Aerated concrete block cured by cement kiln tail gas and preparation method thereof

Abstract

The application discloses an aerated concrete block cured by cement kiln tail flue gas and a preparation method thereof, and belongs to the technical field of concrete materials. The aerated concrete block comprises 20-30 parts of carbon-fixing cementitious material, 30-40 parts of dry sand, 1-5 parts of heavy calcium powder, 0-5 parts of dihydrate gypsum and 35-45 parts of water. The preparation method comprises the steps of batching, stirring and pouring, static stopping, cutting and curing. The application is scientific and reasonable in design and convenient to use. The carbon-fixing cementitious material is used to prepare the aerated concrete, and the aerated concrete is cured by the cement kiln tail flue gas. The alkaline mineral in the aerated concrete can quickly react with the acid gas in the flue gas, the hydration-heat combination-acidification ternary reaction of the aerated concrete body is realized, the strength of the aerated concrete is quickly improved, and energy saving and emission reduction are truly realized.

Description

Technical Field

[0001] This invention belongs to the field of concrete materials technology, specifically relating to aerated concrete blocks cured using cement kiln tail flue gas and their preparation method. Background Technology

[0002] Autoclaved aerated concrete (AAC) is a porous concrete produced through a chemical reaction to obtain gas. It boasts advantages such as light weight, good thermal insulation, and non-combustibility. AAC can be broadly categorized into two types based on its curing method: atmospheric pressure steam curing and high-pressure steam curing. Atmospheric pressure steam curing (hereinafter referred to as steam curing) involves curing the AAC blank under saturated steam conditions below 100℃. High-pressure steam curing (hereinafter referred to as autoclaving) involves curing the blank under saturated steam conditions of 174.5–200.5℃ and 0.8–1.5 MPa, also known as hydrothermal synthesis reaction (hereinafter referred to as thermal reaction). Because steam-cured AAC exhibits significant shrinkage and poor carbonation resistance, it has remained largely a research-oriented process in laboratories, failing to achieve industrial application. However, after autoclaving, a series of physicochemical reactions occur between the constituent materials of AAC, resulting in increased strength. Furthermore, autoclaved AAC exhibits less shrinkage and better carbonation resistance, thus autoclaving is widely used in AAC production in my country.

[0003] However, based on the current situation in my country, the unit coal consumption of autoclaved aerated concrete products is generally between 35 and 55 kg of standard coal / m³. 3In comparison, steam-cured aerated concrete (AAC) is costly. To reduce the energy consumption of AAC curing, patent publication number CN113698229A, entitled "A Process for Coupling Steam and Carbon Dioxide Curing of Fly Ash AAC Blocks," describes a method that couples steam curing and carbon dioxide mineralization to cure fly ash AAC blocks. Compared to steam curing alone, steam curing transforms fly ash into a tobermorite cross-linked structure, providing a basic framework for the AAC blocks. Carbon dioxide mineralization rapidly generates carbonate gel, filling voids and further enhancing the strength of the fly ash AAC blocks. It also reduces steam consumption, improves production efficiency, and achieves carbon dioxide solidification and sequestration, reducing greenhouse gas emissions. However, this invention uses a CO2 concentration of at least 80%. High-concentration CO2 is expensive, and the initial mineralization reaction is more vigorous, causing the generated calcium carbonate crystals to increase rapidly in size within a short period. This can lead to expansion cracks inside the blocks, damaging their structural strength. Patent publication number CN113561303A, entitled "A Device and Method for CO2 Mineralization Curing of Concrete Blocks," describes a device that connects a CO2 storage tank to external air to regulate CO2 concentration. This invention provides a mineralization curing device that accelerates flue gas flow and disturbance, compensating for insufficient CO2 concentration at the block center and effectively addressing the shortcomings of direct flue gas mineralization curing. It also humidifies the mineralization environment in the later stages of the mineralization reaction. However, the curing temperature is limited to below 100℃, resulting in low curing efficiency, and the performance indicators of the cured aerated concrete are not described.

[0004] The flue gas from cement kilns contains not only the greenhouse gas CO2, but also the acidic gases SO2 and NO. x Meanwhile, the temperature of the kiln tail flue gas exceeds 300℃. Industrially, the kiln tail flue gas can be passed through a boiler to utilize waste heat to generate steam or for power generation; SO2 and NO X Specialized desulfurization and denitrification technologies are required to treat the flue gas, and emissions can only proceed after the levels meet emission requirements. CO2 in the flue gas is treated using decarbonization technologies such as MEA chemical absorption, cooling ammonia water, and separate calcium circulation. However, these desulfurization, denitrification, and decarbonization technologies have high heat and electricity consumption, resulting in poor economic efficiency.

[0005] Therefore, the present invention provides aerated concrete blocks cured using cement kiln tail flue gas and a method for preparing the same, in order to at least solve some of the above-mentioned technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide aerated concrete blocks cured by cement kiln tail flue gas and the preparation method thereof, so as to at least solve some of the above-mentioned technical problems.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] Aerated concrete blocks cured using cement kiln tail gas include the following raw materials in weight configuration:

[0009] Carbon-fixing cementitious material: 20-30 parts;

[0010] Dry sand: 30-40 parts;

[0011] Heavy calcium carbonate powder: 1-5 parts;

[0012] Dihydrate gypsum: 0-5 parts;

[0013] Water: 35-45 parts.

[0014] Furthermore, the carbon-fixing cementitious material comprises the following components by weight percentage:

[0015] f-CaO: 24–40 wt.%;

[0016] C2S: 30-55 wt.%;

[0017] 1–20 wt.%;

[0018] C4AF: 0.1–10 wt.%;

[0019] CaSO4: 0.1–10 wt.%.

[0020] Furthermore, the specific surface area of ​​the carbon-fixing cementitious material is 320–450 m². 2 / kg.

[0021] Furthermore, the dry sand contains at least SiO2 and Al2O3, and the residue on an 80μm sieve is 3–15 wt.%.

[0022] Furthermore, the fineness of the heavy calcium carbonate powder is 400 mesh.

[0023] Furthermore, it also includes aluminum powder paste, wherein the amount of aluminum powder paste is 0.3 to 0.7‰ of the total raw material mass.

[0024] Furthermore, it also includes a foam stabilizer, wherein the amount of the foam stabilizer is 0 to 1% of the total raw material mass.

[0025] Furthermore, the foam stabilizer is any one of soluble oil, soapberry powder, SP foam stabilizer, and TS foam stabilizer.

[0026] A method for preparing aerated concrete blocks cured using cement kiln tail gas includes the following steps:

[0027] Step 1: Weigh each ingredient according to the specified proportions;

[0028] Step 2: Add the weighed raw materials to the mixer and mix them into a uniform material. Then pour the mixture into the mold and vibrate it.

[0029] Step 3: Place the poured and vibrated slurry in a humid and hot environment to stand still, and obtain a gas-generating and hardened green body;

[0030] Step 4: Divide and trim the hardened blank to obtain the concrete blank;

[0031] Step 5: Curing the concrete billet, specifically including:

[0032] Step 51: Place the concrete blank in an autoclave and create a vacuum.

[0033] Step 52: Pass the high-temperature kiln tail flue gas into the heat exchanger to prepare saturated steam at a temperature above 180°C, and slowly pass the saturated steam into the autoclave to raise the temperature of the autoclave to above 180°C.

[0034] Step 53: Intermittently introduce saturated steam into the autoclave to maintain the autoclave temperature at 180-190℃. Introduce kiln tail flue gas that has been heat-exchanged by the boiler heat exchanger into the autoclave. Open the micro-opening exhaust valve on the autoclave to allow gas flow inside the autoclave while ensuring that the working pressure of the autoclave is 1.5-1.7MPa for 7-9 hours.

[0035] Step 54: Quickly exhaust and cool down the air, then remove the aerated concrete blocks.

[0036] Further, in step 2, the weighed raw materials are added to a mixer and stirred into a uniform material with a consistency of 220-240 mm, and then poured into a mold and vibrated for 20 seconds using an immersion vibrator.

[0037] In step 3, the poured and vibrated slurry is placed in a humid and hot environment of 40-60℃ and left to stand for 2-3 hours to obtain a green body after gas condensation.

[0038] In step 52, the CO2 volume concentration of the high-temperature kiln tail gas is 5-20%, and the NO concentration is... X The volume concentration is 0–2%, and the SO2 volume concentration is 0.01–1%.

[0039] In step 53, the temperature of the kiln tail flue gas after heat exchange in the heat exchanger is 70-120℃.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] This invention is scientifically and rationally designed and easy to use. It uses carbon-fixing cementitious materials to prepare aerated concrete and utilizes the flue gas from the cement kiln tail to cure the aerated concrete. This promotes the rapid reaction between the alkaline minerals in the aerated concrete and the acidic gases in the flue gas, realizing a ternary reaction of hydration, heat sealing, and acidification in the aerated concrete body. This rapidly improves the strength of the aerated concrete and truly achieves energy conservation and emission reduction. Attached Figure Description

[0042] Figure 1 This is an X-ray diffraction pattern of the aerated concrete of the present invention after curing with kiln tail flue gas.

[0043] Figure 2 This is a macroscopic view of the external pore wall morphology of the aerated concrete after curing with kiln tail flue gas according to the present invention.

[0044] Figure 3 This is a macroscopic morphology of the internal pore walls of the aerated concrete after curing with kiln tail flue gas according to the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] The curing process during the preparation of this invention can further improve the performance of concrete. The curing mechanism is as follows: During the entire curing process, the aerated concrete blank undergoes a ternary reaction of hydration-heat sealing-acidification.

[0047] First, during the static resting stage, the aerated concrete slurry poured into the mold undergoes aeration, thickening, initial setting, and hardening processes. During this series of processes, the carbon-fixing cementitious material undergoes a hydration reaction, generating hydration products such as Ca(OH)2, AFt, and CSH gel. These products overlap with each other, promoting the hardening of the green body.

[0048] Secondly, during the initial stage of heat preservation and flue gas ventilation, the following acidification reactions occur at the outer edge of the aerated concrete: (1) the hydration products Ca(OH)2, AFt, CSH, and f-CaO and C2S in the unhydrated cement particles react with CO2 in the kiln tail flue gas to generate CaCO3 crystals, silica gel, and aluminum glue; (2) the hydration products Ca(OH)2, AFt, CSH, and f-CaO and C2S in the unhydrated cement particles react with SO2 in the kiln tail flue gas to generate CaSO4 crystals, silica gel, and aluminum glue; (3) the hydration products Ca(OH)2, AFt, CSH, and f-CaO and C2S in the unhydrated cement particles react with NO in the kiln tail flue gas.x The reaction produces Ca(NO) x CaCO3 crystals, CaSO4 crystals, Ca(NOx)2 crystals, silica gel, and aluminum glue intertwine to form a whole, filling the microscopic voids in the aerated concrete and improving the strength of the green body. Simultaneously, a hydrothermal synthesis (thermal synthesis) reaction occurs at the center of the aerated concrete green body: under high temperature, high pressure, and humid heat conditions, the hydration products Ca(OH)2 and CSH gel in the center of the aerated concrete react with SiO2 and Al2O3 in the dry sand to generate tobermorite, aluminum-substituted tobermorite, and hydrogarnet, further enhancing the internal strength of the green body.

[0049] Finally, based on the three-dimensional gas diffusion mechanism, the relationship between the acidification reaction and the curing time is α=1-[1-(1-t / τ)] 1 / 2 ] 3 In the formula, α represents the degree of acidification reaction, t represents the holding time, and τ represents the time for complete carbonization of the aerated concrete billet. Generally, the holding time t is less than τ. According to the above formula, as the holding time increases, the acidification reaction penetrates deeper into the billet, increasing the levels of CO2, SO2, and NO in the flue gas. x It reacts with hydrothermal synthesis products tobermorite and hydrogarnet to partially transform into CaCO3 crystals, CaSO4 crystals, Ca(NOx)2 crystals, silica gel, and aluminum glue.

[0050] Therefore, the exterior of aerated concrete gains strength through an acidification reaction, while the center of aerated concrete gains strength through a hydrothermal synthesis reaction.

[0051] This invention uses carbon-fixing cementitious materials as the main raw materials for aerated concrete, comprising the following raw materials by mass percentage: f-CaO: 24–40 wt.%; C2S: 30–55 wt.%; C4A3: 1–20 wt.%; C4A F 0.1–10 wt.%; CaSO4: 0.1–10 wt.%; The specific surface area of ​​the carbon-fixing cementitious material is 320–450 m². 2 / kg. No additional quicklime is needed, simplifying the production process. The carbon-fixing cementitious material is... In the preparation of aerated concrete, f-CaO in the gypsum system can react rapidly with water to form Ca(OH)2, and release a large amount of heat during the reaction process, which promotes the gasification of aluminum powder and accelerates the hardening of the green body. It can promote faster setting and hardening of aerated concrete and regulate the thickening process of aerated concrete; C2S is beneficial to the stable growth of the later strength of aerated concrete products; CaSO4 participates in the formation of hydrated calcium sulfoaluminate during static curing, which improves the strength of the green body; during the heat preservation process, CaSO4 in gypsum can promote the hydrothermal reaction, converting CSH to tobermorite, while inhibiting the formation of hydrogarnet, thus improving the strength of the green body. The combined effect of the various mineral components of the carbon-fixing cementitious material described in this invention is beneficial to improving the performance of aerated concrete blocks. In addition...

[0052] In addition, its main components f-CaO, C4A3S and C2S readily absorb acidic gases from the kiln tail flue gas, generating mineralized products that fill the gaps between particles, thus densifying the aerated concrete structure.

[0053] The main component of the heavy calcium carbonate powder described in this invention is CaCO3. An appropriate amount of CaCO3 powder can significantly improve the reaction degree of CO2 curing of aerated concrete: CaCO3 powder can promote the reaction between C2S and CO2, induce the generation of more CaCO3, polymeric calcium silicate or amorphous silica gel, resulting in fewer micropores on the macroscopic pore walls of the green body and denser pore walls.

[0054] This invention utilizes the heat from cement kiln tail gas to prepare saturated steam. The saturated steam and the kiln tail gas after heat exchange are then introduced into an autoclave, causing a ternary reaction of hydration, heat treatment, and acidification in the aerated concrete, thereby improving its strength. This invention not only proposes a new curing mode for aerated concrete but also solves the problems of heat reuse in cement kiln tail gas and the control of acidic gases (CO2, SO2, NO) in the flue gas. X (Curing problem)

[0055] Figure 1 This is an X-ray diffraction pattern of the aerated concrete of the present invention after curing with kiln tail flue gas. After curing with kiln tail flue gas, the aerated concrete undergoes an acidification reaction on the outside, and the main products are aragonite, limestone, anhydrite, etc.; a hydrothermal synthesis reaction occurs in the center, and the main product is tobermorite. The above products are confirmed by X-ray diffraction analysis. Figure 2 and Figure 3 These are macroscopic morphological images of the external and internal pore walls of the aerated concrete after curing with kiln tail flue gas according to the present invention.

[0056] Example 1, aerated concrete blocks cured using cement kiln tail gas, comprising the following raw materials by weight:

[0057] Carbon-fixing cementitious material: 20 parts;

[0058] Dry sand: 30 parts;

[0059] Heavy calcium carbonate powder: 5 parts;

[0060] Dihydrate gypsum: 0 parts;

[0061] Water: 35 parts;

[0062] The aluminum powder paste is added at a rate of 0.5‰ of the total raw material mass.

[0063] The dosage of SP foam stabilizer is 0.5% of the total mass of the above raw materials.

[0064] In this embodiment, the carbon-fixing cementitious material comprises the following raw materials by mass percentage: f-CaO: 38%;

[0065] — C2S: 50%; C4A3S: 8%; C4AF: 2%; CaSO4: 2%; The specific surface area of ​​the carbon-fixing cementitious material is 350 m². 2 / kg. The SiO2 content in the dry sand is 84%, and the residue on an 80μm sieve is 15wt.%. The fineness of the heavy calcium carbonate powder is 400 mesh.

[0066] The preparation method of aerated concrete blocks cured using cement kiln tail flue gas is as follows:

[0067] Step 1, Ingredient Preparation: Weigh each ingredient according to the specified proportions;

[0068] Step 2, Mixing and pouring: Add the weighed raw materials to the mixer and mix them into a uniform material with a consistency of 230 mm. Then pour the mixture into the mold and use an immersion vibrator to vibrate it for 20 seconds.

[0069] Step 3, Static Rest: Place the poured and vibrated slurry in a humid and hot environment at 50℃ for 2.5 hours to obtain a gas-generating and hardened green body;

[0070] Step 4, Cutting: Divide and trim the hardened blank to obtain the concrete blank;

[0071] Step 5, Curing: Curing the concrete billet, specifically including:

[0072] Step 51, Feeding: Place the concrete billet in the autoclave and vacuum it;

[0073] Step 52, Heating: High-temperature kiln tail flue gas is introduced into the boiler heat exchanger to prepare saturated steam above 180℃. The saturated steam is then slowly introduced into the autoclave, raising the autoclave temperature to above 180℃ over 2 hours. The CO2 volume concentration in the high-temperature kiln tail flue gas is 15%, and the NO concentration is... X The volume concentration is 2%, and the SO2 volume concentration is 1%.

[0074] Step 53, heat preservation and flue gas circulation: Saturated steam is intermittently introduced into the autoclave to maintain the autoclave temperature at 185°C. Kiln tail flue gas at 70°C after heat exchange with the boiler heat exchanger is introduced into the autoclave. The micro-opening exhaust valve on the autoclave is opened to allow gas flow in the autoclave while ensuring that the working pressure of the autoclave is 1.6MPa. The process lasts for 8 hours.

[0075] Step 54, Cooling: Quickly exhaust the air to cool down, then remove the aerated concrete blocks.

[0076] Example 2, aerated concrete blocks cured using cement kiln tail gas, comprising the following raw materials by weight:

[0077] Carbon-fixing cementitious material: 28 parts;

[0078] Dry sand: 35 parts;

[0079] Heavy calcium carbonate powder: 3 parts;

[0080] Dihydrate gypsum: 5 parts;

[0081] Water: 43 parts;

[0082] The aluminum powder paste dosage is 0.6‰ of the total raw material mass mentioned above;

[0083] The amount of soapberry powder added is 1% of the total mass of the above raw materials.

[0084] In this embodiment, the carbon-fixing cementitious material comprises the following raw materials by mass percentage: f-CaO: 34%;

[0085] — C2S: 43%; C4A3S: 10%; C4AF: 7%; CaSO4: 6%; The specific surface area of ​​the carbon-fixing cementitious material is 400 m². 2 / kg. The SiO2 content in the dry sand is 87%, and the residue on an 80μm sieve is 15wt.%. The fineness of the heavy calcium carbonate powder is 400 mesh.

[0086] The preparation method of aerated concrete blocks cured using cement kiln tail flue gas is as follows:

[0087] Step 1, Ingredient Preparation: Weigh each ingredient according to the specified proportions;

[0088] Step 2, Mixing and pouring: Add the weighed raw materials to the mixer and mix them into a uniform material with a consistency of 240 mm. Then pour the mixture into the mold and use an immersion vibrator to vibrate it for 20 seconds.

[0089] Step 3, Static Stopping: Place the poured and vibrated slurry in a humid and hot environment at 40℃ for static stopping for 3 hours to obtain a gas-generating and hardened green body;

[0090] Step 4, Cutting: Divide and trim the hardened blank to obtain the concrete blank;

[0091] Step 5, Curing: Curing the concrete billet, specifically including:

[0092] Step 51, Feeding: Place the concrete billet in the autoclave and vacuum it;

[0093] Step 52, Heating: High-temperature kiln tail flue gas is introduced into a boiler heat exchanger to prepare saturated steam above 180℃. The saturated steam is then slowly introduced into an autoclave, raising the autoclave temperature to above 180℃ over 2 hours. The CO2 volume concentration in the high-temperature kiln tail flue gas is 5%, and the NO concentration is... X The volume concentration is 1%, and the SO2 volume concentration is 1%.

[0094] Step 53, heat preservation and flue gas circulation: Saturated steam is intermittently introduced into the autoclave to maintain the autoclave temperature at 190°C. Kiln tail flue gas at 120°C after heat exchange with the boiler heat exchanger is introduced into the autoclave. The micro-opening exhaust valve on the autoclave is opened to allow gas flow in the autoclave while ensuring that the working pressure of the autoclave is 1.7MPa. The process lasts for 9 hours.

[0095] Step 54, Cooling: Quickly exhaust the air to cool down, then remove the aerated concrete blocks.

[0096] Example 3, aerated concrete blocks cured using cement kiln tail gas, comprising the following raw materials by weight:

[0097] Carbon-fixing cementitious material: 30 parts;

[0098] Dry sand: 40 parts;

[0099] Heavy calcium carbonate powder: 1 part;

[0100] Dihydrate gypsum: 5 parts;

[0101] Water: 45 parts;

[0102] The aluminum powder paste dosage is 0.7‰ of the total raw material mass mentioned above;

[0103] The dosage of TS foam stabilizer is 0.3% of the total mass of the above raw materials.

[0104] In this embodiment, the carbon-fixing cementitious material comprises the following raw materials by mass percentage: f-CaO: 34%;

[0105] — C2S: 46%; C4A3S: 13%; C4AF: 5%; CaSO4: 2%; The specific surface area of ​​the carbon-fixing cementitious material is 380 m². 2 / kg. The SiO2 content in the dry sand is 80%, and the residue on an 80μm sieve is 15wt.%. The fineness of the heavy calcium carbonate powder is 400 mesh.

[0106] The preparation method of aerated concrete blocks cured using cement kiln tail flue gas is as follows:

[0107] Step 1, Ingredient Preparation: Weigh each ingredient according to the specified proportions;

[0108] Step 2, Mixing and pouring: Add the weighed raw materials to the mixer and mix them into a uniform material with a consistency of 220 mm. Then pour the mixture into the mold and use an immersion vibrator to vibrate it for 20 seconds.

[0109] Step 3, Static Stopping: Place the poured and vibrated slurry in a humid and hot environment at 60℃ for static stopping for 2 hours to obtain a gas-generating and hardened green body;

[0110] Step 4, Cutting: Divide and trim the hardened blank to obtain the concrete blank;

[0111] Step 5, Curing: Curing the concrete billet, specifically including:

[0112] Step 51, Feeding: Place the concrete billet in the autoclave and vacuum it;

[0113] Step 52, Heating: High-temperature kiln tail flue gas is introduced into a boiler heat exchanger to prepare saturated steam above 180℃. The saturated steam is then slowly introduced into an autoclave, raising the autoclave temperature to above 180℃ over 2 hours. The CO2 volume concentration in the high-temperature kiln tail flue gas is 20%, and the NO concentration is... X The volume concentration is 0%, and the SO2 concentration is 1%.

[0114] Step 53, heat preservation and flue gas circulation: Saturated steam is intermittently introduced into the autoclave to maintain the autoclave temperature at 180℃. Kiln tail flue gas at 70℃ after heat exchange with the boiler heat exchanger is introduced into the autoclave. The micro-opening exhaust valve on the autoclave is opened to allow gas flow in the autoclave while ensuring that the working pressure of the autoclave is 1.5MPa. The process lasts for 7 hours.

[0115] Step 54, Cooling: Quickly exhaust the air to cool down, then remove the aerated concrete blocks.

[0116] Comparative Example 1: This comparative example utilizes the raw materials of conventional autoclaved aerated concrete (AAC) for kiln tail flue gas curing. The quality of the raw materials used in its preparation is as follows:

[0117] P.O42.5R cement: 15 parts;

[0118] quicklime: 5 parts

[0119] Dry sand: 30 parts;

[0120] Dihydrate gypsum: 3 parts;

[0121] Water: 35 parts;

[0122] The aluminum powder paste is added at a rate of 0.5‰ of the total raw material mass.

[0123] The dosage of SP foam stabilizer is 0.5% of the total mass of the above raw materials.

[0124] Compared with Example 1, the raw materials used in this comparative example are all conventional raw materials for the production of aerated concrete: P.O42.5R cement and quicklime, with the addition of some dihydrate gypsum. The preparation steps and curing methods are the same as in Example 1.

[0125] Comparative Example 2 has the same raw material ratio as Example 1, including the following raw materials configured by weight:

[0126] Carbon-fixing cementitious material: 20 parts;

[0127] Dry sand: 30 parts;

[0128] Heavy calcium carbonate powder: 5 parts;

[0129] Dihydrate gypsum: 0 parts;

[0130] Water: 35 parts;

[0131] The aluminum powder paste is added at a rate of 0.5‰ of the total raw material mass.

[0132] The dosage of SP foam stabilizer is 0.5% of the total mass of the above raw materials.

[0133] In this comparative example, the carbon-fixing cementitious material comprises the following components by mass percentage: f-CaO: 38%;

[0134] — C2S: 50%; C4A3S: 8%; C4AF: 2%; CaSO4: 2%; The specific surface area of ​​the carbon-fixing cementitious material is 350 m². 2 / kg. The SiO2 content in the dry sand is 84%, and the residue on an 80μm sieve is 16.5%. The fineness of the heavy calcium carbonate powder is 400 mesh.

[0135] In this comparative example, the preparation steps, including ingredient mixing, stirring and pouring, static curing, and cutting, were the same as in Example 1. Conventional autoclaving was used for curing.

[0136] Conventional autoclaving is as follows:

[0137] 1. Feeding: Place the aerated concrete blank in the autoclave and evacuate it;

[0138] 2. Heating: High-temperature steam is introduced into the autoclave, and the autoclave temperature rises to 190℃ and pressure to 1.2MPa in 2.5 hours;

[0139] 3. Heat preservation: Saturated steam is intermittently introduced into the autoclave to maintain the autoclave temperature at 185℃. The heat preservation process lasts for 8 hours.

[0140] 4. Cooling: Quickly exhaust air to cool down, then remove the aerated concrete blocks.

[0141] The strength and density of the aerated concrete prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1 below:

[0142] Table 1. Strength and density of aerated concrete prepared in Examples 1-3 and Comparative Examples 1-2

[0143]

[0144] As shown in Table 1, the strength and density of Examples 1, 2, and 3 meet the requirements of GB / T11968-2020 "Autoclaved Aerated Concrete Blocks" B07, B06, and B05, respectively, indicating that the performance of the autoclaved aerated concrete blocks cured by the three-dimensional mechanism of hydration-heat sealing-acidification meets the specifications of the current autoclaving mechanism.

[0145] Comparing the strength and density data of Comparative Example 1 and Example 1, it was found that under the curing conditions of kiln tail flue gas, the strength of aerated concrete prepared by traditional P.O42.5R and quicklime after hydration-heat sealing-acidification reaction was lower than that of aerated concrete prepared by the new low-carbon cementitious material.

[0146] Comparing the strength and density data of Comparative Example 2 and Example 1, it was found that the aerated concrete prepared with carbon-fixing cementitious materials, after steam curing, had a strength 0.3 MPa higher than that of concrete cured with kiln tail flue gas; at the same time, its density was 53 kg / m³ lower. 3 The reason is that aerated concrete absorbs CO2, SO2 and NO from flue gas. x It plays a role in fixing carbon, sulfur, and nitrate, thus increasing the bulk density.

[0147] This invention enables the production of carbon-fixing cementitious materials, the mixing and pouring of aerated concrete, and the production of aerated concrete blocks using cement kiln tail flue gas curing in cement plants. It changes the traditional aerated concrete production process and is original and novel.

[0148] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. An aerated concrete block cured using cement kiln tail flue gas, characterized in that, Including the following raw materials configured by weight: Carbon-fixing cementitious material: 20-30 parts; Dry sand: 30-40 parts; Heavy calcium carbonate powder: 1-5 parts; Dihydrate gypsum: 0-5 parts; Water: 35-45 parts; The carbon-fixing cementitious material comprises the following components by weight percentage: f-CaO: 24–40 wt.%; C2S: 30-55 wt.%; 1~20wt.%; C4AF: 0.1–10 wt.%; CaSO4: 0.1–10 wt.%; The method for preparing the aerated concrete blocks includes the following steps: Step 1: Weigh each ingredient according to the specified proportions; Step 2: Add the weighed raw materials to the mixer and mix them into a uniform material. Then pour the mixture into the mold and vibrate it. Step 3: Place the poured and vibrated slurry in a humid and hot environment to stand still, and obtain a gas-generating and hardened green body; Step 4: Divide and trim the hardened blank to obtain the concrete blank; Step 5: Curing the concrete billet, specifically including: Step 51: Place the concrete blank in an autoclave and create a vacuum. Step 52: Pass the high-temperature kiln tail flue gas into the heat exchanger to prepare saturated steam at a temperature above 180°C, and slowly pass the saturated steam into the autoclave to raise the temperature of the autoclave to above 180°C. Step 53: Intermittently introduce saturated steam into the autoclave to maintain the autoclave temperature at 180-190℃. Introduce kiln tail flue gas that has been heat-exchanged by the boiler heat exchanger into the autoclave. Open the micro-opening exhaust valve on the autoclave to allow gas flow inside the autoclave while ensuring that the working pressure of the autoclave is 1.5-1.7MPa for 7-9 hours. Step 54: Quickly exhaust and cool down the air, then remove the aerated concrete blocks.

2. The aerated concrete block cured using cement kiln tail flue gas according to claim 1, characterized in that, The specific surface area of ​​the carbon-fixing cementitious material is 320–450 m². 2 / kg.

3. The aerated concrete block cured using cement kiln tail flue gas according to claim 1, characterized in that, The dry sand contains at least SiO2 and Al2O3, and the residue on an 80μm sieve is 3-15 wt.%.

4. The aerated concrete block cured using cement kiln tail flue gas according to claim 1, characterized in that, The fineness of the heavy calcium carbonate powder is 400 mesh.

5. The aerated concrete block cured using cement kiln tail flue gas according to claim 1, characterized in that, It also includes aluminum powder paste, wherein the amount of aluminum powder paste is 0.3 to 0.7‰ of the total raw material mass.

6. The aerated concrete block cured using cement kiln tail flue gas according to claim 1, characterized in that, It also includes a foam stabilizer, wherein the amount of the foam stabilizer is 0 to 1% of the total raw material mass.

7. The aerated concrete block cured using cement kiln tail flue gas according to claim 6, characterized in that, The foam stabilizer is any one of soluble oil, soapberry powder, SP foam stabilizer, and TS foam stabilizer.

8. The aerated concrete block cured using cement kiln tail flue gas according to claim 1, characterized in that, In step 2, the weighed raw materials are added to a mixer and stirred into a uniform material with a consistency of 220-240 mm. Then, the mixture is poured into a mold and vibrated for 20 seconds using an immersion vibrator. In step 3, the poured and vibrated slurry is placed in a humid and hot environment at 40-60℃ and left to stand for 2-3 hours to obtain a green body with gas condensation. In step 52, the CO2 volume concentration of the high-temperature kiln tail gas is 5-20%, and the NO concentration is... X The volume concentration is 0–2%, and the SO2 volume concentration is 0.01–1%. In step 53, the temperature of the kiln tail flue gas after heat exchange in the heat exchanger is 70-120℃.

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