Low-carbon cement clinker and method for producing the same

Abstract

The application discloses a kind of low-carbon cement clinker, its mineral composition is mainly C7MS4 and β-C2S, wherein the content of C7MS4 is 40-60wt%, the content of β-C2S is 30-50wt%, the content of chemical component MgO is 2-5wt%.The application first proposes the introduction of high content C7MS4 in low-carbon cement clinker mineral, effectively improves the defects such as β-C2S carbonation rate too fast, product internal and external carbonization is uneven;And by adjusting the content of MgO, the activity of C7MS4 is improved, which can effectively ensure the carbon sequestration effect;Especially under the carbonation conditions of industrial tail gas with low CO2 concentration and low air pressure, high carbonation strength can be achieved, the required carbonation time is less, and it has good carbonation condition adaptability;And the preparation method is relatively simple, easy to operate, and suitable for popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a low-carbon cement clinker and its preparation method. Background Technology

[0002] Cement manufacturing is one of the world's largest sources of carbon dioxide emissions, and reducing carbon dioxide emissions is an unavoidable issue in the pursuit of high-quality development. Low-carbon cement clinker is typically composed of low-calcium minerals C3S2, CS, β-C2S, and γ-C2S. Compared to silicate cement clinker, which is mainly composed of C3S minerals, it requires less limestone in its batching, has a lower calcination temperature, and can absorb a large amount of CO2 gas, thus reducing carbon emissions in multiple ways. It can also be used to prepare building materials with excellent physical properties. β-C2S and γ-C2S have a higher calcium-silicon ratio than C3S2 and CS, a wider firing range, and contain less of the essentially non-carbonizing C2AS and the low-carbonizing-activity C2MS2, resulting in a higher absolute value of CaCO3 formed through carbonization and achieving a higher upper limit of carbonization strength.

[0003] In practical applications, to reduce industrial carbon emissions, industrial exhaust gas is typically used instead of CO2 cylinders with 99-100% concentration for carbonization. The CO2 concentration in industrial exhaust gas is generally below 50%, and the Ca of β-C2S... 2+ The dissolution rate in water is relatively fast, and the carbonization rate is too fast, which easily leads to uneven carbonization inside and outside the carbonized product under low CO2 concentration and low pressure conditions. γ-C2S has the same calcium-silicon ratio as β-C2S and is a product of β-C2S pulverization. 2+ The dissolution rate in water is slower than that of β-C2S, and the carbonization rate is also slower than that of β-C2S. This can improve the uneven carbonization phenomenon, but the defects of compression molding are greater, and the carbonization time required is longer than that of β-C2S. Furthermore, moisture loss is inevitable during the carbonization process, and under the conditions of slow carbonization, low CO2 concentration, and low pressure, it is impossible to guarantee an effective carbonization time. In addition, the chemical composition of conventional raw materials and fuels is more complex, and the cooling rate is difficult to control. This makes it difficult to control the pulverization of clinker during the cooling process in existing cement processes. Moreover, clinker dust is generated when the clinker is cooled by the grate cooler, which is difficult for the zipper machine to collect, resulting in clinker waste. A large amount of clinker dust can also damage the equipment. All of these factors restrict the application of low-carbon cement clinker.

[0004] Designing low-carbon cement clinker that is adaptable to carbonization conditions and suitable for carbon sequestration in industrial exhaust gas has become an urgent technical problem to be solved. Summary of the Invention

[0005] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a low-carbon cement clinker that is well-adapted to carbonation conditions. In particular, it can still achieve high carbonation strength when carbonized in industrial exhaust gas with low CO2 concentration and low pressure, and requires less carbonation time, making it suitable for widespread application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A low-carbon cement clinker, whose mineral composition is mainly C7MS4 and β-C2S, wherein the content of C7MS4 is 40-60wt% and the content of β-C2S is 30-50wt%.

[0008] Furthermore, the MgO content in the low-carbon cement clinker is 2-5%.

[0009] According to the above scheme, the CO2 concentration in the industrial exhaust gas is less than 50 vol%.

[0010] The above-mentioned method for preparing low-carbon cement clinker suitable for carbon sequestration in industrial exhaust gas includes the following steps:

[0011] (1) Obtain limestone and auxiliary raw materials, adjust the total CaO to SiO2 mass ratio and the designed MgO content in cement clinker, and then mix and grind them.

[0012] (2) The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace;

[0013] (3) After decomposition, it enters a rotary kiln for calcination to obtain low-carbon cement clinker.

[0014] According to the above scheme, the MgO content of the limestone in step (1) is 2-4%.

[0015] According to the above scheme, the auxiliary raw materials mentioned in step (1) include one or any mixture of coal gangue, sandstone, fly ash, silica, and clay.

[0016] Furthermore, the MgO content in the auxiliary raw materials is 0-4%.

[0017] According to the above scheme, in step (1), the mass ratio of total CaO to SiO2 in the chemical composition of the ingredients is 1.6-1.9; and the designed content of MgO in the cement clinker (the MgO content in the low-carbon cement clinker obtained after calcination) is controlled to be 2-5 wt%.

[0018] Furthermore, in the ingredient preparation step (1), the KH content is controlled to be 0.5-0.6, the SM content to be 2-6, and the IM content to be 1-2.

[0019] Furthermore, the residue on the 80μm sieve after grinding does not exceed 20%.

[0020] According to the above scheme, the decomposition temperature of the decomposition furnace is 850-950℃, and the decomposition time is 5-10 minutes.

[0021] According to the above scheme, the calcination temperature of the rotary kiln in step (3) is 1300-1350℃ and the calcination time is 5-10min.

[0022] The low-carbon cement clinker prepared according to the above scheme has good adaptability to carbonation conditions. In particular, it can still achieve high carbonation strength when the CO2 concentration is low and the gas pressure is low, and the required carbonation time is short.

[0023] Furthermore, the low-carbon cement clinker obtained by adopting the above scheme can achieve a carbonation strength (compressive strength) of 110-120 MPa after carbonation for 20 hours at a CO2 concentration of 15-20 vol% and normal pressure, and a carbonation strength (compressive strength) of 120-140 MPa after carbonation for 72 hours.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) This invention proposes for the first time to introduce high content of C7MS4 into low carbon cement clinker minerals. Its carbonization rate is relatively slow, which can improve the defects such as excessively fast carbonization rate of β-C2S and uneven carbonization inside and outside the product. By adjusting the content of MgO to improve the activity of C7MS4, the carbonization effect can be effectively guaranteed while improving the adaptability of carbon fixation using industrial tail gas (taking into account good carbonization strength and carbonization time, etc.).

[0026] (2) Compared with the traditional control method of reducing the total CaO to SiO2 mass ratio to below 1.6, reducing the β-C2S content, and introducing C3S2 into β-C2S to improve the defects of excessively fast carbonization rate of β-C2S and uneven carbonization inside and outside the product, the present invention further controls the total CaO to SiO2 mass ratio of low carbon cement clinker to not less than 1.6, which can effectively take into account the advantages of fewer pressing and molding defects, less carbonization time required to achieve high strength, wide firing range, less generation of low carbonization active components (such as C2AS without carbonization activity and C2MS2 with low carbonization activity), and high absolute value of CaCO3 that can be carbonized.

[0027] (3) Compared with the method of improving the defects of excessive carbonization rate of β-C2S and uneven carbonization inside and outside the product by increasing the calcium-silicon ratio to more than 1.9 to pulverize a large amount of β-C2S into γ-C2S, the low-carbon cement clinker obtained by the present invention can effectively take into account the advantages of fewer defects in pressing and molding, less carbonization time required to reach high strength, more stable firing and no need to impose high requirements on cooling rate.

[0028] (4) The present invention introduces a certain amount of MgO to promote the formation of C7MS4 and improve its activity. MgO can be included in the formation of calcium silicate minerals in the same way as CaO, so that low-carbon cement clinker has a higher calcium-silicon ratio than the actual calcium-silicon ratio. This can further reduce the defects of compression molding and the amount of carbonized active mineral C2AS generated. Attached Figure Description

[0029] Figure 1 XRD patterns of low-carbon cement clinker obtained in each embodiment and comparative example. Detailed Implementation

[0030] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

[0031] The following specific embodiments describe the acquisition and testing of raw materials:

[0032] Limestone and auxiliary raw materials were obtained, dried, crushed, and ground, and then subjected to chemical composition analysis. The measured chemical compositions are shown in Table 1.

[0033] Table 1. Chemical composition of raw materials (%)

[0034] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> ordinary limestone 40.44 5 1.18 0.82 48.85 2.59 0.02 0.21 0.06 Coal gangue 4.64 78.08 6.16 4.3 2.29 2.11 0.47 1.1 0.48 High-purity limestone 43.12 0.44 0.3 0.28 54.15 0.57 0.01 0.12 0.03 High magnesium limestone 39.42 8 1.82 0.95 41.25 6.9 0.33 0.51 0.27

[0035] Example 1

[0036] A low-carbon cement clinker suitable for carbon sequestration in industrial exhaust gas is prepared by the following steps:

[0037] 1. Proportioning Design

[0038] After crushing and drying, ordinary limestone and coal gangue were mixed at a weight ratio of 77:23, then ground until the residue on an 80μm sieve was 15%. The mixing conditions and corresponding chemical composition indicators are shown in Tables 2 and 3, respectively.

[0039] Table 2 Chemical composition and proportions of raw materials

[0040] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> Proportion ordinary limestone 40.44 5 1.18 0.82 48.85 2.59 0.02 0.21 0.06 77 Coal gangue 4.64 78.08 6.16 4.3 2.29 2.11 0.47 1.1 0.48 23

[0041] Table 3. Ingredient design parameters and MgO content in clinker

[0042] KH SM IM <![CDATA[Total CaO:SiO2]]> MgO content in clinker 0.551 5.527 1.435 1.749 3.658％

[0043] 2. Decomposition of carbonates

[0044] The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace at a temperature of 870℃ for 5 minutes.

[0045] 3. Calcination to obtain clinker

[0046] After decomposition, the material enters a rotary kiln for calcination and is cooled to obtain low-carbon cement clinker. The rotary kiln temperature is set at 1330℃ and the calcination time is 6 minutes.

[0047] Example 2

[0048] A low-carbon cement clinker suitable for carbon sequestration in industrial exhaust gas is prepared by the following steps:

[0049] 1. Proportioning Design

[0050] After crushing and drying, ordinary limestone and coal gangue were mixed at a weight ratio of 76.2:23.8, and then ground until the residue on an 80μm sieve was 15%. The mixing conditions and corresponding chemical composition indicators are shown in Tables 4 and 5, respectively.

[0051] Table 4 Chemical composition and proportion of raw materials

[0052] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> Proportion ordinary limestone 40.44 5 1.18 0.82 48.85 2.59 0.02 0.21 0.06 76.2 Coal gangue 4.64 78.08 6.16 4.3 2.29 2.11 0.47 1.1 0.48 23.8

[0053] Table 5. Ingredient design parameters and MgO content in clinker

[0054] KH SM IM <![CDATA[Total CaO:SiO2]]> MgO content in clinker 0.530 5.579 1.435 1.687 3.637％

[0055] 2. Decomposition of carbonates

[0056] The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace at a temperature of 870℃ for 5 minutes.

[0057] 3. Calcination to obtain clinker

[0058] After decomposition, the material enters a rotary kiln for calcination and is cooled to obtain low-carbon cement clinker. The rotary kiln temperature is set at 1310℃ and the calcination time is 6 minutes.

[0059] Comparative Example 1

[0060] A low-carbon cement clinker, the preparation method of which includes the following steps:

[0061] 1. Proportioning Design

[0062] After crushing and drying, high-purity limestone and coal gangue were mixed at a weight ratio of 71.5:28.5, then ground until the residue on an 80μm sieve was 15%. The proportions and corresponding chemical composition indicators are shown in Tables 6 and 7, respectively.

[0063] Table 6 Chemical composition and proportions of raw materials

[0064] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> Proportion High-purity limestone 43.12 0.44 0.3 0.28 54.15 0.57 0.01 0.12 0.03 71.5 Coal gangue 4.64 78.08 6.16 4.3 2.29 2.11 0.47 1.1 0.48 28.5

[0065] Table 7. Batching design parameters and MgO content in clinker

[0066] KH SM IM <![CDATA[Total CaO:SiO2]]> MgO content in clinker 0.562 6.646 1.382 1.745 1.487％

[0067] 2. Decomposition of carbonates

[0068] The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace at a temperature of 870℃ for 5 minutes.

[0069] 3. Calcination to obtain clinker

[0070] After decomposition, the material enters a rotary kiln for calcination. After cooling, low-carbon cement clinker is obtained. The temperature of the rotary kiln is set at 1330℃, and the calcination time is 6 minutes.

[0071] Comparative Example 2

[0072] A low-carbon cement clinker, the preparation method of which includes the following steps:

[0073] 1. Proportioning Design

[0074] After crushing and drying, high-magnesium limestone and coal gangue were mixed at a weight ratio of 83.1:16.9, then ground until the residue on an 80μm sieve was 15%. The proportions and corresponding chemical composition indicators are shown in Tables 8 and 9, respectively.

[0075] Table 8 Chemical composition and proportions of raw materials

[0076] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> Proportion High magnesium limestone 39.42 8 1.82 0.95 41.25 6.9 0.33 0.51 0.27 83.1 Coal gangue 4.64 78.08 6.16 4.3 2.29 2.11 0.47 1.1 0.48 16.9

[0077] Table 9. Ingredient design parameters and MgO content in clinker

[0078] KH SM IM <![CDATA[Total CaO:SiO2]]> MgO content in clinker 0.534 4.876 1.684 1.747 9.164％

[0079] 2. Decomposition of carbonates

[0080] The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace at a temperature of 870℃ for 5 minutes.

[0081] 3. Calcination to obtain clinker

[0082] After decomposition, the material enters a rotary kiln for calcination. After cooling, low-carbon cement clinker is obtained. The temperature of the rotary kiln is set at 1330℃, and the calcination time is 6 minutes.

[0083] Comparative Example 3

[0084] A low-carbon cement clinker, the preparation method of which includes the following steps:

[0085] 1. Proportioning Design

[0086] After crushing and drying, ordinary limestone and coal gangue were mixed at a weight ratio of 74.4:25.6, then ground until the residue on an 80μm sieve was 15%. The proportions and corresponding chemical composition indicators are shown in Tables 10 and 11, respectively.

[0087] Table 10 Chemical composition and proportions of raw materials

[0088] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> Proportion ordinary limestone 40.44 5 1.18 0.82 48.85 2.59 0.02 0.21 0.06 74.4 Coal gangue 4.64 78.08 6.16 4.3 2.29 2.11 0.47 1.1 0.48 25.6

[0089] Table 11. Batching design parameters and MgO content in clinker

[0090] KH SM IM <![CDATA[Total CaO:SiO2]]> MgO content in clinker 0.485 5.691 1.435 1.558 3.590％

[0091] 2. Decomposition of carbonates

[0092] The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace at a temperature of 870℃ for 5 minutes.

[0093] 3. Calcination to obtain clinker

[0094] After decomposition, the material enters a rotary kiln for calcination. After cooling, low-carbon cement clinker is obtained. The temperature of the rotary kiln is set at 1300℃, and the calcination time is 6 minutes.

[0095] Comparative Example 4

[0096] A low-carbon cement clinker, the preparation method of which includes the following steps:

[0097] 1. Proportioning Design

[0098] After crushing and drying, ordinary limestone and coal gangue were mixed at a weight ratio of 79:21, then ground until the residue on an 80μm sieve was 15%. The proportions and corresponding chemical composition indicators are shown in Tables 12 and 13, respectively.

[0099] Table 12 Chemical composition and proportions of raw materials

[0100] name Loss on ignition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> Proportion ordinary limestone 40.44 5 1.18 0.82 48.85 2.59 0.02 0.21 0.06 79 Coal gangue 4.64 78.08 6.16 4.3 2.29 2.11 0.47 1.1 0.48 21

[0101] Table 13 Ingredient design parameters and MgO content in clinker

[0102] KH SM IM <![CDATA[Total CaO:SiO2]]> MgO content in clinker 0.610 5.388 1.435 1.920 3.711％

[0103] 2. Decomposition of carbonates

[0104] The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace at a temperature of 870℃ for 5 minutes.

[0105] 3. Calcination to obtain clinker

[0106] After decomposition, the material enters a rotary kiln for calcination. After cooling, low-carbon cement clinker is obtained. The temperature of the rotary kiln is set at 1330℃, and the calcination time is 6 minutes.

[0107] The mineral composition of the clinker from each embodiment and comparative example was quantitatively analyzed using Jade XRD patterns, and the results are shown in Table 14.

[0108] Table 14. Main mineral content (%) in clinker

[0109] project <![CDATA[C7MS4]]> <![CDATA[β-C2S]]> <![CDATA[γ-C2S]]> <![CDATA[C3S2]]> <![CDATA[C2AS]]> <![CDATA[C2MS2]]> MgO <![CDATA[SiO2]]> Example 1 52.4 38.8 0 0 6.2 2.6 0 0 Example 2 50.3 38.1 0 0 5.5 6.1 0 0 Comparative Example 1 24.1 69.7 0 0 4.5 1.7 0 0 Comparative Example 2 56.9 32.5 4.6 0 1.3 0 4.7 0 Comparative Example 3 28.5 37.9 0 3.2 8.1 20.8 0 1.5 Comparative Example 4 14.5 47.7 31.3 0 2.9 1.4 2.2 0

[0110] Sample preparation before carbonization: Low-carbon cement clinker was ground to R45μm≤20%, and cylindrical samples with a diameter of 2cm and a height of 2cm were prepared by holding the mixture at a water-to-solid ratio of 0.15 and a molding pressure of 10MPa for 30s.

[0111] The measured porosity results are shown in Table 15. The method for measuring the porosity was as follows: the mass of low-carbon clinker used for molding a cylindrical sample with a diameter of 2 cm and a height of 2 cm was m. c The unit is g; the density of low-carbon cement clinker is measured as ρ. c Unit: g / cm 3 The true density was measured using a densitometer; the molding porosity p was calculated as p = (6.283 - m). c / ρ c ) / 6.283.

[0112] Table 15 Molding porosity p (%)

[0113] project Molding porosity Example 1 36.83 Example 2 37.61 Comparative Example 1 37.52 Comparative Example 2 38.15 Comparative Example 3 40.66 Comparative Example 4 41.14

[0114] The pressed and molded samples were carbonized for 1 h, 4 h, and 20 h under the conditions of 99% CO2 concentration, 30℃ temperature, 60% humidity, and 0.3 MPa pressure (pressure gauge reading 0.3 MPa). The carbon fixation rate and compressive strength were then measured, and the results are shown in Table 16. The pressed and molded samples were then carbonized for 20 h and 72 h under the conditions of 20% CO2 concentration, 30℃ temperature, 60% humidity, and normal pressure (pressure gauge reading 0 MPa). The carbon fixation rate and compressive strength were then measured, and the results are shown in Table 17.

[0115] Table 16 Carbonation conditions and strength after carbonation of low-carbon cement clinker

[0116]

[0117] Table 17 Carbonation conditions and strength after carbonation of low-carbon cement clinker

[0118]

[0119]

[0120] The results show that the molding porosity of Examples 1 and 2 of the present invention is low (few molding defects), and can still achieve high carbonization strength when CO2 concentration is low and gas pressure is low, and the required carbonization time is short, thus showing good adaptability to carbonization conditions.

[0121] Comparative Example 1 used high-purity limestone and introduced less MgO. Although it achieved higher strength in a shorter time than Examples 1 and 2 when CO2 concentration and gas pressure were high, the high β-C2S content and excessively fast carbonization rate made it more difficult for CO2 to penetrate into the interior when CO2 concentration and gas pressure were low. This resulted in uneven carbonization, a significant decrease in strength, and poorer adaptability to carbonization conditions compared to Examples 1 and 2.

[0122] Comparative Example 2 used high-magnesium limestone, which introduced more MgO. XRD showed that the crystallinity of C7MS4 was more complete. However, the excessive MgO significantly reduced the carbonization activity of C7MS4 compared to Examples 1 and 2, resulting in a significant decrease in carbonization strength.

[0123] Comparative Example 3 reduced the content of β-C2S by decreasing the total CaO to SiO2 mass ratio to improve adaptability to carbonization conditions. However, this increased the molding porosity (large molding defects), narrowed the firing range, and resulted in a higher amount of C2AS (which has virtually no carbonization activity) and C2MS2 (which has low carbonization activity), leading to lower carbonization strength.

[0124] Comparative Example 4 reduced the β-C2S content by increasing the total CaO to SiO2 mass ratio to partially pulverize β-C2S into γ-C2S, thereby improving adaptability to carbonization conditions. However, this increased the molding porosity (resulting in larger molding defects), and the carbonization time required to achieve high carbonization strength was longer than that of Examples 1 and 2. Furthermore, moisture loss was unavoidable during carbonization, and the effective carbonization time could not be guaranteed under conditions of slower carbonization, low CO2 concentration, and low gas pressure.

[0125] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A low-carbon cement clinker, characterized in that, Its mineral composition is mainly C7MS4 and β-C2S, with C7MS4 content of 40-60wt% and β-C2S content of 30-50wt%. The total CaO to SiO2 mass ratio in the low-carbon cement clinker is 1.6-1.9; and the designed MgO content in the cement clinker is controlled at 2-5 wt%. The resulting low-carbon cement clinker has a carbonation strength of 110-120 MPa after carbonation for 20 hours at a CO2 concentration of 15-20 vol% and normal pressure, and a carbonation strength of 120-140 MPa after carbonation for 72 hours.

2. The method for preparing low-carbon cement clinker according to claim 1, characterized in that, Includes the following steps: (1) Obtain limestone and auxiliary raw materials, adjust the total CaO to SiO2 mass ratio and the designed MgO content in cement clinker, and then mix and grind them. (2) The resulting mixture is preheated in a preheater and then decomposed in a decomposition furnace; (3) After decomposition, it enters a rotary kiln for calcination to obtain low-carbon cement clinker.

3. The preparation method according to claim 2, characterized in that, The limestone contains 2-4 wt% MgO.

4. The preparation method according to claim 2, characterized in that, The auxiliary raw materials include one or more of the following: coal gangue, sandstone, fly ash, silica, and clay.

5. The preparation method according to claim 2, characterized in that, In step (1), the proportions of KH, SM, and IM in the batching process are controlled to be 0.5-0.6, 2-6, and 1-2.

6. The preparation method according to claim 2, characterized in that, In step (1), the residue on the 80μm sieve after grinding shall not exceed 20%.

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