina powder, andalusite powder and clay to obtain a second mixed powder; mix the weighed raw materials 65 porous mullite and 60 homogeneous bauxite granules to obtain a second mixed granular material; add a binder dextrin solution to the obtained second mixed granular material and wet mix for 6 minutes; then add the obtained second mixed powder and continue wet grinding for 20 minutes to obtain the insulation layer mud.

[0049] c. Add the obtained working layer impermeable and wear-resistant brick mortar and the heat insulation layer mortar to both sides of the partition mold, remove the partition, and press it into brick blanks with a molding pressure of 630 tons.

[0050] d. The obtained brick blanks are dried at 120℃ for 10 hours; after drying, they are placed in a tunnel kiln for firing at 1420℃, and the highest temperature zone is kept warm for 8 hours; after firing, the product is obtained: anti-permeability and wear-resistant bricks for hazardous waste rotary kilns.

[0051] The relevant performance test indicators of the anti-permeability and wear-resistant bricks for hazardous waste rotary kilns prepared using Examples 1-3 of the present invention are detailed in Table 1.

[0052] Table 1. Relevant performance indicators of the anti-permeability and wear-resistant bricks prepared according to the embodiments of the present invention.

[0053]

Claims

1. A type of impermeable and wear-resistant brick for use in hazardous waste rotary kilns, characterized in that: The impermeable and wear-resistant bricks include a working layer of impermeable and wear-resistant bricks and a heat insulation layer bonded thereto; The raw material composition of the working layer anti-permeability and wear-resistant brick, expressed as a percentage by mass, is as follows: 8-17% homogeneous bauxite (60%), 30-55% high-purity mullite (75%), 15-30% andalusite, 4-10% alumina powder, 5-15% silicon carbide powder, 1-5% metallic silicon powder, 3-10% kaolin powder, and 1-3% silica fume; in addition, a binder accounting for 2-4% of the total weight of all raw materials in the working layer is added. The raw material composition of the insulation layer, expressed as a percentage by mass, is as follows: 20-50% porous mullite (65%), 15-38% homogeneous bauxite (60%), 3-10% alumina powder, 6-20% andalusite powder, and 5-12% clay. In addition, a binder accounting for 3-5% of the total weight of the raw materials of the insulation layer is added.

2. The anti-permeability and wear-resistant brick for hazardous waste rotary kilns according to claim 1, characterized in that: The raw material composition of the working layer anti-permeability and wear-resistant bricks includes: 60 homogeneous bauxite with a particle size ≤ 5 mm, 75 high-purity mullite with a particle size ≤ 3 mm, andalusite with a particle size ≤ 1 mm, alumina powder with a particle size < 30 μm, silicon carbide powder with a particle size ≤ 1 mm, metallic silicon powder with a particle size < 20 μm, kaolin powder with a particle size < 0.074 mm, and silica fume with a particle size < 2 μm.

3. The anti-permeability and wear-resistant brick for hazardous waste rotary kilns according to claim 2, characterized in that: The andalusite with a particle size ≤1mm includes andalusite granules of 0-1mm andalusite powder of 200 mesh, with a ratio of 3:1 between granules and powder.

4. The anti-permeability and wear-resistant brick for hazardous waste rotary kilns according to claim 1, characterized in that: In the raw material composition of the insulation layer, the particle size of 65 porous mullite is ≤5mm, the particle size of 60 homogeneous bauxite is ≤3mm, the particle size of alumina powder is <30μm, the particle size of andalusite powder is <0.074mm, and the particle size of clay is <0.074mm.

5. The anti-permeability and wear-resistant brick for hazardous waste rotary kilns according to claim 1, characterized in that: The binder is a dextrin solution with a specific gravity of 1.15–1.25 g / mL.

6. The anti-permeability and wear-resistant brick for hazardous waste rotary kilns according to claim 1, characterized in that: The thickness of the working layer of the anti-permeability and wear-resistant brick is 230-250mm, and the thickness of the heat insulation layer is 50-70mm.

7. A method for preparing the anti-permeability and wear-resistant brick for hazardous waste rotary kilns as described in claim 1, characterized in that, The preparation method includes the following steps: a. Weigh various raw materials according to the raw material composition of the working layer anti-permeability and wear-resistant brick as described in claim 1, and mix the weighed raw materials andalusite powder, alumina powder, silicon carbide powder, metallic silicon powder, kaolin powder and silica fume to obtain a first mixed powder; mix raw materials 60 homogeneous bauxite, 75 high-purity mullite and andalusite granules to obtain a first mixed granular material; add a binder to the first mixed granular material and wet mix for 5-7 minutes; then add the obtained first mixed powder and continue wet grinding for 15-30 minutes to obtain the working layer anti-permeability and wear-resistant brick mortar. b. Weigh various raw materials according to the raw material composition of the insulation layer as described in claim 1, mix the weighed raw materials alumina powder, andalusite powder and clay to obtain a second mixed powder; mix the weighed raw materials 65 porous mullite and 60 homogeneous bauxite granules to obtain a second mixed granular material; add a binder to the obtained second mixed granular material and wet mix for 5-7 minutes; then add the obtained second mixed powder and continue wet grinding for 15-30 minutes to obtain the insulation layer mud material; c. Add the obtained working layer impermeable and wear-resistant brick mortar and the heat insulation layer mortar to both sides of the partition mold, remove the partition, and press it into brick blanks with a molding pressure of 630 tons. d. Dry the obtained brick blanks at 100-120℃ for 10-12 hours; after drying, place them in a tunnel kiln for firing at a temperature of 1350-1450℃, and keep them at the highest temperature for 8 hours; after firing, the product, impermeable and wear-resistant bricks for hazardous waste rotary kilns, is obtained.

8. The method for preparing the anti-permeability and wear-resistant brick for hazardous waste rotary kilns according to claim 7, characterized in that: In step c, the two opposite sides of the partition in the partition mold are serrated.

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