Time-controlled self-triggering type carbon dioxide sustained-release capsule for carbonized soil and preparation method thereof

Abstract

The invention discloses a time-control self-triggering type carbon dioxide sustained-release capsule for carbonized soil and a preparation method of the time-control self-triggering type carbon dioxide sustained-release capsule. The capsule comprises a gas production core and a sustained-release coating layer from inside to outside, the preparation method comprises the following steps: mixing the gas production core powder; the method comprises the following steps: uniformly mixing dry gas production formula powder according to a set proportion in a dry environment; granulating, rolling and drying the gas production core master batch; preparing coating powder; uniformly mixing the dried coating formula powder in proportion under a drying condition; the surface of the core is wet; the slow-release coating layer wraps the core; and drying at low temperature and taking out to obtain a carbon dioxide sustained-release capsule final product with complete structure and stable performance. The carbon sequestration soil is uniform in carbonization and high in strength, the problems of surface layer hardening and internal non-uniformity caused by carbonization from outside to inside are avoided, and therefore the overall strength of the carbon sequestration soil is remarkably improved; the initial release and continuous release time of the carbon dioxide is accurately controlled, so that the carbon dioxide is perfectly matched with a construction process, and the carbon dioxide is efficiently utilized for carbonization reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering and engineering materials, and particularly relates to a time-controlled self-triggering type carbon dioxide slow-release capsule for carbonized soil and a preparation method thereof. BACKGROUND

[0002] In recent years, the field of geotechnical engineering has been committed to the research and development of various soil carbonization technologies. This technology is mainly based on magnesium oxide, lime and other materials, as well as some industrial by-products and biological solidification agents, which react with carbon dioxide to generate carbonate products that can replace cement. This method not only effectively avoids the large amount of carbon emissions generated during the production and use of traditional cement, but also further achieves emission reduction by absorbing carbon dioxide, thus having significant environmental benefits. Such carbonized materials can be widely used in various geotechnical engineering scenarios such as roadbeds, dams, tunnels, etc., and show good application prospects.

[0003] However, the existing carbonization process usually requires injecting pressurized gaseous carbon dioxide into the material to be reacted. This process relies on special pressurizing equipment, injection devices and professional operators, and has high requirements for the site and conditions. In some extreme or special engineering environments, such methods face serious challenges: in deep water and high pressure environments such as deep sea or underwater foundation, it is extremely difficult to inject carbon dioxide gas into the pile body, and it is necessary to overcome the huge hydrostatic pressure, which significantly increases the complexity and cost of the equipment; at the same time, carbon dioxide is easily dissolved in water under high pressure, resulting in a large amount of loss; in limited spaces such as tunnels, building structures, underground pipe corridors or equipment foundations, large carbon dioxide storage tanks, pressurization and injection equipment are difficult to deploy; for reinforcement of special-shaped members or existing structures, it is also difficult to achieve effective sealing and uniform gas injection; in remote areas such as highlands, frontiers and islands, the transportation of large equipment is difficult and costly; and in emergency rescue after disasters such as earthquakes and landslides, the equipment cannot be transported in time due to road interruptions and power shortages, which delays the critical reinforcement opportunity. Therefore, it is necessary to develop a low-cost carbon dioxide slow-release capsule material that can be embedded in soil. SUMMARY

[0004] The present application aims to provide a time-controlled self-triggering type carbon dioxide slow-release capsule for carbonized soil and a preparation method thereof.

[0005] Technical solution: The time-controlled self-triggering type carbon dioxide slow-release capsule for carbonized soil according to the present application comprises, from the inside to the outside, a gas-producing core and a slow-release coating layer; the gas-producing core is composed of a solid powder mixture that generates carbon dioxide gas in a water environment through chemical reaction; the slow-release coating layer is wrapped outside the gas-producing core and is composed of a water-soluble polymer material and clay particles; the thickness of the slow-release coating layer is used to control the rate of external water penetration into the gas-producing core, thereby achieving the timed release of carbon dioxide gas.

[0006] The preparation method of the time-controlled self-triggering carbon dioxide release capsule for carbonized soil comprises the following steps:

[0007] Step 1: mixing of the gas-producing core powder; in a dry environment, dry gas-producing formula powders are uniformly mixed in a set proportion;

[0008] Step 2: granulation, rolling and drying of the gas-producing core master batch;

[0009] Step 3: preparation of the coating powder; dry coating formula powders are uniformly mixed in a proportion under dry conditions;

[0010] Step 4: surface wetting of the core and wrapping of the release coating layer;

[0011] Step 5: low-temperature drying is performed, and after the drying is completed, the carbon dioxide release capsule end product with complete structure and stable performance is obtained;

[0012] The gas-producing formula powder of step 1 comprises sodium bicarbonate, calcium oxide and a cementing agent; wherein the sodium bicarbonate accounts for 80%-90% of the total mass of the core powder; the calcium oxide accounts for 10%-20%; and the cementing agent is selected from ethyl cellulose EC or polyvinylpyrrolidone PVP, and accounts for 1%-4%.

[0013] Further, the gas-producing formula powder of step 1 further comprises sodium bicarbonate, an acid-producing substance and a cementing agent; wherein the sodium bicarbonate accounts for 60%-70% of the total mass of the core powder; the acid-producing substance is selected from citric acid or aluminum sulfate, and accounts for 30%-40%; and the cementing agent is preferably EC or PVP, and accounts for 2%-4%.

[0014] Further, the granulation of the gas-producing core master batch of step 2 comprises:

[0015] The mixed powder prepared in step 1 is placed in a granulator, and the granulator is started to keep the mixed powder in a uniform and continuous rolling state in the disc; a small amount of anhydrous ethanol is sprayed during the rolling process, and the "small amount and multiple times" principle is followed, and each spraying lasts for about 1-2 seconds; after the powder preliminarily shows a tendency to stick and forms small particles, spraying is paused, and rolling lasts for about 3-5 minutes to preliminarily volatilize the ethanol and slightly dry the surface of the particles; the process is repeated until most of the powder forms a master batch with a particle size of 1-3 mm.

[0016] Further, the rolling and drying of the gas-producing core of step 2 comprises:

[0017] The formed master batch is continuously rolled for about 10-15 minutes to further dry and roll the surface of the master batch by using rolling friction and air flow, and the master batch forms moist particles with a relatively smooth surface and a certain mechanical strength; and low-temperature drying is performed for about 2 hours until the particles are completely dried and hardened and have no ethanol odor, and the gas-producing core particles are obtained.

[0018] Further, the step 3 coating powder is composed of water-soluble polymer material and dried clay particles, wherein the polymer material is selected from hydroxypropyl methyl cellulose HPMC, polyvinyl alcohol PVA or ethyl cellulose EC, and the mass of the polymer material accounts for 1-4% of the mass of the gas production core; the clay particles account for 10-20% of the mass of the gas production core, and the total mass of the polymer material and the clay particles is changed according to the designed thickness of the coating.

[0019] Further, the step 3 coating powder is composed of water-soluble polymer material and dried clay particles, wherein the polymer material is selected from hydroxypropyl methyl cellulose HPMC, polyvinyl alcohol PVA or ethyl cellulose EC, and the mass of the polymer material accounts for 1-4% of the mass of the gas production core; the clay particles account for 10-20% of the mass of the gas production core, and the total mass of the polymer material and the clay particles is changed according to the designed thickness of the coating.

[0020] Further, the step 4 core surface wetting includes placing the gas production core particles prepared in step 2 into a granulator, starting the granulator to make the core particles roll uniformly, and spraying anhydrous ethanol onto the rolling core particles for 0.5-1 seconds to make the surface slightly wet.

[0021] Further, the step 4 slow-release coating layer wrapping includes:

[0022] A small amount of the coating powder prepared in step 3 is uniformly sprayed on the surface of the wet particles, and the particles are continuously rolled for 1-2 minutes to make the coating powder firmly adhere, and the surface ethanol is volatilized and preliminarily dried by rolling and air flow; if the particles are too wet during the process, the spraying should be stopped immediately, and the rolling time should be extended for drying; this step is repeated until all the coating powder is used up, and a complete coating layer is formed on the surface of the particles; the total amount of the added coating powder and the number of cycles of this step are controlled to accurately control the thickness of the coating layer.

[0023] Further, the step 5 is carried out at a low temperature below 40°C, and the carbon dioxide slow-release capsule final product is stored in a cool and dry place.

[0024] Beneficial effects: Compared with the prior art, the present application has the following obvious advantages:

[0025] Simplified construction and reduced cost: The external carbon dioxide gas source, pressurization and injection equipment are omitted, the construction process is simplified, and the equipment and operation cost is reduced;

[0026] Uniform carbonization and high strength: Carbon dioxide is generated in situ inside the pile body, and the distribution is extremely uniform, which avoids the problems of surface hardening and internal unevenness caused by traditional methods of carbonization from the outside to the inside, thereby significantly improving the overall strength of the carbon sequestration soil;

[0027] Controllable and efficient release: By designing the thickness and composition of the slow-release coating layer, the timing of the start and continuous release of carbon dioxide can be precisely controlled, making it perfectly matched with the construction process and ensuring that carbon dioxide is efficiently utilized in the carbonization reaction.

[0028] With its diverse applications, the convenience and spontaneity of carbon dioxide sustained-release capsules make them suitable for use in underwater foundations, hydraulic dams, construction in narrow spaces and irregular structures, or disaster relief in remote areas. They can also be used as an auxiliary carbonization method for existing processes, making up for the shortcomings of existing carbonization processes.

[0029] Environmentally friendly: It utilizes the carbon sequestration properties of industrial by-products to achieve carbon dioxide sequestration, making it a green foundation treatment technology;

[0030] High safety: Similar to the ordinary concrete mixing process, only slow-release carbon dioxide capsules need to be added during the mixing process. The replacement of carbon dioxide injection avoids the dangers of pressurized carbon dioxide and eliminates the need for professional operators. Attached Figure Description

[0031] Figure 1 This is a flowchart of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of a carbon dioxide sustained-release capsule;

[0033] Figure 3 This is a schematic diagram illustrating the working principle of a carbon dioxide sustained-release capsule. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0035] like Figure 1 As shown, the method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to the present invention includes the following steps:

[0036] Step 1: Mixing the gas-generating core powder

[0037] In a dry environment, the dried gas-generating formulation powder is uniformly mixed according to a set ratio. Two feasible powder formulations are provided below:

[0038] Formula 1: Composed of sodium bicarbonate, calcium oxide, and a binder. Sodium bicarbonate, as a carbon dioxide generation source, accounts for 80%–90% of the total mass of the core powder; calcium oxide, as a catalyst and reaction initiator, accounts for 10%–20%; the binder, preferably ethyl cellulose (EC) or polyvinylpyrrolidone (PVP), is used to bind the mixture and improve the mechanical strength of the core, and accounts for 1%–4%.

[0039] Formula 2: composed of sodium bicarbonate, acid-generating substance and cementing agent. Among them, sodium bicarbonate as the source of carbon dioxide, accounts for 60-70% of the total mass of the core powder; acid-generating substance is preferably citric acid or aluminum sulfate, accounts for 30-40%; the cementing agent acts as above, preferably EC or PVP, accounts for 2-4%.

[0040] As shown in Figure 2 The structure of the carbon dioxide slow-release capsule is shown, from inside to outside, including a gas-producing core 1 and a slow-release coating layer 2; the gas-producing core 1 is composed of a solid powder mixture that can react chemically in a water environment and produce carbon dioxide gas; the slow-release coating layer 2 is wrapped outside the gas-producing core 1 and is composed of water-soluble polymer material and clay particles. The thickness of the slow-release coating layer 2 is used to control the rate of external moisture penetrating into the gas-producing core, so as to achieve the timed release of carbon dioxide gas.

[0041] Gas-producing core 1: It is the functional source of the capsule, composed of a uniform solid mixture of at least one carbonate / bicarbonate (such as sodium bicarbonate) and at least one acid agent or thermal decomposition catalyst (such as alum, calcium oxide). This mixture can continuously produce carbon dioxide gas through acid-base reaction or catalytic thermal decomposition pathway after encountering water.

[0042] Slow-release coating layer 2: It acts as a control valve, completely wrapped around the periphery of the gas-producing core 1. The coating layer is made of water-soluble polymer material (such as hydroxypropyl methyl cellulose HPMC) and clay particles, which precisely delays and regulates the process of external moisture penetrating into the gas-producing core 1 through its specific thickness and dissolution characteristics. This ensures that the capsule can start and maintain carbon dioxide release for a certain period of time after being buried in the soil, thus meeting the carbonation needs of deep soil. As shown in Figure 3 The working principle diagram of the carbon dioxide slow-release capsule is shown, and the chemical reaction equation involved is:

[0043] Formula 1: Exothermic reaction of calcium oxide and water CaO + H2O = CaOH2

[0044] Thermal decomposition of sodium bicarbonate 2NaHCO3≜Na2CO3+H2O+CO2↑

[0045] Formula 2: Reaction of sodium bicarbonate and acid to generate carbon dioxide (ionic reaction) HCO3−+H+=H2O+CO2↑

[0046] Step 2: Granulation, rolling and drying of gas-producing core master batch

[0047] Step 2-1: Granulation of gas-producing core master batch

[0048] Put the mixed powder prepared in Step 1 into the granulator, start the granulator, and keep the mixed powder in a uniform and continuous rolling state in the tray. Spray a small amount of anhydrous ethanol during the rolling process, and use the solubility of the adhesive in ethanol to make the powder stick together and form granular gas-producing cores. Follow the "little and often" principle, and each spraying lasts about 1 to 2 seconds. After the powder shows a tendency to stick together and form small particles, stop spraying and roll for about 3 to 5 minutes to allow the ethanol to evaporate and the particle surface to dry slightly. Repeat this process until most of the powder forms parent particles with a particle size of 1-3 mm.

[0049] Step 2-2: Rolling and drying of gas-producing cores

[0050] Continue rolling the formed parent particles for about 10-15 minutes to further dry and roll the surface of the particles using rolling friction and air flow to form smooth and mechanically strong wet particles. Dry at low temperature for about 2 hours until the particles are completely dry, hard, and have no ethanol odor, and the gas-producing core particles are obtained.

[0051] Step 3: Preparation of coating powder

[0052] Mix the dry coating powder in proportion under dry conditions. The coating powder is composed of water-soluble polymer material and dried clay particles, where the polymer material is preferably hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol (PVA), or ethyl cellulose (EC), with a mass of 1%–4% of the mass of the gas-producing core; clay particles account for 10%–20% of the mass of the gas-producing core, and the total mass of the polymer material and clay particles can be changed according to the thickness designed for the specific coating. The clay particles can form a complex pore structure together with the water-soluble polymer material, allowing water molecules to slowly penetrate the coating, and by adjusting the thickness of the coating layer, the time required for water to penetrate the core can be accurately controlled.

[0053] Step 4: Core surface wetting and slow-release coating layer wrapping

[0054] Step 4-1: Core surface wetting

[0055] Put the gas-producing core particles prepared in Step 2-2 into the granulator, start the granulator, and roll the core particles uniformly. Spray a small amount of anhydrous ethanol (about 0.5 to 1 second) onto the rolling core particles for a short time to make the surface slightly wet.

[0056] Step 4-2: Slow-release coating layer wrapping

[0057] The coating powder prepared in step 3 is sprayed on the surface of the wet particles in small amounts and evenly, and the particles are rolled for 1 to 2 minutes to make the coating powder firmly adhere and the surface ethanol volatilize and preliminarily dry by means of rolling and air flow. If the particles are too wet during the process, spraying should be stopped immediately and the rolling time should be extended for drying. This step is repeated until all the coating powder is used up and the particles form a complete coating layer on the surface. The thickness of the coating layer is accurately controlled by controlling the total amount of the coating powder added and the number of cycles of this step. The main function of the slow-release coating layer is to isolate the gas-producing core from the external magnesium oxide and other substances in the carbonized soil, ensuring that sodium bicarbonate and acid-producing substances react to generate carbon dioxide first.

[0058] Step 5: Final drying and storage

[0059] Low-temperature drying is performed below 40°C, and after drying is completed, the carbon dioxide slow-release capsules are taken out to obtain the final product with complete structure and stable performance, which is then stored in a cool and dry place.

[0061] The carbon dioxide slow-release capsules are uniformly mixed into the soil material for making carbonized soil at a mass content of 20%-30%, and are buried underground. When the water in the soil penetrates through the slow-release coating layer, the internal gas-producing core is triggered to react, thereby continuously generating carbon dioxide, which reacts with the solidifying agent in the soil to achieve carbonization and reinforcement of the soil. By controlling the thickness of the coating, the gas-producing reaction time can be controlled to achieve a time-controlled effect.

Claims

1. A time-controlled, self-triggered, sustained-release carbon dioxide capsule for carbonized soil, characterized in that, From the inside out, it includes a gas-generating core (1) and a slow-release coating layer (2); the gas-generating core (1) is composed of a solid powder mixture that undergoes a chemical reaction in a water environment to generate carbon dioxide gas; the slow-release coating layer (2) is wrapped around the gas-generating core (1) and is composed of water-soluble polymer materials and clay particles. The thickness of the slow-release coating layer (2) is used to control the rate at which external moisture penetrates into the gas-generating core, thereby realizing the timed release of carbon dioxide gas.

2. A method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil, characterized in that, Includes the following steps: Step 1: Mixing the core gas-generating powder; Under a dry environment, mix the dried gas-generating formula powder evenly according to the set ratio; Step 2: Granulation, compaction and drying of gas-generating core masterbatch; Step 3: Preparation of coating powder; Mix the dried coating powder formula evenly in proportion under dry conditions; Step 4: Wetting the core surface and encapsulating it with a slow-release coating layer; Step 5: Perform low-temperature drying. After drying, remove the capsules to obtain a final product of carbon dioxide sustained-release capsules with intact structure and stable performance. The gas-generating powder in step 1 consists of sodium bicarbonate, calcium oxide, and a binder; wherein sodium bicarbonate accounts for 80%–90% of the total mass of the core powder; calcium oxide accounts for 10%–20%; and the binder is selected from ethyl cellulose EC or polyvinylpyrrolidone PVP, accounting for 1%–4%.

3. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, The gas-generating formulation powder in step 1 also includes sodium bicarbonate, acid-generating substances, and a binder; wherein, sodium bicarbonate accounts for 60%–70% of the total mass of the core powder; the acid-generating substances are selected from citric acid or aluminum sulfate, accounting for 30%–40%; and the binder is preferably EC or PVP, accounting for 2%–4%.

4. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, Step 2, granulation of the gas-generating core masterbatch, includes: Place the mixed powder prepared in step 1 into a granulator, start the granulator, and keep the mixed powder rolling evenly and continuously in the pan. During the rolling process, spray a small amount of anhydrous ethanol, following the principle of "small amount, multiple times". Each spray lasts for about 1 to 2 seconds. After the powder initially shows a tendency to stick together and forms small particles, stop spraying and roll for about 3 to 5 minutes to allow the ethanol to initially evaporate and the particle surface to dry slightly. Repeat this process until most of the powder forms masterbatch with a particle size of 1-3 mm.

5. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, Step 2, core compaction and drying of the gas-producing area, includes: The formed masterbatch is continuously rolled for about 10-15 minutes. The rolling friction and air flow are used to further dry and compact its surface, forming relatively smooth, moist particles with a certain mechanical strength. The particles are then dried at low temperature for about 2 hours until they are completely dry, hard, and have no ethanol odor, thus obtaining the gas-producing core particles.

6. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, The coating powder in step 3 consists of water-soluble polymer materials and dried clay particles. The polymer materials are selected from hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol (PVA), or ethyl cellulose (EC), and their mass accounts for 1%–4% of the mass of the gas-generating core. The clay particles account for 10%–20% of the mass of the gas-generating core, and the total mass of the polymer materials and clay particles added varies according to the thickness designed for the specific coating.

7. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, The coating powder in step 2 is composed of water-soluble polymer materials and dried clay particles. The clay particles and water-soluble polymer materials together form a porous structure, allowing water molecules to slowly permeate the coating. By adjusting the thickness of the coating layer, the time required for soil moisture to penetrate to the core can be precisely controlled.

8. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, Step 4, core surface wetting, involves placing the gas-generating core particles obtained in step 2 into a granulator, starting the granulator to make the core particles roll evenly, and briefly spraying anhydrous ethanol onto the rolling core particles for 0.5-1 seconds to make their surface slightly wet.

9. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, The sustained-release coating layer in step 4 includes: Sprinkle a small amount of the coating powder prepared in step 3 evenly onto the surface of the damp granules, and continue rolling the granules for 1 to 2 minutes to ensure that the coating powder adheres firmly. The rolling and airflow will help the surface ethanol evaporate and begin to dry. If the granules become too wet during the process, stop spraying immediately and extend the rolling time to allow them to dry. Repeat this step until all the coating powder has been used up and a complete coating layer has been formed on the surface of the granules. The thickness of the coating layer can be precisely controlled by controlling the total amount of coating powder added and the number of cycles in this step.

10. The method for preparing time-controlled self-triggered carbon dioxide sustained-release capsules for carbonized soil according to claim 2, characterized in that, Step 5 includes low-temperature drying and storing the final product of the carbon dioxide sustained-release capsules in a cool, dry place.

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