A low-carbon portland cement clinker and a method for preparing the same

Abstract

This application relates to the field of building materials and discloses a low-carbon silicate cement clinker and its preparation method. The low-carbon silicate cement clinker, by weight, comprises the following components: copper smelting sludge, limestone, sandstone, coal gangue, iron tailings, and a carbonaceous reducing agent. On one hand, the firing temperature of this invention is 50-100°C lower than the conventional silicate cement clinker firing temperature of 1450°C, reducing coal consumption without affecting the quality of the silicate cement clinker. On the other hand, the cement clinker prepared by this invention can consume a large amount of copper smelting sludge. Through high-temperature firing, it can effectively solidify the heavy metal elements in the copper smelting sludge, and utilize the non-carbonate calcareous materials in the copper smelting sludge to replace part of the limestone, significantly reducing carbon dioxide emissions. Simultaneously, it can achieve resource utilization of various industrial waste residues, which has significant economic, low-carbon, and environmental benefits.

Description

Technical Field

[0001] This application relates to the field of building materials, specifically to a low-carbon silicate cement clinker and its preparation method. Background Technology

[0002] The main source of copper smelting sludge is the large amount of acidic wastewater generated after the flue gas from copper pyrometallurgical processes is used to produce acid. This wastewater is treated using a lime-neutralization precipitation process, resulting in a large amount of sludge, collectively referred to as copper sludge. Because this sludge contains a certain amount of arsenic (As) and heavy metals such as copper (Cu), zinc (Zn), cadmium (Gd), and lead (Pb), it must be effectively treated. Direct landfilling or simple stockpiling without treatment will cause significant harm to the surrounding environment. The main component of copper smelting sludge is CaSO4·xH2O, with a small amount of CaCO3. It can be used as a raw material for cement production. High-temperature sintering can effectively solidify the arsenic and other heavy metals in the copper smelting sludge, reducing the disposal cost.

[0003] Silicate cement and its concrete are currently the most widely used building materials in construction projects. Direct CO2 emissions from the cement industry mainly originate from the decomposition of limestone carbonates during the calcination of silicate cement clinker and coal combustion. While ensuring that the total cement supply does not decrease, seeking alternative limestone resources is currently an effective means for the cement industry to achieve its carbon reduction goals. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for efficiently preparing low-carbon silicate cement clinker using copper smelting sludge, significantly replacing limestone, a calcareous raw material in cement, with non-carbonate calcareous materials such as calcium sulfate from copper smelting sludge, thereby reducing carbon dioxide emissions during the calcination and decomposition stage of silicate cement clinker. The present invention utilizes sandstone and industrial solid waste coal gangue to replace clay-based raw materials in cement, primarily providing silicate-aluminate compounds that form silicate and aluminate minerals that contribute to cement strength and setting hardening properties during calcination; it also utilizes iron tailings to replace iron-based raw materials in cement, primarily providing iron compounds necessary for forming ferroaluminate-iron phase solid solutions that enhance cement durability, such as abrasion resistance, during calcination. A carbonaceous reducing agent can react with calcium sulfate during clinker calcination, promoting calcium oxide formation, lowering the decomposition temperature of calcium sulfate, reducing coal consumption, and without affecting the quality of silicate cement clinker. This invention fully utilizes industrial solid waste that can replace cement production raw materials, achieving comprehensive resource utilization on a large scale and possessing significant environmental benefits.

[0005] This application proposes a low-carbon silicate cement clinker, which comprises the following components by weight: 25-40 parts copper smelting sludge, 40-55 parts limestone, 5-12 parts sandstone, 4-10 parts coal gangue, 3-8 parts iron tailings, and 0-3 parts carbonaceous reducing agent.

[0006] More specifically, in the above technical solution, the low-carbon silicate cement clinker, calculated by weight, includes the following components: 30-38 parts copper smelting sludge, 42-50 parts limestone, 7-10 parts sandstone, 5-8 parts coal gangue, 4-7 parts iron tailings, and 1-2 parts carbonaceous reducing agent.

[0007] More specifically, in the above technical solution, the copper smelting sludge is copper sludge generated by treating acidic wastewater using the lime-neutralization precipitation method. Its composition, calculated by mass percentage, includes 55-70% CaSO4·xH2O, 6-10% CaCO3, 5-7% arsenate, and 1-3% hydroxides of Cu, Zn, Gd, and Pb.

[0008] More specifically, in the above technical solution, the mass percentage of CaO in the copper smelting sludge is 43-46%, and the mass percentage of CaO in the limestone is 52-54%.

[0009] More specifically, in the above technical solution, the mass percentage of CaO in the sandstone is 3-5%, the mass percentage of SiO2 is 67-75%, the mass percentage of Al2O3 is 5-8%, and the mass percentage of Fe2O3 is 3-5%.

[0010] More specifically, in the above technical solution, the mass percentage of CaO in the coal gangue is 2-3%, the mass percentage of SiO2 is 44-48%, the mass percentage of Al2O3 is 15-20%, and the mass percentage of Fe2O3 is 7-10%.

[0011] More specifically, in the above technical solution, the mass percentage of CaO in the iron tailings is 6-10%, the mass percentage of SiO2 is 47-52%, the mass percentage of Al2O3 is 7-12%, and the mass percentage of Fe2O3 is 18-25%.

[0012] More specifically, in the above technical solution, the oxides of the raw meal of the cement clinker include: CaO: 58-66%, Al2O3: 4-7%, SiO2: 14-18%, Fe2O3: 3-5%.

[0013] More specifically, in the above technical solution, the carbonaceous reducing agent includes one or more of coke, bituminous coal, and charcoal.

[0014] This application also proposes a method for preparing low-carbon silicate cement clinker, comprising the low-carbon silicate cement clinker described in any of the above claims, wherein the raw materials are mixed evenly and then ground until the particle size reaches 15-18% residue on a 0.07-0.09 mm square hole sieve, and then calcined at a temperature of 1350-1400℃ for 30-40 minutes, and then cooled to room temperature to obtain low-carbon silicate cement clinker.

[0015] Compared with the prior art, the embodiments of this application have the following beneficial effects:

[0016] 1. The proportion of copper smelting sludge in the mixture is high, reaching up to 38% of cement raw materials;

[0017] 2. The firing temperature of this low-carbon silicate cement clinker is 50-100℃ lower than that of traditional silicate cement clinker (1450℃), and the CO2 emissions are more than 20% lower than those of greenhouse gases emitted from the production of traditional cement.

[0018] 3. Cement prepared using the low-carbon silicate cement clinker of the present invention can achieve a 28-day strength of 45MPa to 55MPa, a strength grade of 42.5, low water demand, and good stability. Detailed Implementation

[0019] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrase "some embodiments" appearing in various parts of this specification does not necessarily refer to the same embodiment, but rather means "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless otherwise specifically emphasized.

[0022] All materials and reagents used in this application can be purchased commercially.

[0023] This application proposes a low-carbon silicate cement clinker, which comprises the following components by weight: 25-40 parts copper smelting sludge, 40-55 parts limestone, 5-12 parts sandstone, 4-10 parts coal gangue, 3-8 parts iron tailings, and 0-3 parts carbonaceous reducing agent.

[0024] The cement clinker prepared by this invention can consume a large amount of copper smelting sludge. Through high-temperature firing, it can effectively solidify the heavy metal elements in the copper smelting sludge, and utilize the non-carbonate calcareous materials in the copper smelting sludge to replace part of the limestone, significantly reducing carbon dioxide emissions. At the same time, it can also realize the resource utilization of various industrial waste residues, which has important economic, low-carbon and environmental protection significance.

[0025] This invention utilizes sandstone and industrial solid waste coal gangue to replace clay-based raw materials in cement, primarily providing silicate and aluminate compounds that form the strength and setting hardening properties of cement during calcination; it also utilizes iron tailings to replace iron-based raw materials in cement, primarily providing the iron compounds required to form the iron-aluminate phase solid solution that meets the durability requirements of cement, such as wear resistance, during calcination; and a carbonaceous reducing agent that can react with calcium sulfate during clinker calcination, promoting the formation of calcium oxide, lowering the decomposition temperature of calcium sulfate, reducing coal consumption, and without affecting the quality of silicate cement clinker.

[0026] Limestone in low-carbon silicate cement clinker can provide calcium, regulate the cement reaction rate, and adjust cement properties to meet different engineering requirements.

[0027] This invention makes full use of industrial solid waste that can replace cement production raw materials, realizes comprehensive utilization of resources on a large scale, and has high environmental benefits; the addition of carbonaceous reducing agent in the clinker calcination process can promote the decomposition of CaSO4 in copper smelting sludge into CaO and reduce the temperature of the decomposition reaction.

[0028] In some embodiments, the low-carbon silicate cement clinker comprises, by weight, the following components: 30-38 parts copper smelting sludge, 42-50 parts limestone, 7-10 parts sandstone, 5-8 parts coal gangue, 4-7 parts iron tailings, and 1-2 parts carbonaceous reducing agent.

[0029] In some embodiments, the copper smelting sludge is copper sludge generated by treating acidic wastewater using a lime-neutralization precipitation method, and its composition, calculated by mass percentage, includes 55-70% CaSO4·xH2O, 6-10% CaCO3, 5-7% arsenate, and 1-3% hydroxides of Cu, Zn, Gd, and Pb.

[0030] The lime-neutralization precipitation method is a common wastewater treatment method in which lime (calcium hydroxide) is used to neutralize acidic wastewater. This helps to neutralize acidic substances in acidic wastewater to neutral or alkaline conditions, thereby reducing the acidification impact of wastewater on the environment. Copper sludge generated from treating acidic wastewater using the lime-neutralization precipitation method can effectively treat wastewater, precipitate heavy metals, solidify arsenates, reduce environmental pollution, and at the same time contribute to resource recovery and comprehensive utilization.

[0031] In some embodiments, the mass percentage of CaO in the copper smelting sludge is 43-46%, and the mass percentage of CaO in the limestone is 52-54%.

[0032] CaO is one of the main components of cement clinker. It participates in the calcination process of cement clinker and plays an important role in the hardening and strength of cement. Ensuring that there is enough CaO can meet the process requirements and ensure the quality of cement.

[0033] In some embodiments, the sandstone contains 3-5% CaO by mass, 67-75% SiO2 by mass, 5-8% Al2O3 by mass, and 3-5% Fe2O3 by mass.

[0034] The chemical composition of sandstone, such as the content of CaO, SiO2, Al2O3 and Fe2O3, can affect the balance of oxides in cement raw materials, helping to ensure that the produced cement has a consistent chemical composition, improve product quality and stability, and play an important role in the strength and setting hardening properties of cement.

[0035] In some embodiments, the coal gangue contains 2-3% CaO by mass, 44-48% SiO2 by mass, 15-20% Al2O3 by mass, and 7-10% Fe2O3 by mass.

[0036] Using coal gangue as part of cement raw materials has a series of advantages, such as raw material diversity, cost reduction, formation of silicon, aluminum and iron compounds, oxide balance and sustainability.

[0037] In some embodiments, the iron tailings contain 6-10% CaO, 47-52% SiO2, 7-12% Al2O3, and 18-25% Fe2O3 by mass.

[0038] Using iron tailings in cement raw materials can effectively recover waste iron resources, reduce waste, and reduce the need for new iron ore mining, which is in line with the principle of sustainable resource utilization.

[0039] In some embodiments, the oxides of the raw meal of the cement clinker include: CaO: 58-66%, Al2O3: 4-7%, SiO2: 14-18%, Fe2O3: 3-5%.

[0040] The content of these oxides has a direct impact on the strength and hardening properties of cement. Among them, CaO (calcium oxide) is one of the main components of cement and is crucial for the cement hardening process; compounds such as Al2O3 (alumina), SiO2 (silicon dioxide) and Fe2O3 (iron oxide) can form silicate, ferrate and aluminate minerals in cement, which also play a key role in the strength and hardening properties of cement.

[0041] In some embodiments, the carbonaceous reducing agent includes one or more of coke, bituminous coal, and charcoal.

[0042] The use of a variety of carbonaceous reducing agents increases the flexibility of the production process. Different reducing agents can be selected and adjusted according to specific production needs to obtain the best clinker performance.

[0043] Furthermore, the main mineral composition of the clinker includes 27-32% C3S, 30-40% C2S, 5-8% C4A3S, 7-10% C4AF, and 8-12% Ca5F(AsO4)3.

[0044] C3S, C2S, and C4A3S may form cement creva mineral (CSH) cementitious material during cement calcination, which plays a key role in the hardening process and strength of cement, and has an important effect on the strength and hardening performance of cement; by adjusting their content, the hardening process of cement can be controlled.

[0045] Minerals containing Ca5F(AsO4)3 can improve the cement's resistance to sulfate attack, thereby increasing the durability of cement products.

[0046] This application also proposes a method for preparing low-carbon silicate cement clinker, comprising the low-carbon silicate cement clinker described in any of the above claims, wherein the raw materials are mixed evenly and then ground until the particle size reaches 15-18% residue on a 0.07-0.09 mm square hole sieve, and then calcined at a temperature of 1350-1400℃ for 30-40 minutes, and then cooled to room temperature to obtain low-carbon silicate cement clinker.

[0047] Specifically, the preparation method includes the following steps.

[0048] a. Mix the above raw materials in proportion, crush and grind them after mixing, and control the 80μm sieve residue of the powder after grinding to be within 15% to obtain powdered raw material;

[0049] b. After homogenizing the powdered raw material obtained in step s, add water and press it into cake-shaped raw material;

[0050] c. The cake-shaped raw material obtained in step b is calcined at 1350-1400℃ for 30-40 minutes and then cooled to room temperature to obtain low-carbon silicate cement clinker.

[0051] This method utilizes waste materials such as copper smelting sludge to replace some of the cement raw materials, which helps reduce carbon emissions. Furthermore, by lowering the calcination temperature and controlling the calcination time, energy consumption can also be reduced, thus achieving the production of low-carbon cement.

[0052] The firing temperature of this invention is 50-100°C lower than the firing temperature of traditional silicate cement clinker (1450°C), which reduces coal consumption without affecting the quality of silicate cement clinker.

[0053] Lower firing temperatures mean that less energy, especially coal, is needed during the calcination process, which helps reduce emissions of carbon dioxide and other greenhouse gases, contributing to addressing climate change and mitigating the environmental burden.

[0054] Calcination at 1100-1300℃ can effectively solidify the As element and heavy metals such as Cu, Zn, Gd, and Pb in copper smelting sludge.

[0055] Unless otherwise specified, the raw materials and equipment used in this application are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0056] Unless otherwise specified, the terms used in this specification have the same meaning as those commonly understood by those skilled in the art; however, in the event of any conflict, the definitions in this specification shall prevail.

[0057] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0058] The experimental raw materials used in this invention include copper smelting sludge, limestone, coal gangue and iron tailings, the composition of which is shown in Table 1-2.

[0059] Table 1 Chemical composition of experimental materials

[0060]

[0061] Table 2

[0062]

[0063] Example 1

[0064] Take 30 parts of dried copper smelting sludge, 50 parts of limestone, 9 parts of sandstone, 6 parts of coal gangue, 4 parts of iron tailings, and 1 part of carbonaceous reducing agent by weight and mix them. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. Add it to an electric furnace for calcination at 1390℃ for 35 minutes. Remove it and cool it in the atmosphere to obtain low-carbon silicate cement clinker.

[0065] Example 2

[0066] Take 32 parts of dried copper smelting sludge, 48 parts of limestone, 9 parts of sandstone, 6 parts of coal gangue, 4 parts of iron tailings, and 1 part of carbonaceous reducing agent by weight and mix them. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. After homogenization and forming into cakes, add them to an electric furnace for calcination at 1390℃ for 35 minutes. Remove and cool in the atmosphere to obtain low-carbon silicate cement clinker.

[0067] Example 3

[0068] Take 34 parts of dried copper smelting sludge, 46 parts of limestone, 9 parts of sandstone, 6 parts of coal gangue, 4 parts of iron tailings, and 1 part of carbonaceous reducing agent by weight and mix them. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. Add it to an electric furnace for calcination at 1390℃ for 35 minutes. Remove it and cool it in the atmosphere to obtain low-carbon silicate cement clinker.

[0069] Example 4

[0070] Take 36 parts of dried copper smelting sludge, 44 parts of limestone, 9 parts of sandstone, 6 parts of coal gangue, 4 parts of iron ore, and 1 part of carbonaceous reducing agent by weight and mix them. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. Add it to an electric furnace for calcination at 1390℃ for 35 minutes. Remove it and cool it in the atmosphere to obtain low-carbon silicate cement clinker.

[0071] Example 5

[0072] Take 38 parts of dried copper smelting sludge, 42 parts of limestone, 9 parts of sandstone, 6 parts of coal gangue, 4 parts of iron tailings, and 1 part of carbonaceous reducing agent by weight and mix them. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. Add it to an electric furnace for calcination at 1390℃ for 35 minutes. Remove it and cool it in the atmosphere to obtain low-carbon silicate cement clinker.

[0073] Comparative Example 1

[0074] Commercially available PO42.5 ordinary Portland cement was selected.

[0075] Comparative Example 2

[0076] Take 80 parts of dried limestone, 10 parts of sandstone, 6 parts of coal gangue and 4 parts of iron tailings by weight, grind them together until the particle size reaches 15% residue on a 0.08mm square hole sieve, homogenize and make into cakes, then put them into an electric furnace for calcination at 1450℃ for 35 minutes. Remove and cool in the atmosphere to obtain silicate cement clinker.

[0077] Comparative Example 3

[0078] Take 34 parts of dried copper smelting sludge, 46 parts of limestone, 15 parts of sandstone, 4 parts of iron tailings, and 1 part of carbonaceous reducing agent by weight. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. After homogenization and forming into cakes, add them to an electric furnace for calcination at 1390℃ for 35 minutes. Remove and cool in the atmosphere to obtain low-carbon silicate cement clinker.

[0079] Comparative Example 4

[0080] Take 34 parts of dried copper smelting sludge, 46 parts of limestone, 15 parts of coal gangue, 4 parts of iron tailings, and 1 part of carbonaceous reducing agent by weight. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. After homogenization and forming into cakes, add them to an electric furnace for calcination at 1390℃ for 35 minutes. Remove and cool in the atmosphere to obtain low-carbon silicate cement clinker.

[0081] Comparative Example 5

[0082] Take 34 parts of dried copper smelting sludge, 46 parts of limestone, 11 parts of coal gangue, 6 parts of iron tailings, and 1 part of carbonaceous reducing agent by weight. Grind the mixture until the particle size reaches 15% residue on a 0.08mm square hole sieve. After homogenization and forming into cakes, add them to an electric furnace for calcination at 1390℃ for 35 minutes. Remove and cool in the atmosphere to obtain low-carbon silicate cement clinker.

[0083] The cement clinker from the above embodiments and comparative examples 2-5 were each mixed with 5% gypsum powder and ground to a specific surface area of ​​380 m². 2 / kg cement. The above examples and comparative examples were tested for cement abrasion resistance, setting time and mortar strength according to GB / T 13693, GB / T 1346 and GB / T 17671. The main properties of the cement in the examples and comparative examples were tested and the carbon emissions were calculated. The main clinker mineral composition after calcination is shown in Table 3, and the main properties and carbon emissions are shown in Table 4.

[0084] Table 3

[0085]

[0086]

[0087] Table 4

[0088]

[0089]

[0090] The leaching toxicity of the low-carbon cement in each embodiment was determined and evaluated in accordance with GB / T 30810 "Determination of Leachable Heavy Metals in Cement Mortar" and GB 5085.3 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification". The content of leached heavy metals was also determined.

[0091] Table 5. Heavy metal content (mg / L) in leaching toxicity tests for each example.

[0092] Test No. Arsenic (As) Lead (Pb) Cadmium (Cd) Copper (Cu) Zinc (Zn) Limit 5 5 1 100 100 Example 1 0.141 0.166 0.035 0.067 2.156 Example 2 0.143 0.177 0.035 0.062 2.045 Example 3 0.148 0.172 0.038 0.065 2.189 Example 4 0.157 0.186 0.034 0.073 2.321 Example 5 0.159 0.175 0.033 0.087 2.356

[0093] As shown in Table 4, the low-carbon cement prepared in Examples 1-5 of this invention exhibits superior early 3-day and 28-day strengths compared to silicate cement without copper smelting sludge and commercially available PO42.5 ordinary silicate cement. Furthermore, the raw material usage involves less limestone, greater solid waste utilization, and lower calcination temperature, resulting in a carbon reduction of over 20% compared to the comparative silicate cement, demonstrating a significant low-carbon effect. In Comparative Example 3 of this invention, the complete replacement of coal gangue with sandstone leads to an excessive decrease in aluminum content and an increase in silica content in the cement raw material system. This reduces the formation of tricalcium aluminate minerals in the cement clinker, significantly lowering the early strength and delaying the setting time. In Comparative Example 4 of this invention, the complete replacement of sandstone with coal gangue also results in an excessive decrease in silica content and an increase in aluminum content in the cement raw material system. This leads to an excessive formation of tricalcium aluminate minerals in the cement clinker, reducing the formation of calcium silicate minerals. This results in an excessively short setting time, which is detrimental to construction, and also leads to excessively high early strength and low later strength. In Comparative Example 5 of this invention, iron tailings were not used, resulting in insufficient iron materials in the cement raw material system and a reduction in iron phase solid solution minerals in the cement clinker. This would lead to lower wear resistance of the cement and a significant decrease in its early flexural strength.

[0094] As shown in Table 5, the leaching rates of arsenic, copper, zinc, cadmium, and other heavy metals in the molten products are very low, all below the emission standards. High-temperature molten roasting not only causes some heavy metals to volatilize into the flue gas and re-condense, but also alters the form of some heavy metals, transforming them into more easily migratable forms and effectively solidifying arsenic and other heavy metals in copper smelting sludge, thus reducing the harm of copper tailings sludge to the ecological environment.

[0095] The technical features of the above-described embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The embodiments described above are merely illustrative of several implementations of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the appended claims.

Claims

1. A low-carbon silicate cement clinker, characterized in that, The low-carbon silicate cement clinker, by weight, comprises the following components: 25-40 parts copper smelting sludge, 40-55 parts limestone, 5-12 parts sandstone, 4-10 parts coal gangue, 3-8 parts iron tailings, and 0-3 parts carbonaceous reducing agent. The copper smelting sludge is copper sludge produced by treating acidic wastewater using the lime-neutralization precipitation method. Its composition, calculated by mass percentage, includes 55-70% CaSO4·xH2O, 6-10% CaCO3, 5-7% arsenate, and 1-3% hydroxides of Cu, Zn, Gd, and Pb.

2. The low-carbon silicate cement clinker according to claim 1, characterized in that, The low-carbon silicate cement clinker, by weight, comprises the following components: 30-38 parts copper smelting sludge, 42-50 parts limestone, 7-10 parts sandstone, 5-8 parts coal gangue, 4-7 parts iron tailings, and 1-2 parts carbonaceous reducing agent.

3. The low-carbon silicate cement clinker according to claim 2, characterized in that, The mass percentage of CaO in the copper smelting sludge is 43-46%, and the mass percentage of CaO in the limestone is 52-54%.

4. The low-carbon silicate cement clinker according to claim 2, characterized in that, The sandstone contains 3-5% CaO, 67-75% SiO2, 5-8% Al2O3, and 3-5% Fe2O3 by mass.

5. The low-carbon silicate cement clinker according to claim 2, characterized in that, The coal gangue contains 2-3% CaO, 44-48% SiO2, 15-20% Al2O3, and 7-10% Fe2O3 by mass.

6. The low-carbon silicate cement clinker according to claim 3, characterized in that, The iron tailings contain 6-10% CaO, 47-52% SiO2, 7-12% Al2O3, and 18-25% Fe2O3 by mass.

7. The low-carbon silicate cement clinker according to any one of claims 1-6, characterized in that, The oxides in the raw meal of the cement clinker include: CaO: 58-66%, Al2O3: 4-7%, SiO2: 14-18%, Fe2O3: 3-5%.

8. The low-carbon silicate cement clinker according to claim 1, characterized in that, The carbonaceous reducing agent includes one or more of coke, bituminous coal, and charcoal.

9. A method for preparing low-carbon silicate cement clinker, characterized in that, The low-carbon silicate cement clinker, as described in any one of claims 1-8, is obtained by uniformly mixing the raw materials and grinding them until the particle size reaches 15-18% residue on a 0.07-0.09mm square hole sieve, then calcining at 1350-1400℃ for 30-40 minutes, and cooling to room temperature.

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