Method for preparing aluminate cement clinker by calcining secondary aluminum ash
By calcining the secondary aluminum ash and adding a regulator and a water reducer, the problems of decreased strength and high production cost after hydration of aluminate cement are solved, and the effect of improving compressive strength, flexural strength and sintering properties is achieved. Reduced the water-cement ratio.
Patent Information
- Application Number
- CN202411623421.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2025-02-18
AI Technical Summary
In the late hydration stage, the existing aluminate cement has transformed into a stable state due to metastable calcium aluminate hydrate and lost bound water, resulting in an increase in porosity and a decrease in strength. At the same time, its production cost is relatively high and the water-cement ratio does not increase. Convenient for construction.
By calcining the secondary aluminum ash, increasing the aluminum-silicon ratio, and adding a regulator and a water reducer, the compressive strength, flexural strength and sintering properties of aluminate cement are improved, and production costs are reduced.
The compressive strength and flexural strength of aluminate cement are improved, the water-cement ratio is reduced, the sintering property is enhanced, the problem of decrease in strength after hydration is solved, and the recycling of resources and the reduction of production costs are achieved.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of solid waste treatment, and in particular to a method for preparing aluminate cement clinker by calcining secondary aluminum ash. Background Art
[0002] At present, the main way to deal with aluminum ash is storage or landfill. When the air is humid or it rains, toxic and harmful ions (such as fluoride ions) in the aluminum ash will seep into the ground, causing soil and groundwater pollution. In addition, when the weather is hot and humid, substances such as aluminum nitride and aluminum carbide in the aluminum ash will react with water to produce gases such as ammonia and methane, causing air pollution.
[0003] With the continuous consumption of high-grade bauxite resources in China, the price of bauxite has risen rapidly. How to reduce the production cost of aluminate cement and make its excellent performance better applied is a crucial issue. The Al2O3 content in primary / secondary aluminum ash is high, and it has the potential to partially replace high-alumina bauxite.
[0004] As the most widely used high-temperature binder in the field of refractory castables and refractory profiles, aluminate cement has the characteristics of early strength, high temperature resistance, low alkali, slight expansion and low shrinkage. However, in the later stage of hydration of aluminate cement, due to the transformation of metastable hydrated calcium aluminate to a stable state, the bound water is lost, resulting in increased porosity and decreased strength. Therefore, it is necessary to physically or chemically modify aluminate cement.
[0005] Based on the urgent need for high-grade bauxite alternative raw materials in the development of aluminate cement industry, the use of aluminum ash as raw material to prepare new refractory aluminate cement materials can reduce costs while increasing the sinterability of aluminate cement and achieve resource recycling. However, the water consumption of the standard consistency of aluminate cement mortar prepared with aluminum ash as raw material and the water-cement ratio for cement strength molding also increase accordingly, which is a problem that urgently needs to be improved. Summary of the invention
[0006] In view of the deficiencies in the prior art, the present invention provides a method for preparing aluminate cement clinker by calcining secondary aluminum ash, thereby improving the sinterability of aluminate cement. The present invention uses calcined secondary aluminum ash to prepare aluminate cement clinker. During the calcination process, AlN and Al in the secondary aluminum ash are oxidized into Al2O3, thereby increasing the aluminum-silicon ratio of the raw material. In order to solve the problem that in the late stage of aluminate cement hydration, due to the transformation of metastable hydrated calcium aluminate to a stable state, bound water is lost, resulting in increased porosity and decreased strength, the present invention adds a regulator to improve the compressive strength and flexural strength of aluminate cement. The addition of aluminum ash may require a larger water-cement ratio for the strength molding of aluminate cement, so the present invention also adds a water reducer.
[0007] The method for preparing aluminate cement clinker by calcining secondary aluminum ash of the present invention has the following specific preparation steps:
[0008] S1. The calcined secondary aluminum ash is ball-milled in a vertical ball mill, and the particle size is required to be ≥200 mesh;
[0009] Calcined secondary aluminum ash is obtained by calcining secondary aluminum ash at 800-1400℃ for 1-3h. Its main purpose is to oxidize AlN and Al in the secondary aluminum ash into Al2O3 and centrally treat the generated waste gas. This process can increase the aluminum-silicon ratio of the raw material composition, which is conducive to the formation of CA phase and CA2 phase. The mass fraction of each component in the calcined secondary aluminum ash is as follows: Al2O3>70wt%, Si2O3<15wt%, Fe2O3<3wt%, K<0.5wt%.
[0010] S2. Mix the calcined secondary aluminum ash after ball milling with deionized water in a mass ratio of 1:6, heat it at 60-120°C for 1-3 hours, take it out, and dry it at 100-150°C for 3-6 hours. This process can remove most of the moisture left in the washing process.
[0011] S3. Mix the dried calcined secondary aluminum ash and fly ash in a stirring barrel according to a mass ratio, and then continue to dry at 100-150° C. for 12-24 hours to obtain a mixture of calcined secondary aluminum ash and fly ash.
[0012] S4. Mix limestone, a mixture of calcined secondary aluminum ash and fly ash, and raw bauxite in a mass ratio, and ball-mill the mixture in a vertical ball mill to obtain aluminate cement raw material. The particle size requirement is ≥200 mesh. After ball milling, filter with a square hole sieve, and the sieve residue is less than 10%.
[0013] The limestone is crushed and ground to a particle size of 1 to 10 mm; the mass fraction of Al2O3 in raw bauxite is greater than 70wt%.
[0014] The aluminate cement raw material is prepared, which comprises the following components in parts by weight: 5-20 parts of calcined secondary aluminum ash, 30-50 parts of limestone, 30-60 parts of raw bauxite, and 1-20 parts of fly ash.
[0015] S5, heating the aluminate cement raw material to 1000-1500° C. at a rate of 5-15° C. / min, and calcining at the temperature for 1-3 h to obtain initial aluminate cement clinker;
[0016] S6. Weigh the initial aluminate cement clinker according to the mass ratio, cool it to room temperature, put it into a mixer with the regulator and water reducer, mix them evenly, and then use a vertical ball mill to ball mill. The particle size requirement is ≥200 mesh; the ball-milled mixture is cured at a temperature of 60-120°C for 1-3h to prepare aluminate cement clinker.
[0017] The composition of the initial aluminate cement clinker, the regulator and the water reducer in terms of weight percentage is as follows: 90-99 parts of the initial aluminate cement clinker, 1-5 parts of the regulator and 1-5 parts of the water reducer.
[0018] The regulator is one of water glass, sodium citrate, sodium dihydrogen phosphate or a mixture of several of them in any proportion; the water reducer is one of polycarboxylic acid water reducer, naphthalene water reducer, wood calcium water reducer or a mixture of several of them in any proportion.
[0019] The mass fraction requirements of each component in the clinker are: Al2O3: 50-60wt%, Si2O3<9wt%, Fe2O3<3wt%, Na<0.5wt%, K<0.5wt%.
[0020] Beneficial effects of the present invention:
[0021] (1) The secondary aluminum ash is calcined at 800-1400°C and washed with water. This process can remove AlN and Al in the secondary aluminum ash and oxidize them into Al2O3, thereby increasing the aluminum-silicon ratio of the raw material. The water washing treatment can remove the fusible salt in the calcined secondary aluminum ash and prevent the cement from setting too quickly, which is not conducive to construction.
[0022] (2) The special properties of calcined secondary aluminum ash are large porosity and high reactivity, which can reduce the sintering time of aluminate cement clinker.
[0023] (3) The preparation of aluminate cement using calcined secondary aluminum ash is an energy-saving, environmentally friendly and low-cost preparation method that can promote the reduction of carbon emissions.
[0024] (4) The calcined secondary aluminum ash contains a large amount of active Al2O3 and SiO2, and the mechanical properties are significantly increased after the hydration reaction, making the aluminate cement paste have stronger flexural strength and compressive strength.
[0025] (5) The present invention adds a regulator to improve the compressive strength and flexural strength of aluminate cement, and solves the problem that in the late stage of aluminate cement hydration, due to the transformation of metastable hydrated calcium aluminate to a stable state, the bound water is lost, resulting in increased porosity and decreased strength.
[0026] (6) The present invention adds a water reducing agent to solve the problem that aluminate cement strength molding requires a larger water-cement ratio. DETAILED DESCRIPTION
[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0028] Example 1
[0029] The secondary aluminum ash is fed into a high temperature furnace and calcined at 1400°C for 3 hours to produce calcined secondary aluminum ash.
[0030] Calcined secondary aluminum ash, limestone, raw bauxite and fly ash are weighed in the following mass proportions: 17 parts, 40 parts, 38 parts and 5 parts respectively (calculated as solid matter after drying).
[0031] The calcined secondary aluminum ash is ball-milled in a vertical ball mill, and the particle size is required to be ≥200 mesh; then the ball-milled calcined secondary aluminum ash is mixed with deionized water in a mass ratio of 1:6, heated at 90°C for 2h, taken out, and dried at 120°C for 3h; the dried calcined secondary aluminum ash is mixed with fly ash in a mixing barrel in a mass ratio and dried at 120°C for 24h. Limestone is mixed with the mixture of calcined secondary aluminum ash and fly ash and raw bauxite in a mass ratio, and the mixed materials are ball-milled in a vertical ball mill to obtain aluminate cement raw material, and the aluminate cement raw material obtained by ball milling is transported to a calcining furnace for calcination, and the temperature is raised to 1450°C at a rate of 10°C / min, and calcined at 1450°C for 150 minutes to obtain initial aluminate cement clinker.
[0032] Then the initial aluminate cement clinker, sodium dihydrogen phosphate, and wood calcium water reducing agent were weighed in the following mass proportions: 97 parts, 2 parts, and 1 part, respectively, put into a mixer and mixed evenly, and then ball-milled with a vertical ball mill and cured at 60° C. for 1 hour to obtain aluminate cement clinker, and the aluminate cement clinker 325 mesh residue was less than 5%. The water-cement ratio for cement strength molding was 0.45, and the cement mortar strength test results showed that the 6h and 24h compressive strengths were 21.6MPa and 42.3MPa, respectively, and the 6h and 24h flexural strengths were 3.6MPa and 5.7MPa, respectively. It can be seen that the late strength of the aluminate cement clinker in this embodiment has been well developed.
[0033] Example 2
[0034] The secondary aluminum ash is fed into a high temperature furnace and calcined at 1400°C for 3 hours to produce calcined secondary aluminum ash.
[0035] Calcined secondary aluminum ash, limestone, raw bauxite and fly ash are weighed in the following mass proportions: 15 parts, 38 parts, 37 parts and 10 parts respectively (calculated as solid matter after drying).
[0036] The calcined secondary aluminum ash is ball-milled in a vertical ball mill, and the particle size is required to be ≥200 mesh; then the ball-milled calcined secondary aluminum ash is mixed with deionized water in a mass ratio of 1:6, heated at 80°C for 3 hours, taken out, and dried at 110°C for 3 hours; the dried calcined secondary aluminum ash is mixed with fly ash in a mixing barrel according to the mass ratio and dried at 110°C for 18 hours. Limestone is mixed with the mixture of calcined secondary aluminum ash and fly ash and raw bauxite according to the mass ratio, and the mixed materials are ball-milled in a vertical ball mill to obtain aluminate cement raw material, and the aluminate cement clinker obtained by ball milling is transported to a calcining furnace for calcination, and the temperature is raised to 1350°C at a rate of 10°C / min, and calcined at 1350°C for 180 minutes to obtain the initial aluminate cement clinker.
[0037] Then the initial aluminate cement clinker, sodium dihydrogen phosphate, and wood calcium water reducing agent are weighed in the following mass parts: 97 parts, 2 parts, and 1 part, respectively, put into a mixer and mix evenly, then ball milled with a vertical ball mill and cured at 60° C. for 1 hour to obtain aluminate cement clinker, and the aluminate cement clinker 325 mesh residue is less than 5%. The water-cement ratio for cement strength molding is 0.45, and the cement mortar strength test results show that the 6h and 24h compressive strengths are 22.3MPa and 41.7MPa respectively, and the 6h and 24h flexural strengths are 3.2MPa and 5.5MPa respectively. It can be seen that the late strength of the aluminate cement clinker of this embodiment has been well developed.
[0038] Example 3
[0039] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned Example 1, except that: the calcination temperature of the aluminate cement clinker in this example is 1500°C, and the cement mortar strength test results show that the 6h and 24h compressive strengths are 22.9MPa and 42.5MPa respectively, and the 6h and 24h flexural strengths are 3.5MPa and 5.6MPa respectively.
[0040] Example 4
[0041] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned embodiment 1, except that: the calcined secondary aluminum ash, limestone, raw bauxite, and fly ash in this embodiment are weighed in the following mass proportions: 12 parts, 40 parts, 43 parts, and 5 parts (calculated as solid matter after drying), and the cement mortar strength test results show that the 6h and 24h compressive strengths are 19.5MPa and 40.7MPa, respectively, and the 6h and 24h flexural strengths are 3.4MPa and 5.6Mpa, respectively.
[0042] Example 5
[0043] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned embodiment 1, except that: the calcined secondary aluminum ash, limestone, raw bauxite, and fly ash in this embodiment are weighed in the following mass proportions: 5 parts, 40 parts, 50 parts, and 5 parts (calculated as solid matter after drying), and the cement mortar strength test results show that the 6h and 24h compressive strengths are 17.9MPa and 40.5MPa respectively, and the 6h and 24h flexural strengths are 2.9MPa and 5.4Mpa respectively.
[0044] Example 6
[0045] A method for calcining secondary aluminum ash to prepare aluminate cement clinker is the same as the above-mentioned embodiment 1, except that: the aluminate cement raw material obtained by ball milling is transported to a calcining furnace for calcination, the temperature is raised to 1450°C at a rate of 5°C / min, and the initial aluminate cement clinker is calcined at 1450°C for 150 minutes. The cement mortar strength test results show that the 6h and 24h compressive strengths are 15.8MPa and 39.3MPa respectively, and the 6h and 24h flexural strengths are 1.8MPa and 4.9MPa respectively.
[0046] Example 7
[0047] A method for calcining secondary aluminum ash to prepare aluminate cement clinker is the same as the above-mentioned embodiment 1, except that: the aluminate cement raw material obtained by ball milling is transported to a calcining furnace for calcination, the temperature is raised to 1450°C at a rate of 15°C / min, and the initial aluminate cement clinker is obtained by calcining at 1450°C for 150 minutes. The cement mortar strength test results show that the 6h and 24h compressive strengths are 19.6MPa and 40.1MPa respectively, and the 6h and 24h flexural strengths are 2.7MPa and 5.2Mpa respectively.
[0048] Example 8
[0049] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned embodiment 1, except that: the calcination temperature of the aluminate cement clinker in this embodiment is 1100°C, and the cement mortar strength test results show that the 6h and 24h compressive strengths are 5.0MPa and 38.6MPa respectively, and the 6h and 24h flexural strengths are 1.5MPa and 4.5MPa respectively.
[0050] Comparative Example 1
[0051] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned embodiment 1, except that: in this embodiment, no fly ash is added, and the mass number of raw bauxite is 43 parts. The cement mortar strength test results show that the 6h and 24h compressive strengths are 5.2MPa and 34.6MPa respectively, and the 6h and 24h flexural strengths are 2.2MPa and 4.1MPa respectively.
[0052] Comparative Example 2
[0053] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned Example 1, except that: in this example, no regulator is added, and the initial aluminate cement clinker and wood calcium water reducer are weighed in the following mass numbers: 99 parts and 1 part, respectively. The cement mortar strength test results show that the 6h and 24h compressive strengths are 13.2MPa and 38.9MPa, respectively, and the 6h and 24h flexural strengths are 1.6MPa and 4.3MPa, respectively.
[0054] Comparative Example 3
[0055] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned embodiment 1, except that the calcined secondary aluminum ash is not washed with water, and the initial setting time of the cement mortar is 18 minutes, which is less than 30 minutes, and is not conducive to construction.
[0056] Comparative Example 4
[0057] A method for preparing aluminate cement clinker by calcining secondary aluminum ash is the same as the above-mentioned Example 1, except that: in this example, no water reducer is added, and the initial aluminate cement clinker and sodium dihydrogen phosphate are weighed in the following mass numbers: 98 parts and 2 parts, respectively, and the water-cement ratio for cement strength molding is 0.51.
Claims
1. A method for preparing aluminate cement clinker by calcining secondary aluminum ash, characterized in that: The method steps are as follows: S1. The calcined secondary aluminum ash is ball-milled in a vertical ball mill, and the particle size is required to be ≥200 mesh; S2, mixing the ball-milled calcined secondary aluminum ash with deionized water in a mass ratio of 1:6, heating at 60-120° C. for 1-3 hours, taking out, and drying at 100-150° C. for 3-6 hours; S3, mixing the dried calcined secondary aluminum ash and fly ash evenly according to a mass ratio, and drying at 100-150° C. for 12-24 hours to obtain a mixture of calcined secondary aluminum ash and fly ash; S4, mixing limestone, a mixture of calcined secondary aluminum ash and fly ash, and raw bauxite according to a mass ratio, and then ball-milling to obtain aluminate cement raw meal, the particle size of which is required to be ≥200 mesh, and then filtering with a square hole sieve, with the sieve residue being less than 10%, to obtain aluminate cement raw meal; S5, calcining aluminate cement raw material to obtain initial aluminate cement clinker; S6. After the initial aluminate cement clinker is cooled to room temperature, it is put into a mixer together with a regulator and a water reducer, mixed evenly, and then ball-milled in a vertical ball mill. The particle size requirement is ≥325 mesh; it is cured at a temperature of 60-120°C for 1-3h to prepare aluminate cement clinker.
2. The method for preparing aluminate cement clinker by calcining secondary aluminum ash according to claim 1, characterized in that: The calcined secondary aluminum ash is obtained by calcining secondary aluminum ash at a high temperature of 800 to 1400° C. for 1 to 3 hours.
3. The method for preparing aluminate cement clinker by calcining secondary aluminum ash according to claim 1, characterized in that: The mass percentage of each component in the calcined secondary aluminum ash is as follows: Al2O3>70wt%, Si2O3<15wt%, Fe2O3<3wt%, K<0.5wt%.
4. The method for preparing aluminate cement clinker by calcining secondary aluminum ash according to claim 1, characterized in that: The limestone is crushed and ground to a particle size of 1 to 10 mm; the mass fraction of Al2O3 in the raw bauxite is greater than 70wt%.
5. The method for preparing aluminate cement clinker by calcining secondary aluminum ash according to claim 1, characterized in that: The raw material composition of the aluminate cement raw material is as follows: 5-20 parts of calcined secondary aluminum ash, 30-50 parts of limestone, 30-60 parts of raw bauxite, and 1-20 parts of fly ash in terms of mass percentage.
6. The method for preparing aluminate cement clinker by calcining secondary aluminum ash according to claim 1, characterized in that: The initial aluminate cement clinker is obtained by heating to 1000-1500° C. at a rate of 5-15° C. / min and calcining for 1-3 hours.
7. The method for preparing aluminate cement clinker by calcining secondary aluminum ash according to claim 1, characterized in that: The raw materials for making aluminate cement clinker are composed of 90-99 parts of initial aluminate cement clinker, 1-5 parts of regulator, and 1-5 parts of water reducing agent in terms of mass fraction.
8. The method for preparing aluminate cement clinker by calcining secondary aluminum ash according to claim 7, characterized in that: The regulator is one of water glass, sodium citrate, sodium dihydrogen phosphate or a mixture of several of them in any proportion; the water reducer is one of polycarboxylic acid water reducer, naphthalene water reducer, wood calcium water reducer or a mixture of several of them in any proportion.
9. Aluminate cement clinker prepared according to the method according to any one of claims 1 to 8, characterized in that: The mass percentage requirements of the main chemical components in the aluminate cement clinker are: Al2O3: 50-60wt%, Si2O3<9wt%, Fe2O3<3wt%, Na<0.5wt%, K<0.5wt%.