A dicalcium silicate-calcium sulfoaluminate-calcium sulfo-silicate cement clinker and an industrialized preparation method thereof

Abstract

The application discloses a kind of dicalcium silicate-calcium sulphoaluminate-calcium sulphosilicate cement clinker and its industrialized preparation method, it is related to building material technical field, method includes steps: S1, raw material preparation, calcareous, siliceous and sulphuric raw materials are proportioned according to proportion, raw material rate value is limestone saturation coefficient 0.9~1.0, aluminium sulphur ratio ≤2.2, aluminium silicon ratio ≤1.0;S2, preheating decomposition, raw meal is handled by multistage cyclone preheater and decomposition furnace, the temperature of first-stage cyclone preheater outlet ≤310 ℃, the middle part temperature of decomposition furnace 770±10 ℃;S3, calcination, material enters rotary kiln, sintering zone temperature 1200~1250 ℃, weak oxidation or neutral atmosphere in kiln;S4, quenching, kiln clinker is cooled by grate cooler, 15~25min is cooled to 100 ℃ below from 1200~1250 ℃;S5, crushing storage, after cooling clinker is crushed and is stored, finished product is obtained, solve the problem that existing dicalcium silicate-calcium sulphoaluminate-calcium sulphosilicate cement clinker is easily decomposed at high temperature, sintering temperature zone is narrow, industrialized mineral composition fluctuation is big and kiln system is easily crust blocking.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker and its industrial preparation method. Background Technology

[0002] Silicate cement is currently the most widely used man-made building material. Its CO2 emissions during production mainly come from the decomposition of calcium carbonate (accounting for approximately 60% of total emissions) and fuel combustion. Developing low-carbon cement clinker systems has become a research hotspot in the cement industry. Traditional silicate cement clinker typically requires firing temperatures as high as 1400-1450℃, resulting in high energy consumption and a strong dependence on limestone resources.

[0003] Dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker is a new type of low-calcium cement system. Compared with traditional silicate cement, this system has the following significant advantages: (1) Low firing temperature: The theoretical firing temperature is about 1200~1300℃, which can significantly reduce fuel consumption and reduce the emission of pollutants such as NOx; (2) Low limestone content: The design content of CaO in this system is much lower than that of traditional silicate cement, which can reduce the proportion of limestone in the batch, thereby directly reducing the CO2 emission generated during the decomposition of raw materials; (3) Excellent performance: This system has both early strength performance (derived from calcium sulfoaluminate) and later strength stability (derived from dicalcium silicate), and the hydration reaction of calcium sulfoaluminate is conducive to improving the compactness of the clinker microstructure.

[0004] Currently, researchers have conducted extensive laboratory studies on the mineral formation mechanism, ion solid solution characteristics, and hydration hardening mechanism of this system. Through methods such as doping with ions or adjusting the doping rate, qualified small-scale samples can be prepared in laboratory electric furnaces or high-temperature furnaces. Although the dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate system exhibits excellent low-carbon potential at the laboratory level, its transformation to industrial production, especially when using existing new dry-process cement rotary kilns for large-scale production, still faces a series of insurmountable technical bottlenecks, severely restricting its commercial application. (1) The target mineral has a narrow firing window, and the stability of the thermal regime is difficult to guarantee: Although calcium sulfosilicate (C5S2$) is a high-temperature stable phase, its thermal stability is poor. When the temperature is higher than 1250℃, it is very easy to decompose into dicalcium silicate and calcium sulfate. In the rotary kiln of industrial continuous production such as 500t / d, the temperature inside the kiln is difficult to be as precisely constant as that of the laboratory muffle furnace. Once local overheating occurs, calcium sulfosilicate will decompose in large quantities, causing the clinker mineral composition to deviate from the design expectation and the performance to decline.

[0005] (2) Scabbing and ring formation are easily generated in the kiln, affecting the equipment operation cycle: This system is a high-sulfur and high-alumina system. In the preheater and decomposition furnace system of the 500t / d new dry kiln, volatile components such as alkali, chlorine, and sulfur are easily enriched in circulation and form a low eutectic liquid phase at a lower temperature, which leads to scabbing and blockage of the preheater cyclone.

[0006] (3) Lack of industrial process control parameters suitable for this system: The operating procedures of existing new dry process cement kilns are all based on traditional silicate cement clinker (for example, using free calcium as the main basis for judging clinker quality), while the free calcium content of the dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker system is usually extremely low. At present, there is a lack of online detection methods for calcium sulfosilicate content, and there is a lack of matching control models for firing zone temperature, atmosphere, cooling regime, etc., which makes it impossible for operators to achieve precise control, resulting in large fluctuations in product quality.

[0007] Therefore, how to overcome the above-mentioned technical bottlenecks and develop an industrial preparation method for the stable, efficient, and large-scale production of dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker based on the existing 500t / d new dry process cement kiln, so as to realize the continuous production of low-carbon cement clinker, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to solve the technical problems of calcium sulfosilicate (C5S2) being easily decomposed at high temperatures, having a narrow firing temperature range, large fluctuations in mineral composition during industrial production, and easy scaling and blockage of the kiln system in the existing preparation process of dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker. The invention proposes a dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker and its industrial preparation method.

[0009] This invention is achieved through the following technical solution: An industrial preparation method for dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker includes the following steps: S1: Raw meal preparation—Calcium raw materials, silica-alumina raw materials, and sulfur raw materials are mixed in a certain proportion to prepare raw meal. The ratio range of the raw meal is: limestone saturation coefficient (C S 0.9~1.0, aluminum-sulfur ratio (P) ≤2.2, aluminum-silicon ratio (N) ≤1.0; S2: Preheating and decomposition—The raw material prepared in step S1 is fed into the preheating and decomposition system for preheating and decomposition treatment in sequence; wherein, the preheating and decomposition system includes a multi-stage cyclone preheater and a decomposition furnace, the outlet temperature of the first-stage cyclone preheater is controlled to be ≤310℃, and the temperature in the middle of the decomposition furnace is controlled to be 770±10℃. S3: Calcination - The preheated and decomposed material is fed into a rotary kiln for calcination, and the temperature of the calcination zone is controlled at 1200~1250℃. A weak oxidizing atmosphere or a neutral atmosphere is maintained in the kiln. S4: Rapid cooling—The clinker exiting the kiln is fed into a grate cooler for rapid cooling, so that the clinker exiting the kiln is rapidly cooled from 1200~1250℃ to below 100℃ within 15~25 minutes. S5: Crushing and Storage — After the cooled clinker is crushed, it is stored in a warehouse to obtain dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker.

[0010] Furthermore, in step S1, the fineness of the raw material satisfies that the residue on an 80μm sieve is ≤15%.

[0011] Furthermore, in step S2, the raw material feeding rate is controlled at 24.0t / h~25.5t / h, and the residence time of the material in the decomposition furnace is 25~40s. By adjusting the raw material feeding amount and the system air volume, the preheater system is prevented from forming a crust and becoming clogged.

[0012] Furthermore, in step S3, the calcination process monitors the composition of the raw material entering the kiln using an online X-ray fluorescence analyzer, and automatically adjusts the coal feed rate and kiln speed at the kiln head based on fluctuations in the raw material composition. The shape of the flame and the condition of the kiln skin are monitored by high-temperature industrial television at the kiln head. When the temperature inside the kiln is detected to be ≥1250℃, the coal feed rate at the kiln head is automatically reduced or the kiln speed is increased. The coal feed rate at the kiln head is controlled at 0.7t / h~1.0t / h, and the kiln speed is controlled at 4.0~5.0r / min.

[0013] Furthermore, in step S3, the weak oxidizing atmosphere or neutral atmosphere in the kiln is controlled by adjusting the primary air volume at the kiln head and the exhaust air volume at the kiln tail, so that the O2 content in the flue gas at the kiln tail is 1.5~2.5% and the CO content is <0.1%.

[0014] Furthermore, in step S4, a grate cooler is used for segmented cooling: the first stage has a cooling air pressure ≥2500Pa and a cooling rate ≥80℃ / second to rapidly cool the clinker to below 600℃; the second stage has a cooling air pressure ≥1600Pa and a cooling rate ≥50℃ / second to cool the clinker to below 100℃.

[0015] Furthermore, in step S1, the calcium-based raw material is limestone, wherein the CaO content is ≥52.00 wt.% and the SiO2 content is ≤3.0 wt.%. The aluminosilicate raw material is one or more of low-grade bauxite, fly ash, and coal gangue, wherein the bauxite contains Al2O3 ≥ 52 wt.% and SiO2 ≤ 20 wt.%; the fly ash contains Al2O3 ≥ 30 wt.% and SiO2 ≤ 60 wt.%; and the coal gangue contains Al2O3 ≥ 20 wt.% and SiO2 ≤ 55 wt.%. The sulfur-containing raw material is one or more of phosphogypsum and anhydrite, wherein SO3 ≥ 38 wt.%.

[0016] Furthermore, it also includes process quality control steps: after the production line is running stably, samples are taken to test the liter weight, free calcium content and mineral composition of cement clinker, and the liter weight and mineral composition of clinker are used as the basis for judging the quality of cement clinker. The mineral composition of the clinker was determined using an XRD diffraction analyzer, and the results were subjected to full-spectrum fitting using TOPAS. The quantitative fitting error factor Rwp < 10%.

[0017] Furthermore, the industrial preparation method has a continuous and stable operating time of ≥72h in a 500t / d dry process cement rotary kiln production line; The content of each mineral component in the obtained cement clinker fluctuates within the following ranges: calcium sulfoaluminate ≤ ±2 wt.%, calcium sulfosilicate ≤ ±3 wt.%, dicalcium silicate ≤ ±2 wt.%, calcium sulfate ≤ ±2 wt.%, and the free calcium content ≤ 1.0 wt.%.

[0018] Furthermore, in step S2, the preheating decomposition system includes a five-stage cyclone preheater.

[0019] A type of dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker, prepared by the method described above, comprises, by mass percentage: 25-35 wt.% calcium sulfoaluminate, 5-20 wt.% calcium sulfosilicate, 35-46 wt.% dicalcium silicate, 5-10 wt.% calcium sulfate, 0-10 wt.% iron phase, and 0-1.0% free calcium.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. Achieving stable low-temperature calcination and inhibiting high-temperature decomposition of calcium sulfosilicate: This invention effectively inhibits the high-temperature decomposition of calcium sulfosilicate by precisely controlling the calcination temperature within a narrow temperature range of 1200~1250℃ and regulating a weakly oxidizing / neutral atmosphere. This process has been successfully applied to industrial production lines, stably producing clinker with the target calcium sulfosilicate content, providing a solid guarantee for the continuous improvement of cement strength in later stages.

[0021] 2. This invention effectively solves the problem of scaling and clogging in high-sulfur systems by optimizing core process parameters, ensuring the stable operation of the production line. Specifically, by controlling the C1 outlet temperature to ≤310℃, the temperature in the middle of the decomposition furnace to within the range of 770±10℃, and adopting a thin-material, fast-firing method, the kiln speed is appropriately increased to shorten the residence time of materials in the high-temperature zone, thereby reducing sulfate decomposition. The synergistic effect of these control measures significantly alleviates the scaling and clogging problem in the production system, achieving continuous and stable operation of the production line.

[0022] 3. Optimize mineral composition stability and improve product quality uniformity: This invention integrates an online analyzer and a high-temperature industrial television monitoring system, enabling dynamic control of raw material composition fluctuations and kiln thermal regimes. This system ensures stable content of key mineral components in the clinker, significantly improving the quality uniformity of multi-mineral clinker systems.

[0023] 4. Expanding the range of raw material adaptability and promoting the resource utilization of solid waste: This invention has excellent environmental adaptability to raw materials and can widely use various industrial solid wastes such as low-grade bauxite, fly ash, and phosphogypsum as raw materials. While achieving high-performance cement clinker, it effectively reduces production costs, possessing both significant economic value and environmental benefits. Attached Figure Description

[0024] Figure 1 This is the XRD pattern of the cement clinker prepared in Example 1.

[0025] Figure 2 This is the XRD pattern of the cement clinker prepared in Example 2.

[0026] Figure 3 This is the XRD pattern of the cement clinker prepared in Example 3.

[0027] Figure 4 The image shows the XRD pattern of the cement clinker prepared in Comparative Example 1. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0029] Example 1 To facilitate public understanding of the present invention, this embodiment takes an industrial preparation method of dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker as an example. The method is implemented on a 500t / d new dry process cement rotary kiln production line, and the composition of the obtained cement clinker is tested to examine the performance of the clinker product.

[0030] Specifically, the industrial-scale preparation method includes the following steps: S1: Raw material preparation—Calcium raw materials, silicon-aluminum raw materials and sulfur raw materials are mixed in proportion to form raw materials, which, by weight, include 58.2 parts of calcium material, 27.1 parts of silicon-aluminum material and 14.7 parts of sulfur material.

[0031] The calcareous material is limestone, wherein the limestone contains 53.08 wt.% CaO and 1.52 wt.% SiO2. The aluminosilicate material is selected from 12.1 parts bauxite and 15.0 parts fly ash. The bauxite contains 53.03 wt.% Al2O3 and 16.63 wt.% SiO2; the fly ash contains 30.37 wt.% Al2O3 and 57.15 wt.% SiO2. The sulfur-based material is anhydrite, and the anhydrite contains 45.00 wt.% SO3. The raw material was ground in a vertical mill to a fineness of 80μm with a residue of 15%.

[0032] The raw material ratio is controlled as follows: limestone saturation coefficient C S The value is 0.9743, the aluminum-sulfur ratio P is 1.58, and the aluminum-silicon ratio N is 0.88.

[0033] The design values ​​for clinker composition are shown in Table 1.

[0034] Table 1

[0035] The design values ​​for the mineral composition of clinker are shown in Table 2.

[0036] Table 2

[0037] S2: Preheating and decomposition—The raw material prepared in step S1 is fed into the preheating and decomposition system at a rate of 24.73 t / h for preheating and decomposition treatment. The preheating and decomposition system includes a five-stage cyclone preheater and a decomposition furnace. The outlet temperature of the first-stage cyclone preheater (C1 cylinder outlet) is controlled at 308℃, and the temperature in the middle of the decomposition furnace is controlled at 774℃. The material residence time in the decomposition furnace is 30s, and no crusting or blockage occurs.

[0038] S3: Calcination—The preheated and decomposed material is fed into a rotary kiln for calcination, with the calcination zone temperature controlled at 1200~1250℃. The coal feeding rate at the kiln head is controlled at 1.0 t / h, and the kiln speed is controlled at 4.5 r / min. By adjusting the primary air volume at the kiln head and the exhaust air volume at the kiln tail, a weakly oxidizing atmosphere is maintained inside the kiln, ensuring that the O2 content in the flue gas at the kiln tail is 2.0% and the CO content is 0.02%.

[0039] S4: Rapid cooling—The clinker exiting the kiln is fed into a grate cooler for segmented rapid cooling: the first stage cooling air pressure is ≥2500Pa and the cooling rate is ≥80℃ / second, rapidly cooling the clinker to below 600℃; the second stage cooling air pressure is ≥1600Pa and the cooling rate is ≥50℃ / second, cooling the clinker to below 100℃.

[0040] S5: Crushing and Storage — After the cooled clinker is crushed, it is stored in a warehouse to obtain dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker.

[0041] After stable operation, samples were taken for testing, and the clinker weight gain stabilized at 1000 g / L.

[0042] The phase composition of the obtained clinker was determined by X-ray diffraction (XRD), and the XRD patterns are shown below. Figure 1 X-ray diffraction analysis and full-spectrum fitting by TOPAS showed a quantitative fitting error factor Rwp < 10, indicating that all indicators met the requirements.

[0043] Example 2 An industrial preparation method for dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker was implemented on a 500t / d new dry process cement rotary kiln production line. The composition of the obtained cement clinker was tested, and the performance of the clinker product was investigated.

[0044] Specifically, the industrial-scale preparation method includes the following steps: S1: Raw meal preparation—Calcium raw materials, silicon-aluminum raw materials and sulfur raw materials are mixed in proportion to form raw meal, which, by weight, includes 55.8 parts of calcium material, 26.2 parts of silicon-aluminum material, 16.5 parts of sulfur material and 1.5 parts of other materials.

[0045] The calcareous material is limestone, wherein the limestone contains 53.08 wt.% CaO and 1.52 wt.% SiO2. The aluminosilicate material was selected from 14.5 parts bauxite and 11.7 parts fly ash. The bauxite contained 53.03 wt.% Al₂O₃ and 16.63 wt.% SiO₂; the fly ash contained 30.37 wt.% Al₂O₃ and 57.15 wt.% SiO₂. The sulfur-based material is anhydrite, and the SO3 content in the anhydrite is 45.00 wt.%. The other materials are conditioning materials, with an F content of 1.23% and a Na2O content of 2.57%. The raw material was ground in a vertical mill to a fineness of 80μm with a residue of 14%.

[0046] The raw material ratio is controlled as follows: limestone saturation coefficient C S The value is 0.9723, the aluminum-sulfur ratio P is 1.45, and the aluminum-silicon ratio N is 1.00.

[0047] The design values ​​for clinker composition are shown in Table 3.

[0048] Table 3

[0049] The design values ​​for the mineral composition of the clinker are shown in Table 4.

[0050] Table 4

[0051] S2: Preheating and decomposition—The raw material prepared in step S1 is fed into the preheating and decomposition system at a rate of 25.26 t / h for preheating and decomposition treatment. The preheating and decomposition system includes a five-stage cyclone preheater and a decomposition furnace. The outlet temperature of the first-stage cyclone preheater (C1 cylinder outlet) is controlled at 308℃, and the temperature in the middle of the decomposition furnace is controlled at 774℃. The material residence time in the decomposition furnace is 30s, and no crusting or blockage occurs.

[0052] S3: Calcination—The preheated and decomposed material is fed into a rotary kiln for calcination, with the calcination zone temperature controlled at 1200~1250℃. The coal feeding rate at the kiln head is controlled at 0.8t / h, and the kiln speed is controlled at 5.0 r / min. By adjusting the primary air volume at the kiln head and the exhaust air volume at the kiln tail, a weakly oxidizing atmosphere is maintained inside the kiln, ensuring that the O2 content in the flue gas at the kiln tail is 1.5% and the CO content is 0.03%.

[0053] S4: Rapid cooling—The clinker exiting the kiln is fed into a grate cooler for segmented rapid cooling: the first stage cooling air pressure is ≥2500Pa and the cooling rate is ≥80℃ / second, rapidly cooling the clinker to below 600℃; the second stage cooling air pressure is ≥1600Pa and the cooling rate is ≥50℃ / second, cooling the clinker to below 100℃.

[0054] S5: Crushing and Storage — After the cooled clinker is crushed, it is stored in a warehouse to obtain dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker.

[0055] After stable operation, samples were taken for testing, and the clinker weight gain was stable at 980 g / L.

[0056] The phase composition of the obtained clinker was determined by X-ray diffraction (XRD), and the XRD patterns are shown below. Figure 2 X-ray diffraction analysis and full-spectrum fitting by TOPAS showed a quantitative fitting error factor Rwp < 10, indicating that all indicators met the requirements.

[0057] Example 3 An industrial preparation method for dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker was implemented on a 500t / d new dry process cement rotary kiln production line. The composition of the obtained cement clinker was tested, and the performance of the clinker product was investigated.

[0058] Specifically, the industrial-scale preparation method includes the following steps: S1: Raw meal preparation—Calcium raw materials, silicon-aluminum raw materials and sulfur raw materials are mixed in proportion to form raw meal, which includes 57.5 parts calcium material, 24.4 parts silicon-aluminum material and 18.1 parts sulfur material by weight.

[0059] The calcareous material is limestone, wherein the limestone contains 53.08 wt.% CaO and 1.52 wt.% SiO2. The aluminosilicate material was selected from 9.8 parts bauxite and 14.6 parts fly ash. The bauxite contained 53.03 wt.% Al₂O₃ and 16.63 wt.% SiO₂; the fly ash contained 30.37 wt.% Al₂O₃ and 57.15 wt.% SiO₂. The sulfur-based material is phosphogypsum, wherein the phosphogypsum contains 38.87 wt.% SO3, 1.27 wt.% F, and 0.96 wt.% P2O5. The raw material was ground in a vertical mill to a fineness of 80μm with a residue of 13%.

[0060] The raw material ratio is controlled as follows: limestone saturation coefficient C S The aluminum-sulfur ratio (P) is 0.9816, the aluminum-sulfur ratio (P) is 1.31, and the aluminum-silicon ratio (N) is 0.76.

[0061] The design values ​​for clinker composition are shown in Table 5.

[0062] Table 5

[0063] The design values ​​for the mineral composition of the clinker are shown in Table 6.

[0064] Table 6

[0065] S2: Preheating and decomposition—The raw material prepared in step S1 is fed into the preheating and decomposition system at a rate of 24.10 t / h for preheating and decomposition treatment. The preheating and decomposition system includes a five-stage cyclone preheater and a decomposition furnace. The outlet temperature of the first-stage cyclone preheater (C1 cylinder outlet) is controlled at 305℃, and the temperature in the middle of the decomposition furnace is controlled at 772℃. The material residence time in the decomposition furnace is 30s, and no crusting or blockage occurs.

[0066] S3: Calcination—The preheated and decomposed material is fed into a rotary kiln for calcination, with the calcination zone temperature controlled at 1200~1250℃. The coal feeding rate at the kiln head is controlled at 0.7t / h, and the kiln speed is controlled at 5.0r / min. By adjusting the primary air volume at the kiln head and the exhaust air volume at the kiln tail, a weakly oxidizing atmosphere is maintained inside the kiln, ensuring that the O2 content in the kiln tail flue gas is 2.5% and the CO content is 0.01%.

[0067] S4: Rapid cooling—The clinker exiting the kiln is fed into a grate cooler for segmented rapid cooling: the first stage cooling air pressure is ≥2500Pa and the cooling rate is ≥80℃ / second, rapidly cooling the clinker to below 600℃; the second stage cooling air pressure is ≥1600Pa and the cooling rate is ≥50℃ / second, cooling the clinker to below 100℃.

[0068] S5: Crushing and Storage — After the cooled clinker is crushed, it is stored in a warehouse to obtain dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker.

[0069] After stable operation, samples were taken for testing, and the clinker weight gain stabilized at 870 g / L.

[0070] The phase composition of the obtained clinker was determined by X-ray diffraction (XRD), and the XRD patterns are shown below. Figure 3 X-ray diffraction analysis and full-spectrum fitting by TOPAS showed a quantitative fitting error factor Rwp < 10, indicating that all indicators met the requirements.

[0071] Comparative Example 1 The raw materials and target mineral composition of this comparative example are the same as those of Example 1, but the existing process for producing sulfoaluminate cement clinker was adopted. While ensuring normal clinker granulation and stable operation of the grate cooler, the firing temperature was gradually reduced to the target control range for dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker. The firing temperature of Comparative Example 1 was within the cooling range.

[0072] S1: Raw material preparation: Same as in Example 1.

[0073] S2: Preheating and decomposition—The raw material prepared in step S1 is fed into the preheating and decomposition system at a rate of 27.15 t / h for preheating and decomposition treatment. The preheating and decomposition system includes a five-stage cyclone preheater and a decomposition furnace. The outlet temperature of the first-stage cyclone preheater (C1 cylinder outlet) is controlled at 320℃, and the temperature in the middle of the decomposition furnace is controlled at 850℃. The material residence time in the decomposition furnace is 50s, and no crusting or blockage occurs.

[0074] S3: Calcination—The preheated and decomposed material is fed into a rotary kiln for calcination, with the calcination zone temperature controlled at 1250~1300℃. The coal feeding rate at the kiln head is controlled at 1.4t / h, and the kiln speed is controlled at 4.0r / min. By adjusting the primary air volume at the kiln head and the exhaust air volume at the kiln tail, a weakly oxidizing atmosphere is maintained inside the kiln, ensuring that the O2 content in the flue gas at the kiln tail is 2.0% and the CO content is 0.02%.

[0075] S4: Rapid cooling—The clinker exiting the kiln is fed into a grate cooler for segmented rapid cooling: the first stage cooling air pressure is ≥2500Pa and the cooling rate is ≥80℃ / second, rapidly cooling the clinker to below 600℃; the second stage cooling air pressure is ≥1600Pa and the cooling rate is ≥50℃ / second, cooling the clinker to below 100℃.

[0076] S5: Crushing and Storage — After the cooled clinker is crushed, it is stored in a warehouse to obtain dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker.

[0077] After stable operation, samples were taken for testing, and the clinker weight gain stabilized at 1100 g / L.

[0078] The phase composition of the obtained clinker was determined by X-ray diffraction (XRD), and the XRD patterns are shown below. Figure 4 X-ray diffraction analysis and full-spectrum fitting by TOPAS showed a quantitative fitting error factor Rwp < 10, indicating that all indicators met the requirements.

[0079] Comparative Example 2 The only difference between this comparative example and Example 1 is that: S3: Calcination—The preheated and decomposed material is fed into a rotary kiln for calcination, and the kiln speed is controlled at 3.5 r / min.

[0080] The thickening of the material layer inside the kiln led to ring formation at the rear end of the firing zone, resulting in poorer uniformity of clinker particles and a significant increase in large pieces. Sampling and testing showed a clinker weight gain of 1120 g / L. The phase composition of the obtained clinker was analyzed using X-ray diffraction (XRD). X-ray diffraction analysis, fitted to the full spectrum by TOPAS, showed a quantitative fitting error factor Rwp < 10, indicating that all indicators met the requirements.

[0081] test.

[0082] 1. The phase composition of the clinker was detected by X-ray diffraction (XRD), and the detection data were quantitatively analyzed by full-spectrum fitting using TOPAS software. The quantitative fitting error factor Rwp was less than 10, which is far better than the international standard requirement (Rwp < 15%), and the fitting results are accurate and reliable.

[0083] The test results of the main mineral content of the cement clinker samples of each embodiment and comparative example are detailed in Table 7.

[0084] Table 7: Content (wt%) of major mineral components in each cement clinker sample.

[0085]

[0086] As shown in Table 7, the clinker prepared in Examples 1-3 of this invention has a small deviation from the design value in terms of the main mineral content, and the fluctuation range meets the preset control requirements. The specific control standards are: calcium sulfoaluminate content fluctuation ≤ ±2wt.%, calcium sulfosilicate content fluctuation ≤ ±3wt.%, dicalcium silicate content fluctuation ≤ ±2wt.%, calcium sulfate content fluctuation ≤ ±2wt.%, and free calcium content ≤ 1.0wt.%.

[0087] Comparative analysis shows that, due to excessively high calcination temperature, calcium sulfosilicate underwent a large amount of decomposition in Comparative Example 1, with the measured C5S2 content being only 0.83%, and the clinker mineral composition deviating significantly from the design value.

[0088] In Comparative Example 2, due to the excessively low kiln speed and excessively thick material layer, the material was not heated evenly, and the solid-phase reaction was insufficient. CaO did not react fully with SiO2 to form dicalcium silicate C2S (dicalcium silicate, i.e., belite). At the same time, Al2O3 was fixed by C2AS, resulting in insufficient liquid phase or delayed liquid phase formation. It was difficult to dissolve and assimilate the residual free calcium oxide. Ultimately, the contents of calcium sulfoaluminate, dicalcium silicate, and calcium sulfosilicate were all lower than the design values, while the contents of calcium aluminum feldspar (C2AS) and free calcium oxide were significantly higher.

[0089] 2. Add 12 wt.% of anhydrite to the cement clinker of each embodiment and comparative example, and mix and grind until the specific surface area is 400 ± 10 m². 2 / kg, to obtain the cement to be tested. The mechanical properties of the obtained cement were tested according to "Sulfoaluminate Cement" (GB 20472—2006). The water content was controlled at a water-cement ratio of 0.47 (211.5mL), and the mortar flowability was ensured to be within the range of 165mm~175mm. The mechanical property test results are detailed in Table 8.

[0090] Table 8: Test results of mechanical properties of cement samples prepared using various cement clinkers.

[0091]

[0092] As shown in Table 8, the 3-day compressive strength of the cements prepared in Examples 1-3 is not less than 30.0 MPa, and the 28-day compressive strength is not less than 55.0 MPa. Among them, the 28-day compressive strength of the cement prepared in Example 1 is higher than that in Comparative Example 1. Due to its mineral composition deviating from the design value, Comparative Example 1 has a lower calcium sulfosilicate content. The later mechanical properties of the cement mainly rely on the hydration of dicalcium silicate, lacking the later strength compensation effect of calcium sulfosilicate, resulting in a 28-day compressive strength lower than 50.0 MPa. The clinker used in Comparative Example 2 has a higher free calcium oxide content, which causes flash setting during cement mortar molding, leading to molding difficulties.

[0093] The above results demonstrate that the method of the present invention can significantly improve the mechanical properties of cement by effectively protecting calcium sulfosilicate and optimizing the mineral composition of clinker. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. An industrial preparation method for dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker, characterized in that, Includes the following steps: S1: Raw meal preparation—Calcium raw materials, siliceous aluminous raw materials and sulfur raw materials are mixed in proportion to prepare raw meal. The ratio of raw meal is controlled within the following range: limestone saturation coefficient 0.9~1.0, aluminum-sulfur ratio ≤2.2, aluminum-silicon ratio ≤1.0; S2: Preheating and decomposition—The raw material prepared in step S1 is fed into the preheating and decomposition system for preheating and decomposition treatment in sequence; wherein, the preheating and decomposition system includes a multi-stage cyclone preheater and a decomposition furnace, the outlet temperature of the first-stage cyclone preheater is controlled to be ≤310℃, and the temperature in the middle of the decomposition furnace is controlled to be 770±10℃. S3: Calcination - The preheated and decomposed material is fed into a rotary kiln for calcination, and the temperature of the calcination zone is controlled at 1200~1250℃. A weak oxidizing atmosphere or a neutral atmosphere is maintained in the kiln. S4: Rapid cooling—The clinker exiting the kiln is fed into a grate cooler for rapid cooling, so that the clinker exiting the kiln is rapidly cooled from 1200~1250℃ to below 100℃ within 15~25 minutes. S5: Crushing and Storage — After the cooled clinker is crushed, it is stored in a warehouse to obtain dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker.

2. The industrial preparation method according to claim 1, characterized in that: In step S1, the fineness of the raw material meets the requirement that the residue on an 80μm sieve is ≤15%.

3. The industrial preparation method according to claim 1, characterized in that: In step S2, the raw material feeding rate is controlled at 24.0t / h~25.5t / h, and the residence time of the material in the decomposition furnace is 25~40s; The preheating and decomposition system includes a five-stage cyclone preheater.

4. The industrial preparation method according to claim 1, characterized in that: In step S3, the calcination process monitors the composition of the raw materials entering the kiln using an online X-ray fluorescence analyzer, and automatically adjusts the coal feed rate and kiln speed at the kiln head based on fluctuations in the raw material composition. The shape of the flame and the condition of the kiln skin are monitored by high-temperature industrial television at the kiln head. When the temperature inside the kiln is detected to be ≥1250℃, the coal feed rate at the kiln head is automatically reduced or the kiln speed is increased. The coal feed rate at the kiln head is controlled at 0.7t / h~1.0t / h, and the kiln speed is controlled at 4.0~5.0r / min.

5. The industrial preparation method according to claim 1, characterized in that: In step S3, the weak oxidizing atmosphere or neutral atmosphere in the kiln is controlled by adjusting the primary air volume at the kiln head and the exhaust air volume at the kiln tail, so that the O2 content in the flue gas at the kiln tail is 1.5~2.5% and the CO content is <0.1%.

6. The industrial preparation method according to claim 1, characterized in that: In step S4, the rapid cooling adopts a grate cooler segmented cooling process: the first stage cooling air pressure is ≥2500Pa and the cooling rate is ≥80℃ / second, which rapidly cools the clinker to below 600℃; the second stage cooling air pressure is ≥1600Pa and the cooling rate is ≥50℃ / second, which cools the clinker to below 100℃.

7. The industrial preparation method according to claim 1, characterized in that: In step S1, the calcium-based raw material is limestone, wherein the CaO content is ≥52.00 wt.% and the SiO2 content is ≤3.0 wt.%. The aluminosilicate raw material is one or more of bauxite, fly ash, and coal gangue, wherein the bauxite contains Al2O3 ≥ 52 wt.% and SiO2 ≤ 20 wt.%; the fly ash contains Al2O3 ≥ 30 wt.% and SiO2 ≤ 60 wt.%; and the coal gangue contains Al2O3 ≥ 20 wt.% and SiO2 ≤ 55 wt.%. The sulfur-containing raw material is one or more of phosphogypsum and anhydrite, wherein SO3 ≥ 38 wt.%.

8. The industrial preparation method according to claim 1, characterized in that, It also includes process quality control steps: after the production line is running stably, samples are taken to test the clinker's liter weight, free calcium content and mineral composition, and the clinker's liter weight and mineral composition are used as the basis for judging the quality of the clinker. The mineral composition of the clinker was determined using an XRD diffraction analyzer, and the results were subjected to full-spectrum fitting using TOPAS. The quantitative fitting error factor Rwp < 10%.

9. The industrial preparation method according to claim 1, characterized in that: The industrial preparation method has a continuous and stable operating time of ≥72h in a 500t / d dry process cement rotary kiln production line; The content of each mineral component in the obtained cement clinker fluctuates within the following ranges: calcium sulfoaluminate ≤ ±2 wt.%, calcium sulfosilicate ≤ ±3 wt.%, dicalcium silicate ≤ ±2 wt.%, calcium sulfate ≤ ±2 wt.%, and the free calcium content ≤ 1.0 wt.%.

10. A type of dicalcium silicate-calcium sulfoaluminate-calcium sulfosilicate cement clinker, characterized in that: The cement clinker prepared by the method described in any one of claims 1 to 9, by mass percentage, comprises the following mineral composition: 25-35 wt.% calcium sulfoaluminate, 5-20 wt.% calcium sulfosilicate, 35-46 wt.% dicalcium silicate, 5-10 wt.% calcium sulfate, 0-10 wt.% iron phase, and 0-1.0% free calcium.

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