Carbon-negative backfill mining method using gangue high-porosity material

Abstract

A carbon-negative backfill mining method using a gangue high-porosity material, relating to the technical fields of CO2 sequestration and backfill mining. The method comprises: spraying a rapid-setting cementitious material (7) during discharge of a gangue (1) bulk material, thereby forming a high-porosity backfill body (2) in a goaf; and then continuously injecting liquid CO2 (4) into the sealed high-porosity backfill body (2) through a conveying pipe (3), thereby achieving highly efficient underground sequestration of CO2. The present method involves simple design and combines the backfilling technology and CO2 sequestration to achieve highly efficient mining and backfilling without affecting coal resource mining, promoting green mining and carbon-negative backfill implementation for mines, and proposing a new concept of carbon sequestration, thus having great application and research significance. Compared with solid backfill mining methods, using the rapid-setting adhesive material to fix gangue to form the high-porosity material having load-bearing performance can reduce the cost of the backfill mining technology and simplify an original tamping process.

Description

A method for mining high-porosity gangue materials with negative carbon filling Technical Field

[0001] The present invention relates to the field of filling mining methods, and in particular to a negative carbon filling mining method for gangue high-porosity materials. Background Art

[0002] In 2020, the coal industry accounted for 70% to 80% of China's total CO2 emissions, approximately 7.605 billion tons. To achieve the strategic goals of "carbon peak and carbon neutrality," and to reduce coal CO2 emissions overall, it is imperative to vigorously develop mine-negative carbon filling technology. Currently, the most mature method for CO2 storage is geological storage, but its high geological requirements and slow stratum adsorption rate have limited its development. In recent years, green mining and filling technology in mines has developed rapidly, not only disposing of large quantities of solid waste such as gangue, fly ash, and slag, but also preventing large-scale migration of overburden and surface subsidence. Currently, the main filling methods are high in cost and energy-intensive in raw material processing, and they also face development difficulties. Therefore, the proposal is to combine filling mining with CO2 storage. A new method for negative carbon filling mining using gangue high-porosity materials is urgently needed. Summary of the Invention

[0003] In response to the above-mentioned technical deficiencies, the purpose of the present invention is to provide a method for negative carbon filling and mining of high-porosity gangue materials. It addresses the problem of the lack of existing carbon fixation methods and utilizes negative carbon filling and mining of high-porosity gangue materials to open up a new idea for underground CO2 storage.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for negative carbon filling of high-porosity gangue materials. While the gangue bulk material is being dropped, a fast-setting material is sprayed to form a high-porosity filling body in the goaf. Liquid CO2 is then continuously injected into the closed high-porosity filling body through a pipeline to achieve efficient CO2 storage underground. The specific steps include:

[0006] (1) Filling preparation stage: The filling station prepares the gangue and fast-setting materials crushed to the specified particle size, and arranges the CO2 delivery pipeline on the ground in advance; inspects and prepares the delivery equipment and pipelines to ensure efficient preparation and rapid delivery of materials;

[0007] (2) Filling and mining stage: While the working face is being mined, the crushed gangue is transported to the goaf via a multi-hole bottom-discharging conveyor mounted on the rear top beam of the hydraulic support. The multi-angle automatic grouting device mounted behind the hydraulic support base sprays the fast-setting material synchronously with the gangue falling speed. The fast-setting material expands and solidifies rapidly, forming a high-porosity filling body with load-bearing performance.

[0008] (3) Retaining wall laying stage: After the working face advances a certain distance, a high-strength concrete is sprayed using a shotcrete device to form a concrete retaining wall to seal the filled filling area I. After the sealing is completed, the same method is used to fill and seal the subsequent filling area II, and so on;

[0009] (4) CO2 storage stage: Liquid CO2 is transported to each closed filling area through the pre-buried transmission pipeline. Following the progress of filling and coal mining, CO2 is stored underground in each filling area in turn.

[0010] Preferably, the size of each filling area and the spacing between CO2 transport boreholes are determined by comprehensively considering the storage capacity, filling load requirements and diffusion range, and are integer multiples of the coal mining step distance.

[0011] Preferably, the concrete retaining wall is formed by spraying high-strength concrete on the surface of the high-porosity filling body using a spraying device, and its strength meets the support requirements and CO2 sealing requirements and is not less than 10MPa.

[0012] Preferably, the arrangement of the liquid CO2 transmission pipeline includes ground vertical drilling, high-position dedicated lane drilling, and adjacent surface grouting drilling.

[0013] Preferably, the spraying device for spraying the fast-setting material is a multi-angle automatic spraying device, which is installed behind the hydraulic support base. The spraying device can also be a filling device disclosed in Chinese patent application No. CN117090629A, "An efficient filling device and method for high-porosity waste rock materials."

[0014] Preferably, the rapid bonding material is a high-strength material generated by acid-base reaction and physical action of metal oxides and inorganic salts at room temperature. It will quickly solidify within a few minutes at room temperature, and the bonding strength between it and the solid waste material can reach 5MPa in 1 hour.

[0015] The beneficial effects of the present invention are:

[0016] The present invention mainly fills the goaf with high-porosity materials, and continuously introduces liquid CO2 after sealing to achieve the purpose of efficient CO2 storage underground. Compared with the solid filling mining method, this method uses fast-setting materials to fix the gangue to form a high-porosity material with load-bearing properties, reducing the cost of filling mining technology and simplifying the original compaction process.

[0017] Liquid CO2 is transported to a closed filling area, and the hydration reaction fixes a certain amount of CO2. The high-porosity material of the filling body can also seal a large amount of CO2. This technology is safe, efficient, and feasible, and is conducive to the coal mining industry to complete the new answer to the green development of the mining industry under the "dual carbon" goal. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] FIG1 is a cross-sectional view of negative carbon filling mining of high-porosity gangue material provided by the present invention.

[0020] FIG2 is a plan view of negative carbon filling mining of high-porosity gangue materials provided by the present invention.

[0021] In the figure: 1-waste rock; 2-high-porosity filling material; 3-transmission pipeline; 4-liquid CO2; 5-retaining wall; 6-multi-porous bottom discharge conveyor; 7-fast-setting material; 8-multi-angle automatic spraying device; 9-hydraulic support; DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] A mining area uses a negative carbon filling mining method with high-porosity gangue materials to fill goaf and store CO2. As shown in Figures 1 and 2, this embodiment provides a negative carbon filling mining method with high-porosity gangue materials. The specific steps are as follows:

[0024] (1) According to the laboratory ratio, the particle size of the gangue 1 is 40-50 mm, the porosity of the high-porosity filling material is 30%, and the strength is about 80% of the dense filling, about 3.5 MPa, which basically meets the rock control requirements. The gangue is crushed to 40-50 mm on the ground and stored in the finished gangue bin.

[0025] (2) Vertical feeding drilling holes, rapid viscous material conveying drilling holes, and CO2 conveying drilling holes are arranged on the ground to the underground. The filling station equipment includes jaw crusher, vibrating screen, belt conveyor, mixer, CO2 condenser, pressure pump, etc.

[0026] (3) Finished gangue prepared on the surface is transported underground via a vertical feeding drill hole and then dropped to the rear of a hydraulic support 9 via a belt conveyor and a conveying device. A multi-angle automatic grouting device 8, mounted behind the base of the hydraulic support, sprays the fast-setting material 7 synchronously with the gangue dropping speed. The fast-setting material rapidly expands and solidifies, forming a highly porous filling body 2 with load-bearing properties. The hydraulic support automatically moves as the coal mining progresses, and the dropping speed and grouting speed are regulated according to the coal mining speed. The multi-angle automatic grouting device 8 uses an existing grouting device, which is prior art and will not be described in detail.

[0027] (4) According to theoretical analysis, the length of a carbon injection cycle is 200m, that is, after each 200m advance of the working face, a concrete retaining wall 5 is made by high-strength concrete spraying. After that, the liquid CO24 is delivered to the closed filling area through a borehole pump pre-buried on the ground and a delivery pipeline 3. Following the progress of filling and coal mining, the CO2 is sequentially stored underground in multiple closed filling areas (filling area I, filling area II, filling area III, etc.) of the working face. The recoverable reserves of this working face are 600,000 tons, and the fixed CO2 storage capacity is about 90,000 tons.

[0028] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for mining high-porosity gangue materials with negative carbon filling, characterized in that: While the loose gangue material is being dropped, a fast-setting material is sprayed to form a highly porous filling body in the goaf. Liquid CO2 is then continuously injected into the sealed highly porous filling body through a pipeline to achieve efficient CO2 storage underground. The specific steps include: (1) Filling preparation stage: The filling station prepares the gangue and fast-setting materials crushed to the specified particle size, and arranges the CO2 transmission pipeline on the ground in advance; (2) Filling and mining stage: While the working face is being mined, the crushed gangue is transported to the goaf, and the rapid-setting material is sprayed synchronously with the gangue falling speed using a grouting device. The rapid-setting material expands and solidifies rapidly, forming a high-porosity filling body with load-bearing performance; (3) Retaining wall laying stage: After the working face advances a certain distance, a high-strength concrete is sprayed using a shotcrete device to form a concrete retaining wall to seal the filled filling area I. After the sealing is completed, the same method is used to fill and seal the subsequent filling area II, and so on; (4) CO2 storage stage: Liquid CO2 is transported to each closed filling area through the pre-buried transmission pipeline. Following the progress of filling and coal mining, CO2 is stored underground in each filling area in turn.

2. The method for negative carbon filling mining of high-porosity gangue materials according to claim 1, characterized in that: The size of each filling area and the spacing between CO2 transport boreholes are determined by comprehensively considering the storage capacity, filling load requirements and diffusion range, and are integer multiples of the coal mining step distance.

3. The method for negative carbon filling mining of high-porosity gangue materials according to claim 1, characterized in that: The concrete retaining wall is formed by spraying concrete onto the surface of the high-porosity filling body with a spraying device. Its strength meets the support requirements and CO2 sealing requirements and is not less than 10MPa.

4. The method for negative carbon filling mining of high-porosity gangue materials according to claim 1, characterized in that: The layout methods of liquid CO2 transmission pipelines include vertical ground drilling, high-position dedicated tunnel drilling, and adjacent surface grouting drilling.

5. The method for mining high-porosity gangue materials with negative carbon filling according to claim 1, characterized in that: The spraying device for spraying fast-setting materials uses a multi-angle automatic spraying device, which is installed behind the hydraulic support base.

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