Method for sealing carbon dioxide by using industrial solid waste and filling large-area hanging roof goaf

Abstract

The present application relates to the technical field of mine goaf filling, and particularly relates to a method for sealing carbon dioxide by using industrial solid waste and filling large-area suspended roof goaf, which comprises the following steps: determining the range of the suspended roof area and the range of the roof collapse abnormal area in the room-and-pillar goaf; arranging an industrial solid waste carbon dioxide sealing system, wherein a crushing device and a carbon dioxide collecting device are connected with a carbon fixation reaction device, the carbon fixation reaction device is connected with a pumping device, a negative pressure pump is connected with a gas storage tank; pumping grouting slurry from a self-grouting borehole to the roof collapse abnormal area to cement an isolation wall; extracting gas; making the carbon dioxide and the mixed slurry of the solid waste fully react to realize carbon dioxide mineralization and form sealing materials; and pumping the sealing materials to the suspended roof area device to fill the suspended roof area.

Description

Technical Field

[0001] This invention relates to the field of mine goaf filling technology, and in particular to a method for using industrial solid waste to seal carbon dioxide and fill large-area suspended goaf areas. Background Technology

[0002] Strengthening the utilization of mine solid waste and industrial solid waste, as well as the mineralization and sequestration of carbon dioxide, is currently a research hotspot in the mining field. At present, carbon dioxide sequestration in goafs is mostly used in fully mechanized mining goafs. However, based on actual coal mining conditions, many coal mines still used room-and-pillar mining several years ago, resulting in large areas of overhanging roofs. Unlike fully mechanized goafs, room-and-pillar goafs are not completely collapsed, and their internal space is vast and well-sealed. Utilizing the mineralization properties of carbon dioxide and filling the goaf with the reacted material can simultaneously sequester carbon dioxide and treat mine and industrial solid waste, eliminating the danger of large-scale overhanging roofs. However, room-and-pillar goafs have a large number of overhanging roofs in stable coal pillar areas and roof collapse in unstable coal pillar areas. How to achieve goaf filling and carbon dioxide sequestration under these conditions is a challenge. This patent can reduce industrial solid waste, reduce carbon dioxide, reduce stress concentration in coal pillars in goafs, reduce ground subsidence in goafs, and reduce goaf disasters, achieving "five reductions." Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method for sealing carbon dioxide using industrial solid waste and filling large-area suspended roof goaf areas, comprising the following steps:

[0004] Step S1: Conduct transient electromagnetic physical detection on the selected room-and-pillar goaf.

[0005] Step S2: Obtain the apparent resistivity cross-sectional diagram of each transient electromagnetic survey line, interpret and analyze it, and determine the range of the suspended roof area and the range of the abnormal roof collapse area in the room-and-pillar goaf.

[0006] Step S3: Verify the suspended roof area and the abnormal roof collapse area determined in step S2 using verification boreholes, and then seal the boreholes after completion.

[0007] Step S4: Deploy an industrial solid waste carbon dioxide storage system. The industrial solid waste carbon dioxide storage system includes a carbon dioxide collection device, a crushing device, a carbon fixation reaction device, a pumping device, a negative pressure pump, and a gas storage tank. The crushing device and the carbon dioxide collection device are respectively connected to the carbon fixation reaction device through pipelines. The carbon fixation reaction device is connected to the pumping device, and the negative pressure pump is connected to the gas storage tank.

[0008] S5, along the boundary between the suspended roof area and the abnormal roof collapse area, drill grouting holes on the side of the abnormal roof collapse area, connect the grouting holes to the pumping device, and pump grouting slurry from the grouting holes to the abnormal roof collapse area. The grouting slurry and the broken roof rock blocks in the abnormal roof collapse area are cemented together to form an isolation wall.

[0009] Step S6: Drill extraction boreholes into the sealed suspended goaf area and connect them to a negative pressure pump to extract gas from the sealed suspended goaf area.

[0010] Step S7: Industrial solid waste and coal gangue are transported to the crushing device for crushing and grinding. Cement and fly ash are then added to the crushing device. The mixed solid waste mixture is transported to the carbon fixation reactor. A certain proportion of water is added to the carbon fixation reactor and continuously stirred to form a solid waste mixture slurry. Carbon dioxide from the carbon dioxide collection device is transported to the carbon fixation reactor and continuously stirred to allow the carbon dioxide to fully react with the solid waste mixture slurry to achieve carbon dioxide mineralization and form a storage material.

[0011] Step S8: Drill a sealing borehole and connect it to a pumping device to pump the fully reacted sealing material to the overhead area device until the overhead area is filled.

[0012] Preferably, in step S3, verification boreholes are arranged on both sides of the boundary line between the suspended roof area and the abnormal roof collapse area determined in step S2.

[0013] Preferably, in step S5, a cement and fly ash mixture is selected and 5% by mass of cement expansion agent is added as the grouting material.

[0014] Preferably, in step S5, a cement quick-setting agent is also added to the grouting material.

[0015] Preferably, in step S5, the grouting process involves pumping the grout to the abnormal collapse zone of the roof slab, monitoring the grouting flow rate and pressure in real time, initially selecting a pumping pressure of 3 MPa, increasing the pumping pressure to 4 MPa when the flow rate approaches zero and the pressure continues to rise, increasing the pumping pressure to 5 MPa when the flow rate approaches zero and the pressure continues to rise, and stopping the grouting process when the flow rate approaches zero and the pressure continues to rise.

[0016] Preferably, in step S7, the coal gangue is crushed to a particle size of less than 10 mm, and the proportion of particles with a particle size of less than 2 mm is not less than 1 / 3, and the industrial solid waste is ground to a particle size of 0.25 mm-0.35 mm.

[0017] Preferably, in step S7, the mass ratio of cement:fly ash:industrial solid waste and coal gangue is 1:5:4, and the mass ratio of water and solid waste mixture is 1:1.3.

[0018] Beneficial effects: 1. This invention utilizes alkaline substances such as calcium oxide and magnesium oxide in industrial solid waste to react with carbon dioxide, thereby treating industrial solid waste while simultaneously sequestering carbon dioxide, which is of great significance for the comprehensive utilization of industrial solid waste and carbon dioxide sequestration.

[0019] 2. Based on the utilization of industrial solid waste to seal carbon dioxide, this invention uses mine gangue solid waste as aggregate and binder as filling material, and mixes them to form sealing material to fill the suspended roof area of ​​the goaf, thereby realizing the treatment of mine gangue solid waste.

[0020] 3. Based on the utilization of industrial solid waste to seal carbon dioxide, this invention also utilizes the space of the room-and-pillar goaf, sealing industrial solid waste and carbon dioxide while eliminating the large-area roof hazard caused by the room-and-pillar goaf. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0022] Figure 1a Transient electromagnetic exploration range and survey line layout map;

[0023] Figure 1b Schematic diagram of the extent of the roof collapse anomaly zone in the goaf area explored by transient electromagnetic exploration;

[0024] Figure 1c A schematic diagram of the borehole layout and the abnormal roof collapse zone in the goaf after verification.

[0025] Figure 2 A plan view (top view) of the method for sealing carbon dioxide and filling the goaf of a room-pillar type mining area according to the present invention;

[0026] Figure 3 A flowchart (cross-section) of the filling system for the method of sealing carbon dioxide and filling goaf in a room-and-pillar type goaf according to the present invention;

[0027] In the attached diagram: 1-Industrial solid waste; 2-Carbon dioxide collection device; 3-Pulverizing device; 4-Valve 1; 5-Valve 2; 6-Carbon fixation reaction device; 7-Pumping device; 8-Valve 3; 9-Valve 4; 10-Valve 5; 11-Grouting borehole; 12-Sealing borehole; 13-Isolation wall; 14-Coal pillar; 15-Goaf; 16-Extraction borehole; 17-Negative pressure pump; 18-Gas storage tank; 19-Valve 6; 20-Abnormal roof collapse zone. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or mining system referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] As shown in Figures 1-3, this invention proposes a method for sequestering carbon dioxide from industrial solid waste and filling large-area suspended roof goaf areas, comprising the following steps:

[0031] Step S1: Select the coal mine goaf 15 as the exploration object, and arrange transient electromagnetic survey lines in combination with the surface topography of the goaf 15. Prioritize the selection of areas with no or small surface subsidence for the transient electromagnetic survey lines. Generally, the transient electromagnetic survey lines are arranged according to the principle that the survey lines are perpendicular to the strata.

[0032] like Figure 1a As shown, taking a certain mine as an example, the basic grid for the transient electromagnetic survey line layout is 40m×20m (line spacing 40m, point spacing 20m), with a total of 33 transient electromagnetic survey lines and 1140 transient electromagnetic survey points. The system quality is tested at 3%, with a total of 34 test points. The data quality meets the relevant specifications.

[0033] Step S2 involves obtaining apparent resistivity cross-sectional maps of each transient electromagnetic survey line through exploration. These maps are then interpreted and analyzed. Combined with the coal seam floor contour map, the extent of the suspended roof zone within the room-and-pillar goaf 15 and the extent of the abnormal roof collapse zone 20 are determined. Figure 1b As shown, the suspended roof area refers to the area where the stable roof of coal pillar 14 has not collapsed, and the abnormal roof collapse area refers to the area where the unstable roof of coal pillar 14 collapses.

[0034] Step S3, as follows Figure 1cAs shown, verification boreholes are arranged on both sides of the boundary line between the suspended roof area and the abnormal roof collapse area 20 determined in step S2 to further determine the distribution range of the suspended roof area and the abnormal roof collapse area 20; the verification boreholes are drilled vertically from the ground to the goaf area 15, and the depth of the verification boreholes should reach at least 3m below the coal seam floor. The boreholes are corrected every 50m, and are also corrected once after encountering bedrock, the coal seam floor, and after the end of the borehole. The error per 100m should not exceed ±0.15m.

[0035] The verification borehole is constructed on coal pillar 14 in the suspended roof area. Based on the sudden drop of the drill bit, burial of the drill bit, stuck drill bit, water leakage or increased consumption, rock fragmentation, water return throughout the borehole, smooth drilling, visible silt and / or powdery coal slag in the drilling water, blackening of the return water, etc., and combined with the in-hole camera, it is determined whether the goaf is a suspended roof area or an abnormal roof collapse area. If the sudden drop of the drill bit, burial of the drill bit, stuck drill bit, water leakage or increased consumption are encountered, it is considered an abnormal roof collapse area, otherwise it is a normal goaf area.

[0036] In this embodiment, a total of 16 verification boreholes were arranged, including 10 boreholes in the suspended roof area and 6 boreholes in the abnormal roof collapse area, which are consistent with the distribution of abnormal roof collapse areas. The locations of the verification boreholes and the distribution of abnormal roof collapse areas after verification are as follows: Figure 1c As shown.

[0037] The verification borehole was sealed according to the drilling engineering technical requirements. The sealing materials were cement, pure sand and clean water, with a water:cement:sand ratio of 0.6:1:2. The grouting method was pump injection, and the sealing depth was 5m above the bedrock surface.

[0038] Step S4, as follows Figure 3 As shown, an industrial solid waste carbon dioxide sequestration system is arranged. This system includes a carbon dioxide collection device 2, a crushing device 3, a carbon sequestration reaction device 6, a pumping device 7, a negative pressure pump 17, and a gas storage tank 18. The crushing device 3 and the carbon dioxide collection device 2 are connected to the carbon sequestration reaction device 6 via pipeline one and pipeline two, respectively. Valves one 4 and two 5 are respectively installed on pipeline one and pipeline two. The crushing device 3 is used to crush industrial solid waste 1. Industrial solid waste 1 mainly refers to various waste residues, dust, and other pollutants discharged into the environment during industrial production processes. Waste materials, such as blast furnace slag, steel slag, red mud, non-ferrous metal slag, coal slag, sulfuric acid slag, waste gypsum, desulfurization ash, carbide slag, and salt mud, are used in this embodiment. The industrial solid waste contains more than 50% calcium oxide and magnesium oxide. The output end of the carbon fixation reaction device 6 is connected to the input end of the pumping device 7. The output end of the pumping device 7 is connected to the input end of pipeline three. The output end of pipeline three is divided into two lines and connected to pipeline four and pipeline five respectively. Valves four 9 and five 10 are respectively installed on pipeline four and pipeline five. The output end of the negative pressure pump 17 is connected to the gas storage tank 18.

[0039] S5, such as Figure 2-3 As shown, along the boundary between the suspended roof area and the abnormal roof collapse area, a grouting borehole 11 is drilled on the side of the abnormal roof collapse area. The grouting borehole 11 is connected to the output end of pipeline five. Grouting slurry is pumped from the grouting borehole 11 to the abnormal roof collapse area 20. The grouting slurry and the broken roof rock blocks in the abnormal roof collapse area are cemented together to form an isolation wall 13. The isolation wall 13 separates the suspended roof area and the abnormal roof collapse area, so that the suspended roof area forms a sealed storage space.

[0040] The construction method of grouting borehole 11 is as follows: Drill the first section of grouting borehole in the loose strata to the stable bedrock strata. The diameter of the first section of grouting borehole is 300mm. After drilling is completed, install a metal protective sleeve in the hole and pour cement mortar into the sleeve to prevent the hole from collapsing. On the basis of the first section of grouting borehole, continue to excavate the second section of grouting borehole, penetrating the bedrock strata to the bottom plate of the goaf area of ​​the house and pillars. The diameter of the second section of grouting borehole is 200mm.

[0041] The grouting slurry is prepared as follows: Since the sealing of carbon dioxide requires high airtightness in the suspended roof area, a mixture of cement and fly ash with 5% cement expansion agent by mass is selected as the grouting material. To improve the compaction rate of the grout filling the broken roof rock blocks, an appropriate amount of cement quick-setting agent can also be added to the grouting slurry to shorten the setting time. The cement-to-fly ash mass ratio is 2–8:1, and the water-to-solid ratio is 1:1.2.

[0042] The grouting process is as follows: Cement, fly ash, water, and cement expansion agent are placed into the carbon fixation reaction device 6 in the above proportions and stirred evenly. Valves 3 (8) and 5 (10) are opened, valve 4 (9) is closed, and pumping device 7 is turned on to pump the grout to the abnormal collapse zone of the roof. The grouting flow rate and pressure are monitored in real time. Initially, a pumping pressure of 3 MPa is selected. When the flow rate approaches zero and the pressure continues to rise, the pumping pressure is increased to 4 MPa. When the flow rate approaches zero and the pressure continues to rise, the pumping pressure is increased to 5 MPa. When the flow rate approaches zero and the pressure continues to rise, the filling grouting is stopped, and valves 3 (8), 5 (10), and pumping device 7 are closed.

[0043] Step S6: Drill borehole 16 is constructed into the sealed goaf area. Pipeline 6 connects the drilling borehole to the negative pressure pump 17. Valve 19 is installed on pipeline 6. When valve 19 is opened, the negative pressure pump 17 extracts gas from the sealed goaf area. At the same time, the gas concentration in the goaf area is monitored by a gas monitor installed on pipeline 6. If the extracted gas concentration is lower than 10%, the extraction work of negative pressure pump 17 is stopped, valve 19 is closed, and the gas extraction is completed.

[0044] The construction method for extraction borehole 16 is as follows: the first extraction borehole is drilled in the loose strata to the stable bedrock strata. The diameter of the first extraction borehole is 200mm. After drilling is completed, a metal casing is installed in the borehole and cement mortar is poured into the casing to prevent borehole collapse. Based on the first extraction borehole, the second extraction borehole is continued to be excavated, penetrating the bedrock strata to the top of the goaf of the house and pillar. The diameter of the second extraction borehole is 150mm.

[0045] Step S7: Industrial solid waste and coal gangue are transported to crushing device 3 for crushing and grinding. The coal gangue is crushed to a particle size of less than 10mm, and the proportion of particles smaller than 2mm is not less than 1 / 3. The industrial solid waste is ground to a particle size of 0.25mm-0.35mm. Cement and fly ash are then added to the crushing device, making the mass ratio of cement:fly ash:industrial solid waste and coal gangue 1:5:4. Valve 4 is opened to transport the mixed solid waste mixture to carbon fixation reactor 6. A certain proportion of water is added to carbon fixation reactor 6 and continuously stirred to form a solid waste slurry. The mass ratio of water to solid waste mixture is 1:1.3. The valve is then closed. 1. Open valve 2.5 to transport carbon dioxide from carbon dioxide collection device 2 to carbon sequestration reaction device 6, and continuously stir to increase the contact area between carbon dioxide and solid waste mixture slurry, so that carbon dioxide and solid waste mixture slurry can fully react to achieve carbon dioxide mineralization and form sequestration material; through the carbon dioxide detection device set in carbon sequestration reaction device 6, the carbon dioxide concentration is monitored in real time. When the carbon dioxide concentration changes from continuously decreasing to remaining constant or continuously increasing, it indicates that carbon dioxide and solid waste mixture slurry have reacted fully. Close valve 2.5 to stop the supply of carbon dioxide; finally, the slump of the sequestration material after stirring is not less than 150mm.

[0046] The main reaction equations for the reaction between solid waste mixed slurry and carbon dioxide are:

[0047] MgO + H₂O → Mg(OH)₂

[0048] Mg(OH)₂ + CO₂ → MgCO₃

[0049] CaO + CO2 → CaCO3

[0050] Step S8: Drill the sealing borehole 12 and connect it to pipeline four. Open valve three 8 and valve four 9, start the pumping device 7, and pump the fully reacted sealing material to the suspended roof area device until the suspended roof area is filled.

[0051] The construction method for sealing borehole 12 is as follows: the first sealing borehole is drilled in the loose strata to the stable bedrock strata. The diameter of the first sealing borehole is 300mm. After drilling is completed, a metal casing is installed in the borehole and cement mortar is poured into the casing to prevent borehole collapse. Based on the first sealing borehole, the second sealing borehole is continued to be excavated, penetrating the bedrock strata to the bottom plate of the goaf area of ​​the house and pillars. The diameter of the second sealing borehole is 200mm.

[0052] The above description of the disclosed embodiments is presented in a progressive manner to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for sealing carbon dioxide by using industrial solid waste and filling large-area hanging roof goaf, characterized in that, The method comprises the steps of: Step S1, transient electromagnetic physical detection is performed on the selected room-and-pillar type goaf; Step S2, apparent resistivity section maps of each transient electromagnetic measuring line are obtained, interpretation and analysis are performed, the range of the suspended roof area and the range of the roof collapse abnormal area in the room-and-pillar type goaf are determined, the suspended roof area refers to the area where the roof of the coal pillar is stable and has not collapsed, and the roof collapse abnormal area refers to the area where the roof of the coal pillar has collapsed due to instability; Step S3, the ranges of the suspended roof area and the roof collapse abnormal area determined in step S2 are verified by using verification drill holes, the verification drill holes are arranged on both sides of the boundary between the suspended roof area and the roof collapse abnormal area, and the holes are sealed after the verification is completed; Step S4, an industrial solid waste carbon dioxide storage system is arranged, the industrial solid waste carbon dioxide storage system comprises a carbon dioxide collecting device, a crushing device, a carbon sequestration reaction device, a pumping device, a negative pressure pump and a gas storage tank, the crushing device and the carbon dioxide collecting device are connected to the carbon sequestration reaction device through pipelines, the carbon sequestration reaction device is connected to the pumping device, and the negative pressure pump is connected to the gas storage tank; S5, along the boundary between the suspended roof area and the roof collapse abnormal area, a grouting drill hole is drilled and bored on the side of the roof collapse abnormal area, the grouting drill hole is connected to the pumping device, grouting material slurry is pumped from the grouting drill hole to the roof collapse abnormal area, and the grouting material slurry is cemented with the broken roof rock in the roof collapse abnormal area to form a partition wall; cement and fly ash mixed slurry with 5% cement expansive agent by mass ratio are selected as the grouting material; Step S6, extraction drill holes are constructed in the closed suspended roof goaf and connected to the negative pressure pump, and the gas in the closed suspended roof goaf is extracted by the negative pressure pump; Step S7, the industrial solid waste and the coal gangue are transported to the crushing device for crushing and grinding, cement and fly ash are added to the crushing device, the mixed solid waste mixture is transported to the carbon sequestration reaction device, a certain proportion of water is added to the carbon sequestration reaction device for continuous stirring to form a solid waste mixed slurry, carbon dioxide in the carbon dioxide collecting device is transported to the carbon sequestration reaction device, and continuous stirring is performed to enable the carbon dioxide to fully react with the solid waste mixed slurry to realize carbon dioxide mineralization and form a storage material; Step S8, a storage drill hole is drilled and connected to the pumping device, and the fully reacted storage material is pumped to the suspended roof area to fill the suspended roof area.

2. The method for sealing carbon dioxide and filling large area hanging roof goaf by using industrial solid waste according to claim 1, characterized in that, In step S5, a cement accelerator is further added to the grouting material.

3. The method for sealing carbon dioxide and filling large area hanging roof goaf by using industrial solid waste according to claim 1 or 2, characterized in that, In step S5, the grouting process is that the grouting material slurry is pumped to the roof collapse abnormal area, the grouting flow and pressure are monitored in real time, a pumping pressure of 3 MPa is first selected, when the flow tends to be zero and the pressure continuously rises, the pumping pressure is increased to 4 MPa, when the flow tends to be zero and the pressure continuously rises, the pumping pressure is increased to 5 MPa, and when the flow tends to be zero and the pressure continuously rises, the filling grouting is stopped.

4. The method for sealing carbon dioxide and filling large area hanging roof goaf by using industrial solid waste according to claim 1, characterized in that, In step S7, the particle size of the coal gangue is crushed to less than 10 mm, and the proportion of the particle size of less than 2 mm is not less than 1 / 3, and the industrial solid waste is ground to a particle size of 0.25 mm-0.35 mm.

5. The method for sealing carbon dioxide and filling large area hanging roof goaf by using industrial solid waste according to claim 1 or 4, characterized in that, In step S7, the mass ratio of cement: fly ash: industrial solid waste and coal gangue is 1:5:4, and the mass ratio of water and solid waste mixture is 1:1.3.

Images