Slurry control method for kiln coating of alumina production clinker kiln

Abstract

The invention discloses a slurry control method for kiln coating hanging of an alumina production clinker kiln, and belongs to the technical field of alumina production. The weight ratio of aluminum oxide to silicon dioxide in slurry is determined according to the formula target A / S = A / S0 + K1 + K2, A / S0 is raw slurry A / S used in the main process of the sintering method and is equal to homogenized ore A / S-0. 6, K1 is the fluctuation upper limit absolute value of the A / S, K is larger than or equal to 0.10 and smaller than or equal to 0.25, and K2 is the influence coefficient of the A / S of the slurry for kiln coating hanging on the clinker kiln coating; (2) key components are synergistic, the iron-aluminum ratio [Fe2O3 / Al2O3] is controlled to be 0.08-0.12, the alkali ratio [Na2O / (Al2O3 + Fe2O3)] is 0.90-0.95, and the calcium ratio [CaO / SiO2] is 1.90-2.00; (3) high-aluminum ore adaptation: when high-aluminum ore is adopted, the aluminum-silicon ratio of the high-aluminum ore is calculated according to A / S1 = A / S0 + K1 + K2 + 0.6; and 4) kiln coating dynamic balance operation: the temperature of a firing zone is 1250-1350 DEG C, the kiln speed is 1.5-2.0 rpm, and the fluctuation of the feeding amount is maintained to be less than or equal to + / -3%. The anti-denudation performance of the kiln coating is improved by 40%, the operation period of the clinker kiln is prolonged to more than one year, and the problem that the kiln coating falls off due to the fact that traditional slurry components are not matched with kiln coating hanging requirements is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of sintering alumina production, and in particular relates to a slurry control method for a clinker kiln lining. Background Art

[0002] In the sintering process of alumina production, raw meal preparation and clinker sintering are the foundational and key steps in alumina production. The clinker kiln is the core thermal equipment, responsible for the critical reaction task of converting raw meal into soluble sodium aluminate. The kiln lining is a protective layer of clinker formed after the slurry is sintered and bonded to the surface of the refractory bricks in the clinker kiln's firing zone. High-quality kiln lining is crucial to the stable operation of the clinker kiln and is crucial for improving the kiln's operating cycle, production capacity, and clinker quality. On the one hand, the kiln lining prevents chemical attack and abrasion of refractory bricks by materials in the high-temperature zone, thereby extending the service life of the bricks. On the other hand, a good kiln lining reduces heat loss and promotes calcination and chemical reactions. The composition of the kiln lining is determined by the composition of the slurry, which directly affects the quality and stability of the kiln lining.

[0003] In traditional clinker kiln cladding, after replacing refractory bricks in the clinker kiln firing zone, the pyrotechnician adheres the slurry to the refractory brick surface according to the cladding procedure to form the kiln cladding. The disadvantage of this control method is that conventional slurry is used for kiln cladding and repair operations, without fully considering the reality that the composition of conventional slurry does not match the requirements for cladding. Furthermore, during the later operation of the clinker kiln, when the slurry is calcined under high temperature conditions, a high aluminum-silicon ratio (i.e., the weight ratio of alumina to silica in the slurry, hereinafter referred to as A / S) can negatively impact the kiln cladding system, causing the kiln cladding strength to fail to meet the requirements for long-term operation and increased production capacity of the clinker kiln.

[0004] During normal alumina production, the A / S ratio of the slurry generally fluctuates within a range of ±0.25. When the Al2O3 content in the slurry is high, a higher activation energy is required for the Al2O3 to form sodium aluminate mineral reaction during the sintering process. At this time, the clinker kiln system requires a higher sintering temperature to produce qualified clinker. However, the industry still uses conventional slurries with relatively low A / S to fire clinker kiln linings. The corresponding melting temperature when the kiln lining liquid phase is formed is relatively low, and the resistance to erosion and wear of high-temperature flames and materials is not strong. When the slurry composition fluctuates, the change in sintering temperature often leads to the shedding of the clinker kiln lining, causing the clinker kiln temperature to rise and even "red kiln" accidents, which reduces the operation cycle of the clinker kiln.

[0005] How to adjust the slurry composition for clinker kiln lining, improve the quality of clinker kiln lining, and overcome the defects of slurry composition in daily production and the impact of fluctuations on the kiln lining during clinker kiln operation are urgent problems to be solved in sintered alumina. Summary of the Invention

[0006] In view of the above problems existing in the prior art, the present invention aims to provide a method for preparing a special slurry composition for a clinker kiln with a strong and dense kiln lining, ensuring that the formed kiln lining meets the requirements of good working conditions and long-term operation of the clinker kiln.

[0007] The present invention provides a method for controlling the slurry for the kiln lining of an alumina clinker kiln, characterized in that the weight ratio (A / S) of alumina to silicon dioxide in the slurry for the kiln lining is determined according to the following formula:

[0008] A / S=A / S0+K1+K2

[0009] Wherein, A / S0 is the reference weight ratio of alumina to silica in the raw slurry during the three-stage batching process of alumina production by sintering method; K1 is the upper limit of the absolute value of fluctuation of A / S0, and it satisfies 0.10≤K1≤0.25; K2 is the influence coefficient of the A / S ratio of the slurry used for kiln lining on the clinker kiln lining, and K2=2×K1;

[0010] In addition, the ingredients of the slurry must simultaneously meet the following requirements:

[0011] The iron-aluminum ratio is controlled at 0.08 to 0.12, where the iron-aluminum ratio is the molar ratio of ferric oxide to aluminum oxide;

[0012] The alkali ratio is controlled at 0.90 to 0.95, where the alkali ratio is the molar ratio of sodium oxide to aluminum oxide and iron oxide;

[0013] The calcium ratio is controlled at 1.90 to 2.00, where the calcium ratio is the molar ratio of calcium oxide to silicon oxide.

[0014] Furthermore, the weight ratio of alumina to silica (A / S1) in the high-alumina ore raw material used to prepare the slurry is determined according to the following formula: A / S1=A / S0+K1+K2+0.6.

[0015] Furthermore, the fineness of the slurry satisfies that after being sieved through a 120-mesh standard sieve, the mass percentage of the residue on the sieve is less than 16%; and the moisture content of the slurry is controlled within a mass percentage range of 36.0% to 38.0%.

[0016] Furthermore, the slurry is used to carry out kiln lining firing and hanging of the clinker kiln, and the hanging and dynamic balance of the kiln lining are achieved through the following thermal parameters and kiln body operations: the firing zone temperature is 1250-1350°C, the kiln speed is controlled at 1.5-2.0rpm, and the feed amount fluctuation value is maintained at ≤±3%.

[0017] The slurry A / S ratio in the sintering process for alumina production is the most critical slurry composition indicator and also significantly influences the clinker sintering temperature. The slurry A / S ratio significantly impacts the sintering process and kiln lining stability. The average slurry A / S ratio is primarily determined by the homogenized ore A / S ratio, with the difference being: slurry A / S = homogenized ore A / S ratio - 0.5 (or 0.6). To ensure continuous and stable operation of the alumina production system, the homogenized ore A / S ratio is generally required to be relatively stable within a certain range. If the A / S of the slurry used in production is higher than the A / S of the slurry used when the kiln lining was originally formed, the high temperature during the sintering process will inevitably be higher than the melting temperature when the kiln lining was originally formed, which will cause the kiln lining to be eroded or even fall off. Therefore, the A / S of the slurry used for hanging the kiln lining must be higher than the A / S of the slurry in normal production. Even when the flame temperature is slightly higher, the high A / S kiln lining is less sensitive to the flame shape and temperature changes, so it can effectively avoid the kiln lining from being melted or falling off during the sintering process, and it is more helpful to stabilize the thermal system in the kiln and reduce the risk of damage to the kiln lining due to operational errors.

[0018] A high aluminum content in the slurry increases the viscosity of the liquid phase. This high-viscosity liquid phase forms a denser, stronger kiln lining structure upon cooling, thereby reducing the risk of the kiln lining falling off due to thermal expansion and contraction or material erosion. This characteristic is particularly suitable for handling high-temperature fluctuations or chemically corrosive environments within the kiln. At the same time, clinker kilns using higher slurry A / S ratios require the kiln to provide higher sintering temperatures and form a liquid phase. The formation of the kiln lining requires a certain amount of liquid phase to promote material adhesion and sintering, providing conditions for the kiln lining to attach. Furthermore, according to reaction kinetics, high temperatures can promote bonding between particles, reduce porosity, promote sintering densification, and increase the mechanical strength of the kiln lining. The rough surface of the kiln lining with a high A / S ratio may be more conducive to extending the reaction time of the material within the kiln and promoting the formation of clinker minerals.

[0019] The main technical indicators of slurry include moisture, aluminum-silicon ratio, alkali ratio, calcium ratio, iron-aluminum ratio, and fineness. These various slurry indicators are mutually restrained and affect the chemical reaction of the slurry in the clinker kiln and the melting characteristics of the material. Based on the characteristics of the high-hanging A / S kiln lining, the requirements for the slurry composition are as follows:

[0020] 1. Iron-aluminum ratio (the molar ratio of ferric oxide to aluminum oxide in the slurry)

[0021] Fe2O3 in the raw material slurry is the primary mineralizer during clinker sintering, lowering both the sintering temperature and the clinker melting temperature. The raw material sintering temperature decreases with increasing iron-aluminum ratios. As a flux, Fe2O3 lowers the liquidus formation temperature to around 1250°C, enhancing material viscosity and promoting kiln lining adhesion, acting as a key "lubricant" for kiln lining formation.

[0022] The present invention controls the iron-aluminum ratio of the kiln lining slurry in the range of 0.08-0.12, which can appropriately reduce the sintering temperature, facilitate the high A / S slurry to form a Na2O·Fe2O3-2CaO·SiO2 solid solution liquid phase, strengthen the adhesion of materials, and promote the formation of kiln lining.

[0023] 2. Alkali ratio (molar ratio of sodium oxide to aluminum oxide and iron oxide in the slurry)

[0024] The sintering process typically requires the addition of soda ash to promote the reaction. A too low alkali ratio results in insufficient sodium aluminate (Na2O·Al2O3) production, incomplete sintering, poor kiln lining adhesion, and difficulty forming the lining. A too high alkali ratio results in excessive production of low-melting-point substances (such as Na2O·Fe2O3), resulting in an excessively large liquid phase and a thick or uneven kiln lining. Therefore, the present invention controls the alkali ratio of the kiln lining slurry to between 0.90 and 0.95 (molar ratio) to improve kiln lining adhesion and ensure uniform kiln lining thickness.

[0025] 3. Calcium ratio (molar ratio of calcium oxide to silicon oxide in the slurry)

[0026] Calcium oxide, as a flux, influences the melting temperature and viscosity of the material during the sintering process. Sufficient CaO promotes the formation of dicalcium silicate (2CaO·SiO2). Excessively high CaO ratios can lead to overburning of the clinker and brittle kiln lining, while low CaO ratios can affect the stability of the mineral phase. The present invention controls the CaO ratio of the kiln lining slurry to between 1.90 and 2.00 (molar ratio), enhancing the mechanical strength and high-temperature resistance of the kiln lining and promoting structural stability.

[0027] 4. Physical properties of raw slurry

[0028] The present invention requires that the slurry particles have a residue of less than 16% on a 120-mesh standard sieve to ensure a high reaction speed and completeness; the moisture content is controlled at 36.0% to 38.0%. Too high a moisture content will reduce the thermal efficiency in the kiln and affect the kiln skin formation temperature.

[0029] The slurry components need to be mixed evenly to avoid local fluctuations in liquid phase volume that lead to uneven kiln lining thickness.

[0030] The beneficial technical effects of the present invention include:

[0031] (1) It is applicable to alumina production plants with sintering process and related production fields using clinker kilns, which can greatly extend the operation cycle of clinker kilns and create conditions for stable and efficient operation of clinker kilns; (2) By regulating the influence coefficient K2 of the kiln skin slurry A / S on the clinker kiln skin, the clinker kiln is promoted to form a dense and solid kiln skin structure, which has the characteristics of advanced guidance and strong operability; (3) Based on the A / S of the kiln skin slurry, the alkali ratio, calcium ratio, iron-aluminum ratio and physical properties of the slurry are organically combined, and specific quantitative data are used to determine the reasonable kiln skin slurry, and guide the slurry mixing operation, which not only solves the disadvantage of the uncertainty of the composition of the kiln skin slurry in the past. At the same time, the kiln skin slurry control process can be further quantified, and the accuracy of the kiln skin operation of the clinker kiln is improved; (4) The factors affecting the kiln skin effect of the clinker kiln are slurry composition as the core, and the change trend of the ore supply composition (mainly the homogenized ore A / S) is extracted, and the idea of ​​using the slurry A / S as the core for the kiln skin is determined, and the internal connection between the slurry A / S change and the adjustment of other slurry indicators is straightened out, overcoming the problem of poor kiln skin quality caused by the use of conventional slurry composition that does not match the kiln skin demand in the previous technology, improving the standardization of slurry preparation during the kiln skin operation, and improving the quality of the clinker kiln skin and the efficiency of kiln skin maintenance work in daily operation. DETAILED DESCRIPTION

[0032] Example 1

[0033] The A / S ratio of the homogenized ore produced by the current sintering method is about 3.80, and the corresponding raw material slurry A / S0 for the main process is about 3.20. The fluctuation range of the slurry A / S is 3.20±0.25. Based on this process index, the various components of the slurry for the kiln lining are adjusted as follows:

[0034] First, determine that the A / S ratio of the kiln lining slurry is 3.20+0.25+2×0.25=3.95. Based on this, confirm that the A / S1 of the high-alumina ore used for the kiln lining should be 3.95+0.6=4.55. In other words, provide the slurry preparation system with homogenized ore with an A / S1 of approximately 4.55, which can meet the requirement of the kiln lining slurry A / S of 3.95.

[0035] On the premise that the A / S of the kiln lining slurry is 3.95, the iron-aluminum ratio of the slurry is controlled at 0.10 (molar ratio), the alkali ratio is controlled at 0.92 (molar ratio), the calcium ratio is controlled at 1.95 (molar ratio), the slurry fineness is controlled at less than 16% of the residue on the 125-mesh standard sieve, and the slurry moisture is controlled at 36.0% to 38.0% by mass, thus forming the components of the special slurry for the clinker kiln lining of this embodiment.

[0036] By using the special slurry to hang the kiln lining of this embodiment, a uniform, strong and dense kiln lining is formed in the clinker kiln. The operation cycle of the clinker kiln reaches 383 days, the kiln condition is stable, and the quality of the clinker produced is improved.

[0037] Example 2

[0038] The A / S ratio of the homogenized ore produced by the current sintering method is about 4.0, and the corresponding raw material slurry A / S0 for the main process is about 3.40. The fluctuation range of the slurry A / S is 3.40±0.25. Based on this process index, the various components of the slurry for the kiln lining are adjusted as follows:

[0039] First, determine that the A / S ratio of the kiln lining slurry is 3.40+0.25+2×0.25=4.15. Based on this, confirm that the A / S1 of the high-alumina ore used for the kiln lining should be 4.15+0.6=4.75. In other words, provide the slurry preparation system with homogenized ore with an A / S ratio of about 4.75, which can meet the requirement of the kiln lining slurry A / S reaching 4.15.

[0040] On the premise that the A / S of the kiln lining slurry is 4.15, the iron-aluminum ratio of the slurry is controlled at 0.09 (molar ratio), the alkali ratio is controlled at 0.94 (molar ratio), the calcium ratio is controlled at 1.92 (molar ratio), the slurry fineness is controlled at less than 16% of the residue on the 120-mesh standard sieve, and the slurry moisture is controlled at 36.0% to 38.0% by mass, which forms the components of the special slurry for the clinker kiln lining of this embodiment.

[0041] The special slurry coating of this embodiment forms a uniform, strong, and dense kiln lining within the clinker kiln. The kiln can operate continuously for 375 days, exceeding a year, with stable kiln conditions and improved clinker quality.

[0042] Comparative Example 1

[0043] The kiln lining operation was performed using the same conventional slurry as used in normal production, with an A / S ratio of approximately 3.20 ± 0.25. Other parameters (iron-aluminum ratio, alkali ratio, calcium ratio, etc.) were controlled within the normal production range, specifically an iron-aluminum ratio of 0.075, an alkali ratio of 0.90, and a calcium ratio of 1.98. No special optimization of the kiln lining slurry was performed.

[0044] The kiln lining formed in this comparative example had a relatively loose structure and uneven thickness. This made it sensitive to fluctuations in slurry composition and thermal changes during subsequent production, leading to localized spalling. The average operating cycle of a clinker kiln is approximately 180 days, resulting in frequent kiln lining maintenance and significant fluctuations in clinker quality.

[0045] Table 1

[0046]

[0047] The present invention scientifically quantifies the composition of the kiln lining slurry of the clinker kiln. While meeting the aluminum-silicon ratio, the physical performance indicators such as the alkali ratio, calcium ratio, and iron-aluminum ratio in the slurry components are coordinated to increase the liquid phase amount in the process of hanging the high A / S kiln lining, thereby ensuring that the clinker kiln forms a dense, high-temperature resistant and stable kiln lining. The method is simple and highly operational. The clinker kiln lining hung with the slurry controlled by the method of the present invention has the characteristics of being firm, dense, and highly resistant to erosion, thereby enhancing the stability and durability of the kiln lining, extending the service life of refractory bricks, optimizing thermal efficiency and energy saving, reducing the impact of operation fluctuations on the kiln lining, and improving the clinker quality and kiln system stability.

[0048] The above are preferred embodiments of the present invention. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for controlling slurry in a clinker kiln for alumina production, characterized in that: The weight ratio of alumina to silica (A / S) in the slurry for kiln lining is determined by the following formula: A / S=A / S0+K1+K2 Wherein, A / S0 is the reference weight ratio of alumina to silica in the raw slurry during the three-stage batching process of alumina production by sintering method; K1 is the upper limit of the absolute value of fluctuation of A / S0, and it satisfies 0.10≤K1≤0.25; K2 is the influence coefficient of the A / S ratio of the slurry used for kiln lining on the clinker kiln lining, and K2=2×K1; In addition, the ingredients of the slurry must simultaneously meet the following requirements: The iron-aluminum ratio is controlled at 0.08 to 0.12, where the iron-aluminum ratio is the molar ratio of ferric oxide to aluminum oxide; The alkali ratio is controlled at 0.90 to 0.95, where the alkali ratio is the molar ratio of sodium oxide to aluminum oxide and iron oxide; The calcium ratio is controlled at 1.90 to 2.00, where the calcium ratio is the molar ratio of calcium oxide to silicon oxide.

2. The control method according to claim 1, characterized in that: The weight ratio of alumina to silica (A / S1) in the high aluminum ore raw material used to prepare the slurry is determined by the following formula: A / S1=A / S0+K1+K2+0.6 The definitions of A / S0, K1, and K2 are the same as those in claim 1.

3. The control method according to claim 1 or 2, characterized in that: The fineness of the slurry satisfies the requirement that after being sieved through a 120-mesh standard sieve, the mass percentage of the residue on the sieve is less than 16%; and the moisture content of the slurry is controlled within a mass percentage range of 36.0% to 38.0%.

4. The control method according to any one of claims 1 to 3, characterized in that: The slurry is used to carry out kiln lining firing and hanging of the clinker kiln, and the hanging and dynamic balance of the kiln lining are achieved through the following thermal parameters and kiln body operation: the firing zone temperature is 1250-1350°C, the kiln speed is controlled at 1.5-2.0rpm, and the feed amount fluctuation value is maintained at ≤±3%.

Images