Continuous purification treatment process for rare earth ore acid leaching solution

Abstract

The rare earth ore acid leaching solution continuous purification treatment process comprises the following steps: adding the enriched purified organic phase into the most upstream mixing tank and continuously pumping the rare earth ore acid leaching solution; starting the operation of the agitator in each mixing tank to form a fully mixed solution flowing downstream and separating into the lower clarified rare earth ore acid leaching solution and the upper enriched purified organic phase and the scum in each clarifying tank, the enriched purified organic phase is automatically returned into the inside of the most upstream mixing tank under the action of gravity through the organic phase return pipe; controlling the volume ratio of the upper enriched purified organic phase and the lower clarified rare earth ore acid leaching solution in each clarifying tank; continuously removing the scum formed in each clarifying tank; and continuously pumping the clarified rare earth ore acid leaching solution from the lower part of the most downstream clarifying tank. The present application realizes the full-process continuous and efficient non-disturbance impurity removal / purification process.

Description

Technical Field

[0001] This invention relates to the field of rare earth hydrometallurgy technology, and in particular to a purification or impurity removal method for acid leaching solutions of low-grade impure rare earth ores before extraction. Background Technology

[0002] Solvent extraction is a key technology for separating and purifying rare earth elements. The purity of the acid leaching solution from rare earth ores, used as the extraction raw material, directly affects extraction efficiency, product quality, and the stability of the equipment operation. Secondary ores or tailings from the sorted rare earth ore contain only 30%–40% rare earth elements. The acid leaching solution obtained from these low-grade rare earth ores after roasting, acid leaching, alkali conversion, and impurity removal processes contains suspended solids, insoluble impurities such as silica and silt, as well as small amounts of non-rare earth metal ions such as aluminum and calcium. These insoluble impurities and non-rare earth metal ions not only increase the difficulty of filtration and washing, leading to a relatively higher rare earth content in the filter residue and wasting resources, but also cause emulsification, reduced mass transfer efficiency, contamination of the organic phase, and increased difficulty of back-extraction after entering the extraction tank. In severe cases, they can even cause production shutdowns for maintenance, becoming a key bottleneck restricting the continuous and stable operation of the unit and the improvement of product quality.

[0003] CN108486372B discloses a method for removing impurities from rare earth ore leaching solutions: a flocculation and trapping system is formed using polyacrylamide / barium chloride / diatomaceous earth / polyethylene glycol or a composite polyaluminum-iron mixture. Suspended solids, silt, and dissolved silica are simultaneously removed through stirring and settling, generating easily filterable solid residue. An N235-diluent-alcohol extraction system is used to extract and remove iron / copper / lead / zinc under residual acid conditions in the leaching solution, and the metals are recovered through back-extraction. This method has a complex production process, demanding operating conditions, and is difficult to scale up for continuous production. Furthermore, it consumes a large amount of impurity removal agents, has a low comprehensive utilization rate, and may introduce secondary pollution or waste. In addition, its impurity removal effect is limited by the characteristics of the impurities, and its ability to handle colloids / fine particles is insufficient.

[0004] CN114427043B discloses a high-efficiency automatic impurity removal device for rare earth element extraction and separation. The specific impurity removal process is as follows: a drive motor drives the fan blades to rotate, forcing outside air into the bottom of the device. The air is then sprayed into the mixture of extractant and rare earth liquid through a high-pressure nozzle, and the upward floating force of the airflow promotes vertical mixing. After extraction, an electromagnetic opening component switches the airflow path, guiding air above the semi-permeable membrane and pressing it downward, allowing the liquid to flow upward through the membrane, while the emulsion phase and precipitated impurities are trapped and suppressed. Subsequently, the high-pressure nozzle is sealed by an electromagnetic plate, and the air pressure pushes the bottom plate and attached impurities upward. Finally, the precipitated impurities and emulsion phase are thrown into the discharge pipe and discharged by a rotating arc plate. However, in this method, the semi-permeable membrane is easily clogged by fine particles or colloidal impurities, resulting in a decrease in permeation efficiency. Furthermore, cleaning or replacing the membrane module is a complex operation that seriously affects continuous production. The device has a complex structure involving multiple moving parts and sealing points, resulting in a high failure rate and high maintenance costs. It also has poor adaptability to impurity characteristics; for example, impurities with densities close to the feed liquid or that easily form a stable emulsion phase will affect its separation effect. Summary of the Invention

[0005] The purpose of this invention is to provide a method for purifying rare earth ore acid leaching solutions, which can at least achieve effective industrial-scale purification of acid leaching solutions, especially those of low-grade rare earth ore.

[0006] The continuous purification process for rare earth ore acid leaching solution according to the present invention includes: A series of mixing tanks are provided, wherein adjacent upstream mixing tanks and downstream mixing tanks are in liquid communication with each other through a vertical communication vessel formed between them, the vertical communication vessel having an upper inlet open on one side of the adjacent upstream mixing tank and a lower outlet open on one side of the downstream mixing tank, and each mixing tank is provided with an agitator. The system provides interconnected clarification tanks, wherein vertical baffles are suspended between adjacent upstream and downstream clarification tanks and are liquid-connected to each other through the upper and lower gaps of the vertical baffles, and the upstreammost clarification tank is liquid-connected to the downstreammost mixing tank through an overflow connection pipe. An organic phase reflux pipe is provided, with its upper end opening above the interior of one of the clarification tanks and its lower end opening below the interior of the upstream mixing tank; An enriched and purified organic phase is added to the upstream mixing tank and a rare earth ore acid leaching solution is continuously pumped in. The enriched and purified organic phase consists of a rare earth extractant and kerosene in a volume ratio of 1: (50~200). The agitators in each mixing tank are started to run to form a fully mixed solution flowing downstream and separated in each clarification tank into a lower clarified rare earth ore acid leaching solution and an upper enriched and purified organic phase and scum. The enriched and purified organic phase flows back into the lower part of the uppermost mixing tank under the action of gravity through the organic phase return pipe. The volume ratio of the enriched and purified organic phase in the upper part to the clarified rare earth ore acid leaching solution in the lower part of each clarification tank is controlled to be (1~5):1; Continuously remove the scum formed in each clarification tank; and continuously pump out the clarified rare earth ore acid leaching solution from the bottom of the downstream clarification tank.

[0007] The continuous purification process according to the present invention may further include: providing a slag scraper located above each clarification tank and continuously scraping off the scum in each clarification tank by the slag scraper.

[0008] The continuous purification process according to the present invention may further include: sending the pumped clarified rare earth ore acid leaching solution into a subsequent extraction unit.

[0009] According to the continuous purification process of the present invention, the rare earth extractant is preferably P-507 (chemical name 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester).

[0010] According to the continuous purification process of the present invention, the mixing tank is preferably three mixing tanks connected in series, the clarification tank is also preferably three clarification tanks connected in series, and the upper end of the organic phase reflux pipe is preferably open above the interior of the middle clarification tank.

[0011] The continuous purification process according to the present invention may further include: recovering and purifying the enriched and purified organic phase. The recovery and purification process preferably includes: back-extracting the enriched and purified organic phase with 3-6 mol / L hydrochloric acid, followed by separating and removing the back-extraction solution.

[0012] According to the continuous purification process of the present invention, it is preferred to control the time of rare earth ore acid leaching solution passing through the series mixing tank to be 5~10 min.

[0013] According to the continuous purification process of the present invention, it is preferred to control the time of rare earth ore acid leaching solution passing through the series clarification tanks to be 5~20 min.

[0014] The purification process of the present invention is particularly suitable for leaching solutions of low-grade rare earth minerals, such as rare earth mineral leaching solutions with a turbidity of 426.87~513.89 NTU and a suspended solids concentration of 978.54~1172.64 mg / L.

[0015] In this invention, the enriched and purified organic phase and the rare earth ore acid leaching solution are thoroughly mixed in a series mixing tank to ensure that the mass transfer process approaches equilibrium. The mixed emulsion begins to clarify and separate in a series clarifying tank. The enriched and purified organic phase rises, allowing the effectively enriched scum on it to be efficiently and continuously removed; the clarified rare earth ore acid leaching solution sinks and is ultimately and continuously discharged. Throughout the process, the enriched and purified organic phase is automatically refluxed via gravity through an organic phase reflux pipe, forming a continuous circulation loop. This invention thus achieves a continuous and efficient non-disturbance impurity removal / purification process throughout the entire process.

[0016] The purification process of this invention is simple, safe to operate, generates no waste liquid, is suitable for industrial scale-up, and has the advantages of low equipment and operating costs.

[0017] The enrichment and purification organic phase used in this invention has mild configuration conditions, a safe and controllable process, and can be recycled. It can also be restored to its optimal enrichment and purification capacity through periodic recycling and purification.

[0018] This invention can effectively remove suspended solids, silicon, silt and other insoluble impurities, as well as a small amount of non-rare earth metal ions from the acid leaching solution of low-grade rare earth ores. After impurity removal, the solution is clear and transparent and easy to filter, which effectively reduces the generation of third-phase substances and emulsification during subsequent extraction. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the purification process according to the present invention; Figure 2 for Figure 1 A partial structural diagram of the purification treatment device used. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments. However, it should be understood that the present invention is not limited to these embodiments.

[0021] Figure 1 A schematic flow diagram of the rare earth ore acid leaching solution purification process according to the present invention is shown, wherein the purification device involved includes a rare earth ore acid leaching solution storage tank 1, a series mixing tank 2, a series clarification tank 3, an organic phase reflux pipe 4, an extraction unit 5, an organic phase purification tank 6, a slag discharge tank 7, etc. Figure 2 It shows Figure 1 A partial structural diagram of the purification treatment device used.

[0022] Rare earth ore acid leaching solution storage tank 1 is used to store rare earth ore acid leaching solution, such as hydrochloric acid leaching solution from Sichuan fluorocarbon cerium ore, which contains rare earth elements such as La, Ce, Pr, Nd, Sm, Eu and Gd, as well as suspended solids, silicon and silt and other insoluble impurities, and non-rare earth impurity elements such as Al and Ca; its turbidity is usually 426.87~513.89 NTU, and the suspended solids concentration is usually 978.54~1172.64 mg / L.

[0023] The series mixing tank 2 consists of an upstream mixing tank 21, an intermediate mixing tank 22, and a downstream mixing tank 23 connected in series. Each mixing tank is equipped with a stirrer (speed 220~300 rpm). The series mixing tank 2 receives rare earth ore acid leaching solution from the rare earth ore acid leaching solution storage tank 1 through the liquid inlet 20.

[0024] A vertical connecting vessel consisting of an upper partition 24 and a lower partition 25 is formed between the upstream mixing tank 21 and the intermediate mixing tank 22. This vertical connecting vessel has an upper inlet open on the upstream mixing tank 21 side and a lower outlet open on the intermediate mixing tank 22 side, allowing the rare earth ore acid leaching solution to flow only from the upper part of the upstream mixing tank 21 to the lower part of the intermediate mixing tank 22. Similarly, a vertical connecting vessel consisting of an upper partition 26 and a lower partition 27 is also formed between the intermediate mixing tank 22 and the downstream mixing tank 23.

[0025] The series-connected clarification tank 3 consists of an upstream clarification tank 31, an intermediate clarification tank 32, and a downstream clarification tank 33 connected in series. The upstream clarification tank 31 and the downstream mixing tank 23 are in liquid communication with each other through an overflow connection pipe 28.

[0026] A vertical baffle 37 is suspended between the upstream clarifier 31 and the intermediate clarifier 32, and the two are in liquid communication with each other through the upper and lower gaps of the vertical baffle 37, respectively. Similarly, a vertical baffle 38 is also suspended between the intermediate clarifier 32 and the downstream clarifier 33.

[0027] The upper end 41 of the organic phase reflux pipe 4 is open above the interior of the intermediate clarification tank 32, while the lower end 42 is open below the interior of the upstream mixing tank 21.

[0028] Each clarification tank is equipped with a chain scraper 34 covered by a protective cover 35. The scraper moves along the entire liquid surface to continuously scrape off the scum in each clarification tank and discharges the scum to the discharge tank 7 through the discharge port 36.

[0029] The bottom of the downstream clarification tank 33 is provided with a drain outlet 39, through which the clarified rare earth ore acid leaching solution is continuously pumped to the extraction unit 5.

[0030] The organic phase purification tank 6 can selectively receive the enriched and purified organic phase from the organic phase reflux pipe 4. After adding hydrochloric acid to the organic phase purification tank 6, the enriched and purified organic phase is back-extracted. The back-extraction solution is then separated and removed to obtain the purified enriched and purified organic phase. The back-extraction process can include multiple stages, such as 3-6 stages. The hydrochloric acid concentration can be 3-6 mol / L, for example, 5 mol / L, and the back-extraction ratio can be 1:1. The back-extraction solution can also be further used to recover elements such as Al, Ca, and Fe.

[0031] The purification process of rare earth ore acid leaching solution according to the present invention is briefly described below.

[0032] First, enriched and purified organic phase is added to the upstream mixing tank 21 and rare earth ore acid leaching solution is continuously pumped into the rare earth ore acid leaching solution storage tank 1 (feeding is stopped after the amount of enriched and purified organic phase added reaches the set amount). The agitators in each mixing tank are started to form a mixed solution and pass through each mixing tank in sequence through the corresponding vertical connectors. Then, it enters the upstream clarification tank 31 through the overflow connection pipe 28 and is separated into the lower part of the clarified rare earth ore acid leaching solution and the upper part of the enriched and purified organic phase and scum. During the process, the enriched and purified organic phase flows back from the upper part of the intermediate clarifying tank 32 into the lower part of the uppermost mixing tank 21 under the action of gravity through the organic phase return pipe 4, thereby circulating and mixing with the new rare earth ore acid leaching solution that continuously enters the uppermost mixing tank 21. During the process, the scum formed in each clarification tank is continuously removed by the scum scraper 34 (the collected scum can be used to prepare bricks and stones after pressure filtration). Finally, the clarified rare earth ore acid leaching solution is continuously pumped out from the lower part of the downstream clarification tank 33 and sent to the extraction unit 5 for subsequent extraction treatment.

[0033] Example 1

[0034] The parameters of the acid leaching solution for rare earth minerals to be purified are as follows: REO is 350 g / L, containing rare earth elements such as La, Ce, Pr, Nd, Sm, Eu, and Gd, as well as non-rare earth impurities such as Al, Ca, Si, Ba, and Fe, and some suspended solids, silt, and other impurities. The concentrations of Al, Ca, Si, Ba, Fe, and Pb are 1.16 g / L, 16.28 g / L, 5.36 g / L, 4.59 g / L, 0.13 g / L, and 0.12 g / L, respectively. The turbidity is 451.38 NTU, and the suspended solids concentration is 1033.21 mg / L.

[0035] The enriched and purified organic phase P-507 and kerosene were composed at a volume ratio of 1:50. The volume ratio of the upper enriched and purified organic phase to the lower clarified rare earth ore acid leaching solution in each clarification tank was controlled at 3:1. The time for the rare earth ore acid leaching solution to pass through the series mixing tank was controlled at 5 min; the time to pass through the series clarification tank was controlled at 15 min.

[0036] The test results of the rare earth ore acid leaching solution after purification were as follows: the appearance was clear and transparent, with no obvious insoluble impurities; the Al concentration was 0.25 g / L, the Ca concentration was 13.37 g / L, the Si concentration was 0.18 g / L, the Ba concentration was 2.63 g / L, the Fe concentration was <0.018 g / L, the Pb concentration was 0.04 g / L, the turbidity was 19.21 NTU, and the suspended solids concentration was 54.68 mg / L.

[0037] Example 2

[0038] The parameters of the acid leaching solution for rare earth minerals to be purified are as follows: REO is 350 g / L, containing rare earth elements such as La, Ce, Pr, Nd, Sm, Eu, and Gd, as well as non-rare earth impurities such as Al, Ca, Si, Ba, and Fe, and some suspended solids, silt, and other impurities. The concentrations of Al, Ca, Si, Ba, Fe, and Pb are 2.10 g / L, 16.01 g / L, 3.43 g / L, 4.34 g / L, 0.11 g / L, and 0.09 g / L, respectively. The turbidity is 426.87 NTU, and the concentration of suspended solids is 978.54 mg / L.

[0039] The enriched and purified organic phase P-507 and kerosene were composed at a volume ratio of 1:100. The volume ratio of the upper enriched and purified organic phase to the lower clarified rare earth ore acid leaching solution in each clarification tank was controlled at 1:1. The time for the rare earth ore acid leaching solution to pass through the series mixing tank was controlled at 10 min; the time to pass through the series clarification tank was controlled at 20 min.

[0040] The test results of the rare earth ore acid leaching solution after purification were as follows: the appearance was clear and transparent, with no obvious insoluble impurities. The concentration of Al in the rare earth ore acid leaching solution was 0.28 g / L, the concentration of Ca was 12.16 g / L, the concentration of Si was 0.22 g / L, the concentration of Ba was 2.28 g / L, the concentration of Fe was <0.018 g / L, the concentration of Pb was 0.06 g / L, the turbidity was 26.47 NTU, and the concentration of suspended solids was 70.87 mg / L.

[0041] Example 3

[0042] The parameters of the acid leaching solution for rare earth minerals to be purified are as follows: REO is 350 g / L, containing rare earth elements such as La, Ce, Pr, Nd, Sm, Eu, and Gd, as well as non-rare earth impurities such as Al, Ca, Si, Ba, and Fe, and some suspended solids, silt, and other impurities. The concentrations of Al, Ca, Si, Ba, Fe, and Pb are 2.03 g / L, 17.28 g / L, 4.13 g / L, 2.38 g / L, 0.07 g / L, and 0.20 g / L, respectively. The turbidity is 513.89 NTU, and the suspended solids concentration is 1172.64 mg / L.

[0043] The enriched and purified organic phase P-507 and kerosene were composed at a volume ratio of 1:200. The volume ratio of the upper enriched and purified organic phase to the lower clarified rare earth ore acid leaching solution in each clarification tank was controlled at 5:1. The time for the rare earth ore acid leaching solution to pass through the series mixing tank was controlled at 5 min; the time to pass through the series clarification tank was controlled at 10 min.

[0044] The test results of the rare earth ore acid leaching solution after purification were as follows: the appearance was clear and transparent, with no obvious insoluble impurities. The concentration of Al in the rare earth ore acid leaching solution was 0.39 g / L, the concentration of Ca was 14.75 g / L, the concentration of Si was 0.14 g / L, the concentration of Ba was 1.68 g / L, the concentration of Fe was 0.02 g / L, the concentration of Pb was 0.07 g / L, the turbidity was 30.35 NTU, and the concentration of suspended solids was 79.53 mg / L.

[0045] In this invention, the enriched and purified organic phase and the rare earth ore acid leaching solution are fully mixed in a series mixing tank 2. Driven by the hydrodynamic force generated by stirring, the mixed emulsion overflows sequentially through a vertical connector into the downstream mixer for subsequent two stages of mixing, ensuring that the mass transfer process approaches equilibrium. The fully mixed emulsion then enters the upstream clarification tank 31 through the overflow connection pipe 28 for clarification and separation. The enriched and purified organic phase rises and sequentially enters the downstream clarification tank through the upper passage of the corresponding vertical baffles, while insoluble impurities and other scum accumulate on the surface of the enriched and purified organic phase for continuous removal. The clarified rare earth ore acid leaching solution sinks and sequentially enters the downstream clarification tank through the lower passage of the corresponding vertical baffles, and is ultimately continuously discharged. Throughout the process, the enriched and purified organic phase is returned by gravity through the organic phase return pipe 4, forming a continuous circulation loop. This invention thus achieves a continuous and efficient non-disturbance impurity removal / purification process.

[0046] In summary, this invention can simultaneously remove multiple non-rare earth metal ions from rare earth ore acid leaching solutions, effectively reducing turbidity and suspended solids content.

Claims

1. A continuous purification process for rare earth ore acid leaching solution, comprising: A series of mixing tanks are provided, wherein adjacent upstream mixing tanks and downstream mixing tanks are in liquid communication with each other through a vertical communication vessel formed between them, the vertical communication vessel having an upper inlet open on one side of the adjacent upstream mixing tank and a lower outlet open on one side of the downstream mixing tank, and each mixing tank is provided with an agitator. The system provides interconnected clarification tanks, wherein vertical baffles are suspended between adjacent upstream and downstream clarification tanks and are liquid-connected to each other through the upper and lower gaps of the vertical baffles, and the upstreammost clarification tank is liquid-connected to the downstreammost mixing tank through an overflow connection pipe. An organic phase reflux pipe is provided, with its upper end opening above the interior of one of the clarification tanks and its lower end opening below the interior of the upstream mixing tank; An enriched and purified organic phase is added to the upstream mixing tank and a rare earth ore acid leaching solution is continuously pumped in. The enriched and purified organic phase consists of a rare earth extractant and kerosene in a volume ratio of 1: (50~200). The agitators in each mixing tank are started to run to form a fully mixed solution flowing downstream and separated in each clarification tank into a lower clarified rare earth ore acid leaching solution and an upper enriched and purified organic phase and scum. The enriched and purified organic phase flows back into the lower part of the uppermost mixing tank under the action of gravity through the organic phase return pipe. The volume ratio of the enriched and purified organic phase in the upper part to the clarified rare earth ore acid leaching solution in the lower part of each clarification tank is controlled to be (1~5):1; Continuously remove the scum that forms in each clarifier tank; and Clarified rare earth ore acid leaching solution is continuously pumped out from the bottom of the downstream clarification tank.

2. The process according to claim 1 further includes: A scum scraper is provided at the top of each clarification tank, and the scum scraper continuously removes the floating scum in each clarification tank.

3. The process according to claim 1 further includes: The clarified rare earth ore acid leaching solution pumped out is sent to the subsequent extraction unit.

4. The process according to claim 1, wherein the rare earth extractant is P-507.

5. The process according to claim 1, wherein the mixing tank is three mixing tanks connected in series, the clarification tank is also three clarification tanks connected in series, and the upper end of the organic phase reflux pipe is open above the interior of the middle clarification tank.

6. The process according to claim 1, further comprising: The enriched and purified organic phase is recovered and purified.

7. The process according to claim 6, wherein the recycling and purification treatment includes: The enriched and purified organic phase was back-extracted with 3-6 mol / L hydrochloric acid, and then the back-extraction solution was separated and removed.

8. According to the process described in claim 1, the time for the rare earth ore acid leaching solution to pass through the series mixing tank is controlled to be 5-10 minutes.

9. According to the process described in claim 1, the time for the rare earth ore acid leaching solution to pass through the series clarification tanks is controlled to be 5~20 min.

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