RU2620319C2 - Electrolytic cell for manufacturing rare-earth metals - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: electrolytic cell comprises a housing formed with one or more oblique channels in the housing bottom for draining molten rare earth metals. One or more cathodes are suspended in the cell housing in vertical alignment with one or more channels. The respective cathodes of the opposed surfaces are inclined downwardly and outwardly at an angle from the vertical. One or more pairs of anodes suspended in the cell body. Each anode in one or more pairs has a front surface, the deviation from the vertical and spaced apart in parallel alignment with the respective opposite inclined surfaces of one or more cathodes. The electrolytic cell also includes a collection for the reception of molten rare earth metals from the channel. Separation of molten rare earth metals from the cathode (s) and anode (s) prevents contamination of volatile carbon, rising from the anode (s), or the reverse reaction with the exhaust gases.

EFFECT: increased efficiency of energy consumption and the reduction of product contamination.

13 cl, 2 dwg

Description

Field of Invention

The present invention relates generally to electrolytic cells, in particular electrolytic cells adapted for the production of rare earth metals such as neodymium, praseodymium, cerium, lanthanum, and mixtures thereof, using an electrolysis process in an electrolytic bath of fluoride or chloride melt.

BACKGROUND OF THE INVENTION

Electrolytic cells for the production of aluminum in a bath of molten fluoride or chloride are well known, and many of their structural features solve important problems. In particular, it is important to maintain a stable and small anode-cathode distance (AKP) as a measure of energy conservation in an extremely energy-intensive process. Maintaining constant ACP can be difficult when molten aluminum builds up on the surface of the cathode and is affected by hydrodynamic forces exerted by strong magnetic fields. Accordingly, in some cell configurations, the cathodes can be suspended above the bottom of the cell on which molten aluminum accumulates. In other configurations, the cathodes may be provided with channels into which molten aluminum can collect, thereby removing molten aluminum from the surface of the cathode as soon as it is formed to maintain a constant AKP.

It is also important that the electrolytic cell is capable of releasing carbon dioxide, which is released on the surface of the anode during electrolysis, from the interelectrode space to substantially prevent a “back reaction” with aluminum metal when it forms on the surface of the cathode, thereby reducing the efficiency of the electrolysis process .

Neodymium and praseodymium, their mixtures and other rare-earth metals, are also currently being produced on an industrial scale using the electrolysis process in a molten bath of a mixed fluoride salt. Unlike the electrolytic production of aluminum, the anodes and cathodes are arranged in a vertical orientation, and the molten metal is collected in a receiving vessel at the bottom of the cell. The interelectrode space is not affected by the accumulation of molten metal, but, nevertheless, is subject to change by continuous electrolytic depletion of the surfaces of the carbon anode. Cathodes are typically composed of an inert metal such as molybdenum or tungsten.

Because the anodes are depleted, there is no effective way to keep the anode-cathode separation even. Since the bulk of the process heat is generated by the ohmic resistance of the distance between the electrodes, the process temperature is extremely variable and is generally controlled by a decrease in the current supplied to the cell. This is impractical in larger scale operations in which a number of cells are connected electrically in series. In addition, attenuation of the current during the electrolysis process is also undesirable for the reason that it reduces the production capacity of the cell. Most importantly, the inability to accurately control the process temperature reduces the technological yield, or Faraday efficiency, and leads to the formation of an insoluble precipitate that settles to the bottom of the cell. Therefore, the electrolysis must be stopped periodically to remove sediment from the cell, thereby preventing continuous electrolysis.

Poor process temperature control also increases steam emissions from the cell, which are harmful to the working atmosphere and the environment, if not restrained.

Additionally, as the anodes are depleted, the volume displaced by them in the electrolyte decreases, and the electrolyte level in the cell decreases. This reduces the working area of the anode immersed in the electrolyte, to the detriment of process efficiency, including power consumption and the increased likelihood of “anode effects” creating highly polluting gases.

Moreover, the rare earth metal of the product can react with carbon at the process temperature. Carbon is an extremely undesirable impurity for some rare earth metal product applications. Reducing the likelihood of contact between the volatile carbon in the cell and the metal and / or the residence time of the product metal in the cell are desirable design features that are not available in existing designs of industrial cells. This specific task is not a factor in the design of electrolytic cells for aluminum production, since under such conditions aluminum does not react with carbon.

Additionally, in existing rare earth metal electrolytic cell designs, it is difficult to maintain the rare earth product metals in a molten state, since operating temperatures are preferably only 10-30 ° C. above the solidification point of the rare earth metal product. This disadvantage is not a problem and cannot be solved in electrolytic cells for the electrolytic production of aluminum, since the process temperature is approximately 300 ° C above the solidification point of aluminum.

The existing commercial activity for the electrolytic production of rare-earth metals is small, labor-intensive and is carried out in a semi-periodic mode. Several disadvantages make it difficult to scale up the process to achieve greater productivity, continuous electrolysis and high standards of environmental friendliness, occupational health and safety.

Firstly, electrolytic cells usually operate in a limited current range, from 5 to 10 kiloamperes, corresponding to low power production.

There is poor control of the material of rare earth oxides in the cell, leading to the accumulation of insoluble precipitates, which require frequent cleaning of the cell, thus preventing continuous electrolysis. Additionally, the loading material is fed into the cell manually, without a known reference to the current oxide concentration in the cell.

Existing technology uses vertical electrode devices. Such devices are not inclined to achieve high Faraday efficiency. For example, gas bubbles that arise and rise from the surface of the anode are highly likely to be entrained in the electrolyte flows and come into contact with the product metal formed on the cathode plates, thereby reducing the process yield due to the reverse oxidation of the product metal.

Keller in US Pat. No. 5,810,993 describes a method for producing neodymium in an electrolytic cell designed to operate without anode effects, therefore, avoiding the creation and release of extremely polluting perfluorocarbon (PFC) gases. In this invention, goals are achieved, firstly, by providing a plurality of anode plates, so that the density of the anode current remains significantly lower than that at which the anode effect can occur, and, secondly, by physically separating the vertical cathodes from the vertical anodes using an inert a barrier material that remains permeable to neodymium ions, so that a higher concentration of dissolved neodymium oxide can be maintained in the anode region than in the cathode region. However, the disclosed invention has several disadvantages and impractical features. In the examples given, it is not shown that the barrier material (boron nitride) is in fact permeable to neodymium ions, as is required for a continuous electrolysis process.

In addition, the proposed design of the anode is complex, and it can be expected that the wear rate of the anode plates will be extremely uneven and wasteful. The separation into compartments of the anode and cathode regions also leads to a large interelectrode separation distance, and the resulting inefficient energy consumption. In addition, the invention proposes to use coal as an inert cathode material, although it is well known that coal reacts with and pollutes the metal of the product.

Therefore, there is a need for alternative or improved electrolytic cells and processes for the production of rare earth metals.

The above references to the prior art are not an acknowledgment that this prior art is part of the usual well-known knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the electrolytic cell, as described herein.

The essence of the invention

The first feature discloses an electrolytic cell for the production of rare earth metals, containing:

the cell body provided with one or more inclined channels located at the bottom of the cell body, molten rare earth metals produced in the electrolytic cell can flow through this channel (s);

one or more cathodes suspended in the cell body substantially in vertical alignment with one or more channels, while the corresponding opposite surfaces of one or more cathodes are inclined downward and outward at an angle from the vertical;

one or more pairs of anodes suspended in the cell body, each anode in one or more pairs having a front surface deviated from the vertical and spaced in parallel alignment with the corresponding opposite inclined surfaces of one or more cathodes in order to determine a substantially constant anode cathode distance between them; and

a collector for receiving molten rare earth metals from the channel, the collector being at a distance and isolated from one or more cathodes and one or more pairs of anodes suspended in the cell body.

In a second feature, an electrolytic cell for the production of rare earth metals is disclosed, comprising:

cell body for holding an electrolytic bath;

one or more cathodes suspended in a cell body;

one or more pairs of sacrificial anodes suspended in the cell body, each anode in one or more pairs located at a distance from the respective opposite sides of the cathode; and

an extrusion device to control the height of the electrolytic bath contained in the cell body.

In one embodiment, said displacement device controls the height of the electrolytic bath contained in the cell body in response to anode consumption and the volume of the rare earth metal product contained in the cell body.

In a third feature, an electrolytic cell for the production of rare earth metals is disclosed, comprising:

cell body;

one or more cathodes suspended in a cell body;

one or more pairs of sacrificial anodes suspended in the cell body, each anode in one or more pairs located at a distance from the respective opposite sides of the cathode; and

a device operably coupled to one or more pairs of sacrificial anodes to control the distance between the anodes and the cathode in response to the consumption of the anode.

In yet another aspect, a system for electrolytic production of rare earth metals is disclosed, comprising:

an electrolytic cell in accordance with one of the first, second or third features, as defined above;

feed material containing one or more rare earth metal compounds capable of undergoing electrolysis to produce rare earth metals;

an electrolyte in the molten state of which the loading material can dissolve; and

a direct current source adapted to conduct current between the anode and cathode of the electrolytic cell in order to electrolyze the feed material and thereby produce a product of molten rare earth metal.

In another feature, a process for electrolytic production of rare earth metals is disclosed, comprising:

providing an electrolytic cell in accordance with a second feature;

filling the electrolyte cell with a feed material containing one or more rare earth metal compounds capable of undergoing electrolysis to produce rare earth metals and an electrolytic bath containing molten electrolyte in which the feed material can dissolve;

passing a direct current between at least one sacrificial anode and a cathode in an electrolytic cell to electrolyze the feed material and thereby produce a product of molten rare earth metal; and

displacing the molten electrolyte in the electrolytic cell to maintain the height of the electrolytic bath in the electrolytic cell.

In one embodiment, the displacement step is performed in response to anode consumption rate and / or a change in the volume of the rare earth metal product contained in the electrolytic cell.

Another feature discloses a process for electrolytic production of rare earth metals, including:

providing an electrolytic cell in accordance with a third feature;

filling the electrolyte cell with a feed material containing one or more rare earth metal compounds capable of undergoing electrolysis to produce rare earth metals and a molten electrolyte in which the feed material can dissolve;

passing a direct current between at least one sacrificial anode and a cathode in an electrolytic cell to electrolyze the feed material and thereby produce a product of molten rare earth metal; and

translating each sacrificial anode towards the cathode in response to the rate of expenditure of the anode in order to maintain a constant anode-cathode distance in the electrolytic cell.

The disclosed embodiments provide an improved ability to control the anode-cathode distance (AKP), and hence the process temperature, improved control of the height of the electrolytic bath in the electrolytic cell and immersion of the anode, better mixing of the electrolyte to facilitate dissolution of the feed material, and higher Faraday efficiency, by restrictions on the possibility of the reverse reaction of the anode gas with the produced metal.

A brief description of the graphic materials

Regardless of other forms that may fall within the scope of the invention, as set forth in the brief description, specific embodiments will now be described, solely by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a side view of an electrolytic cell in accordance with one specific embodiment; and

Figure 2 is a cross-sectional image of the electrolytic cell shown in Figure 1.

Detailed Description of Specific Embodiments

The description in general terms relates to an electrolytic cell adapted for the production of rare earth metals using an electrolysis process in a bath of molten electrolytic salt.

The rare earth metals produced in the electrolytic cell disclosed herein include rare earth metals having a melting point below 1100 ° C. Exemplary rare earth metals include, but are not limited to, Ce, La, Nd, Pr, Sm, Eu, and alloys thereof, including didyme and mischmetal. The electrolytic cell disclosed herein is also suitable for the production of rare earth metal alloys with iron.

The molten electrolytic salt bath behaves like a solvent in relation to the feed material. The electrolyte for use in a bath of molten electrolytic salt may contain halide salts, in particular fluoride salts.

Examples of “fluoride salts” include, but are not limited to, metal fluoride salts, including rare earth fluorides such as LaF ₃ , CeF ₃ , NdF ₃ and PrF ₃ , alkali metal fluorides such as LiF, KF, and alkaline earth metal fluorides such as CaF ₂ , BaF ₂ .

The choice of feed material for the electrolysis process depends on the desired rare earth metal product and the electrolyte composition. When the electrolyte is composed of fluoride salts, the feed material that undergoes the electrolysis process may contain rare earth metal oxides.

The term "rare earth oxide" in the broad sense refers to any oxide or any precursors of such rare earth oxides, including rare earth metal hydroxides, carbonates or oxalates. Rare earth metals are a set of seventeen chemical elements in the periodic table, namely fifteen lanthanides plus scandium and yttrium. Scandium and yttrium are considered rare earth metals because they are usually found in the same ore deposits as lanthanides and exhibit similar chemical properties. Lanthanides include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

Suitable examples of feed material for the electrolytic production of neodymium or praseodymium include neodymium oxide (Nd ₂ O ₃ ) or praseodymium oxide (Pr ₆ O ₁₁ ). When the desired product is an alloy, such as give, the feed material may contain two or more rare earth oxides (e.g., Nd ₂ O ₃ and Pr ₆ O ₁₁ ) in the desired stoichiometric ratio of the desired alloy. Michemetal can be prepared from oxides of several rare-earth metals, such as Ce, La, Nd, Pr, and the ratio of rare-earth metals in mischmetal corresponds to the ratio of rare-earth oxides in the feed material.

In another case, when the electrolyte is composed of chloride salts, the feed material may contain rare earth chloride salts.

In one embodiment, the electrolyte comprises one or more rare earth metal fluorides and lithium fluoride. One or more rare earth fluorides may be present in the electrolyte in the range of about 70-95% by weight with a residue in the form of lithium fluoride. Optionally, the electrolyte may also contain up to 20 wt.% Calcium fluoride and / or barium fluoride.

Those skilled in the art will understand that the operating temperature of the electrolytic cell depends on the target product of the rare earth metal or rare earth alloy, the composition of the electrolyte, and therefore the corresponding solidification points of the rare earth metal, alloy, and electrolyte. In one embodiment, the operating temperature of the electrolytic cell may be in the range of 5-50 ° C above the solidification point of the electrolyte, and preferably 10-20 ° C above the melting point of the electrolyte. The composition of the electrolyte is selected so that the liquidus of the electrolyte can be in the range of 5-50 ° C above the solidification point of the metal.

In some embodiments, when the target product of the rare earth metal is mischmetal (a mixture of cerium, lanthanum, neodymium and praseodymium), the curing point is variable, depending on the composition of the mischmetal and the relative ratios of the rare earth metals in it, but, be that as it may, approximately 800 ° C. In these embodiments, the electrolyte may include barium or calcium fluorides, as described above, to achieve an electrolyte liquidus in the range of 5-50 ° C. above the solidification point of the mischmetal.

In other embodiments, when the solidification points of the alloys or mixtures of rare earth metals are 800 ° C. or lower, the electrolyte may optionally contain one or more chloride salts of rare earth metals and lithium chloride salts.

Turning to Figures 1 and 2, in which like numbers refer to like parts, an embodiment of an electrolytic cell 10 for the production of rare earth metals is presented. Cell 10 includes a housing 12 having a bottom 14, a collector 16, one or more cathodes 18, and one or more pairs of anodes 20.

The housing 12 is formed of anticorrosive materials that are inert due to the electrolyte composition and operating conditions, as described in the previous paragraphs. In particular, the anti-corrosion materials used to clad the housing 12 from the inside must be resistant to the formation of an alloy with the rare earth metals produced therein. In one embodiment, the housing 12 may be internally lined with refractory materials. Suitable refractory materials include, but are not limited to, carbon, silicon carbide, silicon nitride, boron nitride, or certain stainless steels, such as are known to those skilled in the art.

The inclined bottom 14 has one or more inclined channels 22 located on it, through which molten rare earth metals produced in the electrolytic cell 10 can flow. In one embodiment, one or more inclined channels 22 are deflected from the horizontal by an angle α to 10 °.

In the embodiment shown in FIG. 2, channel 22 has a rectangular cross section. However, it will be understood that in alternative embodiments, the cross section of the channel 26 may take other forms such as a V-shape or a U-shape.

In some forms of the invention, the bottom 14 may be provided with more than one inclined channel 22, as shown in Figure 2. In these specific forms, the channels 22 are arranged in adjacent lateral parallel alignment with each other. In general, the channel (s) 22 may be aligned along or equidistant from the central longitudinal axis of the bottom 14 in the housing 12. In this device, the channel (s) 22 on the bottom 14 may be located adjacent to the lower side 24 of one or more cathodes 18 to receive molten rare earth metals produced at one or more cathodes 18.

The bottom 14 or the upper surface of the bottom 14 can be formed of anti-corrosion materials, the same or similar to those materials that are selected for facing the cell body 12. All surfaces in direct contact with the rare earth metal product, including channel (s) 22 and collector 16, must be resistant to the formation of rare earth metal alloys produced in an electrolytic bath. Suitable lining materials for channel (s) 22 and collector 16 include, but are not limited to, metals such as tungsten, molybdenum, or tantalum.

Collector 16 is adapted to receive, in use, molten rare earth metal produced at one or more cathodes 18, which collects in a channel and flows to the lower end 26 of channel 22. Collector 16 is spaced and isolated from one or more cathodes 18 and one or more anodes 20.

Collector 16 may be provided with a heater to maintain a temperature above the liquidus of the molten rare earth metal. Collector 16 may also be provided with an opening (not shown) from which rare earth metal may be poured if necessary. The collection 16 may be formed from inert metals similar to those used for the housing 12.

The device allows you to continuously remove the product of molten rare earth metal from the bottom 14 of the cell 10, which prevents the accumulation of the product of molten rare earth metal and, therefore, provides several advantages. In electrolytic cells of the prior art, where the formation of a product of molten rare earth metal is allowed to accumulate, in particular at the bottom of the cell or on the cathode surface, the product of molten rare earth metal is often contaminated with a “precipitate” that contains undissolved and partially molten rare earth feed material, intermediate reaction products and by-products. In the electrolytic cell 10 disclosed herein, in the absence of a product of molten rare earth metal, the precipitate remains in contact with the molten electrolyte and thus becomes redissolved in the molten electrolyte.

The molten rare earth metal product collected in the collection vessel 16 is spaced apart and isolated from one or more cathodes 18 and one or more anodes 20. Consequently, the molten rare earth metal is protected from reaction and / or contamination with volatile carbon rising from one or more anodes 20 , and reverse reactions with gases leaving one or more anodes 20.

One or more cathodes 18 are suspended in an electrolytic bath 11 contained in the cell body 12 above the channel 22 in a substantially vertical alignment with it. In the present form, the cathodes 18 comprise plates of cathode material having an upper surface 28 and opposite elongated surfaces 30, the lower side 24 being located above the channel 22 so that the molten rare-earth metal produced on the opposite surfaces 30 can fall under the influence of gravity directly into the underlying channel 22. Opposite surfaces 30 of cathodes 18 are supported by an inert refractory filling material 32, which further eliminates the formation of inactive electrolytic ones in the cell 10.

The cathodes 18 are adapted in adjacent alignment with each other, so that the opposite elongated surfaces 30 of the adjacent cathodes 18 are respectively aligned with each other in the longitudinal direction, and the corresponding opposite end surfaces of the adjacent cathodes 18 are facing each other. Those skilled in the art will understand that the gap between the opposite opposite end surfaces of adjacent cathodes 18 is as narrow as possible.

The plates of the cathode material have an appropriate size, so that, in a device like the one described above, the effective length of the adjacent cathodes 18 is substantially the same or slightly shorter than the length of the channel 22.

Alternatively, a single cathode 18 having a length similar to the length of channel 22 can be used in an electrolytic cell 10, such as described herein.

Opposite oblong surfaces 30 of the cathodes 18 are inclined downward and outward at an angle from the vertical, so that the cross-sectional shape of the cathode 18 is substantially triangular. Opposite elongated surfaces 30 can be deflected from the vertical by an angle β to 45 °, and preferably 2 ° from 10 °.

The tilt angle is selected based on the optimized bubble-driven electrolyte flow to obtain good mixing with the feed material and maintain a high Faraday yield. The desired angle β can be determined by numerical simulation for a particular cell geometry.

In embodiments where the desired electrolytic product is a single rare earth metal or an alloy of rare earth metals, the cathodes 18 can be formed of an electrically conductive material with sufficient resistive thermal properties to guarantee a free flow of molten rare earth metals at temperatures slightly above their melting points. Such materials must be resistant to the formation of alloys with rare earth metals produced in an electrolytic bath. Suitable materials include, but are not limited to, metals such as tungsten, molybdenum, or tantalum.

In alternative embodiments, when an alloy of iron with one or more rare earth metals is desired, the cathode 18 may be formed from iron. Those skilled in the art will understand that in these specific embodiments, the cathode 18 will be consumed during the electrolysis process to produce an alloy of iron and rare earth metal.

In the embodiment shown in Figures 1 and 2, a plurality of pairs of anodes 12 are suspended in the cell housing 12. Each anode 20 is paired with the respective opposed elongated surfaces 30 of the cathodes 18. In the form shown, the anodes 20 comprise consumable plates anode material having an upper surface 32, a lower surface 34, opposing the distal and proximal oblong surfaces 36a, 36b, and opposite ends 38. The distal oblong surface 36a of each anode 20 can be substantially Vertical, or it may be inclined from vertical. The proximal oblong surface 36b is deflected from the vertical. The proximal proximal side 36b can be deflected from the vertical by an angle β ′ to about 45 °, and preferably from 2 ° to 10 °, tapering to the bottom surface 34 of the anode 20.

The adjacent elongated surfaces 36b of the anodes 18 are facing the respective opposite elongated surfaces 30 of the cathodes 18. Both surfaces 36b and 30 are deflected from the vertical by the corresponding angle β ', so that these surfaces 36b and 30 are spaced parallel to each other, so as to determine to a large extent constant anode-cathode distance between them.

The anodes 20 are adapted in adjacent alignment with each other, so that the opposite elongated surfaces 36a, 36b of the adjacent anodes 20 are respectively aligned with each other in the longitudinal direction, and the corresponding opposite ends 38 of the adjacent anodes 20 are facing each other. Those skilled in the art will understand that the gap between the opposite opposite ends 38 of adjacent anodes 20 is as narrow as possible.

The plates of the anode material have a corresponding size, so that, in a device like the one described above, the effective length of adjacent anodes 20 is substantially the same or slightly shorter than the length of the channel 22.

Alternatively, in an electrolytic cell 10, such as described herein, a single pair of anodes 20 having a length similar to the length of channel 22 can be used.

Suitable examples of consumable anode material include, but are not limited to, carbon-based materials, in particular high purity coal, electrode-grade graphite, calcined petroleum coke and coal tar compositions. Such compositions are well known to those skilled in the art related to the electrolytic production of rare earth metals and other metals such as aluminum.

Anodes are consumed as the electrolysis process goes through, and the angle of inclination β of the proximal oblong side 36b remains substantially constant. The gas bubbles discharged from the anode 20 are therefore held against the proximal oblong surface 36b when the gas bubbles rise to the surface of the electrolyte using the oblique profile of the proximal oblong surface 36b, as shown in Figure 2. This advantageously reduces the possibility of contact of the gas with the metal formed at cathode 18, thereby improving the efficiency of Faraday and avoiding the formation of insoluble precipitates formed by the reverse reaction with them.

Under most operating conditions, the AKP in an electrolytic cell, such as that disclosed herein, can be from about 30 mm to about 200 mm, although AKP from about 50 mm to about 100 mm is preferred. A person skilled in the art can easily determine the proper AKP depending on the desired heat generation in the electrolytic zone, electrolytic flows for optimal solubility of the feed material and optimization of the process yield (Faraday efficiency).

The anode is consumed during electrolysis, which means that as AKP undergoes electrolysis, it can increase. The electrolytic cell 10 disclosed herein may be provided with a device 40 operably coupled to one or more anodes 20 to control the ACP, in particular to maintain a substantially constant ACP. Said device 40 may comprise a horizontal positioning apparatus in operative connection with one or more anodes 20. When used, the horizontal positioning apparatus can move one or more anodes 20 toward the cathode 18 in response to the speed at which the anode 20 is consumed, so that the AKP can remain largely constant. The anode consumption rate may be determined by reference to an electric current. Alternatively, the horizontal positioning apparatus may move one or more anodes 20 in response to a change in cell resistance from a predetermined value.

Due to the consumption of the anode, the volume occupied by the anodes 20 in the electrolytic cell 10 is reduced, thereby lowering the height of the electrolytic bath in the housing 12. Similarly, intermittent cell operations, such as replacing the used anodes with new anodes and removing the rare earth metal product from the cell, leads to a significant and an undesirable change in the height of the electrolytic bath and the immersion depth of the electrode. The electrolytic cell 10 disclosed herein may be provided with an extrusion device 42 to control the height of the electrolytic bath in the housing 12, in particular in order to maintain a substantially constant height of the electrolytic bath in the housing 12. The extrusion device 42 may contain an inert body that suspended in the housing 12 and can be positioned in the vertical direction. In use, an inert body can move up or down in response to a particular cell operation, so that the height of the electrolytic bath can be kept substantially constant. The inert body may have any suitable shape, for example, the shape of a beam, as shown in the Figures.

The extrusion device 42 may be formed from the same refractory materials as the interior of the housing 12, as described above.

When used, the electrolysis process can be performed by loading the expanded electrolyte into the electrolytic cell 10, as described herein. Alternating current can be supplied between the cathodes 18 and anodes 20, and the resistance of the electrodes 18, 20 raises the working temperature of the electrolytic cell 10 to a predetermined temperature. The feed material is then loaded into the electrolytic cell 10 and dissolved in the molten electrolyte. A direct current in the range of 5-10 kiloamperes is supplied to the anodes 20, after which the electrolysis of the dissolved loading material begins. In an electrolytic reaction, the feed material is reduced to molten rare-earth metal (s) on opposite elongated surfaces 30 of the cathode 18. The molten rare-earth metal (s) then falls into channel 22 and flows down channel 22 into collector 16, which is emptied as necessary. The feed material can be regularly loaded into the electrolytic cell 10 in the region of a strong electrolyte flow, at a speed more or less consistent with the consumption rate. Those skilled in the art will understand that the loading speed can be precisely controlled to achieve the target cell resistance corresponding to the desired loading concentration in the electrolyte.

The electrolysis process can be carried out under an inert or low oxygen atmosphere in the electrolytic cell 10. An inert atmosphere can be established and maintained by supplying an inert gas or gas mixtures to the electrolytic cell 10 to eliminate air from there and thereby prevent undesired reactions with molten electrolyte and / or electrodes 18, 20. Suitable examples of inert gases include, but are not limited to, helium, argon, and nitrogen.

Numerous changes and modifications will themselves be understood by specialists in the relevant field of technology, in addition to those already described, without departing from the main innovative ideas. All such changes and modifications should be considered to fall within the scope of the present invention, the nature of which should be determined by the foregoing description.

In the following claims and in the foregoing description, unless the context requires otherwise due to an exact expression or necessary logical conclusion, the word “contain” and its variants, such as “contains” or “comprising”, are used in an inclusive sense, i.e. e. to determine the presence of the claimed features, but not to exclude the presence or addition of additional features in various embodiments of the device and method, as they are disclosed in this document.

Claims (29)

1. Electrolytic cell for the production of rare earth metals, containing: cell body made with one or more inclined channels located at the bottom of the cell body for draining molten rare earth metals produced in an electrolytic cell, one or more cathodes suspended in the cell body substantially in vertical alignment with one or more channels, while the corresponding opposing surfaces of the one or more cathodes are inclined downward and outward at an angle from the vertical, one or more pairs of anodes suspended in the cell body, each anode in one or more pairs having a front surface deviated from the vertical and spaced in parallel alignment with the corresponding opposite inclined surfaces of one or more cathodes to determine a substantially constant anode-cathode the distance between them, and a collector for receiving molten rare earth metals from a channel, the collector being at a distance and isolated from one or more cathodes and one or more anodes. 2. The electrolytic cell according to claim 1, characterized in that it further comprises an extrusion device for controlling the height of the electrolytic bath contained in the cell body. 3. The electrolytic cell according to claim 1, characterized in that it further comprises a device operably connected to one or more anodes to control the distance between the anodes and the opposite sides of the cathode when the anode is consumed. 4. The electrolytic cell according to p. 2, characterized in that the displacement device contains an inert body, which is suspended in the housing and has the ability to position in the vertical direction. 5. The electrolytic cell according to claim 3, characterized in that the device functionally associated with one or more anodes contains a horizontal positioning device. 6. The electrolytic cell according to claim 5, characterized in that the horizontal positioning device is configured to laterally move one or more anodes to the cathode in accordance with the speed at which the anodes are consumed. 7. The electrolytic cell according to claim 1, characterized in that one or more channels in the housing are deflected from the horizontal by an angle of up to about 10 °. 8. The electrolytic cell according to claim 1, characterized in that one or more channels have a cross-sectional shape that is rectangular, V-shaped or U-shaped. 9. The electrolytic cell according to claim 1, characterized in that the opposite sides of the cathode and the front sides of the anode are angled up to 45 ° from the vertical. 10. The electrolytic cell according to claim 9, characterized in that the opposite sides of the cathode and the front sides of the anode are angled from 2 to 10 ° from the vertical. 11. A system for electrolytic production of rare earth metals, comprising: an electrolytic cell according to any one of claims 1 to 10, feed material containing one or more rare earth metal compounds capable of electrolysis and production of rare earth metals, molten electrolyte capable of dissolving the feed material, and a direct current source adapted to conduct current between the anode and cathode of the electrolytic cell for electrolysis of the feed material and production of a product of molten rare earth metal in the electrolytic cell. 12. The method of electrolytic production of rare earth metals, including: the use of an electrolytic cell according to claim 2, filling the electrolytic cell with a loading material containing one or more rare earth metal compounds capable of undergoing electrolysis for the production of rare earth metals, and an electrolytic bath containing a molten electrolyte capable of dissolving the loading material, transmitting direct current between at least one sacrificial anode and cathode in an electrolytic cell for electrolyzing the feed material and producing a molten rare earth metal product at the cathode and displacing the molten electrolyte in the electrolytic cell to maintain the height of the electrolytic bath in the electrolytic cell. 13. The method of electrolytic production of rare earth metals, including: the use of an electrolytic cell according to claim 3, filling the electrolyte cell with a loading material containing one or more rare earth metal compounds capable of undergoing electrolysis for the production of rare earth metals and a molten electrolyte capable of dissolving the loading material, transmitting direct current between at least one sacrificial anode and cathode in an electrolytic cell for electrolyzing the feed material and producing a molten rare earth metal product at the cathode and the movement of each sacrificial anode in the direction of the cathode in accordance with the rate of expenditure of the anode to maintain a constant anode-cathode distance in the electrolytic cell.

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