A method for in-situ mining zoning and injection seepage control of ionic rare earth ore

Abstract

The invention discloses a method for in-situ mining zoning and injection seepage control of ionic rare earth ore. The method is based on underground water level, bedrock undulations and differences in sand and soil permeability, and adopts measures such as ridge zoning, seepage isolation, deep and shallow injection well networks and pulse injection. The method can solve the problems of unreasonable injection zoning, excessive local injection, underground seepage deviation loss and low leaching efficiency, and can effectively improve the leaching efficiency and the controllability of leaching solution seepage, reduce leaching solution losses, and reduce the incidence of leaching solution overflow, local landslides and leaching solution leakage caused by excessive leaching solution injection and seepage deviation. The method provides technical support for the quality improvement, efficiency enhancement and innovative development of the in-situ leaching mining process of ionic rare earth mines, and is helpful to build a new model of ecological green mining for sustainable development of mines.

Description

Technical Field

[0001] The invention belongs to the technical field of in-situ leaching mining of ionic rare earths, and in particular relates to an in-situ mining zoning and injection seepage control method for ionic rare earth ores. Background Art

[0002] Ionic rare earth ore, also known as weathering crust elution rare earth ore, is a rare earth deposit dominated by medium and heavy rare earth elements. It is widely distributed in southern my country. Rare earth ions are adsorbed in the form of ions on clay minerals such as kaolin, montmorillonite, and illite. At present, ionic rare earth ore is mainly mined using the in-situ leaching process, which is a mining method that injects electrolyte solution into the rare earth ore layer through the injection hole, selectively leaches rare earth ions from the clay mineral to generate soluble compounds, and collects the soluble compounds. This mining process does not require cutting down trees, stripping the surface soil, or destroying the ore body. It has low labor intensity and low production cost. It can make full use of low-grade rare earth resources and is a relatively efficient, environmentally friendly and economical mining method.

[0003] Due to the differences in the diagenetic environment of the rare earth-bearing parent rock, the geological tectonic movement of the mineralization area, and the geological effects of weathering, erosion, transportation, and sedimentation, the geological conditions of different ionic rare earth mines vary greatly. Some have gentle terrain, some have steep mountains, some have deep bedrock, some have exposed bedrock (or shallowly buried), some have thick and rich ore bodies, and some have poor and thin ore bodies. According to the geological conditions and ore body characteristics of different ionic rare earth mines, the mining process should also adopt different mining methods.

[0004] However, most of the current mining processes of ionic rare earth mines lack detailed comprehensive geological surveys, and the mining zoning, injection engineering facilities and injection management are mainly based on the experience of technical personnel. For example, the mining zoning is based on the surface ridgeline, and the inconsistency between the underground bedrock ridgeline and the surface ridgeline causes the loss of leaching liquid in local areas; the injection well network lacks deep well drainage and formation permeability testing, which easily leads to excessive or insufficient local injection; there is a lack of effective methods for injection operation, and it depends entirely on manual repeated well-by-well adjustments; the seepage deviation of the leaching liquid often occurs, so repeated injection is required to increase the leaching rate. Due to the unreasonable layout of the injection well network structure and the injection operation, it is easy to cause significant resource loss and environmental pollution problems, and in severe cases, geological disasters such as mountain collapse, landslide or mudslide may occur. Therefore, it is necessary to improve the existing mining zoning and seepage control technology. Summary of the invention

[0005] In order to solve the resource and environmental problems caused by unreasonable mining zoning and poor injection seepage control during the in-situ solution mining of ionic rare earths, the present invention proposes an in-situ mining zoning and injection seepage control method for ionic rare earth mines. Based on the underground water level, bedrock undulation and sand permeability difference in the mining area, combined with technical measures such as underground complete bedrock ridge zoning, boundary seepage well isolation, deep and shallow injection well matching and staged pulse injection, the injection accuracy, leaching efficiency and controllability of leaching solution seepage are effectively improved, the leaching solution loss is reduced, and the incidence of leaching solution overflow, local landslide and leaching solution leakage caused by excessive leaching solution injection and seepage deviation is reduced.

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

[0007] A method for in-situ mining zoning and injection seepage control of ionic rare earth ore, the steps of which are as follows:

[0008] First, we sorted out the comprehensive geological survey data of the ionic rare earth mining area, mapped the complete bedrock undulations hidden underground, and carried out in-situ mining zoning according to the ridgeline trend of the complete bedrock underground;

[0009] Secondly, after the in-situ mining is divided into zones, a seepage isolation well is set on one side of the injection mining area based on the ridgeline trend of the intact bedrock;

[0010] Then, based on the topographic contour lines of the ground, a deep and shallow injection well network is laid out in the injection production area, and the injection well network includes a number of deep injection wells and a number of shallow injection wells;

[0011] Finally, during the mining process, the injection intensity of the leaching solution in each injection well is periodically adjusted to achieve pulse injection control in the injection area; and the seepage isolation wells that diffuse outside the injection mining area are drained and monitored.

[0012] Furthermore, the complete bedrock undulating surface is obtained by extracting relevant data from comprehensive geological surveys and performing a series of operations such as preprocessing, interpolation, fitting and verification in the software. It can be used to produce two-dimensional bedrock surface contours or three-dimensional bedrock surface forms to facilitate the drawing of complete bedrock ridges and the layout of seepage isolation wells.

[0013] Furthermore, the seepage isolation well is laid out on one side of the injection area, offset from the complete bedrock ridgeline by 0.2-0.5m, and the laying requirements are: the spacing between single-row wells is greater than 2m, the aperture of a single well is greater than 50mm, and the depth of a single well is based on penetrating the sandy soil layer or reaching groundwater; the seepage isolation well contains a plastic pipe coated with sand-proof filler, and the well can be drilled using a simple mechanical drilling rig or a manual Luoyang shovel. Due to the well-developed cracks and good water permeability of the weakly weathered bedrock, the seepage isolation well penetrates the sandy soil layer with poor water permeability, and thus can guide the lateral seepage of the leaching solution to quickly vertically seep to the complete bedrock surface, and migrate and converge along the bedrock surface to the downstream low-lying area; in addition, by monitoring the liquid level in the seepage isolation well, it can be determined whether there is a risk of groundwater overflow in the injection area.

[0014] Furthermore, the deep and shallow injection well network is displayed as a matrix structure along the contour lines of the surface terrain in plane projection, with 2-4 shallow injection wells between two deep injection wells. Among them, the spacing between deep injection wells is greater than 5m, the row spacing is greater than 5m, the single well aperture is greater than 50mm, and the vertical height difference between the bottom of the well and the top of the liquid collection facility is greater than 3m; the deep injection well has a large permeability area and a high water head, which can enhance the diffusion speed of the leaching solution to the surroundings in the saturated injection stage, and can guide the lateral seepage to migrate vertically quickly in the unsaturated injection stage. Among them, the spacing between shallow injection wells is 1-2m, the single well aperture is greater than 50mm, and the well depth is 3-5m; the shallow injection wells have a small permeability area and low water head, and are mainly used to maintain the water content of the ore layer to reach a saturated water content of more than 60%. They have good annular diffusion performance in the saturated injection stage, which helps to increase the water content of local sand and accelerate the leaching and migration rate of ionic rare earths; the internal structures of deep injection wells and shallow wells are the same, and both are arranged with plastic pipes coated with sand-proof fillers. The upper part of the plastic pipe is a full pipe without holes, and the lower part is a porous flower pipe. Multiple sections of plastic pipes are clamped or bonded by connecting rings.

[0015] Furthermore, the pulse injection control method in the mining process includes two stages: saturated injection and unsaturated injection. Saturated injection is an injection operation to maintain the liquid level in the injection wellbore at a certain height (the liquid level gradually decreases with the extension of mining time) (generally arranged on rainless days, requiring uninterrupted manual inspection), and unsaturated injection is an injection operation without liquid accumulation in the injection wellbore.

[0016] During the mining process, the pulse injection control at different mining stages is specifically manifested as follows: (1) In the initial saturated injection stage of mining, the liquid level in each injection hole is maintained at the top of the ore layer (generally 3 m from the ground surface) and no overflow occurs. The saturated injection time is 12-36 hours, and the unsaturated injection time is 12-36 hours. (2) In the mid-term saturated injection stage of mining, the liquid level in each deep well injection hole is maintained in the middle of the ore layer, and the liquid level in each shallow well injection hole is maintained at the top of the ore layer and no overflow occurs. The saturated injection time is 12-36 hours, and the unsaturated injection time is 48-72 hours. (3) In the late saturated injection stage of mining, the liquid level in each deep well injection hole is maintained at the bottom of the ore layer, and the liquid level in each shallow well injection hole is maintained at the top of the ore layer and no overflow occurs. The saturated injection time is 12-36 hours, and the unsaturated injection time is 72 hours.

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

[0018] 1. Taking the complete underground bedrock ridgeline of the ionic rare earth mining area as the basis for mining zoning, it effectively avoids the local seepage and overflow of leaching solution caused by the ridgeline zoning of the surface terrain, and improves the recovery rate of the leaching solution.

[0019] 2. The seepage isolation wells arranged at the boundary of the mining and injection area effectively restrict the lateral seepage and rapid migration of the leaching solution, which helps to determine the risk of groundwater overflow in the injection area.

[0020] 3. The mining and injection area is subdivided into columnar seepage units through a combination of deep and shallow injection wells. The rapid diversion performance of deep wells is used to effectively reduce the local stagnation of leaching liquid and reduce the risk of landslides.

[0021] 4. The use of sand-proof fillers in injection wells reduces the phenomenon of sand mud siltation.

[0022] 5. By introducing a pulse injection mechanism to ensure that no collapse or landslide occurs, local leaching liquid saturation of the ore layer can be achieved, which helps to reduce injection blind areas and improve mining recovery rates; at the same time, it is combined with deep wells to further improve leaching efficiency, reduce tailing phenomena, and shorten the mining cycle.

[0023] 6. The in-situ mining zoning and seepage control method for ionic rare earth ores provided by the present invention is particularly suitable for ionic rare earth mines where the underground intact bedrock surface is higher than the underground water table, effectively solving the resource loss and environmental pollution problems in the mining process of such mines; at the same time, the boundary seepage well isolation, deep and shallow injection well matching and phased pulse injection in the method can be promoted and applied in various types of mines, providing a new injection seepage control technical solution for the development of ionic rare earth ores. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The figure is a schematic cross-sectional diagram of pulse injection control for deep and shallow wells according to a specific implementation of the present invention.

[0025] Figure 2 It is a cross-sectional schematic diagram of a liquid injection well pulse according to a specific embodiment of the present invention.

[0026] Figure 3 It is a plane schematic diagram of a deep and shallow well pattern matrix specifically implemented in the present invention.

[0027] Figure 4 The present invention is a surface topographic contour map of a certain ore block specifically implemented by the present invention.

[0028] Figure 5 The present invention is a specific implementation of the underground bedrock surface contour map of a certain ore block.

[0029] Figure 6 The present invention is a schematic plan view of a mining area and injection engineering of a certain ore block specifically implemented by the present invention. DETAILED DESCRIPTION

[0030] In order to better understand the purpose and technical implementation scheme of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0031] The present embodiment provides a method for in-situ mining zoning and seepage control of ionic rare earth ores, with "underground complete bedrock ridge zoning, boundary seepage well isolation, deep and shallow injection well matching and staged pulse injection" as the main technical solution, to solve the problems of resource loss, environmental pollution and geological disasters that may be caused by existing mining zoning and injection methods, while achieving the purpose of reducing injection blind areas, shortening mining cycles and increasing economic benefits.

[0032] As shown in the attached Figure 1-6 As shown, the specific implementation steps of the present invention are as follows:

[0033] 1. Drawing of complete underground bedrock ridges and mining zoning

[0034] like Figure 4 , Figure 5The figure shows the contour lines of the ground topography and the contour lines of the underground complete bedrock surface of a certain ionic rare earth ore block. The ridges drawn by the upper and lower strata have a certain overlap in direction, but the overall difference is significant. If the mining area is divided according to the ground topography ridges, the flow direction of the leaching solution in the local area will be seriously deviated during the injection process, resulting in the seepage and overflow loss of the leaching solution. Therefore, it is more scientific and reasonable to use the underground complete bedrock ridges for zoning. The specific operation is as follows: (1) Based on the detailed comprehensive geological survey data of the ionic rare earth mining area, the parameters such as topography, resource distribution, stratum occurrence, bedrock fluctuation and underground water level are sorted and extracted; (2) The ground topography contour lines, the boundary between the ore body and the mining area, the underground complete bedrock fluctuation surface and the bedrock ridge line are drawn in engineering design software such as CAD; (3) The mining zoning is based on the underground complete bedrock fluctuation surface and bedrock ridge line, and the injection area is subdivided in combination with the production and processing capacity of the mining enterprise and the boundary and reserves of the ore body.

[0035] like Figure 6 As shown, the entire mining area is divided into four blocks based on the complete bedrock ridge line. When a block is actually mined, the block can be divided into multiple mining and injection areas from top to bottom or multiple blocks can be mined at the same time to meet resource reserves and production plans.

[0036] 2. Construction of boundary seepage isolation wells

[0037] like Figure 6 As shown in the figure, when a single No. 4 ore block just meets the production demand, a seepage isolation well should be laid along the complete bedrock ridgeline of the No. 4 ore block (laid along the ore body boundary when the ore body boundary is smaller) to control the lateral seepage of the leaching solution at the injection boundary. The isolation well is on one side of the injection area, offset by 0.5m from the complete bedrock ridgeline; a simple mechanical drilling rig or a manpower Luoyang shovel is used to drill the well, with a single row of wells spaced 4m apart, a single well aperture of 150mm, and a single well depth based on penetrating the sandy soil layer or reaching groundwater. A plastic pipe coated with sand-proof filler is installed in the well (to prevent hole collapse and blockage). The plastic pipe has a diameter of 100mm, a wall aperture of 5mm, a sand-proof filler of 20mm, and an aperture of 0.5mm. The upper part of the plastic pipe is a non-porous full pipe, and the lower part is a porous flower pipe. Multiple sections of the plastic pipe are connected or bonded by connecting rings. During the injection period, regular inspections are conducted to monitor the liquid level in the seepage isolation well, and a natural underground water level curve is drawn to determine whether there is a risk of leaching solution overflow in the injection area.

[0038] 3. Construction of deep and shallow injection well network

[0039] The injection range is delineated according to the injection boundary of the ore block (seepage isolation well) and resource distribution, and a staggered injection well network of deep and shallow depths is constructed along the contour lines in the mining injection area. The spacing between injection wells depends on the regional ore layer permeability and the shear strength of the sand.

[0040] like Figure 1-2As shown, the spacing between deep injection wells is 5m, there are two shallow injection wells between two deep injection wells, the deep wells are spaced 5m apart, the single well aperture is 125mm, and the vertical height difference between the well bottom and the top of the liquid collection facility is 4m; the shallow wells are spaced 1.6m apart, the spacing is 5m apart, the single well aperture is 125mm, and the well depth is 5m; plastic pipes coated with sand-proof fillers are installed in both deep and shallow wells. The plastic pipe has a diameter of 76mm, a wall aperture of 5mm, a sand-proof filler of 20mm, and an aperture of 0.5mm. The upper part of the plastic pipe is a full pipe without holes, and the lower part is a porous flower pipe. Multiple sections of plastic pipes are clamped or bonded by connecting rings.

[0041] like Figure 3 As shown, the injection well network appears as a matrix structure in plane projection, and each row of deep wells is arranged in a staggered plum blossom pile layout.

[0042] like Figure 6 As shown in Figure 1, the injection well pattern is laid out along the contour lines of the surface terrain. Figure 6 Only a small part of the area is drawn in the figure, and the well patterns in other areas are arranged in a similar way.

[0043] 4. Pulse injection and seepage control

[0044] After the completion and acceptance of the injection and liquid collection project, the injection operation is carried out, such as Figure 1 As shown in the figure, in the early stage of mining, the injection intensity of each well is adjusted manually or by an intelligent control system (which can be calculated by comprehensive exploration data on the permeability coefficient of each formation, the spacing between deep and shallow well networks, and well completion parameters) to ensure that the liquid level of the injection wells on the same surface topographic contour line is maintained at the following Figure 1 At position A shown in the figure (i.e. the top of the ore layer, if the thickness of the topsoil layer is less than 3m, the vertical distance between position A and the ground surface is 3m), saturated liquid injection is achieved for 24 hours (if there is medium to high intensity rainfall, it is switched to unsaturated liquid injection or the injection is stopped); then the injection intensity of each well is adjusted manually or by the intelligent control system to ensure that the liquid level of the injection wells on the same surface topographic contour line is maintained at the bottom of the well (water accumulation at the bottom of the well is less than 0.1m), so as to achieve unsaturated liquid injection for 24 hours. During the mining process, the above-mentioned pulse injection operation is continuously repeated. When the rare earth concentration of the recovered leaching solution no longer increases, the pulse control liquid level of the deep injection well is gradually adjusted down from position A to position B, the pulse control liquid level of the shallow injection well is maintained at position A, and the unsaturated injection time is adjusted to 48 hours; when the rare earth concentration of the recovered leaching solution shows a downward trend, the pulse control liquid level of the deep injection well is gradually adjusted down from position B to position C, the pulse control liquid level of the shallow injection well is maintained at position A, and the unsaturated injection time is adjusted to 72 hours; when the rare earth concentration of the recovered leaching solution drops below the economic concentration limit, the pulse injection is stopped and the ore washing and mine closure operations are started.

[0045] 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 of the technical features. These modifications or replacements should still be included in the scope of the technical solutions of the present invention.

Claims

1. A method for in-situ mining zoning and injection seepage control of ionic rare earth ore, characterized in that: The following steps are involved: First, we sorted out the comprehensive geological survey data of the ionic rare earth mining area, mapped the complete bedrock undulations hidden underground, and carried out in-situ mining zoning according to the ridgeline trend of the complete bedrock underground; Secondly, after the in-situ mining is divided into zones, a seepage isolation well is set on one side of the injection mining area based on the ridgeline trend of the intact underground bedrock; Then, based on the topographic contour lines of the ground, a deep and shallow injection well network is laid out in the injection production area, and the injection well network includes a number of deep injection wells and a number of shallow injection wells; Finally, during the mining process, the injection intensity of the leaching solution in each injection well is periodically adjusted to achieve pulse injection control in the injection area; and the seepage isolation wells that diffuse outside the injection mining area are drained and monitored.

2. The method for in-situ mining zoning and injection seepage control of ionic rare earth ore according to claim 1, characterized in that: After extracting relevant data from the comprehensive geological survey data, at least preprocessing, interpolation, fitting, verification and overlay operations are performed before drawing to obtain the complete bedrock undulating surface hidden underground.

3. The method for in-situ mining zoning and injection seepage control of ionic rare earth ore according to claim 1, characterized in that: The seepage isolation wells are arranged at a position 0.2-0.5m away from the underground complete bedrock ridgeline on one side of the injection and mining area; the spacing between single rows of seepage isolation wells is >2m, the aperture of a single well is >50mm, and the depth of a single well is based on penetrating the sandy soil stratum or reaching groundwater.

4. The method for in-situ mining zoning and injection seepage control of ionic rare earth ore according to claim 1 or 3, characterized in that: The seepage isolation well is used to guide the leaching solution to migrate rapidly downstream through the bedrock surface, while monitoring the groundwater in the injection area for any overflow risk.

5. The method for in-situ mining zoning and injection seepage control of ionic rare earth ore according to claim 1, characterized in that: The deep and shallow injection well network is displayed as a matrix structure along the contour lines of the surface terrain in plane projection; wherein, in the injection well network, the well spacing of the deep injection wells is greater than 5m, the single well diameter of the deep injection wells is greater than 50mm, and the vertical height difference between the bottom of the deep injection well and the top of the liquid collection facility is greater than 3m, which is used for regional enhanced injection and rapid diversion of leaching liquid; wherein, in the injection well network, the well spacing of the shallow injection wells is 1-2m, the single well diameter of the shallow injection wells is greater than 50mm, the depth of the shallow injection wells is 3-5m, and the saturated water content of the ore layer is more than 60%; in the injection well network, the internal structure of all injection wells is a plastic pipe coated with sand-proof filler, and the plastic pipe is composed of a non-porous full pipe at the top and a porous flower pipe at the bottom.

6. The method for in-situ mining zoning and injection seepage control of ionic rare earth ore according to claim 1, characterized in that: The pulse injection control implemented in the production process includes saturated injection and unsaturated injection; wherein, saturated injection is an injection operation to maintain a certain height of liquid level in the injection wellbore, and unsaturated injection is an injection operation without liquid accumulation in the injection wellbore.

7. The method for in-situ mining zoning and injection seepage control of ionic rare earth ore according to claim 1 or 6, characterized in that: The pulse injection control at different mining stages during the mining process is as follows: (1) In the initial stage of mining, when saturated liquid is injected, the liquid level in each injection well is maintained at the top of the ore layer and no overflow occurs; (2) In the middle stage of mining, when saturated liquid injection is carried out, the liquid level in each deep injection well is maintained in the middle of the ore layer, and the liquid level in each shallow injection well is maintained at the top of the ore layer without overflow; (3) At the end of mining, when saturated liquid injection is performed, the liquid level in each deep injection well is maintained at the bottom of the ore layer, and the liquid level in each shallow injection well is maintained at the top of the ore layer without overflow.

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