Method for filling and recovering empty coal seam by columnar solid carbon dioxide

Abstract

The application discloses a method for filling columnar solid carbon dioxide to recover the empty coal seam. The method first identifies the feasibility of upward mining of the empty coal seam, and proves the distribution characteristics of the columnar residual mining area coal column group; then, the solid carbon dioxide is injected into the underlying goaf, and the condensing pipe is placed to continuously condense the solid carbon dioxide in the underlying goaf, so that certain bearing capacity is formed, and the resources of the empty coal seam working face are gradually mined. The method realizes the filling and reinforcement of the underlying goaf, realizes the carbon dioxide storage, and guarantees the safety of the recovery of the empty coal seam. The two technologies of carbon dioxide storage and residual coal recovery are combined together, and the safety of the columnar residual mining area is guaranteed.

Description

Technical Field

[0001] This invention relates to a backfilling mining method in the field of coal mining technology, specifically to a method for re-mining vacant coal seams using column-type solid carbon dioxide backfilling. Background Technology

[0002] Currently, many patents involve carbon sequestration in abandoned goaf spaces and residual coal remining technologies. Chinese patent CN107780965A provides a method for storing waste concrete and sequestering carbon dioxide in abandoned mines. It involves filling the goaf with waste concrete and then sequestering carbon dioxide, effectively achieving carbon sequestration. Chinese patent CN104790952A involves single-sided filling next to pillars on one side of a goaf group. This not only provides lateral support for the knife-pillar coal pillar group but also forms a common load-bearing structure, reducing stress concentration. However, patents that consider carbon dioxide sequestration while reinforcing and supporting residual mining areas are relatively few.

[0003] In summary, this invention proposes a method for remining vacant coal seams by injecting solid carbon dioxide into the residual mining area, which has high development prospects and research value. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a method for remining goaf coal seams using column-type solid carbon dioxide filling. This method achieves filling and reinforcement of the underlying goaf area, and seals carbon dioxide, thus ensuring the safety of remining goaf coal seams.

[0005] This invention is mainly aimed at the re-mining of coal seams in the absence of coal seams. It combines carbon dioxide sequestration with the mining process in the absence of coal seams. Current patents related to mining in the absence of coal seams all involve backfilling the absence area with slurry (including full backfilling, partial backfilling, and unilateral backfilling), but there are no patents that use solid carbon dioxide (dry ice) for backfilling. This invention solves the problem of partial carbon dioxide sequestration while ensuring the safety and stability of mining in the absence of coal seams.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for re-mining a goaf coal seam using column-type solid carbon dioxide filling. First, the feasibility of upward mining of the goaf coal seam is determined, and the distribution characteristics of the coal pillar group in the column-type residual mining area are explored. Solid carbon dioxide is injected into the underlying goaf area, and a condenser is placed to allow the solid carbon dioxide in the underlying goaf area to continuously condense, forming a certain bearing capacity, and gradually extracting the resources of the goaf coal seam working face.

[0007] The technical solution is implemented according to the following steps:

[0008] (1) Determine the feasibility of mining the coal seam above the pillar-type residual mining area;

[0009] (2) Based on the existing geological and technical data of the mine, investigate and find out the distribution of coal pillar groups and void groups in the underlying residual mining area of ​​the coal seam, and compile a morphological distribution map of the underlying residual mining area coal pillar groups and void groups to guide safe production.

[0010] (3) Arrange the mining roadway for the working face of the exposed coal seam and arrange the working face of the exposed coal seam;

[0011] (4) When the working face of the coal seam is advancing and passes directly above the underlying goaf, boreholes are arranged between the underlying goaf.

[0012] (5) Particle solid carbon dioxide is placed along the borehole, and a condenser is placed along the borehole to continuously condense the solid carbon dioxide in the underlying goaf.

[0013] (6) When it is detected that the underlying goaf is filled with solid carbon dioxide particles and forms a bearing capacity of more than 5 MPa, the working face of the goaf is advanced.

[0014] Preferably, step (1) uses the traditional "three-zone" discrimination method, surrounding rock balance method, ratio discrimination method, numerical analysis method and quantitative discrimination method to comprehensively judge the feasibility of mining the overlying void coal seam in the pillar residual mining area.

[0015] Preferably, in step (2), the width and height of the goaf group and coal pillar group under the goaf coal seam are determined by investigating the original geological and technical data of the mine, and the distribution range, size and volume of the pillar-type residual goaf group are accurately detected by using a three-dimensional laser scanner.

[0016] Preferably, the working face and mining roadway of the overlying coal seam in step (3) are arranged above the coal pillar and goaf of the underlying overlying coal seam investigated in step (2) under the condition that the overlying coal seam in the residual mining area is feasible to be mined upwards as determined in step (1).

[0017] Preferably, in step (4), casing drilling technology is used for drilling construction, with a hole diameter of 180mm, a hole spacing of 20~25m, and the drilling depth is determined by the distance between the exposed coal seam and the underlying goaf.

[0018] Preferably, in step (5), the solid carbon dioxide is absorbed by a carbon dioxide trap on the ground and transported to a solid carbon dioxide converter arranged on the coal seam roadway, and the two are connected by a pipeline.

[0019] Preferably, in step (5), the condenser pipe and the solid carbon dioxide transport pipeline are both arranged in the borehole. The solid carbon dioxide transport pipeline is connected to the solid carbon dioxide converter. The refrigeration machine is arranged on the working face and connected to the power supply. The condenser pipe is connected to the refrigeration machine. After the condenser pipe is put into the space of the underlying goaf through the borehole, it can keep the surrounding environment at an ambient temperature below -78.5℃.

[0020] Preferably, the particulate solid carbon dioxide in step (5) is formed after conversion by a carbon dioxide converter.

[0021] Preferably, the bearing capacity of the underlying goaf after filling in step (6) is tested by high-density electrical resistivity tomography to detect the voids and compaction degree of the underlying goaf. When the bearing strength exceeds 5 MPa, the bearing strength requirement is met.

[0022] By adopting the above technical solution, the beneficial effects of the present invention are:

[0023] Based on determining the feasibility of upward mining of the goaf and understanding the distribution characteristics of the underlying goaf groups and coal pillar groups, this invention addresses the issue by injecting granular solid carbon dioxide into the underlying goaf through boreholes, gradually extracting the coal resources from the goaf. This invention combines carbon dioxide sequestration and residual coal remining technologies, ensuring safe mining in pillar-type residual mining areas. Attached Figure Description

[0024] Figure 1 A schematic diagram of the solid carbon dioxide filling structure next to the first coal pillar of the column-type hollow coal seam working face in the residual mining area.

[0025] Figure 2 A top view of the solid carbon dioxide filling structure next to the first coal pillar of the column-type hollow coal seam working face in the residual mining area.

[0026] Figure 3 A top view of the structural principle of the first coal pillar after gas filling in the pillar-type coal face of the residual mining area.

[0027] Figure 4 A schematic diagram of the solid carbon dioxide filling structure next to the Nth coal pillar in the column-type hollow coal seam working face of the residual mining area.

[0028] Figure 5 A top view of the solid carbon dioxide filling structure next to the Nth coal pillar in the column-type hollow coal seam working face of the residual mining area.

[0029] Figure 6 Top view of the structural principle of the Nth coal pillar after gas filling in the column-type coal face of the residual mining area;

[0030] In the diagram, 1. Goaf, 2. Interlayer structure, 3. Refrigeration unit, 4. Goaf working face, 5. Goaf, 6. Condenser pipe, 7. Carbon dioxide converter, 8. Borehole, 9. Solid carbon dioxide transport pipeline, 10. Coal pillar, 11. Solid carbon dioxide particles, 12. Underlying goaf space. Detailed Implementation

[0031] The following examples are intended to illustrate and explain the invention, and do not limit the scope of the invention.

[0032] To provide a clearer understanding of the technical objectives, features, and effects of the present invention, a method for re-mining vacant coal seams using column-type solid carbon dioxide filling is now described in further detail with reference to the accompanying drawings.

[0033] To ensure its designed production output, a certain mine violated conventional mining procedures by placing its production roadways within the thicker No. 9 coal seam. The 9301 working face of the No. 9 coal seam was mined using a pillar-type mining method. However, as the 9301 working face approached the shutdown line, the mine faced resource depletion and a tight mining continuity. To meet its coal production targets, it was forced to adopt upward mining, re-mining the thinner No. 4 coal seam above. This is a typical example of upward mining of overlying, hollowed-out coal seams in a pillar-type residual mining area. The distance between the No. 9 and No. 4 coal seams is 45-50 meters. In light of the above situation, the implementation process of this invention will be further described in detail below with reference to the accompanying drawings. The specific implementation steps are as follows:

[0034] Step 1: Using the traditional "three-zone" discrimination method, surrounding rock balance method, ratio discrimination method, mathematical analysis method and quantitative discrimination method, the feasibility of mining the No. 4 vented coal seam 1 in this mine is comprehensively judged. It can be seen that the vented coal seam 1 is located in the bending and subsidence zone of the interlayer rock stratum 2, and the degree of structural damage is relatively small. Therefore, it is feasible to mine the vented coal seam 1 over the knife pillar residual mining area.

[0035] Step two: Based on existing geological and technical data, it is known that the widths of the coal pillar group 10 and the empty area group 12 in the 9301 knife-pillar residual mining area of ​​the No. 9 coal seam are 10-15m and 15-20m respectively, with a mining height of 3.5m. A three-dimensional laser scanner is used to accurately survey the distribution, size, and volume of the coal pillar group 10 and the empty area group 12 in the 931 knife-pillar residual mining area, and a distribution morphology map of the coal pillar group 10 and the empty area group 12 in the No. 9 coal seam is compiled to guide the safe remining of coal resources in the 1st empty coal seam.

[0036] Step 3: Start excavating the return roadway of the hollow coal seam 1 above the coal pillar of the residual mining area identified in Step 2, and set up the hollow coal seam working face 4.

[0037] Step 4: Using casing drilling technology, borehole 8 is drilled into the underlying goaf area below the bottom plate of the working face 4 of the goaf. The borehole diameter is 180mm, the spacing between boreholes is 20~25m, and the drilling depth is 45~50m.

[0038] Step 5: The carbon dioxide gas collected on the ground is converted into solid carbon dioxide particles 11 through the carbon dioxide converter 7, and then transported to the underlying goaf space 12 through the solid carbon dioxide transport pipeline 9 along the borehole 8.

[0039] Specifically, the particulate solid carbon dioxide described in this invention is formed after conversion by a carbon dioxide converter.

[0040] Carbon dioxide is absorbed by a carbon dioxide trap on the ground and transported to a solid carbon dioxide converter arranged on the goaf roadway. The carbon dioxide trap and the solid carbon dioxide converter are connected by a pipeline. The condenser pipe and the solid carbon dioxide transport pipeline are both arranged in borehole 8. The solid carbon dioxide transport pipeline is connected to the solid carbon dioxide converter. The condenser pipe is connected to the chiller, and the chiller is connected to the power supply. After the condenser pipe is placed in the underlying goaf space, it can make the surrounding environment continuously condense.

[0041] Step 6: Insert the condenser pipe 6 along the borehole 8 into the underlying mining space 12 filled with solid carbon dioxide particles 11. The refrigeration unit 3 continuously delivers cold air to the underlying mining space 12, so that the mining space maintains an ambient temperature below -78.5℃.

[0042] Step 7: When the solid carbon dioxide particles 11 filling the underlying goaf space 12 are detected by high-density electrical resistivity tomography and the bearing capacity exceeds 5 MPa, the carbon dioxide converter 7 and the solid carbon dioxide transport pipeline 9 are removed, while the refrigeration unit 3 and the condenser pipe 6 are retained to continuously condense the solid carbon dioxide in the underlying goaf (continuous condensation is required in the future, so solid carbon dioxide (dry ice) is retained in the goaf); the working face 1 of the goaf coal seam is rearranged, and the advance is continued, and the operation is repeated.

[0043] The above description represents the preferred embodiments of the present invention. It should be noted that any improvements or modifications made to the above-described implementation methods without departing from the technical essence and principles of the present invention are within the protection scope of the present invention.

Claims

1. A method for pillar solid carbon dioxide filling for repeated mining of empty coal seam, characterized in that, Firstly, the feasibility of upward mining of the overlying coal seam is determined, and the distribution characteristics of the coal pillar group in the pillar-type residual mining area are ascertained; solid carbon dioxide is injected into the underlying goaf, and a condensing pipe is placed to continuously condense the solid carbon dioxide in the underlying goaf, so as to form a certain bearing capacity, and the resources in the overlying coal seam working face are gradually mined out; The method for filling the overlying coal seam by the columnar solid carbon dioxide comprises the following steps: (1) determining the feasibility of upward mining of the overlying coal seam above the pillar-type residual mining area; (2) according to the original geological and technical data of the mine, the distribution of the coal pillar group and the goaf group in the underlying residual mining area of the overlying coal seam is investigated and ascertained, and a distribution map of the shape of the coal pillar group and the goaf group in the underlying residual mining area is prepared to guide the safety production; (3) arranging the recovery roadway of the overlying coal seam working face and the overlying coal seam working face; (4) when the overlying coal seam working face advances above the underlying goaf, drilling holes are arranged in the underlying goaf; (5) along the drilling holes, granular solid carbon dioxide is placed, and a condensing pipe is placed along the drilling holes to continuously condense the solid carbon dioxide in the underlying goaf; (6) when it is detected that the solid carbon dioxide particles fill the underlying goaf and form a bearing capacity of more than 5 MPa, the overlying coal seam working face is advanced.

2. The method for filling and recovering the empty coal seam by the columnar solid carbon dioxide according to claim 1, characterized in that, In step (1), the traditional "three zone" discrimination method, surrounding rock balance method, ratio discrimination method, numerical analysis method and quantitative discrimination method are used to comprehensively determine the feasibility of upward mining of the overlying coal seam above the pillar-type residual mining area.

3. The method of claim 1, wherein the method further comprises, In step (2), the width and height of the goaf group and the coal pillar group in the underlying residual mining area of the overlying coal seam are ascertained by investigating the original geological and technical data of the mine, and the distribution range, size and volume of the goaf group in the pillar-type residual mining area are accurately detected by using a three-dimensional laser scanner.

4. The method of claim 1, wherein the method further comprises, In step (3), the overlying coal seam working face and the recovery roadway are arranged above the underlying residual mining area under the condition that the overlying coal seam above the residual mining area is determined to be feasible for upward mining in step (1).

5. The method of claim 1, wherein the method further comprises, In step (4), the drilling holes are drilled by using the casing drilling technology, the hole diameter is 180 mm, the hole spacing is 20-25 m, and the drilling depth is determined by the distance between the overlying coal seam and the underlying goaf.

6. The method of claim 1, wherein the method further comprises, In step (5), the granular solid carbon dioxide is converted by a solid carbon dioxide converter.

7. The method of claim 6, wherein the method further comprises, The solid carbon dioxide is absorbed by a carbon dioxide collector on the ground, transmitted to a solid carbon dioxide converter arranged in the crossheading of the overlying coal seam, and converted into solid carbon dioxide. The carbon dioxide collector and the solid carbon dioxide converter are connected by a pipeline.

8. The method of claim 1, wherein the method further comprises, In step (5), the condensing pipe is connected to a refrigeration machine, and can continuously maintain the ambient temperature around the underlying goaf at below -78.5℃ after being placed in the space of the underlying goaf.

9. The method of claim 1, wherein the method further comprises, In step (6), the bearing capacity of the underlying goaf after filling is detected by using the high-density electrical method to detect the voids and compaction degree of the underlying goaf.

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