Cement production method by combining low-grade limestone with coal gasification slag

Abstract

The invention relates to the technical field of cement production, and discloses a method for producing cement by combining low-grade limestone with coal gasification slag. A process technology for producing the cement clinker by blending combustion of coal gasification slag mixed with low-grade limestone and a coal gasification slag alternative fuel resource utilization technology are adopted, through research on raw material proportioning and homogenization, a clinker sintering process and cement clinker performance optimization, the cement clinker is produced by blending combustion, comprehensive utilization of resources is realized, and the production cost is reduced. The dependence on natural raw materials is reduced. By adding the coal gasification slag, the physical properties such as compressive strength, tensile strength and freezing resistance of the cement can be improved. Meanwhile, the active ingredients in the coal gasification slag can promote the hydration reaction of the cement, so that the early strength of the cement is improved, the hardening time of the cement is shortened, and the production efficiency is improved. On the other hand, cement clinker production cost is reduced, and economic benefits are improved.

Description

Technical Field

[0001] The present application relates to the technical field of cement production, and in particular to a method for producing cement by combining low-grade limestone with coal gasification slag. Background Art

[0002] Coal gasification slag is a solid waste generated during the coal gasification process. In recent years, after being added and processed by grinding, coal gasification slag can be used as a mixed material to replace part of cement clinker, which can reduce the cost of cement production and reduce energy consumption and carbon dioxide emissions in the clinker production process. At present, the technology of applying coal gasification slag to the field of cement clinker production is quite mature, but coal gasification slag can only be used in combination with high-grade limestone for clinker production at this stage. Some areas are limited by the quality of mines and do not have high-grade limestone. The rash use of low-grade limestone combined with cement mixed materials such as coal gasification slag for production will lead to a decrease in the subsequent cement quality. Therefore, low-grade limestone is forced to use higher-cost mixed materials to produce cement clinker. Summary of the invention

[0003] In view of the above problems, the embodiments of the present application provide a method for producing cement using low-grade limestone combined with coal gasification slag. Under the premise of not affecting the quality of cement, low-grade limestone and coal gasification slag can be used simultaneously to produce cement and cement clinker, thereby solving the problem of limited use of low-grade limestone in some mining areas.

[0004] According to one aspect of the embodiment of the present application, a method for producing cement using low-grade limestone combined with coal gasification slag is provided. The method for producing cement using low-grade limestone combined with coal gasification slag comprises the following steps:

[0005] Raw material selection:

[0006] Select coal gasification slag to dry in a drying chamber, then grind the dried coal gasification slag and pass it through a 100-125 mesh fine sieve to obtain gasification slag powder, select cyanamide slag to grind it and pass it through a 200-250 mesh fine sieve to obtain cyanamide slag powder;

[0007] Configure white raw material:

[0008] 77-100 components of low-grade limestone are sieved, 2-5 components of fly ash are sieved, 0.9-1.4 components of sulfuric acid slag are sieved, 1.25-6 components of the above-mentioned cyanamide slag powder, 1-8 components of the above-mentioned gasification slag powder, 0-6 components of calcium hydroxide are sieved, and 0-1 component of magnesium slag powder are sieved and mixed to obtain white raw material, wherein the CaO content in the low-grade limestone is 34%-48%;

[0009] Firing clinker:

[0010] After feeding the mixed fuel into the rotary kiln, control the temperature of the rotary kiln to rise to 800 - 850 °C, and feed the above-mentioned raw meal into the rotary kiln for preliminary sintering for 10 - 12 min. Subsequently, control the temperature of the rotary kiln to rise to 1250 °C - 1350 °C within 5 - 8 min and maintain it within this temperature range for 15 - 18 min to complete the final calcination. After cooling, cement clinker is obtained;

[0011] After adding the mixture to the cement clinker, the finished cement is obtained.

[0012] According to the cement production method using low-grade limestone combined with coal gasification slag as claimed in claim 1, it is characterized in that the step of obtaining the finished cement by adding the mixture to the cement clinker specifically includes the following steps;

[0013] Step 1: Crush the cement clinker to form clinker blocks;

[0014] Step 2: Grind the clinker blocks to form cement clinker powder;

[0015] Step 3: Sieve the cement clinker powder separately;

[0016] Step 4: Configure the mixture and the sieved cement clinker powder according to a certain ratio and send them together into a mixer for mixing, and then send them into a ball mill again for secondary grinding and sieving to obtain the finished cement.

[0017] In some embodiments, during the process of firing the clinker, when the clinker completes the final calcination, a grate cooler is used for rapid cooling.

[0018] In some embodiments, the specific requirement for sieving in the step of then sending it into a ball mill again for secondary grinding and sieving to obtain the finished cement is that the sieve residue passing through a 200-mesh sieve ≤ 10%.

[0019] In some embodiments, the lime saturation factor of the raw meal is 0.86 - 0.96.

[0020] In some embodiments, the silica modulus of the raw meal is 2.0 - 2.8.

[0021] In some embodiments, the alumina modulus of the raw meal is 1.3 - 1.7.

[0022] The beneficial effects in this application are:

[0023] 1. The process technologies of using coal gasification slag to mix with low-grade limestone for co-firing to produce cement clinker and the resource utilization technology of using coal gasification slag to replace fuel are adopted. Through the research on raw material ratio and homogenization, clinker burning process, and optimization of cement clinker performance, co-firing is used to produce cement clinker, realizing the comprehensive utilization of resources and reducing the dependence on natural raw materials.

[0024] 2. The addition of coal gasification slag can improve the physical properties of cement such as compressive strength, tensile strength and frost resistance. At the same time, the active components in the coal gasification slag can also promote the hydration reaction of cement, improve the early strength of cement, shorten the hardening time of cement, and improve production efficiency.

[0025] 3. Reduce the production cost of cement clinker and improve economic benefits.

[0026] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the specific embodiments of this application are given below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of this application. And throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0028] Figure 1 is a schematic flow chart of a cement production method combining low-grade limestone and coal gasification slag provided by an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The embodiments of the technical solution of this application will be described in detail below with reference to the drawings. The following embodiments are only used to illustrate the technical solution of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0030] Specifically, please refer to Figure 1 , Figure 1 is a schematic flow chart of a cement production method combining low-grade limestone and coal gasification slag provided by an embodiment of this application.

[0031] The cement production method combining low-grade limestone and coal gasification slag includes the following steps;

[0032] Raw material selection and preparation:

[0033] Select the coal gasification slag and dry it in a drying chamber. Then, grind the dried coal gasification slag and pass it through a 100 - 125 mesh fine sieve to obtain gasification slag powder. Select the dicyandiamide slag, grind it, and pass it through a 200 - 250 mesh fine sieve to obtain dicyandiamide slag powder;

[0034] Prepare the raw white material:

[0035] Select low - grade limestone with 77 - 100 components screened, fly ash with 2 - 5 components screened, sulfuric acid slag with 0.9 - 1.4 components screened, 1.25 - 6 components of the above - mentioned dicyandiamide slag powder, 1 - 8 components of the above - mentioned gasification slag powder, calcium hydroxide with 0 - 6 components screened, and magnesium slag powder with 0 - 1 component screened, and then mix them to obtain the raw white material. The CaO content in the low - grade limestone is 34% - 48%;

[0036] Fire the clinker:

[0037] After feeding the mixed fuel into the rotary kiln, control the temperature of the rotary kiln to rise to 800 - 850 °C, and feed the above - mentioned raw white material into the rotary kiln for preliminary sintering for 10 - 12 min. Then, control the temperature of the rotary kiln to rise to 1250 °C - 1350 °C within 5 - 8 min and maintain it in this temperature range for 15 - 18 min to complete the final calcination. After cooling, obtain the cement clinker;

[0038] Add the mixture to the cement clinker to obtain the finished cement.

[0039] According to the cement production method using low - grade limestone combined with coal gasification slag as claimed in claim 1, it is characterized in that the step of adding the mixture to the cement clinker to obtain the finished cement specifically includes the following steps;

[0040] Step 1: Crush the cement clinker to form clinker blocks;

[0041] Step 2: Grind the clinker blocks to form cement clinker powder;

[0042] Step 3: Screen the cement clinker powder separately;

[0043] Step 4: Configure the mixture and the screened cement clinker powder according to a certain ratio, then send them together into a mixer for mixing, and then send them into a ball mill again for secondary grinding and screening to obtain the finished cement.

[0044] In some embodiments, during the process of firing the clinker, when the clinker completes the final calcination, a grate cooler is used for rapid cooling.

[0045] In some embodiments, the specific requirement for screening in the step of then sending it into the ball mill again for secondary grinding and screening to obtain the finished cement is that the screen residue passing through a 200 - mesh sieve ≤ 10%.

[0046] In some embodiments, the lime saturation factor of the raw meal is 0.86 - 0.96.

[0047] In some embodiments, the silica modulus of the raw meal is 2.0 - 2.8.

[0048] In some embodiments, the alumina modulus of the raw meal is 1.3 - 1.7.

[0049] Example 1:

[0050] Charge materials are prepared with limestone having a CaO content of 44.0%, fly ash, sulfuric acid residue, 2% dicyandiamide residue, and 1% coal gasification residue;

[0051] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Limestone 90.85 33.11 10.58 1.74 0.88 40.02 1.94 0.17 0.43 0.018 Fly ash 4.75 0.15 2.29 1.35 0.33 0.20 0.06 0.01 0.06 0.000 Sulfuric acid residue 1.40 (0.06) 0.43 0.10 0.73 0.04 0.04 0.00 0.02 0.000 Cyanamide residue 2.00 0.92 0.06 0.01 0.01 0.98 0.01 0.00 0.00 0.000 Magnesium slag 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000 Gasification slag 1.00 0.10 0.46 0.16 0.09 0.12 0.02 0.01 0.02 0.000 White raw meal 100.00 34.21 13.83 3.36 2.04 41.35 2.07 0.19 0.53 0.019

[0052] Through calculation, it can be obtained that:

[0053] Raw meal modulus values: KH = 0.906, N = 2.56, P = 1.65;

[0054] Control the temperature of the rotary kiln to rise to 800 - 850 °C, feed the above-mentioned raw meal into the rotary kiln for preliminary sintering for 10 - 12 min, then control the temperature of the rotary kiln to rise to 1250 °C - 1350 °C within 5 - 8 min and maintain it in this temperature range for 15 - 18 min to complete the final calcination, and obtain cement clinker after cooling.

[0055] The chemical calculation of the clinker is shown in the following table:

[0056] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Clinker composition 100.00 / 21.72 5.33 3.25 64.15 3.22 0.38 0.83 0.030

[0057] Through calculation, it can be obtained that:

[0058] ① Clinker modulus values: KH = 0.892, N = 2.53, P = 1.64;

[0059] ② Silicate minerals: C3S + C2S: 75.96%;

[0060] ③ Flux minerals: C3A: 8.61%, C4AF: 9.88%;

[0061] ④ Chloride ion content: 0.025%, R2O: 0.83%, liquid phase content 27.35%.

[0062] After testing, the clinker strength is: 40.7 MPa (3 days), 58.4 MPa (28 days).

[0063] Example 2:

[0064] Use limestone with a CaO content of 44.0%, fly ash, sulfuric acid slag, 4% dicyandiamide slag, 1% coal gasification slag, and 1% magnesium slag for batching.

[0065] The chemical calculation of the raw meal is shown in the following table:

[0066] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Limestone 87.75 31.98 10.22 1.68 0.85 38.65 1.87 0.17 0.41 0.018 Fly ash 4.85 0.15 2.34 1.38 0.34 0.20 0.06 0.01 0.06 0.000 Sulfuric acid residue 1.40 (0.06) 0.43 0.10 0.73 0.04 0.04 0.00 0.02 0.000 Cyanamide residue 4.00 1.84 0.12 0.03 0.02 1.95 0.02 0.00 0.00 0.001 Magnesium slag 1.00 (0.01) 0.32 0.01 0.05 0.57 0.07 0.00 0.00 0.000 Gasification slag 1.00 0.10 0.46 0.16 0.09 0.12 0.02 0.01 0.02 0.000 White raw meal 100.00 34.00 13.90 3.36 2.08 41.53 2.08 0.19 0.52 0.019

[0067] Through calculation, it can be obtained that:

[0068] Raw meal modulus: KH = 0.906, N = 2.56, P = 1.62;

[0069] Control the temperature of the rotary kiln to rise to 800 - 850 °C, feed the above-mentioned white raw meal into the rotary kiln for preliminary sintering for 10 - 12 minutes, then control the temperature of the rotary kiln to rise to 1250 - 1350 °C within 5 - 8 minutes and maintain it in this temperature range for 15 - 18 minutes to complete the final calcination, and obtain cement clinker after cooling.

[0070] The chemical calculation of the clinker is shown in the following table:

[0071] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Clinker composition 100.00 / 21.73 5.30 3.29 64.15 3.23 0.37 0.81 0.029

[0072] Through calculation, it can be obtained that:

[0073] ① Clinker modulus: KH = 0.892, N = 2.53, P = 1.61;

[0074] ② Silicate minerals: C3S + C2S: 76.01%;

[0075] ③ Flux minerals: C3A: 8.47%, C4AF: 10.00%;

[0076] ④ Chloride ion content: 0.029%, R2O: 0.81%, liquid phase content 27.34%.

[0077] After testing, the clinker strength is: 40.2 MPa (3 days), 56.8 MPa (28 days).

[0078] Example 3:

[0079] Use limestone with a CaO content of 44.0%, fly ash, sulfuric acid slag, 2% dicyandiamide slag, 2% coal gasification slag, and 2% calcium hydroxide for batching.

[0080] The chemical calculation of the raw meal is shown in the following table:

[0081] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Limestone 88.15 32.12 10.27 1.69 0.86 38.83 1.88 0.17 0.37 0.016 Fly ash 4.45 0.14 2.15 1.27 0.31 0.18 0.06 0.01 0.07 0.000 Sulfuric acid residue 1.40 (0.06) 0.43 0.10 0.73 0.04 0.04 0.00 0.02 0.000 Cyanamide residue 2.00 0.92 0.06 0.01 0.01 0.98 0.01 0.00 0.00 0.001 Gasification slag 2.00 0.19 0.91 0.32 0.18 0.25 0.04 0.02 0.00 0.001 Calcium hydroxide 2.00 0.46 0.04 0.02 0.01 1.45 0.03 0.00 0.01 0.000 White raw meal 100.00 33.77 13.86 3.41 2.09 41.72 2.05 0.20 0.47 0.018

[0082] Through calculation, it can be obtained that:

[0083] Raw meal modulus values: KH = 0.911, N = 2.52, P = 1.63;

[0084] Control the temperature of the rotary kiln to rise to 800 - 850 °C, feed the above-mentioned white raw meal into the rotary kiln for preliminary sintering for 10 - 12 min, then control the temperature of the rotary kiln to rise to 1250 - 1350 °C within 5 - 8 min and maintain it in this temperature range for 15 - 18 min to complete the final calcination, and obtain the cement clinker after cooling.

[0085] The chemical calculation of the clinker is shown in the following table:

[0086] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Clinker composition 100.00 / 21.61 5.35 3.30 64.23 3.17 0.38 0.83 0.029

[0087] It can be obtained through calculation:

[0088] ① Clinker modulus values: KH = 0.896, N = 2.50, P = 1.62;

[0089] ② Silicate minerals: C3S + C2S: 75.88%;

[0090] ③ Flux minerals: C3A: 8.59%, C4AF: 10.03%;

[0091] ④ Chloride ion content: 0.029%, R2O: 0.83%, liquid phase content 27.49%.

[0092] The strength of the tested clinker is: 41.6 MPa (3 days), 58.7 MPa (28 days).

[0093] Example 4:

[0094] Use limestone with a CaO content of 44.0%, fly ash, sulfuric acid slag, 4% dicyandiamide slag, 4% coal gasification slag, and 3% calcium hydroxide for batching.

[0095] The chemical calculation of the raw meal is shown in the following table:

[0096] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Limestone 84.15 30.66 9.80 1.62 0.82 37.07 1.79 0.16 0.40 0.017 Fly ash 3.60 0.11 1.74 1.02 0.25 0.15 0.05 0.01 0.04 0.000 Sulfuric acid residue 1.25 (0.05) 0.39 0.09 0.65 0.03 0.04 0.00 0.01 0.000 Cyanamide residue 4.00 1.84 0.12 0.03 0.02 1.95 0.02 0.00 0.00 0.001 Gasification slag 4.00 0.38 1.83 0.64 0.35 0.49 0.08 0.04 0.09 0.001 Calcium hydroxide 3.00 0.69 0.06 0.03 0.01 2.17 0.04 0.00 0.00 0.000 White raw meal 100.00 33.64 13.93 3.42 2.10 41.86 2.01 0.21 0.55 0.019

[0097] It can be obtained through calculation:

[0098] Raw meal modulus values: KH = 0.910, N = 2.52, P = 1.63;

[0099] Control the temperature of the rotary kiln to rise to 800 - 850 °C, feed the above-mentioned white raw meal into the rotary kiln for preliminary sintering for 10 - 12 min, then control the temperature of the rotary kiln to rise to 1250 - 1350 °C within 5 - 8 min and maintain it in this temperature range for 15 - 18 min to complete the final calcination, and obtain the cement clinker after cooling.

[0100] The chemical calculation of the clinker is shown in the following table:

[0101] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Clinker composition 100.00 / 21.64 5.35 3.30 64.22 3.10 0.40 0.86 0.029

[0102] Through calculation, it can be obtained that:

[0103] ① Clinker modulus: KH = 0.895, N = 2.50, P = 1.62;

[0104] ② Silicate minerals: C3S + C2S: 75.90%;

[0105] ③ Flux minerals: C3A: 8.59%, C4AF: 10.05%;

[0106] ④ Chloride ion content: 0.029%, R2O: 0.86%, liquid phase content 27.46%.

[0107] The strength of the tested clinker is: 38.5 MPa (3 days), 54.4 MPa (28 days).

[0108] Example 5:

[0109] Ingredients are made with limestone with a CaO content of 44.0%, fly ash, sulfuric acid slag, 6% dicyandiamide slag, 8% coal gasification slag, and 6% calcium hydroxide.

[0110] The chemical calculation of the raw meal is shown in the following table:

[0111] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Limestone 77.20 28.13 8.99 1.48 0.75 34.01 1.64 0.15 0.36 0.015 Fly ash 1.90 0.06 0.92 0.54 0.13 0.08 0.02 0.00 0.02 0.000 Sulfuric acid residue 0.90 (0.04) 0.28 0.06 0.47 0.02 0.03 0.00 0.01 0.000 Cyanamide residue 6.00 2.76 0.18 0.04 0.02 2.93 0.04 0.01 0.01 0.001 Gasification slag 8.00 0.77 3.66 1.27 0.71 0.98 0.15 0.08 0.18 0.002 Calcium hydroxide 6.00 1.38 0.12 0.06 0.02 4.34 0.08 0.00 0.01 0.000 White raw meal 100.00 33.06 14.14 3.46 2.10 42.36 1.96 0.24 0.59 0.019

[0112] Through calculation, it can be obtained that:

[0113] Raw meal modulus: KH = 0.907, N = 2.54, P = 1.64;

[0114] Control the temperature of the rotary kiln to rise to 800 - 850 °C, feed the above-mentioned white raw meal into the rotary kiln for preliminary sintering for 10 - 12 min, then control the temperature of the rotary kiln to rise to 1250 °C - 1350 °C within 5 - 8 min and maintain it in this temperature range for 15 - 18 min to complete the final calcination, and obtain the cement clinker after cooling.

[0115] The chemical calculation of the clinker is shown in the following table:

[0116] Name Ratio (%) LOSS <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO SO3 <![CDATA[R2O]]> cl- Clinker composition 100.00 / 21.71 5.35 3.27 64.24 2.99 0.44 0.90 0.029

[0117] Through calculation, it can be obtained that:

[0118] ① Clinker modulus: KH = 0.896, N = 2.52, P = 1.64;

[0119] ② Silicate minerals: C3S + C2S: 76.00%;

[0120] ③ Flux minerals: C3A: 8.64%, C4AF: 9.94%;

[0121] ④ Chloride ion content: 0.029%, R2O: 0.90%, liquid phase content 27.30%.

[0122] The measured strength of the clinker is: 38.3 MPa (3 days), 54.7 MPa (28 days).

[0123] According to the analysis of the above embodiments, through the cement production method of combining low-grade limestone and coal gasification slag of the present invention, not only coal gasification slag is co-fired in the cement production process, but also low-grade limestone is combined for production, and a production method of proportioning low-grade limestone and coal gasification slag together is proposed for the first time. Moreover, the strength of the final finished cement meets the standard, the early strength of the cement produced under most of the existing technologies is improved, and the hardening time of the cement is shortened.

[0124] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cement production method using low-grade limestone combined with coal gasification slag, characterized in that, It includes the following steps; Raw material selection and preparation: Select the coal gasification slag and dry it in a drying chamber. Then, grind the dried coal gasification slag and pass it through a 100 - 125 mesh fine sieve to obtain gasification slag powder. Select the dicyandiamide slag, grind it and pass it through a 200 - 250 mesh fine sieve to obtain dicyandiamide slag powder; Preparation of white raw meal: Select 77 - 100 parts of low - grade limestone after sieving, 2 - 5 parts of fly ash after sieving, 0.9 - 1.4 parts of sulfuric acid slag after sieving, 1.25 - 6 parts of the above - mentioned dicyandiamide slag powder, 1 - 8 parts of the above - mentioned gasification slag powder, 0 - 6 parts of calcium hydroxide after sieving, 0 - 1 part of magnesium slag powder after sieving and mix them to obtain white raw meal. The CaO content in the low - grade limestone is 34% - 48%; Firing of clinker: After feeding the mixed fuel into the rotary kiln, control the temperature of the rotary kiln to rise to 800 - 850 °C, and feed the above - mentioned white raw meal into the rotary kiln for preliminary sintering for 10 - 12 min. Then, control the temperature of the rotary kiln to rise to 1250 - 1350 °C within 5 - 8 min and maintain it in this temperature range for 15 - 18 min to complete the final calcination. After cooling, obtain cement clinker; Add admixture to the cement clinker to obtain the finished cement.

2. The cement production method using low-grade limestone combined with coal gasification slag according to claim 1, characterized in that, The step of adding admixture to the cement clinker to obtain the finished cement specifically includes the following steps; Step 1: Crush the cement clinker to form clinker blocks; Step 2: Grind the clinker blocks to form cement clinker powder; Step 3: Sieve the cement clinker powder separately; Step 4: Mix the admixture and the sieved cement clinker powder according to a certain ratio, then send them into a mixer for mixing, and then send them into a ball mill for secondary grinding and sieving to obtain the finished cement.

3. The cement production method using low-grade limestone combined with coal gasification slag according to claim 2, characterized in that, During the process of firing the clinker, when the clinker completes the final calcination, use a grate cooler for rapid cooling.

4. The cement production method using low-grade limestone combined with coal gasification slag according to claim 2, characterized in that, The specific requirement for sieving in the step of then sending it into a ball mill for secondary grinding and sieving to obtain the finished cement is that the sieve residue passing through a 200 - mesh sieve ≤ 10%.

5. The cement production method using low-grade limestone combined with coal gasification slag according to claim 1, characterized in that, The lime saturation factor of the white raw meal is 0.86 - 0.

96.

6. The cement production method using low-grade limestone combined with coal gasification slag according to claim 1, characterized in that, The silica ratio of the white raw meal is 2.0 - 2.

8.

7. The cement production method using low-grade limestone combined with coal gasification slag according to claim 1, characterized in that, The alumina ratio of the white raw meal is 1.3 - 1.7.

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