A method for preparing a paste filling body with carbon sequestration and energy absorption functions based on SC-CO2 foaming

Abstract

The application discloses a method for preparing a paste filling body with carbon sequestration and energy absorption functions based on SC-CO2 foaming, and belongs to the technical field of coal mining. After being crushed and ground, coal-based solid waste raw materials are mixed with mixed water at a speed of less than 60 r / min to prepare coal-based solid waste slurry; supercritical CO2 is continuously injected in the mixing process until the same pressure is reached, the supercritical CO2 penetrates into the coal-based solid waste slurry, forming a supercritical CO2 and coal-based solid waste slurry mixture, the supercritical CO2 and coal-based solid waste slurry mixture is mixed by a turbine type mixer to form a foamed paste filling body masterbatch, the foamed paste filling body masterbatch is controlled to keep temperature and pressure for 10-30 min in a high-temperature and high-pressure mixer, and then is rapidly depressurized to form a large amount of coal-based solid waste foamed paste filling body taking supercritical CO2 as a bubble nucleus, the foaming of the paste filling body masterbatch is realized, and the filling body has the advantages of low density, good heat insulation performance and controllable cell structure.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, specifically to a method for preparing a paste-like filler with carbon fixation and energy absorption functions based on SC-CO2 foaming. Background Technology

[0002] Coal plays a vital role in ensuring my country's energy security, but it still faces a fundamental shift from traditional utilization methods to low-carbon, high-efficiency mining. With the increasing severity of global climate change and carbon emissions, the mining industry urgently needs to develop backfill materials with carbon sequestration capabilities to reduce carbon dioxide emissions and promote green mine construction. Solving the practical problem of large-scale goaf formation and significant CO2 emissions during coal mining and consumption is now a pressing issue.

[0003] The preparation of traditional carbon-fixing backfill materials requires significant time and resources, and typically generates substantial carbon dioxide emissions during the process. Traditional backfill materials are mostly based on cement and gangue or waste rock, resulting in high density and poor energy absorption capacity, making it difficult to meet the high compressive strength and high energy absorption requirements for dynamic disaster prevention in mining. Furthermore, existing paste-based backfill materials also have significant shortcomings in terms of lightweighting and thermal insulation, making them ill-suited to the actual needs of dynamic environments and dynamic disaster prevention in mines. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems in the prior art and provide a method for preparing a paste filling material with carbon fixation and energy absorption function based on SC-CO2 foaming. The paste filling material prepared has low density, high strength, good thermal insulation performance and controllable cell structure, and can be used for a long time under various extreme environmental conditions, and can better adapt to the actual needs of mine dynamic environment and dynamic disaster prevention and control.

[0005] The present invention provides a method for preparing a paste-like filler with carbon fixation and energy absorption function based on SC-CO2 foaming, comprising the following steps: crushing and grinding coal-based solid waste raw materials and mixing them with mixing water at a speed of less than 60 r / min to prepare a coal-based solid waste slurry;

[0006] The prepared coal-based solid waste slurry is injected into a preheated high-temperature and high-pressure mixer for stirring, and supercritical CO2 is continuously injected during the stirring process. The temperature of the high-temperature and high-pressure mixer is maintained above 31°C and the pressure is maintained above 7.3 MPa, so that the supercritical CO2 is kept in a supercritical stable state in the high-temperature and high-pressure mixer, and can fully penetrate into the coal-based solid waste slurry to form a mixture of supercritical CO2 and coal-based solid waste slurry.

[0007] Supercritical CO2 and coal-based solid waste slurry are mixed and stirred under high temperature and high pressure to form foam paste filling material masterbatch. The foam paste filling material masterbatch is then depressurized after being kept at high temperature and high pressure for 10-30 minutes. During the depressurization process, supercritical CO2 changes from supercritical to gaseous state and gradually forms bubbles in the coal-based solid waste slurry, forming a large number of paste filling materials with carbon fixation and energy absorption functions with supercritical CO2 as bubble nuclei.

[0008] As a preferred embodiment, the volume of the coal-based solid waste slurry injection is 1 / 3 to 1 / 2 of the volume of the high-temperature and high-pressure mixer.

[0009] As a preferred method, when preparing coal-based solid waste slurry, the mixture is stirred at a speed of less than 60 r / min for 6-10 min.

[0010] As a preferred method, the mixing speed of the supercritical CO2 and coal-based solid waste slurry mixture in the high-temperature and high-pressure mixer is 300-400 r / min, and the mixing time is 8-10 min.

[0011] As a preferred method, when the foam paste filler masterbatch is depressurized after heat preservation and pressure holding, the depressurization rate is controlled at 2.5MPa / s, so that the pressure in the high temperature and high pressure mixer is gradually reduced to 0-7.4MPa.

[0012] As a preferred method, the proportion of particles with a diameter of less than 20μm in the powder formed after crushing and grinding coal-based solid waste raw materials reaches more than 15%.

[0013] The present invention also provides a method for preparing a paste filler with carbon fixation and energy absorption function based on SC-CO2 foaming, and the obtained paste filler with carbon fixation and energy absorption function.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The coal-based solid waste raw material in the present invention is crushed and ground into fine particles with a particle size of less than 20 μm. At the same time, in the process of preparing the coal-based solid waste slurry, a low-speed stirring method is adopted, which can avoid the mixing of air. At the same time, when injecting supercritical CO2 into the prepared coal-based solid waste slurry, it is injected while stirring under high temperature and high pressure. This can ensure that the supercritical CO2 is stable in the supercritical state and can penetrate more fully into the coal-based solid waste slurry, forming a mixture of supercritical CO2 and coal-based solid waste slurry. At the same time, the mixture of supercritical CO2 and coal-based solid waste slurry is mixed and stirred under high temperature and high pressure, which avoids the problem that when supercritical carbon dioxide is injected into the coal-based solid waste slurry, the slurry is compacted due to high pressure, making it difficult to form pores and preventing the formation of foamed paste filling body. The carbon fixation and energy absorption paste filler prepared by the above preparation method of the present invention has excellent performance, with advantages such as low density, light weight, high compressive strength, good thermal insulation performance and controllable cell structure. It can be used for a long time under various extreme environmental conditions and meets the actual needs of mine dynamic environment and dynamic disaster prevention and control.

[0015] In this invention, due to the dissolution of CO2 and the reaction with water to produce carbonic acid, the minerals in the slurry of the coal-based solid waste foamed paste filling body undergo carbonation and hardening, giving the filling body better strength and durability. Furthermore, due to the dissolution of CO2 bubbles and the chemical reaction effect, the number of pores with a diameter greater than 1000 nanometers is reduced, which enhances the compressive strength of the coal-based solid waste foamed paste filling body slurry and minimizes the negative impact of increased porosity on the coal-based solid waste CO2 foamed paste filling body.

[0016] This invention utilizes supercritical carbon dioxide as a physical foaming agent. Compared to traditional chemical foaming agents, it is non-toxic, environmentally friendly, and low-cost to produce. It exhibits high diffusivity and strong permeability, and its carbonization reaction with coal-based solid waste slurry does not produce harmful byproducts. Its foaming efficiency is significantly higher than that of traditional chemical foaming agents. Furthermore, the proportion of the foaming agent can be dynamically adjusted based on the coal-based solid waste production in a designated space to be filled (mined-out area), saving materials and sealing CO2 within the foam pores. This creates internal pressure to withstand the dynamic and static loads imposed by the overlying mining rock mass, while simultaneously absorbing and dissipating the stress wave propagation generated by the fracturing of the overlying strata. Ultimately, this achieves near-zero ecological damage, near-zero rockburst, and negative carbon mining throughout the entire coal development and utilization process. This invention addresses the requirements of lightweight, high compressive strength, energy absorption, carbon sequestration, and low cost for mine filling materials, ensuring a stable energy supply, promoting the green and low-carbon development of coal resources, and solving the practical problems of safe, efficient, green, and low-carbon coal mining. It has significant theoretical and practical implications. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the preparation principle of a paste-like filler with carbon fixation and energy absorption function according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of a paste filling device with carbon fixation and energy absorption function according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of a paste filling device with carbon fixation and energy absorption function placed in a constant temperature chamber according to an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0021] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described objects changes, the relative positional relationship may also change accordingly.

[0022] In the field of mine backfilling, backfill materials with uniform and fine pore structure have outstanding energy absorption performance, which is in high demand for stress wave absorption in underground mines. The pore structure inside the backfill material can deform to absorb and dissipate impact energy, exhibiting excellent gradient energy absorption performance, which is of great significance for preventing chain mine dynamic disasters such as rock bursts and gas explosions.

[0023] With increasing demands for environmental protection and mine safety, and driven by the "dual-carbon driven high-quality development" strategy, low-carbon foaming technology using supercritical CO2 as a foaming agent has gained market recognition in the polymer foaming field. Its excellent carbon fixation and energy absorption effects are particularly effective in energy absorption and shock absorption, with military explosion-proof applications and athletic shoe sole shock absorption being prominent examples. However, in the field of mine backfilling, there is currently no precedent for using supercritical carbon dioxide as a foaming agent for coal-based solid waste. This invention is the first to apply and attempt this technology in the field of paste backfilling in mine mining. In preparing the paste backfilling with carbon fixation and energy absorption functions, the coal-based solid waste raw material selected in this invention is crushed and ground to particles with a diameter of less than 20μm. The high-temperature and high-pressure mixer used in this invention has a stirring function, giving SC-CO2 high diffusivity and permeability, allowing it to quickly penetrate into the coal-based solid waste slurry, fully ensuring the penetration reaction between supercritical CO2 and the coal-based solid waste slurry.

[0024] This embodiment presents a method for preparing a paste-like filler with carbon fixation and energy absorption function based on SC-CO2 foaming, comprising the following steps:

[0025] Coal-based solid waste raw materials are crushed and ground into powder with a particle size of less than 20 μm accounting for more than 15% of the powder. This powder is then mixed with water at a speed of less than 60 r / min to prepare a coal-based solid waste slurry. In this embodiment, the coal-based solid waste raw materials are coal gangue, fly ash, and other coal-based solid waste materials.

[0026] The prepared coal-based solid waste slurry is injected into a preheated high-temperature and high-pressure mixer for stirring. During the stirring process, supercritical CO2 is continuously injected until the pressure of the high-temperature and high-pressure mixer is the same as that of the CO2 supply device. In this invention, the supercritical CO2 is obtained by pressurizing the CO2 supply device through a high-pressure pump and stored in the high-temperature and high-pressure reactor 4.

[0027] The temperature of the high-temperature and high-pressure mixer 10 is maintained above 31°C and the pressure is maintained above 7.3MPa, so that the supercritical CO2 is kept in a supercritical stable state in the high-temperature and high-pressure mixer 10, and can fully penetrate into the coal-based solid waste slurry to form a mixture of supercritical CO2 and coal-based solid waste slurry.

[0028] Supercritical CO2 and coal-based solid waste slurry are mixed and stirred in a high-temperature, high-pressure mixer 10 to form a foam paste filling material masterbatch. In this embodiment, the supercritical CO2 is maintained in a supercritical state under the high temperature and high pressure of the high-temperature, high-pressure mixer 10. At the same time, the stirring method avoids the problem of compaction of the coal-based solid waste slurry due to high pressure when supercritical carbon dioxide is injected into it, which makes pore formation difficult and prevents the formation of foam paste filling material. In this embodiment, the high temperature and high pressure refer to the temperature of the high-temperature, high-pressure mixer being maintained above 31°C and the pressure being maintained above 7.3 MPa.

[0029] The foam paste filling masterbatch is depressurized after being kept at a controlled temperature and pressure for 10-30 minutes in the high-temperature and high-pressure mixer 10. In this embodiment, the foam paste filling masterbatch is depressurized after being kept at a controlled temperature and pressure for 10-30 minutes in the high-temperature and high-pressure mixer 10 because supercritical CO2 needs a certain amount of time to undergo carbonization reaction with the coal-based solid waste slurry mixture to form a stable cell structure. At the same time, under high temperature and high pressure conditions, supercritical CO2 can diffuse evenly in the coal-based solid waste slurry mixture, providing a basis for the formation of uniform bubbles during the subsequent depressurization process. During the depressurization process, CO2 in the mixer changes from supercritical to gaseous state, and gradually forms bubbles in the coal-based solid waste slurry, thereby forming a large amount of coal-based solid waste foamed paste filling slurry with supercritical CO2 as the bubble nucleus, realizing the foaming of the paste filling masterbatch.

[0030] Figure 1 This illustration shows the preparation process of the carbon-fixing and energy-absorbing paste filler in this embodiment. In this embodiment, coal-based solid waste raw materials are crushed, ground, and then mixed with mixing water at a speed of less than 60 r / min to prepare a coal-based solid waste slurry. Supercritical CO2 is continuously injected into a turbine mixer until it reaches the set pressure. The supercritical CO2 permeates into the coal-based solid waste slurry, forming a mixture of supercritical CO2 and coal-based solid waste slurry. This mixture is then thoroughly mixed by turbine mixing to form the masterbatch for the foam paste filler. Figure 1 The paste filling masterbatch is prepared by controlling the temperature and pressure in a high-temperature and high-pressure mixer for 10-30 minutes and then rapidly depressurizing to form a large amount of coal-based solid waste foamed paste filling slurry with supercritical CO2 as the foam nucleus. This process foams the paste filling masterbatch, which has low density, good thermal insulation performance and controllable cell structure. It can suppress the incubation conditions of deep coal mine dynamic disasters from the source, and is expected to realize the transformation from passive defense to active regulation, interrupt the chain reaction of disasters and achieve the effect of multi-hazard coordinated prevention and control.

[0031] In one embodiment of the present invention, the injection volume of the coal-based solid waste slurry is 1 / 3 to 1 / 2 of the volume of the high-temperature and high-pressure mixer. This ensures that supercritical CO2 fully permeates the coal-based carbon-fixing slurry within the high-temperature and high-pressure mixer 10, providing sufficient space to form a uniform foam structure. If the proportion of the coal-based solid waste slurry in the high-temperature and high-pressure mixer 10 is too large, the diffusion and permeation rate of CO2 may be affected, impacting the foaming results. Simultaneously, excessive pressure within the high-temperature and high-pressure mixer 10 should be avoided, as this could compromise equipment safety. Furthermore, this range prevents the high-temperature and high-pressure mixer from becoming completely filled with coal-based solid waste slurry, causing slurry return blockage, resulting in difficulty in mixing, uneven CO2 distribution, and premature coagulation of the coal-based solid waste slurry.

[0032] In another preferred embodiment, when preparing the coal-based solid waste slurry, the stirring time at a speed of less than 60 r / min is 6-10 min. Stirring at a speed of less than 60 r / min within this time range can avoid air mixing and is more conducive to the subsequent full penetration reaction with supercritical CO2.

[0033] In another preferred embodiment, the mixing speed of the supercritical CO2 and coal-based solid waste slurry mixture is 300-400 r / min, and the mixing time is 8-10 min.

[0034] When the foam paste filler masterbatch is depressurized after heat preservation and pressure holding, the depressurization rate is controlled at 2.5MPa / s to gradually reduce the pressure in the high-temperature and high-pressure mixer to 0-7.4MPa.

[0035] This embodiment also provides a coal-based solid waste CO2 foamed paste filler prepared by the above-described method for preparing a paste filler with carbon fixation and energy absorption function based on SC-CO2 foaming.

[0036] The aforementioned preparation method will now be described in further detail with reference to specific embodiments.

[0037] When implementing the aforementioned preparation method in this embodiment, it is necessary to build corresponding preparation equipment. This equipment can be existing technology equipment that meets the usage requirements, or it can be the equipment built as in this embodiment. The preparation equipment built in this embodiment is as follows: Figure 2 As shown, the system includes a CO2 gas supply device 1, a high-temperature and high-pressure reactor 4, a high-temperature and high-pressure mixer 10, a curing and oxidation chamber 12, and a constant temperature chamber 13, all connected in sequence by pipelines. Pressure gauges 2 are installed at the top of the CO2 gas supply device 1 and the high-temperature and high-pressure reactor 4. Delivery valves 3 are installed on the pipelines between the CO2 gas supply device 1 and the high-temperature and high-pressure reactor 4, as well as on the pipelines between the high-temperature and high-pressure reactor 4 and the high-temperature and high-pressure mixer 10. Pressure sensors 6 and temperature sensors 7 are installed on the high-temperature and high-pressure mixer 10 to detect the internal pressure and temperature. The high-temperature and high-pressure mixer 10 is also equipped with a slurry inlet 9 and a pressure relief valve 8. A stirring device 11 is installed vertically inside the high-temperature and high-pressure mixer 10.

[0038] like Figure 3As shown, the high-temperature and high-pressure reactor 4, high-pressure pump 5, pressure sensor 6, temperature sensor 7, pressure relief valve 8, slurry inlet 9, high-temperature and high-pressure mixer 10, stirring device 11, and curing chamber 12 are all located in a constant temperature chamber 13. This ensures that all equipment operates within the set temperature range during the experiment, avoiding interference from external temperature fluctuations on the experimental results. Simultaneously, the sensors monitor temperature and pressure changes in real time, providing a stable working environment for the high-temperature and high-pressure mixer 10 and stirring device 11, ensuring the slurry is fully mixed at the ideal temperature and avoiding experimental errors caused by uneven temperature. After the preparation equipment is built, the present invention crushes and grinds coal gangue, fly ash, and other coal-based solid waste raw materials into powder with a particle size of less than 20μm and a particle size ratio of more than 15%. This powder is then mixed with mixing water at a low speed of 60r / min for 6-10 minutes. This low-speed mixing method avoids air contamination. After mixing, a coal-based solid waste slurry is obtained, which is then ready to be injected into the high-temperature and high-pressure mixer.

[0039] The high-temperature and high-pressure mixer 10 is preheated to reduce the waiting time of the subsequently injected coal-based solid waste slurry in the high-temperature and high-pressure mixer.

[0040] Preheat the high-temperature and high-pressure reactor 4 to prevent sudden temperature changes from causing sudden pressure changes. Adjust the pressure and temperature inside the high-temperature and high-pressure reactor 4 to keep the high temperature within the range of 31°C and the high pressure within the range of 7.3MPa, so as to achieve coordinated regulation of pressure and temperature in the gaseous CO2 phase change supercritical CO2 process in the high-temperature and high-pressure reactor 4.

[0041] Open the delivery valve between CO2 supply device 1 and high-temperature and high-pressure reactor 4. CO2 is continuously injected into high-temperature and high-pressure reactor 4 through the pressure difference between CO2 supply device 1 and high-temperature and high-pressure reactor 4. At this time, the high-temperature and high-pressure reactor 4 is in a vacuum state, about -0.02MPa. When the pressure in high-temperature and high-pressure reactor 4 is approximately the same as the pressure in CO2 supply device 1, close the delivery valve.

[0042] The gaseous CO2 injected into the high-temperature and high-pressure reactor 4 is kept at this pressure and temperature range (high temperature within 31℃ range, high pressure maintained within 7.3MPa range) until the gaseous CO2 in the high-temperature and high-pressure reactor 4 reaches the phase change transformation and becomes supercritical carbon dioxide, i.e., SC-CO2 state.

[0043] The prepared coal-based solid waste slurry is injected into the container through the slurry inlet above the high-temperature and high-pressure mixer 10. When the injection volume is 1 / 3 of the volume of the high-temperature and high-pressure mixer 10, the injection is completed and the coal-based solid waste slurry inlet is closed. When injecting the coal-based solid waste slurry, the high-temperature and high-pressure mixer 10 is in a vacuum state, which is about -0.02MPa.

[0044] In this embodiment, a stirring device 11 is provided vertically inside the high-temperature and high-pressure mixer 10. The stirring device 11 in this embodiment is preferably a turbine agitator. After the coal-based solid waste slurry is injected and the coal-based solid waste slurry inlet is closed, the spiral stirring rod inside the high-temperature and high-pressure mixer 10 is started to stir the injected coal-based solid waste slurry.

[0045] During the mixing process of the coal-based solid waste slurry, the delivery valve 3 between the high-temperature and high-pressure reactor 4 and the high-temperature and high-pressure mixer 10 is opened, and the high-pressure pump is started. Supercritical carbon dioxide (SC-CO2) is continuously pumped into the high-temperature and high-pressure mixer 10 at a constant temperature and pressure during the mixing process. The mixing continues until the pressure of the CO2 supply device 1 and the high-temperature and high-pressure mixer 10 is the same, after which the delivery valve 3 is closed. In this embodiment, the continuous injection of CO2 into the coal-based solid waste slurry during the mixing process can improve the compressive strength of the solidified filling material.

[0046] Furthermore, by adjusting the pressure sensor 6 and temperature sensor 7 above the high-temperature and high-pressure mixer 10, the high-temperature and high-pressure mixer 10 is kept in a state of heat preservation and pressure preservation, that is, within a temperature range of 31°C and a pressure range of 7.3MPa, so that supercritical CO2 can be fully permeated into the coal-based solid waste slurry to form a mixture of supercritical CO2 and coal-based solid waste slurry.

[0047] Then, under high pressure and high temperature conditions, the mixture in the high-temperature and high-pressure mixer 10 is stirred and mixed by a spiral stirring rod. The stirring speed is 300-400 r / min and the stirring time is 8-10 min to form a foam paste filling material masterbatch. Since the stirring process is carried out under high pressure and high temperature conditions, SC-CO2 has high diffusivity and permeability and can quickly penetrate into coal-based solid waste slurry.

[0048] After stirring, the foam paste filling masterbatch is kept under pressure in the high-temperature and high-pressure mixer 10 for 10 minutes. By controlling the pressure holding time, premature coagulation of the coal-based solid waste slurry is avoided, and the slurry has sufficient fluidity. The pressure relief valve 8 above the high-temperature and high-pressure mixer 10 is opened, and the pressure relief rate is controlled at 2.5 MPa / s. The pressure relief rate should not be too fast, otherwise the CO2 in the high-temperature and high-pressure mixer 10 will generate dry ice, affecting the foaming effect. The pressure in the high-temperature and high-pressure mixer 10 is gradually reduced to 0 MPa. At this time, the SC-CO2 in the high-temperature and high-pressure mixer 10 is under reduced pressure, which causes the higher density CO2 to dedissolve. The CO2 changes from supercritical to gaseous, and the CO2 in the solution is released. The gas volume expands rapidly and forms a large number of bubbles, which realizes the foaming of the paste filling masterbatch and forms a large amount of coal-based solid waste foamed paste filling slurry with supercritical CO2 as the bubble nucleus.

[0049] Due to the dissolution of CO2 and the reaction with water to produce carbonic acid, the minerals in the slurry of the coal-based solid waste foamed paste filling body undergo carbonation hardening, giving the filling body better strength and durability. Furthermore, due to the dissolution and chemical reaction effects of CO2 bubbles, the number of pores with a diameter greater than 1000 nanometers is reduced, which enhances the compressive strength of the coal-based solid waste foamed paste filling body slurry and minimizes the negative impact of increased porosity on the coal-based solid waste CO2 foamed paste filling body.

[0050] The coal-based solid waste backfill slurry from the high-temperature and high-pressure mixer is injected into the curing chamber 12. After curing over time, a solidified coal-based solid waste CO2 foamed paste backfill is formed. The originally loose paste backfill is transformed into a honeycomb-shaped (CO2 pore structure) high-strength, high-elasticity backfill with energy absorption properties through the foaming process.

[0051] The development of porosity in supercritical CO2 foamed fillers is influenced by the diffusion-dissolution-reaction behavior of CO2 in the supercritical CO2-filler system.

[0052] This embodiment also verifies the density and porosity effects of the cured paste filling material with carbon fixation and energy absorption function. The cell morphology of the paste filling material with carbon fixation and energy absorption function was observed using a 3D microscope, and the true density and porosity were tested using a BSD-TD-K fully automatic true density and porosity analyzer. The results show that the density of the prepared paste filling material with carbon fixation and energy absorption function is 35%-50% lower than that of traditional cement-based filling materials, and the porosity is in the range of 45%-80%, which is significantly better than that of traditional cementitious filling materials.

[0053] This embodiment also verifies the energy absorption performance of the cured CO2 foamed coal-based solid waste backfill by testing. Simulating a real mine environment, a pressure sensor is used to test the energy absorption characteristics of the CO2 foamed coal-based solid waste backfill. The results show that the paste backfill with carbon fixation and energy absorption function prepared in this embodiment can absorb 50%-70% of the energy of the shock wave, which is 30%-50% higher than that of traditional backfill (such as cement and gypsum-based backfill materials).

[0054] This embodiment also verifies the carbon fixation function of the cured paste filling material with carbon fixation and energy absorption function by testing. X-ray diffraction (XRD) technology was used to test the paste filling material with carbon fixation and energy absorption function, which verified that CO reacts with the minerals in the coal-based solid waste slurry. The prepared CO2 foamed coal-based solid waste filling material has a carbon fixation rate of 6%-11% during the foaming process and a carbon storage capacity of 1-2 kg per cell.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art 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 appended claims and their equivalents.

Claims

1. A method for preparing a paste-like filler with carbon fixation and energy absorption function based on SC-CO2 foaming, characterized in that, Includes the following steps: Coal-based solid waste raw materials are crushed and ground, and then mixed with mixing water at a speed of less than 60 r / min to prepare coal-based solid waste slurry. In the powder formed after crushing and grinding the coal-based solid waste raw materials, the proportion of particles with a particle size of less than 20 μm reaches more than 15%. The prepared coal-based solid waste slurry is injected into a preheated high-temperature and high-pressure mixer for stirring, and supercritical CO2 is continuously injected during the stirring process. The volume of the coal-based solid waste slurry injected is 1 / 3 to 1 / 2 of the volume of the high-temperature and high-pressure mixer to ensure that the supercritical CO2 fully penetrates the coal-based carbon sequestration slurry in the high-temperature and high-pressure mixer, providing sufficient space to form a uniform pore structure. The temperature of the high-temperature and high-pressure mixer is maintained above 31°C and the pressure is maintained above 7.3 MPa, so that the supercritical CO2 is kept in a supercritical stable state under the high temperature and high pressure in the high-temperature and high-pressure mixer and fully penetrates into the coal-based solid waste slurry to form a mixture of supercritical CO2 and coal-based solid waste slurry. Supercritical CO2 and coal-based solid waste slurry are mixed and stirred under high temperature and high pressure to form a foam paste filling material masterbatch. The foam paste filling material masterbatch is then depressurized after being kept at high temperature and high pressure for 10-30 minutes. By controlling the pressure holding time, premature coagulation of the coal-based solid waste slurry is avoided, ensuring that the slurry has sufficient fluidity. When depressurizing the foam paste filling material masterbatch after keeping at high temperature and pressure, the depressurization rate is controlled at 2.5 MPa / s, gradually reducing the pressure in the high-temperature and high-pressure mixer to 0-7.4 MPa. The depressurization rate should not be too fast, otherwise the CO2 in the high-temperature and high-pressure mixer will generate dry ice, affecting the foaming effect, and forming a large amount of paste filling material with carbon fixation and energy absorption function with supercritical CO2 as the bubble nucleus. The stirring process is carried out under high pressure and high temperature conditions, which makes SC-CO2 have high diffusivity and permeability, and can quickly penetrate into the coal-based solid waste slurry.

2. The method for preparing a paste-like filler with carbon fixation and energy absorption function based on SC-CO2 foaming as described in claim 1, characterized in that, When preparing coal-based solid waste slurry, stir at a speed of less than 60 r / min for 6-10 min.

3. The method for preparing a paste-like filler with carbon fixation and energy absorption function based on SC-CO2 foaming as described in claim 1, characterized in that, The mixing speed of the supercritical CO2 and coal-based solid waste slurry mixture in the high-temperature and high-pressure mixer is 300-400 r / min, and the mixing time is 8-10 min.

4. The paste filling material with carbon fixation and energy absorption function prepared by the method for preparing paste filling material with carbon fixation and energy absorption function based on SC-CO2 foaming as described in any one of claims 1-3.

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