CN111020242B - Process method for smelting and separating uranium, thorium and rare earth from monazite concentrate - Google Patents

Abstract

The invention provides a process method for smelting and separating uranium, thorium and rare earth from monazite concentrate, which takes the monazite concentrate as a raw material, and adopts the steps of wet-method bead grinding and magnetic separation for deferrization, alkali decomposition and transformation, trisodium phosphate product preparation, alkaline cake hydrochloric acid adding for preferential dissolution, rare earth chloride mixture product preparation, preferential dissolution slag hydrochloric acid adding for complete dissolution, amine extraction for uranium and uranium product preparation, acidic phosphorus-containing extraction for thorium and crude thorium product preparation, wastewater treatment and the like, so that the recovery rate of valuable resources such as uranium, thorium, rare earth and the like is more than 95 percent. After thorium is extracted, the extracted water phase returns to the optimal solution to recycle the rare earth chloride mixture, most of the production process water directly returns for recycling, and a small part of wastewater returns to the system for utilization after comprehensive treatment, thereby realizing zero discharge of wastewater. The invention has reliable process technology, common chemical materials and low consumption. The method ensures green and environment-friendly resource utilization of monazite, high-efficiency clean production and has obvious social and economic benefits.

Description

Process method for smelting and separating uranium, thorium and rare earth from monazite concentrate

Technical Field

The invention belongs to the technical field of uranium and thorium recovery, and particularly relates to a process method for smelting and separating uranium, thorium and rare earth from monazite concentrate.

Background

Monazite is a phosphate mineral of rare earth, thorium and uranium, is one of important rare earth minerals, and is also a rare earth ore which enters industrial utilization at the earliest. The process method of firstly carrying out alkali decomposition and then carrying out hydrochloric acid preferential dissolution on the mixture of the separated and recovered chlorinated rare earth is generally adopted, but the process method has the problems of low rare earth recovery rate, unrecoverable and utilized valuable resources such as uranium, thorium and the like, large wastewater discharge amount, difficult standard discharge, large amount of waste slag, incapability of being properly stored, non-compliance with relevant regulations of safety management regulations of GB14584-93 uranium, thorium ore and metallurgical radioactive waste safety management technical regulations, great danger to people in life, harm to ecological environment and the like. For example, the existing Xiangjiang rare earth plants and the Shangling far-reaching rare earth plants in Hunan province adopt that monazite is firstly subjected to alkali decomposition and transformation into alkali cakes, trisodium phosphate byproducts are recovered, then the alkali cakes are dissolved by hydrochloric acid, and chlorinated rare earth mixture products are recovered.

In the traditional process of recycling chlorinated rare earth mixture products by monazite smelting, the pH value of the optimized solution is higher due to the adoption of the alkali cake, and the rare earth is not completely dissolved, so that the rare earth element has certain loss, the rare earth recovery rate is lower, and the recovery rate is difficult to break through 93%.

Due to the fact that the mining, processing and recycling technology of the co-associated uranium ore resources has certain challenges, the utilization technology of the thorium resources in monazite is still in the research and development stage, and comprehensive recycling of valuable resources in the optimal slag is not paid attention. In the traditional monazite concentrate smelting separation and rare earth chloride mixture recovery process, valuable resources such as uranium and thorium are not comprehensively recovered, so that a large amount of excellent dissolved slag can be generated by the existing monazite treatment enterprises, radionuclides such as uranium and thorium in the excellent dissolved slag are abandoned, and the ecological environment is seriously damaged.

In conclusion, an improved method for separating uranium, thorium and rare earth from monazite concentrate is urgently needed, and the method is environment-friendly, efficient, clean and environment-friendly.

Disclosure of Invention

The invention mainly aims to provide a process method for smelting and separating uranium, thorium and rare earth from monazite concentrate, so that the recovery rate of valuable resources in the monazite concentrate is improved, and zero discharge of wastewater is realized.

The technical scheme adopted by the invention is as follows:

a process method for smelting and separating uranium, thorium and rare earth from monazite concentrate comprises the following steps:

(1) wet bead grinding crushing and magnetic separation iron removal: conveying monazite concentrate with the passing rate of more than 99.5 percent and the granularity of-80 meshes to a high-level stock bin through an automatic bag breaking and belt conveyer, dropping the monazite concentrate into a pulp making tank from the high-level stock bin to mix with a 50-60 percent NaOH solution, pumping the uniformly mixed slurry into a bead mill to perform wet bead milling crushing until the granularity of more than 99.5 percent is-320 meshes, pumping the monazite concentrate ore pulp with the milled granularity of-320 meshes into a magnetic separator to enrich valuable resources such as uranium, thorium and rare earth in the monazite concentrate, and dividing the ore pulp which is enriched in valuable resources such as rare earth, uranium, thorium and the like after the grinding and sorting into an alkali decomposition high-level tank; the refractory minerals containing titanium iron ore, rutile, zircon, etc. are disposed in the form of tailings.

(2) Alkali decomposition and alkali cake washing and filtering: pumping the grinded and selected qualified ore pulp into a quintuplet integrated alkali decomposition tank, wherein the quintuplet integrated alkali decomposition tank is a decomposition tank which is connected in series and integrates the functions of alkali decomposition, aging, pulping, washing and the like; controlling the initial sodium hydroxide concentration to be 50-60% NaOH solution, controlling the volume of the sodium hydroxide solution/the weight of the ground monazite concentrate to be 0.8-2.5/1, carrying out long-time continuous high-temperature alkali decomposition, adding water for heat preservation and aging after complete reaction, and siphoning supernatant in an alkali decomposition tank to obtain trisodium phosphate solution; adding hot water into the slurry at the bottom of the alkali decomposition tank after the supernatant liquid is siphoned for heat preservation pulping, siphoning the supernatant liquid again, adding hot water into the slurry after the supernatant liquid is siphoned for pulping, feeding the pulp into a multistage thickener for countercurrent washing and dephosphorization, and obtaining a filter cake as an alkali cake after the solid-liquid separation.

(3) Trisodium phosphate by-product preparation: immediately adding zinc powder and ferrous sulfate into the hot trisodium phosphate solution which is just separated out for precipitation and impurity removal treatment, and performing sealed barreling storage on filter residues obtained after solid-liquid separation; directly carrying out evaporation concentration, cooling crystallization and centrifuge filtration on the filtered liquid after impurity removal to obtain a crude product of solid trisodium phosphate, washing and impurity removal treatment on the crude product by pulping, and filtering and separating by the centrifuge to obtain a solid trisodium phosphate product, wherein the product quality meets the standard requirement of trisodium phosphate industrial (HGT2517 + 2009); the washed filtered mother liquor enters a waste alkali liquor evaporation concentration system, lime milk is added for desilicification treatment after concentration, NaOH in the obtained waste alkali liquor is more than 30%, and the obtained waste alkali liquor returns to the wet method bead grinding and magnetic separation deironing process for preparing 50-60% NaOH alkali liquor.

(4) Preferential dissolution of hydrochloric acid: adding the alkali cake into a 6-stage continuous dissolution optimum tank for hydrochloric acid optimum dissolution, wherein the initial acidity of hydrochloric acid is 6mol/L, stirring, heating for dissolution, controlling the pH value of the residual acid of the reaction to be 2.0-2.5, supplementing monazite alkali cake, adjusting the pH value to be 3.5-4.5, and precipitating and separating radionuclide and other impurities; the solution after separation and impurity removal is boiled, aged, subjected to solid-liquid separation and the like to obtain a rare earth chloride clear solution which is used for preparing a rare earth chloride mixture product in the subsequent step; the filtered residue is the optimum dissolved residue.

(5) Preparing a rare earth mixture product: adding a barium chloride solution and an ammonium sulfate solution into the rare earth chloride clear liquid, stirring and heating for removing and aging, aging and the like, storing filtered filter residues in a sealed barrel, evaporating, concentrating, cooling and crystallizing the filtrate to obtain a flaky mixed rare earth chloride product, wherein the product quality meets the GB/T4148-2015 standard requirement.

(6) Fully dissolving hydrochloric acid: putting the excellent dissolving slag in the step (4) into a 6-stage continuous dissolving full dissolving tank, controlling the reaction temperature and time and the acidity of residual acid, cooling to 50-60 ℃ after boiling, adding hydrogen peroxide with the concentration of 31% into the dissolved solution to ensure that valuable resources such as uranium, thorium, rare earth and the like in monazite concentrate fully react with hydrochloric acid and are transferred into the dissolved solution, siphoning to obtain a full dissolving solution, adding water into slurry after siphoning, stirring, and performing liquid-solid separation; and combining the last stage of washing water of the countercurrent washing with the hydrochloric acid full solution to obtain the extraction stock solution for uranium-thorium extraction.

(7) Extracting uranium and recycling: extracting uranium for the second time by using an N235 system extracting agent; extracting uranium from the extraction stock solution in the first extraction process to obtain a uranium-containing loaded organic phase; carrying out back extraction on the loaded organic phase by high-concentration hydrochloric acid to obtain a uranyl chloride solution; extracting enriched uranium for the second time from the uranyl chloride solution by using an N235 system extracting agent; carrying out back extraction by using a slightly acidic hydrochloric acid solution to obtain a uranyl chloride qualified solution, adding caustic soda flakes to the uranyl chloride qualified solution to precipitate uranium, and preparing a solid sodium uranate product; and carrying out back extraction on the iron chloride in the loaded organic phase after the uranium is back extracted by the high-concentration hydrochloric acid to remove the iron so as to obtain an iron chloride solution, and entering an acidic wastewater treatment system.

(8) Extraction and thorium recovery: the extraction water phase after uranium extraction also contains valuable resources such as thorium, rare earth and the like, and thorium is extracted by using an acidic phosphorus-containing extractant to obtain a thorium-containing loaded organic phase and a rare earth element-containing extraction water phase; washing the loaded organic phase of thorium with hydrogen peroxide to remove impurities, transferring the organic phase to a thorium hydroxide precipitation back-extraction tank, and adding alkali to carry out precipitation back-extraction to obtain a rough thorium hydroxide product; and (4) the extracted water phase after thorium extraction contains rare earth, and the extracted water phase returns to the hydrochloric acid preferential dissolution process to recover the rare earth chloride mixture.

(9) Wastewater treatment: carrying out superconducting magnetization treatment on the acidic wastewater generated in the uranium extraction and recovery system in the step (7) and the thorium extraction and recovery system in the step (8), loading an organic phase-reversal extraction ferric chloride solution in the step (7), returning effluent treated by the acidic wastewater treatment system to the extraction uranium extraction and recovery system in the step (7) for recycling, and packaging and storing precipitation slag obtained by superconducting magnetization by using a container; the extraction uranium extraction and recovery system in the step (7) and the extraction thorium extraction and recovery system in the step (8) are separated in the way of nano-filtration → electrodialysis → multi-effect evaporator and the like, nano-filtering the uranyl chloride precipitation mother liquor in the step (7) and the thorium chloride precipitation mother liquor in the step (8), the substance with molecular weight more than 200 enters a multi-effect evaporator evaporation concentration system, the substance with molecular weight less than 200 is treated by electrodialysis, the high-salinity waste liquid obtained by electrodialysis treatment is combined with the treatment water with molecular weight more than 200, concentrating and desalting by evaporation and concentration of a multi-effect evaporator, returning condensed water evaporated and concentrated by the multi-effect evaporator and light water prepared by electrodialysis to alkali decomposition and alkali cake washing and filtration, optimal hydrochloric acid solution and full hydrochloric acid solution utilization, and packaging and storing solid chloride obtained by evaporation, concentration, cooling and crystallization of the multi-effect evaporator by using a container.

Wherein, in the step (1), the monazite concentrate with the outsourcing granularity of-80 meshes is transported to a high-level bunker by adopting a belt conveying system after automatic unpacking, the monazite concentrate is discharged from a discharge hole of the high-level bunker and enters a pulping tank, mixing the pulp with 50-60% sodium hydroxide solution uniformly to prepare pulp, wherein the ratio of the volume of the sodium hydroxide solution to the weight of the ground monazite concentrate is 0.8-2.5/1, feeding the pulp into a wet bead mill through a rubber tube pump after uniform mixing, under the condition of normal pressure or micro pressure, the ore pulp of-320 meshes obtained after grinding is classified by a built-in grading device and discharged out of a bead mill, the monazite concentrate ore pulp of-320 meshes after bead milling is pumped into a permanent magnet magnetic separator, and (3) selecting insoluble substances such as ilmenite, rutile, zirconite and the like in the monazite concentrate ore pulp, wherein the selection rate is 5%. The magnetic impurities in the concentrate are less than 2%, the non-magnetic impurities are less than 1%, the light minerals are less than 1.8%, and the granularity is less than-320 meshes (more than 99.5%); the combined amount of rare earth in the monazite concentrate after magnetic separation is correspondingly improved by 1-10 percent, the content of Fe is less than 1.0 percent, and the quality of the monazite concentrate completely meets the XB/T104-2015 standard requirement of the monazite concentrate. And (3) carrying out dense water separation treatment on the monazite concentrate ore pulp enriched with uranium, thorium and rare earth after magnetic separation to obtain qualified ore pulp meeting the requirements, and pumping the qualified ore pulp into an alkali decomposition elevated tank by using a pump.

In the step (2), the qualified ore pulp in the elevated tank is pumped into a quintuplet integrated alkali decomposition tank, the initial concentration of sodium hydroxide in the pulp is 50-60 percent NaOH, the liquid-solid ratio is 0.8-2.5/1 (volume/weight), and the pulp is heated for high-temperature alkali decompositionThe reaction is complete, the reaction temperature is 140-150 ℃, and the continuous alkali decomposition reaction time is 4-14 h. The alkali decomposition rates of valuable resources of uranium, thorium and rare earth in monazite concentrate are respectively that REO is more than or equal to 95 percent and U is₃O₈≥98％，ThO₂More than or equal to 98 percent. Adding 90 ℃ production water with the volume being one time of the weight of the ore pulp into the alkaline decomposition slurry for heat preservation and aging, wherein the temperature for heat preservation and aging is not lower than 90 ℃ and the time is 12 hours. After the 1 st standing, the supernatant is decomposed by adopting siphon separation alkali to recover trisodium phosphate solution; adding water into the alkaline decomposition bottom slurry, stirring to prepare uniform slurry, then carrying out the 2 nd standing siphon separation to recover supernatant, combining the two times of standing siphon supernatant to obtain trisodium phosphate solution, and preparing a crude trisodium phosphate product by adopting a triple-effect evaporation concentration and cooling crystallization mode. And (3) standing and separating the bottom slurry for the 2 nd time to obtain bottom slag, adding hot water, and stirring to prepare slurry, wherein the bottom slurry is 1: (4-5) (v/v), transferring the stirred homogenate to a thickener by using a pump for sedimentation separation, and separating liquid and solid by using a 2-4-stage countercurrent thickener for sedimentation separation and a 1-2-stage box filter press. After the alkaline cake is subjected to multistage countercurrent washing dephosphorization treatment, the pH value of the last alkaline cake washing water is controlled to be 7-8, and P in the washing water₂O₅Less than 1.2g/L, and can enter subsequent hydrochloric acid for preferential dissolution.

And (3) concentrating the filtered mother liquor obtained after washing the crude trisodium phosphate product until NaOH in the solution is more than 30%, transferring the concentrated mother liquor to a silicon removal tank, adding lime milk to remove silicon, returning the waste alkali liquor obtained after silicon removal to an alkali liquor preparation tank, adding solid sodium hydroxide in proportion, and pumping the solution into an alkali liquor head tank for later use when the prepared liquid contains 50-60% of NaOH. The primary aged and secondary standing siphoned supernatants from the alkaline decomposer were combined to a pre-concentrated trisodium phosphate solution. Adding zinc powder 0.25% times (monazite) ore weight and ferrous sulfate 1% times (monazite) ore weight into hot trisodium phosphate solution, stirring, maintaining the temperature, removing impurities, filtering with a box-type filter press, separating out filter residue, storing the filter residue in a sealed barrel, and removing trisodium phosphate from the filtrate to perform evaporation and concentration. And (3) evaporating and concentrating the obtained trisodium phosphate filtrate by using a triple-effect evaporator, and transferring the concentrated supersaturated trisodium phosphate solution into a crystallizer for cooling crystallization when the Baume degree is 28-32 Be degrees. And filtering the cooled and crystallized trisodium phosphate crystal slurry by using a two-stage piston pusher centrifuge to obtain a crude trisodium phosphate product, adding deionized water with the volume of 0.5-1 time of that of the crude trisodium phosphate product to perform pulping and washing, and separating by using the two-stage piston pusher centrifuge to obtain a trisodium phosphate byproduct, wherein the product quality meets the standard of industrial trisodium phosphate (HGT 2517-2009).

In the step (4), an alkali cake obtained by alkali decomposition is added into a hydrochloric acid optimum solution tank to perform 6-level hydrochloric acid optimum solution, the initial concentration of hydrochloric acid used for dissolving is 6mol/L, the hydrochloric acid is prepared from an extracted water phase after thorium extraction and a certain amount of concentrated hydrochloric acid, heating, stirring and dissolving are performed, the pH value of the optimum solution is controlled to be 2.0-2.5 after the optimum solution is completely dissolved, the alkali cake is added to adjust the pH value of the optimum solution, the acidity of the optimum solution is controlled to be 3.5-4.5, heating, stirring and reacting are continuously performed for 4-6 h, boiling is performed for 0.5-1 h, aging is performed for 8-12 h, elements such as Fe, Al, U, Th and the like are fully precipitated, solid-liquid separation is performed through a chamber filter press, and rare earth chloride clear liquid (REO is required to be not less than 150g/L) is obtained to be used for preparing rare earth chloride mixture products, and the optimum solution slag is used for the subsequent hydrochloric acid total-dissolved uranium-thorium separation process.

In the step (5), adding a barium chloride solution and an ammonium sulfate solution into a rare earth chloride impurity removal tank, removing impurities and removing impurities from the rare earth chloride solution, wherein the impurity removal temperature is more than 40 ℃, the time is 0.5-1.5 hours, and the aging time is more than 8 hours, filtering the mixture by using a box filter press, storing the filter residues in a sealed barrel, evaporating and concentrating the filtrate by using a multi-effect evaporator, controlling the temperature to be 102-150 ℃, and the vacuum degree to be 600-700 mmHg, concentrating to obtain a supersaturated rare earth chloride solution, cooling and crystallizing the supersaturated rare earth chloride solution on a crystallization and sheet-making device to obtain a flaky rare earth chloride product, wherein the product quality meets the GB/T4148 ion 2015 standard requirement.

In the step (6), the optimal solution slag is added into an acid complete solution tank to carry out 6-stage hydrochloric acid dissolution, the initial concentration of dilute hydrochloric acid used for hydrochloric acid complete solution is 6mol/L, the solid-to-liquid ratio of the optimal solution slag (kg) to the dilute hydrochloric acid (L) is 1 (1-1.5), the reaction temperature is 80-95 ℃, the reaction time is 4-6 h, the acidity of the residual acid is controlled to be 2-3 mol/L HCl, the solution is boiled for 1-1.5 h, 31% hydrogen peroxide is added when the temperature of the solution is reduced to 50-60 ℃ after boiling, the proportion of the hydrogen peroxide is added according to (0.010-0.200) t hydrogen peroxide/t wet optimal solution slag, aging is carried out for more than 8h, so that valuable resources in the optimal solution slag are completely dissolved and enter a liquid phase, and valuable resources such as uranium, thorium, rare earth and the like are collected by adopting a siphon supernatant method. Adding hot washing water into a stirring tank with slurry stored after siphoning, uniformly stirring and pulping according to the liquid-solid ratio of the volume of the hot washing water to the volume of the slurry being (1-3): 1(V/V), pumping into a thickener, and filtering by adopting 2-4 stages of countercurrent dense settling separation and 1-2 stages of van-type filter press to perform liquid-solid separation. Supernatant of the first-stage thickener overflows to uranium extraction stock solution for preparation, washing water of the second-stage thickener is pumped into a stirring tank below the last-stage thickener for pulping and washing, and is pumped into the first-stage thickener for precipitation and separation; the underflow slurry of the thickener flows into a pulping tank and then enters the next thickener, the underflow slurry of the last thickener enters a van-type filter press for filtration, and acid insoluble slag is packaged and stored by a container. And (3) combining the last stage of washing water with dissolving liquid containing valuable resources such as uranium, thorium, rare earth and the like in countercurrent washing to obtain the extraction stock solution for uranium-thorium extraction.

In the step (7), 2-5-stage countercurrent extraction is carried out in the first uranium extraction process to extract uranium, and the loaded organic phase obtained by extraction contains uranium and iron. Firstly, carrying out 4-9 level back extraction by using 2.0-3 mol/L hydrochloric acid to obtain a uranyl chloride solution with a lower concentration, and then carrying out 4-9 level back extraction by using 0.1mol/L hydrochloric acid to remove iron to obtain an iron chloride solution, and feeding the iron chloride solution into a subsequent wastewater treatment system; and (3) taking the uranyl chloride solution with lower concentration generated in the primary extraction uranium extraction process as an extraction stock solution to carry out secondary extraction enriched uranium, loading organic phase to carry out reverse extraction on uranium and iron to obtain a lean organic phase, regenerating, washing and acidifying the lean organic phase through sodium carbonate, and enabling the organic phase to enter the next cyclic extraction uranium extraction and recovery process, wherein the organic phase is recycled. And adding alkali into the obtained uranyl chloride solution to precipitate uranium to prepare a solid sodium uranate product, wherein the quality of the uranium product meets the standard requirement of technical conditions of diuranate (EJ/T803-93). And (3) thorium and rare earth are contained in the extracted water phase after uranium extraction, and thorium is recovered through subsequent extraction separation.

In the step (8), the raffinate water phase after uranium extraction also contains valuable resources such as thorium and rare earth, thorium is extracted by using an acidic phosphorus-containing extractant, one or a combination of P204, P507, Cyanex272 and TBP is used as a thorium extraction organic phase, 4-level countercurrent extraction is carried out to obtain a thorium-containing loaded organic phase, the raffinate water phase after thorium extraction is a rare earth chloride-containing solution, and the raffinate water phase is returned to the step (4) to recover rare earth chloride mixtures. Washing and impurity removing are carried out on the loaded organic phase containing thorium chloride, then the loaded organic phase is transferred to a thorium hydroxide precipitation back extraction tank, and hot sodium hydroxide solution is added for precipitation back extraction to obtain a rough thorium hydroxide product.

In the step (9), adding the thorium hydroxide crude product obtained by the system into the ferric chloride wastewater, adjusting the pH to 4.5 +/-1, reacting for 30-90 min, filtering and deslagging by a box filter press, adding magnetic seeds into the filtrate, stirring and fully mixing, adding a mixed flocculant, and controlling the concentration of the flocculant in the solution to be 200 multiplied by 10^-6PAC+2×10^-6PAM, then settling and separating by a thickener, introducing overflow supernatant into a superconducting magnetization separation system for superconducting magnetization treatment, returning superconducting magnetization separation effluent to the system for recycling, discharging mud in filter residues through a sludge discharge port, storing by a packaging container, and returning separated magnetic seeds to the wastewater treatment system for utilization. Firstly, carrying out nanofiltration treatment on uranium precipitation mother liquor and thorium precipitation mother liquor, intercepting chlorate with molecular weight more than 200, carrying out electrodialysis treatment on substances with molecular weight less than 200, returning light water to alkali decomposition and alkali cake washing and filtering, hydrochloric acid optimum solution and hydrochloric acid total solution utilization, combining obtained high-salinity concentrated wastewater and chlorate wastewater with molecular weight more than 200, carrying out evaporation concentration desalting treatment through a multi-effect evaporator, returning condensate water obtained by evaporation concentration of the multi-effect evaporator to alkali decomposition and alkali cake washing and filtering, hydrochloric acid optimum solution and hydrochloric acid total solution utilization, and storing solid chlorate obtained by evaporation concentration of the multi-effect evaporator by using a packaging container; the electrodialysis treatment can also be an ultrafiltration treatment.

The invention has the beneficial effects that:

1. the problems that uranium and thorium resources are wasted and the like in the prior art are solved, the recovery rates of valuable resources such as uranium, thorium and rare earth are all larger than 95%, and the recovery rate of valuable resources in monazite concentrate is improved.

2. The chemical material consumption is low, and the process is simple and flexible.

3. Most of process water generated in the production process is directly returned to the system for reuse, and part of wastewater is returned to the system for utilization after being treated by the wastewater treatment system, so that zero discharge of wastewater is realized, the technology is green, environment-friendly, efficient and clean in production, environment-friendly is realized, and obvious social and economic benefits are achieved

4. The extraction process has no emulsification phenomenon, the consumption of the extracting agent is low, and the efficiency of extracting uranium and thorium is up to more than 99%.

Drawings

FIG. 1 is a flow chart of a process for smelting and separating uranium, thorium and rare earth from monazite concentrate.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

As shown in figure 1, the invention provides a process method for smelting and separating uranium, thorium and rare earth from monazite concentrate, which comprises the following steps:

(1) wet bead milling and magnetic separation iron removal: the monazite concentrate with the granularity of minus 80 meshes (accounting for more than 99.5 percent) is conveyed to a high-level stock bin through an automatic bag breaking and belt conveyer, the monazite concentrate falls into a pulp making tank from the high-level stock bin to be mixed with 50-60 percent NaOH solution, the uniformly mixed slurry is pumped into a bead mill to be subjected to wet bead milling until the granularity is minus 320 meshes (accounting for more than 99.5 percent), and the monazite concentrate pulp with the granularity of minus 320 meshes after being milled is pumped into a permanent magnet magnetic separator, so that valuable resources such as uranium, thorium, rare earth and the like in the monazite concentrate are enriched, and insoluble minerals such as titanium-containing iron ore, rutile, zirconite and the like are treated in a tailing mode. And pumping the ore pulp which is subjected to grinding and sorting and is enriched with valuable resources such as rare earth, uranium, thorium and the like into an alkali decomposition head tank after water separation, and then entering alkali decomposition.

(2) Alkali decomposition and alkali cake washing and filtering: pumping the ground qualified ore pulp into a quintuplet continuous alkali decomposition tank, carrying out long-time continuous high-temperature alkali decomposition with the initial sodium hydroxide concentration of 50-60% NaOH and the liquid-solid ratio of 0.8-2.5/1 (volume/weight), adding water after the reaction is completed, keeping the temperature and aging, siphoning supernatant to obtain trisodium phosphate solution, heating washing water in the bottom pulp of the decomposition tank, carrying out heat preservation stirring pulping, washing with multiple counter-currents to remove P, and finally carrying out solid-liquid separation through a box filter press to obtain a filter cake as an alkali cake.

(3) Trisodium phosphate by-product preparation: adding a certain amount of zinc powder and ferrous sulfate into a hot trisodium phosphate solution for impurity removal, sealing and barreling filter residue after solid-liquid separation for storage, carrying out evaporation concentration and cooling crystallizer on a filtrate, separating crystals and a mother solution by centrifugal filtration, pulping, washing and impurity removal treatment on a coarse crystal, and carrying out centrifugal filtration to obtain a trisodium phosphate product, wherein the trisodium phosphate product meets the standard of industrial trisodium phosphate (HGT 2517-. Evaporating and concentrating the crystallized mother liquor, adding lime milk to carry out causticization and desilicification treatment, adding caustic soda flakes to prepare 50-60% NaOH solution after concentrating and desilicifying the waste alkali liquor, and returning to the ore grinding process.

(4) Preferential dissolution of hydrochloric acid: adding a certain amount of thorium raffinate and hydrochloric acid into an alkali cake to perform hydrochloric acid preferential dissolution, heating to dissolve the initial hydrochloric acid with acidity of 6mol/L HCl, controlling the reaction time, the temperature and the pH value of a dissolved solution, adding the alkali cake into the dissolved solution to adjust the pH value (the pH value is 3.5-5.5) when the pH value of the solution is 2.0-2.5, boiling, aging and performing solid-liquid separation to obtain a rare earth chloride solution, wherein the filtrate is used for preparing a rare earth chloride mixture product, and the filter residue (preferential dissolution residue) enters a subsequent hydrochloric acid complete dissolution process.

(5) Preparing a rare earth mixture product: adding a certain amount of barium chloride and ammonium sulfate solution into the rare earth chloride solution, stirring and heating for radioactive substance removal treatment, aging and filtering, sealing filter residues for barreled storage, evaporating, concentrating, cooling, slicing to obtain a flaky mixed rare earth chloride product, wherein the product quality meets the standard requirement of GB/T4148-.

(6) Fully dissolving hydrochloric acid: putting the optimal dissolving slag into an acid dissolving tank for hydrochloric acid total dissolution, controlling the reaction temperature and time and the acidity of the residual acid, cooling to a certain temperature interval after boiling, adding a proper amount of hydrogen peroxide with the concentration of about 31% into a dissolved solution to enable valuable resources such as uranium, thorium, rare earth and the like in monazite concentrate to fully react with the hydrochloric acid and be completely dissolved, standing and cooling, siphoning to obtain a total dissolved solution, adding water into slurry after siphoning, stirring, pulping and washing, performing liquid-solid separation, performing countercurrent washing, and combining the last washing water and a uranium, thorium and rare earth containing total solution into an extraction stock solution for uranium-thorium extraction, wherein the content of hydrochloric acid in the extraction stock solution is 2-3 mol/L HCl.

(7) Extracting uranium and recycling: extracting uranium for the second time by using an N235 system extracting agent; extracting uranium from the extraction stock solution in the first extraction process to obtain a uranium-containing loaded organic phase; carrying out back extraction on the loaded organic phase by high-concentration hydrochloric acid to obtain a uranyl chloride solution; extracting enriched uranium for the second time from the uranyl chloride solution by using an N235 system extracting agent; carrying out back extraction by using a slightly acidic hydrochloric acid solution to obtain a uranyl chloride qualified solution, adding caustic soda flakes to the uranyl chloride qualified solution to precipitate uranium, and preparing a solid sodium uranate product; and carrying out back extraction on the iron chloride in the loaded organic phase after the uranium is back extracted by the high-concentration hydrochloric acid to remove the iron so as to obtain an iron chloride solution, and entering an acidic wastewater treatment system.

(8) Extraction and thorium recovery: and (3) extracting thorium and rare earth in the raffinate water phase after uranium extraction, extracting thorium by adopting an acidic phosphorus-containing extractant to obtain a thorium-containing loaded organic phase and a raffinate water phase containing rare earth elements, washing the loaded organic phase of thorium with hydrogen peroxide to remove impurities, transferring the washed organic phase to a thorium hydroxide precipitation back-extraction tank, and adding alkali for precipitation to obtain a rough thorium hydroxide product. And (4) extracting thorium to obtain an extracted water phase containing rare earth, and returning to the hydrochloric acid preferential dissolution process to recover the chlorinated rare earth mixture.

(9) Wastewater treatment: carrying out superconducting magnetization treatment on the acidic wastewater generated in the uranium extraction and recovery system in the step (7) and the thorium extraction and recovery system in the step (8), loading an organic phase-reversal extraction ferric chloride solution in the step (7), returning effluent treated by the acidic wastewater treatment system to the extraction uranium extraction and recovery system in the step (7) for recycling, and packaging and storing precipitation slag obtained by superconducting magnetization by using a container; the extraction uranium extraction and recovery system in the step (7) and the extraction thorium extraction and recovery system in the step (8) are separated in the way of nano-filtration → electrodialysis → multi-effect evaporator and the like, nano-filtering the uranyl chloride precipitation mother liquor in the step (7) and the thorium chloride precipitation mother liquor in the step (8), the substance with molecular weight more than 200 enters a multi-effect evaporator evaporation concentration system, the substance with molecular weight less than 200 is treated by electrodialysis, the high-salinity waste liquid obtained by electrodialysis treatment is combined with the treatment water with molecular weight more than 200, concentrating and desalting by evaporation and concentration of a multi-effect evaporator, returning condensed water evaporated and concentrated by the multi-effect evaporator and light water prepared by electrodialysis to alkali decomposition and alkali cake washing and filtration, optimal hydrochloric acid solution and full hydrochloric acid solution utilization, and packaging and storing solid chloride obtained by evaporation, concentration, cooling and crystallization of the multi-effect evaporator by using a container.

In the step (1), the monazite concentrate with the granularity of-80 meshes (accounting for more than 99.5%) is unpacked by an automatic unpacking system, the mineral is conveyed to a monazite bin by a belt conveying system for temporary storage, the concentrate is discharged through a discharge hole at the lower part of the bin and is sent into a pulping stirring tank, 50% -60% of sodium hydroxide solution is added, pulping is carried out according to the liquid-solid ratio of the volume of the sodium hydroxide solution to the weight of the monazite concentrate being 0.8-2.5/1 (volume/weight), the uniformly mixed ore pulp is sent into a wet bead mill through a rubber tube pump, under the condition of normal pressure or micro pressure, ore pulp with the granularity of-320 meshes (accounting for more than 99.5%) is obtained after grinding, and the ore pulp is discharged out of the mill in a grading way through a built-in grading device.

In the step (1), the ore pulp of-320 meshes (accounting for more than 99.5%) obtained after grinding is pumped into a permanent magnet magnetic separator, and the processing capacity of the permanent magnet magnetic separator is as follows: 4-7T/h, and the magnetic separation intensity of a magnetic separator is 0.5-1.8T; and selecting insoluble minerals such as ilmenite, rutile, zirconite and the like in the monazite concentrate ore pulp in a tailing slag mode, wherein the selection rate is 5%. The magnetic impurities in the concentrate are less than 2%, the non-magnetic impurities are less than 1%, and the light minerals are less than 1.8%; the total amount of rare earth in the monazite concentrate is correspondingly improved by 1 to 10 percent, and the Fe in the monazite concentrate is ensured₂O₃Content (Fe)₂O₃Less than 1.5 percent of the total weight of the iron-containing iron-based rare earth completely meets the quality standard requirement of monazite concentrate (XB/T104-2015), and the iron content of the iron-containing rare earth is less than 1.0 percent. And then carrying out dense water separation on the qualified monazite concentrate ore pulp subjected to the magnetic separation by the mill to obtain qualified ore pulp with the granularity meeting the alkali decomposition requirement, and pumping the qualified ore pulp subjected to the mill into an alkali decomposition head tank by a pump for later use.

In the step (2), the qualified ore pulp in the head tank is pumped into a quintuplet continuous alkali decomposition tank, and the initial concentration of a sodium hydroxide solution in alkali decomposition is 50 percent60 percent of NaOH, when the concentration is not enough, the initial concentration of NaOH in the slurry can be ensured by supplementing a proper amount of solid sodium hydroxide, the liquid-solid ratio is 0.8-2.5/1 (volume/weight), the high-temperature alkaline decomposition is carried out by heating, the reaction temperature is 140-150 ℃, the continuous alkaline decomposition reaction time is 4-14 h, the conversion rates of alkaline decomposition of valuable resources of uranium, thorium and rare earth in monazite concentrate are respectively equal to or more than 95 percent, and U is equal to or more than 95 percent₃O₈≥98％，ThO₂≥98％。

In the step (2), production water (hot water at 90 ℃) with one time volume is added into the bottom slurry of the alkali decomposition reactor for heat preservation and aging for 12 hours, the supernatant (trisodium phosphate solution) of the alkali decomposition is recovered by adopting a siphon separation mode after standing, an alkali cake and washing water are obtained by a multi-stage countercurrent thickener settling separation and box filter press filtering separation method, and the dephosphorization treatment of the alkali cake is carried out.

In the step (2), after the 1 st standing of the alkali decomposition reactor, recovering the supernatant of alkali decomposition by adopting a siphon separation method, adding water into the bottom slurry and uniformly stirring to prepare pulp, recovering the supernatant by still adopting a standing siphon separation method, combining the two times of standing and siphon supernatants, obtaining a solution after impurity removal and desorption treatment and washing and impurity removal treatment of trisodium phosphate coarse crystal pulp, and preparing the trisodium phosphate byproduct by adopting an evaporation concentration and cooling crystallization method.

In the step (2), adding hot water into the bottom slurry obtained by the 2 nd standing separation in the alkali decomposition reactor, stirring and pulping, transferring the mixture into a thickener through a pump for sedimentation separation, and separating liquid and solid through 2-4-stage countercurrent thickener sedimentation separation and 1-2-stage box filter press separation. The bottom slurry is made into pulp by a stirring tank below a thickener and a chamber filter press, enters a next-stage thickener for sedimentation separation or a chamber filter press for alkali cake and washing water separation, and after multi-stage countercurrent washing dephosphorization, the washing water overflowing from the first-stage thickener automatically flows into an alkali decomposing tank for pulping and washing; the pH value of the last washing water is controlled to be 7-8, and P in the washing water₂O₅Less than 1.2g/L, and the washed alkali cake enters the subsequent hydrochloric acid preferential dissolution process.

In the step (3), the supernatant obtained by standing siphon separation in the alkaline decomposition reactor and the supernatant of the standing wash water washed for the 1 st time in the alkaline decomposition reactor are combined into the trisodium phosphate solution before concentration. Adding zinc powder which is 0.25 percent of the weight of the monazite ore and ferrous sulfate which is 1 percent of the weight of the monazite ore into the obtained hot trisodium phosphate solution, removing impurities and discharging, reacting for 0.5-4 h at the reaction temperature of 25-80 ℃, aging for 45-60 min, filtering, conveying the filtrate to a receiving tank for temporary storage of the filtrate which is removed by the trisodium phosphate, and sealing and storing the filtrate which is low-discharge tailings which are the filter residues generated in the process of removing impurities and discharging.

And (3) evaporating and concentrating the obtained trisodium phosphate clear solution by using a three-effect evaporator, and transferring the concentrated trisodium phosphate supersaturated solution into a crystallizer for cooling and crystallizing when the solution is concentrated to a Baume degree of 28-32 Be degrees. Filtering the trisodium phosphate supersaturated slurry by a double-stage piston pusher centrifuge to respectively obtain trisodium phosphate crystallization filtering mother liquor and a trisodium phosphate crude product. Evaporating and concentrating the obtained crystallization filtering mother liquor until the concentration of sodium hydroxide in the solution is more than 30%, adding quicklime for causticizing and desiliconizing to obtain concentrated solution, and returning to the bead milling process for preparing the sodium hydroxide solution. And adding deionized water with the volume of 0.5-1.0 BV into the coarse trisodium phosphate product obtained by centrifugation for pulping and washing, and filtering by using a two-stage piston pusher centrifuge to obtain a solid trisodium phosphate product which meets the standard requirement of trisodium phosphate industrial (HGT 2517-. The liquid trisodium phosphate-containing solution obtained by filtering can be subjected to activated carbon adsorption decoloration treatment and then returned to an evaporation concentration station for recrystallization treatment.

In the step (4), the alkali cake obtained in the alkali decomposition step is added with a dilute hydrochloric acid solution 1-2 times (ore pulp) in weight, and dissolved in a six-stage continuous dissolution tank, the dilute hydrochloric acid is prepared by adding a certain amount of industrial hydrochloric acid into the raffinate water phase after thorium extraction, and the acidity of the dilute hydrochloric acid is about 6 mol/L. Stirring, heating and dissolving, wherein the dissolving temperature is controlled to be 80-95 ℃; simultaneously adding a proper amount of hydrogen peroxide to completely dissolve cerium in the alkali cake, wherein the reaction residence time of each dissolving tank from the 1 st stage to the 3 rd stage of dissolving process is 1.5-2.0h, after the total reaction time of the first three stages of dissolving is 4-6 h, the pH value of hydrochloric acid in the dissolving solution after complete dissolving is controlled to be about pH: 2.0 to 2.5. Adding a proper amount of alkali cake into the 4 th-stage dissolving tank, adjusting the pH value of preferential dissolution of hydrochloric acid, controlling the reaction residence time of each dissolving tank from the 4 th stage to the 6 th stage in the dissolving process to be 2.0-2.5 h, and controlling the pH value of the suspension liquid discharged from the 6 th-stage dissolving tank to be pH: 3.5 to 5.5. Then transferring to the preferential solution aging process.

And (4) pumping the slurry obtained by the preferential dissolution into an ageing tank, boiling for 0.5-1 h, preserving heat and ageing for 8-12 h, performing solid-liquid separation on the suspension obtained by the ageing through a box filter press to obtain a rare earth chloride solution (REO is more than or equal to 150g/L) for preparing a mixed rare earth chloride product in the subsequent step, and using filter residues (preferential dissolution residues) in the subsequent uranium-thorium fully-dissolved hydrochloric acid separation process.

In the step (5), barium chloride (1 kgBaCl) is added to the rare earth chloride solution obtained by preferential dissolution of hydrochloric acid₂/m³Rare earth chloride solution) and ammonium sulfate (2kg (NH)₄)₂SO₄/m³Rare earth chloride solution) is subjected to impurity removal and radioactive substance removal treatment, the impurity removal and radioactive substance removal temperature is 45 ℃, the time is 0.5-1.5 h, and the aging time is more than 8 h. And filtering the obtained rare earth chloride solution by using a box type filter press, removing impurities and radium, washing filter residues, and storing the filter residues in a radioactivity-removed residue storage filled in a sealed barrel.

In the step (5), evaporating, concentrating, cooling and crystallizing the rare earth chloride filtrate after removing impurities and radium, controlling the evaporating and concentrating temperature of the multi-effect evaporator to be 102-150 ℃, controlling the vacuum degree to be 600-700 mmHg, and obtaining a sheet rare earth chloride product on a crystallization and sheet-making device by using the concentrated supersaturated solution of the rare earth chloride, wherein the product quality meets the standard requirement of GB/T4148-.

In the step (6), the prepared 6mol/L solution is measured by a dilute hydrochloric acid high-level metering tank and then injected into a dissolving tank, stirring is started, heating and preheating are carried out, when the temperature is raised to 40 ℃, monazite excellent dissolving slag with the liquid-solid ratio (1-1.5): 1 is added into the dissolving tank, heating, stirring and dissolving are carried out, the reaction temperature is controlled to be 80-95 ℃, the reaction time is 4-6 hours, the acidity of the residual hydrochloric acid is about 2-3 mol/L HCl, and then boiling is carried out (1-1.5 hours).

In the step (6), heating is stopped after boiling, cooling water in a jacket of the reaction kettle is started for condensation, when the temperature of the dissolved solution is reduced to 50-60 ℃, 31% hydrogen peroxide is added according to (0.010-0.200) t hydrogen peroxide/t optimal dissolved slag (wet), heat preservation and aging are carried out for more than 8 hours, valuable resources in the optimal dissolved slag are completely dissolved and enter a liquid phase, a dissolved solution containing valuable resources such as uranium, thorium, rare earth and the like is obtained, the dissolution rate reaches more than 98%, and the dissolved solution is extracted by adopting siphon supernatant and a checking and filtering mode and is used for preparing an extraction stock solution.

In the step (6), the slurry after siphoning is treated by 3-stage countercurrent pulping and washing, and is subjected to solid-liquid separation in 2-4-stage countercurrent dense sedimentation and liquid-solid separation in 1-2-stage chamber filter press filtration respectively. Adding a proper amount of washing water into the siphoned slurry stirring tank, pulping and washing each time, uniformly stirring according to the liquid-solid ratio of the volume of the washing water to the volume of the slurry being (1-3): 1(V/V), pumping the mixture into a next-stage thickener by using a pump for sedimentation separation, overflowing the supernatant of the first-stage thickener to uranium extraction stock solution for preparation, pumping the washing water of the second-stage thickener into the stirring tank below the previous-stage thickener for pulping and washing, and pumping the washing water into the first-stage thickener for sedimentation separation; the underflow slurry of the thickener flows into a pulping tank and then enters the next thickener, the underflow slurry of the last thickener enters a van-type filter press for filtration, and insoluble slag is packaged and stored by a container. And (3) combining the last washing water of the countercurrent washing with dissolving liquid containing valuable resources such as uranium, thorium, rare earth and the like to obtain extraction stock solution for uranium-thorium extraction. Extracting stock solution components: HCl: 2-3 mol/L, U: 0.5-10 g/L, Th: 20-60 g/L, REO: 20-60 g/L, and the solid content is less than 100 ppm.

In the step (7), extracting uranium from a uranium-thorium extraction stock solution by using an N235 system extracting agent, extracting uranium by using N235+ TBP + sec-octanol + sulfonated kerosene as an extraction organic phase through 2-5 stages of countercurrent extraction, wherein the two-phase contact ratio is O/A (1-2)/1, the stirring contact time is 5-10 min, the clarification phase separation time is 10-20 min, and the extraction temperature is normal temperature (in the claims). Obtaining the loaded organic phase containing uranium and iron, wherein the extraction efficiency of uranium is more than 99.5%, and the extraction efficiency of iron is more than 99.8%. And (3) carrying out back extraction on the loaded organic phase containing uranium and iron by using 2.0-3 mol/L HCl solution, wherein the number of the back extraction stages is 4-9, the contact phase ratio of two phases is O/A (3-5)/1, the stirring contact time is 5-10 min, the clarification phase separation time is 10-20 min, the back extraction temperature is normal temperature, and the low-concentration uranyl chloride solution is obtained by back extraction. And back-extracting the loaded organic phase subjected to uranium recovery by back extraction by using 0.1mol/L HCl solution to remove iron, wherein the number of the back-extraction iron removal is 6, the contact phase ratio of the two phases is O/A (4-10)/1, the contact time is 5-10 min, the clarification phase separation time is 10-20 min, the temperature is normal temperature, the back-extraction efficiency is more than 99.6%, and the iron chloride solution obtained by back extraction enters a subsequent wastewater treatment system to remove iron and salt.

In the step (7), extracting enriched uranium from a low-concentration uranyl chloride solution by using an N235 system extracting agent, taking (5% -15%) N235+ (10% -20%) sec-octanol + (10% -15%) TBP + sulfonated kerosene as an extraction organic phase, extracting the enriched uranium by 5-10 levels of countercurrent extraction, wherein the two-phase contact ratio is O/A (1-2)/1, the stirring contact time is 5-10 min, the clarification phase separation time is 10-20 min, obtaining a loaded organic phase containing the high-concentration uranium by extraction, and then carrying out back extraction on the loaded organic phase by using 0.1mol/L HCl solution to recover uranium, the number of the back extraction is 5-12 levels, the two-phase contact ratio is O/A (4-10)/1, the contact time is 5-10 min, the clarification phase separation time is 10-20 min, and the recovery efficiency of the back extraction uranium is more than 99.8%. U in the stripping solution is more than 40 g/L.

In the step (7), the poor organic phase is obtained, and is subjected to regeneration treatment by 5% -10% of sodium carbonate, wherein the regeneration stage number is 3, the temperature is 50 ℃, and the two-phase contact phase ratio is as follows: O/A is (8-10)/1, and the stirring contact time is as follows: 5-10 min, clarifying and phase-splitting time: 20-30 min. U < 15mg/L, Fe in the lean organic phase was < 30 mg/L. The organic phase is regenerated and then enters uranium extraction of the next link, and then is washed and acidified by grade 1 water, and the acidifying agent is: 2-3 mol/L HCl, and the acidification phase ratio is as follows: O/A is 3-4/1, and the contact time is as follows: 5-10 min, clarifying and phase-splitting time: and (3) after 10-20 min, allowing the acidified organic phase to enter the next uranium extraction cycle, and recycling the organic phase.

In the step (7), adding 30% sodium hydroxide solution into the stripping solution of uranium to precipitate uranium, wherein the reaction temperature is as follows: 55 +/-5 ℃, the end point pH value is 6.8-7.2, and the time is as follows: the time of the reaction lasts for 60-90min,aging the precipitate for 2.0-2.5 hr. And (3) carrying out liquid-solid separation on the precipitated slurry to obtain a solid sodium diuranate product, wherein the quality of the uranium product meets the standard requirement of technical conditions of diuranate (EJ/T803-93). Wherein the uranium content (dry basis) is U not less than 50%, and the water content (natural basis) is H₂O<30% and a phosphate radical content (dry basis) of PO₄ ^3-Not more than 5 percent, and the content of silicon dioxide (dry basis) is SiO₂Less than or equal to 2 percent, and the fluorine content (dry basis) is F^-≤0.2％。

In the step (8), thorium is extracted from the solution containing thorium and rare earth obtained after uranium extraction by using an acidic phosphorus-containing extractant, and 4-level countercurrent extraction is performed by using (15% -25%) P204+ (5% -15%) P507+ (5% -10%) TBP + sulfonated kerosene as an organic phase for thorium extraction to obtain a thorium-containing loaded organic phase, wherein the two-phase contact ratio is as follows: O/A is (3-5)/1, contact time: 5-10 min, clarifying and phase-splitting time: 10-20 min at normal temperature. And (3) extracting and separating the uranium and the thorium to obtain a thorium and rare earth-containing solution in the extracted water phase, and returning to the preferential dissolving process to recover the rare earth chloride mixture.

In the step (8), the obtained loaded organic phase contains thorium chloride, and the loaded organic phase is subjected to 1-stage washing for impurity removal, wherein a washing agent is 4mol/L HCl + 5% H₂O₂The contact phase ratio of two phases of the solution is O/A (5-10)/1, the contact time is 5-10 min, the clarification phase separation time is 10-20 min, and the temperature is normal temperature. Transferring the washed and impurity-removed loaded organic phase containing thorium chloride to a thorium precipitation and back extraction tank, adding a hot 3mol/L NaOH solution into the tank to perform precipitation and back extraction, wherein the precipitation and back extraction reaction temperature is 70 +/-5 ℃, the reaction time is 30-60 min, the clarification and phase separation time is 45min compared with O/A (1-3)/1, and a solid thorium hydroxide crude product is obtained. And the extracted water phase after thorium extraction is a rare earth chloride-containing solution, and the solution is returned to the hydrochloric acid preferential dissolution process to recover a rare earth chloride mixture.

In the step (9), ferric chloride wastewater is added into a thorium hydroxide crude product obtained by the system to adjust the pH value to 4.5-5.5, a box-type filter press is filtered to remove residues and other pretreatments, magnetic seeds and a mixed flocculant are added into a filtrate, then sedimentation separation is carried out by a thickener, an overflowing supernatant enters a superconducting magnetization separation system, superconducting magnetization separation effluent returns to the system for recycling, mud in the filter residues is discharged through a sludge discharge port and is stored by a packaging container, and the separated magnetic seeds return to the wastewater treatment system for utilization.

In the step (9), the uranium precipitation mother liquor and the thorium precipitation mother liquor are subjected to nanofiltration treatment, chloride with the molecular weight of more than 200 is intercepted, substances with the molecular weight of less than 200 are subjected to electrodialysis or ultrafiltration treatment, 70-80% of light water of produced water is returned to a system for utilization, the obtained 20-30% high-salinity concentrated wastewater is combined with chloride wastewater with the molecular weight of more than 200, the treatment is carried out by a multi-effect evaporator evaporation concentration desalination technology, condensed water obtained by evaporation concentration of the multi-effect evaporator is returned to the system for utilization, and solid chloride obtained by evaporation concentration of the multi-effect evaporator is stored in a packaging container.

Example 1

Subjecting monazite concentrate (REO: 52.61%, ThO) with particle size of-80 mesh (more than 99.5%)₂：4.03％，CaO：2.06％，TiO₂:1.84％，ZrO₂：2.85％，SiO₂：2.73％，Fe₂O₃:2.92％，U₃O₈: 1.14%), unpacked, conveyed to a single-dwelling stone bin by a belt conveying system, discharged through a discharge port at the lower part of the bin, conveyed into a 50-60% sodium hydroxide solution in a stirring pulping tank, pulped according to the volume of 1 time and the weight ratio of ore pulp, uniformly mixed, conveyed into a bead mill by a rubber tube pump, ground under the condition of normal pressure or micro pressure to obtain ore pulp with the granularity of-320 meshes (accounting for more than 99.5%) and discharged out of the mill in a grading way by a built-in grading device.

Pumping the ground ore pulp with the granularity of 320 meshes (accounting for more than 99.5%) into a permanent magnet magnetic separator, wherein the magnetic separation intensity of the magnetic separator is 1.2T; selecting refractory minerals such as ilmenite, rutile, zirconite and the like in the monazite concentrate ore pulp in a tailing slag mode, and detecting the iron content Fe in the selected monazite concentrate₂O₃:0.98％，TiO₂:0.58％，ZrO₂：1.65％，ThO₂: 4.85%, REO: 55.35 percent. Adding the monazite concentrate subjected to ore grinding and magnetic separation to remove part of impurities into ore pulp discharged by middle grinding, and carrying out dense water separation to obtain qualified ore pulp meeting the alkali decomposition requirement,pumping the qualified ground ore pulp into an alkali decomposition head tank by a pump for later use.

Pumping qualified ore pulp in the head tank into a continuous alkali decomposition tank, wherein the initial concentration of a sodium hydroxide solution in alkali decomposition is 50-60 percent NaOH, the liquid-solid ratio is 1.4/1 (volume/weight), heating and reacting at the temperature of 145 +/-5 ℃, and the continuous alkali decomposition reaction time is 12 hours, so that the conversion rates of valuable resource alkali decomposition of uranium, thorium and rare earth in monazite concentrate are respectively 95.92 percent and U₃O₈：99.17％、ThO₂: 98.84 percent. And adding production water (90 ℃ hot water) with one time volume (slurry weight) into the alkali decomposition reactor for heat preservation and aging, wherein the aging time is 12 hours, standing, siphoning and recovering alkali decomposition supernatant, obtaining alkali cake and washing water by a 4-stage countercurrent thickener settling separation method and a 2-stage chamber filter press filtering separation method, and carrying out alkali cake dephosphorization treatment. The pH value of the last washing water is 7.8, and P is contained in the washing water₂O₅：1.019g/L。

And combining the supernatant obtained by standing and siphoning separation in the alkaline decomposition reactor and the supernatant of the standing washing water washed for the 1 st time in the alkaline decomposition reactor into a trisodium phosphate solution before concentration. Adding zinc powder which is 0.25 percent of the weight of the monazite ore and ferrous sulfate which is 1 percent of the weight of the monazite ore into the obtained hot trisodium phosphate solution, removing impurities and discharging, reacting for 3 hours at the reaction temperature of 75 ℃, aging for 45min, and filtering to obtain trisodium phosphate filtrate.

Evaporating and concentrating the obtained clear solution of the trisodium phosphate by a triple-effect evaporator, transferring the solution into a DTB crystallizer when the solution is concentrated to 32Be degrees, cooling and crystallizing, and filtering crystal slurry by an HR400-N type double-stage piston pusher centrifuge to respectively obtain a trisodium phosphate crystal filtering mother solution and a trisodium phosphate crude product. Adding the crude trisodium phosphate into deionized water with the volume of 0.5-1.0 BV for pulping and washing, and filtering by an HR400-N type double-stage piston pusher centrifuge to obtain a solid trisodium phosphate product, wherein the product quality is as follows: na (Na)₃PO₄·12H₂O：98.10％，pH：11.9，SO₄ ^2-:0.06％，Cl^-: 0.32%, Fe: 0.005%, As: 0.004%, water-insoluble matter: 0.03 percent.

Adding 1.2 times (ore pulp) weight of dilute hydrochloric acid solution into the alkali cake, and dissolving in a dissolving tank, wherein the acidity of the initial dilute hydrochloric acid is 6mol/L HCl. Stirring, heating and dissolving at 85 +/-5 ℃; simultaneously adding a proper amount of hydrogen peroxide, wherein the reaction residence time of each dissolving tank is 1.5h, and after the total time of the first three stages of dissolving reactions is 4.5h, the acidity of hydrochloric acid in the dissolved solution is controlled to be about 2.2. Adding a proper amount of alkali cake into the 4 th-stage dissolving tank, adjusting the pH value of hydrochloric acid optimum solution, and controlling the acidity of the residual acid of the 6 th-stage dissolving solution to be 4.3. Then transferring to the preferential solution aging process.

Pumping the slurry obtained by preferential dissolution into an aging tank, boiling for 1h, preserving heat and aging for 12h, performing solid-liquid separation on the suspension obtained by aging through a box filter press to obtain a rare earth chloride solution, and adding barium chloride (1 kgBaCl) into the rare earth chloride solution obtained by preferential dissolution of hydrochloric acid₂/m³Solution) and ammonium sulfate (2kg (NH)₄)₂SO₄/m³Solution) is subjected to impurity removal and radioactive substance removal treatment, the impurity removal and radioactive substance removal temperature is 40 ℃, the time is 1.5h, and the aging time is more than 11 h. Obtaining the rare earth chloride solution after removing impurities and radium.

Evaporating, concentrating, cooling and crystallizing the rare earth chloride filtrate after removing impurities and radium, controlling the temperature of evaporation and concentration of a multi-effect evaporator to be 145 +/-5 ℃, controlling the vacuum degree to be 700mmHg, and obtaining a sheet rare earth chloride product on crystallization and sheet-making equipment from the concentrated supersaturated solution of the rare earth chloride, wherein the product quality meets the standard requirement of GB/T4148-. The product quality is as follows: REO: 45.81% of Fe₂O₃：0.046％，BaO：0.065％，CaO+MgO：1.682％，Na₂O：0.34％，ThO₂:0.002％，SO₄ ^2-:0.004％，PO₄ ^3-: 0.0043%, total α: 2.4X 10³Bq/kg。

Metering a prepared 6mol/L HCl solution in a dilute hydrochloric acid high-level metering tank, injecting the solution into a dissolving tank, starting stirring, heating and preheating, adding monazite-based dissolving slag with a liquid-solid ratio of 1.5:1 into the dissolving tank when the temperature is raised to 40 ℃, heating, stirring and dissolving, controlling the reaction temperature to be 92 +/-2 ℃, the reaction time to be 6 hours, boiling for 1.5 hours, and the boiling temperature to be 105 +/-2 ℃. Stopping heating after boiling, starting cooling water in a jacket of the reaction kettle for condensation, adding 31% hydrogen peroxide into 0.050t hydrogen peroxide/t optimal slag (wet) when the temperature of the solution is reduced to 51 ℃, continuing heat preservation and aging for 12 hours, siphoning supernate and extracting the solution in a checking and filtering mode. And (3) performing 3-stage countercurrent pulping and washing on the slurry after siphoning, wherein the solid-to-solid ratio of the washing liquid for each pulping is 1.5:1(V/V), uniformly stirring, and combining the last-stage washing water and the siphoning supernatant into an extraction stock solution. Extracting stock solution components: HCl: 2.51mol/L, U: 1.57g/L, Th: 59.60g/L, REO: 55.10g/L, Fe: the solid content of 4.59g/L was 41 ppm.

Extracting uranium by 4-stage countercurrent extraction at normal temperature by using 15% of N235, 10% of secondary octanol, 10% of TBP and 65% of sulfonated kerosene as an extraction organic phase, wherein the two-phase flow ratio and the contact ratio are both O/A (1/1), the stirring contact time is 5min, and the clarification phase separation time is 10 min. And (2) carrying out back extraction on the uranium-containing loaded organic phase by using 2.5mol/L HCl solution, wherein the number of the back extraction stages is 8, the contact phase ratio of two phases is O/A (5/1), the contact time is 5min, the clarification phase separation time is 10min, the back extraction temperature is normal temperature, and the low-concentration uranyl chloride solution is obtained by back extraction. And carrying out back extraction on the loaded organic phase subjected to back extraction and uranium recovery by using 0.1mol/L HCl solution to remove iron, wherein the number of the back extraction iron removal stages is 6, the two-phase contact phase ratio is O/A (5/1), the contact time is 5min, and the clarification phase separation time is 10 min.

15% N235+ 10% sec-octanol + 10% TBP + 65% sulfonated kerosene is an extraction organic phase, at normal temperature, uranium is subjected to 8-stage countercurrent extraction for enrichment and thickening, the two-phase flow ratio and the contact ratio are O/A (1/1), the stirring contact time is 5min, the clarification phase separation time is 10min, a load organic phase containing high-concentration uranium is obtained through extraction, the load organic phase is subjected to reverse extraction with 0.1mol/L HCl solution for uranium recovery, the number of stages of the reverse extraction is 10, the two-phase contact ratio is O/A (5/1), the contact time is 5min, and the clarification phase separation time is 10 min. In the back extraction liquid, the ratio of U to U is 38.56g/L, Fe: 2.16g/L, Th: 0.012g/L, RE: 0.016 g/L.

Adding 30% NaOH into a stripping solution of uranium in a uranium precipitation tank to precipitate uranium, wherein the reaction temperature is 55 +/-5 ℃, the end point pH value is 7.1, the time is 90min, and the precipitation aging time is 2.0 h. The precipitated slurry is subjected to liquid-solid separation by a box type filter press to obtain a solid sodium diuranate product, and the quality of the uranium product meets the requirement of heavyThe technical conditions of uranate (EJ/T803-93) standard. Wherein the uranium content (dry basis) is U: 62.68% and a water content (natural group) of H₂O: 21.06% and the phosphate content (dry basis) is PO₄ ^3-: 0.012% and the content (dry basis) of silica is SiO₂: 0.051% and F as fluorine content (dry basis)^-: 0.002% and Cl content (dry basis)^-：0.281％。

Extracting uranium to obtain an extraction water phase containing thorium and rare earth, taking 20% P204+ 10% P507+ 5% TBP + sulfonated kerosene as an organic phase for extracting thorium, and carrying out 4-stage countercurrent extraction at normal temperature, wherein the two-phase contact ratio is as follows: o/a-4/1, contact time: 5min, clarifying and phase-splitting time: 10min, then carrying out grade 1 washing impurity removal on the loaded organic phase, wherein the detergent is 4mol/L HCl + 5% H₂O₂The solution has two-phase contact phase ratio of O/A5/1, contact time of 5min, settling phase separation time of 10min, and normal temperature.

And adding a hot 3mol/L NaOH solution into the thorium chloride solution precipitation and back-extraction tank to perform precipitation and back-extraction, wherein the precipitation and back-extraction reaction temperature is 70 +/-5 ℃, the reaction time is 60min compared with O/A (3/1), and the clarification phase-separation time is 45min, so as to obtain a solid thorium hydroxide crude product.

Ferric chloride and thorium obtained by the system are poor in acidification wastewater, and the wastewater comprises the following components: HCl: 0.53mol/L, U: 0.012g/L, Th: 0.018g/L, REO: 0.042g/L, Fe: 17.69g/L, CODcr: 6.2, SS: 102 mg/L. Adding a solid thorium hydroxide crude product prepared by the system, adjusting the pH value to 4.5, filtering and deslagging by a box filter press, adding 0.4kg of magnetic seeds, 0.2kg of PAC and 0.002kg of PAM into each cubic of filtrate, performing sedimentation separation by a thickener, feeding the overflowing supernatant into a superconducting magnetization separation system, returning the superconducting magnetization separation effluent to the system for recycling, discharging mud in the filter residue through a sludge discharge port, storing by a packaging container, and returning the separated magnetic seeds to the wastewater treatment system for utilization.

The uranium precipitation mother liquor and the thorium precipitation mother liquor obtained by the system are combined and enter an alkaline wastewater treatment system, firstly, the salt chloride with the molecular weight of more than 200 is intercepted through nanofiltration treatment, then, electrodialysis or ultrafiltration treatment is carried out, 70-80% of light water obtained is returned to the system for utilization, 20-30% of concentrated wastewater obtained is combined with the salt chloride wastewater with the molecular weight of more than 200, the condensate water obtained by evaporation concentration and desalination of a multi-effect evaporator is treated by using the evaporation concentration desalination technology of the multi-effect evaporator and is returned to the system for utilization, and the salt chloride obtained by evaporation concentration of the multi-effect evaporator is stored by using a packaging container.

Example 2

Subjecting monazite concentrate (REO: 50.82%, ThO) with particle size of-80 mesh (more than 99.5%)₂：4.29％，CaO：2.63％，TiO₂:2.82％，ZrO₂：6.71％，SiO₂：3.46％，Fe₂O₃:3.09％，U₃O₈: 0.98%) is unpacked, conveyed to a single-dwelling stone bin by a belt conveying system, discharged through a discharge port at the lower part of the bin, sent into a 50-60% sodium hydroxide solution in a stirring pulping tank, pulped according to the volume of 1 time and the weight ratio of ore pulp, uniformly mixed, sent into a bead mill by a rubber tube pump, ground under the condition of normal pressure or micro pressure to obtain ore pulp with the granularity of-320 meshes (accounting for more than 99.5%) and discharged out of the mill in a grading way by a built-in grading device.

Pumping the ground ore pulp with the granularity of 320 meshes (accounting for more than 99.5%) into a permanent magnet magnetic separator, wherein the magnetic separation intensity of the magnetic separator is 1.2T; selecting refractory minerals such as ilmenite, rutile, zirconite and the like in the monazite concentrate ore pulp in a tailing slag mode, and detecting the iron content Fe in the selected monazite concentrate₂O₃:1.2％，REO：53.6％，TiO₂:1.03％，ThO₂：4.98％，ZrO₂: 4.12 percent. And (3) carrying out ore grinding and magnetic separation on the monazite concentrate pulp from which part of impurities are removed to obtain qualified pulp meeting the alkali decomposition requirement after dense water separation, and pumping the ground qualified pulp into an alkali decomposition head tank by using a pump for later use.

Pumping qualified ore pulp in the head tank into a continuous alkali decomposition tank, wherein the initial concentration of a sodium hydroxide solution in alkali decomposition is 50-60 percent NaOH, the liquid-solid ratio is 1.4/1 (volume/weight), heating reaction is carried out at the temperature of 145 +/-5 ℃, the continuous alkali decomposition reaction time is 12 hours, and the conversion rates of alkali decomposition of valuable resources of uranium, thorium and rare earth in monazite concentrate are 95.28 percent REO and U₃O₈：98.67％、ThO₂: 98.49 percent. And adding production water (90 ℃ hot water) with one time volume (slurry weight) into the alkali decomposition reactor for heat preservation and aging, wherein the aging time is 12 hours, standing, siphoning and recovering alkali decomposition supernatant, obtaining alkali cake and washing water by a 4-stage countercurrent thickener settling separation method and a 2-stage chamber filter press filtering separation method, and carrying out alkali cake dephosphorization treatment. The pH value of the last washing water is 7.8, and P is contained in the washing water₂O₅：0.852g/L。

And combining the supernatant obtained by standing and siphoning separation in the alkaline decomposition reactor and the supernatant of the standing washing water washed for the 1 st time in the alkaline decomposition reactor into a trisodium phosphate solution before concentration. Adding zinc powder which is 0.25 percent of the weight of the monazite ore and ferrous sulfate which is 1 percent of the weight of the monazite ore into the obtained hot trisodium phosphate solution, removing impurities and discharging, reacting for 3 hours at the reaction temperature of 75 ℃, aging for 45min, and filtering to obtain trisodium phosphate filtrate.

And (3) evaporating and concentrating the obtained clear solution of the trisodium phosphate by using a triple-effect evaporator, transferring the solution into a DTB crystallizer when the solution is concentrated to the Baume degree of 31Be degrees, cooling and crystallizing, and filtering the crystal slurry by using an HR400-N type double-stage piston pusher centrifuge to respectively obtain a trisodium phosphate crystal filtering mother solution and a trisodium phosphate crude product. Adding the crude trisodium phosphate into deionized water with the volume of 0.5-1.0 BV for pulping and washing, and filtering by an HR400-N type double-stage piston pusher centrifuge to obtain a solid trisodium phosphate product, wherein the product quality is as follows: na (Na)₃PO₄·12H₂O：98.21％，pH：12.1，SO₄ ^2-:0.08％，Cl^-: 0.27%, Fe: 0.006%, As: 0.003%, water-insoluble matter: 0.04 percent.

Adding 1.2 times (ore pulp) weight of dilute hydrochloric acid solution into the alkali cake, and dissolving in a dissolving tank, wherein the acidity of the initial dilute hydrochloric acid is 6mol/L HCl. Stirring, heating and dissolving at 85 +/-5 ℃; simultaneously adding a proper amount of hydrogen peroxide, wherein the reaction residence time of each dissolving tank is 1.5h, the total time of the first three stages of dissolving reactions is 4.5h, and the pH value of hydrochloric acid in the dissolved solution is controlled to be 2.0 after dissolving. Adding a proper amount of alkali cake into the 4 th-stage dissolving tank, adjusting the pH value of hydrochloric acid optimum solution, and controlling the acidity of the residual acid of the 6 th-stage dissolving solution to be 4.2. Then transferring to the preferential solution aging process.

Pumping the slurry obtained by preferential dissolution into an aging tank, boiling for 1h, preserving heat and aging for 12h, performing solid-liquid separation on the suspension obtained by aging through a box filter press to obtain a rare earth chloride solution, and adding barium chloride (1 kgBaCl) into the rare earth chloride solution obtained by preferential dissolution of hydrochloric acid₂/m³Solution) and ammonium sulfate (2kg (NH)₄)₂SO₄/m³Solution) is subjected to impurity removal and radioactive substance removal treatment, the impurity removal and radioactive substance removal temperature is 40 ℃, the time is 1.2h, and the aging time is more than 11 h. Obtaining the rare earth chloride solution after removing impurities and radium.

Evaporating, concentrating, cooling and crystallizing the rare earth chloride filtrate after removing impurities and radium, controlling the temperature of evaporation and concentration of a multi-effect evaporator to be 145 +/-5 ℃, controlling the vacuum degree to be 700mmHg, and obtaining a sheet rare earth chloride product on crystallization and sheet-making equipment from the concentrated supersaturated solution of the rare earth chloride, wherein the product quality meets the standard requirement of GB/T4148-. The product quality is as follows: REO: 45.21%, Fe₂O₃：0.040％，BaO：0.059％，CaO：0.82％，MgO：0.02％，Na₂O：0.26％，ThO₂:0.001％，SO₄ ^2-:0.054％，PO₄ ^3-: 0.0087%, total alpha: 2.6X 10³Bq/kg。

Metering a prepared 6mol/L HCl solution in a dilute hydrochloric acid high-level metering tank, injecting the solution into a dissolving tank, starting stirring, heating and preheating, adding monazite-based dissolving slag with a liquid-solid ratio of 1.5:1 into the dissolving tank when the temperature is raised to 40 ℃, heating, stirring and dissolving, controlling the reaction temperature to be 85 +/-2 ℃, the reaction time to be 5 hours, boiling for 1.5 hours, and the boiling temperature to be 105 +/-2 ℃. Stopping heating after boiling, starting cooling water in a jacket of the reaction kettle for condensation, adding 31% hydrogen peroxide according to 0.050t hydrogen peroxide/t optimal slag (wet) when the temperature of the solution is reduced to 55 ℃, preserving heat and aging for 10 hours, and extracting the solution by siphoning supernatant and checking and filtering. And (3) performing 3-stage countercurrent pulping and washing on the slurry after siphoning, wherein the solid-to-solid ratio of pulping and washing liquid is 1.5:1(V/V), uniformly stirring, and combining the last-stage washing water and siphoning supernatant into an extraction stock solution. Extracting stock solution: HCl: 2.69mol/L, U: 0.91g/L, Th: 51.97g/L, REO: 52.11g/L, Fe: 5.68g/L and a solid content of 72 ppm.

Extracting uranium by 4-stage countercurrent extraction at normal temperature by using 15% of N235, 10% of secondary octanol, 10% of TBP and 65% of sulfonated kerosene as an extraction organic phase, wherein the contact phase ratio of two phases is O/A (1/1), the stirring contact time is 5min, and the clarification phase separation time is 10 min. And (2) carrying out back extraction on the uranium-containing loaded organic phase by using 2.5mol/L HCl solution, wherein the number of the back extraction stages is 8, the contact phase ratio of two phases is O/A (5/1), the contact time is 5min, the clarification phase separation time is 10min, the back extraction temperature is normal temperature, and the low-concentration uranyl chloride solution is obtained by back extraction. And carrying out back extraction on the loaded organic phase subjected to the back extraction and uranium recovery by using a 0.1mol/L HCl solution to remove iron, wherein the number of the back extraction and iron removal stages is 6, the two-phase contact phase ratio is O/A (5/1), the contact time is 5min, and the clarification and phase separation time is 10 min.

15% N235+ 10% sec-octanol + 10% TBP + 65% sulfonated kerosene is used as an extraction organic phase, at normal temperature, uranium is subjected to enrichment by 8-stage countercurrent extraction, the two-phase contact ratio is O/A (1/1), the stirring contact time is 5min, the clarification phase separation time is 10min, a loaded organic phase containing high-concentration uranium is obtained by extraction, and then the loaded organic phase is subjected to reverse extraction with 0.1mol/L HCl solution to recover uranium, the number of stages of the reverse extraction is 10, the two-phase contact ratio is O/A (5/1), the contact time is 5min, and the clarification phase separation time is 10 min. In the stripping solution, the ratio of U to the total weight of the stripping solution is 22.19g/L, Fe: 1.97g/L, Th: 0.018g/L, RE: 0.025 g/L.

Adding 30% NaOH into the stripping liquid of uranium to precipitate uranium, wherein the reaction temperature is 55 +/-5 ℃, the end point pH value is 7.1, the time is 90min, and the precipitation aging time is 2.0 h. And carrying out liquid-solid separation on the precipitated slurry by using a box type filter press to obtain a solid sodium diuranate product, wherein the quality of the uranium product meets the standard requirement of technical conditions of diuranate (EJ/T803-93). Wherein the uranium content (dry basis) is U: 60.13%, water content (natural group) is H₂O: 28.24% and a phosphate content (dry basis) of PO₄ ^3-: 0.012% and the content (dry basis) of silica is SiO₂: 0.041%, fluorine content (dry basis) is F^-: 0.008% and Cl in dry basis^-：0.151％。

The thorium-rare earth-containing solution obtained after uranium extraction uses 20% P204+ 10% P507+ 5% TBP + sulfonated kerosene as thorium-extracting organic materialAnd (3) performing 4-stage countercurrent extraction at normal temperature, wherein the two-phase contact phase ratio is as follows: o/a-4/1, contact time: 5min, clarifying and phase-splitting time: 10min, then carrying out grade 1 washing impurity removal on the loaded organic phase, wherein the detergent is 4mol/L HCl + 5% H₂O₂The solution has two-phase contact phase ratio of O/A5/1, contact time of 5min, settling phase separation time of 10min, and normal temperature.

And adding a hot 3mol/L NaOH solution into a thorium chloride solution precipitation tank to carry out precipitation and back extraction, wherein the reaction temperature of the precipitation and back extraction is 70 +/-5 ℃, the reaction time is 60min compared with O/A which is 3/1, and the time of clarification and phase separation is 45min, so that a solid thorium hydroxide crude product is obtained.

Ferric chloride and thorium obtained by the system are poor in acidification wastewater, and the wastewater comprises the following components: HCl: 0.48mol/L, U: 0.011g/L, Th: 0.010g/L, REO: 0.035g/L, Fe: 27.89g/L, CODcr: 10.8, SS: 115 mg/L. Adding a solid thorium hydroxide crude product prepared by the system, adjusting the pH value to 4.5, filtering and deslagging by a box filter press, adding 0.4kg of magnetic seeds, 0.2kg of PAC and 0.002kg of PAM into each cubic of filtrate, performing sedimentation separation by a thickener, feeding the overflowing supernatant into a superconducting magnetization separation system, returning the superconducting magnetization separation effluent to the system for recycling, discharging mud in the filter residue through a sludge discharge port, storing by a packaging container, and returning the separated magnetic seeds to the wastewater treatment system for utilization.

The method comprises the steps of firstly carrying out nanofiltration treatment on uranium precipitation mother liquor and thorium precipitation mother liquor, intercepting chlorate with molecular weight of more than 200, carrying out electrodialysis or ultrafiltration treatment, returning 70-80% of obtained light water to a system for utilization, combining obtained 20-30% concentrated wastewater with chlorate wastewater with molecular weight of more than 200, treating condensate water obtained by evaporation concentration of a multi-effect evaporator by using an evaporation concentration desalination technology of the multi-effect evaporator, returning the condensate water to the system for utilization, and storing the chlorate obtained by evaporation concentration of the multi-effect evaporator by using a packaging container.

Example 3

Subjecting monazite concentrate (REO: 51.24%, ThO) with particle size of-80 mesh (more than 99.5%)₂：4.01％，CaO：2.01％，TiO₂:2.28％，ZrO₂：2.79％，SiO₂：2.86％，Fe₂O₃:2.87％，U₃O₈: 1.58 percent) and then unpacked, conveyed to a single-dwelling stone bin by a belt conveying system, discharged through a discharge port at the lower part of the bin, sent into a 50 to 60 percent sodium hydroxide solution in a stirring pulping tank, pulped according to the volume of 1 time and the weight ratio of the ore pulp, uniformly mixed, sent into a bead mill by a rubber tube pump, ground under the condition of normal pressure or micro pressure to obtain the ore pulp with the granularity of-320 meshes (more than 99.5 percent) and discharged out of the mill in a grading way by a built-in grading device.

Pumping the ground ore pulp with the granularity of 320 meshes (accounting for more than 99.5%) into a permanent magnet magnetic separator, wherein the magnetic separation intensity of the magnetic separator is 1.2T; selecting refractory minerals such as ilmenite, rutile, zirconite and the like in the monazite concentrate ore pulp in a tailing slag mode, and detecting the iron content Fe in the selected monazite concentrate₂O₃:0.74％，TiO₂:1.21％，ZrO₂: 1.85%, REO: 53.10 percent. And (3) carrying out ore grinding and magnetic separation on the monazite concentrate pulp from which part of impurities are removed to obtain qualified pulp meeting the alkali decomposition requirement after dense water separation, and pumping the ground qualified pulp into an alkali decomposition head tank by using a pump for later use. .

Pumping qualified ore pulp in the head tank into a continuous alkali decomposition tank, wherein the initial concentration of a sodium hydroxide solution in alkali decomposition is 50-60 percent NaOH, the liquid-solid ratio is 1.4/1 (volume/weight), heating and reacting at the temperature of 145 +/-5 ℃, and the continuous alkali decomposition reaction time is 12 hours, so that the conversion rates of valuable resource alkali decomposition of uranium, thorium and rare earth in monazite concentrate are 95.83 percent and U is respectively 95.83 percent and 95 h percent₃O₈：98.69％、ThO₂: 99.10 percent. And adding production water (90 ℃ hot water) with one time volume (slurry weight) into the alkali decomposition reactor for heat preservation and aging, wherein the aging time is 12 hours, standing, siphoning and recovering alkali decomposition supernatant, obtaining alkali cake and washing water by a 4-stage countercurrent thickener settling separation method and a 2-stage chamber filter press filtering separation method, and carrying out alkali cake dephosphorization treatment. The pH value of the last washing water is 7.7, and P is contained in the washing water₂O₅：0.924g/L。

And combining the supernatant obtained by standing and siphoning separation in the alkaline decomposition reactor and the supernatant of the standing washing water washed for the 1 st time in the alkaline decomposition reactor into a trisodium phosphate solution before concentration. Adding zinc powder which is 0.25 percent of the weight of the monazite ore and ferrous sulfate which is 1 percent of the weight of the monazite ore into the obtained hot trisodium phosphate solution, removing impurities and discharging, reacting for 3 hours at the reaction temperature of 75 ℃, aging for 45min, and filtering to obtain trisodium phosphate filtrate.

And (3) evaporating and concentrating the obtained clear solution of the trisodium phosphate by using a triple-effect evaporator, transferring the solution into a DTB crystallizer when the solution is concentrated to the Baume degree of 31Be degrees, cooling and crystallizing, and filtering the crystal slurry by using an HR400-N type double-stage piston pusher centrifuge to respectively obtain a trisodium phosphate crystal filtering mother solution and a trisodium phosphate crude product. Adding the crude trisodium phosphate into deionized water with the volume of 0.5-1.0 BV for pulping and washing, and filtering by an HR400-N type double-stage piston pusher centrifuge to obtain a solid trisodium phosphate product, wherein the product quality is as follows: na (Na)₃PO₄·12H₂O：98.07％，pH：11.5，SO₄ ^2-:0.07％，Cl^-: 0.29%, Fe: 0.004%, As: 0.003%, water-insoluble matter: 0.02 percent.

The alkaline cake was dissolved in a dissolution tank by adding 1.2 times (pulp) weight of dilute hydrochloric acid solution, with an initial dilute hydrochloric acid acidity of about 5.74mol/L HCl. Stirring, heating and dissolving at 85 +/-5 ℃; simultaneously adding a proper amount of hydrogen peroxide, wherein the reaction residence time of each dissolving tank is 1.5h, and after the total time of the first three stages of dissolving reactions is 4.5h, the acidity of hydrochloric acid in the dissolved solution is controlled to be about 1.9. Adding a proper amount of alkali cake into the 4 th-stage dissolving tank, adjusting the pH value of hydrochloric acid optimum solution, and controlling the acidity of the residual acid of the 6 th-stage dissolving solution to be 4.1. Then transferring to the preferential solution aging process.

Pumping the slurry obtained by preferential dissolution into an aging tank, boiling for 1h, preserving heat and aging for 12h, performing solid-liquid separation on the suspension obtained by aging through a box filter press to obtain a rare earth chloride solution, and adding barium chloride (1 kgBaCl) into the rare earth chloride solution obtained by preferential dissolution of hydrochloric acid₂/m³Solution) and ammonium sulfate (2kg (NH)₄)₂SO₄/m³Solution) is subjected to impurity removal and radioactive substance removal treatment, the impurity removal and radioactive substance removal temperature is 40 ℃, the time is 1.2h, and the aging time is more than 11 h. Obtaining the rare earth chloride solution after removing impurities and radium.

Remove impurities and removeAnd (3) evaporating, concentrating, cooling and crystallizing the radium-containing rare earth chloride filtrate, controlling the evaporating and concentrating temperature of the multi-effect evaporator to be 145 +/-5 ℃, controlling the vacuum degree to be 700mmHg, and concentrating the concentrated rare earth chloride supersaturated solution to obtain a flaky rare earth chloride product on crystallization and sheet-making equipment, wherein the product quality meets the standard requirement of GB/T4148-. The product quality is as follows: REO: 45.45% of Fe₂O₃：0.038％，BaO：0.051％，CaO：0.91％，MgO：0.02％，Na₂O：0.084％，ThO₂:0.002％，SO₄ ^2-:0.021％，PO₄ ^3-: 0.0059%, total alpha: 3.1X 10³Bq/kg。

Metering a prepared 6mol/L HCl solution in a dilute hydrochloric acid high-level metering tank, injecting the solution into a dissolving tank, starting stirring, heating and preheating, adding monazite-based dissolving slag with a liquid-solid ratio of 1.5:1 into the dissolving tank when the temperature is raised to 40 ℃, heating, stirring and dissolving, controlling the reaction temperature to be 85 +/-2 ℃, the reaction time to be 5 hours, boiling for 1.5 hours, and the boiling temperature to be 105 +/-2 ℃. Stopping heating after boiling, starting cooling water in a jacket of the reaction kettle for condensation, adding 31.8 percent hydrogen peroxide into 0.050t hydrogen peroxide/t optimal slag (wet) when the temperature of the solution is reduced to 55 ℃, preserving heat and aging for 10 hours, and extracting the solution by siphoning supernatant and checking and filtering. And (3) performing 3-stage countercurrent pulping and washing on the slurry after siphoning, wherein the solid-to-solid ratio of pulping and washing liquid is 1.5:1(V/V), uniformly stirring, and combining the last-stage washing water and siphoning supernatant into an extraction stock solution. Extracting stock solution: HCl: 2.31mol/L, U: 1.56g/L, Th: 53.14g/L, REO: 54.87g/L, Fe: 3.51g/L, and a solid content of 37 ppm.

Extracting uranium by 4-stage countercurrent extraction at normal temperature by using 15% of N235, 10% of secondary octanol, 10% of TBP and 65% of sulfonated kerosene as an extraction organic phase, wherein the contact phase ratio of two phases is O/A (1/1), the stirring contact time is 5min, and the clarification phase separation time is 10 min. And (2) carrying out back extraction on the uranium-containing loaded organic phase by using 2.5mol/L HCl solution, wherein the number of the back extraction stages is 8, the contact phase ratio of two phases is O/A (5/1), the contact time is 5min, the clarification phase separation time is 10min, the back extraction temperature is normal temperature, and the low-concentration uranyl chloride solution is obtained by back extraction. And carrying out back extraction on the loaded organic phase subjected to the back extraction and uranium recovery by using a 0.1mol/L HCl solution to remove iron, wherein the number of the back extraction and iron removal stages is 6, the two-phase contact phase ratio is O/A (5/1), the contact time is 5min, and the clarification and phase separation time is 10 min.

15% N235+ 10% sec-octanol + 10% TBP + 65% sulfonated kerosene is used as an extraction organic phase, at normal temperature, uranium is subjected to enrichment by 8-stage countercurrent extraction, the two-phase contact ratio is O/A (1/1), the stirring contact time is 5min, the clarification phase separation time is 10min, a loaded organic phase containing high-concentration uranium is obtained by extraction, and then the loaded organic phase is subjected to reverse extraction with 0.1mol/L HCl solution to recover uranium, the number of stages of the reverse extraction is 10, the two-phase contact ratio is O/A (5/1), the contact time is 5min, and the clarification phase separation time is 10 min. In the stripping solution, the ratio of U to the total weight of the stripping solution is 34.12g/L, Fe: 1.25g/L, Th: 0.056g/L, RE: 0.146 g/L.

Adding 30% NaOH into the stripping liquid of uranium to precipitate uranium, wherein the reaction temperature is 55 +/-5 ℃, the end point pH value is 7.1, the time is 90min, and the precipitation aging time is 2.0 h. And carrying out liquid-solid separation on the precipitated slurry by using a box type filter press to obtain a solid sodium diuranate product, wherein the quality of the uranium product meets the standard requirement of technical conditions of diuranate (EJ/T803-93). Wherein the uranium content (dry basis) is U: 58.42%, the water content (natural base) is H₂O: 28.04% and a phosphate radical content (dry basis) of PO₄ ^3-: 0.087% and a silica content (dry basis) of SiO₂: 0.081%, fluorine content (dry basis) is F^-: 0.004%, the chlorine content (dry basis) is Cl^-：0.148％。

The thorium-containing rare earth solution obtained after uranium extraction uses 20% P204+ 10% P507+ 5% TBP + sulfonated kerosene as the organic phase for thorium extraction, and carries out 4-stage countercurrent extraction at normal temperature, and the two-phase contact ratio is as follows: o/a-4/1, contact time: 5min, clarifying and phase-splitting time: 10min, then carrying out grade 1 washing impurity removal on the loaded organic phase, wherein the detergent is 4mol/L HCl + 5% H₂O₂The solution has two-phase contact phase ratio of O/A5/1, contact time of 5min, settling phase separation time of 10min, and normal temperature.

And adding a hot 3mol/L NaOH solution into a thorium chloride solution precipitation tank to carry out precipitation and back extraction, wherein the reaction temperature of the precipitation and back extraction is 70 +/-5 ℃, the reaction time is 60min compared with O/A which is 3/1, and the time of clarification and phase separation is 45min, so that a solid thorium hydroxide crude product is obtained.

Ferric chloride and thorium obtained by the system are poor in acidification wastewater, and the wastewater comprises the following components: HCl: 0.78mol/L, U: 0.015g/L, Th: 0.042g/L, REO: 0.035g/L, Fe: 21.34g/L, CODcr: 9.4, SS: 86 mg/L. Adding a solid thorium hydroxide crude product prepared by the system, adjusting the pH value to 4.5, filtering and deslagging by a box filter press, adding 0.4kg of magnetic seeds, 0.2kg of PAC and 0.002kg of PAM into each cubic of filtrate, performing sedimentation separation by a thickener, feeding the overflowing supernatant into a superconducting magnetization separation system, returning the superconducting magnetization separation effluent to the system for recycling, discharging mud in the filter residue through a sludge discharge port, storing by a packaging container, and returning the separated magnetic seeds to the wastewater treatment system for utilization.

The method comprises the steps of firstly carrying out nanofiltration treatment on uranium precipitation mother liquor and thorium precipitation mother liquor, intercepting chlorate with molecular weight of more than 200, carrying out electrodialysis or ultrafiltration treatment, returning 70-80% of obtained light water to a system for utilization, combining obtained 20-30% concentrated wastewater with chlorate wastewater with molecular weight of more than 200, treating condensate water obtained by evaporation concentration of a multi-effect evaporator by using an evaporation concentration desalination technology of the multi-effect evaporator, returning the condensate water to the system for utilization, and storing the chlorate obtained by evaporation concentration of the multi-effect evaporator by using a packaging container.

Claims (10)

1. A process method for smelting and separating uranium, thorium and rare earth from monazite concentrate is characterized by comprising the following steps: the method comprises the following steps:

(1) wet bead grinding crushing and magnetic separation iron removal: conveying monazite concentrate with the passing rate of more than 99.5 percent and the granularity of-80 meshes to a high-level stock bin through an automatic bag breaking and belt conveyer, enabling the monazite concentrate to fall into a pulp making tank from the high-level stock bin to be mixed with 50-60 percent NaOH solution, pumping the uniformly mixed slurry into a bead mill for wet bead milling crushing until the granularity of more than 99.5 percent is-320 meshes, pumping the monazite concentrate ore pulp with the milled granularity of-320 meshes into a magnetic separator to enrich uranium-thorium and rare earth in the monazite concentrate, and pumping the ore pulp enriched with the rare earth, uranium and thorium after grinding and selection into an alkali decomposition high-level tank after water separation; the indissolvable minerals containing ilmenite, rutile and zircon are treated in a tailing mode;

(2) alkali decomposition and alkali cake washing and filtering: pumping the grinded and selected qualified ore pulp into a quintuplet integrated alkali decomposition tank, wherein the quintuplet integrated alkali decomposition tank is a decomposition tank which is connected in series and integrates the functions of alkali decomposition, aging, pulping and washing; controlling the initial sodium hydroxide concentration to be 50-60% NaOH solution, controlling the volume of the sodium hydroxide solution/the weight of the ground monazite concentrate to be 0.8-2.5/1, carrying out long-time continuous high-temperature alkali decomposition, adding water for heat preservation and aging after complete reaction, and siphoning supernatant in an alkali decomposition tank to obtain trisodium phosphate solution; adding hot water into the slurry at the bottom of the alkali decomposition tank after siphoning the clear liquid for heat preservation pulping, siphoning the clear liquid again, adding hot water into the slurry after siphoning the clear liquid for pulping, feeding the slurry after pulping into a multistage thickener for countercurrent washing and dephosphorization, and obtaining a filter cake as an alkali cake after solid-liquid separation;

(3) trisodium phosphate by-product preparation: immediately adding zinc powder and ferrous sulfate into the hot trisodium phosphate solution which is just separated out for precipitation and impurity removal treatment, and performing sealed barreling storage on filter residues obtained after solid-liquid separation; directly carrying out evaporation concentration, cooling crystallization and centrifuge filtration on the filtered solution after impurity removal to obtain a crude product of the solid trisodium phosphate, washing the crude product for impurity removal by pulping, and filtering and separating by the centrifuge to obtain a solid trisodium phosphate product; the washed filtered mother liquor enters a waste alkali liquor evaporation concentration system, lime milk is added for desilicification treatment after concentration, NaOH in the obtained waste alkali liquor is more than 30 percent, and the obtained waste alkali liquor returns to the wet method bead grinding and magnetic separation deironing process for preparing 50-60 percent NaOH alkali liquor;

(4) preferential dissolution of hydrochloric acid: adding the alkali cake into a 6-stage continuous dissolution optimum tank for hydrochloric acid optimum dissolution, wherein the initial acidity of hydrochloric acid is 6mol/L, stirring, heating for dissolution, controlling the pH value of the residual acid of the reaction to be 2.0-2.5, supplementing monazite alkali cake, adjusting the pH value to be 3.5-4.5, and precipitating and separating radionuclide and other impurities; boiling, aging and carrying out solid-liquid separation on the solution after separation and impurity removal to obtain a rare earth chloride clear solution which is used for preparing a rare earth chloride mixture product in the subsequent step; filtering residue to obtain optimal dissolving residue;

(5) preparing a rare earth mixture product: adding a barium chloride solution and an ammonium sulfate solution into the rare earth chloride clear liquid, stirring and heating for removing and aging, storing filtered filter residues in a sealed barrel, evaporating and concentrating the filtrate, cooling and crystallizing to obtain a flaky mixed rare earth chloride product;

(6) fully dissolving hydrochloric acid: putting the excellent dissolving slag in the step (4) into a 6-stage continuous dissolving full dissolving tank, controlling the reaction temperature and time and the acidity of residual acid, cooling to 50-60 ℃ after boiling, adding hydrogen peroxide with the concentration of 31% into the dissolved solution to ensure that uranium, thorium and rare earth in monazite concentrate fully react with hydrochloric acid and are transferred into the dissolved solution, siphoning to obtain a full dissolving solution, adding water into slurry after siphoning, stirring, and performing liquid-solid separation; merging the last stage washing water of the countercurrent washing with the hydrochloric acid full solution to obtain an extraction stock solution for uranium-thorium extraction;

(7) extracting uranium and recycling: extracting uranium for the second time by using an N235 system extracting agent; extracting uranium from the extraction stock solution in the first extraction process to obtain a uranium-containing loaded organic phase; carrying out back extraction on the loaded organic phase by high-concentration hydrochloric acid to obtain a uranyl chloride solution; extracting enriched uranium for the second time from the uranyl chloride solution by using an N235 system extracting agent; carrying out back extraction by using a slightly acidic hydrochloric acid solution to obtain a uranyl chloride qualified solution, adding caustic soda flakes to the uranyl chloride qualified solution to precipitate uranium, and preparing a solid sodium uranate product; carrying out back extraction on the uranium by using low-concentration hydrochloric acid to remove iron to obtain an iron chloride solution, and entering an acidic wastewater treatment system;

(8) extraction and thorium recovery: extracting the thorium by using an acidic phosphorus-containing extractant to obtain a thorium-containing loaded organic phase and a rare earth-containing extraction aqueous phase; washing the loaded organic phase of thorium with hydrogen peroxide to remove impurities, transferring the organic phase to a thorium hydroxide precipitation back-extraction tank, and adding alkali to carry out precipitation back-extraction to obtain a rough thorium hydroxide product; the extracted water phase after thorium extraction contains rare earth, and the rare earth is returned to the hydrochloric acid preferential dissolution process to recover a chlorinated rare earth mixture;

(9) wastewater treatment: carrying out superconducting magnetization treatment on the acidic wastewater generated in the uranium extraction and recovery system in the step (7) and the thorium extraction and recovery system in the step (8), loading an organic phase-reversal extraction ferric chloride solution in the step (7), returning effluent treated by the acidic wastewater treatment system to the extraction uranium extraction and recovery system in the step (7) for recycling, and packaging and storing precipitation slag obtained by superconducting magnetization by using a container; the extraction uranium extraction and recovery system in the step (7) and the extraction thorium extraction and recovery system in the step (8) are separated and treated in a mode of nano-filtration → electrodialysis → multi-effect evaporator, nano-filtering the uranyl chloride precipitation mother liquor in the step (7) and the thorium chloride precipitation mother liquor in the step (8), the substance with molecular weight more than 200 enters a multi-effect evaporator evaporation concentration system, the substance with molecular weight less than 200 is treated by electrodialysis, the high-salinity waste liquid obtained by electrodialysis treatment is combined with the treatment water with molecular weight more than 200, concentrating and desalting by evaporation and concentration of a multi-effect evaporator, returning condensed water evaporated and concentrated by the multi-effect evaporator and light water prepared by electrodialysis to alkali decomposition and alkali cake washing and filtration, optimal hydrochloric acid solution and full hydrochloric acid solution utilization, and packaging and storing solid chloride obtained by evaporation, concentration, cooling and crystallization of the multi-effect evaporator by using a container.

2. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (1), monazite concentrate with the granularity of-80 meshes is purchased, the monazite concentrate subjected to automatic unpacking is conveyed to a high-position bin by a belt conveying system, the monazite concentrate is discharged from a discharge hole stored in the high-position bin and enters a pulping groove to be uniformly mixed with 50-60% of sodium hydroxide solution for pulping, the ratio of the volume of the sodium hydroxide solution to the weight of the ground monazite concentrate is 0.8-2.5/1, the ore pulp after uniform mixing is conveyed into a wet type bead mill by a rubber tube pump, under the condition of normal pressure or micro pressure, ore pulp with-320 meshes is obtained after grinding and is subjected to grading discharge from the bead mill by a built-in grading device, the monazite concentrate with the granularity of-320 meshes after bead milling is pumped into a permanent magnet separator, the ilmenite, the rutile and the zirconite in the ore pulp are selected, the separation rate is 5%, and the magnetic impurities in the ore pulp are less than 2%, the non-magnetic impurities are less than 1 percent, the light minerals are less than 1.8 percent, and the granularity is less than-320 meshes; the combined amount of rare earth in the monazite concentrate after magnetic separation is correspondingly improved by 1 to 10 percent, and the content of Fe is less than 1.0 percent; and (3) carrying out dense water separation treatment on the monazite concentrate ore pulp enriched with uranium, thorium and rare earth after magnetic separation to obtain qualified ore pulp meeting the requirements, and pumping the qualified ore pulp into an alkali decomposition elevated tank by using a pump.

3. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (2), the qualified ore pulp in the elevated tank is pumped into a quintuplet integrated alkali decomposition tank, the initial concentration of sodium hydroxide in the pulp is 50-60% NaOH, the liquid-solid ratio is 0.8-2.5/1 (volume/weight), the high-temperature alkali decomposition reaction is completed by heating, the reaction temperature is 140-150 ℃, and the continuous alkali decomposition reaction time is 4-14 h; the alkali decomposition rates of valuable resources of uranium, thorium and rare earth in monazite concentrate are respectively that REO is more than or equal to 95 percent and U is₃O₈≥98％，ThO₂More than or equal to 98 percent; adding 90 ℃ production water with the volume being one time of the weight of the ore pulp into the alkaline decomposition slurry for heat preservation and aging, wherein the temperature for heat preservation and aging is not lower than 90 ℃ and the time is 12 hours; after the 1 st standing, the supernatant is decomposed by adopting siphon separation alkali to recover trisodium phosphate solution; adding water into the alkaline decomposition bottom slurry, stirring to prepare uniform slurry, then performing 2 nd standing siphon separation to recover supernatant, combining the two-time standing siphon supernatant to obtain trisodium phosphate solution, and preparing a crude trisodium phosphate product by adopting a triple-effect evaporation concentration and cooling crystallization mode; and (3) standing and separating the bottom slurry for the 2 nd time to obtain bottom slag, adding hot water, and stirring to prepare slurry, wherein the bottom slurry is 1: (4-5) (v/v), uniformly stirring, transferring the homogenate into a thickener by using a pump for sedimentation separation, and separating liquid and solid by using a 2-4-stage countercurrent thickener for sedimentation separation and a 1-2-stage van filter press; after the alkaline cake is subjected to multistage countercurrent washing dephosphorization treatment, the pH value of the last alkaline cake washing water is controlled to be 7-8, and P in the washing water₂O₅Less than 1.2g/L, and entering subsequent hydrochloric acid for preferential dissolution.

4. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (3), the 50-60% sodium hydroxide solution is prepared by concentrating the filtered mother liquor after washing the crude trisodium phosphate product until NaOH in the solution is more than 30%, transferring the filtered mother liquor to a silicon removal tank, adding lime cream to remove silicon, returning the waste alkali liquor after silicon removal to an alkali liquor preparation tank, adding solid sodium hydroxide in proportion, and pumping the solution into an alkali liquor head tank for later use when the prepared liquid contains 50-60% NaOH; mixing the primary aging and secondary standing siphon supernatant in an alkali decomposer to obtain a trisodium phosphate solution before concentration; adding zinc powder 0.25% times the weight of monazite ore and ferrous sulfate 1% times the weight of monazite ore into hot trisodium phosphate solution, stirring, maintaining the temperature, removing impurities, filtering by a box filter press to separate out filter residue, storing the filter residue in a sealed barrel, and removing trisodium phosphate from the filtrate to perform evaporation concentration; evaporating and concentrating the obtained trisodium phosphate filtrate by using a triple-effect evaporator, and transferring the concentrated supersaturated trisodium phosphate solution into a crystallizer for cooling crystallization when the Baume degree is 28-32 Be degrees; and filtering the cooled and crystallized trisodium phosphate crystal slurry through a two-stage piston pusher centrifuge to obtain a crude trisodium phosphate product, adding deionized water with the volume of 0.5-1 time of that of the crude trisodium phosphate product to perform pulping and washing, and separating through the two-stage piston pusher centrifuge to obtain a trisodium phosphate byproduct.

5. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (4), an alkali cake obtained by alkali decomposition is added into a hydrochloric acid optimum solution tank to perform 6-level hydrochloric acid optimum solution, the initial concentration of hydrochloric acid used for dissolving is 6mol/L, the hydrochloric acid is prepared from an extracted water phase after thorium extraction and a certain amount of concentrated hydrochloric acid, heating, stirring and dissolving are performed, the pH value of the optimum solution is controlled to be 2.0-2.5 after the optimum solution is completely dissolved, the alkali cake is added to adjust the pH value of the optimum solution, the acidity of the optimum solution is controlled to be 3.5-4.5, heating, stirring and reacting are continuously performed for 4-6 h, boiling is performed for 0.5-1 h, aging is performed for 8-12 h, Fe, Al, U and Th elements are fully precipitated, solid-liquid separation is performed through a chamber filter press, rare earth chloride clear liquid with REO being more than or equal to 150g/L is obtained and used for preparing rare earth chloride mixture products, and the optimum solution slag is used for the subsequent thorium full-solution uranium separation process by hydrochloric acid.

6. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (5), a barium chloride solution and an ammonium sulfate solution are added into a rare earth chloride impurity removal tank, impurity removal and discharge removal are carried out on the rare earth chloride solution, the impurity removal temperature is higher than 40 ℃, the time is 0.5-1.5 hours, the aging time is longer than 8 hours, the mixture is filtered through a box filter press, filter residues are stored in a sealed barrel, filtrate is evaporated and concentrated through a multi-effect evaporator, the temperature is controlled to be 102-150 ℃, the vacuum degree is 600-700 mmHg, a supersaturated rare earth chloride solution is obtained through concentration, and the supersaturated rare earth chloride solution is cooled and crystallized on a crystallization piece-making device to obtain a flaky rare earth chloride product.

7. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (6), adding the optimal dissolving slag into an acid complete dissolving tank, dissolving 6-grade hydrochloric acid, wherein the initial concentration of dilute hydrochloric acid used for completely dissolving the hydrochloric acid is 6mol/L, the solid-to-liquid ratio of the optimal dissolving slag (kg) to the dilute hydrochloric acid (L) is 1 (1-1.5), the reaction temperature is 80-95 ℃, the reaction time is 4-6 h, the acidity of the residual acid is controlled to be 2-3 mol/L HCl, then boiling for 1-1.5 h, cooling the temperature of the dissolved solution to 50-60 ℃ after boiling, adding 31% hydrogen peroxide, aging for more than 8h according to the proportion of (0.010-0.200) t hydrogen peroxide/t wet optimal dissolving slag, completely dissolving valuable resources in the optimal dissolving slag and allowing the valuable resources to enter a liquid phase, and collecting valuable resources containing uranium, thorium and rare earth by adopting a siphon supernatant method; adding hot washing water into a stirring tank in which the slurry is stored after siphoning, uniformly stirring and pulping according to the liquid-solid ratio of the volume of the hot washing water to the volume of the slurry being (1-3): 1(V/V), pumping into a thickener, and filtering by adopting 2-4 stages of countercurrent dense settling separation and 1-2 stages of van-type filter presses to perform liquid-solid separation; supernatant of the first-stage thickener overflows to uranium extraction stock solution for preparation, washing water of the second-stage thickener is pumped into a stirring tank below the last-stage thickener for pulping and washing, and is pumped into the first-stage thickener for precipitation and separation; the underflow slurry of the thickener flows into a pulping tank and then enters the next thickener, the underflow slurry of the last thickener enters a van-type filter press for filtration, and acid insoluble slag is packaged and stored by a container; and (3) combining the last stage of washing water with valuable resource dissolving liquid containing uranium, thorium and rare earth in countercurrent washing to obtain extraction stock solution for uranium-thorium extraction.

8. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (7), 2-5-stage countercurrent extraction is carried out in the first uranium extraction process to extract uranium, and the loaded organic phase obtained by extraction contains uranium and iron; firstly, carrying out 4-9-stage back extraction by using 2.0-3 mol/L hydrochloric acid to obtain a uranyl chloride solution with a low concentration; then, carrying out back extraction on the iron by using 0.1mol/L hydrochloric acid by using 4-9 levels to obtain an iron chloride solution, and feeding the iron chloride solution into a subsequent wastewater treatment system; carrying out secondary extraction enriched uranium by taking a uranyl chloride solution with low concentration generated in the primary extraction uranium extraction process as an extraction stock solution, loading organic phase to carry out reverse extraction on uranium and iron to obtain a lean organic phase, carrying out sodium carbonate regeneration, water washing and acidification on the lean organic phase, and then enabling the organic phase to enter the next cyclic extraction uranium extraction and recovery process, wherein the organic phase is recycled; and adding alkali into the obtained uranyl chloride solution to precipitate uranium to prepare a solid sodium diuranate product, wherein an extracted water phase after uranium extraction contains thorium and rare earth, and performing subsequent extraction, separation and thorium recovery.

9. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (8), the raffinate aqueous phase after uranium extraction also contains thorium and rare earth, thorium is extracted by using an acidic phosphorus-containing extractant, one or a combination of P204, P507, Cyanex272 and TBP is used as a thorium extraction organic phase, 4-level countercurrent extraction is carried out to obtain a thorium-containing loaded organic phase, the raffinate aqueous phase after thorium extraction is a rare earth chloride-containing solution, and the raffinate aqueous phase is returned to the step (4) to recover rare earth chloride mixture; washing and impurity removing are carried out on the loaded organic phase containing thorium chloride, then the loaded organic phase is transferred to a thorium hydroxide precipitation back extraction tank, and hot sodium hydroxide solution is added for precipitation back extraction to obtain a rough thorium hydroxide product.

10. The process for the metallurgical separation of uranium, thorium and rare earth from monazite concentrates according to claim 1, characterized in that: in the step (9), adding the thorium hydroxide crude product obtained by the system into the ferric chloride wastewater to adjust the pH value to 4.5 +/-1,the reaction time is 30-90 min, the chamber filter press filters and removes slag, the magnetic seeds are added into the filtrate, the mixed flocculant is added after the mixture is stirred and fully mixed, and the concentration of the flocculant in the solution is controlled to be 200 multiplied by 10^-6PAC+2×10^-6PAM, then settling and separating by a thickener, allowing overflow supernatant to enter a superconducting magnetization separation system for superconducting magnetization treatment, returning superconducting magnetization separation water to the system for recycling, discharging mud in filter residues through a sludge discharge port, storing by a packaging container, and returning separated magnetic seeds to the wastewater treatment system for utilization; the method comprises the steps of carrying out nanofiltration treatment on uranium precipitation mother liquor and thorium precipitation mother liquor, intercepting chlorate with the molecular weight of more than 200, carrying out electrodialysis treatment on substances with the molecular weight of less than 200, returning light water to alkali decomposition and alkali cake washing and filtering, hydrochloric acid optimum solution and hydrochloric acid total solution utilization, combining obtained high-salinity concentrated wastewater and chlorate wastewater with the molecular weight of more than 200, carrying out evaporation concentration desalination technology treatment through a multi-effect evaporator, returning condensate water obtained by evaporation concentration through the multi-effect evaporator to alkali decomposition and alkali cake washing and filtering, hydrochloric acid optimum solution and hydrochloric acid total solution utilization, and storing solid chlorate obtained by evaporation concentration through the multi-effect evaporator by using a packaging container.

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