Method and device for recovering rare earth and china clay in china clay raw ore

Abstract

The invention provides a recovery method and a recovery device for rare earth and porcelain clay in porcelain clay raw ore, and relates to the technical field of comprehensive utilization of porcelain clay raw ore, the recovery device comprises: a plate-and-frame filter press for pressing porcelain clay raw ore pulp into a filter cake, and leaching the filter cake into a rare earth-containing leaching solution under the action of a purifying agent, washing the residual salt-containing filter cake, and discharging to obtain a porcelain clay product; and the sedimentation tank is used for collecting the rare earth-containing immersion liquid and carrying out sedimentation treatment on the rare earth-containing immersion liquid to obtain rare earth concentrate. According to the method, the plate-and-frame filter press is used for leaching the rare earth, the porcelain clay product is obtained, the recycling method has the advantage that the using amount of the purifying agent is small, the ion phase rare earth in the porcelain clay raw ore can be efficiently and rapidly removed, and the method has a good large-scale application prospect.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of kaolin ore, and in particular to a method and apparatus for recovering rare earth elements and kaolin from kaolin ore. Background Technology

[0002] Kaolin is mainly used in papermaking, ceramics, paints and plastics. About 80% of China's kaolin is used in low- to mid-end industries such as ceramics, while most of the high-whiteness, papermaking and coating grade high-end kaolin products rely on imports.

[0003] Currently, the industrial process commonly uses wet separation to produce high-quality kaolin products. This involves crushing the raw ore, mixing it with water and other substances in a slurry machine to make a slurry, and removing sand and gravel at the same time. The slurry is first desanded by a rake washing box, a flotation classifier, or a hydrocyclone, and then separated into coarse and fine particle sizes by a continuous centrifuge, hydrocyclone, hydraulic separator, or vibrating fine screen. The fine particle product obtained by the classifier is leached with iron oxide. The slurry obtained after leaching is then treated with alum to coagulate the clay minerals, and finally dewatered to obtain high-quality kaolin products.

[0004] The weathered crust type kaolin deposits widely distributed in my country often contain 0.01% to 0.05% ionic rare earth elements, resulting in substandard color of the kaolin. To address this, a combination of wet separation and ammonium sulfate or magnesium sulfate leaching processes is generally used to remove rare earth elements, improve the quality of the kaolin, and achieve rare earth recovery. For example: One existing technology uses ammonium sulfate for rare earth leaching in a mechanical classifier, achieving a rare earth leaching rate greater than 90%. The kaolin product is then obtained through screening and hydrocyclone classification. Another existing technology proposes a method for simultaneously recovering kaolin and rare earth from ion-adsorption type rare earth ores. This involves adding sulfuric acid, ammonium bisulfate, or ammonium sulfate as a leaching agent during the slurrying process, causing an ion exchange reaction between the rare earth and the leaching agent. The resulting product is then subjected to wet beneficiation and filtration to obtain a filter cake containing kaolin and a filtrate containing rare earth, achieving a rare earth leaching rate of 88%. Yet another existing technology proposes a method for extracting rare earth from kaolin containing ion-adsorption rare earth. This involves first mixing the kaolin product with an ammonium sulfate solution to form a slurry, then continuously stirring in a leaching tank to ensure a full reaction between the rare earth and ammonium sulfate in the kaolin product. Finally, the product is filtered using a plate and frame filter press to obtain a kaolin-containing product. The existing technology proposes a comprehensive treatment process for rare earth ore using ion adsorption, which involves leaching rare earth ore through a 60-mesh sieve with ammonium sulfate or ammonium carbonate using stirring, achieving a rare earth extraction rate of 85%–96%. The rare earth tailings are then subjected to gravity separation-magnetic separation to extract kaolin. Another existing technology proposes a method for leaching rare earths from raw kaolin ore containing rare earths, which involves leaching rare earths from the raw kaolin ore using a magnesium salt solution. The magnesium salt solids are then added sequentially to the primary and secondary slurries for stirring and leaching. The high-alumina sand is washed with clean water, achieving a rare earth leaching rate of over 90%. Subsequently, the rare earth-containing solution is subjected to non-saponification and non-equilibrium coupled extraction as well as centrifugal back-extraction. The raffinate is then recycled back to the raw kaolin ore containing rare earths for stirring and leaching, further reducing the aluminum leaching rate and improving the quality of the kaolin.

[0005] The above methods all combine wet separation processes with ammonium sulfate or magnesium sulfate leaching processes. Essentially, they all employ large-scale agitation leaching to remove impurities from kaolin, requiring a liquid-to-solid ratio of leaching agent to rare earth ore greater than 2.5 to ensure complete leaching. Due to the large amount of leaching agent used, the entire system requires a large amount of washing water to wash the filter cake containing high levels of salt (purifying agent), leading to severe leaching solution swelling and overall water imbalance. Furthermore, this method struggles to address the overall water imbalance during leaching solution recycling, and if washing is incomplete, excess ammonia nitrogen or high-salt wastewater remaining in the filter cake after washing requires centralized and standardized treatment to meet standards.

[0006] Therefore, in the field of comprehensive utilization technology of kaolin ore, how to avoid the use of purifying agents while ensuring the removal rate and speed of ionic rare earth elements in kaolin ore during the mining process remains an urgent problem to be solved in the future. Summary of the Invention

[0007] To address the aforementioned problems, in a first aspect, the present invention provides a device for recovering rare earth elements and kaolin clay from raw kaolin ore, characterized in that the recovery device comprises: Plate and frame filter press is used to press the raw kaolin ore slurry into filter cake, and to leach the filter cake with rare earth leaching solution under the action of purifying agent. The remaining salt-containing filter cake is washed and discharged to obtain kaolin product. A sedimentation tank is used to collect rare earth-containing leachate and to perform sedimentation treatment on the rare earth-containing leachate to obtain rare earth concentrate.

[0008] Optionally, the plate and frame filter press is provided with a pressing plate and at least one set of pressing components, the pressing components including filter plates and filter frames; the raw kaolin slurry entering the pressing components is pressurized and dewatered under the action of the pressing plate to obtain filter cake and filtered water.

[0009] Optionally, the bottom of the plate and frame filter press is provided with a collection tank for collecting the washing liquid and filtered water flowing out of the plate and frame filter press.

[0010] Secondly, the present invention provides a method for recovering rare earth elements and kaolin from raw kaolin ore, characterized in that the recovery method includes: The raw kaolin ore slurry is injected into a plate and frame filter press for pressure dewatering to obtain filter cake and filtered water. Purifying agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach rare earth ions in the filter cake for 0.1 h to 2 h, thereby obtaining a rare earth leachate and a salt-containing filter cake. The salt-containing filter cake is washed, purged, and then discharged to obtain the kaolin product. The rare earth-containing leachate is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate. The purifying agent is at least one of ammonium sulfate solution, magnesium sulfate solution, and ammonium nitrate solution.

[0011] Optionally, the amount of the purifying agent is 30-60% of the mass of the filter cake, the concentration of the purifying agent is 0.01 mol / L to 0.2 mol / L, and the pH value of the purifying agent is 1-5.5.

[0012] Optionally, the slurry of raw porcelain clay is obtained by adding water to the crushed raw porcelain clay and removing sand while it is being stirred; wherein the liquid-solid mass ratio of the water to the raw porcelain clay is 0.5:1 to 5:1.

[0013] Optionally, the recycling method further includes: reusing the filtrate to prepare the purifying agent, including: adjusting the pH of the filtrate to 2-3 using an acid containing the anion of the purifying agent, and then reusing it as the purifying agent.

[0014] Optionally, the salt-containing filter cake is washed, and the washing liquid is collected in a collection tank for secondary washing.

[0015] Optionally, the washing time for the salt-containing filter cake is 0.1 h to 2 h. Optionally, the step of transferring the rare earth-containing leachate to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate includes: The rare earth-containing leaching solution is precipitated and filtered in the sedimentation tank using an alkaline precipitant to obtain the rare earth concentrate and the filtrate; the alkaline precipitant is one or more of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate.

[0016] Compared with the prior art, the present invention has the following advantages: This invention provides a method and apparatus for recovering rare earth elements and kaolin clay from raw kaolin ore, relating to the field of comprehensive utilization technology of raw kaolin ore. The recovery apparatus includes: A plate and frame filter press is used to pressurize kaolin ore slurry into a filter cake, and then leaches the filter cake with rare earth-containing solution under the action of a purifying agent. The remaining salt-containing filter cake is washed and discharged to obtain kaolin product. A sedimentation tank is used to collect the rare earth-containing solution and perform sedimentation treatment on the solution to obtain rare earth concentrate. In this invention, the kaolin ore slurry is injected into the plate and frame filter press for pressurized dewatering to obtain filter cake and filtrate. A purifying agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach rare earth ions in the filter cake for 0.1 h to 2 h to obtain rare earth-containing solution and salt-containing filter cake. The salt-containing filter cake is washed to obtain washing liquid and washed filter cake. The washed filter cake is purged and discharged to obtain kaolin product. The rare earth-containing solution is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate. The method provided by this invention can efficiently and quickly obtain ionic rare earth elements and porcelain products from raw kaolin ore, and has good prospects for large-scale application.

[0017] The rare earth leaching method provided in this embodiment of the invention extracts rare earth elements using a plate and frame filter press during the leaching process of kaolin ore. A certain concentration and amount of purifying agent is injected into the plate and frame filter press, followed by pressurized leaching. This pressurized ion exchange method achieves efficient extraction of rare earth elements by the purifying agent. On the one hand, under a certain pressure (0.05 MPa~1.5 MPa), High-pressure ion exchange leaching at MPa can improve the removal rate and efficiency of ionic rare earth elements in kaolin ore, thereby reducing the concentration and dosage of purifying agent. Simultaneously, by extracting rare earth elements from the kaolin ore, the boundary grade of usable rare earth elements in the ore is expanded. Furthermore, using a plate and frame filter press as the key device for pressurized ion exchange artificially divides the leaching process into multiple zones, avoiding runoff or channeling and increasing ion exchange efficiency. The leaching rate of ionic rare earth elements is greater than 94%, and the rare earth yield is higher than that of stirred leaching. This achieves efficient, green, and controllable extraction of rare earth elements from kaolin ore, yielding high-quality kaolin products and rare earth concentrates. Therefore, the method provided by this invention eliminates the need for a high liquid-to-solid ratio to increase the rare earth yield while ensuring the leaching effect, thus avoiding the problems of requiring large amounts of washing water to wash away the large amount of leaching agent remaining in the filter cake and the large footprint of large stirred tanks. This invention utilizes a plate and frame filter press for pressurized ion exchange leaching, which improves the removal rate and speed of ionic rare earth elements in kaolin ore, thereby obtaining high-quality kaolin. Therefore, this invention does not require a combination of wet separation and stirring leaching processes to improve the quality of kaolin.

[0018] Furthermore, no wastewater is generated during the entire production process of this invention, so the method provided by this invention can completely eliminate ammonia nitrogen or high-salt wastewater pollution. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the plate and frame filter press in an embodiment of the present invention; Figure 2 This is a flowchart illustrating a method for recovering rare earth elements and kaolin clay from raw kaolin ore according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating another method for recovering rare earth elements and kaolin clay from raw kaolin ore, provided as an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0022] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0023] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0024] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0025] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Plate and frame filter presses are a well-established industrial device for solid-liquid separation, widely used in chemical, pharmaceutical, food, and environmental protection industries. They form a filtration chamber by stacking plate and frame components, applying pressure to achieve solid-liquid separation—that is, separating suspended solids from a liquid. This process purifies the liquid, recovers slurry, and ultimately yields the desired solid and liquid products. Through rational structural design and operational control, plate and frame filter presses can efficiently process slurry, improve material utilization, and reduce environmental pollution. They also boast advantages such as simple structure, convenient operation, and excellent filtration effect, thus finding widespread application in industrial production.

[0027] In this invention, a plate and frame filter press is used to extract rare earth elements during the leaching process of kaolin ore. A small amount of low-concentration purifying agent is injected into the plate and frame filter press and then pressurized. The rare earth elements are leached by high-pressure ion exchange, which achieves efficient, green and controllable extraction of rare earth elements from kaolin ore to obtain high-quality kaolin products.

[0028] In a first aspect, the present invention provides a device for recovering rare earth elements and kaolin from raw kaolin ore, characterized in that the recovery device comprises: Plate and frame filter press is used to press the raw kaolin ore slurry into filter cake, and to leach the filter cake with rare earth leaching solution under the action of purifying agent. The remaining salt-containing filter cake is washed and discharged to obtain kaolin product. A sedimentation tank is used to collect rare earth-containing leachate and to perform sedimentation treatment on the rare earth-containing leachate to obtain rare earth concentrate.

[0029] This invention utilizes a plate and frame filter press to simultaneously extract kaolin and rare earth elements. The raw kaolin ore slurry is pressed into a filter cake by the plate and frame filter press. A measured amount of purifying agent is then injected into the filter press, and the filter cake leaches a rare earth-containing solution under the action of the purifying agent. The remaining salt-containing filter cake is washed, and after washing, the filter cake is discharged, yielding the kaolin product. The obtained rare earth-containing solution is transferred to a sedimentation tank for precipitation treatment to obtain rare earth concentrate. This invention uses pressurized ion exchange to leach rare earth elements. Pressurized ion exchange leaching under a certain high pressure (0.05 MPa~1.5 MPa) can improve the removal rate and removal speed of ionic rare earth elements in the raw kaolin ore, thereby reducing the concentration and dosage of purifying agent. Simultaneously, because rare earth elements are extracted from the raw kaolin ore, the boundary grade of usable rare earth elements in the raw kaolin ore is expanded.

[0030] See Figure 1 The schematic diagram of the plate and frame filter press shown illustrates that the filter press components include a pressing plate 5 and at least one set of pressing components. The pressing components consist of filter plates 2 and filter frames 3. Each filter frame 3 and filter plate 2 has a through hole at its upper right corner, forming a channel for the flow of the kaolin ore slurry. Similarly, each filter frame 3 and filter plate 2 has a through hole at its upper left corner, forming a channel for the flow of washing water. Each filter plate 2 has a liquid outlet 6 at its bottom. After the pressing plate 5 is tightened, filter chambers are formed between adjacent filter plates 2. The kaolin ore slurry then enters the plate and frame filter press through the liquid inlet 1. After the ion-type rare earth ore slurry fills the filter chamber, the feeding is complete. After feeding, the pressing plate 5 continues to apply pressure, removing water from the kaolin ore slurry. The dewatered kaolin ore slurry is retained in each filter chamber, automatically forming a filter cake. When no liquid or only a small amount of liquid is discharged from the liquid outlet 6 of the plate and frame filter press, it indicates that the filter chamber is completely filled with filter residue, forming a filter cake.

[0031] This invention, through the setting of multiple sets of pressing components, artificially divides the leaching exchange process into multiple regions, avoiding runoff or channeling, increasing ion exchange efficiency, and achieving a leaching rate of over 94% for ion-phase rare earths. The pressing components can be reused multiple times through equipment skid mounting, eliminating the difficulties in developing dedicated pressurized ion exchange devices. This increases ion exchange efficiency, avoids runoff or channeling, and results in higher production efficiency and rare earth yield than in-situ leaching or heap leaching. It can further reduce the boundary grade of rare earth ore, increase the amount of rare earth resources, and thus achieve efficient, green, and controllable extraction of rare earth elements from ion-type rare earth ores, yielding rare earth concentrate.

[0032] See Figure 1 The schematic diagram of the plate and frame filter press shown shows that a collection tank 7 is set at the bottom of the plate and frame filter press. During the pressing of the filter cake, the squeezed filter water flows directly out of the outlet 6 of each filter plate along the grooves of the filter plate. The outflowing filter water can be returned for the preparation of the next batch of kaolin ore. The obtained filter cake is subjected to leaching operation with rare earth leachate. When obtaining rare earth leachate, the remaining salt-containing filter cake can be washed to obtain washing liquid and washed filter cake. The washing liquid is collected in the collection tank 6 and reused for secondary washing. The washed filter cake is discharged after purging and is used as kaolin product.

[0033] Specifically, the steps of the recycling device provided in this embodiment of the invention to perform the leaching task are as follows: the filter plate 2 and the filter frame 3 are pressed together by the pressing plate 5, forming a filter chamber between adjacent filter plates 2. After pressing, the feed pump and feed valve are opened, and feed is fed from the feed port 1 through the upper right corner. The feeding is completed when the kaolin ore slurry fills the filter chamber. After feeding is completed, pressure is continued to be applied to remove the water in the kaolin ore slurry through the filter cloth on the filter plate 2. The dewatered kaolin ore slurry is squeezed into each filter chamber and automatically forms a filter cake. When there is no liquid or only a small amount of liquid at the outlet of the plate and frame filter press, it indicates that the filter residue in the filter chamber has been completely filled to form a filter cake. The squeezed-out filtrate flows directly out from the outlet 6 of each filter plate along the groove of the filter plate. The outflowing filtrate is returned for conditioning the next batch of kaolin ore slurry.

[0034] Furthermore, without unloading the filter cake, a purifying agent of 30-60% of the filter cake mass is continuously pressed into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach rare earth ions in the filter cake for 0.1 h to 2 h, thereby obtaining a rare earth-containing leachate and a salt-containing filter cake.

[0035] Further, washing water is introduced through the feed inlet 1 in the upper left corner to wash the salt-containing filter cake, obtaining washing liquid and washed filter cake. The washing liquid is collected in the collection tank 7 and used as washing water for washing the salt-containing filter cake or recycled for preparing the purifying agent. The feed pump and feed valve are shut off, and the air compressor and air inlet valve are turned on to purge the washed filter cake. After purging, the air compressor and its air inlet valve are closed. After the pressing plate is returned to its original position, the unloading button is pressed, and each filter plate 2 is pulled open in sequence to unload the material, which is used as the kaolin product. The obtained rare earth leaching solution is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate. The filtrate is collected in the collection tank for preparing the rare earth leaching agent. At this point, the entire solid-liquid separation, rare earth extraction, and washing operations of the plate and frame filter press are completed.

[0036] In some implementations, the plate and frame filter press and the collection tank are connected in series or in parallel.

[0037] In this embodiment, a plate and frame filter press is connected in series or in parallel with multiple collection tanks to achieve large-scale production and mining.

[0038] Secondly, the present invention provides a method for recovering rare earth elements and kaolin clay from raw kaolin ore, wherein the recovery method is applied to the recovery apparatus provided in the first aspect above. Figure 2 This is a flowchart illustrating a method for recovering rare earth elements and kaolin clay from raw kaolin ore according to an embodiment of the present invention. Figure 2 As shown, the recycling method includes: S1. The raw kaolin ore slurry is injected into a plate and frame filter press for pressure dewatering to obtain filter cake and filtered water; Specifically, the kaolin ore is a kaolin ore containing rare earth ions. The kaolin ore slurry is obtained by adding water to the crushed kaolin ore under stirring conditions to adjust the slurry and remove sand; the liquid-to-solid mass ratio of water to kaolin ore is 0.5:1 to 5:1. Water is used to adjust the kaolin ore to obtain the kaolin ore slurry, which is used to wet the kaolin ore and ensure that it can be transported to the plate and frame filter press in slurry form; the resulting filtrate is returned for adjusting the slurry for the next batch of kaolin ore.

[0039] In this embodiment, a vertical filter press can also be used for pressure dewatering. During the pressure dewatering process, there are no specific restrictions on the operating pressure and operating time of the plate and frame filter press. When no liquid is discharged or only a small amount of liquid is discharged from the outlet of the plate and frame filter press, it proves that the filter chamber is completely filled and a filter cake has been formed. At this time, the pressure dewatering is completed.

[0040] S2. A purifying agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach the rare earth ions in the filter cake for 0.1 h to 2 h, thereby obtaining a rare earth leachate and a salt-containing filter cake. In this step, the purifying agent can be selected from at least one of ammonium sulfate solution, magnesium sulfate solution, and ammonium nitrate solution; the amount of purifying agent is 30-60% of the mass of the filter cake, the concentration of the purifying agent is 0.01 mol / L to 0.2 mol / L, and the pH value is 1-5.5.

[0041] In some implementations, the amount of purifying agent used is equal to the moisture content of the filter cake. For example, when the moisture content of the filter cake is 32.5%, then purifying agent of 32.5% of the total mass of the filter cake is injected.

[0042] In this embodiment, the entire leaching process is carried out in a plate and frame filter press, but it can also be carried out in a vertical filter press. During the leaching process, the operating pressure of the plate and frame filter press is 0.05 MPa to 1.5 MPa, which ensures the leaching yield and leaching rate of the ionic rare earth elements.

[0043] Specifically, a smaller amount and lower concentration of purifying agent (compared to stirred leaching) is injected into a plate and frame filter press, followed by pressurized ion exchange leaching (0.05 MPa~1.5 MPa) for 0.1 h~2 h to leach rare earth elements. After the exchange leaching is completed, the rare earth concentration (calculated as total rare earth oxides REO) in the final leaching solution flowing out of the plate and frame filter press is less than 0.1 g REO / L [RZH1]. At this point, the rare earth elements in the kaolin ore are basically leached out into a rare earth-containing leaching solution with a high concentration of rare earth elements. This step, through pressurized ion exchange leaching, can improve the removal rate and removal speed of ionic rare earth elements in kaolin ore, thereby reducing the concentration and dosage of purifying agent. Therefore, the method provided by this invention is more suitable for kaolin ore with lower rare earth content, thereby increasing the amount of rare earth resources to a certain extent.

[0044] S3. The salt-containing filter cake is washed, purged, and then discharged to obtain the kaolin product; Continue to flow washing water into the plate and frame filter press to wash the salt-containing filter cake for 0.1–2 hours. When the salt concentration in the washing liquid flowing out of the plate and frame filter press is below 2 g / L, it indicates that the salt in the salt-containing filter cake has been basically washed out, and at this point, stop adding washing water. After washing, the filter cake is purged and discharged to obtain the kaolin product.

[0045] S4. The rare earth-containing leaching solution is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate.

[0046] In practice, an alkaline precipitant is used to remove impurities, precipitate, and filter the leachate containing high concentrations of rare earth elements, resulting in a rare earth concentrate (rare earth ore) and filtrate.

[0047] The method provided in this embodiment, on the one hand, improves the removal rate and speed of ionic rare earth elements in kaolin ore by performing high-pressure ion exchange leaching under a certain high pressure (0.05 MPa~1.5 MPa), thereby reducing the concentration and dosage of purifying agent. At the same time, since rare earth elements are extracted from kaolin ore, the boundary grade of usable rare earth elements in kaolin ore is expanded. On the other hand, by using a plate and frame filter press as the key device for high-pressure ion exchange, the leaching exchange process is artificially divided into multiple regions, avoiding runoff or channeling, increasing ion exchange efficiency, and achieving a leaching rate of more than 94% for ionic rare earth elements. The rare earth yield is higher than that of the stirred leaching method for removing rare earth elements, thereby achieving efficient, green and controllable extraction of rare earth elements from kaolin ore, and obtaining high-quality kaolin products and rare earth concentrates. Therefore, the method provided by this invention eliminates the need for a high liquid-to-solid ratio to increase rare earth yield in order to ensure effective stirring leaching. This avoids the problems of requiring large amounts of washing water to wash away the large amount of leaching agent remaining in the filter cake and the large footprint of large stirring tanks that are necessary to ensure leaching effectiveness. Furthermore, since this invention utilizes a plate and frame filter press for high-pressure ion exchange leaching, it improves the removal rate and efficiency of ionic rare earth elements in the raw kaolin ore, resulting in high-quality kaolin. Therefore, this invention eliminates the need to combine wet separation with stirring leaching to improve the quality of the kaolin.

[0048] Furthermore, no wastewater is generated during the entire production process of this invention, so the method provided by this invention can completely eliminate ammonia nitrogen or high-salt wastewater pollution.

[0049] In some embodiments, the recovery method further includes: reusing the filtrate to prepare the purifying agent, including: adjusting the pH of the filtrate to 2-3 using an acid containing the anion of the purifying agent, and then reusing it as the purifying agent. The salt-containing filter cake is washed, and the washing liquid is collected in a collection tank for secondary washing. The washing time for the salt-containing filter cake is 0.1h to 2h.

[0050] In this embodiment, the filtrate or washing solution is returned to the leaching rare earth for recycling. No wastewater is generated in the entire production process, which can completely eliminate ammonia nitrogen or high-salt wastewater pollution, so as to maintain the total water balance in the leaching process. This makes reasonable use of the process solution and is conducive to mine environmental management.

[0051] Furthermore, no wastewater is generated during the entire production process of this invention, so the method provided by this invention can completely eliminate ammonia nitrogen or high-salt wastewater pollution.

[0052] In some embodiments, transferring the rare earth-containing leachate to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate includes: The rare earth-containing leaching solution is precipitated and filtered in the sedimentation tank using an alkaline precipitant to obtain the rare earth concentrate and the filtrate; the alkaline precipitant is one or more of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate.

[0053] To enable those skilled in the art to better understand the present invention, the preparation method provided by the present invention will be described below through several specific embodiments.

[0054] Example 1 See Figure 3 The recovery process flow chart shown shows that water and raw kaolin ore are mixed at a liquid-to-solid ratio of 4:1 to obtain raw kaolin ore slurry; wherein the raw kaolin ore contains 0.35% rare earth element (REO).

[0055] The raw kaolin ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 25.5%. Under a pressure of 0.5 MPa, a 0.05 mol / L ammonium sulfate solution (25.5% of the total filter cake mass) was slowly injected for high-pressure ion exchange leaching for 0.5 h. Then, under the same pressure, another 0.05 mol / L ammonium sulfate solution (25.5% of the total filter cake mass) was slowly injected. Throughout the leaching process, the rare earth concentration was continuously measured. The rare earth concentration exhibited a peak-shaped curve, initially low, then high, and then gradually decreasing. The rare earth concentration in the leaching solution flowing from the outlet was below 0.1 g / L, completing the leaching process and yielding a salt-containing filter cake and a rare earth-containing leaching solution.

[0056] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. If the washing solution contains a high concentration of ammonium sulfate, sulfuric acid is added to adjust its pH to 2-3 before reuse as a purifying agent. If a low-concentration washing solution is obtained, it is directly reused as washing water. The washed filter cake is then purged and unloaded, yielding a high-quality kaolin product. The residual purifying agent content in the kaolin product is 0.18%.

[0057] Example 2 See Figure 3 The recovery process flow chart shown indicates that water and raw kaolin ore are mixed at a liquid-to-solid ratio of 4:1 to obtain raw kaolin ore slurry; wherein the raw kaolin ore contains 0.05% REO rare earth elements.

[0058] The raw kaolin ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 32.5%. Under a pressure of 0.5 MPa, a 0.1 mol / L ammonium sulfate solution (32.5% of the total filter cake mass) was slowly injected for high-pressure ion exchange leaching for 0.5 h, yielding a rare earth-containing leachate and a salt-containing filter cake. Throughout the leaching process, samples were continuously taken to measure the rare earth concentration, which exhibited a peak-shaped curve showing an initial low concentration followed by a high concentration, and then a gradual decrease.

[0059] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. If the washing solution contains a high concentration of ammonium sulfate, sulfuric acid is added to adjust its pH to 2-3 before reuse as a purifying agent. If a low-concentration washing solution is obtained, it is directly reused as washing water. The washed filter cake is then purged and unloaded, yielding a high-quality kaolin product. The residual purifying agent content in the kaolin product is 0.2%.

[0060] Therefore, it can be seen that, in all embodiments provided by the present invention, the concentration and dosage of the purifying agent can be reduced to 30%-50% of the conventional level, and the residual purifying agent content in the produced kaolin is reduced to a level that has no negative impact on the use of the kaolin.

[0061] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0062] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0063] The above provides a detailed description of a method and apparatus for recovering rare earth elements and kaolin clay from raw kaolin ore. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the invention. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A device for recovering rare earth elements and kaolin clay from raw kaolin ore, characterized in that, The recycling device includes: Plate and frame filter press is used to press the raw kaolin ore slurry into filter cake, and to leach the filter cake with rare earth leaching solution under the action of purifying agent. The remaining salt-containing filter cake is washed and discharged to obtain kaolin product. A sedimentation tank is used to collect rare earth-containing leachate and to perform sedimentation treatment on the rare earth-containing leachate to obtain rare earth concentrate.

2. The recycling device according to claim 1, characterized in that, The plate and frame filter press is equipped with a pressing plate and at least one set of pressing components. The pressing components include filter plates and filter frames. The raw kaolin slurry entering the pressing components is pressurized and dewatered under the action of the pressing plate to obtain filter cake and filtered water.

3. The recycling device according to claim 1, characterized in that, The bottom of the plate and frame filter press is equipped with a collection tank for collecting the washing liquid and filtered water flowing out of the plate and frame filter press.

4. A method for recovering rare earth elements and kaolin clay from raw kaolin ore, characterized in that, The recycling method includes: The raw kaolin ore slurry is injected into a plate and frame filter press for pressure dewatering to obtain filter cake and filtered water. Purifying agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach rare earth ions in the filter cake for 0.1 h to 2 h, thereby obtaining a rare earth leachate and a salt-containing filter cake. The salt-containing filter cake is washed, purged, and then discharged to obtain the kaolin product. The rare earth-containing leachate is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate. The purifying agent is at least one of ammonium sulfate solution, magnesium sulfate solution, and ammonium nitrate solution.

5. The recycling method according to claim 4, characterized in that, The amount of the purifying agent is 30-60% of the mass of the filter cake, the concentration of the purifying agent is 0.01 mol / L to 0.2 mol / L, and the pH value of the purifying agent is 1-5.

5.

6. The recycling method according to claim 4, characterized in that, The slurry of raw porcelain clay is obtained by adding water to the crushed raw porcelain clay and removing sand while it is being stirred; wherein the liquid-solid mass ratio of the water to the raw porcelain clay is 0.5:1 to 5:

1.

7. The recycling method according to claim 4, characterized in that, The recycling method further includes: reusing the filtrate to prepare the purifying agent, including: adjusting the pH value of the filtrate to 2-3 using an acid containing the anion of the purifying agent, and then reusing it as the purifying agent.

8. The recycling method according to claim 4, characterized in that, The salt-containing filter cake is washed, and the washing liquid is collected in a collection tank for secondary washing.

9. The recycling method according to claim 4, characterized in that, The washing time for the salt-containing filter cake is 0.1 h to 2 h.

10. The recycling method according to claim 4, characterized in that, The step of transferring the rare earth-containing leachate to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate includes: The rare earth-containing leaching solution is precipitated and filtered in the sedimentation tank using an alkaline precipitant to obtain the rare earth concentrate and the filtrate; the alkaline precipitant is one or more of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate.

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