Carbon sequestration filling method based on synchronous mining of coal-aluminum symbiotic deposit

Abstract

The invention discloses a carbon sequestration filling method based on coal-aluminum symbiotic deposit synchronous mining, and belongs to the technical field of mining. The method comprises the following steps: S1, synchronously mining lower-layer aluminum ore and upper-layer coal mine; s2, coal gangue generated by coal mining is crushed to serve as filling aggregate; s3, performing carbon sequestration and dealkalization treatment on the red mud generated by aluminum ore smelting to be used as a filling cementing material; s4, mixing the two treated solid wastes, and matching cement to meet the relevant national standard of the filling material; and S5, pumping to a coal mine and aluminum mine goaf through a pipeline system to realize carbon sequestration filling.

Description

Technical Field

[0001] The invention relates to a carbon fixation and filling method based on synchronous mining of coal-aluminum paragenetic deposits, belonging to the technical field of mining. Background Art

[0002] When alumina is produced industrially, a large amount of solid waste - red mud - is generated. Due to the differences in the production processes of various aluminum smelters, about 1.0 to 1.8 tons of red mud will be discharged for every ton of alumina produced. The red mud produced by the Bayer process accounts for more than 90% of the total red mud emissions. The storage and disposal of red mud only temporarily alleviates its harm to the environment, and cannot fundamentally solve the problem of environmental pollution. At the same time, the storage of red mud also poses major safety hazards.

[0003] Gangue is a solid waste discharged during coal mining and washing. Compared with ordinary coal, it has the characteristics of low carbon content, low calorific value and hard texture. It is a kind of solid waste in mines. In addition, the storage and treatment of gangue can cause spontaneous combustion, acid rain, underground infiltration, siltation of rivers, photochemical smog and mudslides. Therefore, the reuse and resource utilization of gangue is imperative.

[0005] Backfilling of goaf can ensure the safety of mining production and increase the stability of surrounding rock in the mining area. However, the cost of backfill materials and the transportation of backfill slurry are the constraints on its technical development. It is of great significance to make full use of the gangue produced by coal mining and the red mud produced by aluminum smelting to prepare backfill materials that meet the relevant working performance and economic benefits.

[0006] Taking into full consideration the alkaline characteristics of red mud, while reducing the amount of cement through solid waste utilization, the alkaline absorption of CO2 by red mud is expected to achieve net zero or even negative carbon emissions for coal and aluminum enterprises.

[0007] In summary, coal and aluminum resources are indispensable for the development of modern society, but the large-scale stacking of coal gangue produced by coal mining and red mud produced by bauxite smelting will cause great environmental and safety problems. Therefore, for coal-aluminum co-existing deposits, a carbon-fixing filling method that can not only ensure the safe and efficient output of mineral resources, but also fill red mud and coal gangue into underground goafs nearby, and can also seal CO2, is urgently needed. Summary of the invention

[0008] In order to solve a series of problems caused by the stacking of red mud and coal gangue, the present invention aims to provide a carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits.

[0009] In the present invention, based on the safe and efficient simultaneous mining of coal-aluminum symbiotic deposits, a green, environmentally friendly, safe and efficient method for simultaneous mining and filling of coal-aluminum symbiotic deposits is provided, through which not only the two major solid wastes, red mud and coal gangue, can be utilized on a large scale, but also the upper aluminum ore and the lower coal ore can be safely and efficiently mined by simultaneous filling. This will greatly alleviate the problems related to the shortage of coal and aluminum resources, the accumulation of red mud and coal gangue occupying land, and the surface subsidence caused by underground mining.

[0010] The present invention provides a carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits, comprising the following process steps: S1, simultaneous mining of coal and aluminum: the aluminum ore in the lower layer and the coal ore in the upper layer are mined simultaneously, wherein the mined aluminum ore is subjected to Bayer process aluminum smelting to obtain Bayer process red mud, and the mined coal ore is subjected to coal sorting and washing to obtain coal gangue; S2, coal gangue processing: crush and screen the selected coal gangue to make its particle size meet the requirements of filling aggregate; S3, red mud carbon fixation and de-alkali treatment: CO2 gas with a purity of more than 99% is introduced into the Bayer red mud for de-alkali treatment to meet the requirements of the filling material; S4, adding cement to the two treated solid wastes, mixing them in a ratio of red mud: coal gangue: cement = 2~4:2~4:2~4, adding water to adjust the solid-liquid ratio to 0.6~1.0 (mass ratio), stirring and preparing filling materials, wherein the obtained filling materials meet the uniaxial compressive strength of 2.5MPa~10MPa and the slump greater than 10mm; S5, through the pipeline pumping system, the filling material is pumped into the coal mine and aluminum mine goaf for filling.

[0011] Furthermore, the simultaneous mining of coal and aluminum in S1 means that the upper coal seam and the lower aluminum ore layer are mined simultaneously while meeting the safety production and relevant standards, and the coal-aluminum mining enterprise has the conditions for smelting aluminum ore nearby, which is convenient for the further processing and transportation of the subsequent Bayer red mud. At the same time, it has the conditions for nearby sorting of coal, which also facilitates the further processing and transportation of coal gangue.

[0012] Furthermore, the gangue in S2 is processed by crushing and sorting the gangue into particles with a size less than 20 mm, and the mass ratio of particles with a size below 5 mm is 30% to 50%.

[0013] Furthermore, in S3, the red mud treatment method is to introduce CO2 gas into the red mud for dealkalization treatment, and through acid-base neutralization reaction, the pH value of the Bayer process red mud is reduced to the range of 6.5 to 8.5, meeting the pH value requirement for red mud landfill.

[0014] Furthermore, S4 is a mixture of treated gangue and treated red mud, with cement added according to the optimal ratio of red mud: gangue: cement = 4:2:4, water is added to adjust the solid-liquid ratio to 0.8, and the uniaxial compressive strength is 7.8 MPa and the slump is 13 cm.

[0015] Furthermore, the pipeline pumping system in S5 uses a steel pipe with a diameter of 20 cm for slurry filling, and the pumping pressure is 1.5 MPa. The filling material is pumped to the coal mine and aluminum mine goaf to implement carbon fixation filling; specifically, a complete filling method is adopted until the goaf is densely packed, and the bulk density of the dense filling body is about 2g / cm 3 The actual uniaxial compressive strength is above 7.0MPa, the filling connection rate is above 90%, and the roof subsidence is alleviated by more than 85%.

[0016] In the above method, a gangue crushing workshop, a red mud carbon fixation and de-alkali workshop, and a filling slurry preparation workshop are set up on the ground above the ore bed, the sorted gangue is transported to the gangue crushing workshop for crushing, the Bayer process red mud is transported to the red mud carbon fixation and de-alkali workshop for de-alkali treatment, and then the crushed gangue and the de-alkali red mud are mixed in the filling slurry preparation workshop, and cement and water are added to make filling materials; a pipeline system is arranged in the filling drilling well, and a coal seam goaf filling pipeline and an aluminum ore layer goaf filling pipeline are set. The pipeline system extends from the ground filling pump station to the coal seam and aluminum ore layer goaf. A steel pipe with a diameter of 20 cm is selected for slurry filling, and the pumping pressure is 1.5 MPa. The filling material is transported through the coal seam goaf filling pipeline to fill the upper coal seam goaf, and at the same time, the filling material is transported through the aluminum ore layer goaf filling pipeline to fill the lower aluminum ore layer goaf.

[0017] Beneficial effects of the present invention: (1) The present invention ensures safe and efficient simultaneous mining of coal-aluminum symbiotic deposits by synchronously filling the coal mine and aluminum mine goafs.

[0018] (2) The present invention makes full use of two solid wastes, red mud produced by aluminum smelting and coal gangue produced by coal washing, thereby reducing environmental pollution and safety problems caused by the accumulation of red mud and coal gangue.

[0019] (3) In the present invention, CO2 is introduced into the red mud during the red mud treatment process to dealkalize the red mud, which not only makes the pH value of the red mud meet the landfill requirements, but also allows the red mud to be used as a cementitious material to permanently seal CO2 underground. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of simultaneous mining and carbon fixation and filling in coal-aluminum symbiotic deposits; Figure 2 This is a schematic diagram of the coal-aluminum strata in the coal-aluminum symbiotic deposit; Figure 3 This is a schematic diagram of the carbon fixation and filling effect of simultaneous mining of coal-aluminum symbiotic deposits; Figure 4 A flow chart for simultaneous mining and carbon fixation and filling of coal-aluminum symbiotic deposits; In the figure: 1—coal seam; 2—aluminum ore seam; 3—gangue crushing workshop; 4—red mud carbon fixation and de-alkali workshop; 5—filling slurry preparation workshop; 6—filling drilling; 7—filling pipeline in coal seam goaf; 8—filling pipeline in aluminum ore seam goaf; 9—filling body; 10—coal washing plant; 11—aluminum smelting plant. DETAILED DESCRIPTION

[0021] The present invention is further illustrated by the following examples, but is not limited to the following examples.

[0022] The present invention provides a carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits, comprising the following process steps: S1, simultaneous mining of coal and aluminum: the aluminum ore in the lower layer and the coal ore in the upper layer are mined simultaneously, wherein the mined aluminum ore is subjected to Bayer process aluminum smelting to obtain Bayer process red mud, and the mined coal ore is subjected to coal sorting and washing to obtain coal gangue; S2, coal gangue processing: crush and screen the selected coal gangue to make its particle size meet the requirements of filling aggregate; S3, red mud carbon fixation and de-alkali treatment: CO2 gas with a purity of more than 99% is introduced into the Bayer red mud for de-alkali treatment to meet the requirements of the filling material; S4, two treated solid wastes are added with cement. S4 is made by mixing treated coal gangue and treated red mud, and adding cement. According to the optimal ratio of red mud: coal gangue: cement = 4:2:4, water is added to adjust the solid-liquid ratio to 0.8, and the uniaxial compressive strength is 7.8MPa and the slump is 13cm; S5, through the pipeline pumping system, a steel pipe with a diameter of 20cm is selected for slurry filling. The pumping pressure is 1.5MPa, and the filling material is pumped into the coal mine and aluminum mine goaf to implement carbon fixation filling; specifically, a complete filling method is adopted until the goaf is densely compacted.

[0023] In the above method, a gangue crushing workshop 3, a red mud carbon fixation and de-alkali workshop 4, and a filling slurry preparation workshop 5 are set up on the ground above the ore bed, the selected gangue is transported to the gangue crushing workshop for crushing, the Bayer red mud is transported to the red mud carbon fixation and de-alkali workshop for de-alkali treatment, and then the crushed gangue and the de-alkali red mud are mixed in the filling slurry preparation workshop, and cement and water are added to make filling materials; a pipeline system is arranged in the filling borehole 6, and a filling slurry preparation workshop is set up. A coal seam goaf filling pipeline 7 and an aluminum ore layer goaf filling pipeline 8 are installed. The pipeline system extends from the ground filling pump station to the coal seam and aluminum ore layer goafs. A steel pipe with a diameter of 20 cm is used for slurry filling. The pumping pressure is 1.5 MPa. The filling material is transported through the coal seam goaf filling pipeline to fill the upper coal seam 1 goaf. At the same time, the filling material is transported through the aluminum ore layer goaf filling pipeline 8 to fill the lower aluminum ore layer 2 goaf.

[0024] In order to have a clearer understanding of the technical objectives, features and effects of the present invention, the method for simultaneous mining and carbon fixation and filling of coal-aluminum symbiotic deposits is now further described in detail in conjunction with the accompanying drawings.

[0025] The stratigraphic relationship between the coal seam and the aluminum ore layer of a coal-aluminum joint venture is shown in Figures 1 and 2. The upper coal seam is 3 meters thick and is a nearly horizontal coal seam. It is mined simultaneously with the lower nearly horizontal aluminum ore layer with a thickness of 2 meters. The interlayer distance between the coal seam and the aluminum ore layer is 50 meters. After the coal seam is mined, the coal is sorted in the coal washing plant 10 located in the surface industrial square to obtain coal gangue, and the bauxite passes through the aluminum smelting plant 11 in the surface industrial square to obtain Bayer red mud. The sorted coal gangue is transported to the coal gangue crushing workshop 3, and it is crushed into a standard standby with a particle size of less than 20 mm and a proportion of 30% to 50% of particles less than 5 mm. The Bayer red mud is transported to the red mud carbon fixation and de-alkali workshop 4, and 99% pure CO2 is introduced to dealkalize the Bayer red mud until the pH value drops to 7.5, meeting the pH value requirements for red mud landfill. Then, in the filling slurry preparation workshop 5, the treated gangue and the treated red mud are mixed, and cement is added. According to the mass ratio of red mud: gangue: cement = 4:2:4, water is added to adjust the solid-liquid ratio to 0.8 and the filling material is mixed. The obtained filling material has a uniaxial compressive strength of 7.8MPa and a slump of 13mm. A pipeline system is arranged in the filling borehole 6. The pipeline system extends from the ground filling pump station to the coal mine aluminum ore layer goaf. A steel pipe with a diameter of 20cm is selected for slurry filling. The pumping pressure is 1.5MPa. Among them, 7 is the coal seam goaf filling pipeline, which is used to fill the upper coal seam goaf, and 8 is the aluminum ore layer goaf filling pipeline, which is used to fill the lower aluminum ore layer goaf. The goaf is filled as much as possible by pumping to form a dense filling body 9. The bulk density of the dense filling body is about 2g / cm 3 The actual uniaxial compressive strength is 7.6MPa, the filling connection rate is 90%, and the roof subsidence is alleviated by more than 85%.

[0026] Through the carbon fixation and filling method based on the simultaneous mining of coal-aluminum symbiotic deposits, the mining efficiency of the company's coal and aluminum resources has been increased by more than 20%, saving the company about 2 million yuan in red mud and coal gangue solid waste treatment expenses. At the same time, the red mud dealkalization process can achieve the effect of fixing 30 kilograms of CO2 per ton of red mud, and the problems of surface subsidence and groundwater resource damage caused by underground mining have been solved.

Claims

1. A carbon fixation filling method based on the synchronous mining of coal-aluminum symbiotic deposits, characterized in that The following steps are involved: S1, simultaneous mining of coal and aluminum: the aluminum ore in the lower layer and the coal ore in the upper layer are mined simultaneously, wherein the mined aluminum ore is subjected to Bayer process aluminum smelting to obtain Bayer process red mud, and the mined coal ore is subjected to coal sorting and washing to obtain coal gangue; S2, coal gangue processing: crush and screen the selected coal gangue to make its particle size meet the requirements of filling aggregate; S3, red mud carbon fixation and de-alkali treatment: CO2 gas with a purity of more than 99% is introduced into the Bayer red mud for de-alkali treatment to meet the requirements of the filling material; S4, adding cement to the two treated solid wastes, mixing them in a ratio of red mud: coal gangue: cement = 2~4:2~4:2~4, adding water to adjust the solid-liquid ratio to 0.6~1.0, and mixing to prepare a filling material, wherein the obtained filling material meets the uniaxial compressive strength of 2.5MPa~10MPa and the slump is greater than 10mm; S5, through the pipeline pumping system, the filling material is pumped into the coal mine and aluminum mine goaf for filling.

2. The carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits according to claim 1 is characterized in that: In S1, simultaneous mining of coal and aluminum means that the upper coal seam and the lower aluminum ore layer are mined simultaneously while meeting safety production and related standards. The coal-aluminum mining enterprise has the conditions for smelting aluminum ore nearby and sorting coal nearby, which facilitates the further processing and transportation of the subsequent Bayer red mud and coal gangue.

3. The carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits according to claim 1 is characterized in that: The gangue in S2 is processed by crushing and sorting the gangue into particles with a size less than 20 mm, with the mass ratio of particles with a size below 5 mm being 30% to 50%.

4. The carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits according to claim 1 is characterized in that: In S3, the red mud treatment method is to pass CO2 gas into the red mud for dealkalization treatment. Through acid-base neutralization reaction, the pH value of the Bayer process red mud is reduced to 6.5~8.5, meeting the pH value requirement for red mud landfill.

5. The carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits according to claim 1 is characterized in that: S4 is a mixture of treated gangue and treated red mud, with cement added according to the optimal ratio of red mud: gangue: cement = 4:2:

4. Water is added to adjust the solid-liquid ratio to 0.8, and the uniaxial compressive strength is 7.8MPa and the slump is 13cm.

6. The carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits according to claim 1 is characterized in that: The pipeline pumping system in S5 uses a steel pipe with a diameter of 20 cm for slurry filling. The pumping pressure is 1.5 MPa. The filling material is pumped into the coal mine and aluminum mine goaf to implement carbon fixation filling.

7. The carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits according to claim 6 is characterized in that: The complete filling method is adopted until the goaf is compacted, and the bulk density of the compacted filling body is 2g / cm 3 The actual uniaxial compressive strength is above 7.0MPa, the filling connection rate is above 90%, and the roof subsidence is alleviated by more than 85%.

8. The carbon fixation and filling method based on the synchronous mining of coal-aluminum symbiotic deposits according to claim 1 is characterized in that: A gangue crushing workshop, a red mud carbon fixation and de-alkali workshop, and a filling slurry preparation workshop are set up on the ground above the ore bed. The sorted gangue is transported to the gangue crushing workshop for crushing, and the Bayer red mud is transported to the red mud carbon fixation and de-alkali workshop for de-alkali treatment. Then, the crushed gangue and the de-alkali red mud are mixed in the filling slurry preparation workshop, and cement and water are added to make filling materials. A pipeline system is arranged in the filling drilling well, and a coal seam goaf filling pipeline and an aluminum ore layer goaf filling pipeline are set. The pipeline system extends from the ground filling pump station to the coal seam and aluminum ore layer goaf. A steel pipe with a diameter of 20 cm is used for slurry filling. The pumping pressure is 1.5 MPa. The filling material is transported through the coal seam goaf filling pipeline to fill the upper coal seam goaf. At the same time, the filling material is transported through the aluminum ore layer goaf filling pipeline to fill the lower aluminum ore layer goaf.

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