CN113101789B

CN113101789B - Method and structure for sealing carbon dioxide by utilizing open pit and mining method

Info

Publication number: CN113101789B
Application number: CN202110457883.9A
Authority: CN
Inventors: 翟圣佳; 周瑜; 吴雪莲; 陈敏娟; 侯振威; 黄怡
Original assignee: Luojia Huanxun Environmental Technology Beijing Co ltd
Current assignee: Luojia Huanxun Environmental Technology Beijing Co ltd
Priority date: 2021-04-27
Filing date: 2021-04-27
Publication date: 2022-04-19
Anticipated expiration: 2041-04-27
Also published as: CN113101789A

Abstract

The invention provides a method and a structure for sealing carbon dioxide by utilizing an open pit and an open pit mining method. The method for sealing carbon dioxide by utilizing the open pit comprises the following steps: treating the bottom of the pit; a step of slope treatment; a material manufacturing step; a first layer construction step; constructing a current layer; injecting carbon dioxide; and according to the sealing requirement, executing the slope processing step, the material manufacturing step, the current layer construction step or the carbon dioxide injection step one or more times. The invention provides a carbon sequestration engineering technology which can solve the problem of cooperative disposal of various industrial solid wastes, realizes the reduction, resource utilization and safe disposal of wastes, synchronously adds carbon dioxide for sealing and storage, greatly improves the utilization value of a mine pit, generates secondary income, realizes a carbon sequestration engineering technology, and provides a solution for realizing carbon neutralization at an early stage.

Description

Method and structure for sealing carbon dioxide by utilizing open pit and mining method

Technical Field

Embodiments of the present invention relate generally to the field of greenhouse gas disposal technology, and more particularly, to methods, structures, and mining methods for sequestration of carbon dioxide using an open pit.

Background

At present, global environmental problems have become the focus of international social attention, and great strategic demands are put forward on environmental science and technology innovation. On the seventh fifteen united nations congress, on day 22 of 9 and 2020, the government of China proposed: china will improve the autonomous contribution of the country, adopt more powerful policies and measures, strive for the carbon dioxide emission to reach the peak value 2030 years ago, strive for the carbon neutralization 2060 years ago. Carbon peak reaching and carbon neutralization are realized, and besides the emission reduction efficiency of the industrial process is improved, the capture and the sealing of carbon dioxide must be realized. Research teams at home and abroad have conducted a great deal of research, and the trapped carbon dioxide is injected into waste oil and gas fields, mines and the like at deep parts of the stratum, and is solidified through multiphase flow in a porous structure of the reservoir and chemical reaction between the trapped carbon dioxide and reservoir water and rocks. However, the technology does not form a real industrial practice case, and the main difficulty lies in that the observation is difficult to be carried out at the deep part of the stratum, the solidification effect is difficult to be judged, and the manual intervention is not facilitated in time when problems occur; meanwhile, the cost for injecting the deep part of the stratum is too high, and the injection is difficult to realize from the economic point of view.

Specifically, the existing solutions for carbon dioxide sequestration and the problems with these solutions, respectively, are as follows.

1. Patent publication CN106946255A proposes a method of mixing solid waste of a pithead coal-fired power plant with cement and a mixing liquid to obtain a mixed material; then backfilling the obtained mixed material into an underground mine of a waste coal mine, and compacting; then injecting hydration liquid into the compacted filler for hydration; and finally, injecting carbon dioxide waste gas of a pithead coal-fired power plant into the hydrated filler, and closing the well to mineralize the carbon dioxide, so that the carbon dioxide is sealed and stored and the waste coal mine is reinforced.

The disclosure only relates to underground mining coal mines, does not give accounting of relevant economic benefits, does not evaluate the reinforcement degree which can be realized on the underground coal mines after the scheme in the patent disclosure is adopted, and cannot evaluate whether the ecological restoration effect brought by realizing backfilling on underground mining coal mines and avoiding surface subsidence can be achieved; the construction process and the underground structures are not clearly described, so that the concrete process and the construction scheme for mixing the carbon dioxide and the solid wastes of the pithead power plant underground cannot be fully known, and the actual operation is not facilitated; the underground water protection scheme of the industrial solid waste of the power plant in the underground backfilling process is not provided, and if the heavy metal in the solid waste is separated out in the reaction process and absorbed by the underground water in the deep layer, the process is an irreversible environment damage process.

2. Patent publication CN107762554A provides a system for old abandonment mine to place abandonment concrete and seal up carbon dioxide, with storage water tank and pulsation pump, three-way valve UNICOM respectively, through many pipelines, fill abandonment concrete in abandonment mine collecting space, fill carbon dioxide gas in the mine collecting space simultaneously to solve the problem that abandonment concrete was placed, abandonment mine was filled and carbon dioxide seals up, reduce land pollution and atmospheric greenhouse effect.

The disclosure only relates to underground mining coal mines, and the implementation scene is single; no accounting is given for the relevant economic benefits; after the scheme in the patent is not evaluated, the reinforcement degree of the underground mine can be realized, and whether the ecological restoration effect brought by backfilling of an underground mining coal mine and surface subsidence is avoided cannot be evaluated; the underground water protection scheme of the industrial solid waste of the power plant in the underground backfilling process is not provided, and if the heavy metal in the solid waste is separated out in the reaction process and absorbed by deep underground water, the process is an irreversible environment damage process; there is no accounting for the amount of carbon dioxide that can be sequestered.

3. Patent publication CN107762554A proposes a method for storing waste concrete and sealing carbon dioxide in a new waste mine, which separates each roadway of the new waste mine and determines the volume of each space after separation; constructing partition walls in sequence from the farthest end from the well mouth of the new abandoned mine according to the determined volume of each space after the partition; conveying the waste concrete to the separated space by adopting a material conveying system of a new waste mine for accumulation, and spraying saturated lime water by adopting a water supply system in the accumulation process; constructing a closed wall to seal the space for accumulating the waste concrete, and arranging a high-pressure pipeline on the closed wall; after the airtight wall meets the airtight requirement, connecting a compressed air pipeline of a new abandoned mine with a high-pressure pipeline, and injecting carbon dioxide gas into the space; stopping and plugging the high-pressure pipeline after the injected carbon dioxide gas amount is finished. The problems of waste concrete placement, filling of new waste mines and carbon dioxide sealing can be solved, and the land pollution and the atmospheric greenhouse effect are reduced.

The disclosure relates only to mines for down-hole mining and not to open pit mines; no accounting is given for the relevant economic benefits; the patent proposes that the investment is greatly increased by additionally spraying lime water; after the scheme in the patent is not evaluated, the reinforcement degree of the underground mine can be realized, and whether the underground mine can be backfilled during underground mining can be evaluated or not can not be evaluated, so that the ecological restoration effect caused by surface subsidence is avoided.

4. Patent publication US20090220303a1 proposes a method of enhancing underground carbon dioxide storage. The method includes positioning a geological formation comprising a first storage container having a first surface and a second surface, a first sealing layer adjacent the first surface of the first storage container, a second sealing layer adjacent the second surface of the first storage container, and a first storage container adjacent the first sealing layer opposite the first storage container; introducing carbon dioxide into a first storage vessel, the carbon dioxide being at a first pressure within the first storage vessel; directing the fluid into a second storage vessel, the fluid being at a second pressure within the second storage vessel; and maintaining the second pressure at a pressure generally the same as or greater than the first pressure of the carbon dioxide to reduce the CO₂Is leaked.

The technical solution of this disclosure is to inject carbon dioxide directly into the ground, using geological formations of sufficient porosity and permeability to store the carbon dioxide, solidifying the carbon dioxide with natural underground rocks and voids, without the concept of co-disposal of industrial solid waste; the technique does not involve ecological remediation; the technique does not account for cost or revenue; there is no accounting for the amount of carbon dioxide that can be sequestered.

5. Patent publication CN107938643A provides a landform and landform treatment method based on waste stone mines, and relates to the technical field of mine treatment. Surveying the terrain; cleaning a mine; dividing areas; backfilling the pit; stably building; vegetation is greened again; building a reservoir; draining rainwater; and (5) recording and maintaining. The invention effectively divides the region of the mine by surveying the topography of the abandoned mine, and fully utilizes the abandoned stone to level the topography of the mine, adopts the geocell, the hanging net for spraying additional soil or the vegetation basin to improve the ecological environment of the mine, effectively changes the conditions that the rock of the mine is exposed, the geology is unstable and the mine is easy to be dangerous, and can generate certain economic benefit.

This disclosure is not directed to the concept and method of sequestering the greenhouse gas carbon dioxide; the technology is only used for distinguishing the difference in the ecological restoration process, and the overall technical method and concept are fundamentally different from the patent.

Disclosure of Invention

In view of the above problems in the background art, it is necessary to develop a better solution that is easy to observe, easy to find and solve problems, and capable of achieving cooperative disposal and economic feasibility.

To this end, a first aspect of the invention provides a method of sequestering carbon dioxide using an open pit, the method comprising: pit bottom treatment steps, including: paving an anti-seepage film at the bottom of the open pit, and constructing a clay layer on the anti-seepage film; arranging a diversion trench around the clay layer, constructing a fluid collecting pool at the bottom of the open pit, and connecting the fluid collecting pool with a water pump arranged on the ground through a pipeline; laying geotextile on the clay layer, and pouring a bottom cement layer on the geotextile; the step of slope treatment comprises the following steps: paving a side slope impermeable film on a side slope of the open pit, and pouring a side slope cement layer on the surface of the side slope impermeable film; the material manufacturing step comprises the following steps: crushing the solid waste, and mixing the crushed solid waste with the liquid to form a mixed material; a first layer construction step comprising: filling the mixed material above the bottom cement layer to form a first mixed material layer, and pouring a first cement layer on the first mixed material layer; a plurality of first-layer pouring holes are formed in the first cement layer, wherein each first-layer pouring hole is provided with a one-way valve, and a first injection pipe is introduced into each first-layer pouring hole; the current layer construction step includes: filling the mixed material above the previous cement layer to form a current mixed material layer; when the thickness of the current mixed material layer is filled to a designed thickness, pouring a current cement layer on the current mixed material layer, wherein the designed thickness is not higher than the thickness of a side slope which is not filled after the side slope is processed; arranging a plurality of current layer pouring holes on the current layer cement layer, wherein each current layer pouring hole is provided with a one-way valve, and a current layer injection pipe is introduced into each current layer pouring hole; a carbon dioxide injection step comprising: after the thickness of the current mixture material layer is filled to the thickness proportion threshold value of the design thickness, injecting supercritical carbon dioxide into the mixture material layer of the previous layer through an injection pipe of the previous layer filled before the current layer; after the carbon dioxide is injected into the mixed material layer of the previous layer, lifting the injection pipe of the previous layer to be separated from the injection hole of the previous layer so as to enable the injection hole of the previous layer to be unidirectionally closed through a one-way valve; and executing the slope processing step, the material manufacturing step, the current layer construction step or the carbon dioxide injection step one or more times according to the sealing requirement.

In some embodiments, the method further comprises: arranging a wastewater treatment device outside the open pit; pumping fluid substances collected in the fluid collecting pool and overflowing from the bottom layer of the pit through the water suction pump; precipitating the extracted fluid substances by the wastewater treatment device to generate recovered liquid and recovered solid waste; and treating the recovered liquid and the recovered solid waste as liquid and solid waste in the material making step, and refilling the mixed material formed after the treatment into the open pit.

In some embodiments, the first layer construction step further comprises: installing a carbon dioxide concentration sensor and/or a pressure sensor in the first mixed material layer; further, the current layer constructing step further includes: and installing a carbon dioxide concentration sensor and/or a pressure sensor in the current mixed material layer.

In some embodiments, the method further comprises: and controlling the gas pressure in the mixed material layer of the previous layer to be in the range of 7-15MPa according to the pressure measurement value of the pressure sensor, and maintaining the gas pressure for 30-80 days.

In some embodiments, the method further comprises: when the height of the current layer of cement layer reaches the natural elevation of the earth surface, the surface of the current layer of cement layer is covered with soil, and vegetation which accords with the local ecological environment is planted after the soil is covered.

In some embodiments, the solid waste comprises one or more of tailings, coal refuse, slag, furnace dust, construction waste, waste cement clinker, waste cement; and the liquid in the material preparation step comprises one or more of mine water burst and city water.

In some embodiments, the mass ratio of solid waste to liquid in the material making step is 1: 1.

In some embodiments, the thickness ratio threshold is in the range of 30% -50%.

In some embodiments, the method further comprises: and after injecting carbon dioxide into the mixture layer of the previous layer and closing for 2-4 years, re-injecting supercritical carbon dioxide into the mixture layer of the previous layer, wherein the mass of the re-injected supercritical carbon dioxide is within 30% of the mass of the first injected supercritical carbon dioxide.

A second aspect of the invention provides a method of open pit mining, the method comprising: mining the open pit in a subarea mode, and forming a mined open pit area and a mined open pit area in the mining process; in the method for sequestering carbon dioxide using a surface pit according to the above embodiment, the solid waste generated during mining of the surface pit area under mining is filled in the mined surface pit area.

A third aspect of the invention provides a structure for sequestration of carbon dioxide using an open pit, the structure comprising: a bottom structure comprising: the anti-seepage film is laid at the bottom of the open pit; an clay layer constructed on the impermeable membrane; the device comprises a diversion trench arranged around the clay layer and a fluid collecting pool constructed at the bottom of the open pit, wherein the fluid collecting pool is connected with a water suction pump arranged on the ground through a pipeline; the geotextile is laid on the clay layer, and the bottom cement layer is poured on the geotextile; a side slope structure comprising: a side slope impermeable film is laid on the side slope of the open pit; and a slope cement layer poured on the surface of the slope impermeable membrane; a plurality of fill-layer structures, wherein each fill-layer structure of the plurality of fill-layer structures comprises: the mixed material layer is positioned above the cement layer of the previous layer, wherein the mixed material layer comprises a mixed material formed by mixing crushed solid waste and liquid, and carbon dioxide is filled in the mixed material layer; a filling layer cement layer poured on the mixed material layer; and a plurality of filling layer pouring holes are formed in the filling layer cement layer, wherein each filling layer pouring hole is provided with a one-way valve capable of being sealed in a one-way mode.

The carbon dioxide sequestration method provided by the embodiment of the invention synchronously realizes the backfilling and sequestration of mining waste rock (or coal gangue), power plant ash (if any), waste water mud clinker or waste water mud (if any), and mining gushing water and carbon dioxide, and backfills all wastes generated by mining to a pit. The mining waste rock (or coal gangue), the ash residue (if any) of the power plant and the waste clinker (if any) are filled in a layered mode, then the supercritical carbon dioxide and the mine water are filled into a waste rock mixed material storage area in a layered mode, so that carbon dioxide solidification and industrial solid waste filling are achieved, ecological restoration is finally achieved, extra economic value is generated, and a closed loop is achieved where resources come from and where resource waste returns.

In addition, it is worth mentioning that the industrial solid waste can be co-buried according to actual needs, and if the landfill needs to be carried out, the landfill can be mixed, because one type of landfill can increase one income, and one specific solid waste generated by the mine can be mixed with carbon dioxide for sealing. No matter which mode, the solid waste that all can solve the strip mine exploitation and produce deals with, solves the actual problem of carbon dioxide solidification in step.

The method can solve the problem of cooperative disposal of various industrial solid wastes, realizes the reduction, resource utilization and safe disposal of the wastes, synchronously adds carbon dioxide for sealing, greatly improves the utilization value of the mine pit, generates secondary income, realizes a carbon sequestration engineering technology, and provides a solution for realizing carbon neutralization at an early stage.

Drawings

The above and other objects, features and advantages of embodiments of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

FIG. 1 shows a simplified flow diagram of a method for sequestration of carbon dioxide using an open pit, according to an embodiment of the present invention;

FIG. 2 shows a schematic filling process diagram of a method for sequestration of carbon dioxide using an open pit according to an embodiment of the present invention;

FIG. 3 shows a schematic diagram of a structure for sequestration of carbon dioxide using an open pit, according to an embodiment of the present invention;

fig. 4 shows a flow diagram of a method for sequestration of carbon dioxide using an open pit, according to another embodiment of the present invention.

Detailed Description

The principles and spirit of the present invention will be described with reference to a number of exemplary embodiments. It is understood that these embodiments are given solely for the purpose of enabling those skilled in the art to better understand and to practice the invention, and are not intended to limit the scope of the invention in any way.

In one aspect, embodiments of the present invention provide a method of sequestering carbon dioxide using an open pit. The carbon dioxide is sealed and stored in the process of solidifying the carbon dioxide into carbonate or directly sealing the surface or underground through chemical reaction. Referring to fig. 1-2, wherein fig. 1 shows a simplified flow diagram of a method 100 for sequestration of carbon dioxide using a surface pit according to an embodiment of the present invention, and fig. 2 shows a filling process schematic of the method for sequestration of carbon dioxide using a surface pit according to an embodiment of the present invention. As shown in FIG. 1, method 100 includes steps S101-S106.

It should be noted that the steps of the method proposed by the embodiment of the present invention described in the specification are only for describing and distinguishing the processes involved in the method, and the execution sequence of the steps is not limited. In implementation, the steps may be performed in other sequences, simultaneously, repeatedly, or nested, i.e., one step is embedded in another step, etc., according to specific scenarios and requirements. The invention is not limited in this respect.

In the present specification, the open pit or the abandoned open pit refers to a surface pit left by losing the mining value of the above resources when or after the open pit mining of coal mine, metal mine and other non-metal ores is performed. The invention does not relate to the related technology of the abandoned underground mine which is mined by the well worker, and all the activities are carried out on the ground.

The pit bottom processing step S101 may include: an impermeable membrane, such as a Polytetrafluoroethylene (PTFE) impermeable membrane, may be laid at the bottom of the open pit, and may have a thickness of 1.5-3mm and a permeability coefficient of less than 10, by way of example only^-7cm/s; building an clay layer on the impermeable membrane, wherein the thickness of the clay layer can be 20cm for example; arranging a diversion trench around the clay layer, for example, the diversion trench can be made of 2205 stainless steel; constructing a fluid collecting pool at the bottom of the open pit, for example, the fluid collecting pool can be constructed at the lowest part of the bottom of the pit and is connected with a water suction pump arranged on the ground through a pipeline; a geotextile is laid over the clay layer and a bottom cement layer is poured over the geotextile, which may be 30-50cm thick, for example. The cement poured here is not waste cement but normal portland cement, the quality of which is to be guaranteed and gas overflow is to be prevented. The cement is then allowed to air dry to harden. As an embodiment of the present invention, in order to ensure a firm foundation, the bottom of the used pit may be finished and leveled before the impermeable membrane is laid.

The seepage prevention and the construction requirements meet the requirements of the class II field of general industrial solid waste storage and landfill pollution control standard (GB 18599-2020). Related requirements and measures for seepage prevention are not provided in the existing technical scheme for sealing and storing carbon dioxide, and the implementation mode of the invention adopts the seepage prevention film meeting the standard, thereby being beneficial to protecting the surrounding underground environment.

As shown in fig. 2, after the pit bottom processing step S101, a bottom structure 201 is formed. The fluid collection tank in the bottom structure 201 is connected via a pipe to a suction pump 210 arranged on the ground.

The slope processing step S102 may include: and paving a side slope impermeable film on the side slope of the open pit, and pouring a side slope cement layer on the surface of the side slope impermeable film for reinforcement. The slope impermeable membrane may be a PTFE impermeable membrane, for example only, and may be 1.5-3mm thick and have a permeability coefficient of less than 10^-7cm/s. As an embodiment of the invention, if the mine pit side slope is not flat, the side slope can be subjected to surface smoothing or slope cutting before the side slope impermeable membrane is laid.

As shown in fig. 2, after the slope processing step S102,

slope structures

202 and 204 are formed. As an embodiment, the slope structure 202 may be formed before the first layer constructing step S104, and the slope structure 204 may be formed before the current layer constructing step S105, that is, the slope structure corresponding to each layer may be formed before filling each layer. As another embodiment, the

slope structures

202 and 204 may be formed at one time before the first-layer constructing step S104. In principle, the slope structure formed is only higher than or equal to the expected height of the layer currently to be filled.

The material making step S103 may include: the solid waste is crushed and mixed with a liquid to form a mixed material. For example, the particle size of the crushed solid waste is in the range of 1-20 mm. The smaller the particle size, the more favorable the reaction with carbon dioxide, and the more advantageous the reaction rate.

The solid waste mentioned in the present specification may also be referred to as bulk solid waste, and as an embodiment of the present invention, may include tailings formed after open mine mining or coal gangue in coal mine, and other industrial solid waste that cannot be utilized in industrial production, such as coal-fired power plant ash, waste gypsum, waste cement, and the like. In short, the solid waste may comprise one or more of tailings, coal gangue, slag, furnace ash, construction waste, waste cement clinker, waste cement. As an embodiment of the present invention, in the case where the solid waste includes waste cement clinker and other solid waste, the mass ratio of the waste cement clinker to the other solid waste is in the range of 1:3 to 2: 3.

The liquid used in the material preparation step comprises one or more of mine water burst and city water. Wherein, the mine water burst is suitable for the situation that a mine or a mine pit still mined exists at the periphery. As an embodiment of the invention, the pH value of the liquid in the material preparation step can be adjusted to be between 7.5 and 8.5, and the alkaline liquid condition is favorable for the chemical reaction of the carbon dioxide and the solid waste.

As an embodiment of the present invention, the mass ratio of the solid waste to the liquid may be 1: 1.

The first layer constructing step S104 may include: filling the mixed material above the bottom cement layer, and compacting if necessary to form a first mixed material layer 203; pouring a first cement layer on the first mixed material layer, wherein the thickness of the cement layer can be in the range of 30-60cm, the cement is not waste cement, but normal portland cement, and the quality of the cement layer is ensured and gas overflow is prevented; a plurality of first-layer pouring holes are formed in the first cement layer, the number of the pouring holes can be flexibly set according to the amount of carbon dioxide to be poured, for example, the number of the pouring holes can be 3-10, and the plurality of the pouring holes can be uniformly distributed; wherein, each first layer perfusion hole is provided with a one-way valve, and a first injection pipe 206 is introduced into each first layer perfusion hole.

The first layer of infusion holes and the first infusion tube are used for infusing carbon dioxide into the first mixture layer. Optionally, the first layer pouring hole and the first injection pipe may also be used for pouring liquid into the first mixture layer.

Optionally, a layer of waste cement clinker can be added above the first mixed material layer, and then the first cement layer is poured.

Alternatively, the thickness of first mixture layer 203 may be in the range of 2 to 8 meters, for example. The thickness of the material layer can be obtained by calculation according to the amount of industrial solid waste to be treated, and simultaneously, the amount of carbon dioxide to be mixed is considered. As an embodiment of the present invention, the thickness of the cement layer of the previous layer is determined according to the design thickness of the current mixed material layer. For example, the greater the thickness of the top course of material, the greater the thickness of the cement at the bottom. The layered pouring height of the side slope can be consistent with the height of the stockpiling layer.

The current layer constructing step S105 may include: filling the mixture above the previous cement layer to form a current mixture layer 205; when the thickness of the current mixed material layer is filled to the designed thickness, pouring a current cement layer on the current mixed material layer, wherein the designed thickness is not higher than the thickness of the side slope which is not filled after the side slope treatment; offer a plurality of current layer filling holes 2031 on current layer cement layer, wherein, every current layer filling hole is provided with check valve to let in current layer injection pipe 206 in every current layer filling hole. The current layer perfusion hole and the current layer injection pipe are used for injecting carbon dioxide into the current mixture layer. Optionally, the current-layer perfusion hole and the current-layer injection pipe can also be used for perfusion of liquid to the current mixture layer.

As an embodiment of the present invention, the method 100 may further include: before the first storey building step S104 and the current storey building step S105, waste cement clinker is injected into the side slopes to protect the slopes.

As an embodiment of the present invention, the porosity of the mixed material in the first mixed material layer and the current mixed material layer may be in the range of 0.3 to 0.5. The density of the mixed material in the first mixed material layer and the current mixed material layer may be in the range of 1.0-1.7 tons/cubic meter, similar to dry tailings.

The carbon dioxide injection step S106 may include: after the thickness of the current mixed material layer is filled to the thickness proportion threshold value of the designed thickness, injecting supercritical carbon dioxide into the mixed material layer of the previous layer through the injection pipe of the previous layer filled before the current layer; after the carbon dioxide is injected into the mixture material layer of the previous layer, for example, after the quality of the carbon dioxide injected into the filler layer reaches the design quality, the injection pipe of the previous layer is lifted to be separated from the injection hole of the previous layer, so that the injection hole of the previous layer is unidirectionally closed through the one-way valve. As an embodiment of the present invention, the thickness ratio threshold may be in a range of 30% to 50%. The storage conditions of the supercritical carbon dioxide are as follows: the critical pressure is 7.4MPa at 31 ℃, and the preparation and the transportation are easy in industry. Due to the higher gas pressure, a small part of the carbon dioxide leaking out with the cement cover will be further absorbed by the upper mixture layer. In theory, the mass of total injected carbon dioxide is about 15% to 40% of the mass of mixed solid waste. The content of calcium oxide, magnesium oxide and silicate in the solid waste needs to be calculated and obtained.

It can be seen that the carbon dioxide injecting step S106 is not necessarily performed after the current layer constructing step S105 is completely performed, but may be performed after the thickness of the current mixed material layer is filled to the thickness ratio threshold of the design thickness, that is, the carbon dioxide injecting step S106 may be performed in the middle of the performing process of the current layer constructing step S105, or a part of the step S105 is performed in a manner of being crossed and nested with the step S106. For example, the carbon dioxide injection step S106 may be started after the thickness of the current mixture layer is filled to the thickness ratio threshold of the design thickness, at which point the execution of the current layer construction step S105 is stopped, and after the execution of the step S106 is completed, the remaining part of the current layer construction step S105 may be continued. For another example, the carbon dioxide injection step S106 may be started after the thickness of the current mixture layer is filled to the thickness ratio threshold of the design thickness, and in this case, the step S105 is not stopped, that is, the remaining part of the current layer construction step S105 is synchronously executed during the execution of the step S106, that is, the mixture layer is synchronously continuously filled with the mixture while the carbon dioxide is injected. The present invention is not limited in this respect as long as it is satisfied that the time point at which the carbon dioxide injection step S106 starts to be performed is after the thickness of the current mixed material layer is filled to the thickness ratio threshold of the design thickness.

In the example shown in fig. 2, the current layer is the second layer and the previous layer to be injected with carbon dioxide is the first layer. In this schematic, the injection of supercritical carbon dioxide into the first layer is initiated when the second layer fills to about 50% of the design thickness. In practice, the current layer may be the nth layer (N >1), and the previous layer may be any one or more of the first layer to the N-1 st layer.

Alternatively, the lifting of the injection pipe of the previous layer from the injection hole of the previous layer may be performed immediately after the carbon dioxide injection of the previous layer is completed, or may be performed at any subsequent time, for example, may be performed after the current layer or any subsequent layer is completely filled, performed after the carbon dioxide injection of the current layer or any subsequent layer, or performed after the carbon dioxide injection of all the filling layers is completed.

It should be noted that, in the example shown in fig. 2, the first layer injection holes and the current layer injection holes are aligned in the vertical direction, the same injection pipe 206 may be used to inject carbon dioxide, and a plurality of nozzles may be involved at different heights in the vertical direction of the injection pipe 206, so that the supercritical carbon dioxide is injected into different filler layers through the nozzles at the same time. In other embodiments, the infusion orifices of each layer may be independent of each other.

According to the sequestration requirement, the slope processing step S102, the material making step S103, the current story building step S105 or the carbon dioxide injection step S106 may be performed once or more times. The sequestration requirements may depend on the amount of solid waste to be filled, the amount of carbon dioxide to be sequestered, the plan for the open pit, geological factors, local environment, and so forth. For example, after the second mixed material layer is filled, the third filler layer is constructed, and when the filling thickness of the third filler layer reaches the thickness proportion threshold value of the design thickness, the supercritical carbon dioxide is injected into the second filler layer. The construction mode and sequence of the subsequent mixed packing layer and the mode of injecting the supercritical carbon dioxide can refer to the steps.

According to the method for sealing carbon dioxide by the open pit, which is provided by the embodiment of the invention, a mixed sealing layer of 20-60 layers can be constructed according to the depth and the area of the waste pit, so that the carbon dioxide and the bulk solid waste can be sealed by utilizing different technical principles.

As an embodiment of the present invention, the method for sequestration of carbon dioxide using an open pit may further comprise: arranging a wastewater treatment device outside the open pit; pumping fluid substances collected in the fluid collecting pool and overflowing from the bottom layer of the pit by a water suction pump; precipitating the extracted fluid substances by a wastewater treatment device to generate recovered liquid and recovered solid waste; the recovered liquid and recovered solid wastes are treated as liquid and solid wastes in the material making step, and the mixed material formed after the treatment is refilled in the open pit.

As an embodiment of the present invention, the first layer constructing step may further include: a carbon dioxide concentration sensor and/or a pressure sensor is/are arranged in the first mixed material layer. The current layer constructing step may further include: a carbon dioxide concentration sensor and/or a pressure sensor is/are installed in the current mixed material layer. In other words, a carbon dioxide concentration sensor and/or a pressure sensor can be installed in each mixture layer.

As an embodiment of the present invention, the method may further include: controlling the gas pressure in the mixed material layer of the previous layer within the range of 7-15MPa according to the pressure measurement value of the pressure sensor, and maintaining for 30-80 days. During which it is ensured that carbon dioxide gas does not leak through the infusion orifice and the infusion tube.

As an embodiment of the present invention, the method may further include: and after injecting carbon dioxide into the mixture layer of the previous layer and sealing for 2-4 years, injecting supercritical carbon dioxide into the mixture layer of the previous layer again, wherein the mass of the injected supercritical carbon dioxide is within 30% of the mass of the supercritical carbon dioxide injected for the first time.

China has many open-pit mines. At present, 77 percent of iron ore is mined in the open pit, 52 percent of nonferrous metal ore is mined in the open pit or combined open pit and underground, 70 percent of chemical mine is mined in the open pit, and almost 100 percent of building material mines are mined in the open pit. Calculated according to the production capacity of the existing mine, the open-air iron ore accounts for about 90 percent, the open-air non-ferrous metal ore accounts for 46 percent, and the trend of growth is in future. According to statistics, as the year 2019, China has 439 seats of open-pit mining coal mines and 1200 seats of other non-coal open-pit mining mines, and the pits for ecological restoration are less than 20%. The open-pit mining obviously disturbs and destroys the ecological environment, causes the groundwater to be dredged, the waste ore is randomly piled and placed, influences the habitat of animals and plants, and the like, so that the method inevitably takes the first place under the current strict environmental protection requirement, becomes the object of strict stimulation and remediation and must carry out ecological restoration. However, the ecological restoration cost is huge, new use must be given to the abandoned mine pit, the value of the abandoned mine pit is exerted, economic benefit is generated by utilizing the abandoned mine pit, the synchronization of the benefit and the ecological restoration is finally realized, and the sustainable development of economic, social and ecological environmental protection can be realized.

Coal-fired power plants, steel plants, nonferrous smelting enterprises, cement plants and the like related to the produced ore species are distributed around most mines, so that the resources are converted on site. The enterprises directly discharge carbon dioxide in the production process or build self-contained power stations to discharge carbon dioxide, and the transportation radius is short after the carbon dioxide is collected, so that the transportation economy of the carbon dioxide is not limited greatly.

The chemical method for curing carbon dioxide by using waste ore, coal gangue, waste cement and ash slag of coal-fired power plant is also mentioned in a plurality of patents in recent years, the chemical principles are basically consistent, and carbon dioxide is chemically reacted with chemical substances such as calcium oxide, magnesium oxide, calcium (magnesium) hydroxide, silicate and the like in the waste ore or the ash slag and the waste cement under the alkalescent condition to generate carbonate so as to achieve the curing effect of the carbon dioxide. However, the reaction can be promoted in various scenes, and places similar to underground temperature, pressure and humidity can be built or constructed in the deep stratum or on the ground, so that the aim of sequestering carbon dioxide is also fulfilled. Building such a site on the ground, the use of abandoned open pit is the best site, with the advantages: 1. compared with an underground mine, the open pit has larger volume and larger volume capable of being cooperatively treated; 2. the operation is carried out in the mining pit, so that the observation and the intervention are convenient; 3. the tailings, the coal gangue and various waste residues can be utilized nearby, and the carbon dioxide is synchronously subjected to synergistic landfill and sealing storage, so that the cost is lower; 4. the basic work of ecological restoration of the open pit is synchronously completed, and multiple purposes are achieved.

The embodiment of the invention also provides a structure for sealing carbon dioxide by using the open pit. This structure can be obtained by implementing the above-described method of sequestering carbon dioxide with an open pit. Referring to fig. 3, a schematic diagram of a structure for sequestration of carbon dioxide using an open pit according to an embodiment of the present invention is shown. As shown in fig. 3, the structure may include a bottom structure 301, a slope structure 302, and a plurality of filling layer structures 303.

The bottom structure 301 may include: an anti-seepage film laid at the bottom of the open pit; an clay layer constructed on the impermeable membrane; the device comprises a diversion trench arranged around a clay layer, and a fluid collecting pool constructed at the bottom of an open pit, wherein the fluid collecting pool is connected with a water pump 310 arranged on the ground through a pipeline; the soil engineering cloth is laid on the clay layer, and the bottom cement layer is poured on the soil engineering cloth.

The slope structure 302 may include: a side slope impermeable membrane is laid on the side slope of the open pit; and a slope cement layer poured on the surface of the slope impermeable membrane.

Each of the plurality of fill-layer structures 303 may include: a mixed material layer positioned above the cement layer of the previous layer, wherein the mixed material layer comprises a mixed material formed by mixing crushed solid waste and liquid, and carbon dioxide is filled in the mixed material layer; a filling layer cement layer poured on the mixture layer; and a plurality of filling layer pouring holes are formed in the filling layer cement layer, wherein each filling layer pouring hole is provided with a one-way valve 3031 capable of being sealed in a one-way mode.

Referring to fig. 4, a flow diagram of a method 400 for sequestration of carbon dioxide using an open pit according to another embodiment of the present invention is shown. The method 400 includes steps S401-S412.

The pit bottom processing step S401 may include: paving an anti-seepage film at the bottom of the open pit, and constructing a clay layer on the anti-seepage film; arranging a diversion trench around the clay layer, constructing a fluid collecting pool at the bottom of the open pit, and connecting the fluid collecting pool with a water pump arranged on the ground through a pipeline; and laying geotextile on the clay layer, and pouring a bottom cement layer on the geotextile.

The first slope processing step S402 may include: and paving a side slope impermeable film on a first side slope of the open pit, and pouring a side slope cement layer on the surface of the side slope impermeable film, wherein the height of the formed first side slope structure is higher than or equal to the expected height of the first layer to be filled.

The first material manufacturing step S403 may include: the solid waste is crushed and mixed with a liquid to form a mixed material.

The first layer building step S404 may include: filling the mixed material above the bottom cement layer to form a first mixed material layer, and pouring a first cement layer on the first mixed material layer; a plurality of first layer pouring holes are formed in the first cement layer, wherein each first layer pouring hole is provided with a one-way valve, and a first injection pipe is introduced into each first layer pouring hole.

It can be seen that the pit bottom processing step S401, the first slope processing step S402, the first material making step S403 and the first layer building step S404 substantially correspond to the steps S101-S104 of the method 100, and the detailed description, examples and technical effects of the steps S401-S404 are as described above for the steps S101-S104.

The nth (N >1) slope processing step S405 may include: and paving a side slope impermeable film on the Nth side slope of the open pit, and pouring a side slope cement layer on the surface of the side slope impermeable film, wherein the height of the formed Nth side slope structure is higher than or equal to the expected height of the Nth layer to be filled.

The nth material manufacturing step S406 may include: the solid waste is crushed and mixed with a liquid to form a mixed material.

The nth bottom half construction step S407 may include: and filling the mixed material above the cement layer of the previous layer to form the current mixed material layer until the thickness of the current mixed material layer reaches the thickness proportion threshold of the design thickness of the Nth layer. As an example, the thickness proportion threshold may be in the range of 30% -50%. In other words, when the nth layer is filled to 30% to 50% of the design thickness, the nth layer lower half portion constructing step S407 is ended, and the process proceeds to the N-1 layer carbon dioxide injecting step S408.

The N-1 th layer carbon dioxide injection step S408 may include: injecting supercritical carbon dioxide into the mixture layer of the N-1 layer through the injection pipe of the N-1 layer; after the carbon dioxide is injected into the mixed material layer of the (N-1) th layer, the injection pipe of the (N-1) th layer is lifted to be separated from the injection hole of the previous layer, so that the injection hole of the (N-1) th layer is unidirectionally closed through the one-way valve. It should be noted that the lifting of the injection pipe of the (N-1) th layer from the injection hole of the previous layer can be performed immediately after the injection of the carbon dioxide of the (N-1) th layer is completed, or can be performed at any subsequent time.

The nth layer upper half constructing step S409 may include: continuously filling the mixed material to the Nth layer until the thickness of the mixed material layer is filled to the designed thickness, and pouring an Nth cement layer on the mixed material layer of the Nth layer; and arranging a plurality of current-layer pouring holes on the Nth cement layer, wherein each current-layer pouring hole is provided with a one-way valve, and each current-layer pouring hole is internally provided with a current-layer injection pipe.

In step S410, it is determined whether to continue the filling according to the sequestration requirement. The sequestration requirements may depend on the amount of solid waste to be filled, the amount of carbon dioxide to be sequestered, the plan for the open pit, geological factors, local environment, and so forth.

If the determination result in step S410 is yes, the filling and injection process of the next layer is entered, the number of N is increased by one (N ═ N +1), and the method returns to step S405.

If the judgment result of the step S410 is negative, the filling is stopped. Optionally, the method 400 may further comprise steps S411-S412. In step S411, it is determined whether the height of the current cement layer reaches the natural elevation of the ground surface. If yes, the method 400 proceeds to step S412, soil is covered on the surface of the current cement layer, the thickness of the soil covering is not less than 2 meters, and vegetation conforming to the local ecological environment is planted after the soil covering. If false, the method 400 ends.

Referring back to fig. 3, optionally, when the height of the cement layer of the uppermost filling layer reaches the natural elevation of the ground surface, the structure for sequestration of carbon dioxide using an open pit shown in fig. 3 may further include a surface cover layer 311 located above the uppermost cement layer, through step S412 of the application method 400, and vegetation conforming to the local ecological environment may be planted on the surface cover layer 311, so as to prevent foreign species from being planted.

After the mine pit is buried to the ground surface elevation, the available value of the mine pit is exerted, soil is covered on the surface of a cement layer reaching the ground surface elevation, native plants meeting the local ecological environment are planted after the soil is covered, ecological restoration is achieved, and the ground surface damage and the ecological damage formed after the mine is opencast are restored to the original state or the biodiversity process exceeding the original state is restored. Therefore, the invention provides the waste open pit cooperative ecological restoration technical method capable of cooperatively storing the carbon dioxide and the bulk solid waste, and realizes the cooperation of carbon dioxide storage, solid waste disposal and ecological restoration of the waste open pit.

A specific example of the method for sequestration of carbon dioxide by an open pit according to the embodiment of the present invention is described above with reference to fig. 4, and the overall idea is to treat the slope corresponding to a layer before filling the layer, process the materials required for filling the layer, and inject carbon dioxide into the previous filling layer after the current layer is filled to a certain ratio. In a specific application, various changes can be made without departing from the idea of the invention, for example, the slope of the whole pit can be processed at one time before the first layer is constructed, so that the slope processing step is not required to be executed each time before the subsequent layer is filled. In addition, for example, the material production may be performed once or in a plurality of times depending on the supply of the solid waste and the liquid, and is not necessarily performed once before the construction step for each layer. For another example, after a plurality of packed beds are constructed, supercritical carbon dioxide may be injected into the plurality of packed beds at the same time.

Embodiments of the present invention also provide a method of open pit mining, which may include: mining the open pit in a subarea manner, and forming a mined open pit area and a mined open pit area in the mining process; with the method for sequestration of carbon dioxide using an open pit described in the above embodiment, solid waste generated during mining of the area of the open pit being mined is filled into the mined area of the open pit.

By the mining method of mining and landfill, the bulk solid waste generated in the mining process can be timely buried, and the problems of storage and disposal of the bulk solid waste generated in the mining process are solved; moreover, different partitions of the same open pit are closer in distance, so that the transportation cost is reduced; in addition, carbon dioxide is synchronously sealed in the landfill process, and additional economic benefits are brought.

Tables 1 to 3 below list the main chemical components and their approximate proportions, respectively, contained in exemplary categories of solid waste. Wherein, the table 1 lists the main component tables of the metal tailings and the non-coal non-metal tailings, the table 2 lists the chemical component table of the coal gangue, and the table 3 lists the chemical component table of the cement clinker.

TABLE 1 Main component Table of Metal tailings and non-coal non-metal tailings

TABLE 2 chemical composition of coal gangue

Component elements	Percentage of	Remarks for note
			SiO₂	52-65	Principal Components
Al₂O₃	16-36	Principal Components
			Fe₂O₃	2.28-14.63	Component with large fluctuation
CaO	0.42-2.32	Component with large fluctuation
			MgO	0.44-2.41	Component with large fluctuation
TiO₂	0.9-4	/
			P₂O₅	0.007-0.24	/
Na₂O+K₂O	1.45-3.9	/
			V₂O₅	0.008-0.03	/

TABLE 3 chemical composition table of cement clinker

Component elements	Percentage of	Remarks for note
			SiO₂	19-24	Principal Components
Al₂O₃	4-7
			Fe₂O₃	2-5
CaO	62-67	Principal Components
			MgO	1-5

In general, in the bulk solid wastes such as the tailings, coal gangue, waste cement clinker, waste ash and the like mentioned in the invention, the chemical components capable of participating in the chemical reaction of curing carbon dioxide comprise CaO, MgO and Na₂O、K₂O four main substances. The reaction formula for the chemical reaction of these four components with carbon dioxide is as follows:

CaO+CO₂＝CaCO₃

MgO+CO₂＝MgCO₃

Na₂O+CO₂＝Na₂CO₃

K₂O+CO₂＝K₂CO₃

therefore, the effect of performing carbon dioxide synergistic solidification by utilizing the magnesium iron silicate type, high calcium silicate type, calcium carbonate type and magnesium carbonate type tailings is better; the effect of utilizing coal gangue to carry out carbon dioxide synergistic curing is relatively poor; the best effect is achieved by using the waste lime clinker to carry out carbon dioxide synergistic solidification. Therefore, when the abandoned coal mine pit is used for cooperative landfill disposal, the waste clinker or the waste cement can be added for mixing, and the carbon dioxide solidification capability is improved.

From the economic point of view, no matter in any mine, under the premise of more economic mixed landfill, quantitative waste clinker or waste cement is mixed, the curing ratio of the mixed material to the carbon dioxide in unit mass can reach 15-55%, and the calculation result shows that the carbon dioxide sequestration amount by adopting the treatment method can reach 400-600 kg/m-³. On average, 1 cubic meter of the batch had an average mass of 1.35 tons and an average of about 0.47 tons of carbon dioxide could be cured. The largest open pit volume of China is about 20 billion cubic meters, calculated according to 1 billion cubic meters of the volume of a small and medium-sized pit, the carbon dioxide which can be sealed in the pit can averagely reach 4700 ten thousand tons, and the value of about 19 billion yuan of RMB can be realized according to the current average transaction price of 40 yuan/ton of carbon dioxide.

Therefore, the method and the structure for sealing and storing the carbon dioxide by using the open pit and the open pit mining method provided by the embodiment of the invention can not only solve the problem of cooperative disposal of various industrial solid wastes and mine water burst, realize the reduction, resource utilization and safe disposal of the wastes, synchronously add the carbon dioxide for sealing and storing, realize the closed loop where the resources come and the resource wastes return, realize a carbon fixation engineering technology, provide a solution for realizing carbon neutralization in the early days, but also generate secondary income and obtain additional economic value. Therefore, a technical route of 'multi-position integration and multiple purposes' is realized.

The foregoing description of the embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method of sequestering carbon dioxide using an open pit, the method comprising:

pit bottom treatment steps, including: paving an anti-seepage film at the bottom of the open pit, and constructing a clay layer on the anti-seepage film; arranging a diversion trench around the clay layer, constructing a fluid collecting pool at the bottom of the open pit, and connecting the fluid collecting pool with a water pump arranged on the ground through a pipeline; laying geotextile on the clay layer, and pouring a bottom cement layer on the geotextile;

the step of slope treatment comprises the following steps: paving a side slope impermeable film on a side slope of the open pit, and pouring a side slope cement layer on the surface of the side slope impermeable film;

the material manufacturing step comprises the following steps: crushing the solid waste, and mixing the crushed solid waste with the liquid to form a mixed material;

a first layer construction step comprising: filling the mixed material above the bottom cement layer to form a first mixed material layer, and pouring a first cement layer on the first mixed material layer; a plurality of first-layer pouring holes are formed in the first cement layer, wherein each first-layer pouring hole is provided with a one-way valve, and a first injection pipe is introduced into each first-layer pouring hole;

the current layer construction step includes: filling the mixed material above the previous cement layer to form a current mixed material layer; when the thickness of the current mixed material layer is filled to a designed thickness, pouring a current cement layer on the current mixed material layer, wherein the designed thickness is not higher than the thickness of a side slope which is not filled after the side slope is processed; arranging a plurality of current layer pouring holes on the current layer cement layer, wherein each current layer pouring hole is provided with a one-way valve, and a current layer injection pipe is introduced into each current layer pouring hole;

a carbon dioxide injection step comprising: after the thickness of the current mixture material layer is filled to the thickness proportion threshold value of the design thickness, injecting supercritical carbon dioxide into the mixture material layer of the previous layer through an injection pipe of the previous layer filled before the current layer; after the carbon dioxide is injected into the mixed material layer of the previous layer, lifting the injection pipe of the previous layer to be separated from the injection hole of the previous layer so as to enable the injection hole of the previous layer to be unidirectionally closed through a one-way valve;

and executing the slope processing step, the material manufacturing step, the current layer construction step or the carbon dioxide injection step one or more times according to the sealing requirement.

2. The method of claim 1, further comprising:

arranging a wastewater treatment device outside the open pit;

pumping fluid substances collected in the fluid collecting pool and overflowing from the bottom layer of the pit through the water suction pump;

precipitating the extracted fluid substances by the wastewater treatment device to generate recovered liquid and recovered solid waste;

and treating the recovered liquid and the recovered solid waste as liquid and solid waste in the material making step, and refilling the mixed material formed after the treatment into the open pit.

3. The method of claim 1, wherein the first layer construction step further comprises: installing a carbon dioxide concentration sensor and/or a pressure sensor in the first mixed material layer; and the number of the first and second electrodes,

the current layer constructing step further includes: and installing a carbon dioxide concentration sensor and/or a pressure sensor in the current mixed material layer.

4. The method of claim 3, further comprising:

and controlling the gas pressure in the mixed material layer of the previous layer to be in the range of 7-15MPa according to the pressure measurement value of the pressure sensor, and maintaining the gas pressure for 30-80 days.

5. The method of claim 1, further comprising:

when the height of the current layer of cement layer reaches the natural elevation of the earth surface, the surface of the current layer of cement layer is covered with soil, and vegetation which accords with the local ecological environment is planted after the soil is covered.

6. The method of claim 1, wherein the solid waste comprises one or more of tailings, coal refuse, slag, furnace dust, construction waste, waste cement clinker, waste cement; and the number of the first and second electrodes,

the liquid in the material making step comprises one or more of mine water burst and city water.

7. The method of claim 1, wherein the mass ratio of solid waste to liquid in the material making step is 1: 1.

8. The method of claim 1, wherein the thickness proportion threshold is in the range of 30% -50%.

9. The method of claim 1, further comprising:

and after injecting carbon dioxide into the mixture layer of the previous layer and closing for 2-4 years, re-injecting supercritical carbon dioxide into the mixture layer of the previous layer, wherein the mass of the re-injected supercritical carbon dioxide is within 30% of the mass of the first injected supercritical carbon dioxide.

10. A method of open pit mining, the method comprising:

mining the open pit in a subarea mode, and forming a mined open pit area and a mined open pit area in the mining process;

method for sequestration of carbon dioxide with a pit according to any of claims 1 to 9, the solid waste produced during the exploitation of the mining pit area is filled into the exploited pit area and carbon dioxide is injected.

11. A structure for sequestration of carbon dioxide using an open pit, said structure comprising:

a bottom structure comprising: the anti-seepage film is laid at the bottom of the open pit; an clay layer constructed on the impermeable membrane; the device comprises a diversion trench arranged around the clay layer and a fluid collecting pool constructed at the bottom of the open pit, wherein the fluid collecting pool is connected with a water suction pump arranged on the ground through a pipeline; the geotextile is laid on the clay layer, and the bottom cement layer is poured on the geotextile;

a side slope structure comprising: a side slope impermeable film is laid on the side slope of the open pit; and a slope cement layer poured on the surface of the slope impermeable membrane;

a plurality of fill-layer structures, wherein each fill-layer structure of the plurality of fill-layer structures comprises: the mixed material layer is positioned above the cement layer of the previous layer, wherein the mixed material layer comprises a mixed material formed by mixing crushed solid waste and liquid, and carbon dioxide is filled in the mixed material layer; a filling layer cement layer poured on the mixed material layer; and a plurality of filling layer pouring holes are formed in the filling layer cement layer, wherein each filling layer pouring hole is provided with a one-way valve capable of being sealed in a one-way mode.