A method for preparing cement clinker by utilizing calcium fluoride sludge mineralization

Abstract

The application discloses a preparation method for utilizing calcium fluoride sludge mineralization to cooperatively control cement clinker, which comprises the following steps: detecting effective CaF2 content of calcium fluoride sludge and converting a dosing amount, and jointly dosing, grinding and calcining lime raw materials, silicate-aluminate raw materials, iron correction materials, sulfur-containing adjusting materials and active SiO2 / Al2O3 adsorption materials; controlling CaF2 content, F content and CaF2 / SO3 mass ratio of the clinker, and feeding back and adjusting the dosing amount according to a skinning trend and clinker detection results, so as to improve burnability and strength of the clinker, and reduce the risk of skinning and fluorine volatilization.

Description

Technical Field

[0001] This invention belongs to the technical field of cement clinker production and industrial solid waste resource utilization, specifically relating to a method for preparing cement clinker by synergistic control of calcium fluoride sludge mineralization. Background Technology

[0002] Cement clinker calcination requires solid-phase and liquid-phase reactions between calcareous raw materials, silica-alumina raw materials, and ferrous corrective agents under high-temperature conditions to form clinker minerals such as tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. The sufficiency of clinker mineral formation directly affects the free calcium oxide content, grindability, early strength, and later strength of the clinker.

[0003] In actual production, some cement enterprises are limited by the conditions of the raw materials in the mines, and the limestone, siliceous raw materials or aluminosilicate raw materials may have problems such as high magnesium and alkali content or insufficient burnability. For such raw material systems, if the clinker reaction is improved by simply increasing the firing temperature, extending the high-temperature residence time or increasing coal consumption, it is easy to cause kiln condition fluctuations, increased risk of crusting, increased energy consumption and fluctuations in clinker quality.

[0004] Calcium fluoride can be used as a mineralizer in cement clinker during the clinker firing process, reducing the difficulty of the firing reaction, promoting mineral formation, and improving the clinker's burnability. However, when using fluorite or other fluorine-containing mineralizers directly, if the dosage is not matched with the sulfur, alkali, aluminum, and silicon components in the system, the fluorine component can easily form low-melting-point eutectics with the alkali and sulfur, which can accumulate, adhere, and form a crust in the preheater, decomposer, or kiln tail, causing blockage in severe cases. At the same time, the fluorine-containing component may also increase the pressure control of fluorine volatiles.

[0005] Calcium fluoride sludge contains usable CaF2 components, and its introduction into cement raw material systems can simultaneously achieve solid waste resource utilization and mineralization modification. However, calcium fluoride sludge typically exhibits fluctuations in moisture content and available CaF2 content. If added directly based on a fixed wet basis weight, it is difficult to maintain a stable amount of available CaF2. If the addition amount is blindly increased solely to improve clinker strength, it can easily lead to crusting in the preheater or decomposer and excessive F content in the clinker.

[0006] Therefore, there is a need for a cement clinker preparation method that can combine the effective CaF2 addition from calcium fluoride sludge, CaF2 / SO3 ratio control, clinker F content upper limit, fluoride control through active SiO2 / Al2O3 adsorption, and kiln system crusting trend feedback adjustment. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing cement clinker by synergistic control of calcium fluoride sludge mineralization, so as to solve the problems of fluctuation in effective CaF2 dosage, unstable mineralization effect, and difficulty in simultaneously controlling clinker F content and preheater / decomposer scaling risk when fluoride-containing sludge is directly incorporated into the raw meal system, and improve clinker burnability and clinker mineral formation while realizing the resource utilization of calcium fluoride sludge.

[0008] To achieve the above objectives, the technical solution and claims of the present invention correspond as follows.

[0009] A method for preparing cement clinker by synergistically controlling the mineralization of calcium fluoride sludge includes the following steps: Step 1: Detection and calculation of calcium fluoride sludge: Detect the effective CaF2 content and moisture content in the calcium fluoride sludge, and use the CaF2 content in the target clinker of 0.4%-0.8% as the mineralization control window to calculate the wet basis dosage of the calcium fluoride sludge. The second step involves co-batching of raw materials: limestone raw materials, silica-alumina raw materials, iron-based corrective materials, sulfur-containing conditioning materials, activated SiO2 / Al2O3 adsorbents, and the calcium fluoride sludge converted in the first step are metered and batched. The calcium fluoride sludge is continuously metered by a batching silo and a belt scale before entering the mixing and conveying system. The amount of activated SiO2 / Al2O3 adsorbent is 1%-3% of the total mass of the raw materials. The third step is raw material co-grinding and homogenization: The batching materials obtained in the second step are fed into a raw material vertical mill for co-grinding, so that CaF2 in the calcium fluoride sludge is dispersed in the raw material to obtain fluorine-containing mineralized raw material. The fourth step is clinker calcination and mineralization control: the fluorine-containing mineralized raw meal is fed into a preheater, decomposition furnace and rotary kiln for calcination to obtain cement clinker. During the calcination process, the F content of the clinker is controlled to be ≤0.15% and the CaF2 / SO3 mass ratio is controlled to be 0.35-0.6. Step 5: Control of crusting and fluorine volatilization risks: Monitor the interstage pressure difference of the preheater, the negative pressure at the kiln tail, the preheater outlet temperature and the decomposition furnace outlet temperature. When the interstage pressure difference of the preheater increases, the ventilation resistance at the kiln tail increases, or the F content of the clinker approaches the upper limit, reduce the amount of calcium fluoride sludge added and / or increase the amount of active SiO2 / Al2O3 adsorbent. Step 6: Clinker testing and feedback correction: Test the free calcium oxide, sulfur content, and strength of the clinker, and make feedback corrections based on the test results for the dosage of calcium fluoride sludge, sulfur-containing conditioning material, and active SiO2 / Al2O3 adsorbent in the next batch or subsequent periods.

[0010] Furthermore, in the first step, the wet basis dosage of calcium fluoride sludge is determined as follows: using the target clinker yield, the CaF2 content in the target clinker, the effective CaF2 content of the dry basis of calcium fluoride sludge, and the moisture content of the calcium fluoride sludge as calculation parameters, the required dry basis calcium fluoride sludge amount is first calculated, and then the wet basis feed setting value of the belt scale is calculated based on the moisture content.

[0011] Furthermore, in the first step, the mineralization control window includes a low mineralization control zone, a stable mineralization control zone, and a risk control zone; when the free calcium oxide in the clinker is higher than the preset value and the F content in the clinker is lower than 0.15%, the CaF2 content in the target clinker is adjusted towards the upper limit of the stable mineralization control zone; when the interstage pressure difference in the preheater increases, the ventilation resistance at the kiln tail increases, or the F content in the clinker approaches 0.15%, the CaF2 content in the target clinker is adjusted towards the lower limit of the stable mineralization control zone.

[0012] Furthermore, in the second step, the active SiO2 / Al2O3 adsorbent is one or more of fly ash, burnt clay, coal gangue, siliceous aluminum tailings, and metakaolin, used to adsorb fluorine-containing volatile components and promote their formation of stable fluorine minerals.

[0013] Furthermore, in the second step, the sulfur-containing conditioning material is gypsum, desulfurized gypsum, sulfur gypsum, or a combination thereof, and the CaF2 / SO3 mass ratio is maintained at 0.35-0.6 by adjusting the amount of sulfur-containing conditioning material.

[0014] Furthermore, in the second step, before the calcium fluoride sludge enters the raw material vertical mill, it is premixed in the mixing and conveying system with at least some of the limestone raw materials, siliceous aluminous raw materials and activated SiO2 / Al2O3 adsorbent to reduce local enrichment of CaF2.

[0015] Furthermore, in the fourth step, the preheater and decomposition furnace avoid localized high temperatures and maintain ventilation in the kiln system; the clinker exiting the kiln is rapidly cooled by a grate cooler to reduce the enrichment of low-melting-point eutectic products formed by fluorine, alkali and sulfur on the walls of the preheater or decomposition furnace.

[0016] Furthermore, in the fifth step, a scaling trend determination value is established, which is determined by the preheater interstage pressure difference change rate, the kiln tail negative pressure change rate, the preheater outlet temperature deviation, and the decomposition furnace outlet temperature deviation. When the scaling trend determination value reaches a preset threshold, at least one of the following is executed: reducing the amount of calcium fluoride sludge added, increasing the amount of active SiO2 / Al2O3 adsorbent, adjusting the amount of sulfur-containing conditioning material, and increasing the ventilation volume.

[0017] The crusting trend determination value K satisfies: K = aΔP + bΔN + cΔT1 + dΔT2, Where ΔP is the rate of change of interstage pressure difference in the preheater, ΔN is the rate of change of negative pressure at the kiln tail, ΔT1 is the temperature deviation at the preheater outlet, ΔT2 is the temperature deviation at the decomposition furnace outlet, and a, b, c, and d are weighting coefficients.

[0018] Furthermore, in the sixth step, when the free calcium oxide in the clinker is higher than the preset value and the F content in the clinker is lower than 0.15%, the amount of calcium fluoride sludge added is increased or the CaF2 control value in the target clinker is increased; when the free calcium oxide in the clinker meets the preset value but the F content in the clinker is close to 0.15% or a crusting trend appears, the amount of calcium fluoride sludge added is reduced and the amount of active SiO2 / Al2O3 adsorbent is increased.

[0019] On the other hand, the present invention also provides a cement clinker, which is prepared by a method for synergistic control of calcium fluoride sludge mineralization.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: First, this invention uses calcium fluoride sludge as a mineralization functional material calculated based on available CaF2, rather than simply adding it as a substitute for ordinary solid waste, which can reduce the impact of sludge moisture content and composition fluctuations on the mineralization effect.

[0021] Secondly, this invention establishes a synergistic relationship between CaF2 mineralization and crusting risk control through triple constraints of the clinker CaF2 target window, the upper limit of clinker F, and the CaF2 / SO3 mass ratio, thus avoiding crusting of fluorine, alkali, and sulfur low-melting-point eutectic by simply increasing the amount of fluorine-containing materials.

[0022] Subsequently, by adding 1%-3% of active SiO2 / Al2O3 adsorbent, the present invention enables the fluorine-containing volatile components to have an adsorption and stabilization pathway in the raw material and high-temperature reaction system, thereby reducing the risk of fluorine-containing waste gas and fluorine cycle enrichment.

[0023] Subsequently, this invention adjusts the calcium fluoride sludge addition by feedback regulation of preheater stage pressure difference, kiln tail negative pressure, temperature deviation and clinker F content, so that the addition is no longer fixed, but dynamically adjusted according to the mineralization effect and crusting trend, which is suitable for continuous industrial production.

[0024] Finally, this invention can improve clinker mineral formation, reduce clinker firing difficulty, and improve clinker quality stability by utilizing the mineralization effect of CaF2 in raw material systems with high magnesium, high alkali, or insufficient calcinability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process for preparing cement clinker using the synergistic control of calcium fluoride sludge mineralization according to the present invention. Figure 2 This is a schematic diagram illustrating the zoning control of mineralization intensity and crusting risk according to the present invention. Detailed Implementation

[0026] These embodiments are provided to make the invention thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0027] This invention provides a method for synergistically controlling the mineralization of cement clinker using calcium fluoride sludge. The method first detects the effective CaF2 content and moisture content of the calcium fluoride sludge, using a CaF2 content of 0.4%-0.8% in the target clinker as the mineralization control window, and then calculates the wet-basis dosage based on the effective CaF2 content and moisture content of the dry-basis calcium fluoride sludge. Therefore, the calcium fluoride sludge is no longer added as a substitute for ordinary calcium by a fixed wet-basis ratio, but rather as a mineralization functional component controlled by the effective CaF2 content.

[0028] In the raw material batching stage, limestone raw materials, silica-alumina raw materials, iron-based corrective agents, sulfur-containing conditioning agents, activated SiO2 / Al2O3 adsorbents, and converted calcium fluoride sludge are batched together. The calcium fluoride sludge is continuously metered via a batching silo and belt scale before entering the mixing and conveying system. It is pre-mixed with other raw materials before entering the raw material vertical mill to reduce localized enrichment of CaF2. The activated SiO2 / Al2O3 adsorbent is added at 1%-3% of the total raw material mass and is used to adsorb fluorine-containing volatile components and promote their formation of stable fluoride minerals.

[0029] During the calcination stage, fluorine-containing mineralized raw materials are calcined in a preheater, decomposition furnace, and rotary kiln to obtain clinker. Simultaneously, the F content of the clinker is controlled to be ≤0.15% and the CaF2 / SO3 mass ratio is 0.35-0.6, keeping CaF2 mineralization, SO3 balance, and the risk of crusting within a controllable range.

[0030] During the process control phase, parameters such as preheater interstage pressure difference, kiln tail negative pressure, preheater outlet temperature, and decomposition furnace outlet temperature are monitored, and feedback adjustments are made in conjunction with clinker fluoride content, clinker free calcium oxide, and clinker strength. When clinker free calcium oxide is higher than the preset value but clinker fluoride content is not close to the upper limit, the amount of calcium fluoride sludge added is increased or the target clinker CaF2 control value is increased. When clinker fluoride content is close to the upper limit, preheater interstage pressure difference increases, or kiln tail ventilation resistance increases, the amount of calcium fluoride sludge added is reduced, the amount of active SiO2 / Al2O3 adsorbent is increased, and sulfur-containing conditioning material, ventilation volume, and temperature control parameters are adjusted.

[0031]

[0032] Table 1: Description of Controlled Objects, Scope, and Functions The following embodiments are used to explain the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adaptive adjustments to the specific parameters without departing from the technical concept of the present invention. Example

[0033] This embodiment provides a method for preparing cement clinker by synergistically controlling the mineralization of calcium fluoride sludge. First, samples of the calcium fluoride sludge are taken and tested. The tests include the effective CaF2 content, moisture content, CaO, SiO2, Al2O3, Fe2O3, SO3, alkali content, chloride ions, and other components that may affect clinker quality. The test results are used to determine whether the calcium fluoride sludge should enter the raw material batching system and to calculate the wet basis feed rate.

[0034] In one specific embodiment, calcium fluoride sludge is loaded into a batching silo by a loader, then conveyed from the silo to a belt scale, and finally fed into a raw material vertical mill via a mixing belt. There, it is ground together with other raw material components, and subsequently calcined in a rotary kiln to produce clinker. This process allows calcium fluoride sludge to be integrated into existing raw material batching and grinding systems, eliminating the need for a separate, independent calcination unit.

[0035] The raw material mix includes calcareous raw materials, silica-alumina raw materials, iron-based corrective agents, sulfur-containing conditioning agents, activated SiO2 / Al2O3 adsorbents, and calcium fluoride sludge. The calcium fluoride sludge is added after conversion to available CaF2, ensuring the CaF2 content in the target clinker is controlled at 0.4%-0.8%. The dosage of activated SiO2 / Al2O3 adsorbent is controlled at 1%-3% of the total raw material mass.

[0036] Raw meal is calcined in a preheater, decomposer, and rotary kiln to obtain cement clinker. During calcination, the sulfur content in the clinker is controlled to be ≤0.15%, and the CaF2 / SO3 mass ratio is controlled to be 0.35-0.6. This ratio control can avoid insufficient CaF2 addition leading to insignificant mineralization, and can also avoid excessive CaF2 relative to SO3 increasing the risk of crusting in low-melting-point eutectic materials.

[0037] like Figure 1 As shown, calcium fluoride sludge is not directly added as a regular raw material. Instead, it undergoes effective CaF2 detection and wet basis calculation before entering the batching, premixing, co-grinding, and calcination systems. Feedback corrections are made based on the clinker F content, CaF2 / SO3 ratio, and crusting trend. Example

[0038] This embodiment further defines the calculation method for the addition of calcium fluoride sludge based on Embodiment 1. Since calcium fluoride sludge usually enters the batching silo in the form of wet-based material, its moisture content and effective CaF2 content will affect the actual amount of mineralized components added. Therefore, it is not advisable to feed it based solely on a fixed wet-based mass.

[0039] Let the target clinker yield be M, the CaF2 mass fraction in the target clinker be T, the effective CaF2 mass fraction on a dry basis of calcium fluoride sludge be C, and the moisture content of the calcium fluoride sludge be W. Then, the wet basis dosage of calcium fluoride sludge can be calculated using M×T / [C×(1-W)]. This calculation formula is used to determine the belt scale feed setting value; in actual production, M can also be corrected based on the raw material loss on ignition and clinker yield.

[0040] When online or batch testing shows that the moisture content of calcium fluoride sludge is increasing, increase the wet feed rate of the belt scale to maintain the effective CaF2 dosage; when the effective CaF2 content of dry calcium fluoride sludge is increasing, reduce the wet feed rate of the belt scale to avoid excessive F content in the clinker and increased risk of crusting.

[0041] This conversion method ensures that the raw material entering the cement system is not the fluctuating wet sludge mass, but rather a relatively stable effective CaF2 mineralization component, thereby improving the repeatability of mineralization control. Example

[0042] This embodiment further incorporates CaF2 / SO3 balance and active SiO2 / Al2O3 adsorption control based on Embodiment 1. The sulfur-containing conditioning material uses gypsum, desulfurized gypsum, sulfur gypsum, or a combination thereof, and its dosage is adjusted to maintain the CaF2 / SO3 mass ratio at 0.35-0.6.

[0043] When the CaF2 / SO3 mass ratio is below 0.35, it indicates insufficient CaF2 mineralization relative to SO3, which may lead to insignificant mineralization. When the CaF2 / SO3 mass ratio is above 0.6, it indicates a relatively high fluorine content, which may increase the risk of fluorine forming low-melting-point eutectic compounds with alkali and sulfur. Therefore, in this embodiment, the CaF2 / SO3 mass ratio is used as a synergistic control indicator between mineralization and anti-scabbing.

[0044] The active SiO2 / Al2O3 adsorbent can be one or more of the following: fly ash, calcined clay, coal gangue, siliceous aluminate tailings, and metakaolin, with a dosage of 1%-3% of the total raw material mass. This adsorbent is used to adsorb fluorine-containing volatile components such as HF, and promotes the formation of stable fluorine minerals during high-temperature reactions, reducing the enrichment of fluorine-containing components in the gas phase or circulating materials.

[0045] When the amount of calcium fluoride sludge added remains constant while the pressure difference between preheater stages increases, the amount of active SiO2 / Al2O3 adsorbent should be increased first, and the mass ratio of CaF2 / SO3 should be checked simultaneously; if the pressure difference continues to increase, the amount of calcium fluoride sludge added should be reduced. Example

[0046] refer to Figure 2This embodiment further incorporates a crusting trend determination feature based on Embodiment 1. The crusting trend determination parameters include the preheater interstage pressure difference, kiln tail negative pressure, preheater outlet temperature, decomposition furnace outlet temperature, and clinker F content.

[0047] In one embodiment, the preheater interstage pressure difference change rate, kiln tail negative pressure change rate, preheater outlet temperature deviation, and decomposer outlet temperature deviation are normalized and then weighted to obtain a scaling trend determination value. This scaling trend determination value is used to determine the trend of enrichment of low-melting-point eutectic compounds of fluorine, alkali, and sulfur on the walls of the preheater or decomposer.

[0048] When the scaling trend judgment value is less than the first threshold, the system is in the stable mineralization zone, and the current calcium fluoride sludge dosage, sulfur-containing conditioning material dosage, and active SiO2 / Al2O3 adsorbent dosage are maintained. When the scaling trend judgment value reaches the first threshold but not the second threshold, the active SiO2 / Al2O3 adsorbent dosage is increased first and the CaF2 / SO3 mass ratio is checked. When the scaling trend judgment value reaches the second threshold, the calcium fluoride sludge dosage is reduced, and the ventilation volume of the kiln system is increased while avoiding local high temperatures in the preheater or decomposition furnace.

[0049] Through the above-mentioned graded feedback adjustment, this embodiment does not wait until severe material blockage occurs before manual treatment is carried out, but rather corrects the fluorine-containing material addition and adsorption control parameters in advance when abnormal trends appear in pressure difference, negative pressure, and temperature. Example

[0050] This embodiment is applicable to production conditions where the MgO or alkali content in the raw materials is high, the clinker strength development in the later stages is insufficient, or the clinker has insufficient calcinability. Using the method described in Example 1, calcium fluoride sludge is introduced into the raw material system as a mineralization functional component.

[0051] Under these raw material conditions, if the free calcium oxide content in the clinker is too high and the F content in the clinker is still not close to 0.15%, it indicates that mineralization promotion is still needed for the formation of clinker minerals. The amount of calcium fluoride sludge added can be appropriately increased or the target clinker CaF2 control value can be adjusted towards 0.8%.

[0052] If the free calcium oxide in the clinker already meets the preset value, but the interstage pressure difference in the preheater increases, the ventilation resistance at the kiln tail increases, or the F content in the clinker is close to the upper limit, it indicates that the mineralization effect is sufficient and the risk of crusting / fluoride control increases. At this time, reduce the amount of calcium fluoride sludge added and increase the amount of active SiO2 / Al2O3 adsorbent to maintain the CaF2 / SO3 mass ratio in the range of 0.35-0.6.

[0053] Therefore, this embodiment forms a two-way feedback control system of "supplementing fluorine when mineralization is insufficient and reducing fluorine and enhancing adsorption when the risk of fluorine control increases". Example

[0054] In one specific production line implementation, calcium fluoride sludge is fed into a batching silo by a loader. A belt scale is installed below the batching silo, which feeds the calcium fluoride sludge to the mixing conveyor belt according to the calculated wet basis feed rate. After being mixed with other raw material components on the mixing conveyor belt, the calcium fluoride sludge enters the raw material vertical mill, where it is co-ground and then enters the subsequent preheating, decomposition, and rotary kiln calcination system.

[0055] To reduce bridging, material shortages, and short-term accumulation of wet sludge, the batching silo can be equipped with anti-bridging structures or periodic arch-breaking operations; the belt scale should be equipped with instantaneous and cumulative flow monitoring. If the instantaneous flow rate of the belt scale deviates from the set value, the feeding device should be corrected first; if the cumulative effective CaF2 dosage deviates from the target value, compensation adjustments should be made in subsequent periods.

[0056] In one embodiment, the wet-based addition amount of calcium fluoride sludge can be 0.5%-2.0% of the total mass of raw materials, and is preferably determined by combining the effective CaF2 content of calcium fluoride sludge and clinker yield. When the existing data of the production line shows that about 2.00% of wet-based calcium fluoride sludge can be connected to the raw material batching system, this value can be used as the initial operating point, and then fine-tuned according to the clinker F content, free calcium oxide and crusting trend.

[0057] Comparison of proportions Comparative Example 1: Sludge without the addition of calcium fluoride.

[0058] Using conventional raw material batching and conventional calcination methods, without adding calcium fluoride sludge, and without setting effective CaF2 conversion, clinker F content control, or CaF2 / SO3 ratio control, this method cannot utilize the CaF2 mineralization effect in the calcium fluoride sludge to improve the burnability of the raw material.

[0059] Comparative Example 2: Calcium fluoride sludge was added according to a fixed wet basis mass.

[0060] A fixed wet basis mass of calcium fluoride sludge was incorporated, but the moisture content and available CaF2 content were not measured. When the sludge moisture content or available CaF2 content fluctuates, the actual amount of CaF2 entering the system fluctuates accordingly, which may result in insufficient mineralization or excessive fluoride content.

[0061] Comparative Example 3: Calcium fluoride sludge was added, but the CaF2 / SO3 mass ratio was not controlled.

[0062] Although this method introduces CaF2 mineralization components, it does not link the amount of sulfur-containing conditioning material with the amount of CaF2 added, making it difficult to balance the mineralization effect with the risk of crusting of low-melting-point eutectic products of fluorine, alkali, and sulfur.

[0063] Comparative Example 4: Calcium fluoride sludge was added, but no activated SiO2 / Al2O3 adsorbent was added.

[0064] This method lacks an adsorption and stabilization pathway for fluorinated volatile components, making it easier for fluorinated components to accumulate in the gas phase or circulating materials, increasing the crusting and control pressure of fluorinated waste gas.

[0065] Comparative Example 5: The dosage was artificially reduced only after severe crusting occurred.

[0066] This approach is a reactive measure and does not utilize the interstage pressure difference in the preheater, the negative pressure at the kiln tail, and the temperature deviation to determine trends, which can easily lead to the accumulation of the risk of crusting.

[0067] To demonstrate the technical effects of this invention, three sets of comparative embodiments are provided. Examples 1 to 3 correspond to the preferred embodiments of this invention under low, medium, and high mineralization conditions, respectively. These embodiments illustrate that within the control range of 0.4% to 0.8% CaF2 content in clinker, 0.35 to 0.6 CaF2 / SO3 mass ratio, and 1% to 3% active SiO2 / Al2O3 adsorbent, stable mineralization control can be achieved through effective CaF2 addition and crusting trend feedback.

[0068]

[0069] Table 2: Comparison Table of Experimental Data The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, equivalent substitutions or modifications can be made to the various structures, materials, dimensions, flow channel forms, and connection forms without departing from the concept of the present invention, and all such equivalent substitutions or modifications should fall within the protection scope of the present invention.

[0070] It should be noted that, in the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention 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, and therefore should not be construed as a limitation of this invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0071] Furthermore, the terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible range of error. "Parallel" is not strictly parallel, but within the permissible range of error. Terms such as "including" or "comprising" mean that the element preceding the word encompasses the element listed after the word, and do not exclude the possibility of encompassing other elements as well.

[0072] It should also be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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. Those skilled in the art can understand the specific meaning of the above terms in this invention depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0073] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this invention pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0074] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0075] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of the invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any manner.

Claims

1. A method for preparing cement clinker by synergistically controlling the mineralization of calcium fluoride sludge, characterized in that, Includes the following steps: S1. Detect the effective CaF2 content and moisture content in the calcium fluoride sludge, and use the CaF2 content in the target clinker of 0.4%-0.8% as the mineralization control window to calculate the wet basis dosage of the calcium fluoride sludge; S2. The limestone raw materials, silica-alumina raw materials, iron-based corrective materials, sulfur-containing conditioning materials, activated SiO2 / Al2O3 adsorbents, and the calcium fluoride sludge converted in step S1 are metered and batched. The calcium fluoride sludge is continuously metered by a batching silo and a belt scale before entering the mixing and conveying system. The amount of activated SiO2 / Al2O3 adsorbent is 1%-3% of the total mass of the raw materials. S3. The batching materials obtained in step S2 are fed into the raw material vertical mill for co-grinding, so that CaF2 in the calcium fluoride sludge is dispersed in the raw material to obtain fluorine-containing mineralized raw material. S4. The fluorine-containing mineralized raw material is fed into a preheater, a decomposition furnace and a rotary kiln for calcination to obtain cement clinker. During the calcination process, the F content of the clinker is controlled to be ≤0.15% and the CaF2 / SO3 mass ratio is controlled to be 0.35-0.

6. S5. Monitor the interstage pressure difference of the preheater, the negative pressure at the kiln tail, the preheater outlet temperature and the decomposition furnace outlet temperature. When the interstage pressure difference of the preheater increases, the ventilation resistance at the kiln tail increases, or the F content of the clinker approaches the upper limit, reduce the amount of calcium fluoride sludge added and / or increase the amount of active SiO2 / Al2O3 adsorbent. S6. Detect the free calcium oxide content, F content, and strength of the clinker, and make feedback corrections based on the test results for the dosage of calcium fluoride sludge, sulfur-containing conditioning material, and active SiO2 / Al2O3 adsorbent in the next batch or subsequent periods.

2. The preparation method according to claim 1, characterized in that, In step S1, the wet basis dosage of calcium fluoride sludge is determined as follows: using the target clinker yield, the CaF2 content in the target clinker, the effective CaF2 content of the dry basis of calcium fluoride sludge, and the moisture content of the calcium fluoride sludge as calculation parameters, the required dry basis calcium fluoride sludge amount is first calculated, and then the wet basis feed setting value of the belt scale is calculated based on the moisture content.

3. The preparation method according to claim 1, characterized in that, In step S1, the mineralization control window includes a low mineralization control zone, a stable mineralization control zone, and a risk control zone. The low mineralization control zone is where the CaF2 content in the target clinker is 0.4% to 0.5%. The stable mineralization control zone is where the CaF2 content is 0.5% to 0.7%. The risk control zone is where the CaF2 content in the clinker is 0.7% to 0.8% or close to 0.15%. When the free calcium oxide in the clinker is higher than the preset value and the clinker F content is lower than 0.15%, the CaF2 content in the target clinker is adjusted towards the upper limit of the stable mineralization control zone. When the interstage pressure difference in the preheater increases, the ventilation resistance at the kiln tail increases, or the clinker F content is close to 0.15%, the CaF2 content in the target clinker is adjusted towards the lower limit of the stable mineralization control zone.

4. The preparation method according to claim 1, characterized in that, In step S2, the active SiO2 / Al2O3 adsorbent is one or more of fly ash, burnt clay, coal gangue, siliceous aluminum tailings, and metakaolin, used to adsorb fluorine-containing volatile components and promote their formation of stable fluorine minerals.

5. The preparation method according to claim 1, characterized in that, In step S2, the sulfur-containing conditioning material is gypsum, desulfurized gypsum, sulfur gypsum or a combination thereof, and the CaF2 / SO3 mass ratio is maintained at 0.35-0.6 by adjusting the amount of sulfur-containing conditioning material.

6. The preparation method according to claim 1, characterized in that, In step S2, before the calcium fluoride sludge enters the raw material vertical mill, it is premixed in the mixing and conveying system with at least some limestone raw materials, siliceous aluminous raw materials and activated SiO2 / Al2O3 adsorbent to reduce local enrichment of CaF2.

7. The preparation method according to claim 1, characterized in that, In step S4, the preheater and decomposition furnace avoid local high temperatures and maintain ventilation in the kiln system; the clinker exiting the kiln is rapidly cooled by a grate cooler to reduce the enrichment of low-melting-point eutectic products formed by fluorine, alkali and sulfur on the walls of the preheater or decomposition furnace.

8. The preparation method according to claim 1, characterized in that, In step S5, a scaling trend determination value is established, which is determined by the preheater interstage pressure difference change rate, the kiln tail negative pressure change rate, the preheater outlet temperature deviation, and the decomposition furnace outlet temperature deviation. When the scaling trend determination value reaches a preset threshold, at least one of the following is executed: reducing the amount of calcium fluoride sludge added, increasing the amount of active SiO2 / Al2O3 adsorbent, adjusting the amount of sulfur-containing conditioning material, and increasing the ventilation volume.

9. The preparation method according to claim 1, characterized in that, In step S6, when the free calcium oxide in the clinker is higher than the preset value and the F content in the clinker is lower than 0.15%, the amount of calcium fluoride sludge added is increased or the CaF2 control value in the target clinker is increased; when the free calcium oxide in the clinker meets the preset value but the F content in the clinker is close to 0.15% or a crusting trend appears, the amount of calcium fluoride sludge added is reduced and the amount of active SiO2 / Al2O3 adsorbent is increased.

10. A type of cement clinker, characterized in that, It is prepared by the method for synergistic control of cement clinker by calcium fluoride sludge mineralization as described in any one of claims 1-9.

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