A deep thermal-electric metal combined mining system and method based on in-situ electro dialysis in a well

Abstract

The application provides a deep thermal-electric metal combined mining system and method based on in-situ electro dialysis in a well, which comprises a ground control and collection station and a downhole mining system in communication with the ground control and collection station, the downhole mining system is a double-well U-shaped closed loop structure, comprising an injection well and a recovery well, the injection well and the recovery well both pass through a target wide and thick inclined ore vein, the two wells are in communication through a fissure network in a deep high temperature area of the ore vein to form a closed loop fluid circulation loop; along a fluid circulation direction, the downhole mining system is sequentially provided with a pulse leaching section, a reservoir heat exchange section, an electro dialysis separation section and a thermoelectric power generation section. The application adopts a downhole full-process integrated architecture of a double-well U-shaped closed loop, along the fluid circulation direction, the pulse leaching section is arranged in the injection well, the reservoir heat exchange section is arranged in the deep part of the ore vein, the electro dialysis separation section and the thermoelectric power generation section are arranged in the recovery well from bottom to top, a downhole closed loop process is formed, and the overall optimal process efficiency of the full process is realized.

Description

Technical Field

[0001] This invention belongs to the field of geothermal development and mineral mining technology, specifically a deep thermal and electrical metal mining system and method based on in-situ electrodialysis in wells. Background Technology

[0002] With the acceleration of the global energy transition and the rapid growth in demand for strategic key metals, the development potential of shallow mineral resources and conventional geothermal resources has become increasingly depleted. Deep strata below 1500m contain both abundant high-temperature geothermal resources and strategic metal mineral resources, and have become a core frontier area for global resource and energy development.

[0003] Among them, the deep thermal power and metal mining technology can simultaneously realize the clean development of geothermal energy and the efficient mining of metal minerals, taking into account both the strategic needs of energy security and resource security. It is currently an international research hotspot in the field of deep resource development. Breakthroughs in this technology have important engineering significance and industrial value for the large-scale, low-cost, and green development of deep unconventional resources.

[0004] Currently, the mainstream deep thermal power metal mining technology in the industry takes the ore body enhanced geothermal system as its core architecture. Its technical route is to construct a geothermal fluid circulation channel through drilling, using the ore-bearing geothermal reservoir as the geothermal reservoir. The circulating fluid is lifted to the surface after mineral leaching and geothermal heat absorption in the strata. On the surface, independent power generation system, metal extraction system and leaching agent preparation system are set up. The surface system first recovers the heat energy of the geothermal fluid to generate electricity, and then completes the extraction and refining of metals through hydrometallurgical process. The treated fluid is then reinjected underground to complete the circulation.

[0005] In practical engineering applications of existing technologies, the above-mentioned technical approach has the following technical drawbacks:

[0006] First, the system is fragmented and has low integration. In existing technologies, the leaching system, power generation system, and metal recycling system are independent of each other and distributed in different areas of the ground, resulting in a large footprint, complex pipelines, and significant heat loss during transmission, leading to low overall energy utilization efficiency.

[0007] Secondly, the surface processing method limits technical efficiency. Traditional methods transport geothermal fluids to the surface for thermoelectric conversion and metal extraction, failing to fully utilize the high-temperature, high-pressure natural reaction environment underground. As the geothermal fluids rise, their temperature continuously decreases, leading to a reduction in usable thermal energy grade. Simultaneously, the chemical reaction rate and separation efficiency under normal surface pressure are far lower than under high-temperature, high-pressure conditions.

[0008] Third, the power generation equipment has a high failure rate. Ground-based organic Rankine cycle power generation systems contain a large number of moving parts such as turbines, compressors, and heat exchangers. When processing geothermal fluids containing minerals, they are prone to scaling, corrosion, and mechanical wear, resulting in high maintenance costs and poor system reliability.

[0009] Fourth, metal extraction processes are complex and highly polluting. Traditional hydrometallurgy requires the use of large amounts of acid and alkali leaching agents, generating substantial amounts of waste liquid and posing high environmental risks. Subsequent processes such as precipitation, filtration, and electrolytic refining involve numerous pieces of equipment and consume enormous amounts of energy.

[0010] Fifth, single-well coaxial structures suffer from significant fluid interference. In traditional coaxial casing single-well structures, the downward-flowing cold fluid and the upward-flowing hot fluid flow within the same wellbore. Even with an insulation layer, a significant thermal short-circuit effect still exists, reducing the system's thermodynamic efficiency. At the same time, the single-well structure limits the effective volume of reservoir heat exchange and the contact area with the ore body. Summary of the Invention

[0011] The purpose of this invention is to provide a highly integrated, rationally designed deep thermal and electrical metal mining system and method based on in-situ electrodialysis, which can fully utilize the advantages of the underground natural environment.

[0012] The deep thermal-electric metal mining system based on in-situ electrodialysis provided by this invention includes a surface control and collection station and an underground mining system connected to the surface control and collection station. The underground mining system is a dual-well U-shaped closed-loop structure, including an injection well and a recovery well. Both the injection well and the recovery well traverse the target wide and thick inclined vein. The two wells are connected in the deep high-temperature zone of the vein through a fracture network to form a closed-loop fluid circulation loop. Along the fluid circulation direction, the underground mining system is sequentially equipped with a pulse leaching section, a reservoir heat exchange section, an electrodialysis separation section, and a thermal-electric power generation section. The pulse leaching section is located in the well section where the injection well traverses a wide and thick inclined vein, performing cold in-situ crushing and preliminary metal leaching of the vein ore; the reservoir heat exchange section is located in the deep high-temperature zone of the wide and thick inclined vein, connecting the bottom of the injection well and the bottom of the recovery well, performing geothermal heating and deep metal leaching of the circulating fluid; the electrodialysis separation section is located in the lower section of the recovery well, performing in-situ separation and concentration of metal ions in the fluid under a high-temperature downhole environment; the thermoelectric power generation section is located in the upper section of the recovery well, utilizing the waste heat of the circulating fluid and the temperature difference of the formation to generate electricity through thermoelectric conversion.

[0013] In one embodiment of the above system, the pulse leaching section includes a high-pressure pulse generator, a pulse electrode array, an electrode protective sleeve, and a fracture monitoring sensor; the high-pressure pulse generator is installed in the upper region of the wellbore; the pulse electrode array includes multiple sets of electrode assemblies distributed along the axial and circumferential directions of the wellbore, each set of electrode assemblies including at least one transmitting electrode and at least one receiving electrode, the electrode assemblies being spaced apart along the extension direction of the wellbore to cover the entire thickness range of the vein; the electrode protective sleeve is fitted onto the outside of the injection well wall corresponding to the position of the pulse electrode array; the fracture monitoring sensor is installed at the top and bottom positions of the electrode protective sleeve; the pulse leaching section also includes a plasma generation unit to assist in the dissolution of metal ions, the plasma generation unit including a microwave generator, a waveguide, and a plasma nozzle.

[0014] In one embodiment of the above system, the reservoir heat exchange section includes a fracture network, a bottom hole fluid distributor, and a downhole sensor array; the fracture network connects the bottom of the injection well and the bottom of the recovery well; the bottom hole fluid distributor is located at the bottom of the injection well and adopts a porous screen structure to evenly distribute the downward fluid into the fracture network; the downhole sensor array is distributed at preset positions in the reservoir heat exchange section to monitor the reservoir temperature, pressure, flow rate, and metal ion concentration in real time, and the ambient temperature range of the reservoir heat exchange section is 150℃ to 280℃.

[0015] In one embodiment of the above system, the electrodialysis separation section includes a high-temperature resistant electrodialysis membrane stack, a concentration chamber, a desalination chamber, a membrane stack electrode system, a concentrate riser, and a desalination reinjection pipe. The high-temperature resistant electrodialysis membrane stack adopts a concentric cylindrical structure, consisting of a central support tube, multiple layers of concentric cylindrical ion exchange membranes, and an outer protective sleeve, arranged sequentially from the inside out. The ion exchange membranes are multiple alternating layers of cation exchange membranes and anion exchange membranes. The concentration chamber is an annular space formed between two adjacent layers of the same type of cation exchange membrane. The desalination chamber is an annular space formed between adjacent cation exchange and anion exchange membranes. The membrane stack electrode system includes an anode and a cathode disposed at both ends of the high-temperature resistant electrodialysis membrane stack. The inlet end of the concentrate riser is connected to the concentration chamber, and the outlet end extends to the ground. The inlet end of the desalination reinjection pipe is connected to the desalination chamber, and the outlet end extends to the corresponding area of ​​the thermoelectric power generation section. The electrodialysis separation section is equipped with a multi-stage series membrane stack system, with each stage of the membrane stack configured with ion exchange membranes selective for different metal ions.

[0016] In one embodiment of the above system, the thermoelectric power generation section is a ring-shaped thermoelectric pile module array, including a hot-end heat conduction component, a thermoelectric conversion layer, a cold-end heat exchange component, and a DC transmission cable. The ring-shaped thermoelectric pile module array is composed of multiple ring-shaped thermoelectric modules arranged in series along the well shaft axis. Each ring-shaped thermoelectric module is provided with a hot-end heat conduction component, a thermoelectric conversion layer, and a cold-end heat exchange component sequentially from the outside to the inside. The hot-end heat conduction component adopts a high thermal conductivity metal fin structure or a gravity heat pipe structure. The thermoelectric conversion layer is made of high-temperature thermoelectric material and is a thermocouple array formed by alternating P-type and N-type thermoelectric arms. The cold-end heat exchange component is in direct contact with the upward-flowing desalination fluid. The DC transmission cable is connected in series with the output end of each thermoelectric module and extends upward to the ground.

[0017] In one embodiment of the above system, the injection well extends obliquely from the ground through the shallow to middle region of a thick, sloping ore vein, and the recovery well extends obliquely from the ground through the middle to deep region of the thick, sloping ore vein, with the two wells spaced 300m to 800m apart on the ground.

[0018] In one embodiment of the above system, the inner walls of the corresponding well sections of the injection well and the recovery well are provided with a heat insulation layer.

[0019] In one embodiment of the above system, the ground control and collection station includes a ground pump station, a DC grid-connected cabinet, a metal concentrate storage tank, an electrolytic refining tank, a fluid replenishment system, a central control system, and an emergency pressure relief system. The ground pump station is connected to the wellhead of the injection well. The input end of the DC grid-connected cabinet is connected to the DC transmission cable of the thermal power generation section. The DC grid-connected cabinet has a DC branch output end that directly supplies power to the electrolytic refining tank. The inlet end of the metal concentrate storage tank is connected to the concentrate riser pipe of the electrodialysis separation section. The inlet end of the electrolytic refining tank is connected to the outlet end of the metal concentrate storage tank. The fluid replenishment system connects the wellhead outlet of the recovery well and the wellhead inlet of the injection well. The central control system is connected to the distributed sensor network of each section of the system through a downhole communication cable. The emergency pressure relief system is connected to the wellbore of the injection well and the recovery well.

[0020] A joint procurement method based on the aforementioned joint procurement system includes the following steps:

[0021] S1. The working fluid is injected underground from the surface pumping station through the injection well;

[0022] S2. In the pulse leaching section where the working fluid passes through the wide and thick inclined vein area in the injection well, the ore is cold-cold in-situ crushed by high-voltage electric pulses across the entire thickness of the vein, accelerating the dissociation and migration of metal ions into the fluid, thus completing the initial leaching.

[0023] S3. The fluid carrying mineral ions continues to descend into the reservoir heat exchange section, where it is heated in the high-temperature environment deep within the vein. The high temperature enhances the deep dissolution of metal ions, and the fluid enters the recovery well side through the fracture network.

[0024] S4. The high-temperature rich ore fluid goes up along the recovery well and enters the electrodialysis separation section. Under high temperature and low viscosity conditions, the target metal ions are selectively separated and enriched by electrodialysis. The enriched metal concentrate is then transported to the surface.

[0025] S5. After ion separation, the desalinated liquid continues to rise along the recovery well into the thermoelectric power generation section, where the waste heat is converted into thermoelectric power to generate electricity using the temperature difference between the desalinated liquid and the formation, and the electricity is transmitted to the surface.

[0026] S6. The fluid after waste heat power generation is returned to the ground from the wellhead of the recovery well. After treatment, it is added to the working fluid circulation to complete the U-shaped closed loop circulation.

[0027] S7. The metal concentrate on the ground is purified by electrolysis to obtain high-purity metal products.

[0028] In step S2, cold in-situ crushing is completed in a low-temperature environment before the fluid is heated by geothermal energy; in step S3, the fluid is heated to 150°C to 280°C in the reservoir heat exchange section; in step S5, the direct current generated by thermoelectric conversion is directly supplied to the electrolytic purification process in step S7.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. An integrated downhole process architecture with a dual-well U-shaped closed-loop circuit is adopted. Along the fluid circulation direction, a pulse leaching section is set in the injection well, a reservoir heat exchange section is set in the deep part of the vein, and an electrodialysis separation section and a thermoelectric power generation section are set from bottom to top in the recovery well, forming a downhole closed-loop process of "cold crushing leaching → geothermal heating enhancement → high-temperature separation and concentration → waste heat power generation recovery". The dual-well separation channel completely eliminates the thermal short-circuit effect of traditional single wells and improves the thermodynamic efficiency of the system. The core process is integrated downhole to avoid heat loss during surface transportation of geothermal fluids and reduce the footprint and pipeline complexity of surface equipment. Following thermodynamic logic, the environmental advantages of different depths downhole are maximized to achieve the global optimal efficiency of the entire process.

[0031] 2. Construct a synergistic integrated structure of in-situ high-temperature electrodialysis separation and cascade thermoelectric conversion in the recovery well. A concentric cylindrical high-temperature resistant electrodialysis membrane stack is installed in the high-temperature zone, with a ring-shaped thermoelectric stack module array on top. The separated desalinated liquid serves as the heat exchange medium at the cold end of the thermoelectric process, and the generated DC electricity is directly supplied to the surface metal electrolytic refining process. The high underground temperature reduces fluid viscosity, improving metal separation efficiency and eliminating the need for large amounts of acid and alkali leaching agents used in traditional hydrometallurgy, thus reducing wastewater discharge and environmental risks. Thermoelectric conversion with no moving parts replaces traditional organic Rankine cycle power generation, solving equipment scaling and corrosion problems, reducing maintenance costs, and improving operational reliability. It achieves cascaded closed-loop utilization of geothermal energy, with generated electricity directly supplied to metal electrolysis, improving the overall system energy utilization efficiency and reducing external energy input.

[0032] 3. For wide, thick, and inclined large veins, a full-coverage pulsed electrode array is installed across the entire thickness of the vein in the injection well to achieve cold-state in-situ fracturing and preliminary leaching. Simultaneously, a fracture network connecting the two wells is constructed deep within the vein, forming an integrated leaching-heat exchange reservoir structure. Cold-state high-pressure pulse fracturing cracks the ore, increasing the contact area between minerals and fluids, accelerating the dissolution of metal ions, and avoiding pulse energy loss at high temperatures. The combination of the full-thickness electrode array and the deep fracture network expands the contact area of ​​the ore body and the effective volume of reservoir heat exchange, adapting to the occurrence characteristics of wide, thick, and inclined large veins. Relying on fracture monitoring sensors, dynamic control of pulse parameters and reservoir transformation is achieved, ensuring long-term stability of leaching and heat exchange. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall system structure according to an embodiment of the present invention;

[0034] Figure 2 for Figure 1 Enlarged schematic diagram of the structure of the medium-pulse leaching section;

[0035] Figure 3 for Figure 1 Schematic diagram of the heat exchange section of the middle reservoir;

[0036] Figure 4 for Figure 1 Enlarged schematic diagram of the electrodialysis separation section;

[0037] Figure 5 for Figure 4 A schematic diagram of the cross-sectional shape of the concentric cylindrical structure of the electrodialysis membrane stack;

[0038] Figure 6 for Figure 1 Enlarged structural diagram of the thermal power generation section;

[0039] Figure 7 for Figure 6 A schematic diagram of the cross-section of a ring-shaped thermopile module;

[0040] Figure 8 This is a schematic diagram of the system's workflow in this embodiment;

[0041] Explanation of markings in the diagram:

[0042] 1-Surface control and collection station; 11-DC grid-connected cabinet; 12-Metal concentrate storage tank; 13-Electrolytic refining tank; 14-Fluid replenishment system; 15-Central control system; 16-Emergency pressure relief system; 2-Pulse leaching section; 21-High-pressure pulse generator; 22-Pulse electrode array; 23-Electrode protective casing; 24-Fractured monitoring sensor; 3-Reservoir heat exchange section; 31-Fractured network; 32-Bottomhole fluid distributor; 33-Downhole sensor array; 4-Electrodialysis Separation section; 41-High-temperature resistant electrodialysis membrane stack; 411-Cation exchange membrane; 412-Anion exchange membrane; 42-Concentration chamber; 43-Desalination chamber; 44-Membrane stack electrode system; 45-Concentrate riser pipe; 46-Desalination reinjection pipe; 5-Thermoelectric power generation section; 51-Hot end heat conduction component; 52-Thermoelectric conversion layer; 53-Cold end heat exchange component; 54-DC transmission cable; 6-Wide and thick inclined vein; 7-Underlying high-temperature rock strata; 8-Injection well; 9-Recovery well; 10-Insulation layer. Detailed Implementation

[0043] The relevant technical solutions will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. The described embodiments are only a part of the embodiments, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, the deep thermoelectric metal mining system based on in-situ electrodialysis disclosed in this embodiment includes a surface control and collection station 1 and an integrated underground mining system.

[0045] The underground integrated mining system adopts a dual-well U-shaped closed-loop structure, including an injection well 8 and a recovery well 9. Both the injection well and the recovery well traverse a wide and thick inclined vein 6. The two wells are connected in the deep high-temperature zone of the wide and thick inclined vein through a fracture network 31 to form a complete closed-loop circuit.

[0046] The broad, thick, dipping vein 6 is a large, dipping mineralized rock layer containing the target metallic mineral, with a dip angle of 20° to 50°, a thickness of 200m to 1000m, and an extension length exceeding 1500m along the dip direction. The vein extends from shallow to deep, with the shallow top boundary buried at a depth of 1500m to 2500m and the deep bottom boundary at a depth of 4500m to 5400m. The temperature at the depth of the vein can reach 150℃ to 280℃. The mineralization types of the broad, thick, dipping vein 6 include porphyry copper deposits, hydrothermal polymetallic deposits, skarn-type deposits, or sedimentary metamorphic deposits. Beneath the broad, thick, dipping vein 6 is an underlying high-temperature rock layer 7, providing a stable geothermal heat source for the system.

[0047] Injection well 8 traverses the shallow to middle section of the thick, inclined ore vein 6 from the surface, with a depth ranging from the surface to 4000m to 5000m. Recovery well 9 traverses the middle to deep section of the thick, inclined ore vein from the surface, with a depth ranging from the surface to 4500m to 5400m. The two wells are spaced 300m to 800m apart on the surface and are hydraulically connected in the high-temperature zone of the deep ore vein through a fracture network 31. This arrangement of two wells traversing the thick, inclined ore vein allows the injection well to penetrate the shallow to middle section of the vein for cold crushing, while the recovery well penetrates the high-temperature zone of the deep ore vein for separation and power generation. The separation channels of the two wells completely eliminate the thermal short-circuit effect, improving the system's thermodynamic efficiency.

[0048] The inner walls of the corresponding well sections of injection well 8 and recovery well 9 are equipped with heat insulation layers 10 to reduce ineffective heat exchange between the fluid inside the well and the external rock mass.

[0049] Along the fluid circulation direction, the downhole integrated mining system is sequentially set up with pulse leaching section 2, reservoir heat exchange section 3, electrodialysis separation section 4, and thermoelectric power generation section 5. The four functional sections are interconnected to form a complete downhole full-process processing link.

[0050] The pulse leaching section 2 is located in the area where the injection well 8 crosses the wide and thick inclined vein 6, with a depth range of 1800m to 3800m. This section runs through the entire thickness direction of the vein along the extension direction of the wellbore and is used to complete the cold crushing and preliminary leaching of the ore before the fluid reaches the high temperature zone.

[0051] like Figure 2 As shown, the pulse leaching section 2 includes a high-pressure pulse generator 21, a pulse electrode array 22, an electrode protective sleeve 23, and a crack monitoring sensor 24.

[0052] The high-voltage pulse generator 21 is installed in the upper part of this section of the wellbore and is used to output high-voltage electrical pulses.

[0053] The pulse electrode array 22 includes multiple sets of electrode assemblies distributed along the shaft axis and circumference. Each set of electrode assemblies includes at least one transmitting electrode and at least one receiving electrode. The electrode assemblies are arranged at intervals along the shaft extension direction to cover the entire vein thickness range. 10 to 50 sets of electrode assemblies can be set along the injection shaft 8 axis, with the spacing between adjacent electrode assemblies being 30m to 80m, to ensure sufficient crushing and leaching of ore throughout the entire vein thickness range.

[0054] The electrode protection sleeve 23 is made of corrosion-resistant and high-temperature resistant insulating material. It is sleeved on the outside of the injection well wall of the injection well 8 at the position corresponding to the pulse electrode array 22. It is used to protect the electrode assembly and guide the pulse energy to be released into the vein.

[0055] The fracture monitoring sensor 24 is installed at the top and bottom of the electrode protective sleeve 23 to monitor the expansion of vein fractures after pulse application.

[0056] The pulse leaching section 2 is also equipped with a plasma generation unit, which includes a microwave generator, a waveguide, and a plasma nozzle, used to generate plasma at the fluid-ore interface to assist in the dissolution of metal ions.

[0057] The reservoir heat exchange section 3 is located in the deep high-temperature zone of the thick and inclined vein 6, with a depth range of 3500m to 5400m. It corresponds to the area at the bottom of the vein and the underlying high-temperature rock layer 7, and is used to geothermally heat the fluid and enhance deep leaching.

[0058] like Figure 3 As shown, the reservoir heat exchange section 3 includes a fracture network 31, a bottom hole fluid distributor 32, and a downhole sensor array 33.

[0059] The fracture network 31 is constructed in the high-temperature region of the deep vein using hydraulic fracturing technology, connecting the bottom of injection well 8 and recovery well 9, providing sufficient heat exchange and leaching reaction contact area for fluids and high-temperature rock mass.

[0060] The bottom fluid distributor 32 is located at the bottom of the injection well 8 and adopts a porous screen tube structure to evenly distribute the downward fluid into the fracture network 31. The inlet end is connected to the downward flow channel of the injection well 8, and the outlet end corresponds to the inlet of the fracture network 31.

[0061] The downhole sensor array 33 is distributed at multiple preset locations in the reservoir heat exchange section 3 to monitor the reservoir temperature, pressure, flow rate and metal ion concentration in real time. The ambient temperature range of the reservoir heat exchange section is 150℃ to 280℃.

[0062] The electrodialysis separation section 4 is located below the recovery well 9, with a depth range of 3000m to 4500m. It is set directly above the reservoir heat exchange section 3 and is used to efficiently separate and concentrate metal ions in a high-temperature and low-viscosity environment.

[0063] like Figure 4 and Figure 5 As shown, the electrodialysis separation section 4 includes a high-temperature resistant electrodialysis membrane stack 41, a concentration chamber 42, a desalination chamber 43, a membrane stack electrode system 44, a concentrate riser pipe 45, and a desalination reinjection pipe 46.

[0064] The high-temperature resistant electrodialysis membrane stack 41 adopts a concentric cylindrical structure, consisting of a central support tube, multiple layers of concentric cylindrical ion exchange membranes, and an outer protective sleeve from the inside out. The ion exchange membranes are multiple alternating layers of cation exchange membrane 411 and anion exchange membrane 412.

[0065] The concentration chamber 42 is an annular space formed between two adjacent layers of the same type of cation exchange membrane 411, which is used to enrich metal cations.

[0066] The desalination chamber 43 is an annular space formed between adjacent cation exchange membranes 411 and anion exchange membranes 412. It is used to collect the desalinated liquid after the removal of metal ions and is also the flow channel for the main body.

[0067] The membrane stack electrode system 44 includes an anode and a cathode disposed at both ends of the high-temperature resistant electrodialysis membrane stack 41, for providing the DC electric field required for electrodialysis.

[0068] The inlet end of the concentrate riser 45 is connected to the concentration chamber 42, and the outlet end extends to the ground, which is used to transport the concentrate rich in metal ions to the ground.

[0069] The inlet end of the desalination liquid reinjection pipe 46 is connected to the desalination chamber 43, and the outlet end extends upward to the corresponding area of ​​the thermoelectric power generation section 5, which is used to continue to transport the desalination liquid upward.

[0070] The electrodialysis separation section 4 is equipped with a multi-stage series membrane stack system. Each stage of the membrane stack is equipped with an ion exchange membrane that is selective for different metal ions, so as to realize the hierarchical separation of multiple metals.

[0071] The thermoelectric power generation section 5 is located above the recovery well 9, with a depth ranging from 500m to 2500m. It is set above the electrodialysis separation section 4 and is used to generate electricity by converting the waste heat of the upward fluid into thermoelectric power.

[0072] like Figure 6 and Figure 7 As shown, the thermoelectric power generation section 5 is a ring-shaped thermoelectric stack module array, including a hot-end heat conduction component 51, a thermoelectric conversion layer 52, a cold-end heat exchange component 53, and a DC transmission cable 54.

[0073] The annular thermoelectric stack module array consists of multiple annular thermoelectric modules arranged in series along the well shaft axis. Each annular thermoelectric module is provided with a hot end heat conduction component 51, a thermoelectric conversion layer 52 and a cold end heat exchange component 53 from the outside to the inside.

[0074] The hot-end heat-conducting component 51 includes metal fins with high thermal conductivity. The outer ends of the metal fins are embedded in the wellbore rock of the recovery well 9, and the inner ends are in close contact with the hot end face of the thermoelectric conversion layer 52. In another embodiment, the hot-end heat-conducting component 51 may also adopt a gravity heat pipe structure, with the heat pipe filled with an alkali metal working fluid. The evaporation section of the heat pipe is embedded in the wellbore rock, and the condensation section of the heat pipe is in contact with the hot end of the thermoelectric conversion layer 52.

[0075] The thermoelectric conversion layer 52 is made of high-temperature thermoelectric material and is a thermocouple array formed by alternating P-type and N-type thermoelectric arms. It can be configured with segmented thermoelectric materials according to the temperature conditions at different depths, so that the thermoelectric modules in each depth range can work in the optimal efficiency range.

[0076] The cold end heat exchange component 53 is in direct contact with the upward desalination liquid fluid, which is used to remove the cold end heat by the fluid and maintain the temperature difference conditions required for thermoelectric conversion.

[0077] The DC transmission cable 54 is connected in series with the output end of each thermoelectric module and extends upward to the ground to transmit the generated electrical energy to the ground control and collection station 1.

[0078] Ground control and collection station 1 is located on the ground and includes a ground pump station, a DC grid-connected cabinet 11, a metal concentrate storage tank 12, an electrolytic refining tank 13, a fluid replenishment system 14, a central control system 15, and an emergency pressure relief system 16.

[0079] The surface pump station is connected to the wellhead of injection well 8, driving the working fluid to circulate in a closed loop.

[0080] The input terminal of the DC grid-connected cabinet 11 is connected to the DC transmission cable 54 to receive DC power generated by the underground thermal power generation section 5. The DC grid-connected cabinet can convert DC power into AC power for grid connection. It also has a DC branch output terminal that can directly supply power to the electrolytic refining tank 13, so that the DC power generated by the underground thermal power generation can be directly used for metal electrolysis, realizing closed-loop energy utilization.

[0081] The inlet end of the metal concentrate storage tank 12 is connected to the outlet end of the concentrate riser pipe 45, and is used to store the high-concentration metal ion solution lifted from the downhole electrodialysis separation section 4.

[0082] The inlet end of the electrolytic refining tank 13 is connected to the outlet end of the metal concentrate storage tank 12, which is used to perform final electrolytic purification of the metal concentrate to obtain high-purity metal products.

[0083] The fluid replenishment system 14 is connected to the wellhead outlet of the recovery well 9 and the wellhead inlet of the injection well 8, and is used to replenish the working fluid lost during the circulation process.

[0084] The central control system 15 is connected to a distributed sensor network installed in each section of the system via downhole communication cables. The distributed sensor network includes temperature sensors, pressure sensors, flow sensors, conductivity sensors, and ion-selective electrodes. The central control system is used to monitor the operating status of the entire unit and adjust its parameters.

[0085] The emergency pressure relief system 16 is connected to the wellbore of injection well 8 and recovery well 9, and is used to quickly release pressure when the downhole pressure is abnormal, so as to ensure the safe operation of the system.

[0086] This system is designed to achieve the coordinated exploitation of deep geothermal energy and metallic mineral resources. Its core operating principle relies on a dual-well U-shaped closed-loop integrated downhole process architecture. Along the fluid circulation direction, it constructs a closed-loop process path encompassing cold-state crushing and leaching, geothermal heating enhancement, high-temperature separation and concentration, and waste heat power generation recovery. This maximizes the utilization of the environmental advantages at different depths of the deep strata, enabling the efficient coordinated exploitation of geothermal energy and metallic resources. The specific working principle is as follows:

[0087] First, the working fluid is injected underground through injection well 8 via a ground pump station. During the downward flow of the working fluid, it first enters the pulse leaching section 2. In the cold environment where the fluid has not yet been heated by geothermal heat, the high-voltage electric pulse generated by the high-voltage pulse generator 21 acts on the ore vein through the pulse electrode array 22, generating electro-hydraulic effect, thermal shock effect and electromigration effect in the ore vein, causing the ore to crack along the grain boundary. Metal ions are dissociated from the ore lattice and migrate into the fluid, completing the cold in-situ crushing and preliminary leaching of the ore, while avoiding pulse energy loss in the high-temperature environment.

[0088] After the initial leaching is completed, the fluid carrying mineral ions continues to descend and enters the fracture network 31 of the reservoir heat exchange section 3 evenly through the bottom fluid distributor 32. The fluid is fully heated in the high-temperature environment of 150°C to 280°C in the deep vein. The high-temperature environment greatly enhances the leaching reaction rate, allowing the residual metal minerals in the ore to be further dissolved. At the same time, the fluid fully completes heat exchange with the high-temperature rock mass to obtain geothermal energy from the formation. Subsequently, the fluid enters the recovery well 9 through the fracture network 31.

[0089] High-temperature fluid carrying a high concentration of metal ions ascends along recovery well 9 and first enters electrodialysis separation section 4. Under high-temperature, low-viscosity conditions, the DC electric field applied by membrane stack electrode system 44 drives metal cations from the desalination chamber through cation exchange membrane 411 into concentration chamber 42 for enrichment. The high-temperature environment significantly reduces fluid viscosity, increases ion migration rate, and greatly improves metal ion separation efficiency. The enriched high-concentration metal solution is directly transported to the metal concentrate storage tank 12 on the ground through concentrate riser pipe 45, while the desalination solution after metal ion removal continues to be transported upwards through desalination reinjection pipe 46.

[0090] After metal ion separation, the desalinated fluid continues to flow upwards along recovery well 9 into the thermoelectric power generation section 5. The desalinated fluid flows through the cold-end heat exchange component 53, providing cold-end heat dissipation for the thermoelectric stack module; simultaneously, the hot-end heat conduction component 51 continuously absorbs formation heat from the wellbore rock mass, creating a stable temperature difference between the hot and cold ends of the thermoelectric conversion layer 52. Based on the Seebeck effect, the thermoelectric material in the thermoelectric conversion layer 52 converts thermal energy into direct current (DC), and the generated electricity is transmitted to the DC grid-connected cabinet 11 on the surface via DC transmission cable 54, realizing the cascade utilization of geothermal energy and waste heat recovery. The insulation layer 10 reduces heat exchange between the descending cold fluid and the wellbore rock mass, ensuring that the fluid maintains a low temperature before reaching the reservoir heat exchange section, thereby maintaining the cold-end temperature conditions required for the thermoelectric power generation section.

[0091] After waste heat power generation, the fluid returns to the surface from the wellhead of recovery well 9. After treatment, it is replenished to the working fluid circulation system through fluid replenishment system 14, completing the entire U-shaped closed-loop cycle. The high-concentration metal solution stored on the surface enters the electrolytic refining tank 13 for final electrolytic purification to obtain high-purity metal products. At the same time, the DC electricity generated by the downhole thermoelectric power generation can be directly supplied to the electrolytic refining tank 13, realizing closed-loop energy utilization, reducing external energy input, and improving the energy utilization efficiency of the entire system.

[0092] like Figure 8 As shown, the present invention also provides a method for deep thermoelectric metal mining based on the above system, comprising the following steps:

[0093] S1. The working fluid is injected underground through injection wells via a surface pumping station;

[0094] S2. The working fluid is subjected to periodic high-voltage electric pulses from a high-voltage pulse generator and a pulse electrode array in the pulse leaching section of the injection well through the wide and thick inclined vein area. This cold in-situ crushing of the ore within the full thickness range of the vein accelerates the dissociation of metal ions from the ore lattice and their migration into the fluid, thus completing the initial leaching.

[0095] S3. The fluid carrying mineral ions continues to descend into the reservoir heat exchange section, where it is heated to 150-250°C in the deep high-temperature environment of the thick and inclined vein. The high temperature enhances the deep dissolution of metal ions, which then enter the recovery well side through the fracture network.

[0096] S4. The high-temperature rich ore fluid flows upward along the recovery well and enters the electrodialysis separation section. Under high temperature and low viscosity conditions, the target metal ions are efficiently and selectively separated and enriched in the concentration chamber through the action of the high-temperature resistant electrodialysis membrane stack and membrane stack electrode system. The concentrate is then transported to the surface metal concentrate storage tank through the concentrate riser pipe.

[0097] S5. After ion separation, the desalinated liquid continues to flow up the recovery well into the thermoelectric power generation section. It flows through the cold end heat exchange component to provide cold end heat dissipation for the thermoelectric stack module. The hot end heat conduction component absorbs heat from the well wall rock mass. The thermoelectric conversion layer uses the temperature difference to convert waste heat into thermoelectric power generation. The electrical energy is transmitted to the ground DC grid-connected cabinet through the DC transmission cable.

[0098] S6. The fluid returns to the surface from the wellhead of the recovery well. After being processed, it is replenished to the working fluid circulation through the fluid replenishment system to complete the U-shaped closed-loop circulation.

[0099] S7. The high-concentration metal solution in the ground metal concentrate storage tank enters the electrolytic refining tank for final electrolytic purification to obtain high-purity metal products.

[0100] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A deep thermal-electric metal mining system based on in-situ electrodialysis, comprising a surface control and collection station and an underground mining system connected to the surface control and collection station, characterized in that: The underground mining system is a dual-well U-shaped closed-loop structure, including an injection well and a recovery well. Both the injection well and the recovery well pass through the target wide and thick inclined vein. The two wells are connected by a fracture network in the high-temperature zone deep in the vein to form a closed-loop fluid circulation loop. Along the fluid circulation direction, the downhole mining system is sequentially equipped with a pulse leaching section, a reservoir heat exchange section, an electrodialysis separation section, and a thermoelectric power generation section; The pulse leaching section is located in the well section where the injection well traverses a wide and thick inclined vein, performing cold in-situ crushing and preliminary metal leaching of the vein ore; the reservoir heat exchange section is located in the deep high-temperature zone of the wide and thick inclined vein, connecting the bottom of the injection well and the bottom of the recovery well, performing geothermal heating and deep metal leaching of the circulating fluid; the electrodialysis separation section is located in the lower section of the recovery well, performing in-situ separation and concentration of metal ions in the fluid under a high-temperature downhole environment; the thermoelectric power generation section is located in the upper section of the recovery well, utilizing the waste heat of the circulating fluid and the temperature difference of the formation to generate electricity through thermoelectric conversion.

2. The deep thermal-electric metal mining system based on downhole in-situ electrodialysis as described in claim 1, characterized in that: The pulse leaching section includes a high-voltage pulse generator, a pulse electrode array, an electrode protective sleeve, and a crack monitoring sensor; The high-voltage pulse generator is installed in the upper region of the wellbore; the pulse electrode array includes multiple sets of electrode assemblies distributed along the axial and circumferential directions of the wellbore, each set of electrode assemblies including at least one transmitting electrode and at least one receiving electrode, the electrode assemblies being spaced apart along the extension direction of the wellbore to cover the entire thickness range of the vein; the electrode protective sleeve is fitted onto the outside of the injection well wall corresponding to the position of the pulse electrode array; the fracture monitoring sensor is installed at the top and bottom positions of the electrode protective sleeve; The pulse leaching section is also equipped with a plasma generation unit to assist in the dissolution of metal ions. The plasma generation unit includes a microwave generator, a waveguide, and a plasma nozzle.

3. The deep thermal-electric metal mining system based on downhole in-situ electrodialysis as described in claim 1, characterized in that: The reservoir heat exchange section includes a fracture network, a bottom-hole fluid distributor, and a downhole sensor array; The fracture network connects the bottom of the injection well and the bottom of the recovery well; the bottom-hole fluid distributor is located at the bottom of the injection well and adopts a porous screen tube structure to evenly distribute the downward fluid into the fracture network; the downhole sensor array is distributed at preset positions in the reservoir heat exchange section to monitor the reservoir temperature, pressure, flow rate and metal ion concentration in real time, and the ambient temperature range of the reservoir heat exchange section is 150℃ to 280℃.

4. The deep thermal-electric metal mining system based on downhole in-situ electrodialysis as described in claim 1, characterized in that: The electrodialysis separation section includes a high-temperature resistant electrodialysis membrane stack, a concentration chamber, a desalination chamber, a membrane stack electrode system, a concentrate riser pipe, and a desalination reinjection pipe; The high-temperature resistant electrodialysis membrane stack adopts a concentric cylindrical structure, consisting of a central support tube, multiple layers of concentric cylindrical ion exchange membranes, and an outer protective sleeve from the inside out. The ion exchange membranes are multiple alternating layers of cation exchange membranes and anion exchange membranes. The concentration chamber is an annular space formed between two adjacent layers of the same type of cation exchange membrane. The desalination chamber is an annular space formed between adjacent cation exchange and anion exchange membranes. The membrane stack electrode system includes an anode and a cathode located at both ends of the high-temperature resistant electrodialysis membrane stack. The inlet end of the concentrate riser is connected to the concentration chamber, and the outlet end extends to the ground. The inlet end of the desalination reinjection pipe is connected to the desalination chamber, and the outlet end extends to the corresponding area of ​​the thermoelectric power generation section. The electrodialysis separation section is equipped with a multi-stage series membrane stack system, with each stage of the membrane stack being equipped with an ion exchange membrane that is selective for different metal ions.

5. The deep thermal-electric metal mining system based on downhole in-situ electrodialysis as described in claim 1, characterized in that: The thermoelectric power generation section is a ring-shaped thermoelectric pile module array, including a hot-end heat conduction component, a thermoelectric conversion layer, a cold-end heat exchange component, and a DC transmission cable; The annular thermoelectric stack module array consists of multiple annular thermoelectric modules arranged in series along the wellbore axis. Each annular thermoelectric module is provided with a hot-end heat conduction component, a thermoelectric conversion layer, and a cold-end heat exchange component sequentially from the outside to the inside. The hot-end heat conduction component adopts a metal fin structure or a gravity heat pipe structure with a high thermal conductivity. The thermoelectric conversion layer is made of high-temperature thermoelectric material and is a thermocouple array formed by alternating P-type and N-type thermoelectric arms. The cold-end heat exchange component is in direct contact with the upward-flowing desalination liquid. The DC transmission cable is connected in series with the output end of each thermoelectric module and extends upward to the ground.

6. The deep thermal-electric metal mining system based on downhole in-situ electrodialysis as described in claim 1, characterized in that: The injection well extends obliquely from the ground through the shallow to middle part of the thick, sloping ore vein, while the recovery well extends obliquely from the ground through the middle to deep part of the thick, sloping ore vein. The two wells are arranged at a distance of 300m to 800m from the ground.

7. The deep thermal-electric metal mining system based on downhole in-situ electrodialysis as described in claim 6, characterized in that: The inner walls of the corresponding well sections of the injection well and the recovery well are all equipped with heat insulation layers.

8. The deep thermal-electric metal mining system based on downhole in-situ electrodialysis as described in claim 1, characterized in that: The ground control and collection station includes a ground pumping station, a DC grid-connected cabinet, a metal concentrate storage tank, an electrolytic refining tank, a fluid replenishment system, a central control system, and an emergency pressure relief system; The surface pump station is connected to the wellhead of the injection well. The input end of the DC grid-connected cabinet is connected to the DC transmission cable of the thermal power generation section. The DC grid-connected cabinet has a DC branch output end that directly supplies power to the electrolytic refining tank. The inlet end of the metal concentrate storage tank is connected to the concentrate riser pipe of the electrodialysis separation section. The inlet end of the electrolytic refining tank is connected to the outlet end of the metal concentrate storage tank. The fluid replenishment system connects the wellhead outlet of the recovery well to the wellhead inlet of the injection well. The central control system is connected to the distributed sensor network of each section of the system through a downhole communication cable. The emergency pressure relief system is connected to the wellbore of the injection well and the recovery well.

9. A method for combined mining based on the deep thermoelectric metal mining system based on downhole in-situ electrodialysis as described in any one of claims 1-8, comprising the following steps: S1. The working fluid is injected underground from the surface pumping station through the injection well; S2. In the pulse leaching section where the working fluid passes through the wide and thick inclined vein area in the injection well, the ore is cold-cold in-situ crushed by high-voltage electric pulses across the entire thickness of the vein, accelerating the dissociation and migration of metal ions into the fluid, thus completing the initial leaching. S3. The fluid carrying mineral ions continues to descend into the reservoir heat exchange section, where it is heated in the high-temperature environment deep within the vein. The high temperature enhances the deep dissolution of metal ions, and the fluid enters the recovery well side through the fracture network. S4. The high-temperature rich ore fluid goes up along the recovery well and enters the electrodialysis separation section. Under high temperature and low viscosity conditions, the target metal ions are selectively separated and enriched by electrodialysis. The enriched metal concentrate is then transported to the surface. S5. After ion separation, the desalinated liquid continues to rise along the recovery well into the thermoelectric power generation section, where the waste heat is converted into thermoelectric power to generate electricity using the temperature difference between the desalinated liquid and the formation, and the electricity is transmitted to the surface. S6. The fluid after waste heat power generation is returned to the ground from the wellhead of the recovery well. After treatment, it is added to the working fluid circulation to complete the U-shaped closed loop circulation. S7. The metal concentrate on the ground is purified by electrolysis to obtain high-purity metal products.

10. The joint procurement method as described in claim 9, characterized in that: In step S2, cold in-situ crushing is completed in a low-temperature environment before the fluid is heated by geothermal energy; in step S3, the fluid is heated to 150°C to 280°C in the reservoir heat exchange section; in step S5, the direct current generated by thermoelectric conversion is directly supplied to the electrolytic purification process in step S7.

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