Preparation method of large-dosage coal gasification slag-based cement

Abstract

The application discloses a preparation method of high-content coal gasification slag-based cement, and belongs to the technical field of solid waste resource utilization. High-carbon coal gasification slag, steel slag, carbide slag and clay are used as raw materials, low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum are used as active admixtures, the rate value is designed and the configuration proportion of various raw materials and active admixtures is calculated according to the chemical composition of the finally prepared high-content coal gasification slag-based cement; then the various raw materials and active admixtures are pretreated, the pretreated raw materials are mixed, ball milled and sieved to prepare cement raw materials and further prepare cement clinker; finally, the cement clinker and the active admixtures are mixed, ball milled and sieved to prepare the high-content coal gasification slag-based cement. The high-content coal gasification slag-based cement is prepared by fully utilizing industrial solid wastes, can replace natural raw materials for producing cement, meets the national "double carbon" planning, and is a low-carbon, environment-friendly and green cement preparation method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource utilization, and in particular to a preparation method of a large-mixing-amount coal gasification slag-based cement. TECHNICAL BACKGROUND

[0002] Coal gasification technology is a front pillar of modern coal chemical industry in China, and its large-scale application will correspondingly produce a large amount of solid waste, i.e. coal gasification slag. The annual emission amount of coal gasification slag in China is more than 50 million tons. At present, the main treatment methods of coal gasification slag are landfill and open-air stacking, and the utilization rate is low. A large amount of stacked coal gasification slag pollutes the ecological environment such as soil and water source.

[0003] Cement is the most widely used building material in the world, and its production is accompanied by a large amount of carbon emission and energy consumption. At present, the carbon emission amount of cement production accounts for 27% of the total global industrial carbon emission amount. At present, under the background of the "double carbon" target, solid waste resource utilization and low-carbon cement production face new opportunities and challenges. The related patents for preparing cement by using coal gasification slag reported at present all have a mixing amount of less than 30%, and most of them are used as active admixture. Therefore, preparation of large-mixing-amount coal gasification slag-based cement not only reduces the CO2 emission amount and the cement production cost from the source, but also solves the stacking problem of coal gasification slag, and provides technical support for large-mixing-amount coal gasification slag-based cement production and large-scale solid waste consumption. SUMMARY

[0004] In view of the above technical problems, the present application aims to provide a preparation method of large-mixing-amount coal gasification slag-based cement. The large-mixing-amount coal gasification slag-based cement provided by the present application meets the standard requirements of GB175-2020 "General Portland Cement", and the preparation process is simple and can meet the industrial application in many aspects. The method uses coal gasification slag as the main raw material, cooperates with other solid wastes such as steel slag and carbide slag, and replaces natural mineral resources to prepare large-mixing-amount coal gasification slag-based cement. The method not only can consume a large amount of stacked coal gasification slag and solid waste such as steel slag, but also can realize low-carbon and green cement production, and has good economic and social benefits.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of large-mixing-amount coal gasification slag-based cement, which comprises the following steps:

[0006] (1) Raw material selection: high-carbon coal gasification slag, steel slag, carbide slag and clay are used as raw materials, and low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum are used as active admixture for preparing large-mixing-amount coal gasification slag-based cement; a rate value is designed according to the chemical composition of the finally prepared large-mixing-amount coal gasification slag-based cement; and the configuration proportion of various raw materials and active admixtures is calculated according to the designed rate value and the chemical composition of the raw materials and active admixtures, and various raw materials and active admixtures are weighed according to the configuration proportion for standby;

[0007] (2) Raw material preparation: The weighed high-carbon coal gasification slag, steel slag, carbide slag, clay, low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum are respectively pretreated and dried to a water content of <1%, and then are preliminarily ground. The preliminarily ground high-carbon coal gasification slag, steel slag, carbide slag and clay are mixed, ball milled and sieved to prepare cement raw material;

[0008] (3) Clinker preparation: water is added to the prepared cement raw material to make it into wet powder, and then the wet powder is pressed and molded, dried to obtain test blocks, and then the test blocks are calcined and post-processed to obtain cement clinker;

[0009] (4) Cement preparation: the prepared cement clinker is mixed with the low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum preliminarily ground in step (2), ball milled and sieved to prepare a large amount of coal gasification slag-based cement. The low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum are not only raw materials for preparing the large amount of coal gasification slag-based cement, but also active admixtures for adjusting and improving the physical and chemical properties and performance indicators of the large amount of coal gasification slag-based cement.

[0010] Preferably, the loss on ignition of the high-carbon coal gasification slag in step (1) is ≥24.8%. At present, most of the coal gasification slag discharged in China has a loss on ignition of 20%-40%. When the loss on ignition is 20%-30%, the coal gasification slag is difficult to be resourcefully utilized. The present application uses this part of the difficult-to-resourcefully-utilize gasification slag as a raw material to prepare low-carbon cement clinker, which can promote the large-scale consumption of coal gasification slag.

[0011] Preferably, the loss on ignition of the low-carbon coal gasification slag in step (1) is ≤5.4%. When the coal gasification slag is used as an active admixture, the loss on ignition of the coal gasification slag should be limited. When the loss on ignition is higher than 5.4%, the water demand of the cement product will increase, and the mechanical properties of the cement will decrease.

[0012] Preferably, the rate value formula in step (1) includes lime saturation coefficient KH, aluminum rate IM and silicon rate SM formula, and the specific formulas are as follows:

[0013]

[0014]

[0015]

[0016] Preferably, the rate values designed in step (1) are as follows: lime saturation coefficient KH = 0.74-0.89, aluminum rate IM = 2.64-3.1, and silicon rate SM = 1.58-1.63.

[0017] Preferably, the preliminary grinding in step (2) is such that the residue of the ground raw material through a 200-mesh sieve is less than or equal to 10%. After the preliminary grinding, the specific surface area of the high-carbon coal gasification slag is 450 m 2 / kg, and the specific surface area of the low-carbon coal gasification slag is 550 m 2 / kg.

[0018] Preferably, the post-treatment in step (3) is specifically crushing, grinding, and sieving the calcined and cooled test block to obtain cement clinker.

[0019] Preferably, in step (4), the prepared cement clinker is mixed with the low-carbon coal gasification slag, circulating fluidized bed fly ash, and desulfurization gypsum after the preliminary grinding in step (1), and then ball-milled and sieved. The sieving is specifically such that the residue of the sieved material through a 200-mesh sieve is less than or equal to 10%.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application first uses high-carbon coal gasification slag as the main raw material, fully utilizes the carbon-containing characteristics of the coal gasification slag, mixes the coal gasification slag with steel slag, carbide slag, and clay to prepare cement clinker, and replaces natural raw material limestone. The low-carbon coal gasification slag, circulating fluidized bed fly ash, and desulfurization gypsum are finely ground to serve as active admixtures, and then mixed with the cement clinker to prepare high-content coal gasification slag-based cement. The SO3 and free calcium oxide in the circulating fluidized bed fly ash can stimulate the active substances in the coal gasification slag to generate more hydration products. The desulfurization gypsum can provide more calcium components and reduce the setting time of the cement. Therefore, the addition of the circulating fluidized bed fly ash and the desulfurization gypsum in the present application can compensate for the low early strength and long setting time of the coal gasification slag-based cement. According to the designed rate value, the ratio of various raw materials is designed according to the physicochemical properties of different raw materials, so that the solid waste addition in the cement clinker is greater than or equal to 80%, and the total addition of the coal gasification slag in the raw materials is greater than or equal to 49%. The present application effectively saves natural raw materials and energy consumption in preparation, and the prepared high-content coal gasification slag-based cement meets the standard requirements of P.O. 42.5 strength grade cement in GB 175-2020 “General Portland Cement”.

[0022] The present application fully utilizes industrial solid waste to prepare high-content coal gasification slag-based cement, which can effectively replace natural raw materials for cement production, conforms to the national “double carbon” plan, and is a low-carbon, environmentally friendly, and green cement preparation method. DETAILED DESCRIPTION

[0023] In order to better explain the technical solutions of the present application, the following will combine the examples of the present application to explain the technical solutions of the present application.

[0024] The raw materials and active admixtures used in the following examples include high-carbon coal gasification slag, steel slag, carbide slag, clay, low-carbon coal gasification slag, circulating fluidized bed fly ash, desulfurization gypsum, and the chemical compositions and loss on ignition (LOI) of the various raw materials and active admixtures are shown in Table 1 below:

[0025] Table 1 Chemical compositions and loss on ignition (LOI) of various raw materials and active admixtures in Example 1-5 of the present application

[0026]

[0027] Table 2 Configuration ratio of raw materials and active admixtures for preparing high-amount coal gasification slag-based cement in the examples of the present application

[0028]

[0029] Example 1

[0030] A method for preparing high-amount coal gasification slag-based cement, comprising the following steps:

[0031] (1) Raw material preparation: The chemical compositions of the high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash, and desulfurization gypsum used in this example are shown in Table 1. According to the chemical composition of the final prepared high-amount coal gasification slag-based cement, the rate value is designed according to the rate value formulas (1)-(3), i.e., lime saturation coefficient KH, aluminum rate IM, and silicon rate SM formulas, wherein the lime saturation coefficient KH = 0.88, the aluminum rate IM = 2.64, and the silicon rate SM = 1.58. The configuration ratio of each raw material and active admixture is calculated according to the designed rate value and the chemical composition of the raw materials and active admixtures, and the specific configuration ratio is shown in Table 2. Then, the various raw materials and active admixtures are weighed according to the configuration ratio for standby use.

[0032] (2) Raw material preparation: First, the weighed high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash, and desulfurization gypsum are pre-dried at 105°C for 24 hours. Then, the preliminarily ground high-carbon coal gasification slag, steel slag, carbide slag, and clay are mixed and ball-milled to pass through a 200-mesh sieve with a sieve residue of ≤10%, to obtain cement raw material.

[0033] (3) Clinker preparation: Water is added to the prepared cement raw material to make it into a wet powder. The wet powder is pressed into a round cake by a full-automatic press under a pressure of 15 MPa and a pressure holding time of 30 seconds, and then dried in a 105°C oven for 24 hours to obtain a test block. The test block is calcined at 1450°C for 35 minutes, naturally cooled, broken by a small crusher, and then ground by a grinding machine to pass through a 200-mesh square hole sieve with a sieve residue of ≤5%, to obtain cement clinker.

[0034] (4) Cement preparation: The prepared cement clinker, low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum after preliminary grinding in step (2) were mixed and ball milled, and then sieved through a 200-mesh screen, with a sieve residue of ≤10%, to prepare a large-dosage coal gasification slag-based cement. The mechanical properties and working performance of the cement met the standard requirements of P.O. 42.5 cement in GB 175-2020 “Common Portland Cement”. The specific data are shown in Tables 3 and 4.

[0035] Example 2

[0036] A method for preparing a large-dosage coal gasification slag-based cement, comprising the following steps:

[0037] (1) Raw material preparation: The chemical compositions of the high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum selected in this example are shown in Table 1. According to the chemical composition of the final prepared large-dosage coal gasification slag-based cement, the rate value design was performed according to the rate value formula, i.e., lime saturation coefficient KH, aluminum rate IM and silicon rate SM formula, wherein the lime saturation coefficient KH = 0.8, the aluminum rate IM = 2.8, and the silicon rate SM = 1.61. The configuration ratio of each raw material and active admixture was calculated according to the designed rate value and the chemical composition of the raw materials and active admixtures, and the specific configuration ratio is shown in Table 2. Then, various raw materials and active admixtures were weighed according to the configuration ratio for standby.

[0038] (2) Raw material preparation: The weighed high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum were first dried at 95°C for 12h. Then, the high-carbon coal gasification slag, steel slag, carbide slag and clay after preliminary grinding were mixed and ball milled through a 200-mesh screen, with a sieve residue of ≤10%, to prepare cement raw material.

[0039] (3) Clinker preparation: Water was added to the prepared cement raw material to make it into a wet powder. The wet powder was pressed into a round cake by a full-automatic press under the conditions of a pressure of 15 MPa and a pressure holding time of 30s, and then dried in a 105°C oven for 24h to obtain a test block. The test block was calcined at 1400°C for 40 minutes, naturally cooled, broken by a small crusher, and then ground finely in a grinding machine. After sieving through a 200-mesh square hole screen, the sieve residue was within 5%, to obtain a cement clinker.

[0040] (4) Cement preparation: The prepared cement clinker, low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum after preliminary grinding in step (2) were mixed and ball milled, and then sieved through a 200-mesh screen, with a sieve residue of ≤10%, to prepare a large-dosage coal gasification slag-based cement. The mechanical properties and working performance of the cement met the standard requirements of P.O. 42.5 cement in GB 175-2020 “Common Portland Cement”. The specific data are shown in Tables 3 and 4.

[0041] Example 3

[0042] The present embodiment provides a preparation method of a large-mixing coal gasification slag-based cement.

[0043] (1) Raw material preparation: The chemical compositions of the high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum selected in the present embodiment are shown in Table 1. According to the chemical composition of the final prepared large-mixing coal gasification slag-based cement, the rate value design is carried out according to the rate value formula, i.e. lime saturation coefficient KH, aluminum rate IM and silicon rate SM formula, wherein the lime saturation coefficient KH = 0.89, the aluminum rate IM = 2.8, and the silicon rate SM = 1.63; the configuration ratio of each raw material and active admixture is calculated according to the designed rate value and the chemical composition of the raw material and active admixture, and the specific configuration ratio is shown in Table 2, and then each raw material and active admixture is weighed according to the configuration ratio for standby.

[0044] (2) Raw material preparation: First, the weighed high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum are respectively pre-dried at 80°C for 24h, and then the high-carbon coal gasification slag, steel slag, carbide slag and clay after preliminary grinding are mixed and ball milled through a 200-mesh sieve with a sieve residue ≤10%, to prepare a cement raw material.

[0045] (3) Clinker preparation: water is added to the prepared cement raw material to make it into a wet powder, which is pressed into a round cake by a full-automatic press under the condition of a pressure of 10MPa and a pressure holding time of 60s, and then dried in a 105°C oven for 24h to obtain a test block. The test block is calcined at 1350°C for 45 minutes, naturally cooled, broken by a small crusher, and then ground finely in a grinding machine, and then sieved through a 200-mesh square hole sieve with a sieve residue ≤5%, to obtain a cement clinker.

[0046] (4) Cement preparation: the prepared cement clinker is mixed with the low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum after preliminary grinding in step (2), and then ball milled and sieved through a 200-mesh sieve with a sieve residue ≤10%, to prepare a large-mixing coal gasification slag-based cement, the mechanical properties and working performance of which meet the standard requirements of P.O.42.5 cement in GB 175-2020 “General Portland Cement”. The specific data are shown in Tables 3 and 4.

[0047] Example 4

[0048] The present embodiment provides a preparation method of a large-mixing coal gasification slag-based cement.

[0049] (1) Raw material preparation: The chemical compositions of high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum selected in this example are shown in Table 1. According to the chemical composition of the finally prepared high-content coal gasification slag-based cement, the rate value formula, i.e. lime saturation coefficient KH, aluminum rate IM and silicon rate SM formula, is used for rate value design, wherein the lime saturation coefficient KH is 0.74, the aluminum rate IM is 3.1, and the silicon rate SM is 1.62; the configuration ratio of each raw material and active admixture is calculated according to the designed rate value and the chemical composition of the raw material and active admixture, and the specific configuration ratio is shown in Table 2, and then various raw materials and active admixtures are weighed according to the configuration ratio for standby.

[0050] (2) Raw material preparation: First, the weighed high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum are respectively pre-dried at 95°C for 24h, then the high-carbon coal gasification slag, steel slag, carbide slag and clay after preliminary grinding are mixed and ball milled through a 200 mesh sieve, and the sieve residue is ≤10%, to prepare the cement raw material.

[0051] (3) Clinker preparation: Water is added to the prepared cement raw material to make it into a wet powder, and then it is pressed into a round cake shape by a full-automatic press under the condition of pressure 15MPa and pressure holding time 60s, and then dried in a 105°C oven for 24h to obtain a test block. The test block is calcined at 1450°C for 35 minutes, naturally cooled, broken by a small crusher, and then ground in a grinding machine, and then passed through a 200 mesh square hole sieve with a sieve residue of less than 5%, to obtain a cement clinker.

[0052] (4) Cement preparation: The prepared cement clinker is mixed with the low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum after preliminary grinding in step (2), and then ball milled and passed through a 200 mesh sieve with a sieve residue of ≤10%, to prepare a high-content coal gasification slag-based cement, and the mechanical properties and working performance meet the standard requirements of P.O.42.5 cement in GB 175-2020 “General Portland Cement”. The specific data are shown in Tables 3 and 4.

[0053] Example 5

[0054] The present example provides a preparation method of a high-content coal gasification slag-based cement.

[0055] (1) Raw material preparation: The chemical compositions of high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum selected in this example are shown in Table 1. According to the chemical composition of the finally prepared high-mix coal gasification slag-based cement, the rate value formula, i.e. lime saturation coefficient KH, aluminum rate IM and silicon rate SM formula, is used for rate value design, wherein the lime saturation coefficient KH is 0.86, the aluminum rate IM is 2.91, and the silicon rate SM is 1.60; the configuration ratio of each raw material and active admixture is calculated according to the designed rate value and the chemical composition of the raw material and active admixture, and the specific configuration ratio is shown in Table 2, and then various raw materials and active admixtures are weighed according to the configuration ratio for standby.

[0056] (2) Raw material preparation: First, the weighed high-carbon coal gasification slag, low-carbon coal gasification slag, steel slag, carbide slag, clay, circulating fluidized bed fly ash and desulfurization gypsum are respectively pre-dried at 80°C for 24h, then the high-carbon coal gasification slag, steel slag, carbide slag and clay after preliminary grinding are mixed and ball milled through a 200 mesh sieve, and the sieve residue is ≤10%, to prepare cement raw material.

[0057] (3) Clinker preparation: water is added to the prepared cement raw material to make it into wet powder, and then it is pressed into a round cake by a full-automatic press under the condition of pressure 10MPa and pressure holding time 60s, and then dried in a 105°C oven for 24h to obtain a test block. The test block is calcined at 1350°C for 45 minutes, naturally cooled, broken by a small crusher, and then ground in a grinding machine, and then sieved through a 200 mesh square hole sieve, and the sieve residue is within 5%, to obtain cement clinker.

[0058] (4) Cement preparation: the prepared cement clinker is mixed with the low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum after preliminary grinding in step (2), and then ball milled and sieved through a 200 mesh sieve, and the sieve residue is ≤10%, to prepare high-mix coal gasification slag-based cement, and the mechanical properties and working performance meet the standard requirements of P.O.42.5 cement in GB 175-2020 “General Portland Cement”. The specific data are shown in Table 3 and Table 4.

[0059] Table 3 Comparison of carbon emission and mechanical properties of high-mix coal gasification slag-based cement prepared in this example and ordinary Portland cement (P.O.42.5)

[0060] Table 3 Comparison of carbon emission and mechanical properties of high-mix coal gasification slag-based cement prepared in this example and ordinary Portland cement (P.O.42.5)

[0061]

[0062] Table 4 Comparison of working performance of high-mix coal gasification slag-based cement prepared in this example and ordinary Portland cement (P.O.42.5)

[0063] Table 4: Comparison of working performance of cement of the application and ordinary Portland cement

[0064]

[0065]

[0066] From Table 3 and Table 4, it can be seen that the coal gasification slag-based cement prepared in the application has excellent mechanical properties, working performance and low carbon dioxide emission, which provides a technical approach for solid waste resource utilization and realization of emission reduction in cement industry production.

[0067] The above description is only the preferred embodiment of the present application, and does not limit the technical scope of the process of the present application. For those skilled in the art, any deformation, equivalent replacement and improvement made on the basis of the technical route of the present application, in accordance with the concept of the present application, does not affect the optimization effect of the present application. Therefore, the patent protection scope of the present application should be subject to the content of the claims.

Claims

1. A method for preparing high-volume coal gasification slag-based cement, characterized in that, Includes the following steps: (1) Raw material selection: High-carbon coal gasification slag, steel slag, carbide slag, and clay are used as raw materials, and low-carbon coal gasification slag, circulating fluidized bed fly ash, and desulfurized gypsum are used as active admixtures for preparing high-volume coal gasification slag-based cement. According to the chemical composition of the final high-volume coal gasification slag-based cement, the rate value is designed according to the rate value formula. Based on the designed rate value and the chemical composition of the raw materials and active admixtures, the configuration ratio of various raw materials and active admixtures is calculated, and various raw materials and active admixtures are weighed according to the configuration ratio for later use. The loss on ignition of the low-carbon coal gasification slag is ≤5.4%. (2) Raw meal preparation: The weighed high-carbon coal gasification slag, steel slag, carbide slag, clay, low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurization gypsum are pretreated and dried to a moisture content of <1%, and then pre-ground; the pre-ground high-carbon coal gasification slag, steel slag, carbide slag and clay are then mixed, ball-milled and sieved to obtain cement raw meal; The aforementioned rate formulas include formulas for the lime saturation coefficient KH, the aluminum ratio IM, and the silicon ratio SM, the specific formulas of which are as follows: （1） （2） （3） The ratios are: lime saturation coefficient KH = 0.74~0.89, aluminum ratio IM = 2.64~3.1, and silicon ratio SM = 1.58~1.

63. (3) Clinker preparation: Water is added to the prepared cement raw meal to make it wet powder, which is then pressed into shape, dried to obtain test blocks, and the test blocks are then calcined and post-treated to obtain cement clinker. (4) Cement preparation: The cement clinker obtained is mixed with the low-carbon coal gasification slag, circulating fluidized bed fly ash and desulfurized gypsum that were initially ground in step (2), ball milled and then sieved to obtain high-volume coal gasification slag-based cement; the sieve residue is ≤10% after passing through a 200-mesh sieve.

2. The method for preparing a high-volume coal gasification slag-based cement according to claim 1, characterized in that: The loss on ignition of the high-carbon coal gasification slag mentioned in step (1) is ≥24.8%.

3. The method for preparing a high-volume coal gasification slag-based cement according to claim 1, characterized in that: In the preliminary grinding in step (2), the amount of residue on the sieve after grinding is ≤10% when the raw material passes through a 200-mesh sieve.

4. The method for preparing a high-volume coal gasification slag-based cement according to claim 1, characterized in that: The post-processing described in step (3) specifically involves crushing, grinding, and sieving the calcined and cooled test blocks to obtain cement clinker.

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