Calcium silicate board synthesized from industrial solid waste and method for preparing the same

Abstract

The present application belongs to the field of comprehensive utilization of solid waste resources, and relates to a calcium silicate board synthesized from industrial solid waste and a preparation method thereof. The calcium silicate board comprises oil-removed waste diatomite, fly ash, slaked lime, fiber and activator. In the present application, wood fiber is modified by hydrothermal treatment with citric acid modification, so as to reduce the water absorption of the wood fiber. The modified wood fiber is compounded with rock wool fiber to exert the tensile strength of the modified wood fiber and the heat resistance and chemical stability of the rock wool fiber. In the present application, a pre-hydration process is designed. After the oil-removed waste diatomite is mixed with the fly ash and reacts with excess calcium hydroxide, the product can provide nucleation sites as crystal nuclei, significantly accelerating the hydration kinetics process of the system. In combination with a continuous two-stage temperature-controlled steam pressure curing process, the crystal phase content of tobermorite in the calcium silicate board is increased, and the macroscopic performance of the material is comprehensively improved. Moreover, the present application can absorb a large amount of oil-containing waste diatomite and fly ash, realizing the resource utilization of industrial solid waste.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of solid waste resources, specifically relating to a calcium silicate board synthesized from industrial solid waste and its preparation method. Background Technology

[0002] Calcium silicate board is made primarily from siliceous and calcareous raw materials, supplemented with fibers and various additives. Its production process mainly includes pulping, molding, pre-curing, autoclaving, drying, cutting, and sanding. Calcium silicate board possesses core advantages such as high strength, excellent fire resistance, and waterproofing and moisture resistance, and has been widely used in civil and industrial construction. In recent years, to add additional functions such as humidity regulation, deodorization, and indoor air purification, calcium silicate boards using diatomaceous earth as the siliceous raw material have gradually emerged. Its unique porous structure endows the board with richer functions. However, this type of calcium silicate board has lower mechanical properties, making it difficult to meet increasingly stringent usage requirements. Furthermore, compared to conventional siliceous raw materials such as fly ash and quartz sand, diatomaceous earth has a higher raw material cost, which also limits its large-scale application in calcium silicate board production.

[0003] In aluminum processing and rolling, when diatomaceous earth is used as a filter aid to filter rolling oil, some oil, aluminum shavings, dust, and oil residue remain in the diatomaceous earth, forming oily waste diatomaceous earth. Approximately 150-200 kg of diatomaceous earth is needed to produce 1 ton of aluminum foil, and the resulting oily waste diatomaceous earth contains about 25%-30% rolling oil. With the continuous increase in my country's aluminum production capacity, the discharge of oily waste diatomaceous earth is increasing year by year, posing significant environmental and safety risks. The rolling oil contained in waste diatomaceous earth has been listed in the "National Hazardous Waste List." Improper storage will pollute soil and groundwater, harm the ecological environment and human health, and easily cause fire hazards. Its volatile vapors can also cause acute poisoning and various occupational health damages. Thermal desorption technology can effectively remove volatile and semi-volatile organic pollutants from solid matrices. This technology has been included in China's "Guidelines for Environmental Management of Onshore Hazardous Waste Mining" and is listed as a priority technology encouraged for application. Oily waste diatomaceous earth can be obtained by first thermally desorbing it and then calcining it to obtain oil-free waste diatomaceous earth from which the rolling oil has been completely removed. Using this oil-free waste diatomaceous earth as the main raw material to prepare calcium silicate boards can realize the resource utilization of solid waste, saving a large amount of natural mineral resources and reducing production costs.

[0004] Based on the above, there is an urgent need to develop calcium silicate board products using degreased waste diatomaceous earth as the main raw material, and at the same time, to develop preparation methods that can improve its mechanical properties. Summary of the Invention

[0005] In view of the above-mentioned technical problems, this invention proposes a calcium silicate board synthesized from two industrial solid wastes, oil-removed waste diatomaceous earth and fly ash, and its preparation method. The comprehensive performance of this calcium silicate board is improved, and it meets the requirements of JC / T564.1-2018 "Fiber-reinforced calcium silicate board Part 1: Asbestos-free calcium silicate board" standard, realizing the resource utilization of oil-containing waste diatomaceous earth and fly ash.

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

[0007] A calcium silicate board synthesized from industrial solid waste comprises the following raw materials in parts by weight: 80-100 parts of degreased waste diatomaceous earth, 10-30 parts of fly ash, 50-70 parts of hydrated lime, 4-8 parts of fiber, and 3-9 parts of activator.

[0008] Furthermore, the degreased waste diatomite is obtained by thermal desorption and calcination to remove oil from oily waste diatomite generated in the aluminum processing industry.

[0009] Preferably, the specific treatment method for oil-removed waste diatomaceous earth is as follows: the oil-containing waste diatomaceous earth is quantitatively fed into a horizontal tubular heating device, nitrogen is introduced, the heating device is heated to 280~350℃, and thermal desorption is carried out by maintaining the temperature; the oil and gas generated by desorption enter the condensation system with the nitrogen to recover the rolling oil, and the waste diatomaceous earth containing a small amount of oil is calcined at 400~450℃ in an oxygen-enriched air atmosphere for 0.5~1 h to obtain oil-removed waste diatomaceous earth without residual oil and carbon.

[0010] Furthermore, the fibers include modified wood fibers and rock wool fibers. The mass ratio of modified wood fibers to rock wool fibers is 1:1.

[0011] Furthermore, the modified wood fiber is prepared by the following method: wood fiber is placed in a citric acid aqueous solution with a mass fraction of 5%~10%, and added to a dynamic hydrothermal reactor at a material-to-liquid ratio of 1:10. After stirring at 140℃ for 1~2 h, it is cooled to room temperature and then dried to obtain citric acid modified wood fiber, i.e., modified wood fiber.

[0012] Preferably, the wood fibers have a length of 1-3 mm and a diameter of 40-60 μm.

[0013] Furthermore, the activator comprises component A and component B, with a mass ratio of component A to component B of 1:1.

[0014] Preferably, component A is at least one of sodium silicate and potassium silicate with a modulus of 2.4 and a Baumé number of 50; component B is at least one of sodium persulfate and potassium persulfate.

[0015] A method for preparing calcium silicate board synthesized from industrial solid waste includes the following steps: Step 1: Weigh 20%~40% of the mass of degreased waste diatomaceous earth and 20%~40% of the mass of fly ash, and mix them thoroughly with activator and quicklime; then, add deionized water at a water-ash ratio of w / c=0.6, stir evenly, and pour into a container; heat the container in a water bath to obtain a pre-hydrated suspension. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold, pressurize and pre-cur it, demold it and then autoclave and dry it to obtain calcium silicate board synthesized from industrial solid waste.

[0016] Furthermore, in step 1, the water bath heating reaction specifically involves: raising the temperature to 60~80℃ and maintaining a constant temperature, continuously stirring, and allowing the reaction to proceed at a constant temperature for 12~20 hours.

[0017] Furthermore, in step 3, the pressurization time is 15-20 minutes, and the pressure is 10-15 MPa.

[0018] Furthermore, in step 3, the pre-curing is carried out at room temperature for 12-24 hours.

[0019] Furthermore, in step 3, the autoclaving adopts a continuous two-stage temperature control method. First, low-temperature autoclaving is carried out for 1.5 to 2 hours at 120~130℃ and 0.19~0.27 MPa, followed by high-temperature autoclaving for 8 to 12 hours at 180~200℃ and 1.2~1.4 MPa.

[0020] Furthermore, in step 3, the drying time is 1~2 hours and the temperature is 100~120℃.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0022] 1. The calcium silicate board synthesized from industrial solid waste prepared by this invention can effectively utilize large quantities of oily waste diatomaceous earth and fly ash, realizing the resource utilization of industrial solid waste and reducing its environmental harm. This technology has both significant economic and environmental benefits, and helps promote the sustainable development of enterprises.

[0023] 2. The high hydroxyl content in the molecular structure of wood fiber makes it prone to absorbing a large amount of free water during mixing with other raw materials, leading to a decrease in the water-cement ratio. This, in turn, increases internal defects in the calcium silicate board during the later curing stage, restricting its mechanical properties. To reduce the water absorption of wood fiber, this invention employs citric acid modification hydrothermal treatment. In a high-temperature acidic aqueous medium, residual lignin, waxes, and oils are removed. Simultaneously, the carboxyl groups in the citric acid molecules undergo esterification with the hydroxyl groups on the surface of the wood fiber, forming stable ester bonds after dehydration, thus achieving covalent grafting of carboxyl functional groups onto the fiber skeleton. When the modified wood fiber comes into contact with calcium hydroxide, the un-esterified carboxyl groups in the grafted citric acid molecules on the fiber surface react chemically with calcium ions in the calcium hydroxide, achieving a strong chemical bond between the modified fiber and calcium hydroxide.

[0024] 3. This invention combines modified wood fiber and rock wool fiber, and incorporates them into the calcium silicate board substrate. This composite incorporation method fully utilizes the excellent tensile strength of modified wood fiber and the excellent heat resistance and chemical stability of rock wool fiber. While ensuring the calcium silicate board maintains its lightweight, environmentally friendly characteristics and controllable cost, this invention significantly improves the mechanical strength and heat resistance of the board, effectively reducing its moisture expansion rate. The improved calcium silicate board is better suited for applications requiring high humidity and high temperature.

[0025] 4. To accelerate the pozzolanic reaction of oil-removed diatomaceous earth and fly ash, this invention designs a pre-hydration process. A portion of the oil-removed diatomaceous earth is mixed with fly ash and then reacted with excess calcium hydroxide (hydrated lime) under specific temperature conditions, allowing the raw materials to dissolve and release silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra. When the silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra in the pre-hydration suspension accumulate to a critical concentration, hydration products such as calcium silicate hydrate (CSH), calcium aluminate hydrate (CAH), and calcium aluminosilicate hydrate (CASH) are generated. Due to the small particle size of these hydration products, they can provide nucleation sites as crystal nuclei in the subsequent pre-curing process, significantly accelerating the hydration kinetics of the system.

[0026] 5. Unlike traditional single-temperature autoclaving curing processes, this invention employs a continuous two-stage temperature-controlled autoclaving curing process. The low-temperature autoclaving curing stage, building upon pre-hydration and pre-curing, further enhances the hydration reaction between the degreased diatomaceous earth and fly ash, constructing a dense green body structure and optimizing its microporous structure. This stage effectively prevents structural damage to the green body under high vapor pressure during subsequent high-temperature autoclaving curing, ultimately increasing the formation of tobermorite and improving the density and mechanical properties of the calcium silicate board matrix.

[0027] 6. Component A (sodium / potassium silicate) in the activator can significantly increase the alkalinity of the reaction system; component B (sodium / potassium persulfate) is activated in an alkaline environment, generating ·SO₄⁻, ·OH free radicals, and SO₄²⁻. 2- The aforementioned free radicals can lower the activation energy barrier for the depolymerization of Si-OT (T is Si or Al) bonds in degreased diatomaceous earth and fly ash, and under the synergistic effect of the system's alkalinity, can significantly accelerate the breaking process of Si-OT bonds. The aluminum-oxygen tetrahedra and Ca in the system... 2+ SO4 2- The reaction produces ettringite, which, by consuming aluminate components, creates a gradient difference in the concentration of relevant ions in the pore solution, thereby promoting the dissolution of fly ash particles. Furthermore, free radicals lower the activation energy required for the formation of new Si-O and Ca-O bonds, promoting the formation of CSH and driving the formation of the tobermorite crystalline phase during autoclaving. Therefore, the synergistic effect of components A and B can effectively regulate the reaction process and significantly improve the overall performance of the calcium silicate board.

[0028] 7. The preparation process of this invention is simple, with low production cost and short production cycle. The resulting calcium silicate board has excellent comprehensive properties: flexural strength can reach 9.78 MPa; density is 1.07~1.21 g·cm³. -3 The water absorption rate is between 17.50% and 24.89%; the wet expansion rate is between 0.126% and 0.156%; and the non-combustibility meets GB8624 Class A. All the above characteristics and properties meet the technical requirements for calcium silicate boards in standard JC / T564.1-2018, and can be widely used in construction projects. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] A calcium silicate board synthesized from industrial solid waste comprises the following raw materials in parts by weight: 80-100 parts of degreased waste diatomaceous earth, 10-30 parts of fly ash, 50-70 parts of hydrated lime, 4-8 parts of fiber, and 3-9 parts of activator.

[0031] In one possible embodiment, the degreased waste diatomite is obtained by thermal desorption and calcination of oily waste diatomite generated in the aluminum processing industry.

[0032] In one possible embodiment, the specific treatment method for oil-removed waste diatomaceous earth is as follows: the oil-containing waste diatomaceous earth is quantitatively fed into a horizontal tubular heating device, nitrogen is introduced, the heating device is heated to 280~350℃, and thermal desorption is carried out by maintaining the temperature; the oil and gas generated by desorption enter the condensation system with the nitrogen to recover the rolling oil, and the waste diatomaceous earth containing a small amount of oil is calcined at 400~450℃ in an oxygen-enriched air atmosphere for 0.5~1h to obtain oil-removed waste diatomaceous earth without residual oil and carbon.

[0033] In one possible embodiment, the fibers include modified wood fibers and rock wool fibers; wherein the mass ratio of modified wood fibers to rock wool fibers is 1:1; the wood fibers have a length of 1~3 mm and a diameter of 40~60 μm.

[0034] In one possible embodiment, the modified wood fiber is prepared by the following method: placing wood fiber in a citric acid aqueous solution with a mass fraction of 5%~10%, adding it to a dynamic hydrothermal reactor at a material-to-liquid ratio of 1:10, stirring at 140°C for 1~2 h, cooling to room temperature and drying to obtain citric acid modified wood fiber, i.e., modified wood fiber.

[0035] In one possible embodiment, the activator comprises component A and component B, wherein the mass ratio of component A to component B is 1:1; component A is at least one of sodium silicate or potassium silicate with a modulus of 2.4 and a Baumé number of 50; and component B is at least one of sodium persulfate or potassium persulfate.

[0036] A method for preparing calcium silicate board synthesized from industrial solid waste includes the following steps: Step 1: Weigh 20%~40% of the mass of degreased waste diatomaceous earth and 20%~40% of the mass of fly ash, and mix them thoroughly with activator and slaked lime; then, add deionized water at a water-ash ratio of w / c=0.6, stir evenly, and pour into a container; subject the container to a water bath heating reaction, specifically: raise the temperature to 60~80℃ and maintain a constant temperature, stir continuously, and wait for the constant temperature reaction for 12~20 hours to obtain a pre-hydrated suspension; Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and pressurize it for 15-20 minutes at a pressure of 10-15 MPa; pre-curing at room temperature for 12-24 hours; after demolding, perform autoclaving, including low-temperature autoclaving at 120-130℃ and 0.19-0.27 MPa for 1.5-2 hours, followed by high-temperature autoclaving at 180-200℃ and 1.2-1.4 MPa for 8-12 hours; dry at 100-120℃ for 1-2 hours to obtain calcium silicate board synthesized from industrial solid waste.

[0037] Example 1.

[0038] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 90 parts of degreased waste diatomaceous earth, 20 parts of fly ash, 60 parts of hydrated lime, 6 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 6 parts of activator (containing component A: sodium silicate; component B: sodium persulfate; the mass ratio of component A to component B is 1:1).

[0039] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 30% of the mass of degreased waste diatomaceous earth and 30% of the mass of fly ash, and mix the two materials thoroughly with activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c=0.6 and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 70°C and maintain the temperature while stirring continuously. After the constant temperature reaction lasts for 16 hours, the pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 15 MPa for 10 min. Step 4: Pre-cur the pressurized wet blank at room temperature for 18 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 120℃ and 0.19 MPa for 1.5 h, and then perform high-temperature autoclaving at 190℃ and 1.2 MPa for 10 h. Step 6: Dry the autoclaved slab for 1.5 hours at a temperature of 110°C to obtain calcium silicate board.

[0040] Example 2.

[0041] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 80 parts of degreased waste diatomaceous earth, 30 parts of fly ash, 50 parts of slaked lime, 4 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 3 parts of activator (containing component A: potassium water glass; component B: potassium peroxymonosulfate; the mass ratio of component A to component B is 1:1).

[0042] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 20% of the mass of degreased waste diatomaceous earth and 20% of the mass of fly ash, and mix the two materials thoroughly with activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c=0.6 and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 60°C and maintain the temperature at a constant temperature while stirring continuously. After the constant temperature reaction lasts for 12 hours, a pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 20 MPa for 15 minutes. Step 4: Pre-cur the pressurized wet blank at room temperature for 12 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 120℃ and 0.19MPa for 2 hours, followed by high-temperature autoclaving at 180℃ and 1.0MPa for 8 hours. Step 6: Dry the autoclaved slab for 1 hour at 100°C to obtain calcium silicate board.

[0043] Example 3.

[0044] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 100 parts of degreased waste diatomaceous earth, 10 parts of fly ash, 70 parts of hydrated lime, 8 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 9 parts of activator (containing component A: sodium silicate; component B: sodium persulfate; the mass ratio of component A to component B is 1:1).

[0045] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 40% of the mass of degreased waste diatomaceous earth and 40% of the mass of fly ash, and mix the two materials thoroughly with activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c=0.6 and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 80°C and maintain the temperature at a constant temperature while stirring continuously. After the constant temperature reaction lasts for 20 hours, a pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 15 MPa for 10 min. Step 4: Pre-cur the pressurized wet blank at room temperature for 24 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: first perform low-temperature autoclaving at 130℃ and 0.27 MPa for 1.5 h, and then perform high-temperature autoclaving at 200℃ and 1.4 MPa for 12 h. Step 6: Dry the autoclaved slab for 2 hours at 120°C to obtain calcium silicate board.

[0046] Example 4.

[0047] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 80 parts of degreased waste diatomaceous earth, 30 parts of fly ash, 60 parts of slaked lime, 4 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 9 parts of activator (containing component A: potassium water glass; component B: potassium peroxymonosulfate; the mass ratio of component A to component B is 1:1).

[0048] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 20% of the mass of degreased waste diatomaceous earth and 40% of the mass of fly ash, and mix the two materials thoroughly with activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c=0.6 and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 70°C and maintain the temperature at a constant temperature while stirring continuously. After the constant temperature reaction lasts for 12 hours, the pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 20 MPa for 15 minutes. Step 4: Pre-cur the pressurized wet blank at room temperature for 18 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 130℃ and 0.27 MPa for 2 hours, followed by high-temperature autoclaving at 180℃ and 1.0 MPa for 12 hours. Step 6: Dry the autoclaved slab for 1 hour at 110°C to obtain calcium silicate board.

[0049] Example 5.

[0050] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 100 parts of degreased waste diatomaceous earth, 10 parts of fly ash, 60 parts of hydrated lime, 8 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1), and 3 parts of activator (containing component A: sodium silicate; component B: sodium persulfate. The mass ratio of component A to component B is 1:1).

[0051] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 40% of the mass of degreased waste diatomaceous earth and 20% of the mass of fly ash, and mix the two materials thoroughly with activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c=0.6 and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 70°C and maintain the temperature while stirring continuously. After the constant temperature reaction lasts for 20 hours, the pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 15 MPa for 15 min. Step 4: Pre-cur the pressurized wet blank at room temperature for 12 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: first perform low-temperature autoclaving at 120℃ and 0.19 MPa for 1.5 h, and then perform high-temperature autoclaving at 200℃ and 1.4 MPa for 8 h. Step 6: Dry the autoclaved slab for 2 hours at 100℃ to obtain calcium silicate board.

[0052] Example 6.

[0053] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 90 parts of degreased waste diatomaceous earth, 20 parts of fly ash, 50 parts of slaked lime, 6 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 9 parts of activator (containing component A: potassium water glass; component B: potassium peroxymonosulfate; the mass ratio of component A to component B is 1:1).

[0054] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 30% of the mass of degreased waste diatomaceous earth and 30% of the mass of fly ash, and mix the two materials thoroughly with activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c=0.6 and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 60°C and maintain the temperature at a constant temperature while stirring continuously. After the constant temperature reaction lasts for 16 hours, a pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 20 MPa for 10 minutes. Step 4: Pre-cur the pressurized wet blank at room temperature for 24 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 120℃ and 0.19 MPa for 2 hours, followed by high-temperature autoclaving at 190℃ and 1.2 MPa for 10 hours. Step 6: Dry the autoclaved slab for 1.5 hours at 120°C to obtain calcium silicate board.

[0055] Comparative Example 1.

[0056] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 90 parts of degreased waste diatomaceous earth, 20 parts of fly ash, 60 parts of hydrated lime, 6 parts of fiber (the mass ratio of unmodified wood fiber to rock wool fiber is 1:1) and 6 parts of activator (containing component A: sodium silicate; component B: sodium persulfate; the mass ratio of component A to component B is 1:1).

[0057] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 30% of the mass of degreased waste diatomaceous earth and 30% of the mass of fly ash, and mix the two materials thoroughly with activator and quicklime. Then, add deionized water at a water-ash ratio of w / c=0.6 and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed, heat the container in a water bath to 70°C and maintain the temperature, while continuously stirring. After the constant temperature reaction lasts for 16 hours, the pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 15 MPa for 10 min. Step 4: Pre-cur the pressurized wet blank at room temperature for 18 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 120℃ and 0.19 MPa for 1.5 h, and then perform high-temperature autoclaving at 190℃ and 1.2 MPa for 10 h. Step 6: Dry the autoclaved slab for 1.5 hours at a temperature of 110°C to obtain calcium silicate board.

[0058] Comparative Example 2.

[0059] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 90 parts of degreased waste diatomaceous earth, 20 parts of fly ash, 60 parts of hydrated lime, 6 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 6 parts of activator (containing component A: sodium silicate; component B: sodium persulfate; the mass ratio of component A to component B is 1:1).

[0060] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Mix the activator, quicklime, degreased waste diatomaceous earth and fly ash, then add water at a water-cement ratio of w / c=0.35 and stir evenly to obtain a wet blank; Step 2: Place the wet blank into the mold and apply pressure at 15 MPa for 10 min. Step 3: Pre-cur the pressurized wet blank at room temperature for 18 hours, and then demold it; Step 4: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 120℃ and 0.19 MPa for 1.5 h, followed by high-temperature autoclaving at 190℃ and 1.2 MPa for 10 h. Step 5: Dry the autoclaved slab for 1.5 hours at a temperature of 110°C to obtain calcium silicate board.

[0061] Comparative Example 3.

[0062] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 90 parts of degreased waste diatomaceous earth, 20 parts of fly ash, 60 parts of hydrated lime, 6 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 6 parts of activator (containing only component A: sodium silicate).

[0063] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 30% of the mass of degreased diatomaceous earth and 30% of the mass of fly ash, and thoroughly mix the two materials with the activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c = 0.6, and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 70°C and maintain the temperature while continuously stirring. After reacting at this constant temperature for 16 hours, a pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 15 MPa for 10 min. Step 4: Pre-cur the pressurized wet blank at room temperature for 18 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 120℃ and 0.19 MPa for 1.5 h, and then perform high-temperature autoclaving at 190℃ and 1.2 MPa for 10 h. Step 6: Dry the autoclaved slab for 1.5 hours at a temperature of 110°C to obtain calcium silicate board.

[0064] Comparative Example 4.

[0065] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 90 parts of degreased waste diatomaceous earth, 20 parts of fly ash, 60 parts of hydrated lime, 6 parts of fiber (the mass ratio of modified wood fiber to rock wool fiber is 1:1) and 6 parts of activator (containing only component B: sodium persulfate).

[0066] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 30% of the mass of degreased diatomaceous earth and 30% of the mass of fly ash, and thoroughly mix the two materials with the activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c = 0.6, and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 70°C and maintain the temperature while continuously stirring. After reacting at this constant temperature for 16 hours, a pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 15 MPa for 10 min. Step 4: Pre-cur the pressurized wet blank at room temperature for 18 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab: First, perform low-temperature autoclaving at 120℃ and 0.19 MPa for 1.5 h, and then perform high-temperature autoclaving at 190℃ and 1.2 MPa for 10 h. Step 6: Dry the autoclaved slab for 1.5 hours at a temperature of 110°C to obtain calcium silicate board.

[0067] Comparative Example 5.

[0068] The calcium silicate board of this embodiment is made from the following raw materials in parts by weight: 90 parts of degreased waste diatomaceous earth, 20 parts of fly ash, 60 parts of hydrated lime, 6 parts of fiber (the mass ratio of unmodified wood fiber to rock wool fiber is 1:1) and 6 parts of activator (containing component A: sodium silicate; component B: sodium persulfate; the mass ratio of component A to component B is 1:1).

[0069] The method for preparing the calcium silicate board in this embodiment includes the following steps: Step 1: Weigh 30% of the mass of degreased diatomaceous earth and 30% of the mass of fly ash, and thoroughly mix the two materials with the activator and slaked lime. Then, add deionized water at a water-ash ratio of w / c = 0.6, and stir until the mixture is homogeneous. Finally, pour the mixture into a container at a uniform speed. Heat the container in a water bath to 70°C and maintain the temperature while continuously stirring. After reacting at this constant temperature for 16 hours, a pre-hydrated suspension can be obtained. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold and apply pressure at 15 MPa for 10 min. Step 4: Pre-cur the pressurized wet blank at room temperature for 18 hours, and then demold it. Step 5: Perform autoclaving on the demolded slab at a temperature of 190℃, a pressure of 1.2 MPa, and a time of 10 h. Step 6: Dry the autoclaved slab for 1.5 hours at a temperature of 110°C to obtain calcium silicate board.

[0070] The calcium silicate board samples prepared in Examples 1-6 and Comparative Examples 1-5 were tested according to relevant standards for flexural strength (GB / T 7019-2024), density (GB / T 7019-2024), water absorption (GB / T 7019-2024), wet expansion rate (GB / T7019-2024), and non-combustibility (GB / T 5464-2010). The results are shown in Table 1.

[0071] Table 1. Performance test results of calcium silicate boards prepared in the examples and comparative examples.

[0072] According to the test results, the comprehensive performance of the samples in Examples 1-6 of this invention is excellent: the flexural strength can reach 9.78 MPa, meeting the requirements of R2 grade (≥7 MPa) in standard JC / T 564.1-2018; the density is 1.07~1.21 g·cm³. -3 The water absorption rate is between 17.50% and 24.89%, meeting the requirements for Class A boards in standard JC / T 564.1-2018 (≤30%); the wet expansion rate is between 0.126% and 0.156%, meeting the requirements in standard JC / T564.1-2018 (≤0.25%); and the non-combustibility meets the requirements of standard JC / T 564.1-2018 and conforms to GB8624 Class A.

[0073] In comparison, the water absorption rate of Comparative Example 1 was higher, at 29.65%, demonstrating that wood fiber modification can reduce the water absorption of calcium silicate board. The flexural strengths of Comparative Examples 1-5 were lower, at 7.45 MPa, 6.12 MPa, 5.87 MPa, 6.49 MPa, and 8.09 MPa respectively, proving that wood fiber modification, pre-hydration process, the synergistic effect of components A and B in the activator, and the continuous two-stage temperature-controlled autoclaving curing process can all effectively improve the flexural strength of calcium silicate board. Besides producing high-performance calcium silicate boards, this invention enables the recycling of large quantities of oily waste diatomaceous earth and fly ash, reducing their environmental harm and lowering the production cost of calcium silicate board.

Claims

1. A calcium silicate board synthesized from industrial solid waste, characterized in that, The raw materials include the following parts by weight: 80-100 parts of degreased waste diatomaceous earth, 10-30 parts of fly ash, 50-70 parts of hydrated lime, 4-8 parts of fiber, and 3-9 parts of activator.

2. The calcium silicate board according to claim 1, characterized in that, The oil-removed waste diatomaceous earth is obtained by thermal desorption and calcination of oil-containing waste diatomaceous earth generated in the aluminum processing industry.

3. The calcium silicate board according to claim 2, characterized in that, The specific treatment method for oil-removed waste diatomaceous earth is as follows: The oil-containing waste diatomaceous earth is quantitatively fed into a horizontal tubular heating device. After nitrogen is introduced, the heating device is heated to 280~350℃ and kept at the temperature for thermal desorption. The oil and gas generated during desorption enter the condensation system with the nitrogen to recover the rolling oil. The waste diatomaceous earth containing a small amount of oil is calcined at 400~450℃ in an oxygen-rich air atmosphere for 0.5~1 h to obtain oil-removed waste diatomaceous earth without residual oil or carbon.

4. The calcium silicate board according to claim 1, characterized in that, The fibers include modified wood fibers and rock wool fibers; the mass ratio of modified wood fibers to rock wool fibers is 1:

1.

5. The calcium silicate board according to claim 4, characterized in that, The modified wood fiber is prepared by the following method: wood fiber is placed in a citric acid aqueous solution with a mass fraction of 5%~10%, and added to a dynamic hydrothermal reactor at a material-to-liquid ratio of 1:

10. After stirring at 140℃ for 1~2 h, it is cooled to room temperature and then dried to obtain citric acid modified wood fiber, i.e., modified wood fiber.

6. The calcium silicate board according to claim 1, characterized in that, The activator comprises component A and component B; component A is at least one of sodium silicate and potassium silicate with a modulus of 2.4 and a Baumé number of 50; component B is at least one of sodium persulfate and potassium persulfate; the mass ratio of component A to component B is 1:

1.

7. A method for preparing calcium silicate board synthesized from industrial solid waste, characterized in that, Includes the following steps: Step 1: Weigh 20%~40% of the mass of degreased waste diatomaceous earth and 20%~40% of the mass of fly ash, and mix them thoroughly with activator and quicklime; then, add deionized water at a water-ash ratio of w / c=0.6, stir evenly, and pour into a container; heat the container in a water bath to obtain a pre-hydrated suspension. Step 2: Mix the prehydrated suspension with the fiber and the remaining degreased diatomaceous earth and fly ash, adjust the water quality to make the water-ash ratio w / c=0.35, and stir to obtain a wet blank. Step 3: Place the wet blank into the mold, pressurize and pre-cur it, demold it and then autoclave and dry it to obtain calcium silicate board synthesized from industrial solid waste.

8. The method for preparing calcium silicate board according to claim 7, characterized in that, In step 1, the water bath heating reaction specifically involves: raising the temperature to 60~80℃ and maintaining a constant temperature, continuously stirring, and waiting for the constant temperature reaction to last for 12~20 hours.

9. The method for preparing calcium silicate board according to claim 7, characterized in that, In step 3, the pressurization time is 15-20 min and the pressure is 10-15 MPa; the pre-curing is at room temperature and the pre-curing time is 12-24 h.

10. The method for preparing calcium silicate board according to claim 7, characterized in that, In step 3, the autoclaving adopts a continuous two-stage temperature control method. First, low-temperature autoclaving is carried out for 1.5 to 2 hours at 120~130℃ and 0.19~0.27 MPa. Then, high-temperature autoclaving is carried out for 8 to 12 hours at 180~200℃ and 1.2~1.4 MPa.

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