Method for batch recovery of neodymium iron boron oil sludge waste, regenerated Ce-Pr-Nd mixed rare earth and application of regenerated Ce-Pr-Nd mixed rare earth

Abstract

The invention provides a method for recycling neodymium iron boron oil sludge waste in batches, regenerated Ce-Pr-Nd mixed rare earth and application of the regenerated Ce-Pr-Nd mixed rare earth. The method comprises the following steps: 1) sequentially mixing, granulating and oxygen-controlled chloridizing roasting the neodymium iron boron oil sludge waste and a solid chlorinating agent, and grinding to obtain a roasted product; 2) sequentially performing water leaching, solid-liquid separation and extraction separation on the roasted product to obtain a loaded organic phase and a water phase; and (3) the water phase is sequentially subjected to extraction, precipitation, calcination and molten salt electrolysis, and the regenerated Ce-Pr-Nd mixed rare earth capable of being directly used for preparing the high-performance regenerated sintered neodymium-iron-boron magnet is obtained. According to the method, selective efficient extraction of rare earth elements in the waste is achieved through oxygen-controlled chloridizing roasting, and the separation efficiency and the recovery rate of the rare earth are greatly improved; the waste and the solid chlorinating agent are mixed in batches through material mixing, and the problem that the rare earth extraction rate is low due to the fact that the reactant mixing uniformity is poor during batch chloridizing roasting is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling and reusing NdFeB waste, and specifically relates to a method for batch recycling NdFeB oil sludge waste, regenerated Ce-Pr-Nd mixed rare earth and application thereof. Background Art

[0003] NdFeB permanent magnets are the largest downstream consumer of rare earths. Due to their excellent magnetic properties, they are widely used in emerging high-tech industries such as new energy vehicles, wind power generation, rail transportation, and intelligent robots. The market demand and output of sintered NdFeB have increased year by year, which has consumed a large amount of rare earth resources such as Pr, Nd, Tb, and Dy, while low-priced high-abundance rare earths are in large backlogs, resulting in an unbalanced utilization of rare earth resources. At the same time, the continuous increase in NdFeB production capacity and the price of rare earth raw materials has also brought challenges to the profit margins and survival pressure of enterprises, and there is an urgent need to find ways to reduce costs. During the processing of NdFeB blanks, NdFeB oil sludge waste will be generated, accounting for about 20-30wt% of the total output. These wastes contain about 30wt.% of rare earth elements and have huge recycling value. Therefore, the recycling of NdFeB oil sludge waste and the efficient and balanced utilization of high-abundance rare earth resources can not only reduce production costs and bring huge economic and social benefits, but also realize the efficient and comprehensive utilization of rare earth resources.

[0004] At present, the traditional hydrometallurgical process is mainly used to separate and extract rare earth elements from sintered NdFeB oil sludge waste in industrial applications. The main method is to separate impurities from rare earths through solvent extraction and precipitation separation after acid dissolution, and further separate single rare earths through solvent extraction to achieve the purpose of recycling and reusing rare earths. At present, the wet recovery routes of NdFeB waste mainly include salt full dissolution method, hydrochloric acid excellent dissolution method, sulfuric acid double salt precipitation method, oxalic acid precipitation method, solvent extraction method, etc.

[0005] Both the complete dissolution method and the sulfate double salt precipitation method use acid to completely dissolve the waste. For example, CN 1058232A discloses a method for extracting neodymium from NdFeB waste, which is to dissolve the waste with hydrochloric acid; when the solution is adjusted to a pH range of 1.5 to 7 with ammonia or / and by heating, an oxalic acid solution is added to produce a neodymium oxalate precipitate; and the separated neodymium oxalate is heated to a decomposition temperature to obtain neodymium oxide. The above method has the disadvantages of large acid consumption, which will increase the consumption of alkali in the subsequent neutralization and iron removal, thereby increasing the amount of wastewater.

[0006] The hydrochloric acid preferential solution method is to preferentially leach the rare earth in the roasted material, while Fe2O3 which is relatively insoluble in hydrochloric acid enters the slag phase. For example, CN 109554549A discloses a method for recovering rare earth in NdFeB waste by leaching at high temperature and high pressure. The NdFeB waste is subjected to oxidative roasting, hydrochloric acid high temperature and high pressure leaching, and Fe 2+The rare earth chloride leachate is obtained by oxidation and impurity removal; and the rare earth chloride leachate can be used as raw materials for subsequent processes and products, to obtain rare earths by extraction and separation, to prepare rare earth carbonates by precipitation, or to prepare rare earth oxides by precipitation-roasting. Although the acid consumption is reduced and the process flow is relatively short in the above method, the acid leaching process still consumes a lot of hydrochloric acid, and a part of the iron will enter the leachate, which needs to be purified and iron removed. At the same time, a large amount of alkali is required to neutralize the acidic wastewater.

[0007] CN 115386722A discloses a method for separating rare earth and iron by roasting NdFeB waste with pyrite, comprising the following steps: mixing NdFeB waste with pyrite, introducing oxygen, and performing selective sulphation roasting; cooling the roasted product, grinding it, and then leaching it in water and filtering it to obtain rare earth leaching solution and iron concentrate. The method converts rare earth into rare earth salt by selective sulphation roasting, and uses water leaching instead of acid leaching, which greatly reduces the acid consumption. However, the sulphur ions in pyrite are easily oxidized to form sulfur dioxide or sulfur trioxide, which is easy to cause environmental pollution.

[0008] In summary, although the traditional wet recovery process can obtain high-purity rare earth compound products, this method not only has a long recovery process, large acid and alkali consumption, and high environmental cost, but also does not meet the current requirements of green environmental protection, energy conservation and sustainable development. In addition, the traditional wet recovery process is limited to separating and extracting a single rare earth chloride or rare earth oxide from NdFeB waste as the final product, and does not achieve high-value recycling of waste to magnetic materials. However, as an important secondary resource of rare earths, NdFeB oil sludge waste has a simpler chemical composition and less impurities than rare earth ore, especially does not contain thorium and other associated radioactive harmful elements in rare earth ores. Although its performance has been deteriorated by corrosion and pollution, it still retains certain physical and chemical properties, which is conducive to eliminating or greatly simplifying the separation and extraction process, which provides the possibility for the direct recycling and reuse of NdFeB waste or the development of short-process regeneration technology of "separation-free extraction". Therefore, it is necessary to combine the characteristics of different types of NdFeB waste materials and develop green and short-process recycling new technologies or processes in a targeted manner, in order to shorten the recycling process, reduce energy consumption, reduce hydrochloric acid consumption and pollutant emissions. On the other hand, the rare earth oxides or metal products of the existing recycling process have low added value, and it is urgent to develop key preparation technologies for high-performance recycled rare earth permanent magnet materials in order to achieve high-value reuse of NdFeB waste materials.

[0009] Therefore, developing a method with a short process, low pollution, and the ability to achieve green and efficient recycling and high-value reuse of waste is a technical problem that needs to be solved urgently. Summary of the invention

[0010] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for batch recovery of NdFeB oil sludge waste, regenerated Ce-Pr-Nd mixed rare earth and its application. The method provided by the present invention greatly improves the rare earth separation efficiency and rare earth recovery rate, realizes efficient recovery and high-value utilization of waste materials; and the method reduces acid consumption, shortens the process flow, reduces pollution to the environment, and has extremely high process operability.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] In a first aspect, the present invention provides a method for batch recovery of NdFeB oil sludge waste, the method comprising the following steps:

[0013] (1) mixing and granulating NdFeB oil sludge waste and solid chlorinating agent in sequence, and then performing oxygen-controlled chlorination roasting in a mixed gas environment, and grinding to obtain a roasted product;

[0014] (2) subjecting the roasted product obtained in step (1) to water immersion, solid-liquid separation, and extraction separation in sequence to obtain a loaded organic phase and an aqueous phase;

[0015] (3) The aqueous phase obtained in step (2) is subjected to sequential impurity removal, precipitation, calcination and molten salt electrolysis to obtain regenerated Ce-Pr-Nd mixed rare earth.

[0016] The present invention selectively chlorinates rare earth components into rare earth chlorides through controlled oxygen chlorination roasting, and all iron components are converted into iron oxides or metallic iron, and then rare earth chloride liquid is obtained through water leaching, precipitation and filtration. Then, Nd / Sm separation is achieved through extraction separation, and the loaded organic phase is stripped to obtain medium and heavy rare earth liquids that enter the separation lines of Sm, Dy, Tb, Ho, etc., and the outlet aqueous phase Ce-Nd light rare earth liquid enters the impurity removal and separation of Ca, Mg and other impurities from light rare earth; the obtained high-purity Ce-Pr-Nd mixed liquid can be prepared through precipitation, calcination and molten salt electrolysis to obtain a new high-purity regenerated Ce-Pr-Nd mixed rare earth product that can be directly used for the preparation of regenerated sintered NdFeB.

[0017] In the present invention, by regulating the ratio and composition of the mixed gas, oxygen-controlled chlorination roasting is carried out to achieve the selective and efficient extraction of rare earth elements in the waste. Compared with general chlorination roasting, the formation of NdFeO3, FeCl3 and REOCl is avoided, and the rare earth separation efficiency and rare earth recovery rate are greatly improved; compared with traditional oxidation roasting, not only can the roasting temperature be reduced, but also the synergistic effect of multiple salt agents can be used to improve the extraction efficiency of rare earth elements, which has the advantage of low energy consumption. In addition, the use of a high-energy mixer to batch mix waste and solid chlorination agent greatly improves the uniformity of the reaction materials, solves the problem of low rare earth extraction rate caused by low uniformity of batch production reaction materials, and lays the foundation for the industrial application of oxygen-controlled chlorination roasting technology. On the other hand, a new product of regenerated Ce-Pr-Nd mixed rare earth is prepared in combination with Nd / Sm line extraction and separation, which can be directly used for the preparation of high-performance regenerated sintered NdFeB magnets, thereby achieving efficient recovery and high-value utilization of waste materials. This method utilizes low-temperature oxygen-controlled chlorination roasting and water leaching to replace traditional high-temperature oxidation roasting and hydrochloric acid leaching. In addition, relatively low-priced light rare earths are recovered in the form of a new Ce-Pr-Nd mixed rare earth product, and high-priced heavy rare earths such as Dy and Tb enter the loaded organic phase and are recovered through separate separation; thereby reducing acid consumption, shortening the process flow, and reducing pollution to the environment, and having extremely high process operability.

[0018] As a preferred technical solution of the present invention, the device used for mixing in step (1) includes a high-energy mixer.

[0019] Preferably, the rotation speed of the stirring plowshare in the mixture in step (1) is 10 to 1000 r / min, for example, it can be 10 r / min, 100 r / min, 200 r / min, 400 r / min, 600 r / min, 800 r / min or 1000 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the rotation speed of the stirring knife in the mixing in step (1) is 50 to 4000 r / min, for example, it can be 50 r / min, 200 r / min, 500 r / min, 1000 r / min, 2000 r / min, 3000 r / min or 4000 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] Preferably, the mixing time in step (1) is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] In the present invention, the high-energy mixer comprises a silo; a feed inlet and two air inlets / outlets are arranged at the top of the silo; a discharge port is arranged at the bottom of the silo;

[0023] Preferably, a circulating water cooling layer is provided on the periphery of the silo;

[0024] Preferably, a stirring plowshare and a stirring flying knife are arranged inside the silo; the mixer includes a flying knife motor for controlling the braking of the stirring flying knife; the mixer includes a plowshare motor for controlling the braking of the stirring plowshare.

[0025] In the present invention, by arranging a double stirring device in the high-energy mixer, sufficient mixing of the waste material and the solid chlorinating agent is achieved, the uniformity of the reaction material is greatly improved, and the problem of low rare earth extraction rate caused by low uniformity of the reaction material in batch production is solved.

[0026] Preferably, when the mixing temperature in step (1) is 80-200°C, an inert gas is mixed to carry out impurity removal treatment, for example, it can be 80°C, 120°C, 160°C or 200°C, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] In the present invention, the stirring and cutting of the flying knife in the mixer will cause the material temperature to rise. When the temperature rises to 80-200°C, inert gas can be circulated through the inlet / outlet to remove and recover the gasified oily organic matter in the NdFeB oil sludge waste.

[0028] Preferably, the inert gas comprises argon and / or nitrogen.

[0029] As a preferred technical solution of the present invention, the solid chlorinating agent in step (1) includes any one of NH4Cl, FeCl2, FeCl3, MgCl2, AlCl3, CoCl2, CaCl2, KCl or NaCl, or a combination of at least two of them. Typical but non-limiting combinations include: a combination of FeCl2 and FeCl3, a combination of FeCl2, FeCl3, MgCl2 and AlCl3, a combination of MgCl2, NaCl, AlCl3 and KCl, or a combination of NH4Cl, FeCl2, FeCl3, MgCl2, AlCl3, CoCl2, NaCl, CaCl2 and KCl, preferably NH4Cl or FeCl3.

[0030] Preferably, based on the conversion of all rare earths contained in the NdFeB oil sludge waste into corresponding rare earth salts, the amount of the solid chlorinating agent is 1 to 3 times the stoichiometric value, for example, it can be 1 time, 1.5 times, 2 times, 2.5 times or 3 times, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; preferably it is 2.5 times.

[0031] As a preferred technical solution of the present invention, the mixed gas in step (1) includes a mixture of an inert gas and oxygen, or a mixture of an inert gas and hydrogen.

[0032] Preferably, the oxygen content in the mixed gas in step (1) is 10 to 100 wt%, for example, it can be 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt% or 100 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the content of hydrogen in the mixed gas in step (1) is 0 to 30 wt%, for example, it can be 0 wt%, 5 wt%, 10 wt%, 20 wt% or 30 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] In the present invention, different selections of mixed gases will result in different forms of iron components in the roasting products. When hydrogen and inert gas mixed reaction gases are used, the iron components in the waste will be completely converted into metallic iron in a reducing atmosphere, while when oxygen and inert gas mixed reaction gases are used, the iron components in the waste will be completely converted into iron oxides, and the rare earth components will be converted into rare earth chlorides. Both can achieve the purpose of water leaching to separate the iron component and the rare earth component, but the solid recovery products are different.

[0035] Preferably, the temperature of the oxygen-controlled chlorination roasting in step (1) is 100 to 750°C, for example, it can be 100, 300°C, 400°C, 500°C, 600°C or 750°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; preferably, it is 300 to 700°C.

[0036] Preferably, the time of the oxygen-controlled chlorination roasting in step (1) is 60 to 360 min, for example, it can be 60 min, 100 min, 140 min, 180 min, 240 min, 300 min or 360 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; preferably 240 min.

[0037] In the present invention, selective and efficient extraction of rare earth elements in waste materials is achieved through oxygen-controlled chlorination roasting, the formation of NdFeO3, FeCl3 and REOCl is avoided, and the rare earth separation efficiency and rare earth recovery rate are greatly improved; if the temperature is too high, on the one hand, the solid chlorinating agent will be gradually decomposed, and the shortage of the solid chlorinating agent will lead to insufficient reaction, and it is easy to produce side reactions to generate REOCl, thereby reducing the rare earth extraction efficiency and rare earth recovery rate; on the other hand, when the solid chlorinating agent is decomposed, the high temperature will easily cause the waste to be over-oxidized to produce NdFeO3, thereby reducing the rare earth extraction efficiency and rare earth recovery rate in the waste; if the temperature is too low, the solid chlorinating agent and the NdFeB waste will not react sufficiently, and the expected effect cannot be achieved, thereby reducing the rare earth extraction efficiency and rare earth recovery rate.

[0038] Preferably, the average particle size of the calcined product in step (1) is 150-450 mesh, for example, 150 mesh, 200 mesh, 250 mesh, 300 mesh, 400 mesh or 450 mesh, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] As a preferred technical solution of the present invention, the water immersion temperature in step (2) is 10-90°C, for example, it can be 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 90°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the water immersion in step (2) is accompanied by stirring.

[0041] Preferably, the stirring time is 10 to 120 min, for example, 10 min, 30 min, 60 min, 90 min or 120 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the stirring speed is 50 to 1000 r / min, for example, it can be 50 r / min, 100 r / min, 200 r / min, 400 r / min, 600 r / min, 800 r / min or 1000 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] In the present invention, the calcined product contains rare earth chloride and iron-containing oxide (or metallic iron), and the separation of iron element and rare earth element is achieved by water immersion.

[0044] As a preferred technical solution of the present invention, the extractant used in the extraction and separation in step (2) includes P507 extractant and / or P204 extractant.

[0045] Preferably, the concentration of the extractant is 0.5-2.0 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1.1 mol / L, 1.4 mol / L, 1.7 mol / L or 2 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the extracted organic phase in the extraction separation comprises an extractant, kerosene, 2-octanol or n-hexane or other diluents.

[0047] In the present invention, Nd / Sm separation in the chloride rare earth liquid is achieved by extraction separation, and a light rare earth aqueous phase containing Nd and a medium and heavy rare earth organic phase containing rare earth elements such as Sm, Dy, Tb, Ho, etc. are separated.

[0048] Preferably, the method further comprises subjecting the loaded organic phase obtained in step (2) to fractional extraction.

[0049] The present invention continues to use P507 extractant and / or P204 extractant, and separates the organic phase one by one through graded extraction to obtain rare earth elements such as Sm, Dy, Tb, and Ho.

[0050] As a preferred technical solution of the present invention, the extractant used for impurity removal in step (3) includes P507-N235.

[0051] Preferably, the precipitating agent used for the precipitation in step (3) comprises any one of oxalic acid, oxalic acid solution, ammonium carbonate, ammonium carbonate solution, ammonium bicarbonate or ammonium bicarbonate solution, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of oxalic acid and oxalic acid solution, a combination of ammonium carbonate and ammonium carbonate solution, a combination of ammonium bicarbonate and ammonium bicarbonate solution, a combination of oxalic acid, ammonium carbonate and ammonium bicarbonate solution, or a combination of oxalic acid solution, ammonium carbonate solution and ammonium bicarbonate solution.

[0052] Preferably, based on the complete precipitation of rare earth after the aqueous phase after impurities are removed and mixed with the precipitant, the amount of the precipitant is 1 to 2 times the stoichiometric amount, for example, it can be 1 time, 1.2 times, 1.4 times, 1.6 times, 1.8 times or 2 times, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] Preferably, after the impurity-removed aqueous phase is mixed with the precipitant, the pH value of the resulting mixed solution is 1 to 3.5, for example, it can be 1, 1.4, 1.8, 2.2, 2.6, 3 or 3.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] Preferably, the calcination temperature in step (3) is 800-950°C, for example, 800°C, 830°C, 860°C, 890°C, 920°C or 950°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] Preferably, the calcination time in step (3) is 1 to 3 hours, for example, 1 hour, 1.4 hours, 1.8 hours, 2.2 hours, 2.6 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] Preferably, the electrolyte system in the molten salt electrolysis in step (3) comprises a REF3-LiF electrolyte system, where RE represents a rare earth element.

[0057] Preferably, the temperature of the molten salt electrolysis in step (3) is 950-1050°C, for example, it can be 950°C, 970°C, 990°C, 1010°C, 1030°C or 1050°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] As a preferred technical solution of the present invention, the method for batch recovery of NdFeB oil sludge waste comprises the following steps:

[0059] (1) mixing and granulating NdFeB oil sludge waste and solid chlorinating agent in sequence, and then performing oxygen-controlled chlorination roasting for 60 to 360 minutes under a mixed gas environment and a temperature of 100 to 750° C., and grinding to obtain a roasted product with an average particle size of 150 to 450 meshes;

[0060] The mixing is carried out in a high-energy mixing process, the speed of the stirring plow blade is 10 to 1000 r / min, the speed of the stirring flying knife is 50 to 4000 r / min, the time is 1 to 5 hours, and when the mixing temperature reaches 80 to 200° C., an inert gas is mixed to remove impurities;

[0061] Based on the fact that all rare earth contained in the NdFeB oil sludge waste is converted into corresponding rare earth salts, the amount of the solid chlorinating agent is 1 to 3 times the stoichiometric amount;

[0062] (2) subjecting the calcined product obtained in step (1) to water immersion, solid-liquid separation and extraction separation at 10 to 90° C. to obtain a loaded organic phase and an aqueous phase;

[0063] Wherein, the water immersion is accompanied by stirring, the stirring time is 10 to 120 minutes, and the rotation speed is 50 to 1000 r / min;

[0064] The extractant used in the extraction separation includes a P507 extractant and / or a P204 extractant with a concentration of 0.5 to 2.0 mol / L;

[0065] (3) using P507-N235 extractant to remove impurities from the aqueous phase obtained in step (2), followed by precipitation, calcination at 800-950° C. for 1-3 h, and molten salt electrolysis to obtain regenerated Ce-Pr-Nd mixed rare earth;

[0066] The amount of the precipitant is 1 to 2 times the stoichiometric amount, based on the complete precipitation of the rare earth after the impurity-removed aqueous phase is mixed with the precipitant; the pH value of the obtained mixed solution after the impurity-removed aqueous phase and the precipitant are mixed is 1 to 3.5;

[0067] The electrolyte system in the molten salt electrolysis includes a REF3-LiF electrolyte system, where RE represents a rare earth element; the temperature of the molten salt electrolysis is 950-1050°C.

[0068] In a second aspect, the present invention provides a regenerated Ce-Pr-Nd mixed rare earth, wherein the regenerated Ce-Pr-Nd mixed rare earth is recovered by the method provided in the first aspect.

[0069] The Ce content in the regenerated Ce-Pr-Nd mixed rare earth is 0-30wt%, for example, it can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt% or 30wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0070] In a third aspect, the present invention provides an application of a regenerated Ce-Pr-Nd mixed rare earth obtained by the method provided in the first aspect, wherein the regenerated Ce-Pr-Nd mixed rare earth is used to prepare a regenerated rare earth permanent magnet material.

[0071] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] (1) The present invention adjusts the composition ratio and gas type of the mixed gas, and combines oxygen-controlled chlorination roasting to selectively chlorinate the rare earth components into rare earth chlorides, and converts all iron components into iron oxides or metallic iron, thereby avoiding the formation of NdFeO3, FeCl3 and REOCl, greatly improving the rare earth separation efficiency and rare earth recovery rate, and realizing the selective and efficient extraction of rare earth elements from waste materials;

[0074] (2) The present invention utilizes a mixer with a dual stirring function to achieve batch mixing of NdFeB oil sludge waste and solid chlorinating agent, which greatly improves the uniformity of the reaction materials and solves the problem of low rare earth extraction rate caused by low mixing uniformity of the reaction materials during batch chlorination roasting;

[0075] At the same time, in the mixing process of the mixer, the inert gas is circulated to remove and recycle the gasified oily organic matter in the sludge waste, which plays a role of "de-oiling" while mixing.

[0076] (3) The method provided by the present invention not only avoids the huge acid consumption in the acid leaching process, but also reduces the single rare earth extraction and separation process in the traditional wet recovery route, shortens the production cycle, and recovers the regenerated Ce-Pr-Nd mixed rare earth new product. It has the advantages of short process, energy saving and environmental protection, low reagent consumption, and can realize the green and efficient recovery and high-value reuse of waste materials;

[0077] (4) The method provided by the present invention is applicable to both unoxidized and oxidized NdFeB waste materials, can be recycled on a large scale, and has considerable economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 is a flow chart of a method for batch recovery of NdFeB oil sludge waste provided in Example 1 of the present invention;

[0079] Figure 2 Phase stability advantage region diagram of MO-Cl system during selective chlorination roasting at different temperatures;

[0080] Figure 3 It is a structural schematic diagram of the high energy mixer provided by the present invention;

[0081] Among them, 1 is the stirring plow blade control motor, and 2 is the stirring flying knife control motor. DETAILED DESCRIPTION

[0082] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0083] Example 1

[0084] This embodiment provides a method for batch recycling of NdFeB oil sludge waste, such as Figure 1 As shown, the method comprises the following steps:

[0085] (1) 50 kg of NdFeB oil sludge waste and 30.60 kg of solid chlorinating agent (NH4Cl) were mixed and granulated in sequence, and then calcined under oxygen-controlled chlorination conditions of 300° C. for 360 min in a mixed gas (oxygen content of 15 wt%) environment, and ground to obtain a calcined product with an average particle size of 300 mesh;

[0086] Wherein, the mixture is Figure 3 In the high-energy mixing shown in the figure, the speed of the stirring coulter is 200r / min, the speed of the stirring flying knife is 3000r / min, the time is 5h, and when the mixing reaches 140°C, the mixed nitrogen is used for impurity removal treatment; the stirring coulter is controlled by the stirring coulter control motor 1, and the stirring flying knife is controlled by the stirring flying knife control motor 2;

[0087] Based on the conversion of all rare earths (calculated as 22 wt% rare earth content) contained in the NdFeB oil sludge waste into corresponding rare earth salts, the amount of the solid chlorinating agent is 2.5 times the stoichiometric amount;

[0088] (2) The calcined product obtained in step (1) is immersed in water at 25° C., and solid-liquid separation is performed to obtain a rare earth chloride solution and a precipitate mainly composed of Fe2O3; then the rare earth chloride solution is extracted and separated to obtain a loaded organic phase and an aqueous phase (high-purity Ce-Pr-Nd mixed rare earth solution);

[0089] The immersion is accompanied by stirring, the stirring time is 60 min, the rotation speed is 200 r / min, and the extractant used in the separation includes a P507 extractant with a concentration of 2.0 mol / L;

[0090] (3) removing impurities from the aqueous phase obtained in step (2) using a P507-N235 extractant, followed by precipitation, calcination at 900° C. for 2 h, and molten salt electrolysis to obtain regenerated Ce-Pr-Nd mixed rare earth;

[0091] The amount of oxalic acid used is 1.5 times the stoichiometric amount, based on the complete precipitation of rare earth after the impurity-removed aqueous phase is mixed with oxalic acid; the pH value of the mixed solution obtained after the impurity-removed aqueous phase is mixed with the precipitant is 3.0;

[0092] The electrolyte system in the molten salt electrolysis includes a REF3-LiF electrolyte system, where RE represents a rare earth element; and the temperature of the molten salt electrolysis is 1000°C.

[0093] The phase stability advantage region of the MO-Cl system during the selective chlorination roasting process at different temperatures in this embodiment is shown in FIG. Figure 2 As shown, according to Figure 2It can be seen from the phase stability region diagram that the area of ​​rare earth chloride phase is much larger than that of ferric chloride, which proves that the chlorination agent has a higher selectivity for rare earth elements. In addition, it can also be seen that the chlorination reaction is related to oxygen, chlorine agent dosage, and temperature. The reaction process can be optimized, the selectivity can be improved, and the rare earth recovery rate can be increased by controlling these factors.

[0094] Example 2

[0095] This embodiment provides a method for batch recycling of NdFeB oil sludge waste, the method comprising the following steps:

[0096] (1) 50 kg of NdFeB oil sludge waste and 10.87 kg of solid chlorinating agent (MgCl2) were mixed and granulated in sequence, and then calcined in a mixed gas (hydrogen content was 20 wt%) environment at 500°C for 300 min under controlled oxygen chlorination conditions, and ground to obtain a calcined product with an average particle size of 450 mesh;

[0097] The mixing is carried out in a high-energy mixing process, the speed of the stirring knife is 2500r / min, the time is 3h, and when the mixing temperature reaches 100°C, argon gas is mixed to remove impurities;

[0098] Based on the fact that all rare earths (calculated as 22 wt% rare earth content) contained in the NdFeB oil sludge waste are converted into corresponding rare earth salts, the amount of the solid chlorinating agent is 1.0 times the stoichiometric amount;

[0099] (2) The calcined product obtained in step (1) is immersed in water at 10° C., and solid-liquid separation is performed to obtain a rare earth chloride solution and a precipitate mainly composed of Fe2O3; then the rare earth chloride solution is extracted and separated to obtain a loaded organic phase and an aqueous phase (high-purity Ce-Pr-Nd mixed rare earth solution);

[0100] The water immersion is accompanied by stirring, the stirring time is 30 minutes, and the rotation speed is 600 r / min;

[0101] The extractant used in the extraction separation includes a P507 extractant with a concentration of 1.5 mol / L;

[0102] (3) using P507-N235 extractant to remove impurities from the aqueous phase obtained in step (2), followed by precipitation, calcination at 800° C. for 3 h, and molten salt electrolysis to obtain regenerated Ce-Pr-Nd mixed rare earth;

[0103] The amount of the ammonium carbonate precipitant is 1 times the stoichiometric amount, based on the complete precipitation of the rare earth after the impurity-removed aqueous phase is mixed with the ammonium carbonate precipitant; the pH value of the obtained mixed solution after the impurity-removed aqueous phase and the precipitant are mixed is 3.5;

[0104] The electrolyte system in the molten salt electrolysis includes a REF3-LiF electrolyte system, where RE represents a rare earth element; and the temperature of the molten salt electrolysis is 950°C.

[0105] Example 3

[0106] This embodiment provides a method for batch recycling of NdFeB oil sludge waste, the method comprising the following steps:

[0107] (1) 50 kg of NdFeB oil sludge waste and 37.11 kg of FeCl3 solid chlorinating agent were mixed and granulated in sequence, and then subjected to oxygen-controlled chlorination roasting for 60 min in a mixed gas (oxygen content was 21 wt%) environment at 750°C, and ground to obtain a roasted product with an average particle size of 150 mesh;

[0108] The mixing is carried out in a high-energy mixing process, the speed of the stirring plow blade is 1000 r / min, the speed of the stirring flying knife is 50 r / min, the time is 4 hours, and when the mixing reaches 200° C., nitrogen is mixed for impurity removal treatment;

[0109] Based on the conversion of all rare earths (calculated as 22 wt% rare earth content) contained in the NdFeB oil sludge waste into corresponding rare earth salts, the amount of the solid chlorinating agent is 3 times the stoichiometric amount;

[0110] (2) The calcined product obtained in step (1) is subjected to water immersion at 10-90° C. and solid-liquid separation to obtain a rare earth chloride solution and a precipitate mainly composed of Fe2O3; the rare earth chloride solution is then extracted and separated to obtain a loaded organic phase and an aqueous phase (high-purity Ce-Pr-Nd mixed rare earth solution);

[0111] The water immersion is accompanied by stirring, the stirring time is 10 minutes, and the rotation speed is 1000 r / min;

[0112] The extractant used in the extraction separation includes a P507 extractant with a concentration of 2.0 mol / L;

[0113] (3) using P507-N235 extractant to remove impurities from the aqueous phase obtained in step (2), followed by precipitation, calcination at 950° C. for 1 h, and molten salt electrolysis to obtain regenerated Ce-Pr-Nd mixed rare earth;

[0114] The amount of the precipitant is 1 times the stoichiometric amount, based on the complete precipitation of the rare earth after the impurity-removed aqueous phase is mixed with the precipitant; the pH value of the resulting mixed solution after the impurity-removed aqueous phase and the precipitant are mixed is 1;

[0115] The electrolyte system in the molten salt electrolysis includes a REF3-LiF electrolyte system, where RE represents a rare earth element; and the temperature of the molten salt electrolysis is 1050°C.

[0116] Example 4

[0117] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0118] In this embodiment, the oxygen content in the mixed gas in step (1) is adjusted to 0 wt %.

[0119] Example 5

[0120] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0121] In this embodiment, the oxygen content in the mixed gas in step (1) is adjusted to 100 wt %.

[0122] Example 6

[0123] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0124] In this embodiment, the temperature of the oxygen-controlled chlorination roasting in step (1) is adjusted to 80°C.

[0125] Example 7

[0126] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0127] In this embodiment, the temperature of the oxygen-controlled chlorination roasting in step (1) is adjusted to 250°C.

[0128] Example 8

[0129] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0130] In this embodiment, the temperature of the oxygen-controlled chlorination roasting in step (1) is adjusted to 500°C.

[0131] Example 9

[0132] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0133] In this embodiment, the temperature of the oxygen-controlled chlorination roasting in step (1) is adjusted to 800°C.

[0134] Example 10

[0135] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0136] In this embodiment, the time of the oxygen-controlled chlorination roasting in step (1) is adjusted to 50 minutes.

[0137] Embodiment 11

[0138] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0139] In this embodiment, the rotation speed of the stirring plowshare in the mixing process of step (1) is adjusted to 0 r / min.

[0140] Example 12

[0141] This embodiment provides a method for batch recovery of NdFeB oil sludge waste, which differs from the method in Embodiment 1 only in that:

[0142] In this embodiment, the rotation speed of the stirring blade in the mixing step (1) is adjusted to 0 r / min.

[0143] Performance testing:

[0144] The results of the purity and rare earth element recovery rate of the regenerated Ce-Pr-Nd mixed rare earth before molten salt electrolysis provided in the above embodiment are shown in Table 1.

[0145] Table 1

[0146]

[0147]

[0148] According to Table 1, we can know the following points:

[0149] (1) Comprehensive analysis of Examples 1-3 shows that the method provided by the present invention can achieve efficient recovery of rare earth elements in waste materials and obtain regenerated Ce-Pr-Nd mixed rare earth with high purity;

[0150] (2) Comprehensive analysis of Example 1 and Examples 4-5 shows that the oxygen content of the mixed gas during the oxygen-controlled chlorination roasting process affects the phase transformation of the roasting product, thereby affecting the rare earth recovery rate. Insufficient oxygen content easily leads to the production of REOCl by-products, and excessive oxygen content leads to the production of NdFeO3 by-products, thereby reducing the rare earth recovery rate;

[0151] (3) Comprehensive analysis of Example 1 and Examples 6-9 shows that the temperature of oxygen-controlled chlorination roasting affects the degree of reaction of the chlorination reaction; if the temperature is too high, the solid chlorinating agent will decompose, resulting in insufficient chlorinating agent and insufficient reaction, resulting in a reduced rare earth recovery rate; if the temperature is too low, the melting point of the solid chlorinating agent cannot be reached, and the solid-solid reaction cannot be converted into a liquid-solid reaction, resulting in an insufficient chlorination reaction, resulting in a reduced rare earth recovery rate;

[0152] (4) Comprehensive analysis of Example 1 and Example 10 shows that the oxygen-controlled chlorination roasting time affects the physical phase of the chlorination roasting product. As the reaction time increases, the FeCl3 intermediate product generated due to excessive chlorinating agent will be oxidized into Fe2O3 and enter the water leaching slag phase, thereby reducing the content of impurity iron in the rare earth feed solution and improving the purity of the mixed rare earth oxide. However, when the reaction time is too long, it will affect the production efficiency; if the reaction time is too short, it will lead to insufficient reaction and reduce the rare earth recovery rate.

[0153] (5) Comprehensive analysis of Example 1 and Examples 11-12 shows that the double stirring mechanism can improve the mixing uniformity of the waste material and the solid chlorinating agent. Omitting either the stirring blade or the stirring plowshare will lead to uneven mixing, making it impossible to achieve mass production.

[0154] In summary, the method provided by the present invention greatly improves the rare earth separation efficiency and rare earth recovery rate, realizes the efficient recovery and high-value utilization of waste materials; and the method reduces acid consumption, shortens the process flow, reduces pollution to the environment, and has extremely high process operability.

[0155] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for batch recovery of NdFeB oil sludge waste, characterized in that: The method comprises the following steps: (1) mixing and granulating NdFeB oil sludge waste and solid chlorinating agent in sequence, and then performing oxygen-controlled chlorination roasting in a mixed gas environment, and grinding to obtain a roasted product; (2) subjecting the calcined product obtained in step (1) to water immersion, solid-liquid separation and extraction separation in sequence to obtain a loaded organic phase and an aqueous phase; (3) The aqueous phase obtained in step (2) is subjected to sequential impurity removal, precipitation, calcination and molten salt electrolysis to obtain regenerated Ce-Pr-Nd mixed rare earth.

2. The method according to claim 1, characterized in that The mixing device in step (1) includes a high-energy mixer; Preferably, the speed of the stirring plowshare in the mixing in step (1) is 10 to 1000 r / min; Preferably, the speed of the stirring blade in the mixing step (1) is 50 to 4000 r / min; Preferably, the mixing time in step (1) is 1 to 5 hours; Preferably, in step (1), when the mixing temperature is 80-200° C., an inert gas is added to carry out impurity removal treatment.

3. The method according to claim 1 or 2, characterized in that: The solid chlorinating agent in step (1) includes any one of NH4Cl, FeCl2, FeCl3, MgCl2, AlCl3, CoCl2, CaCl2, KCl or NaCl, or a combination of at least two thereof; Preferably, based on the conversion of all rare earths contained in the NdFeB oil sludge waste into corresponding rare earth salts, the amount of the solid chlorinating agent is 1 to 3 times the stoichiometric amount, preferably 2.5 times.

4. The method according to any one of claims 1 to 3, characterized in that: The mixed gas in step (1) comprises a mixture of an inert gas and oxygen, or a mixture of an inert gas and hydrogen; Preferably, the content of oxygen in the mixed gas in step (1) is 10 to 100 wt %; Preferably, the content of hydrogen in the mixed gas in step (1) is 0 to 30 wt %; Preferably, the temperature of the oxygen-controlled chlorination roasting in step (1) is 100 to 750° C., preferably 300 to 700° C.; Preferably, the time of the oxygen-controlled chlorination roasting in step (1) is 60 to 360 minutes; Preferably, the average particle size of the calcined product in step (1) is 150-450 mesh.

5. The method according to any one of claims 1 to 4, characterized in that: The water immersion temperature in step (2) is 10 to 90° C. Preferably, the immersion in water in step (2) is accompanied by stirring; Preferably, the stirring time is 10 to 120 minutes; Preferably, the stirring speed is 50-1000 r / min.

6. The method according to any one of claims 1 to 5, characterized in that: The extractant used in the extraction separation in step (2) includes P507 extractant and / or P204 extractant; Preferably, the concentration of the extractant is 0.5 to 2.0 mol / L; Preferably, the method further comprises subjecting the loaded organic phase obtained in step (2) to fractional extraction.

7. The method according to any one of claims 1 to 6, characterized in that: The extractant used for the impurity removal in step (3) includes P507-N235; Preferably, the precipitant used for the precipitation in step (3) comprises any one of oxalic acid, oxalic acid solution, ammonium carbonate, ammonium carbonate solution, ammonium bicarbonate or ammonium bicarbonate solution, or a combination of at least two thereof; Preferably, the amount of the precipitant is 1 to 2 times the stoichiometric amount, based on the complete precipitation of the rare earth after the impurity-removed aqueous phase is mixed with the precipitant; Preferably, after the impurity-removed aqueous phase is mixed with the precipitant, the pH value of the resulting mixed solution is 1 to 3.5; Preferably, the calcination temperature in step (3) is 800-950°C; Preferably, the calcination time in step (3) is 1 to 3 hours; Preferably, the electrolyte system in the molten salt electrolysis in step (3) comprises a REF3-LiF electrolyte system, where RE represents a rare earth element; Preferably, the temperature of the molten salt electrolysis in step (3) is 950-1050°C.

8. The method according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: (1) mixing and granulating NdFeB oil sludge waste and solid chlorinating agent in sequence, and then calcining them in an oxygen-controlled chlorination manner for 60 to 240 minutes at a temperature of 100 to 750° C. in a mixed gas environment, and grinding to obtain a calcined product with an average particle size of 150 to 450 meshes; The mixing is carried out in a high-energy mixing process, the speed of the stirring plow blade is 10 to 1000 r / min, the speed of the stirring flying knife is 50 to 4000 r / min, the time is 1 to 5 hours, and when the mixing temperature reaches 80 to 200° C., an inert gas is mixed to remove impurities; Based on the fact that all rare earth contained in the NdFeB oil sludge waste is converted into corresponding rare earth salts, the amount of the solid chlorinating agent is 1 to 3 times the stoichiometric amount; (2) subjecting the calcined product obtained in step (1) to water immersion, solid-liquid separation and extraction separation at 10 to 90° C. to obtain a loaded organic phase and an aqueous phase; Wherein, the water immersion is accompanied by stirring, the stirring time is 10 to 120 minutes, and the rotation speed is 50 to 1000 r / min; The extractant used in the extraction separation includes a P507 extractant and / or a P204 extractant with a concentration of 0.5 to 2.0 mol / L; (3) using P507-N235 extractant to remove impurities from the aqueous phase obtained in step (2), followed by precipitation, calcination at 800-950° C. for 1-3 h, and molten salt electrolysis to obtain regenerated Ce-Pr-Nd mixed rare earth; The amount of the precipitant is 1 to 2 times the stoichiometric amount, based on the complete precipitation of the rare earth after the impurity-removed aqueous phase is mixed with the precipitant; the pH value of the obtained mixed solution after the impurity-removed aqueous phase and the precipitant are mixed is 1 to 3.5; The electrolyte system in the molten salt electrolysis includes a REF3-LiF electrolyte system, where RE represents a rare earth element; the temperature of the molten salt electrolysis is 950-1050°C.

9. A regenerated Ce-Pr-Nd mixed rare earth, characterized in that: The regenerated Ce-Pr-Nd mixed rare earth is recovered by the method described in any one of claims 1 to 8; The Ce content in the regenerated Ce-Pr-Nd mixed rare earth is 0-30wt%.

10. An application of the regenerated Ce-Pr-Nd mixed rare earth as claimed in claim 9, characterized in that: The regenerated Ce-Pr-Nd mixed rare earth is used to prepare regenerated rare earth permanent magnet material.

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