A method and system for carbon dioxide mineralization packing

Abstract

The application provides a carbon dioxide mineralization filling method and system, and belongs to the technical field of coal mining. First, the initial mineralization of fly ash, coal gangue and water is completed on the ground, the mineralized material that has completed the initial mineralization is mixed with aggregates and cementitious materials through stirring, filling material is prepared and injected into a goaf, and the mineralization filling treatment of the goaf is completed. Therefore, the application not only has low filling cost and simple operation, but also can mineralize carbon dioxide. Further, the problem of solid waste pollution is solved, and large-scale treatment of solid waste is realized.

Description

Technical Field

[0001] This invention belongs to the field of coal mining technology, and in particular relates to a carbon dioxide mineralization backfilling method and system. Background Technology

[0002] Coal, as a basic energy source, generates solid waste such as coal gangue and fly ash during its production and use, which are major sources of pollution that urgently need to be addressed. Furthermore, with the development of coal resources, the area of ​​mined-out areas in mines is expanding. Directly shutting them down would not only result in a huge waste of existing resources (underground space) but could also lead to safety, environmental, and social problems. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a carbon dioxide mineralization backfilling method and system. This method utilizes existing goaf areas as backfilling and carbon sequestration spaces, using coal-based solid waste as raw material and sodium carbonate solution as an intermediate medium to prepare CO2 backfilling materials. This achieves safe CO2 sequestration, solves the solid waste pollution problem, and enables large-scale solid waste treatment.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] One of the technical solutions of the present invention:

[0006] A carbon dioxide mineralization backfilling system includes a backfill material preparation system, a backfill transportation system, and a goaf backfilling system;

[0007] The filling material preparation system and the goaf filling system are connected through the filling transportation system;

[0008] The filling material preparation system includes a reactor, a stirrer 1, a stirrer 2, and a filling device; the reactor and the stirrer 1 are connected sequentially through a pipeline; the outlet end of the stirrer 1 is connected to the inlet end of the stirrer 2 through a pipeline; and the outlet end of the stirrer 2 is connected to the filling device through a pipeline.

[0009] Beneficial effects: The reactor defined in this invention can better absorb carbon dioxide, thereby increasing the reaction contact area and improving the reaction rate for the subsequent agitator reaction; the carbon dioxide mineralization filling system uses two agitators, which can make the solid particles in the filling material (a solid-liquid mixture) finer, making the solid-liquid mixture more thorough (i.e., making the internal material distribution uniform, making the filling material more robust and having excellent sealing performance); and the fluid is completely mixed, causing very little solid-liquid separation during transportation, making it more stable and safe for filling in goaf areas.

[0010] Preferably, a thin carbon dioxide pipe is installed at the bottom of the goaf filling system. Carbon dioxide gas is slowly introduced during the solidification of the filling material to mineralize the filling material, thereby increasing the strength of the filling material and enhancing the safety of the goaf.

[0011] Preferably, the filling and transport system is a PVC pipe with an inner diameter of 160mm.

[0012] The second technical solution of the present invention:

[0013] A carbon dioxide mineralization backfilling method, utilizing the aforementioned carbon dioxide mineralization backfilling system, includes the following steps:

[0014] In the filling material preparation system, sodium carbonate solution is used as an intermediate medium to prepare carbon dioxide mineralized filling material using a two-step method of wet direct mineralization and indirect mineralization.

[0015] The carbon dioxide mineralized backfill material is transported to the goaf backfill system using the backfill transportation system, and carbon dioxide is introduced into the goaf backfill system to reinforce the carbon dioxide mineralized backfill material.

[0016] Before the carbon dioxide mineralized backfill material is transported to the goaf backfilling system, it needs to undergo a fluid test. The final result should be that the slurry layering degree of the carbon dioxide mineralized backfill material is no more than 20 mm and the slump is greater than 180 mm before it is filled by the backfilling device.

[0017] Preferably, the wet direct mineralization method includes the following steps:

[0018] A sodium carbonate solution is introduced into the reactor and carbon dioxide gas is continuously introduced at a flow rate of 1.2 L / min to 1.5 L / min. The reaction produces a sodium bicarbonate solution. When the pH of the solution reaches 8, the introduction of carbon dioxide gas is stopped.

[0019] The sodium bicarbonate solution is fed into the stirrer 1, and carbon dioxide is continuously introduced into it. When there is no obvious precipitate, the carbon dioxide gas is stopped, and fly ash and coal gangue are added and mixed and stirred to carry out the initial mineralization reaction. The mixture obtained from the reaction is filtered to obtain carbonate precipitate and filtrate. The filtrate is returned to the reactor for recycling through a pressure pump.

[0020] Beneficial Effects: The sodium carbonate solution specified in this invention can react with carbon dioxide, thereby converting carbon dioxide from a gaseous form into ionic form in the solution, greatly accelerating the mineralization reaction rate of fly ash and coal gangue with carbon dioxide. Specifically, adding Na₂CO₃ as an intermediate medium in the wet direct mineralization process allows more carbon dioxide gas to dissolve in the solution and become bicarbonate ions, significantly accelerating the carbonation of solid waste. Compared to direct mineralization methods without sodium carbonate, where excess CO₂ reacts with fly ash and coal gangue, resulting in SiO₂ accumulation on their surface, hinders the reaction between carbon dioxide and the fly ash, affecting the reaction rate. Furthermore, excess CO₂ dissolved in water is weakly acidic, which not only hinders the rapid mineralization reaction but also affects the subsequent hardening reaction. In addition, compared to other intermediate mediums such as alcohols and ammonia, the byproducts are highly corrosive, easily corroding pipes and instruments and potentially polluting water resources. This invention, however, uses Na₂CO₃ as the intermediate medium, producing no other harmful byproducts during the reaction process. Moreover, Na₂CO₃ as an intermediate medium can be recycled, achieving green sustainability.

[0021] Furthermore, the concentration of the sodium carbonate solution is 1 mol / L;

[0022] The ratio of sodium carbonate solution, fly ash, and coal gangue is 3:3:5.

[0023] Furthermore, the mixing conditions are: a rotation speed of 300-600 r / min and a time of 30 min.

[0024] Preferably, the indirect mineralization method includes the following steps:

[0025] The carbonate precipitate is fed into a mixer 2, where gel material, aggregate, and water are added and mixed to carry out a secondary mineralization reaction, thereby obtaining the carbon dioxide mineralized filling material.

[0026] Furthermore, the ratio of the carbonate precipitate, gel material, aggregate, and water is 5:2:3:4.

[0027] Furthermore, the gel material is cement;

[0028] The aggregate is gravel and / or sand; its maximum particle size is generally no more than 25 mm to avoid clogging the pipeline.

[0029] Furthermore, the mixing conditions are: a rotation speed of 300-600 r / min and a time of 30 min.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] This invention provides a carbon dioxide mineralization filling method and system, which features low investment, simple equipment and process, and ease of operation. Compared with traditional mineralization methods, it requires minimal modification, has higher reaction efficiency, produces no other by-products, and offers advantages such as high efficiency, no corrosion, and no pollution.

[0032] Furthermore, compared to other mineralization filling methods, the sodium carbonate additive specified in this invention acts as a catalyst, accelerating the mineralization reaction rate and allowing for recycling, thus significantly reducing costs. Moreover, NaHCO3, as an intermediate product, does not produce any other harmful byproducts during the reaction process, unlike other intermediate media such as alcohols and ammonia, whose byproducts are highly corrosive, easily corroding pipes and instruments, and potentially polluting water resources.

[0033] This invention involves continuously introducing carbon dioxide into the goaf to cure the backfill material. During this curing process, mineralization occurs again, altering the porosity of the backfill material and thus affecting its mechanical properties. Specifically, the carbonates generated by the mineralization reaction can fill the original pores, increasing the strength of the backfill. Furthermore, this invention also includes a carbon dioxide detection sensor at the top of the goaf, maximizing carbon fixation while preventing carbon dioxide leakage. In addition, the invention employs two agitators during the backfilling process, resulting in finer particle sizes and more thorough solid-liquid mixing, reducing solid-liquid separation during transportation and ensuring more stable and safe backfilling in the goaf.

[0034] In summary, the entire carbon dioxide mineralization backfilling process of this invention is relatively simple, green, sustainable, and highly operable. First, the initial mineralization of materials such as fly ash, coal gangue, and water is completed on the ground. The mineralized materials are then mixed with aggregates and cementitious materials to form backfill material, which is injected into the goaf to complete the mineralization backfilling and remediation of the goaf. Therefore, this invention not only has low backfilling costs and simple operation but also mineralizes carbon dioxide. It further solves the problem of solid waste pollution and enables large-scale treatment of solid waste. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a schematic diagram of the equipment flow for a carbon dioxide mineralization filling method according to Embodiment 2 of the present invention;

[0037] Figure 2 This is a structural diagram of a stirrer 1 in a carbon dioxide mineralization filling system according to Embodiment 1 of the present invention;

[0038] Figure 3This is a schematic diagram of a carbon dioxide mineralization filling system according to Embodiment 1 of the present invention;

[0039] Figure 4 This is a schematic diagram of the filling material prepared in Example 2 of the present invention being injected into the goaf. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] All raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0046] The technical solution of the present invention will be further illustrated by the following embodiments.

[0047] Example 1

[0048] A carbon dioxide mineralization backfilling system includes: a backfill material preparation system, a backfill transportation system, and a goaf backfilling system;

[0049] The filling material preparation system and the goaf filling system are connected through a filling transportation system (pipeline);

[0050] The filling material preparation system includes a reactor, a stirrer 1, a stirrer 2, and a filling device; the reactor and a stirrer 1 are connected sequentially through pipes; the outlet end of a stirrer 1 is connected to the inlet end of a stirrer 2 through a pipe; and the outlet end of a stirrer 2 is connected to the filling device through a pipe.

[0051] A thin carbon dioxide pipe is installed at the bottom of the goaf filling system, and carbon dioxide gas is slowly introduced during the solidification of the filling material.

[0052] Each section of pipe can be connected to the others. The pipe material is PVC and the inner diameter is 160mm.

[0053] Example 2

[0054] A carbon dioxide mineralization filling method, comprising the following steps within the system of Example 1:

[0055] In the filling material preparation system, sodium carbonate solution is used as an intermediate medium to prepare carbon dioxide mineralized filling material using a two-step method of wet direct mineralization and indirect mineralization.

[0056] Carbon dioxide mineralized backfill material is transported to the goaf backfill system using a backfilling and transportation system, and carbon dioxide is introduced into the goaf backfill system to reinforce the carbon dioxide mineralized backfill material. Before being transported to the goaf backfill system, the carbon dioxide mineralized backfill material needs to undergo a fluid test and then be pressurized by the backfilling device.

[0057] The direct wet mineralization method includes the following steps:

[0058] Fly ash, coal gangue, and sodium bicarbonate solution prepared in the reactor are fed into agitator 1 and then stirred and mixed at a speed of 300-600 r / min for 30 min. Carbon dioxide and water are pumped into agitator 1 to obtain carbon-fixing material (i.e. carbonate precipitate, mainly composed of calcium carbonate and magnesium carbonate precipitate).

[0059] Indirect mineralization includes the following steps:

[0060] Cementitious materials, aggregates (gravel, construction waste), and carbonate precipitates from mixer 1 are transferred to mixer 2. Water is added and the mixture is stirred at 300-600 r / min for 30 min to obtain carbon dioxide mineralized filling material. The mass ratio of sodium carbonate solution, fly ash, and coal gangue is 3:3:5.

[0061] The mass ratio of carbonate precipitate, gel material, aggregate and water is 5:2:3:4.

[0062] Furthermore, the filling material prepared in agitator 2 is transported to the filling device and then pumped to the underground goaf area to complete the carbon dioxide mineralization filling.

[0063] Each section of pipe can be connected to the others. The pipe material is PVC and the inner diameter is 160mm.

[0064] Figure 1 This is a flowchart of a carbon dioxide mineralization filling method according to Embodiment 2 of the present invention. Figure 1 As can be seen, the present invention provides a carbon dioxide mineralization filling method: carbon fixation filling material is prepared by using mineral waste materials, carbon dioxide is mineralized and fixed to obtain carbon dioxide filling material, and then the filling material is transported to the underground goaf area;

[0065] The preparation methods for filling materials include wet direct mineralization and indirect mineralization.

[0066] The direct wet mineralization method includes the following steps:

[0067] Mineral raw materials (fly ash and coal gangue) and sodium bicarbonate solution in the reactor are fed into agitator 1, stirred and mixed, and carbon dioxide is pumped into agitator 1 to obtain carbon-fixing material (carbonate precipitate, mainly composed of calcium carbonate and magnesium carbonate precipitate).

[0068] Indirect mineralization includes the following steps:

[0069] The cementitious material and aggregate are conveyed to mixer 2; the carbonate precipitate in mixer 1 is conveyed to mixer 2, water is added and stirred to obtain carbon dioxide mineralized filling material;

[0070] Furthermore, the filling material prepared in agitator 2 is transported to a filling device for pressurization, and then pumped to the underground goaf area to complete the carbon dioxide mineralization filling.

[0071] The wet direct mineralization method involves passing carbon dioxide into a sodium carbonate solution, where water, carbonate ions, and carbon dioxide react to form bicarbonate ions. These bicarbonate ions are then transported to a stirrer 1, where they react with calcium and magnesium ions to form carbonate precipitates. Carbon dioxide is then continuously passed through the solution to create a cyclic reaction, which greatly accelerates the carbonation reaction.

[0072] Then, the carbonate precipitate is transferred to mixer 2, and cementitious materials and aggregates are added in proportion, followed by continued mixing with water. At this point, the remaining carbon dioxide, carbonate ions, and bicarbonate ions react with the alkaline oxides (MgO, CaO, etc.) in the cementitious materials to form carbonates. The carbonate particles produced by carbonation have certain hardening properties and can serve as fine aggregates and replace part of the cement.

[0073] Finally, by controlling the concentration of the filling material slurry, a filling material with a final stratification of no more than 20 mm and a slump of more than 180 mm is prepared and transported to the goaf of the mine.

[0074] Figure 2 This is a structural diagram of the stirrer 1 in a carbon dioxide mineralization filling system according to Embodiment 1 of the present invention; Figure 2 It is known that the agitator 1 includes a pH value detector, three sets of agitator blades, a pressure pump, a discharge port, a pressure gauge, a stirrer, and a sealing valve. The agitator blades enable fly ash and coal gangue to fully react with carbon dioxide injected into the agitator 1 under pressure by the pressure pump. The stirring speed is set to 300-600 r / min to obtain a more complete slurry with less stratification. The degree of carbon dioxide mineralization is determined based on the pH value change, and the precipitated precipitate is then discharged through the discharge port.

[0075] Figure 3 This is a schematic diagram of a carbon dioxide mineralization filling system according to Embodiment 1 of the present invention. The reaction time is controlled by pH detection in the reactor throughout the process. After the reaction is completed, the mixture is transported to agitator 1 through a pipeline. In agitator 1, carbon dioxide gas is introduced through a pressure pump, and then fly ash and coal gangue are added to react. After the reaction is completed, the mixture is filtered, and the carbonate precipitate in agitator 1 is transported to agitator 2. The waste liquid is transported back to the reactor through a pipeline for recycling.

[0076] Then, gel material and aggregate are added to agitator 2, which is used to input carbonate precipitate, and stirred to obtain filling material. The filling material is then fed into the filling device through a pipeline, pressurized by a filling pump, and transported to the goaf through a delivery pipeline for filling. The initial setting time of the filling material is 4 hours.

[0077] The tanks of the agitators are all made of steel; their inner walls are coated with polytetrafluoroethylene to prevent corrosion and ensure that the mineralization reaction is not disturbed; the covers of agitators 1 and agitators 2 are made of stainless steel, and the sealing structure adopts a common flat gasket seal, with a sealing valve installed on the top. Its structure is simple and highly reliable.

[0078] The carbon dioxide flow rate can be adjusted during the filling process. Considering that the diffusion rate of carbon dioxide varies with different flow rates, and the solidification time of the filling material is 5-9 hours, the detection equipment should remain on the solidified surface of the filling material for 6-8 hours after carbon dioxide is introduced during testing. Once carbon dioxide is detected, the introduction of carbon dioxide should be stopped.

[0079] Figure 4 This is a schematic diagram of the filling material prepared in Embodiment 2 of the present invention being injected into the goaf. A carbon dioxide gas pipeline is laid at the bottom of the goaf underground, with a small opening every 5 meters. A carbon dioxide sensor is installed on the top of the pipeline to detect carbon dioxide gas.

[0080] Pipelines are used to transport filling materials to the goaf for filling.

[0081] After filling is completed, the carbon dioxide gas pipeline is opened and carbon dioxide gas is introduced to further mineralize the filling material, making the interior of the filling material more compact and giving it higher compressive strength.

[0082] The carbon dioxide pipeline is made of PVC material and has an inner diameter of 160mm.

[0083] After filling is completed, carbon dioxide gas is introduced into the pipeline at the bottom of the goaf. The introduction of carbon dioxide gas is stopped when the sensor at the top of the goaf detects the carbon dioxide gas.

[0084] As carbon dioxide gas travels from bottom to top in the goaf, it continuously reacts with the filling material, greatly enhancing its compactness and compressive strength. Furthermore, the unreacted carbon dioxide gas can better maintain the filling material, significantly extending the lifespan of the goaf filling.

[0085] In summary, the entire carbon dioxide mineralization backfilling process of this invention is relatively simple, green, sustainable, and highly operable. First, primary mineralization of materials such as fly ash, coal gangue, and water is completed on the ground. The mineralized materials are then mixed with aggregates and cementitious materials to form backfill material, which is injected into the goaf to complete the mineralization backfilling and remediation of the goaf. Therefore, this invention not only has low backfilling costs and simple operation but also mineralizes carbon dioxide.

[0086] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for carbon dioxide mineralization backfilling, characterized in that, The process utilizes a carbon dioxide mineralization backfilling system, which includes a backfill material preparation system, a backfill transportation system, and a goaf backfilling system. The filling material preparation system and the goaf filling system are connected through the filling transportation system; The filling material preparation system includes a reactor, a first stirrer, a second stirrer, and a filling device; the reactor and the first stirrer are connected sequentially through a pipeline; the outlet end of the first stirrer and the inlet end of the second stirrer are connected through a pipeline. The carbon dioxide mineralization backfilling method includes the following steps: In the filling material preparation system, sodium carbonate solution is used as an intermediate medium to prepare carbon dioxide mineralized filling material using a two-step method of wet direct mineralization and indirect mineralization. The carbon dioxide mineralized backfill material is transported to the goaf backfill system using the backfill transportation system, and carbon dioxide is introduced into the goaf backfill system to reinforce the carbon dioxide mineralized backfill material. The wet direct mineralization method includes the following steps: A sodium carbonate solution and carbon dioxide are introduced into the reactor, and a reaction occurs to obtain a sodium bicarbonate solution. The sodium bicarbonate solution is fed into the first stirrer, carbon dioxide is introduced into it, and fly ash and coal gangue are added and mixed and stirred to carry out the initial mineralization reaction. The mixture obtained from the reaction is filtered to obtain carbonate precipitate and filtrate. The indirect mineralization method includes the following steps: The carbonate precipitate is fed into a second mixer, where gel material, aggregate, and water are added and mixed to carry out a secondary mineralization reaction, thereby obtaining the carbon dioxide mineralized filling material.

2. The carbon dioxide mineralization backfilling method according to claim 1, characterized in that, The concentration of the sodium carbonate solution is 1 mol / L; The mass ratio of the sodium carbonate solution, fly ash, and coal gangue is 3:3:

5.

3. The carbon dioxide mineralization backfilling method according to claim 1, characterized in that, The mixing conditions in the wet direct mineralization method are: rotation speed of 300-600 r / min; and time of 30 min.

4. The carbon dioxide mineralization backfilling method according to claim 1, characterized in that, The mass ratio of the carbonate precipitate, gel material, aggregate, and water is 5:2:3:

4.

5. The carbon dioxide mineralization backfilling method according to claim 1, characterized in that, The gel material is cement; The aggregate is gravel and / or sand.

6. The carbon dioxide mineralization backfilling method according to claim 1, characterized in that, The mixing conditions in the indirect mineralization method are: rotation speed of 300-600 r / min; and time of 30 min.

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