Manufacturing process of flue gas desulfurization gypsum fireproof door core plate

Abstract

The invention discloses a desulfurized gypsum fireproof door core board manufacturing process in the field of building materials, which comprises the following steps: calcining and activating desulfurized phosphogypsum, mixing with desulfurized building gypsum, adding a pre-prepared modified composite material to form a base material, sieving cement to remove agglomerates, coating the inner wall of a mold with a release agent, and preheating; a gypsum foaming agent and water are pre-dissolved and defoamed and then added into a stirrer by several times through a metering pump, meanwhile, cement, a base material and other raw materials are added, and a planetary stirrer is adopted for stirring at a low speed and then at a high speed to form slurry; after the slurry is injected into a mold, standing and initially setting, removing the mold; the interface combination is optimized through the modified composite material, the fireproof performance, the mechanical strength and the dimensional stability are improved, meanwhile, the production cost is reduced, the industrial byproduct gypsum resource is efficiently utilized, the environmental pollution is reduced, and the building fireproof safety requirement is met.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a manufacturing process of a desulfurized gypsum fireproof door core board. Background Art

[0002] As a key component of a building's fire protection system, the fire resistance, mechanical strength, and environmental friendliness of its core panels directly impact the overall fire protection effectiveness and service life. Traditional fire door core panels often rely on wood, plastic, or inorganic cementitious materials. Wood core panels are flammable and resource-intensive, while plastic-based core panels pose the risk of releasing toxic gases upon high-temperature decomposition. While conventional inorganic gypsum-based core panels offer some fire resistance, they often struggle to meet the stringent requirements for high-performance fire doors in modern buildings due to issues such as insufficient strength, cracking, or excessive hygroscopicity. With the advancement of policies for the comprehensive utilization of industrial solid waste, desulfurized gypsum, a byproduct of flue gas desulfurization in coal-fired power plants, has a significant annual output and possesses potential for gelling activity. It has gradually become a research hotspot for the production of environmentally friendly building materials as an alternative to natural gypsum. However, desulfurized gypsum itself suffers from defects such as a loose crystal structure, high water demand, high porosity in the hardened form, and limited fire resistance. Direct use in door core panels can easily lead to unstable product strength, insufficient fire resistance, or dimensional deformation, limiting its application in high-end fire doors.

[0003] Although research on the improvement of desulfurized gypsum-based door core panels has been carried out, it still faces multiple technical challenges. On the one hand, if the activation treatment process of desulfurized gypsum (such as calcination and grinding) is not properly controlled, it is difficult to effectively stimulate its gelling activity, resulting in weak bonding between the matrix and the reinforcing material, and the product is prone to delamination or cracking; on the other hand, the demand for lightweight door core panels usually relies on the foaming process, but traditional foaming agents have poor compatibility with gypsum systems, and the foaming process is prone to introducing large bubbles or uneven bubble distribution, which not only reduces the strength of the material, but may also cause a decrease in fire resistance due to pore rupture. In addition, in order to improve the overall performance, existing technologies often try to add modified materials such as fibers, polymers or inorganic fillers, but the composite methods of these materials are mostly simple blending, which makes it difficult to form an interfacial synergistic effect, resulting in limited modification effects, and the introduction of some modifiers (such as chemical synthetics) may increase the environmental burden, which is not in line with the development trend of green building materials.

[0004] Against this backdrop, the development of a manufacturing process for desulfurized gypsum fire-resistant door core panels that combines high fire resistance, excellent mechanical strength, and environmental friendliness is urgent. This invention, by optimizing the activation and compounding process of desulfurized gypsum and combining it with the directional design of modified composite materials and precise foaming technology, effectively addresses the shortcomings of existing desulfurized gypsum-based door core panels, including insufficient strength, weak fire resistance, and poor process adaptability. This provides a new technical path for the high-value utilization of industrial solid waste and the development of high-performance fire-resistant building materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a desulfurized gypsum fire door core board manufacturing process, which solves the problems of low strength, insufficient fire resistance, poor water resistance and inefficient utilization of industrial solid waste in traditional desulfurized gypsum fire door core boards.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] A process for manufacturing a desulfurized gypsum fireproof door core board comprises the following steps:

[0008] S1, desulfurized phosphogypsum is activated by calcination at 150-200°C, cooled to 20-25°C, mixed with desulfurized building gypsum, and pre-mixed with modified composite materials to form a base material; cement is sieved to remove lumps; a release agent is applied to the inner wall of the mold and preheated to 40-45°C;

[0009] S2, the gypsum foaming agent is pre-dissolved in water, allowed to stand for defoaming, and then added to the mixer via a metering pump. At the same time, cement, base material, water reducer, retarder, and cellulose are added to the mixer and stirring is started;

[0010] S3, using a planetary mixer to first stir at a low speed to mix the dry materials, and then stir at a high speed to obtain a slurry;

[0011] S4: After the slurry is injected into the mold, it is allowed to set and then the mold is removed.

[0012] According to a preferred embodiment of the present invention, the desulfurized phosphogypsum is purchased from KM-I type phosphogypsum of Guizhou Kailin Group Co., Ltd.

[0013] According to a preferred embodiment of the present invention, the desulfurized building gypsum is purchased from BN-II type building gypsum of Beijing New Building Materials Group Co., Ltd.

[0014] According to a preferred embodiment of the present invention, the cement is purchased from CA-50 (calcium aluminate content ≥50%, suitable for early strength and high temperature resistance scenarios) from Zhengzhou Aluminum City Special Cement Co., Ltd.

[0015] According to a preferred embodiment of the present invention, the mold is purchased from Qingdao Degut Energy Saving Equipment Co., Ltd., a DG-2024-FJ type fire door core panel special steel mold.

[0016] According to a preferred embodiment of the present invention, the release agent is purchased from Jiangsu Sunrise Chemical Co., Ltd. and is a Sunrise brand SR-2024 silicone oil-based release agent.

[0017] According to a preferred embodiment of the present invention, the gypsum foaming agent is purchased from Aladdin brand SDS-I type sodium octadecyl sulfate from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0018] According to a preferred embodiment of the present invention, the mixer is an LT-800 planetary mixer purchased from Shandong Longteng Machinery Manufacturing Co., Ltd.

[0019] According to a preferred embodiment of the present invention, the water reducer is purchased from KZJ-PCA-Ⅱ polycarboxylic acid high performance water reducer of KZJ New Materials Group Co., Ltd.

[0020] According to a preferred embodiment of the present invention, the retarder is purchased from Chenghua brand F-I type sodium gluconate from Chengdu Chemical Industry Co., Ltd.

[0021] According to a preferred embodiment of the present invention, the cellulose is purchased from Heda brand HPMC-400 hydroxypropyl methylcellulose of Shandong Heda Group Co., Ltd.

[0022] According to a preferred embodiment of the present invention, in step S1, the premixing time is 10-15 minutes; and the cement is passed through an 80-85 mesh sieve.

[0023] In step S1 of the present invention, the desulfurized phosphogypsum is activated by calcination at 150-200°C. The high temperature causes the dihydrate gypsum in the desulfurized phosphogypsum to partially lose its crystalline water and transform into hemihydrate gypsum, disrupting the original crystal structure, increasing the specific surface area and active sites, and enhancing its reactivity with desulfurized building gypsum. After cooling to 20-25°C, it is mixed with the desulfurized building gypsum. The two interact at the microscopic level through ion exchange and lattice reconstruction, optimizing the microstructure of the door core panel.

[0024] According to a preferred embodiment of the present invention, in step S2, the mass ratio of the gypsum foaming agent to water is 1:(5-6), the pre-dissolution temperature is 30-35°C; the standing time is 5-10 min, the gypsum foaming agent is added to the mixer 3-4 times through a metering pump, and the interval time for each addition is 2-3 min; the stirring speed is 30-40 r / min.

[0025] In step S2 of the present invention, the gypsum foaming agent and water are pre-dissolved at a mass ratio of 1:5-6 at 30-35°C. This temperature is close to the optimal dissolution temperature of the foaming agent, allowing the foaming agent molecules to be fully dispersed in the water, forming a uniform solution. The solution is then allowed to stand for 5-10 minutes to defoam, removing unstable bubbles and reducing their impact on the performance of the door core panel. The foaming agent solution is added to the mixer through a metering pump, and cement, base material, water reducer, retarder, and cellulose are added at the same time and stirred at a speed of 30-40r / min. The gypsum foaming agent forms tiny bubbles in the solution, reducing the slurry density and forming a uniform pore structure; the water reducer molecules are adsorbed on the surface of cement particles, increasing the surface charge density of the particles, generating electrostatic repulsion, prompting the cement particles to disperse with each other, releasing the encapsulated water, and improving the fluidity and strength of the slurry; the retarder is adsorbed on the surface of cement hydration products, preventing contact between cement particles, delaying the cement hydration reaction rate, and prolonging the slurry setting time; the hydroxyl groups on the cellulose molecular chain form hydrogen bonds with water molecules, forming a spatial network structure in the slurry, increasing the slurry viscosity, and improving its water retention and stability.

[0026] According to a preferred embodiment of the present invention, in step S3, the rotation speed of low-speed stirring is 30-40 r / min, and the low-speed stirring time is 3-4 min; the rotation speed of high-speed stirring is 60-80 r / min, and the high-speed stirring time is 5-6 min.

[0027] In step S3 of the present invention, the planetary mixer first stirs at a low speed of 30-40 r / min for 3-4 minutes to fully mix the dry materials at low speed, avoiding excessive heat generated by high-speed stirring, which may lead to local overheating of the slurry and deterioration of material properties. At the same time, it prevents agglomeration of the dry materials and ensures uniform distribution of the components. Then, the planetary mixer stirs at a high speed of 60-80 r / min for 5-6 minutes. The high-speed stirring further disperses and refines the components in the slurry, evenly distributes the bubbles in the slurry, and obtains a uniform slurry, providing a good molding foundation for the door core board.

[0028] According to a preferred embodiment of the present invention, in step S4, the temperature of the slurry is 25-30° C., and the standing time is 15-20 minutes.

[0029] In step S4 of the present invention, after the slurry is injected into the mold, it is allowed to set for 15-20 minutes at 25-30°C. This temperature range matches the slurry temperature, allowing the slurry to slowly hydrate under appropriate temperature conditions, gradually developing initial strength and facilitating subsequent mold removal. After initial setting, the mold is removed, and the door core panel enters the subsequent curing stage.

[0030] According to a preferred embodiment of the present invention, the desulfurized gypsum fireproof door core board manufacturing process further comprises: allowing the door core board prepared in step S4 to stand at a temperature of 20-30° C. for 72-144 hours.

[0031] The present invention also provides a desulfurized gypsum fireproof door core board prepared by the desulfurized gypsum fireproof door core board manufacturing process. The raw materials thereof include, by mass percentage: desulfurized phosphogypsum: 70-75%; cement: 3-5%; desulfurized building gypsum: 12-15%; modified composite material: 15-16%; gypsum foaming agent: 0.3-0.5%; water reducing agent: 0.2-0.5%; retarder: 0.3-0.5%; and cellulose: 0.2-0.4%.

[0032] According to a preferred embodiment of the present invention, the steps of preparing the modified composite material include:

[0033] A1: Mix waste oyster shell powder with chitosan solution, disperse it by ultrasonication, then add calcium acetate and react at 45-50°C to form a biomineralization template solution. Then, immerse the vitrified microspheres in an acrylate monomer containing a photoinitiator, TPO, and irradiate them with a UV lamp to form a pre-polymerized adhesive layer.

[0034] A2, transfer to the fluidized bed, spray the template liquid prepared in step A1, and simultaneously start the near-infrared laser to scan the surface to trigger the local mineralization reaction; the modified fly ash after plasma activation is mixed with the zinc borate@ZIF-8 core-shell flame retardant and directionally deposited into the mineralized layer through an electrostatic adsorption device.

[0035] According to a preferred embodiment of the present invention, the discarded oyster shell powder is purchased from Shandong Qingdao Blue Ocean Shell Resources Comprehensive Utilization Co., Ltd.

[0036] According to a preferred embodiment of the present invention, the chitosan solution is purchased from a food-grade chitosan solution (model: JKB-200, deacetylation degree ≥ 90%) produced by Zhejiang Jinke Biotechnology Co., Ltd.

[0037] According to a preferred embodiment of the present invention, the calcium acetate is purchased from industrial-grade calcium acetate (model: CH-01, purity ≥99%) produced by Hebei Kelong Fine Chemical Co., Ltd.

[0038] According to a preferred embodiment of the present invention, the glass microspheres are purchased from closed-cell glass microspheres produced by Hebei Huamei Energy Saving Technology Group Co., Ltd. (model: HW-GM-1.0, particle size 1-1.5 mm, bulk density 80-100 kg / m 3 ).

[0039] According to a preferred embodiment of the present invention, the photoinitiator TPO is purchased from Beijing Yingli Technology Development Co., Ltd. (model: TPO-99, purity ≥99%).

[0040] According to a preferred embodiment of the present invention, the fluidized bed is purchased from a boiling fluidized bed (model: FG-500, processing capacity 50-200 kg / h) produced by Changzhou Yibu Drying Equipment Co., Ltd.

[0041] According to a preferred embodiment of the present invention, the acrylate monomer is purchased from methyl methacrylate (model: A102501, purity ≥99.5%) produced by Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] According to a preferred embodiment of the present invention, the ultraviolet lamp is purchased from an amalgam ultraviolet lamp (model: ZWX-365, wavelength 365-370nm, power 100W) produced by Shanghai Keheng Industrial Development Co., Ltd.

[0043] According to a preferred embodiment of the present invention, the fly ash is purchased from Grade II low-calcium fly ash (model: Class F Grade II, 45 μm sieve residue ≤ 25%) produced by Anhui Huainan Pingwei Power Generation Co., Ltd.

[0044] According to a preferred embodiment of the present invention, the zinc borate@ZIF-8 core-shell flame retardant is purchased from a functional flame retardant custom-synthesized in the laboratory of the School of Materials Science and Engineering of Beijing University of Chemical Technology (model: ZB-ZIF-8-01, zinc borate content 30-35%, ZIF-8 shell thickness 50-80 nm).

[0045] According to a preferred embodiment of the present invention, the electrostatic adsorption device is purchased from a plate-type electrostatic adsorption machine produced by Jiangsu Boruisi Machinery Manufacturing Co., Ltd. (model: BR-ESD-10, voltage range 0-30kV, processing air volume 500-1500m 3 / h).

[0046] According to a preferred embodiment of the present invention, in step A1, the particle size of the waste oyster shell powder is 200-250 mesh; the mass ratio of the waste oyster shell powder to the chitosan solution is 1:(3-4); the reaction time is 30-40 min; the particle size of the glass microbeads is 1-1.5 mm; the wavelength of the ultraviolet lamp is 365-370 nm; and the irradiation time is 5-8 s.

[0047] In step A1 of the present invention, the discarded oyster shell powder (mainly composed of CaCO3 and containing a small amount of organic matter) is sieved through 200-250 mesh and mixed with chitosan solution (chitosan molecular chain contains a large number of amino groups (-NH2), which needs to be acidified and dissolved in advance to form positively charged -NH3 + ) are mixed in a mass ratio of 1:(3-4), and ultrasonic dispersion (20-40kHz, power 200-300W) is used to evenly disperse the oyster shell powder in the chitosan solution to reduce particle agglomeration. Calcium acetate is then added and reacted at 45-50°C: -NH3 + With Ca2+ Through electrostatic coordination, free CO3 in the solution 2- (from the weak dissolution of oyster shell powder or the dissociation equilibrium of calcium acetate) and Ca 2+ Combined with chitosan molecular chain as a template to guide the growth of CaCO3 nuclei, forming a "chitosan-calcium carbonate" biomineralization composite structure (the CaCO3 loading in the template solution is 15-20% of the chitosan mass). In this process, ultrasonic dispersion promotes the growth of CaCO3 nuclei. 2+ Full contact with chitosan, 45-50 ℃ temperature accelerates Ca 2+ Diffusion and crystallization dynamics. Simultaneously, pretreatment of vitrified microspheres (1-1.5 mm in diameter, inert surface) is performed: immersing them in an acrylate monomer (such as methyl methacrylate, MMA) containing the photoinitiator TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide) and irradiating them with a UV lamp (wavelength 365-370 nm, power 80-100 W) for 5-8 seconds. TPO absorbs UV light and decomposes to produce free radicals (such as tert-butoxy radicals), which initiate free radical polymerization of the acrylate monomer on the surface of the vitrified microspheres, forming a pre-polymerized adhesive layer (acrylate polymer) 10-20 μm thick, which enhances the interfacial bonding between the subsequent mineralized layer and the vitrified microspheres.

[0048] According to a preferred embodiment of the present invention, in step A2, the atomization pressure of spraying the template liquid prepared in step A1 is 0.15-0.2 MPa; the wavelength of the near-infrared laser is 1064-1070 nm, and the power is 50-55 W; the mass ratio of the modified fly ash to the zinc borate@ZIF-8 core is (4-5):1; and the voltage of the electrostatic adsorption device is 15-16 kV.

[0049] In step A2 of the present invention, the template liquid (containing chitosan-calcium carbonate complex) prepared in step A1 is sprayed onto the surface of the vitrified microspheres in the fluidized bed through an atomizing nozzle (pressure 0.15-0.2 MPa), and a near-infrared laser (wavelength 1064-1070 nm, power 50-55 W) is simultaneously turned on for scanning: the near-infrared laser penetrates the template liquid layer, is absorbed by the water molecules (or residual acetate) in the template liquid, and is converted into heat energy, which locally heats up to 50-60° C., triggering the residual Ca in the template liquid to form a precipitate. 2+ With CO3 in solution -Or add carbonate (such as sodium carbonate to adjust the pH) to react and generate nano-scale calcite crystals (CaCO3), which fill the pores of the chitosan template and form a "calcite crystal-chitosan" mineralization layer (thickness 5-15μm), thereby enhancing the surface density of the material. At the same time, modified fly ash (surface treated with silane coupling agent, containing epoxy groups on the surface) and zinc borate @ ZIF-8 core-shell flame retardant (ZIF-8 shell thickness 20-30nm, loading rate 30-40%) are mixed in a mass ratio of (4-5): 1, and an electrostatic adsorption device (voltage 15-16kV) is used to make the particles negatively charged (modified fly ash) and positively charged (CaCO3 on the surface of the mineralization layer due to calcite crystallization) separate. 2+ The mineralized layers of the flame retardant (residue) attract each other and deposit directionally on the surface of the mineralized layer. Zinc borate (ZnB2O4) decomposes upon heating to produce H3BO3 and ZnO. ZIF-8 converts to ZnO at high temperatures and releases N2 / CO2, synergistically inhibiting combustion. Modified fly ash fills the gaps between the flame retardant and enhances the interfacial bonding between the flame retardant layer and the substrate. Ultimately, through the synergistic effects of biomineralization template guidance, photoinitiated polymerization bonding, near-infrared laser-assisted mineralization, and electrostatic adsorption deposition, a multilayer composite structure of "glass microspheres-prepolymerized bonding layer-mineralized layer-flame retardant deposition layer" is formed, achieving improved heat resistance, reinforcement, and flame retardancy of the modified composite material.

[0050] The beneficial effects of the present invention are:

[0051] The present invention significantly improves the comprehensive performance of the fireproof door core board by optimizing the composite process of the desulfurized gypsum base material and the synergistic effect of the modified material. The calcination activation and compounding system of desulfurized phosphogypsum and building gypsum effectively improves the problems of insufficient strength and poor water resistance of traditional gypsum products. The porous structure and inorganic flame retardant components in the modified composite material form a three-dimensional network skeleton, which can effectively block heat transfer and inhibit smoke generation under high temperature conditions. At the same time, the precise introduction of the gypsum foaming agent enables the formation of a uniform closed-cell structure inside the material, which not only reduces the overall density but also enhances the compressive strength. This lightweight and high-strength characteristic enables it to reduce the door body load while meeting fire protection requirements. In the process, the stirring rate, curing temperature and time parameters are precisely controlled to ensure that each component fully reacts and forms a stable phase structure, and finally a new type of fireproof door core material with excellent fire resistance, dimensional stability and environmental adaptability is obtained.

[0052] The innovative preparation technology of modified composite materials has achieved high-value utilization of industrial solid waste and precise control of functional components. The biomineralized layer formed by chitosan induction of discarded oyster shell powder and the pre-polymerized adhesive layer on the surface of the glass microspheres are triggered by near-infrared laser in situ mineralization reaction to form a high-strength interface bonding network, which effectively solves the performance degradation problem caused by uneven dispersion of fillers in traditional composite materials. The plasma-modified fly ash particles and the zinc borate @ZIF-8 core-shell flame retardant are directionally deposited through electrostatic adsorption to construct a distributed flame retardant system inside the material. The nano-scale flame retardant particles can release crystalline water and form an insulating carbon layer at the initial stage of the flame, while the ZIF-8 structure decomposes under heat to produce inert gas to dilute the oxygen concentration. This multi-mechanism synergistic effect enables the material to significantly extend the fire resistance time and inhibit the release of harmful gases during combustion while maintaining a low thermal conductivity.

[0053] This process achieves a high degree of unity between green manufacturing and efficient production through equipment improvement and process innovation. The optimized application of mold preheating and release agent greatly improves the demoulding efficiency and reduces surface defects. The dual-speed design of the planetary stirring system ensures the uniform dispersion of raw materials and avoids bubble bursting caused by excessive shearing. The precise matching of the desulfurized gypsum calcination waste heat recovery system and process parameters reduces production energy consumption by more than 30% compared with traditional processes. The near-infrared laser and plasma combined activation technology used in the preparation of modified composite materials realizes the controllable deposition of nanoscale functional components and significantly improves the isotropy of the material. The intelligent regulation of product curing conditions ensures the full progress of the hydration reaction, so that the final product has stable physical properties and durability. This full-process process optimization not only improves production efficiency, but also promotes the large-scale application of industrial solid waste in the field of green building materials. DETAILED DESCRIPTION

[0054] The following specific implementation methods are only used to further illustrate the present application and should not be understood as limiting the scope of protection of the present application. Technicians in this field may make some non-essential improvements and adjustments to the present application based on the above application content.

[0055] 1. Main raw materials and equipment:

[0056] Desulfurized phosphogypsum: KM-Ⅰ type phosphogypsum purchased from Guizhou Kailin Group Co., Ltd.

[0057] Desulfurized building gypsum: BN-II building gypsum purchased from Beijing New Building Materials Group Co., Ltd.

[0058] Cement: CA-50 purchased from Zhengzhou Aluminum City Special Cement Co., Ltd. (calcium aluminate content ≥50%, suitable for early strength and high temperature resistance).

[0059] Mould: DG-2024-FJ type fire door core board special steel mould purchased from Qingdao Degut Energy Saving Equipment Co., Ltd.

[0060] Release agent: Sunrise brand SR-2024 silicone oil-based release agent purchased from Jiangsu Sunrise Chemical Co., Ltd.

[0061] Gypsum foaming agent: Aladdin brand SDS-Ⅰ type sodium octadecyl sulfate purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0062] Mixer: LT-800 planetary mixer purchased from Shandong Longteng Machinery Manufacturing Co., Ltd.

[0063] Water reducer: KZJ-PCA-Ⅱ polycarboxylic acid high performance water reducer purchased from KZJ New Materials Group Co., Ltd.

[0064] Retarder: Chenghua brand F-I type sodium gluconate purchased from Chengdu Chemical Industry Co., Ltd.

[0065] Cellulose: Heda brand HPMC-400 hydroxypropyl methylcellulose purchased from Shandong Heda Group Co., Ltd.

[0066] Waste oyster shell powder: purchased from Shandong Qingdao Blue Ocean Shell Resources Comprehensive Utilization Co., Ltd.

[0067] Chitosan solution: Food-grade chitosan solution (model: JKB-200, deacetylation degree ≥ 90%) purchased from Zhejiang Jinke Biotechnology Co., Ltd.

[0068] Calcium acetate: industrial-grade calcium acetate (model: CH-01, purity ≥99%) purchased from Hebei Kelong Fine Chemical Co., Ltd.

[0069] Vitrified microspheres: purchased from Hebei Huamei Energy Saving Technology Group Co., Ltd. (model: HW-GM-1.0, particle size 1-1.5 mm, bulk density 80-100 kg / m 3 ).

[0070] Photoinitiator TPO: purchased from Beijing Yingli Technology Development Co., Ltd. Photoinitiator TPO (model: TPO-99, purity ≥99%).

[0071] Fluidized bed: A boiling fluidized bed (model: FG-500, processing capacity 50-200 kg / h) purchased from Changzhou Yibu Drying Equipment Co., Ltd.

[0072] Acrylate monomer: methyl methacrylate (model: A102501, purity ≥99.5%) purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0073] UV lamp: Amalgam UV lamp (model: ZWX-365, wavelength 365-370 nm, power 100 W) purchased from Shanghai Keheng Industrial Development Co., Ltd.

[0074] Fly ash: Class II low-calcium fly ash (model: Class F Class II, 45 μm sieve residue ≤ 25%) purchased from Anhui Huainan Pingwei Power Generation Co., Ltd.

[0075] Zinc borate@ZIF-8 core-shell flame retardant: a functional flame retardant purchased from the laboratory of the School of Materials Science and Engineering of Beijing University of Chemical Technology (model: ZB-ZIF-8-01, zinc borate content 30-35%, ZIF-8 shell thickness 50-80 nm) and custom-synthesized.

[0076] Electrostatic adsorption device: purchased from Jiangsu Boruisi Machinery Manufacturing Co., Ltd. Plate electrostatic adsorption machine (model: BR-ESD-10, voltage range 0-30kV, processing air volume 500-1500m 3 / h).

[0077] 2. Example

[0078] Example 1

[0079] The preparation process of a desulfurized gypsum fire door core board is as follows: 720g of desulfurized phosphogypsum is placed in a calcining furnace, calcined and activated at 180°C for 2h, naturally cooled to 22°C, and poured into a planetary mixer together with 130g of desulfurized building gypsum, 155g of modified composite material is added to the mixer, and premixed at a speed of 12r / min for 12min to form a uniform base material; at the same time, a mold with a size of 500mm×300mm×50mm is taken, and the inner wall is evenly coated with liquid paraffin release agent (the coating thickness is to cover the inner wall and not drip), and the mold is placed in a 42°C oven for preheating for 30min to ensure that the mold temperature is uniform; then 4g of gypsum foaming agent and 22g of water are added to a beaker, placed in a 32°C water bath for predissolution for 10min, and after standing and defoaming for 7min, a metering pump is used at a frequency of "3 times / 2.5min". The mixture was added into a planetary mixer (the mixer and the base material mixer were the same equipment) at a rate (i.e., adding once every 2.5 minutes, for a total of 3 times); at the same time, 40g of cement that had been passed through an 80-mesh sieve to remove lumps, the base material prepared above, 3g of a polycarboxylic acid water reducer (water reduction rate ≥ 25%), 4g of a citric acid retarder (purity ≥ 99%), and 3g of hydroxypropyl methylcellulose (viscosity ≥ 100,000 mPa·s) were added into the mixer, and a low-speed stirring of 35r / min was first started for 3.5min to preliminarily mix the dry materials, and then the high-speed stirring was increased to 70r / min for 5.5min to finally obtain a slurry with a temperature of 28°C; the slurry was then injected into a preheated mold, allowed to stand for initial setting for 18min, and the mold was removed after the slurry was preliminarily hardened; the demoulded door core board was placed in a curing room at 25°C and allowed to stand for 72h to ensure that the hydration reaction was fully carried out;

[0080] The preparation of the modified composite material was completed simultaneously, specifically as follows: 200g of 200-mesh discarded oyster shell powder was mixed with 1000mL of chitosan solution, ultrasonically dispersed for 10min, 50g of calcium acetate was added, and the temperature was raised to 48°C for 35min to form a biomineralization template solution; 100g of glass microspheres with a particle size of 1-1.5mm were immersed in an acrylate monomer containing a photoinitiator, and irradiated with a UV lamp with a wavelength of 368nm and a power of 100W for 6s to form a pre-polymerized bonding layer on the surface; the pre-treated glass microspheres were transferred to a fluidized bed and atomized by pressure. A biomineralization template liquid was sprayed with a nozzle at a force of 0.18 MPa, and a near-infrared laser with a wavelength of 1067 nm and a power of 52 W was simultaneously turned on to scan the surface of the fluidized bed to trigger a local mineralization reaction to form a mineralized layer; 400 g of plasma-activated modified fly ash and 80 g of zinc borate@ZIF-8 core-shell flame retardant (zinc borate content 32%, ZIF-8 shell thickness 65 nm) were mixed evenly and then directionally deposited onto the surface of the mineralized layer through an electrostatic adsorption device with a voltage of 15 kV, so that the flame retardant (zinc borate@ZIF-8) was stably attached to obtain a modified composite material.

[0081] Example 2

[0082] The specific implementation method is the same as that of Example 1, except that 740g of desulfurized phosphogypsum is calcined and activated at 160°C for 1.5h, cooled to 24°C, mixed with 125g of desulfurized building gypsum, added with 158g of modified composite material (preparation method is the same as that of Example 1), and premixed for 11min; the cement is passed through an 82-mesh sieve, and 35g is taken for standby; the mold is preheated to 43°C and coated with a silicone oil release agent. Gypsum foaming agent (3.8g) and 21g of water (mass ratio 1:5.5) are pre-dissolved at 33°C for 8min, allowed to stand for 6min, and added to the mixer 3 times / 2.5min through a metering pump; 35g of cement, the base material prepared above, 2.8g of water reducer, 3.8g of retarder, and 2.8g of cellulose are added at the same time, stirred at a low speed of 32r / min for 3min, and stirred at a high speed of 65r / min for 5min (slurry temperature 26°C). After initial setting, the mold is removed and cured at 28°C for 96h. In the preparation of the modified composite material, the waste oyster shell powder was 250 mesh, the amount of chitosan solution was 1200 mL, the calcium acetate was 60 g, the reaction time was 38 min, the vitrified microbeads were 120 g, the ultraviolet lamp irradiation time was 7 s, the fluidized bed spraying template liquid atomization pressure was 0.16 MPa, the near-infrared laser power was 53 W, the modified fly ash was 420 g, the zinc borate@ZIF-8 core-shell flame retardant was 90 g, and the electrostatic adsorption voltage was 15.5 kV.

[0083] Example 3

[0084] The specific implementation method is the same as that of Example 1, except that 750g of desulfurized phosphogypsum is calcined and activated at 200°C for 2h, cooled to 20°C, mixed with 150g of desulfurized building gypsum, and 160g of modified composite material is added and premixed for 15min; cement is passed through an 85-mesh sieve, and 45g is taken for standby; the mold is preheated to 44°C and coated with vaseline release agent. Gypsum foaming agent (4.5g) and 27g of water (mass ratio 1:6) are pre-dissolved at 34°C for 9min, allowed to stand for 9min, and added to the mixer 3 times / 3min via a metering pump; 45g of cement, the base material prepared above, 4.5g of water reducer, 4.5g of retarder, and 4g of cellulose are added at the same time, stirred at a low speed of 38r / min for 4min and at a high speed of 78r / min for 6min (slurry temperature 30°C). After initial setting, the mold is removed and cured at 30°C for 144h. In the preparation of the modified composite material, the waste oyster shell powder was 220 mesh, the amount of chitosan solution was 1100 mL, the calcium acetate was 55 g, the reaction time was 32 min, the vitrified microbeads were 110 g, the ultraviolet lamp irradiation time was 6 s, the fluidized bed spraying template liquid atomization pressure was 0.19 MPa, the near-infrared laser power was 54 W, the modified fly ash was 450 g, the zinc borate@ZIF-8 core-shell flame retardant was 100 g, and the electrostatic adsorption voltage was 16 kV.

[0085] Comparative Example 1

[0086] The specific implementation method is the same as that of Example 1, except that the calcination temperature of the desulfurized phosphogypsum is 140°C.

[0087] Comparative Example 2

[0088] The specific implementation method is the same as that of Example 1, except that the mass ratio of the gypsum foaming agent to water is 1:4.

[0089] Comparative Example 3

[0090] The specific implementation method is the same as that of Example 1, except that no modified composite material is added.

[0091] 3. Performance Testing

[0092] The desulfurized gypsum fire door core panels prepared by the preparation processes of the above Examples 1-3 and Comparative Examples 1-3 were tested according to the following test method:

[0093] 1. Fire resistance limit test is carried out in accordance with GB / T 9978.1-2008 "Fire resistance test methods for building elements Part 1: General requirements". The specific operation is as follows: select a specimen with a size of 500mm×300mm×50mm, grind the surface flat and fix it in a horizontal fire resistance test furnace. Apply a constant load (about 1.5 times the weight of the specimen) at a rate of 0.8kN / min through the hydraulic loading system. The temperature in the furnace is controlled according to the ISO 834-1999 standard heating curve (initially heating to 540℃ in 30 minutes, and then heating at 8℃ per minute). The time from the start of fire to the loss of bearing capacity of the specimen (manifested as the collapse of the middle of the specimen exceeding 1 / 2 of the span or the displacement of any section exceeding 20% ​​of the initial thickness) is recorded as the fire resistance limit.

[0094] 2. The compressive strength test is based on GB / T 5486-2012 "Test methods for inorganic rigid thermal insulation products". After the specimen is cured for 28 days, its length, width and height are measured with a vernier caliper (accuracy 0.1mm), and the compressive area (length × width) is calculated. The specimen is placed in the center of the lower platen of the pressure testing machine and loaded uniformly at a loading rate of 0.5MPa / s until failure. The maximum failure load is recorded, and the compressive strength is taken as the arithmetic mean of the three specimens (accurate to 0.1MPa).

[0095] 3. Density test is carried out according to GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)". After the specimen is cured for 28 days, its mass is weighed with an electronic balance (accuracy 0.01g), and then the volume is measured by the water displacement method (the specimen is completely immersed in water and the volume of the water is measured). The density calculation formula is mass divided by volume (accurate to 1kg / m 3 ).

[0096] 4. The thermal conductivity coefficient test adopts GB / T 10294-2008 "Insulating materials - Determination of steady-state thermal resistance and related properties - Guarded hot plate method". A test specimen with a thickness of 50 mm was selected, the surface was sandpapered until flat, and after cleaning, it was placed between the upper and lower platens of the guarded hot plate apparatus. A pressure of 0.1 MPa was applied to ensure close contact between the test specimen and the platens. The heating plate was heated from room temperature to 50°C at a rate of 10°C / min and stabilized for 30 minutes. After the heat flux density stabilized, the heat flux output by the heat flux meter and the temperature difference between the two sides of the test specimen were recorded. The thermal conductivity coefficient was calculated as the heat flux multiplied by the test specimen thickness divided by the temperature difference.

[0097] 5. The 28d shrinkage rate test refers to GB / T 25993-2023 "Limits of comprehensive energy consumption per unit product of foam concrete blocks". After the specimen is formed, it is first cured in a standard curing room (20±2℃, humidity ≥90%) for 7d, and then transferred to a drying room (60±2℃) for curing to 28d. The length, width, and thickness are measured at 7d and 28d of curing (using a vernier caliper with an accuracy of 0.02mm), and the shrinkage rate in each direction is calculated (shrinkage rate = (initial size - 28d size) / initial size × 100%), and the average value of the three directions is taken.

[0098] 6. The CO release test is based on GB / T 20285-2006 "Hazard Classification of Smoke Generation of Materials" and uses a cone calorimeter (radiation intensity is set at 50kW / m 2 ), place the specimen in the center of the combustion chamber, ignite the upper surface of the specimen, remove the fire source after the flame burns stably for 30 seconds, collect the flue gas within 30 minutes after combustion, and monitor the CO concentration (ppm) in the flue gas in real time using an infrared gas analyzer. The CO release amount is calculated as follows: CO mass released per unit mass of specimen (g / g) = (CO concentration × flue gas flow × combustion time) / specimen mass.

[0099] 7. Performance test results:

[0100] Table 1: Performance test results of various embodiments and comparative examples

[0101]

[0102]

[0103] As can be seen from Table 1, Examples 1-3 of the present invention effectively solve the problems of low strength, insufficient fire resistance, poor water resistance and inefficient utilization of industrial solid waste in traditional desulfurized gypsum fire door core panels through the synergistic effect of process optimization and modified composite materials: the porous structure formed by biomineralization of discarded oyster shell powder in the modified composite material is synergistically enhanced with the closed-pore characteristics of the vitrified microspheres, and the composite system of desulfurized phosphogypsum and building gypsum significantly improves the compressive strength of the material (the compressive strength of Examples 1-3 reaches 8.2-8.8 MPa, which is much higher than 5.2-7.1 MPa of the comparative example); the zinc borate@ZIF-8 core-shell flame retardant in the modified composite material has a high It decomposes at low temperatures to produce inert gas and form an insulating carbon layer, which, combined with the fire resistance of the desulfurized gypsum itself, greatly extends the fire resistance limit (the fire resistance limit of Examples 1-3 reaches 185-198 minutes, far exceeding the 90-150 minutes of the comparative example); the porous structure of the composite material and the low water absorption of the desulfurized gypsum synergistically improve the water resistance (the shrinkage rate of Examples 1-3 is only 0.2-0.3%, lower than the 0.45-0.5% of the comparative example); at the same time, industrial solid wastes such as discarded oyster shell powder and fly ash are converted into functional fillers through processes such as ultrasonic dispersion, biomineralization and electrostatic adsorption, realizing high-value utilization and solving the problem of low solid waste utilization rate in traditional processes.

[0104] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A process for manufacturing a core board of a desulfurized gypsum fireproof door, characterized in that: The following steps are involved: S1, desulfurized phosphogypsum is activated by calcination at 150-200°C, cooled to 20-25°C, mixed with desulfurized building gypsum, and pre-mixed with modified composite materials to form a base material; cement is sieved to remove lumps; a release agent is applied to the inner wall of the mold and preheated to 40-45°C; S2, the gypsum foaming agent is pre-dissolved in water, allowed to stand for defoaming, and then added to the mixer via a metering pump. At the same time, cement, base material, water reducer, retarder, and cellulose are added to the mixer and stirring is started; S3, using a planetary mixer to first stir at a low speed to mix the dry materials, and then stir at a high speed to obtain a slurry; S4: After the slurry is injected into the mold, it is allowed to set and then the mold is removed.

2. The manufacturing process of the desulfurized gypsum fire door core board according to claim 1, characterized in that: In step S1, the premixing time is 10-15 minutes; and the cement is passed through an 80-85 mesh sieve.

3. The manufacturing process of the desulfurized gypsum fire door core board according to claim 1, characterized in that: In step S2, the mass ratio of the gypsum foaming agent to water is 1:(5-6), the pre-dissolution temperature is 30-35°C; the standing time is 5-10 minutes, the gypsum foaming agent is added to the mixer 3-4 times through a metering pump, and the interval time for each addition is 2-3 minutes; the stirring speed is 30-40 r / min.

4. The manufacturing process of the desulfurized gypsum fire door core board according to claim 1, characterized in that: In step S3, the rotation speed of low-speed stirring is 30-40 r / min, and the low-speed stirring time is 3-4 min; the rotation speed of high-speed stirring is 60-80 r / min, and the high-speed stirring time is 5-6 min.

5. The manufacturing process of the desulfurized gypsum fire door core board according to claim 1, characterized in that: In step S4, the temperature of the slurry is 25-30° C., and the standing time is 15-20 minutes.

6. The manufacturing process of the desulfurized gypsum fire door core board according to claim 1, characterized in that: The desulfurized gypsum fireproof door core board manufacturing process further includes: allowing the door core board prepared in step S4 to stand at a temperature of 20-30° C. for 72-144 hours.

7. A desulfurized gypsum fire door core board prepared according to the desulfurized gypsum fire door core board manufacturing process according to any one of claims 1 to 6, characterized in that: The raw materials include, by mass percentage, desulfurized phosphogypsum: 70-75%; cement: 3-5%; desulfurized building gypsum: 12-15%; modified composite material: 15-16%; gypsum foaming agent: 0.3-0.5%; water reducing agent: 0.2-0.5%; retarder: 0.3-0.5%; and cellulose: 0.2-0.4%.

8. The process for manufacturing the desulfurized gypsum fire door core board according to any one of claims 1 to 6 or the desulfurized gypsum fire door core board according to claim 7, characterized in that: The preparation steps of the modified composite material include: A1: Mix waste oyster shell powder with chitosan solution, disperse it by ultrasonication, then add calcium acetate and react at 45-50°C to form a biomineralization template solution. Then, immerse the vitrified microspheres in an acrylate monomer containing a photoinitiator, TPO, and irradiate them with a UV lamp to form a pre-polymerized adhesive layer. A2, transfer to the fluidized bed, spray the template liquid prepared in step A1, and simultaneously start the near-infrared laser to scan the surface to trigger the local mineralization reaction; the modified fly ash after plasma activation is mixed with the zinc borate@ZIF-8 core-shell flame retardant and directionally deposited into the mineralized layer through an electrostatic adsorption device.

9. The manufacturing process of the desulfurized gypsum fire door core board or the desulfurized gypsum fire door core board according to claim 8, characterized in that: In step A1, the particle size of the waste oyster shell powder is 200-250 mesh; the mass ratio of the waste oyster shell powder to the chitosan solution is 1:(3-4); the reaction time is 30-40 min; the particle size of the vitrified microbeads is 1-1.5 mm; the wavelength of the ultraviolet lamp is 365-370 nm; and the irradiation time is 5-8 s.

10. The manufacturing process of the desulfurized gypsum fireproof door core board or the desulfurized gypsum fireproof door core board according to claim 8, characterized in that: In step A2, the atomization pressure of the template liquid prepared in step A1 is 0.15-0.2 MPa; the wavelength of the near-infrared laser is 1064-1070 nm, and the power is 50-55 W; the mass ratio of the modified fly ash to the zinc borate@ZIF-8 core is (4-5):1; and the voltage of the electrostatic adsorption device is 15-16 kV.

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