A method for continuous leaching of ion-type rare earth ores

Abstract

This invention discloses a continuous leaching method for ion-adsorption rare earth ores, comprising: feeding ion-adsorption rare earth ores and leaching agent solutions into a multi-stage leaching reactor for co-current leaching; obtaining rare earth leachate and leaching tailings after solid-liquid separation; feeding the leaching tailings and clean water into a multi-stage rinsing reactor for co-current rinsing; obtaining coarse-grained tailings, medium-grained tailings, fine-grained tailings, and leachate after classification and solid-liquid separation; enriching the rare earth leachate and / or leachate and recycling it for preparing the leaching agent solution; returning the rare earth leachate to the multi-stage leaching reactor; and returning the leachate to the multi-stage rinsing reactor. Through continuous multi-stage co-current leaching of the leaching agent solution, return of the rare earth leachate for leaching, and continuous multi-stage co-current rinsing of clean water with return of the leachate for rinsing, the rare earth leaching rate and rare earth concentration in the leachate are effectively improved, the consumption of leaching agent is significantly reduced, and the leaching cycle is significantly shortened, achieving full-process water balance and comprehensive utilization of tailings.

Description

Technical Field

[0001] This invention relates to the field of rare earth extraction and enrichment technology, and in particular to a continuous leaching method for ion-type rare earth ores. Background Technology

[0002] Because ion-adsorption rare earth minerals are extremely rare worldwide and have very low rare earth grades (only 0.03%–0.1% REO), there are no similar mineral mining and beneficiation theories and technologies available abroad to draw upon, making it impossible to enrich rare earths using conventional beneficiation methods. Based on the characteristic that rare earths in ion-adsorption rare earth minerals are mainly adsorbed onto clay minerals such as kaolinite in hydrated ionic or hydroxyl hydrated ionic forms, Chinese scientists have conducted long-term research and practice, proposing a unique method for ion exchange leaching of rare earths using electrolyte solutions such as sodium chloride, ammonium sulfate, and magnesium sulfate. They have subsequently developed three generations of leaching processes: pond leaching, heap leaching, and in-situ leaching, enabling the large-scale development and utilization of ultra-low-grade rare earth minerals.

[0003] The mining of ion-adsorption rare earth minerals using heap leaching or in-situ leaching techniques relies on the natural infiltration, diffusion, and mass transfer of the leaching solution within the ore body or heap. However, the following problems exist: 1) Due to the generally poor permeability of ion-adsorption rare earth ore bodies or heaps, the natural infiltration rate of the leaching solution is slow, resulting in low mass transfer efficiency between the leaching agent and clay minerals. The leaching cycle for a single mine or heap typically lasts 3 to 6 months, and sometimes even more than a year. 2) During the natural infiltration of the leaching solution within the ion-adsorption rare earth ore body or heap, a dominant flow is easily formed. Some infiltration channels within the ion-adsorption rare earth ore body or heap cannot be effectively wetted by the leaching solution, making it difficult for clay minerals to effectively contact and transfer mass with the leaching solution, leading to a low rare earth leaching rate. 3) During the leaching process of ion-adsorption rare earth ore bodies or heaps, the distribution of rare earth grades at different ore depths can cause rare earth reverse adsorption during the downward infiltration of the rare earth-bearing leaching solution, resulting in high consumption of leaching agent and high production costs. In addition, when ion-adsorption rare earth ore bodies or heaps are mined by in-situ leaching or heap leaching, even if the ore body or heap is leached, the volume-to-mass ratio of the leaching water to the rare earth ore is usually less than 0.3:1. The resulting leachate is used to replenish the water lost due to the saturation of the ion-adsorption rare earth ore body and leakage in the early stage of leaching in order to achieve water balance in the mining process. However, due to the low mass transfer efficiency of the natural seepage process of the leaching water and the tendency to form a dominant flow, there are still problems such as high consumption of leaching agent and high production cost.

[0004] Therefore, improving the mass transfer efficiency and rare earth leaching rate in the leaching process of ion-adsorption rare earth ores, shortening the leaching cycle, and reducing leaching agent consumption are of great significance for the rapid and efficient mining technology of ion-adsorption rare earth ores. To this end, some patents propose a method for percolation leaching of ion-adsorption rare earth ores using a continuous horizontal vacuum belt filter, where dry ore addition, compaction, percolation leaching, and solid-liquid separation are all completed on a single belt filter. This method achieves mechanized continuous operation of the entire leaching process, but it is essentially similar to the seepage process of heap leaching or in-situ leaching, and also suffers from the following problems: 1) low mass transfer efficiency and rare earth leaching rate; 2) failure to consider washing the leaching tailings, leading to waste of rare earth resources and leaching agents, and high leaching agent consumption. Other patents propose using ammonium sulfate for agitated leaching of ion-adsorption rare earth ores, and performing solid-liquid separation on the agitated leaching slurry in a thickener unit. The overflow leaching liquid is used for subsequent impurity removal and precipitation, while the underflow is sent to the tailings pond. However, this method has the following problems: 1) The slurry obtained from stirring leaching is directly separated into solid and liquid components using a thickener unit. The tailings obtained from the separation are not washed, resulting in a large amount of rare earth-containing leaching solution remaining in the tailings, causing a waste of rare earth resources and leaching agents; 2) When using ammonium sulfate stirring leaching, the tailings obtained from the solid-liquid separation of the thickener unit contain a large amount of ammonium sulfate, which will bring serious environmental and safety risks if directly flowing into the tailings pond. In addition, the above-mentioned continuous horizontal vacuum belt filter percolation leaching or stirring leaching methods also have the following problems: 1) Neither method considers the classification treatment of the leaching tailings, so the obtained leaching tailings cannot be classified and comprehensively utilized. A large number of tailings ponds must be built for storage, resulting in high construction and maintenance costs and risks such as soil erosion; 2) If stirring and washing of the leaching tailings is considered, to achieve efficient washing, the volume-to-mass ratio of replenishing clean water to leaching tailings must be higher than 1.5:1, but it is impossible to achieve water balance throughout the mining process, which will inevitably generate a large amount of wastewater (>2000m³). 3 / t-REO) greatly increases environmental protection costs. Summary of the Invention

[0005] The purpose of this invention is to provide a continuous leaching method for ion-adsorption rare earth ores, which addresses the problems of low mass transfer efficiency, long leaching cycle, low rare earth leaching rate and rare earth concentration in the leachate, and high leaching agent consumption in the heap leaching and in-situ leaching processes of ion-adsorption rare earth ores. This method significantly improves mass transfer efficiency, shortens the leaching cycle, increases the rare earth leaching rate and rare earth concentration in the leachate, reduces leaching agent consumption and production costs, and achieves the tiered comprehensive utilization of different particle size components of ion-adsorption rare earth ores, as well as water recycling and water balance throughout the entire mining process.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a method for continuous leaching of ion-adsorption rare earth ores, comprising the following steps:

[0007] Ionic rare earth ore and leaching agent solution are continuously fed into a multi-stage leaching reactor for co-current leaching. After solid-liquid separation, rare earth leachate and leaching tailings are obtained.

[0008] The leaching tailings and water are continuously fed into a multi-stage leaching reactor for co-current leaching. After continuous classification and solid-liquid separation, coarse-grained tailings, medium-grained tailings, fine-grained tailings and leachate are obtained respectively.

[0009] After enrichment treatment of the rare earth leachate and / or the leaching solution, it is recycled for the preparation of the leaching agent solution.

[0010] In the continuous parallel leaching process, the rare earth leachate is returned to the multi-stage leaching reactor; in the continuous parallel rinsing process, the leaching solution is returned to the multi-stage rinsing reactor.

[0011] Furthermore, the mixing methods in the multi-stage leaching reactor and the multi-stage washing reactor include at least one of the following: stirring mixing, pneumatic mixing, spiral mixing, and pipeline mixing.

[0012] Furthermore, the number of stages in the multi-stage leaching reactor is 2 to 10, the volumetric mass flow ratio of the leaching agent solution to the ion-adsorption rare earth ore is 0.4:1 to 1.5:1, and the single-stage residence time is 5 min to 30 min;

[0013] The multi-stage leaching reactor has 2 to 10 stages, the volumetric mass flow ratio of the clean water to the leaching tailings is 0.3:1 to 1.3:1, and the single-stage residence time is 5 min to 30 min.

[0014] The number of stages in the multi-stage leaching reactor is preferably 2 to 5;

[0015] The number of stages in the multi-stage rinsing reactor is preferably 2 to 5.

[0016] Furthermore, the volumetric mass flow ratio of the rare earth leachate returned to the multi-stage leaching reactor to the ion-adsorption rare earth ore is 1:1 to 4:1.

[0017] The volumetric mass flow ratio of the leachate returned to the multi-stage leaching reactor to the leaching tailings is 1:1 to 4:1.

[0018] Furthermore, during the continuous co-current leaching process, the rare earth leachate is refluxed into the first-stage leaching reactor and the second-stage leaching reactor;

[0019] During the continuous co-current rinsing process, the leaching liquid is returned to the first-stage rinsing reactor and the second-stage rinsing reactor;

[0020] During the continuous co-current leaching process, the rare earth leachate may also be refluxed into the third-stage leaching reactor, or into both the third-stage and fourth-stage leaching reactors;

[0021] During the continuous co-current rinsing process, the leaching liquid may also be returned to the third-stage rinsing reactor, or to both the third-stage and fourth-stage rinsing reactors.

[0022] Furthermore, the leaching agent solution includes at least one of the following: magnesium sulfate, magnesium chloride, calcium chloride, sodium sulfate, sodium chloride, potassium chloride, potassium sulfate, and ferrous sulfate;

[0023] The clean water includes at least one of the following: surface water, groundwater, semi-permeable membrane enriched water, and tap water.

[0024] Furthermore, the hydrogen ion concentration of the leaching agent solution is 0.00001 mol / L to 0.005 mol / L, and the cation concentration other than hydrogen ions is 0.05 mol / L to 0.4 mol / L.

[0025] Furthermore, apart from hydrogen ions, the molar percentages of various cations in the leaching agent solution are as follows: magnesium ions 40%–100%, calcium ions 0%–55%, and sodium ions, potassium ions, and / or ferrous ions 0%–50%.

[0026] Furthermore, the grading method includes at least one of the following: hydrocyclone, spiral classifier, grading centrifuge, and grading vibrating screen;

[0027] The solid-liquid separation method includes at least one of the following: a thickener, a vacuum bag filter, a centrifugal filter, and a horizontal screw centrifuge.

[0028] Furthermore, the coarse-grained tailings have a particle size range of +40 mesh, the medium-grained tailings have a particle size range of -40 mesh to +200 mesh, and the fine-grained tailings have a particle size range of -200 mesh.

[0029] Furthermore, the enrichment treatment method includes at least one of the following: semi-permeable membrane enrichment, adsorption enrichment, extraction enrichment, and precipitation enrichment.

[0030] The semi-permeable membrane includes: nanofiltration membrane and / or reverse osmosis membrane.

[0031] Further, when the sum of the volumetric flow rates of the rare earth leachate and the eluent is greater than the volumetric flow rate of the leaching agent solution, the enrichment treatment method includes:

[0032] The rare earth leachate was treated with a chemical enrichment method to obtain an enriched residue, which was then recycled to prepare the leaching agent solution.

[0033] The leachate is treated using a pre-enrichment method to obtain a concentrated leachate, which is then recycled for the preparation of the leaching agent solution.

[0034] Furthermore, the chemical enrichment method includes: extraction and / or precipitation;

[0035] The pre-enrichment method includes: semi-permeable membrane enrichment and / or adsorption enrichment;

[0036] The semi-permeable membrane includes: nanofiltration membrane and / or reverse osmosis membrane.

[0037] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0038] (1) The leaching agent is continuously leached in multiple stages in parallel, and a portion of the rare earth leaching solution is recycled for leaching of ion-adsorption rare earth ores. The mass transfer efficiency is high, and the leaching agent can fully contact and react with the ion-adsorption rare earth ores in a short time, which greatly shortens the leaching cycle. At the same time, the volume flow rate of the leaching agent solution can be greatly reduced, and the rare earth concentration of the leaching solution can be increased. The leaching tailings are further washed with clean water in multiple stages in parallel, and a portion of the leaching solution is recycled for washing the leaching tailings. The consumption of leaching agent is greatly reduced, and the residue of rare earth in the leaching tailings can be effectively reduced. The rare earth leaching rate is effectively improved, and the amount of clean water used for washing can be greatly reduced, which significantly reduces the production cost.

[0039] (2) After continuous multi-stage co-current leaching of tailings, continuous classification methods such as hydrocyclones are used to efficiently leach and recover rare earth while efficiently separating and recovering fine-grained tailings (mainly clay minerals such as kaolinite and halloysite), medium-grained tailings (mainly feldspar and other minerals), and coarse-grained tailings (mainly quartz and other minerals), so as to achieve the graded comprehensive utilization of different particle size components of ion-adsorption rare earth minerals.

[0040] (3) When the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is less than or equal to the volumetric flow rate of the leaching agent solution, the rare earth leachate and / or leaching solution are enriched and then recycled for the preparation of the leaching agent solution, thereby achieving water recycling and water balance throughout the entire process of ion-adsorption rare earth ore mining. When the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is greater than the volumetric flow rate of the leaching agent solution, the rare earth leachate is enriched using a chemical enrichment method, and the resulting enriched residue is recycled for the preparation of the leaching agent solution. The leaching solution is enriched using a semi-permeable membrane, and the resulting concentrated leaching solution is recycled for the preparation of the leaching agent solution. The resulting semi-permeable membrane enriched water is directly discharged in compliance with standards, thereby achieving water recycling and water balance throughout the entire process of ion-adsorption rare earth ore mining. Therefore, wastewater generation can be avoided at the source, environmental hazards can be eliminated, and production costs can be reduced.

[0041] (4) By adopting continuous multi-stage co-current leaching with leaching agent-continuous solid-liquid separation and continuous multi-stage co-current rinsing with clean water-continuous grading-continuous solid-liquid separation, the entire process of mining ion-adsorption rare earth minerals is mechanized and automated, and continuous production is realized, which greatly reduces labor intensity.

[0042] (5) The use of continuous multi-stage co-current leaching of leaching agent and continuous multi-stage co-current rinsing of clean water can effectively reduce the residue of leaching agent in tailings and avoid the environmental risks caused by a large amount of leaching agent residue in tailings.

[0043] (6) Using magnesium / calcium salt leaching agent for continuous multi-stage parallel leaching and clear water for continuous multi-stage parallel rinsing, the content of magnesium, calcium and other nutrients in tailings can be targeted to regulate according to the actual needs of tailings ecological restoration or comprehensive utilization, improve soil compaction, meet soil nutrient and ratio requirements, and promote plant chlorophyll synthesis.

[0044] (7) The continuous multi-stage co-current leaching of leaching agent and continuous multi-stage co-current rinsing of clear water is adopted, which can be used to treat all minerals containing ionic phase rare earths and has a wide range of applications. Attached Figure Description

[0045] Figure 1a This is a schematic diagram of the material flow direction of the continuous leaching method for ion-type rare earth ores provided in this embodiment of the invention;

[0046] Figure 1b This is a schematic diagram of the material flow direction of the continuous leaching method for ion-type rare earth ores provided in this embodiment of the invention;

[0047] Figure 2a This is a schematic diagram of the process flow of the continuous leaching method for ion-type rare earth ores provided in an embodiment of the present invention;

[0048] Figure 2b This is a schematic diagram of the process flow of the continuous leaching method for ion-type rare earth ores provided in the embodiments of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0050] This invention provides a method for continuous leaching of ion-adsorption rare earth ores, comprising the following steps:

[0051] In step S100, ionic rare earth ore and leaching agent solution are continuously fed into a multi-stage leaching reactor for co-current leaching. After solid-liquid separation, rare earth leachate and leaching tailings are obtained.

[0052] In step S200, the leaching tailings and fresh water are continuously fed into a multi-stage leaching reactor for co-current leaching. After continuous classification and solid-liquid separation, coarse-grained tailings, medium-grained tailings, fine-grained tailings and leachate are obtained respectively.

[0053] In step S300, the rare earth leachate and / or leaching solution are enriched and then recycled for the preparation of the leaching agent solution.

[0054] In the continuous co-current leaching process, the rare earth leachate is returned to the multi-stage leaching reactor; in the continuous co-current rinsing process, the leaching solution is returned to the multi-stage rinsing reactor.

[0055] The above technical solution employs continuous multi-stage co-current leaching with leaching agent, supplemented by rare earth leachate reflux for ion-adsorption rare earth ore leaching. This results in high mass transfer efficiency, allowing the leaching agent to fully contact and react with the ion-adsorption rare earth ore in a short time, significantly shortening the leaching cycle. Simultaneously, it can significantly reduce the volumetric flow rate of the leaching agent solution and increase the rare earth concentration in the leachate. The leaching tailings are further washed using continuous multi-stage co-current rinsing with clean water, supplemented by rinsing with leaching solution reflux. This significantly reduces leaching agent consumption and effectively lowers the residual rare earth in the leaching tailings, effectively increasing the rare earth leaching rate. Furthermore, it significantly reduces the amount of clean water used for rinsing, resulting in a substantial reduction in production costs. Furthermore, after continuous multi-stage co-current leaching of the tailings, continuous classification methods such as hydrocyclones are employed to efficiently leach and recover rare earth elements while simultaneously separating and recovering fine-grained tailings (mainly clay minerals such as kaolinite and halloysite), medium-grained tailings (mainly feldspar), and coarse-grained tailings (mainly quartz), achieving comprehensive utilization of different particle size components in ion-adsorption rare earth ores. When the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is less than or equal to the volumetric flow rate of the leaching agent solution, the rare earth leachate and / or leaching solution is enriched and then recycled entirely for preparing the leaching agent solution. This achieves water recycling and water balance throughout the entire ion-adsorption rare earth mining process, preventing wastewater generation at the source, eliminating environmental hazards, and reducing production costs.

[0056] Furthermore, the mixing methods in the multi-stage leaching reactor and the multi-stage washing reactor include at least one of the following: stirring mixing, pneumatic mixing, spiral mixing, and pipeline mixing.

[0057] Furthermore, the number of stages in the multi-stage leaching reactor is 2 to 10, the volumetric mass flow ratio of the leaching agent solution to the ion-adsorption rare earth ore is 0.4:1 to 1.5:1, and the single-stage residence time is 5 min to 30 min;

[0058] The number of stages in the multi-stage leaching reactor is 2 to 10, the volumetric mass flow ratio of clean water to leaching tailings is 0.3:1 to 1.3:1, and the single-stage residence time is 5 min to 30 min.

[0059] The number of stages in a multi-stage leaching reactor is preferably 2 to 5; the number of stages in a multi-stage rinsing reactor is preferably 2 to 5.

[0060] When the sum of the volumetric flow rates of the rare earth leachate and the eluent is less than or equal to the volumetric flow rate of the leaching agent solution, Figure 1a This is a schematic diagram of the material flow direction in the corresponding continuous leaching method for ion-adsorption rare earth ores.

[0061] Figure 2a This is a schematic diagram of the process flow for a continuous leaching method for ion-adsorption rare earth ores. When the sum of the volumetric flow rates of the rare earth leachate and the eluent exceeds the volumetric flow rate of the leaching agent solution, Figure 1b This is a schematic diagram of the material flow in the corresponding continuous leaching method for ion-adsorption rare earth ores. Figure 2b This is a schematic diagram of the process flow for the corresponding continuous leaching method for ion-adsorption rare earth ores.

[0062] Furthermore, the volumetric mass flow ratio of the rare earth leachate returned to the multi-stage leaching reactor to the ion-adsorption rare earth ore is 1:1 to 4:1; the volumetric mass flow ratio of the leachate returned to the multi-stage washing reactor to the leaching tailings is 1:1 to 4:1.

[0063] Furthermore, during the continuous co-current leaching process, the rare earth leachate is returned to the first-stage leaching reactor and the second-stage leaching reactor; during the continuous co-current rinsing process, the leachate is returned to the first-stage rinsing reactor and the second-stage rinsing reactor.

[0064] During continuous co-current leaching, the rare earth leachate may also be returned to the third-stage leaching reactor, or to both the third-stage and fourth-stage leaching reactors; during continuous co-current rinsing, the leachate may also be returned to the third-stage rinsing reactor, or to both the third-stage and fourth-stage rinsing reactors.

[0065] Furthermore, the leaching agent solution includes at least one of the following: magnesium sulfate, magnesium chloride, calcium chloride, sodium sulfate, sodium chloride, potassium chloride, potassium sulfate, and ferrous sulfate.

[0066] Clean water includes at least one of the following: surface water, groundwater, semi-permeable membrane enrichment water, and tap water.

[0067] Furthermore, the hydrogen ion concentration of the leaching agent solution is 0.00001 mol / L to 0.005 mol / L, and the cation concentration other than hydrogen ions is 0.05 mol / L to 0.4 mol / L.

[0068] Furthermore, apart from hydrogen ions, the molar percentages of various cations in the leaching agent solution are as follows: magnesium ions 40%–100%, calcium ions 0%–55%, and sodium ions, potassium ions, and / or ferrous ions 0%–50%.

[0069] Furthermore, the grading methods include at least one of the following: hydrocyclone, spiral classifier, grading centrifuge, and grading vibrating screen;

[0070] Solid-liquid separation methods include at least one of the following: thickener, vacuum bag filter, centrifugal filter and horizontal screw centrifuge.

[0071] Furthermore, the particle size range of coarse-grained tailings is +40 mesh, the particle size range of medium-grained tailings is -40 mesh to +200 mesh, and the particle size range of fine-grained tailings is -200 mesh.

[0072] Furthermore, the enrichment treatment method includes at least one of the following: semipermeable membrane enrichment, adsorption enrichment, extraction enrichment, and precipitation enrichment.

[0073] The semi-permeable membrane includes: nanofiltration membrane and / or reverse osmosis membrane.

[0074] Referring to Figure 2, when the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is greater than the volumetric flow rate of the leaching agent solution, step S300 includes:

[0075] Step S310: The rare earth leachate is treated with a chemical enrichment method to obtain an enriched residue, which is then recycled for the preparation of the leaching agent solution.

[0076] In step S320, the leachate is treated using a pre-enrichment method to obtain a concentrated leachate, which is then recycled for the preparation of the leaching agent solution.

[0077] Among them, chemical enrichment methods include: extraction and / or precipitation; pre-enrichment methods include: semi-permeable membrane enrichment and / or adsorption enrichment; semi-permeable membranes include: nanofiltration membranes and / or reverse osmosis membranes.

[0078] When the sum of the volumetric flow rates of rare earth leachate and leaching solution is greater than the volumetric flow rate of the leaching agent solution, the above technical solution uses a semi-permeable membrane to enrich the leaching solution. The resulting concentrated leaching solution is entirely recycled for preparing the leaching agent solution, and the semi-permeable membrane enrichment product water is directly discharged in compliance with standards. After the rare earth leachate is enriched by chemical enrichment, the remaining enrichment liquid is entirely recycled for preparing the leaching agent solution. This achieves water recycling and water balance throughout the entire process of ion-adsorption rare earth mining, avoids wastewater generation at the source, eliminates environmental hazards, and reduces production costs.

[0079] The above technical solution will be further illustrated below with several embodiments:

[0080] Example 1

[0081] The ion-phase rare earth grade of the ion-adsorption rare earth ore is 0.05%, and the particle size distribution is as follows: coarse particles (+40 mesh) account for 48%, medium particles (-40 to +200 mesh) account for 29%, and fine particles (-200 mesh) account for 33%.

[0082] Ionic rare earth ore and leaching agent solution were continuously fed into a multi-stage leaching reactor (mixing method was stirring) for co-current leaching. The leaching agent solution contained magnesium sulfate (hydrogen ion concentration of 0.00001 mol / L, cation concentration of ions other than hydrogen ions of 0.20 mol / L). The volumetric mass flow ratio of the leaching agent solution to the ionic rare earth ore was 0.5:1. The leaching reactor consisted of 3 stages, and the residence time of each stage leaching reactor was 30 min. The ore was then subjected to continuous solid-liquid separation by a thickener to obtain rare earth leachate and leaching tailings. The volumetric mass flow ratios of the rare earth leachate to the first and second stage leaching reactors were 1.5:1 and 1:1, respectively. Fresh water and leaching tailings were continuously fed into a multi-stage leaching reactor (mixing method: stirred mixing) for co-current leaching. The volume-to-mass ratio of fresh water to leaching tailings was 0.3:1. The leaching reactor consisted of three stages, with a residence time of 30 minutes per stage. The tailings were then continuously classified by a hydrocyclone and continuously solid-liquid separated by a thickener to obtain coarse, medium, and fine-grained tailings and leachate. The volume-to-mass flow ratios of leachate to leaching tailings returned to the first and second stage leaching reactors were 1.5:1 and 1:1, respectively. The obtained rare earth leachate was enriched for rare earth elements using extraction. The enriched residue was recycled for preparing leaching agent solutions; the obtained leachate was also recycled for preparing leaching agent solutions. Under the above conditions, the rare earth leaching rate was 94.7%, the rare earth concentration in the leaching solution was 946.6 mg / L, the leaching agent consumption was 3.8 t / t-REO, and the leaching cycle was 25.3 days (effective volume of a single leaching reactor 100 m³). 3 (Calculated based on a single mine ore quantity of 100,000 tons); The particle size distribution of the graded tailings is as follows: coarse particles (+40 mesh) account for 45%, medium particles (-40 to +200 mesh) account for 25%, and fine particles (-200 mesh) account for 30%. The graded tailings are comprehensively utilized; the enrichment residue and leachate are all recycled.

[0083] The specific processes of Examples 2-70 and Comparative Examples 1-5 are shown in Tables 1-5.

[0084] Table 1

[0085]

[0086]

[0087]

[0088]

[0089] Table 2

[0090]

[0091]

[0092]

[0093]

[0094] Table 3

[0095]

[0096]

[0097]

[0098]

[0099] Table 4

[0100]

[0101]

[0102]

[0103] Table 5

[0104]

[0105]

[0106]

[0107]

[0108]

[0109] From the information disclosed in Tables 1 to 5, we can see that:

[0110] (1) As can be seen from Example 3, Comparative Examples 1 and 2, based on a single mine ore quantity of 100,000 tons, compared with in-situ leaching and heap leaching, continuous multi-stage co-current leaching using partially refluxed leaching agent (effective volume of a single leaching reactor is 100 m³) is more effective. 3 The continuous multi-stage parallel rinsing with clean water increased the rare earth leaching rate from 89.8%–93.1% to 96.0%, significantly increased the rare earth concentration in the leaching solution (from about 300 mg / L to 960 mg / L), greatly reduced the consumption of leaching agent (from 7.8–10.3 t / t-REO to 3.5 t / t-REO), and significantly shortened the leaching cycle (from 90–120 days to about 25 days), thus achieving the comprehensive utilization of tailings through classification.

[0111] (2) As can be seen from Example 3 and Comparative Example 3, based on a single mine ore quantity of 100,000 tons, and continuous multi-stage co-flow leaching with no backflow of rare earth leaching solution (effective volume of a single leaching reactor is 100m³), 3 Compared to the previous method, the use of partially recirculated leaching agent for continuous multi-stage co-current leaching and continuous multi-stage co-current washing with clean water significantly increased the rare earth leaching rate and rare earth concentration in the leaching solution from 84.5% and 192 mg / L to 96.0% and 960 mg / L, respectively. The consumption of leaching agent was reduced (from 4.7 t / t-REO to 3.5 t / t-REO), and the leaching cycle was significantly shortened (from 67 days to about 25 days), achieving comprehensive utilization of tailings through classification.

[0112] (3) As can be seen from Example 3 and Comparative Example 4, based on a single mine ore quantity of 100,000 tons, and continuous multi-stage co-current leaching with non-backflow rare earth leaching solution (effective volume of a single leaching reactor 100m³), 3 Compared to continuous multi-stage co-current leaching with non-recirculating leachate, continuous multi-stage co-current leaching with partially recirculating leaching agent and continuous multi-stage co-current leaching with clean water achieved comparable rare earth leaching rates (both around 96.0%). However, the rare earth concentration in the leaching solution significantly increased from 192 mg / L to 960 mg / L, leaching agent consumption decreased (from 4.7 t / t-REO to 3.5 t / t-REO), and the leaching cycle was drastically shortened (from 67 days to approximately 25 days). This enabled the comprehensive utilization of tailings through grading and avoided the generation of large amounts of wastewater (3800 m³). 3 / t-REO).

[0113] (4) As can be seen from Example 3 and Comparative Example 5, based on a single mine ore quantity of 100,000 tons, and continuous multi-stage co-flow leaching with no backflow of rare earth leaching solution (effective volume of a single leaching reactor is 100m³), 3 Compared to continuous multi-stage co-current leaching with no recirculation of leachate, the method using partially recirculated leaching agent in continuous multi-stage co-current leaching and clear water in continuous multi-stage co-current leaching achieves roughly the same rare earth leaching rate and leaching agent consumption. The rare earth concentration in the leaching solution significantly increases from 192 mg / L to 960 mg / L, and the leaching cycle is drastically shortened (from 67 days to approximately 25 days), achieving comprehensive utilization of tailings through grading. Furthermore, in Comparative Example 5, since neither the rare earth leaching solution nor the leachate is recirculated, both the rare earth leaching solution and the leachate must undergo pre-concentration to achieve complete water recycling. However, the pre-concentration process requires a large volume (3800 m³). 3 When rare earth leachate (which usually contains high concentrations of calcium sulfate and aluminum sulfate) is enriched using a reverse osmosis membrane, calcium sulfate and aluminum hydroxide scaling are very likely to occur.

[0114] (5) As can be seen from Examples 1 to 8, as the concentration of hydrogen ions in the leaching agent solution increases from 0.00001 mol / L to 0.005 mol / L, the rare earth leaching rate and the rare earth concentration in the rare earth leachate both increase slightly, while the leaching agent consumption decreases slightly. This is because hydrogen ions have a stronger ion exchange capacity than magnesium ions and can also act as a leaching agent. As the concentration of magnesium sulfate in the leaching agent solution increases from 0.05 mol / L to 0.4 mol / L, the rare earth leaching rate and the rare earth concentration in the rare earth leachate both increase slightly, while the leaching agent consumption remains basically the same.

[0115] (6) As shown in Examples 3 and 9-24, when the leaching agent solution is controlled to contain at least one of magnesium sulfate, magnesium chloride, calcium chloride, sodium sulfate, sodium chloride, potassium chloride, potassium sulfate, and ferrous sulfate, and the molar percentages of various cations (excluding hydrogen ions) in the leaching agent solution are as follows: magnesium ions 40%-100%, calcium ions 0%-55%, sodium ions, potassium ions, and / or ferrous ions 0%-50%, rare earth elements can be leached efficiently (rare earth leaching rate > 93.5%). When the leaching agent solution contains both magnesium sulfate and ferrous sulfate, the rare earth leaching rate is the highest and the leaching agent consumption is the lowest; this is because ferrous sulfate has reducing properties and can simultaneously and efficiently leach both the ionic and colloidal phases in ionic rare earth ores, thereby increasing the rare earth leaching rate. When the leaching agent solution does not contain ferrous sulfate and is mainly composed of magnesium sulfate, the rare earth leaching rate is higher than when the leaching agent solution does not contain ferrous sulfate and is mainly composed of calcium salts, sodium salts, and potassium salts.

[0116] (7) As can be seen from Examples 3, 25-26, 43-44 and 70, the number of stages of the leaching reactor and the washing reactor (both 2-10) has no significant effect on the rare earth leaching rate, the rare earth concentration of the rare earth leachate and the consumption of the leaching agent.

[0117] (8) As can be seen from Examples 3 and 27-29, as the volume mass flow ratio of the leaching agent solution to the ionic rare earth ore increases (from 0.4:1 to 1.5:1), the rare earth leaching rate increases slightly, but the rare earth concentration in the rare earth leaching solution decreases significantly (from 1198 mg / L to 321 mg / L), and the leaching cycle is significantly extended (from about 23 days to about 46 days).

[0118] (9) As can be seen from Examples 3 and 30-32, as the residence time of the single-stage leaching reactor is extended from 5 min to 30 min, the rare earth leaching rate, rare earth concentration of rare earth leaching solution and leaching agent consumption change little, but the leaching cycle is extended significantly from about 4 days to about 25 days.

[0119] (10) As can be seen from Examples 3 and 33-36, the volume mass flow ratio of the rare earth leachate back to the leaching reactor to the ion-type rare earth ore, the number of leaching reactor stages to which the rare earth leachate is returned, and the distribution of the return flow rate of each stage have virtually no effect on the rare earth leaching rate, the rare earth concentration of the rare earth leachate, the consumption of the leaching agent, the leaching cycle, etc.

[0120] (11) As can be seen from Examples 3, 37-42, and 56-64, the mixing method (stirring, pneumatic mixing, spiral mixing, pipeline mixing), classification method (hydrocyclone, spiral classifier, classifying centrifuge, classifying vibrating screen), and solid-liquid separation method (thickener, vacuum bag filter, centrifugal filter, horizontal spiral centrifuge) of the leaching reactor and the washing reactor have no significant effect on the rare earth leaching rate, the rare earth concentration of the rare earth leaching solution, and the consumption of the leaching agent; however, the classification method (hydrocyclone, spiral classifier, classifying centrifuge, classifying vibrating screen) will have a certain impact on the yield of tailings of different particle sizes.

[0121] (12) As can be seen from Examples 3 and 45-48, as the volumetric mass flow ratio of fresh water to leaching tailings increases (from 0.3:1 to 1.3:1), the changes in rare earth leaching rate, rare earth concentration in the leaching solution, leaching agent consumption, and leaching cycle are relatively small. Furthermore, although the leachate needs to be pre-enriched, the pre-enrichment treatment volume of the leachate is 400-2000 m³ as the volumetric mass flow ratio of fresh water to leaching tailings increases (from 0.3:1 to 1.3:1). 3 / t-REO (far below 3800m) 3 / t-REO), and because the leaching liquid contains low levels of calcium sulfate and aluminum sulfate, it is less prone to scaling with calcium sulfate and aluminum hydroxide.

[0122] (13) As can be seen from Examples 3 and 49-51, as the residence time of the single-stage leaching reactor is extended from 5 min to 30 min, the changes in rare earth leaching rate, rare earth concentration in rare earth leaching solution, leaching agent consumption, leaching cycle, etc. are relatively small.

[0123] (14) As can be seen from Examples 3 and 52-55, the volume mass flow ratio of the leaching liquid returned to the leaching reactor to the leaching tailings, the number of stages of the leaching reactor to which the leaching liquid is returned, and the distribution of the return flow rate of each stage have basically no effect on the rare earth leaching rate, the rare earth concentration of the rare earth leaching liquid, the consumption of leaching agent, the leaching cycle, etc.

[0124] (15) As can be seen from Examples 3 and 65, Examples 66 and 69, the chemical enrichment method (extraction, precipitation) of rare earth leachate has no significant effect on rare earth leaching rate, rare earth concentration of rare earth leachate, leaching agent consumption, leaching cycle, etc.

[0125] (16) As can be seen from Examples 45-48 and Examples 66-69, when the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is greater than the volumetric flow rate of the leaching agent solution (e.g., the volumetric flow rate ratio of the rare earth leachate to the ion-adsorption rare earth ore, and the volumetric flow rate ratio of the water to the leaching tailings are both 1:1), the leaching solution must be pre-enriched. However, the pre-enrichment treatment volume of the leaching solution is 400-2400 m³. 3 / t-REO (far below 3800m) 3 The leaching solution contains low levels of calcium sulfate and aluminum sulfate, making it less prone to scaling by calcium sulfate and aluminum hydroxide. Furthermore, it has no significant impact on rare earth leaching rate, rare earth concentration in the leaching solution, leaching agent consumption, or leaching cycle.

[0126] This invention aims to protect a continuous leaching method for ion-adsorption rare earth ores. The continuous leaching method includes the following steps: continuously feeding ion-adsorption rare earth ores and leaching agent solutions into a multi-stage leaching reactor for co-current leaching; obtaining rare earth leachate and leaching tailings after solid-liquid separation; feeding the leaching tailings and water into a multi-stage washing reactor for co-current washing; obtaining coarse-grained tailings, medium-grained tailings, fine-grained tailings, and leachate after continuous classification and solid-liquid separation; enriching the rare earth leachate and leachate, and recycling them all for preparing leaching agent solutions; returning the rare earth leachate to the multi-stage leaching reactor; returning the leachate to the multi-stage washing reactor. The above technical solution has the following effects:

[0127] (1) The leaching agent is continuously leached in multiple stages in parallel flow, supplemented by the return of rare earth leachate for ion-adsorption rare earth ore leaching. The mass transfer efficiency is high, and the leaching agent can fully contact and react with the ion-adsorption rare earth ore in a short time, which greatly shortens the leaching cycle. At the same time, the volume flow rate of the leaching agent solution can be greatly reduced, and the rare earth concentration of the leachate can be increased. The leaching tailings are further washed with clean water in multiple stages in parallel flow, supplemented by the return of leachate for leaching tailings. The consumption of leaching agent is greatly reduced, and the residue of rare earth in the leaching tailings can be effectively reduced. The rare earth leaching rate is effectively improved, and the amount of clean water used for leaching can be greatly reduced, which significantly reduces the production cost.

[0128] (2) After continuous multi-stage co-current leaching of tailings, continuous classification methods such as hydrocyclones are used to efficiently leach and recover rare earth while efficiently separating and recovering fine-grained tailings (mainly clay minerals such as kaolinite and halloysite), medium-grained tailings (mainly feldspar and other minerals), and coarse-grained tailings (mainly quartz and other minerals), so as to achieve the graded comprehensive utilization of different particle size components of ion-adsorption rare earth minerals.

[0129] (3) When the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is less than or equal to the volumetric flow rate of the leaching agent solution, the rare earth leachate and / or leaching solution are enriched and then recycled for the preparation of the leaching agent solution, thereby achieving water recycling and water balance throughout the entire process of ion-adsorption rare earth ore mining. When the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is greater than the volumetric flow rate of the leaching agent solution, the rare earth leachate is enriched using a chemical enrichment method, and the resulting enriched residue is recycled for the preparation of the leaching agent solution. The leaching solution is enriched using a semi-permeable membrane, and the resulting concentrated leaching solution is recycled for the preparation of the leaching agent solution. The resulting semi-permeable membrane enriched water is directly discharged in compliance with standards, thereby achieving water recycling and water balance throughout the entire process of ion-adsorption rare earth ore mining. Therefore, wastewater generation can be avoided at the source, environmental hazards can be eliminated, and production costs can be reduced.

[0130] (4) By adopting continuous multi-stage co-current leaching with leaching agent-continuous solid-liquid separation and continuous multi-stage co-current rinsing with clean water-continuous grading-continuous solid-liquid separation, the entire process of mining ion-adsorption rare earth minerals is mechanized and automated, and continuous production is realized, which greatly reduces labor intensity.

[0131] (5) The use of continuous multi-stage co-current leaching of leaching agent and continuous multi-stage co-current rinsing of clean water can effectively reduce the residue of leaching agent in tailings and avoid the environmental risks caused by a large amount of leaching agent residue in tailings.

[0132] (6) Using magnesium / calcium salt leaching agent for continuous multi-stage parallel leaching and clear water for continuous multi-stage parallel rinsing, the content of magnesium, calcium and other nutrients in tailings can be targeted to regulate according to the actual needs of tailings ecological restoration or comprehensive utilization, improve soil compaction, meet soil nutrient and ratio requirements, and promote plant chlorophyll synthesis.

[0133] (7) The continuous multi-stage co-current leaching of leaching agent and continuous multi-stage co-current rinsing of clear water is adopted, which can be used to treat all minerals containing ionic phase rare earths and has a wide range of applications.

[0134] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for continuous leaching of ion-adsorption rare earth ores, characterized in that, Includes the following steps: Ionic rare earth ore and leaching agent solution are continuously fed into a multi-stage leaching reactor for co-current leaching. After solid-liquid separation, rare earth leachate and leaching tailings are obtained. The leaching tailings and water are continuously fed into a multi-stage leaching reactor for co-current leaching. After continuous classification and solid-liquid separation, coarse-grained tailings, medium-grained tailings, fine-grained tailings and leachate are obtained respectively. After enrichment treatment of the rare earth leachate and / or the leaching solution, it is recycled for the preparation of the leaching agent solution. In the continuous co-current leaching process, the rare earth leachate is returned to the multi-stage leaching reactor; in the continuous co-current rinsing process, the leaching solution is returned to the multi-stage rinsing reactor.

2. The continuous leaching method for ion-adsorption rare earth ores according to claim 1, characterized in that, The mixing methods in the multi-stage leaching reactor and the multi-stage rinsing reactor include at least one of the following: stirring mixing, pneumatic mixing, spiral mixing, and pipeline mixing.

3. The continuous leaching method for ion-adsorption rare earth ores according to claim 2, characterized in that, The number of stages in the multi-stage leaching reactor is 2 to 10, the volumetric mass flow ratio of the leaching agent solution to the ion-adsorption rare earth ore is 0.4:1 to 1.5:1, and the single-stage residence time is 5 min to 30 min. The multi-stage leaching reactor has 2 to 10 stages, the volumetric mass flow ratio of the clean water to the leaching tailings is 0.3:1 to 1.3:1, and the single-stage residence time is 5 min to 30 min.

4. The continuous leaching method for ion-adsorption rare earth ores according to claim 3, characterized in that, The number of stages in the multi-stage leaching reactor is 2 to 5; The number of stages in the multi-stage rinsing reactor is 2 to 5.

5. The continuous leaching method for ion-adsorption rare earth ores according to claim 3, characterized in that, The volumetric mass flow ratio of the rare earth leachate returned to the multi-stage leaching reactor to the ion-adsorption rare earth ore is 1:1 to 4:

1. The volumetric mass flow ratio of the leachate returned to the multi-stage leaching reactor to the leaching tailings is 1:1 to 4:

1.

6. The continuous leaching method for ion-adsorption rare earth ores according to claim 5, characterized in that, During the continuous co-current leaching process, the rare earth leachate is refluxed into the first-stage leaching reactor and the second-stage leaching reactor; During the continuous co-current rinsing process, the leaching liquid is returned to the first-stage rinsing reactor and the second-stage rinsing reactor; During the continuous co-current leaching process, the rare earth leachate is also refluxed into the third-stage leaching reactor, or into the third-stage leaching reactor and the fourth-stage leaching reactor; During the continuous co-current rinsing process, the leaching liquid is also returned to the third-stage rinsing reactor, or to both the third-stage and fourth-stage rinsing reactors.

7. The continuous leaching method for ion-adsorption rare earth ores according to claim 6, characterized in that, The leaching agent solution includes at least one of the following: magnesium sulfate, magnesium chloride, calcium chloride, sodium sulfate, sodium chloride, potassium chloride, potassium sulfate, and ferrous sulfate; The clean water includes at least one of the following: surface water, groundwater, semi-permeable membrane enriched water, and tap water.

8. The continuous leaching method for ion-adsorption rare earth ores according to claim 7, characterized in that, The hydrogen ion concentration of the leaching agent solution is 0.00001 mol / L to 0.005 mol / L, and the cation concentration other than hydrogen ions is 0.05 mol / L to 0.4 mol / L.

9. The continuous leaching method for ion-adsorption rare earth ores according to claim 8, characterized in that, Apart from hydrogen ions, the molar percentages of various cations in the leaching agent solution are as follows: magnesium ions 40%–100%, calcium ions 0%–55%, sodium ions, potassium ions and / or ferrous ions 0%–50%.

10. The continuous leaching method for ion-adsorption rare earth ores according to claim 9, characterized in that, The grading method includes at least one of the following: hydrocyclone, spiral classifier, grading centrifuge and grading vibrating screen; The solid-liquid separation method includes at least one of the following: a thickener, a vacuum bag filter, a centrifugal filter, and a horizontal screw centrifuge.

11. The continuous leaching method for ion-adsorption rare earth ores according to claim 10, characterized in that, The coarse-grained tailings have a particle size range of +40 mesh, the medium-grained tailings have a particle size range of -40 mesh to +200 mesh, and the fine-grained tailings have a particle size range of -200 mesh.

12. The continuous leaching method for ion-adsorption rare earth ores according to claim 11, characterized in that, The enrichment process includes at least one of the following: semipermeable membrane enrichment, adsorption enrichment, extraction enrichment and precipitation enrichment. The semi-permeable membrane includes: nanofiltration membrane and / or reverse osmosis membrane.

13. The continuous leaching method for ion-adsorption rare earth ores according to any one of claims 1 to 12, characterized in that, When the sum of the volumetric flow rates of the rare earth leachate and the leaching solution is greater than the volumetric flow rate of the leaching agent solution, the enrichment treatment method includes: The rare earth leachate is treated with a chemical enrichment method to obtain an enriched residue, which is then recycled for the preparation of the leaching agent solution. The leachate is treated using a pre-enrichment method to obtain a concentrated leachate, which is then recycled for the preparation of the leaching agent solution.

14. The continuous leaching method for ion-adsorption rare earth ores according to claim 13, characterized in that, The chemical enrichment method includes: extraction and / or precipitation; The pre-enrichment method includes: semi-permeable membrane enrichment and / or adsorption enrichment; The semi-permeable membrane includes: nanofiltration membrane and / or reverse osmosis membrane.

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