A method for preparing aerated concrete board from lithium-containing residue-steel slag-coal-based solid waste

Abstract

The present application belongs to the technical field of comprehensive utilization of resources, and particularly relates to a method for preparing aerated concrete board from lithium-containing residue, steel slag and coal-based solid waste. The present application utilizes caustic white mud, waste photovoltaic panel, nickel residue, lithium residue, stainless steel residue, coal slime, mirabilite gypsum, titanium gypsum, dicyandiamide waste residue, desulfurization ash and other waste to cooperatively prepare autoclaved aerated concrete board, which replaces traditional clay sintered brick, cement non-burning brick, autoclaved aerated concrete block and other wall materials to be used as industrial and civil building walls, which not only meets the overall concept and development requirements of green building at the present stage, but also can achieve good economic and social benefits. As a new type of building wall material, the autoclaved aerated concrete board wall has a good development prospect.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive resource utilization technology, and in particular relates to a method for preparing aerated concrete panels from lithium slag, steel slag, and coal-based solid waste. Background Technology

[0002] Coal slime, a byproduct of coal washing, accounts for approximately 10-20% of the coal produced. Due to my country's increased emphasis on environmental protection in recent years and the implementation of various environmental policies, the rate of raw coal washing has been rising annually, leading to a corresponding increase in coal slime production. Because of its low calorific value, high water retention, and high ash content, coal slime is often considered a low-quality fuel. The dumping of solid waste coal slime results in large-scale land occupation; when it comes into contact with water, it is lost, and when it loses water, it is carried away by the wind, causing pollution to water and air.

[0003] The production process of dicyandiamide generates a large amount of industrial waste residue. Besides moisture (45%–47%), the waste residue contains calcium carbonate (31%–42% as wet residue). During calcium carbide production, it also contains small amounts of graphitized carbon and calcium cyanamide, generating some free carbon (6.3%–6.5% as wet residue). Additionally, it contains small amounts of inorganic substances (iron, aluminum, silicon dioxide, etc.). The dicyandiamide waste residue is a powdery black solid containing a small amount of Ca(OH)₂, making it alkaline (pH between 8 and 8.5). The waste residue is characterized by a particle size of 0–0.2 mm and a specific surface area of ​​3500–4500 cm². 2 ·g -1 .

[0004] Desulfurization ash is the ash produced to control and reduce SO2 emissions from coal combustion. Its composition is extremely complex, consisting of a reddish-brown powdery mixture of desulfurization reaction products, unreacted desulfurization absorbent, and flue gas fly ash. It has a fine particle size (10-20 μm), a density of 2-2.5 g / cm³, and a specific surface area generally exceeding 3000 cm². 2 The desulfurization ash residue has a moisture content of approximately 1% to 5% and a weight of approximately 0.5%. It is a high-calcium, high-sulfur product, primarily composed of CaSO4, CaCO3, Ca(OH)2, CaO, and SiO2, with CaSO4 being the dominant sulfur-containing phase. Due to the presence of Ca(OH)2, the desulfurization ash residue is alkaline, with a pH value between 11 and 13.

[0005] How to comprehensively utilize diverse solid wastes such as coal slime, dicyandiamide residue, and desulfurization ash to greatly reduce environmental pollution, turn waste into treasure, and achieve significant economic and social benefits is a technical challenge that urgently needs to be solved. Summary of the Invention

[0006] This invention utilizes causticized white clay, waste photovoltaic panels, nickel slag, lithium slag, stainless steel slag, coal slime, mirabilite gypsum, titanium gypsum, dicyandiamide waste residue, desulfurization ash, and other waste materials to co-prepare autoclaved aerated concrete (AAC) panels. These panels replace traditional clay sintered bricks, cement-fired bricks, and AAC blocks for industrial and civil building walls, aligning with current green building concepts and development requirements while offering significant economic and social benefits. As a novel building wall material, AAC panel wallboards have promising prospects for widespread application.

[0007] This invention provides a method for preparing aerated concrete panels from lithium slag, steel slag, and coal-based solid waste. The preparation method includes the following steps:

[0008] S1. Pre-treatment of waste shells: After cleaning, the waste shells are dried to constant weight and then crushed into ≤2mm particles by a crusher for later use.

[0009] S2. Pretreatment of causticized white mud: The causticized white mud is piled up and dried to a moisture content of 15-25%, then dried to constant weight, and crushed into ≤2mm particles in a crusher for later use.

[0010] S3. Pretreatment of quartz tailings: After removing impurities by screening, the quartz tailings are dried to constant weight and then dispersed into ≤2mm particles by ball mill for later use.

[0011] S4. Pre-treatment of waste photovoltaic panels: After cleaning and drying the waste photovoltaic panels with aluminum frames and adhesive strips removed, they are crushed into ≤2mm particles by a crusher for later use.

[0012] S5. Pretreatment of nickel slag / lithium slag / stainless steel slag: First, dry the nickel slag, lithium slag and stainless steel slag to constant weight, then crush them into ≤2mm particles by crusher. Then, mix the nickel slag, lithium slag and stainless steel slag in a mass ratio of 1~2:1~2:1~2 to obtain a mixture of ≤2mm particles.

[0013] S6. Pretreatment of coal slime: The coal slime is piled up in a cool and ventilated place to dry, so that its moisture content is less than 15%, and then dried to constant weight. After cooling, it is dispersed by a ball mill to obtain powder material for later use.

[0014] S7. Pretreatment of Glauber's salt gypsum / titanium gypsum: Dry the Glauber's salt gypsum and titanium gypsum separately in an electric drying oven, then grind them in a ball mill at a mass ratio of 1-2:1-2 until the specific surface area reaches 300-400 m². 2 / kg, yielding powder 1;

[0015] S8. Pressing and molding: Mix the mixture of S1, S2, S3, S4, and S5, and powder 1 from S6 and S7 in a weight ratio of 25-35%:25-35%:10-20%:5-10%:5-10%:5-8%:3-5%, then grind them evenly in a ball mill to obtain a specific surface area of ​​300-500 m². 2 / kg of mixed powder, transfer the mixed powder into a mortar mixer, add 8-10% of its mass of water, mix evenly, put it into a mold, press it into a patty, and place the patty in an electric heating drying oven at 100℃ for 40 minutes.

[0016] S9. High-temperature calcination: The dried cake from step S8 is calcined at high temperature. After calcination, it is rapidly cooled by air to obtain the high-temperature calcined product.

[0017] S10. Pretreatment of low-carbon powder 2: The high-temperature calcined product from step S9 is crushed into 1-3 mm particles using a crusher, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 2 low-carbon powders;

[0018] S11. Pretreatment of dicyandiamide waste residue / desulfurization ash residue: The dried dicyandiamide waste residue and desulfurization ash residue are mixed evenly at a mass ratio of 2 to 4:1, and then ground in a ball mill to a specific surface area of ​​300 to 400 m². 2 / kg, then put the ground material into a mortar mixer, add 8-10% water by weight, mix evenly, put it into a mold, press it into a cake, and place the cake in an electric heating drying oven at 100℃ for 40 minutes; the dried cake is then placed in a muffle furnace for calcination, and after calcination, it is naturally cooled. Then the cooled cake is put into a ball mill and ground to a specific surface area of ​​400-600 m². 2 / kg, yielding 3g of powder;

[0019] S12. Purification of sea sand: Sea sand washed with fresh water is piled up in a cool place to dry, dried to constant weight, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 4g of powder;

[0020] S13. Pretreatment of the board skeleton: The Φ5 or Φ6 bamboo strips that have been peeled, dried and scored are tied into a bamboo strip mesh by using flamed wire, soaked in the anti-corrosion pool for 16 to 32 minutes, taken out and dried; the anti-corrosion bamboo strip mesh is placed into the mold according to the relative position and process dimensions and fixed.

[0021] S14. Casting and molding of the plate: Add powder 1, powder 2, powder 3 and powder 4 to the mixing tank and mix evenly. Add warm water at 52-64% of the total mass of the powder and add foam stabilizer at 5-12‰ of the water mass. After mixing evenly, add aluminum powder at 0.5-0.7‰ of the total mass of the powder and pour the evenly mixed slurry into the mold.

[0022] S15. Curing of the board products: The slurry poured into the mold in S14 is subjected to static curing, blank cutting, and high-temperature autoclaving to obtain aerated concrete board products.

[0023] Optionally, in steps S8 and S11, the pressure for pressing the material into a cake is 15-25 MPa.

[0024] Optionally, in steps S8 and S11, the thickness of the material cake is 1 cm and the diameter is 10 cm.

[0025] Optionally, the calcination process in step S9 is as follows: the temperature is raised from room temperature to 800°C at a rate of 5°C / min, and then held for 20 min; then the temperature is raised from 800°C to 1100-1300°C at a rate of 10°C / min, and then held for 30-60 min.

[0026] Optionally, the cooling in step S9 includes first cooling to 1000°C at a rate of 18-20°C / min, and then cooling from 1000°C to room temperature at a rate of not less than 100°C / min. The purpose is to improve the quality of the low-carbon powder by controlling the cooling temperature; specifically, slow cooling is first used to control C2S formation in the powder, followed by slow cooling from 1000°C to room temperature at a rate of not less than 100°C / min, to obtain low-carbon powder with excellent performance in the early, middle, and late stages.

[0027] Optionally, the calcination process in step S11 is as follows: the temperature is raised from room temperature to 300°C at a rate of 2°C / min, and then held for 20 min; then the temperature is raised from 300°C to 750°C to 850°C at a rate of 3°C / min, and then held for 30 min.

[0028] Optionally, in step S14, powder 1, powder 2, powder 3 and powder 4 are added in a mass ratio of 4-8%: 8-12%: 20-28%: 52-68%.

[0029] Optionally, in step S14, the foam stabilizer is prepared from trinitrotoluene, sodium stearoyl lactylate, and distilled water in a mass ratio of 7.3:2.8:89.9; the aluminum powder has an active Al content of 93%, a residue of 2.4% on a 0.08mm square hole sieve, a gas generation rate of more than 82%, a gas generation time of less than 23 minutes, and a hydrophilicity of less than 19 seconds.

[0030] Optionally, the temperature of the slurry during pouring in step S14 is 45-50°C.

[0031] Optionally, the static curing time in step S15 is 3 to 5 hours, and the curing temperature is 55 to 68°C; the high-temperature steam pressure curing process is as follows: sealing, vacuuming, heating to 180 to 195°C, steam pressure 1.2 to 1.35 MPa, maintaining for 6 to 8 hours, and then naturally cooling to room temperature and pressure.

[0032] The beneficial technical effects of the present invention are as follows:

[0033] (1) This invention provides a method for preparing aerated concrete panels from lithium slag-steel slag-coal-based solid waste. The panels are directly cast into homogeneous aerated concrete panels using a specific calcium silicate formula. This method enables automated mechanical production and integrated molding, which greatly reduces production difficulty and the use of manual labor. It effectively reduces production costs, ensures stable product quality, and achieves efficient and scientific stable control of the production process of new wall materials.

[0034] (2) The present invention utilizes 100% solid waste to prepare autoclaved aerated concrete panels. The solid waste used in the preparation includes: waste seashells, waste photovoltaic panels, quartz tailings, nickel slag, lithium slag, stainless steel slag, coal slime, mirabilite gypsum, titanium gypsum, dicyandiamide waste residue, desulfurization ash residue, etc. The physical and mechanical properties (strength and density) and durability properties (seepage prevention, frost resistance, carbonization resistance) of the panels meet the test index requirements of GB / T 15762-2020 "Autoclaved Aerated Concrete Panels" and GB / T 11968-2020 "Autoclaved Aerated Concrete Blocks", which improves the utilization rate of industrial solid waste raw materials, can significantly reduce the production cost of enterprises, and has significant economic and social environmental benefits.

[0035] (3) The aerated concrete panels proposed in this invention utilize raw materials that replace those used in traditional production processes. Among them, low-carbon powders prepared from non-metallic mine solid waste, power industry solid waste, non-ferrous metallurgical solid waste, iron and steel solid waste and coal-based solid waste are used, which are combined with the mineral composition and content characteristics of new low-carbon cement clinker to replace silicate cement clinker; chemical solid waste and iron and steel solid waste are used to replace all calcareous raw materials quicklime and part of gypsum; purified sea sand is used as a high-silica raw material to replace traditional siliceous raw materials river sand and fly ash; mirabilite gypsum / titanium gypsum is used to replace part of gypsum as a retarder; bamboo reinforcement is used to replace steel reinforcement; the synergistic effect of multiple solid wastes makes the composition of the new aerated concrete panels more scientific and standardized, and more suitable for actual production processes;

[0036] (4) The aerated concrete panel proposed in this invention utilizes purified sea sand that meets the technical requirements of JG / T 494-2016 "Purified Sea Sand for Building and Municipal Engineering", solving the problem of high-silica raw materials in the traditional aerated concrete panel production and replacing river sand and fly ash in the traditional aerated concrete panel production. This can solve the problem of raw material shortage in the production of aerated concrete panels in some areas. The calcium raw material prepared by calcining dicyandiamide waste residue and desulfurization ash residue meets the technical requirements of JC / T 621-2021 "Quicklime for Silicate Building Products", and its calcination temperature is more than 10% lower than the energy consumption of quicklime preparation. The use of bamboo reinforcement to replace the steel reinforcement in the traditional aerated concrete panel production can realize the high added value and large-scale utilization of bamboo. The application of this aerated concrete panel contributes to the green development of the building industrialization.

[0037] (5) This invention, through specific crystalline phase structure design and regulation, enables the low-carbon powder made from the obtained high-temperature calcined product to possess higher physical and mechanical properties in a short time, significantly superior to existing ordinary silicate cement clinker. Simultaneously, the low-carbon powder described in this invention also exhibits excellent characteristics such as high strength, rapid setting, rapid hardening, low carbon content, low alkali content, and low chloride ion content. This can shorten the construction cycle and is of great significance for emergency construction and repair of municipal engineering projects, building decoration, road and bridge repair, as well as for use as material and wartime emergency reserve technology.

[0038] (6) In the process of preparing powder 2 using calcareous materials (waste seashells), siliceous materials (quartz tailings, waste photovoltaic panels, coal slime), ferroaluminous materials (nickel slag, lithium slag, stainless steel slag, coal slime), and sulfurous materials (sodium sulfate gypsum, titanium gypsum) as raw materials, the present invention achieves optimal matching of the four conditions by reasonably controlling the particle size, molding conditions, calcination time, and heat preservation time, and exerting synergistic conditions, so that powder 2 can form a specific crystal phase structure, and achieve excellent early, middle and late stage performance of powder, which can replace silicate cement clinker.

[0039] (7) The low-carbon powder prepared by the present invention has a significant carbon reduction effect. It incorporates coal-based solid waste coal slime, which reduces the firing temperature by 100°C compared to silicate cement clinker and reduces energy consumption by more than 10%. At the same time, the powder uses all solid waste raw materials during firing and does not use limestone, reducing CO2 emissions by more than 20%. This can significantly reduce the production cost of enterprises and has good economic, social and ecological environmental benefits.

[0040] (8) This invention can purposefully and stably control the composition and content ratio of each mineral in the powder. Its performance is excellent and can reach and exceed the existing silicate cement clinker. It can be widely used to replace traditional silicate cement in large quantities and help the cement industry achieve low-carbon and sustainable development. Attached Figure Description

[0041] Figure 1The XRD patterns of the high-temperature calcination products under different holding times in Example 2 of this invention;

[0042] Figure 2 SEM images of the high-temperature calcination products under different holding times in Example 2 of this invention;

[0043] Figure 3 This is the EDS image of the high-temperature calcination product after holding at a temperature of 40 min in Example 2 of this invention;

[0044] Figure 4 The compressive strength of the mortar of powder 2 after 40 minutes of heat preservation in Embodiment 2 of the present invention;

[0045] Figure 5 This is the FT-IR image of the aerated concrete panel product in Embodiment 2 of the present invention;

[0046] 1- Green body without static curing, 2- Green body after static curing for 4 hours, 3- Product after autoclaving for 7 hours;

[0047] Figure 6 This is a DSC-TG image of the aerated concrete panel product in Embodiment 2 of the present invention;

[0048] 1- Green body without static curing, 2- Green body after static curing for 4 hours, 3- Product after autoclaving for 7 hours;

[0049] Figure 7 This is a SEM image of the aerated concrete panel product in Embodiment 2 of the present invention;

[0050] (a) - Green body that has not undergone static curing and gas generation, (a1) - Figure 7 (a) is an enlarged view of the marked area.

[0051] (b)-The green body after static curing for 4 hours, (b1)- Figure 7 (b) is an enlarged view of the marked area.

[0052] (c) - Products cured by autoclaving for 7 hours; (c1) - Figure 7 (c) is an enlarged view of the marked area.

[0053] Figure 8 In Implementation Example 2 of the present invention Figure 7 EDS plots for regions 1 and 2 marked in the middle. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0055] Example 1

[0056] A method for preparing aerated concrete panels from lithium slag-steel slag-coal-based solid waste includes the following steps:

[0057] S1. Pre-treatment of waste shells: After cleaning, the waste shells are dried to constant weight and then crushed into ≤2mm particles by a crusher for later use.

[0058] S2. Pretreatment of causticized white mud: The causticized white mud is piled up and dried to a moisture content of 15-25%, then dried to constant weight, and crushed into ≤2mm particles in a crusher for later use.

[0059] S3. Pretreatment of quartz tailings: After removing impurities by screening, the quartz tailings are dried to constant weight and then dispersed into ≤2mm particles by ball mill for later use.

[0060] S4. Pre-treatment of waste photovoltaic panels: After cleaning and drying the waste photovoltaic panels with aluminum frames and adhesive strips removed, they are crushed into ≤2mm particles by a crusher for later use.

[0061] S5. Pretreatment of nickel slag / lithium slag / stainless steel slag: First, dry the nickel slag, lithium slag and stainless steel slag to constant weight, then crush them into ≤2mm particles by crusher. Then, mix the nickel slag, lithium slag and stainless steel slag in a mass ratio of 1:1:1 to obtain a mixture of ≤2mm particles.

[0062] S6. Pretreatment of coal slime: The coal slime is piled up in a cool and ventilated place to dry, so that its moisture content is less than 15%, and then dried to constant weight. After cooling, it is dispersed by a ball mill to obtain powder material for later use.

[0063] S7. Pretreatment of Glauber's salt gypsum / titanium gypsum: Dry the Glauber's salt gypsum and titanium gypsum separately in an electric drying oven, then grind them in a ball mill at a mass ratio of 1:1 until the specific surface area is 300-400 m². 2 / kg, yielding powder 1;

[0064] S8. Pressing and molding: Mix the mixture of S1, S2, S3, S4, and S5, and powder 1 from S6 and S7 in a weight ratio of 30%:25%:15%:10%:10%:5%:5%, then put it into a ball mill and grind it to obtain a specific surface area of ​​300-500 m². 2 / kg of mixed powder, transfer the mixed powder into a mortar mixer, add 8% of its mass of water, mix evenly and put it into a mold, press it into a material cake with a thickness of 1cm and a diameter of 10cm under a pressure of 15MPa, and place the material cake in an electric heating drying oven at 100℃ for 40min.

[0065] S9. High-Temperature Calcination: The dried material cake from step S8 is calcined at a high temperature. The calcination process is as follows: the temperature is raised from room temperature to 800°C at a rate of 5°C / min, and then held for 20 minutes; then raised from 800°C to 1100°C at a rate of 10°C / min, and then held for 60 minutes. After calcination, the material is rapidly cooled by air to obtain the high-temperature calcined product. The cooling process is as follows: first, the temperature is cooled to 1000°C at a rate of 18°C / min, and then cooled from 1000°C to room temperature at a rate of 100°C / min. The purpose is to improve the quality of the low-carbon powder by controlling the cooling temperature. Specifically, slow cooling is used first to control the formation of C2S in the powder, and after slow cooling, the material is cooled from 1000°C to room temperature at a rate of 100°C / min to obtain low-carbon powder with excellent performance in the early, middle, and late stages.

[0066] S10. Pretreatment of low-carbon powder 2: The high-temperature calcined product from step S9 is crushed into 1-3 mm particles using a crusher, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 2 low-carbon powders;

[0067] S11. Pretreatment of dicyandiamide waste residue / desulfurization ash residue: The dried dicyandiamide waste residue and desulfurization ash residue are mixed evenly at a mass ratio of 2:1, and then ground in a ball mill to a specific surface area of ​​300-400 m². 2 / kg, then the ground material is placed in a mortar mixer, water is added at 8% of its mass, and after being mixed evenly, it is placed in a mold and pressed into a cake with a thickness of 1cm and a diameter of 10cm under a pressure of 15MPa. The cake is then placed in an electric heating drying oven and dried at 100℃ for 40min. The dried cake is then placed in a muffle furnace for calcination. The calcination regime is as follows: the temperature is raised from room temperature to 300℃ at a rate of 2℃ / min, and then held for 20min; then raised from 300℃ to 750℃ at a rate of 3℃ / min, and then held for 30min. After calcination, the cake is allowed to cool naturally, and then the cooled cake is placed in a ball mill and ground to a specific surface area of ​​400-600m². 2 / kg, yielding 3g of powder;

[0068] S12. Purification of sea sand: Sea sand washed with fresh water is piled up in a cool place to dry, dried to constant weight, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 4g of powder;

[0069] S13. Pretreatment of the board skeleton: The Φ5 or Φ6 bamboo strips that have been peeled, dried and scored are tied into a bamboo strip mesh by using flamed wire, soaked in the anti-corrosion pool for 16 to 32 minutes, taken out and dried; the anti-corrosion bamboo strip mesh is placed into the mold according to the relative position and process dimensions and fixed.

[0070] S14. Casting and Molding of the Plate: Powder 1, Powder 2, Powder 3, and Powder 4 are added to a mixing tank in a mass ratio of 4%:8%:20%:68% and mixed evenly. Warm water is added at 52% of the total powder mass, and a foam stabilizer is added at 5‰ of the water mass. After mixing evenly, aluminum powder is added at 0.5‰ of the total powder mass. The evenly mixed slurry is poured into the mold; the temperature of the slurry entering the mold during casting is ensured to be 45℃. The foam stabilizer is prepared from trinitrotoluene, sodium stearoyl lactylate, and distilled water, with a corresponding mass ratio of 7.3:2.8:89.9. The aluminum powder has an active Al content of 93%, a sieve residue of 2.4% on a 0.08mm square hole sieve, a gas evolution rate greater than 82%, a gas evolution time of less than 23 minutes, and a hydrophilicity of less than 19 seconds.

[0071] S15. Curing of the board products: The slurry poured into the mold in S14 is subjected to static gas-generating curing, blank cutting, and high-temperature autoclaving to obtain aerated concrete board products; wherein, the static gas-generating curing time is 3 hours and the curing temperature is 55℃; the high-temperature autoclaving process is as follows: sealing, vacuuming, heating to 180℃, autoclaving pressure 1.2MPa, maintaining for 8 hours, and then cooling to room temperature and pressure.

[0072] The powder 1 prepared in step S7, a 1:1 mixture of mirabilite gypsum and titanium gypsum, meets the technical specifications specified in GB / T21371-2019 "Industrial By-product Gypsum for Cement". The mixed industrial by-product gypsum contains 85% CaSO4 and CaSO4·2H2O (specification requirement ≥75%), 0.46% chloride ion content (specification requirement ≤0.5%), a pH value of 4.7 (specification requirement ≤5), and radioactive material limits that meet the requirements of GB6566 (internal exposure index ≤1.0, external exposure index ≤1.0).

[0073] In Example 1, the chemical composition analysis of low-carbon powder 2 in step S10 (see Table 1) and its activity index (see Table 2) are shown. The physicochemical properties of powder 3 in step S11 (see Table 3) are shown. The technical indicators of sea sand in powder 4 in step S12 (see Table 4) are shown. The radioactivity results of the mixture in step S14 (see Table 5) are shown. The performance indicators of aerated concrete panels in step S15 (see Table 6) are shown.

[0074] Table 1 Chemical composition of low-carbon powder 2 in Example 1-S10

[0075]

[0076] Table 2 Activity index of low-carbon powder 2 in Examples 1-S10

[0077]

[0078] Table 3 Physicochemical properties of powder 3 in Examples 1-S11

[0079]

[0080] Note 1: Technical specifications for quicklime for silicate building products (JC / T621-2021).

[0081] Table 4 Technical specifications of powder 4 / purified sea sand in Examples 1-S12

[0082]

[0083] Note 2: Technical specifications for "Purified Sea Sand for Building and Municipal Engineering" JG / T494-2016.

[0084] Table 5. Radioactivity test results of the mixture in Examples 1-S14

[0085]

[0086] Note 3: These are the test index requirements in GB6566-2010, "Limits of Radionuclides in Building Materials".

[0087] Table 6 Performance indicators of aerated concrete panels in Examples 1-S15

[0088]

[0089] Notes 4 and 5: These are the test index requirements in GB / T15762-2020 "Autoclaved Aerated Concrete Slabs" and GB / T11968-2020 "Autoclaved Aerated Concrete Blocks".

[0090] Example 2

[0091] A method for preparing aerated concrete panels from lithium slag-steel slag-coal-based solid waste includes the following steps:

[0092] S1. Pre-treatment of waste shells: After cleaning, the waste shells are dried to constant weight and then crushed into ≤2mm particles by a crusher for later use.

[0093] S2. Pretreatment of causticized white mud: The causticized white mud is piled up and dried to a moisture content of 15-25%, then dried to constant weight, and crushed into ≤2mm particles in a crusher for later use.

[0094] S3. Pretreatment of quartz tailings: After removing impurities by screening, the quartz tailings are dried to constant weight and then dispersed into ≤2mm particles by ball mill for later use.

[0095] S4. Pre-treatment of waste photovoltaic panels: After cleaning and drying the waste photovoltaic panels with aluminum frames and adhesive strips removed, they are crushed into ≤2mm particles by a crusher for later use.

[0096] S5. Pretreatment of nickel slag / lithium slag / stainless steel slag: First, dry the nickel slag, lithium slag and stainless steel slag to constant weight, then crush them into ≤2mm particles by crusher. Then, mix the nickel slag, lithium slag and stainless steel slag in a mass ratio of 2:1:1 to obtain a mixture of ≤2mm particles.

[0097] S6. Pretreatment of coal slime: The coal slime is piled up in a cool and ventilated place to dry, so that its moisture content is less than 15%, and then dried to constant weight. After cooling, it is dispersed by a ball mill to obtain powder material for later use.

[0098] S7. Pretreatment of Glauber's salt gypsum / titanium gypsum: Dry the Glauber's salt gypsum and titanium gypsum separately in an electric drying oven, then grind them in a ball mill at a mass ratio of 1:2 until the specific surface area is 300-400 m². 2 / kg, yielding powder 1;

[0099] S8. Pressing and molding: Mix the mixture of S1, S2, S3, S4, and S5, and powder 1 from S6 and S7 in a weight ratio of 35%:35%:10%:5%:5%:5%:5%, then put it into a ball mill and grind it to obtain a specific surface area of ​​300-500 m². 2 / kg of mixed powder, transfer the mixed powder into a mortar mixer, add 9% of its mass of water, mix evenly and put it into a mold, press it into a material cake with a thickness of 1cm and a diameter of 10cm under a pressure of 20MPa, and place the material cake in an electric heating drying oven at 100℃ for 40min.

[0100] S9. High-Temperature Calcination: The dried material cake from step S8 is calcined at a high temperature. The calcination process is as follows: the temperature is raised from room temperature to 800°C at a rate of 5°C / min, and then held for 20 minutes; then raised from 800°C to 1200°C at a rate of 10°C / min, and then held for 40 minutes. After calcination, the material is rapidly cooled by air to obtain the high-temperature calcined product. The cooling process is as follows: first, the temperature is cooled to 1000°C at a rate of 19°C / min, and then cooled from 1000°C to room temperature at a rate of 120°C / min. The purpose is to improve the quality of the low-carbon powder by controlling the cooling temperature. Specifically, slow cooling is used first to control the formation of C2S in the powder, and after slow cooling, the powder is cooled from 1000°C to room temperature at a rate of 120°C / min to obtain low-carbon powder with excellent performance in the early, middle, and late stages.

[0101] S10. Pretreatment of low-carbon powder 2: The high-temperature calcined product from step S9 is crushed into 1-3 mm particles using a crusher, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 2 low-carbon powders;

[0102] S11. Pretreatment of dicyandiamide waste residue / desulfurization ash residue: The dried dicyandiamide waste residue and desulfurization ash residue are mixed evenly at a mass ratio of 3:1, and then ground in a ball mill to a specific surface area of ​​300-400 m². 2 / kg, then the ground material is placed in a mortar mixer, and water is added at 9% of its mass. After mixing evenly, it is placed in a mold and pressed into a cake with a thickness of 1cm and a diameter of 10cm under a pressure of 20MPa. The cake is then placed in an electric drying oven and dried at 100℃ for 40min. The dried cake is then placed in a muffle furnace for calcination. The calcination regime is as follows: the temperature is raised from room temperature to 300℃ at a rate of 2℃ / min, and then held for 20min; then raised from 300℃ to 800℃ at a rate of 3℃ / min, and then held for 30min. After calcination, the cake is allowed to cool naturally, and then the cooled cake is placed in a ball mill and ground to a specific surface area of ​​400-600m². 2 / kg, yielding 3g of powder;

[0103] S12. Purification of sea sand: Sea sand washed with fresh water is piled up in a cool place to dry, dried to constant weight, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 4g of powder;

[0104] S13. Pretreatment of the board skeleton: The Φ5 or Φ6 bamboo strips that have been peeled, dried and scored are tied into a bamboo strip mesh by using flamed wire, soaked in the anti-corrosion pool for 16 to 32 minutes, taken out and dried; the anti-corrosion bamboo strip mesh is placed into the mold according to the relative position and process dimensions and fixed.

[0105] S14. Casting and Molding of the Plate: Powder 1, Powder 2, Powder 3, and Powder 4 are added to a mixing tank in a mass ratio of 4%:8%:24%:64% and mixed evenly. Warm water is added at 60% of the total mass of the powders, and a foam stabilizer is added at 8‰ of the water mass. After mixing evenly, aluminum powder is added at 0.6‰ of the total mass of the powders. The evenly mixed slurry is poured into the mold; the temperature of the slurry entering the mold during pouring is ensured to be 50℃. The foam stabilizer is prepared from trinitrotoluene, sodium stearoyl lactylate, and distilled water, with a corresponding mass ratio of 7.3:2.8:89.9. The aluminum powder has an active Al content of 93%, a sieve residue of 2.4% on a 0.08mm square hole sieve, a gas evolution rate greater than 82%, a gas evolution time of less than 23 minutes, and a hydrophilicity of less than 19 seconds.

[0106] S15. Curing of the board products: The slurry poured into the mold in S14 is subjected to static gas-generating curing, blank cutting, and high-temperature autoclaving to obtain aerated concrete board products; wherein, the static gas-generating curing time is 4 hours and the curing temperature is 60℃; the high-temperature autoclaving process is as follows: sealing, vacuuming, heating to 190℃, autoclaving pressure 1.3MPa, maintaining for 7 hours, and then cooling to room temperature and pressure.

[0107] The powder 1 prepared in step S7, a 1:2 mixture of mirabilite gypsum and titanium gypsum, meets the technical specifications specified in GB / T21371-2019 "Industrial By-product Gypsum for Cement". The mixed industrial by-product gypsum contains 92% CaSO4 and CaSO4·2H2O (the specification requires ≥75%), 0.39% chloride ion content (the specification requires ≤0.5%), a pH value of 4.2 (the specification requires ≤5), and radioactive material limits that meet the requirements of GB6566 (internal exposure index ≤1.0, external exposure index ≤1.0).

[0108] In Example 2, the chemical composition analysis of low-carbon powder 2 in step S10 (see Table 7), the activity index (see Table 8), the physicochemical properties of powder 3 in step S11 (see Table 9), the technical indicators of sea sand of powder 4 in step S12 (see Table 10), the radioactivity results of the mixture in step S14 (see Table 11), and the performance indicators of aerated concrete panels in step S15 (see Table 12).

[0109] Table 7 Chemical composition of low-carbon powder 2 in Example 2-S10

[0110]

[0111] Table 8 Activity Index of Low-Carbon Powder 2 in Example 2-S10

[0112]

[0113] Table 9 Physicochemical properties of powder 3 in Example 2-S11

[0114]

[0115] Note 1: Technical specifications for quicklime for silicate building products (JC / T621-2021).

[0116] Table 10 Technical Specifications of Powder 4 / Purified Sea Sand in Example 2-S12

[0117]

[0118] Note 2: Technical specifications for "Purified Sea Sand for Building and Municipal Engineering" JG / T494-2016.

[0119] Table 11. Radioactivity test results of the mixture in Example 2-S14

[0120]

[0121] Note 3: These are the test index requirements in GB6566-2010, "Limits of Radionuclides in Building Materials".

[0122] Table 12 Performance indicators of aerated concrete panels in Examples 2-S15

[0123]

[0124] Notes 4 and 5: These are the test index requirements in GB / T15762-2020 "Autoclaved Aerated Concrete Slabs" and GB / T11968-2020 "Autoclaved Aerated Concrete Blocks".

[0125] Example 3

[0126] A method for preparing aerated concrete panels from lithium slag-steel slag-coal-based solid waste includes the following steps:

[0127] S1. Pre-treatment of waste shells: After cleaning, the waste shells are dried to constant weight and then crushed into ≤2mm particles by a crusher for later use.

[0128] S2. Pretreatment of causticized white mud: The causticized white mud is piled up and dried to a moisture content of 15-25%, then dried to constant weight, and crushed into ≤2mm particles in a crusher for later use.

[0129] S3. Pretreatment of quartz tailings: After removing impurities by screening, the quartz tailings are dried to constant weight and then dispersed into ≤2mm particles by ball mill for later use.

[0130] S4. Pre-treatment of waste photovoltaic panels: After cleaning and drying the waste photovoltaic panels with aluminum frames and adhesive strips removed, they are crushed into ≤2mm particles by a crusher for later use.

[0131] S5. Pretreatment of nickel slag / lithium slag / stainless steel slag: First, dry the nickel slag, lithium slag and stainless steel slag to constant weight, then crush them into ≤2mm particles by crusher. Then, mix the nickel slag, lithium slag and stainless steel slag in a mass ratio of 1:2:2 to obtain a mixture of ≤2mm particles.

[0132] S6. Pretreatment of coal slime: The coal slime is piled up in a cool and ventilated place to dry, so that its moisture content is less than 15%, and then dried to constant weight. After cooling, it is dispersed by a ball mill to obtain powder material for later use.

[0133] S7. Pretreatment of Glauber's salt gypsum / titanium gypsum: Dry the Glauber's salt gypsum and titanium gypsum separately in an electric drying oven, then grind them in a ball mill at a mass ratio of 2:1 until the specific surface area is 300-400 m².2 / kg, yielding powder 1;

[0134] S8. Pressing and molding: Mix the mixture of S1, S2, S3, S4, and S5, and powder 1 from S6 and S7 in a weight ratio of 25%:30%:20%:7%:7%:8%:3%, then put it into a ball mill and grind it to obtain a specific surface area of ​​300-500 m². 2 / kg of mixed powder, transfer the mixed powder into a mortar mixer, add 10% of its mass of water, mix evenly and put it into a mold, press it into a material cake with a thickness of 1cm and a diameter of 10cm under a pressure of 25MPa, and place the material cake in an electric heating drying oven at 100℃ for 40min.

[0135] S9. High-Temperature Calcination: The dried material cake from step S8 is calcined at a high temperature. The calcination process is as follows: the temperature is raised from room temperature to 800°C at a rate of 5°C / min, and then held for 20 minutes; then raised from 800°C to 1300°C at a rate of 10°C / min, and then held for 30 minutes. After calcination, the material is rapidly cooled by air to obtain the high-temperature calcined product. The cooling process is as follows: first, the temperature is cooled to 1000°C at a rate of 20°C / min, and then cooled from 1000°C to room temperature at a rate of 130°C / min. The purpose is to improve the quality of the low-carbon powder by controlling the cooling temperature. Specifically, slow cooling is used first to control the formation of C2S in the powder, and after slow cooling, the powder is cooled from 1000°C to room temperature at a rate of 130°C / min to obtain low-carbon powder with excellent performance in the early, middle, and late stages.

[0136] S10. Pretreatment of low-carbon powder 2: The high-temperature calcined product from step S9 is crushed into 1-3 mm particles using a crusher, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 2 low-carbon powders;

[0137] S11. Pretreatment of dicyandiamide waste residue / desulfurization ash residue: The dried dicyandiamide waste residue and desulfurization ash residue are mixed evenly at a mass ratio of 4:1, and then ground in a ball mill to a specific surface area of ​​300-400 m². 2 / kg, then the ground material is placed in a mortar mixer, water of 10% by weight is added, and after being mixed evenly, it is placed in a mold and pressed into a cake with a thickness of 1cm and a diameter of 10cm under a pressure of 25MPa. The cake is then placed in an electric heating drying oven and dried at 100℃ for 40min. The dried cake is then placed in a muffle furnace for calcination. The calcination regime is as follows: the temperature is raised from room temperature to 300℃ at a rate of 2℃ / min, and then held for 20min; then raised from 300℃ to 850℃ at a rate of 3℃ / min, and then held for 30min. After calcination, the cake is allowed to cool naturally, and then the cooled cake is placed in a ball mill and ground to a specific surface area of ​​400-600m².2 / kg, yielding 3g of powder;

[0138] S12. Purification of sea sand: Sea sand washed with fresh water is piled up in a cool place to dry, dried to constant weight, and then ground in a ball mill to a specific surface area of ​​400-600 m². 2 / kg, yielding 4g of powder;

[0139] S13. Pretreatment of the board skeleton: The Φ5 or Φ6 bamboo strips that have been peeled, dried and scored are tied into a bamboo strip mesh by using flamed wire, soaked in the anti-corrosion pool for 16 to 32 minutes, taken out and dried; the anti-corrosion bamboo strip mesh is placed into the mold according to the relative position and process dimensions and fixed.

[0140] S14. Casting and Molding of the Plate: Powder 1, Powder 2, Powder 3, and Powder 4 are added to a mixing tank at a mass ratio of 8%:12%:28%:52% and mixed evenly. Warm water is added at 64% of the total powder mass, and a foam stabilizer is added at 12‰ of the water mass. After mixing evenly, aluminum powder is added at 0.7‰ of the total powder mass. The evenly mixed slurry is poured into the mold; the temperature of the slurry entering the mold during pouring is ensured to be 48℃. The foam stabilizer is prepared from trinitrotoluene, sodium stearoyl lactylate, and distilled water, with a corresponding mass ratio of 7.3:2.8:89.9. The aluminum powder has an active Al content of 93%, a sieve residue of 2.4% on a 0.08mm square hole sieve, a gas evolution rate greater than 82%, a gas evolution time of less than 23 minutes, and a hydrophilicity of less than 19 seconds.

[0141] S15. Curing of the board products: The slurry poured into the mold in S14 is subjected to static gas-generating curing, blank cutting, and high-temperature autoclaving to obtain aerated concrete board products; wherein, the static gas-generating curing time is 5 hours and the curing temperature is 68℃; the high-temperature autoclaving process is as follows: sealing, vacuuming, heating to 195℃, autoclaving pressure 1.35MPa, maintaining for 6 hours, and then cooling to room temperature and pressure.

[0142] The powder mixture of mirabilite gypsum and titanium gypsum prepared in step S7, in a 2:1 ratio, meets the technical specifications specified in GB / T 21371-2019 "Industrial By-product Gypsum for Cement". The mixed industrial by-product gypsum contains 89% CaSO4 and CaSO4·2H2O (specification requirement ≥75%), 0.43% chloride ion content (specification requirement ≤0.5%), a pH value of 4.4 (specification requirement ≤5), and radioactive material limits that meet the requirements of GB 6566 (internal exposure index ≤1.0, external exposure index ≤1.0).

[0143] In Example 3, the chemical composition analysis of low-carbon powder 2 in step S10 (see Table 13), the activity index (see Table 14), the physicochemical properties of powder 3 in step S11 (see Table 15), the technical indicators of sea sand of powder 4 in S12 (see Table 16), the radioactivity results of the mixture in step S14 (see Table 17), and the performance indicators of aerated concrete panels in step S15 (see Table 18).

[0144] Table 13 Chemical composition of low-carbon powder 2 in Example 3-S10

[0145]

[0146] Table 14 Activity Index of Low-Carbon Powder 2 in Example 3-S10

[0147]

[0148] Table 15 Physicochemical properties of powder 3 in Example 3-S11

[0149]

[0150] Note 1: Technical specifications for quicklime for silicate building products (JC / T621-2021).

[0151] Table 16 Technical Specifications of Powder 4 / Purified Sea Sand in Example 3-S12

[0152]

[0153]

[0154] Note 2: Technical specifications for "Purified Sea Sand for Building and Municipal Engineering" JG / T494-2016.

[0155] Table 17. Radioactivity test results of the mixture in Example 3-S14

[0156]

[0157] Note 3: These are the test index requirements in GB6566-2010, "Limits of Radionuclides in Building Materials".

[0158] Table 18 Performance indicators of aerated concrete panels in Examples 3-S15

[0159]

[0160] Notes 4 and 5: These are the test index requirements in GB / T15762-2020 "Autoclaved Aerated Concrete Slabs" and GB / T11968-2020 "Autoclaved Aerated Concrete Blocks".

[0161] The present invention will be further described below with reference to the accompanying drawings:

[0162] Analysis of the composition, morphology and properties of the high-temperature calcination product in step S9 of Example 2

[0163] 1. Mineral composition of the high-temperature calcination product

[0164] Depend on Figure 1 It can be seen that the prepared high-temperature calcined product contains, in addition to In addition to C2S and C4AF, there is also C 12 A7, C3A, and trace amounts of CaSO4. From Figure 1 The comparison graphs of heat preservation for 30 min, 40 min, 50 min, and 60 min show that as the heat preservation time increases, The content of C4AF and C3A decreased, while the content of C3A increased. C4AF and C3A melted with MgO and alkali at 1200℃ to form a liquid phase. The increase in the amount of liquid phase promoted the absorption of f-CaO. Table 19 shows the f-CaO content determination results. Holding for more than 40 minutes reduced the f-CaO content in cement clinker to below 1.5%. Holding for more than 40 minutes easily caused… Synthesized and then decomposed, leading to The decrease in quantity can be described by formulas (1) and (2):

[0165] (1)

[0166] (2) CA + CaO → C3A

[0167] However, the system did not contain a large amount of CaSO4, indicating that CaSO4 continued to decompose into CaO and SO3, which were absorbed and released respectively. C3A solidifies quickly and contributes significantly to early strength; however, if the solidification rate is not properly controlled, rapid solidification can easily occur. Therefore, the holding time in this invention should be controlled to be around 40 minutes.

[0168] Table 19. Results of f-CaO content determination (wt%) in high-temperature calcination products.

[0169]

[0170] 2. Microstructure of the high-temperature calcination products

[0171] Figure 2 The microstructures of the products calcined at high temperatures for 30 min, 40 min, 50 min, and 60 min are shown in the figures. As can be seen from the figures, the two minerals with better crystallinity are... C2S and C2S grow separately. The particle size is 2–4 μm, and it appears as irregular, multifaceted particles. C2S particles can reach over 10 μm in size, and most are elliptical in shape. With prolonged holding time and a gradually increasing amount of liquid phase, The decomposition process results in a more compact bond between clinker mineral particles, with the particle boundaries gradually becoming blurred. A holding time of less than 20 minutes leads to finer crystal particles, which not only facilitates grinding but also provides superior hydration performance due to the relatively large specific surface area of ​​the mineral particles.

[0172] EDS analysis was performed on points A and B of powder 2 after a heat preservation time of 40 min. Figure 3 The elemental statistics are shown in Table 20. The mineral at point A is... The crystal grain size is between 2 and 4 μm. The mineral at point B is C2S, with trace amounts of Al, S, Mg, Na, and K entering the C2S lattice. The inclusion of impurity elements in the lattice can stabilize C2S in the β-type and increase its hydration reactivity.

[0173] Table 20 Figure 3 Statistical results of EDS analysis at points A and B (mol%)

[0174]

[0175] 3. Properties of high-temperature calcined products

[0176] In Example 2, an appropriate amount of gypsum was added to powder 2 prepared from the high-temperature calcination product. A mortar strength test was conducted with a water-cement ratio of 0.5 and a sand-cement ratio of 3. A reference cement was used as a control sample, and its mortar compressive strength was tested using the same water-cement ratio and sand-cement ratio. The compressive strength was measured at 1 day, 3 days, 7 days, 28 days, and 90 days of curing. The mortar strengths of the reference cement and powder 2 were obtained as follows: Figure 4 As shown in the figure, the 1-day and 3-day compressive strength of cement prepared from powder 2 is significantly higher than that of the reference cement. It typically reaches the 7-day strength level of the reference cement at 3 days. The 28-day strength of cement prepared from powder 2 is comparable to that of the reference cement, and with the extension of the curing age, its 90-day strength exceeds that of the reference cement. The strength performance of powder 2 depends on the optimized matching relationship of various minerals within its system, effectively ensuring the optimal ratio of several minerals in powder 2, guaranteeing synergistic hydration among the minerals, and promoting the stable performance of powder 2's strength. Furthermore, the performance of powder 2 is similar to or even better than that of silicate cement clinker, indicating that powder 2 can widely replace traditional silicate cement.

[0177] Phase composition and structural analysis of the aerated concrete panel product in step S15 of Example 2

[0178] Figure 5Comparative FT-IR spectra of aerated concrete (ACF) panel samples are presented: hardened preforms without static gas-generating curing, hardened preforms after 4 hours of static gas-generating curing, and products after 7 hours of autoclaving curing. The spectra show that all absorption peaks shift towards lower wavenumbers. In curve 1 of the hardened preform without static gas-generating curing, the strongest absorption region is 1100–1250 cm⁻¹. -1 This is a quartz absorption band, belonging to the Si-O asymmetric stretching vibration, consisting of a weak absorption band from 1160 to 1250 cm⁻¹. -1 and a strong absorption band of 1076–1100 cm⁻¹ -1 Its composition has a wide and strong absorption bandwidth, of which 1076 cm⁻¹ is the largest. -1 The characteristic peak at this point is the asymmetric stretching vibration of Si-O, with a wavenumber of 777 cm⁻¹. -1 There is a moderately strong absorption peak at 460 cm⁻¹, belonging to the Si-O-Si symmetric stretching vibration, which is a characteristic peak of quartz group minerals. -1 The characteristic peak at this point is attributed to the bending vibration of Si-O. The wavenumber is at 3650 cm⁻¹. -1 The absorption bands around the left and right are attributed to the stretching vibrations of the hydroxyl groups in Ca(OH)₂, with a wavenumber of 3450 cm⁻¹. -1 The characteristic peaks nearby represent the stretching vibrations of adsorbed water in the hydration products CSH gel or ettringite (AFt); the wavenumber is around 1623 cm⁻¹. -1 The absorption bands on the left and right are attributed to the bending vibrations of hydroxyl groups adsorbed in water within the CSH gel or AFt; the wavenumber is around 1433 cm⁻¹. -1 The absorption band at that location is attributed to CO3 in calcite. 2- The asymmetric stretching vibration is caused by carbonization of the product; the wavenumber is around 1000 cm⁻¹. -1 ~1050cm -1 The broader spectral bands around 640 cm⁻¹ belong to the stretching vibrations of the Si-O bond, caused by the hydration product CSH gel; the wavenumber is around 640 cm⁻¹. -1 ~700cm -1 The band at this point represents the bending vibration of O-Si(Al)-O, which belongs to the vibrational spectrum of the purified sea sand minerals in powder 4.

[0179] Figure 5 The infrared spectra of the aerated concrete slab product after 7 hours of autoclaving (curve 3) and the hardened green body after 4 hours of static curing (curve 2) are similar, showing no significant changes. After 4 hours of static curing and 7 hours of high-temperature autoclaving, the wavenumber is 1076 cm⁻¹. -1 1004cm -1 683cm -1 645cm -1 and 460cm -1The characteristic peaks representing quartz group minerals disappear, and the wavenumber representing quartz in curve 2 is 777 cm⁻¹. -1 The characteristic spectral bands weakened and disappeared in curve 3, indicating that with increasing temperature and pressure, the active SiO2 and Al2O3 in the sea sand underwent a chemical reaction with Ca(OH)2, forming corresponding hydration products in greater quantities, showing a tendency to crystallize. The wavenumber in curve 3 is 3450 cm⁻¹. -1 The disappearance of the stretching vibration characteristic peak attributable to the hydroxyl group in Ca(OH)₂ fully proves this point. Meanwhile, the peak at 1623 cm⁻¹ in curve 1... -1 The absorption bands attributable to ettringite (AFt) disappear in curves 2 and 3 upon increasing temperature, indicating that AFt decomposes under higher temperature conditions. New characteristic peaks appear in curves 2 and 3, with wavenumbers of 1630 cm⁻¹. -1 978m -1 and 451cm -1 The wave number is 978 cm⁻¹. -1 The nearby absorption band is the Q in the [SiO4] structure. 2 This is caused by the symmetric stretching vibration of Si-O, and the characteristic peak absorption intensity at this location is very high, indicating that this vibration has strong infrared activity; the wavenumber is 451 cm⁻¹. -1 The nearby characteristic peaks are caused by the Si-O bending vibrations in the [SiO4] structure. The wavenumber is 978 cm⁻¹. -1 and 451cm -1 The characteristic peaks are all attributed to the layered structure of tobermorite.

[0180] Figure 6 DSC-TG analysis charts of aerated concrete panel samples are presented for hardened preforms without static gas-generating curing, hardened preforms after static gas-generating curing for 4 hours, and products after autoclaving curing for 7 hours. Figure 6 (1) Figure 6 (2) Figure 6 In (3), an endothermic peak exists between 80℃ and 200℃, mainly attributed to the hydration product AFt and the removal of free water, adsorbed water, and weak crystal water from the CSH gel. Figure 6(1) It can be seen that endothermic peaks appeared at 107℃, 463℃, 577℃ and 762℃ on the DSC curve. The endothermic peak at 107℃ is relatively sharp, accompanied by a weight loss of 4.38%. The endothermic peak at this point is formed by the dehydration of AFt. With continued heating, there is a large endothermic peak at 463℃, mainly due to the removal of structural water by Ca(OH)2 formed by cement hydration or lime slaking in the green body that has not undergone static gas-generating curing. The endothermic peak at 577℃ is formed by the crystal transformation of quartz in lead-zinc tailings, mainly the transformation from β-quartz to -α-quartz. At this time, there is no obvious weight loss on the TG curve. The endothermic peak at 762℃ is caused by the loss of structural water by CSH gel. At the same time, the endothermic peak of calcite decomposition is also near this temperature. Therefore, the resulting endothermic peak is relatively large.

[0181] Figure 6 In (2), the endothermic peak appearing at around 114℃ is due to the dehydration of ettringite. The peak between 360℃ and 400℃ is caused by the loss of crystal water by gypsum; the endothermic peak appearing at around 460℃ is formed by the dehydration of Ca(OH)₂. Figure 6 (2) Regarding the lower intensity of this peak, this is because after static gasification curing, the Ca(OH)2 in the system combines with the active components SiO2 and Al2O3 in the lead-zinc tailings to form corresponding hydration products, consuming the Ca(OH)2 in the system. This is consistent with the FT-IR analysis results. The absorption peak at 757℃ and Figure 6 The absorption peaks of (1) are the same, which is caused by the dehydration of CSH gel. The endothermic peak at 578℃ is formed by the crystal transformation of quartz in powder 4.

[0182] Combination Figure 5 The FT-IR analysis results show that the main hydration product of the aerated concrete after autoclaving is tobermorite. Figure 6 (3) The strong exothermic peak at 861℃ is due to the crystal transformation of tobermorite crystals. Furthermore, the endothermic peak at 751℃ is formed by the decomposition of calcium carbonate, and the endothermic peak around 577℃ is due to the endothermic transformation of residual quartz particles in the sample. Meanwhile, Figure 6 (3) No endothermic peak for Ca(OH)2 dehydration was found, which indicates that after steaming and pressing, all of Ca(OH)2 participated in the reaction, which is consistent with the FT-IR analysis results.

[0183] Figure 7 , Figure 8 SEM and EDS spectra of hardened preforms and aerated concrete products before and after static curing with gas evaporation. Preforms without static curing with gas evaporation. Figure 7 (a) and Figure 7As can be seen from (a1), the main hydration product is CSH gel with poor crystal structure and loose structure. Figure 7 (a1) is Figure 7 (a) is an enlarged view of the marked area. Figure 7 In the field of view of (a1), the hydration products are mainly covered by needle-like AFt and loosely crystalline CSH gel, with the CSH gel located on the right side of the figure. Figure 8 region1 is Figure 7 The EDS spectrum of region 1 marked in (a1) shows that the main elements are Ca, S, and Al, consistent with the composition of AFt. CSH gel formation is mainly due to cement hydration in the lead-zinc tailings aerated concrete raw material system, while the presence of gypsum in the powder raw materials and material system promotes AFt formation. Figure 7 (b) and Figure 7 (b1) is a cross-sectional view of the green body after static curing for 4 hours. The figure shows CSH gel with high crystallinity and good crystal form, as well as a large number of thin and unevenly thick plate-like hydration products. Figure 8 region2 is Figure 7 (b1) shows the EDS spectrum of region 2. This analysis reveals the presence of Al in the hydration products. This is likely due to the presence of Al in the lead-zinc tailings and the addition of aluminum powder paste to the raw material system, resulting in the replacement of some [SiO4] tetrahedra with [AlO4] tetrahedra. The hydration products in region 2 are similar to tobermorite (Ca5(OH)2Si6O). 16 The composition of ·4H2O is basically the same. From Figure 7 (b) and Figure 7 The absence of AFt in the field of view of (b1) indicates that after 4 hours of static curing at 60°C, AFt decomposed under high temperature conditions, consistent with the analyses of FT-IR and DSC-TG. Simultaneously, the increased crystallinity of the CSH gel after static curing and the formation of abundant hydration products provided sufficient strength for the green body, facilitating its cutting and autoclaving. Due to the short curing time and low temperature, the hydration products were fewer, resulting in a less dense structural system.

[0184] Figure 7 (c) shows the hydration products of aerated concrete products after 7 hours of autoclaving. The products are mainly tobermorite and a small amount of CSH gel. The area marked in the figure is enlarged. Figure 7(c1) shows the formation of numerous visible plate-like tobermorite crystals, approximately 0.1–0.2 μm thick. The crystallinity of these plate-like tobermorite crystals is significantly enhanced, and they intertwine to form the skeletal structure of the aerated concrete product, giving it sufficient strength. After high-temperature autoclaving, the solubility of the active components SiO2 and Al2O3 in the sea sand increases under alkaline hydrothermal conditions, enhancing their ability to participate in chemical reactions and playing a positive role in improving the crystallinity of the hydration products.

[0185] In summary, this invention utilizes solid waste to prepare aerated concrete panels, which improves physical and mechanical properties (strength and density) and durability (impermeability, frost resistance, and carbonation resistance), surpassing existing products on the market and is worthy of vigorous promotion.

[0186] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing aerated concrete panels from lithium slag-steel slag-coal-based solid waste, the method comprising the following steps: S1. Pre-treatment of waste shells: After cleaning, the waste shells are dried to constant weight and then crushed into ≤2mm particles by a crusher for later use. S2. Pretreatment of causticized white mud: The causticized white mud is piled up and dried to a moisture content of 15-25%, then dried to constant weight, and then crushed into ≤2mm particles in a crusher for later use. S3. Pretreatment of quartz tailings: After removing impurities by screening, the quartz tailings are dried to constant weight and then dispersed into ≤2mm particles by ball mill for later use. S4. Pre-treatment of waste photovoltaic panels: After cleaning and drying the waste photovoltaic panels with aluminum frames and adhesive strips removed, they are crushed into ≤2mm particles by a crusher for later use. S5. Pretreatment of nickel slag / lithium slag / stainless steel slag: First, dry the nickel slag, lithium slag and stainless steel slag to constant weight, then crush them into ≤2mm particles by crusher. Then, mix the nickel slag, lithium slag and stainless steel slag in a mass ratio of 1~2:1~2:1~2 to obtain a mixture of ≤2mm particles. S6. Pretreatment of coal slime: The coal slime is piled up in a cool and ventilated place to dry, so that its moisture content is less than 15%, and then dried to constant weight. After cooling, it is dispersed by a ball mill to obtain powder material for later use. S7. Pretreatment of Glauber's salt gypsum / titanium gypsum: Dry the Glauber's salt gypsum and titanium gypsum separately in an electric drying oven, then grind them in a ball mill at a mass ratio of 1~2:1~2 until the specific surface area is 300~400 m². 2 / kg, yielding powder 1; S8. Compression Molding: The granules treated by S1, S2, S3, S4, and S5, the powder material treated by S6, and the powder material treated by S7 are mixed evenly in a weight ratio of 25-35%:25-35%:10-20%:5-10%:5-10%:5-8%:3-5%, and then placed in a ball mill for grinding to obtain a specific surface area of ​​300-500 m². 2 / kg of mixed powder, transfer the mixed powder into a mortar mixer, add 8~10% of its mass of water, mix evenly, put it into a mold, press it into a patty, and place the patty in an electric heating drying oven at 100℃ for 40 minutes. S9. High-temperature calcination: The dried cake from step S8 is calcined at high temperature. After calcination, it is rapidly cooled by air to obtain the high-temperature calcined product. S10. Pretreatment of low-carbon powder 2: The high-temperature calcined product from step S9 is crushed into 1-3mm particles using a crusher, and then ground in a ball mill to a specific surface area of ​​400-600m². 2 / kg, yielding 2 low-carbon powders; S11. Pretreatment of dicyandiamide waste residue / desulfurization ash residue: The dried dicyandiamide waste residue and desulfurization ash residue are mixed evenly at a mass ratio of 2~4:1, and then ground in a ball mill to a specific surface area of ​​300~400m². 2 / kg, then put the ground material into a mortar mixer, add 8-10% water by weight, mix evenly, put it into a mold, press it into a cake, and place the cake in an electric heating drying oven at 100℃ for 40 minutes; the dried cake is then placed in a muffle furnace for calcination, and after calcination, it is naturally cooled. Then the cooled cake is put into a ball mill and ground to a specific surface area of ​​400-600 m². 2 / kg, yielding 3g of powder; S12. Purification of sea sand: Sea sand washed with fresh water is piled up in a cool place to dry, dried to constant weight, and then ground in a ball mill to a specific surface area of ​​400~600 m². 2 / kg, yielding 4g of powder; S13. Pretreatment of the board skeleton: The Φ5 or Φ6 bamboo strips that have been peeled, dried and scored are tied into a bamboo strip mesh by using flamed wire. The mesh is then soaked in an anti-corrosion tank for 16-32 minutes, removed and dried. The anti-corrosion bamboo strip mesh is placed into the mold according to the relative position and process dimensions and fixed. S14. Casting and molding of the plate: Add powder 1, powder 2, powder 3 and powder 4 to the mixing tank in a mass ratio of 4~8%:8~12%:20~28%:52~68%, mix evenly, add warm water at 52~64% of the total mass of powder, add foam stabilizer at 5~12‰ of the water mass, stir evenly, add aluminum powder at 0.5~0.7‰ of the total mass of powder, and pour the evenly stirred slurry into the mold; S15. Curing of the board products: The slurry poured into the mold in S14 is subjected to static curing, blank cutting, and high-temperature autoclaving to obtain aerated concrete board products.

2. The method for preparing aerated concrete slabs from lithium-containing slag-steel slag-coal-based solid waste according to claim 1, characterized in that, In steps S8 and S11, the pressure for pressing the material into cakes is 15~25 MPa.

3. The method for preparing aerated concrete slabs from lithium-containing slag-steel slag-coal-based solid waste according to claim 1, characterized in that, In steps S8 and S11, the thickness of the material cake is 1 cm and the diameter is 10 cm.

4. The method for preparing aerated concrete panels from lithium-containing slag-steel slag-coal-based solid waste according to claim 1, characterized in that, The calcination process in step S9 is as follows: the temperature is raised from room temperature to 800°C at a rate of 5°C / min, and then held for 20 min; then the temperature is raised from 800°C to 1100~1300°C at a rate of 10°C / min, and then held for 30~60 min.

5. The method for preparing aerated concrete panels from lithium-containing slag-steel slag-coal-based solid waste according to claim 1, characterized in that, The cooling process in step S9 includes first cooling to 1000°C at a rate of 18~20°C / min, and then cooling from 1000°C to room temperature at a rate of not less than 100°C / min.

6. The method for preparing aerated concrete slabs from lithium-containing slag-steel slag-coal-based solid waste according to claim 1, characterized in that, The calcination process in step S11 is as follows: the temperature is raised from room temperature to 300°C at a rate of 2°C / min, and then held for 20 min; then the temperature is raised from 300°C to 750°C~850°C at a rate of 3°C / min, and then held for 30 min.

7. The method for preparing aerated concrete slabs from lithium-containing slag-steel slag-coal-based solid waste according to claim 1, characterized in that, In step S14, the foam stabilizer is prepared from trinitrotoluene, sodium stearoyl lactylate, and distilled water in a mass ratio of 7.3:2.8:89.

9. The aluminum powder has an active Al content of 93%, a residue of 2.4% on a 0.08mm square hole sieve, a gas generation rate of more than 82%, a gas generation time of less than 23 minutes, and a hydrophilicity of less than 19 seconds.

8. The method for preparing aerated concrete slabs from lithium-containing slag-steel slag-coal-based solid waste according to claim 1, characterized in that, The temperature of the slurry during pouring in step S14 is 45~50℃.

9. The method for preparing aerated concrete panels from lithium slag-steel slag-coal-based solid waste according to any one of claims 1 to 8, wherein the static curing time in step S15 is 3 to 5 hours and the curing temperature is 55 to 68°C; the high-temperature autoclaving process is as follows: sealing, vacuuming, heating to 180 to 195°C, autoclaving pressure of 1.2 to 1.35 MPa, maintaining for 6 to 8 hours, and then naturally cooling to room temperature and pressure.

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