High-strength refractory brick for waste incinerator and preparation method thereof

Abstract

The application relates to the technical field of firebrick production, and discloses a high-strength firebrick for a waste incinerator and a preparation method thereof, which comprises the following raw materials in parts by mass: fly ash 32-45 parts, diatomite 18-30 parts, modified aluminum silicate fiber 6-10 parts, scale graphite powder loaded with nano zirconium silicate 20-30 parts, metal oxide 7-10 parts and auxiliary materials 1-3 parts. The fly ash and the diatomite are used as raw materials, and the modified aluminum silicate fiber, the scale graphite powder loaded with nano zirconium silicate, the metal oxide and the auxiliary materials are compounded, so that the prepared firebrick has high mechanical strength, fire resistance and oxidation resistance; the product quality of the firebrick is improved; the firebrick is prevented from cracking during the waste incineration process; and the service life of the firebrick is prolonged.

Description

Technical Field

[0001] This invention relates to the field of refractory brick production technology, specifically to a high-strength refractory brick for waste incinerators and its preparation method. Background Technology

[0002] Waste incineration is suitable for municipal solid waste, medical waste, and general industrial waste. Compared with landfill and composting, waste incineration saves more land and does not cause pollution to surface water and groundwater. Waste incinerators are usually made of refractory bricks, which are refractory materials made by firing refractory clay or other refractory raw materials. They are light yellow or brown and can withstand high temperatures of 1580-1770℃.

[0003] Refractory bricks prepared by mixing fly ash, diatomaceous earth, fillers, and additives, followed by pressing, drying, and calcination, exhibit strong thermal stability, good slag resistance, low cost, and excellent mechanical properties. However, these refractory bricks suffer from insufficient strength and high-temperature resistance during use, making them prone to cracking. Adding aluminosilicate fibers to the refractory bricks can help them bear stress and improve the mechanical strength of refractory bricks used in waste incinerators. However, during the high-temperature calcination of aluminosilicate fibers, mullite and cristobalite are easily precipitated, leading to embrittlement of the aluminosilicate fibers and affecting the strength of the refractory bricks. Summary of the Invention

[0004] This invention provides a high-strength refractory brick for waste incinerators and its preparation method, which solves the problems of insufficient strength and high-temperature resistance, and easy cracking of refractory bricks during use.

[0005] The technical solution of the present invention:

[0006] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 32-45 parts fly ash, 18-30 parts diatomaceous earth, 6-10 parts modified aluminosilicate fiber, 20-30 parts flake graphite powder loaded with nano-zirconium silicate, 7-10 parts metal oxide and 1-3 parts auxiliary materials.

[0007] Among them, the modified aluminum silicate fiber is obtained by forming a silica coating layer on the surface of aluminum silicate fiber and then reacting it with cobalt nitrate hexahydrate, ammonium fluoride and urea;

[0008] The nano-zirconium silicate-loaded flake graphite powder is obtained by coating the surface of the flake graphite powder with nano-zirconium silicate through carboxymethyl cellulose.

[0009] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0010] S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide. Stir and mix at 500-800 r / min for 20-40 min. Add auxiliary materials and continue stirring and mixing for 20-40 min to obtain a mixture.

[0011] S2. The mixture is pressed, dried, calcined, and then cooled to room temperature to obtain high-strength refractory bricks.

[0012] Furthermore, in step S2, the pressing pressure is 30-50 MPa; the drying temperature is 80-100℃; and the drying time is 10-12 h.

[0013] Furthermore, in step S2, the calcination temperature is 1200-1300℃ and the calcination time is 6-8h.

[0014] Furthermore, the density of fly ash is 1.8-2 g / cm³. 3 The magnesium oxide content in fly ash is 0.5-1%.

[0015] Furthermore, diatomaceous earth contains 78-85% silicon dioxide and 0.3-0.7% iron oxide.

[0016] Furthermore, the metal oxide is selected from any one of aluminum oxide, calcium oxide, and magnesium oxide.

[0017] Furthermore, the auxiliary material is a mixture of binder and water in a mass ratio of (1-2):(5-10).

[0018] Furthermore, the binder is selected from aluminum phosphate or aluminum hydroxide.

[0019] Furthermore, the modified aluminosilicate fibers are specifically prepared by the following steps:

[0020] A1. Add aluminum silicate fiber to ethanol and deionized water, sonicate, add tetraethyl orthosilicate and sulfuric acid aqueous solution, stir and react at 45-55℃ for 2-5 hours, filter, wash and dry to obtain pretreated aluminum silicate fiber.

[0021] A2. Cobalt nitrate hexahydrate, ammonium fluoride and urea are added to deionized water and stirred evenly. Pretreated aluminosilicate fibers are added and stirred. The mixture is stirred and reacted at 120-130℃ for 3-5 hours. The mixture is cooled to room temperature, the solid is collected, washed and dried, and calcined at 850-950℃ for 2-4 hours. The mixture is then cooled to room temperature to obtain modified aluminosilicate fibers.

[0022] Furthermore, during the A1 reaction process described above, the hydroxyl groups generated by the hydrolysis of tetraethyl orthosilicate can chemically bond with the hydroxyl groups on the surface of aluminum silicate fibers, thereby coating the surface of aluminum silicate fibers with silica produced by the hydrolysis of tetraethyl orthosilicate, resulting in pretreated aluminum silicate fibers.

[0023] Furthermore, in the A2 reaction process described above, cobalt nitrate hexahydrate undergoes a hydrothermal reaction under the catalysis of ammonium fluoride and urea, resulting in the dehydroxylation and decarbonization of cobalt nitrate hexahydrate to form cobalt oxide. Calcination at 900°C allows the formed cobalt oxide to react with the silica on the surface of the pretreated aluminosilicate fiber, forming a cobalt silicate layer on the surface of the pretreated aluminosilicate fiber through silicon-oxygen-cobalt bonds, thus obtaining modified aluminosilicate fiber.

[0024] Further, in step A1, the mass ratio of aluminum silicate fiber, ethanol, deionized water, tetraethyl orthosilicate and sulfuric acid aqueous solution is (3.5-4.5):(35-45):(15-25):(2-3):(0.4-0.8).

[0025] Further, in step A2, the mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water and pretreated aluminosilicate fiber is (0.4-0.6):(0.1-0.2):(0.2-0.4):(45-55):(2-2.6).

[0026] Furthermore, the aluminum silicate fiber has a diameter of 2-4.5 μm and a length of 10-20 mm.

[0027] Furthermore, the flake graphite powder supported on nano-zirconium silicate is prepared by the following steps:

[0028] B1. Add carboxymethyl cellulose to deionized water, stir evenly, add flake graphite powder, heat to 40-60℃, stir at 800-1000r / min for 5-10min, filter, wash, and dry to obtain pretreated flake graphite powder.

[0029] B2. Add the pretreated flake graphite powder and nano-zirconium silicate to deionized water, stir and mix at 40-60℃ for 20-30 min, filter, wash and dry to obtain flake graphite powder loaded with nano-zirconium silicate.

[0030] Furthermore, during the B1 reaction process described above, carboxymethyl cellulose dissolves in deionized water and has excellent adhesive properties, enabling it to adhere to the surface of flake graphite powder and impart polar functional groups to the flake graphite powder, thus obtaining pretreated flake graphite powder.

[0031] Furthermore, during the B2 reaction process described above, the pretreated flake graphite powder contains a large number of carboxyl functional groups on its surface and has adhesive properties, which can adhere nano-zirconium silicate to the surface of the pretreated flake graphite powder, thus obtaining flake graphite powder loaded with nano-zirconium silicate.

[0032] Further, in step B1, the mass ratio of carboxymethyl cellulose, deionized water and flake graphite powder is (1-2):(45-55):(2.1-2.5).

[0033] Further, in step B2, the mass ratio of pretreated flake graphite powder, nano-zirconium silicate and deionized water is (1.5-2.5):(0.5-1.5):(45-55).

[0034] Furthermore, the particle size of the flake graphite powder is 25-35 μm.

[0035] Furthermore, the nano-zirconium silicate has a particle size of 50-100 nm.

[0036] The present invention has the following beneficial effects:

[0037] (1) In the technical solution of the present invention, a silica coating layer is formed on the surface of aluminosilicate fiber, which can provide a large amount of silica on the surface of aluminosilicate fiber, which is beneficial to the synthesis of cobalt silicate on the surface of aluminosilicate fiber. In the process of synthesizing cobalt silicate, the silica provided participates in the synthesis reaction of cobalt silicate, which can avoid excessive consumption of silica in aluminosilicate fiber, resulting in a decrease in the mechanical properties of aluminosilicate fiber. In addition, during the sintering process of refractory brick, the silica on the surface can delay the diffusion reaction of alumina and silica inside the fiber, reduce high-temperature crystallization, and extend service life.

[0038] (2) In the technical solution of the present invention, pretreated aluminosilicate fibers are mixed and reacted with cobalt nitrate hexahydrate, ammonium fluoride and urea to synthesize a cobalt silicate layer on the surface of the pretreated aluminosilicate fibers, thereby obtaining modified aluminosilicate fibers. On the one hand, the melting point of the synthesized cobalt silicate is higher than that of the aluminosilicate fibers, which improves the high temperature resistance of the aluminosilicate fibers and avoids the easy precipitation of mullite and cristobalite during the high temperature calcination process, which leads to the embrittlement of the aluminosilicate fibers. Moreover, the cobalt silicate layer and a small amount of silica layer on the surface of the aluminosilicate fibers can block oxygen from directly contacting the fibers, reduce high temperature oxidation, and maintain the high temperature stability of the aluminosilicate fibers. On the other hand, the excellent aspect ratio of the aluminosilicate fibers, which are uniformly dispersed in the refractory bricks, plays a role in bearing stress and significantly improves the mechanical strength of the refractory bricks used in waste incinerators.

[0039] (3) In the technical solution of the present invention, nano-zirconium silicate is coated on the surface of flake graphite powder with carboxymethyl cellulose to obtain flake graphite powder loaded with nano-zirconium silicate. On the one hand, when nano-zirconium silicate is added to refractory bricks and sintered at high temperature, it can react with carbon elements in flake graphite powder to produce zirconium carbide phase, which fills the gaps in refractory bricks, improves the density of refractory bricks, and enhances the mechanical strength of refractory bricks. On the other hand, nano-zirconium silicate is loaded onto the surface of flake graphite powder, increasing the surface roughness of flake graphite powder and increasing the contact area between flake graphite powder loaded with nano-zirconium silicate and refractory brick matrix. In addition, during the high-temperature sintering process, some of the flake graphite powder generates free graphite phase that covers the surface of refractory bricks, improving the oxidation resistance of refractory bricks and preventing the alkaline environment during waste incineration from easily corroding weather-resistant bricks and affecting the performance of refractory bricks. Furthermore, the random distribution of flake graphite powder in refractory bricks can absorb external stress and enhance the mechanical properties of refractory bricks.

[0040] (4) In the technical solution of the present invention, fly ash and diatomaceous earth are used as raw materials, and modified aluminum silicate fiber, flake graphite powder loaded with nano zirconium silicate, metal oxide and auxiliary materials are compounded to prepare refractory bricks with high mechanical strength, fire resistance and oxidation resistance, which improves the product quality of refractory bricks, avoids cracking of refractory bricks during waste incineration and extends the service life of refractory bricks. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0043] The density of fly ash is 1.9 g / cm³. 3 The magnesium oxide content in fly ash is 0.8%.

[0044] Diatomaceous earth contains 82% silicon dioxide and 0.5% iron oxide.

[0045] The metal oxide is aluminum oxide with a particle size of 0.8 μm.

[0046] The auxiliary material is a mixture of binder and water in a mass ratio of 1.5:8, and the binder is aluminum phosphate.

[0047] The aluminum silicate fiber has a diameter of 3μm and a length of 15mm.

[0048] The flake graphite powder has a particle size of 30μm, is branded as Malin, and was purchased from Malin Mineral Products Processing Plant in Lingshou County.

[0049] The nano-zirconium silicate has a particle size of 80 nm.

[0050] Example 1

[0051] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 32 parts fly ash, 18 parts diatomaceous earth, 6 parts modified aluminosilicate fiber, 20 parts flake graphite powder loaded with nano-zirconium silicate, 7 parts metal oxide and 1 part auxiliary material.

[0052] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0053] S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide, stir at 500 r / min for 20 min, add auxiliary materials, and continue stirring for 20 min to obtain a mixture;

[0054] S2. The mixture is pressed into shape at 30MPa, dried at 80℃ for 10h, calcined at 1200℃ for 6h, and cooled to room temperature to obtain high-strength refractory bricks.

[0055] Modified aluminosilicate fibers are prepared by the following steps:

[0056] A1. Alumina silicate fibers were added to ethanol and deionized water and sonicated at 40 kHz for 1 hour. Then, tetraethyl orthosilicate and a 2.5% sulfuric acid aqueous solution were added, and the mixture was stirred and reacted at 45°C for 2 hours. After filtration, the mixture was washed three times with deionized water and three times with ethanol, and then dried in an oven at 70°C for 10 minutes to obtain pretreated alumina silicate fibers. The mass ratio of alumina silicate fibers, ethanol, deionized water, tetraethyl orthosilicate, and sulfuric acid aqueous solution was 3.5:35:15:2:0.4.

[0057] A2. Cobalt nitrate hexahydrate, ammonium fluoride, and urea were added to deionized water and stirred until homogeneous. Pretreated aluminosilicate fibers were then added, and the mixture was stirred at 500 r / min for 30 min. The mixture was then reacted at 120 °C for 3 h, cooled to room temperature, and the solid was collected. The solid was washed three times with deionized water, dried in a 60 °C oven for 10 min, placed in a muffle furnace, and calcined at 850 °C for 2 h. The mixture was then cooled to room temperature to obtain modified aluminosilicate fibers. The mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water, and pretreated aluminosilicate fibers was 0.4:0.1:0.2:45:2.

[0058] The flake graphite powder loaded with nano-zirconium silicate is prepared by the following steps:

[0059] B1. Add carboxymethyl cellulose to deionized water, stir evenly, add flake graphite powder, heat to 40℃, stir at 800 r / min for 5 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain pretreated flake graphite powder; the mass ratio of carboxymethyl cellulose, deionized water and flake graphite powder is 1:45:2.1.

[0060] B2. Add pretreated flake graphite powder and nano-zirconium silicate to deionized water, stir and mix at 40℃ for 20 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain flake graphite powder loaded with nano-zirconium silicate; the mass ratio of pretreated flake graphite powder, nano-zirconium silicate and deionized water is 1.5:0.5:45.

[0061] Example 2

[0062] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 40 parts fly ash, 24 parts diatomaceous earth, 8 parts modified aluminosilicate fiber, 25 parts flake graphite powder loaded with nano-zirconium silicate, 9 parts metal oxide and 2 parts auxiliary materials.

[0063] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0064] S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide, stir at 700 r / min for 30 min, add auxiliary materials, and continue stirring for 30 min to obtain a mixture;

[0065] S2. The mixture is pressed into shape at 40MPa, dried at 90℃ for 11h, calcined at 1250℃ for 7h, and cooled to room temperature to obtain high-strength refractory bricks.

[0066] Modified aluminosilicate fibers are prepared by the following steps:

[0067] A1. Alumina silicate fibers were added to ethanol and deionized water and sonicated at 40 kHz for 1 hour. Then, tetraethyl orthosilicate and a 2.5% sulfuric acid aqueous solution were added, and the mixture was stirred and reacted at 50°C for 3 hours. After filtration, the mixture was washed three times with deionized water and three times with ethanol, and then dried in an oven at 70°C for 10 minutes to obtain pretreated alumina silicate fibers. The mass ratio of alumina silicate fibers, ethanol, deionized water, tetraethyl orthosilicate, and sulfuric acid aqueous solution was 4:40:20:2.5:0.6.

[0068] A2. Cobalt nitrate hexahydrate, ammonium fluoride, and urea were added to deionized water and stirred until homogeneous. Pretreated aluminosilicate fibers were then added, and the mixture was stirred at 500 r / min for 30 min. The mixture was then reacted at 125 °C for 4 h, cooled to room temperature, and the solid was collected. The solid was washed three times with deionized water, dried in an oven at 60 °C for 10 min, placed in a muffle furnace, and calcined at 900 °C for 3 h. The mixture was then cooled to room temperature to obtain modified aluminosilicate fibers. The mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water, and pretreated aluminosilicate fibers was 0.5:0.15:0.3:50:2.3.

[0069] The flake graphite powder loaded with nano-zirconium silicate is prepared by the following steps:

[0070] B1. Add carboxymethyl cellulose to deionized water, stir evenly, add flake graphite powder, heat to 50℃, stir at 900 r / min for 8 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain pretreated flake graphite powder; the mass ratio of carboxymethyl cellulose, deionized water and flake graphite powder is 1.5:50:2.3.

[0071] B2. Add pretreated flake graphite powder and nano-zirconium silicate to deionized water, stir and mix at 50℃ for 25 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain flake graphite powder loaded with nano-zirconium silicate; the mass ratio of pretreated flake graphite powder, nano-zirconium silicate and deionized water is 2:1:50.

[0072] Example 3

[0073] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 45 parts fly ash, 30 parts diatomaceous earth, 10 parts modified aluminosilicate fiber, 30 parts flake graphite powder loaded with nano-zirconium silicate, 10 parts metal oxide and 3 parts auxiliary materials.

[0074] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0075] S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide, stir at 800 r / min for 40 min, add auxiliary materials, and continue stirring for 40 min to obtain a mixture;

[0076] S2. The mixture is pressed into shape at 50 MPa, dried at 100℃ for 12 h, calcined at 1300℃ for 8 h, and cooled to room temperature to obtain high-strength refractory bricks.

[0077] Modified aluminosilicate fibers are prepared by the following steps:

[0078] A1. Alumina silicate fibers were added to ethanol and deionized water and sonicated at 40 kHz for 1 hour. Then, tetraethyl orthosilicate and a 2.5% sulfuric acid aqueous solution were added, and the mixture was stirred and reacted at 55°C for 5 hours. After filtration, the mixture was washed three times with deionized water and three times with ethanol, and then dried in an oven at 70°C for 10 minutes to obtain pretreated alumina silicate fibers. The mass ratio of alumina silicate fibers, ethanol, deionized water, tetraethyl orthosilicate, and sulfuric acid aqueous solution was 4.5:55:25:3:0.8.

[0079] A2. Cobalt nitrate hexahydrate, ammonium fluoride, and urea were added to deionized water and stirred until homogeneous. Pretreated aluminosilicate fibers were then added, and the mixture was stirred at 500 r / min for 30 min. The mixture was then reacted at 130 °C for 5 h, cooled to room temperature, and the solid was collected. The solid was washed three times with deionized water, dried in an oven at 60 °C for 10 min, placed in a muffle furnace, and calcined at 950 °C for 4 h. The mixture was then cooled to room temperature to obtain modified aluminosilicate fibers. The mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water, and pretreated aluminosilicate fibers was 0.6:0.2:0.4:55:2.6.

[0080] The flake graphite powder loaded with nano-zirconium silicate is prepared by the following steps:

[0081] B1. Add carboxymethyl cellulose to deionized water, stir evenly, add flake graphite powder, heat to 60℃, stir at 1000 r / min for 10 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain pretreated flake graphite powder; the mass ratio of carboxymethyl cellulose, deionized water and flake graphite powder is 2:55:2.5;

[0082] B2. Add pretreated flake graphite powder and nano-zirconium silicate to deionized water, stir and mix at 60℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain flake graphite powder loaded with nano-zirconium silicate; the mass ratio of pretreated flake graphite powder, nano-zirconium silicate and deionized water is 2.5:1.5:55.

[0083] Comparative Example 1

[0084] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 45 parts fly ash, 30 parts diatomaceous earth, 10 parts modified aluminosilicate fiber, 30 parts flake graphite powder loaded with nano-zirconium silicate, 10 parts metal oxide and 3 parts auxiliary materials.

[0085] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0086] S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide, stir at 800 r / min for 40 min, add auxiliary materials, and continue stirring for 40 min to obtain a mixture;

[0087] S2. The mixture is pressed into shape at 50 MPa, dried at 100℃ for 12 h, calcined at 1300℃ for 8 h, and cooled to room temperature to obtain high-strength refractory bricks.

[0088] Modified aluminosilicate fibers are prepared by the following steps:

[0089] Cobalt nitrate hexahydrate, ammonium fluoride, and urea were added to deionized water and stirred until homogeneous. Aluminum silicate fibers were then added, and the mixture was stirred at 500 r / min for 30 min. The reaction was carried out at 130 °C for 5 h, cooled to room temperature, and the solid was collected. The solid was washed three times with deionized water, dried in an oven at 60 °C for 10 min, placed in a muffle furnace, and calcined at 950 °C for 4 h. After cooling to room temperature, modified aluminum silicate fibers were obtained. The mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water, and aluminum silicate fibers was 0.6:0.2:0.4:55:2.6.

[0090] The flake graphite powder loaded with nano-zirconium silicate is prepared by the following steps:

[0091] B1. Add carboxymethyl cellulose to deionized water, stir evenly, add flake graphite powder, heat to 60℃, stir at 1000 r / min for 10 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain pretreated flake graphite powder; the mass ratio of carboxymethyl cellulose, deionized water and flake graphite powder is 2:55:2.5;

[0092] B2. Add pretreated flake graphite powder and nano-zirconium silicate to deionized water, stir and mix at 60℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain flake graphite powder loaded with nano-zirconium silicate; the mass ratio of pretreated flake graphite powder, nano-zirconium silicate and deionized water is 2.5:1.5:55.

[0093] Comparative Example 2

[0094] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 45 parts fly ash, 30 parts diatomaceous earth, 10 parts pretreated aluminosilicate fiber, 30 parts flake graphite powder loaded with nano-zirconium silicate, 10 parts metal oxide and 3 parts auxiliary materials.

[0095] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0096] S1. Mix fly ash, diatomaceous earth, pretreated aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide. Stir and mix at 800 r / min for 40 min. Add auxiliary materials and continue stirring and mixing for 40 min to obtain a mixture.

[0097] S2. The mixture is pressed into shape at 50 MPa, dried at 100℃ for 12 h, calcined at 1300℃ for 8 h, and cooled to room temperature to obtain high-strength refractory bricks.

[0098] Pretreated aluminosilicate fibers are prepared by the following steps:

[0099] Aluminosilicate fibers were added to ethanol and deionized water and sonicated at 40 kHz for 1 hour. Then, tetraethyl orthosilicate and a 2.5% sulfuric acid aqueous solution were added, and the mixture was stirred and reacted at 55°C for 5 hours. After filtration, the mixture was washed three times with deionized water and three times with ethanol, and then dried in an oven at 70°C for 10 minutes to obtain pretreated aluminosilicate fibers. The mass ratio of aluminosilicate fibers, ethanol, deionized water, tetraethyl orthosilicate, and sulfuric acid aqueous solution was 4.5:55:25:3:0.8.

[0100] The flake graphite powder loaded with nano-zirconium silicate is prepared by the following steps:

[0101] B1. Add carboxymethyl cellulose to deionized water, stir evenly, add flake graphite powder, heat to 60℃, stir at 1000 r / min for 10 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain pretreated flake graphite powder; the mass ratio of carboxymethyl cellulose, deionized water and flake graphite powder is 2:55:2.5;

[0102] B2. Add pretreated flake graphite powder and nano-zirconium silicate to deionized water, stir and mix at 60℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 60℃ for 10 min to obtain flake graphite powder loaded with nano-zirconium silicate; the mass ratio of pretreated flake graphite powder, nano-zirconium silicate and deionized water is 2.5:1.5:55.

[0103] Comparative Example 3

[0104] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 45 parts fly ash, 30 parts diatomaceous earth, 10 parts modified aluminosilicate fiber, 30 parts flake graphite powder loaded with nano-zirconium silicate, 10 parts metal oxide and 3 parts auxiliary materials.

[0105] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0106] S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide, stir at 800 r / min for 40 min, add auxiliary materials, and continue stirring for 40 min to obtain a mixture;

[0107] S2. The mixture is pressed into shape at 50 MPa, dried at 100℃ for 12 h, calcined at 1300℃ for 8 h, and cooled to room temperature to obtain high-strength refractory bricks.

[0108] Modified aluminosilicate fibers are prepared by the following steps:

[0109] A1. Alumina silicate fibers were added to ethanol and deionized water and sonicated at 40 kHz for 1 hour. Then, tetraethyl orthosilicate and a 2.5% sulfuric acid aqueous solution were added, and the mixture was stirred and reacted at 55°C for 5 hours. After filtration, the mixture was washed three times with deionized water and three times with ethanol, and then dried in an oven at 70°C for 10 minutes to obtain pretreated alumina silicate fibers. The mass ratio of alumina silicate fibers, ethanol, deionized water, tetraethyl orthosilicate, and sulfuric acid aqueous solution was 4.5:55:25:3:0.8.

[0110] A2. Cobalt nitrate hexahydrate, ammonium fluoride, and urea were added to deionized water and stirred until homogeneous. Pretreated aluminosilicate fibers were then added, and the mixture was stirred at 500 r / min for 30 min. The mixture was then reacted at 130 °C for 5 h, cooled to room temperature, and the solid was collected. The solid was washed three times with deionized water, dried in an oven at 60 °C for 10 min, placed in a muffle furnace, and calcined at 950 °C for 4 h. The mixture was then cooled to room temperature to obtain modified aluminosilicate fibers. The mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water, and pretreated aluminosilicate fibers was 0.6:0.2:0.4:55:2.6.

[0111] The flake graphite powder loaded with nano-zirconium silicate is prepared by the following steps:

[0112] Flake graphite powder and nano-zirconium silicate were added to deionized water and stirred at 60°C for 30 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 60°C for 10 min to obtain flake graphite powder loaded with nano-zirconium silicate. The mass ratio of flake graphite powder, nano-zirconium silicate and deionized water was 2.5:1.5:55.

[0113] Comparative Example 4

[0114] A high-strength refractory brick for a waste incinerator comprises the following raw materials in parts by weight: 45 parts fly ash, 30 parts diatomaceous earth, 10 parts modified aluminosilicate fiber, 30 parts pretreated flake graphite powder, 10 parts metal oxide and 3 parts auxiliary materials.

[0115] A method for preparing high-strength refractory bricks for waste incinerators includes the following preparation steps:

[0116] S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, pretreated flake graphite powder, and metal oxide, stir at 800 r / min for 40 min, add auxiliary materials, and continue stirring for 40 min to obtain a mixture;

[0117] S2. The mixture is pressed into shape at 50 MPa, dried at 100℃ for 12 h, calcined at 1300℃ for 8 h, and cooled to room temperature to obtain high-strength refractory bricks.

[0118] Modified aluminosilicate fibers are prepared by the following steps:

[0119] A1. Alumina silicate fibers were added to ethanol and deionized water and sonicated at 40 kHz for 1 hour. Then, tetraethyl orthosilicate and a 2.5% sulfuric acid aqueous solution were added, and the mixture was stirred and reacted at 55°C for 5 hours. After filtration, the mixture was washed three times with deionized water and three times with ethanol, and then dried in an oven at 70°C for 10 minutes to obtain pretreated alumina silicate fibers. The mass ratio of alumina silicate fibers, ethanol, deionized water, tetraethyl orthosilicate, and sulfuric acid aqueous solution was 4.5:55:25:3:0.8.

[0120] A2. Cobalt nitrate hexahydrate, ammonium fluoride, and urea were added to deionized water and stirred until homogeneous. Pretreated aluminosilicate fibers were then added, and the mixture was stirred at 500 r / min for 30 min. The mixture was then reacted at 130 °C for 5 h, cooled to room temperature, and the solid was collected. The solid was washed three times with deionized water, dried in an oven at 60 °C for 10 min, placed in a muffle furnace, and calcined at 950 °C for 4 h. The mixture was then cooled to room temperature to obtain modified aluminosilicate fibers. The mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water, and pretreated aluminosilicate fibers was 0.6:0.2:0.4:55:2.6.

[0121] The pretreated flake graphite powder is prepared by the following steps:

[0122] Carboxymethyl cellulose was added to deionized water and stirred evenly. Flake graphite powder was then added, and the mixture was heated to 60°C and stirred at 1000 r / min for 10 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 60°C for 10 min to obtain pretreated flake graphite powder. The mass ratio of carboxymethyl cellulose, deionized water, and flake graphite powder was 2:55:2.5.

[0123] The performance of the high-strength refractory bricks prepared in Examples 1-3 and Comparative Examples 1-4 was then tested.

[0124] Compressive strength test: The compressive strength of the high-strength refractory bricks prepared above was tested in accordance with GB / T5072-2008 "Test method for compressive strength of refractory materials at room temperature".

[0125] Flexural strength test: The room temperature flexural strength of the high-strength refractory bricks prepared above was tested according to GB / T3001-2017 Test method for flexural strength of refractory materials at room temperature.

[0126] High-temperature flexural strength test: According to GB / T3002-2017 Test method for high-temperature flexural strength of refractory materials, the high-strength refractory bricks prepared above were treated at 1400℃ for 30 minutes, and the high-temperature flexural strength of the refractory bricks was tested.

[0127] Antioxidant test: The high-strength refractory bricks prepared above (dimensions 240×115×50mm, thickness D0=50mm) were treated at 1250℃ for 5h, cooled to room temperature, and the thickness (D1) of the refractory bricks after heat treatment was measured with vernier calipers. The surface oxidation thickness was recorded as D1-D0.

[0128] As shown in Table 1 below.

[0129] Table 1. Performance testing of high-strength refractory bricks prepared in Examples 1-3 and Comparative Examples 1-4

[0130]

[0131] As can be seen from the data in Table 1, the high-strength refractory bricks prepared in Examples 1-3 have good resistance to high-temperature oxidation and mechanical strength.

[0132] In Comparative Example 1, the modified aluminosilicate fibers prepared by replacing the pretreated aluminosilicate fibers with aluminosilicate fibers were added to the high-strength refractory bricks, resulting in a decrease in their mechanical properties. This demonstrates that the formation of a silica coating layer on the surface of the aluminosilicate fibers can prevent excessive consumption of silica in the aluminosilicate fibers during the synthesis of cobalt silica, thus avoiding a decrease in the mechanical properties of the aluminosilicate fibers. Furthermore, during the sintering process of the refractory bricks, the silica on the surface can delay the diffusion reaction of alumina and silica inside the fibers, reduce high-temperature crystallization, and extend the service life.

[0133] In Comparative Example 2, when modified aluminosilicate fibers were replaced with pretreated aluminosilicate fibers added to high-strength refractory bricks, their mechanical properties and oxidation resistance decreased. This demonstrates that synthesizing a cobalt silicate layer on the surface of pretreated aluminosilicate fibers improves their high-temperature resistance. Furthermore, the cobalt silicate layer and a small amount of silica layer on the surface of the aluminosilicate fibers can prevent oxygen from directly contacting the fibers, reduce high-temperature oxidation, maintain the high-temperature stability of the aluminosilicate fibers, and improve the mechanical properties of the high-strength refractory bricks.

[0134] In Comparative Example 3, when pretreated flake graphite powder was replaced with flake graphite powder loaded with nano-zirconium silicate, the mechanical properties of the high-strength refractory brick decreased. This demonstrates that carboxymethyl cellulose adheres to the surface of the flake graphite powder, imparting polar functional groups to it, which is beneficial for the adhesion of nano-zirconium silicate to the surface of the flake graphite powder. This allows the nano-zirconium silicate to be evenly distributed in the refractory brick through the flake graphite powder, thereby enhancing the mechanical strength of the refractory brick.

[0135] In Comparative Example 4, replacing the nano-zirconium silicate-loaded flake graphite powder with pretreated flake graphite powder and adding it to the high-strength refractory brick resulted in a decrease in its mechanical properties and oxidation resistance. This demonstrates that loading nano-zirconium silicate onto the surface of the flake graphite powder increases the surface roughness of the flake graphite powder, increases the contact area between the nano-zirconium silicate-loaded flake graphite powder and the refractory brick matrix, and improves the mechanical properties of the refractory brick. Furthermore, during the high-temperature sintering process, some of the flake graphite powder generates free graphite phase that covers the surface of the refractory brick, thereby improving the oxidation resistance of the refractory brick.

[0136] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0137] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A high-strength refractory brick for a waste incinerator, characterized in that, The raw materials include the following parts by weight: 32-45 parts fly ash, 18-30 parts diatomaceous earth, 6-10 parts modified aluminum silicate fiber, 20-30 parts flake graphite powder loaded with nano-zirconium silicate, 7-10 parts metal oxides, and 1-3 parts auxiliary materials. The modified aluminosilicate fiber is specifically prepared by the following steps: A1. Add aluminum silicate fiber to ethanol and deionized water, sonicate, then add tetraethyl orthosilicate and sulfuric acid aqueous solution, stir and react at 45-55℃ for 2-5 hours, filter, wash and dry to obtain pretreated aluminum silicate fiber; the mass ratio of aluminum silicate fiber, ethanol, deionized water, tetraethyl orthosilicate and sulfuric acid aqueous solution is (3.5-4.5):(35-45):(15-25):(2-3):(0.4-0.8); A2. Cobalt nitrate hexahydrate, ammonium fluoride and urea are added to deionized water and stirred evenly. Pretreated aluminosilicate fibers are added and stirred. The mixture is stirred and reacted at 120-130℃ for 3-5 hours. The mixture is cooled to room temperature, the solid is collected, washed and dried, and calcined at 850-950℃ for 2-4 hours. The mixture is then cooled to room temperature to obtain modified aluminosilicate fibers. The flake graphite powder loaded with nano-zirconium silicate is specifically prepared by the following steps: B1. Add carboxymethyl cellulose to deionized water, stir evenly, add flake graphite powder, heat to 40-60℃, stir at 800-1000 r / min for 5-10 min, filter, wash, and dry to obtain pretreated flake graphite powder; the mass ratio of carboxymethyl cellulose, deionized water and flake graphite powder is (1-2):(45-55):(2.1-2.5); B2. Add the pretreated flake graphite powder and nano-zirconium silicate to deionized water, stir and mix at 40-60℃ for 20-30 min, filter, wash and dry to obtain flake graphite powder loaded with nano-zirconium silicate.

2. The high-strength refractory brick for a waste incinerator according to claim 1, characterized in that, In step A2, the mass ratio of cobalt nitrate hexahydrate, ammonium fluoride, urea, deionized water and pretreated aluminosilicate fiber is (0.4-0.6):(0.1-0.2):(0.2-0.4):(45-55):(2-2.6).

3. The high-strength refractory brick for a waste incinerator according to claim 1, characterized in that, In step B2, the mass ratio of the pretreated flake graphite powder, nano zirconium silicate and deionized water is (1.5-2.5):(0.5-1.5):(45-55).

4. The high-strength refractory brick for a waste incinerator according to claim 1, characterized in that, The metal oxide is selected from any one of aluminum oxide, calcium oxide, and magnesium oxide.

5. The high-strength refractory brick for a waste incinerator according to claim 1, characterized in that, The auxiliary material is a mixture of binder and water in a mass ratio of (1-2):(5-10); The binder is selected from aluminum phosphate or aluminum hydroxide.

6. A method for preparing high-strength refractory bricks for waste incinerators as described in any one of claims 1-5, characterized in that, The preparation steps include the following: S1. Mix fly ash, diatomaceous earth, modified aluminum silicate fiber, flake graphite powder loaded with nano-zirconium silicate, and metal oxide. Stir and mix at 500-800 r / min for 20-40 min. Add auxiliary materials and continue stirring and mixing for 20-40 min to obtain a mixture. S2. The mixture is pressed, dried, calcined, and then cooled to room temperature to obtain high-strength refractory bricks.

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