Method for improving the strength of silicate clinker by using phosphogypsum as a raw material admixture in conjunction with phosphate tailings

Abstract

This invention relates to the field of building materials technology, specifically disclosing a method for improving the strength of silicate clinker by using phosphate tailings and phosphogypsum as raw material admixtures. The method includes the following steps: S1, using phosphate tailings and phosphogypsum as raw material admixtures, designing a proportion where, by mass percentage, the phosphate tailings content is 2%-15% and the phosphogypsum content is 0.4-2%; mixing and grinding the phosphate tailings and phosphogypsum with other raw materials; S2, the powder obtained in S1 is preheated, decomposed, calcined, and cooled to prepare silicate clinker. In this invention, phosphate tailings mainly replace limestone, a calcareous material in the raw material, to reduce production costs. The main function of phosphogypsum is to regulate the relative content of C3S and C2S in the clinker and the proportion of M1 type C3S, thereby optimizing and improving the 3-day and 28-day strength of the clinker. This invention not only consumes two major solid wastes—high-magnesium phosphate tailings and phosphogypsum—but also improves the strength of silicate clinker.

Description

Technical Field

[0001] This invention relates to the field of cement building materials technology, specifically to a method for using phosphogypsum in conjunction with phosphorus tailings as a raw material admixture to improve the strength of silicate clinker. Background Technology

[0002] Phosphate tailings are produced during the purification and refining of phosphate rock. They typically contain 30%-40% calcium oxide, some phosphorus pentoxide and sulfur trioxide, but also a high magnesium oxide content, generally around 18%, which limits their resource utilization. Phosphogypsum is a solid waste product generated during the wet-process phosphoric acid production process, with gypsum dihydrate as the main mineral phase. Currently, the annual production of phosphogypsum in China is approximately 80 million tons, with small quantities currently used in cement retarders, roadbed materials, building gypsum powder and products.

[0003] Silicate cement clinker is prepared by calcining four elements: calcium, silicon, aluminum, and iron. Phosphate tailings, in addition to containing a certain amount of CaO, also have high magnesium content and contain phosphorus due to residual fluorapatite. Phosphogypsum, with dihydrate gypsum as its main mineral phase, contains high levels of sulfur. The introduction of these Mg, P, and S impurities affects the clinker's mineral composition and properties. In actual silicate clinker production, the amount of phosphate tailings added and the content of phosphorus and magnesium impurities vary, ultimately introducing different amounts of phosphorus and magnesium. These variable factors are complex, leading to different conclusions. Without understanding the influence of boundary conditions on clinker, it is difficult to guide and optimize actual production.

[0004] Therefore, for the use of phosphate tailings in silicate clinker calcination, more refined resource utilization and control methods need to be developed based on actual conditions. This is especially true when using sulfur-containing raw materials (such as phosphogypsum), where the risk of scale formation due to sulfur-containing gypsum in the batch may increase, affecting the stable operation of the kiln system. This invention, by mastering a more refined method for controlling the calcination of silicate clinker using phosphate tailings in combination with phosphogypsum, can solve the problems of phosphate tailings affecting clinker quality and the inability to use clinker due to its high magnesium oxide content (greater than 2.0%). Furthermore, it can also improve clinker strength. Summary of the Invention

[0005] To address the aforementioned issues, this invention discloses a method for improving the strength of silicate clinker based on mineral and crystal composition analysis. This method allows for the simultaneous use of phosphate tailings and phosphogypsum in silicate clinker calcination, solving the problems of phosphate tailings affecting clinker quality as a raw material for silicate cement clinker calcination and the inability to use clinker due to its high magnesium oxide content (greater than 2.0%). Simultaneously, it can also improve clinker strength.

[0006] The technical solution of the present invention is a method for improving the strength of silicate clinker by using phosphogypsum in conjunction with phosphate tailings as a raw material admixture, comprising the following steps: S1. Use phosphorus tailings and phosphogypsum as raw material admixtures and design the proportion. By mass percentage, the proportion of phosphorus tailings in the raw material is 2%-15% and the proportion of phosphogypsum is 0.4-2%. Mix and grind phosphorus tailings and phosphogypsum with other raw material raw materials. The powders obtained from S2 and S1 are fed into a preheater, a decomposition furnace, a rotary kiln, and a cooler for preheating, decomposition, calcination, and cooling, respectively. The oxygen content at the outlet of the decomposition furnace and the smoke chamber of the rotary kiln is controlled to be 1.0%~3.5% to prepare silicate clinker.

[0007] Optionally, the contents of MgO, CaO and P2O5 in the phosphate tailings are 10%-25%, 25%-40% and 4%-8% by mass percentage, respectively.

[0008] Optionally, when designing the proportions in S1, the amount of phosphorus tailings added is determined based on the magnesium oxide content of the clinker, the calcinability of the raw material, and the influence of phosphorus tailings on the formation of C3S in silicate clinker: (1) When the MgO content in the clinker is ≤1.9%, the MgO introduced by the phosphorus tailings has a significant impact on the mineral content in the clinker. When the addition of phosphorus tailings results in a decrease in the strength of the clinker at 3d and 28d, the clinker saturation ratio and / or aluminum ratio are adjusted. The saturation ratio KH is reduced by 0.001-0.005, and the aluminum ratio IM is increased by 0.05-0.15; (2) When If the MgO content in the clinker exceeds 1.9%, the MgO introduced by the phosphate tailings has little impact on the mineral content of the clinker. In this case, the phosphate tailings can continue to be added, while controlling the MgO content in the clinker to ≤5.0% and ensuring that the clinker stability is up to standard. At the same time, consider whether the phosphorus element in the phosphate tailings affects the burnability of the raw meal and the formation of C3S in the clinker. If there is no effect, continue to increase the amount of phosphate tailings. If increasing the amount of phosphate tailings has no significant effect on the burnability of the raw meal and the calcination in the kiln, but the amount of C3S formed in the clinker decreases, then increase the clinker saturation ratio KH by 0.001-0.010. If increasing the amount of phosphate tailings has a significant adverse effect on the burnability of the raw meal and the calcination in the kiln, then the amount of phosphate tailings should be reduced.

[0009] Furthermore, the clinker contains four minerals: C3S, C2S, C3A, and C4AF.

[0010] Furthermore, the SO3 content of the phosphogypsum is 30%-45%.

[0011] Furthermore, when designing the proportion of phosphogypsum, its dosage should be controlled between 0.55 and 0.95 for the sulfur-alkali ratio of the clinker.

[0012] Furthermore, the specific dosage of phosphogypsum is determined based on the clinker sulfur-alkali ratio level, the risk of crusting in the kiln system, and its impact on the formation of C3S in silicate clinker: (1) When the raw meal burnability index K 1450When the sulfur-alkali ratio is ≤45, the sulfur-alkali ratio should be controlled at 0.55-0.75; (2) When the raw material burnability index K 1450 At 45-70, the sulfur-alkali ratio should be controlled at 0.65-0.85; (3) When the raw material burnability index K 1450 When the sulfur content exceeds 70, the sulfur-alkali ratio should be controlled between 0.70 and 0.95.

[0013] Furthermore, the amount of phosphogypsum added to the raw meal and the sulfur-alkali ratio of the clinker also need to take into account the amount of chloride (Cl) in the kiln system. The range of phosphogypsum introduction to adjust the sulfur-alkali ratio should be determined in combination with the distribution area of ​​sulfur and chloride content in the hot raw meal to prevent the kiln system from forming a crust, thereby stabilizing the calcination in the kiln: (1) When the distribution point of sulfur and chloride content in the hot raw meal is in the low-risk area of ​​crust formation, adjust the sulfur-alkali ratio according to the upper limit specified by the burnability index; (2) When the distribution point of sulfur and chloride content in the hot raw meal is in the medium-risk area of ​​crust formation, adjust the sulfur-alkali ratio according to the lower limit specified by the burnability index; (3) When the distribution point of sulfur and chloride content in the hot raw meal is in the high-risk area of ​​crust formation, stop adding phosphogypsum to control the sulfur-alkali ratio.

[0014] Furthermore, the oxygen content in the decomposer outlet and rotary kiln flue gas chamber of S2 is 2%~3%.

[0015] Furthermore, after the addition of phosphogypsum to the phosphate tailings, the 28-day compressive strength of the clinker did not decrease, and the 3-day compressive strength increased.

[0016] The present invention has the following beneficial effects: This invention utilizes phosphate tailings in conjunction with phosphogypsum to enhance the strength of silicate clinker. Phosphate tailings primarily replace limestone, a calcareous material in the raw meal, reducing production costs. The main function of phosphogypsum is to regulate the relative content of C3S and C2S in the clinker, as well as the proportion of M1-type C3S, thereby optimizing and improving the 3-day and 28-day strength of the clinker. This invention determines the amount of phosphate tailings to incorporate based on the clinker's magnesium oxide content, the calcinability of the raw meal, and the impact of phosphate tailings on C3S formation in silicate clinker. The amount of phosphogypsum to incorporate is determined based on the clinker's sulfur-alkali ratio, the risk of crusting in the kiln system, and its impact on C3S formation in silicate clinker. By incorporating phosphogypsum, the clinker's sulfur-alkali ratio is controlled between 0.55 and 0.95, thereby increasing the proportion of M1-type C3S in the clinker and improving the 3-day and 28-day strength of the clinker. When introducing phosphogypsum into the raw meal, the oxygen content in the kiln tail flue and the decomposition furnace outlet must be strictly controlled to prevent the formation of a reducing atmosphere that could cause calcium sulfate decomposition, leading to crusting and excessive sulfur dioxide levels in the flue gas.

[0017] The method provided by this invention can not only consume two major solid wastes, high magnesium phosphate tailings and phosphogypsum, but also improve the 3-day compressive strength of clinker while maintaining the 28-day compressive strength of clinker without affecting it, thus effectively improving the strength of silicate clinker. Attached Figure Description

[0018] Figure 1The distribution of Cl and SO3 content in C5A hot feedstock in Example 1; Figure 2 The distribution of Cl and SO3 content in C5B hot feedstock in Example 1; Figure 3 The distribution of Cl and SO3 content in the C5A hot feedstock in Example 3; Figure 4 The distribution of Cl and SO3 content in the C5B hot feedstock in Example 3 is shown. Detailed Implementation

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used are commercially available.

[0020] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0021] Example 1: Without the addition of phosphate tailings, the clinker's three ratios are controlled as follows: saturation ratio KH 0.900±0.02, silicon content SM 2.55±0.10, aluminum content IM 1.55±0.10, MgO 1.1%-1.3%, sulfur-alkali ratio around 0.4, and raw meal burnability index K. 1450 Between 45 and 48. The specific steps for calcining low-magnesium (MgO ≤ 1.9%) silicate clinker using a combination of phosphate tailings and phosphogypsum are as follows: 1) In the raw material batching and grinding stage, 3% of phosphorus tailings and 0.4% of phosphogypsum, along with limestone, siliceous materials, aluminous materials, and ferrous materials, are added to the raw material mill according to the batching design and the designed mass percentage. The phosphorus tailings and phosphogypsum can be weighed and fed separately by belt scale, or they can be arranged on the limestone in the stockpile by belt according to the proportion. 2) The ratio control during the batching design and clinker production process is adjusted as follows: saturation ratio KH is 0.895±0.02, aluminum ratio IM is 1.65±0.10, and silicon ratio SM remains unchanged.

[0022] 3) According to the above-designed batching scheme, the raw meal powder is fed into the preheater, decomposition furnace, rotary kiln and cooler to complete the clinker calcination and cooling. During the clinker calcination process, the cooling air of the grate cooler is controlled to ensure sufficient secondary and tertiary air entering the rotary kiln and decomposition furnace. The oxygen content at the smoke chamber and decomposition furnace outlet is controlled to be 2.0%-3.0%. At the same time, the raw meal burnability index, Cl and SO3 content of the raw meal entering the kiln and the hot raw meal entering the kiln are monitored to assess the burnability of the raw meal and the risk of crusting, so as to determine whether it is necessary to adjust the proportion of phosphogypsum in the raw meal.

[0023] The raw material ratios, clinker ratios, MgO content, mineral composition, and strength indices of Example 1 and each comparative example are compared in Tables 1 and 2, respectively. Comparative Example 1: No phosphate tailings were added; Comparative Example 2: Phosphate tailings were added, but no adjustments were made; Comparative Example 3: Phosphate tailings were added, and the clinker ratios were adjusted, but phosphogypsum was not added; Comparative Example 4: Phosphate tailings and 0.4% phosphogypsum were added, but the clinker ratios were not adjusted; Comparative Example 5: Phosphate tailings were added, and the clinker ratios were adjusted, but the phosphogypsum content was higher, reaching 0.8%.

[0024] Table 1 Raw material proportions and clinker ratio values

[0025] Table 2. XRD mineral composition and strength of clinker (containing 4% refined gypsum)

[0026] Data from Tables 1 and 2 show that introducing 3% phosphate tailings as an ingredient increases the MgO content in the clinker, but not by more than 1.9%. Compared to Comparative Example 1, which did not include phosphate tailings, Example 1, which simultaneously introduced phosphate tailings and 0.4% phosphogypsum, increased the 3-day compressive strength of the clinker by more than 2 MPa, without adversely affecting the 28-day compressive strength. Comparative Example 2, which included phosphate tailings without adjustment, resulted in an increase in MgO in the clinker, a significant increase in C3S content, and a significant decrease in C2S content, especially insufficient αH-C2S content, which was detrimental to the 28-day strength growth of the clinker. Furthermore, the C3A content in the clinker decreased significantly (while the C4AF content increased). Comparative Example 3 incorporated phosphate tailings, adjusting the clinker's three ratios (C3S, C2S, C3A, and C4AF) to correct imbalances. However, without phosphogypsum, similar to Comparative Example 1, the proportion of M1-type C3S (M1 / M3) in the clinker was too low, thus affecting clinker strength. Comparative Example 4 incorporated phosphate tailings and 0.4% phosphogypsum. Although the proportion of M1-type C3S (M1 / M3) in the clinker increased, the three ratios were not adjusted. The C3S content in the clinker increased significantly, while the C2S content decreased significantly, especially the αH-C2S content, which was insufficient and thus detrimental to the 28-day strength growth of the clinker. Furthermore, the C3A content in the clinker decreased significantly (while the C4AF content increased significantly). Comparative Example 5, with the addition of phosphate tailings, adjusted the clinker's three ratios (calcium, sulfur, and sulfur content). While the C3A and C4AF contents in the clinker were corrected, the higher phosphogypsum content (0.8%) resulted in a higher sulfur-alkali ratio and sulfur content, leading to a significant decrease in C3S content (and an increase in C2S content). This, in turn, hindered the growth of 3-day and 28-day strength, affecting the raw meal burnability index K. 1450 There has been a relatively more significant decline.

[0027] In addition, during the trial production process, the chlorine and sulfur trioxide content of the hot raw materials was monitored, such as... Figures 1 to 2As shown (where C5 represents the fifth-stage preheater, and A and B indicate that this production line uses a dual-series preheater), the distribution points of chlorine and sulfur trioxide content in the hot raw materials in each case are all in the low-risk zone, and the oxygen content in the kiln tail flue and decomposition furnace is appropriately controlled. The kiln system operates stably, and there is no significant change in SO2 emissions from the kiln tail flue gas. Therefore, only the raw material burnability index and the actual clinker strength index are needed to adjust the clinker sulfur-alkali ratio.

[0028] Example 2: Based on Example 1, the proportion of phosphate tailings was further increased, and high-magnesium (MgO > 1.9%) clinker was calcined using phosphate ore beneficiation tailings. The specific steps are as follows: 1) In the raw material batching and grinding stage, 5% of phosphorus tailings and 0.4% of phosphogypsum, along with limestone, siliceous materials, aluminous materials, and ferrous materials, are added to the raw material mill according to the batching design and the designed mass percentage. The phosphorus tailings and phosphogypsum can be weighed and fed separately by belt scale, or they can be arranged on the limestone in the stockpile by belt according to the proportion. 2) The batching design and rate control during the clinker production process are the same as in Example 1: the saturation ratio KH is 0.895±0.02, the aluminum ratio IM is 1.65±0.10, and the silicon ratio SM remains unchanged.

[0029] 3) According to the above-designed batching scheme, the raw meal powder is fed into the preheater, decomposition furnace, rotary kiln and cooler to complete the clinker calcination and cooling. During the clinker calcination process, the cooling air of the grate cooler is controlled to ensure sufficient secondary and tertiary air entering the rotary kiln and decomposition furnace. The oxygen content at the smoke chamber and decomposition furnace outlet is controlled to be 2.0%-3.0%. At the same time, the raw meal burnability index, Cl and SO3 content of the raw meal entering the kiln and the hot raw meal entering the kiln are monitored to assess the burnability of the raw meal and the risk of crusting, so as to determine whether it is necessary to adjust the proportion of phosphogypsum in the raw meal.

[0030] Example 3: Based on Example 2, the proportion of phosphate tailings was further increased, and high-magnesium (MgO > 1.9%) clinker was calcined using phosphate ore beneficiation tailings. The specific steps are as follows: 1) In the raw material batching and grinding stage, 7% of phosphorus tailings and 0.4% of phosphogypsum, along with limestone, siliceous materials, aluminous materials, and ferrous materials, are added to the raw material mill according to the batching design and the designed mass percentage. The phosphorus tailings and phosphogypsum can be weighed and fed separately by belt scale, or they can be arranged on the limestone in the stockpile by belt according to the proportion. 2) The ratio control in the batching design and clinker production process is higher than that in Example 2, with the saturation ratio KH being 0.900±0.02, while the aluminum ratio IM and silicon ratio SM remain unchanged.

[0031] 3) According to the above-designed batching scheme, the raw meal powder is fed into the preheater, decomposition furnace, rotary kiln and cooler to complete the clinker calcination and cooling. During the clinker calcination process, the cooling air of the grate cooler is controlled to ensure sufficient secondary and tertiary air entering the rotary kiln and decomposition furnace. The oxygen content at the smoke chamber and decomposition furnace outlet is controlled to be 2.0%-3.0%. At the same time, the axial flow air of the pulverized coal injection pipe is adjusted to strengthen the clinker calcination. The raw meal burnability index, Cl and SO3 content of the raw meal and the hot raw meal entering the kiln are monitored respectively to assess the burnability of the raw meal and the risk of crusting, so as to determine whether it is necessary to adjust the proportion of phosphogypsum in the raw meal.

[0032] The comparison of raw material ratios, clinker ratios, MgO content, mineral composition, and strength in Examples 2, 3, etc., are shown in Tables 3 and 4, respectively. Comparative Example 1 is the same as in Tables 1 and 2: no phosphorus tailings were added; Comparative Example 6: 7% phosphorus tailings and 0.4% phosphogypsum were added, but the saturation ratio remained the same as in Example 2; Comparative Example 7: 9% phosphorus tailings and 0.4% phosphogypsum were added, and the clinker ratios were the same as in Example 3.

[0033] Table 3 Raw material proportioning and clinker ratio values

[0034] Table 4. XRD mineral composition and strength of clinker (containing 4% refined gypsum)

[0035] Data from Tables 3 and 4 show that the introduction of 5%, 7%, and 9% phosphate tailings as feedstock further increased the clinker MgO content, all exceeding 1.9%. Compared to Comparative Example 1 without phosphate tailings, Example 2, by simultaneously introducing 5% phosphate tailings and 0.4% phosphogypsum, maintained the clinker's three-factor ratio at the control levels of Example 1, increased the 3-day compressive strength by more than 2 MPa, and did not adversely affect the 28-day compressive strength. Comparative Example 6, by incorporating 7% phosphate tailings and 0.4% phosphogypsum, maintained the clinker's three-factor ratio at the control levels of Examples 1 and 2, but the raw meal burnability index K... 1450 The C3S content in clinker decreased, as the P2O5 introduced by the phosphate tailings began to significantly affect the formation of C3S, leading to a decrease in its content and an increase in C2S content. Consequently, the 3-day and 28-day strength of the clinker decreased compared to Example 2. Example 3 incorporated 7% phosphate tailings and 0.4% phosphogypsum. Compared to Examples 1 and 2, the clinker saturation ratio KH was increased to 0.900. Without increasing the amount of coal used, the clinker calcination was strengthened by optimizing the axial flow air in the pulverized coal injection pipe. The C3S content in the clinker returned to a reasonable level. Compared to Comparative Example 1, the 3-day compressive strength of the clinker was still increased by more than 2 MPa, and the 28-day compressive strength was not adversely affected. Comparative Example 7 incorporated 9% phosphate tailings and 0.4% phosphogypsum. The three ratios of the clinker were the same as in Example 3, but the raw meal burnability index K...1450 The decrease is significant, making it difficult to adjust the C3S content in clinker back to a reasonable level without increasing coal consumption by optimizing the air intake of the pulverized coal injection system. The introduced P2O5 has a significant adverse impact on C3S formation in the clinker, leading to a significant decrease in C3S content (and a significant increase in C2S content). Compared to Example 3, the 3-day and 28-day compressive strength of the clinker decreased significantly. Therefore, considering the burnability of the raw materials at this plant, it is not advisable to increase the proportion of phosphate tailings in the feedstock to 9%.

[0036] In addition, during the trial production process, the chlorine and sulfur trioxide content of the hot raw materials was monitored, such as... Figures 3 to 4 As shown, compared to Comparative Example 1, the other cases had higher chlorine content in the hot raw materials due to the use of a small amount of alternative fuels. However, the distribution points of chlorine and sulfur trioxide content in the hot raw materials in each case were still within the low-risk zone, and the oxygen content in the kiln tail flue and decomposition furnace was appropriately controlled. The kiln system operated stably, and there was no significant change in SO2 emissions from the kiln tail flue gas. Therefore, only the raw material burnability index and the actual clinker strength index are needed to control the clinker sulfur-alkali ratio.

[0037] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for improving the strength of silicate clinker by using phosphogypsum in conjunction with phosphate tailings as a raw material admixture, characterized in that, Includes the following steps: S1. Use phosphorus tailings and phosphogypsum as raw material admixtures and design the proportion. By mass percentage, the proportion of phosphorus tailings in the raw material is 2%-15% and the proportion of phosphogypsum is 0.4-2%. Mix and grind phosphorus tailings and phosphogypsum with other raw material raw materials. The powders obtained from S2 and S1 are fed into a preheater, a decomposition furnace, a rotary kiln, and a cooler for preheating, decomposition, calcination, and cooling, respectively. The oxygen content at the outlet of the decomposition furnace and the smoke chamber of the rotary kiln is controlled to be 1.0%~3.5% to prepare silicate clinker.

2. The method according to claim 1, characterized in that: By mass percentage, the contents of MgO, CaO and P2O5 in phosphate tailings are 10%-25%, 25%-40% and 4%-8%, respectively.

3. The method according to claim 1, characterized in that, When designing the proportions in S1, the amount of phosphorus tailings is determined based on the magnesium oxide content of the clinker, the calcinability of the raw material, and the influence of phosphorus tailings on the formation of C3S in silicate clinker: (1) When the MgO content in the clinker is ≤1.9%, the MgO introduced by the phosphorus tailings has a significant impact on the mineral content in the clinker. When the addition of phosphorus tailings results in a decrease in the strength of the clinker at 3d and 28d, the clinker saturation ratio and / or aluminum ratio are adjusted. The saturation ratio KH is reduced by 0.001-0.005, and the aluminum ratio IM is increased by 0.05-0.15; (2) When the clinker If the MgO content in the clinker exceeds 1.9%, the MgO introduced by the phosphorus tailings will not significantly affect the mineral content in the clinker. In this case, phosphorus tailings can continue to be added, while controlling the MgO content in the clinker to ≤5.0% and ensuring that the clinker stability is up to standard. At the same time, consider whether the phosphorus element in the phosphorus tailings affects the burnability of the raw meal and the formation of C3S in the clinker. If there is no effect, continue to increase the amount of phosphorus tailings added. If increasing the amount of phosphorus tailings added has no significant effect on the burnability of the raw meal and the calcination in the kiln, but the amount of C3S formed in the clinker decreases, then increase the clinker saturation ratio KH by 0.001-0.

010. If increasing the amount of phosphorus tailings added has a significant adverse effect on the burnability of the raw meal and the calcination in the kiln, then the amount of phosphorus tailings added should be reduced.

4. The method according to claim 3, characterized in that: The clinker contains four minerals: C3S, C2S, C3A, and C4AF.

5. The method according to claim 1, characterized in that: The SO3 content of the phosphogypsum is 30%-45%.

6. The method according to claim 1, characterized in that: When designing the proportions of phosphogypsum, its dosage should be controlled to maintain the sulfur-alkali ratio of the clinker between 0.55 and 0.

95.

7. The method according to claim 6, characterized in that: The specific dosage of phosphogypsum is determined based on the clinker sulfur-alkali ratio, the risk of crusting in the kiln system, and its impact on the formation of C3S in silicate clinker: (1) When the raw material burnability index K 1450 When the sulfur-alkali ratio is ≤45, the sulfur-alkali ratio should be controlled at 0.55-0.75; (2) When the raw material burnability index K 1450 At 45-70, the sulfur-alkali ratio should be controlled at 0.65-0.85; (3) When the raw material burnability index K 1450 When the sulfur content exceeds 70, the sulfur-alkali ratio should be controlled between 0.70 and 0.

95.

8. The method according to claim 7, characterized in that: The amount of phosphogypsum added to the raw meal and the sulfur-alkali ratio of the clinker also need to take into account the amount of chloride (Cl) in the kiln system. The range of phosphogypsum introduction to adjust the sulfur-alkali ratio should be determined in combination with the distribution point of sulfur and chloride content in the hot raw meal to prevent the kiln system from forming a crust, thereby stabilizing the calcination in the kiln: (1) When the distribution point of sulfur and chloride content in the hot raw meal is in the low-risk area of ​​crust formation, adjust the upper limit of the sulfur-alkali ratio in combination with the burnability index; (2) When the distribution point of sulfur and chloride content in the hot raw meal is in the medium-risk area of ​​crust formation, adjust the lower limit of the sulfur-alkali ratio in combination with the burnability index; (3) When the distribution point of sulfur and chloride content in the hot raw meal is in the high-risk area of ​​crust formation, stop adding phosphogypsum to control the sulfur-alkali ratio.

9. The method according to any one of claims 1 to 8, characterized in that: The oxygen content at the outlet of the decomposer and in the rotary kiln flue in S2 is 2%~3%.

10. The method according to any one of claims 1-9, characterized in that: When phosphogypsum is added to phosphate tailings, the 28-day compressive strength of the clinker does not decrease, and the 3-day compressive strength increases.

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