Method and device for in-situ recovery of precious metals in tailings

Abstract

The invention discloses a method and device for in-situ recovery of precious metals in tailings, and relates to the field of resource recovery and environmental engineering, and the method comprises the following steps: site isolation; liquid injection and pumping drainage are conducted, specifically, leaching agent liquid is injected into the recovery area through a liquid injection system, meanwhile, soil body pore liquid is pumped and drained through a pumping drainage system, the pumped and drained liquid is returned to the liquid injection system after the leaching agent is supplemented, and liquid injection and pumping drainage are continuously conducted till the concentration of the leaching agent meets the preset requirement; standing and soaking are conducted, specifically, liquid injection and pumping drainage are stopped, and the tailing soil body is subjected to standing and soaking; sampling and detecting; extracting a pregnant solution; and liquid medicine leaching: injecting clear water into the tailing soil body and pumping and draining pore liquid until the concentration of a leaching agent in the pumping and draining liquid is lower than a preset environmental protection limit value, and finishing recovery. According to the method, proper leaching agent liquid medicine is injected into the tailing soil body, precious metal components are dissociated through soaking, high-grade precious metal products are refined, and precious metal remaining in the tailings is efficiently recycled in situ.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of resource recycling and environmental engineering, and particularly relates to a method and device for in-situ recovery of precious metals from tailings. BACKGROUND

[0002] For the recovery of tailings containing a certain grade of precious metals, a common method is to soak the tailings with leaching agent solution, separate the precious metals into the solution, and then adsorb and enrich the solution containing the precious metals (noble liquid), and further refine high-grade precious metal products.

[0003] However, there are two technical problems to be solved for in-situ recovery of precious metal tailings: one is how to effectively inject leaching agent solution into deep tailings soil layer, and fully soak the tailings, and then smoothly pump out the noble liquid soaked with precious metals; the other is that the tailings are mainly fine sand and silt, and have high permeability. When the leaching agent solution is injected into the tailings soil layer, the solution will spread everywhere due to the high permeability of the tailings soil, and cannot be limited and maintained within the range of the tailings where the precious metals are to be recovered, which not only wastes the solution, but also causes loss of the noble liquid, and may also pollute the surrounding soil.

[0004] Therefore, it is necessary to develop a method and device for in-situ recovery of precious metal tailings, which can accurately control the leaching process, realize recycling of the solution, and efficiently enrich the noble liquid. SUMMARY

[0005] The purpose of the present application is to solve the above important technical problems, and to provide a method and device for in-situ recovery of precious metals in tailings, which can accurately control the leaching process, realize recycling of the solution, and efficiently enrich the noble liquid, effectively recover the precious metals, and realize secondary development and utilization of tailings resources.

[0006] The technical scheme of the present application is as follows: In a first aspect, the present application provides a method for in-situ recovery of precious metals from tailings, comprising the following steps: Site isolation, which includes constructing an isolation system around and at the bottom of the recovery area; Liquid injection and pumping, which includes injecting leaching agent solution into the recovery area through the liquid injection system, and pumping out the pore liquid of the soil through the pumping system, and returning the pumped liquid to the liquid injection system after supplementing the leaching agent, and continuously injecting and pumping until the concentration of the leaching agent in the pumped liquid reaches the preset requirement; Static soaking, which includes static soaking of the tailings soil; Sampling and detection, which includes sampling and detecting the grade of precious metals in the soil, and if the grade reaches the preset range, the next step of noble liquid refining is entered, otherwise the static soaking step is repeated; The process of refining precious liquid includes: extracting soil pore liquid into precious liquid for precious metal refining; after refining, the tail liquid discharged is replenished with leaching agent and then returned to the injection system for reinjection into the soil; and the refining continues until the precious metal grade of the discharged liquid is lower than the preset lower limit. The chemical leaching process includes: injecting clean water into the tailings soil and pumping out the pore liquid until the concentration of the leaching agent in the pumped liquid is lower than the preset environmental protection limit, at which point the mining is completed.

[0007] A preferred method for in-situ mining of precious metals from tailings, wherein the isolation system includes a sealing sidewall surrounding the mining area and a sealing bottom wall at the bottom of the area, wherein the sealing sidewall is formed by continuous interlocking of steel sheet piles or by overlapping of mud mixing piles, and the sealing bottom wall is formed by construction using a high-pressure jet grouting device.

[0008] The preferred method for in-situ recovery of precious metals from tailings includes a system deployment step between the site isolation step, the injection and drainage step, and the system deployment specifically includes: constructing an injection system, a drainage system, and installing a refining system. The injection system includes a liquid tank for storing leaching agent solution, an injection pump, an injection pipeline with its inlet connected to the liquid tank, an injection outer pipe inserted into the tailings soil, and an injection core pipe nested inside each injection outer pipe for delivering the leaching agent solution to different soil depths.

[0009] A more preferred method for in-situ recovery of precious metals from tailings, wherein the pumping system includes a pumping pipe for collecting liquids within the recovery area, a pumping pump, a return liquid pool A, a return liquid pool B, and a drainage plate inserted into the tailings soil; the pumping pipe leads to the inlet of the pumping pump and the outlet of the pumping pump is provided with a return pipe leading to the return liquid pool A; the return liquid pool A is connected to the return liquid pool B via a first pumping pipe; and the return liquid pool B is connected to the chemical solution pool via a second pumping pipe.

[0010] A more preferred method for in-situ recovery of precious metals from tailings, wherein the refining system includes a refining pipeline connected in parallel with the reflux pipeline and refining equipment disposed on the refining pipeline.

[0011] A more preferred method for in-situ recovery of precious metals from tailings, wherein in the injection and drainage steps, a leaching agent solution of standard concentration C0 is continuously injected into the tailings soil of the recovery area from the leaching pool via the injection system, while the pore liquid of the soil is drained via the drainage system and directly transported to the return pool A through the return pipeline, and then pumped to the return pool B to replenish the leaching agent until the standard concentration C0 is reached; the leaching agent solution with a concentration of C0 in the return pool B is drained to the leaching pool of the injection system, and the injection and drainage are continued until the leaching agent concentration C1 ≥ 90%C0 of the liquid directly extracted from the soil is obtained.

[0012] A more preferred method for in-situ recovery of precious metals from tailings, wherein in the static soaking step, the initial static soaking time is a preset time T0, where T0 is 15 to 20 days; If the precious metal grade of the extracted liquid does not reach the preset range during the sampling and testing step, it is necessary to repeat the standing soaking. The soaking time for each subsequent soaking is T0 / 3~T0.

[0013] A more preferred method for in-situ recovery of precious metals from tailings, wherein in the precious metal extraction step, The pore liquid in the soil is pumped out by the pumping system and sent to the refining equipment as a precious liquid. The refining equipment is used to extract precious metals. The tail liquid discharged from the refining equipment is returned to the return liquid pool A and pumped to the return liquid pool B to adjust the concentration of the solution to the standard concentration C0. Then it is pumped to the solution pool of the injection system and reinjected into the soil. The refining continues until the precious metal grade of the pumped liquid is lower than the preset lower limit.

[0014] A more preferred method for in-situ recovery of precious metals from tailings, wherein in the leaching and replacement step, clean water is injected into the recovery area through an injection system, and at the same time, the pore liquid of the tailings soil is pumped out to return liquid pool A and / or return liquid pool B for treatment through a pumping system, until the concentration of the leaching agent in the liquid directly pumped out from the soil is lower than the preset environmental protection limit M, where M = 5%~10% CO.

[0015] The present invention also provides an apparatus for the above-mentioned in-situ recovery of precious metals from tailings, comprising: The isolation system includes a sealing sidewall surrounding the mining area and a sealing bottom wall at the bottom of the area, wherein the sealing sidewall and the sealing bottom wall enclose an isolation reaction zone. The injection system includes a liquid tank for storing leaching agent solution, an injection pump, an injection pipe with an inlet connected to the liquid tank, an injection outer pipe inserted into the tailings soil, and an injection core pipe nested inside each injection outer pipe for delivering the leaching agent solution to different soil depths. The pumping system includes a pumping pipe for collecting liquid in the mining area, a pumping pump, a return liquid pool A and a return liquid pool B, and a drainage plate inserted into the tailings soil. The pumping pipe leads to the inlet of the pumping pump and the outlet of the pumping pump is provided with a return pipe leading to the return liquid pool A. The return liquid pool A is connected to the return liquid pool B via a first pumping pipe, and the return liquid pool B is connected to the chemical liquid pool via a second pumping pipe. The refining system includes refining equipment connected in parallel on a reflux pipeline. Both the refining pipeline and the reflux pipeline are equipped with control valves on the downstream pipe sections near the parallel connection point to control the flow of the pumped liquid to the refining equipment or the return liquid pool A.

[0016] The preferred method for in-situ recovery of precious metals from tailings uses an apparatus in which, when the sealing sidewall is a mud mixing pile wall, the diameter of a single mud mixing pile is A=600~800mm, the overlap size of adjacent mixing piles is ≥200mm, and the width of the sealing sidewall is C=1.0m~1.2m.

[0017] The preferred method for in-situ mining of precious metals from tailings uses a device in which a high-pressure jet grouting pile is used to form a sealing wall at the bottom of the mining area. The triple-pipe construction process is adopted, with overlapping arrangement. The pile spacing G = 1.5~2.0m, the overlap size of adjacent jet grouting piles ≥300mm, and the actual pile length 0.8~1.5m.

[0018] In a preferred method for in-situ recovery of precious metals from tailings, the apparatus includes a plurality of isolation spray devices spaced along the length of the injection core tube. Each isolation spray device comprises a core tube section with multiple discharge holes in its wall, and rubber isolation rings located at both ends of the core tube section. The rubber isolation rings are tightly fitted to the inner wall of the injection outer tube. On the wall of the injection outer tube, corresponding to each isolation spray device, a rubber one-way valve is provided that allows only liquid to be discharged outwards. More preferably, each isolation spray device is 40-50 cm in length, and two rubber isolation rings are provided at each end of the core tube section.

[0019] The preferred in-situ method for recovering precious metals from tailings uses an apparatus in which the injection pipeline is connected to the injection core tubes inside each injection outer tube via a T-joint. The T-joint has a T-shaped structure, with its lower port connected to the injection core tube via a connecting fitting, and its upper two ports connected to the injection pipeline.

[0020] The preferred in-situ method for recovering precious metals from tailings uses an apparatus in which geotextile and a sealing membrane are laid sequentially upwards on the surface of the recovery area, and the injection pipe and the extraction pipe pass through the sealing membrane in a sealed manner via a membrane exit device.

[0021] The preferred method for in-situ recovery of precious metals from tailings uses an apparatus in which the refining equipment is an activated carbon adsorption column, an ion exchange column, or a resin adsorption column.

[0022] The beneficial effects of this invention are: (1) The method of the present invention can simultaneously and extensively mine precious metals in the deep tailings soil layer of the tailings pond without the need for digging and transporting tailings. It has low unit cost, significant economies of scale, and great value for the secondary development and utilization of precious metal tailings.

[0023] (2) In the method of the present invention, the leaching agent is filled into the deep tailings soil layer through the injection system and the pumping system, and the precious liquid is extracted by static leaching. Then, the precious liquid is transported to the refining system through the pumping system and adsorbed and enriched into high-grade precious metal products. A complete and efficient tailings recovery precious metal production line is formed on the tailings dam site. This integrated design eliminates the delay and loss in the connection between various links in the traditional method, thereby realizing the simultaneous improvement of recovery efficiency and speed.

[0024] (3) The established isolation system can keep the leaching agent and precious metal-containing solution within the range of the mined soil, ensuring the leaching effect and preventing the loss of precious solution. At the same time, the isolation system prevents the leakage of the solution and avoids pollution of the surrounding soil.

[0025] (4) The injection core pipe inside the injection pipe is equipped with an isolation spray device at different depths, which can effectively control the liquid to be injected into the tailings soil at a predetermined depth, avoid the situation where the injected liquid flows back to the shallow layer or even the ground along the pipeline, and ensure the uniformity of the liquid distribution in the vertical direction, thereby forming an effective seepage and rinsing path in the entire depth range.

[0026] (5) The injection system and the pumping system of the present invention are organically combined to achieve multiple effects: When injecting the liquid into the soil, the pumped liquid already contains the liquid for a period of time in the initial period of time. It is then transported back to the return pool through the loop, and after adding an appropriate amount of leaching agent, it is returned to the injection system, which reduces the consumption of fresh leaching agent; the tailings soil can be statically soaked or circulated and rinsed; for tailings with very low precious metal grade, the grade of precious liquid can be increased by multiple circulated injections, and then adsorption enrichment and refining can be carried out to improve the refining efficiency of precious liquid and reduce the refining cost; if necessary, clean water can be injected to rinse and replace the liquid in the soil to meet the environmental protection purification requirements of the soil.

[0027] (6) This invention achieves efficient recycling of the leaching agent by designing a closed-loop pipeline from the leaching pool to the mining area, the return pool, and the leaching agent replenishment, and by combining concentration monitoring with leaching agent replenishment. This significantly reduces the consumption of leaching agents and operating costs, while also reducing the risk of secondary pollution.

[0028] (7) This invention can effectively treat tailings with extremely low initial grade by repeatedly displacing the leaching agent solution and continuously concentrating and enriching the precious solution within the system, so that residual precious metals can be recovered, greatly expanding the boundaries of resource utilization.

[0029] (8) From the source isolation and seepage prevention, the process of chemical recycling, to the final leaching and purification of the soil, the entire process system of this invention prevents the spread of harmful chemicals to the surrounding environment to the greatest extent, and achieves the goal of meeting environmental protection requirements while recycling resources. It is a green and sustainable tailings treatment method. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method of the present invention. Figure 2 This is a schematic diagram of the overall device of the present invention (vertical). Figure 3 Schematic diagram of the layout of the sealing sidewalls and drainage board / injection pipes Figure 4 Schematic diagram of steel sheet pile sealing sidewall Figure 5 Schematic diagram of the sealing sidewall structure for mud mixing piles Figure 6 Schematic diagram of the sealing bottom wall structure for jet grouting piles Figure 7 Schematic diagram of the isolation spray device The components are as follows: 1. Mining area; 2. Drainage board; 3. Injection pipe; 4. Extraction pipe; 5. Injection pipe; 6. Injection pump; 7. Drainage pump; 8. Chemical tank; 9. Return tank A; 10. Return tank B; 11. Leaching agent solution; 12. Drainage liquid; 13. Sealed sidewall; 14. Sealed bottom wall; 15. Refining equipment; 16. Steel sheet pile; 17. Control valve; 18. Connecting fittings; 19. T-joint; 21. Injection core pipe; 22. Rubber check valve; 23. Liquid outlet; 24. Rubber isolation ring; 30. Return pipe; 31. First pumping pipeline; 32. Second pumping pipeline; 33. Refining pipeline. Detailed Implementation

[0031] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. The following specific embodiments will further describe the present invention in detail.

[0032] like Figures 2-7 As shown, the present invention provides an apparatus for in-situ recovery of precious metals from tailings, which is mainly composed of four organically integrated parts: an isolation system, a liquid injection system, a pumping system, and a refining system.

[0033] The isolation system is the basis for implementing in-situ mining. Its function is to form an isolated reaction zone with an open top to prevent the loss of chemical and precious liquids. It consists of a sealing sidewall 13 and a sealing bottom wall 14. The sealing sidewall needs to penetrate 0.8~1.5m through the bottom of the mining tailings area.

[0034] The sealing wall 13 can be formed by continuously interlocking a single row of steel sheet piles 16 to create a water-stopping sealing wall, or it can be formed by using double rows of mud-mixing piles. The sealing wall 13 is preferably constructed using steel sheet piles 16 because steel sheet piles can be reused and do not occupy tailings resources. Mud-mixing pile sealing walls require tailings soil resources and can be used when the tailings soil is very thick.

[0035] In some preferred embodiments, the sheet pile 16 can be a U-shaped Larssen sheet pile, such as... Figure 4 As shown, different sheet pile models are selected based on the tailings soil thickness: (i) When the tailings thickness is ≤8m, model SP-II (width 400mm, height 100mm, thickness 10.5mm, theoretical weight per meter of single pile 48kg) is selected; (ii) When 8m≤tailings thickness ≤12m, model SP-III (width 400mm, height 125mm, thickness 13mm, theoretical weight per meter of single pile 60kg) is selected; (iii) When 12m≤tailings thickness ≤18m, model SP-IV (width 400mm, height 170mm, thickness 15.5mm, theoretical weight per meter of single pile 76.1kg) is selected. The width D of the sealing sidewall formed by the sheet pile 16 is approximately twice the height C of the selected single sheet pile.

[0036] In some preferred examples, double-row mud mixing piles, such as Figure 5 As shown, the diameter of a single mud mixing pile is A=600~800mm, the overlap size of adjacent mixing piles is ≥200mm, the width of the sealed sidewall is B=1.0m~1.2m, the depth of the mixing pile should enter the bottom of the mining area by 0.8~1.2m, and the permeability coefficient of the pile wall should be less than 10~5cm / s.

[0037] In some preferred embodiments, the sealing bottom wall 14 is formed at the bottom of the mining area using high-pressure jet grouting piles, employing a triple-pipe construction technique with overlapping joints, such as... Figure 6 As shown, the pile spacing G = 1.5~2.0m, the overlap size of adjacent jet grouting piles ≥300mm, and the actual pile length (i.e., the vertical thickness of the wall) 0.8~1.5m, to ensure reliable bottom sealing.

[0038] The injection system is used to precisely and uniformly inject leaching agent solution 11 into tailings soil at different depths. For example... Figure 1 As shown, the injection system includes an off-site chemical tank 8, an injection pump 6, an injection pipeline 5 with its inlet connected to the chemical tank 8, and an injection outer pipe 3 inserted into the tailings soil. Each injection outer pipe 3 contains an independent injection core pipe 21. Figure 7As shown, multiple isolation spray devices are spaced along the length of the outer wall of the injection core tube 21. Each isolation spray device includes a core tube section with multiple discharge holes 23 in its wall, and rubber isolation rings 24 at both ends of the core tube section. These rubber isolation rings 24 fit tightly against the inner wall of the injection outer tube 3, dividing the annular cavity between the injection outer tube 3 and the injection core tube 21 into multiple independent compartments that are sealed to each other in the longitudinal direction. On the wall of the injection outer tube 3, at positions corresponding to each isolation spray device, mounting holes are provided and fitted with rubber one-way valves 22. These valves only allow liquid to be discharged unidirectionally from the inside of the tube to the outside, effectively preventing soil particles from entering and pore liquid from flowing back in.

[0039] In some preferred embodiments, each isolation spray device has a vertical length of 40-50 cm, and the isolation spray devices are installed starting at a depth of 2-6 m above the ground, with a spacing of 0.4-0.6 m between adjacent isolation spray devices. The outlet holes 23 are arranged in rows at intervals along the length of the pipe, with multiple outlet holes 23 spaced circumferentially along the pipe wall. In some preferred embodiments, two rubber sealing rings are installed at each of the upper and lower ends of the core pipe section, enhancing the sealing reliability of the isolation spray device through the double sealing rings at both ends. Multiple rubber one-way valves 22, corresponding to each isolation spray device, can be arranged circumferentially on the wall of the injection outer pipe 3.

[0040] The injection pipeline 5 connects to the top of each injection core tube 21 via a tee connector 19 on the surface of the mining area 1. The tee connector 19 has a T-shaped structure, with its lower end connected to the injection core tube 21 via a connecting fitting 18 (such as a steel wire hose), and its upper two ends connected to the injection pipeline 5. In some preferred embodiments, the injection outer pipe 3 is open at the top and closed at the bottom; the upper end of the injection core tube 21 is connected to the connecting fitting 18, and the lower end is either open or closed.

[0041] The extraction and drainage system is used to extract precious metal-containing liquids (precious solutions) from the reaction zone and transport them to a designated location. For example... Figure 1 As shown, the drainage system includes a drainage pipe 4, a drainage pump 7, a return liquid pool assembly, and a drainage plate 2 inserted into the tailings soil. The drainage pipe 4 connects to the top of the drainage plate 2 at the surface of the mining area 1. Preferably, the top of the drainage plate 2 is wrapped and tied to the drainage pipe 4. The outlet end of the drainage pipe 4 leads to the inlet of the drainage pump 7. The outlet of the drainage pump 7 is provided with a return pipe 30 leading to the return liquid pool assembly. The return liquid pool assembly includes a return liquid pool A9 and a return liquid pool B10. The chemical pool 8, return liquid pool A9, and return liquid pool B10 are preferably located on the same side outside the mining area 1 for easy management. The outlet of the return pipe 30 leads to the return liquid pool A9. The return liquid pool A9 leads to the return liquid pool B10 via a first pumping pipe 31. The return liquid pool B10 leads to the chemical pool 8 via a second pumping pipe 32, thus forming a complete chemical liquid circulation loop.

[0042] by Figure 3The vertical direction of the mining area 1 is considered longitudinal, while the horizontal direction is considered transverse. The arrangement of the drainage boards 2 and injection pipes 3 is as follows: multiple drainage boards 2 are arranged in rows at equal intervals along the longitudinal direction of the mining area 1, and multiple injection pipes 3 are also arranged in rows at equal intervals along the longitudinal direction. The multiple rows of drainage boards 2 and multiple rows of injection pipes 3 are arranged alternately at equal intervals along the transverse direction. The width of each drainage board 2 is set along the longitudinal direction. This arrangement helps to uniformly inject liquid and uniformly drain pore liquid from the soil in the plane area of ​​the mining area 1. The drainage boards are plastic drainage boards commonly used in vacuum preloading, with grooves on the surface along the length direction.

[0043] The refining system is used to extract precious metal products from precious liquids. The refining equipment 15 is connected in parallel with the return pipe 30 via a refining pipe 33. Control valves 17 are installed on the downstream sections of both the refining pipe 33 and the return pipe 30 near the parallel connection point. By controlling the opening and closing of these two control valves 17, the pumped liquid 12 can be selectively directed to the refining equipment 15 for gold extraction, or directed to the return liquid pool A9 for recycling. The refining equipment 15 can be selected from existing mature gold extraction equipment such as activated carbon adsorption columns, ion exchange columns, or resin adsorption columns, depending on the occurrence state of precious metals in the tailings and the grade of the precious liquid.

[0044] To maintain the system's operating environment, a layer of woven geotextile is first laid on the surface of the mining area 1 above the injection pipe 5 and the extraction pipe 4 to protect the sealing membrane, and then covered with another layer of sealing membrane. The injection pipe 5 and the extraction pipe 4 can pass through the sealing membrane through a dedicated sealing membrane exit device to ensure the sealing under the membrane.

[0045] like Figure 1 As shown, the in-situ recovery of precious metals from tailings according to the present invention is carried out using the above-mentioned device in the following steps. Before on-site construction, preparatory work must be completed: ① Conduct exploration of the tailings dam where precious metals are to be recovered, and understand the distribution of tailings soil in the dam, the physical and mechanical properties of the tailings soil, the grade of precious metals, the types of precious metals, and their existing forms in the tailings soil. ② Select an appropriate leaching agent based on the type and occurrence state of the precious metal and the characteristics of this method. The selection principle is: high recovery rate of precious metals in the tailings to be mined, environmentally friendly and non-toxic, and good stability. For cases where the precious metal is gold, lime-sulfur mixture, potassium perchlorate, or other environmentally friendly leaching agents can be used. ③Batch tests were conducted on precious metal tailings soil samples in the laboratory to determine the concentration C0 of the leaching agent and the intended soaking time T0, and to analyze and estimate the precious metal grade P0 of the precious metal solution extracted from the tailings after soaking.

[0046] S1. Site Isolation and Pretreatment An isolation system was constructed around and at the bottom of mining area 1. Then, a predetermined volume of leaching agent solution was injected into the tailings soil within the mining area and stirred, as detailed below.

[0047] 1) Use sheet piles or mixing piles to construct sealed sidewalls The specific process for constructing the sealed sidewall using steel sheet piles is as follows: A Larssen steel sheet pile wall self-seepage prevention system is adopted, with a seepage prevention grade of not less than P6. Its waterproofing employs a lock-type waterproofing structure. The type of steel sheet pile is determined based on the thickness of the tailings soil layer to be mined: (i) when the tailings thickness is ≤8m, type SP-II is selected; (ii) when 8m≤tailings thickness ≤12m, type SP-III is selected; (iii) when 12m≤tailings thickness ≤18m, type SP-IV is selected. Steel sheet piles are driven to the required depth around the planned tailings mining area according to relevant technical specifications.

[0048] The specific process for constructing a sealed sidewall using mixing piles is as follows: Double-row interlocking mixing piles are used for sealing and water stoppage. Bentonite is used as the mixing material for the slurry, with a slurry specific gravity of 1.30~1.40 and a slurry mixing ratio >20~35% (the ratio of slurry volume to the volume of the reinforced soil). The permeability coefficient of the slurry mixing pile wall is ≤1×10⁻⁶. -5 cm / s. A four-spray, four-mix construction process was adopted, and mud-mixing piles were driven to the predetermined requirements according to relevant specifications.

[0049] 2) Construction of sealed base wall A triple-tube high-pressure jet grouting system is used to inject slurry into the bottom to form a sealed base wall 14. Bentonite is used as the slurry material, with a water-cement ratio of 1:0.8~1.2, and 400~600 kg of bentonite is used per linear meter. The high-pressure jet grouting piles are arranged in an overlapping manner, with a pile spacing G=1.5~2.0m, an effective overlap dimension of ≥300mm between two adjacent high-pressure jet grouting piles, and a solid pile length of 0.8~1.5m.

[0050] S2, System Deployment The construction fluid injection system, pumping and drainage system, and installation refining system are detailed below.

[0051] Construction drainage board: Drainage board 2 is installed using a board-inserting machine according to the plan layout required by the design; the depth of drainage board 2 in the soil reaches the bottom of the mining area 1.

[0052] Construction of the injection outer pipe 3: According to the design requirements, a pre-drilling hole is made using a drilling rig to the bottom of the mining area 1, with the hole diameter being 10-30mm larger than the outer diameter of the injection outer pipe; the injection outer pipe 3 is then inserted; the gap between the drilled hole and the injection outer pipe 3 is backfilled with fine sand, and mud is backfilled 0.5-1.0m below the ground surface. An injection core pipe 21 is installed inside the injection outer pipe 3, and a corresponding isolation spraying device is assembled. The injection core pipe 21 is connected to the upper connecting pipe fitting 18.

[0053] Install pumping pump 7 and injection pump 6 outside the mining site, and excavate chemical solution pool 8, return solution pool A9 and return solution pool B10.

[0054] Connection of the injection system: Lay an infusion pipe 5 on the ground, one end of which is connected to the injection core tube 21 inside the injection outer tube 3, and the other end is connected to the injection pump 6 through the sealing membrane via the membrane outlet device.

[0055] Connection of the pumping system: The pumping pipe 4 is laid on the ground, and the top of the drainage board 2 is connected to the pumping pipe 4 by wrapping. The pumping pipe 4 is connected to the pumping pump 7 through the membrane outlet device and the sealing membrane.

[0056] Laying the sealing membrane: First, dig a membrane pressing trench around the mining area 1; first, lay a layer of woven geotextile on the ground, then lay the sealing membrane, and step the sealing membrane into the membrane pressing trench and backfill and compact it.

[0057] Install refining equipment and related pipelines: Install reflux pipeline 30 to connect the outlet of pump 7 to return liquid pool A9, install refining pipeline 33 in parallel on reflux pipeline 30, install refining equipment 15 on refining pipeline 33, install control valve 17 near the parallel connection point of reflux pipeline 30 and refining pipeline 33, install first pumping pipeline 31 to connect return liquid pool A9 to return liquid pool B10, and install second pumping pipeline 32 to connect return liquid pool B10 to chemical liquid pool 8.

[0058] S3, Injection and Drainage Start the injection pump 6 to inject the standard concentration C0 (C0=0.05~0.3mol / L) leaching agent solution 11 from the solution tank 8 into the tailings soil at different depths through the injection core tube 21 at an injection pressure of 0.1~10MPa; at the same time, start the pump 7 to pump out the original pore fluid in the soil at a vacuum pressure of 10~60kPa under the membrane. The concentration of the leachate in the liquid directly extracted from the soil is tested. The injection and extraction are continued until the concentration of the leachate in the directly extracted liquid, C1, is ≥ 90%C0. During the injection and extraction process, the extracted liquid 12 enters the return liquid pool A9 through the return pipe 30 via the control valve 17 (i.e., the control valve 17 on the return pipe 30 is open and the control valve 17 on the refining pipe 33 is closed), and then is pumped to the return liquid pool B10 through the first pumping pipe 31. An appropriate amount of leachate is added to the return liquid pool B10 to make its concentration reach the standard concentration C0. Then it is pumped to the chemical pool 8 through the second pumping pipe 32 for injection into the mining area 1.

[0059] S4. Let it stand and soak. When the pump is stopped, the tailings in the mining area are left to stand and soak in the leaching agent solution for the first soaking time, which is a preset time T0 (T0 = 15~20 days).

[0060] S5, Sampling and Testing Start the pumping pump 7 for approximately 15-30 minutes to extract and sample the tailings from the mining area, and test the precious metal grade P of the extracted precious liquid sample. If the precious metal grade of the precious liquid reaches the preset range P≥50%P0, proceed to the next step; otherwise, repeat the previous step of static soaking, continuing the soaking time T0 / 3~T0 until the precious metal grade P of the precious liquid meets the preset range, which can be optionally set to P≥50%P0.

[0061] S6, Precious Liquor Refining After the precious metal grade P of the pumped liquid is sampled and tested to be within the preset range, the control valve 17 is switched (i.e., the control valve 17 on the return pipeline 30 is closed, and the control valve 17 on the refining pipeline 33 is opened), and the pumping pump 7 is started to transport the precious liquid to the refining equipment 15. The precious liquid is adsorbed, enriched, and refined to produce a high-grade precious metal product. The liquid discharged from the refining system is returned to the return liquid pool B10, and an appropriate amount of leaching agent is added to make the concentration of the solution reach the standard concentration C0. Then, it is pumped back to the solution pool 8 and used as the standard concentration leaching agent solution to continue to be injected into the tailings soil. The above process of pumping out the precious liquid, refining the high-grade precious metal product, and injecting the leaching agent solution continues until the grade of the pumped out precious liquid can no longer effectively refine the precious metal product, that is, the precious metal grade P is lower than the preset grade lower limit N (optional N=0.05g / t, i.e., the refining ends when P<0.05g / t).

[0062] S7, rinsing with medicine solution Add clean water to the chemical solution tank 8, and start the injection pump 6 to inject clean water into the tailings soil in the mining area; at the same time, start the drainage pump 7 to pump the pore liquid of the tailings soil to the return liquid tank A9, and treat the discharged liquid appropriately. Repeat the above process of injecting clean water into the tailings soil and pumping out the pore liquid until the concentration of the leachate directly pumped out of the soil is lower than the preset environmental limit value M, M=5%~10% C0, then stop water injection and pumping.

[0063] The precious metal recycling project was completed after the injection pump, drainage pump, and related construction materials were dismantled.

Claims

1. A method of in situ recovery of precious metals from tailings, characterized in that, The method comprises the following steps: Site isolation, which comprises constructing an isolation system around the periphery and bottom of the mining area (1); Liquid injection and pumping, which comprises injecting leaching agent liquid into the mining area (1) through the liquid injection system, pumping the pore liquid of the soil through the pumping system, and returning the pumped liquid to the liquid injection system after supplementing the leaching agent, and continuously injecting and pumping until the concentration of the leaching agent in the pumped liquid directly pumped from the soil reaches the preset requirement; Static soaking, which comprises statically soaking the tailings soil; Sampling and detection, which comprises sampling and detecting the grade of precious metals in the soil, and if the grade reaches the preset range, the next step of precious liquid refining is entered, otherwise the step of static soaking is repeated; Precious liquid refining, which comprises pumping the pore liquid of the soil as precious liquid for precious metal refining, and returning the tail liquid discharged after the refining to the liquid injection system after supplementing the leaching agent, and continuously refining until the grade of precious metals in the pumped liquid is lower than the lower limit of the preset grade; Liquid washing, which comprises injecting clean water into the tailings soil and pumping the pore liquid, until the concentration of the leaching agent in the pumped liquid is lower than the preset environmental protection limit value, and the mining is completed.

2. The method of in situ recovery of tailings precious metals as claimed in claim 1, wherein, The isolation system comprises a sealing side wall (13) arranged around the mining area (1) and a sealing bottom wall (14) arranged at the bottom of the area, the sealing side wall (13) is formed by continuously buckling steel sheet piles (16) or formed by overlapping mud mixing piles, and the sealing bottom wall (14) is formed by using high-pressure rotary jet equipment.

3. The method of in situ recovery of tailings precious metals as claimed in claim 2, wherein, Between the site isolation step and the liquid injection and pumping step, a system layout step is further included, which specifically comprises constructing the liquid injection system, the pumping system and installing the refining system; The liquid injection system comprises a liquid pool (8) for storing leaching agent liquid, a liquid injection pump (6), a liquid injection pipeline (5) connected to the liquid pool (8), an injection outer pipe (3) inserted into the tailings soil, and an injection core pipe (21) nested in the injection outer pipe (3) for delivering the leaching agent liquid to different soil depths.

4. The method of in situ recovery of tailings precious metals of claim 3, wherein, The pumping system comprises a liquid pumping pipeline (4) for collecting liquid in the mining area (1), a pumping pump (7), a liquid return pool A (9), a liquid return pool B (10), and a drainage plate (2) inserted into the tailings soil; the liquid pumping pipeline (4) is connected to the inlet of the pumping pump (7), and the outlet of the pumping pump (7) is provided with a return pipeline (30) connected to the liquid return pool A (9); the liquid return pool A (9) is connected to the liquid return pool B (10) through a first pumping pipeline (31); the liquid return pool B (10) is connected to the liquid pool (8) through a second pumping pipeline (32).

5. The method of in situ recovery of tailings precious metals as claimed in claim 4, wherein, The refining system comprises a refining pipeline (33) connected in parallel with the return pipeline (30) and a refining device (15) arranged on the refining pipeline (33).

6. The method of in situ recovery of tailings precious metals of claim 4, wherein, The injection and pumping steps, through the injection system from the leaching agent liquid pool (8) to the tailings soil body in the mining area continuously injects the leaching agent liquid with standard concentration C0, and at the same time, the pumping system pumps the soil pore liquid, which is directly transported to the liquid return pool A (9) through the return pipeline (30), and then pumped to the liquid return pool B (10) to supplement the leaching agent to reach the standard concentration C0; the leaching agent liquid with concentration C0 in the liquid return pool B (10) is pumped to the liquid pool (8) of the injection system, and the injection and pumping are continuously carried out until the leaching agent concentration C1 of the directly pumped liquid from the soil body is greater than or equal to 90% C0.

7. The method of in situ recovery of tailings precious metals of claim 1, wherein, In the soaking step, the first standing soaking time is a preset time T0, and T0 is 15-20 days; When the sampling and detection step, if the pumping liquid noble metal grade does not reach the preset range, the soaking time is T0 / 3-T0 each time.

8. The method of in situ recovery of tailings precious metals of claim 6, wherein, In the noble liquid refining step, Through the pumping system, the soil pore liquid is pumped as noble liquid to the refining equipment (15), the noble metal is refined by using the refining equipment (15), the tail liquid refined and discharged by the refining equipment (15) is returned to the liquid return pool A (9), pumped to the liquid return pool B (10) to adjust the liquid concentration to the standard concentration C0, and then pumped to the liquid pool (8) of the injection system, and injected back to the soil body, and the continuous refining is carried out until the pumping liquid noble metal grade is lower than the lower limit of the preset grade.

9. The method of in situ recovery of tailings precious metals of claim 6, wherein, In the leaching displacement step, the injection system injects clean water into the mining area (1), and at the same time, the pumping system pumps the tailings soil pore liquid to the liquid return pool A (9) and / or the liquid return pool B (10) for treatment until the leaching agent concentration of the directly pumped liquid from the soil body is lower than the preset environmental protection limit value M, M=5%-10% C0.

10. An apparatus for use in a process for in situ recovery of precious metals from tailings as claimed in any one of claims 1 to 9, characterised in that, It comprises: An isolation system comprising a sealing side wall (13) arranged around the mining area (1) and a sealing bottom wall (14) arranged at the bottom of the area, and the sealing side wall (13) and the sealing bottom wall (14) form an isolated reaction zone; An injection system comprising a liquid pool (8) for storing leaching agent liquid, an injection pump (6), an injection pipeline (5) connected to the liquid pool (8), an injection outer pipe (3) inserted into the tailings soil body, and an injection core pipe (21) nested in the injection outer pipe (3) for delivering the leaching agent liquid to different soil depths; A pumping system, the pumping system comprises a pumping pipeline (4) for collecting liquid in the mining area (1), a pumping pump (7), a liquid return pool A (9) and a liquid return pool B (10), and a drainage plate (2) inserted into the tailings soil body, the pumping pipeline (4) is connected to the inlet of the pumping pump (7), and the outlet of the pumping pump (7) is provided with a return pipeline (30) connected to the liquid return pool A (9), the liquid return pool A (9) is connected to the liquid return pool B (10) through a first pumping pipeline (31), and the liquid return pool B (10) is connected to the liquid pool (8) through a second pumping pipeline (32); The refining system comprises a refining device (15) connected in parallel to a reflux conduit (30), said refining conduit (33) and reflux conduit (30) each being provided with a control valve (17) on a downstream pipe section adjacent to the parallel connection point, for controlling the flow of liquid drawn off towards the refining device (15) or towards the liquid return tank A (9).

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