A dry-process clinker cement and its preparation process

Abstract

The present application relates to the technical field of cement preparation, and specifically discloses a dry clinker cement and a preparation process thereof. A dry clinker cement comprises the following raw materials in parts by weight: 180-200 parts of limestone; 30-50 parts of iron ore tailings powder; 20-30 parts of coal gangue; 10-20 parts of fly ash; 5-8 parts of calcium fluoride; 5-8 parts of nano-silicon dioxide; 1-5 parts of nano-calcium carbonate; 1-5 parts of sodium sulfide; 1-5 parts of biochar-ferrous sulfate loading material; 100-200 parts of water; 5-20 parts of calcining aid; the biochar-ferrous sulfate loading material is obtained by loading ferrous sulfate on biochar particles. The dry clinker cement of the present application can effectively enhance the reducing activity and chromium removal efficiency of ferrous sulfate by the biochar-ferrous sulfate loading material, so that hexavalent chromium in cement can be efficiently removed with a small amount of ferrous sulfate, reducing costs while enabling cement to maintain good compressive strength.

Description

Technical Field

[0001] The present application relates to the technical field of cement preparation, and more specifically, to a dry-process clinker cement and a preparation process thereof. Background Art

[0002] In the cement production process, the selection and processing of raw materials are crucial. Limestone, clay, iron ore tailings, etc. are the main raw materials for cement production. They will undergo a series of complex chemical reactions under the oxidizing conditions of high-temperature rotary kilns. Among them, the trivalent chromium Cr(III) originally present in the raw materials will be converted into hexavalent chromium Cr(VI) under the action of high temperature and oxidizing atmosphere. Cr(VI) is a substance with extremely stable chemical properties. It is not easily biodegraded in nature and poses a potential threat to human health. Although its direct carcinogenicity requires further scientific research and confirmation under specific conditions, Cr(VI) can indeed cause allergic reactions or other adverse health effects in the human body through skin contact, inhalation or environmental exposure. Therefore, reducing the content of hexavalent chromium in cement is not only responsible for the health of workers, but also a guarantee for environmental safety.

[0003] To ensure the safety of cement products, the industry has strict control requirements for the content of water-soluble Cr(VI) in cement. To achieve this goal, the industry generally adopts the strategy of adding reducing agents to convert harmful Cr(VI) into relatively harmless Cr(III). Among the many reducing agent options, ferrous sulfate is highly favored due to its significant cost-effectiveness. However, ferrous sulfate has exposed some technical difficulties in its actual application. First, ferrous sulfate is relatively inefficient in reducing Cr(VI). To achieve the ideal chromium reduction effect, large quantities of ferrous sulfate are often required, which not only increases production costs but also significantly increases the SO3 content in cement. Excessive SO3 reacts with the aluminates in the cement to form ettringite. Etchingite may later be converted into monosulfide calcium sulfoaluminate hydrate, causing volume expansion and generating internal stress, thereby reducing the compressive strength of the cement. Summary of the Invention

[0004] In order to reduce the hexavalent chromium content in cement while ensuring that the cement has good compressive strength, the present application provides a dry clinker cement and a preparation process thereof.

[0005] The dry process clinker cement provided in this application adopts the following technical solution:

[0006] A dry process clinker cement comprising the following raw materials in parts by weight:

[0007] 180-200 parts of limestone;

[0008] 30-50 parts of iron ore tailings powder;

[0009] 20-30 parts of coal gangue;

[0010] 10-20 parts fly ash;

[0011] 5-8 parts of calcium fluoride;

[0012] 5-8 parts of nano silicon dioxide;

[0013] 1-5 parts of nano calcium carbonate;

[0014] 1-5 parts of sodium sulfide;

[0015] 1-5 parts of biochar-ferrous sulfate loading material;

[0016] 100-200 parts water;

[0017] 5-20 parts of sintering aid;

[0018] The biochar-ferrous sulfate loading material is obtained by loading ferrous sulfate on biochar particles.

[0019] By adopting the above technical solutions, using iron tailings powder and coal gangue as raw materials can effectively collect and utilize large amounts of solid waste, thereby improving the environmental friendliness of cement; calcium fluoride is used as a mineralizer to improve the formation conditions of clinker minerals and enhance cement strength; nano-SiO2 and nano-CaCO3 are used as nucleating agents to promote cement hydration reactions, thereby improving the early strength of cement. By adding special biochar-ferrous sulfate loading materials, the porous biochar material has rich micropores and mesopore structures, and these pores provide a good loading environment for ferrous sulfate. In an alkaline cement environment, Fe 2+ Easily oxidized to Fe 3+ , and the pore structure of porous biochar can limit Fe 2+ In addition, the functional groups on the surface of biochar (such as hydroxyl, carboxyl, etc.) may react with Fe 2+ Therefore, the porous biochar is loaded with Fe 2+ , which can slow down the Fe 2+ The release rate of ferrous sulfate can be reduced to avoid its rapid oxidation in an alkaline environment, thereby maintaining the activity of the reducing agent, reducing the actual amount of ferrous sulfate used, ensuring efficient chromium removal efficiency, and avoiding adverse effects on the compressive strength of cement.

[0020] The loaded biochar-ferrous sulfate material was prepared by 2+ Fixed in the pores and surface of biochar, effectively preventing Fe 2+ Oxidation during storage and use. The pore structure of biochar is Fe 2+It provides a relatively stable microenvironment and reduces its contact with oxygen. In addition, the dispersion of biochar also promotes the 2+ Uniform distribution in cement. When biochar-ferrous sulfate loading material is added to cement, Fe 2+ The biochar can be evenly distributed in the cement matrix as it is dispersed, thereby improving the uniformity and efficiency of the reduction reaction. This dispersion not only helps to reduce the content of Cr(VI), but also avoids local Fe 2+ Excessive use will lead to increased SO3 content and decreased cement strength.

[0021] In summary, the clinker cement made from the above raw materials can effectively enhance the reduction activity and chromium removal efficiency of ferrous sulfate through the biochar-ferrous sulfate loading material. Therefore, hexavalent chromium in cement can be efficiently removed with a smaller amount of ferrous sulfate, reducing costs while maintaining good compressive strength of cement.

[0022] Optionally, the method for preparing the biochar-ferrous sulfate loaded material comprises the following steps:

[0023] A. Add organic biomass into a heating furnace and perform pyrolysis under nitrogen protection for 3-5 hours. After the pyrolysis is completed, block biochar is obtained, and then the block biochar is crushed to obtain biochar particles;

[0024] B. Immersing the biochar particles in a nitric acid solution, and then adding nano-alumina powder to obtain a mixture, and then heating the mixture with ultrasonic treatment at a heating temperature of 50-60° C., an ultrasonic power of 300-500 W, and a treatment time of 3-5 hours. After the treatment is completed, the modified biochar particles are obtained by filtering, washing, and drying;

[0025] C. Add the modified biochar particles and ferrous sulfate to the ethanol solution, then heat it to 40-50°C and stir the mixture at a constant temperature for 30-60 minutes; then add the β-alanine solution and continue stirring the mixture until the solution system cools to room temperature. Then, filter the solution system, wash the solid, and dry it to obtain a biochar-ferrous sulfate loaded material.

[0026] By adopting the above technical solution, organic biomass is pyrolyzed to produce biochar blocks, which are then broken into biochar particles. This process not only recycles organic biomass but also reduces waste emissions, thus complying with environmental protection principles. Immersing the biochar particles in a nitric acid solution introduces negative charges, enhancing the adsorption capacity of the biochar surface. This step is crucial for the subsequent loading of ferrous sulfate, as it improves the biochar's ability to adsorb and fix ferrous sulfate. Adding nano-alumina powder and performing ultrasonic heating further enhances the specific surface area and pore structure of the biochar particles. The increase in specific surface area means more adsorption sites, while the optimized pore structure facilitates the uniform distribution and stable loading of ferrous sulfate. Through the above modification treatment, the surface properties and structure of the biochar particles are significantly improved, allowing them to load more ferrous sulfate. This structurally stable and well-loaded material can maintain high reduction activity and chromium removal efficiency in cement.

[0027] In step C, the addition of β-alanine solution can improve the dispersibility of ferrous sulfate in the ethanol solvent. This step ensures that ferrous sulfate is evenly distributed on the biochar particles, avoiding local excess or deficiency, thereby improving the overall performance and stability of the loaded material.

[0028] The resulting biochar-ferrous sulfate-loaded material exhibits excellent performance. It not only efficiently reduces hexavalent chromium in cement, but also maintains the cement's compressive strength. Furthermore, by reducing the amount of ferrous sulfate used, production costs are lowered.

[0029] Optionally, the organic biomass in step A includes one or more of plant straw, seed husks and feces.

[0030] By adopting the above technical solution, the biochar obtained by pyrolysis of these biomasses has a rich pore structure and a high specific surface area, which provides an ideal loading platform for the loading of ferrous sulfate, further enhancing the chromium removal ability of the biochar-ferrous sulfate loading material.

[0031] Optionally, the mass concentration of the nitric acid solution in step B is 10%-20%.

[0032] By adopting the above technical solution, the nitric acid solution in the above mass concentration range ensures the effect of biochar modification and the stability of subsequent ferrous sulfate loading, avoiding the adverse effects of excessively high or low concentration on material properties.

[0033] Optionally, the amount of nano-alumina added in step B is 2%-8% of the mass of the biochar particles.

[0034] By adopting this technical solution, the amount of nano-alumina added was optimized, which not only enhanced the biochar's pore structure and specific surface area but also provided more active sites for ferrous sulfate loading. This optimization allowed the ferrous sulfate to be more evenly distributed on the biochar, increasing its contact with hexavalent chromium and further improving chromium removal efficiency.

[0035] Optionally, in step C, the mass ratio of the modified biochar particles, ferrous sulfate and ethanol solution is 1:(0.01-0.03):5.

[0036] By adopting the above technical solution and controlling the mass ratio appropriately, the loading and dispersion of ferrous sulfate on biochar are ensured. This optimized loading and dispersion allows ferrous sulfate to react more fully with hexavalent chromium, thereby improving the rate and efficiency of chromium removal.

[0037] Optionally, the mass concentration of the ethanol solution in step C is 10%-30%; the mass concentration of the β-alanine solution is 5%-15%.

[0038] By adopting this technical solution, the concentrations of the ethanol solution and β-alanine solution are clearly defined, which facilitates the uniform dispersion and stable loading of ferrous sulfate on the biochar. This stable loading structure facilitates the sustained action of ferrous sulfate in the cement environment, avoiding the decrease in chromium removal efficiency caused by unstable loading.

[0039] The present application also provides a method for preparing dry-process clinker cement, which adopts the following technical solution:

[0040] A method for preparing dry clinker cement comprises the following steps:

[0041] S1, crushing and ball-milling limestone, iron ore tailings powder and coal gangue to obtain raw meal;

[0042] S2, adding water and a sintering aid to the raw material, stirring and compacting, calcining, and cooling to obtain clinker;

[0043] S3. Mixing the clinker with fly ash, calcium fluoride, nano-silicon dioxide, nano-calcium carbonate, sodium sulfide and biochar-ferrous sulfate loading material to obtain a clinker mixture, and then ball-milling the clinker mixture to obtain dry-process clinker cement.

[0044] In summary, this application has the following beneficial effects:

[0045] 1. This application uses large solid wastes such as iron tailings powder and coal gangue as raw materials for cement raw materials, which not only realizes the effective utilization of waste, but also significantly improves the environmental friendliness of cement. At the same time, by adding mineralizers and nucleating agents such as calcium fluoride, nano-silica, and nano-calcium carbonate, the formation conditions of clinker minerals are improved, and the hydration reaction of cement is promoted, thereby improving the early strength and overall performance of cement. What is more worth mentioning is that this application innovatively introduces biochar-ferrous sulfate loading materials, which have rich pore structures and high specific surface area, providing a good loading environment for ferrous sulfate and effectively slowing down the Fe 2+ The oxidation rate in an alkaline cement environment maintains the activity of the reducing agent. Therefore, the cement of the present application can efficiently remove hexavalent chromium from cement with a small amount of ferrous sulfate, which not only reduces production costs but also ensures that the compressive strength of the cement is not affected.

[0046] 2. The present application loads ferrous sulfate with biochar particles to ensure the efficient chromium removal performance of the biochar-ferrous sulfate loaded material. During the preparation process, the organic biomass is pyrolyzed to obtain block biochar, which is then crushed, modified, loaded and other steps to finally obtain a biochar-ferrous sulfate loaded material with a stable structure and sufficient load. Among them, the modification treatment with nitric acid solution introduces negative charges and enhances the adsorption capacity of the biochar surface; the addition of nano-alumina further optimizes the pore structure and specific surface area of ​​the biochar; the addition of β-alanine solution improves the dispersibility and stability of ferrous sulfate on biochar. The combined effect of these steps enables the loaded material to maintain efficient reduction activity and chromium removal efficiency in cement, thereby achieving efficient removal of hexavalent chromium.

[0047] 3. The dry-process clinker cement preparation method of the present application is simple, feasible, and easy to industrialize. Raw materials such as limestone, iron ore tailings powder, and coal gangue are crushed and ball-milled to obtain raw materials, and then water and burning aids are added to stir, compact, and calcine to obtain clinker. The clinker is then mixed with fly ash, calcium fluoride, nano-silicon dioxide, nano-calcium carbonate, sodium sulfide, and biochar-ferrous sulfate loading materials and ball-milled to obtain dry-process clinker cement. During the entire preparation process, raw materials are easily available, the process is simple, and energy consumption is low, and the prepared cement has excellent performance and environmental friendliness. Therefore, the cement preparation method of the present application has broad application prospects and market value. DETAILED DESCRIPTION

[0048] The present application is further described in detail below with reference to the embodiments.

[0049] Preparation example of biochar-ferrous sulfate loaded material

[0050] Preparation Example 1

[0051] The biochar-ferrous sulfate loading material is prepared by the following method:

[0052] A. Add organic biomass into a heating furnace and perform pyrolysis under nitrogen protection for 3 hours at a pyrolysis temperature of 500°C. After the pyrolysis is completed, block biochar is obtained, which is then crushed to obtain biochar particles.

[0053] B. Immerse 1 kg of biochar particles in a 10% mass concentration nitric acid solution, then add 0.02 kg of nano-alumina powder to obtain a mixture, and then heat and ultrasonicate the mixture at a heating temperature of 50°C, an ultrasonic power of 300 W, and a treatment time of 3 hours. After the treatment, the modified biochar particles are obtained by filtering, washing, and drying;

[0054] C. Mix 1 kg of modified biochar particles, 0.01 kg of ferrous sulfate and 5 kg of 10% ethanol solution, then heat to 40°C and stir at constant temperature for 30 minutes; then add 0.1 kg of 5% β-alanine solution, continue stirring and react until the solution system cools to room temperature, then filter the solution system, wash and dry the solid to obtain a biochar-ferrous sulfate loaded material.

[0055] Preparation Example 2

[0056] The biochar-ferrous sulfate loading material is prepared by the following method:

[0057] A. Add organic biomass into a heating furnace and perform pyrolysis under nitrogen protection for 4 hours at a pyrolysis temperature of 500°C. After the pyrolysis is completed, block biochar is obtained, which is then crushed to obtain biochar particles.

[0058] B. Immerse 1 kg of biochar particles in a 15% mass concentration nitric acid solution, then add 0.05 kg of nano-alumina powder to obtain a mixture, and then heat and ultrasonicate the mixture at a heating temperature of 55°C, an ultrasonic power of 400 W, and a treatment time of 4 hours. After the treatment, the modified biochar particles are obtained by filtering, washing, and drying;

[0059] C. Mix 1 kg of modified biochar particles, 0.02 kg of ferrous sulfate and 5 kg of 20% ethanol solution, then heat to 45°C and stir at constant temperature for 50 minutes; then add 0.1 kg of 10% β-alanine solution, continue stirring and react until the solution system cools to room temperature, then filter the solution system, wash the solid, and dry it to obtain a biochar-ferrous sulfate loaded material.

[0060] Preparation Example 3

[0061] The biochar-ferrous sulfate loading material is prepared by the following method:

[0062] A. Add organic biomass into a heating furnace and perform pyrolysis under nitrogen protection for 5 hours at a pyrolysis temperature of 500°C. After the pyrolysis is completed, block biochar is obtained, which is then crushed to obtain biochar particles.

[0063] B. Immerse 1 kg of biochar particles in a 20% mass concentration nitric acid solution, then add 0.08 kg of nano-alumina powder to obtain a mixture, and then heat and ultrasonicate the mixture at a heating temperature of 60°C, an ultrasonic power of 500 W, and a treatment time of 5 hours. After the treatment, the modified biochar particles are obtained by filtering, washing, and drying;

[0064] C. Mix 1 kg of modified biochar particles, 0.03 kg of ferrous sulfate and 5 kg of 30% ethanol solution, then heat to 45°C and stir at constant temperature for 50 minutes; then add 0.1 kg of 15% β-alanine solution, continue stirring and react until the solution system cools to room temperature, then filter the solution system, wash and dry the solid to obtain a biochar-ferrous sulfate loaded material.

[0065] Preparation Example 4

[0066] The biochar-ferrous sulfate supported material is different from Preparation Example 3 in that the biochar particles are not modified in this Preparation Example. The specific preparation method is as follows:

[0067] A. Add organic biomass into a heating furnace and perform pyrolysis under nitrogen protection for 5 hours at a pyrolysis temperature of 500°C. After the pyrolysis is completed, block biochar is obtained, which is then crushed to obtain biochar particles.

[0068] B. Mix 1 kg of biochar particles, 0.03 kg of ferrous sulfate and 5 kg of 30% ethanol solution, then heat to 45°C and stir at constant temperature for 50 minutes; then add 0.1 kg of 15% β-alanine solution, continue stirring and react until the solution system cools to room temperature, then filter the solution system, wash the solid, and dry it to obtain a biochar-ferrous sulfate loaded material.

[0069] Preparation Example 5

[0070] The biochar-ferrous sulfate loaded material is different from Preparation Example 3 in that no β-alanine solution is added in Step C of this Preparation Example.

[0071] Preparation Example 6

[0072] The biochar-ferrous sulfate loading material is different from that of Preparation Example 3 in that the amount of ferrous sulfate used in step C of this Preparation Example is 0.1 kg.

[0073] Example

[0074] Example 1

[0075] A dry-process clinker cement, the raw material components and usage are shown in Table 1, wherein the biochar-ferrous sulfate loading material is the biochar-ferrous sulfate loading material prepared in Preparation Example 1, and the sintering aid is potassium nitrate.

[0076] A dry process clinker cement is prepared by the following method:

[0077] S1, crushing and ball-milling limestone, iron ore tailings powder and coal gangue to obtain raw meal;

[0078] S2. Add water and sintering aid to the raw material, stir and compact, calcine at 1300°C for 60 minutes, and cool to obtain clinker;

[0079] S3. Mixing the clinker with fly ash, calcium fluoride, nano-silicon dioxide, nano-calcium carbonate, sodium sulfide and biochar-ferrous sulfate loading material to obtain a clinker mixture, and then ball-milling the clinker mixture to obtain dry-process clinker cement.

[0080] Example 2

[0081] A dry-process clinker cement, the raw material components and amounts of which are shown in Table 1, wherein the biochar-ferrous sulfate loading material is the biochar-ferrous sulfate loading material prepared in Preparation Example 2, and the sintering aid is sodium nitrate.

[0082] A dry process clinker cement is prepared by the following method:

[0083] S1, crushing and ball-milling limestone, iron ore tailings powder and coal gangue to obtain raw meal;

[0084] S2. Add water and sintering aid to the raw material, stir and compact, calcine at 1350°C for 50 minutes, and cool to obtain clinker;

[0085] S3. Mixing the clinker with fly ash, calcium fluoride, nano-silicon dioxide, nano-calcium carbonate, sodium sulfide and biochar-ferrous sulfate loading material to obtain a clinker mixture, and then ball-milling the clinker mixture to obtain dry-process clinker cement.

[0086] Example 3

[0087] A dry-process clinker cement, the raw material components and usage are shown in Table 1, wherein the biochar-ferrous sulfate loading material is the biochar-ferrous sulfate loading material prepared in Preparation Example 3, and the sintering aid is sodium nitrate.

[0088] A dry process clinker cement is prepared by the following method:

[0089] S1, crushing and ball-milling limestone, iron ore tailings powder and coal gangue to obtain raw meal;

[0090] S2. Add water and sintering aid to the raw material, stir and compact, calcine at 1400°C for 30 minutes, and cool to obtain clinker;

[0091] S3. Mixing the clinker with fly ash, calcium fluoride, nano-silicon dioxide, nano-calcium carbonate, sodium sulfide and biochar-ferrous sulfate loading material to obtain a clinker mixture, and then ball-milling the clinker mixture to obtain dry-process clinker cement.

[0092] Table 1 Raw material components and dosage of cement in Examples 1-3 (kg)

[0093]

[0094] Example 4

[0095] A dry process clinker cement is different from Example 1 in that the biochar-ferrous sulfate loading material in this embodiment is the biochar-ferrous sulfate loading material of Preparation Example 4.

[0096] Example 5

[0097] A dry process clinker cement is different from Example 1 in that the biochar-ferrous sulfate loading material in this embodiment is the biochar-ferrous sulfate loading material of Preparation Example 5.

[0098] Example 6

[0099] A dry-process clinker cement is different from Example 1 in that the biochar-ferrous sulfate loading material in this embodiment is the biochar-ferrous sulfate loading material of Preparation Example 6.

[0100] Comparative Example

[0101] Comparative Example 1

[0102] Conch brand ordinary Portland cement was purchased from Anhui Xuancheng Conch Cement Co., Ltd.

[0103] Comparative Example 2

[0104] A dry process clinker cement is different from Example 1 in that an equal amount of ferrous sulfate is used instead of the biochar-ferrous sulfate loading material in this comparative example.

[0105] Comparative Example 3

[0106] A dry process clinker cement is different from Example 1 in that equal amounts of limestone are used instead of nano-silicon dioxide and nano-calcium carbonate in this comparative example.

[0107] Performance testing

[0108] Experiment 1

[0109] The cements of Examples 1-6 and Comparative Examples 1-3 of this application were tested for their water-soluble chromium (VI) content. The specific testing method was based on the requirements of GB31893-2015, "Limits and Determination of Water-Soluble Chromium (VI) in Cement." The sample was prepared by mixing 450g of cement, 1350g of Chinese ISO standard sand, and 225mL of water. Two tests were performed, and the average of the two experimental results is presented as the test result. The test results for the water-soluble chromium (VI) content of the environmentally friendly cements produced in this application are shown in Table 2.

[0110] Experiment 2

[0111] The 28d compressive strength of the cement of Examples 1-6 and Comparative Examples 1-3 of the present application was tested. The specific test method was based on GB / T17671-2020 "Test method for strength of cement mortar (ISO method)" to measure the 28d compressive strength of clinker cement. The test results are shown in Table 2.

[0112] Table 2 Test results

[0113]

[0114] From the above test results, it can be seen that the water-soluble chromium (VI) content in the cement of Examples 1-3 is less than 2.25 mg / kg, far below the standard limit, and the compressive strength reaches more than 58.5 MPa, showing good physical properties. This shows that the use of biochar-ferrous sulfate loading material as a reducing agent can not only effectively reduce the content of water-soluble chromium (VI) in cement, but also keep the compressive strength of cement unaffected. The biochar-ferrous sulfate loading material provides a good loading environment for ferrous sulfate through the pore structure of porous biochar, slows down the oxidation rate of Fe²⁺ in the alkaline cement environment, maintains the activity of the reducing agent, and thus achieves an efficient chromium removal effect. Because the biochar-ferrous sulfate loading material can efficiently reduce Cr (VI), the actual amount of ferrous sulfate used is reduced, thereby reducing the content of SO3 in cement, avoiding the reaction of excessive SO3 with aluminates in cement to form ettringite, thereby ensuring that the compressive strength of cement is not affected.

[0115] From the correspondence between Examples 4-6 and the preparation examples, it can be seen that the difference in preparation methods has a significant impact on the performance of the biochar-ferrous sulfate supported material.

[0116] The biochar-ferrous sulfate loading material in Example 4 was not modified during preparation, so the adsorption and fixation capacity of biochar on ferrous sulfate was poor, resulting in a decrease in the chromium removal effect of the biochar-ferrous sulfate loading material, and the compressive strength was also reduced. β-alanine solution was not added in Example 5, which also affected the dispersibility and stability of the loading material, resulting in a poor chromium removal efficiency of the biochar-ferrous sulfate loading material. In Example 6, the amount of ferrous sulfate was too much, and although the chromium removal effect was better, it resulted in an increase in SO3 content, which affected the compressive strength of the cement.

[0117] Comparative Example 1 is ordinary Portland cement, which has a high water-soluble chromium (VI) content and a low compressive strength, indicating that cement without special treatment is difficult to meet environmental protection and performance requirements.

[0118] Comparative Example 2 uses an equal amount of ferrous sulfate instead of the biochar-ferrous sulfate loading material. Although it can reduce the water-soluble chromium (VI) content, the large amount used results in a large amount of SO3 residue and a significant decrease in compressive strength.

[0119] Comparative Example 3 uses an equal amount of limestone to replace nano-silica and nano-calcium carbonate. Although it has little effect on the chromium removal effect, it significantly reduces the compressive strength of cement, indicating that the addition of nanomaterials plays an important role in improving cement performance.

[0120] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A dry process clinker cement, characterized in that: The raw materials include the following parts by weight: 180-200 parts of limestone; 30-50 parts of iron ore tailings powder; 20-30 parts of coal gangue; 10-20 parts of fly ash; 5-8 parts of calcium fluoride; 5-8 parts of nano-silicon dioxide; 1-5 parts of nano-calcium carbonate; 1-5 parts of sodium sulfide; 1-5 parts of biochar-ferrous sulfate loading material; 100-200 parts of water; 5-20 parts of sintering aid; The preparation method of the biochar-ferrous sulfate loaded material comprises the following steps: A. Add organic biomass into a heating furnace and perform pyrolysis under nitrogen protection for 3-5 hours. After the pyrolysis is completed, block biochar is obtained, and then the block biochar is crushed to obtain biochar particles; B. Immersing the biochar particles in a nitric acid solution, and then adding nano-alumina powder to obtain a mixture, and then heating the mixture with ultrasonic treatment at a heating temperature of 50-60° C., an ultrasonic power of 300-500 W, and a treatment time of 3-5 hours. After the treatment is completed, the modified biochar particles are obtained by filtering, washing, and drying; C. Add the modified biochar particles and ferrous sulfate to the ethanol solution, then heat it to 40-50°C and stir the mixture at a constant temperature for 30-60 minutes; then add the β-alanine solution and continue stirring the mixture until the solution system cools to room temperature. Then, filter the solution system, wash the solid, and dry it to obtain a biochar-ferrous sulfate loaded material.

2. The dry process clinker cement according to claim 1, characterized in that: The organic biomass in step A includes one or more of plant straw, seed husks and feces.

3. The dry process clinker cement according to claim 1, characterized in that: The mass concentration of the nitric acid solution in step B is 10%-20%.

4. The dry process clinker cement according to claim 1, characterized in that: In step B, the amount of nano-alumina added is 2%-8% of the mass of the biochar particles.

5. The dry process clinker cement according to claim 1, characterized in that: In step C, the mass ratio of the modified biochar particles, ferrous sulfate, and ethanol solution is 1:(0.01-0.03):

5.

6. The dry process clinker cement according to claim 1, characterized in that: In step C, the mass concentration of the ethanol solution is 10%-30%; the mass concentration of the β-alanine solution is 5%-15%.

7. A method for preparing dry-process clinker cement according to any one of claims 1 to 6, characterized in that: The steps include: S1, crushing and ball-milling limestone, iron ore tailings powder and coal gangue to obtain raw meal; S2, adding water and a sintering aid to the raw material, stirring and compacting, calcining, and cooling to obtain clinker; S3. Mixing the clinker with fly ash, calcium fluoride, nano-silicon dioxide, nano-calcium carbonate, sodium sulfide and biochar-ferrous sulfate loading material to obtain a clinker mixture, and then ball-milling the clinker mixture to obtain dry-process clinker cement.

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