A method for preparing high-insulation aerated concrete blocks from municipal solid waste ash by sulfuric acid modification.

Abstract

This invention proposes a method for preparing high-insulation aerated concrete (AAC) bricks from municipal solid waste ash using sulfuric acid modification. The steps are as follows: ash pretreatment by acid washing; preparation of high-insulation AAC bricks; and curing with carbon dioxide and alkali spraying. This invention uses a metal chelating agent and low-temperature pyrolysis to detoxify fly ash, followed by acid washing and modification of the fly ash and slag using H2SO4 solution. The resulting liquid phase is utilized for resource recovery, while the solid phase is mixed with ammonia and Al2(SO4)3 to generate aluminosilicate gel, enhancing the insulation effect of the AAC bricks. The resulting dried solid is mixed with slag and Al powder solution to prepare AAC bricks, which are then mineralized and cured using CO2 bubbling. During natural curing, Ca(OH)2 solution is periodically sprayed for alkali spraying to improve the compressive strength of the AAC bricks and reduce carbon emissions. This invention solves the problems of fly ash harmlessness and solid waste resource utilization. The AAC bricks are prepared entirely from solid waste, meet the performance requirements of national standards for AAC concrete, and have social and economic value.

Description

Technical Field

[0001] This invention belongs to the field of hazardous waste disposal, and relates to the technology for the resource utilization of detoxified fly ash and ash residue, and in particular to a method for preparing high-insulation aerated bricks by modifying municipal solid waste ash residue with sulfuric acid. Background Technology

[0002] Currently, fly ash from incineration power generation technology is classified as hazardous waste due to its high concentration of heavy metal leaching, dioxins, and furans. In recent years, landfill capacity has been decreasing annually, while landfill costs have been rising, gradually diminishing the cost advantage of fly ash landfilling. To further promote the construction of "zero-waste cities," efforts are underway to achieve near-zero landfilling of solid waste, including fly ash. This necessitates the urgent development of technologies for the harmless treatment of ash residue without landfilling, and the development of technologies for the detoxification of fly ash and the resource utilization of ash residue. According to the "Technical Specifications for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial Implementation)" and related technical standards, pretreatment to remove dioxins and heavy metals from fly ash is required before its resource utilization.

[0003] The aforementioned solid waste belongs to the CaO-SiO2-Al2O3 (Fe2O3) system, which can be used to prepare green low-carbon cement, concrete admixtures, and building bricks. Autoclaved aerated concrete (AAC) is made from raw materials such as siliceous and calcareous materials through processes including gasification with a gas-generating agent, mixing, and autoclaving. It has advantages such as being lightweight, heat-insulating, and thermally insulating, and its production scale is expanding daily. For some locations with high requirements for thermal insulation performance, existing AAC bricks still do not meet the standards in terms of thermal insulation effect; therefore, a high-insulation AAC material needs to be developed. Traditional AAC brick production requires autoclaving to improve the strength of AAC, which consumes a large amount of energy. Therefore, autoclaved aerated concrete bricks are gradually becoming a major market demand. CO2 mineralization curing technology differs from other curing methods. Its principle is that carbon dioxide reacts with alkaline components in concrete to accelerate carbonation, generating calcium carbonate crystals, which can permanently seal carbon dioxide into the concrete. Industrial solid waste, such as fly ash from municipal solid waste and slag, contains alkaline components that can react with carbon dioxide.

[0004] In existing technologies, CN113264715 A discloses the preparation of concrete bricks using fly ash from municipal solid waste incineration, fly ash, and industrial solid waste slag mixed with sand, achieving a compressive strength of 37.91 MPa after 28 days of curing. CN117923874A discloses the preparation of concrete bricks using municipal solid waste fly ash, phosphate, and fly ash, achieving a compressive strength of 46.15 MPa after 28 days of curing, but this process requires calcination to 1000℃, consuming a large amount of energy. CN117142834A discloses the preparation of non-fired bricks using lightly calcined magnesium oxide and municipal solid waste incineration fly ash; a mass ratio of 5–15:100 is most favorable for the performance of the prepared high-strength non-fired bricks, achieving a compressive strength of 30.37 MPa after 28 days of curing. How to ensure that the concrete strength meets national standards while shortening the curing time is a key issue in the resource utilization of detoxified fly ash.

[0005] Researchers have recently been using carbon dioxide to cure aerated concrete blocks made from different solids, with the cement content reaching as high as 40%. Ensuring that the concrete strength meets national standards while reducing the cement content is a key technology for carbon dioxide curing of aerated concrete made from solid waste.

[0006] The current situation is that fly ash from the incineration of solid waste and municipal solid waste poses a serious threat to the environment, thus creating an urgent need for non-landfill harmless treatment technologies for solid waste. There is a need to develop a treatment method that reduces the cement content in concrete, shortens the curing time of bricks, improves the thermal insulation performance of aerated concrete, while meeting national standards for heavy metal concentration and compressive strength. Summary of the Invention

[0007] The purpose of this invention is to address the issues of increased solid waste volume, carbon emissions, and energy consumption by providing a method for preparing high-insulation aerated bricks from municipal solid waste ash residue through sulfuric acid modification.

[0008] To achieve the above objectives, the technical solution of this invention is as follows: A method for preparing high-insulation aerated concrete bricks by modifying municipal solid waste ash with sulfuric acid is provided. Specifically, the fly ash from municipal solid waste incineration is first detoxified and pretreated, and slag is used to replace cement to form a cementitious material. Aerated concrete is then prepared by adding municipal solid waste incineration slag, and carbon dioxide curing replaces traditional autoclaving. The steps are as follows:

[0009] Fly ash is detoxified to reduce the concentration of dioxins and heavy metals in it, thus obtaining detoxified fly ash.

[0010] Acid washing modification treatment was carried out on the detoxified fly ash and slag;

[0011] Weigh out 18-22% of the acid-washed detoxified fly ash, 38-42% of the acid-washed slag, and 38-42% of the blast furnace slag by mass percentage, mix them, add water at a liquid-to-solid ratio of 0.36-0.40, and stir until homogeneous; weigh out 0.004-0.006% aluminum powder by mass percentage, dilute it with water to form a suspension, and pour it in; stir to form a slurry, pour it into a mold, aerate, cut off the excess, and demold.

[0012] After demolding, the specimens were allowed to cure naturally, then placed in a carbon dioxide curing chamber for carbon dioxide curing, and then removed for alkali spray curing.

[0013] Furthermore, the detoxification process includes the following steps:

[0014] A heavy metal chelating agent is added, the mass of which is 5-10% of the fly ash mass, and the heavy metal chelating agent is an organic chelating agent;

[0015] Low-temperature pyrolysis is carried out at a temperature of 250–350℃.

[0016] Furthermore, the organic chelating agent is one of an amino acid chelating agent and a peptide chelating agent.

[0017] Preferably, the organic chelating agent is formazan.

[0018] Furthermore, the acid washing modification treatment includes the following steps:

[0019] For the first pickling, add 60-70% H2SO4 solution at a liquid-to-solid ratio of 1:4-5, let stand for 1-2 hours, and then shake horizontally to separate the solid and liquid.

[0020] For the second acid wash, add 5-10% H2SO4 solution at a liquid-to-solid ratio of 1:4-5, let stand for 1-2 hours, and then centrifuge.

[0021] Furthermore, the horizontal oscillation time is 15–25 min, the centrifugation speed is 2500–3000 rpm, and the centrifugation time is 15–25 min.

[0022] Preferably, the method further includes: after acid washing, adding 5-10% ammonia water to the obtained dry solid phase for neutralization, then adding 20-40% Al2(SO4)3 solution for mixing, letting it stand for 1-2 hours, and drying; wherein the liquid-solid ratio of the ammonia water solution, Al2(SO4)3 solution and the dry solid phase is 1:4-5.

[0023] Preferably, the mixture also includes grinding the acid-washed detoxified fly ash, acid-washed slag, and mineral slag to 180-200 mesh before mixing.

[0024] Furthermore, the gas generation temperature is 25±2℃, and the time is 1 day; the natural curing time is 3 days, the temperature is 25℃±5℃, and the humidity is 70%~100%; the carbon dioxide curing time is 2 hours, the temperature of the carbon dioxide curing chamber is set at 60±2℃, the pressure is 0.4~0.5MPa, the relative humidity is 50%~80%, and the carbon dioxide concentration range is 70%~99%; the alkali spraying curing specifically involves: natural curing for 3 days, and spraying a Ca(OH)2 solution with a mass concentration of 2~5% twice a day.

[0025] Preferably, the carbon dioxide curing chamber uses a bubbling method to deliver CO2.

[0026] The present invention also provides a high-insulation aerated brick prepared by the above method.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. In this invention, aerated concrete blocks are prepared by using slag, municipal solid waste incineration fly ash, and furnace slag, combined with carbon dioxide curing. This not only solves the problem of difficult solid waste disposal but also achieves carbon dioxide fixation and storage. Furthermore, the cement-free materials used in this method further reduce carbon emissions.

[0029] 2. After acid washing of ash residue, ammonia water is added for neutralization, and then mixed with Al2(SO4)3 solution to produce aluminum silicate gel. Aluminum silicate gel is a high thermal insulation material, and aerated concrete blocks made from it have strong thermal insulation performance.

[0030] 3. The compressive strength of the prepared aerated concrete meets the national standard GB / T 11968-2020, and the heavy metal concentration meets the limit of GB / T 30760-2014. Based on this, a proper way to treat waste incineration fly ash is proposed, which can reduce the harm of waste incineration fly ash while making resource utilization of waste incineration fly ash. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of a method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0033] The high-insulation aerated brick of the present invention comprises slag, waste incineration detoxified fly ash and slag as raw materials, which are aerated by a gasifying agent, stirred and cured with carbon dioxide. The components are weighed by mass percentage as follows: 18-22% detoxified fly ash, 38-42% acid-washed slag, 38-42% slag, and aluminum powder is weighed by mass percentage as 0.004-0.006% of the solid phase (the aforementioned detoxified fly ash, acid-washed slag and slag). The liquid-solid ratio is 0.36-0.40.

[0034] This invention first addresses the dioxin problem, employing a low-temperature thermal decomposition technology with mild reaction conditions (200-600℃) and high processing capacity. The solid-phase dioxin degradation rate (removal rate) can reach over 90%, offering advantages such as environmental friendliness and low investment costs. Heavy metal treatment in fly ash mainly involves chemical leaching and chelation stabilization. The key to promoting heavy metal removal from solid-phase water washing chemical leaching lies in pH value; acidic conditions not only promote the leaching of heavy metals and soluble metal salts but also promote the dissolution of fly ash structures, accelerating the leaching kinetics. Heavy metals precipitate with chelating agents to form solid-phase compounds, thereby achieving the stable disposal of heavy metals.

[0035] This invention utilizes the activating effect of alkaline waste incineration fly ash on slag, creating an alkaline environment for waste incineration slag. Waste incineration slag and slag have similar compositions, mainly containing CaO and SiO2, while detoxified waste incineration fly ash has a single composition, primarily containing Ca. This promotes the formation of hydration products such as CSH gel, F salt, and ettringite in aerated concrete blocks.

[0036] This invention uses a specific ratio of waste incineration fly ash, waste incineration slag and mineral slag to maximize the effect of each component, that is, to achieve higher compressive strength and carbon fixation rate while treating as much fly ash as possible.

[0037] This invention discovers that waste incinerator slag and mineral slag contain a high proportion of Si. After sulfuric acid washing pretreatment, a certain amount of silica hydrogel can be generated. After adding ammonia water for neutralization, and then mixing with Al2(SO4)3 solution, aluminum hydroxide gel is generated, thereby increasing the thermal insulation performance of aerated concrete.

[0038] The chemical formula for generating aluminum silicate gel is shown below, where m is the modulus, typically between 3.0 and 3.3.

[0039] Na2O·mSiO2+H2SO4→Na2SO4+mSiO2+H2O

[0040] Al2(SO4)2+6NH4OH→3(NH4)2SO4+2Al(OH)4

[0041] The preparation method of the high-insulation aerated concrete block of the present invention is not particularly limited, and its typical preparation process includes the following steps:

[0042] (1) Pretreatment of fly ash by acid washing: First, the fly ash is detoxified by using a metal chelating agent and low-temperature pyrolysis to reduce the concentration of dioxins and heavy metals in the fly ash. The heavy metal chelating agent is an organic chelating agent, which accounts for 5-10% of the mass of the fly ash. The organic chelating agent is selected from amino acid chelating agents and peptide chelating agents. In this invention, sodium formazan (dimethyl dithiocarbamate) is used. The low-temperature pyrolysis temperature is 250-350℃. Then, 60-70% H2SO4 solution is added to acid wash and modify the detoxified fly ash and slag. After horizontal shaking, solid-liquid separation is performed. This acid washing pretreatment selects two-stage centrifugal acid washing. The second acid washing liquid uses 5-10% H2SO4 solution. In the acid washing pretreatment of ash residue, the liquid-to-solid ratio is set to 1:4-5, and the residue is allowed to stand for 1-2 hours before proceeding to the next step. The horizontal oscillation time is 15-25 minutes, the centrifugation speed is set to 2500-3000 rpm, and the centrifugation time is 15-25 minutes.

[0043] (2) Preparation of high-insulation aerated concrete blocks: The dried solid phase obtained from the acid washing unit is neutralized with 5-10% ammonia water, and then mixed with 20-40% Al2(SO4)3 solution. This process generates aluminosilicate gel to enhance the insulation effect of the aerated concrete blocks. The liquid-to-solid ratio of the ammonia solution, Al2(SO4)3 solution, and dried solid phase is 1:4-5. After standing for 1-2 hours and drying, the following steps are performed. Slag, Al powder aqueous solution, and water are added and stirred into a slurry. The slurry is then poured into a mold. The mold is placed at 25±2℃ for 1 day to generate gas. The specimen is then removed, excess material is cut off, and the mold is demolded to obtain the specimen.

[0044] (3) Carbon dioxide and alkali spraying curing: After demolding, the aerated concrete specimens were pre-cured in a natural environment (temperature 25℃±5℃, humidity 70%~100%) for 3 days; then placed in a carbon dioxide curing chamber for 2 hours and removed. The temperature in the carbon dioxide curing chamber was selected as 60±2℃, the pressure was set as 0.4~0.5MPa, the relative humidity was 50%~80%, and the carbon dioxide concentration range was 70%~99%. CO2 was delivered to the curing chamber by bubbling; finally, natural curing (temperature 25℃±5℃, humidity 70%~100%) was carried out for 3 days, and a Ca(OH)2 solution with a mass concentration of 2~5% was sprayed twice a day.

[0045] In step (2), a mold coated with a release agent is preferably used, wherein the release agent is a common release oil, such as waste engine oil, which can be used to prepare aerated concrete.

[0046] During the curing process, the humidity of the aerated concrete can be maintained by spraying water, in the same way as spraying Ca(OH)2 solution.

[0047] The technical solution of the present invention will be illustrated intuitively below with reference to embodiments and comparative examples. These embodiments are not intended to limit the scope of the present invention.

[0048] Comparative Example 1:

[0049] The ratio of waste incineration fly ash, waste incineration slag, and cement is 0.2:0.4:0.4, and the fineness of all components is guaranteed to be between 180 and 200 mesh. Aluminum powder constitutes 0.004% to 0.006% of the solid phase (0.004% in this example). The liquid-to-solid ratio is 0.36. Before weighing and mixing, the fly ash is detoxified according to the aforementioned steps. The detoxified fly ash and slag are then acid-washed and modified. Ammonia water is added to the dried solid phase obtained from acid washing according to the aforementioned dosage for neutralization, followed by the addition of Al2(SO4)3 solution for mixing. The mixture is then allowed to stand and dry. The specific steps are as follows:

[0050] Weigh the fly ash, slag, and cement from municipal solid waste incineration according to the raw material ratio, mix them evenly, weigh the corresponding weight of water according to the liquid-solid ratio, add it to the mortar mixer, and maintain a uniform mixing speed to obtain a composite cementitious material mixture.

[0051] Weigh the corresponding aluminum powder, dilute it with water to make a suspension, pour the suspension into the raw material slurry and continue stirring to prepare the gas-generating slurry. After uniform and rapid stirring, a composite slurry mixture is obtained.

[0052] The slurry was poured into a mold (100mm×50mm cylindrical mold), sealed with a sealing film, and allowed to aerate in a natural environment at 25±2℃ for 1 day. After the aerated concrete bricks were formed and reached the demolding hardness, the specimens were removed, excess parts were cut off, and the molds were removed to obtain standard specimens.

[0053] The aerated concrete blocks were first placed indoors (measured at 25±2℃) for 3 days of pre-curing, and then sprayed with alkali and naturally cured for another 3 days to obtain sample 1.

[0054] Comparative Example 2:

[0055] The ratio of waste incineration fly ash, waste incineration slag, and cement is 0.2:0.4:0.4, and the fineness of all components is guaranteed to be between 180 and 200 mesh. Aluminum powder constitutes 0.004% to 0.006% of the solid phase (0.004% in this example). The liquid-to-solid ratio is 0.36. Before weighing and mixing, the fly ash is detoxified according to the aforementioned steps. The detoxified fly ash and slag are then acid-washed and modified. Ammonia water is added to the dried solid phase obtained from acid washing according to the aforementioned dosage for neutralization, followed by the addition of Al2(SO4)3 solution for mixing. The mixture is then allowed to stand and dry. The specific steps are as follows:

[0056] Weigh the fly ash, slag, and cement from municipal solid waste incineration according to the raw material ratio, mix them evenly, weigh the corresponding weight of water according to the liquid-solid ratio, add it to the mortar mixer, and maintain a uniform mixing speed to obtain a composite cementitious material mixture.

[0057] Weigh the corresponding aluminum powder, dilute it with water to make a suspension, pour the suspension into the raw material slurry and continue stirring to prepare the gas-generating slurry. After uniform and rapid stirring, a composite slurry mixture is obtained.

[0058] The slurry was poured into a mold (100mm×50mm cylindrical mold), sealed with a sealing film, and allowed to aerate in a natural environment at 25±2℃ for 1 day. After the aerated concrete bricks were formed and reached the demolding hardness, the specimens were removed, excess parts were cut off, and the molds were removed to obtain standard specimens.

[0059] The aerated concrete blocks were first placed indoors (measured at 25±2℃) for pre-curing for 3 days, then placed in a curing room for CO2 curing for 2 hours, and then sprayed with alkali for natural curing for 3 days to obtain sample 2.

[0060] Comparative Example 3:

[0061] The ratio of waste incineration fly ash, waste incineration slag, cement, and slag is 0.2:0.4:0.3:0.1, and the fineness of all components is guaranteed to be between 180 and 200 mesh. Aluminum powder constitutes 0.004% to 0.006% of the solid phase (0.004% in this example). The liquid-to-solid ratio is 0.36. Before weighing and mixing, the fly ash is detoxified according to the aforementioned steps. The detoxified fly ash and slag are then acid-washed and modified. Ammonia water is added to the dried solid phase obtained from acid washing according to the aforementioned dosage for neutralization, followed by the addition of Al2(SO4)3 solution for mixing. The mixture is then allowed to stand and dry. The specific steps are as follows:

[0062] Weigh the fly ash, slag, and cement from municipal solid waste incineration according to the raw material ratio, mix them evenly, weigh the corresponding weight of water according to the liquid-solid ratio, add it to the mortar mixer, and maintain a uniform mixing speed to obtain a composite cementitious material mixture.

[0063] Weigh the corresponding aluminum powder, dilute it with water to make a suspension, pour the suspension into the raw material slurry and continue stirring to prepare the gas-generating slurry. After uniform and rapid stirring, a composite slurry mixture is obtained.

[0064] The slurry was poured into a mold (100mm×50mm cylindrical mold), sealed with a sealing film, and allowed to aerate in a natural environment at 25±2℃ for 1 day. After the aerated concrete bricks were formed and reached the demolding hardness, the specimens were removed, excess parts were cut off, and the molds were removed to obtain standard specimens.

[0065] The aerated concrete blocks were first placed indoors (measured at 25±2℃) for pre-curing for 3 days, then placed in a curing room for CO2 curing for 2 hours, and then sprayed with alkali for natural curing for 3 days to obtain sample 3.

[0066] Comparative Example 4:

[0067] The ratio of waste incineration fly ash, waste incineration slag, cement, and slag is 0.2:0.4:0.2:0.2, and the fineness of all components is guaranteed to be between 180 and 200 mesh. Aluminum powder constitutes 0.004% to 0.006% of the solid phase (0.004% in this example). The liquid-to-solid ratio is 0.36. Before weighing and mixing, the fly ash is detoxified according to the aforementioned steps. The detoxified fly ash and slag are then acid-washed and modified. Ammonia water is added to the dried solid phase obtained from acid washing to neutralize it according to the aforementioned dosage, followed by the addition of Al2(SO4)3 solution for mixing. The mixture is then allowed to stand and dry. The specific steps are as follows:

[0068] Weigh the fly ash, slag, and cement from municipal solid waste incineration according to the raw material ratio, mix them evenly, weigh the corresponding weight of water according to the liquid-solid ratio, add it to the mortar mixer, and maintain a uniform mixing speed to obtain a composite cementitious material mixture.

[0069] Weigh the corresponding aluminum powder, dilute it with water to make a suspension, pour the suspension into the raw material slurry and continue stirring to prepare the gas-generating slurry. After uniform and rapid stirring, a composite slurry mixture is obtained.

[0070] The slurry was poured into a mold (100mm×50mm cylindrical mold), sealed with a sealing film, and allowed to aerate in a natural environment at 25±2℃ for 1 day. After the aerated concrete bricks were formed and reached the demolding hardness, the specimens were removed, excess parts were cut off, and the molds were removed to obtain standard specimens.

[0071] The aerated concrete blocks were first placed indoors (measured at 25±2℃) for pre-curing for 3 days, then placed in a curing room for CO2 curing for 2 hours, and then sprayed with alkali for natural curing for 3 days to obtain sample 4.

[0072] Comparative Example 5:

[0073] The ratio of waste incineration fly ash, waste incineration slag, cement, and slag is 0.2:0.4:0.1:0.3, and the fineness of all components is guaranteed to be between 180 and 200 mesh. Aluminum powder constitutes 0.004% to 0.006% of the solid phase (0.004% in this example). The liquid-to-solid ratio is 0.36. Before weighing and mixing, the fly ash is detoxified according to the aforementioned steps. The detoxified fly ash and slag are then acid-washed and modified. Ammonia water is added to the dried solid phase obtained from acid washing to neutralize it according to the aforementioned dosage, followed by the addition of Al2(SO4)3 solution for mixing. The mixture is then allowed to stand and dry. The specific steps are as follows:

[0074] Weigh the fly ash, slag, and cement from municipal solid waste incineration according to the raw material ratio, mix them evenly, weigh the corresponding weight of water according to the liquid-solid ratio, add it to the mortar mixer, and maintain a uniform mixing speed to obtain a composite cementitious material mixture.

[0075] Weigh the corresponding aluminum powder, dilute it with water to make a suspension, pour the suspension into the raw material slurry and continue stirring to prepare the gas-generating slurry. After uniform and rapid stirring, a composite slurry mixture is obtained.

[0076] The composite slurry was poured into a mold (100mm×50mm cylindrical mold), sealed with a sealing film, and allowed to gasify in a natural environment at 25±2℃ for 1 day. After the aerated concrete bricks were formed and reached the demolding hardness, the specimens were removed, excess parts were cut off, and the molds were removed to obtain standard specimens.

[0077] The aerated concrete blocks were first placed indoors (measured at 25±2℃) for pre-curing for 3 days, then placed in a curing room for CO2 curing for 2 hours, and then sprayed with alkali for natural curing for 3 days to obtain sample 5.

[0078] Example 1:

[0079] The ratio of waste incineration fly ash, waste incineration slag, and mineral slag is 0.2:0.4:0.4, and the fineness of all components is guaranteed to be between 180 and 200 mesh. Aluminum powder constitutes 0.004% to 0.006% of the solid phase (0.004% in this example). The liquid-to-solid ratio is 0.36. Before weighing and mixing, the fly ash is detoxified according to the aforementioned steps. The detoxified fly ash and slag are then acid-washed and modified. Ammonia water is added to the dried solid phase obtained from acid washing according to the aforementioned dosage for neutralization, followed by the addition of Al2(SO4)3 solution for mixing. The mixture is then allowed to stand and dry. The specific steps are as follows:

[0080] Weigh the fly ash, slag, and cement from municipal solid waste incineration according to the raw material ratio, mix them evenly, weigh the corresponding weight of water according to the liquid-solid ratio, add it to the mortar mixer, and maintain a uniform mixing speed to obtain a composite cementitious material mixture.

[0081] Weigh the corresponding aluminum powder, dilute it with water to make a suspension, pour the suspension into the raw material slurry and continue stirring to prepare the gas-generating slurry. After uniform and rapid stirring, a composite slurry mixture is obtained.

[0082] The slurry was poured into a mold (100mm×50mm cylindrical mold), sealed with a sealing film, and allowed to aerate in a natural environment at 25±2℃ for 1 day. After the aerated concrete bricks were formed and reached the demolding hardness, the specimens were removed, excess parts were cut off, and the molds were removed to obtain standard specimens.

[0083] The aerated concrete blocks were first placed indoors (measured at 25±2℃) for pre-curing for 3 days, then placed in a curing room for CO2 curing for 2 hours, and then sprayed with alkali for natural curing for 3 days to obtain sample 6.

[0084] Example of obtaining sample evaluation

[0085] The compressive strength and heavy metal leaching concentration of the aerated concrete blocks prepared in the examples and comparative examples were tested. The compressive strength test was conducted in accordance with the national standard GB-T 11968-2020 "Production of Autoclaved Aerated Concrete Blocks". The heavy metal leaching concentration test was conducted in accordance with the national standard HJ557-2009 "Test Method for Leaching Toxicity of Solid Waste - Horizontal Oscillation Method".

[0086] The CO2 absorption capacity of the specimens in this invention is characterized by the apparent carbon fixation rate, which is mainly calculated using the weighing method, and the ratio of the difference in mass before and after curing to the dry mass of the specimen is calculated, as shown in the following formula:

[0087] ω=(m2-m1) / [m1 / (1+w / s)]

[0088] Table 1. Performance test results of aerated bricks in each embodiment.

[0089]

[0090] As shown in Table 1, the strength of the aerated concrete blocks prepared in Comparative Examples 2-5 and Example 1 of this invention shows a trend of first decreasing and then increasing with the increase of mineral powder. After carbon dioxide curing, the cured aerated concrete blocks meet the national standard GB / T 11968-2020B03 A1.5 grade aerated concrete products, and the heavy metal leaching concentration is lower than the limit value of GB / T 30760-2014. This invention demonstrates that it is entirely feasible to utilize slag, municipal solid waste fly ash, and furnace slag. The harmful substances in municipal solid waste incineration fly ash are effectively solidified, greatly solving the problem of resource utilization of municipal solid waste incineration fly ash.

[0091] Comparative Example 2 and Example 1 of the present invention utilize slag to replace cement. The strength of Comparative Example 2 is lower than that of Example 1, which illustrates the possibility of using slag to replace cement. This method can reduce cement usage while sealing CO2, which is beneficial for reducing carbon emissions.

[0092] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-insulation aerated concrete blocks by modifying municipal solid waste ash with sulfuric acid, characterized in that, Includes the following steps: Fly ash is detoxified to reduce the concentration of dioxins and heavy metals in it, thus obtaining detoxified fly ash. Acid washing modification treatment was carried out on the detoxified fly ash and slag; After acid washing, 5-10% ammonia water (by mass) was added to the obtained dry solid phase to neutralize it, and then 20-40% Al2(SO4)3 solution (by mass) was added to mix it. The mixture was then allowed to stand and dry. The liquid-solid ratio of the ammonia solution, Al2(SO4)3 solution and the dry solid phase was 1:4-5. Weigh out 18-22% of the dried detoxified fly ash, 38-42% of the dried slag, and 38-42% of the blast furnace slag by mass percentage, mix them, add water at a liquid-to-solid ratio of 0.36-0.40, and stir until homogeneous; weigh out 0.004-0.006% aluminum powder by mass percentage, dilute it with water to form a suspension, and pour it in; stir to form a slurry, pour it into a mold, aerate, and demold; After demolding, the specimens were allowed to cure naturally, then placed in a carbon dioxide curing chamber for carbon dioxide curing, and then removed for alkali spray curing.

2. The method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid according to claim 1, characterized in that, The detoxification process includes the following steps: A heavy metal chelating agent is added, the mass of which is 5-10% of the fly ash mass, and the heavy metal chelating agent is an organic chelating agent; Low-temperature pyrolysis is carried out at a temperature of 250–350℃.

3. The method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid according to claim 2, characterized in that, The organic chelating agent is one of amino acid chelating agents and peptide chelating agents.

4. The method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid according to claim 1, characterized in that, The acid washing modification treatment includes the following steps: For the first pickling, add 60-70% H2SO4 solution at a liquid-to-solid ratio of 1:4-5, let stand, and then shake horizontally to separate the solid and liquid. For the second acid wash, add 5-10% H2SO4 solution at a liquid-to-solid ratio of 1:4-5, let stand, and centrifuge.

5. The method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid according to claim 4, characterized in that, The horizontal oscillation time is 15-25 min, the centrifugation speed is 2500-3000 rpm, and the centrifugation time is 15-25 min.

6. The method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid according to claim 1, characterized in that, Also includes: Before mixing, the acid-washed detoxified fly ash, acid-washed slag, and blast furnace slag are ground to 180-200 mesh.

7. The method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid according to claim 1, characterized in that, The gas generation temperature is 25±2℃, and the time is 1 day; the natural curing time is 3 days, the temperature is 25℃±5℃, and the humidity is 70%~100%; the carbon dioxide curing time is 2 hours, the temperature of the carbon dioxide curing chamber is set at 60±2℃, the pressure is 0.4~0.5MPa, the relative humidity is 50%~80%, and the carbon dioxide concentration range is 70%~99%; the alkali spraying curing specifically involves: natural curing for 3 days, and spraying a 2~5% Ca(OH)2 solution twice a day.

8. The method for preparing high-insulation aerated bricks by modifying municipal solid waste ash with sulfuric acid according to claim 7, characterized in that, The carbon dioxide curing chamber uses a bubbling method to deliver CO2.

9. A high-insulation aerated concrete block prepared by the method according to any one of claims 1-8.

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