A solid waste-based retarder and preparation method thereof

Abstract

The present invention discloses a solid waste-based retarder, which is obtained by mixing pretreated CFB slag with carbide slag and grinding them; wherein the pretreated CFB slag is obtained by sequentially screening and treating the CFB slag with a composite separation liquid. The present invention uses CFB slag as the main raw material, performs screening and composite separation liquid treatment, and then combines grinding with carbide slag to effectively promote the dissolution of calcium and sulfur components, so that the expansion caused by the CFB slag mainly occurs in the plastic stage, and generates calcium sulfonate in the plastic stage of the cement-based material, which forms a coating on the cement particles and hydration products, achieving a better retarding effect; at the same time, the introduced and stimulated hydration active components are used to effectively improve the early and late strengths. The present invention realizes the resource utilization of industrial wastes such as CFB slag by relatively simple means, can effectively improve the retarding performance of the cement-based system, and takes into account good early and late strengths, and is suitable for promotion and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of industrial solid waste, and particularly relates to a solid waste-based retarder and a preparation method thereof. Background Art

[0002] Circulating fluidized bed (CFB) coal-fired technology is a new clean coal combustion technology. Compared to conventional pulverized coal boilers, CFB boiler technology offers advantages such as wide combustion adaptability, high combustion intensity, high sulfur capture efficiency, and the ability to calcine low-calorific value fuels such as gangue and coal slime. It has rapidly developed in the thermal power generation sector. However, the solid waste produced by circulating fluidized bed boilers—CFB ash (the ash collected by dust collectors after combustion with the flue gas is called "CFB fly ash," and the slag discharged from the furnace bottom is called "CFB slag," collectively referred to as "CFB ash")—is emitted in high quantities, necessitating solutions for the treatment and resource utilization of CFB ash. However, the high content of f-CaO and SO₃, its porous structure, and its high water requirement have hindered its large-scale application in the building materials industry.

[0003] In traditional cement production, natural dihydrate gypsum is often added as a cement retarder to prevent excessively rapid setting, making it unworkable. Studies have also shown that using natural anhydrite or industrial byproduct gypsum instead of natural dihydrate gypsum as a cement retarder can also adjust the setting time of cement to a certain extent. However, natural anhydrite has a dense structure, slow dissolution, and low hydration activity, making it generally unsuitable for direct use and requiring physical or chemical activation or modification. CFB slag, due to the sulfur fixation process during its production, contains large amounts of anhydrite and free calcium oxide. Therefore, the anhydrite contained in CFB slag can be used as a cement retarder instead of ordinary natural dihydrate gypsum. However, the anhydrite (II-CaSO4) in CFB slag is calcined at high temperatures of 850-900°C and has different properties from traditional dihydrate gypsum or natural gypsum. Its dissolution rate is very slow, and it tends to dissolve and participate in reactions in the late stages of hydration, which can adversely affect the stability of cement. Summary of the Invention

[0004] The main purpose of the present invention is to address the problems and shortcomings of the existing technology and provide a solid waste-based retarder prepared using CFB slag, which can effectively improve the retarding performance of cement-based systems while taking into account good early and late strength; and achieve the comprehensive utilization of industrial waste such as CFB slag through relatively simple means, which has important economic and environmental effects.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A solid waste-based retarder is obtained by mixing pretreated CFB slag and carbide slag and grinding them; wherein the pretreated CFB slag is obtained by sequentially screening the CFB slag and treating it with a composite separation liquid.

[0007] In the above scheme, the screening step is to pass through a square hole sieve with a pore size of 0.6 mm.

[0008] In the above scheme, the composite separation liquid treatment step includes: adding the small-particle CFB slag obtained by screening into the composite separation liquid, mixing evenly, sealing to obtain scum and sediment; taking the sediment, washing and drying (50-60°C).

[0009] In the above scheme, the composite separation liquid is a mixture of anhydrous ethanol and tetrabromoethane, and its density is 2.6-2.9 g / cm 3

[0010] In the above solution, the mass ratio of the small-particle CFB slag to the composite separation liquid is 1:20-30.

[0011] In the above solution, the sealing treatment time is 8 to 12 hours.

[0012] Preferably, the mixture is stirred several times during the sealing process.

[0013] In the above solution, the main chemical components of the pre-treated CFB slag and their mass percentages include: SO3 10-20%, f-CaO 1-10%, Al2O3 35-50%, and SiO2 20-35%.

[0014] In the above scheme, the amount of the carbide slag is 2 to 5 wt% of the mass of the pre-treated CFB slag.

[0015] In the above scheme, the carbide slag is obtained by drying carbide mud at 100-110° C. for 6-12 hours.

[0016] In the above scheme, the main chemical component of the carbide slag is Ca(OH)2, and its content is greater than 90wt%.

[0017] In the above scheme, the grinding step includes: grinding in a ball mill with a mill speed of 20-22 rpm, grinding bodies using steel balls with a filling rate of 30-35%, and a grinding time of 2-5 min.

[0018] In the above scheme, the particle size of the solid waste-based retarder is less than 0.075 mm, and the specific surface area is 300-500 kg / m 3 .

[0019] In the above scheme, the solid waste-based retarder is added to cement in an amount of 15-30%, which can achieve the effects of retarding the setting of cement-based materials and simultaneously enhancing them (strength above 3d).

[0020] The principle of the present invention is:

[0021] The present invention uses CFB slag as the main raw material, and first performs screening and organic solution density separation treatment to remove impurities to a certain extent and enrich II-CaSO4; then, the loose and porous structure of the CFB slag is destroyed by grinding to reduce the water demand, and combined with calcium carbide slag to effectively promote the dissolution of calcium and sulfur components, so that the expansion caused by the CFB slag occurs in the plastic stage, reducing the expansion rate; at the same time, in the alkaline environment of calcium carbide slag, the CaSO4 and f-CaO contained in the CFB slag or the Ca(OH)2 contained in the calcium carbide slag react with aluminum to generate ettringite (AFt) in the plastic stage of the cement-based material, forming a coating on the cement particles and hydration products, thereby achieving a better retarding effect; in addition, the active SiO2 and Al2O3 contained in it are also used to hydrate to improve the early and late strength.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The solid waste-based retarder of the present invention has good stability, obvious retarding effect, and can significantly improve the early and late strength of cement;

[0024] 2) The present invention can significantly dispose of solid waste CFB slag and promote the resource utilization of solid waste;

[0025] 3) The preparation process of the present invention is simple, pollution-free, low-cost, and suitable for popularization and application. DETAILED DESCRIPTION

[0026] The present invention is not limited to the above-described embodiments. Persons skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are deemed to be within the scope of protection of the present invention. Any matters not described in detail in this specification constitute prior art known to those skilled in the art.

[0027] In the following embodiments, the CFB slag used is provided by different power plants in a certain area of ​​Shanxi Province, and its main chemical components and contents are as follows: Example 1: SO3 content is 3.2%, f-CaO content is 1.5%, Al2O3 content is 29.4%, and SiO2 content is 41.6%; Example 2: SO3 content is 5.3%, f-CaO content is 2.3%, Al2O3 content is 27.6%, and SiO2 content is 46.1%; Example 3: SO3 content is 6.2%, f-CaO content is 2.7%, Al2O3 content is 32.6%, and SiO2 content is 43.6%; Example 4: SO3 content is 8.3%, f-CaO content is 2.9%, Al2O3 content is 33.1%, and SiO2 content is 41.7%; Example 5: SO3 content is 8.9%, f-CaO content is 4.6%, Al2O3 content is 34.6%, and SiO2 content is 45.7%

[0028] Example 1

[0029] A solid waste-based retarder, the preparation method of which comprises the following steps:

[0030] 1) Use a square hole sieve with a pore size of 0.6 mm to sieve the CFB slag, and take the small particle size CFB slag under the sieve; use anhydrous ethanol and tetrabromoethane to prepare a slag with a density of 2.6 g / cm 3 The small-sized CFB slag under the sieve is mixed with the composite separation liquid in a mass ratio of 1:20, sealed and allowed to stand for 8 hours, stirred three times during the period, to obtain scum and sediment; the sediment is washed with anhydrous ethanol and then dried at 50° C. to obtain pretreated CFB slag;

[0031] The obtained pretreated CFB slag has a SO3 content of 11.6%, a f-CaO content of 2.3%, an Al2O3 content of 48.3%, and a SiO2 content of 28.9%;

[0032] 2) Grind the mixture of pre-treated CFB slag and carbide slag in a ball mill at a speed of 20 rpm and a grinding body filling rate of 30% for 2 minutes to obtain a solid waste-based retarder with a specific surface area of ​​300 kg / m 3 The Ca(OH)2 content of the carbide slag used is 93.5wt%, and the amount of carbide slag added relative to the pretreated CFB slag is 4.3wt%.

[0033] The solid waste-based retarder obtained in this example and a commercially available ordinary dihydrate gypsum retarder (Comparative Example 1) were applied to cement for performance testing. The commercially available ordinary dihydrate gypsum retarder used in Comparative Example 1 had an SO3 content of 46.745%. The specific test results are shown in Table 1.

[0034] Table 1 Performance test results of cement obtained by using the retarder described in Example 1 and Comparative Example 1

[0035]

[0036] It can be seen from the above results that the solid waste-based retarder obtained in this embodiment has good stability, low water demand, obvious retarding effect, and significantly improved early and late strength compared to the traditional dihydrate gypsum retarder; it is also conducive to reasonably reducing the amount of cement used, and has significant economic and environmental benefits.

[0037] Example 2

[0038] A solid waste-based retarder, the preparation method of which comprises the following steps:

[0039] 1) Use a square hole sieve with a pore size of 0.6 mm to sieve the CFB slag, and take the small particle size CFB slag under the sieve; use anhydrous ethanol and tetrabromoethane to prepare a slag with a density of 2.7 g / cm 3 The small-sized CFB slag under the sieve was mixed with the composite separation liquid in a mass ratio of 1:22, sealed and allowed to stand for 9 hours, stirred three times during the period, to obtain scum and sediment; the sediment was washed with anhydrous ethanol and then dried at 55° C. to obtain pretreated CFB slag;

[0040] The obtained pretreated CFB slag has a SO3 content of 14.8%, a f-CaO content of 3.4%, an Al2O3 content of 38.7%, and a SiO2 content of 22.3%;

[0041] 2) The mixture of pre-treated CFB slag and carbide slag was ground in a ball mill at a speed of 22 rpm and a grinding body filling rate of 31% for 3 minutes to obtain a solid waste-based retarder with a specific surface area of ​​350 kg / m 3 Among them, the Ca(OH)2 content in the carbide slag used is 91.8%, and the content of carbide slag relative to the pretreated CFB slag is 3.4%.

[0042] The solid waste-based retarder obtained in this example and the above-mentioned commercially available ordinary dihydrate gypsum retarder were added to cement for performance comparison. The specific test results are shown in Table 2.

[0043] Table 2 Performance test results of cement obtained by using the retarder described in Example 2 and Comparative Example 1

[0044]

[0045] It can be seen from the above results that the solid waste-based retarder obtained in this embodiment has good stability, low water demand, obvious retarding effect, and significantly improved early and late strength compared to the traditional dihydrate gypsum retarder; it is also conducive to reasonably reducing the amount of cement used, and has significant economic and environmental benefits.

[0046] Example 3

[0047] A solid waste-based retarder, the preparation method of which comprises the following steps:

[0048] 1) Use a square hole sieve with a pore size of 0.6 mm to sieve the CFB slag, and take the small particle size CFB slag under the sieve; use anhydrous ethanol and tetrabromoethane to prepare a slag with a density of 2.8 g / cm 3 The small-sized CFB slag under the sieve was mixed with the composite separation liquid in a mass ratio of 1:25, and the mixture was sealed and allowed to stand for 10 hours, during which the mixture was stirred three times to obtain scum and sediment; the sediment was washed with anhydrous ethanol and then dried at 57° C. to obtain pretreated CFB slag;

[0049] The obtained pretreated CFB slag has a SO3 content of 16.3%, a f-CaO content of 4.7%, an Al2O3 content of 42.7%, and a SiO2 content of 25.6%;

[0050] 2) The mixture of pre-treated CFB slag and carbide slag was ground in a ball mill at a speed of 20 rpm and a grinding body filling rate of 31% for 3.5 min; the solid waste-based retarder obtained had a specific surface area of ​​400 kg / m 3 Among them, the Ca(OH)2 content in carbide slag is 92.6%, and the carbide slag dosage is 3.8%.

[0051] The solid waste-based retarder obtained in this example and the above-mentioned commercially available ordinary dihydrate gypsum retarder were added to cement for performance comparison. The specific test results are shown in Table 3.

[0052] Table 3 Performance test results of cement obtained by using the retarder described in Example 3 and Comparative Example 1

[0053]

[0054] It can be seen from the above results that the solid waste-based retarder obtained in this embodiment has good stability, low water demand, obvious retarding effect, and significantly improved early and late strength compared to the traditional dihydrate gypsum retarder; it is also conducive to reasonably reducing the amount of cement used, and has significant economic and environmental benefits.

[0055] Example 4

[0056] A solid waste-based retarder, the preparation method of which comprises the following steps:

[0057] 1) Use a square hole sieve with a pore size of 0.6 mm to sieve the CFB slag, and take the small particle size CFB slag under the sieve; use anhydrous ethanol and tetrabromoethane to prepare a slag with a density of 2.9 g / cm 3The small-sized CFB slag under the sieve was mixed with the composite separation liquid in a mass ratio of 1:27, sealed and allowed to stand for 11 hours, stirred three times during the period, to obtain scum and sediment; the sediment was washed with anhydrous ethanol and then dried at 53°C to obtain pretreated CFB slag;

[0058] The obtained pretreated CFB slag has a SO3 content of 18.1%, a f-CaO content of 6.5%, an Al2O3 content of 41.7%, and a SiO2 content of 32.1%;

[0059] 2) The mixture of pre-treated CFB slag and carbide slag was ground in a ball mill at a speed of 21 rpm and a grinding body filling rate of 33% for 4 minutes to obtain a solid waste-based retarder with a specific surface area of ​​450 kg / m 3 Among them, the Ca(OH)2 content in carbide slag is 90.6%, and the carbide slag dosage is 2.9%.

[0060] The solid waste-based retarder obtained in this example and the above-mentioned commercially available ordinary dihydrate gypsum retarder were added to cement for performance comparison. The specific test results are shown in Table 4.

[0061] Table 4 Performance test results of cement obtained by using the retarder described in Example 4 and Comparative Example 1

[0062]

[0063] It can be seen from the above results that the solid waste-based retarder obtained in this embodiment has good stability, low water demand, obvious retarding effect, and significantly improved early and late strength compared to the traditional dihydrate gypsum retarder; it is also conducive to reasonably reducing the amount of cement used, and has significant economic and environmental benefits.

[0064] Example 5

[0065] A solid waste-based retarder, the preparation method of which comprises the following steps:

[0066] 1) Use a square hole sieve with a pore size of 0.6 mm to sieve the CFB slag, and take the small particle size CFB slag under the sieve; use anhydrous ethanol and tetrabromoethane to prepare a slag with a density of 2.9 g / cm 3 The small-sized CFB slag under the sieve was mixed with the composite separation liquid in a mass ratio of 1:30, sealed and allowed to stand for 12 hours, stirred three times during the period, to obtain scum and sediment; the sediment was washed with anhydrous ethanol and dried at 60°C to obtain pretreated CFB slag;

[0067] The obtained pretreated CFB slag has a SO3 content of 19.8%, a f-CaO content of 8.9%, an Al2O3 content of 43.7%, and a SiO2 content of 34.6%;

[0068] 2) The mixture of pre-treated CFB slag and carbide slag was ground in a ball mill at a speed of 22 rpm and a grinding body filling rate of 33% for 5 min; the solid waste-based retarder obtained had a specific surface area of ​​500 kg / m 3 ; Among them, the Ca(OH)2 content in carbide slag is 91.5%, and the carbide slag dosage is 2.4%.

[0069] The solid waste-based retarder obtained in this example and the above-mentioned commercially available ordinary dihydrate gypsum retarder were added to cement for performance comparison. The specific test results are shown in Table 5.

[0070] Table 5 Performance test results of cement obtained by using the retarder described in Example 5 and Comparative Example 1

[0071]

[0072] It can be seen from the above results that the solid waste-based retarder obtained in this embodiment has good stability, low water demand, obvious retarding effect, and significantly improved early and late strength compared to the traditional dihydrate gypsum retarder; it is also conducive to reasonably reducing the amount of cement used, and has significant economic and environmental benefits.

[0073] Comparative Example 2

[0074] A solid waste-based retarder, the preparation method of which is substantially the same as that of Example 1, except that carbide slag is not introduced.

[0075] The solid waste-based retarders obtained in Comparative Example 2 and Example 1 were added to cement for performance testing. The addition amount of both in cement was 29.5%. The properties of the prepared cement are shown in Table 6.

[0076] Table 6 Performance test results of cement obtained by using the retarder described in Example 1 and Comparative Example 2

[0077]

[0078] It can be seen from Table 6 that the solid waste-based retarder without carbide slag has a poor retarding effect and cannot play a good retarding and strengthening role.

[0079] Comparative Example 3

[0080] A solid waste-based retarder, the preparation method of which is substantially the same as that of Example 1, except that a 2.36 mm pore square sieve is used for screening the CFB slag.

[0081] The solid waste-based retarders obtained in Comparative Example 3 and Example 1 were added to cement for performance testing. The dosage of both in cement was 29.5%. At the same time, the dosage of Comparative Example 3 in cement was further increased (47.1%) so that the SO3 content of the prepared cement was the same as that of Example 1 (the SO3 content was 3.42%). The performance of the prepared cement is shown in Table 7.

[0082] Table 7 Performance test results of cement obtained by using the retarder described in Example 1 and Comparative Example 3

[0083]

[0084]

[0085] It can be seen from Table 7 that the solid waste-based retarder prepared by using undersize CFB slag screened with an aperture greater than 0.6 mm has a poor retarding effect and cannot guarantee good retarding and strengthening effects.

[0086] Obviously, the above preferred embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. However, any obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A solid waste-based retarder, characterized in that: The pretreated CFB slag is mixed with carbide slag and ground to obtain the slag; wherein the pretreated CFB slag is obtained by screening the CFB slag and treating it with a composite separation liquid in sequence; The sieving step is to pass through a square hole sieve with a pore size of 0.6 mm; The amount of the carbide slag is 2-5 wt% of the mass of the pre-treated CFB slag; The composite separation liquid is a mixture of anhydrous ethanol and tetrabromoethane, and its density is 2.6-2.9 g / cm 3 ; The main chemical components of pretreated CFB slag and their mass percentages include: SO3 10~20%, f-CaO 1~10%, Al2O3 35~50%, SiO2 20~35%; The main chemical component of the carbide slag is Ca(OH)2, and its content is greater than 90 wt%.

2. The solid waste-based retarder according to claim 1, characterized in that: The composite separation liquid treatment step comprises: adding the small-particle CFB slag obtained by screening into the composite separation liquid, mixing evenly, sealing to obtain scum and sediment; taking the sediment, washing and drying.

3. The solid waste-based retarder according to claim 1, characterized in that: The grinding step includes: grinding with a ball mill, the mill speed is 20-22 rpm, the grinding body is steel balls, the filling rate is 30-35%, and the grinding time is 2-5 minutes.

4. The solid waste-based retarder according to claim 1, characterized in that: The solid waste-based retarder has a particle size of less than 0.075 mm and a specific surface area of ​​300 to 500 kg / m³.

5. The solid waste-based retarder according to claim 1, characterized in that: The solid waste-based retarder is added in an amount of 15-30% in cement.

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