Regulation process of weak base temperature stabilization and anti-coating for three-stage preheater of rotary kiln

Abstract

This invention discloses a control process for weak alkali-based temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln, relating to the field of cement kiln calcination technology. The process includes the following steps: S1, Raw material ratio control: controlling the total alkali content of the raw material entering the kiln to ≤0.85%, chlorine content to ≤0.06%, and sulfur content to ≤0.65%, maintaining an alkali-sulfur mass ratio of 0.8~1.1; S2, Decomposition furnace zoned temperature stabilization: the coal distribution ratio between the upper and lower parts of the decomposition furnace is 55%:45%, and the decomposition furnace outlet temperature is stabilized at 870~890℃; S3, Three-stage gradient parameter control: C 1. Outlet temperature 460~490℃, negative pressure -1900~-2200Pa; C2 outlet temperature 680~720℃, negative pressure -1500~-1700Pa; C3 outlet temperature 840~880℃, negative pressure -900~-1100Pa, eliminating local high-temperature stagnant areas inside the equipment; S4. Kiln air volume coupling control: the kiln tail ventilation air volume is maintained at 175000~185000m³ / h, and the tertiary air opening is set to 70%~75%, shortening the residence time of fine particulate materials on the cylinder wall to within 0.5s.

Description

Technical Field

[0001] This invention relates to the field of cement kiln calcination technology, and in particular to a control process for weak alkali temperature stabilization and anti-scabbing in a three-stage preheater of a rotary kiln. Background Technology

[0002] A Φ4.3×62m rotary kiln paired with a three-stage cyclone preheater production line is a common equipment configuration in the cement clinker calcination field. In actual production, it produces 2800 to 3200 tons of clinker per day. The system has a large total ventilation volume, high heat load, and a relatively high material circulation ratio. During production, volatile components such as alkalis (K₂O, Na₂O), chlorine, and sulfur introduced by raw materials and fuels continuously circulate and accumulate in the high-temperature zones C2 and C3 of the preheater. Alkali metals react with SO₃ and Cl₂... - Under high-temperature conditions, low-melting-point compounds (such as double salts of K2SO4, Na2SO4, and CaO) are generated. These compounds precipitate in a molten state within the temperature range of 850~900℃ and adhere to the cone and cylinder wall surface of the preheater cyclone, gradually accumulating to form a crust. In addition, the temperature and pressure parameters of this type of preheater fluctuate greatly, the outlet temperature of the decomposition furnace fluctuates widely, and local high-temperature zones and airflow stagnation zones coexist, further accelerating the formation and thickening of the crust, frequently causing material blockage failures, and seriously affecting the production line's capacity and energy consumption indicators.

[0003] To address the aforementioned preheater scaling problem, existing technologies generally employ methods such as adjusting a single process parameter or periodically shutting down the system for manual unclogging. However, these methods only provide temporary relief and cannot eradicate the conditions for scaling formation at the process mechanism level, leading to recurring scaling issues. This not only significantly increases on-site maintenance workload and operational safety risks but also causes a series of adverse effects, including increased system heat consumption, limited clinker production, and shortened refractory material lifespan. Therefore, there is an urgent need to develop a control method that fully adapts to the operating characteristics of this three-stage preheater system, requires no equipment modification, and systematically inhibits scaling formation at its source. This method would have significant engineering application value for ensuring the long-term stable, efficient, and low-consumption operation of the production line. Summary of the Invention

[0004] This invention provides a control process for weak alkali temperature stabilization and anti-scabbing in a three-stage preheater of a rotary kiln. This process can solve the technical problem in the prior art that can only temporarily alleviate the fault phenomenon and cannot eliminate the conditions for the formation of scale from the process mechanism level, resulting in the recurrence of scale problems.

[0005] A control process for weak alkali-based temperature stabilization and anti-scaling in a three-stage preheater of a rotary kiln includes the following steps: S1, Raw material ratio control: controlling the total alkali content of the raw material entering the kiln to ≤0.85%, chlorine content to ≤0.06%, and sulfur content to ≤0.65%, maintaining the alkali-sulfur mass ratio at 0.8~1.1; S2, Decomposition furnace zone temperature stabilization: the coal distribution ratio between the upper and lower parts of the decomposition furnace is 55%:45%, and the decomposition furnace outlet temperature is stabilized at 870~890℃; S3, Three-stage gradient parameter control: the C1 outlet temperature is 460~49℃. 0℃, negative pressure -1900~-2200Pa, C2 outlet temperature 680~720℃, negative pressure -1500~-1700Pa, C3 outlet temperature 840~880℃, negative pressure -900~-1100Pa, eliminating local high-temperature stagnant areas inside the equipment; S4, kiln air volume coupling control: the kiln tail ventilation air volume is maintained at 175000~185000m³ / h, and the tertiary air opening is set to 70%~75%, shortening the residence time of fine particulate materials on the cylinder wall to within 0.5s.

[0006] The present invention provides a control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln, which, compared with the prior art, has the following beneficial effects, but is not limited to: The control process of weak alkali temperature stabilization and anti-scaling in the three-stage preheater of the rotary kiln achieves a synergistic effect throughout the entire process, from raw material chemical composition control, decomposition furnace temperature field zoning control, three-stage temperature and pressure gradient standardized management to kiln air volume matching optimization. This extends the scalding removal cycle from 1-2 times per week to 25-30 days and controls the system negative pressure fluctuation within ±80Pa. It systematically eliminates the conditions for scalding formation at the process mechanism level, effectively solving the comprehensive technical problems of increased maintenance workload, high coal consumption, and limited output caused by existing technologies that can only temporarily alleviate the fault but cannot fundamentally solve the scalding problem.

[0007] Furthermore, in step S2, the temperature stabilization of the decomposition furnace zone also includes: controlling the tertiary air temperature at 980~1020℃, and controlling the fluctuation range of the decomposition furnace outlet temperature within ±10℃.

[0008] Furthermore, in step S3, the outlet temperatures of C1 to C3 increase in a stepwise manner, the temperature difference between adjacent preheaters is stabilized within the range of 160~220℃, and the system negative pressure fluctuation is controlled within ±80Pa.

[0009] Furthermore, in step S4, the kiln tail temperature is maintained at 1050~1200℃, and the airflow velocity inside cylinders C2 and C3 is controlled at 12~18m / s.

[0010] Further, in step S1, the alkali-sulfur mass ratio is the ratio of the total mass of K2O and Na2O in the raw material fed into the kiln to the mass of SO3.

[0011] Furthermore, in step S2, the outlet temperature of the decomposition furnace is stabilized at 875~885℃.

[0012] Furthermore, in step S3, the outlet temperature of C3 is controlled at 855~875℃.

[0013] Furthermore, in step S1, low-alkali limestone is used in combination with low-sulfur coal, along with iron or silicon corrective raw materials, to control the total alkali content of the raw materials entering the kiln to below 0.7% and the sulfur content to below 0.55%.

[0014] Furthermore, in step S3, the temperature difference between the C3 outlet temperature and the decomposition furnace outlet temperature in step S2 is controlled within 10~30℃.

[0015] Furthermore, in step S4, the adjustment range of the kiln tail ventilation air volume and the tertiary air opening is matched in conjunction with the negative pressure changes of cylinders C2 and C3. When the negative pressure of cylinder C2 or C3 deviates from the gradient range set in step S3, the kiln tail exhaust air volume and the tertiary air valve opening are adjusted accordingly. Attached Figure Description

[0016] Figure 1 A flowchart of a method for regulating the temperature stability and anti-scabbing process of a three-stage preheater in a rotary kiln according to an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, specific embodiments of this application are described clearly and completely below with reference to the accompanying drawings. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0018] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," "comprise," etc., in the specification, claims, and accompanying drawings of this application are open-ended terms, indicating that a method comprises one or more steps, or an apparatus comprises one or more elements, but do not exclude the inclusion of other steps or elements. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or primary / secondary relationship. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0022] like Figure 1As shown in the embodiment of the present invention, a control process for weak alkali temperature stabilization and anti-scaling in a three-stage preheater of a rotary kiln includes the following steps: S1, Raw material ratio control: control the total alkali content of the raw material entering the kiln to ≤0.85%, chlorine content to ≤0.06%, and sulfur content to ≤0.65%, and maintain the alkali-sulfur mass ratio at 0.8~1.1; S2, Decomposition furnace zone temperature stabilization: the coal distribution ratio between the upper and lower parts of the decomposition furnace is 55%:45%, and the outlet temperature of the decomposition furnace is stabilized at 870~890℃; S3, Three-stage gradient parameter control: C1 The outlet temperature is 460~490℃ and the negative pressure is -1900~-2200Pa. The outlet temperature of C2 is 680~720℃ and the negative pressure is -1500~-1700Pa. The outlet temperature of C3 is 840~880℃ and the negative pressure is -900~-1100Pa, eliminating local high-temperature stagnant areas inside the equipment. S4, kiln air volume coupling control: the kiln tail ventilation air volume is maintained at 175000~185000m³ / h, and the tertiary air opening is set to 70%~75%, shortening the residence time of fine particulate materials on the cylinder wall to within 0.5s.

[0023] In this embodiment, step S1 controls the total alkali content of the raw feed to be ≤0.85%, chlorine content ≤0.06%, and sulfur content ≤0.65%, while maintaining the alkali-sulfur mass ratio at 0.8~1.1. This allows alkali metals to preferentially combine with sulfur to form high-melting-point sulfates, reducing the amount of low-melting-point eutectic compounds in the 850~900℃ temperature range from the source of chemical composition. This cuts off the material basis for crust formation and solves the problem of existing technologies that only adjust a single component and cannot simultaneously achieve synergistic enrichment of alkali, chlorine, and sulfur. Step S2 sets the coal distribution ratio between the upper and lower parts of the decomposition furnace to 55%:45% and stabilizes the decomposition furnace outlet temperature. The temperature is controlled at 870~890℃ to ensure a uniform temperature distribution within the decomposition furnace, preventing localized overheating that could cause temperatures to exceed the critical value of 900℃ and lead to the formation of a large amount of precursor substances for crust formation. This solves the problems of wide temperature fluctuations at the decomposition furnace outlet and the lack of differentiated configuration between the upper and lower sections in existing technologies. Step S3 standardizes the gradient control of the C1 outlet temperature (460~490℃, negative pressure -1900~-2200Pa), C2 outlet temperature (680~720℃, negative pressure -1500~-1700Pa), and C3 outlet temperature (840~880℃, negative pressure -900~-1100Pa) to ensure uniform temperature distribution within the furnace. The preheater's temperature and pressure parameters form a stable gradient that decreases stepwise from bottom to top, eliminating localized high-temperature stagnant areas inside the cylinder and solving the problems of large fluctuations in temperature and pressure parameters and the lack of standardized gradient control for each stage of the preheater in existing technologies. Through step S4, the kiln tail ventilation airflow is maintained at 175,000~185,000 m³ / h, and the tertiary air opening is set to 70%~75%, optimizing the kiln airflow matching and shortening the residence time of fine particles on the cylinder wall to less than 0.5s. The high air velocity creates a continuous scouring effect on the C2 and C3 cylinder walls, removing the precursor materials from the wall surface before they harden and adhere, thus solving the problems of existing technologies. The previous approach relied solely on passively addressing the issue of blockages by shutting down the machine, which failed to suppress wall adhesion at the flow field level. The four steps mentioned above, from raw material chemical composition control, decomposition furnace temperature field zoning control, three-level temperature and pressure gradient standardized management to kiln air volume matching optimization, form a synergistic effect throughout the entire process. This extends the scale removal cycle from 1-2 times per week to 25-30 days, and controls system negative pressure fluctuations within ±80Pa. It systematically eliminates the conditions for scale formation at the process mechanism level, effectively solving the comprehensive technical problems of increased maintenance workload, high coal consumption, and limited output caused by existing technologies that can only temporarily alleviate faults but cannot fundamentally solve the scale problem.

[0024] C1, C2, and C3 refer to the three-stage cyclone preheater system, which consists of three cyclone tubes from top to bottom. The material flows from top to bottom (raw material is fed in from the top of C1 and passes through C2 and C3 in sequence before entering the decomposition furnace), while the high-temperature flue gas flows from bottom to top (hot flue gas enters the bottom of C3 from the decomposition furnace and is discharged through C2 and C1).

[0025] Furthermore, in step S2, the temperature stabilization of the decomposition furnace zone also includes: controlling the tertiary air temperature at 980~1020℃, and controlling the fluctuation range of the decomposition furnace outlet temperature within ±10℃.

[0026] In this embodiment, by controlling the tertiary air temperature at 980~1020℃, a stable and sufficiently hot high-temperature combustion air is provided to the decomposition furnace. This ensures that the coal distributed in a 55%:45% ratio in the upper and lower parts of the decomposition furnace can burn fully and stably. The tertiary air temperature and the decomposition furnace outlet temperature of 870~890℃ form a reasonable gradient match. At the same time, the fluctuation range of the decomposition furnace outlet temperature is controlled within ±10℃, so that the internal temperature field of the decomposition furnace remains uniform and stable. This avoids the formation of a large amount of alkali-sulfur eutectic due to intermittent temperature exceeding the 900℃ critical value, and also prevents incomplete combustion of pulverized coal due to excessively low temperatures, which could lead to reduction. The improved atmosphere eliminates the temperature conditions required for the formation of crust precursors from a thermal regime perspective, solving the technical problems of repeated crust formation caused by large fluctuations in tertiary air temperature and wide fluctuations in decomposer outlet temperature in existing technologies. In addition, the stable and controllable thermal regime of the decomposer effectively reduces frequent manual intervention and shutdown for unblocking operations due to abnormal temperature fluctuations, reducing maintenance workload and system heat consumption. It also provides a stable thermal premise for maintaining the kiln tail ventilation air volume at 175,000~185,000 m³ / h and the tertiary air opening at 70%~75%, making the temperature and pressure gradient control of the entire preheater system more precise and reliable.

[0027] The tertiary air refers to the high-temperature hot air introduced into the decomposition furnace from the grate cooler (clinker cooling equipment at the kiln head). The high-temperature clinker (approximately 1400℃) fired in the rotary kiln enters the grate cooler and is rapidly cooled by the blown-in cold air. This cold air absorbs the heat from the clinker and becomes high-temperature hot air. Part of this hot air enters the kiln to aid combustion (called "secondary air"), while the other part is separately sent to the decomposition furnace through the "tertiary air duct" (called "tertiary air"). Tertiary air is the main source of oxygen and heat for pulverized coal combustion and raw material decomposition in the decomposition furnace. Its temperature directly determines the combustion temperature within the decomposition furnace. Controlling it at 980~1020℃ ensures stable ignition and combustion of the pulverized coal in the decomposition furnace, thus coordinating with step S2 to stabilize the decomposition furnace outlet temperature at 870~890℃.

[0028] Furthermore, in step S3, the outlet temperatures of C1 to C3 increase in a stepwise manner, the temperature difference between adjacent preheaters is stabilized within the range of 160~220℃, and the system negative pressure fluctuation is controlled within ±80Pa.

[0029] In this embodiment, by setting the outlet temperatures of C1 to C3 to increase in a stepped manner (C1 outlet temperature 460~490℃, C2 outlet temperature 680~720℃, C3 outlet temperature 840~880℃), the gas-solid heat exchange efficiency in each stage of the preheater is progressively improved. As the high-temperature flue gas moves upwards, heat is recovered and utilized step by step, achieving efficient stepwise heat transfer of the flue gas and overcoming the deficiency of low heat exchange efficiency caused by unclear temperature differences between preheaters in existing technologies. By stabilizing the temperature difference between adjacent preheaters within the range of 160~220℃, each stage of the preheater undertakes a clear and balanced temperature increase task, avoiding excessive heat load on the lower stage preheater due to excessive temperature differences. This approach prevents localized overheating while avoiding wasted heat energy due to insufficient heat transfer caused by excessively small temperature differences. By controlling the system's negative pressure fluctuations within ±80Pa, the airflow distribution inside the preheater remains uniform and stable, avoiding localized stagnation zones caused by sudden changes in negative pressure leading to airflow deviation or short circuits. Through the synergistic effect of stable temperature gradient and precise control of negative pressure fluctuations, the conditions for the formation of localized high-temperature stagnation zones inside the C2 and C3 cylinders are eliminated from both temperature and flow field dimensions. This solves the technical problem of accelerated crust thickening caused by large fluctuations in temperature and pressure parameters and the lack of gradient-based standard control at each level in existing technologies, and provides a stable thermal foundation for subsequent kiln airflow coupling control and systemic crust suppression throughout the entire process.

[0030] Furthermore, in step S4, the kiln tail temperature is maintained at 1050~1200℃, and the airflow velocity inside cylinders C2 and C3 is controlled at 12~18m / s.

[0031] In this embodiment, by maintaining the kiln tail temperature at 1050~1200℃, the temperature field of the calcination zone inside the rotary kiln is kept stable, ensuring sufficient heat supply for clinker calcination. Simultaneously, a reasonable heat-airflow matching relationship is formed with the kiln tail ventilation airflow of 175,000~185,000 m³ / h and the tertiary air opening of 70%~75%. This avoids the risks of insufficient clinker calcination due to excessively low kiln tail temperature, and increased system heat consumption and overheating of the kiln shell due to excessively high temperature. This provides a reliable thermal premise for the stable control of airflow velocity in cylinders C2 and C3. By controlling the airflow velocity in cylinders C2 and C3 at 12~18 m / s, a strong rotating airflow is formed in each cyclone separator, significantly enhancing gas-solid separation efficiency. The high wind speed creates a continuous scouring and shearing effect on the cylinder wall, removing suspended dust and other pollutants. The unhardened, adherent crust precursor material is quickly removed from the wall surface, effectively shortening the residence time of fine particles on the cylinder wall. This overcomes the defect in existing technologies where insufficient airflow velocity leads to excessive material adhesion time on the wall surface, accelerating crust thickening. The synergistic effect of stable kiln tail temperature and optimized airflow velocity achieves precise matching of kiln air volume, resulting in a uniform and orderly flow field distribution within cylinders C2 and C3. This avoids increased system resistance and energy consumption due to excessively high airflow velocity, and also prevents aggravated material settling and local stagnation due to excessively low airflow velocity. It fundamentally eliminates the flow field conditions for material retention and adhesion on the wall surface, solving the technical problem in existing technologies where passive treatment by simply stopping the machine to clear blockages is insufficient to systematically suppress crust formation from the perspective of airflow matching and flow field optimization. This provides a stable and reliable thermal and flow field guarantee for the whole-process weak alkali stable temperature synergistic crust suppression.

[0032] Further, in step S1, the alkali-sulfur mass ratio is the ratio of the total mass of K2O and Na2O in the raw material fed into the kiln to the mass of SO3.

[0033] In this embodiment, by explicitly defining the alkali-sulfur mass ratio as the ratio of the total mass of K2O and Na2O to the mass of SO3 in the raw feed, the process parameter of the alkali-sulfur mass ratio has an accurate and unified stoichiometric meaning. This avoids the deviation in batching control caused by the ambiguous definition or inconsistent calculation method of the alkali-sulfur ratio in the prior art. It ensures that operators can accurately calculate and adjust the raw feed ratio according to this definition, so that alkali metals preferentially combine with sulfur to form high-melting-point sulfates rather than low-melting-point silicates or chlorides. From the chemical composition level, it precisely suppresses the output of molten viscous materials in the 850~900℃ temperature range and reduces the self-adhesion performance of high-temperature materials. Together with the limits of total alkali content ≤0.85%, chlorine content ≤0.06%, and sulfur content ≤0.65% in step S1, it constitutes a complete raw feed chemical composition control system. This provides a stable and reliable material basis for subsequent zoned temperature stabilization of the decomposition furnace, three-level gradient parameter control, and kiln airflow coupling regulation. It solves the technical problem of repeated crust formation caused by the synergistic enrichment of alkali, chlorine, and sulfur in the prior art from the source of the process.

[0034] Furthermore, in step S2, the outlet temperature of the decomposition furnace is stabilized at 875~885℃, and in step S3, the outlet temperature of C3 is controlled at 855~875℃.

[0035] In this embodiment, by precisely controlling the outlet temperature of the decomposition furnace within the preferred narrow range of 875~885℃, the pulverized coal combustion efficiency and raw material decomposition rate within the decomposition furnace are simultaneously brought to an optimal balance. Compared to the wider control range of 870~890℃, this further narrows the temperature fluctuation range, effectively avoiding the risk of a significant acceleration in the formation rate of alkali-sulfur eutectic when the temperature approaches the upper limit of 890℃, while also preventing the hidden danger of incomplete material decomposition when the temperature drops below 875℃. By controlling the C3 outlet temperature within the range of 855~875℃, the C3 cylinder outlet temperature is always lower than the decomposition furnace outlet temperature, maintaining a reasonable temperature difference gradient of 10~30℃ between the two. This avoids the formation of local overheated stagnant zones within the C3 cylinder due to excessively high temperatures. Under the premise of ensuring sufficient heat exchange of materials within the C3 cylinder, the temperature conditions for the large-scale formation of alkali-sulfur eutectic are eliminated, further enhancing the crusting inhibition effect in the high-temperature region of C3 from the perspective of precise temperature control.

[0036] Furthermore, in step S1, low-alkali limestone is used in combination with low-sulfur coal, along with iron or silicon corrective raw materials, to control the total alkali content of the raw materials entering the kiln to below 0.7% and the sulfur content to below 0.55%.

[0037] In this embodiment, by using low-alkali limestone and low-sulfur coal in combination with iron or silica correcting raw materials, the total alkali content of the raw meal entering the kiln is controlled below 0.7% and the sulfur content is controlled below 0.55%. Based on the total alkali content ≤0.85% and sulfur content ≤0.65%, the upper limit of alkali and sulfur components entering the kiln is further tightened, which significantly reduces the amount of alkali-sulfur eutectic generated in the 850~900℃ temperature range. At the same time, the incorporation of iron or silica correcting raw materials adjusts the silica ratio and alumina ratio of the raw meal, improves the sintering reaction characteristics of the material at high temperature, and further weakens the tendency of material wall adhesion. From the raw material end, a cleaner material basis is provided for the whole process synergistic inhibition of scale formation.

[0038] Furthermore, in step S3, the temperature difference between the C3 outlet temperature and the decomposition furnace outlet temperature in step S2 is controlled within 10~30℃.

[0039] In this embodiment, by controlling the temperature difference between the C3 outlet temperature and the decomposition furnace outlet temperature within 10~30℃, the C3 cylinder outlet temperature is kept close to the decomposition furnace outlet temperature but always lower than the latter. This ensures that the material in the C3 cylinder receives sufficient heat for carbonate decomposition, while also preventing the formation of an independent local overheating stagnation zone in the C3 cylinder due to excessively high temperatures (approaching or exceeding the critical value of 900℃). This eliminates the temperature conditions under which a large amount of alkali-sulfur eutectic is generated in the C3 cylinder and adheres to the wall surface, thus creating a smooth thermal transition between the decomposition furnace and the C3 cylinder. Together with the limitation of the C3 outlet temperature to 840~880℃, this constitutes a complete technical solution for precise temperature control in the high-temperature region of C3, effectively curbing the formation of scale in the most prone area of ​​the tertiary preheater (C3 cylinder) from a thermal perspective.

[0040] Furthermore, in step S4, the adjustment range of the kiln tail ventilation air volume and the tertiary air opening is matched in conjunction with the negative pressure changes of cylinders C2 and C3. When the negative pressure of cylinder C2 or C3 deviates from the gradient range set in step S3, the kiln tail exhaust air volume and the tertiary air valve opening are adjusted accordingly.

[0041] In this embodiment, the adjustment range of the kiln tail ventilation air volume and the tertiary air opening is linked and matched according to the negative pressure changes of cylinders C2 and C3. When the negative pressure of cylinders C2 or C3 deviates from the gradient range set in step S3, the kiln tail exhaust air volume and the opening of the tertiary air valve are adjusted accordingly. This makes the air volume parameter in S4 no longer a fixed set value, but dynamically and adaptively adjusted according to the actual negative pressure feedback of cylinders C2 and C3. This ensures that the temperature and pressure gradient of each stage of the preheater can still be maintained within the standardized range set in step S3 when external disturbances occur (such as fluctuations in feed amount, changes in coal quality, etc.). This avoids the deterioration of airflow distribution, the recurrence of local stagnation zones, and the accelerated formation of crusts caused by negative pressure deviation. This ensures that the coordinated control of the four steps of the entire process remains effective under dynamic operating conditions. This solves the technical problem in the prior art that fixed parameter settings cannot cope with operating condition fluctuations and can only be handled by stopping the machine after negative pressure instability.

[0042] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln, characterized in that, Includes the following steps: S1. Raw meal ratio control: Control the total alkali content of raw meal entering the kiln to ≤0.85%, chlorine content to ≤0.06%, and sulfur content to ≤0.65%, and maintain the alkali-sulfur mass ratio at 0.8~1.1; S2. Zoned temperature stabilization of the decomposition furnace: The coal distribution ratio between the upper and lower parts of the decomposition furnace is 55%:45%, and the outlet temperature of the decomposition furnace is stabilized at 870~890℃. S3, Three-level gradient parameter control: C1 outlet temperature 460~490℃, negative pressure -1900~-2200Pa, C2 outlet temperature 680~720℃, negative pressure -1500~-1700Pa, C3 outlet temperature 840~880℃, negative pressure -900~-1100Pa, eliminating local high-temperature stagnation areas inside the equipment; S4. Kiln air volume coupling control: The ventilation air volume at the kiln tail is maintained at 175,000~185,000 m³ / h, and the opening degree of the tertiary air is set to 70%~75%, shortening the residence time of fine particulate materials on the cylinder wall to within 0.5s.

2. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S2, the temperature stabilization of the decomposition furnace zone also includes: controlling the temperature of the tertiary air at 980~1020℃, and controlling the fluctuation range of the decomposition furnace outlet temperature within ±10℃.

3. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S3, the outlet temperatures of C1 to C3 increase in a stepwise manner, the temperature difference between two adjacent preheaters is stabilized within the range of 160~220℃, and the system negative pressure fluctuation is controlled within ±80Pa.

4. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S4, the kiln tail temperature is maintained at 1050~1200℃, and the airflow velocity inside cylinders C2 and C3 is controlled at 12~18m / s.

5. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S1, the alkali-sulfur mass ratio is the ratio of the total mass of K2O and Na2O in the raw feed entering the kiln to the mass of SO3.

6. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S2, the outlet temperature of the decomposition furnace is stabilized at 875~885℃.

7. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S3, the outlet temperature of C3 is controlled at 855~875℃.

8. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S1, low-alkali limestone and low-sulfur coal are used in combination with iron or silicon corrective raw materials to control the total alkali content of the raw materials entering the kiln to below 0.7% and the sulfur content to below 0.55%.

9. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S3, the temperature difference between the outlet temperature of C3 and the outlet temperature of the decomposition furnace in step S2 is controlled within 10~30℃.

10. The control process for weak alkali temperature stabilization and synergistic anti-scaling in a three-stage preheater of a rotary kiln as described in claim 1, characterized in that, In step S4, the adjustment range of the kiln tail ventilation air volume and the tertiary air opening is matched in conjunction with the negative pressure changes of cylinders C2 and C3. When the negative pressure of cylinder C2 or C3 deviates from the gradient range set in step S3, the kiln tail exhaust air volume and the tertiary air valve opening are adjusted accordingly.

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