A corundum-mullite silicon nitride brick for waste incinerators and its preparation method

Abstract

This invention discloses a corundum-mullite-silicon nitride brick for waste incinerators and its preparation method. The corundum-mullite-silicon nitride brick is composed of 6-10% dense corundum (5-3 mm), 18-22% dense corundum (3-1 mm), 14-18% dense corundum (1-0 mm), 12-16% high-purity mullite (3-1 mm), 8-12% high-purity mullite (1-0 mm), 18-22% dense corundum (<0.088 mm), 4-8% high-purity mullite (<0.088 mm), and 4-8% silicon nitride with a particle size of 325 mesh. Additionally, a binder accounting for 3-4% of the total weight of all raw materials is added. First, the aggregates are mixed, then the binder is added and mixing continues, followed by the addition of powder and further mixing to obtain a mixture. The resulting mixture is pressed into brick blanks, which are then dried, fired, and cooled to obtain the finished corundum-mullite-silicon nitride brick. The product prepared by this invention has low bulk density, high strength, good wear resistance, excellent erosion resistance, good thermal shock stability, and is environmentally friendly and energy-saving, fully meeting the requirements of different environments for waste incinerators.

Description

I. Technical Field:

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a corundum mullite silicon nitride brick for waste incinerators and its preparation method. II. Background Technology:

[0002] Waste incinerators typically require refractory materials to protect the furnace structure from high temperatures and corrosive gases such as caustic soda. Selecting appropriate refractory materials is crucial for the lifespan and performance of waste incinerators.

[0003] When the incinerated waste is a non-homogeneous mixture of different compositions, its type, quantity, and calorific value vary greatly. Therefore, the physical and chemical properties of the lining must adapt to the requirements of different stages of operation. The operating temperature of a waste incinerator generally does not exceed 1200℃, but the complex working environment (such as gas erosion, wear and impact on the furnace interior during high-temperature movement of waste) necessitates the use of high-performance refractory linings, and this demand will continue to increase.

[0004] In waste incinerators, the input and discharge of waste causes wear and impact to the internal structure, requiring refractory materials to possess excellent wear resistance and strength. Waste produces corrosive gases at high temperatures, necessitating corrosion resistance in the refractory materials. Significant temperature fluctuations within the incinerator necessitate good thermal shock resistance in the refractory materials. Furthermore, considering environmental friendliness and economic efficiency, the refractory materials must also exhibit good energy-saving and environmentally friendly properties. III. Summary of the Invention:

[0005] The technical problem this invention aims to solve is: addressing the comprehensive requirements of waste incinerators for the performance of refractory materials, this invention provides a corundum-mullite silicon nitride brick for waste incinerators with high wear resistance, erosion resistance, and good thermal shock stability, as well as its preparation method. The corundum-mullite silicon nitride brick for waste incinerators prepared using the technical solution of this invention exhibits high wear resistance, erosion resistance, and good thermal shock stability. Furthermore, this corundum-mullite silicon nitride brick has a lower bulk density, which can replace some of the currently commonly used alumina-chrome bricks, making it more economical and reducing environmental pollution caused by the conversion of trivalent chromium to hexavalent chromium, thus benefiting environmental protection.

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

[0007] This invention provides a corundum-mullite-silicon nitride brick for waste incinerators. Expressed as a weight percentage, the corundum-mullite-silicon nitride brick is mainly composed of aggregate and powder. The aggregate consists of 6-10% dense corundum (5-3 mm), 18-22% dense corundum (3-1 mm), 14-18% dense corundum (1-0 mm), 12-16% high-purity mullite (3-1 mm), and 8-12% high-purity mullite (1-0 mm). The powder consists of 18-22% dense corundum (<0.088 mm), 4-8% high-purity mullite (<0.088 mm), and 4-8% silicon nitride with a particle size of 325 mesh. Additionally, a binder comprising 3-4% of the total weight of the aggregate and powder is added.

[0008] According to the aforementioned corundum mullite silicon nitride brick for waste incinerators, the dense corundum contains ≥98.5% Al2O3 and ≤0.5% SiO2.

[0009] According to the above-mentioned corundum mullite silicon nitride bricks for waste incinerators, the high-purity mullite contains Al2O3 content ≥70% and SiO2 content ≤28%.

[0010] According to the above-mentioned corundum mullite silicon nitride bricks for waste incinerators, the Si3N4 content in the silicon nitride is ≥99%.

[0011] According to the above-mentioned corundum mullite silicon nitride bricks for waste incinerators, the binder is sulfite pulp waste liquid with a specific gravity of 1.24 to 1.28.

[0012] In addition, a method for preparing corundum mullite silicon nitride bricks for waste incinerators is provided, the method comprising the following steps:

[0013] a. Mixing: First, weigh all the raw materials according to the above proportions of corundum mullite silicon nitride bricks. Add the weighed aggregates to the mixer and mix (mixing time is 1-2 minutes). Then add the binder and continue mixing (mixing time is 2-3 minutes). Then add the powder and continue mixing (mixing time is 5-10 minutes) to obtain the mixture.

[0014] b. Molding: The resulting mixture is pressed into brick blanks using a press.

[0015] c. Drying: Dry the obtained brick blanks;

[0016] d. The dried brick blanks are placed in a high-temperature tunnel kiln for firing, and then cooled to obtain the product, corundum mullite silicon nitride bricks for waste incinerators.

[0017] According to the above-described method for preparing corundum-mullite silicon nitride bricks for waste incinerators, during the pressing process described in step b, the pressure of the press is controlled to be 630–1000 tons; the bulk density of the resulting brick blank is controlled to be 2.92–2.95 g / cm³. 3 .

[0018] According to the above-mentioned preparation method of corundum mullite silicon nitride bricks for waste incinerators, a dryer is used for drying in step c, the temperature of the dryer is controlled at 110-130℃, and the residual moisture in the brick blank after drying is ≤0.5%.

[0019] According to the above-mentioned preparation method of corundum mullite silicon nitride bricks for waste incinerators, during the firing process described in step d, the firing temperature is 1600-1630℃, and the holding time at the firing temperature is 4-6h.

[0020] The positive and beneficial effects of this invention are:

[0021] 1. In the composition of the corundum-mullite-silicon nitride bricks of this invention, the addition of Si3N4 fine powder is beneficial because silicon nitride is hard and belongs to high-hardness refractory materials. It has high mechanical strength and strong wear resistance, which can improve the wear resistance of the product and effectively resist the wear and impact of waste input and falling on the furnace body. Secondly, silicon nitride has good oxidation resistance and strong resistance to acid and alkali corrosion, making it suitable for the complex atmosphere environment of waste incinerators. In addition, Si3N4 has a low coefficient of thermal expansion, is not prone to thermal stress, and has excellent thermal shock resistance, making it suitable for long-term use at high temperatures.

[0022] 2. In the composition of the corundum-mullite silicon nitride brick of this invention, dense corundum is added because its high hardness improves the wear resistance of the product. Simultaneously, high-purity mullite, a high-toughness refractory material, is added. The unique layered structure of mullite effectively fills the gaps between corundum particles, enhancing the overall density of the material, thereby reducing cracks and porosity and improving strength and stability. Secondly, the robust interface formed between mullite and corundum greatly enhances the interfacial stability of the material, effectively resisting the formation of interfacial cracks. Furthermore, mullite has a low coefficient of thermal expansion, which complements the high coefficient of thermal expansion of corundum, absorbing some of the thermal expansion stress and reducing the internal stress caused by thermal expansion, thus reducing the risk of cracking. Finally, the addition of mullite allows for precise control of the thermal conductivity of the corundum brick, slowing down the heat conduction rate and effectively reducing the accumulation and propagation of thermal shock stress, thereby comprehensively improving the thermal shock resistance of the corundum-mullite silicon nitride brick. Moreover, the corundum-mullite phase has certain resistance to alkali erosion and carbon monoxide erosion. Therefore, the product prepared by this invention has good thermal shock resistance, chemical erosion resistance, wear resistance and atmosphere change resistance, and has a wider range of applications. It can exert its excellent properties in non-homogeneous waste mixtures with different furnace types and different components in waste incinerators.

[0023] 3. The corundum mullite silicon nitride brick prepared using the technical solution of this invention has a low bulk density and is chromium-free, which can effectively reduce the pollution of hexavalent chromium to the environment and is beneficial to environmental protection; it also has good economic benefits.

[0024] 4. The relevant performance parameters of the corundum mullite silicon nitride bricks for waste incinerators prepared using the technical solution of this invention are detailed in Table 1.

[0025] Table 1. Performance test data of the corundum-mullite-silicon nitride bricks for waste incinerators of the present invention.

[0026] Testing items Standard value Bulk density (g / cm3) 2.92-2.95 Apparent porosity (%) 17-19 Compressive strength at room temperature (MPa) ＞100 Load softening temperature (°C) ＞1700 Thermal shock stability (1100℃ water cooling cycle) ＞25 <![CDATA[Wear resistance (cm 3 )]]> ＜3

[0027] In summary, the corundum mullite silicon nitride bricks prepared using the technical solution of this invention have low bulk density, high strength, good wear resistance, excellent erosion resistance, good thermal shock stability, and are environmentally friendly and energy-saving, fully meeting the requirements of different environments in waste incinerators. IV. Detailed Implementation Methods:

[0028] 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 solution of the present invention.

[0029] In the following examples, the dense corundum used has an Al2O3 content ≥98.5% and a SiO2 content ≤0.5%; the high-purity mullite has an Al2O3 content ≥70% and a SiO2 content ≤28%; the silicon nitride has a Si3N4 content ≥99%; and the binder is sulfite pulp waste liquor with a specific gravity of 1.24 to 1.28.

[0030] Example 1:

[0031] This invention relates to corundum-mullite-silicon nitride bricks for waste incinerators. Expressed by weight percentage, the bricks consist of aggregates and powder. The aggregates are composed of 8% dense corundum (5-3 mm), 20% dense corundum (3-1 mm), 16% dense corundum (1-0 mm), 14% high-purity mullite (3-1 mm), and 10% high-purity mullite (1-0 mm). The powder consists of 20% dense corundum (<0.088 mm), 6% high-purity mullite (<0.088 mm), and 6% silicon nitride (325 mesh). Additionally, 3.5% of the total weight of the aggregates and powder is added as a binder, sulfite pulp waste liquor.

[0032] Example 2:

[0033] This invention relates to corundum-mullite-silicon nitride bricks for waste incinerators. Expressed by weight percentage, the bricks consist of aggregates and powder. The aggregates are composed of 7% dense corundum (5-3 mm), 21% dense corundum (3-1 mm), 15% dense corundum (1-0 mm), 13% high-purity mullite (3-1 mm), and 11% high-purity mullite (1-0 mm). The powder consists of 21% dense corundum (<0.088 mm), 5% high-purity mullite (<0.088 mm), and 7% silicon nitride (325 mesh). Additionally, 3.5% of the total weight of the aggregates and powder is added as a binder, sulfite pulp waste liquor.

[0034] Example 3:

[0035] This invention relates to corundum-mullite-silicon nitride bricks for waste incinerators. Expressed by weight percentage, the bricks consist of aggregates and powder. The aggregates are composed of 10% dense corundum (5-3 mm), 18% dense corundum (3-1 mm), 17% dense corundum (1-0 mm), 15% high-purity mullite (3-1 mm), and 11% high-purity mullite (1-0 mm). The powder consists of 19% dense corundum (<0.088 mm), 5% high-purity mullite (<0.088 mm), and 5% silicon nitride (325 mesh). Additionally, 3.5% of the total weight of the aggregates and powder is added as a binder, sulfite pulp waste liquor.

[0036] Example 4:

[0037] This invention relates to corundum-mullite-silicon nitride bricks for waste incinerators. Expressed by weight percentage, the bricks consist of aggregates and powder. The aggregates are composed of 6% dense corundum (5-3 mm), 22% dense corundum (3-1 mm), 14% dense corundum (1-0 mm), 16% high-purity mullite (3-1 mm), and 8% high-purity mullite (1-0 mm). The powder consists of 22% dense corundum (<0.088 mm), 5% high-purity mullite (<0.088 mm), and 7% silicon nitride (325 mesh). Additionally, 3.5% of the total weight of the aggregates and powder is added as a binder, sulfite pulp waste liquor.

[0038] The preparation method of corundum mullite silicon nitride bricks for waste incinerators described in Examples 1-4 of this invention comprises the following detailed steps:

[0039] a. Mixing: First, weigh all the raw materials according to the proportion of corundum mullite silicon nitride bricks described in any of Examples 1 to 4. Add the weighed aggregates to the mixer and mix for 2 minutes. Then add the binder and continue mixing for 3 minutes. Then add the powder and continue mixing for 6 minutes to obtain the mixture.

[0040] b. Molding: The resulting mixture is pressed into brick blanks using a press. The pressure of the press is controlled at 650-700 tons, and the bulk density of the resulting brick blanks is 2.92-2.95 g / cm³. 3 ;

[0041] c. Drying: Place the obtained brick blanks in a dryer for drying. The temperature of the dryer is controlled at 110-130℃. The residual moisture content in the brick blanks after drying is ≤0.5%.

[0042] d. The dried brick blanks are placed in a high-temperature tunnel kiln for firing at a temperature of 1600-1630℃ for 6 hours. After firing, they are cooled to obtain the product, corundum mullite silicon nitride bricks for waste incinerators.

[0043] Comparative Example 1:

[0044] A type of corundum-mullite-silicon nitride brick for waste incinerators, expressed as a weight percentage, has the following raw material composition:

[0045] Aggregate composition: 8% dense corundum of 5-3mm, 20% dense corundum of 3-1mm, 26% dense corundum of 1-0mm and 14% high-purity mullite of 3-1mm;

[0046] Powder composition: 20% dense corundum <0.088mm, 6% high-purity mullite <0.088mm, and 6% silicon nitride with a particle size of 325 mesh;

[0047] In addition, sulfite pulp waste liquor, accounting for 3.5% of the total weight of all the above raw materials, is added as a binder.

[0048] In Comparative Example 1, no high-purity mullite of 1-0 mm was added to the raw material composition.

[0049] Comparative Example 2:

[0050] A type of corundum-mullite-silicon nitride brick for waste incinerators, expressed as a weight percentage, has the following raw material composition:

[0051] Aggregate composition: 8% dense corundum of 5-3mm, 34% dense corundum of 3-1mm, 16% dense corundum of 1-0mm and 10% high-purity mullite of 1-0mm.

[0052] Powder composition: 20% dense corundum <0.088mm, 6% high-purity mullite <0.088mm, and 6% silicon nitride with a particle size of 325 mesh;

[0053] In addition, sulfite pulp waste liquor, accounting for 3.5% of the total weight of all the above raw materials, is added as a binder.

[0054] In Comparative Example 2, no 3-1 mm of high-purity mullite was added to the raw material composition.

[0055] Comparative Example 3:

[0056] A type of corundum-mullite-silicon nitride brick for waste incinerators, expressed as a weight percentage, has the following raw material composition:

[0057] Aggregate composition: 8% dense corundum of 5-3mm, 20% dense corundum of 3-1mm, 16% dense corundum of 1-0mm, 14% high-purity mullite of 3-1mm and 10% high-purity mullite of 1-0mm.

[0058] Powder composition: 26% dense corundum <0.088mm and 6% high-purity mullite <0.088mm;

[0059] In addition, sulfite pulp waste liquor, accounting for 3.5% of the total weight of all the above raw materials, is added as a binder.

[0060] In Comparative Example 3, no 325-mesh silicon nitride was added to the raw material composition.

[0061] The preparation methods of the corundum mullite silicon nitride bricks for waste incinerators described in Comparative Examples 1 to 3 are the same as the preparation methods in Examples 1 to 4 of the present invention.

[0062] Table 2 shows a detailed comparison of the relevant performance data of the products prepared in Examples 1-4 and Comparative Examples 1-3 of this invention.

[0063] Table 2. Relevant performance data of the products prepared in Examples 1-4 and Comparative Examples 1-3 of the present invention.

[0064]

[0065] As can be seen from the relevant performance test data of the corundum mullite silicon nitride products prepared by the embodiments and comparative examples of the present invention in Table 2, the corundum mullite silicon nitride bricks prepared by the technical solution of the present invention have low bulk density, high strength, good wear resistance, excellent erosion resistance, good thermal shock stability, and are environmentally friendly and energy-saving, which can fully meet the different environmental requirements of waste incinerators.

Claims

1. A corundum-mullite silicon nitride brick for a waste incinerator, characterized in that, Expressed by weight percentage, the corundum mullite silicon nitride brick is mainly composed of aggregate and powder. The aggregate consists of 6-10% dense corundum of 5-3 mm, 18-22% dense corundum of 3-1 mm, 14-18% dense corundum of 1-0 mm, 12-16% high-purity mullite of 3-1 mm, and 8-12% high-purity mullite of 1-0 mm. The powder consists of 18-22% dense corundum of <0.088 mm, 4-8% high-purity mullite of <0.088 mm, and 4-8% silicon nitride with a particle size of 325 mesh. In addition, a binder accounting for 3-4% of the total weight of aggregate and powder is added.

2. The corundum-mullite silicon nitride brick for waste incinerators according to claim 1, characterized in that: The dense corundum contains ≥98.5% Al2O3 and ≤0.5% SiO2.

3. The corundum mullite silicon nitride brick for waste incinerators according to claim 1, characterized in that: The high-purity mullite contains ≥70% Al2O3 and ≤28% SiO2.

4. The corundum mullite silicon nitride brick for waste incinerators according to claim 1, characterized in that: The silicon nitride contains ≥99% Si3N4.

5. The corundum-mullite silicon nitride brick for waste incinerators according to claim 1, characterized in that: The binder is sulfite pulp waste liquor with a specific gravity of 1.24 to 1.

28.

6. A method for preparing corundum mullite silicon nitride bricks for waste incinerators, characterized in that, The preparation method includes the following steps: a. Mixing: First, weigh various raw materials according to the proportion of the corundum mullite silicon nitride brick described in claim 1. Add the weighed aggregate to the mixer and mix. Then add the binder and continue mixing. Then add the powder and continue mixing to obtain the mixed material. b. Molding: The resulting mixture is pressed into brick blanks using a press. c. Drying: Dry the obtained brick blanks; d. The dried brick blanks are placed in a high-temperature tunnel kiln for firing, and then cooled to obtain the product, corundum mullite silicon nitride bricks for waste incinerators.

7. The method for preparing corundum mullite silicon nitride bricks for waste incinerators according to claim 6, characterized in that: During the pressing process described in step b, the pressure of the press is controlled at 630–1000 tons; the bulk density of the resulting brick blank is controlled at 2.92–2.95 g / cm³. 3 .

8. The method for preparing corundum mullite silicon nitride bricks for waste incinerators according to claim 6, characterized in that: In step c, a dryer is used for drying, and the temperature of the dryer is controlled at 110-130℃. After drying, the residual moisture in the brick blank is ≤0.5%.

9. The method for preparing corundum mullite silicon nitride bricks for waste incinerators according to claim 6, characterized in that: During the firing process described in step d, the firing temperature is 1600–1630°C, and the holding time at the firing temperature is 4–6 hours.

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