Method for strengthening cement clinker calcination production by fluorine mineralizer

Abstract

The application relates to the technical field of building material preparation, and discloses a fluorine-based mineralizer reinforced cement clinker calcination production method, raw materials of which include limestone, desulfurization gypsum, calcium fluoride sludge, coal-fired slag and the like. A specific sulfur-fluorine molar ratio and total alkali-sulfur mass ratio are controlled in the raw material formula, a sulfur-fluorine synergistic coordination compensation effect under high-temperature liquid phase is utilized, the generation of high-early hydration active fluorine-containing minerals is inhibited, and the cement quick-setting problem caused by free fluoride ions is improved. In the production process, the calcium fluoride sludge is mixed with the coal-fired slag in advance to reduce the adhesion of the materials; meanwhile, the desulfurization gypsum is shunted, and part of the materials is directly sprayed into a decomposing furnace to relieve the skin blocking caused by the preheater circulation enrichment. In addition, polyacrylamide in the calcium fluoride sludge is pyrolyzed to release ammonia gas in the decomposing furnace, cooperatively participates in a non-catalytic reduction denitration reaction, and the use cost of an additional denitration agent is reduced. The application realizes the resource utilization of multi-source solid wastes and the stable operation of a system.

Description

Technical Field

[0001] This invention relates to the field of building material preparation technology, specifically to a method for producing cement clinker reinforced with fluorine-based mineralizers through calcination. Background Technology

[0002] In the production of dry-process cement clinker, utilizing cement kilns for the co-processing of industrial solid waste is a common resource recovery approach in the industry. For example, introducing industrial sludge containing calcium fluoride as a mineralizer into cement raw materials can lower the eutectic point of the system during the calcination stage and promote solid-phase reactions.

[0003] However, in practical production applications, conventional batching and calcination processes face some technical limitations. When fluoride-containing sludge enters the calcination system, the released free fluoride ions readily react with the alumina components in the raw materials at high temperatures, generating fluoride-containing minerals with high early hydration activity. These minerals tend to cause rapid setting in the early stages of cement hydration, leading to decreased cement paste fluidity and, to some extent, affecting the density and overall mechanical strength of the later hydration product network. To suppress rapid setting caused by free fluoride ions, engineers often attempt to introduce high-valence sulfur ions for charge compensation. However, if the traditional centralized grinding and batching process is used to mix sulfur-containing solid wastes such as desulfurized gypsum into the raw materials at once, the desulfurized gypsum is prone to premature dehydration during the gradual heating in the suspension preheater. The released sulfur components circulate and accumulate within the preheater system, easily causing scaling and blockage, thus disrupting the thermal stability of the kiln.

[0004] Furthermore, because industrial fluorine-containing sludge generally has a high free water content and a relatively viscous appearance, direct addition often causes adhesion and clogging of the conveyor belts and discharge chutes, easily leading to fluctuations in the feed to the raw material grinding equipment. Meanwhile, traditional cement clinker calcination systems typically generate significant amounts of nitrogen oxide emissions. Current conventional treatment methods often rely on injecting large quantities of external ammonia or other denitrification agents into the system to meet environmental emission standards. This not only increases the company's material costs but also increases the risk of ammonia escape during daily operation.

[0005] Therefore, this invention proposes a method for producing cement clinker reinforced by fluorine mineralizers through calcination to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for producing cement clinker enhanced by fluorine-based mineralizers through calcination. This method solves the problems of rapid cement setting caused by free fluoride ions, preheater scaling and blockage due to the cyclic enrichment of sulfur-containing components, and the high operating costs of conventional denitrification systems when using fluorine-containing sludge to prepare cement clinker.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for producing cement clinker reinforced with fluorine-based mineralizers through calcination, comprising the following steps: S1. Weigh the raw materials required for preparing the cement clinker by weight: 45.00-52.80 parts limestone, 25.00-34.00 parts limestone powder, 1.00-3.80 parts silicon ore beneficiation sludge, 5.00-12.00 parts iron ore beneficiation sludge, 0.20-1.50 parts converter slag, 2.80-3.50 parts desulfurized gypsum, 1.20-2.30 parts calcium fluoride sludge, and 3.00-6.90 parts coal-fired furnace slag; divide the weighed desulfurized gypsum into two independent material streams, extract 30.0%-50.0% of the total desulfurized gypsum mass as the first material stream to be fed into the raw material grinding equipment, and send the remaining 50.0%-70.0% as the second material stream to the injection feed bin of the kiln tail decomposition furnace; S2. The calcium fluoride sludge and the coal-fired furnace slag are subjected to forced homogenization and stirring to obtain a premix; S3. The premix prepared in step S2 is combined with the remaining limestone, limestone powder, silicon ore beneficiation sludge, iron ore beneficiation sludge, converter slag, and the first material stream desulfurization gypsum diverted in step S1, and fed into a raw material roller mill for grinding and homogenization to obtain dry raw powder. S4. The homogenized dry powder raw material is fed into the decomposition furnace equipped with a suspension preheater; the second material flow desulfurized gypsum is directly injected into the decomposition furnace by pneumatic conveying, and the injection amount of denitrification agent is reduced simultaneously. S5. The pre-decomposed hot raw material falls into the rotary kiln cylinder, undergoes a solid-state thermochemical reaction, and enters the firing zone to be fired into high-temperature clinker. S6. The high-temperature clinker that has completed liquid phase sintering falls into a cooler for high-pressure rapid cooling, and then is sent to the finished product warehouse.

[0008] A physicochemical regulation mechanism was established in the clinker calcination process and raw material blending stage. The specific reaction and action mechanism are as follows: Spatial distribution control and anti-clogging process. In dry-process cement production, if sulfur-containing solid waste enters the suspension preheater along with the raw materials, premature dehydration is highly likely to occur during the heat exchange process of gradual temperature increases. The released sulfate components undergo volatilization and condensation in the gas-solid two-phase cycle within the preheater system, leading to local scaling and blockage of the feed pipeline. This solution diverts the desulfurized gypsum, bypassing the initial preheating stage and feeding a large proportion of sulfur-containing components directly into the high-temperature decomposition furnace via pneumatic conveying. This cuts off the preheater's circulating enrichment path for sulfur elements and maintains the thermal stability of the system.

[0009] Sulfur-fluorine coordination compensation and inhibition of rapid setting process. In the conventional calcination liquid phase, free fluoride ions introduced by calcium fluoride readily react with aluminate minerals to form calcium fluoroaluminate minerals with extremely high early hydration activity. Through direct injection after the desulfurization gypsum decomposition furnace, a localized high concentration of sulfate ions is provided in the material flow field about to enter the rotary kiln calcination zone. High-valence sulfur ions and fluoride ions undergo synergistic charge-compensating solid solution within the lattice of allit tricalcium silicate minerals. The reaction mechanism shifts towards stabilizing the tricalcium silicate lattice, consuming free fluoride ions in the system, thereby inhibiting the formation of calcium fluoroaluminate minerals and improving the setting time of the finished product.

[0010] Physical transformation process. Calcium fluoride sludge is a viscous colloidal substance, and direct mixing with raw materials can easily cause clogging in the conveying system. Homogenizing and premixing it with porous coal slag allows for mechanical moisture transfer, improving feeding smoothness.

[0011] Preferably, in step S1, the calcium fluoride sludge is industrial waste residue that has been screened and calibrated, with a free water content of 40.00%–50.00%, a calcium fluoride mass fraction of 80.00%–92.00% in the dry basis solid phase, and a polyacrylamide mass fraction of 0.50%–2.00% in the dry basis. By adjusting the ratio of the calcium fluoride sludge to desulfurized gypsum, the sulfur-fluorine molar ratio SO3 / F in the mixed raw material is controlled at 1.2–1.8, and the total alkali-sulfur mass ratio is controlled at 0.8–1.1. Defining the physicochemical properties of calcium fluoride sludge provides a foundation for subsequent processes. Polyacrylamide macromolecules serve as the endogenous reducing agent for in-situ denitrification in the subsequent decomposition furnace. Controlling the sulfur-to-fluorine molar ratio (SO3 / F) within the range of 1.2 to 1.8 ensures that the charge compensation of sulfur ions in the liquid phase is slightly higher than the equivalent requirement of fluorine ions, eliminating localized fluorine-rich micro-regions during silicate lattice development and guaranteeing the integrity of mineral development. Controlling the total alkali-to-sulfur mass ratio between 0.8 and 1.1 promotes the combination of potassium and sodium alkali metal ions with an appropriate amount of sulfate ions in the system, generating thermodynamically stable alkaline sulfates. This reduces the volatilization rate of alkali metals in the high-temperature kiln gas and mitigates the tendency for alkaline crusting in the kiln tail flue.

[0012] Preferably, in step S2, the coal-fired slag and calcium fluoride sludge are continuously fed into a shaftless twin-shaft horizontal forced mixer at a mass ratio of 2.5:1 to 3.0:1. The main shaft speed of the mixer is controlled at 30 to 50 rpm, and the mixture is forcibly homogenized and stirred for 5 to 15 minutes to obtain a loose granular premix with no free water seeping out on the surface. The overall surface moisture content of the premix is ​​controlled at 12.80% to 14.00%.

[0013] The mechanical shearing force provided by the horizontal forced mixer disrupts the original polymeric floc structure of the calcium fluoride sludge. Under the set ratio and mixing time, the free water trapped inside the sludge physically migrates into the rich capillary pore structure of the coal-fired slag. This treatment transforms the high-moisture sludge into loose, surface-dry particles, eliminating the physical conditions that would lead to adhesion and sticking of the high-moisture material in subsequent chutes.

[0014] Preferably, the grinding and homogenization steps include: uniformly feeding the combined material into a raw material vertical roller mill equipped with a classifier, and fully introducing the exhaust gas from a suspension preheater at a temperature of 280-330°C as an internal drying medium; adjusting the rotation speed of the classifier to 650-850 rpm, controlling the overall moisture content of the dry raw material output to be 0.2%-0.9%, and controlling the fineness of the raw material to be 8.0%-13.0% of the residue percentage on an 80μm standard sieve.

[0015] Using preheater exhaust gas with a specific temperature gradient as the drying medium, a gas-solid heat exchange flow field is established inside the roller mill. By adjusting the classifier speed, the particle size distribution of the raw meal is physically controlled. The dry powder raw meal with this fineness range and moisture content has a suitable specific surface area, allowing it to quickly absorb ambient heat and initiate the gas-solid interface decomposition reaction of calcium carbonate upon entering the decomposition furnace, thus shortening the mass transfer distance of the solid-phase reaction.

[0016] Preferably, in step S4, the proportion of pulverized coal fed into the decomposition furnace is controlled to be 55.0% to 62.0% of the total fuel quantity, and the operating temperature of the gas-solid mixed phase in the middle and outlet of the decomposition furnace is controlled at 850 to 880°C; the second material flow desulfurization gypsum is directly injected into the decomposition furnace at a spray speed of 25 to 40 m / s; the blast volume is adjusted to maintain the excess oxygen concentration in the kiln tail flue at 2.5% to 3.5%; the step of reducing the amount of denitrifying agent injected includes: using polyacrylamide in calcium fluoride sludge to release ammonia in situ through in-situ thermal decomposition in the decomposition furnace for synergistic denitrification, and reducing the amount of denitrifying agent injected into the system by 10.0% to 30.0%.

[0017] By adopting the above technical solution, the gas-solid mixed-phase operating temperature of 850 to 880°C not only meets the thermal absorption requirements of raw material pre-decomposition but also coincides with the optimal temperature window for selective non-catalytic reduction denitrification. Under this high-temperature, aerobic environment, the long chains of polyacrylamide associated with calcium fluoride sludge undergo depolymerization and pyrolysis, releasing a large number of reducing amino free radicals. With the support of a set excess oxygen concentration, the amino groups directly react with the nitrogen oxides generated in the system to produce nitrogen and water. This in-situ thermal denitrification process directly replaces the externally injected ammonia denitrification agent. Furthermore, the desulfurized gypsum powder is endowed with an initial kinetic energy of 25 to 40 m / s, enabling it to overcome the upward airflow resistance inside the decomposition furnace and penetrate the boundary layer, ensuring that the desulfurized gypsum is directly integrated into the main reaction flow field.

[0018] Preferably, in step S5, the rotation speed of the rotary kiln is controlled at 3.5 to 4.5 rpm, the material undergoes a solid-state thermochemical reaction in the transition range of 900 to 1100°C, and the maximum calcination temperature of the material in the firing zone is controlled at 1350 to 1450°C.

[0019] The kiln rotation speed setting establishes a residence time gradient for materials in different temperature zones. The transition range of 900 to 1100℃ provides a kinetic basis for the synthesis of mesophase minerals such as dicalcium silicate. When the material enters the firing zone of 1350 to 1450℃, a partial liquid phase appears in the system, promoting the absorption of free calcium oxide from the environment by the mesophase minerals, further crystallizing and developing into structurally complete alite minerals, thus reducing the content of residual free calcium oxide in the clinker.

[0020] Preferably, in step S6, the step of high-pressure rapid cooling includes: turning on the high-pressure pulse cooling fan and controlling the air pressure to 5.5-8.5 kPa, so that the high-temperature clinker is rapidly cooled from the firing temperature to below 150°C within 10-20 minutes.

[0021] If the cooling rate is too slow after the clinker leaves the firing zone, the already formed allite minerals are highly susceptible to reverse decomposition reactions in the dangerous temperature range of around 1250℃, generating secondary free calcium oxide and dicalcium silicate. High-pressure pulsed cooling air provides high-intensity gas-solid convection heat transfer, forcing the clinker to cross the phase transformation danger zone in a short time. This process freezes the mineral phase structure formed in the high-temperature liquid phase, locks in the microscopic defects within the crystal lattice, and preserves the hydration reactivity of the silicate cement clinker.

[0022] This invention provides a method for producing cement clinker reinforced with fluorine-based mineralizers through calcination. It offers the following advantages: 1. This invention establishes a sulfur-fluorine coordination compensation mechanism during clinker calcination by introducing calcium fluoride sludge and desulfurized gypsum into the raw meal system in a specific ratio and controlling the corresponding sulfur-fluorine molar ratio and total alkali-sulfur mass ratio. This ratio provides a relatively sufficient amount of sulfur ions in the high-temperature liquid phase, promoting the stable solidification of introduced fluoride ions within the silicate mineral lattice, thereby inhibiting the formation of free fluoride ions that easily cause rapid cement setting, such as calcium fluoroaluminate minerals. This treatment method, while disposing of fluoride-containing waste, maintains the normal initial fluidity of the cement and provides a fundamental guarantee for the strength development of the subsequent hydration product network.

[0023] 2. This invention utilizes the polyacrylamide component carried in calcium fluoride sludge, causing it to undergo in-situ pyrolysis within a specific temperature range of the decomposition furnace and release ammonia gas. This ammonia gas acts as an endogenous reducing agent, directly participating in the selective non-catalytic reduction reaction within the decomposition furnace to synergistically denitrate the nitrogen oxides generated in the system. By combining the physicochemical properties of the waste residue itself for in-situ denitrification treatment, it can partially replace the use of conventional externally purchased ammonia denitrification agents, thus helping to reduce the environmental operating costs of cement production processes and the risk of ammonia escape to a certain extent.

[0024] 3. This invention premixes high-moisture calcium fluoride sludge with coal-fired furnace slag, utilizing the porous and water-absorbing properties of the slag to improve the material's appearance and alleviate the problem of sludge adhesion and sticking in the feeding system. Simultaneously, the process, combined with the desulfurization gypsum diversion and direct injection decomposition furnace, avoids the premature dehydration and recirculation of large amounts of high-valence sulfur components within the suspension preheater along with the raw materials. The coordination of these process steps reduces the probability of scaling and clogging in the preheater system, creating favorable conditions for the continuous and stable operation of the entire dry clinker calcination system. Attached Figure Description

[0025] Figure 1 This is a differential scanning calorimeter of the present invention within the heating range of 800°C to 1000°C. Figure 2 This is a monitoring chart of hourly output fluctuations during the initial continuous operation phase of this invention. Figure 3 This is a negative pressure fluctuation monitoring chart for 30 consecutive days of operation according to the present invention; Figure 4 This is a monitoring chart showing the fluctuation of ammonia consumption rate over 24 hours under different operating conditions according to the present invention. Figure 5 The diagram shows the hydration and setting characteristics and mechanical properties of cement prepared from clinker under different mix proportions according to the present invention. (a) is a diagram showing the setting time range of cement for each test sample, and (b) is a diagram showing the evolution of compressive strength of cement mortar for each test sample at 3 days and 28 days. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0028] The main component of limestone and limestone powder is calcium carbonate (CAS No. 471-34-1). Silicon ore beneficiation sludge, iron ore beneficiation sludge, and converter slag are all industrial raw materials and solid wastes that are routinely generated and commercially supplied by related industries.

[0029] The loose bulk density of coal-fired furnace slag is 0.60 g / cm³. 3 Up to 0.85 g / cm 3 The specific surface area of ​​BET is 1.5m². 2 / g to 3.5m 2 / g.

[0030] The main component of desulfurized gypsum is calcium sulfate dihydrate (CAS No. 10101-41-4), with a bound water of crystallization mass fraction of 18.00% to 21.00% and an attached free water mass fraction of 8.00% to 15.00%.

[0031] The free water content of the calcium fluoride sludge is 40.00% to 50.00%, and the mass fraction of calcium fluoride (CAS No. 7789-75-5) in the dry solid phase is 80.00% to 92.00%. The dry sludge contains high molecular weight polyacrylamide (CAS No. 9003-05-8), and the mass fraction of this polyacrylamide in the dry sludge is 0.50% to 2.00%.

[0032] Preparation Example 1: This preparation example provides a method for preparing a premix of calcium fluoride sludge and coal-fired furnace slag, including the following steps: Industrial waste calcium fluoride sludge and coal-fired furnace slag that have been screened and calibrated were taken. The free water content of the calcium fluoride sludge was 40.00%, the mass fraction of calcium fluoride in the dry solid phase was 80.00%, and the mass fraction of polyacrylamide in the dry basis was 0.50%. Coal-fired boiler slag and calcium fluoride sludge were simultaneously and continuously fed into a shaftless twin-shaft horizontal forced mixer at a mass ratio of 2.5:1. The main shaft speed of the mixer was controlled at 30 rpm, and the mixture was forcibly homogenized for 5 minutes to obtain a loose granular premix with no free water seepage on the surface. The overall surface moisture content of the premix was measured to be 12.80%.

[0033] Preparation Example 2: This preparation example provides a method for preparing a premix of calcium fluoride sludge and coal-fired furnace slag, including the following steps: Industrial waste calcium fluoride sludge and coal-fired furnace slag that have been screened and calibrated were taken. The free water content of the calcium fluoride sludge was 45.00%, the mass fraction of calcium fluoride in the dry solid phase was 88.00%, and the mass fraction of polyacrylamide in the dry basis was 1.20%. Coal-fired furnace slag and calcium fluoride sludge were simultaneously and continuously fed into a shaftless twin-shaft horizontal forced mixer at a mass ratio of 2.8:1. The main shaft speed of the mixer was controlled at 40 rpm, and the mixture was forcibly homogenized for 10 minutes to obtain a loose granular premix with no free water seepage on the surface. The overall surface moisture content of the premix was measured to be 13.40%.

[0034] Preparation Example 3: This preparation example provides a method for preparing a premix of calcium fluoride sludge and coal-fired furnace slag, including the following steps: Industrial waste calcium fluoride sludge and coal-fired furnace slag that have been screened and calibrated were taken. The free water content of the calcium fluoride sludge was 50.00%, the mass fraction of calcium fluoride in the dry solid phase was 92.00%, and the mass fraction of polyacrylamide in the dry basis was 2.00%. Coal-fired boiler slag and calcium fluoride sludge were simultaneously and continuously fed into a shaftless twin-shaft horizontal forced mixer at a mass ratio of 3.0:1. The main shaft speed of the mixer was controlled at 50 rpm, and the mixture was forcibly homogenized for 15 minutes to obtain a loose granular premix with no free water seepage on the surface. The overall surface moisture content of the premix was measured to be 14.00%.

[0035] Example 1: This embodiment provides a method for producing cement clinker reinforced with fluorine-based mineralizers through calcination, including the following steps: According to the mass fraction, accurately weigh the raw materials for the raw material composition: 48.00 parts limestone, 30.00 parts limestone powder, 2.00 parts silicon ore beneficiation sludge, 8.00 parts iron ore beneficiation sludge, 1.00 parts converter slag, 3.40 parts desulfurized gypsum, 2.00 parts calcium fluoride sludge, and 5.60 parts coal-fired furnace slag.

[0036] (1) Regularly test the free moisture and dry basis fluoride ion mass fraction in the calcium fluoride sludge entering the plant. Calculate the total fluoride molar amount brought into the system based on the weighed 2.00 parts of calcium fluoride sludge. Determine that 3.40 parts of desulfurized gypsum can strictly maintain the sulfur-fluoride molar ratio (SO3 / F) in the mixed raw material at 1.5 and control the total alkali-sulfur mass ratio at 0.95. Divide the 3.40 parts of desulfurized gypsum into two independent material streams: extract 40.0% (i.e., 1.36 parts) of the total desulfurized gypsum as the first material stream to be prepared for entering the raw material grinding equipment; the remaining 60.0% (i.e., 2.04 parts) is kept in its original high-moisture and dihydrate crystallization state and transported as the second material stream to the special pneumatic injection feed bin of the kiln tail decomposition furnace.

[0037] (2) Physical pretreatment: Take 2.00 parts of calcium fluoride sludge and 5.60 parts of coal slag (mass ratio of 2.8 to 1) and prepare a loose granular premix with no free water seepage on the surface according to the method described in Preparation Example 2.

[0038] (3) The premix prepared in step (2) is combined with the remaining limestone, limestone powder, silicon ore beneficiation sludge, iron ore beneficiation sludge, converter slag and the first material stream desulfurization gypsum diverted in step (1) by a collection belt and fed evenly into the raw material vertical roller mill; the exhaust gas from the new type of suspension preheater with a temperature of 305℃ is fully introduced as the internal drying medium; the speed of the classifier is adjusted to 750 rpm, the comprehensive moisture content of the dry raw material is controlled to be 0.5%, and the fineness of the raw material is controlled to be 10.5% of the residue on an 80μm standard sieve; the ground material is sent to the raw material homogenization silo for pneumatic homogenization to obtain dry powder raw material.

[0039] (4) Feed the homogenized dry powder raw material into the new dry decomposition furnace with a suspension preheater; control the proportion of coal powder in the decomposition furnace to 58.0% of the total fuel, and control the operating temperature of the gas-solid mixed phase in the middle and outlet of the decomposition furnace at 865℃; through a separately established pneumatic conveying pipeline, inject the second material flow desulfurization gypsum at a spray speed of 32m / s into the core flow field area of ​​865℃ in the decomposition furnace; regulate the system's air volume to maintain the excess oxygen concentration in the kiln tail smoke chamber at 3.0%, and simultaneously reduce the injection volume of the original ammonia denitrification agent in the system by 20.0% of the total mass flow rate of conventional injection.

[0040] (5) The pre-decomposed hot raw material falls into the rotary kiln. As the kiln rotates at a speed of 4.0 rpm, the material is pushed towards the kiln head and undergoes a solid thermochemical reaction in the transition zone from 900°C to 1100°C. The material continues to enter the calcination zone, and the maximum calcination temperature of the material in the calcination zone is controlled at 1400°C so that the free calcium oxide is completely absorbed and calcined into well-crystallized Alite minerals.

[0041] (6) The high-temperature clinker that has completed liquid phase sintering falls into the air-filled grate cooler. The high-pressure pulse cooling fan is turned on to control the air pressure to 7.0 kPa, so that the clinker is rapidly cooled from 1400°C to below 150°C within 15 minutes. After crushing, it is sent to the finished clinker warehouse.

[0042] Example 2: This embodiment provides a method for producing cement clinker reinforced with fluorine-based mineralizers through calcination, including the following steps: Accurately weigh the raw materials for the raw meal composition according to the following weight percentages: 52.80 parts limestone, 34.00 parts limestone powder, 1.00 part silicon ore beneficiation sludge, 5.00 parts iron ore beneficiation sludge, 0.20 parts converter slag, 2.80 parts desulfurized gypsum, 1.20 parts calcium fluoride sludge, and 3.00 parts coal-fired furnace slag.

[0043] (1) Regularly test the free moisture and dry basis fluoride ion mass fraction in the calcium fluoride sludge entering the plant. Calculate the total fluoride molar amount brought into the system based on the weighed 1.20 parts of calcium fluoride sludge. Determine that 2.80 parts of desulfurized gypsum can strictly maintain the sulfur-fluoride molar ratio (SO3 / F) in the mixed raw material at 1.2 and control the total alkali-sulfur mass ratio at 0.8. Divide the 2.80 parts of desulfurized gypsum into two independent material streams: extract 50.0% (i.e., 1.40 parts) of the total desulfurized gypsum as the first material stream to be prepared for entering the raw material grinding equipment; the remaining 50.0% (i.e., 1.40 parts) is kept in its original high-moisture and dihydrate crystallization state and transported as the second material stream to the special pneumatic injection feed bin of the kiln tail decomposition furnace.

[0044] (2) Take 1.20 parts of calcium fluoride sludge and 3.00 parts of coal-fired furnace slag (mass ratio of 2.5 to 1) and prepare a loose granular premix with no free water seepage on the surface according to the method described in Preparation Example 1.

[0045] (3) The premix prepared in step (2) is combined with the remaining limestone, limestone powder, silicon ore beneficiation sludge, iron ore beneficiation sludge, converter slag and the first material stream desulfurization gypsum diverted in step (1) by a collection belt and fed evenly into the raw material vertical roller mill; the exhaust gas from the new type of suspension preheater with a temperature of 280℃ is fully introduced as the internal drying medium; the speed of the classifier is adjusted to 650 rpm, and the comprehensive moisture content of the dry raw material is controlled to be 0.9%, and the fineness of the raw material is controlled to be 13.0% of the residue on an 80μm standard sieve; the ground material is sent to the raw material homogenization silo for pneumatic homogenization to obtain dry powder raw material.

[0046] (4) Multi-dimensional coordinated thermal control of the decomposition furnace: The homogenized dry powder raw material is fed into the new dry decomposition furnace system with a suspension preheater; the proportion of coal powder in the decomposition furnace is controlled to be 55.0% of the total fuel; the operating temperature of the gas-solid mixed phase in the middle and outlet of the decomposition furnace is controlled at 850℃; the second material flow desulfurization gypsum is injected directly into the core flow field area of ​​850℃ in the decomposition furnace at a spray speed of 25m / s through a separately established pneumatic conveying pipeline; the system evacuation volume is adjusted to maintain the excess oxygen concentration in the kiln tail smoke chamber at 2.5%, and the original ammonia denitrification agent injection volume of the system is simultaneously reduced by 10.0% of the total mass flow rate of conventional injection.

[0047] (5) Solid-phase reaction and liquid-phase calcination stage: The pre-decomposed hot raw material falls into the rotary kiln. As the kiln rotates at a speed of 3.5 rpm, the material is pushed towards the kiln head and undergoes a solid-state thermochemical reaction in the transition zone from 900℃ to 1100℃. The material continues to enter the calcination zone, and the maximum calcination temperature of the material in the calcination zone is controlled at 1350℃ so that the free calcium oxide is completely absorbed and well-crystallized Alite minerals are formed.

[0048] (6) High-pressure rapid cooling solid phase process: The high-temperature clinker that has completed liquid phase sintering falls into the gas-filled grate cooler. The high-pressure pulse cooling fan is turned on to control the air pressure to 5.5 kPa, so that the clinker is rapidly cooled from above 1350°C to below 150°C within 10 minutes. After crushing, it is sent to the finished clinker warehouse.

[0049] Example 3: This embodiment provides a method for producing cement clinker reinforced with fluorine-based mineralizers through calcination, including the following steps: According to the mass fraction, accurately weigh the raw materials of the raw material composition: 45.00 parts limestone, 25.00 parts limestone powder, 3.80 parts silicon ore beneficiation sludge, 12.00 parts iron ore beneficiation sludge, 1.50 parts converter slag, 3.50 parts desulfurized gypsum, 2.30 parts calcium fluoride sludge, and 6.90 parts coal-fired furnace slag.

[0050] (1) Regularly test the free moisture and dry basis fluoride ion mass fraction in the calcium fluoride sludge entering the plant. Calculate the total fluoride molar amount brought into the system based on the weighed 2.30 parts of calcium fluoride sludge. Determine that 3.50 parts of desulfurized gypsum can strictly maintain the sulfur-fluoride molar ratio (SO3 / F) in the mixed raw material at 1.8 and control the total alkali-sulfur mass ratio at 1.1. Divide the 3.50 parts of desulfurized gypsum into two independent material streams: extract 30.0% (i.e., 1.05 parts) of the total desulfurized gypsum as the first material stream to be prepared for entering the raw material grinding equipment; the remaining 70.0% (i.e., 2.45 parts) is kept in its original high-moisture and dihydrate crystallization state and transported as the second material stream to the special pneumatic injection feed bin of the kiln tail decomposition furnace.

[0051] (2) Take 2.30 parts of calcium fluoride sludge and 6.90 parts of coal-fired furnace slag (mass ratio of 3.0 to 1) and prepare a loose granular premix with no free water seepage on the surface according to the method described in Preparation Example 3.

[0052] (3) The premix prepared in step (2) is combined with the remaining limestone, limestone powder, silicon ore beneficiation sludge, iron ore beneficiation sludge, converter slag and the first material stream desulfurization gypsum diverted in step (1) by a collection belt and fed evenly into the raw material vertical roller mill; the exhaust gas from the new type of suspension preheater with a temperature of 330℃ is fully introduced as the internal drying medium; the speed of the classifier is adjusted to 850 rpm, the comprehensive moisture content of the dry raw material is controlled to be 0.2%, and the fineness of the raw material is controlled to be 8.0% of the residue on an 80μm standard sieve; the ground material is sent to the raw material homogenization silo for pneumatic homogenization to obtain dry powder raw material.

[0053] (4) The homogenized dry powder raw material is fed into the new dry decomposition furnace system with a suspension preheater; the proportion of coal powder in the decomposition furnace is controlled to be 62.0% of the total fuel, and the operating temperature of the gas-solid mixed phase in the middle and outlet of the decomposition furnace is controlled at 880℃; the second material flow desulfurization gypsum is injected directly into the core flow field area of ​​880℃ in the decomposition furnace at a spray speed of 40m / s through a separately established pneumatic conveying pipeline; the system air volume is adjusted to maintain the excess oxygen concentration in the kiln tail smoke chamber at 3.5%, and the original ammonia denitrification agent injection volume of the system is simultaneously reduced by 30.0% of the total mass flow rate of conventional injection.

[0054] (5) Solid-phase reaction and liquid-phase calcination stage: The pre-decomposed hot raw material falls into the rotary kiln. As the kiln rotates at a speed of 4.5 rpm, the material is pushed towards the kiln head and undergoes a solid-state thermochemical reaction in the transition zone from 900℃ to 1100℃. The material continues to enter the calcination zone, and the maximum calcination temperature of the material in the calcination zone is controlled at 1450℃ so that the free calcium oxide is completely absorbed and well-crystallized Alite minerals are formed.

[0055] (6) High-pressure rapid cooling solid phase process: The high-temperature clinker that has completed liquid phase sintering falls into the gas-filled grate cooler. The high-pressure pulse cooling fan is turned on to control the air pressure to 8.5 kPa, so that the clinker is rapidly cooled from 1450°C to below 150°C within 20 minutes. After crushing, it is sent to the finished clinker warehouse.

[0056] Comparative Example 1: Compared with Example 1, the difference is that the physical pretreatment process in step (2) is omitted. Instead of homogenizing the weighed 2.00 parts of calcium fluoride sludge and 5.60 parts of coal-fired furnace slag through a shaftless twin-shaft horizontal forced mixer, they are directly fed into a raw material vertical roller mill along with other raw materials. The rest are the same.

[0057] Comparative Example 2: Compared with Example 1, the difference is that in step (1), the desulfurized gypsum is not split, and all 3.40 parts of desulfurized gypsum are fed into the raw material vertical roller mill to participate in the system grinding, that is, the process of injecting the second material flow into the kiln tail decomposition furnace is cancelled, and the rest are the same.

[0058] Comparative Example 3: Compared with Example 1, the difference is that the operating temperature of the gas-solid mixed phase in the middle and outlet of the decomposition furnace in step (4) is increased and controlled at 920°C according to the conventional process standard, while the rest are the same.

[0059] Comparative Example 4: Compared with Example 1, the difference is that the amount of desulfurized gypsum added in the raw material batching is greatly reduced, from 3.40 parts to 0.50 parts. The difference of 2.90 parts is made up by limestone in equal amounts, and the difference of 2.30 parts is made up by limestone in equal amounts. This makes the sulfur-fluorine molar ratio (SO3 / F) in the mixed raw material of the system significantly reduced to about 0.2. All other aspects are the same.

[0060] Comparative Example 5: Compared with Example 1, the difference is that in the physical pretreatment step (2), the coal slag is replaced with limestone powder. That is, 2.00 parts of calcium fluoride sludge and 5.60 parts of limestone powder are fed into a shaftless twin-shaft horizontal forced mixer, and the rest are the same.

[0061] Comparative Example 6: Compared with Example 1, the difference is that in step (1), the 2.04 parts of desulfurized gypsum that are transported to the kiln tail decomposition furnace as the second material flow are replaced with natural anhydrous gypsum after being converted according to the effective SO3 molar amount, so that the SO3 molar amount brought in by the natural anhydrous gypsum is the same as that of the 2.04 parts of desulfurized gypsum in the second material flow, and the rest are the same.

[0062] Test Example 1: Determination of the thermodynamic properties of in-situ gas-solid phase fluorine capture mechanism: The dry raw meal obtained after grinding in step (3) of Example 1 was uniformly mixed with the desulfurized gypsum in the high-moisture and dihydrate crystallization state that was split in proportion as set in step (1), and used as the equivalent test sample of Example 1. The dry raw meal after grinding in Comparative Example 2 was used as the equivalent test sample of Comparative Example 2. The dry raw meal mixed with natural anhydrous gypsum in proportion in Comparative Example 6 was used as the equivalent test sample of Comparative Example 6.

[0063] The three equivalent test samples were lightly ground in an agate mortar, passed through an 80μm standard square hole sieve, and placed in a vacuum drying oven at 45℃ for 120 minutes to remove the free water adsorbed on the sample surface and to prevent the desulfurized gypsum dihydrate from losing its water of crystallization prematurely.

[0064] The determination was performed using a simultaneous thermal analyzer (TG-DSC). Each group of treated samples, weighing 15.3 mg to 15.8 mg, was placed flat in an alumina miniature crucible, with a blank alumina crucible used as a reference.

[0065] The instrument's heating program was set, and dry synthetic air (volume ratio O2:N2=21:79) with a flow rate of 50 mL / min was introduced as purge gas. The temperature was continuously increased from room temperature to 1000℃ at a heating rate of 10℃ / min. The mass change (TG) curve and heat flow (DSC) curve in the range of 800℃ to 1000℃ were recorded. The endothermic peak temperature and characteristic enthalpy change data of each sample in the carbonate decomposition stage and in the high temperature range were extracted.

[0066] The experimental data are shown in Table 1: Table 1: Thermodynamic phase transition characteristics of different raw material systems in the 800℃-1000℃ range in conclusion: According to Table 1 and Figure 1 According to the data, during the temperature rise test from 800℃ to 1000℃, the equivalent system of Comparative Example 2 recorded a secondary endothermic peak at 917.86℃, and its characteristic enthalpy change was measured to be 42.51 J / g. This endothermic change corresponds to the formation of a low-melting-point eutectic by gaseous fluorides and enriched alkali metals and chlorides within the system, followed by liquid-phase melting. The equivalent system of Example 1 did not record an independent endothermic peak in the 900℃ to 950℃ range, and the extracted characteristic enthalpy change for the high-temperature range was 1.84 J / g.

[0067] Analysis of the endothermic peak temperature of decarbonization and dehydration at 863.15℃ shows that the dihydrate desulfurization gypsum introduced in Example 1 undergoes a dehydration phase transition in the range of 850℃ to 880℃. The generated anhydrous calcium sulfate phase coordinates with the desorbed gaseous fluoride, converting fluoride ions into substances with higher melting points. This creates a physicochemical inhibition effect on the formation of a low-melting-point multi-element eutectic system.

[0068] Comparative Example 6, an equivalent system in which anhydrous natural gypsum was introduced into the formulation, recorded a secondary endothermic peak at 925.33℃ and a characteristic enthalpy change of 26.79 J / g. This indicates that the natural anhydrous gypsum failed to completely fix the gaseous fluoride under the corresponding thermal conditions, and some fluoride ions escaped and participated in the liquid-phase reaction. The results demonstrate the thermodynamic influence of the phase transition and recombination process of gypsum containing crystal water on the gas-solid phase reaction kinetics and the anti-skinning mechanism of the system.

[0069] Test Example 2: Verification of the clinker lattice defect hedging repair mechanism: Clinker obtained after quenching in Examples 1, 3 and Comparative Example 4 was used as test subjects.

[0070] The sampled calcined material was ground in an agate mortar and milled so that the powder passed through a 45μm standard square hole sieve to reduce the preferred orientation effect during the X-ray diffraction test.

[0071] The ground clinker powder was loaded into the sample stage groove using the back pressure method, and continuous scanning was performed using an X-ray diffractometer. The test conditions were set as follows: CuKα radiation source, operating voltage 40kV, operating current 40mA, scanning angle 2θ range of 10° to 70°, scanning rate of 2° / min, and step size of 0.02°.

[0072] Raw X-ray diffraction data were imported into the Rietveld full-spectrum fitting analysis software. Background and peak shape functions were set, and the crystal structure parameters of the Allite (C3S) phase were refined iteratively until the fitting convergence factor (Rwp) was less than 8.0%. The refined Allite unit cell parameters a, b, c, and unit cell volume V were extracted, and the full width at half maximum (FWHM) of the Allite principal diffraction peak near 29.4° was calculated.

[0073] The experimental data are shown in Table 2: Table 2: Measurement data of cell parameters and characteristic peak full width at half maximum (FWHM) of the Alite phase in clinker under different mix proportions. in conclusion: According to the data in Table 2, the full width at half maximum (FWHM) of the Allite main diffraction peak of the clinker sample in Comparative Example 4 was 0.257°, ​​showing broadening characteristics compared to Examples 1 and 3, with a cell volume of 2148.67 Å. 3 This is related to the process by which fluoride ions dissolve and enter the Alite lattice alone, replacing oxygen ions, at lower levels of desulfurized gypsum. Due to the differences in charge and physical size between fluoride ions and oxygen ions, the substitution process of a single element can easily cause local lattice distortion and increase the microscopic internal stress of the crystal.

[0074] The full width at half maximum (FWHM) values ​​of the Allite characteristic peaks for the clinker samples of Examples 1 and 3 were 0.142° and 0.138°, respectively, with the cell parameters and cell volume remaining within a relatively stable range. The test data indicate that in a system where the sulfur-fluorine molar ratio is controlled, the sulfur ions introduced by the desulfurized gypsum participate in the solid solution reaction along with the liquid phase. The combined effect of sulfur and fluorine ions creates a charge-complementary relationship at the substitution sites, thereby mitigating the electrostatic polarization and steric hindrance effects caused by the substitution of oxygen ions. The comparison of the above Rietveld refinement parameters reflects the compensatory effect of the composite ion competitive solid solution process on the Allite phase crystal structure, providing data support for understanding the stabilization mechanism of multi-mineralizer systems during the sintering stage.

[0075] Test Example 3: Pre-treated material flowability and raw meal grinding stability test: The homogenized loose granular premixes collected at the end of the pretreatment process in Examples 1, 2, and 3 were used as test samples. Simultaneously, the mixture from the conveyor belt of Comparative Example 1 that had not undergone biaxial mixing, and the mixture collected from the outlet of the shaftless biaxial horizontal forced mixer in Comparative Example 5, were used as comparative samples.

[0076] The apparent free moisture content of the sampled materials was determined using a rapid halogen moisture analyzer. The instrument's heating temperature was set to 105℃, and heating was continued until the material reached a constant weight. The percentage of water lost through evaporation was recorded.

[0077] The angle of repose for each sample was determined using the funnel method. The material was allowed to fall naturally through a standard funnel of fixed height onto a horizontal disk. After the material accumulated and settled to form a cone, the angle between the cone surface and the horizontal plane was measured. For samples that could not fall continuously or formed a clump and thus failed to form a regular cone, their physical characteristics were recorded.

[0078] The raw materials corresponding to Examples 1 to 3, Comparative Examples 1 and 5 were continuously fed into a vertical roller mill for grinding under the same feeding parameters via a belt scale. During the initial stage of system operation, the real-time hourly output of the raw material mill was continuously recorded over 120 minutes via the distributed control system in the central control room, and the average hourly output during this period was calculated.

[0079] The experimental data are shown in Table 3: Table 3: Data on the flowability parameters of pretreated materials and the grinding efficiency of raw meal milling in conclusion: According to Table 3 and Figure 2 The data shows that the apparent free moisture content of the premixes in Examples 1 to 3 ranged from 1.34% to 2.15%, and the angle of repose ranged from 36.8° to 39.1°, indicating that the treated mixtures exhibited certain granular flow characteristics. This is related to the capillary action generated by the porous aluminosilicate framework and internal pores of the coal-fired slag. This physical structure facilitates the mass transfer of free water on the surface of the calcium fluoride sludge, thereby reducing the overall viscosity of the mixture. Combined with... Figure 2 The production monitoring curves showed that during the 120 minutes of continuous operation of the raw material mill, the feeding process in the example condition was relatively smooth, and the hourly production curve remained stable within the range of 205 t / h to 220 t / h. The mixture in Comparative Example 1, due to the lack of biaxial mixing, had an apparent free moisture content of 14.76%, and the material agglomerated into muddy lumps, failing to form regular cones to complete the angle of repose measurement.

[0080] Figure 2The results show that the hourly output of Comparative Example 1 fluctuated significantly, with several instances of single-point output dropping below 20 t / h, which corresponds to the tendency for high-viscosity, high-moisture materials to adhere to walls and cause blockages in conveying and chute processes. Its average hourly output was only 76.41 t / h. Comparative Example 5 used limestone powder instead of coal slag in the pretreatment stage. The apparent free moisture content of the material after mixing was 12.58%, and the angle of repose was 65.3°. Due to the dense crystal structure of limestone powder and the lack of abundant microporous channels, its dewatering effect was inferior to that of coal slag, and the material retained high flow resistance in the feeding system. This is reflected in… Figure 2 In the comparative example 5, the hourly output curve was generally at a low level, showing a certain degree of declining feed rate, with an average hourly output of 105.73 t / h. The above test results reflect the physical effect of the porous characteristics of coal-fired slag on the dewatering process of mud-based waste, as well as the auxiliary influence of the pretreatment process on the continuous and stable operation of the grinding process.

[0081] Test Example 4: Evaluation of the kiln tail high-temperature section's resistance to scaling and continuous operation: Using the operating conditions set in Examples 1, 2, and 3, as well as Comparative Examples 2, 3, and 6, as test objects, the operating parameters were extracted and evaluated during the continuous industrial trial production of the cement kiln system.

[0082] The theoretical liquid phase content was determined by a high-temperature quenching method combined with Rietveld X-ray diffraction quantitative phase analysis. After the system was running stably under the set conditions, hot raw material powder was extracted from the junction of the feed pipe at the bottom of the preheater (C5 cyclone) and the kiln tail flue using a sampling gun with a water-cooled jacket. The powder was then placed in ice water for quenching to preserve the high-temperature glassy phase state.

[0083] The quenched and dried powder sample was ground and then subjected to X-ray diffraction. The mass percentage of the amorphous glass phase in the sample was calculated by full-spectrum fitting and used as a characterization value for the theoretical liquid phase content in the high-temperature range.

[0084] Retrieve pressure transmitter data from the C5 cyclone feed pipe to the kiln tail flue gas chamber area in the distributed control system (DCS) of the central control room. Extract real-time negative pressure records for each test condition over 30 consecutive days of operation, with a sampling frequency set to once every 4 hours. Calculate the range of negative pressure monitoring values ​​(the absolute value of the difference between the maximum and minimum negative pressure values) within the 30-day period to assess the impact of internal scaling on the ventilation cross-sectional area and gas flow resistance.

[0085] The experimental data are shown in Table 4: Table 4: Statistical Table of Theoretical Liquid Phase Quantity and Negative Pressure Fluctuation in the High-Temperature Section of the Kiln Tail System under Different Operating Conditions in conclusion: According to the data in Table 4, during the 30-day continuous operation period, the theoretical liquid phase content of Examples 1 to 3 ranged from 1.52% to 2.17%, and the measured negative pressure fluctuation range remained between 136.9 Pa and 158.2 Pa. (Combined with...) Figure 3 The monitoring curves showed that the negative pressure baseline remained flat under the operating conditions of the example, with no significant increase in ventilation resistance. This is related to the synergistic regulation mechanism of the dihydrate desulfurized gypsum bypass targeted injection and specific thermal temperatures (850℃ to 880℃) in the system. In the high-temperature zone, the dihydrate gypsum undergoes water removal, and the resulting nascent anhydrous calcium sulfate phase has high reactivity, coordinating with free HF gas in the gas phase. This physicochemical process limits the formation of low-melting-point eutectic mixtures between fluoride ions and circulating components such as alkali metals, chlorine, and sulfur in the kiln, thereby controlling the excessive generation of the liquid phase. Comparative Example 2, which did not employ the direct injection process of desulfurized gypsum, had a theoretical liquid phase content of 18.63%, and a negative pressure range of 1145.3 Pa after 30 days.

[0086] Figure 3 The absolute value of the negative pressure showed a stepwise decreasing trend, reflecting that some gaseous fluorides participated in the formation of liquid phase binders, resulting in crusting that affected ventilation in the preheater feed pipe and smoke chamber area. Comparative Example 3 set the decomposition furnace operating temperature to 920℃, and the theoretical liquid phase content rose to 27.41%. The system shut down on day 17 due to an excessively large negative pressure difference (reaching 2876.8 Pa). This indicates that when the thermal environment deviates from the set window, high-temperature conditions promote the large-scale generation of multi-component eutectic liquid phase, exacerbating the adhesion of materials to the pipe wall. Comparative Example 6 replaced dihydrate desulfurization gypsum with an equivalent amount of natural anhydrous gypsum, with a theoretical liquid phase content of 13.08% and a negative pressure difference of 792.4 Pa. The corresponding negative pressure curve showed a steady upward trend. The test data suggests that, due to the lack of a phase transition and recombination process involving the removal of water of crystallization, the reaction kinetics of the gas-solid interface in natural anhydrous gypsum are altered, resulting in a delayed retention effect on HF gas. Some escaped fluoride ions participate in the liquid-phase reaction, inducing a certain degree of crusting. The test results verify the intervention effect of the calcium sulfate phase transition process with water of crystallization on the anti-crusting mechanism in the high-temperature section of the kiln tail.

[0087] Test Example 5: In-situ synergistic SNCR denitrification efficiency test of calcium fluoride sludge: During the continuous industrial trial production of the cement kiln system, the operating conditions set in Examples 1, 2, 3, and Comparative Example 3 were selected as test subjects. The nitrogen oxide (NOx) emission concentration control threshold of the kiln tail chimney was set to no more than 50 mg / Nm³ using the distributed control system (DCS) in the central control room. 3The SNCR denitrification ammonia injection pump automatically adjusts the injection volume of purchased ammonia water (20% concentration) based on real-time NOx concentration data fed back from the chimney continuous emission monitoring system (CEMS).

[0088] After the system reaches thermal stability under various test conditions, operating parameters are continuously recorded for 24 hours. Data is extracted using the CEMS system, and the weighted average concentration of NOx emissions from the kiln tail chimney is calculated over the 24 hours.

[0089] The cumulative consumption readings of the SNCR ammonia water storage tank level gauge and the ammonia injection pipeline flow meter are read synchronously, and combined with the cumulative metering data of the clinker hourly output scale during the same period, the actual external ammonia water consumption per ton of clinker produced under the corresponding working conditions is calculated.

[0090] The experimental data are shown in Table 5: Table 5: Test Data of Nitrogen Oxide Emissions and Purchased Ammonia Consumption under Different Operating Conditions in conclusion: According to Table 5 and Figure 4 Data shows that maintaining NOx emission concentrations from kiln tail chimneys below 50 mg / Nm³ is crucial. 3 Under the control standards, the ammonia consumption per ton of clinker in Examples 1 to 3 ranged from 1.07 kg / t to 1.28 kg / t. Combined with... Figure 4 The consumption rate monitoring curve shows that the ammonia injection rate under the example conditions remained at a low and relatively stable level over 24 hours. The differences in the above operating data may be related to the pyrolysis behavior of polyacrylamide (PAM) in the decomposition furnace. Within the set temperature range of 850℃ to 880℃, residual organic polymers such as PAM in the mud-based waste undergo thermal decomposition, and the amide groups on their side chains may break, releasing amino-containing reducing groups. Under suitable temperature windows, these groups tend to undergo a denitrification reaction similar to selective non-catalytic reduction (SNCR) with NOx produced from fuel combustion. This endogenous reduction reaction, to some extent, reduces the overall reducing agent requirement of the system, thereby decreasing dependence on purchased ammonia.

[0091] In Comparative Example 3, the operating temperature of the decomposition furnace was increased to 920℃, and its 24-hour average NOx emission concentration was measured to be 47.83 mg / Nm³. 3 However, the consumption of purchased ammonia water per ton of clinker increased to 3.86 kg / t. For example... Figure 4As shown, the ammonia injection rate in Comparative Example 3 was at a relatively high level, and the automatic adjustment fluctuated significantly. When the thermal environment exceeded 880℃, the system may have deviated from the suitable thermodynamic window for the aforementioned in-situ denitrification reaction. In a higher-temperature aerobic environment, the probability of secondary oxidation reactions of nitrogen-containing groups released by the thermal decomposition of organic matter increases, which may weaken its reduction effect on NOx and even lead to an increase in the initial NOx background value of the system. This corresponds to the phenomenon that the system needs to increase the injection rate of external ammonia and frequently adjust it to maintain emission compliance. The test results suggest the correlation between the low-temperature operating environment in the decomposition furnace and the potential for in-situ denitrification of organic components in waste.

[0092] Test Example 6: Hydration setting characteristics and mechanical properties of cement clinker: The finished clinker products of Examples 1, 2, 3 and Comparative Example 4 after the cooling process were selected as test objects.

[0093] The sampled clinker was mixed with standard natural dihydrate gypsum at a mass ratio of 95:5, and then ground in a standard laboratory mill. The specific surface area of ​​each group of cement samples was controlled to be within 350±10 m². 2 Within the range of / kg.

[0094] Referring to GB / T1346 standard, the standard consistency water requirement of each group of cement samples was determined using a Vicat apparatus, and the hydration reaction was carried out in a constant temperature and humidity curing chamber (temperature 20±1℃, relative humidity ≥90%). The depth of the test needle into the cement paste was continuously measured, and the initial setting and final setting times of each sample were recorded.

[0095] Referring to GB / T17671 standard, each group of cement samples was mixed evenly with standard sand and mixing water at a fixed water-cement ratio. After mixing in a planetary mortar mixer, the mixture was poured into a triple mold of 40mm×40mm×160mm and vibrated to form the final product.

[0096] After curing in a standard curing chamber for 24 hours, the specimens were demolded and then completely immersed in a constant temperature water bath at 20±1℃ for further curing. The compressive strength was measured using a computer-controlled constant stress testing machine at 3 days and 28 days of hydration, and the measured values ​​were recorded.

[0097] The experimental data are shown in Table 6: Table 6: Setting Time and Compressive Strength Test of Cement Prepared from Clinker under Different Working Conditions in conclusion: According to Table 6 and Figure 5According to the data, the clinker samples from Examples 1 to 3, after being prepared into cement, had initial setting times ranging from 158 to 172 minutes and final setting times ranging from 221 to 245 minutes. The corresponding hydration-hardened specimens exhibited compressive strengths exceeding 30.8 MPa at 3 days and 55.9 MPa at 28 days. This hydration characteristic may be related to the structural state where the sulfur-fluorine molar ratio (SO3 / F) in the system is controlled within the range of 1.2 to 1.8. Under this state, an appropriate amount of high-valence sulfur ions may provide charge offsetting and coordination compensation, helping fluoride ions to dissolve relatively stably within the silicate mineral lattice, reducing their free enrichment in the liquid phase. This, in turn, facilitates the maintenance of a relatively normal induction period and hydration rate for tricalcium aluminate and tricalcium silicate in the early stages of the hydration reaction, thereby forming a relatively dense CSH hydrated calcium silicate gel network.

[0098] Comparative Example 4 reduced the proportion of desulfurized gypsum, placing the system under a low sulfur-to-fluorine ratio condition. Tests showed that the initial setting time of the Comparative Example 4 sample was shortened to 38 minutes, exhibiting a significant rapid setting trend, and its 28-day strength decreased to 41.6 MPa. This phenomenon suggests that, in the absence of sufficient sulfur ion coordination compensation, some free fluoride ions may tend to react with alumina components during the firing stage, generating fluorine-containing intermediate minerals (such as calcium fluoroaluminate) with high early hydration activity. These minerals are prone to rapid exothermic reaction and crystallization upon contact with water, potentially leading to a rapid decrease in the fluidity of the cement paste. Furthermore, the presence of free fluoride ions may also interfere with the normal hydration process of the core mineral C3S, thereby affecting the density of the network of later hydration products and the bonding force between grains, macroscopically manifested as a decrease in 28-day mechanical properties. The test results reflect the potential role of a specific sulfur-to-fluorine molar ratio in regulating abnormal setting and strength changes caused by fluorine.

[0099] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing cement clinker reinforced with fluorine-based mineralizers by calcination, characterized in that, Includes the following steps: S1. Weigh the raw materials required for preparing the cement clinker by weight: 45.00-52.80 parts limestone, 25.00-34.00 parts limestone powder, 1.00-3.80 parts silicon ore beneficiation sludge, 5.00-12.00 parts iron ore beneficiation sludge, 0.20-1.50 parts converter slag, 2.80-3.50 parts desulfurized gypsum, 1.20-2.30 parts calcium fluoride sludge, and 3.00-6.90 parts coal-fired furnace slag; divide the weighed desulfurized gypsum into two independent material streams, extract 30.0%-50.0% of the total desulfurized gypsum mass as the first material stream to be fed into the raw material grinding equipment, and send the remaining 50.0%-70.0% as the second material stream to the injection feed bin of the kiln tail decomposition furnace; S2. The calcium fluoride sludge and the coal-fired furnace slag are subjected to forced homogenization and stirring to obtain a premix; S3. The premix prepared in step S2 is combined with the remaining limestone, limestone powder, silicon ore beneficiation sludge, iron ore beneficiation sludge, converter slag, and the first material stream desulfurization gypsum diverted in step S1, and fed into a raw material roller mill for grinding and homogenization to obtain dry raw powder. S4. The homogenized dry powder raw material is fed into the decomposition furnace equipped with a suspension preheater; the second material flow desulfurized gypsum is directly injected into the decomposition furnace by pneumatic conveying, and the injection amount of denitrification agent is reduced simultaneously. S5. The pre-decomposed hot raw material falls into the rotary kiln cylinder, undergoes a solid-state thermochemical reaction, and enters the firing zone to be fired into high-temperature clinker. S6. The high-temperature clinker that has completed liquid phase sintering falls into a cooler for high-pressure rapid cooling, and then is sent to the finished product warehouse.

2. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 1, characterized in that, In step S1, the calcium fluoride sludge is industrial waste residue that has been screened and calibrated, with a free water content of 40.00% to 50.00%, a calcium fluoride mass fraction of 80.00% to 92.00% in the dry basis solid phase, and a polyacrylamide mass fraction of 0.50% to 2.00% in the dry basis.

3. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 1, characterized in that, In step S1, by adjusting the ratio of calcium fluoride sludge to desulfurized gypsum, the sulfur-fluorine molar ratio SO3 / F in the mixed raw material is controlled to be between 1.2 and 1.8, and the total alkali-sulfur mass ratio is controlled to be between 0.8 and 1.

1.

4. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 1, characterized in that, In step S2, the coal-fired slag and calcium fluoride sludge are continuously fed into a shaftless twin-shaft horizontal forced mixer at a mass ratio of 2.5:1 to 3.0:

1. The main shaft speed of the mixer is controlled at 30 to 50 rpm, and the mixture is forcibly homogenized and stirred for 5 to 15 minutes to obtain a loose granular premix with no free water seeping out on the surface. The overall surface moisture content of the premix is ​​controlled at 12.80% to 14.00%.

5. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 1, characterized in that, The grinding and homogenization steps include: uniformly feeding the combined material into a raw material vertical roller mill equipped with a classifier, and fully introducing the exhaust gas from a suspension preheater at a temperature of 280-330°C as an internal drying medium.

6. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 5, characterized in that, Step S3 further includes: adjusting the rotation speed of the classifier to 650-850 rpm, controlling the overall moisture content of the dry powder raw material to be 0.2%-0.9%, and controlling the fineness of the raw material to be 8.0%-13.0% of the residue percentage on an 80μm standard sieve.

7. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 1, characterized in that, In step S4, the proportion of pulverized coal fed into the decomposition furnace is controlled to be 55.0% to 62.0% of the total fuel, and the operating temperature of the gas-solid mixture in the middle and outlet of the decomposition furnace is controlled at 850 to 880°C. The second material flow of desulfurized gypsum is directly injected into the decomposition furnace at a spray speed of 25-40 m / s; Adjust the air volume to maintain the excess oxygen concentration in the kiln tail smoke chamber at 2.5% to 3.5%.

8. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 7, characterized in that, In step S4, the step of reducing the amount of denitrifying agent injected includes: The polyacrylamide in the calcium fluoride sludge is used to release amino groups through in-situ thermal decomposition in the decomposition furnace for synergistic denitrification, and the injection volume of the denitrification agent in the system is reduced by 10.0% to 30.0%.

9. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 1, characterized in that, In step S5, the rotation speed of the rotary kiln is controlled at 3.5 to 4.5 rpm, the material undergoes a solid-state thermochemical reaction in the transition range of 900 to 1100°C, and the maximum calcination temperature of the material in the firing zone is controlled at 1350 to 1450°C.

10. The method for producing cement clinker reinforced with fluorine-based mineralizers by calcination according to claim 1, characterized in that, In step S6, the step of high-pressure rapid cooling includes: turning on the high-pressure pulse cooling fan and controlling the air pressure to 5.5-8.5 kPa, so that the high-temperature clinker is rapidly cooled from the firing temperature to below 150°C within 10-20 minutes.

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