Method for preparing cement clinker using magnesium slag and carbide slag

Abstract

The invention relates to a method for preparing cement clinker by utilizing magnesium slag and carbide slag, and belongs to the technical field of cement materials. The cement clinker adopts carbide slag, modified magnesium slag, activated converter slag and coal gangue as main raw materials. The modified magnesium slag is magnesium slag modified by ball milling with an Mg(H2PO4)2 aqueous solution and a ferulic acid ethanol solution to form a Mg3(PO4)2 protective layer. The activated converter slag is converter slag activated by roasting with Na2CO3. The four raw materials are mixed in a certain proportion, a Li2B4O7-CaF2 composite mineralizer is added for low-temperature calcination, and a proper amount of SO2 is introduced to induce the generation of a new three-phase system of calcite-dicalcium silicate-spinel. The method can effectively reduce carbon emissions and save fuel and energy consumption. The obtained cement clinker has high early strength, a good balance between early strength and late strength stability, is not easy to crack, and has excellent sulfate erosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of cement materials, and particularly relates to a method for preparing cement clinker by utilizing magnesium slag and carbide slag. Background Art

[0002] Cement, an indispensable building block for modern construction, is widely used in various construction projects and plays a vital role in promoting social and economic development. Among the various cement varieties, Portland cement dominates the market due to its excellent performance and wide applicability. Portland cement clinker is a semi-finished product that is crucial for determining its performance.

[0003] In terms of production process, silicate cement clinker is made from calcium (limestone accounts for about 80%) and siliceous materials as the main raw materials. The raw materials are prepared in appropriate proportions, crushed, batched, and ground into raw materials. Then, they are calcined in a cement kiln until partially melted, and cooled to obtain a product with calcium silicate as the main mineral component. However, in the actual production process, the following problems exist: First, for some typical low-grade limestone mines, with the country's regulation of mine resources, purchased limestone resources are becoming increasingly tight. There is an urgent need to find high-grade limestone or alternative materials to match the low-grade limestone from its own mines, reduce waste emissions, and extend the service life of mines; second, the cement industry's own process characteristics determine that its carbon emissions problem is serious. About 60% of CO2 in traditional clinker production comes from limestone decomposition, causing serious environmental pollution; third, the temperature required for limestone (CaCO3) decomposition is above 900°C, and the clinker burning temperature is high, generally around 1450°C, and the burning time is long, resulting in high fuel and energy consumption; fourth, traditional silicate cement clinker has poor early strength after cement is prepared, and cannot achieve the effect of quickly reaching the design strength to shorten the construction period. The early-strength cement currently available on the market often has problems such as insufficient later strength development and easy cracking; and various cements generally have insufficient resistance to sulfate erosion.

[0004] How to balance the early strength and later strength stability of cement, improve its resistance to sulfate erosion, and achieve energy conservation, carbon reduction and green transformation has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] In view of the increasingly scarce limestone resources, serious carbon emission problems of materials, high fuel and energy consumption for firing, poor early strength of cement, difficulty in balancing early strength and late strength stability, easy cracking, and insufficient resistance to sulfate erosion, the present invention provides a method for preparing cement clinker using magnesium slag and carbide slag, which uses carbide slag, modified magnesium slag, activated converter slag and coal gangue as main raw materials, adds Li2B4O7-CaF2 composite mineralizer for low-temperature calcination, and introduces an appropriate amount of SO2 to induce the formation of a new three-phase system of calcite-dicalcium silicate-spinel, effectively reducing carbon emissions and saving fuel and energy consumption. The obtained cement clinker has high early strength, good balance between early strength and late strength stability, is not easy to crack, and has excellent resistance to sulfate erosion. The specific technical scheme is as follows:

[0006] A method for preparing cement clinker using magnesium slag and carbide slag comprises the following steps:

[0007] S1: drying and crushing the carbide slag to obtain carbide slag powder;

[0008] S2: The magnesium slag is crushed to obtain magnesium slag powder, an Mg(H2PO4)2 aqueous solution is added, a ferulic acid ethanol solution is added, ball milling is performed, and drying is performed to form a Mg3(PO4)2 protective layer on the surface of the magnesium slag powder particles to obtain modified magnesium slag powder;

[0009] S3: crushing the converter slag to obtain converter slag powder, adding Na2CO3 to mix, and roasting to obtain activated converter slag powder;

[0010] S4: crushing the coal gangue to obtain coal gangue powder;

[0011] S5: Calculated by mass, 50 to 60 parts of carbide slag powder, 25 to 30 parts of modified magnesium slag powder, 3 to 5 parts of activated converter slag powder, 12 to 15 parts of coal gangue powder and 5 to 8 parts of Li2B4O7-CaF2 composite mineralizer are mixed evenly, preheated at 800°C to 900°C for 20 to 30 minutes, and a CO2-H2O mixed gas is introduced at the same time; then, the mixture is kept warm and calcined at 1100°C to 1200°C for 2 to 3 hours, and 0.3 vol% to 0.5 vol% SO2 is added during the 50 to 70 minutes of the calcination to induce the formation of a new three-phase system of calcite-dicalcium silicate-spinel; cooled to obtain cement clinker.

[0012] In S1 of the above method, the carbide slag is dried to a moisture content of less than 1 wt%; and the particle size of the carbide slag powder is sieved through a 200-250 mesh sieve.

[0013] In S2 of the above method, the concentration of the Mg(H2PO4)2 aqueous solution is 3wt% to 5wt%; the amount of the Mg(H2PO4)2 aqueous solution added is 10% to 20% of the mass of the magnesium slag powder;

[0014] In S2 of the above method, the concentration of the ferulic acid ethanol solution is 6 wt% to 8 wt%; the amount of the ferulic acid ethanol solution added is 5% to 10% of the mass of the magnesium slag powder;

[0015] In S2 of the above method, the particle size of the magnesium slag powder is sieved through a 250-325 mesh sieve; the ball mill is milled at a speed of 15 r / min to 20 r / min for 1.5 h to 2 h; the diameter of the grinding balls used in the ball mill is 8 mm to 15 mm, and the filling rate of the grinding balls is 30% to 40%; after drying, the grinding balls are sieved to remove the grinding balls.

[0016] In S3 of the above method, the particle size of the converter slag powder is sieved through a 150-200 mesh sieve; the amount of Na2CO3 added is 4%-6% of the mass of the converter slag powder; and the roasting is performed at 400°C-500°C for 30-40 minutes.

[0017] In S4 of the above method, the particle size of the coal gangue powder is sieved through 200-250 meshes.

[0018] In S5 of the above method, the Li2B4O7-CaF2 composite mineralizer is a mixture of Li2B4O7 and CaF2 in a mass ratio of (1.5-3):(1-2); the volume ratio of the CO2-H2O mixed gas is CO2:H2O=(3-4):(1-1.2); and the amount of the CO2-H2O mixed gas introduced is 0.8L / min-1.2L / min per kilogram of material.

[0019] In S5 of the above method, the MgO content in the cement clinker is ≤5wt%; and the SO3 content in the clinker is <1wt%.

[0020] In the above method, the cement clinker is used in combination with additives, which include but are not limited to 5wt% to 8wt% of gypsum powder, 2wt% to 4wt% of silica fume, 0.1wt% to 0.2wt% of polyacrylamide and 1wt% to 2wt% of polycarboxylic acid water-reducing agent powder.

[0021] The present invention provides a method for preparing cement clinker using magnesium slag and carbide slag, which has the following beneficial effects:

[0022] 1. Modification of magnesium slag powder: Adding an appropriate amount of Mg(H2PO4)2 aqueous solution will form a Mg3(PO4)2 protective layer on the surface of the magnesium slag powder particles. This protective layer can prevent the magnesium oxide and other components in the magnesium slag from reacting with other substances too quickly, as well as hydration and expansion, so that the magnesium slag can play a more stable and continuous role in the cement clinker formation process. At the same time, adding an appropriate amount of ferulic acid ethanol solution can improve the surface properties of the magnesium slag particles, stimulate the activity of the magnesium slag, and improve its compatibility with other materials. The ferulic acid in the appropriate amount of ferulic acid ethanol solution is adsorbed on the surface of the magnesium slag particles, reducing the surface energy between the particles and reducing the agglomeration of the particles, so that the magnesium slag particles can be more evenly dispersed during the ball milling process, thereby improving the ball milling efficiency and modification effect. During the ball milling process, the ferulic acid ethanol solution helps to further refine the magnesium slag particles, improve their activity, and enable the magnesium slag to better participate in the formation reaction of cement clinker, ultimately improving the quality and performance of cement clinker.

[0023] Second, BOF slag powder is mixed with Na2CO3 and roasted. During the roasting process, Na2CO3 reacts with certain components in the BOF slag, lowering its melting point and allowing it to undergo a solid-phase reaction at a lower temperature, thereby increasing its activity. The activated BOF slag powder contributes more active ingredients to the formation of cement clinker, including tetracalcium aluminoferrite, helping to improve the mineral composition of the cement clinker and enhance its strength and other properties.

[0024] 3. Calcium carbide slag, magnesium slag, converter slag, and coal gangue, when used in specific proportions, can effectively improve the early strength of cement, balance early strength and later strength stability, resist cracking, and exhibit excellent resistance to sulfate attack. Li2B4O7-CaF2 composite mineralizers, mixed in specific mass ratios and added to the raw materials, can significantly reduce the firing temperature of cement clinker, allowing the materials to fully react at relatively low temperatures and promoting the formation and development of minerals. This not only saves energy but also reduces the wear and tear on equipment caused by high-temperature calcination. Furthermore, the composite mineralizer helps induce the formation of a new three-phase system of calcite-dicalcium silicate-spinel, improving the mineral composition of the cement clinker and thereby enhancing cement properties such as early strength, later strength, and durability.

[0025] Fourth, during preheating, a CO2-H2O mixture is introduced to adjust the reaction atmosphere of the materials, promoting the decomposition of some carbonates, making it easier for calcium carbonate and other carbonates to decompose into calcium oxide, providing a sufficient source of calcium for the subsequent formation of minerals in cement clinker. Furthermore, the CO2-H2O mixture reacts with some components in the materials, increasing their reactivity and making the subsequent heat-insulating calcination more complete and efficient. This is beneficial for the formation of minerals and the development of crystals, thereby improving the quality of the cement clinker.

[0026] Fifth, introducing trace amounts of SO2 during the appropriate timeframe of the heat-insulating calcination process can induce the formation of a new three-phase system of gehelite, dicalcium silicate, and spinel, optimizing the mineral composition of the cement clinker. Furthermore, SO2 can regulate the sulfur content in the clinker. The appropriate amount of sulfur reacts with other cement components, improving the cement's setting time and ensuring it better meets construction requirements during use. Furthermore, precise control prevents excessive sulfur introduction.

[0027] The formation of calcined feldspar (C2AS) and spinel (MA) mainly occurs in the early stage of calcination. Adding 0.3vol% to 0.5vol% SO2 during the 50-70min period of heat preservation calcination can significantly reduce the risk of sulfur residue in the clinker while still effectively inducing the formation of the target mineral phase; sulfur is mainly fixed by forming sulfoaluminate (precursor of ettringite) or dissolving in silicate minerals; the oxidizing atmosphere of SO2 can regulate the Fe 3+ / Fe 2+ The ratio stabilizes the spinel structure. By not introducing SO2 later in the process, sulfur can be prevented from interfering with the C2S crystal transformation. If sulfur is introduced throughout the insulated calcination process, excessive sulfur can form free CaSO4 or unreacted sulfur oxides, leading to residual risks. By limiting the SO2 introduction time to the critical stages of mineral formation (including the nucleation of gessenite and spinel), the amount of sulfur involved in the reaction can be precisely controlled, avoiding the introduction of excessive sulfur later in the process, which could trigger expansion (delayed formation of ettringite).

[0028] VI. This invention designs additives with specific compositions and proportions based on the characteristics of cement clinker. An appropriate amount of gypsum acts as a retarder to regulate setting time and participate in the C3A hydration reaction, preventing instantaneous setting. An appropriate amount of silica fume, a highly active siliceous material, fills pores and promotes later strength development. An appropriate amount of polyacrylamide improves particle dispersion and reduces the risk of cracking. An appropriate amount of polycarboxylate superplasticizer reduces the water-cement ratio and improves density. These ingredients work together to enhance the various properties of cement clinker.

[0029] 7. Control mineral composition: Control the MgO content in magnesium slag to ≤5wt%. On the one hand, it can prevent excessive hydration and expansion. On the other hand, it can partially replace CaO in clinker, promote the formation of silicate minerals (C3S, C2S) and intermediate phases (including C4AF), and at the same time generate a small amount of minerals such as forsterite (Mg2SiO4), thereby optimizing the early strength and sulfate corrosion resistance of clinker.

[0030] 8. Improve burnability: The highly active CaO in carbide slag and the trace elements (including Fe and Al) in magnesium slag can reduce the liquid phase formation temperature of the raw material, accelerate the formation reaction of clinker minerals, and shorten the firing time.

[0031] In summary, carbide slag replaces limestone, reducing carbon emissions from CaCO₃ decomposition. Modified magnesium slag introduces MgO, but the magnesium phosphate protective layer suppresses the expansion of free MgO. Activated converter slag provides Al₂O₃ and Fe₂O₃, promoting the formation of grosslandite (C₂AS). The Li₂B₄Oₐ-CaF₂ composite mineralizer lowers the liquid phase formation temperature and synergistically promotes mineral phase reconstruction with SO₂. The formulation design balances resource utilization, process optimization, and performance, demonstrating excellent practical value. DETAILED DESCRIPTION

[0032] Example 1: A method for preparing cement clinker using magnesium slag and carbide slag, comprising the following steps:

[0033] S1: Carbide slag is dried, crushed, and passed through a 200-mesh sieve to obtain carbide slag powder;

[0034] S2: The magnesium slag is crushed and passed through a 250-mesh sieve to obtain magnesium slag powder, and a 3wt% Mg(H2PO4)2 aqueous solution with a concentration of 10% by weight of the magnesium slag powder is added, and a 6wt% ferulic acid ethanol solution with a concentration of 5% by weight of the magnesium slag powder is added, and ball milling is performed. The diameter of the grinding balls is 8 mm, the filling rate of the grinding balls is 30%, and the ball milling is carried out at a speed of 15 r / min for 1.5 h. After drying, the grinding balls are sieved to remove the grinding balls. A Mg3(PO4)2 protective layer is formed on the surface of the magnesium slag powder particles to obtain modified magnesium slag powder;

[0035] S3: The converter slag is crushed and passed through a 150-mesh sieve to obtain converter slag powder, and Na2CO3 (4% by weight of the converter slag powder) is added to the mixture, and the mixture is calcined at 400°C for 30 minutes to obtain activated converter slag powder;

[0036] S4: Grinding the gangue and passing it through a 200-mesh sieve to obtain gangue powder;

[0037] S5: Calculated by weight, 50 parts of calcium carbide slag powder, 25 parts of modified magnesium slag powder, 3 parts of activated converter slag powder, 12 parts of coal gangue powder and 5 parts of Li2B4O7-CaF2 composite mineralizer are mixed evenly, preheated at 800℃ for 20 minutes, and a CO2-H2O mixed gas is introduced at the same time; then, the mixture is kept at 1100℃ for 2 hours, and 0.3vol% SO2 is added within 50-70 minutes of the calcination to induce the formation of a new three-phase system of gessamite-dicalcium silicate-spinel; and cooled to obtain cement clinker with a MgO content of 4.3wt% and a SO3 content of 0.4wt% in the clinker.

[0038] Among them, the Li2B4O7-CaF2 composite mineralizer is a mixture of Li2B4O7 and CaF2 in a mass ratio of 1.5:1; the volume ratio of the CO2-H2O mixed gas is CO2:H2O=3:1; and the amount of the CO2-H2O mixed gas introduced is 0.8L / min per kilogram of material.

[0039] Example 2: A method for preparing cement clinker using magnesium slag and carbide slag, comprising the following steps:

[0040] S1: Carbide slag is dried, crushed, and passed through a 200-mesh sieve to obtain carbide slag powder;

[0041] S2: The magnesium slag is crushed and passed through a 325-mesh sieve to obtain magnesium slag powder, and a 5wt% Mg(H2PO4)2 aqueous solution with a concentration of 10% by weight of the magnesium slag powder is added, and a 6.5wt% ferulic acid ethanol solution with a concentration of 5% by weight of the magnesium slag powder is added, and ball milling is performed. The diameter of the grinding balls is 8 mm, the filling rate of the grinding balls is 40%, and the ball milling is performed at a speed of 15 r / min for 2 h. After drying, the grinding balls are sieved to remove the grinding balls. A Mg3(PO4)2 protective layer is formed on the surface of the magnesium slag powder particles to obtain modified magnesium slag powder;

[0042] S3: The converter slag is crushed and passed through a 150-mesh sieve to obtain converter slag powder, and Na2CO3 (6% by weight of the converter slag powder) is added to the mixture, and the mixture is calcined at 400°C for 40 minutes to obtain activated converter slag powder;

[0043] S4: Grinding the gangue and passing it through a 200-mesh sieve to obtain gangue powder;

[0044] S5: Calculated by mass, 60 parts of calcium carbide slag powder, 25 parts of modified magnesium slag powder, 5 parts of activated converter slag powder, 12 parts of coal gangue powder and 8 parts of Li2B4O7-CaF2 composite mineralizer are mixed evenly, preheated at 800℃ for 30 minutes, and a CO2-H2O mixed gas is introduced at the same time; then, the mixture is kept at 1100℃ for 3 hours, and 0.3vol% SO2 is added within 50-70 minutes of the calcination to induce the formation of a new three-phase system of gessamite-dicalcium silicate-spinel; and cooled to obtain cement clinker with a MgO content of 3.4wt% and a SO3 content of 0.5wt% in the clinker.

[0045] Among them, the Li2B4O7-CaF2 composite mineralizer is a mixture of Li2B4O7 and CaF2 in a mass ratio of 3:1; the volume ratio of the CO2-H2O mixed gas is CO2:H2O=4:1; and the injection amount of the CO2-H2O mixed gas is 1.2L / min per kilogram of material.

[0046] Example 3: A method for preparing cement clinker using magnesium slag and carbide slag, comprising the following steps:

[0047] S1: Carbide slag is dried, crushed, and passed through a 200-mesh sieve to obtain carbide slag powder;

[0048] S2: The magnesium slag is crushed and passed through a 325-mesh sieve to obtain magnesium slag powder, and a 4wt% Mg(H2PO4)2 aqueous solution with a concentration of 15% by weight of the magnesium slag powder is added, and a 7wt% ferulic acid ethanol solution with a concentration of 8% by weight of the magnesium slag powder is added, and ball milling is performed. The diameter of the grinding balls is 10 mm, and the filling rate of the grinding balls is 35%. The grinding is carried out at a speed of 20 r / min for 1.5 h and then dried. The grinding balls are sieved to remove the grinding balls. A Mg3(PO4)2 protective layer is formed on the surface of the magnesium slag powder particles to obtain modified magnesium slag powder;

[0049] S3: The converter slag is crushed and passed through a 200-mesh sieve to obtain converter slag powder, and Na2CO3 (5% by weight of the converter slag powder) is added to the mixture, and the mixture is calcined at 450°C for 35 minutes to obtain activated converter slag powder;

[0050] S4: Grinding the gangue and passing it through a 200-mesh sieve to obtain gangue powder;

[0051] S5: Calculated by weight, 55 parts of carbide slag powder, 28 parts of modified magnesium slag powder, 4 parts of activated converter slag powder, 13 parts of coal gangue powder and 7 parts of Li2B4O7-CaF2 composite mineralizer are mixed evenly, preheated at 850℃ for 25 minutes, and a CO2-H2O mixed gas is introduced at the same time; then, the mixture is kept at 1150℃ for 2.5 hours, and 0.4vol% SO2 is added within 50-70 minutes of the calcination to induce the formation of a new three-phase system of gessamite-dicalcium silicate-spinel; and cooled to obtain cement clinker with a MgO content of 4.1wt% and a SO3 content of 0.7wt% in the clinker.

[0052] Among them, the Li2B4O7-CaF2 composite mineralizer is a mixture of Li2B4O7 and CaF2 in a mass ratio of 2:1.5; the volume ratio of the CO2-H2O mixed gas is CO2:H2O=3.5:1; and the amount of the CO2-H2O mixed gas introduced is 1.0L / min per kilogram of material.

[0053] Example 4: A method for preparing cement clinker using magnesium slag and carbide slag, comprising the following steps:

[0054] S1: drying and crushing the carbide slag, and passing it through a 250-mesh sieve to obtain carbide slag powder;

[0055] S2: The magnesium slag is crushed and passed through a 250-mesh sieve to obtain magnesium slag powder, and a 3wt% Mg(H2PO4)2 aqueous solution with a concentration of 20% by weight of the magnesium slag powder is added, and a 7.5wt% ferulic acid ethanol solution with a concentration of 10% by weight of the magnesium slag powder is added, and ball milling is performed. The diameter of the grinding balls is 15 mm, the filling rate of the grinding balls is 30%, and the ball milling is carried out at a speed of 20 r / min for 1.5 h. After drying, the grinding balls are sieved to remove the grinding balls. A Mg3(PO4)2 protective layer is formed on the surface of the magnesium slag powder particles to obtain modified magnesium slag powder;

[0056] S3: The converter slag is crushed and passed through a 200-mesh sieve to obtain converter slag powder, and Na2CO3 (4% by weight of the converter slag powder) is added to the mixture, and the mixture is calcined at 500°C for 30 minutes to obtain activated converter slag powder;

[0057] S4: Grinding the coal gangue and passing it through a 250-mesh sieve to obtain coal gangue powder;

[0058] S5: 50 parts by mass of carbide slag powder, 30 parts by mass of modified magnesium slag powder, 3 parts by mass of activated converter slag powder, 15 parts by mass of coal gangue powder, and 5 parts by mass of Li2B4O7-CaF2 composite mineralizer are mixed evenly, preheated at 900°C for 20 minutes, and simultaneously introduced with a CO2-H2O mixed gas; then, calcined at 1200°C for 2 hours, and 0.5 vol% SO2 is added within 50 to 70 minutes of the calcination to induce the formation of a new three-phase system of gessamite-dicalcium silicate-spinel; cooled to obtain cement clinker, wherein the MgO content in the clinker is 5.0 wt% and the SO3 content in the clinker is 0.9 wt%;

[0059] Among them, the Li2B4O7-CaF2 composite mineralizer is a mixture of Li2B4O7 and CaF2 in a mass ratio of 1.5:2; the volume ratio of the CO2-H2O mixed gas is CO2:H2O=3:1.2; and the amount of the CO2-H2O mixed gas introduced is 0.8L / min per kilogram of material.

[0060] Example 5: A method for preparing cement clinker using magnesium slag and carbide slag, comprising the following steps:

[0061] S1: drying and crushing the carbide slag, and passing it through a 250-mesh sieve to obtain carbide slag powder;

[0062] S2: The magnesium slag is crushed and passed through a 325-mesh sieve to obtain magnesium slag powder, and a 5wt% Mg(H2PO4)2 aqueous solution with a concentration of 20% by weight of the magnesium slag powder is added, and an 8wt% ferulic acid ethanol solution with a concentration of 10% by weight of the magnesium slag powder is added, and ball milling is performed. The diameter of the grinding balls is 15 mm, the filling rate of the grinding balls is 40%, and the ball milling is performed at a speed of 20 r / min for 2 h. After drying, the grinding balls are sieved to remove the grinding balls. A Mg3(PO4)2 protective layer is formed on the surface of the magnesium slag powder particles to obtain modified magnesium slag powder;

[0063] S3: The converter slag is crushed and passed through a 200-mesh sieve to obtain converter slag powder, and Na2CO3 (6% by weight of the converter slag powder) is added to the mixture, and the mixture is calcined at 500°C for 40 minutes to obtain activated converter slag powder;

[0064] S4: Grinding the coal gangue and passing it through a 250-mesh sieve to obtain coal gangue powder;

[0065] S5: Calculated by mass, 60 parts of calcium carbide slag powder, 30 parts of modified magnesium slag powder, 5 parts of activated converter slag powder, 15 parts of coal gangue powder and 8 parts of Li2B4O7-CaF2 composite mineralizer are mixed evenly, preheated at 900℃ for 30 minutes, and a CO2-H2O mixed gas is introduced at the same time; then, the mixture is kept at 1200℃ for 3 hours, and 0.5vol% SO2 is added within 50-70 minutes of the calcination to induce the formation of a new three-phase system of gessamite-dicalcium silicate-spinel; and cooled to obtain cement clinker with a MgO content of 3.9wt% and a SO3 content of 0.8wt% in the clinker.

[0066] Among them, the Li2B4O7-CaF2 composite mineralizer is a mixture of Li2B4O7 and CaF2 in a mass ratio of 3:2; the volume ratio of the CO2-H2O mixed gas is CO2:H2O=4:1.2; and the injection amount of the CO2-H2O mixed gas is 1.2L / min per kilogram of material.

[0067] The cement clinker prepared in the above embodiments is used in combination with additives, including but not limited to 5wt% to 8wt% gypsum powder, 2wt% to 4wt% silica fume, 0.1wt% to 0.2wt% polyacrylamide and 1wt% to 2wt% polycarboxylate water-reducing agent powder.

[0068] In order to ensure comparability of sample testing, the cement samples of each embodiment were prepared by adding 6 wt% of gypsum powder, 3 wt% of silica fume, 0.15 wt% of polyacrylamide, and 1.5 wt% of polycarboxylic acid water-reducing agent powder to cement clinker as additives.

[0069] Sources of raw materials in the above embodiments: Calcium carbide slag is sourced from Shaanxi Jintai Chlor-Alkali Chemical Co., Ltd. Magnesium slag is sourced from Shaanxi Jiaxian Hengsheng Magnesium Co., Ltd. The supplier of converter slag is Shanxi Hongmo Logistics Co., Ltd., and the manufacturer is Shanxi Gaoyi Iron and Steel Co., Ltd. The supplier of coal gangue is Yulin Jinshunhui Transportation Co., Ltd., and the manufacturer is Zizhou Yongxing Coal Industry Co., Ltd. Mg(H2PO4)2 is sourced from Zhengzhou Shengfeng Chemical Products Co., Ltd., with a purity of 98%. Ferulic acid is sourced from Shaanxi Yinuo Biotechnology Co., Ltd., model YN-01, with a purity of 98%. Na2CO3 is sourced from Weifang Haizhiyuan Chemical Co., Ltd. Li2B4O7 is sourced from Henan Wanshan New Materials Technology Co., Ltd., with a purity of 99%. CaF2 is sourced from Hebei Guanting Building Materials Technology Co., Ltd., with a purity of 97%. Gypsum powder is sourced from Jinhai Gypsum Products Factory, Yicheng District, Zaozhuang City, model jh-001. Silica fume is sourced from Lingshou Muchen New Materials Technology Co., Ltd., with a silicon content of 96% and a particle size of 1200 mesh. Polyacrylamide was sourced from Henan Hangrui Environmental Protection Technology Co., Ltd., model anion 16 million. Polycarboxylate water-reducing agent powder was sourced from Wuhan Huaxuan High-tech Co., Ltd., model PC-1006.

[0070] Comparative Example 1

[0071] In S2, the modified magnesium slag powder is replaced by magnesium slag powder (without modification); other parameters and methods are the same as in Example 1.

[0072] Comparative Example 2

[0073] In S2, no ferulic acid ethanol solution was added; other parameters and methods were the same as in Example 1.

[0074] Comparative Example 3

[0075] In S2, the concentration of the ferulic acid ethanol solution is 15 wt %, and the added amount is 10% of the mass of the magnesium slag powder; other parameters and methods are the same as in Example 1.

[0076] Comparative Example 4

[0077] In S2, the concentration of the Mg(H2PO4)2 aqueous solution is 15wt%, and the added amount is 20% of the mass of the magnesium slag powder; other parameters and methods are the same as in Example 1.

[0078] Comparative Example 5

[0079] In S2, the modified magnesium slag powder is replaced by magnesium slag powder (without modification), and Mg3(PO4)2 powder of 0.5% by mass of the magnesium slag powder is directly added and dry-mixed uniformly; other parameters and methods are the same as in Example 1.

[0080] Comparative Example 6

[0081] In S3, the activated converter slag powder is replaced by converter slag powder (without activation); other parameters and methods are the same as in Example 1.

[0082] Comparative Example 7

[0083] In S3, the calcination temperature is 300° C.; other parameters and methods are the same as in Example 1.

[0084] Comparative Example 8

[0085] In S5, no Li2B4O7-CaF2 composite mineralizer is added; other parameters and methods are the same as in Example 1.

[0086] Comparative Example 9

[0087] In S5, the composite mineralizer is entirely Li2B4O7; other parameters and methods are the same as in Example 1.

[0088] Comparative Example 10

[0089] In S5, CaF2 is used as the composite mineralizer; other parameters and methods are the same as those in Example 1.

[0090] Comparative Example 11

[0091] In S5, the addition amount of Li2B4O7-CaF2 composite mineralizer is 15 parts; other parameters and methods are the same as those in Example 1.

[0092] Comparative Example 12

[0093] In S5, there are 25 parts of calcium carbide slag powder and 50 parts of modified magnesium slag powder; other parameters and methods are the same as in Example 1.

[0094] Comparative Example 13

[0095] In S5, 15 parts of activated converter slag powder and 5 parts of coal gangue powder were used; other parameters and methods were the same as those in Example 1.

[0096] Comparative Example 14

[0097] In S5, there are 25 parts of calcium carbide slag powder, 50 parts of modified magnesium slag powder, 15 parts of activated converter slag powder, and 5 parts of coal gangue powder; other parameters and methods are the same as in Example 1.

[0098] Comparative Example 15

[0099] In S5, SO2 is not introduced during the 50-70 min period of heat preservation calcination; other parameters and methods are the same as those in Example 1.

[0100] Due to the changes in ingredients or processes in the comparative examples, the contents of MgO and SO3 in the cement clinker products are different from those in Example 1.

[0101] 1. Determination of setting time:

[0102] The initial setting time is measured in accordance with GB / T 1346, "Test Methods for Water Consumption, Setting Time, and Soundness of Cement at Standard Consistency." Cement clinker and water are mixed at a water-cement ratio of 0.45 to form a cement paste. This is then placed in a test mold and a test rod lowered to the surface of the paste. The time required for the rod to sink into the paste and remain 6 mm ± 1 mm from the bottom plate is recorded. The final setting time is when the test rod sinks 0.5 mm into the specimen, i.e., when the annular attachment no longer leaves a mark on the specimen. The experimental environment is 20°C and the relative humidity is 60%.

[0103] 2. Strength determination:

[0104] The cement sample includes cement clinker and additives (the additives are 6wt% gypsum powder, 3wt% silica fume, 0.15wt% polyacrylamide, and 1.5wt% polycarboxylate superplasticizer powder in cement clinker). The cement clinker is first ground to a specific surface area of 350±10m² / kg, and then stirred with other additives in a planetary mixer at a speed of 120r / min for 5min to fully mix the materials to obtain the cement sample.

[0105] According to GB / T 17671, "Test Method for Cement Mortar Strength (ISO Method)", 40 mm × 40 mm × 160 mm cement mortar specimens were prepared. The mortar mix ratio was 1:3:0.5 cement sample (including additives): standard sand: water. The specimens were cured under standard curing conditions (temperature 20°C, relative humidity 90%) for 3 and 28 days, respectively, and then compressive strength tests were performed using a pressure testing machine.

[0106] 3. Cracking test:

[0107] According to the strength test formula preparation method, thin plate specimens with a size of 400mm×400mm×60mm were made. After curing under standard curing conditions for 28 days, cracks on the surface of the specimens were observed using a crack width gauge, and the number of cracks and the maximum width of the cracks were recorded.

[0108] 4. Sulfate corrosion resistance test:

[0109] Cement mortar specimens measuring 40 mm x 40 mm x 160 mm were prepared according to the strength test recipe. Following the standard curing method for 28 days, the specimens were immersed in a 5 wt% sodium sulfate solution. After 90 days, the specimens were removed and observed for changes in appearance (e.g., spalling, expansion, cracks), their compressive strength was measured, and the strength loss rate was calculated.

[0110] Table 1 Performance test results

[0111]

[0112] From the above results, it can be seen that the cement clinkers of Examples 1 to 5 can not only avoid the addition of a large amount of limestone, effectively reduce carbon emissions, have a low calcination temperature, and save fuel energy, but also have a faster setting time, shorten the construction period, and the cement has high early strength, stable early strength and late strength, is not easy to crack, and has better resistance to sulfate erosion.

[0113] In Comparative Example 1, modified magnesium slag powder was substituted with magnesium slag powder. Unmodified magnesium slag reacts more slowly with other raw materials during the calcination process. During the cement hydration process, the lack of the specialized structure and active substances formed by the modification slows the formation of hydration products. In the initial stages of cement hydration, the formation of hydration products such as ettringite slows, increasing the time required for the cement paste to transition from a plastic state to a solid state with a certain strength. During the cement hydration process, magnesium oxide more readily hydrates to form magnesium hydroxide, which has a high volume expansion rate and prolongs both initial and final setting times. The strength of cement primarily comes from the dense structure formed by the interweaving of various hydration products produced during cement hydration. Unmodified magnesium slag is insufficiently active and cannot fully participate in the reaction to form high-strength mineral phases during the calcination process, resulting in a relative reduction in the content of effective strength-contributing phases (including minerals such as calcium silicate) in the cement clinker. During the cement hydration process, the lack of the promoting effect of the modification affects both the quantity and quality of the hydration products. The production of CSH gel (the primary strength contributor to cement hydration) is reduced, and its structure is less dense, making the cement paste more susceptible to damage when subjected to external forces. The addition of unmodified magnesium slag reduces the uniformity of the cement paste's internal structure, causing magnesium oxide to expand easily and more susceptible to microcracks. Sulfate ions in sulfate solutions react with certain components of the cement paste (including calcium hydroxide and tricalcium aluminate) to form expansive products (including secondary formation of ettringite and gypsum crystals). Unmodified magnesium slag affects the overall structural uniformity and density of the cement paste and fails to effectively inhibit the occurrence and progression of these harmful reactions, leading to expansion and cracking of the cement paste, increased strength loss, and decreased sulfate resistance.

[0114] In Comparative Example 2, no ferulic acid ethanol solution was added. Ferulic acid ethanol solution plays an important role in the magnesium slag modification process. It can act as a surfactant and dispersant to improve the dispersibility and adsorption of the Mg(H2PO4)2 aqueous solution on the surface of the magnesium slag powder, allowing the Mg3(PO4)2 protective layer to form more evenly and densely on the surface of the magnesium slag powder particles. When ferulic acid ethanol solution is not added, the formation of the Mg(H2PO4)2 protective layer is less than ideal, and the active sites on the surface of some magnesium slag powder particles are not fully exposed, which reduces the degree of reaction with other raw materials during the calcination process, thereby affecting the formation and quality of the mineral phase in the cement clinker. Without the effect of ferulic acid ethanol solution, the crystal morphology and growth pattern of the cement hydration products will change, and the connection between the crystals will not be tight enough, resulting in a slight decrease in the strength of the cement paste. In terms of sulfate corrosion resistance, due to slight changes in the internal structure of the cement paste, the sulfate solution is more likely to penetrate into the cement paste and react with the cement paste components. Although this effect is relatively small, it still leads to a decrease in sulfate corrosion resistance.

[0115] In Comparative Example 3, the concentration of the ferulic acid ethanol solution is 15wt%, and the addition amount is 10% of the mass of the magnesium slag powder. Excessively high concentrations of ferulic acid ethanol solution will form an excessively thick adsorption layer on the surface of the magnesium slag powder. Although this adsorption layer can protect the magnesium slag powder to a certain extent, it will hinder the sufficient reaction of the Mg(H2PO4)2 aqueous solution with the magnesium slag powder, so that the formation process of the Mg3(PO4)2 protective layer is suppressed, resulting in insufficient formation of the protective layer and a less than ideal structure. During the calcination process, the excessively thick adsorption layer will decompose to produce some gases and other by-products. These by-products will form tiny pores and defects inside the cement clinker, affecting the microstructure of the cement clinker. These microstructural changes have a negative impact on the strength and corrosion resistance of cement. The presence of pores will reduce the density of the cement paste, making the cement paste more susceptible to erosion by external corrosive media (such as sulfate solution).

[0116] In Comparative Example 4, the concentration of the Mg(H2PO4)2 aqueous solution was 15 wt%, and the addition amount was 20% of the mass of the magnesium slag powder. Excessive concentrations and additions of Mg(H2PO4)2 aqueous solution will result in excessive Mg3(PO4)2 formation on the surface of the magnesium slag powder. Excessive Mg3(PO4)2 forms an overly dense protective layer on the surface of the magnesium slag powder. While this dense protective layer can protect the magnesium slag powder to a certain extent, it can severely hinder chemical reactions between the magnesium slag powder and other raw materials during the calcination process. Because chemical reactions require sufficient contact and material exchange between the raw materials, an overly dense protective layer makes it difficult for other raw materials to react with the active components within the magnesium slag powder, inhibiting the formation of some important mineral phases in the cement clinker (including calcium silicate and calcium aluminate). Excessive Mg3(PO4)2 can affect the release and migration of ions during cement hydration, disrupting the normal hydration reaction. It can also affect the release rate and diffusion path of calcium ions, resulting in reduced production of hydration products such as CSH gel and poorer crystal morphology, thereby reducing the strength of the cement paste. In terms of sulfate resistance, changes in the mineral composition and structure of cement paste reduce its ability to resist sulfate attack. Sulfate solutions react more easily with unstable components in cement paste, producing more expansive products, which accelerate the destruction of cement paste and lead to poor sulfate resistance.

[0117] In Comparative Example 5, modified magnesium slag powder was replaced with magnesium slag powder, and Mg3(PO4)2 powder was directly added at 0.5% of the weight of the magnesium slag powder. Direct dry-mixing with Mg3(PO4)2 powder failed to adhere as tightly to the surface of the magnesium slag particles as the in-situ generated Mg3(PO4)2 protective layer, and its distribution was uneven. The resulting performance was equivalent to that of unmodified magnesium slag powder.

[0118] In Comparative Example 6, activated converter slag powder was substituted for converter slag powder. When converter slag is unactivated, its active components (including the vitreous phase and some unstable mineral phases) remain relatively stable, making it difficult for them to fully participate in reactions during the cement clinker calcination process. During calcination, the chemical reaction between unactivated converter slag and other raw materials (such as carbide slag and magnesium slag) is low, failing to effectively promote the formation and optimization of mineral phases in the cement clinker. This results in a reduction in the content of effective strength-contributing minerals in the cement clinker. Unactivated converter slag has a weak ability to release active ions during cement hydration, failing to adequately promote cement hydration. This results in a reduced production of hydration products and poorer quality. It also fails to effectively promote the growth and development of CSH gel, resulting in reduced strength of the cement paste. Regarding sulfate resistance, defects in the mineral composition and structure of the cement paste reduce its ability to resist sulfate attack. Unactivated converter slag cannot effectively inhibit the harmful reactions between sulfate and cement paste components, making the cement paste more susceptible to expansion and cracking.

[0119] In Comparative Example 7, the calcination temperature was 300°C. The calcination temperature is crucial in the converter slag activation process. A calcination temperature of 300°C is too low to adequately disrupt and restructure the crystal structure within the converter slag, nor to fully activate the active components within the slag. At lower temperatures, some chemical bonds within the converter slag fail to break, and active sites are not fully exposed, resulting in limited improvement in converter slag activity and a decrease in various indicators.

[0120] In Comparative Example 8, no Li2B4O7-CaF2 composite mineralizer was added. The Li2B4O7-CaF2 composite mineralizer plays an important mineralizing role during cement clinker calcination. It can lower the temperature at which cement clinker minerals form, promoting the formation and development of various mineral phases. Without the addition of the composite mineralizer, the reaction between the raw materials during cement clinker calcination requires higher temperatures and longer times to reach the desired reaction level. Under actual calcination conditions, the lack of the promoting effect of the mineralizer inhibits the formation of some important mineral phases (including tricalcium silicate and tricalcium aluminate), resulting in a reduction in the content of these high-strength mineral phases in the cement clinker.

[0121] Due to the suboptimal mineral composition of cement clinker, the quantity and quality of hydration products generated during cement hydration decrease. The production of key strength-contributing substances, such as CSH gel, is significantly reduced, and its loose structure makes the cement paste more susceptible to damage when subjected to external forces, significantly reducing its strength. Regarding crack resistance, due to increased defects and heterogeneity in the cement paste's internal structure, microcracks are more likely to form during the hardening process. These microcracks provide pathways for corrosive media. During sulfate corrosion tests, sulfate solutions more easily enter the cement paste, reacting with its components to produce a large number of expansive products. This causes the cement paste to expand and crack, increasing its strength loss rate and deteriorating its crack resistance and sulfate corrosion resistance.

[0122] In Comparative Example 9, the composite mineralizer used exclusively is Li2B4O7. Li2B4O7 has different mechanisms of action within the composite mineralizer, and their interaction is crucial for achieving optimal mineralization. While Li2B4O7 alone can reduce the temperature of cement clinker mineral formation to a certain extent, it lacks the unique benefits of CaF2. CaF2 promotes the formation of certain mineral phases (including tricalcium silicate), alters the crystal morphology and size of the minerals, and makes the crystals finer and more uniform, thereby improving the microstructure of the cement paste. The lack of CaF2 impairs the formation and development of cement clinker minerals, reducing the quantity and quality of some key mineral phases and the quality of the cement clinker. Changes in the mineral composition and structure of the cement clinker also affect the formation and development of hydration products. The crystal morphology and growth pattern of hydration products, such as CSH gel, change, resulting in less tight connections between crystals and a reduction in the strength of the cement paste. Regarding sulfate resistance, defects in the cement paste's microstructure allow sulfate solutions to more easily penetrate the interior, reacting with its components and deteriorating its sulfate resistance.

[0123] In Comparative Example 10, CaF2 was used exclusively as the composite mineralizer. Although CaF2 has a certain mineralizing effect during cement clinker calcination, its use alone cannot fully replace the effectiveness of the Li2B4O7-CaF2 composite mineralizer. Li2B4O7 regulates the liquid phase properties during cement clinker mineral formation, promoting the dissolution and recrystallization of certain mineral phases, while also having a certain regulatory effect on cement properties such as setting time. When CaF2 is used alone, the cement clinker calcination process lacks the synergistic effect of Li2B4O7, resulting in imperfect formation and development of mineral phases. This affects the formation of some minerals that contribute to strength and durability (including the optimized formation of calcium aluminate minerals), resulting in a reduction in the content of effective strength-contributing phases in the cement clinker and a decrease in various cement properties.

[0124] In Comparative Example 11, the amount of Li2B4O7-CaF2 composite mineralizer added was 15 parts. When the composite mineralizer is added in too much amount, although it can promote the formation of mineral phases to a certain extent, it will cause the amount of liquid phase to be too much and the liquid phase properties to change during the cement clinker calcination process. Excessive mineralizers will interfere with the crystallization process of some mineral phases, resulting in coarse and uneven mineral crystallization, which will destroy the microstructure of the cement clinker. It will cause tricalcium silicate crystals to grow too large, weakening the bonding force between the crystals and affecting the strength of the cement paste. Due to changes in the microstructure of the cement clinker, the formation and development of hydration products are also affected. Although the hydration reaction will be accelerated by the action of the mineralizer in the early stage, due to structural defects in the later stage, the connection between the hydration products is not tight enough, resulting in the strength growth of the cement paste being restricted and the strength slightly decreasing. In terms of sulfate corrosion resistance, due to defects in the microstructure of the cement paste, sulfate solution is more likely to penetrate into the interior of the cement paste and react with the cement paste components, resulting in a slight decrease in sulfate corrosion resistance.

[0125] In comparative example 12, there are 25 parts of carbide slag powders and 50 parts of modified magnesium slag powders. The ratio of carbide slag and modified magnesium slag changes, causing the chemical composition and mineral composition of the raw material system to change significantly. Carbide slag is the main raw material providing calcium, and its reduction can make the supply of calcium element in cement clinker relatively insufficient, affecting the formation of important mineral phases such as calcium silicate and calcium aluminate. And the modified magnesium slag ratio is too high, and can introduce components such as too much magnesium element. If these components can not react and balance well with other components during cement clinker calcining, it can cause the cement clinker mineral composition to be unreasonable. Due to the change of mineral composition, the process and product of hydration reaction are affected. Calcium content deficiency can affect the generation of hydration products such as CSH gel, causing its generated amount to reduce and quality to deteriorate, thereby reducing the strength of cement stone. Unreasonable mineral composition makes the internal structure of cement stone uneven, and micro cracks are more likely to appear during the hardening process. These micro cracks become channels for the entry of corrosive media. In the sulfate corrosion resistance test, sulfate solution is more likely to enter the interior of cement stone and react with the components in cement stone, resulting in reduced crack resistance and sulfate corrosion resistance.

[0126] In Comparative Example 13, 15 parts of activated converter slag powder and 5 parts of coal gangue powder were used. The change in the ratio of activated converter slag powder to coal gangue powder affects the chemical reactions and mineral formation during the cement clinker calcination process. Too much activated converter slag powder and too little coal gangue powder can cause an imbalance in the proportions of certain components in the raw material system. Activated converter slag powder mainly provides some active ingredients and trace elements, while coal gangue powder provides components such as silicon. This imbalance in the proportions can affect the formation of mineral phases in the cement clinker, causing changes in the composition and structure of calcium silicate minerals, which is not conducive to the formation and stability of high-strength mineral phases. Due to the change in the mineral composition of the cement clinker, the generation and development of hydration products are affected. The quantity and quality of hydration products such as CSH gel decrease, resulting in a decrease in the strength of the cement paste. Due to the imbalance in the ratio of activated converter slag powder to coal gangue powder, the microstructure inside the cement paste becomes more complex and uneven. This unevenness makes the cement paste more susceptible to stress concentration and localized failure when subjected to external stress and erosion. During the process of resisting sulfate erosion, sulfate solution can more easily penetrate along the weak points of the structure and accelerate the erosion of cement stone.

[0127] Furthermore, changes in the ratio can also affect the stability of cement hydration products. When the coal gangue content is insufficient, it lacks sufficient silica to form a stable CSH gel structure, weakening the gel's erosion resistance. Excessive activated converter slag introduces excessive active ingredients, which, when reacting with sulfate, are more likely to form expansive products (including secondary ettringite). These expansive products can induce significant expansion stresses within the cement paste, promoting the expansion of microcracks, thereby reducing the cement paste's strength and significantly decreasing its sulfate resistance.

[0128] In Comparative Example 14, 25 parts of calcium carbide slag powder, 50 parts of modified magnesium slag powder, 15 parts of activated converter slag powder, and 5 parts of coal gangue powder were used. The simultaneous changes in the proportions of multiple raw materials caused a significant change in the chemical composition of the entire raw material system, seriously deviating from the appropriate proportion range. The reduction in calcium carbide slag resulted in insufficient calcium source, which could not meet the demand for forming sufficient amounts of major mineral phases such as calcium silicate and calcium aluminate; the high proportion of modified magnesium slag introduced too much magnesium and other components, exceeding the system's equilibrium tolerance; the excessive amount of activated converter slag powder and the insufficient amount of coal gangue powder further exacerbated the imbalance in the proportions of elements such as silicon, aluminum, and iron, disrupting the cement clinker mineral formation process and seriously degrading various performance properties.

[0129] In Comparative Example 15, SO2 is not introduced during the 50-70 min period of heat preservation calcination. The purpose of introducing SO2 is to induce the formation of a new three-phase system of calcite-dicalcium silicate-spinel. When SO2 is not introduced, this special three-phase system cannot be formed efficiently, so that the mineral composition of the cement clinker is mainly limited to traditional silicate minerals and other conventional mineral phases. Compared with cement clinker containing the new three-phase system, cement clinker lacking the three-phase system has defects in mineral composition, and some mineral phases with special properties are missing, resulting in a decrease in the overall performance of the cement clinker. The three-phase system of calcite-dicalcium silicate-spinel can synergistically interact with each other during the cement hydration process to promote the formation and development of strength-contributing phases such as CSH gel. In the absence of this three-phase system, the quantity and quality of cement hydration products are affected, the amount of CSH gel generated is reduced, and the crystal structure is not dense enough, making the cement stone more susceptible to damage when subjected to external forces. Some minerals in the gehelite-dicalcium silicate-spinel three-phase system (including spinel) possess a certain resistance to sulfate attack, inhibiting the harmful reactions of sulfate ions with other components in the cement paste. The absence of these key anti-erosion mineral phases in cement paste makes it easier for sulfate solutions to react with components in the cement paste, such as calcium hydroxide and tricalcium aluminate, significantly reducing its sulfate resistance.

Claims

1. A method for preparing cement clinker using magnesium slag and carbide slag, characterized in that: The steps include: S1: drying and crushing the carbide slag to obtain carbide slag powder; S2: The magnesium slag is crushed to obtain magnesium slag powder, an Mg(H2PO4)2 aqueous solution is added, a ferulic acid ethanol solution is added, ball milling is performed, and drying is performed to form a Mg3(PO4)2 protective layer on the surface of the magnesium slag powder particles to obtain modified magnesium slag powder; S3: crushing the converter slag to obtain converter slag powder, adding Na2CO3 to mix, and roasting to obtain activated converter slag powder; S4: crushing the coal gangue to obtain coal gangue powder; S5: Calculated by mass, 50 to 60 parts of carbide slag powder, 25 to 30 parts of modified magnesium slag powder, 3 to 5 parts of activated converter slag powder, 12 to 15 parts of coal gangue powder and 5 to 8 parts of Li2B4O7-CaF2 composite mineralizer are mixed evenly, preheated at 800°C to 900°C for 20 to 30 minutes, and a CO2-H2O mixed gas is introduced at the same time; then, the mixture is kept warm and calcined at 1100°C to 1200°C for 2 to 3 hours, and 0.3 vol% to 0.5 vol% SO2 is added during the 50 to 70 minutes of the calcination to induce the formation of a new three-phase system of calcite-dicalcium silicate-spinel; cooled to obtain cement clinker.

2. The method for preparing cement clinker by utilizing magnesium slag and carbide slag according to claim 1, wherein: In S1, the carbide slag is dried to a moisture content of less than 1 wt %; and the particle size of the carbide slag powder is sieved through a 200-250 mesh sieve.

3. The method for preparing cement clinker by utilizing magnesium slag and carbide slag according to claim 1, wherein: In S2, the concentration of the Mg(H2PO4)2 aqueous solution is 3wt% to 5wt%; the amount of the Mg(H2PO4)2 aqueous solution added is 10% to 20% of the mass of the magnesium slag powder.

4. The method for preparing cement clinker by utilizing magnesium slag and carbide slag according to claim 1, wherein: In S2, the concentration of the ferulic acid ethanol solution is 6wt% to 8wt%; the amount of the ferulic acid ethanol solution added is 5% to 10% of the mass of the magnesium slag powder.

5. The method for preparing cement clinker by utilizing magnesium slag and carbide slag according to claim 1, wherein: In S2, the particle size of the magnesium slag powder is sieved through a 250-325 mesh sieve; the ball mill is milled at a speed of 15 r / min to 20 r / min for 1.5 h to 2 h; the diameter of the grinding balls used in the ball mill is 8 mm to 15 mm, and the filling rate of the grinding balls is 30% to 40%; after drying, the grinding balls are sieved to remove the grinding balls.

6. The method for preparing cement clinker using magnesium slag and carbide slag according to claim 1, wherein: In S3, the particle size of the converter slag powder is sieved through 150-200 mesh; the amount of Na2CO3 added is 4%-6% of the mass of the converter slag powder; and the roasting is performed at 400°C-500°C for 30-40 minutes.

7. The method for preparing cement clinker using magnesium slag and carbide slag according to claim 1, wherein: In S4, the particle size of the coal gangue powder is sieved through a 200-250 mesh sieve.

8. The method for preparing cement clinker using magnesium slag and carbide slag according to claim 1, wherein: In S5, the Li2B4O7-CaF2 composite mineralizer is a mixture of Li2B4O7 and CaF2 in a mass ratio of (1.5-3): (1-2); the volume ratio of the CO2-H2O mixed gas is CO2:H2O=(3-4):(1-1.2); and the amount of the CO2-H2O mixed gas introduced is 0.8 L / min-1.2 L / min per kilogram of material.

9. The method for preparing cement clinker using magnesium slag and carbide slag according to claim 1, wherein: In S5, the MgO content in the cement clinker is ≤5wt%; the SO3 content in the clinker is <1wt%.

10. The method for preparing cement clinker by utilizing magnesium slag and carbide slag according to claim 1, characterized in that: The cement clinker is used in combination with additives, which include but are not limited to 5wt% to 8wt% of gypsum powder, 2wt% to 4wt% of silica fume, 0.1wt% to 0.2wt% of polyacrylamide and 1wt% to 2wt% of polycarboxylic acid water-reducing agent powder.

Images