Ash-based all-solid waste cementing material for circulating fluidized bed and preparation method of ash-based all-solid waste cementing material

Abstract

The invention relates to the technical field of comprehensive utilization of solid waste materials, and particularly provides a circulating fluidized bed ash-based all-solid waste cementing material and a preparation method thereof. The cementing material is prepared from the following components in parts by mass: 25 to 55 parts of granulated blast furnace slag, 5 to 25 parts of CFB fly ash and 25 to 65 parts of CFB slag, an exciting agent accounting for 0-5% of the basic component is doped; the specific surface area of the cementing material is not less than 600m < 2 > / kg. Through solid waste compounding, physical grinding and chemical excitation, it is ensured that the solid waste cementing material has high cementing activity and strength; the main raw materials are industrial solid wastes, and the product can replace cement to be used for preparing concrete, prefabricated parts and the like, so that the utilization rate of the solid wastes is increased, the ecological environment problem caused by stockpiling is reduced, and the requirement of green building development in the future is met.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of solid waste materials, and particularly to a circulating fluidized bed ash-based all-solid waste cementitious material and a preparation method thereof. Background Art

[0002] Currently, the cumulative stockpile of bulk solid waste is about 60 billion tons, and the annual new stockpile is nearly 3 billion tons. It is necessary to vigorously promote the source reduction, resource utilization and harmless disposal of bulk solid waste, strengthen the whole-chain governance, focus on solving prominent contradictions and problems, and promote the new development of the resource comprehensive utilization industry.

[0003] At present, cement is the traditional cementitious material with the widest application range and the largest usage amount in construction engineering. However, the problems of resource and energy consumption and environmental pollution caused by cement production are becoming increasingly prominent, especially the CO2 emission problem. Solid waste has potential activity and cementitiousness. By using solid waste as raw material and treating it by physical and chemical means, a solid waste-based cementitious material with performance comparable to that of cement can be obtained. After its large-scale utilization, it can not only reduce waste and carbon emissions, but also have significant economic and environmental benefits. In "A Retarding Expansive Cement Prepared from CFB Ash Residue and Its Preparation Method", 35-45% CFB ash residue is added with an activator with a specific composition to prepare a retarding expansive cement, which has the advantages of high strength, retarding, controllable expansibility and good durability. However, due to the few high-value utilization ways of CFB ash residue, its consumption capacity is low. Therefore, developing new ways for the resource utilization of CFB ash residue and expanding its application in more new fields play a positive role in solving solid waste and the resulting resource waste and environmental problems. Summary of the Invention

[0004] Based on the above situation, the purpose of the present invention is to provide an all-solid waste cementitious material. By grinding granulated blast furnace slag and CFB ash residue, the cementitious activity of the raw materials is activated, meeting the characteristics of low construction requirements, low energy consumption, high strength and good durability of the cementitious material. At the same time, it has good economic benefits and carbon emission benefits, can effectively replace traditional cement-based materials, provides new ideas for the selection of construction engineering materials, and can greatly improve the utilization rate of industrial solid waste, thus overcoming the deficiencies of existing construction engineering materials and other problems.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions: The basic components of a circulating fluidized bed ash-based all-solid waste cementitious material are composed of the following components in parts by mass: 25-55 parts of granulated blast furnace slag, 5-25 parts of CFB fly ash, and 25-65 parts of CFB slag; 0-5% of an activator is externally added based on the basic components; the specific surface area of the solid waste cementitious material is not less than 600 m 2 / kg.

[0006] The preparation method of the circulating fluidized bed ash-based all-solid waste cementitious material includes the following steps: (1) Pre-grind granulated blast furnace slag and CFB slag to obtain slag powder and furnace slag powder; (2) Mix the slag powder, furnace slag powder, CFB fly ash and an appropriate amount of activator evenly according to the proportion and then grind to obtain the all-solid waste cementitious material.

[0007] The granulated blast furnace slag in the raw materials refers to the blast furnace slag for ironmaking, which is formed by rapidly cooling the molten blast furnace slag in water and has a chemical composition similar to that of cement clinker; CFB slag is the bottom slag produced by in-furnace desulfurization in the circulating fluidized bed boiler of a coal-fired power plant; CFB fly ash is the powder collected by dust removal from the flue gas of the circulating fluidized bed boiler (CFB) of a coal-fired power plant.

[0008] For the all-solid waste cementitious material, the preferred basic components include: 30-50 parts of granulated blast furnace slag, 10-20 parts of CFB fly ash, 30-60 parts of CFB slag, and 1-3% of activator is added externally based on the basic components.

[0009] In step (1), the moisture content of the granulated blast furnace slag and CFB slag is not more than 1%, and it is ground to a specific surface area of not less than 300 m 2 / kg. The contents of SiO2, Al2O3, MgO, and CaO in the chemical composition of the selected granulated blast furnace slag are not less than 90%; in step (2), the main chemical components affecting the pozzolanic activity of CFB fly ash and furnace slag powder are SiO2, Al2O3, and f-CaO, and the total content is not less than 80%. The sulfur content can reach 10% and above in terms of SO3. The main form of these sulfur-containing minerals in the ash and slag is type II anhydrite. Among them, f-CaO reacts with water to generate Ca(OH)2, which can stimulate the chemical activity of SiO2 and Al2O3 to a certain extent; therefore, the activity of the circulating fluidized bed ash and slag mainly comes from amorphous SiO2 and Al2O3. The granulated blast furnace slag contains more than 60% of the vitreous structure and the CaO content is not less than 35%; the granulated blast furnace slag reacts with the chemical components in the circulating fluidized bed ash and slag to generate calcium silicate hydrate and ettringite (AFt), improving the hydration activity and hydraulicity of the cementitious material.

[0010] The activator in step (2) is one or more of calcium chloride, sodium sulfate, calcium oxide, and triethanolamine.

[0011] In step (1), a roller mill is used for grinding, and the grinding process adopts a closed-circuit mode to ensure the fineness of pre-grinding; in step (2), a double-chamber ultrafine ball mill is used, and the grinding process adopts an open-circuit mode to ensure fineness and gradation at the same time.

[0012] The circulating fluidized bed ash-based all-solid waste cementitious material mentioned above, calculated by molar ratio, has a calcium-silicon ratio (Ca / Si) of 0.5 - 0.8 and a silicon-aluminum ratio (Si / Al) of 1.4 - 1.7.

[0013] Compared with the prior art, the present invention has the following beneficial effects: According to the raw material composition and characteristics, the present invention reasonably compounded the raw materials, which can effectively improve the hydration rate of the cementitious material system and give full play to the solid waste synergistic coupling effect; Granulated blast furnace slag reacts with the chemical components in the circulating fluidized bed ash as a calcium source to generate calcium silicate hydrate and ettringite (AFt), effectively improving the hydration activity and hydraulicity of the cementitious material; (2) By mechanical grinding and refining, the surface properties of particles can be significantly improved, promoting the dissolution of type II anhydrite in CFB ash, avoiding the late expansion problem caused by its slow dissolution rate, increasing the dissolution rate of reactive silicon and aluminum, enhancing the pozzolanic activity, promoting the formation of hydration products and the optimization of the microstructure, and thus improving the macroscopic mechanical properties of the cementitious material; The increase in the fineness of granulated blast furnace slag can homogenize the glassy structure of the slag, causing microcracks in the particles, and ions or molecules in the reactants can enter the cracks, promoting the increase in the solubility of the glass body.

[0014] (3) The chemical activation adopted in the present invention, on the one hand, is conducive to promoting the dissolution of anhydrite in the ash, re-arranging the aluminum oxide and silicon oxide interfaces therein, reducing the polymerization degrees of SiO4 and AlO6, effectively controlling the expansion, and significantly enhancing the pozzolanic activity of the ash; on the other hand, silicates, aluminates and a large amount of calcium-containing vitreous substances in granulated blast furnace slag can harden when encountering water under the excitation of the activator.

[0015] (4) The present invention can significantly improve the utilization rate of solid waste, especially the utilization of CFB ash, has the characteristics of simple process, low carbon emissions, easy industrial application, reduces the environmental protection pressure, provides a new direction for the resource utilization of solid waste, and realizes the efficient development of industrial solid waste resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 SEM photograph of the hydration products of the all-solid waste cementitious material prepared by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The technical solutions of the present invention will be further described below through specific examples. Those skilled in the art should understand that the specific embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0018] Raw material ratios of Examples 1 - 6: Table 1 Raw material ratio table

[0019] The preparation operation steps of the all-solid waste cementitious materials in Examples 1-6 are as follows: (1) Pre-grind granulated blast furnace slag and CFB slag to obtain slag powder and furnace slag powder; (2) Mix the slag powder, furnace slag powder, CFB fly ash and an appropriate amount of activator evenly according to the ratio and then grind to obtain the all-solid waste cementitious material.

[0020] Prepare mortar specimens with the cementitious materials described in Examples 1-6 respectively for performance testing. The tests are carried out with reference to the "Test Regulations for Cement and Cement Concrete in Highway Engineering" (JTG 3420-2020). The water requirement for standard consistency, setting time and soundness are tested with reference to the "Test Method for Water Requirement for Standard Consistency, Setting Time and Soundness of Cement" (GB / T 1346-2011).

[0021] Test results of the physical properties of the all-solid waste cementitious material: Table 2 Test results of the physical properties of the all-solid waste cementitious material

[0022] Test results of the mechanical properties of the all-solid waste cementitious material: Table 3 Test results of the mechanical properties of the all-solid waste cementitious material

[0023] It can be seen from Tables 2-3 that the all-solid waste cementitious material in the present invention has good mechanical properties and a short initial setting time. Because ultrafine grinding can significantly improve the particle morphology and pore structure of circulating fluidized bed ash slag, increase the bulk density and powder fluidity, and reduce its water requirement ratio. Ultrafine grinding destroys the partial crystal ordered structure of circulating fluidized bed ash slag, increases lattice defects, thereby enhancing the dissolution rate of active silicon and aluminum therein, enhancing the pozzolanic activity, promoting the formation of hydration products and the optimization of the microstructure, and further improving the macroscopic mechanical properties of its cementitious material. Adding different types of activators can improve the fluidity, increase the strength of the all-solid waste cementitious material, and shorten the initial setting and final setting times of the cementitious material. The activator accelerates the hydration reaction rate of the early cementitious material, effectively improves the hydration activity of the cementitious material, and thus increases the strength.

[0024] There is a synergistic effect between the industrial solid waste and the activator in the present invention, which can jointly improve the compressive strength and flexural strength of the product. If it is applied on a large scale, it can not only consume a large amount of solid waste materials such as industrial solid waste, but also reduce the demand for raw materials such as cement and lime in engineering construction, greatly reducing the project cost, and having important social and economic benefits.

[0025] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, for those of ordinary skill in the art, it is still possible to modify the technical solutions described in the foregoing embodiments, or to equivalently replace some of the technical features thereof; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions required to be protected by the present invention.

Claims

1. A circulating fluidized bed ash-based all-solid waste cementitious material, characterized in that: The raw materials of the circulating fluidized bed ash-based all-solid waste cementitious material, the basic components of which include: 25-55 parts of granulated blast furnace slag, 5-25 parts of CFB fly ash, 25-65 parts of CFB slag; 0-5% of the basic components of the activator; the specific surface area of ​​the solid waste cementitious material is not less than 600m2 / kg; The circulating fluidized bed ash-based all-solid waste cementitious material has a calcium-silicon ratio (Ca / Si) of 0.5-0.8 and a silicon-aluminum ratio (Si / A1) of 1.4-1.7 calculated according to the molar ratio.

2. The circulating fluidized bed ash-based all-solid waste cementitious material according to claim 1, characterized in that: The preparation of the circulating fluidized bed ash-based all-solid waste cementitious material comprises the following steps: (1) Pre-grinding granulated blast furnace slag and CFB slag to obtain slag powder and slag powder; (2) Slag powder, furnace slag powder, CFB fly ash and an appropriate amount of activator are mixed evenly in proportion and then ground to obtain a fully solid waste cementitious material.

3. The circulating fluidized bed ash-based all-solid waste cementitious material according to claim 1, characterized in that: The basic components of the all-solid waste cementitious material include 30-50 parts of granulated blast furnace slag, 10-20 parts of CFB fly ash, 30-60 parts of CFB slag, and 1-3% of the basic components of an activator.

4. The circulating fluidized bed ash-based all-solid waste cementitious material according to claim 1, characterized in that: The preferred composition is as follows: the granulated blast furnace slag and CFB slag used in step (1) have a moisture content of no more than 1% and are ground to a specific surface area of ​​no less than 300 m 2 / kg, of which the contents of SiO2, Al2O3, MgO and CaO in the chemical composition of granulated blast furnace slag are not less than 90%.

5. The circulating fluidized bed ash-based all-solid waste cementitious material according to claim 1, characterized in that: The activator in step (2) is a mixture of one or more of calcium chloride, sodium sulfate, calcium oxide and triethanolamine.

6. The circulating fluidized bed ash-based all-solid waste cementitious material according to claim 1, characterized in that: In step (1), a roller mill is used for grinding, and the grinding process adopts a closed-circuit mode; in step (2), a double-chamber ultrafine ball mill is used, and the grinding process adopts an open-circuit mode.

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