A cement production process for reducing carbon emissions

Abstract

The present invention provides a cement production process for reducing carbon emissions, belonging to the field of cement technology, and comprising the following steps: immersing zeolite in an aqueous solution of NH4HCO3, standing still under vacuum, and filtering to obtain zeolite loaded with ammonium bicarbonate; adding β-type hemihydrate gypsum to a mixed solution of myristic acid and methanol, stirring, filtering under vacuum, and drying to obtain myristic acid-modified phosphogypsum; uniformly mixing β-type hemihydrate gypsum, limestone, eggshell powder, bauxite, and water, pressing into a mold, drying, heating to 1250 °C for calcination, cooling, and grinding to obtain calcium sulfoaluminate clinker; uniformly mixing calcium sulfoaluminate clinker, dicalcium silicate, myristic acid-modified phosphogypsum, zeolite loaded with ammonium bicarbonate, polycarboxylate superplasticizer, defoaming agent, and malic acid to obtain cement. The present invention can reduce carbon emissions during cement production while improving the durability and compressive strength of cement.

Description

Technical Field

[0001] The present invention relates to the technical field of cement, and specifically relates to a cement production process for reducing carbon emissions. Background Art

[0002] The problem of greenhouse gas emissions has become the focus of attention in the world today. Reducing greenhouse gas emissions is no longer a simple issue of climate change; it will involve various aspects such as politics and economy of countries around the world. The cement industry is a major emitter of CO2, with its emissions accounting for about 5% of the total CO2 generated by human activities. The global cement industry must overcome the issue of CO2 emissions reduction in its future development. The cement industry has currently been listed as a key area that must carry out low-carbon governance by the country.

[0003] In the production of cement clinker, fuel-related CO2 emissions account for 1 / 3. Therefore, there is great potential to reduce CO2 emissions by using alternative fuels. Ordinary Portland cement (OPC) is used in various types of buildings due to its good mechanical properties. However, the production of OPC requires a large amount of energy and non-renewable minerals, and a large amount of CO2 is emitted into the atmosphere during the calcination process at high temperature (2000°C). Several low-carbon cement alternatives have been proposed, such as belite-rich cement, magnesium cement, carbonizable calcium silicate cement, calcium sulfoaluminate cement, and geopolymers, etc.

[0004] CN118993590A discloses a phosphogypsum-based cement. A large amount of phosphogypsum is used in this phosphogypsum cement to replace limestone in traditional cement, achieving the resource utilization of phosphogypsum waste while reducing the carbon dioxide generated during the calcination process of limestone, and having good workability and strong plasticity. However, the water content in phosphogypsum is relatively high, which will affect the stability and hardening effect of the cement, and the poor waterproof property leads to poor durability, and cracks are likely to appear after long-term use.

[0005] Therefore, it is necessary to provide a cement production process for reducing carbon emissions to solve the problems existing in the above-mentioned prior art. Summary of the Invention

[0006] In view of this, the present invention provides a cement production process for reducing carbon emissions, which can reduce carbon emissions during cement production while improving the durability and compressive strength of the cement.

[0007] To achieve the above object, the present invention provides a cement production process for reducing carbon emissions, including the following steps:

[0008] S1. Immerse zeolite in an aqueous solution of NH4HCO3, stand still under vacuum, and filter to obtain zeolite loaded with ammonium bicarbonate;

[0009] S2. Add β - hemihydrate gypsum into the mixed solution of myristic acid and methanol, stir, filter under vacuum, and dry to obtain myristic acid - modified phosphogypsum;

[0010] S3. Uniformly mix β - hemihydrate gypsum, limestone, eggshell powder, bauxite and water, press into shape, dry, heat to 1250 °C for calcination, then cool and grind to obtain calcium sulfoaluminate clinker;

[0011] S4. Uniformly mix calcium sulfoaluminate clinker, dicalcium silicate, myristic acid - modified phosphogypsum, zeolite loaded with ammonium bicarbonate, polycarboxylate superplasticizer, defoamer, and malic acid to obtain cement.

[0012] In industrial production, a large amount of untreated phosphogypsum not only occupies a large amount of land resources but also causes serious environmental pollution to soil, water and the atmosphere. The present invention uses phosphogypsum to replace natural gypsum to produce calcium sulfoaluminate clinker as a part of the base material in cement. P2O5 in phosphogypsum promotes the formation of calcium sulfoaluminate clinker; in addition, the structure of calcium carbonate in eggshells is trigonal calcite, the same as that of limestone, and it has similar properties to limestone. Therefore, eggshell powder waste is used to replace a part of limestone to realize the resource utilization of waste. And in the process of producing calcium sulfoaluminate clinker, the calcination temperature can be carried out at 1250 °C, which further reduces the sintering temperature and coal consumption, and thus reduces the carbon emission in the production of cement clinker.

[0013] The present invention uses dicalcium silicate as another part of the cement base material. Dicalcium silicate, as carbonatable calcium silicate cement, has the ability of carbonation. In the carbonation process, dicalcium silicate reacts with CO2 in the air to generate stable calcium carbonate. This reaction can absorb CO2 in the atmosphere. After solidification, it not only no longer releases CO2 but also can store CO2. However, due to the need to absorb external CO2, that is, the diffusion reaction from the surface to the core is hindered by the outer - layer carbonation products, which hinders the further penetration of CO2, resulting in insufficient carbonation in the core of the material and limiting the enhancement of the overall mechanical properties. Therefore, porous zeolite loaded with ammonium bicarbonate is added here to continuously provide CO3 2- , promoting the internal carbonation of dicalcium silicate and increasing the overall compressive strength of the cement.

[0014] The myristic acid-modified phosphogypsum prepared by the present invention is added to cement, which makes up for the disadvantage of poor water resistance of phosphogypsum and improves the hydrophobicity and thermal stability of the overall cement material. And malic acid is added as an additive in the cement, which can combine with the excess calcium ions in the cement to form a stable complex. This complex will adsorb on the surface of the cement material to form a protective layer, effectively slowing down the dissolution rate of the cement, thereby slowing down the early hydration reaction of the cement and avoiding the situation of insufficient concrete strength caused by excessive hydration. By delaying the setting time, the cement reaches a higher degree of hydration, thereby reducing the demand for the total amount of cement, indirectly reducing the consumption of cement, and also reducing the carbon emissions generated during the cement production process from the source.

[0015] Optionally, in step S1, the zeolite is dried at 80 °C for 24 h, naturally cooled, and then immersed in a beaker containing an aqueous NH4HCO3 solution. The beaker is placed in a vacuum chamber, and the air is evacuated by a vacuum pump until the vacuum degree reaches less than 20 Pa. After standing for 6 h, it is filtered, and the solution on the surface of the zeolite is wiped with a wet cloth soaked in the aqueous NH4HCO3 solution to obtain zeolite loaded with ammonium bicarbonate.

[0016] Optionally, the molar concentration of the aqueous NH4HCO3 solution is 0.5 - 2.0 mol / L.

[0017] Optionally, in step S2, the β-type hemihydrate gypsum is prepared by washing phosphogypsum and heating it for dehydration at 150 °C.

[0018] Optionally, in step S2, the β-type hemihydrate gypsum is ground into powder, added to a mixed solution of myristic acid and methanol, stirred for 30 - 60 min until the pH is 6.8 - 7.2, then filtered using a filter screen under a vacuum environment, and dried at 60 °C to obtain myristic acid-modified phosphogypsum; wherein, the mass fraction ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol is 1:7.

[0019] The present invention uses myristic acid to modify β-type hemihydrate gypsum. Myristic acid combines with the calcium ions on the surface of β-type hemihydrate gypsum to form calcium myristate, thereby forming a hydrophobic film, further improving the hydrophobicity of the overall cement material and enhancing the overall durability.

[0020] Optionally, in step S3, the β-type hemihydrate gypsum, limestone, eggshell powder and bauxite are mixed, added with water and uniformly mixed, formed under a pressure of 8 MPa, dried at 50 °C, and then heated to 1250 °C at a rate of 10 °C / min and calcined for 1 h, cooled, and ground to a specific surface area of 400 ± 10 m 2 / kg to obtain calcium sulfoaluminate clinker.

[0021] Optionally, heat-treated bamboo sawdust is also added before stirring in step S4.

[0022] Optionally, the heat-treated bamboo sawdust is prepared by heating bamboo sawdust to 100 °C at -0.1 MPa and holding for 1 h, then heating to 160 °C at a heating rate of 10 °C / min, cooling to 40 °C at 10 °C / min, placing it in a dryer to cool to room temperature, and screening out 20 mesh with a vibrating screen.

[0023] In the present invention, the surface of bamboo sawdust is modified by heat treatment. After heat treatment, the hydroxyl groups on the fiber surface in the bamboo sawdust decrease, hemicellulose degrades, and lignin is partially dehydrated, thereby promoting the rearrangement of fibers to improve the bonding strength between the fibers and the cement matrix and further effectively improving the flexural strength of the cement-based material. In addition, heat treatment removes some soluble sugars, which not only improves the interfacial compatibility between bamboo sawdust and cement, but also improves the alkali corrosion resistance of bamboo sawdust, thereby improving the durability of the overall components. At the same time, bamboo fibers themselves can sequester carbon, fix part of the carbon when mixed with cement, achieve a certain degree of carbon sequestration, and reduce carbon emissions.

[0024] Optionally, the stirring time in step S4 is 30 min; the defoaming agent is one of polyether defoaming agent and silicone defoaming agent; the model of the polyether defoaming agent is preferably PX-130, and the model of the silicone defoaming agent is preferably PX-122.

[0025] Optionally, the cement comprises the following raw materials in parts by mass: 300 - 350 parts of calcium sulfoaluminate clinker, 200 - 300 parts of dicalcium silicate, 90 - 120 parts of myristic acid-modified phosphogypsum, 22 - 28 parts of heat-treated bamboo sawdust, 20 - 25 parts of porous zeolite loaded with ammonium bicarbonate, 5 - 7 parts of polycarboxylate superplasticizer, 1.5 parts of defoaming agent, and 12 - 24 parts of malic acid.

[0026] The above technical solutions of the present invention have at least the following beneficial effects:

[0027] 1. In the present invention, phosphogypsum is used to replace natural gypsum to produce calcium sulfoaluminate clinker as a part of the base material in cement. P2O5 in phosphogypsum promotes the formation of calcium sulfoaluminate clinker. In addition, eggshells are used to replace a large amount of limestone to realize the resource utilization of waste. And in the process of producing calcium sulfoaluminate clinker, the calcination temperature is carried out at 1250 °C, reducing the sintering temperature and coal consumption, and thus reducing carbon emissions in the production of cement clinker.

[0028] 2. The present invention uses dicalcium silicate as another part of the cement base material. As a carbonizable dicalcium silicate cement, dicalcium silicate has the ability of carbonization. Dicalcium silicate can absorb CO2 in the atmosphere to form stable calcium carbonate to achieve negative carbon emissions. And in order to make the carbonization inside the material core sufficient, porous zeolite loaded with ammonium bicarbonate is added to continuously provide CO3 2- , promoting the internal carbonization of dicalcium silicate and improving the overall compressive strength of the cement.

[0029] 3. When the myristic acid-modified phosphogypsum prepared by the present invention is added to cement, it makes up for the disadvantage of poor water resistance of phosphogypsum, and improves the hydrophobicity and thermal stability of the overall cement material. And adding malic acid as an additive to the cement can combine with the excess calcium ions in the cement to form a stable complex, thereby slowing down the early hydration reaction of the cement and improving the overall strength of the cement material; by delaying the setting time, the cement reaches a higher degree of hydration, thereby reducing the demand for the total amount of cement, and reducing the carbon emissions generated during the cement production process from the source. Specific Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are part of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention fall within the scope of protection of the present invention.

[0031] Example 1

[0032] Put 100 parts of bamboo sawdust into a vacuum drying oven. After heating to 100 °C at -0.1 MPa and holding for 1 h, heat it to 160 °C at a heating rate of 10 °C / min, then cool it to 40 °C at 10 °C / min, put it into a dryer and cool it to room temperature, and then use a vibrating screen to screen out 20 meshes to obtain heat-treated bamboo sawdust.

[0033] Dry zeolite at 80 °C for 24 h, and after natural cooling, immerse the zeolite in a beaker containing an aqueous solution of 2.0 mol / L NH4HCO3. Then place the beaker in a vacuum chamber and evacuate the air through a vacuum pump until the vacuum degree reaches below 20 Pa. Let the beaker stand for 6 h, then filter it using a filter screen, and wipe the solution on the surface of the zeolite with a wet cloth soaked in an aqueous solution of 2.0 mol / L NH4HCO3 to obtain zeolite loaded with ammonium bicarbonate.

[0034] Wash 500 parts of phosphogypsum to remove residual acid, and heat and dehydrate it into β-type hemihydrate gypsum at 150 °C; grind 250 parts of β-type hemihydrate gypsum into powder, add it to a mixed solution of 800 parts of myristic acid and methanol, stir for 50 min until the pH is 7.0, then filter it using a filter screen in a vacuum environment, and dry it at 60 °C to obtain myristic acid-modified phosphogypsum; wherein, the mass ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol is 1:7.

[0035] After mixing 110 parts of β - hemihydrate gypsum, 50 parts of limestone, 60 parts of eggshell powder and 210 parts of bauxite, 80 parts of water was added and mixed evenly. After molding under a pressure of 8 MPa and drying the molded specimen in an oven at 50 °C, it was calcined in a high - temperature electric furnace at a heating rate of 10 °C / min to 1250 °C for 1 h, taken out of the furnace, quickly cooled with a blower, and then ground to a specific surface area of 400 ± 10 m 2 / kg to obtain calcium sulfoaluminate clinker. 300 parts of calcium sulfoaluminate clinker, 300 parts of dicalcium silicate, 110 parts of myristic acid - modified phosphogypsum, 25 parts of heat - treated bamboo sawdust, 22 parts of zeolite loaded with ammonium bicarbonate, 6 parts of polycarboxylate superplasticizer, 1.5 parts of polyether defoamer (PX - 130), and 18 parts of malic acid were stirred for 30 min to prepare cement.

[0036] Example 2

[0037] 100 parts of bamboo sawdust was put into a vacuum drying oven, heated to 100 °C at - 0.1 MPa and kept for 1 h, then heated to 160 °C at a heating rate of 10 °C / min, cooled to 40 °C at a rate of 10 °C / min, cooled to room temperature in a dryer, and screened through a 20 - mesh sieve to obtain heat - treated bamboo sawdust.

[0038] The zeolite was dried at 80 °C for 24 h and cooled naturally. After the zeolite was immersed in a beaker containing 1.0 mol / L NH4HCO3 aqueous solution, the beaker was placed in a vacuum chamber, and air was evacuated by a vacuum pump until the vacuum degree reached less than 20 Pa. After the beaker was allowed to stand for 6 h, it was filtered using a filter screen, and the solution on the surface of the zeolite was wiped with a wet cloth soaked with 1.0 mol / L NH4HCO3 aqueous solution to obtain zeolite loaded with ammonium bicarbonate.

[0039] 500 parts of phosphogypsum was washed to remove residual acid and heated and dehydrated to β - hemihydrate gypsum at 150 °C; 250 parts of β - hemihydrate gypsum was ground into powder and added to a mixed solution of 800 parts of myristic acid and methanol, stirred for 60 min until the pH reached 7.0, then filtered using a filter screen in a vacuum environment and dried at 60 °C to obtain myristic acid - modified phosphogypsum; among them, the mass ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol was 1:7.

[0040] After mixing 110 parts of β - hemihydrate gypsum, 50 parts of limestone, 60 parts of eggshell powder and 210 parts of bauxite, 80 parts of water was added and mixed evenly. After molding under a pressure of 8 MPa and drying the molded specimen in an oven at 50 °C, it was calcined in a high - temperature electric furnace at a heating rate of 10 °C / min to 1250 °C for 1 h, taken out of the furnace, quickly cooled with a blower, and then ground to a specific surface area of 400 ± 10 m 2Calcium sulfoaluminate clinker was prepared after calcination at [specific temperature] / kg. 350 parts of calcium sulfoaluminate clinker, 200 parts of dicalcium silicate, 120 parts of myristic acid-modified phosphogypsum, 28 parts of heat-treated bamboo sawdust, 20 parts of zeolite loaded with ammonium bicarbonate, 7 parts of polycarboxylate superplasticizer, 1.5 parts of silicone defoamer (PX-122), and 24 parts of malic acid were stirred for 30 min to obtain cement.

[0041] Example 3

[0042] 100 parts of bamboo sawdust were placed in a vacuum drying oven. After heating to 100 °C at -0.1 MPa and holding for 1 h, it was heated to 160 °C at a heating rate of 10 °C / min, then cooled to 40 °C at a rate of 10 °C / min, cooled to room temperature in a dryer, and sieved through a 20-mesh sieve to obtain heat-treated bamboo sawdust.

[0043] The zeolite was dried at 80 °C for 24 h and cooled naturally. Then the zeolite was immersed in a beaker containing an aqueous solution of 0.5 mol / L NH4HCO3. The beaker was placed in a vacuum chamber, and air was evacuated by a vacuum pump until the vacuum degree reached below 20 Pa. After allowing the beaker to stand for 6 h, it was filtered using a filter mesh, and the solution on the surface of the zeolite was wiped with a wet cloth soaked in an aqueous solution of 0.5 mol / L NH4HCO3 to obtain zeolite loaded with ammonium bicarbonate.

[0044] 500 parts of phosphogypsum were washed to remove residual acid and heated and dehydrated to β-type hemihydrate gypsum at 150 °C; 250 parts of β-type hemihydrate gypsum were ground into powder and added to a mixed solution of 800 parts of myristic acid and methanol, stirred for 30 min until the pH reached 7.2, then filtered using a filter mesh under a vacuum environment and dried at 60 °C to obtain myristic acid-modified phosphogypsum; among them, the mass ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol was 1:7.

[0045] 110 parts of β-type hemihydrate gypsum, 50 parts of limestone, 60 parts of eggshell powder, and 210 parts of bauxite were mixed, 80 parts of water were added and mixed evenly, molded under a pressure of 8 MPa, the molded specimen was dried in an oven at 50 °C, then heated to 1250 °C at a rate of 10 °C / min in a high-temperature electric furnace, calcined for 1 h, taken out of the furnace, and quickly cooled with a blower, then ground to a specific surface area of 400 ± 10 m 2 Calcium sulfoaluminate clinker was prepared after calcination at [specific temperature] / kg. 320 parts of calcium sulfoaluminate clinker, 240 parts of dicalcium silicate, 90 parts of myristic acid-modified phosphogypsum, 28 parts of heat-treated bamboo sawdust, 25 parts of zeolite loaded with ammonium bicarbonate, 5 parts of polycarboxylate superplasticizer, 1.5 parts of silicone defoamer (PX-122), and 12 parts of malic acid were stirred for 30 min to obtain cement.

[0046] Example 4

[0047] Put 100 parts of bamboo sawdust into a vacuum drying oven. After heating to 100 °C at -0.1 MPa and holding for 1 h, heat it to 160 °C at a heating rate of 10 °C / min, then cool it to 40 °C at 10 °C / min. After putting it into a dryer and cooling to room temperature, sieve it with a vibrating sieve to obtain heat-treated bamboo sawdust of 20 mesh.

[0048] Dry zeolite at 80 °C for 24 h. After natural cooling, immerse the zeolite in a beaker containing an aqueous solution of 1.6 mol / L NH₄HCO₃. Then place the beaker in a vacuum chamber and evacuate the air through a vacuum pump until the vacuum degree reaches below 20 Pa. Let the beaker stand for 6 h, then filter it using a filter mesh, and wipe the solution on the surface of the zeolite with a wet cloth soaked in an aqueous solution of 1.6 mol / L NH₄HCO₃ to obtain zeolite loaded with ammonium bicarbonate.

[0049] Wash 500 parts of phosphogypsum to remove residual acid, and heat it at 150 °C for dehydration into β-type hemihydrate gypsum; grind 250 parts of β-type hemihydrate gypsum into powder and add it to a mixed solution of 800 parts of myristic acid and methanol, stir for 40 min until the pH is 7.0, then filter it using a filter mesh in a vacuum environment, and dry it at 60 °C to obtain myristic acid-modified phosphogypsum; among them, the mass ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol is 1:7.

[0050] Mix 110 parts of β-type hemihydrate gypsum, 50 parts of limestone, 60 parts of eggshell powder and 210 parts of bauxite, add 80 parts of water and mix evenly, and mold it under a pressure of 8 MPa. After drying the molded specimen in an oven at 50 °C, heat it in a high-temperature electric furnace to 1250 °C at 10 °C / min and calcine for 1 h, then take it out of the furnace and quickly cool it with a blower, and grind it to a specific surface area of 400 ± 10 m 2 / kg to obtain calcium sulfoaluminate clinker. Mix 310 parts of calcium sulfoaluminate clinker, 220 parts of dicalcium silicate, 100 parts of myristic acid-modified phosphogypsum, 28 parts of heat-treated bamboo sawdust, 20 parts of zeolite loaded with ammonium bicarbonate, 6 parts of polycarboxylate superplasticizer, 1.5 parts of polyether defoamer (PX-130), and 16 parts of malic acid and stir for 30 min to obtain cement.

[0051] Example 5

[0052] Put 100 parts of bamboo sawdust into a vacuum drying oven. After heating to 100 °C at -0.1 MPa and holding for 1 h, heat it to 160 °C at a heating rate of 10 °C / min, then cool it to 40 °C at 10 °C / min. After putting it into a dryer and cooling to room temperature, sieve it with a vibrating sieve to obtain heat-treated bamboo sawdust of 20 mesh.

[0053] The zeolite was dried at 80 °C for 24 h, and after natural cooling, the zeolite was immersed in a beaker containing an aqueous solution of 1.8 mol / L NH4HCO3. Then, the beaker was placed in a vacuum chamber, and air was evacuated through a vacuum pump until the vacuum reached below 20 Pa. After allowing the beaker to stand for 6 h, filtration was carried out using a filter screen, and the solution on the surface of the zeolite was wiped with a wet cloth soaked in an aqueous solution of 1.8 mol / L NH4HCO3 to obtain zeolite loaded with ammonium bicarbonate.

[0054] 500 parts of phosphogypsum were washed to remove residual acid and heated and dehydrated to β-type hemihydrate gypsum at 150 °C. 250 parts of β-type hemihydrate gypsum were ground into powder and added to a mixed solution of 800 parts of myristic acid and methanol. After stirring for 40 min until the pH reached 7.0, filtration was carried out using a filter screen under a vacuum environment, and drying was carried out at 60 °C to obtain myristic acid-modified phosphogypsum. Among them, the mass ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol was 1:7.

[0055] 110 parts of β-type hemihydrate gypsum, 50 parts of limestone, 60 parts of eggshell powder and 210 parts of bauxite were mixed, 80 parts of water was added and mixed evenly, and molding was carried out under a pressure of 8 MPa. After drying the molded specimen in an oven at 50 °C, it was calcined in a high-temperature electric furnace at a heating rate of 10 °C / min to 1250 °C for 1 h, then taken out of the furnace and quickly cooled with a blower, and then ground to a specific surface area of 400 ± 10 m 2 / kg to obtain calcium sulfoaluminate clinker. 310 parts of calcium sulfoaluminate clinker, 260 parts of dicalcium silicate, 120 parts of myristic acid-modified phosphogypsum, 24 parts of heat-treated bamboo sawdust, 23 parts of zeolite loaded with ammonium bicarbonate, 6 parts of polycarboxylate superplasticizer, 1.5 parts of organosilicon defoamer (PX-122), and 20 parts of malic acid were stirred for 30 min to obtain cement.

[0056] Example 6

[0057] 100 parts of bamboo sawdust were placed in a vacuum drying oven, heated to 100 °C under -0.1 MPa and held for 1 h, then heated to 160 °C at a heating rate of 10 °C / min, and then cooled to 40 °C at a rate of 10 °C / min. After being cooled to room temperature in a dryer, it was sieved through a vibrating screen with 20 meshes to obtain heat-treated bamboo sawdust.

[0058] The zeolite was dried at 80 °C for 24 h, and after natural cooling, the zeolite was immersed in a beaker containing an aqueous solution of 1.7 mol / L NH4HCO3. Then, the beaker was placed in a vacuum chamber, and air was evacuated through a vacuum pump until the vacuum reached below 20 Pa. After allowing the beaker to stand for 6 h, filtration was carried out using a filter screen, and the solution on the surface of the zeolite was wiped with a wet cloth soaked in an aqueous solution of 1.7 mol / L NH4HCO3 to obtain zeolite loaded with ammonium bicarbonate.

[0059] Wash 500 parts of phosphogypsum to remove residual acid, and heat it at 150 °C for dehydration to form β-type hemihydrate gypsum; grind 250 parts of β-type hemihydrate gypsum into powder, add it to a mixed solution of 800 parts of myristic acid and methanol, stir for 60 min until the pH is 6.8, then filter it using a filter screen in a vacuum environment, and dry it at 60 °C to obtain myristic acid-modified phosphogypsum; among them, the mass ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol is 1:7.

[0060] Mix 110 parts of β-type hemihydrate gypsum, 50 parts of limestone, 60 parts of eggshell powder and 210 parts of bauxite, add 80 parts of water and mix evenly, and mold it under a pressure of 8 MPa. After drying the molded specimen in an oven at 50 °C, heat it to 1250 °C at a rate of 10 °C / min in a high-temperature electric furnace and calcine it for 1 h, then take it out of the furnace and quickly cool it with a blower, and grind it to a specific surface area of 400 ± 10 m 2 / kg to obtain calcium sulfoaluminate clinker. Mix 340 parts of calcium sulfoaluminate clinker, 200 parts of dicalcium silicate, 120 parts of myristic acid-modified phosphogypsum, 25 parts of heat-treated bamboo sawdust, 22 parts of zeolite loaded with ammonium bicarbonate, 5 parts of polycarboxylate superplasticizer, 1.5 parts of polyether defoamer (PX-130), and 18 parts of malic acid and stir for 30 min to obtain cement.

[0061] The present invention also carried out comparative examples and related tests.

[0062] Comparative Example 1

[0063] Compared with Example 1, the difference is that conventional phosphogypsum is added instead of myristic acid-modified phosphogypsum, and other components and preparation steps are exactly the same, and finally cement is obtained.

[0064] Comparative Example 2

[0065] Compared with Example 1, the difference is that zeolite loaded with ammonium bicarbonate is not added, and other components and preparation steps are exactly the same, and finally cement is obtained.

[0066] Comparative Example 3

[0067] Compared with Example 1, the difference is that malic acid is not added, and other components and preparation steps are exactly the same, and finally cement is obtained.

[0068] Comparative Example 4

[0069] Compared with Example 1, the difference is that the method in the patent application document with the publication number CN118993590A is used to produce cement.

[0070] Performance detection test

[0071] The cement and water prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were poured into a blender and stirred for 3 minutes. Then, the mixture was evenly stirred and poured into a cement-sand triad test mold of 40 mm × 40 mm × 160 mm. After being left at room temperature for 24 hours, it was demolded. The specimens were cured in a thermostatic and humidity-controlled box for 28 days according to the standard of GB / T50081-2002 to test the mechanical properties, and the freeze-thaw experiment was carried out according to the test method in the Test Methods for Long-Term Performance and Durability of Concrete of GB / T50082-2024, and the anti-freeze performance index after 5 freeze-thaw cycles was calculated according to Equation (Ⅰ). BDR To evaluate the durability of the prepared cement.

[0072] BDR × 100% (Ⅰ)

[0073] In the formula, BDR is the compressive strength loss rate during freeze-thaw cycles / %; is the compressive strength after freeze-thaw / MPa; is the compressive strength without freeze-thaw / MPa. The test results of relevant mechanical properties and durability are shown in Table 1.

[0074] Table 1

[0075]

[0076] From the performance data in Table 1, it can be seen that the cement provided by the present invention using myristic acid-modified phosphogypsum has significantly higher compressive strength and flexural strength compared to the conventional phosphogypsum used in Comparative Example 1, and obvious cracks appeared at 28 days due to the poor waterproof performance of the conventional phosphogypsum; at the same time, according to Example 1 and Comparative Example 2, it can be seen that the addition of zeolite loaded with ammonium bicarbonate significantly improves the compressive strength and flexural strength of the cement; from Comparative Example 3 and Example 1, it can be seen that the addition of malic acid makes the hydration sufficient, and the compressive strength and flexural strength of the prepared specimens are also significantly improved. The phosphogypsum-based cement prepared by the preparation method in the patent application document in Comparative Example 4 has poor compressive strength and flexural strength and cracks appear. In addition, in Example 1, due to the addition of myristic acid-modified phosphogypsum, the compressive strength loss rate is significantly decreased, and due to the addition of malic acid and zeolite loaded with ammonium bicarbonate, the compressive strength loss rate is also decreased, indicating that the strength loss after freeze-thaw of Example 1 is very small compared to Comparative Examples 1 to 4, and it further shows that the durability of the cement prepared in Example 1 is significantly improved.

[0077] Regarding the carbon emissions of the specimens in Examples 1 to 6 and Comparative Examples 1 to 4 during the production stage, referring to the basic carbon accounting method (emission factor method) provided by the IPCC, the carbon emissions during the production stage were calculated according to Equation (Ⅱ). The results are shown in Table 2.

[0078] C P (II)

[0079] Among them, C P is the carbon emission (kgCO2 / m 3 ) in the block production stage; M j is the dosage (t) of the j th raw material; F j is the carbon emission coefficient (kgCO2 / unit quantity) of the j th raw material.

[0080] Table 2

[0081]

[0082] From the performance data in Table 2, it can be seen that when Examples 1 - 6 are compared with Comparative Examples 1 - 4, the cement provided by the present invention can better cooperate synergistically with other components such as calcium sulfoaluminate clinker and dicalcium silicate during production to reduce carbon emissions and energy consumption.

[0083] The above are the preferred embodiments of the present invention. Without departing from the principle of the present invention, those of ordinary skill in the art can also make several improvements and refinements, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A cement production process for reducing carbon emissions, characterized in that, It includes the following steps: S1. Immerse zeolite in an aqueous solution of NH4HCO3, stand still under vacuum, filter, and obtain zeolite loaded with ammonium bicarbonate; S2. Grind β-type hemihydrate gypsum into powder, add it to a mixed solution of myristic acid and methanol, stir for 30 - 60 min until the pH is 6.8 - 7.2, then filter using a filter screen under a vacuum environment, and dry at 60 °C to obtain myristic acid-modified phosphogypsum; S3. Uniformly mix β-type hemihydrate gypsum, limestone, eggshell powder, bauxite, and water, press into shape, dry, heat to 1250 °C for calcination, then cool and grind to obtain calcium sulfoaluminate clinker; S4. Uniformly mix calcium sulfoaluminate clinker, dicalcium silicate, myristic acid-modified phosphogypsum, zeolite loaded with ammonium bicarbonate, polycarboxylate superplasticizer, defoamer, and malic acid to obtain cement; In step S4 before stirring, heat-treated bamboo sawdust is also added; The cement includes the following raw materials in parts by mass: 300 - 350 parts of calcium sulfoaluminate clinker, 200 - 300 parts of dicalcium silicate, 90 - 120 parts of myristic acid-modified phosphogypsum, 22 - 28 parts of heat-treated bamboo sawdust, 20 - 25 parts of zeolite loaded with ammonium bicarbonate, 5 - 7 parts of polycarboxylate superplasticizer, 1.5 parts of defoamer, and 12 - 24 parts of malic acid.

2. A cement production process for reducing carbon emissions according to claim 1, characterized in that, In step S1, dry the zeolite at 80 °C for 24 h, naturally cool it, then immerse it in a beaker containing an aqueous solution of NH4HCO3, place the beaker in a vacuum chamber, evacuate the air through a vacuum pump until the vacuum degree reaches less than 20 Pa, stand still for 6 h, then filter, and wipe the solution on the surface of the zeolite with a wet cloth soaked in an aqueous solution of NH4HCO3 to obtain zeolite loaded with ammonium bicarbonate.

3. A cement production process for reducing carbon emissions according to claim 1, characterized in that, The molar concentration of the aqueous solution of NH4HCO3 is 0.5 - 2.0 mol / L.

4. A cement production process for reducing carbon emissions according to claim 1, characterized in that, In step S2, β-type hemihydrate gypsum is obtained by washing phosphogypsum and heating it for dehydration at 150 °C.

5. A cement production process for reducing carbon emissions according to claim 1, characterized in that In step S2, the mass ratio of myristic acid to methanol in the mixed solution of myristic acid and methanol is 1:

7.

6. A cement production process for reducing carbon emissions according to claim 1, characterized in that, In the step S3, after mixing β-type hemihydrate gypsum, limestone, eggshell powder and bauxite, water is added and uniformly mixed, and then it is molded under a pressure of 8 MPa, dried at 50 °C, heated to 1250 °C at a rate of 10 °C / min and calcined for 1 h, cooled, and ground to a specific surface area of 400 ± 10 m 2 / kg to obtain calcium sulfoaluminate clinker.

7. A cement production process for reducing carbon emissions according to claim 1, characterized in that, The heat-treated bamboo sawdust is obtained by heating bamboo sawdust to 100 °C at -0.1 MPa and holding for 1 h, then heating at a heating rate of 10 °C / min to 160 °C, then cooling to 40 °C at a rate of 10 °C / min, putting it into a dryer to cool to room temperature, and screening out 20 mesh with a vibrating screen.

8. The cement production process for reducing carbon emissions according to claim 1, characterized in that, In step S4, the stirring time is 30 min; the defoamer is one of polyether defoamer and silicone defoamer, the model of the polyether defoamer is PX-130, and the model of the silicone defoamer is PX-122.

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