Mine subsidence area soil filling method based on carbon sequestration technology
Through the combination of biochar and activated magnesium oxide carbonization technology, a multi-stage pore network and chemical carbon sequestration reaction are built, which solves the problems of complex construction of soil filling methods in mining areas and insufficient water and fertilizer retention capabilities, and achieves the strengthening of soil structure and the improvement of environmental benefits.
Patent Information
- Application Number
- CN202510707196.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-29
- Publication Date
- 2025-08-01
AI Technical Summary
In the prior art, the soil filling method in the subsidence areas of the mining area is complex, and the water and fertilizer retention capacity is poor, making it difficult to achieve a coordinated improvement of soil structure improvement and environmental benefits.
Biochar is used to improve the soil, combined with activated magnesium oxide carbonization technology, through the grading application of bamboo charcoal and the construction of sediment carbon sediment layer, a multi-stage pore network and chemical carbon sediment reaction are formed to improve the soil's water and fertilizer retention ability.
The soil structure strengthening, carbon sequestration and plant growth environment reconstruction have been achieved in the mining area, the reclamation period has been shortened, the soil's water and fertilizer retention capacity has been improved, the raw material cost has been reduced, and the high consumption and high carbon emissions of traditional materials have been avoided.
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Figure CN120401461A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of mine ecological restoration, and particularly relates to a method for filling soil in a subsidence area of a mining area based on carbon sequestration technology. Background Art
[0002] Long-term mining activities in mineral resource-rich areas have led to complex ecological damages such as surface subsidence and destruction of soil and water structures. In the field of subsidence area restoration, sandy admixtures (such as the Yellow River sediment) are mostly used as filling matrices in the existing technology, and its technical paths can be summarized into two categories: 1. As a supplement to soil materials; 2. As an auxiliary material for soil materials. However, the Yellow River sediment has a large sand content and is not water- and fertilizer-retaining, and it needs to be improved by methods such as interlayer filling and adding modifiers. Especially, adding an interlayer in the Yellow River sediment filling layer can significantly improve the water- and fertilizer-retaining ability of the Yellow River sediment layer above the interlayer. After using single-layer or double-layer Yellow River sediment to replace the subsoil below 50 cm from the ground surface, the crop yields are no different from those of the surrounding farmland (see Journal of China University of Mining & Technology, 2022, 51(1): 1-15), making the existing filling and reclamation methods have problems of complex construction and poor water- and fertilizer-retaining ability. How to achieve the coordinated improvement of soil structure and environmental benefits through the innovation of carbon sequestration materials has become a technical bottleneck that urgently needs to be broken through in the field of mine ecological restoration.
[0003] The reclamation method of the present invention innovatively integrates biochar for soil improvement and reactive magnesium oxide carbonation technology to construct a mine restoration system with the synergistic effect of "carbon sequestration - structure - ecology". Aiming at the characteristics of the Yellow River sediment, first, the graded application of bamboo charcoal is used to regulate the fertility gradient: small-sized bamboo charcoal (0.05 - 0.5 mm) is applied to the surface soil layer, and its high specific surface area and abundant surface functional groups can significantly retain nitrogen nutrients, and at the same time, the micron-sized pores can increase the field water holding capacity to form a water- and fertilizer-retaining plant growth matrix; large-sized bamboo charcoal (3 - 5 mm) is selected for the carbon sequestration layer to construct a rigid framework. The large-sized pores can adjust the seepage rate, and at the same time, as a rigid framework structure, it can prevent the soil from being overly compacted. On this basis, the reactive magnesium oxide carbonation technology is introduced into the sediment carbon sequestration layer. Through a series of carbonation reactions between reactive magnesium oxide and CO2, colloidal substances such as magnesium carbonate are generated to cement the Yellow River sediment particles into a dense whole, further improving the soil water holding capacity and having a stronger water locking ability, so that more plant cultivation species are suitable for the Yellow River sediment. This method breaks through the limitation of ecological damage of traditional engineering materials and realizes the systematic integration of strengthening the mine soil structure, carbon sequestration and reconstruction of the plant growth environment, providing a solution for the filling and reclamation method of the subsidence area of the mining area. Summary of the Invention
[0004] Aiming at the problems existing in the prior art, the present invention provides a method for filling soil in a subsidence area of a mining area based on carbon sequestration technology.
[0005] To solve the above technical problems, the present invention adopts the following technical solutions: A method for filling soil in a subsided area of a mining area based on carbon sequestration technology, comprising the following steps: (1) According to the subsidence depth of the subsided area of the mining area and the elevation to be reclaimed, determine the thickness of soil stripping in the area to be filled. According to the thickness of soil stripping in the area to be filled, strip the soil in the area to be filled and stack it separately according to the topsoil and subsoil; simultaneously establish a reserve warehouse for Yellow River sediment raw materials to realize the three-dimensional control of in-situ soil and filling base materials in different zones; (2) According to the subsidence depth of the subsided area of the mining area, the elevation to be reclaimed, and the thickness of soil stripping in the area to be filled, determine that the soil reconstruction profile characteristics in the area to be filled from bottom to top are: sediment carbon sequestration layer - subsoil - sediment carbon sequestration layer - subsoil - mixed topsoil layer; (3) According to the structural characteristics of the sediment carbon sequestration layer - subsoil - sediment carbon sequestration layer - subsoil - mixed topsoil layer, sequentially backfill and cover the corresponding soil particles and soil and level them, and that's it.
[0006] Further, the soil particles of the sediment carbon sequestration layer are prepared by the following process: (A) Pretreatment of Yellow River sediment: dehydrate the Yellow River sediment in an oven to obtain Yellow River sediment with a moisture content of 10 - 25%; (B) Mixing: Mix the Yellow River sediment with a moisture content of 10 - 25% obtained in step (A) with reactive magnesium oxide and large particle size bamboo charcoal according to a mass ratio of 100: (5 - 15): (5 - 15), and mix them evenly in a mixer to obtain a mixture; (C) Granulation: Feed the mixture obtained in step (B) into a granulator for granulation to obtain spherical particles; (D) Carbonization and curing: Feed the spherical particles obtained in step (C) into a carbonization device for carbonization, and then cure them in a curing box to obtain the soil particles of the sediment carbon sequestration layer.
[0007] Further, the soil particles of the mixed topsoil layer are prepared by the following process: (S1) Pretreatment of Yellow River sediment: dehydrate the Yellow River sediment in an oven to obtain Yellow River sediment with a moisture content of 10 - 25%; (S2) Mixing: Mix the Yellow River sediment with a moisture content of 10 - 25% obtained in step (S1) with small particle size bamboo charcoal according to a mass ratio of 100: (5 - 15), and mix them evenly in a mixer to obtain a mixture; (S3) Compound mixing: Mix the mixture obtained in step (S2) evenly with the topsoil obtained by stripping the soil in the area to be filled, and then the soil particles of the mixed topsoil layer are obtained.
[0008] Further, in step (1), the thickness of soil stripping in the area to be filled is 0.6 - 0.9 meters, the thickness of the topsoil layer is 0.3 - 0.5 meters, and the thickness of the subsoil layer is 0.1 - 0.6 meters.
[0009] Further, in step (2), the thickness of each layer of sediment carbon sequestration layer is 0.1 - 0.6 m, the thickness of each layer of subsoil is 0.05 - 0.3 m, and the thickness of the mixed topsoil layer is 0.4 - 0.6 m.
[0010] Further, in step (3), the soil of the subsoil is the subsoil soil obtained by stripping the soil in the area to be filled.
[0011] Further, in step (3), the particle size of the soil particles in the sediment carbon sequestration layer is 0.5 - 1 mm, the pore size is 1 - 2 μm; the soil particles in the sediment carbon sequestration layer are spherical; the porosity of the soil particles in the sediment carbon sequestration layer is 60 - 80%.
[0012] Further, the temperature of the dehydration treatment in step (A) is 150 - 200 °C; in step (B), the particle size of the large - particle bamboo charcoal is 3 - 5 mm; the particle size of the spherical particles obtained in step (C) is 0.5 - 1 mm.
[0013] Further, in step (D), carbonization is carried out by inputting gas CO2 into the carbonization device. The concentration of CO2 gas is 80 - 100%, the CO2 ventilation pressure is 50 - 300 kPa, and the carbonization time for every 100 kg of raw material of the Yellow River sediment is 0.5 - 1 h; the curing temperature is 20 - 25 °C, the humidity is 95 - 98%, and the curing time is 7 - 14 days.
[0014] Further, the particle size of the small - particle bamboo charcoal is 0.05 - 0.5 mm, and the mass ratio of the mixture obtained in step (S2) to the topsoil soil obtained by stripping the soil in the area to be filled is 1:(1 - 3).
[0015] The topsoil refers to the soil position in the upper layer of the soil profile. The subsoil refers to the soil position in the middle layer of the soil profile.
[0016] The oven, mixer, granulator, carbonization device, and curing box can all be selected from the equipment or devices in the prior art. The carbonization device is a device that can introduce carbon dioxide gas and maintain a certain pressure and time. In this carbonization device, the raw material can react with carbon dioxide for carbonization.
[0017] The bamboo charcoal is obtained by passing the purchased existing bamboo charcoal products through 300 - mesh sieve, 0.5 - mm sieve, 3 - mm sieve, and 5 - mm sieve.
[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By stripping the soil in the area to be filled, determining the soil reconstruction profile characteristics of the area to be filled, and filling according to the soil reconstruction profile characteristics of the area to be filled, especially the use of soil particles in the sediment carbon sequestration layer and the mixed topsoil layer, the reclamation period is shortened, and the problem of complex construction in the existing filling and reclamation methods is solved.
[0019] (2) In the filling method of the present invention, the sediment carbon sequestration layer and the mixed topsoil layer are strengthened by double-sized bamboo charcoal grading: large-sized bamboo charcoal (3 - 5 mm) in the carbon sequestration layer regulates the water seepage through its multi-level pore network, and at the same time adsorbs nitrogen and CO2 by means of surface oxygen-containing functional groups to form a physical carbon sequestration carrier; on this basis, active magnesium oxide is introduced, and the magnesium hydroxide generated by its hydration reacts with CO2 to undergo a directional carbonization reaction, cementing the bamboo charcoal particles and the Yellow River sediment particles into a dense whole, realizing the synergistic effect of chemical carbon sequestration (MgO - CO2 reaction) and physical carbon sequestration (stable sequestration of bamboo charcoal); small-sized bamboo charcoal (0.05 - 0.5 mm) relies on its rich micron pores and surface active functional groups to lock water and nutrients through the dual effects of capillary adsorption and chemical bonding, establishing a dynamic water and fertilizer slow-release system in the plant root growth environment, and promoting the efficient utilization of water by plant roots. Under the synergistic action of the two, the soil not only avoids the deterioration of air permeability caused by compaction, but also solves the defect of insufficient water retention capacity of traditional filling materials, is beneficial to plant growth, and can be widely used in mine soil restoration.
[0020] (3) The filling method of the present invention provides an effective utilization way for the Yellow River sediment, alleviates the environmental pressure brought by the Yellow River sediment, and at the same time reduces the raw material cost of soil particles.
[0021] (4) The soil particles in the sediment carbon sequestration layer and the mixed topsoil layer used in the filling method of the present invention are obtained by mixing active magnesium oxide, double-sized bamboo charcoal with the Yellow River sediment, and then carbonizing and curing with CO2 gas, which makes the soil particle strength increase rapidly and significantly, and the compressive strength reaches 2 - 3 MPa. It can not only sequester and fix carbon dioxide, but also avoid the use of traditional materials such as cement and lime with high consumption and high carbon emissions. A regenerated soil system with both structural stability and ecological suitability is successfully constructed. Description of the Drawings
[0022] Figure 1 It is a flow chart of the method of the present invention; Figure 2 It is the principle of sediment carbonization and solidification of the method of the present invention; Figure 3 It is a schematic diagram of the filling soil reconstruction profile of the embodiment of the method of the present invention; Figure 4 It is a particle size distribution diagram of the Yellow River sediment particles carbonized after adding large-sized (3 - 5 mm) biochar and active MgO in the method of the present invention. Specific implementation manners
[0023] The following further describes the present invention in detail in conjunction with embodiments. The following embodiments are only used to illustrate the technical solutions of the present invention and do not limit it; although the present invention has been described in detail with reference to the following embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
[0024] Embodiment 1 A method for filling soil in a mined subsidence area based on carbon sequestration technology includes the following steps: (1) Soil stripping in the area to be filled: In this example, the subsidence depth of the mined subsidence area is 0.8 m, the designed reclamation elevation is the same as the ground surface, the soil stripping thickness in the area to be filled is 0.6 m, the topsoil layer thickness is 0.5 m, and the subsoil layer thickness is 0.1 m. According to the soil stripping thickness in the area to be filled, the soil in the area to be filled is stripped and stacked separately according to the topsoil layer and the subsoil layer; at the same time, a sufficient amount of Yellow River sediment is stacked as the filling base material; (2) Determining the soil reconstruction profile characteristics in the area to be filled: According to the subsidence depth (0.8 m) of the mined subsidence area, the reclamation elevation (the same as the ground surface), and the soil stripping thickness in the area to be filled, the soil reconstruction profile characteristics in the area to be filled from bottom to top are: sediment carbon sequestration layer - subsoil layer - sediment carbon sequestration layer - subsoil layer - mixed topsoil layer; the thickness of each sediment carbon sequestration layer is 0.3 m, the thickness of each subsoil layer is 0.1 m, and the thickness of the mixed topsoil layer is 0.6 m; The soil particles of the sediment carbon sequestration layer are prepared by the following method: (A) Yellow River sediment pretreatment: the Yellow River sediment is dehydrated in an oven at a temperature of 150° C. to obtain Yellow River sediment with a moisture content of 10%; (B) mixing: the Yellow River sediment with a moisture content of 10% obtained in step (A) is mixed with 0.0043 mm particle size activated magnesium oxide and 3-5 mm particle size bamboo charcoal in a mass ratio of 100:5:5, and mixed evenly in a blender to obtain a mixture; (C) granulation: the mixture obtained in step (B) is fed into a granulator for granulation to obtain spherical particles with a particle size of 100:5:5. (D) Carbonization and curing: The spherical particles obtained in step (C) are fed into a carbonization device for carbonization at a CO2 gas concentration of 80%, a CO2 ventilation pressure of 50 kPa, and a carbonization time of 0.5 h per 100 kg of Yellow River sediment raw material. The particles are then cured in a curing box at a temperature of 20° C., a humidity of 95%, and a curing time of 7 days to obtain soil particles of a sediment carbon sequestration layer; the soil particles of the sediment carbon sequestration layer have a particle size of 1 mm and a pore size of 2 μm; the soil particles of the sediment carbon sequestration layer are spherical; and the porosity of the soil particles of the sediment carbon sequestration layer is 60%; Figure 1 The particle size distribution of the Yellow River sediment after carbonization with large-size biochar (3-5 mm) and activated MgO is shown in the particle size distribution curve ( Figure 4 ) analysis reveals that the material's particle size distribution exhibits a continuous gradation characterized by "fine particles predominating, coarse particles supplementing." The curve rises rapidly in the fine-grained region (<1 mm), reflecting a significant enrichment of silt and clay-sized particles, forming a dense microporous matrix. In the coarse-grained region (1-5 mm), the curve flattens out, indicating that a small amount of medium-coarse sand-sized particles acts as a framework, forming a multi-scale coupled structure with the fine particles. This gradation enhances water-holding and carbon-sequestration capacity through the high specific surface area of fine particles, while also enhancing compressive stability through the supportive role of the coarse particles. This provides an optimization direction for the functional design and engineering adaptation of ecological restoration materials.
[0025] The soil of the subsoil layer is the subsoil layer soil obtained by stripping the soil of the area to be filled; The soil particles of the mixed topsoil layer are prepared by the following method: (E) mixing: the Yellow River sediment with a moisture content of 10% obtained in step (A) and bamboo charcoal with a particle size of 0.05-0.5 mm are mixed in a mass ratio of 100:5 and mixed evenly in a blender to obtain a mixture; (F) compounding: the mixture obtained in step (E) is mixed evenly with the topsoil layer soil obtained by stripping the soil in the area to be filled in a mass ratio of 1:2 to obtain the soil particles of the mixed topsoil layer; (3)Backfill according to the soil reconstruction profile characteristics of the area to be filled: According to the structural characteristics of the sediment carbon sequestration layer - subsoil layer - sediment carbon sequestration layer - subsoil layer - mixed topsoil layer, sequentially backfill and level the corresponding soil particles and soil, and that's it.
[0026] Example 2 A soil filling method for mined - out areas in mining areas based on carbon sequestration technology, comprising the following steps: (1)Soil stripping in the area to be filled: In this example, the subsidence depth of the mined - out area in the mining area is 0.9 m, the designed reclamation elevation is the same as the ground surface, the soil stripping thickness in the area to be filled is 0.9 m, the topsoil layer thickness is 0.3 m, and the subsoil layer thickness is 0.6 m. According to the soil stripping thickness in the area to be filled, strip the soil in the area to be filled and stack it separately according to the topsoil layer and the subsoil layer; simultaneously stack a sufficient amount of Yellow River sediment as the filling base material; (2)Determination of the soil reconstruction profile characteristics in the area to be filled: According to the subsidence depth (0.9 m) of the mined - out area in the mining area, the reclamation elevation (the same as the ground surface), and the soil stripping thickness in the area to be filled, determine that the soil reconstruction profile characteristics in the area to be filled from bottom to top are: sediment carbon sequestration layer - subsoil layer - sediment carbon sequestration layer - subsoil layer - mixed topsoil layer; the thickness of each sediment carbon sequestration layer is 0.5 m, the thickness of each subsoil layer is 0.2 m, and the thickness of the mixed topsoil layer is 0.4 m; The soil particles of the sediment carbon sequestration layer are prepared by the following method: (A) Pretreatment of Yellow River sediment: Dehydrate the Yellow River sediment in an oven at a temperature of 180 °C to obtain Yellow River sediment with a moisture content of 20%; (B) Mixing: Mix the Yellow River sediment with a moisture content of 20% obtained in step (A) with 0.0043 - mm - particle - size active magnesium oxide and 3 - 5 - mm - particle - size bamboo charcoal according to a mass ratio of 100:10:10, and mix evenly in a mixer to obtain a mixture; (C) Granulation: Feed the mixture obtained in step (B) into a granulator for granulation to obtain spherical particles with a particle size of 0.8 mm; (D) Carbonization and curing: Feed the spherical particles obtained in step (C) into a carbonization device for carbonization, with a CO2 gas concentration of 90%, a CO2 ventilation pressure of 150 kPa, a carbonization time of 0.8 h for every 100 kg of Yellow River sediment raw material, and then cure in a curing box at a temperature of 25 °C, a humidity of 98%, and a curing time of 7 days to obtain the soil particles of the sediment carbon sequestration layer; the particle size of the soil particles of the sediment carbon sequestration layer is 0.8 mm, the pore size is 1.5 μm; the soil particles of the sediment carbon sequestration layer are spherical; the porosity of the soil particles of the sediment carbon sequestration layer is 70%; The soil of the subsoil layer is the subsoil soil obtained by stripping the soil in the area to be filled; The soil particles of the mixed topsoil layer are prepared by the following method: (E) Mixing: Mix the Yellow River sediment with a moisture content of 20% obtained in step (A) and small particle size bamboo charcoal in a mass ratio of 100:10, and mix them evenly in a blender to obtain a mixture; (F) Compound mixing: Mix the mixture obtained in step (E) with the topsoil layer soil obtained by stripping the soil in the area to be filled in a mass ratio of 1:2, and the soil particles of the mixed topsoil layer are obtained; (3) Backfill according to the soil reconstruction profile characteristics of the area to be filled: According to the structural characteristics of the sediment carbon sequestration layer - subsoil layer - sediment carbon sequestration layer - subsoil layer - mixed topsoil layer, backfill and cover the corresponding soil particles and soil in sequence and level them, and it can be done.
[0027] Example 3 A soil filling method for mining subsidence areas based on carbon sequestration technology includes the following steps: (1) Soil stripping in the area to be filled: In this example, the subsidence depth of the mining subsidence area is 0.8 m, the designed reclamation elevation is the same as the ground surface, the soil stripping thickness in the area to be filled is 0.8 m, the topsoil layer thickness is 0.4 m, and the subsoil layer thickness is 0.4 m. According to the soil stripping thickness in the area to be filled, strip the soil in the area to be filled and stack it separately according to the topsoil layer and the subsoil layer; Stack a sufficient amount of Yellow River sediment as the filling base material synchronously; (2) Determination of the soil reconstruction profile characteristics in the area to be filled: According to the subsidence depth (0.8 m), reclamation elevation (the same as the ground surface), and soil stripping thickness in the area to be filled in the mining subsidence area, determine that the soil reconstruction profile characteristics in the area to be filled from bottom to top are: sediment carbon sequestration layer - subsoil layer - sediment carbon sequestration layer - subsoil layer - mixed topsoil layer; The thickness of each sediment carbon sequestration layer is 0.3 m, the thickness of each subsoil layer is 0.2 m, and the thickness of the mixed topsoil layer is 0.6 m; The soil particles of the sediment carbon sequestration layer are prepared by the following method: (A) Yellow River sediment pretreatment: the Yellow River sediment is dehydrated in an oven at a temperature of 200° C. to obtain Yellow River sediment with a moisture content of 25%; (B) mixing: the Yellow River sediment with a moisture content of 25% obtained in step (A) is mixed with 0.0043 mm particle size activated magnesium oxide and 3-5 mm particle size bamboo charcoal in a mass ratio of 100:15:15, and mixed evenly in a blender to obtain a mixture; (C) granulation: the mixture obtained in step (B) is fed into a granulator for granulation to obtain spherical particles with a particle size of (D) Carbonization and curing: The spherical particles obtained in step (C) are fed into a carbonization device for carbonization at a CO2 gas concentration of 100%, a CO2 ventilation pressure of 300 kPa, and a carbonization time of 1 hour per 100 kg of Yellow River sediment raw material. The particles are then cured in a curing box at a temperature of 20° C., a humidity of 98%, and a curing time of 14 days to obtain soil particles of a sediment carbon sequestration layer; the soil particles of the sediment carbon sequestration layer have a particle size of 1 mm and a pore size of 1 μm; the soil particles of the sediment carbon sequestration layer are spherical; and the porosity of the soil particles of the sediment carbon sequestration layer is 80%; The soil of the subsoil layer is the subsoil layer soil obtained by stripping the soil of the area to be filled; The soil particles of the mixed topsoil layer are prepared by the following method: (E) mixing: the Yellow River sediment with a moisture content of 25% obtained in step (A) and bamboo charcoal with a particle size of 0.05-0.5 mm are mixed in a mass ratio of 100:15 and mixed evenly in a blender to obtain a mixture; (F) compounding: the mixture obtained in step (E) is mixed evenly with the topsoil layer soil obtained by stripping the soil in the area to be filled in a mass ratio of 1:2 to obtain the soil particles of the mixed topsoil layer; (3) Filling is carried out according to the reconstructed soil profile characteristics of the area to be filled: according to the structural characteristics of the sediment carbon fixation layer-subsoil layer-sediment carbon fixation layer-subsoil layer-mixed topsoil layer, the corresponding soil particles and soil are backfilled, covered and leveled in turn.
[0028] Table 1 Test results of Examples 1-3 As shown in Table 1, the reclamation method of the present invention shortens the reclamation period by stripping the soil in the area to be filled, determining the reconstructed profile characteristics of the soil in the area to be filled, and performing filling according to the reconstructed profile characteristics of the soil in the area to be filled, especially by using soil particles from the sediment carbon-fixing layer and soil particles from the mixed topsoil layer. The filling method of the present invention is carbon sequestration-oriented, with the Yellow River sediment as the main base material. Through the synergistic regulation of pore structure by the carbonization of active magnesium oxide and the bamboo charcoal grading technology, the two-way improvement of the soil's carbon sequestration, fertilizer retention, and water retention capabilities is achieved. In the sediment carbon sequestration layer, large-sized bamboo charcoal serves as a rigid framework, which not only inhibits pore collapse through three-dimensional support but also adsorbs nitrogen through the hydroxyl groups on the surface of biochar, increasing soil fertility. On this basis, the introduction of active magnesium oxide enables the abundant silica and clay particles in the Yellow River sediment to react with active magnesium oxide to form colloidal magnesium carbonate while forming a micron-scale honeycomb-like pore network, endowing the soil particles with capillary water-holding characteristics and increasing the soil's water retention capacity, thereby improving the CO2 sequestration capacity and fertilizer and water retention functions of the carbon sequestration layer.
[0029] The soil particles prepared by the present invention have a porosity between 60% and 80% and a water retention rate between 65% and 90%. They have good water retention, fertilizer retention, and air permeability, which are beneficial to plant growth and can be widely used in the restoration of mining area soils.
[0030] The filling method of the present invention provides an effective utilization way for the Yellow River sediment, alleviates the environmental pressure brought by the Yellow River sediment, and at the same time reduces the raw material cost of soil particles.
[0031] In the filling method of the present invention, the soil particles of the sediment carbon sequestration layer and the soil particles of the mixed surface layer are obtained by mixing active magnesium oxide, double-sized bamboo charcoal, and the Yellow River sediment, and then carbonizing with CO2 gas and curing, which enables the strength of the soil particles to increase rapidly and significantly, and the compressive strength reaches 2 - 3 MPa. It can not only sequester and fix carbon dioxide but also avoid the use of traditional materials such as cement and lime with high consumption and high carbon emissions.
Claims
1. A method for soil filling in a subsidence area of a mining area based on carbon sequestration technology, characterized in that, The following steps are involved: (1) According to the subsidence depth of the mining area and the elevation to be reclaimed, determine the thickness of the soil stripping in the area to be filled. According to the thickness of the soil stripping in the area to be filled, strip the soil in the area to be filled and pile it up according to the topsoil layer and the subsoil layer. Simultaneously, establish a Yellow River sediment raw material reserve to achieve zoning and three-dimensional control of the in-situ soil and filling base material. (2) According to the subsidence depth of the mining area, the elevation to be reclaimed, and the thickness of the soil stripping in the area to be filled, the soil reconstructed profile characteristics of the area to be filled are determined from bottom to top as follows: sediment carbon fixation layer-subsoil layer-sediment carbon fixation layer-subsoil layer-mixed topsoil layer; (3) According to the structural characteristics of sediment carbon fixation layer-subsoil layer-sediment carbon fixation layer-subsoil layer-mixed topsoil layer, the corresponding soil particles and soil are backfilled, covered and leveled in turn.
2. The method for filling soil in the subsidence area of a mining area based on carbon sequestration technology according to claim 1, wherein The soil particles of the sediment carbon sequestration layer are prepared by the following process: (A) Yellow River sediment pretreatment: dehydrating the Yellow River sediment in an oven to obtain Yellow River sediment with a moisture content of 10-25%; (B) mixing: the Yellow River sediment with a moisture content of 10-25% obtained in step (A) is mixed with activated magnesium oxide and large-particle bamboo charcoal in a mass ratio of 100:(5-15):(5-15) and uniformly mixed in a blender to obtain a mixture; (C) granulation: the mixture obtained in step (B) is fed into a granulator for granulation to obtain spherical particles; (D) carbonization and curing: the spherical particles obtained in step (C) are fed into a carbonization device for carbonization, and then cured in a curing box to obtain soil particles of the sediment carbon sequestration layer.
3. The method for filling soil in the subsidence area of a mining area based on carbon sequestration technology according to claim 1, wherein, The soil particles of the mixed topsoil layer are prepared by the following process: (S1) Yellow River sediment pretreatment: dehydrating the Yellow River sediment in an oven to obtain Yellow River sediment with a moisture content of 10-25%; (S2) mixing: the Yellow River sediment with a moisture content of 10-25% obtained in step (S1) is mixed with small-particle bamboo charcoal in a mass ratio of 100:(5-15), and mixed evenly in a blender to obtain a mixture; (S3) compounding: mixing the mixture obtained in step (S2) with the topsoil layer soil obtained by stripping the soil in the area to be filled evenly to obtain the soil particles of the mixed topsoil layer.
4. The method for filling and reclaiming a mined-out area based on the Yellow River sediment according to claim 1, wherein In step (1), the thickness of the soil stripping in the area to be filled is 0.6-0.9 meters, the thickness of the topsoil layer is 0.3-0.5 meters, and the thickness of the subsoil layer is 0.1-0.6 meters.
5. The method for filling and reclaiming the subsidence area in the mining area based on the Yellow River sediment according to claim 1, characterized in that In step (2), the thickness of each sediment carbon fixation layer is 0.1-0.6 m, the thickness of each subsoil layer is 0.05-0.3 m, and the thickness of the mixed topsoil layer is 0.4-0.6 m.
6. The method for filling soil in the subsidence area of a mining area based on carbon sequestration technology according to claim 2, wherein The temperature of the dehydration treatment in step (A) is 150-200° C.; in step (B), the particle size of the large-particle bamboo charcoal is 3-5 mm; and the particle size of the spherical particles obtained in step (C) is 0.5-1 cm.
7. The method for filling soil in a subsidence area of a mining area based on carbon sequestration technology according to claim 2, wherein, In step (D), carbonization is carried out on the input gas CO2 in the carbonization device. The concentration of the CO2 gas is 80 - 100%, the CO2 ventilation pressure is 50 - 300 kPa, and the carbonization time for every 100 kg of the raw material of the Yellow River sediment is 0.5 - 1 h. The curing temperature is 20 - 25 °C, the humidity is 95 - 98%, and the curing time is 7 - 14 days.
8. The method for filling soil in the subsidence area of a mining area based on carbon sequestration technology according to claim 3, characterized in that, The particle size of the small particle size bamboo charcoal is 0.05 - 0.5 mm, and the mass ratio of the mixture obtained in step (S2) to the topsoil obtained by soil stripping in the area to be filled is 1:(1 - 3).
9. The method for filling soil in the subsidence area of a mining area based on carbon sequestration technology according to claim 1, wherein In step (3), the soil of the subsoil layer is the subsoil layer soil obtained by soil stripping in the area to be filled.