Plastic refractory for prolonging shelf life of boiler and preparation method of plastic refractory

Abstract

The invention discloses a quality guarantee period-prolonging plastic refractory for boilers and a preparation method thereof, and belongs to the technical field of plastic materials. According to the key point of the technical scheme, the plastic refractory is prepared from the following raw materials in parts by weight: 40-50 parts of low-iron flint clay aggregate, 15-20 parts of low-iron flint clay fine powder, 4-10 parts of aluminum oxide micro powder, 4-8 parts of kyanite, 2-6 parts of Guangxi white mud, 2-6 parts of sodium bentonite, 2-5 parts of a composite quality guarantee agent and a binding agent accounting for 10-15% of the total weight of the raw materials, and the effect of prolonging the quality guarantee period of the plastic refractory is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic materials, and in particular to a plastic refractory for boilers with an extended shelf life and a preparation method thereof. Background Art

[0002] Plastic refractory is a traditional unshaped refractory material, which is a mud-like material formed by fully mixing materials, water or other binders according to a determined ratio. At the same time, this type of material maintains a certain viscosity and has excellent properties such as good plasticity, convenient construction, good spalling resistance and long service life. Therefore, refractory plastic refractory has advantages that other refractory materials cannot match in construction, with flexible construction, which can improve production efficiency. Moreover, refractory plastic refractory occupies a large market share in repair operations such as boilers, has excellent repair ability for local damages, and can improve efficiency and reduce production costs.

[0003] The existing plastic refractory will affect its use performance after long-term storage. The reason is that the binder in the plastic refractory reacts with some impurities contained in the raw materials of the plastic refractory during storage, mainly metallic iron in the form of simple substances, which reacts with the phosphate binder to generate hydrogen gas, resulting in the expansion of the plastic refractory, making the material loose and not conducive to maintaining the plasticity of the plastic refractory. Therefore, the shelf life of conventional phosphate plastic refractory is about 2 months, and some are even shorter, thus shortening the shelf life of the plastic refractory. For marine boilers, due to long-term operation outside and inconvenient maintenance, a longer shelf life of the plastic refractory is required, but the existing plastic refractory cannot meet this requirement. Summary of the Invention

[0004] In order to solve the problems in the prior art, the present invention provides a plastic refractory for boilers with an extended shelf life and a preparation method thereof, so as to improve the shelf life of the plastic refractory.

[0005] The first aspect of the present invention is to provide a plastic refractory for boilers with an extended shelf life, adopting the following technical solution: A plastic refractory for boilers with an extended shelf life, comprising the following raw materials in parts by weight: 40 - 50 parts of low-iron chamotte aggregate, 15 - 20 parts of low-iron chamotte fine powder, 4 - 10 parts of alumina micropowder, 4 - 8 parts of cyanite, 2 - 6 parts of Guangxi white clay, 2 - 6 parts of sodium-based bentonite, 2 - 5 parts of a composite shelf-life extender, and a binder accounting for 10 - 15% of the total weight of the above raw materials.

[0006] By adopting the above technical solution, through the screening of the calcined bauxite raw materials, the amount of iron in the calcined bauxite reacting with the binder is reduced. In addition, the combined use of the calcined bauxite aggregate and fine powder can improve the density and durability of the plastic mass; the combined action of alumina micro-powder and kyanite plays a role in enhancing the high-temperature resistance and chemical stability, effectively improving the thermal shock resistance and corrosion resistance of the plastic mass. At the same time, as a highly plastic clay, the combination of Guangxi white clay and sodium-based bentonite can not only improve the plasticity of the plastic mass, but also help to tightly combine the aggregate and other powders together to form a uniform and stable whole. Therefore, through the screening of the above raw materials and their combined use with the composite preservative, not only the shelf life of the plastic mass is extended, but also the plastic mass has good plasticity and compressive strength.

[0007] Preferably, the composite preservative is composed of an organic acid, a cellulose ether, a hydroxycarboxylate, a phosphate, and a polyphosphate in a weight ratio of (1.0 - 2.0):(0.3 - 0.5):(0.2 - 0.6):(0.2 - 0.5):(0.3 - 0.5).

[0008] By adopting the above technical solution, after the composite preservative is composed of an organic acid, a cellulose ether, a hydroxycarboxylate, a phosphate, and a polyphosphate, the shelf life of the plastic mass can be effectively extended, and the shelf life of the plastic mass can reach more than 6 months. The reason may be that: the organic acid can react with the iron in the calcined bauxite to reduce the amount of iron reacting with the binder, and the combination of the cellulose ether and the hydroxycarboxylate can form hydrogen bonds with the active groups such as hydroxyl groups on the surface of inorganic materials such as calcined bauxite and kyanite, thereby enhancing the cohesion and stability of the whole plastic mass material. The phosphate and the polyphosphate can not only form stable complexes by complexing with metal ions such as aluminum ions to enhance the structural stability of the whole plastic mass material, but also the polyphosphate can further enhance the corrosion resistance of the plastic mass material. Therefore, the selection of each raw material in the composite preservative in this application not only reduces the amount of iron reacting with the binder initially, but also ensures the structural stability of the whole plastic mass material, thereby extending the shelf life of the plastic mass material.

[0009] Preferably, the polyphosphate is at least one of sodium tripolyphosphate and sodium hexametaphosphate.

[0010] Preferably, the organic acid is at least one of oxalic acid and citric acid.

[0011] Preferably, the iron content in the low-iron calcined bauxite aggregate and the low-iron calcined bauxite fine powder is < 0.5%.

[0012] Preferably, the particle size of the low-iron calcined bauxite aggregate consists of two gradations of 3 - 1mm and 1 - 0mm, and the weight ratio of the 3 - 1mm low-iron calcined bauxite aggregate is 50%.

[0013] By adopting the above technical solution, when the low-iron chamotte aggregate consists of two kinds of aggregates with different gradations, it can not only prevent the plastic mass material from undergoing excessive deformation under external force, ensuring the overall stability of the plastic mass material, but also the finer chamotte aggregate fills the gaps between the coarse aggregates, improving the density and uniformity of the plastic mass material. At the same time, it also helps to improve the surface quality and processing performance of the plastic mass material, making the plastic mass easier to form and process.

[0014] Preferably, the particle size of the low-iron chamotte fine powder is 200 mesh.

[0015] Preferably, the particle size of the alumina micro-powder is 5 μm.

[0016] Preferably, the binder adopts aluminum dihydrogen phosphate.

[0017] The second aspect of the present invention is to provide a preparation method of the plastic mass for prolonging the shelf life of a boiler as described above, including the following steps: After uniformly mixing the low-iron chamotte aggregate, low-iron chamotte fine powder, alumina micro-powder, cyanite, Guangxi white clay, sodium-based bentonite and composite shelf-life preservative, add 30% of the total amount of the binder, stir and seal, and then add the remaining binder after aging for 24 - 48 h and mix and knead to obtain the plastic mass.

[0018] By adopting the above technical solution, in this application, after first uniformly mixing 30% of the binder with the low-iron chamotte aggregate, low-iron chamotte fine powder, alumina micro-powder, cyanite, Guangxi white clay, sodium-based bentonite and composite shelf-life preservative and sealing and aging, the impurity iron in the chamotte can react in advance, thus greatly reducing the amount of reaction between the impurity iron and the binder during the later storage process of the plastic mass, and fully ensuring that the shelf life of the plastic mass can be more than 6 months.

[0019] In summary, the present invention has the following beneficial effects: The combined use of each raw material in this application makes the structure of the plastic mass material stable, and the selection of low-iron chamotte and the addition of organic acids in the composite shelf-life preservative reduce the amount of reaction between impurity iron and the binder. At the same time, in the preparation of the plastic mass material in this application, the impurity iron is preferentially made to participate in the reaction during the aging period, thereby reducing the amount of reaction between the impurity iron and the binder during the storage process of the plastic mass, and effectively prolonging the shelf life of the plastic mass, so that the shelf life of the plastic mass can reach more than 6 months. Specific Embodiments

[0020] The following further elaborates on the present invention with reference to embodiments.

[0021] All raw materials used in this application can be obtained commercially without special instructions.

[0022] Any one of oxalic acid and citric acid can be used as the organic acid in the composite preservative to achieve basically the same effect. In the examples of this application, oxalic acid is taken as an example for illustration.

[0023] Any one of sodium tripolyphosphate and sodium hexametaphosphate can be used as the polyphosphate in the composite preservative to achieve basically the same effect. In the examples of this application, sodium tripolyphosphate is taken as an example for illustration.

[0024] Example 1 A preparation method of plastic mass for extending the shelf life of a boiler, comprising the following preparation steps: Pour 4 kg of low-iron pyrophyllite aggregate, 1.5 kg of low-iron pyrophyllite fine powder, 0.4 kg of alumina micropowder, 0.4 kg of kyanite, 0.2 kg of Guangxi white clay, 0.2 kg of sodium-based bentonite and 0.2 kg of composite preservative into a mixer and mix for 5 min, then add 30% of the total amount of aluminum dihydrogen phosphate (i.e., 0.207 kg), stir for 10 min, then discharge and seal. After aging for 24 h, pour it into a roller mixer and add the remaining 0.483 kg of aluminum dihydrogen phosphate, mix and stir, and then extrude to obtain the plastic mass; Among them, the iron content in both the low-iron pyrophyllite aggregate and the low-iron pyrophyllite fine powder is <0.5%; The low-iron pyrophyllite aggregate is composed of two particle size gradations of 3 - 1 mm and 1 - 0 mm, and the weight ratio of the two gradations is 1:1; The particle size of the low-iron pyrophyllite fine powder is 200 mesh, and the particle size of the alumina micropowder is 5 μm; The composite preservative is composed of oxalic acid, cellulose ether, hydroxycarboxylate, calcium phosphate and sodium tripolyphosphate with a weight ratio of 1:0.3:0.2:0.2:0.3, that is, 0.1 kg of oxalic acid, 0.03 kg of cellulose ether, 0.02 kg of hydroxycarboxylate, 0.02 kg of calcium phosphate and 0.03 kg of sodium tripolyphosphate.

[0025] Example 2 A preparation method of plastic mass for extending the shelf life of a boiler, comprising the following preparation steps: Pour 4.5 kg of low-iron pyrophyllite aggregate, 1.8 kg of low-iron pyrophyllite fine powder, 0.7 kg of alumina micropowder, 0.6 kg of kyanite, 0.4 kg of Guangxi white clay, 0.4 kg of sodium-based bentonite and 0.3 kg of composite preservative into a mixer and mix for 5 min, then add 30% of the total amount of aluminum dihydrogen phosphate (i.e., 0.3915 kg), stir for 15 min, then discharge and seal. After aging for 24 h, pour it into a roller mixer and add the remaining 0.9135 kg of aluminum dihydrogen phosphate, mix and stir, and then extrude to obtain the plastic mass; Among them, the iron content in both the low-iron pyrophyllite aggregate and the low-iron pyrophyllite fine powder is <0.5%; The low-iron calcined bauxite aggregate consists of two gradations with particle sizes of 3-1 mm and 1-0 mm, and the weight ratio of the two gradations is 1:1; The particle size of the low-iron calcined bauxite fine powder is 200 mesh, and the particle size of the alumina fine powder is 5 μm; The composite preservative is composed of oxalic acid, cellulose ether, hydroxycarboxylate, calcium phosphate and sodium tripolyphosphate with a weight ratio of 1:0.3:0.2:0.2:0.3, that is, 0.15 kg of oxalic acid, 0.045 kg of cellulose ether, 0.03 kg of hydroxycarboxylate, 0.03 kg of calcium phosphate and 0.045 kg of sodium tripolyphosphate.

[0026] Example 3 A preparation method of a plastic refractory with an extended shelf life for boilers includes the following preparation steps: Pour 5 kg of low-iron calcined bauxite aggregate, 2 kg of low-iron calcined bauxite fine powder, 1 kg of alumina fine powder, 0.8 kg of cyanite, 0.6 kg of Guangxi white clay, 0.6 kg of sodium-based bentonite and 0.5 kg of composite preservative into a mixer and mix for 5 minutes, then add 30% of the total amount of aluminum dihydrogen phosphate (i.e., 0.4725 kg), stir for 15 minutes, discharge and seal, let it stand for 24 hours, and then pour it into a roller mixer and add the remaining 1.1025 kg of aluminum dihydrogen phosphate for mixing and stirring, and then extrude and form to obtain the plastic refractory; Among them, the iron content in both the low-iron calcined bauxite aggregate and the low-iron calcined bauxite fine powder is <0.5%; The low-iron calcined bauxite aggregate consists of two gradations with particle sizes of 3-1 mm and 1-0 mm, and the weight ratio of the two gradations is 1:1; The particle size of the low-iron calcined bauxite fine powder is 200 mesh, and the particle size of the alumina fine powder is 5 μm; The composite preservative is composed of oxalic acid, cellulose ether, hydroxycarboxylate, calcium phosphate and sodium tripolyphosphate with a weight ratio of 1:0.3:0.2:0.2:0.3, that is, 0.25 kg of oxalic acid, 0.075 kg of cellulose ether, 0.05 kg of hydroxycarboxylate, 0.05 kg of calcium phosphate and 0.075 kg of sodium tripolyphosphate.

[0027] Example 4 A preparation method of a plastic refractory with an extended shelf life for boilers, which is different from Example 2 in that after standing for 48 hours, it is poured into a roller mixer and the remaining 0.9135 kg of aluminum dihydrogen phosphate is added for mixing and stirring, and then extruded and formed to obtain the plastic refractory, and the others are the same as Example 2.

[0028] Example 5 A preparation method of plastic refractory for boilers with extended shelf life, which is different from Example 2 in that the total amount of the composite preservative remains unchanged at 0.3 kg, and the proportions of the raw materials in the composite preservative change. Specifically, the composite preservative is composed of oxalic acid, cellulose ether, hydroxycarboxylate, calcium phosphate and sodium tripolyphosphate with a weight ratio of 1.5:0.4:0.4:0.3:0.4, that is, 0.15 kg of oxalic acid, 0.04 kg of cellulose ether, 0.04 kg of hydroxycarboxylate, 0.03 kg of calcium phosphate and 0.04 kg of sodium tripolyphosphate, and the others are the same as in Example 2.

[0029] Example 6 A preparation method of plastic refractory for boilers with extended shelf life, which is different from Example 2 in that the total amount of the composite preservative remains unchanged at 0.3 kg, and the proportions of the raw materials in the composite preservative change. Specifically, the composite preservative is composed of oxalic acid, cellulose ether, hydroxycarboxylate, calcium phosphate and sodium tripolyphosphate with a weight ratio of 2:0.5:0.6:0.5:0.5, that is, 0.15 kg of oxalic acid, 0.037 kg of cellulose ether, 0.044 kg of hydroxycarboxylate, 0.037 kg of calcium phosphate and 0.032 kg of sodium tripolyphosphate, and the others are the same as in Example 2.

[0030] Comparative Example 1 A preparation method of plastic refractory for boilers with extended shelf life, which is different from Example 2 in that there is no composite preservative in the raw materials, and the others are the same as in Example 2.

[0031] Comparative Example 2 A preparation method of plastic refractory for boilers with extended shelf life, which is different from Example 2 in that the composite preservative is composed of cellulose ether, hydroxycarboxylate, calcium phosphate and sodium tripolyphosphate with a weight ratio of 0.3:0.2:0.2:0.3, that is, oxalic acid is missing, 0.09 kg of cellulose ether, 0.06 kg of hydroxycarboxylate, 0.06 kg of calcium phosphate and 0.09 kg of sodium tripolyphosphate, and the others are the same as in Example 2.

[0032] Comparative Example 3 A preparation method of plastic refractory for boilers with extended shelf life, which is different from Example 2 in that the composite preservative is composed of oxalic acid, hydroxycarboxylate, calcium phosphate and sodium tripolyphosphate with a weight ratio of 1:0.2:0.2:0.3, that is, cellulose ether is missing, 0.18 kg of oxalic acid, 0.035 kg of hydroxycarboxylate, 0.035 kg of calcium phosphate and 0.05 kg of sodium tripolyphosphate, and the others are the same as in Example 2.

[0033] Comparative Example 4 A preparation method of plasticine for boilers with extended shelf life, which is different from Example 2 in that the composite preservative is composed of oxalic acid, cellulose ether, hydroxycarboxylate and sodium tripolyphosphate with a weight ratio of 1:0.3:0.2:0.3, that is, calcium phosphate is missing, 0.17 kg of oxalic acid, 0.05 kg of cellulose ether, 0.03 kg of hydroxycarboxylate, and 0.05 kg of sodium tripolyphosphate, and the others are the same as in Example 2.

[0034] Comparative Example 5 A preparation method of plasticine for boilers with extended shelf life, which is different from Example 2 in that the composite preservative is composed of oxalic acid, cellulose ether, hydroxycarboxylate and calcium phosphate with a weight ratio of 1:0.3:0.2:0.2, that is, 0.18 kg of oxalic acid, 0.053 kg of cellulose ether, 0.0335 kg of hydroxycarboxylate, and 0.0335 kg of calcium phosphate, and the others are the same as in Example 2.

[0035] Comparative Example 6 A preparation method of plasticine for boilers with extended shelf life, which is different from Example 2 in that the particle size of low-iron chamotte aggregate is 3 - 1 mm, and the others are the same as in Example 2.

[0036] Performance testing Perform plasticity and physical property tests on the plasticine obtained from the above examples and comparative examples, and the test results are shown in Table 1.

[0037] The plasticity of the plasticine is characterized by the Marsh value measured by a Marsh value measuring instrument. Therefore, the shelf life of the plasticine is judged by testing the Marsh values of the plasticine at 0 months, 2 months, 4 months, 6 months and 8 months (using a Marsh value less than 1.5 MPa as the judgment index). The test is carried out by pressing the plasticine into a 250 mm×200 mm×100 mm billet and storing it sealed for testing.

[0038] Physical property test: Make the plasticine into a specimen of 40 mm×40 mm×160 mm, and use the test method in GB / T4513.6 - 2017 to test the flexural strength and compressive strength at 110°C.

[0039] Table 1 Test results of plasticine performance It can be seen from Table 1 that: The plasticity materials obtained in Examples 1-6 of this application have Marsh values lower than 1.5 MPa in 6 months, and the plasticity materials obtained in Examples 2-6 still have Marsh values lower than 1.5 MPa in 8 months, indicating that the shelf life of the plasticity materials obtained in this application can be extended to 6 months and above. In addition, the plasticity materials still have good high-temperature flexural strength and compressive strength at 6 months, indicating that the combination of the raw materials in this application effectively improves the shelf life and physical properties of the plasticity materials.

[0040] Compared with Example 2, in Comparative Example 1, when the composite shelf life agent was missing in the raw materials, the Marsh value of the plasticity material obtained in Comparative Example 1 was greater than 1.5 MPa at 4 months, and the high-temperature flexural strength and compressive strength were both lower than those in Example 2. It can be seen that the combined use of the composite shelf life agent and other raw materials effectively extends the shelf life of the plasticity material, and at the same time, the plasticity material still has good physical properties.

[0041] Compared with Example 2, in Comparative Examples 2-5, when one kind of raw material in the composite shelf life agent was missing, the shelf lives of the plasticity materials obtained in Comparative Examples 2-4 did not reach 6 months. Thus, it can be seen that the combined use of the substances in the composite shelf life agent effectively extends the shelf life of the plasticity material.

[0042] Compared with Example 2, in Comparative Example 6, when only one gradation of low-iron calcined bauxite aggregate was used, the flexural strength and compressive strength of the plasticity material obtained in Comparative Example 6 both decreased, and its Marsh value at 8 months was 1.5 MPa, indicating that its shelf life was lower than that in Example 2. It can be seen that the combined use of two gradations of low-iron calcined bauxite aggregate can effectively improve the overall stability of the plasticity material and also help to extend the shelf life of the plasticity material.

[0043] The examples of this specific implementation manner are all preferred examples of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A plastic material for extending the shelf life of a boiler, characterized in that: The invention comprises the following raw materials in parts by weight: 40-50 parts of low-iron coke gem aggregate, 15-20 parts of low-iron coke gem fine powder, 4-10 parts of alumina micropowder, 4-8 parts of kyanite, 2-6 parts of Guangxi white mud, 2-6 parts of sodium bentonite, 2-5 parts of composite quality-preserving agent and 10-15% of the total weight of the above raw materials as a binder.

2. The plastic material for extending the shelf life of a boiler according to claim 1, characterized in that: The composite quality-maintaining agent is composed of organic acid, cellulose ether, hydroxycarboxylate, phosphate and polyphosphate in a weight ratio of (1.0-2.0):(0.3-0.5):(0.2-0.6):(0.2-0.5):(0.3-0.5).

3. The plastic material for extending the shelf life of a boiler according to claim 2, characterized in that: The polyphosphate is at least one of sodium tripolyphosphate and sodium hexametaphosphate.

4. The plastic material for extending the shelf life of a boiler according to claim 2, characterized in that: The organic acid is at least one of oxalic acid and citric acid.

5. The plastic material for extending the shelf life of a boiler according to claim 1, characterized in that: The iron content in the low-iron coke gem aggregate and the low-iron coke gem fine powder is less than 0.5%.

6. The plastic material for extending the shelf life of a boiler according to claim 1, characterized in that: The particle size of the low-iron coke gem aggregate consists of two gradations of 3-1mm and 1-0mm, and the weight proportion of the 3-1mm low-iron coke gem aggregate is 50%.

7. The plastic material for extending the shelf life of a boiler according to claim 1, characterized in that: The particle size of the low-iron coke gemstone fine powder is 200 meshes.

8. The plastic material for extending the shelf life of a boiler according to claim 1, characterized in that: The particle size of the alumina powder is 5 μm.

9. The plastic material for extending the shelf life of a boiler according to claim 1, characterized in that: The binder is aluminum dihydrogen phosphate.

10. A method for preparing a plastic material for a boiler with a prolonged shelf life as claimed in any one of claims 1 to 9, characterized in that: The method comprises the following steps: evenly mixing low-iron coke gem aggregate, low-iron coke gem fine powder, alumina micropowder, kyanite, Guangxi white mud, sodium-based bentonite and a composite quality-preserving agent, adding 30% of the total amount of a binder, stirring and sealing, trapping the material for 24-48 hours, and then adding the remaining binder, mixing and grinding to obtain a plastic material.

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