A gob CO2 mineralization filling method and filling system

Abstract

The present invention discloses a method for CO2 mineralization filling in a gob area, which belongs to the technical field of coal mining; the filling method comprises the following steps: First, a gelling agent, an admixture, water, and fly ash are used as mineralization materials for primary mineralization. The materials after primary mineralization are mixed with a foaming agent and a foam stabilizer for foaming and pore opening, and then stirred and mixed evenly with filling aggregates; the prepared paste is injected into the mining face. After the gob area is completely filled, CO2 is injected into the gob area continuously for mineralization by using the porous structure formed by the foamed paste; the present invention also provides a CO2 mineralization filling system for a gob area, which utilizes the above mineralization filling method. The mineralization filling system comprises a filling material preparation system, a filling material transportation system, and a working face filling system. The present invention is simple to operate, reduces the filling cost, completely seals the gob area while completing the mining of the working face, and completes the mineralization filling treatment of the gob area.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mining, and more specifically, relates to a method and a filling system for CO2 mineralization filling in a goaf. Background Art

[0002] After coal mining, problems such as roof caving and surface subsidence usually occur. When coal mining operations are carried out at the coal mining face, paste filling is carried out simultaneously, which effectively avoids these problems. Based on this, many domestic mines adopt the paste filling mining method for mining, which can not only effectively control the ground pressure activities of the mine, but also effectively solve the problem of how to mine coal resources "under the three protections" (buildings, railways, and water bodies).

[0003] The paste is prepared on the ground and then transported to the coal mining face. After solidifying into blocks, it has high strength and is not easy to deform, which can play a role in supporting and protecting the goaf. At present, the problems of isolation and plugging leakage and poor sealing in the area to be filled are still one of the main difficulties restricting the paste filling mining technology. Summary of the Invention

[0004] The present invention aims at the technical problems existing in the prior art and provides a method for CO2 mineralization filling in a goaf.

[0005] To solve the above technical problems, the mineralization filling method of the present invention includes the following steps:

[0006] First, use a gelling agent, an admixture, water, and fly ash as mineralization materials for primary mineralization. The materials after primary mineralization are mixed with a foaming agent and a foam stabilizer for foaming and pore opening, and then stirred and mixed evenly with a filling aggregate; inject the prepared paste into the coal mining face. When the goaf is completely filled, use the porous structure formed by the foamed paste to inject CO2 into the goaf continuously for mineralization.

[0007] Specifically, the mineralization filling method includes the following steps:

[0008] Select each mineralization material: select an admixture, a gelling agent, a filling aggregate, fly ash, a foaming agent, and a foam stabilizer;

[0009] Conduct a proportioning experiment: optimize the proportion of each mineralization material, conduct a proportioning experiment, and determine the CO2 flow rate, stirring speed, and stirring time;

[0010] Construct a mineralized paste preparation system: construct a mineralized paste preparation system on the ground. The preparation system includes a silo, an aggregate crushing system, and a conveying system. After each mineralization material is transported, stirred, and mixed, and the whole process is carried out under CO2 conditions to complete primary mineralization. Add a foaming agent and a foam stabilizer to the mixed mineralization materials for foaming and pore opening, and then stir and mix the crushed filling aggregate with the mineralization materials through the conveying system;

[0011] Construct a filling material conveying system and a working face filling system: The filling material conveying system is connected to the mineralized paste preparation system. The filling material conveying system includes a filling device and a conveying pipeline connecting the filling material conveying system and the working face filling system. The paste is pressurized by the filling device and then enters the conveying pipeline, and is transported to the underground filling working face for filling.

[0012] Carry out cyclic slurry preparation and transportation filling for the working face: First, determine the required amount of materials, then add materials to each system, stir and mineralize, and foam and open holes. Then, transport them to the filling working face through the constructed filling material conveying system and working face filling system for filling.

[0013] Adopt the "mining - filling - solidification" mode to cycle for working face filling and mining, and carry out CO2 transportation in the mode of "filling while injecting".

[0014] Preferably, the selected mineralized materials are: Use Na2CO3 and NaHCO3 as admixtures, use recycled micro - powder of construction waste as a gelling agent, use coal gangue and construction waste as filling aggregates, use hydrogen peroxide as a foaming agent, and use cetyltrimethylammonium bromide as a foam stabilizer.

[0015] Preferably, the ratio experiment process is as follows: First, group the various mineralized materials according to different ratios, stir the grouped materials, then add water and introduce CO2 and continue stirring. At this time, different CO2 flow rates L, stirring speeds V, and initial stirring times T1 can be set; then add the foaming agent and the foam stabilizer and continue stirring for a stirring time T2, and add the aggregates and stir evenly; after stirring is completed, measure the paste layer separation degree, slump, and setting time, and conduct a compressive strength test after the paste test block has completely solidified under natural conditions.

[0016] Preferably, the design standards for each index parameter are: Taking the paste slurry layer separation degree not greater than 20mm, slump greater than 180mm, pumpable time not less than 4h, initial setting time of 4h, final setting time not less than 8h, and the compressive strength of the paste at 8h not less than 0.1MPa as the standard.

[0017] Preferably, during filling and mining, when the length of the filled area is greater than the diffusion radius R of CO2, lay a CO2 conveying pipeline to connect with the ground CO2 storage tank, adjust the CO2 flow rate L2, inject CO2 into the paste through the reserved pipeline. Under the cyclic mining mode, until the entire goaf is completely filled, continue to use the paste to fill each shaft roadway, seal the goaf, and wait to continuously input CO2 into the filled goaf for mineralization.

[0018] Preferably, while carrying out cyclic slurry preparation and transportation filling on the working face, a CO2 transportation pipeline is reserved at the filling working face. A section of CO2 transportation pipeline is laid in each cycle, and the length of each section of the pipeline corresponds to the filling process of each cycle.

[0019] The present invention also provides a gob CO2 mineralization filling system, which utilizes the above-mentioned mineralization filling method. The mineralization filling system includes a filling material preparation system, a filling material transportation system, and a working face filling system. The filling material transportation system is used to connect the filling material preparation system and the working face filling system; the filling material preparation system includes a material bin, a material stirring device, and a material transportation system. The filling material transportation system includes a filling device and a transportation pipeline. The working face filling system is provided with a working face filling pipeline and a distribution pipe, and the working face filling pipeline is connected to the transportation pipeline.

[0020] Preferably, the filling material preparation system includes bins for storing various mineralization materials, feeders, an aggregate crushing system, mixing barrels, and a pipeline transportation system. The materials mixed and stirred in the mixing barrels are transported to the filling equipment after mineralization and foam opening. The filling materials are transported to the mining working face through the filling equipment and the transportation pipeline for filling mining, and a CO2 transportation pipeline is laid at the mining working face.

[0021] The present invention also provides a method for working face mining using paste filling, which utilizes the above-mentioned gob CO2 mineralization filling method to complete the support of the gob while completing the working face mining, and at the same time complete the mineralization filling treatment of the gob.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The whole paste mineralization filling process of the present invention is relatively simple, green and sustainable, and highly operable; first, the initial mineralization of materials such as fly ash, cementitious agent, admixture, and water is completed on the ground. The mineralized materials that have completed the initial mineralization are mixed with a foaming agent and a foam stabilizer for foam opening, and then stirred and mixed with filling aggregates such as coal gangue to form a paste and inject it into the mining working face; when the gob is completely filled, the porous structure formed by the foamed paste is utilized to inject CO2 continuously into the gob for mineralization, so that the gob is completely sealed, and the support of the gob is completed while completing the working face mining, and at the same time the mineralization filling treatment of the gob is completed.

[0024] The present invention not only has low filling cost and simple operation, forms support and protection for the gob, but also can continuously mineralize CO2. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for use in the embodiments or the description of the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic structural diagram of the gob CO2 mineralization filling system of the present invention;

[0027] Figure 2 It is a schematic diagram of the filling material transportation system and the working face filling system of the present invention;

[0028] Figure 3 It is a schematic structural diagram of the mixing barrel of the present invention;

[0029] Figure 4 It is a schematic structural diagram and a position layout diagram of the CO2 reserved pipeline of the present invention.

[0030] Symbol markings in the figure:

[0031] 1. Filling material preparation system; 11. Admixture bin; 12. Cementitious agent bin; 13. Fly ash bin; 14. Water tank; 15. Filling aggregate bin; 16. CO2 storage tank; 17. Feeder; 18. Material conveying pipeline; 191. Primary mixing barrel; 192. Secondary mixing barrel; 193. Sealing cover; 194. Flow regulating valve; 195. Flowmeter; 196. Safety valve; 197. Agitator; 198. Slurry conveying valve; 199. Buffer hopper;

[0032] 2. Filling material transportation system; 21. Filling pump; 22. Ground conveying pipe; 23. Underground main pipeline;

[0033] 3. Working face filling system; 31. Working face branch pipe; 32. Distribution pipe;

[0034] 4. Filling area;

[0035] 5. Mining face;

[0036] 6. Filling shaft;

[0037] 7. Slurry conveying pipe;

[0038] 8. CO2 conveying pipeline. Detailed implementation manners

[0039] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the following further details this application in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0040] Please refer to Figure 1 , the present invention provides a goaf CO2 mineralization filling system. The mineralization filling system includes a filling material preparation system 1, a filling material transportation system 2 and a working face filling system 3. The filling material transportation system 2 is used to connect the filling material preparation system 1 and the working face filling system 3; the filling material preparation system 1 includes a material bin, a material mixing device and a material conveying system. The filling material transportation system 2 includes a filling device and a conveying pipeline. The working face filling system 3 is provided with a working face filling pipeline and a distributing pipe, and the working face filling pipeline is connected to the conveying pipeline.

[0041] Specifically, the filling material preparation system 1 is arranged on the ground. The material bin it is provided with includes an admixture bin 11 for storing admixtures, a gelling agent bin 12 for storing gelling agents, a fly ash bin 13 for storing fly ash, a water tank 14 for storing water, a filling aggregate bin 15 for storing filling aggregates and a CO2 storage tank 16 for storing CO2; the material mixing device is provided with a mixing barrel, and the mixing barrel is used for mixing and stirring mineralized materials, primary mineralization and foaming and opening of materials; the material conveying system is provided with a feeder 17 and a material conveying pipeline 18, and the material bin conveys each mineralized material to the mixing barrel through the material conveying system.

[0042] Furthermore, the mixing barrel includes a primary mixing barrel 191 and a secondary mixing barrel 192. The primary mixing barrel 191 is arranged at the front end of the secondary mixing barrel 192, and the primary mixing barrel 191 and the secondary mixing barrel 192 are connected by a conveying pipeline.

[0043] The main functions of the primary mixing barrel 191 are: to perform primary mineralization on each mineralized material except the filling aggregate in a CO2 atmosphere, and it has functions of stirring, sealing, pressure relief and explosion protection, and regulating the CO2 flow rate; the main functions of the secondary mixing barrel 192 are: to perform foaming treatment on the slurry that has completed primary mineralization from the primary mixing barrel 191, and add filling aggregates for stirring to prepare a filling paste that meets the requirements, and it has functions of stirring, sealing and pressure relief.

[0044] Furthermore, the admixture bin 11, the cementitious agent bin 12, and the fly ash bin 13 respectively convey the admixture, the cementitious agent, and the fly ash to the primary stirring barrel 191 through the feeder 17 and the conveying pipeline. The filled aggregate is crushed by the aggregate crushing system, vibration-screened, weighed, and then input into the secondary stirring barrel 192 through the belt conveyor. Water pipelines are laid between the water tank 14 and the primary stirring barrel 191 and the secondary stirring barrel 192, and water pumps and valves are set for conveying management.

[0045] The CO2 captured by the thermal power plant is pressurized and then injected into the CO2 storage tank 16. The CO2 storage tank 16 is closely connected to the primary stirring barrel 191 through a pipeline, and a flow regulator is configured to ensure that the entire stirring process can always be carried out under the condition of the optimal CO2 concentration atmosphere; the primary stirring barrel 191 is provided with a sealing cover 193, and the sealing cover 193 has a tight interface connected to the CO2 conveying pipeline to ensure that CO2 does not leak during the initial mineralization process.

[0046] Each material bin is conveyed into the primary stirring barrel 191 through the material conveying system to complete mixing and stirring. The whole process is carried out in the atmosphere of CO2 to complete the initial mineralization; then, a foaming agent and a foam stabilizer are added to the slurry after pulping in the primary stirring barrel 191 for foaming and opening pores, and then the filled aggregate after crushing treatment is respectively input into the secondary stirring barrel 192 through pipelines and conveyors for stirring and mixing. After sufficient stirring and mixing, it is ready to be filled into the goaf underground.

[0047] As Figure 2 shown, specifically, the filling material transportation system 2 includes a filling pump 21 and a conveying pipeline. The conveying pipeline is provided with a ground conveying pipe 22 and an underground main pipeline 23. The ground conveying pipe 22 is used to transport the paste material prepared by the filling material preparation system to the filling pump 21. The underground main pipeline 23 is arranged in the filling shaft 6 and is used to connect the filling pump 21 with the working face filling system 3.

[0048] Furthermore, the underground main pipeline 23 can adopt a pipeline with the same specification as the ground conveying pipe 22, and the inner diameter of each pipeline can be selected as 150 mm.

[0049] Specifically, the working face filling system 3 is arranged in the mining working face 5. The working face filling system 3 is provided with a working face branch pipe 31 and a distributing pipe 32. The distributing pipe 32 is arranged at the front end of the working face branch pipe 31. The other end of the working face branch pipe 31 is connected to the underground main pipeline 23; to realize the movement of the filling working face along with the mining, the working face branch pipe 31 is selected as a sectional steel pipe, and each section of the steel pipe is provided with a distributing pipe 32 and a valve for convenient filling.

[0050] Furthermore, a CO2 conveying pipeline is reserved at the filling working face during filling. In the figure, 4 is the filling area.

[0051] The paste made in the secondary stirring tank 192 enters the filling pump 21 through the ground delivery pipe 22. After being pressurized by the filling pump 21, the paste enters the delivery pipeline and is transported to the underground filling working face through the shaft for filling mining.

[0052] Furthermore, as a preferred embodiment of the present invention, as Figure 3 shown, a delivery pipeline is installed between the CO2 storage tank 16 and the primary stirring tank 191. A flow regulating valve 194 and a flowmeter 195 are connected to the delivery pipeline, enabling the constant-speed delivery of CO2 to the primary stirring tank 191.

[0053] Specifically, the delivery pipeline is made of PVC material, which has good corrosion resistance, low price, and is easy to lay; the flow regulating valve 194 is made of stainless steel and can be screwed to the pipeline, and is equipped with a sealing gasket to ensure airtightness and reliability in use; the flowmeter 195 is an electronic flowmeter with high sensitivity.

[0054] Furthermore, as a preferred embodiment of the present invention, sealing covers 193 and safety valves 196 are provided at the tops of both the primary stirring tank 191 and the secondary stirring tank 192, and a stirrer 197 is arranged inside the tanks.

[0055] Specifically, the tank bodies of the stirring tanks are all made of steel, and the inner walls of the stirring tanks are coated with a polytetrafluoroethylene coating, which can prevent the tank bodies from being corroded and ensure that the mineralization reaction is not disturbed; the sealing cover 193 is made of stainless steel, and the sealing structure adopts a common flat gasket seal, which has a simple structure and high reliability.

[0056] Furthermore, the safety valve 196 is of the spring slightly opening type, its installation position is not restricted, it is less sensitive to vibration, and has strong applicability; the stirrer 197 is a paddle stirrer, which has a simple structure and is suitable for the dissolution of solid particles.

[0057] Furthermore, as a preferred embodiment of the present invention, a slurry outlet and a slurry delivery valve 198 are provided at the bottom of the primary stirring tank 191, and the materials are all the same as those of the tank body, and a polytetrafluoroethylene coating is applied to its inner wall. A buffer hopper 199 is provided between the primary stirring tank 191 and the secondary stirring tank 192. It has an overall conical funnel-shaped structure and is made of steel structure, which plays a buffering role to prevent the sudden injection of the slurry from the primary stirring tank 191 from causing a large impact on the secondary stirring tank 192, playing a buffering and protective role; the bottom of the buffer hopper 199 is connected to the upper part of the secondary stirring tank 192 through a slurry delivery pipe 7 for transporting the slurry.

[0058] Moreover, the connection methods of the primary stirring tank 191, the secondary stirring tank 192 with the pipelines and valves all adopt socket connection.

[0059] The present invention also provides a gob CO2 mineralization filling method, which uses the above-mentioned gob CO2 mineralization filling system for mineralization filling; first, a gelling agent, an admixture, water, and fly ash are used as mineralization materials for primary mineralization. The materials after primary mineralization are mixed with a foaming agent and a foam stabilizer for foaming and pore opening, and then stirred and mixed evenly with the filling aggregate; the prepared paste is injected into the mining face, which can play a supporting role in the gob. When the gob is completely filled, the porous structure formed by the foamed paste is conducive to storing CO2, and the materials can undergo continuous mineralization reaction with CO2, enabling the CO2 injected later to undergo continuous natural mineralization.

[0060] Specifically, the mineralization filling method includes the following steps:

[0061] 1) Select each mineralization material:

[0062] Respectively select an admixture, a gelling agent, a filling aggregate, fly ash, a foaming agent, and a foam stabilizer:

[0063] Use Na2CO3 and NaHCO3 as the admixture, which can provide an alkaline environment and accelerate the process of primary mineralization reaction; use recycled fine powder of construction waste after appropriate screening and grinding as the gelling agent. This type of recycled fine powder contains many alkaline metals, which not only has the function of gelling various mineralization materials but also is conducive to the recycling of construction waste; use coal gangue and construction waste as the filling aggregate. Coal gangue, as a by-product of coal mining, is huge in quantity and stable in structure. Using it as the filling aggregate can not only meet the requirements of the paste structure but also facilitate the recycling of solid waste resources. After the construction waste is crushed, the part with a particle size meeting the requirements is screened out and mixed with coal gangue to meet the demand for the amount of filling aggregate.

[0064] Use hydrogen peroxide as the foaming agent and cetyltrimethylammonium bromide as the foam stabilizer. The use effects of hydrogen peroxide and cetyltrimethylammonium bromide are better; both fly ash and CO2 are generated from the emissions of thermal power plants, with wide raw material sources and large quantities.

[0065] 2) Conduct proportioning experiments:

[0066] To ensure the stability, fluidity, plasticity, pore-opening effect, and compressive strength of the finally prepared paste after solidification, multiple proportioning experiments need to be carried out before filling to optimize the proportion of each mineralization material and determine the optimal CO2 flow rate, stirring speed, stirring time, etc.

[0067] The proportioning experiment process is as follows: First, group the mineralization materials according to different proportions, add the grouped materials into a sealed mineralization reactor for stirring. The stirring time is about 180 s. Then add water and introduce CO2 and continue stirring for a certain time. At this time, different CO2 flow rates L, stirring speeds V, and initial stirring times T1 can be set. Then add the foaming agent and foam stabilizer and continue stirring for a certain time, and the stirring time is T2. Finally, add the aggregate and stir evenly. After stirring, measure the bleeding rate, slump, setting time, etc. of the paste, and conduct a compressive strength test on the paste specimen under natural conditions after it is completely solidified.

[0068] Ultimately, it should be based on the standard that the bleeding rate of the paste slurry is not more than 20 mm, the slump is greater than 180 mm, the pumpable time is not less than 4 h, the initial setting time is about 4 h, the final setting time is not less than 8 h, the compressive strength of the paste at 8 h is not less than 0.1 MPa, and the foaming and pore-opening of the paste do not affect its strength to determine the optimal proportions of each material, the CO2 flow rate L1, the stirring speed V, and the stirring times T1 and T2.

[0069] Furthermore, the foaming and pore-opening of the paste not affecting its strength means that under the premise of ensuring requirements such as slump and pumpable time, a compressive strength test is conducted on the paste after solidifying for 8 h to ensure that its strength meets the standard.

[0070] To prevent pipe blockage and ensure dense filling, the maximum particle size of the filling aggregate generally does not exceed 25 mm. Aggregates with a particle size of less than 5 mm and aggregates with a particle size of 5 - 25 mm can be mixed and transported according to the required proportions. The mass ratio of coal gangue to construction waste in the filling aggregate is selected as 2:8.

[0071] Specifically, conduct a proportioning experiment under laboratory conditions. For example: When in a mineralization reactor with a volume of 1.5 L, add 200 g of mineralization materials and 100 g of water in total to conduct a mineralization reaction experiment. The measured optimal CO2 flow rate range is 1.2 L / min - 1.5 L / min, the optimal stirring speed is 100 r / min - 150 r / min, and the optimal stirring time is 90 s - 180 s.

[0072] Specific optimal parameters for each item are analyzed and adjusted according to the specimens obtained from the experiment.

[0073] 3) Construct a filling material preparation system on the ground:

[0074] Such as Figure 1As shown, each material bin is transported into the first-stage mixing tank 191 through the material conveying system to complete mixing and stirring. The whole process is carried out in the atmosphere of CO2 to complete the primary mineralization. Then, a foaming agent and a foam stabilizer are added to the slurry after the pulping in the first-stage mixing tank 191 to carry out foaming and pore-opening. Then, the crushed filling aggregate is respectively input into the second-stage mixing tank 192 through a pipeline and a conveyor for stirring and mixing. After sufficient stirring and mixing, it is ready to be filled into the underground goaf.

[0075] 4) Construct a filling material conveying system and a working face filling system:

[0076] As Figure 2 shown, the paste made in the second-stage mixing tank 192 enters the filling pump 21 after passing through the slurry buffer hopper 199. The paste is pressurized by the filling pump 21 and then enters the conveying pipeline, and is transported to the underground mining working face 5 through the filling shaft 6 for filling. The initial setting time of the paste is about 4h. The "mining - filling - solidification" mode can be used for cyclic filling mining, that is, each cycle of mining and filling process is about 5m. When the mining is completed, the filling operation is carried out. When the filled paste solidifies and forms, the next cycle is carried out until the working face is completely filled.

[0077] 5) Carry out cyclic pulping, conveying and filling on the working face:

[0078] First, determine the amount of each material required according to the material ratio determined by the ratio experiment and the total amount of paste to be injected in each "mining - filling - solidification" cycle. Then, input the admixture, gelling agent, fly ash, water, and CO2 into the first-stage mixing cylinder, and carry out stirring and mineralization according to the optimal stirring speed V, stirring time T1, and CO2 flow rate L1 in the previous ratio experiment.

[0079] After mixing, stirring and mineralization, it is transported into the second-stage mixing tank 192, and the foam stabilizer and foaming agent are input according to the experimental optimal ratio for stirring, and the stirring time is T2. After foaming is completed, the crushed and weighed coal gangue aggregate is transported into the second-stage mixing tank 192 according to the particle size and ratio requirements, and after stirring evenly, it is transported to the filling working face through the conveying system and the filling system for filling.

[0080] 6) Reserve a CO2 conveying pipeline at the filling working face:

[0081] As Figure 4 shown, while carrying out cyclic pulping, conveying and filling on the working face, a CO2 conveying pipeline 8 is reserved at the filling working face. One section of the CO2 conveying pipeline 8 can be laid in each "mining - filling - solidification" cycle, and the length of each section of the pipeline corresponds to each cycle of filling process, which should be about 5m.

[0082] Furthermore, each section of the pipeline can be docked with each other. The pipeline is made of PVC material with an inner diameter of 150mm.

[0083] During the previous "mining - filling - solidification" cycle process, a CO₂ diffusion radius test experiment can be carried out to determine the CO₂ diffusion radius R, the optimal CO₂ flow rate L2, and complete the opening design of the CO₂ reserved pipeline.

[0084] Specifically, an opening is made at the end of the CO₂ pipeline reserved in the first "mining - filling - solidification" cycle, and the opening diameter is 10 mm to wait for the injection of CO₂ for the experiment; when the first cycle is completely over, that is, when the paste is completely solidified, a CO₂ delivery pipeline 8 is laid and connected to the ground CO₂ storage tank 16, and a flow meter and a regulating valve are designed. CO₂ is injected into the paste through the reserved pipeline, and SF6 detection gas is mixed into the CO₂. Use SF6 detection equipment at the solidification surface of the paste to check whether CO₂ overflows. If SF6 is detected, it means that the CO₂ diffusion radius is greater than one process, that is, 5 m; if SF6 is not detected, it means that the CO₂ diffusion radius is less than 5 m. Each subsequent cycle is detected once, and the detection process is the same as that of the first cycle, but the reserved CO₂ delivery pipeline in the later stage can be not opened until the detection equipment fails to detect SF6, then the CO₂ diffusion radius R inside the paste can be determined.

[0085] During the experiment, the CO₂ flow rate can be adjusted. Considering different flow rates, the CO₂ diffusion speeds are different. During detection, after injecting CO₂, the detection equipment should stay at the solidification surface of the paste for a period of time. Also considering that the solidification time of the paste is 4 h - 8 h, in order to ensure that the finally determined diffusion radius does not affect the later "filling while injecting" (that is, taking the CO₂ diffusion radius as the standard, injecting CO₂ gas after the length of the filled area is greater than the diffusion radius), the residence time should be about 8 h. If no detection is made after more than 8 h, the filled length that has been carried out is regarded as the CO₂ diffusion radius R under this flow rate condition, and the flow rate at this time is determined as the optimal CO₂ flow rate L2.

[0086] Considering making full use of the opening structure of the paste to store CO₂, the pipelines laid in the paste are opened at intervals, and the openings are made at intervals of the CO₂ diffusion radius R, with an opening diameter of 10 mm. At this time, the CO₂ gas can diffuse around through the pipeline openings, improving the mineralization efficiency; moreover, through the reserved CO₂ delivery pipeline, the cumbersome operations of drilling and laying pipelines in the goaf in the later stage are avoided, reducing the filling cost.

[0087] 7) The working face is filled and mined in a cycle using the "mining - filling - solidification" mode:

[0088] The working face is filled and mined in a cycle using the "mining - filling - solidification" mode, and CO₂ is transported in the "filling while injecting" mode.

[0089] That is, when the length of the filled area is greater than the diffusion radius R of CO2, a CO2 delivery pipeline 8 is laid and connected to the ground CO2 storage tank 16, and the flow rate of CO2 is adjusted to L2 through a flow meter 195 and a flow regulating valve 194, and CO2 is injected into the paste through a reserved pipeline; in the mining under the cyclic mode, until the entire goaf is completely filled, the paste is continuously used to fill each shaft roadway. In the connection area between each shaft roadway and the ground, the part of each shaft opening close to the ground is sealed with concrete and anti-seepage materials to ensure the sealing of the goaf, so as to continuously input CO2 into the filled goaf for mineralization.

[0090] The whole paste mineralization filling process of the present invention is relatively simple, green and sustainable, and highly operable; first, the initial mineralization of materials such as fly ash, cementitious agent, admixture, and water is completed on the ground. The mineralized materials that have completed the initial mineralization are mixed with a foaming agent and a foam stabilizer for foaming and pore opening, and then stirred and mixed with filling aggregates such as gangue, and the prepared paste is injected into the mining face; when the goaf is completely filled, CO2 is continuously injected into the interior of the goaf by using the porous structure formed by the foamed paste for mineralization, so that the goaf is completely sealed, the support of the goaf is completed while the mining of the working face is completed, and at the same time, the mineralization filling treatment of the goaf is completed. The present invention not only has low filling cost and simple operation, forms support and protection for the goaf, but also can continuously mineralize CO2.

[0091] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0092] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more, unless otherwise specifically defined.

[0093] The above are only the preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for CO2 mineralization filling in a goaf, characterized in that It includes the following steps: First, use the gelling agent, admixture, water, and fly ash as mineralization materials for primary mineralization. The materials after primary mineralization are mixed with the foaming agent and foam stabilizer for foaming and pore opening, and then stirred and mixed evenly with the filling aggregate. Inject the prepared paste into the coal mining face. After the goaf is completely filled, use the porous structure formed by the foamed paste to inject CO2 into the goaf continuously for mineralization.

2. A method for CO2 mineralization filling in a goaf, characterized in that, It includes the following steps: Select each mineralization material: Select the admixture, gelling agent, filling aggregate, fly ash, foaming agent, and foam stabilizer; The selected mineralization materials are respectively: Use Na2CO3 and NaHCO3 as the admixture, use recycled fine powder of construction waste as the gelling agent, use coal gangue and construction waste as the filling aggregate, use hydrogen peroxide as the foaming agent, and use cetyltrimethylammonium bromide as the foam stabilizer; Conduct proportioning experiments: Optimize the proportion of each mineralization material, conduct proportioning experiments, and determine the CO2 flow rate, stirring speed, and stirring time; Construct a mineralized paste preparation system: Construct a mineralized paste preparation system on the ground. The preparation system includes a silo, an aggregate crushing system, and a conveying system. After the gelling agent, admixture, and fly ash in each mineralization material are transported, stirred, and mixed, and the whole process is carried out under CO2 conditions to complete primary mineralization. Add the foaming agent and foam stabilizer to the mixed mineralization materials for foaming and pore opening, and then stir and mix the crushed filling aggregate with the mineralization materials through the conveying system; Construct a filling material conveying system and a working face filling system: The filling material conveying system is connected to the mineralized paste preparation system. The filling material conveying system includes a filling device and a conveying pipeline connecting the filling material conveying system and the working face filling system. The paste enters the conveying pipeline after being pressurized by the filling device and is transported to the underground filling working face for filling; Carry out cyclic slurry preparation, transportation, and filling of the working face: First, determine the amount of materials required, then add materials to each system, stir and mineralize, foam and open pores, and then transport them to the filling working face through the constructed filling material conveying system and working face filling system for filling; Adopt the "mining - filling - solidification" mode to cycle the filling and mining of the working face, and carry out CO2 transportation in the mode of "filling while injecting".

3. The method for CO2 mineralization filling in a goaf according to claim 2, characterized in that, The process of the proportioning experiment is as follows: First, group each mineralization material according to different proportions, stir the grouped materials, then add water and introduce CO2 to continue stirring. At this time, different CO2 flow rates L, stirring speeds V, and primary stirring times T1 can be set; then add the foaming agent and foam stabilizer and continue stirring for the stirring time T2, and add the aggregate and stir evenly. After stirring is completed, measure the bleeding rate, slump, and setting time of the paste, and conduct a compressive strength test after the paste test block is completely solidified under natural conditions.

4. A gob CO2 mineralization filling method according to claim 3, characterized in that, The design standards for each index parameter are: based on the bleeding rate of the paste slurry not being greater than 20 mm, the slump being greater than 180 mm, the pumpable time not being less than 4 h, the initial setting time being 4 h, the final setting time not being lower than 8 h, and the compressive strength of the paste at 8 h not being less than 0.1 MPa as the standard.

5. A method for CO2 mineralization filling in a gob area according to claim 2, characterized in that, When carrying out filling mining, when the length of the filled area is greater than the diffusion radius R of CO2, lay a CO2 pipeline to connect with the ground CO2 storage tank, adjust the CO2 flow rate L2, and inject CO2 into the paste through the reserved pipeline. Under the mining of the circulation mode, until the entire goaf is completely filled, continue to use the paste to fill each shaft roadway, seal the goaf, and wait to continuously input CO2 into the filled goaf for mineralization.

6. The method for CO2 mineralization filling in a goaf according to claim 2, wherein, While carrying out cyclic slurry transportation and filling of the working face, reserve a CO2 pipeline at the filling working face. Lay a section of CO2 pipeline in each cycle, and the length of each section of the pipeline corresponds to the filling process of each cycle.

7. A method for working face mining using paste filling, characterized in that, It uses the goaf CO2 mineralization filling method described in any one of claims 1-6 to complete the support of the goaf while completing the mining of the working face, and at the same time complete the mineralization filling treatment of the goaf.

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