Method for continuously leaching ionic rare earth ore

Abstract

Disclosed in the present invention is a method for continuously leaching an ionic rare earth ore. The method comprises: putting an ionic rare earth ore and a leaching agent solution to a multi-stage leaching reactor for co-current leaching, and carrying out solid-liquid separation to obtain a rare earth leachate and leached tailings; putting the leached tailings and clear water into a multi-stage elution reactor for co-current elution, and carrying out classification and solid-liquid separation to respectively obtain coarse-sized tailings, medium-sized tailings, fine-sized tailings, and an eluate; and enriching the rare earth leachate and / or the eluate, and then circulating same to prepare the leaching agent solution, wherein the rare earth leachate flows back to the multi-stage leaching reactor, and the eluate flows back to the multi-stage elution reactor. By means of the continuous multi-stage co-current leaching with the leaching agent solution and the backflow of the rare earth leachate for leaching, and the continuous multi-stage co-current elution with clear water and the backflow of the eluate for elution, the rare earth leaching rate and the rare earth concentration in the leachate are effectively improved, the consumption of the leaching agent is greatly reduced, the ore leaching period is significantly shortened, and full-process water balance and tailing classification and comprehensive utilization are achieved.

Description

A continuous leaching method for ionic rare earth ores

[0001] Cross-references

[0002] This application is based on the Chinese patent application with application number 202410170738.6 and application date of February 6, 2024, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference. Technical Field

[0003] The present invention relates to the technical field of rare earth extraction and enrichment, in particular to a continuous leaching method for ionic rare earth ores. Background Art

[0004] Because ionic rare earth ores are rare worldwide and contain extremely low rare earth grades (only 0.03% to 0.1% REO), there are no comparable mining and processing theories and technologies available internationally, making it impossible to enrich rare earths using conventional beneficiation methods. However, due to the fact that the rare earths in ionic rare earth ores are primarily adsorbed on clay minerals such as kaolinite in the form of hydrated ions or hydroxyl hydrated ions, Chinese scientists and researchers have conducted extensive research and practice, developing a unique method for extracting rare earths through ion exchange using electrolyte solutions such as sodium chloride, ammonium sulfate, and magnesium sulfate. Furthermore, they have developed three generations of leaching processes: tank leaching, heap leaching, and in situ leaching, enabling the large-scale development and utilization of ultra-low-grade rare earth ores.

[0005] The mining of ionic rare earth ores using heap leaching or in situ leaching technology both achieves rare earth leaching through the natural infiltration, diffusion and mass transfer of the leaching solution in the ore body or ore pile. However, the following major problems exist: 1) Due to the generally poor permeability of ionic rare earth ore bodies or ore piles, the natural infiltration rate of the leaching solution is slow, and the mass transfer efficiency between the leaching agent in the leaching solution and the clay minerals is low. The leaching cycle of a single mine or ore pile is usually as long as 3 to 6 months, and some even last for more than 1 year. 2) Due to the tendency of the leaching solution to form a dominant flow during the natural seepage of the ionic rare earth ore body or ore pile, some seepage channels in the ionic rare earth ore body or ore pile cannot be effectively infiltrated by the leaching solution, making it difficult for the clay minerals to effectively contact and transfer with the leaching solution, resulting in a low rare earth leaching rate. 3) During the leaching process of ionic rare earth ore bodies or ore piles, due to the influence of the rare earth grade distribution at different depths of the ore layer, rare earth back adsorption is easily caused during the downward seepage of the rare earth-containing leaching solution, resulting in high leaching agent consumption and production costs. In addition, ionic rare earth ore bodies or ore piles are mined by in-situ leaching or heap leaching. Even if the ore body or ore pile is leached, the volume mass ratio of clean water to rare earth ore used for leaching is usually less than 0.3:1. The obtained leachate is used to replenish the water lost in the initial saturation of the ionic rare earth ore body and leakage, so as to achieve water balance in the mining process. However, due to the low mass transfer efficiency of the natural infiltration process of clean water and the easy formation of dominant flow, there are still problems such as high leaching agent consumption and high production cost.

[0006] Therefore, improving mass transfer efficiency and rare earth leaching rates during the leaching process of ionic rare earth ores, shortening the leaching cycle, and reducing leaching agent consumption are crucial for the rapid and efficient mining of ionic rare earth ores. To this end, a patent proposes a method for percolation leaching of ionic rare earth ores using a continuous horizontal vacuum belt filter. This method combines dry ore loading, compaction, percolation leaching, and solid-liquid separation on a single belt filter. This method achieves a mechanized, continuous leaching process, but is essentially similar to the percolation process of heap leaching or in situ leaching and suffers from the following issues: 1) low mass transfer efficiency and rare earth leaching rates; 2) the lack of consideration for washing the leached tailings, resulting in waste of rare earth resources and leaching agents, and high leaching agent consumption. Another patent proposes using ammonium sulfate agitation leaching for ionic rare earth ores, with the agitation leaching slurry undergoing solid-liquid separation in a thickener. The overflow leachate is used for subsequent impurity removal and sedimentation, while the underflow is sent to a tailings pond. However, this method has the following problems: 1) The stirred leaching slurry is directly subjected to solid-liquid separation by a thickening unit, and the separated tail stream is not subjected to a washing operation, resulting in a large amount of rare earth leaching liquid remaining in the tail stream, causing a waste of rare earth resources and leaching agents; 2) When ammonium sulfate is used for stirring leaching, the tail stream obtained after solid-liquid separation by the thickening unit contains a large amount of ammonium sulfate, which directly flows into the tailings pond, bringing serious environmental and safety risks. In addition, the above-mentioned continuous horizontal vacuum belt filter percolation leaching or stirring leaching method also has the following problems: 1) Neither of them considers the classification of the leached tailings, and the obtained leached tailings cannot be graded and comprehensively utilized. A large number of tailings ponds must be built for storage, with high construction and maintenance costs, and there are risks such as soil erosion; 2) If stirring and leaching of the leached tailings is considered, in order to achieve efficient leaching, the volume-to-mass ratio of supplementary clean water to leached tailings must be higher than 1.5:1, but it is impossible to achieve water balance in the entire mining process, and a large amount of wastewater (>2000m 3 / t-REO), which greatly increases environmental protection costs.

[0007] Summary of the Invention

[0008] The purpose of the embodiments of the present invention is to provide a continuous leaching method for ionic rare earth ores. This method 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 ionic rare earth ores. The method significantly improves the 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 realizes the cascaded comprehensive utilization of different particle size components of the ionic rare earth ores, as well as water recycling and water balance throughout the mining process.

[0009] To solve the above technical problems, an embodiment of the present invention provides a continuous leaching method for ionic rare earth ores, comprising the following steps:

[0010] Ionic rare earth ore and leaching agent solution are continuously put into a multi-stage leaching reactor for parallel leaching, and rare earth leachate and leaching tailings are obtained after solid-liquid separation;

[0011] The leached tailings and clean water are continuously fed into a multi-stage leaching reactor for parallel leaching, and after continuous classification and solid-liquid separation, coarse-grained tailings, medium-grained tailings, fine-grained tailings and leachate are obtained respectively;

[0012] After the rare earth leachate and / or the leachate are enriched and / or recycled for preparing the leaching agent solution;

[0013] In the continuous parallel leaching process, the rare earth leachate flows back into the multi-stage leaching reactor; in the continuous parallel elution process, the leachate flows back into the multi-stage elution reactor.

[0014] Furthermore, the mixing methods in the multi-stage leaching reactor and the multi-stage elution reactor include at least one of stirring mixing, pneumatic mixing, spiral mixing and pipeline mixing.

[0015] Furthermore, the number of stages of the multi-stage leaching reactor is 2 to 10, the volume mass flow ratio of the leaching agent solution to the ionic rare earth ore is 0.4:1 to 1.5:1, and the single-stage residence time is 5 min to 30 min;

[0016] The number of stages of the multi-stage leaching reactor is 2 to 10, the volume mass flow ratio of the clean water to the leached tailings is 0.3:1 to 1.3:1, and the single-stage residence time is 5 minutes to 30 minutes;

[0017] The number of stages of the multi-stage leaching reactor is preferably 2 to 5;

[0018] The number of stages of the multi-stage elution reactor is preferably 2 to 5.

[0019] Furthermore, the volume mass flow ratio of the rare earth leachate refluxed into the multi-stage leaching reactor to the ionic rare earth ore is 1:1 to 4:1;

[0020] The volume mass flow ratio of the leachate flowing back into the multi-stage elution reactor to the leached tailings is 1:1 to 4:1.

[0021] Furthermore, in the continuous co-current leaching process, the rare earth leachate is refluxed into the first-stage leaching reactor and the second-stage leaching reactor;

[0022] During the continuous co-current elution process, the eluate flows back into the first stage elution reactor and the second stage elution reactor;

[0023] During the continuous co-current leaching process, the rare earth leachate may also flow back into the third-stage leaching reactor, or into the third-stage leaching reactor and the fourth-stage leaching reactor;

[0024] During the continuous co-current elution process, the eluate may also flow back into the third-stage elution reactor, or into the third-stage elution reactor and the fourth-stage elution reactor.

[0025] Furthermore, the leaching agent solution includes at least one of magnesium sulfate, magnesium chloride, calcium chloride, sodium sulfate, sodium chloride, potassium chloride, potassium sulfate and ferrous sulfate;

[0026] The clean water includes at least one of surface water, groundwater, semi-permeable membrane enriched water and tap water.

[0027] 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.

[0028] Furthermore, except for hydrogen ions, the molar percentages of various cations in the leaching agent solution are: magnesium ions are 40% to 100%, calcium ions are 0% to 55%, and sodium ions, potassium ions and / or ferrous ions are 0% to 50%.

[0029] Furthermore, the classification method includes: at least one of a hydrocyclone, a spiral classifier, a classification centrifuge and a classification vibrating screen;

[0030] The solid-liquid separation method includes: at least one of a thickener, a vacuum bag filter, a centrifugal filter and a horizontal spiral centrifuge.

[0031] Furthermore, the particle size range of the coarse-grained tailings is +40 mesh, the particle size range of the medium-grained tailings is -40 mesh to +200 mesh, and the particle size range of the fine-grained tailings is -200 mesh.

[0032] Furthermore, the enrichment treatment method includes at least one of: semipermeable membrane enrichment, adsorption enrichment, extraction enrichment and precipitation enrichment;

[0033] The semipermeable membrane includes: a nanofiltration membrane and / or a reverse osmosis membrane.

[0034] Furthermore, when the sum of the volume flow rates of the rare earth leachate and the leachate is greater than the volume flow rate of the leaching agent solution, the enrichment treatment method includes:

[0035] Treating the rare earth leachate with a chemical enrichment method to obtain an enriched residual solution, which is circulated for preparing the leaching agent solution;

[0036] The leachate is treated by a pre-enrichment method to obtain a concentrated leachate, which is then recycled to prepare the leaching agent solution.

[0037] Furthermore, the chemical enrichment method includes: extraction and / or precipitation;

[0038] The pre-enrichment method includes: semi-permeable membrane enrichment and / or adsorption enrichment;

[0039] The semipermeable membrane includes: a nanofiltration membrane and / or a reverse osmosis membrane.

[0040] The above technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0041] (1) The continuous multi-stage parallel flow leaching of the leaching agent is supplemented by the return of a portion of the rare earth leachate for leaching of ionic rare earth ores. The mass transfer efficiency is high, and the leaching agent can fully contact and react with the ionic rare earth ores in a short time. The leaching cycle is greatly shortened. 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 leached tailings are further washed with continuous multi-stage parallel flow of clean water, supplemented by the return of a portion of the leachate for leaching of the leached tailings. The consumption of the leaching agent is greatly reduced, and the residual rare earth in the leached tailings can be effectively reduced. The rare earth leaching rate is effectively improved. At the same time, the amount of clean water used for leaching can be greatly reduced, and the production cost is significantly reduced.

[0042] (2) After continuous multi-stage parallel leaching of the leached tailings, continuous classification methods such as hydrocyclones are used to efficiently separate and recover fine-grained tailings (mainly clay minerals such as kaolinite and halloysite), medium-grained tailings (mainly feldspar, etc.), and coarse-grained tailings (mainly quartz, etc.) while efficiently leaching and recovering rare earths, thereby achieving the graded and comprehensive utilization of different particle size components of ionic rare earth ores.

[0043] (3) When the sum of the volume flow rates of the rare earth leachate and the leachate is less than or equal to the volume flow rate of the leaching agent solution, the rare earth leachate and / or the leachate are enriched and treated and then all recycled for the preparation of the leaching agent solution, thereby realizing the water recycling and water balance of the whole process of ionic rare earth mining; when the sum of the volume flow rates of the rare earth leachate and the leachate is greater than the volume flow rate of the leaching agent solution, the rare earth leachate is enriched with rare earths by a chemical enrichment method, and the enriched residual liquid obtained is all recycled for the preparation of the leaching agent solution, and the leachate is enriched by a semipermeable membrane, and the concentrated leachate obtained is all recycled for the preparation of the leaching agent solution, and the semipermeable membrane enriched water is directly discharged in compliance with the standards, thereby realizing the water recycling and water balance of the whole process of ionic rare earth mining. Therefore, the generation of wastewater can be avoided at the source, environmental risks can be eliminated, and production costs can be reduced.

[0044] (4) By adopting continuous multi-stage parallel flow leaching of leaching agents - continuous solid-liquid separation, and continuous multi-stage parallel flow elution of clean water - continuous classification - continuous solid-liquid separation, the mechanized and automated continuous production of the entire process of ionic rare earth mining is realized, which greatly reduces labor intensity.

[0045] (5) The use of continuous multi-stage parallel leaching of leaching agents and continuous multi-stage parallel leaching of clean water can effectively reduce the residual leaching agents in the tailings and avoid the environmental risks caused by a large amount of residual leaching agents in the tailings.

[0046] (6) By using continuous multi-stage parallel leaching with magnesium / calcium salt extractants and continuous multi-stage parallel leaching with clean water, the content of nutrients such as magnesium and calcium in the tailings can be regulated in a targeted manner according to the actual needs of tailings ecological restoration or comprehensive utilization, thereby improving soil compaction, meeting soil nutrient and ratio requirements, and promoting plant chlorophyll synthesis.

[0047] (7) The continuous multi-stage parallel leaching of leaching agents and continuous multi-stage parallel leaching of clean water can be used to treat all minerals containing ionic phase rare earths and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG1a is a schematic diagram of material flow of a continuous leaching method for ionic rare earth ores according to an embodiment of the present invention;

[0049] FIG1b is a second schematic diagram of the material flow of the continuous leaching method for ionic rare earth ores provided by an embodiment of the present invention;

[0050] FIG2a is a schematic diagram of a process flow of a continuous leaching method for ionic rare earth ores according to an embodiment of the present invention;

[0051] FIG2 b is a second process flow diagram of the continuous leaching method for ionic rare earth ores provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0053] The embodiment of the present invention provides a continuous leaching method for ionic rare earth ores, comprising the following steps:

[0054] In step S100, the ionic rare earth ore and the leaching agent solution are continuously put into a multi-stage leaching reactor for parallel leaching, and rare earth leachate and leaching tailings are obtained after solid-liquid separation.

[0055] In step S200, the leached tailings and clean water are continuously fed into a multi-stage leaching reactor for parallel leaching, and coarse-grained tailings, medium-grained tailings, fine-grained tailings and leachate are obtained after continuous classification and solid-liquid separation.

[0056] In step S300, the rare earth leachate and / or leaching solution is enriched and then recycled for preparing a leaching agent solution.

[0057] In the continuous parallel flow leaching process, the rare earth leachate flows back to the multi-stage leaching reactor; in the continuous parallel flow elution process, the leachate flows back to the multi-stage elution reactor.

[0058] The above technical solution adopts continuous multi-stage parallel flow leaching of the leaching agent, supplemented by the reflux of rare earth leachate for leaching of ionic rare earth ores, with high mass transfer efficiency. The leaching agent can fully contact and react with the ionic rare earth ore in a short time, and the leaching cycle is greatly shortened. 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 leached tailings are further washed with continuous multi-stage parallel flow of clean water, supplemented by the reflux of leachate for leaching of the leached tailings, which greatly reduces the consumption of the leaching agent, and can also effectively reduce the residual rare earth in the leached tailings, effectively improve the rare earth leaching rate, and at the same time can greatly reduce the amount of clean water used for leaching, and significantly reduce the production cost. In addition, after continuous multi-stage parallel leaching of the leached tailings, continuous classification methods such as hydrocyclones are used to efficiently separate and recover fine-grained tailings (primarily clay minerals such as kaolinite and halloysite), medium-grained tailings (primarily feldspar, etc.), and coarse-grained tailings (primarily quartz, etc.) while efficiently leaching and recovering rare earths. This achieves the graded and comprehensive utilization of different particle size components of ionic rare earth ores. When the sum of the volume flow rates of the rare earth leachate and leachate is less than or equal to the volume flow rate of the leaching agent solution, the rare earth leachate and / or leachate are enriched and treated and then recycled in its entirety for the preparation of the leaching agent solution, thereby achieving water recycling and water balance throughout the entire process of ionic rare earth mining, avoiding wastewater generation at the source, eliminating environmental risks, and reducing production costs.

[0059] Furthermore, the mixing methods in the multi-stage leaching reactor and the multi-stage elution reactor include at least one of stirring mixing, pneumatic mixing, spiral mixing and pipeline mixing.

[0060] Furthermore, the number of stages of the multi-stage leaching reactor is 2 to 10, the volume mass flow ratio of the leaching agent solution to the ionic rare earth ore is 0.4:1 to 1.5:1, and the single-stage residence time is 5 minutes to 30 minutes;

[0061] The number of stages of the multi-stage leaching reactor is 2 to 10, the volume mass flow ratio of clean water to leached tailings is 0.3:1 to 1.3:1, and the single-stage residence time is 5 minutes to 30 minutes.

[0062] The number of stages of the multi-stage leaching reactor is preferably 2 to 5; the number of stages of the multi-stage elution reactor is preferably 2 to 5.

[0063] When the sum of the volumetric flow rates of the rare earth leachate and leachate is less than or equal to the volumetric flow rate of the leaching agent solution, Figure 1a is a schematic diagram of the material flow for the corresponding continuous leaching method for ionic rare earth ores; Figure 2a is a schematic diagram of the process flow for the corresponding continuous leaching method for ionic rare earth ores. When the sum of the volumetric flow rates of the rare earth leachate and leachate is greater than the volumetric flow rate of the leaching agent solution, Figure 1b is a schematic diagram of the material flow for the corresponding continuous leaching method for ionic rare earth ores; Figure 2b is a schematic diagram of the process flow for the corresponding continuous leaching method for ionic rare earth ores.

[0064] Furthermore, the volume mass flow ratio of the rare earth leachate returned to the multi-stage leaching reactor to the ionic rare earth ore is 1:1 to 4:1; the volume mass flow ratio of the leachate returned to the multi-stage leaching reactor to the leached tailings is 1:1 to 4:1.

[0065] Furthermore, in the continuous co-current leaching process, the rare earth leachate flows back to the first-stage leaching reactor and the second-stage leaching reactor; in the continuous co-current elution process, the leachate flows back to the first-stage elution reactor and the second-stage elution reactor.

[0066] During the continuous co-current leaching process, the rare earth leachate may also flow back into the third-stage leaching reactor, or into the third-stage leaching reactor and the fourth-stage leaching reactor; during the continuous co-current elution process, the leachate may also flow back into the third-stage elution reactor, or into the third-stage elution reactor and the fourth-stage elution reactor.

[0067] Furthermore, the leaching agent solution includes at least one of magnesium sulfate, magnesium chloride, calcium chloride, sodium sulfate, sodium chloride, potassium chloride, potassium sulfate and ferrous sulfate.

[0068] The clean water includes at least one of surface water, groundwater, semi-permeable membrane enriched water and tap water.

[0069] 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.

[0070] Furthermore, except for hydrogen ions, the molar percentages of various cations in the leaching agent solution are: magnesium ions are 40% to 100%, calcium ions are 0% to 55%, and sodium ions, potassium ions and / or ferrous ions are 0% to 50%.

[0071] Furthermore, the classification method includes at least one of a hydrocyclone, a spiral classifier, a classification centrifuge and a classification vibrating screen;

[0072] The solid-liquid separation method includes: at least one of a thickener, a vacuum bag filter, a centrifugal filter and a horizontal spiral centrifuge.

[0073] Furthermore, the particle size range of the coarse-grained tailings is +40 mesh, the particle size range of the medium-grained tailings is -40 mesh to +200 mesh, and the particle size range of the fine-grained tailings is -200 mesh.

[0074] Furthermore, the enrichment treatment method includes at least one of: semipermeable membrane enrichment, adsorption enrichment, extraction enrichment and precipitation enrichment;

[0075] The semipermeable membrane includes: a nanofiltration membrane and / or a reverse osmosis membrane.

[0076] Referring to FIG. 2 , when the sum of the volume flow rates of the rare earth leachate and the elution is greater than the volume flow rate of the leaching agent solution, step S300 includes:

[0077] Step S310: Treat the rare earth leachate with a chemical enrichment method to obtain an enriched residual solution, which is circulated for preparing a leaching agent solution.

[0078] In step S320, the leachate is treated by a pre-enrichment method to obtain a concentrated leachate, and the concentrated leachate is recycled for preparing a leaching agent solution.

[0079] 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.

[0080] When the sum of the volume flow rates of the rare earth leachate and the leachate is greater than the volume flow rate of the leaching agent solution, the above technical solution adopts a semipermeable membrane to enrich the leachate, and the obtained concentrated leachate is all recycled for the preparation of the leaching agent solution. The obtained semipermeable membrane enriched water is directly discharged in compliance with the standards. After the rare earth leachate is enriched with rare earths by a chemical enrichment method, the obtained enriched residual liquid is all recycled for the preparation of the leaching agent solution, thereby realizing water recycling and water balance in the entire process of ionic rare earth mining, avoiding the generation of wastewater at the source, eliminating environmental risks, and reducing production costs.

[0081] The above technical solution is further described below with reference to several embodiments:

[0082] Example 1

[0083] The ionic rare earth grade of the ionic rare earth ore is 0.05%, and the particle size distribution is as follows: coarse particle size (+40 mesh) accounts for 48%, medium particle size (-40 to +200 mesh) accounts for 29%, and fine particle size (-200 mesh) accounts for 33%.

[0084] The ionic rare earth ore and the leaching agent solution are continuously fed into a multi-stage leaching reactor (mixing mode is stirring mixing) for parallel leaching, the leaching agent solution contains magnesium sulfate (hydrogen ion concentration is 0.00001 mol / L, and the cation concentration other than hydrogen ion is 0.20 mol / L), the volume mass flow ratio of the leaching agent solution to the ionic rare earth ore is 0.5:1, the number of leaching reactor stages is 3, the residence time of the single-stage leaching reactor is 30 minutes, and then the solid-liquid separation is continuously carried out in a thickener to obtain rare earth leachate and leached tailings; the volume mass flow ratios of the rare earth leachate refluxed to the first and second stage leaching reactors to the ionic rare earth ore are 1.5:1 and 1:1, respectively. Clean water and leached tailings are continuously fed into a multi-stage leaching reactor (mixed by stirring) for co-current leaching. The volume-to-mass ratio of clean water to leached tailings is 0.3:1. The leaching reactor has three stages, and the residence time in a single-stage leaching reactor is 30 minutes. The tailings are then continuously classified in a hydrocyclone and subjected to continuous solid-liquid separation in a thickener to produce coarse, medium, and fine-grained tailings and leachate. The leachate returning to the first and second stage leaching reactors has a volume-to-mass ratio of 1.5:1 and 1:1 to the leached tailings, respectively. The resulting rare earth leachate is enriched with rare earths by extraction, and the resulting enriched raffinate is recycled to prepare the leaching agent solution. The resulting leachate is then recycled to prepare the leaching agent solution. Under the above conditions, the rare earth leaching rate is 94.7%, the rare earth concentration of the rare earth leachate is 946.6 mg / L, the leaching agent consumption is 3.8t / t-REO, and the leaching cycle is 25.3 days (the effective volume of a single leaching reactor is 100m 3 , calculated based on the ore volume of a single mine being 100,000 tons); the particle size distribution of the graded tailings is as follows: coarse-grained (+40 mesh) accounts for 45%, medium-grained (-40 to +200 mesh) accounts for 25%, and fine-grained (-200 mesh) accounts for 30%. The graded tailings are comprehensively utilized; the enrichment residual liquid and leachate are all recycled.

[0085] The specific processes of Examples 2 to 70 and Comparative Examples 1 to 5 are shown in Tables 1 to 5.

[0086] Table 1

[0087] Table 2

[0088] Table 3

[0089] Table 4

[0090] Table 5

[0091] From the disclosed contents in Tables 1 to 5, we can see that:

[0092] (1) As can be seen from Example 3, Comparative Examples 1 and 2, based on the ore volume of a single mine of 100,000 tons, compared with in situ leaching and heap leaching, the continuous multi-stage parallel leaching (effective volume of a single leaching reactor of 100m3) with partial reflux of the leaching agent is more effective than that of the in situ leaching and heap leaching. 3 ), continuous multi-stage parallel leaching with clean water, the rare earth leaching rate increased from 89.8% to 93.1% to 96.0%, the rare earth concentration of the rare earth leachate increased significantly (from about 300 mg / L to 960 mg / L), the leaching agent consumption was greatly reduced (from 7.8 to 10.3 t / t-REO to 3.5 t / t-REO), the leaching cycle was greatly shortened (from 90 to 120 days to about 25 days), and the graded and comprehensive utilization of tailings was realized.

[0093] (2) From Example 3 and Comparative Example 3, it can be seen that the amount of ore in a single mine is 100,000 tons, and the continuous multi-stage parallel leaching without reflux of rare earth leaching solution (the effective volume of a single leaching reactor is 100m3) is the best. 3 ), the rare earth leaching rate and rare earth concentration of the rare earth leachate were significantly improved from 84.5% and 192 mg / L to 96.0% and 960 mg / L respectively, the leaching agent consumption was reduced (from 4.7 t / t-REO to 3.5 t / t-REO), the leaching cycle was greatly shortened (from 67 days to about 25 days), and the graded and comprehensive utilization of tailings was realized.

[0094] (3) From Example 3 and Comparative Example 4, it can be seen that the amount of ore in a single mine is 100,000 tons, and the continuous multi-stage parallel leaching without reflux of rare earth leaching solution (the effective volume of a single leaching reactor is 100m3) is the best. 3) and continuous multi-stage parallel flow leaching without leachate reflux. Compared with continuous multi-stage parallel flow leaching with partial reflux of leaching agent and continuous multi-stage parallel flow leaching with clean water, the rare earth leaching rate is similar (both about 96.0%), the rare earth concentration of rare earth leachate is significantly increased from 192 mg / L to 960 mg / L, the leaching agent consumption is reduced (from 4.7 t / t-REO to 3.5 t / t-REO), the leaching cycle is greatly shortened (from 67 days to about 25 days), the graded comprehensive utilization of tailings is realized, and the generation of a large amount of wastewater (3800m 3 / t-REO).

[0095] (4) From Example 3 and Comparative Example 5, it can be seen that the amount of ore in a single mine is 100,000 tons, and the continuous multi-stage parallel leaching without reflux of rare earth leaching solution (the effective volume of a single leaching reactor is 100m3) is 3 ) and continuous multi-stage parallel flow leaching without reflux of leachate, the rare earth leaching rate and leaching agent consumption are basically the same by using continuous multi-stage parallel flow leaching of partial reflux of leaching agent and continuous multi-stage parallel flow leaching of clean water. The rare earth concentration of rare earth leachate is significantly increased from 192mg / L to 960mg / L, and the leaching cycle is greatly shortened (from 67 days to about 25 days), realizing the graded comprehensive utilization of tailings. In addition, in Comparative Example 5, since the rare earth leachate and leachate are not refluxed, in order to realize the full recycling of water, the rare earth leachate and leachate must be pre-enriched, but the pre-enrichment processing volume is large (3800m 3 / t-REO), and when the rare earth leachate (usually containing high concentrations of calcium sulfate and aluminum sulfate) is enriched by reverse osmosis membrane, calcium sulfate and aluminum hydroxide scaling are very likely to occur.

[0096] (5) It can be seen from Examples 1 to 8 that as the hydrogen ion concentration 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, and the unit consumption of the leaching agent decreases slightly. This is because the ion exchange capacity of hydrogen ions is stronger than that of magnesium ions and they can also act as a leaching agent; as the magnesium sulfate concentration 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, and the unit consumption of the leaching agent is basically the same.

[0097] (6) From Examples 3 and 9 to 24, it can be seen that when the leaching agent solution is controlled to be 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 (except hydrogen ions) in the leaching agent solution are as follows: magnesium ions are 40% to 100%, calcium ions are 0% to 55%, sodium ions, potassium ions and / or ferrous ions are 0% to 50%, rare earths can be efficiently leached (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 efficiently leach both the ionic phase and the colloidal phase in the ionic rare earth ore, 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 salt, sodium salt or potassium salt.

[0098] (7) From Examples 3, 25-26, 43-44, and 70, it can be seen that the number of stages of the leaching reactor and the elution reactor (all 2-10) has no significant effect on the rare earth leaching rate, rare earth concentration of the rare earth leachate, and leaching agent consumption.

[0099] (8) It can be seen from Examples 3 and 27 to 29 that 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 of the rare earth leachate 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).

[0100] (9) It can be seen from Examples 3 and 30 to 32 that 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 the rare earth leachate, and leaching agent consumption change slightly, but the leaching cycle is significantly extended from about 4 days to about 25 days.

[0101] (10) It can be seen from Examples 3 and 33 to 36 that the volume mass flow ratio of the rare earth leachate to the ionic rare earth ore returned to the leaching reactor, the number of leaching reactor stages for the rare earth leachate return, and the distribution of the reflux rate at each stage have basically no effect on the rare earth leaching rate, rare earth concentration of the rare earth leachate, leaching agent consumption, leaching cycle, etc.

[0102] (11) From Examples 3, 37 to 42, and 56 to 64, it can be seen that the mixing mode of the leaching reactor and the elution reactor (stirring mixing, pneumatic mixing, spiral mixing, pipeline mixing), the classification mode (hydrocyclone, spiral classifier, classification centrifuge, classification vibrating screen), and the solid-liquid separation mode (thickener, vacuum bag filter, centrifugal filter, horizontal spiral centrifuge) have no significant effect on the rare earth leaching rate, rare earth concentration of rare earth leachate, and leaching agent consumption; however, the classification mode (hydrocyclone, spiral classifier, classification centrifuge, classification vibrating screen) will have a certain impact on the yield of tailings of different particle sizes.

[0103] (12) From Examples 3 and 45 to 48, it can be seen that as the volume mass flow ratio of clean water to leached tailings increases (from 0.3:1 to 1.3:1), the rare earth leaching rate, rare earth concentration of rare earth leachate, leaching agent consumption, leaching cycle, etc. change slightly. In addition, although the leachate must be pre-enriched, as the volume mass flow ratio of clean water to leached tailings increases (from 0.3:1 to 1.3:1), the leachate pre-enrichment processing capacity is 400 to 2000m 3 / t-REO (much lower than 3800m 3 / t-REO), and due to the low content of calcium sulfate and aluminum sulfate in the leachate, calcium sulfate and aluminum hydroxide scaling are not likely to occur.

[0104] (13) It can be seen from Examples 3 and 49 to 51 that 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 of rare earth leachate, leaching agent consumption, leaching cycle, etc. are relatively small.

[0105] (14) It can be seen from Example 3 and Examples 52 to 55 that the volume mass flow ratio of the leachate returned to the leaching reactor to the leached tailings, the number of leaching reactor stages for the leachate return, and the distribution of the reflux rate at each stage have basically no effect on the rare earth leaching rate, rare earth concentration of the rare earth leachate, leaching agent consumption, leaching cycle, etc.

[0106] (15) It can be seen from Examples 3, 65, 66 and 69 that the chemical enrichment methods (extraction and precipitation) of rare earth leachate have no significant effect on the rare earth leaching rate, rare earth concentration of rare earth leachate, leaching agent consumption, leaching cycle, etc.

[0107] (16) It can be seen from Examples 45 to 48 and Examples 66 to 69 that when the sum of the volume flow rates of the rare earth leachate and the leachate is greater than the volume flow rate of the leaching agent solution (e.g., the volume mass flow ratio of the rare earth leachate to the ionic rare earth ore, and the volume mass flow ratio of the clean water to the leached tailings are both 1:1), the leachate must be pre-enriched, but the leachate pre-enrichment processing capacity is 400 to 2400 m 3 / t-REO (much lower than 3800m 3 / t-REO), and due to the low content of calcium sulfate and aluminum sulfate in the leachate, calcium sulfate and aluminum hydroxide scaling are not easily generated. In addition, its impact on rare earth leaching rate, rare earth concentration in rare earth leachate, leaching agent consumption, leaching cycle, etc. is not significant.

[0108] The embodiment of the present invention is intended to protect a continuous leaching method for ionic rare earth ores, which includes the following steps: continuously feeding the ionic rare earth ore and the leaching agent solution into a multi-stage leaching reactor for parallel leaching, and obtaining rare earth leachate and leached tailings after solid-liquid separation; feeding the leached tailings and clean water into a multi-stage leaching reactor for parallel leaching, and 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 then recycling them all 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 leaching reactor. The above technical solution has the following effects:

[0109] (1) The continuous multi-stage parallel flow leaching of the leaching agent is supplemented by the reflux of the rare earth leachate for leaching of ionic rare earth ores. The mass transfer efficiency is high, and the leaching agent can fully contact and react with the ionic rare earth ores in a short time. The leaching cycle is greatly shortened. 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 leached with continuous multi-stage parallel flow of clean water, supplemented by the reflux of the leachate for leaching the leaching tailings. The consumption of the leaching agent is greatly reduced, and the residual rare earth in the leached tailings can be effectively reduced. The rare earth leaching rate is effectively improved. At the same time, the amount of clean water used for leaching can be greatly reduced, and the production cost is significantly reduced.

[0110] (2) After continuous multi-stage parallel leaching of the leached tailings, continuous classification methods such as hydrocyclones are used to efficiently separate and recover fine-grained tailings (mainly clay minerals such as kaolinite and halloysite), medium-grained tailings (mainly feldspar, etc.), and coarse-grained tailings (mainly quartz, etc.) while efficiently leaching and recovering rare earths, thereby achieving the graded and comprehensive utilization of different particle size components of ionic rare earth ores.

[0111] (3) When the sum of the volume flow rates of the rare earth leachate and the leachate is less than or equal to the volume flow rate of the leaching agent solution, the rare earth leachate and / or the leachate are enriched and treated and then all recycled for the preparation of the leaching agent solution, thereby realizing the water recycling and water balance of the whole process of ionic rare earth mining; when the sum of the volume flow rates of the rare earth leachate and the leachate is greater than the volume flow rate of the leaching agent solution, the rare earth leachate is enriched with rare earths by a chemical enrichment method, and the enriched residual liquid obtained is all recycled for the preparation of the leaching agent solution, and the leachate is enriched by a semipermeable membrane, and the concentrated leachate obtained is all recycled for the preparation of the leaching agent solution, and the semipermeable membrane enriched water is directly discharged in compliance with the standards, thereby realizing the water recycling and water balance of the whole process of ionic rare earth mining. Therefore, the generation of wastewater can be avoided at the source, environmental risks can be eliminated, and production costs can be reduced.

[0112] (4) By adopting continuous multi-stage parallel flow leaching of leaching agents - continuous solid-liquid separation, and continuous multi-stage parallel flow elution of clean water - continuous classification - continuous solid-liquid separation, the mechanized and automated continuous production of the entire process of ionic rare earth mining is realized, which greatly reduces labor intensity.

[0113] (5) The use of continuous multi-stage parallel leaching of leaching agents and continuous multi-stage parallel leaching of clean water can effectively reduce the residual leaching agents in the tailings and avoid the environmental risks caused by a large amount of residual leaching agents in the tailings.

[0114] (6) By using continuous multi-stage parallel leaching with magnesium / calcium salt extractants and continuous multi-stage parallel leaching with clean water, the content of nutrients such as magnesium and calcium in the tailings can be regulated in a targeted manner according to the actual needs of tailings ecological restoration or comprehensive utilization, thereby improving soil compaction, meeting soil nutrient and ratio requirements, and promoting plant chlorophyll synthesis.

[0115] (7) The continuous multi-stage parallel leaching of leaching agents and continuous multi-stage parallel leaching of clean water can be used to treat all minerals containing ionic phase rare earths and has a wide range of applications.

[0116] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A continuous leaching method for ionic rare earth ores, characterized in that: The steps include: Ionic rare earth ore and leaching agent solution are continuously put into a multi-stage leaching reactor for parallel leaching, and rare earth leachate and leaching tailings are obtained after solid-liquid separation; The leached tailings and clean water are continuously fed into a multi-stage leaching reactor for parallel leaching, and after continuous classification and solid-liquid separation, coarse-grained tailings, medium-grained tailings, fine-grained tailings and leachate are obtained respectively; After the rare earth leachate and / or the leachate are enriched and / or recycled for preparing the leaching agent solution; In the continuous parallel leaching process, the rare earth leachate flows back into the multi-stage leaching reactor; in the continuous parallel elution process, the leachate flows back into the multi-stage elution reactor.

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

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

4. The continuous leaching method for ionic rare earth ores according to claim 3, characterized in that: The volume mass flow ratio of the rare earth leachate refluxed into the multi-stage leaching reactor to the ionic rare earth ore is 1:1 to 4:1; The volume mass flow ratio of the leachate flowing back into the multi-stage elution reactor to the leached tailings is 1:1 to 4:

1.

5. The continuous leaching method for ionic rare earth ores according to claim 4, 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 elution process, the eluate flows back into the first stage elution reactor and the second stage elution reactor; During the continuous co-current leaching process, the rare earth leachate may also flow back into the third-stage leaching reactor, or into the third-stage leaching reactor and the fourth-stage leaching reactor; During the continuous co-current elution process, the eluate may also flow back into the third-stage elution reactor, or into the third-stage elution reactor and the fourth-stage elution reactor.

6. The continuous leaching method for ionic rare earth ores according to claim 5, characterized in that: The leaching agent solution includes: at least one of 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 surface water, groundwater, semi-permeable membrane enriched water and tap water.

7. The continuous leaching method for ionic rare earth ores according to claim 6, 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.

8. The continuous leaching method for ionic rare earth ores according to claim 7, characterized in that: Except for hydrogen ions, the molar percentages of various cations in the leaching agent solution are: magnesium ions are 40% to 100%, calcium ions are 0% to 55%, and sodium ions, potassium ions and / or ferrous ions are 0% to 50%.

9. The continuous leaching method for ionic rare earth ores according to claim 8, characterized in that: The classification method includes: at least one of a hydrocyclone, a spiral classifier, a classification centrifuge and a classification vibrating screen; The solid-liquid separation method includes: at least one of a thickener, a vacuum bag filter, a centrifugal filter and a horizontal spiral centrifuge.

10. The continuous leaching method for ionic rare earth ores according to claim 9, characterized in that: The particle size range of the coarse-grained tailings is +40 mesh, the particle size range of the medium-grained tailings is -40 mesh to +200 mesh, and the particle size range of the fine-grained tailings is -200 mesh.

11. The continuous leaching method for ionic rare earth ores according to claim 10, characterized in that: The enrichment treatment method includes: at least one of semipermeable membrane enrichment, adsorption enrichment, extraction enrichment and precipitation enrichment; The semipermeable membrane includes: a nanofiltration membrane and / or a reverse osmosis membrane.

12. The continuous leaching method for ionic rare earth ores according to any one of claims 1 to 11, characterized in that: When the sum of the volume flow rates of the rare earth leachate and the leachate is greater than the volume flow rate of the leaching agent solution, the enrichment treatment method comprises: Treating the rare earth leachate with a chemical enrichment method to obtain an enriched residual solution, and recycling the enriched residual solution for preparing the leaching agent solution; The leachate is treated by a pre-enrichment method to obtain a concentrated leachate, which is then recycled to prepare the leaching agent solution.

13. The continuous leaching method for ionic rare earth ores according to claim 12, 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 semipermeable membrane includes: a nanofiltration membrane and / or a reverse osmosis membrane.

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