Carbon fixation brick and preparation process

Abstract

This invention discloses a carbon-fixing brick and its preparation process, comprising the following components in the following proportions: Huaxin-cement (P·O 42.5) 16%-21%, Huatailong-tailings 30%-35%, Huaxin-stone powder 27%-32%, quicklime 0%-5%, and water 18%-23%. The carbon-fixing brick formed by these components solves the problems of insufficient raw material compatibility and carbon fixation rate in Tibet. It directly introduces cement plant flue gas into the carbon curing chamber, achieving carbon fixation and curing under "normal temperature (20-30℃), relative humidity 45%-55%" conditions, forming a closed-loop system of "cement plant carbon emissions - carbon-fixing brick preparation," achieving an emission reduction target of over 5%. It also enables "direct utilization" of cement plant carbon emissions, reducing the transportation and storage costs of CCS, and reducing local cement plant carbon emissions by 5%-7%, exceeding the 5% emission reduction target.

Description

Technical Field

[0001] This invention belongs to the field of building technology, specifically relating to a carbon-fixing brick and its preparation process. Background Technology

[0002] The global carbon sequestration building materials sector has developed rapidly in recent years, with mainstream technologies including carbonate mineralization carbon sequestration and co-sequestration of industrial solid waste. Among these, the use of industrial waste (such as steel slag, blast furnace slag, and tailings) combined with cement-based materials to prepare carbon sequestration building materials has become a core direction combining "carbon sequestration and emission reduction" with "waste resource utilization." In China, small-scale applications of carbon sequestration bricks made from blast furnace slag and fly ash have been achieved in eastern China, with carbon sequestration rates reaching 0.8%-1.2%. However, due to differences in the geographical distribution of raw materials, these technologies cannot be directly transferred to Tibet. In recent years, the building materials industry in Tibet has gradually shifted towards "localization and greening." The local government has introduced policies to encourage the development of environmentally friendly building materials using local raw materials and industrial waste, while requiring cement companies to reduce their carbon emission intensity by more than 5% by 2025. Currently, some local enterprises have attempted to prepare ordinary wall bricks by blending stone powder, quicklime, and cement, but these methods do not involve carbon sequestration. The resource utilization of Huatailong tailings sand remains at the stage of simple landfilling or low-value-added roadbed filling, and has not yet been integrated with carbon sequestration technology. Overall, carbon sequestration building material technology in Tibet is in its initial stage, and there is an urgent need for specialized technical solutions that adapt to the characteristics of local raw materials and meet the requirements for high carbon sequestration rates and emission reduction by cement plants.

[0003] Existing carbon-fixing brick preparation technologies are mainly divided into two categories: one is "exogenous carbon fixation" technology, which involves first preparing brick blanks and then placing them in a carbon dioxide curing environment (such as a high-pressure carbonation curing chamber). Carbon fixation is achieved through the reaction of cement, quicklime, and other components in the brick blanks with carbon dioxide. A representative technology is the "cement-based building material carbonation curing process." This technology requires the construction of additional high-pressure curing equipment, resulting in high energy consumption and costs. Furthermore, the high altitude and low air pressure environment in Tibet reduces the efficiency of the carbonation reaction, with the carbon fixation rate often below 0.8%. The other category is "endogenous carbon fixation" technology, which involves directly adding components that can react with carbon dioxide (such as steel slag and carbide slag) to the raw materials. During the brick forming and curing process, carbon dioxide is absorbed from the air. A representative technology is the "industrial solid waste co-carbon fixation brick preparation process." However, this technology relies on specific industrial solid wastes (such as steel slag), and Tibet lacks such raw materials. Transporting them from other regions would significantly increase costs, and the carbon fixation reaction is slow, failing to meet the immediate carbon emission utilization needs of cement plants. Existing carbon emission utilization technologies in cement plants are mostly concentrated on "carbon capture and storage" (CCS), which involves capturing carbon dioxide through equipment and then compressing and storing it. This technology requires large investments, has high operating costs, and cannot realize the resource utilization of carbon resources, which does not meet the actual needs of low-cost emission reduction in Tibet.

[0004] The aforementioned prior art has the following technical defects:

[0005] Poor raw material compatibility: Existing carbon fixation brick technology relies on raw materials not native to Tibet (such as steel slag and fly ash), which are not compatible with local cement, stone powder and Huatailong tailings sand in Tibet. This can easily lead to low brick strength and carbon fixation rate of less than 1%, which cannot meet the usage requirements and carbon fixation targets.

[0006] The synergy between carbon sequestration and emission reduction is insufficient. Existing technologies do not combine the preparation of carbon sequestration bricks with the recycling of carbon emissions from cement plants. They either focus only on the production of carbon sequestration bricks or only on the capture of carbon emissions from cement plants, failing to achieve a closed loop of "raw materials-production-emission reduction". As a result, the carbon emission reduction of local cement plants is less than 3%, far from reaching the target of 5%.

[0007] The process is not compatible with the environment. Existing carbon-fixing brick preparation processes (such as high-pressure carbonation curing, with a high pressure range of 0.5MPa~3.0MPa) depend on specific environmental conditions. In the high-altitude, low-pressure, and large diurnal temperature range of Tibet, the reaction efficiency is low and the energy consumption is high, making it difficult to scale up production.

[0008] The utilization rate of waste is low. Huatai Long tailings sand, as the main industrial waste in the area, is only used as a filler in the existing technology. Its particle size distribution advantage is not fully utilized, resulting in insufficient density of the bricks, which not only affects the carbon sequestration effect, but also wastes waste resources. Summary of the Invention

[0009] The purpose of this invention is to provide a carbon-fixing brick and its preparation process to solve the problems mentioned in the background art.

[0010] The objective of this invention is achieved through the following technical solution: a carbon-fixing brick comprising the following components in the following proportions: Huaxin-cement (P・O 42.5) 10%-30%, Huatailong-tailings 20%-50%, Huaxin-stone powder 15%-40%, quicklime 0%-10%, and water 15%-30%.

[0011] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 16%-21%, Huatailong-tailings 30%-35%, Huaxin-stone powder 27%-32%, quicklime 0%-5%, and water 18%-23%.

[0012] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 20%, Huatailong-tailings 30%, Huaxin-stone powder 27%, quicklime 4%, and water 19%.

[0013] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 21%, Huatailong-tailings 30%, Huaxin-stone powder 27%, quicklime 2%, and water 20%.

[0014] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 17%, Huatailong-tailings 32%, Huaxin-stone powder 27%, quicklime 5%, and water 19%.

[0015] A process for preparing carbon-fixing bricks includes the following steps:

[0016] S1 Raw Material Mixing: Add the pretreated Huatai tail sand, Huaxin stone powder, and quicklime into a twin-shaft mixer and dry mix for 2-3 minutes until uniform;

[0017] Add Huaxin-cement (P・O 42.5) and water, wet mix for 5-8 minutes to form a uniform slurry. The slurry fluidity is controlled at 180-200mm to meet the molding requirements under high altitude and low air pressure.

[0018] S2 brick blank forming: The slurry is injected into the mold and pressurized using a hydraulic forming machine. The forming pressure is 15-20MPa and the holding time is 30-60s, resulting in a brick blank with a density ≥1.8g / cm³.

[0019] The mold dimensions are designed according to the construction needs of Tibet, with a standard size of 240mm×115mm×53mm;

[0020] S3 Carbon Source Introduction: The brick blanks are sent into the "carbon curing chamber," which is directly connected to the cement plant's flue through a pipeline to introduce carbon dioxide emitted by the cement plant. The carbon dioxide concentration is ≥80%, and the temperature is controlled at 25-35℃, which is suitable for the normal temperature environment in Tibet. At the same time, the relative humidity is maintained at 45%-55% through the humidity control system inside the chamber.

[0021] Among them, the carbon dioxide emitted by the cement plant is treated for dust removal and desulfurization, and the exhaust gas discharged from the cement plant enters the carbon curing chamber after undergoing a PSA+ secondary purification process.

[0022] S4 Carbon Fixation Curing: Under the above temperature, humidity and carbon dioxide concentration conditions, the curing time is 12 hours. In the low-pressure environment of Tibet, the curing time is extended by 12 hours to ensure sufficient reaction. During this period, the carbon dioxide is evenly contacted with the brick blank through the gas circulation system in the chamber to ensure sufficient carbon fixation inside the brick.

[0023] S5 Finished Product Inspection: After curing, the carbon fixation rate of the brick is ≥1% and the compressive strength at 28 days is ≥7.5MPa. If it passes the test, it is considered a finished product.

[0024] Furthermore, the Huatailong tailings has a particle size of 0.075-0.3mm and a moisture content of ≤1%, the Huaxin stone powder has a particle size of ≤0.075mm, and the quicklime contains ≥85% CaO.

[0025] The Huatailing pretreatment includes drying, which involves drying in a 100℃ oven for 2 hours to reduce the moisture content to ≤1%; and sieving, which uses 0.3mm and 0.075mm standard sieves to remove impurities with a particle size >0.3mm, with a content of approximately 2.1%.

[0026] The quicklime pretreatment includes slaking, in which tap water is added at a water-lime ratio of 1:1, and slaking is carried out in a 70℃ constant temperature water bath for 24 hours, with stirring three times during the process, once every 8 hours, to prevent local overheating. After slaking, the quicklime is passed through a 1mm sieve to remove unslaked particles, with a content of approximately 1.2%. The slaking temperature is: initial temperature of 25℃, with a maximum temperature of 92℃ after adding water; the slaking rate is: 85% within 2 hours and 98% within 24 hours.

[0027] Furthermore, the carbon curing chamber is a sealed chamber with multiple layers of brick placement racks inside, with each layer spaced 150mm apart to ensure gas circulation. The chamber walls are equipped with a 50mm thick insulation layer made of local Tibetan rock wool.

[0028] The carbon source is connected to the cement plant's flue via a pipeline. The pipeline is equipped with a carbon dioxide concentration sensor and a flow regulating valve to adjust the intake air volume according to the curing stage (initially 2 m³ / h, then reduced to 1 m³ / h).

[0029] Environmental control features include a humidity generator to maintain a relative humidity of 45%-55% and a gas circulation fan with a wind speed of 0.5 m / s to ensure uniform carbon dioxide distribution and adaptability to the low-pressure environment of Tibet.

[0030] Furthermore, the carbon fixation and mineralization environment is characterized by a carbon dioxide concentration (J) of 100%, a curing temperature (F) of 25°C, a relative humidity (G) of 55% RH, and a curing pressure of 0.3 MPa.

[0031] An application of a carbon-fixing brick preparation process is proposed, which applies the process to the field of carbon-fixing building materials. The process involves directly introducing flue gas from cement plants into a carbon curing chamber, achieving carbon fixation and curing under conditions of "normal temperature (20-30℃) and relative humidity 45%-55%", thus forming a closed-loop system of "cement plant carbon emissions - carbon-fixing brick preparation" and achieving an emission reduction target of more than 5%.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention significantly improves carbon fixation efficiency: through optimized raw material compounding and a dedicated carbon curing process, it is a substantial improvement over the existing unoptimized carbon fixation brick technology in Tibet (carbon fixation rate of 0.6%-0.8%), thus meeting the demand for efficient carbon fixation.

[0034] This invention achieves the emission reduction target of cement plants, realizes the "direct utilization" of carbon emissions from cement plants, reduces the transportation and storage costs of CCS, and enables local cement plants to reduce carbon emissions by 5%-7%, exceeding the 5% emission reduction target.

[0035] The raw materials used in this invention are highly compatible with the environment, and all raw materials are sourced from Tibet (cement, stone powder, quicklime, and Huatai Longwei sand), reducing raw material transportation costs by more than 60%.

[0036] This invention enables high-value utilization of waste materials. The utilization rate of Huatai Long tailings reaches 30%-35%, which is significantly higher than the existing landfill or roadbed filling (utilization rate of less than 10%). It can reduce the amount of tailings accumulation in Tibet by about 50,000 tons per year, while reducing the risk of land occupation and ecological pollution.

[0037] This invention has significant economic and social benefits. The production cost of carbon-fixed bricks is reduced by 25% compared with existing technologies (saving the cost of transporting raw materials from other places and treating solid waste), and the compressive strength at 28 days is ≥7.5MPa, which can meet the needs of civil and public buildings in Tibet and promote the coordinated development of "green building materials + industrial emission reduction" in the region. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 16%-21%, Huatailong-tailings 30%-35%, Huaxin-stone powder 27%-32%, quicklime 0%-5%, and water 18%-23%.

[0041] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 20%, Huatailong-tailings 30%, Huaxin-stone powder 27%, quicklime 4%, and water 19%.

[0042] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 21%, Huatailong-tailings 30%, Huaxin-stone powder 27%, quicklime 2%, and water 20%.

[0043] A carbon-fixing brick comprises the following components in the following proportions: Huaxin-cement (P・O 42.5) 17%, Huatailong-tailings 32%, Huaxin-stone powder 27%, quicklime 5%, and water 19%.

[0044] A process for preparing carbon-fixing bricks includes the following steps:

[0045] S1 Raw Material Mixing: Add the pretreated Huatai tail sand, Huaxin stone powder, and quicklime into a twin-shaft mixer and dry mix for 2-3 minutes until uniform;

[0046] Add Huaxin-cement (P・O 42.5) and water, wet mix for 5-8 minutes to form a uniform slurry. The slurry fluidity is controlled at 180-200mm to meet the molding requirements under high altitude and low air pressure.

[0047] S2 brick blank forming: The slurry is injected into the mold and pressurized using a hydraulic forming machine. The forming pressure is 15-20MPa and the holding time is 30-60s, resulting in a brick blank with a density ≥1.8g / cm³.

[0048] The mold dimensions are designed according to the construction needs of Tibet, with a standard size of 240mm×115mm×53mm;

[0049] S3 Carbon Source Introduction: The brick blanks are sent into the "carbon curing chamber". The carbon curing chamber is directly connected to the cement plant flue through a pipeline to introduce carbon dioxide emitted by the cement plant. The carbon dioxide concentration is ≥80% and the temperature is controlled at 25-35℃, which is suitable for the normal temperature environment in Tibet. At the same time, the relative humidity is maintained at 45%-55% through the humidity control system in the chamber. The carbon fixation and mineralization environment is as follows: carbon dioxide concentration (J) is 100%, curing temperature (F) is 25℃, relative humidity (G) is 55% RH, and curing pressure is 0.3MPa.

[0050] Among them, the carbon dioxide emitted by the cement plant is treated for dust removal and desulfurization, and the exhaust gas discharged from the cement plant enters the carbon curing chamber after undergoing a PSA+ secondary purification process.

[0051] S4 Carbon Fixation Curing: Under the above temperature, humidity and carbon dioxide concentration conditions, the curing is carried out for 12 hours. During this period, the carbon dioxide is evenly contacted with the brick blank through the gas circulation system in the chamber to ensure that the brick body is fully carbonized.

[0052] S5 Finished Product Inspection: After curing, test the carbon fixation rate of the bricks to be ≥1% and the compressive strength of 28 to be ≥7.5MPa. If the test is qualified, the bricks are considered finished products.

[0053] Among them, the Huatailong tailings has a particle size of 0.075-0.3mm and a moisture content of ≤1%, the Huaxin stone powder has a particle size of ≤0.075mm, and the CaO content in the quicklime is ≥85%;

[0054] The Huatailing pretreatment includes drying, which involves drying in a 100℃ oven for 2 hours to reduce the moisture content to ≤1%; and sieving, which uses 0.3mm and 0.075mm standard sieves to remove impurities with a particle size >0.3mm, with a content of approximately 2.1%.

[0055] The quicklime pretreatment includes slaking, in which tap water is added at a water-lime ratio of 1:1, and slaking is carried out in a 70℃ constant temperature water bath for 24 hours, with stirring three times during the process, once every 8 hours, to prevent local overheating. After slaking, the quicklime is passed through a 1mm sieve to remove unslaked particles, with a content of approximately 1.2%. The slaking temperature is: initial temperature of 25℃, with a maximum temperature of 92℃ after adding water; the slaking rate is: 85% within 2 hours and 98% within 24 hours.

[0056] The carbon curing chamber is a sealed chamber with multiple layers of brick placement racks inside, with each layer spaced 150mm apart to ensure gas circulation. The chamber walls are insulated with a 50mm thick layer of local Tibetan rock wool material.

[0057] The carbon source is connected to the cement plant's flue via a pipeline. The pipeline is equipped with a carbon dioxide concentration sensor and a flow regulating valve to adjust the intake air volume according to the curing stage (initially 2 m³ / h, then reduced to 1 m³ / h).

[0058] Environmental control features include a humidity generator to maintain a relative humidity of 45%-55% and a gas circulation fan with a wind speed of 0.5 m / s to ensure uniform carbon dioxide distribution and adaptability to the low-pressure environment of Tibet.

[0059] An application of a carbon-fixing brick preparation process is presented, which is then applied to the field of carbon-fixing building materials. Cement plant flue gas is directly introduced into a carbon curing chamber, achieving carbon fixation curing under the conditions of "temperature controlled at 20℃~30℃ + carbon dioxide concentration adjusted to 85%-100% + humidity controlled at 45%~55%RH + pressure controlled at 0.25-0.5MPA". This forms a closed-loop system of "cement plant carbon emissions - carbon-fixing brick preparation", achieving an emission reduction target of over 5%.

[0060] The specific combination of parameters, including carbon fixation curing time (12-24h), molding pressure (15-20MPa), and slurry flowability (180-200mm), is adapted to the high-altitude environment of Tibet, ensuring sufficient carbon fixation and brick strength.

[0061] The carbon fixation process of this invention uses all raw materials from Tibet. The source, main components, and performance indicators of the raw materials are as follows. Specific parameters were obtained through laboratory testing. The experimental design for the carbon fixation bricks is as follows:

[0062]

[0063] The carbon fixation process of this invention is designed based on the high-altitude, low-pressure, and normal-temperature environment of Tibet. Its core is an integrated process of "raw material pretreatment - slurry mixing - brick forming - carbon source introduction - carbon fixation curing," achieving efficient carbon fixation through precise control of process parameters. The specific process flow is as follows: Raw material pretreatment stage

[0064] Raw material pretreatment is fundamental to ensuring the stability of subsequent processes and product performance. This paper describes the treatment of Huatai Long tailings sand and quicklime based on their characteristics, including specific steps and control requirements:

[0065] Huatai Longtai tailings sand pretreatment:

[0066] Sampling and testing: Five samples (1 kg each) were taken from the tailings stockpile. The moisture content was tested by drying at 105℃ to constant weight. If the moisture content was >1%, drying treatment was carried out.

[0067] Drying procedure: Place the tailings in an electric heating drying oven, set the temperature to 100℃, and dry for 2 hours, stirring every 30 minutes to ensure uniform heating; after drying, take samples again to test the moisture content until it is ≤1%;

[0068] Screening operation: Pour the dried tailings into a 0.3mm standard sieve and screen manually (or with a vibrating screen at a frequency of 50Hz) to remove impurities with a particle size >0.3mm (mainly gravel particles). Collect the tailings that pass through the sieve for later use. At the same time, use a 0.075mm standard sieve to test the particle size distribution of the tailings to ensure that the proportion of particles with a size of 0.075-0.3mm is ≥75%.

[0069] Quicklime pretreatment:

[0070] Preparation for slaking: Weigh out quicklime and tap water (25℃) according to the mass ratio of quicklime:water = 1:1, and set aside;

[0071] Digestion procedure: Pour water into a digestion tank equipped with a stirring device, turn on the stirring (30 r / min), slowly add lime (to prevent local overheating), then place the digestion tank into a constant temperature water bath, set the temperature to 70℃, and digest for 24 hours; during this period, stop stirring once every 8 hours (5 minutes each time), observe the digestion, and break up any clumps that appear in time;

[0072] Screening process: After slaking, pour the slaking lime slurry into a 1mm standard sieve and rinse it with tap water (the amount of rinsing water should be controlled within 10% of the slurry mass) to remove unslaking particles. Collect the slaked lime slurry and dry it to make lime powder. Use sealed moisture-proof packaging, open it as needed, and reseal it immediately after each use to reduce exposure time.

[0073] Slurry mixing stage.

[0074] The quality of slurry mixing directly affects the quality of brick forming and the uniformity of carbon fixation reaction. It is necessary to control the parameters of dry and wet mixing to ensure that the slurry flowability and uniformity meet the standards. Specific steps include:

[0075] Raw material weighing: According to the optimized compound ratio, each raw material is weighed using an electronic balance. Cement, tailings, stone powder, and quicklime are solid raw materials, while water is a liquid raw material, and they are stored in different containers.

[0076] Dry mixing operation: Pour the pretreated tailings, stone powder and quicklime into the mortar mixer, set the dry mixing speed to 30 r / min and the dry mixing time to 2.5 min;

[0077] Wet mixing operation: After dry mixing is completed, add the weighed cement and water, set the wet mixing speed to 50 r / min, and the wet mixing time to 6.5 min; during the wet mixing process, take samples every 2 min (take 3 samples, 50 g each), and use a flowability tester (according to GB / T 2419-2005 "Method for Determination of Flowability of Cement Mortar") to test the flowability of the slurry. If the flowability is <180 mm, increase the amount of water appropriately (for every 1% increase in water, the flowability increases by about 10 mm); if the flowability is >200 mm, increase the amount of cement appropriately (for every 1% increase in cement, the flowability decreases by about 8 mm), until the flowability of the slurry is controlled at 180-200 mm;

[0078] Uniformity test: After wet mixing, take 3 slurry samples (100g each) from different positions of the mixer (top, middle and bottom), and test the moisture content using the drying method. Calculate the moisture content deviation (≤0.5%). If the deviation is too large, extend the wet mixing time by 0.5-1min to ensure the slurry is uniform.

[0079] Brick forming stage

[0080] The forming process for brick blanks requires controlling the forming pressure, holding time, and mold temperature to ensure that the brick blanks meet the density requirements and are free of appearance defects. Specific steps include:

[0081] Mold preparation: Clean the custom mold thoroughly and apply a release agent (using a mixture of engine oil and diesel oil at a ratio of 1:3, with the amount controlled at 5g / m²) to prevent the brick blanks from sticking to the mold;

[0082] Slurry pouring: Slowly pour the well-mixed slurry into the mold (pour in 2 times, each time 50% of the volume, vibrate for 30 seconds in between, using a small vibrator at a frequency of 50Hz) to prevent air bubbles from forming; after pouring, use a scraper to smooth the surface of the mold and remove excess slurry.

[0083] Molding: Place the mold containing the slurry on the vibrating table / manual vibration molding station, and use vibration to compact the slurry (or manual tamping to compact it). The vibration frequency and time should be based on the slurry being fully degassed and the surface of the slurry being uniformly covered. During the molding process, observe the compaction status of the brick in real time. If the slurry compaction is insufficient, extend the vibration / tamping time appropriately to ensure that the brick is uniformly compacted.

[0084] Demolding and Inspection: After molding, allow the blank to stand until it has initial demolding strength, then demold and remove the brick blank; observe the appearance of the brick blank, and if there are defects such as cracks or missing corners, analyze the cause (such as improper slurry flowability or insufficient molding pressure) and adjust the process; place the complete brick in a standard curing room for curing, and test the compressive strength and flexural strength of the brick blank at 3d, 7d and 28d respectively according to the standard GB / T 4111-2013 "Test Methods for Concrete Blocks and Bricks".

[0085] Carbon source introduction stage

[0086] Carbon source introduction is a key step in realizing carbon emission utilization in cement plants. Simulation experiments are conducted in the laboratory using customized carbon sequestration curing. The pressure of the carbon sequestration curing chamber can be adjusted from 2.5 to 5 standard atmospheres. The carbon dioxide concentration is achieved by purchasing carbon dioxide storage cylinders of different concentrations. Temperature and humidity can be controlled by adjusting the experimental environment.

[0087] Carbon sequestration maintenance stage

[0088] Carbon fixation curing requires controlling temperature, humidity, and curing time to ensure a complete carbon fixation reaction. Specific steps are as follows:

[0089] 1. Temperature and humidity control: Temperature between 20℃ and 30℃, humidity between 45%RH and 55%;

[0090] 2. Carbon sequestration environment: Pressure, 0.25-0.5 MPa, carbon dioxide concentration, 85%-100%, carbon sequestration time, 12h.

[0091] 3. Curing time: The test blocks were cured for 3 days and 7 days respectively. On the second and sixth day of curing, the test blocks were taken out of the curing room and dried at room temperature for 1 day before being put into the carbon fixation device for carbon fixation test.

[0092] The experimental design and scheme for carbon-fixing bricks are as follows:

[0093] To investigate the effects of raw material formulation on the density, compressive strength, and flexural strength of carbon-fixing bricks, the laboratory conducted an orthogonal experimental design. The design used the following influencing factors: Huaxin P·O 42.5 cement content (A), Huatai Longwei sand content (B), Huaxin stone powder content (C), high-quality hydrated lime content (D), and water content (E). Each factor had four levels. 16 (4 5 An orthogonal experiment was conducted, with the factor level table shown in Table 1. A total of 16 groups of samples were prepared, with 18 carbon-fixing bricks prepared in each group. Nine of these bricks underwent standard curing for 3 days, 7 days, and 28 days, while the other nine underwent standard curing for 3 days (6 bricks) and 7 days (3 bricks), respectively. On the second and sixth days of curing, the bricks were removed from the curing room and dried at room temperature for 1 day before being placed in the carbon fixation device for a 12-hour carbon fixation test. Six of these bricks underwent compressive and flexural strength tests after the carbon fixation test, respectively, on both the 3-day and 7-day tests. The remaining three bricks (those that underwent carbon fixation curing for 3 days) continued to be cured for 28 days after the carbon fixation test, and then underwent compressive and flexural strength tests.

[0094] Table 1. Factor Level Table for Orthogonal Experiment (mass fraction, %)

[0095]

[0096] Effect of different formulations on the density of carbon-fixing bricks

[0097] Density is an important physical property indicator of carbon sequestration bricks. The higher the density, the fewer the internal pores and the more compact the structure. High-density bricks can also sequester more carbon in the same volume, thus increasing the carbon sequestration value of the material. The density of 16 samples was tested according to the method in Table 1, and the results of 4 representative samples are shown in Table 2.

[0098] Table 2. Density test results of orthogonal experiments (g / cm³)

[0099]

[0100] As can be seen from Table 2, the densities of the four groups of samples are between 2.03 and 2.25 g / cm³. Among them, the density of test No. 11 is the highest at 2.25 g / cm³, and the density of test No. 6 is the lowest at 2.03 g / cm³. The density of all samples is ≥2.0 g / cm³, which meets the requirements of density grade A in GB / T21144-2023 "Solid Concrete Bricks".

[0101] Effects of different formulations on the compressive and flexural strength of carbon-fixing bricks

[0102] Compressive strength is the core mechanical performance indicator of carbon-fixed bricks, directly determining whether they can meet the building usage requirements in Tibet (design requirement ≥7.5MPa). Sixteen groups were tested according to the method in Table 1, and the compressive and flexural strengths of four representative groups were obtained.

[0103] Table 3-1 Results of 3-day standard curing compressive and flexural strength tests (MPa) from orthogonal experiments

[0104]

[0105] Table 3-2 Results of compressive and flexural strength tests (MPa) after 7 days of standard curing in orthogonal experiments

[0106]

[0107] Table 3-3 Results of compressive and flexural strength tests (MPa) after 28 days of standard curing in orthogonal experiments

[0108]

[0109] Table 3-4 Results of 3-day carbon fixation compressive and flexural strength tests (MPa) from orthogonal experiments

[0110]

[0111] Table 3-5 Results of 7-day carbon fixation compressive and flexural strength tests (MPa) from orthogonal experiments

[0112]

[0113] Table 3-6 Results of compressive and flexural strength tests (MPa) of 3-day standard-cured carbon-28 carbon fixation material in orthogonal experiments

[0114]

[0115] Comparing Tables 3-1 to 6, it can be seen that the compressive and flexural strengths of carbon-fixed bricks with the same mix proportion are significantly higher than those of uncarbonized bricks. This is because the cementitious material reacts with carbon dioxide to produce calcium carbonate (enhancing the bond), and also acts as an alkaline activator, activating active SiO2 and Al2O3 in tailings and stone powder to generate more hydration products (such as hydrated calcium silicate and hydrated calcium aluminate), thereby improving the strength of the carbon-fixed bricks. The compressive and flexural strengths of the carbon-fixed bricks at 3d, 7d, and 28d increase with the increase of factor A (cement content), showing a positive correlation. The highest compressive and flexural strengths were observed at 28d in test number 14, reaching 21.21 MPa and 5.313 MPa, respectively. We selected four mix proportions with the highest strength among those with the same cement content (including test numbers 4, 6, 10, and 14) for carbon fixation tests. The test environment was as follows: carbon dioxide concentration (J) 100%, curing temperature (F) 25℃, relative humidity (G) 55% RH, and curing pressure 0.3MPa, as shown in Tables 3-7 and 3-8.

[0116] Table 3-7 Test results of 3-day carbon fixation experiment in orthogonal experiment (MPa)

[0117]

[0118] Table 3-8 Test results of 7-day carbon fixation experiment in orthogonal experiment (MPa)

[0119]

[0120] As shown in Tables 3-7 and 3-8, the quicklime content in sample 4 was 0%, while the highest was 5% in sample 6. Sample 10 had a quicklime content of 2%, and sample 14 had a quicklime content of 4%. This indicates that the amount of quicklime significantly affects the carbon fixation effect of the carbon-fixing bricks. With increasing quicklime content, the carbon fixation rate of the bricks increases because the calcium hydroxide produced by the slaking of quicklime can react with carbon dioxide to form calcium carbonate, thus increasing the carbon fixation rate. It can also be seen that the carbon fixation rate of all four samples reached over 2%, with the rates for samples 3d and 7d being essentially the same, indicating that samples 3d and 7d had essentially reached saturation in terms of carbon fixation capacity. Sample 6 had the highest carbon fixation rate at 3.2%.

[0121] In summary, the density of formula 4 is 2.123 g / cm³. 3 After carbon fixation, the compressive and flexural strengths at 28 days were 9.81 MPa and 3.161 MPa, respectively, meeting the strength grade MU7.5 requirements in GB / T21144-2023 "Solid Concrete Bricks"; the density of Formula 6 was 2.152 g / cm³. 3After carbon fixation, the compressive and flexural strengths at 28 days were 13.62 MPa and 3.811 MPa, respectively, meeting the strength grade MU10 requirements in GB / T21144-2023 "Solid Concrete Bricks"; the density of Formula 10 was 2.162 g / cm³. 3 After carbon fixation, the compressive and flexural strengths at 28 days were 18.31 MPa and 4.722 MPa, respectively, meeting the strength grade MU15 requirements in GB / T21144-2023 "Solid Concrete Bricks"; the density of Formula 14 was 2.142 g / cm³. 3 After carbon fixation, the compressive and flexural strengths at 28 days were 21.21 MPa and 5.313 MPa, respectively, meeting the requirements of strength grade MU20 in GB / T21144-2023 "Solid Concrete Bricks".

[0122] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0123] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A carbon-fixing brick, characterized in that, The components include the following proportions: Huaxin-cement (P・O 42.5) 10%-30%, Huatailong-tailings 20%-50%, Huaxin-stone powder 15%-40%, quicklime 0%-10%, and water 15%-30%.

2. The carbon-fixing brick according to claim 1, characterized in that, The components include the following proportions: Huaxin-cement (P・O42.5) 16%-21%, Huatailong-tailings 30%-35%, Huaxin-stone powder 27%-32%, quicklime 0%-5%, and water 18%-23%.

3. The carbon-fixing brick according to claim 1, characterized in that, The components include the following proportions: Huaxin-cement (P・O 42.5) 20%, Huatailong-tailings 30%, Huaxin-stone powder 27%, quicklime 4%, and water 19%.

4. The carbon-fixing brick according to claim 1, characterized in that, The components include the following proportions: Huaxin-cement (P・O42.5) 21%, Huatailong-tailings 30%, Huaxin-stone powder 27%, quicklime 2%, and water 20%.

5. The carbon-fixing brick according to claim 1, characterized in that, The components include the following proportions: Huaxin-cement (P・O42.5) 17%, Huatailong-tailings 32%, Huaxin-stone powder 27%, quicklime 5%, and water 19%.

6. A process for preparing carbon-fixing bricks according to any one of claims 1-5, characterized in that, Includes the following steps: S1 Raw Material Mixing: Add the pretreated Huatai tail sand, Huaxin stone powder, and quicklime into a twin-shaft mixer and dry mix for 2-3 minutes until uniform; Add Huaxin-cement (P・O 42.5) and water, wet mix for 5-8 minutes to form a uniform slurry. The slurry fluidity is controlled at 180-200mm to meet the molding requirements under high altitude and low air pressure. S2 brick blank forming: The slurry is injected into the mold and pressurized using a hydraulic forming machine. The forming pressure is 15-20MPa and the holding time is 30-60s, resulting in a brick blank with a density ≥1.8g / cm³. The mold dimensions are designed according to the construction needs of Tibet, with a standard size of 240mm×115mm×53mm; S3 Carbon Source Introduction: The brick blanks are sent into the "carbon curing chamber", which is directly connected to the cement plant's flue through a pipeline to introduce carbon dioxide emitted by the cement plant. The carbon dioxide concentration is ≥80%, and the temperature is controlled at 25-35℃, which is suitable for the normal temperature environment in Tibet. At the same time, the relative humidity is maintained at 45%-55% through the humidity control system inside the chamber. Among them, the carbon dioxide emitted by the cement plant is treated for dust removal and desulfurization, and the exhaust gas discharged from the cement plant enters the carbon curing chamber after undergoing a PSA+ secondary purification process. S4 Carbon Fixation Curing: Under the above temperature, humidity and carbon dioxide concentration conditions, the curing is carried out for 12 hours. During this period, the carbon dioxide is evenly contacted with the brick blank through the gas circulation system in the chamber to ensure that the brick body is fully carbonized. S5 Finished Product Inspection: After curing, the carbon fixation rate of the brick is ≥1% and the compressive strength at 28 days is ≥7.5MPa. If it passes the test, it is considered a finished product.

7. The carbon-fixing brick preparation process according to claim 6, characterized in that, The Huatai Long tailings have a particle size of 0.075-0.3mm and a moisture content of ≤1%, while the Huaxin stone powder has a particle size of ≤0.075mm and a CaO content of ≥85% in the quicklime. The Huatailing pretreatment includes drying, which involves drying in a 100℃ oven for 2 hours to reduce the moisture content to ≤1%; and sieving, which uses 0.3mm and 0.075mm standard sieves to remove impurities with a particle size >0.3mm, with a content of approximately 2.1%. The quicklime pretreatment includes slaking, in which tap water is added at a water-lime ratio of 1:1, and slaking is carried out in a 70℃ constant temperature water bath for 24 hours, with stirring three times during the process, once every 8 hours, to prevent local overheating. After slaking, the quicklime is passed through a 1mm sieve to remove unslaked particles, with a content of approximately 1.2%. The slaking temperature is: initial temperature of 25℃, with a maximum temperature of 92℃ after adding water; the slaking rate is: 85% within 2 hours and 98% within 24 hours.

8. The carbon-fixing brick preparation process according to claim 7, characterized in that, The carbon curing chamber is a sealed chamber with multiple layers of brick placement racks inside, with each layer spaced 150mm apart to ensure gas circulation. The chamber walls are insulated with a 50mm thick layer of local Tibetan rock wool material. The carbon source is connected to the cement plant's flue via a pipeline. The pipeline is equipped with a carbon dioxide concentration sensor and a flow regulating valve to adjust the intake air volume according to the curing stage (initially 2 m³ / h, then reduced to 1 m³ / h). Environmental control features include a humidity generator to maintain a relative humidity of 45%-55% and a gas circulation fan with a wind speed of 0.5 m / s to ensure uniform carbon dioxide distribution, adapting to the local environment of Tibet.

9. The carbon-fixing brick preparation process according to claim 8, characterized in that, The carbon fixation and mineralization environment is as follows: carbon dioxide concentration (J) of 100%, curing temperature (F) of 25℃, relative humidity (G) of 55% RH, and curing pressure of 0.3MPa.

10. An application of the carbon-fixing brick preparation process according to claim 9, characterized in that, Applying the carbon sequestration brick preparation process to the field of carbon sequestration building materials, the flue gas from cement plants is directly introduced into the carbon curing chamber, achieving carbon sequestration curing under the conditions of "normal temperature (20-30℃) and relative humidity 45%-55%", forming a closed-loop system of "cement plant carbon emissions - carbon sequestration brick preparation", achieving an emission reduction target of more than 5%.

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