A step-by-step liquid collection method for in-situ mining of ionic rare earth ores

Abstract

The present invention discloses a tiered liquid collection method for the in-situ mining process of ionic rare earth ores. For ionic rare earth mines with high mountains and steep slopes or large ore volumes, the method utilizes tiered divisions and liquid collection facility layouts based on geological conditions such as the area of ​​the injection mining area, topography, and rock formation occurrence. Multiple layers of leaching diversion holes, leaching collection trenches, and rainwater drainage trenches are arranged from top to bottom to collect leaching liquid and drain natural rainfall. An anti-seepage curtain is constructed along the foot of the mountain to prevent leaching liquid from overflowing and leaking. A leaching collection well with multiple layers of leaching diversion holes is installed in the liquid accumulation area inside the anti-seepage curtain to recover the leaching liquid and control the groundwater level in the accumulation area. This method can effectively control landslides, mudslides, and debris flows that are prone to occur during the injection process in mines with high mountains and steep slopes. It can also achieve tiered mining, effective leaching liquid collection, and reduced leaching agent loss in mines with large ore volumes, contributing to the establishment of a new model of ecological and green mining for sustainable development.

Description

Technical Field

[0001] The invention belongs to the technical field of in-situ leaching mining of ionic rare earth ores, and particularly relates to a step-by-step liquid collection method in the in-situ mining process of ionic rare earth ores. Background Art

[0002] Ionic rare earth ore, also known as weathering crust elution-type rare earth ore, is a type of rare earth deposit primarily composed of medium and heavy rare earth elements. It is widely distributed in South my country. Rare earth ions are adsorbed in ionic form on clay minerals such as kaolin, montmorillonite, and illite. Currently, ionic rare earth ores are primarily mined using an in-situ leaching process. This involves injecting an electrolyte solution into the rare earth ore layer through an injection hole, selectively leaching the rare earth ions from the clay minerals to form soluble compounds, which are then collected. This process does not require deforestation, stripping of the surface soil, or destruction of the ore body. It is labor-intensive, has low production costs, and fully utilizes low-grade rare earth resources, making it a highly efficient, environmentally friendly, and economical mining method.

[0003] Due to differences in the diagenetic environment of the rare earth-bearing parent rock, geological tectonic movements in the mineralization areas, and geological processes such as weathering, erosion, transportation, and sedimentation, the geological conditions of different ionic rare earth mines vary significantly. Some have gentle terrain, others steep, some have deeply buried bedrock, others have exposed (or shallowly buried) bedrock, and some have thick and rich ore bodies, while others have poor and thin ore bodies. Different mining methods should be adopted based on the geological conditions and ore body characteristics of different ionic rare earth mines. However, the mining process of most ionic rare earth mines currently lacks detailed and comprehensive geological exploration, and the design of liquid recovery facilities is relatively simple and crude, with only simple liquid collection pipes / tunnels constructed to recover the leaching solution.

[0004] Based on the differences in geological conditions of ionic rare earth mines, in order to avoid the problems of resource loss, environmental pollution and geological disasters that may be caused by the existing liquid collection method of liquid accumulation pipelines / tunnels; the present invention takes ionic rare earth mines with high mountains and steep slopes or large ore volumes as the main targets, divides the mining and injection areas into steps based on detailed comprehensive geological exploration data of the mining area, and then constructs a leaching liquid cascade collection system consisting of leaching diversion holes, leaching liquid collection ditches, leaching liquid collection wells, rainwater drainage ditches and anti-seepage curtains, replacing the traditional pipeline / tunnel liquid collection method, and proposing a cascade liquid collection method for the in-situ mining process of ionic rare earth mines; providing a new engineering and technical solution for the development of ionic rare earth mines, contributing to the innovative development of in-situ leaching mining technology, and contributing to the construction of ecologically green and sustainable mines. Summary of the Invention

[0005] The present invention is mainly aimed at ionic rare earth mines with high mountains and steep slopes or large ore volumes. It proposes a cascade liquid collection method for the in-situ mining process of ionic rare earth ores to solve the problems of resource loss, environmental pollution and geological disasters that may be caused by existing liquid collection methods. At the same time, it achieves the goals of improving the leaching liquid collection rate, reducing the loss of leaching agents and increasing economic benefits.

[0006] The technical solution provided by the present invention includes the following steps:

[0007] A. Based on a detailed and comprehensive geological survey of the ionic rare earth mining area, data will be collated and analyzed to clearly define the tiered division of the mining area. Leachate diversion holes, leachate collection ditches, and rainwater drainage ditches will be constructed at each level according to the tiered divisions. An anti-seepage curtain will be constructed along the foot of the mountain, and a leachate collection well will be constructed in the liquid accumulation area inside the anti-seepage curtain.

[0008] B. During the in-situ mining process of ionic rare earth ores, a large amount of leaching liquid, after dissolving the rare earth ions in the ore body, seeps into the leaching diversion holes set in each layer of the ore body. A small amount of leaching liquid seeps from top to bottom in the ore body along the intact bedrock surface in the form of undercurrent and gathers at the foot of the mountain;

[0009] C. The leaching solution that flows to the foot of the mountain is blocked by the anti-seepage curtain, forming a groundwater accumulation area inside the anti-seepage curtain; when the groundwater level in the inner accumulation area is higher than the preset value, the leaching solution is extracted from the leaching collection well;

[0010] D. The leaching liquid collected through each leaching liquid collection ditch and leaching liquid collection well is transported to the designated location for rare earth separation and extraction. The leaching liquid after separation and extraction is returned to the mining area for injection, forming a closed-loop circulation mode of "injection-collection-separation-injection".

[0011] Furthermore, in step A, the comprehensive geological survey data required for the tiered mining area should include at least: topography, climate type, resource distribution, mining area boundaries, stratum occurrence, bedrock undulations, distribution of fractured and fractured zones, groundwater levels, groundwater flow direction, and geochemical properties. Fractured and fractured zones within the tiered areas should be repaired or diverted for seepage prevention. Based on the production plan, mining area boundaries, and resource reserve distribution, top-down injection production should be implemented in each tiered area.

[0012] Furthermore, in step A, the leaching diversion holes, leaching collection ditches, rainwater drainage ditches, leaching collection wells, and anti-seepage curtains together constitute a leaching liquid cascade collection system, wherein the leaching diversion holes, leaching collection ditches, and leaching collection wells are used to collect rare earth-rich leaching liquid, the rainwater drainage ditches are used to prevent surface water formed by rainfall from mixing with the leaching liquid, and the anti-seepage curtains are used to block underground subsurface leakage formed by the leaching liquid.

[0013] Furthermore, in step A, each layer of rainwater drainage ditch is constructed above the immersion diversion hole, and each layer of immersion collection ditch is constructed below the immersion diversion hole. Cement, canvas or plastic anti-seepage layers are provided in the rainwater drainage ditch and the immersion collection ditch. The water flow surface of the rainwater drainage ditch or the immersion collection ditch is determined by the rainfall or injection volume in the stepped partition.

[0014] Furthermore, in step A, the leaching diversion holes penetrate the ore layer and extend deep into the slightly weathered bedrock layer. Construction requirements include: an elevation angle > 2°, hole spacing > 0.5m, hole diameter < 200mm, and hole depth < 200m. A porous conduit coated with filter material is installed within the hole, with a non-porous conduit at the orifice. A connecting ring connects the conduits and secures the filter material. The outlet of the leaching diversion hole is located directly above the leaching collection ditch. Design options include: conduit diameter > 50mm, filter layer thickness > 15mm, and filter layer pore size < 0.5mm. The filter material and conduit should be made of corrosion-resistant materials such as plastic, plant fiber, or stainless steel.

[0015] Furthermore, in step A, the immersion collection well can be a single-hole well or a composite well. The single-hole well is mainly used in areas where bedrock fractures and cracks are developed or where composite well construction is difficult. The well has a porous protective wall casing and a filter layer. The bottom of the wellbore is more than 1 meter deep into the intact bedrock without fractures. The wellbore diameter is <300mm. A water well drilling rig is generally used for drilling and forming the well. The composite well is mainly used in areas where bedrock fractures and cracks are not developed. It consists of a liquid collection main well and a liquid collection branch pipe. The liquid collection main well is a square or circular water pool with a protective wall. The liquid collection main well penetrates the sandy soil layer and penetrates into the slightly weathered bedrock layer. The equivalent diameter / diameter of the main well is >3m. Multiple layers of radial liquid collection branches are set on the protective wall of the main well with an interlayer spacing of 5-15m. The internal structure and shape parameters of a single liquid collection branch pipe are the same as the immersion diversion hole.

[0016] Furthermore, in step A, the anti-seepage curtain is generally constructed by preparing a slurry using one or more environmentally friendly anti-seepage materials such as clay, cement, sodium silicate, acrylates, polyurethanes, etc., and is constructed by drilling / trenching and pouring. Its permeability coefficient is <1×10 -5 cm / s, thickness>1.5m, the top of the anti-seepage curtain is higher than the underground water table, the bottom of the anti-seepage curtain is more than 1m deep into the intact bedrock without broken cracks, and the two ends of the anti-seepage curtain are connected to the intact bedrock ridge line that is higher than the natural water table (if there is an area below the natural water table in the intact bedrock ridge line, or there is a broken crack zone passing through, it is necessary to use drilling grouting and other methods to fill the area), so that together with the intact bedrock ridge line, it forms a blocking wall above the natural water table to block the leakage and migration of the leaching solution into the groundwater.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. Divide the mining area into tiers based on detailed comprehensive geological survey data to effectively reduce the phenomenon of excessive leaching liquid confluence or channeling in local areas, and effectively avoid the risk of difficulty in collecting liquid due to bedrock fractures and cracks;

[0019] 2. By replacing traditional liquid-filled pipes / tunnels with immersion diversion holes, the filter material and conduit provide support for the rock and soil, avoiding the risks of pipe / tunnel collapse, hole blockage, and sand outflow, while also reducing the amount of abandoned soil.

[0020] 3. Effective diversion of rainwater and leaching solution is achieved through rainwater drainage ditches and leaching solution collection ditches, which reduces the dilution of leaching solution by rainwater and reduces the subsequent rare earth separation and extraction costs;

[0021] 4. The combination of the leachate collection well and the anti-seepage curtain reduces the risk of the leachate migrating through underground seepage, improves the leachate collection rate, and reduces the loss of leachate;

[0022] 5. The leaching solution cascade collection system provided by the present invention is widely applicable to ionic rare earth mines with high mountains and steep slopes or large ore volumes. It effectively solves the problems of resource loss and environmental pollution in the mining process of such mines and contributes to the innovative development of in-situ leaching mining technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a schematic cross-sectional layout diagram of a cascaded liquid collection system for leaching liquid according to a specific embodiment of the present invention.

[0024] Figure 2 The figure is a schematic diagram of the plan layout of the leaching solution cascade collection system according to the specific embodiment of the present invention.

[0025] Figure 3 The figure is a schematic diagram of the axial cross-sectional structure of the immersion guide hole according to a specific embodiment of the present invention.

[0026] Figure 4 It is a schematic diagram of the radial cross-sectional structure of the immersion guide hole according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0027] To better understand the purpose and technical implementation of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and examples. The examples provided herein will convey the complete and comprehensive concept of the present invention to those skilled in the art, and the present invention will be limited only by the claims. It should be noted that the present invention may have a variety of different forms of implementation, and the specific examples described herein should not be construed as limiting the present invention.

[0028] This embodiment provides a tiered liquid collection method for the in-situ mining process of ionic rare earth ores, with "tiered division of the mining area, diversion of surface rainfall, graded diversion / drainage of leaching liquid, and isolation of leaking leaching liquid" as the main technical solution, to solve the problems of resource loss, environmental pollution, and geological disasters that may be caused by existing liquid collection methods.

[0029] The specific implementation steps of the step-by-step liquid collection method provided in this embodiment are as follows:

[0030] 1. Cascade division of mining areas and engineering design

[0031] like Figure 1-2 As shown in the figure, first, based on the detailed comprehensive geological survey data of the ionic rare earth mining area, the parameter information such as topography, climate type, resource distribution, mining area boundary, stratum occurrence, bedrock undulation, fracture zone distribution, underground water level, groundwater flow direction and rock and soil physical and chemical properties are sorted and extracted; then, the terrain contour lines, natural underground water level curves, complete bedrock ridges, bedrock areas above the natural water level, fracture zone distribution and ore body boundaries are drawn in CAD and other engineering design software; secondly, based on the production and processing capacity and economic and technical indicators of the mining enterprise, combined with the data such as rainfall in the mining area, rainfall infiltration coefficient, injection intensity, hydraulic gradient, stratum occurrence, ore layer permeability coefficient and shear strength, the boundary condition parameters for safe mining are clarified; finally, a safe, controllable, economically reasonable and easy-to-implement mining area tiered division scheme is calculated and planned in CAD and other engineering design software, as shown in the figure. Figure 2 As shown, the first phase ore block is divided into two levels.

[0032] 2. Construction of leaching liquid cascade collection system

[0033] (1) Rainwater drainage ditch

[0034] Conduct survey and wiring according to the verified coordinates of the ionic rare earth mining engineering design plan, such as Figure 2 The stormwater drainage ditch shown is located 3-5 meters above the leachate collection ditch. Manual or simple mechanical methods are then used for surface clearing, trenching, tamping, and laying of a 0.5mm HDPE plastic impermeable membrane. The drainage ditch has an inclination of at least 2°, is 0.4m wide, and 0.4m deep. It typically converges at both ends, with a small grit chamber located at the center. After converging, rainwater is discharged into the rainwater tank via a 160mm diameter plastic pipe. During the installation of the impermeable layer within the ditch, it is embedded in the sandy soil layer facing the incoming water flow and compacted and secured with sand, stones, and rivets. During routine inspections, branches, grass leaves, and sediment in the drainage ditch should be removed, and damaged areas of the impermeable layer should be promptly repaired.

[0035] (2) Immersion diversion hole

[0036] The immersion diversion hole survey line is arranged according to the verified coordinates of the ionic rare earth mining project design plan, and then a 1.0-1.5m drilling platform is leveled and compacted by manual or simple mechanical means. After the preparation of manpower, machine and materials, a simple hydraulic / wind drilling rig is used to drill the immersion diversion holes at a position 0.2-0.5m above the drilling platform, with an inclination angle of >2°, a hole diameter of 100mm, a hole depth of 50m, and a hole spacing of 1.0m. After the drilling is completed, a porous PVC / PE plastic conduit coated with filter material is installed section by section. The porous conduit has a diameter of 50mm and a length of 4.0m. The recycled PVC / PP filter layer has a thickness of 15mm. Each section of the conduit is connected with a plastic connecting ring buckle (such as Figure 3-4 As shown), it is manually pushed into the hole section by section. The hole mouth section (generally less than 4.0m) uses a non-porous plastic conduit. After the diversion pipe is installed, the hole mouth is sealed with foam glue and fixed with rivets.

[0037] (3) Immersion liquid collection groove

[0038] After the diversion holes are constructed, manual or mechanical methods are used on the drilling platform to clear the surface, dig trenches, tamp the trenches, and lay a 0.5mm HDPE plastic anti-seepage membrane within the trenches. The collection trenches have an inclination of at least 2°, are 0.4m wide and 0.4m deep, and typically converge at both ends. A small grit chamber is located at the central point where the leaching liquid flows. After converging, the leaching liquid is discharged into the rainwater tank via a 160mm diameter plastic pipe. During the laying of the HDPE anti-seepage layer within the trench, it is embedded in the sandy soil layer facing the incoming water flow and compacted and fixed with sand, stones, and rivets. During routine inspections, branches, grass leaves, and sediment are removed from the drainage trenches, and damaged areas of the anti-seepage layer are promptly repaired.

[0039] (4) Leachate collection well

[0040] The leachate collection well is primarily used in conjunction with the anti-seepage curtain to collect leachate that has not entered the leachate diversion holes on each layer. Therefore, the leachate collection well is located below the lowest layer of leachate diversion holes. In relatively flat and open areas, a composite leachate collection well is preferred, while in narrow areas, a single-hole leachate collection well is preferred.

[0041] like Figure 2The square composite leaching collection well shown is located on the center line of the mining area, about 10-15m away from the lowest layer of leaching diversion holes, in order to maximize the liquid collection efficiency of each layer of the liquid collection branch pipes in the well. Single-hole wells are constructed in the corners of the mining area and in areas that cannot be covered by the radial liquid collection branch pipes. The main liquid collection well of the composite well is excavated manually or with simple machinery under the support of a square / prototype steel frame. A protective plate is installed on the outer layer of the steel frame. Each layer of the steel frame is 1m high and has an equivalent diameter / diameter of 3m. During the excavation process, sand and soil are lifted and underground seepage is pumped out by a mortar pump. The main well penetrates the sand layer and penetrates 1m deep into the slightly weathered bedrock layer. After the main well is completed, a simple hydraulic / wind drilling rig is used to drill holes for each layer of radial liquid collection branch pipes in the well. After drilling, a porous PVC / PE plastic conduit coated with filter material is installed. The porous conduit has a diameter of 50mm and a length of 4.0m. The recycled PVC / PP filter layer has a thickness of 1.5mm. Each section of the conduit is connected with a plastic connecting ring buckle (such as Figure 3-4 As shown), push the pipe into the hole section by section manually. After the guide pipe is installed, seal the hole with foam glue and fix it with rivets. Figure 2 As shown, two single-hole wells were drilled using a water well drilling rig. The bottom of the wellbore was 2 meters deep into intact bedrock without fractures. The wellbore diameter was 200 mm. A 160 mm φ porous plastic casing was installed inside the wellbore to protect the wall. The plastic casing was wrapped with a 1 mm thick non-woven fabric filter layer. After the leachate collection well was completed, an automatic liquid level control device was installed in the well, and the wellhead was capped and equipped with safety protection facilities.

[0042] (5) Anti-seepage curtain

[0043] The anti-seepage curtain is typically located at the edge of the ore body or in a flat area easily accessible for construction. The curtain's lines are mapped and positioned according to the coordinates verified in the ionic rare earth mining project design. A 1.5-2.0m working platform is then leveled and compacted manually or mechanically. Once personnel, equipment, and materials are prepared, a drill is used to drill grouting holes and grouting is performed with a slurry made from one or more environmentally friendly anti-seepage materials, such as clay, cement, sodium silicate, acrylates, and polyurethanes. After grouting, >10% of the holes are randomly inspected for permeability testing. Any substandard sections are re-grouted until the curtain meets design requirements. Generally, double rows of grouting holes are used, with a spacing of 3m and rows of 2-3m. Grouting is performed in stages and in a sequential manner. Expensive anti-seepage materials such as acrylates and polyurethanes are used only in specialized areas where anti-seepage is more challenging.

[0044] 3. Operation of the leaching liquid cascade collection system

[0045] After the establishment of the leaching solution cascade collection system, the topmost blocks in the mining area are injected first. When the leaching solution flows out from the leaching solution diversion holes of the corresponding layer and the leaching solution collection rate is above 70%, the next layer of blocks are injected, and the injection of the entire mining area is completed from top to bottom. The leaching solution collected by the system is transported to the rare earth separation and extraction workshop, and the leaching solution after separation and extraction is returned to the mining area for injection, forming a closed loop of "injection-collection-separation". During the operation of the entire system, attention should be paid to the balance of injection and collection in each block. During daily inspections, attention should be paid to whether there is local surface runoff in each injection area and the operation of the system, and problems such as blockage, sedimentation, and damage should be solved in a timely manner. The leaching solution collection well will automatically start the liquid level control device only when the natural groundwater level is higher than the preset value to reduce the risk of leakage and migration of the leaching solution.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention. Ordinary technicians in this field may modify the technical solutions of the embodiments, or make equivalent replacements of some / all technical features. These modifications or replacements should still be included in the scope of the technical solutions of the present invention.

Claims

1. A step-by-step liquid collection method for in-situ mining of ionic rare earth ores, characterized in that The following steps are involved: A. Based on a detailed and comprehensive geological survey of the ionic rare earth mining area, data will be collated and analyzed to clearly define the tiered division of the mining area. Leachate diversion holes, leachate collection ditches, and rainwater drainage ditches will be constructed at each level according to the tiered divisions. An anti-seepage curtain will be constructed along the foot of the mountain, and a leachate collection well will be constructed in the liquid accumulation area inside the anti-seepage curtain. The comprehensive geological exploration data required for the tiered division of the mining area should at least include: topography, climate type, resource distribution, stratum occurrence, bedrock undulation, distribution of fractured and fractured zones, underground water level, groundwater flow direction, and rock and soil physical and chemical properties; the leaching diversion holes, leaching collection ditches, rainwater drainage ditches, leaching collection wells, and anti-seepage curtains together constitute a tiered leaching liquid collection system, wherein the leaching diversion holes, leaching collection ditches, and leaching collection wells are used to collect rare earth-rich leaching liquid, the rainwater drainage ditches are used to prevent surface water formed by rainfall from mixing with the leaching liquid, and the anti-seepage curtains are used to block underground subsurface leakage formed by the leaching liquid; The immersion collection well is a single-hole well or a composite well; when the immersion collection well is a single-hole well, the single-hole well is a pumping well with a porous protective wall casing and a filter layer, and the wellbore diameter is less than 300 mm; when the immersion collection well is a composite well, the composite well is composed of a liquid collection main well and a liquid collection branch pipe, and the liquid collection main well is a square or circular water tank with a protective wall, and the main well equivalent diameter / diameter is greater than 3 m. Multiple layers of radial liquid collection branches are arranged on the protective wall of the main well, with a layer spacing of 5-15 m. The internal structure and hole formation parameters of a single liquid collection branch pipe are the same as those of the immersion diversion hole; B. During the in-situ mining process of ionic rare earth ores, a large amount of leaching liquid, after dissolving the rare earth ions in the ore body, seeps into the leaching diversion holes set in each layer of the ore body. A small amount of leaching liquid seeps from top to bottom in the ore body along the intact bedrock surface in the form of undercurrent and gathers at the foot of the mountain; C. The leaching solution that flows to the foot of the mountain is blocked by the anti-seepage curtain, forming an underground liquid accumulation area inside the anti-seepage curtain; when the underground water level in the inner liquid accumulation area is higher than the preset value, the leaching solution is extracted from the leaching liquid collection well; D. Separate and extract the leachate collected from each leachate collection ditch and leachate collection well, and return the separated and extracted leachate to the mining area for injection, forming a closed-loop circulation mode according to "injection-collection-separation-injection".

2. The stepwise liquid collection method for in-situ mining of ionic rare earth ores according to claim 1, characterized in that: In step A, each layer of rainwater drainage ditch is constructed above the immersion diversion hole, and each layer of immersion collection ditch is constructed below the immersion diversion hole. An anti-seepage layer is provided in both the rainwater drainage ditch and the immersion collection ditch.

3. The stepwise liquid collection method for in-situ mining of ionic rare earth ores according to claim 1, characterized in that: In step A, the immersion diversion hole penetrates the ore layer and penetrates into the slightly weathered bedrock layer. The construction requirements of the immersion diversion hole are: elevation angle>2°, hole spacing>0.5m, hole diameter<200mm, and hole depth<200m; wherein, the hole mouth section is a non-porous conduit, and a porous conduit coated with a filter material is provided in the hole. The filter material and the conduit are made of plastic, plant fiber or stainless steel.

4. The stepwise liquid collection method for in-situ mining of ionic rare earth ores according to claim 1, characterized in that: In step A, the top of the anti-seepage curtain is higher than the natural underground water level, the bottom of the anti-seepage curtain penetrates more than 1 meter into the intact bedrock without broken cracks, and both ends of the anti-seepage curtain are connected to the intact bedrock ridge line above the water level.

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