A high-efficiency mineralization filling method using phase change microcapsules

Abstract

The application discloses a high-efficiency mineralization filling method using phase change microcapsules, and relates to the technical field of coal mining, which comprises the following steps: preparing phase change microcapsules, wherein the phase change microcapsules comprise a shell and a composite core material filled in the shell, and the composite core material comprises a mineralization activator and a phase change material; stirring the filling material and water uniformly to obtain a filling slurry and adding the phase change microcapsules into the filling slurry; conveying the filling slurry mixed with the phase change microcapsules to a filling area; introducing CO2 into the filling area to contact the filling slurry and cause a mineralization reaction; the phase change microcapsules absorb heat released in the mineralization reaction process, and when the phase change threshold is reached, the phase change material is phase-changed to produce instantaneous volume expansion stress, the shell is broken, and the mineralization activator in the phase change microcapsules is released to accelerate the mineralization reaction. The application can effectively reduce the resistance of the filling slurry during conveying, avoid the occurrence of pipe blockage accidents, greatly improve the filling efficiency, and improve the stability of the filling body.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a highly efficient mineralization filling method utilizing phase change microcapsules. Background Technology

[0002] Coal mining processes create numerous goaf areas, which not only pose risks such as spontaneous combustion of residual coal and water accumulation, but also cause surface subsidence and aquifer damage. Cemented backfill mining technology uses cement and other cementing materials to mix fly ash, coal gangue, and other coal-based solid wastes, preparing backfill materials for refilling the goaf areas, thereby controlling surface subsidence and disposing of solid waste. Meanwhile, the large amounts of CO2 emitted during coal production and utilization have become a pressing issue. CO2 capture, utilization, and storage technologies can effectively alleviate carbon emission pressures. Among these, mineralization storage can utilize cemented backfill materials as CO2 absorption carriers to achieve long-term geological CO2 sequestration.

[0003] To improve mineralization efficiency, mineralization activators are typically added to the backfill slurry. However, these activators react rapidly with other materials in the slurry, leading to problems such as sedimentation and pipe blockage during transport, thus affecting efficiency. Furthermore, the mineralization reaction of CO2 with the backfill slurry quickly forms a dense carbonate deposit. This carbonate precipitate surrounds unreacted particles, hindering subsequent hydration and mineralization reactions. Simultaneously, the strong exothermic heat released during the mineralization reaction accumulates rapidly within the large-volume backfill, and the resulting temperature difference can easily cause cracking of the backfill, compromising the stability of the support structure. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one objective of this invention is to propose a highly efficient mineralization filling method utilizing phase change microcapsules. This mineralization filling method can effectively reduce the frictional resistance during filling slurry transport, avoid pipe blockage accidents, greatly improve filling efficiency, and also enhance the stability of the filling material.

[0005] According to the present invention, a highly efficient mineralization filling method utilizing phase change microcapsules includes the following steps: Step S1: Fabricate phase change microcapsules. The phase change microcapsules include a shell and a composite core material filled in the shell. The composite core material is formed by uniformly mixing a variety of core material raw materials, including a mineralization activator and a phase change material. First, the various core material raw materials are uniformly mixed to form the composite core material. Then, the composite core material is wrapped with a shell substrate and dried to obtain the phase change microcapsules. Step S2: Mix the filling material and water evenly at the ground mixing plant to obtain filling slurry. Add the phase change microcapsules to the filling slurry and mix evenly again. Step S3: Using a delivery pipeline and a delivery pump, the filling slurry mixed with the phase change microcapsules obtained in step S2 is delivered to the filling area; Step S4: After the filling slurry containing the phase change microcapsules is transported to the filling area, CO2 is introduced into the filling area through a pre-embedded gas injection pipeline to contact the filling slurry and cause a mineralization reaction. Step S5: During the mineralization reaction, heat will be released. The phase change microcapsule will absorb the heat released during the mineralization reaction. When the absorbed heat reaches the phase change threshold of the phase change microcapsule, the phase change material inside the phase change microcapsule undergoes a phase change, generating instantaneous volume expansion stress, which bursts the shell of the phase change microcapsule from the inside out. The mineralization activator inside the phase change microcapsule is released, accelerating the mineralization reaction between the filling slurry and CO2.

[0006] Optionally, the composite core material further includes a density modifier.

[0007] Optionally, in step S1, the mass ratio of each material in the composite core material ranges as follows: mineralization activator 40%~60%, phase change material 30%~50%, and density regulator 5%~15%.

[0008] Optionally, in step S2, the added mass of the phase change microcapsules is 1.5wt%-3.0wt% of the mass of the filling material.

[0009] Optionally, the conveying pipeline is provided with a drag-reducing layer.

[0010] Optionally, in step S4, introducing CO2 into the filling area includes a first stage and a second stage. In the first stage, the temperature of the CO2 introduced is 5°C to 15°C, and the duration is 10 min to 30 min. After the first stage ends, the second stage begins, and the temperature of the CO2 introduced in the second stage is room temperature.

[0011] Optionally, when the phase change microcapsule reaches its phase change threshold, the instantaneous volume expansion stress P of the phase change material inside the phase change microcapsule and the ultimate tensile strength of the shell are... The following relationship exists between them: In the formula, R is the thickness of the shell of the phase change microcapsule, in mm, ranging from 0.5 mm to 5 mm; R is the radius of the phase change microcapsule, in mm, ranging from 0.1 mm to 2.5 mm. The volume change rate of the phase change material within the phase change microcapsule during a phase change is 10% to 15%.

[0012] Optionally, the mineralization activator includes CaO, Na2CO3, and C6H5Na3O7, wherein the mass ratio of each component is CaO: 55%~70%, Na2CO3: 25%~40%, and C6H5Na3O7: 1%~10%; the phase change material is n-eicosane; the density regulator is hollow glass microspheres; and the shell of the phase change microcapsule is made of urea-formaldehyde resin, polyurethane, or ethyl cellulose.

[0013] Optionally, the apparent density of the phase change microcapsules With respect to the overall density of the filling slurry The following relationship must be satisfied: .

[0014] Compared with the prior art, the efficient mineralization filling method utilizing phase change microcapsules of the present invention has the following advantages: (1) In this invention, the mineralization activator is added to the filling slurry by means of phase change microcapsules. The mineralization activator is encapsulated by the shell, which can avoid the filling slurry from directly contacting the mineralization activator and reacting rapidly during pipeline transportation. This can effectively reduce the frictional resistance of the filling slurry transportation, avoid pipe blockage accidents, and greatly improve filling efficiency.

[0015] (2) The phase change microcapsules of the present invention contain phase change materials. The phase change materials absorb the heat released during the mineralization reaction. When the phase change threshold of the phase change materials is reached, the volume expansion stress generated by the phase change materials can break the shell of the phase change microcapsules, thereby releasing the mineralization activator. The mineralization activator reacts with CO2, thereby improving the efficiency of the mineralization reaction and increasing the amount of CO2 sealed (i.e., carbon fixation).

[0016] (3) The present invention utilizes the latent heat characteristics of phase change materials to absorb the heat released during the mineralization reaction, thereby effectively suppressing the generation of cracks caused by thermal stress, greatly improving the compressive strength of the filling body, and ensuring the integrity and stability of the filling body structure.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of an efficient mineralization filling method using phase change microcapsules according to an embodiment of the present invention; Figure 2Compressive strength diagrams at various ages of Examples 1, 2 and Comparative Examples of the High-Efficiency Mineralization Filling Method Utilizing Phase Change Microcapsules according to embodiments of the present invention; Figure 3 The graphs show the carbon sequestration at different ages of Examples 1, 2 and the comparative examples of the efficient mineralization filling method using phase change microcapsules according to embodiments of the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] The following is for reference. Figures 1-3 This invention describes an efficient mineralization filling method utilizing phase change microcapsules according to embodiments of the present invention.

[0021] Please see Figure 1 The efficient mineralization filling method using phase change microcapsules according to embodiments of the present invention includes the following steps: Step S1: Fabricate phase change microcapsules. The phase change microcapsules include a shell and a composite core material filled inside the shell. The composite core material is made by uniformly mixing a variety of core material raw materials, including a mineralization activator and a phase change material. First, the various core material raw materials are uniformly mixed to form a composite core material. Then, the composite core material is wrapped with a shell substrate and dried to obtain the phase change microcapsules.

[0022] Optionally, the mineralization activator may include CaO, Na2CO3, and C6H5Na3O7, wherein the mass ratios of each component are CaO: 55%~70%, Na2CO3: 25%~40%, and C6H5Na3O7: 1%~10%. The phase change material may be n-eicosane, in which case the phase change threshold of the phase change material is 36.8℃. The shell of the phase change microcapsule may be made of urea-formaldehyde resin, polyurethane, or ethyl cellulose.

[0023] Step S2: At the ground mixing plant, the backfill material and water are mixed evenly to obtain a backfill slurry. The phase change microcapsules are then added to the backfill slurry and mixed evenly again. Optionally, the backfill material may include coal gangue, fly ash, and cement.

[0024] Step S3: Using a delivery pipeline and a delivery pump, the filling slurry mixed with phase change microcapsules obtained in step S2 is transported to the filling area. Optionally, the filling area can be an underground goaf or other rock mass fissures.

[0025] Step S4: After the filling slurry containing phase change microcapsules is transported to the filling area, CO2 is introduced into the filling area through the pre-embedded gas injection pipeline to contact the filling slurry and cause a mineralization reaction.

[0026] Step S5: During the mineralization reaction, heat will be released. The phase change microcapsules will absorb the heat released during the mineralization reaction. When the absorbed heat reaches the phase change threshold of the phase change microcapsules, the phase change material inside the phase change microcapsules undergoes a phase change, generating instantaneous volume expansion stress, which bursts the shell of the phase change microcapsules from the inside out. The mineralization activator inside the phase change microcapsules is released, accelerating the mineralization reaction between the filling slurry and CO2.

[0027] The efficient mineralization filling method utilizing phase change microcapsules according to the present invention has the following beneficial effects: (1) In this invention, the mineralization activator is added to the filling slurry by means of phase change microcapsules. The mineralization activator is encapsulated by the shell, which can avoid the filling slurry from directly contacting the mineralization activator and reacting rapidly during pipeline transportation. This can effectively reduce the frictional resistance of the filling slurry transportation, avoid pipe blockage accidents, and greatly improve filling efficiency.

[0028] (2) The phase change microcapsules of the present invention contain phase change materials. The phase change materials absorb the heat released during the mineralization reaction. When the phase change threshold of the phase change materials is reached, the volume expansion stress generated by the phase change materials can break the shell of the phase change microcapsules, thereby releasing the mineralization activator. The mineralization activator reacts with CO2, thereby improving the efficiency of the mineralization reaction and increasing the amount of CO2 sealed (i.e., carbon fixation).

[0029] (3) The present invention utilizes the latent heat characteristics of phase change materials to absorb the heat released during the mineralization reaction, thereby effectively suppressing the generation of cracks caused by thermal stress, greatly improving the compressive strength of the filling body, and ensuring the integrity and stability of the filling body structure.

[0030] In some embodiments of the present invention, the composite core material further includes a density modifier. That is, the shell of the phase change microcapsule also contains a density modifier. By incorporating the density modifier, the apparent density of the phase change microcapsule in the filling slurry can be reduced, thereby better reducing frictional resistance, preventing pipe blockage accidents, and greatly improving filling efficiency.

[0031] Optionally, the density regulator is hollow glass microspheres.

[0032] Furthermore, by adjusting the doping amount of hollow glass microspheres, the apparent density of the phase change microcapsules was increased. Overall density of the filling slurry The following relationship must be satisfied: .

[0033] This allows the phase change microcapsules to remain in a state of isodense suspension in the filling slurry, preventing stratification and sedimentation during the pumping process.

[0034] In some embodiments of the present invention, in step S1, the mass ratio of each material in the composite core material ranges as follows: mineralization activator 40%~60%, phase change material 30%~50%, and density regulator 5%~15%.

[0035] In some embodiments of the present invention, in step S2, the added mass of phase change microcapsules is 1.5wt%-3.0wt% of the mass of the filling material.

[0036] In some embodiments of the present invention, the delivery pipeline is provided with a drag-reducing layer. The drag-reducing layer can be formed of a polymeric material, polyacrylamide, thereby forming a highly lubricated, low-shear fluid film on the inner wall of the delivery pipeline, reducing wear on the phase change microcapsules during delivery, and thus preventing the phase change microcapsules from rupturing during the pipeline delivery of the filling slurry.

[0037] In some embodiments of the present invention, step S4, introducing CO2 into the filling area includes a first stage and a second stage. In the first stage, the temperature of the CO2 introduced is 5°C to 15°C, and the duration is 10 min to 30 min. After the first stage, the second stage begins, in which the temperature of the CO2 introduced is room temperature. Specifically, the CO2 gas introduced in the first stage is pre-cooled to 5°C to 15°C. By injecting low-temperature CO2, the temperature of the filling slurry is initially locally reduced, slowing down the initial mineralization reaction rate between the filling slurry and CO2, and avoiding the formation of hydration products due to excessively rapid early reaction. After 10 min to 30 min, the process switches to room temperature CO2 injection in the second stage.

[0038] Optionally, the pre-embedded gas injection pipeline is a porous dispersion gas injection system, consisting of a main pipeline and uniformly distributed branch pipelines with micropores, with a gas injection pressure of 0.1MPa~0.5MPa.

[0039] In some embodiments of the present invention, when the phase change microcapsule reaches its phase change threshold, the instantaneous volume expansion stress P of the phase change material inside the phase change microcapsule and the ultimate tensile strength of the shell are... The following relationship exists between them: In the formula, R is the thickness of the shell of the phase change microcapsule, in mm, ranging from 0.5 mm to 5 mm; R is the radius of the phase change microcapsule, in mm, ranging from 0.1 mm to 2.5 mm. The volume change rate of the phase change material within the phase change microcapsule during a phase change is 10% to 15%.

[0040] By adjusting the instantaneous volume expansion stress P of the phase change material within the phase change microcapsule and the ultimate tensile strength of the shell... The above relationship is satisfied, ensuring that the instantaneous volume expansion stress of the phase change material within the phase change microcapsule is much greater than the ultimate tensile strength of the microcapsule shell. This guarantees that the phase change microcapsule can fully rupture when it reaches its phase change threshold, allowing the mineralization activator to be released smoothly, thus ensuring the mineralization reaction can proceed fully.

[0041] The following describes specific examples (Example 1, Example 2, and Comparative Example). In these examples, the water-cement ratio is fixed at 0.5, meaning the mass ratio of water to filling material is 0.5.

[0042] Example 1:

[0043] A highly efficient mineralization filling method utilizing phase change microcapsules, the specific steps of which are as follows: Step S1: Weigh the core material raw materials for the phase change microcapsules according to the following mass ratios: 40% mineralization activator (where the mass ratio of each component is CaO:Na2CO3:C6H5Na3O7=0.6:0.35:0.05), 50% phase change material (eicosane), and 10% density regulator (hollow glass microspheres). Mix the core material raw materials evenly to obtain the composite core material of the phase change microcapsules. Then, encapsulate it with a shell substrate (ethyl cellulose) and place it in a drying oven at 20°C for vacuum drying for 6 hours to obtain the phase change microcapsules.

[0044] Step S2: At the ground mixing plant, 60% by mass of coal gangue with a particle size of 5mm, 30% by mass of fly ash, 8% by mass of cement and water are poured into the mixing drum and stirred evenly at a speed of 300r / min for 5 minutes to obtain filling slurry. Then, 2% by mass of phase change microcapsules are added to the filling slurry and stirred at a speed of 100r / min for 5 minutes.

[0045] Step S3: Pour the filling slurry mixed with phase change microcapsules obtained in step S2 into a cylindrical mold with a size of 50×100mm, and place it in a CO2 curing chamber for curing. The curing periods are 7 days, 14 days and 28 days. The temperature of the curing chamber is 20℃ and the humidity is 99%.

[0046] Step S4: The filling materials cured for 7 days, 14 days and 28 days were taken out of the curing box for compression test and thermogravimetric test. The results are shown in Table 1 below.

[0047] Table 1 Example 2:

[0048] A highly efficient mineralization filling method utilizing phase change microcapsules, the specific steps of which are as follows: Step S1: Weigh the core material raw materials for the phase change microcapsules according to the following mass ratios: 60% mineralization activator (where the mass ratio of each component is CaO:Na2CO3:C6H5Na3O7=0.6:0.35:0.05), 30% phase change material (eicosane), and 10% density regulator (hollow glass microspheres). Mix the core material raw materials evenly to obtain the composite core material of the phase change microcapsules. Then, encapsulate it with a shell substrate (ethyl cellulose) and place it in a drying oven at 20°C for vacuum drying for 6 hours to obtain the phase change microcapsules.

[0049] Step S2: At the ground mixing plant, 60% by mass of coal gangue with a particle size of 5mm, 30% by mass of fly ash, 8% by mass of cement and water are poured into the mixing drum and stirred evenly at a speed of 300r / min for 5 minutes to obtain filling slurry. Then, 2% by mass of phase change microcapsules are added to the filling slurry and stirred at a speed of 100r / min for 5 minutes.

[0050] Step S3: Pour the filling slurry mixed with phase change microcapsules obtained in step S2 into a cylindrical mold with a size of 50×100mm, and place it in a CO2 curing chamber for curing. The curing periods are 7 days, 14 days and 28 days. The temperature of the curing chamber is 20℃ and the humidity is 99%.

[0051] Step S4: Remove the filling materials after curing for 7 days, 14 days, and 28 days from the curing box for compression tests and thermogravimetric tests. The results are shown in Table 2 below.

[0052] Table 2 Comparative example: A highly efficient mineralization filling method utilizing phase change microcapsules, the specific steps of which are as follows: In step S1, 60% by mass of coal gangue with a particle size of 5mm, 30% by mass of fly ash, 8% by mass of cement, and water are poured into the mixing drum at the ground mixing plant. The mixture is stirred evenly at a speed of 300r / min for 5 minutes to obtain filling slurry. Then, 2% by mass of mineralization activator (where the mass ratio of each component is CaO:Na2CO3:C6H5Na3O7=0.6:0.35:0.05) is added and stirred at a speed of 100r / min for 5 minutes.

[0053] Step S2: Pour the filling slurry obtained in step S1 into a cylindrical mold with a size of 50×100mm, and place it in a CO2 curing chamber for curing. The curing periods are 7 days, 14 days and 28 days. The temperature of the curing chamber is 20℃ and the humidity is 99%.

[0054] Step S3: Remove the filling materials after curing for 7 days, 14 days, and 28 days from the curing box for compression tests and thermogravimetric tests. The results are shown in Table 3 below.

[0055] Table 3 By comparing the data in Tables 1, 2, and 3, and combining them... Figure 2 and Figure 3 The present invention utilizes a highly efficient mineralization filling method based on phase change microcapsules. After incorporating phase change microcapsules, the compressive strength and carbon fixation performance of the filling material are significantly improved. Furthermore, the compressive strength and carbon fixation gradually increase with increasing curing age. Additionally, the compressive strength and carbon fixation of the filling material increase with increasing content of the mineralization activator in the phase change microcapsules. In other words, the highly efficient mineralization filling method based on phase change microcapsules of the present invention can not only effectively reduce frictional resistance during slurry transportation, avoiding pipe blockage accidents and greatly improving filling efficiency, but also increase CO2 sequestration (i.e., carbon fixation) and the compressive strength of the filling material.

[0056] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0057] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A highly efficient mineralization filling method utilizing phase change microcapsules, characterized in that, Includes the following steps: Step S1: Fabricate phase change microcapsules. The phase change microcapsules include a shell and a composite core material filled in the shell. The composite core material is formed by uniformly mixing a variety of core material raw materials, including a mineralization activator and a phase change material. First, the various core material raw materials are uniformly mixed to form the composite core material. Then, the composite core material is wrapped with a shell substrate and dried to obtain the phase change microcapsules. Step S2: Mix the filling material and water evenly at the ground mixing plant to obtain filling slurry. Add the phase change microcapsules to the filling slurry and mix evenly again. Step S3: Using a delivery pipeline and a delivery pump, the filling slurry mixed with the phase change microcapsules obtained in step S2 is delivered to the filling area; Step S4: After the filling slurry containing the phase change microcapsules is transported to the filling area, CO2 is introduced into the filling area through a pre-embedded gas injection pipeline to contact the filling slurry and cause a mineralization reaction. Step S5: During the mineralization reaction, heat will be released. The phase change microcapsule will absorb the heat released during the mineralization reaction. When the absorbed heat reaches the phase change threshold of the phase change microcapsule, the phase change material inside the phase change microcapsule undergoes a phase change, generating instantaneous volume expansion stress, which bursts the shell of the phase change microcapsule from the inside out. The mineralization activator inside the phase change microcapsule is released, accelerating the mineralization reaction between the filling slurry and CO2.

2. The efficient mineralization filling method using phase change microcapsules according to claim 1, characterized in that, The composite core material also includes a density regulator.

3. The efficient mineralization filling method using phase change microcapsules according to claim 2, characterized in that, In step S1, the mass ratio of each material in the composite core material ranges as follows: mineralization activator 40%~60%, phase change material 30%~50%, and density regulator 5%~15%.

4. The efficient mineralization filling method using phase change microcapsules according to claim 1, characterized in that, In step S2, the added mass of the phase change microcapsules is 1.5wt%-3.0wt% of the mass of the filling material.

5. The efficient mineralization filling method using phase change microcapsules according to claim 1, characterized in that, The conveying pipeline is equipped with a drag-reducing layer.

6. The efficient mineralization filling method using phase change microcapsules according to claim 1, characterized in that, In step S4, introducing CO2 into the filling area includes a first stage and a second stage. In the first stage, the temperature of the CO2 introduced is 5°C to 15°C and the duration is 10 min to 30 min. After the first stage ends, the second stage begins, in which the temperature of the CO2 introduced is room temperature.

7. The efficient mineralization filling method using phase change microcapsules according to claim 1, characterized in that, When the phase change microcapsule reaches its phase change threshold, the instantaneous volume expansion stress P of the phase change material inside the microcapsule and the ultimate tensile strength of the shell are... The following relationship exists between them: In the formula, The thickness of the shell of the phase change microcapsule is expressed in mm and ranges from 0.5 mm to 5 mm. R is the radius of the phase change microcapsule, in mm, and its range is 0.1 mm to 2.5 mm; The volume change rate of the phase change material within the phase change microcapsule during a phase change is 10% to 15%.

8. The efficient mineralization filling method using phase change microcapsules according to claim 2, characterized in that, The mineralization activator includes CaO, Na2CO3 and C6H5Na3O7, wherein the mass ratio of each component is CaO: 55%~70%, Na2CO3: 25%~40%, and C6H5Na3O7: 1%~10%. The phase change material is n-eicosane; The density regulator is hollow glass microspheres; The shell of the phase change microcapsule is made of urea-formaldehyde resin, polyurethane, or ethyl cellulose.

9. The efficient mineralization filling method using phase change microcapsules according to claim 8, characterized in that, Apparent density of the phase change microcapsules With respect to the overall density of the filling slurry The following relationship must be satisfied: 。

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