A method for preparing cement using phosphate ore beneficiation waste and the cement itself.

Abstract

This invention relates to the field of cement building materials technology, and in particular to a method for preparing cement using phosphate rock beneficiation waste residue, and the cement thereof. The method includes: designing the batching based on the oxide content in the raw meal; calculating the first saturation ratio, first silica ratio, first alumina ratio, and first MgO content of the clinker; determining the percentage of phosphate rock beneficiation waste residue incorporated based on the first saturation ratio, first silica ratio, first alumina ratio, and first MgO content; adjusting the batching of the raw meal with incorporated phosphate rock beneficiation waste residue to adjust the first saturation ratio to a second saturation ratio, the first silica ratio to a second silica ratio, and the first alumina ratio to a second alumina ratio, thereby stabilizing and ensuring the mineral composition and quality of the clinker; grinding the adjusted raw meal in a raw meal mill; and calcining the ground powder in a preheater, decomposition furnace, rotary kiln, and cooler to obtain clinker with the desired MgO content.

Description

Technical Field

[0001] This invention relates to the field of cement building materials technology, and in particular to a method for preparing cement using phosphate rock beneficiation waste residue and the cement itself. Background Technology

[0002] Phosphate rock is the raw material for producing phosphoric acid. Phosphate rock used for phosphoric acid production generally requires a P2O5 content of over 28%, and strict control of magnesium oxide impurities is necessary. Most of my country's phosphate rock is of medium to low grade, and it contains various mineral phases, including carbonates and quartz, with carbonates (such as dolomite) being the most prevalent. Therefore, most phosphate rock requires purification, which generates a large amount of phosphate ore beneficiation waste. The waste generated from beneficiating phosphate rock, which is mainly composed of carbonates, typically has a CaO content of 30%-40%, contains some P2O5 and SO3, but also has a high MgO content, generally around 18%, limiting its resource utilization. Most phosphate chemical companies resort to stockpiling, but constructing seepage-proof storage ponds requires significant investment and long-term land occupation.

[0003] Actual production research has revealed that using high-magnesium phosphate ore beneficiation waste as a calcium-based raw material leads to an increase in clinker magnesium oxide levels, generally reducing clinker strength. Excessively high levels can also affect the stability of the clinker and cement production. Furthermore, due to the thorough agitation, mixing, calcination, and fusion of materials within the rotary kiln, the effects of elements such as magnesium, phosphorus, and sulfur in phosphate ore beneficiation waste on clinker are highly complex compared to the effects of a single element. Moreover, because the materials are calcined under agitated and mixed conditions within the rotary kiln, the solid solution capacity of the clinker for each element differs from that of laboratory pelleting and calcination. Typically, in industrial clinker calcination production, the solid solution and interactions of elements such as magnesium, sulfur, phosphorus, and alkali in the clinker minerals are more pronounced, and their impact on the mineral composition and strength of the clinker is more complex. Figure 2 As shown, with the increase of MgO, the content of tetracalcium aluminoferrite (C4AF) in the clinker does not increase continuously. Instead, it increases first, and then, after reaching a certain value, significant periclase crystallization occurs during the clinker cooling process. At this point, tetracalcium aluminoferrite does not continue to dissolve magnesium oxide; instead, excessive periclase crystallization causes the content of tetracalcium aluminoferrite in the clinker to decrease again. Therefore, when using phosphate rock beneficiation waste in cement production, it is necessary to combine the actual situation and formulate more detailed and in-depth methods for the resource utilization of phosphate rock beneficiation waste in cement production. This will solve the problems of phosphate rock beneficiation waste affecting clinker quality when used as a raw material for silicate cement clinker calcination, and the reluctance or inability to use phosphate rock beneficiation waste due to the high magnesium oxide content (greater than 2.0%) in the clinker itself.

[0004] In large-scale projects or scenarios requiring extended pouring and paving times, it may be necessary to extend the cement setting time to ensure construction quality and efficiency, providing workers with more operating time and reducing construction pressure caused by time constraints. In the actual production of retarded cement, commonly used retarding materials include sodium aluminate, sodium phosphate, magnesium sulfate, and calcium phosphate. However, from a resource utilization perspective, using these materials as retarding materials is not the optimal choice for resource utilization.

[0005] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a way to combine phosphate ore beneficiation waste with cement production to prepare cement that meets the strength and setting time requirements, and to solve the problem of difficult storage of phosphate ore beneficiation waste.

[0007] In a first aspect, the present invention provides a method for preparing cement using phosphate ore beneficiation waste, comprising:

[0008] The batching design is carried out based on the oxide content in the raw meal, and the first saturation ratio, first silicon ratio, first aluminum ratio and first MgO content of the clinker are calculated.

[0009] The percentage of phosphate rock beneficiation waste incorporated is determined based on the first saturation ratio, the first silicon ratio, the first aluminum ratio, and the first MgO content.

[0010] The raw meal mixed with phosphate rock beneficiation waste is adjusted in order to adjust the first saturation ratio to the second saturation ratio, the first silicon ratio to the second silicon ratio, and the first aluminum ratio to the second aluminum ratio, so as to stabilize and ensure the mineral composition and quality of the clinker.

[0011] The adjusted raw materials are added to a raw material mill for grinding.

[0012] The ground powder is fed into a preheater, decomposition furnace, rotary kiln and cooler for calcination to obtain clinker with the expected MgO content.

[0013] Preferably, the raw material is prepared by mixing calcareous materials, siliceous materials, aluminum materials and iron materials in a preset mass percentage ratio.

[0014] Preferably, the first saturation ratio and the second saturation ratio are determined by the content of the calcium material, the first silicon ratio and the second silicon ratio are determined by the silicon material, and the first aluminum ratio and the second aluminum ratio are determined by the aluminum material.

[0015] Preferably, when the first saturation ratio is controlled to be 0.910±0.02, the first silicon content is 2.55±0.10, the first aluminum content is 1.55±0.10, and the first MgO content is less than 2.3%, and a clinker with an expected MgO content of less than 2.3% is required, 1%-10% of the phosphate rock beneficiation waste residue is added.

[0016] Preferably, after adding 1%-10% of the phosphate rock beneficiation waste to the raw meal, the raw meal is batched to control the second saturation ratio to be 0.900±0.02, the second silicon content to be 2.65±0.10, and the second aluminum content to be 1.65±0.10.

[0017] The raw materials are ground and then calcined to obtain clinker with an expected MgO content of less than or equal to 2.3%.

[0018] Preferably, when the first saturation ratio is controlled to be 0.910±0.02, the first silicon content is 2.55±0.10, the first aluminum content is 1.55±0.10, and the first MgO content is less than 2.3%, and a clinker with a expected MgO content greater than 2.3% is required, 2%-20% of the phosphate rock beneficiation waste residue is added.

[0019] Preferably, after adding 2%-20% of the phosphate rock beneficiation waste to the raw meal, the raw meal is batched to control the second saturation ratio to be 0.890±0.02, the second silicon content to be 2.60±0.10, and the second aluminum content to be 1.60±0.10.

[0020] The raw materials are ground and then calcined to obtain clinker with a expected MgO content of ≥2.3%.

[0021] Secondly, based on the first aspect, the present invention further provides a method for preparing cement using phosphate ore beneficiation waste, the method further comprising:

[0022] Phosphate ore beneficiation waste residue, clinker, neutralized modified phosphogypsum, limestone powder, fly ash and slag are added to the cement grinding system for grinding according to the preset mass ratio.

[0023] The process parameters of the air classifier are adjusted to the preset parameters to classify cement particles and obtain cement powder with the expected qualified specific surface area. This powder is then fed into the cement silo, thus completing the preparation of retarded cement.

[0024] Preferably, the proportion of the phosphate rock beneficiation waste residue incorporated into clinker, neutralized modified phosphogypsum, limestone powder, fly ash, and slag is 0%-15%. Within this range, the higher the proportion of the phosphate rock beneficiation waste residue incorporated, the longer the cement setting time.

[0025] In a second aspect, the present invention provides cement prepared from phosphate ore beneficiation waste residue, which is prepared according to the method for preparing cement from phosphate ore beneficiation waste residue as described in the first aspect.

[0026] In summary, the beneficial effects of this invention are as follows: Firstly, by combining phosphate ore beneficiation waste with cement preparation processes, phosphate ore beneficiation waste is added to the raw materials used in traditional cement preparation. After adding the phosphate ore beneficiation waste, the cement process parameters are adjusted again to meet the expected cement performance requirements without affecting the quality of clinker and cement. This achieves the resource utilization of phosphate ore beneficiation waste in cement production and solves the problem that phosphate ore beneficiation waste is either unusable or cannot be used in cement production.

[0027] Secondly, adding phosphate ore beneficiation waste as a retarding material to the cement preparation process alleviates the problem of slag storage difficulties compared to the traditional use of sodium aluminate sulfate, sodium phosphate, magnesium sulfate, calcium phosphate, and other materials as retarding materials. Furthermore, the main phases of high-magnesium phosphate ore beneficiation waste are dolomite, hydroxyl or fluorapatite, and quartz, with fewer minerals such as mica and clay that have a significant impact on cement performance. At the same time, magnesium oxide exists in dolomite, so there is no problem of later expansion in cement application, thus realizing the resource utilization of phosphate ore beneficiation waste as a retarding material. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0029] Figure 1 This is a schematic flowchart of a method for preparing cement using phosphate rock beneficiation waste provided in Embodiment 1 of the present invention;

[0030] Figure 2 This is a schematic diagram showing the changes in clinker mineral composition with different magnesium oxide contents in a method for preparing cement using phosphate rock beneficiation waste provided in Embodiment 1 of the present invention.

[0031] Figure 3a This is a schematic diagram of the first set of raw material batching and clinker ratio values ​​for a method of preparing cement using phosphate rock beneficiation waste provided in Embodiment 1 of the present invention;

[0032] Figure 3b This is a schematic diagram of the mineral composition and performance indicators of the first group of clinker X-ray diffraction (XRD) of a method for preparing cement using phosphate rock beneficiation waste provided in Embodiment 1 of the present invention.

[0033] Figure 4a This is a schematic diagram of the second set of raw material batching and clinker ratio values ​​for a method of preparing cement using phosphate ore beneficiation waste provided in Embodiment 2 of the present invention;

[0034] Figure 4b This is a schematic diagram of the second set of raw material batching and clinker ratio values ​​for a method of preparing cement using phosphate ore beneficiation waste provided in Embodiment 2 of the present invention;

[0035] Figure 5 This is a schematic diagram of the preparation process of retarded cement using phosphate rock beneficiation waste slag, as provided in Embodiment 3 of the present invention.

[0036] Figure 6 This is a schematic diagram illustrating the performance indicators of different retarded cements prepared using phosphate rock beneficiation waste, as provided in an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] In the description of this invention, the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and do not require that this invention must be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0039] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0040] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] Example 1:

[0042] Embodiment 1 of the present invention provides a method for preparing cement using phosphate ore beneficiation waste, such as... Figure 1 As shown, it includes:

[0043] In step 1, the batching design is carried out based on the oxide content in the raw material, and the first saturation ratio, first silicon ratio, first aluminum ratio and first MgO content of the clinker are calculated.

[0044] Specifically, the raw material is prepared by mixing calcareous materials, siliceous materials, aluminous materials, and ferrous materials in a preset mass percentage ratio. In one embodiment, the calcareous material can be limestone, the siliceous material can be shale or sandstone, the aluminous material can be wet fly ash, and the ferrous material can be iron ore, iron powder, or ferroalloy.

[0045] In step 2, the percentage of phosphate rock beneficiation waste incorporated is determined based on the first saturation ratio, the first silicon ratio, the first aluminum ratio, and the first MgO content.

[0046] In step 3, the raw material mixed with phosphate ore beneficiation waste is adjusted to adjust the first saturation ratio to the second saturation ratio, the first silicon ratio to the second silicon ratio, and the first aluminum ratio to the second aluminum ratio, so as to stabilize and ensure the mineral composition and quality of the clinker.

[0047] In practical applications, cement plants use three ratios (i.e., saturation ratio, silicon ratio, and aluminum ratio) to control the mineral composition of the final clinker. However, the calculation of the three ratios does not take into account the MgO content. During the clinker firing process, MgO will affect the mineral composition of the clinker. Therefore, in this embodiment of the invention, it is proposed to adjust the three ratios (i.e., the second saturation ratio, the second silicon ratio, and the second aluminum ratio) of the clinker under different MgO contents to stabilize the mineral composition and performance of the clinker.

[0048] Wherein, the first saturation ratio and the second saturation ratio are determined by the content of the calcium material, the first silicon ratio and the second silicon ratio are determined by the silicon material, and the first aluminum ratio and the second aluminum ratio are determined by the aluminum material.

[0049] Specifically, increasing or decreasing the first saturation ratio and the second saturation ratio is mainly achieved by increasing or decreasing the content of calcium materials in the raw material batch. An increase in calcium material content leads to an increase in both the first and second saturation ratios, while a decrease in calcium material content leads to a decrease in both the first and second saturation ratios. Similarly, increasing or decreasing the first silicon ratio and the second silicon ratio is mainly achieved by increasing or decreasing the content of silicon materials in the raw material batch. An increase in silicon material content leads to an increase in both the first and second silicon ratios, while a decrease in silicon material content leads to a decrease in both the first and second silicon ratios. Likewise, increasing or decreasing the first aluminum ratio and the second aluminum ratio is mainly achieved by increasing or decreasing the content of aluminum materials in the raw material batch. An increase in aluminum material content leads to an increase in both the first and second aluminum ratios, while a decrease in aluminum material content leads to a decrease in both the first and second aluminum ratios.

[0050] The formulas for calculating the first and second saturation ratios mentioned in the above steps can be KH = (CaO - 1.65Al2O3 - 0.35Fe2O3 - 0.7SO3) / 2.8 * SiO2; the formulas for calculating the first and second silicon ratios are SM = SiO2 / (Al2O3 + Fe2O3); and the formulas for calculating the first and second aluminum ratios are IM = Al2O3 / Fe2O3. The first MgO content and the clinker with the expected MgO content obtained at the end are obtained from the raw material or clinker using instrumental fluorescence analysis or manual chemical analysis. Similarly, the contents of CaO, Al2O3, Fe2O3, SO3, and SiO2 mentioned in the above formulas are all obtained from instrumental fluorescence analysis or manual chemical analysis.

[0051] In this embodiment, in step 3, the three ratios of the clinker (i.e., the second saturation ratio KH, the second silicon ratio SM, and the second aluminum ratio IM) are adjusted. The adjustment method is based on the MgO content in clinker produced under normal and stable conditions without using phosphate rock beneficiation waste. The adjustment principle is based on the interaction and solid solution law of MgO, P2O5, SO3, and R2O content in clinker minerals, and the correlation between the three ratios of clinker (second saturation ratio KH, second silicon ratio SM, and second aluminum ratio IM) and the actual mineral composition of the clinker. The specific adjustment method is as follows:

[0052] (1) If the MgO content of clinker produced by calcining without using phosphate ore beneficiation tailings does not exceed 2.3%, and the MgO content of clinker produced by calcining with phosphate ore beneficiation tailings does not exceed 2.3%, compared with phosphate ore beneficiation tailings, the second saturation ratio KH of the clinker is reduced according to the increase in MgO, P2O5 and SO3 in the clinker, with a relative reduction range of 0-0.03. The second silicon ratio SM is appropriately increased, with a relative increase range of 0-0.15. The second aluminum ratio IM is appropriately increased, with a relative increase range of 0-0.25. The greater the increase in MgO, P2O5 and SO3 in the clinker, the greater the adjustment range of the three ratios of the clinker (second saturation ratio KH, second silicon ratio SM and second aluminum ratio IM).

[0053] When the proportion of phosphate ore beneficiation tailings is further increased, resulting in a MgO content greater than 2.3% in the clinker, the second saturation ratio KH of the clinker should be further reduced, with a reduction range of 0-0.02 compared to the previous value. The second silicon ratio SM can be appropriately adjusted back, with a reduction range of 0-0.10 compared to the previous value. The second aluminum ratio IM should also be appropriately adjusted back, with a reduction range of 0-0.20 compared to the previous value. The greater the increase in MgO, P2O5, and SO3 in the clinker, the greater the adjustment range of the three ratios of the clinker (second saturation ratio KH, second silicon ratio SM, and second aluminum ratio IM).

[0054] (2) When the MgO content in clinker obtained by calcination without using phosphate ore beneficiation tailings is already greater than 2.3%, compared with clinker obtained by calcination using phosphate ore beneficiation tailings, the second saturation ratio KH of the clinker should be reduced to a range of 0-0.02, the second silicon ratio SM should be appropriately reduced to a range of 0-0.10, and the second aluminum ratio IM should be appropriately reduced to a range of 0-0.20. The greater the increase in MgO, P2O5 and SO3 in the clinker, the greater the adjustment range of the three ratios of the clinker (i.e., the second saturation ratio KH, the second silicon ratio SM and the second aluminum ratio IM).

[0055] Specifically, the control principle is based on the interaction and solid solution rules of MgO, P2O5, SO3, and R2O in clinker minerals. In practical applications, these interactions and solid solution rules manifest as follows: the influence of MgO, SO3, and R2O (K2O and Na2O) content is not considered in the calculation of the three ratios. However, these elements interact and dissolve in the clinker minerals during clinker calcination, leading to a significant deviation between the mineral content controlled by the three ratios and the expected values. For example, MgO readily dissolves in C3S (A mineral) and C4AF. An increase in C3S (A mineral) and C4AF content will lead to an increase in C3S (A mineral) content and C4AF content. When the MgO content in the clinker increases to about 2.3%, significant periclase crystallization occurs, and the C3S (A mineral) and C4AF contents decrease. Then, as the MgO content increases, the content tends to stabilize, but at the same time, a large amount of periclase is formed, affecting the stability of clinker and cement.

[0056] In step 4, the adjusted raw material is added to the raw material mill for grinding.

[0057] In step 5, the ground powder is fed into a preheater, decomposition furnace, rotary kiln and cooler for calcination to obtain clinker with the expected MgO content.

[0058] In summary, by combining phosphate ore beneficiation waste with cement production processes, adding phosphate ore beneficiation waste to the raw materials used in traditional cement production, and then readjusting the cement process parameters after adding the waste to meet the expected cement performance requirements without affecting clinker and cement quality, the resource utilization of phosphate ore beneficiation waste in cement production is realized, and the problem of not daring to use or being unable to use phosphate ore beneficiation waste in cement production is solved.

[0059] The above solution will be described in detail below using the research process of an embodiment of the present invention as an example.

[0060] Phosphate ore beneficiation waste is the residue generated after phosphate rock beneficiation. Its MgO, CaO, P2O5, and SO3 contents are 10%-25%, 25%-40%, 3%-9%, and 1%-7%, respectively. Compared to limestone used in silicate cement clinker calcination, it has significantly higher magnesium content and contains higher levels of phosphorus and sulfur. Its main minerals are dolomite, apatite, quartz, and calcite. Silicate cement clinker calcination requires calcium-based raw materials. Although the CaO content of phosphate ore beneficiation waste is lower than that of limestone, it is relatively high. Therefore, it can be considered as a calcium-based raw material to replace part of the limestone calcium materials in clinker calcination. Furthermore, because the main carbonate mineral phase of phosphate ore beneficiation waste is dolomite, its decomposition temperature is lower than that of calcite in limestone. In addition, it contains certain amounts of phosphorus and fluorine, which act as mineralizers. Adding it to cement raw materials can improve the burnability of the raw materials and reduce the energy consumption of clinker calcination.

[0061] Regarding the effects of MgO, P2O5, and SO3 on the mineral composition of clinker, most studies have shown that increasing MgO leads to a decrease in the content of M1 type tricalcium silicate (C3S, A mineral) in the clinker, while increasing the content of M3 type C3S, which in turn leads to a decrease in clinker strength. By increasing the SO3 content, the content of M1 type C3S can be increased, thereby improving the clinker strength.

[0062] Regarding the effect of P2O5 on clinker, it is generally believed that appropriate addition can reduce the amount of free calcium oxide (f-CaO) in the clinker and improve its scalability. However, excessive P2O5 content can lead to the decomposition of C3S, resulting in an increase in f-CaO. Additionally, regarding the effect of MgO on the mineral composition of clinker, such as... Figure 2 As shown in the experimental results, actual research revealed that the C4AF content in clinker does not increase continuously with the increase of MgO. Instead, it increases initially, and then, after reaching a certain value, significant periclase crystallization occurs during the clinker cooling process. At this point, C4AF does not continue to dissolve magnesium oxide; instead, excessive periclase crystallization causes the C4AF content in the clinker to decrease again. When the MgO content is 2.15%, the C4AF content reaches a maximum of 18.92%. Therefore, different adjustment schemes and adjustment ranges should be made in clinker batching based on changes in MgO content to stabilize the mineral composition of clinker and ensure the stability of clinker and cement performance.

[0063] Based on the above background, in the research process of this invention embodiment, according to the proportioning experiment of phosphate ore beneficiation waste and cement raw meal, and the detection of MgO, P2O5, SO3 and alkali R2O content of multiple batches of clinker after proportioning, the optimal proportion of phosphate ore beneficiation waste added to the raw meal is 2%-12%. It should be reasonably added according to the needs, and the MgO and P2O5 content in the final calcined clinker should be controlled to not exceed 5.0% and 0.4% respectively, and the sulfur-alkali ratio (SO3 to R2O molar ratio) should be below 0.9, so as to stabilize and ensure the mineral composition and quality of the clinker.

[0064] In one embodiment, when calcining low-magnesium (MgO≤2.3%) clinker using phosphate rock beneficiation waste residue, when the first saturation ratio is 0.910±0.02, the first silicon ratio is 2.55±0.10, the first aluminum ratio is 1.55±0.10, and the first MgO content is less than 2.3%, and a clinker with an expected MgO content of less than 2.3% is required, 1%-10% of the phosphate rock beneficiation waste residue is added. To rationally control the three ratios and mineral composition of clinker, stabilize clinker performance indicators, and fully utilize high-magnesium phosphate ore beneficiation waste in raw meal grinding and clinker calcination without adversely affecting clinker quality, especially clinker strength, 1%-10% of the aforementioned phosphate ore beneficiation waste is added to the raw meal. The raw meal is then batched, controlling the second saturation ratio at 0.900±0.02, the second silicon content at 2.65±0.10, and the second aluminum content at 1.65±0.10. The raw meal is then ground and calcined to obtain clinker with a desired MgO content of less than or equal to 2.3%. Following the above batching scheme, the ground raw meal powder is fed into a preheater, decomposition furnace, rotary kiln, and cooler to complete clinker calcination, thus achieving the production of low-magnesium (MgO≤2.3%) clinker using phosphate ore beneficiation waste as raw material.

[0065] Based on the above methods, in the actual research process, such as Figure 3a As shown, experiments were conducted to compare the raw meal ratios and clinker performance indicators such as the three ratios (calcium, phosphorus, and sulfur content), MgO content, mineral composition, and strength of clinker before and after adding phosphate ore beneficiation waste (Comparative Example 1) and after adding phosphate ore beneficiation waste without adjustment (Comparative Example 2). In Example 1, the phosphate ore beneficiation waste content was 2%, the limestone content was 82.39%, the sandstone content was 10.07%, the iron content was 1.07%, the contaminated soil content was 2.50%, and the wet fly ash content was 1%. 0.34%; in Comparative Example 1, the limestone content was 84.27%, sandstone content was 10.45%, ferrous material content was 1.32%, contaminated soil content was 2.50%, and wet fly ash content was 1.47%; in Comparative Example 2, the limestone content was 82.35%, phosphate ore beneficiation waste content was 2.00%, sandstone content was 10.38%, ferrous material content was 1.29%, contaminated soil content was 2.50%, and wet fly ash content was 1.48%.

[0066] The comparison results are as follows Figure 3bAs shown in the figure, the data reveals that in Comparative Example 2, when the MgO content in the clinker does not exceed 2.3%, the addition of phosphate ore beneficiation waste leads to an increase in phosphorus and magnesium elements in the clinker. Without adjusting the three ratios of the clinker, the actual mineral composition of the clinker will deviate significantly from the original composition. In particular, the C3S content increases significantly, while the C2S content decreases significantly, resulting in a significant decrease in the 28-day strength of the clinker. Simultaneously, the C3A content decreases, while the C4AF content increases significantly. These changes are due to the simultaneous solid solution and interaction of MgO in the C3S and C4AF of the clinker. In the aforementioned method, by utilizing phosphate tailings for batching and appropriately adjusting the second saturation ratio, second silica ratio, and second alumina ratio of the clinker, the actual mineral composition of the clinker can be maintained within a suitable range, thereby stabilizing the clinker quality and, in particular, reducing the adverse effects on the 28-day strength of the clinker.

[0067] In addition, the clinker in Example 1 reached 350±10m³. 2 The grinding time for clinker with a surface area of ​​ / kg was 30 minutes, and the clinker in Comparative Example 1 reached 350±10m³. 2 The grinding time for clinker with a specific surface area of ​​ / kg was 30.5 min, while that for Comparative Example 2, the clinker reached 350 ± 10 m³ / kg. 2 The grinding time of 32 min for / kg specific surface area indicates that the grindability of clinker in Example 1 did not deteriorate when using phosphate ore beneficiation waste to produce clinker. However, in Comparative Example 2, where the second saturation ratio, second silicon ratio, and second aluminum ratio were not adjusted, the clinker not only showed a significant decline in 28-day strength (related to the low total C2S content), but also experienced a relatively large adverse impact on grindability (related to the increased C4AF content).

[0068] Example 2:

[0069] Based on the method of calcining low-magnesium (MgO≤2.3%) clinker using phosphate ore beneficiation waste mentioned in Example 1, this invention proposes a method of calcining high-magnesium (MgO>2.3%) clinker using phosphate ore beneficiation waste.

[0070] In one embodiment, high-magnesium (MgO > 2.3%) clinker is calcined using phosphate rock beneficiation waste. When the first saturation ratio is controlled at 0.910 ± 0.02, the first silicon content at 2.55 ± 0.10, the first aluminum content at 1.55 ± 0.10, and the first MgO content at less than 2.3%, and a clinker with a desired MgO content greater than 2.3% is required, 2%-20% of the phosphate rock beneficiation waste is added. After adding 2%-20% of the phosphate rock beneficiation waste to the raw meal, the raw meal is batched, and the second saturation ratio is controlled at 0.890 ± 0.02, the second silicon content at 2.60 ± 0.10, and the second aluminum content at 1.60 ± 0.10. According to the above batching scheme, the raw meal is ground into powder and fed into a preheater, a decomposition furnace, a rotary kiln, and a cooler to complete the clinker calcination. The raw meal is ground and then calcined to obtain clinker with a desired MgO content greater than or equal to 2.3%.

[0071] Based on the above methods, in the actual research process, such as Figure 4a As shown, the raw meal ratio, clinker ratio, MgO content, mineral composition, and strength, etc., of the unadjusted phosphate rock beneficiation waste (Comparative Example 3) were experimentally compared with those of Example 2, which incorporated phosphate rock beneficiation waste and underwent adjustments. The comparison results are as follows: Figure 4b As shown in the figure, the data indicates that when the MgO content in the clinker exceeds 2.3%, the phosphorus and magnesium content in the clinker increases with the incorporation of phosphate ore tailings. In Comparative Example 3, if the second saturation ratio, second silica ratio, and second alumina ratio of the clinker are not adjusted, the actual mineral composition of the clinker will deviate significantly from the original composition. However, this differs from the case when the MgO content in the clinker does not exceed 2.3%. Although Comparative Example 3 still shows an increase in C3S content and a decrease in C2S content, resulting in a significant decrease in the clinker's strength at 28 days, the C3A content does not decrease, while the C4AF content decreases, and the periclase content increases significantly. At this point, the excessive MgO in the liquid phase of the clinker can provide sufficient periclase crystal nuclei during the clinker cooling process, leading to more periclase crystallization. The MgO content dissolved in C4AF decreases significantly, resulting in a decrease in C4AF content. However, the MgO that has entered the C3S minerals is relatively difficult to precipitate from the solid C3S particles, and the C3S content does not show a decrease. Experimental measurements show that the total C3S and C2S content in the finished cement clinker is generally around 75%. When C3S is too low (C2S content is too high), it leads to a significant decrease in 3-day strength and poorer grindability. Conversely, when C3S is too high (C2S content is too low), it is beneficial to 3-day strength, but the 28-day strength decreases significantly, while grindability improves. Furthermore, the solid solution of other elements such as phosphorus in C3S minerals also contributes to a more complex clinker mineral composition.

[0072] In addition, in Example 2, the clinker grinding reached 350±10m. 2The grinding time for the clinker with a surface area of ​​ / kg was 30.5 min, and the grinding time for the clinker in Comparative Example 3 reached 350 ± 10 m³. 2 The grinding time of 30 min for the clinker with a specific surface area of ​​ / kg indicates that the grindability of the clinker in Example 2 is close to that of Comparative Example 1 (see Example 1) without the use of phosphate ore beneficiation waste, and the grindability of the clinker in Comparative Example 3 is slightly improved. However, it can be seen that the 28-day strength of the clinker in Comparative Example 3 is only 58.2 MPa, which is a significant decline. In contrast, Example 2, while utilizing phosphate tailings as feedstock, establishes the complex laws and correlations of solid solution of elements such as phosphorus and magnesium in clinker and their influence on the mineral composition of clinker. By appropriately controlling the second saturation ratio, second silica ratio, and second alumina ratio of the clinker, the actual mineral composition of the clinker can be kept within a suitable range, thereby stabilizing the clinker quality. The grindability does not fluctuate greatly, and the 28-day strength does not decrease significantly.

[0073] Example 3:

[0074] Based on Examples 1 and 2, this invention also proposes a method for preparing cement using phosphate rock beneficiation waste residue. This method is mainly used for preparing retarded cement. Figure 5 As shown, the method further includes:

[0075] In step 6, phosphate ore beneficiation waste, clinker, neutralized modified phosphogypsum, limestone powder, fly ash and slag are added to the cement grinding system for grinding according to a preset mass ratio.

[0076] During the experimental research, it was found that the proportion of the phosphate ore beneficiation waste residue added to clinker, neutralized modified phosphogypsum, limestone powder, fly ash and slag was 0%-15%. Within this range, the higher the proportion of the phosphate ore beneficiation waste residue added, the longer the cement setting time.

[0077] In step 7, the process parameters of the air classifier are adjusted to the preset parameters to classify the cement particles and obtain cement powder with the expected qualified specific surface area. This powder is then input into the cement silo, thus completing the preparation of retarded cement.

[0078] Specifically, in one embodiment, adjusting the process parameters of the air classifier to preset parameters specifically involves adjusting the rotation speed of the air classifier to 27-34 Hz; the air classification of cement particles to obtain cement powder with a qualified specific surface area, wherein the qualified specific surface area cement powder has a specific surface area of ​​330-360 m². 2 / kg of cement powder.

[0079] According to the above method, phosphate ore beneficiation waste is added to the cement preparation process as a retarding material. Compared with the traditional use of sodium aluminate sulfate, sodium phosphate, magnesium sulfate, calcium phosphate and other materials as retarding materials, the use of phosphate ore beneficiation waste alleviates the problem of difficult slag storage. In addition, the main phases of high magnesium phosphate ore beneficiation waste are dolomite, hydroxyl or fluorapatite and quartz, and it contains less mica, clay and other minerals that have a greater impact on cement performance. At the same time, magnesium oxide exists in dolomite, so there is no problem of later expansion in cement application, realizing the resource utilization of phosphate ore beneficiation waste as a retarding material.

[0080] In one embodiment, the phosphate ore beneficiation waste residue, clinker, neutralized modified phosphogypsum, limestone powder, fly ash, and slag are added to a cement grinding system for grinding according to a preset mass ratio. The preset mass ratio is as follows: phosphate ore beneficiation waste residue content is 6% ± 2%, clinker content is 70% ± 2%, neutralized modified phosphogypsum content is 5% ± 2%, limestone powder content is 5% ± 2%, fly ash content is 7% ± 2%, and slag content is 7% ± 2%.

[0081] This example uses phosphate ore beneficiation waste slag content of 6%, clinker content of 70%, neutralized modified phosphogypsum content of 5%, limestone powder content of 5%, fly ash content of 7%, and slag content of 7%. Figure 6 As shown in the table, Example 3 presents the performance parameters of cement prepared using the above proportions. To demonstrate the difference in retarding time between cement prepared using phosphate rock beneficiation waste and other materials, Comparative Examples 4, 5, and 6 were designed as comparative materials for analysis during the actual research process. Comparative Example 4 uses limestone instead of phosphate rock beneficiation waste as a blending material to produce cement with the following performance indicators: clinker content 70%, neutralized modified phosphogypsum content 5%, limestone powder content 11%, fly ash content 7%, and slag content 7%. Comparative Examples 5 and 6 do not use phosphate rock beneficiation waste as a blending material; both use undisturbed phosphogypsum to produce retarded cement. The difference lies in the batch of undisturbed phosphogypsum used; the cement proportions for both are: clinker content 70%, undisturbed phosphogypsum content 5%, limestone powder content 11%, fly ash content 7%, and slag content 7%.

[0082] from Figure 6The table data shows that Example 3, using phosphate ore beneficiation waste as a blending material, achieves a setting time that meets the requirements of GB / T 35162 "Retarded Cement for Road Base Courses," which specifies an initial setting time of not less than 300 minutes and a final setting time of not less than 360 minutes and not exceeding 720 minutes. Furthermore, its 3-day flexural strength reaches 4.8 MPa, its 28-day flexural strength reaches 7.4 MPa, its 3-day compressive strength reaches 25.6 MPa, its 28-day compressive strength reaches 47.2 MPa, and its overall strength grade reaches 42.5. In contrast, Comparative Example 4, which does not use phosphate ore beneficiation waste and employs neutralized modified phosphogypsum (lime or calcium hydroxide-modified phosphogypsum), cannot achieve an initial setting time exceeding 300 minutes. Additionally, Comparative Examples 5 and 6, which use undisturbed phosphogypsum to produce retarded cement, show significant fluctuations in setting time, primarily due to variations in the content of impurities such as phosphorus and fluorine in the undisturbed phosphogypsum. Therefore, using phosphate ore beneficiation waste to adjust cement setting time is more controllable than using undisturbed phosphogypsum, and compared with modified phosphogypsum, it can produce cement with a longer setting time requirement. The main mineral composition of phosphate ore beneficiation waste is dolomite, hydroxyl or fluorapatite, with less quartz, mica, clay and other minerals, so it has less impact on cement strength, water demand and other properties, and can replace limestone powder to regulate cement setting time.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing cement using phosphate ore beneficiation waste, characterized in that, include: The batching design is carried out based on the oxide content in the raw meal, and the first saturation ratio, first silicon ratio, first aluminum ratio and first MgO content of the clinker are calculated. The percentage of phosphate rock beneficiation waste incorporated is determined based on the first saturation ratio, the first silicon ratio, the first aluminum ratio, and the first MgO content. The raw meal mixed with phosphate rock beneficiation waste is adjusted in order to adjust the first saturation ratio to the second saturation ratio, the first silicon ratio to the second silicon ratio, and the first aluminum ratio to the second aluminum ratio, so as to stabilize and ensure the mineral composition and quality of the clinker. The adjusted raw materials are added to a raw material mill for grinding. The ground powder is fed into a preheater, decomposition furnace, rotary kiln and cooler for calcination to obtain clinker with the expected MgO content; When the clinker has a first saturation ratio of 0.910±0.02, a first silicon content of 2.55±0.10, a first aluminum content of 1.55±0.10, and an expected MgO content of less than or equal to 2.3%, 1%-10% of the phosphate rock beneficiation waste residue is added. When the first saturation ratio is 0.910±0.02, the first silicon content is 2.55±0.10, the first aluminum content is 1.55±0.10, and the first MgO content is less than 2.3%, and a clinker with a expected MgO content greater than 2.3% is required, 2%-20% of the phosphate rock beneficiation waste residue is added.

2. The method for preparing cement using phosphate ore beneficiation waste as described in claim 1, characterized in that, The raw material is prepared by mixing calcareous materials, siliceous materials, aluminum materials and ferrous materials in a preset mass percentage ratio.

3. The method for preparing cement using phosphate ore beneficiation waste as described in claim 2, characterized in that, The first saturation ratio and the second saturation ratio are determined by the content of the calcium material, the first silicon ratio and the second silicon ratio are determined by the silicon material, and the first aluminum ratio and the second aluminum ratio are determined by the aluminum material.

4. The method for preparing cement using phosphate rock beneficiation waste as described in claim 1, characterized in that, After adding 1%-10% of the phosphate rock beneficiation waste to the raw meal, the raw meal is adjusted to control the second saturation ratio to be 0.900±0.02, the second silicon content to be 2.65±0.10, and the second aluminum content to be 1.65±0.

10. The raw materials are ground and then calcined to obtain clinker with an expected MgO content of less than or equal to 2.3%.

5. The method for preparing cement using phosphate rock beneficiation waste as described in claim 1, characterized in that, After adding 2%-20% of the phosphate ore beneficiation waste to the raw meal, the raw meal is adjusted to control the second saturation ratio to be 0.890±0.02, the second silicon content to be 2.60±0.10, and the second aluminum content to be 1.60±0.

10. The raw materials were ground and then calcined to obtain clinker with a desired MgO content of more than 2.3%.

6. The method for preparing cement using phosphate rock beneficiation waste according to any one of claims 1-5, characterized in that, The method further includes: Phosphate ore beneficiation waste residue, clinker, neutralized modified phosphogypsum, limestone powder, fly ash and slag are added to the cement grinding system for grinding according to the preset mass ratio. Adjust the process parameters of the air classifier to the preset parameters to classify cement particles and obtain cement powder with the expected qualified specific surface area.

7. The method for preparing cement using phosphate rock beneficiation waste as described in claim 6, characterized in that, The proportion of the phosphate ore beneficiation waste residue added to clinker, neutralized modified phosphogypsum, limestone powder, fly ash and slag is 0%-15%. Within this range, the higher the proportion of the phosphate ore beneficiation waste residue added, the longer the cement setting time.

8. A type of cement prepared using phosphate rock beneficiation waste, characterized in that, It is prepared according to the method for preparing cement using phosphate rock beneficiation waste as described in any one of claims 1-7.

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