KR102023751B1 - Electrolytic cell for production of rare earth metals - Google Patents

Abstract

Electrolytic cells for the production of rare earth metals are described. The electrolytic cell is a cell housing, provided with at least one inclined channel disposed at the bottom of the cell housing, wherein the molten rare earth metal produced in the electrolytic cell along the channel (s) can be discharged. And a housing. One or more cathodes are arranged substantially perpendicular to the one or more channels and are suspended in the cell housing. Each opposing surface of the one or more cathodes is angled at an angle from perpendicular to downward and outward. At least one pair of anodes is suspended within the cell housing; Each anode in the one or more pairs has opposite surfaces spaced apart from each other in an array parallel to the respective inclined surfaces of the one or more cathodes to define a substantially constant anode cathode distance therebetween. Has opposite surfaces. The electrolytic cell also includes a sump for receiving molten rare earth metal from the channel, wherein the sump is isolated from one or more cathodes and one or more anodes. Separation of the molten rare earth metal from the cathode (s) and the anode (s) prevents reaction with scattering carbon generated from the anode (s) and / or reverse reaction with contaminated or released gases.

Description

Electrolytic cell for production of rare earth metals

The present disclosure relates generally to electrolytic cells, particularly electrolytic cells adapted to produce rare earth metals such as neodymium, praseodymium, cerium, lanthanum, and mixtures thereof by electrolytic processes in molten fluoride or chloride electrolyte baths.

Electrolytic cells for producing aluminum in molten fluoride or chloride salt baths are well known and many of their design features are associated with important considerations. In particular, it is important to maintain a stable and low anode-cathode distance (ACD) as a means of energy saving in high energy intensive processes. It can prove difficult to maintain a constant ACD where molten aluminum collects on the cathode surface and is subjected to hydrodynamic forces imposed by strong magnetic fields. Thus, in some cell configurations, the cathode may be suspended above the cell bottom where molten aluminum is collected. In other configurations, the cathode may be provided with a channel through which molten aluminum can be collected, thereby allowing molten aluminum to be ejected from the cathode as soon as molten aluminum is formed to maintain a constant ACD.

It is also important for the electrolysis cell to be configured to release carbon dioxide gas generated at the anode surface from the space between the electrodes during electrolysis, which can reduce the efficiency of the electrolysis process when aluminum metal is formed on the cathode surface. To substantially prevent "back reaction" with the product.

Neodymium and praseodymium, mixtures thereof, and other rare earth metals are also currently commercially produced by electrolytic processes in melt mixed fluoride salt baths. In contrast to the electrolytic production of aluminum, the anodes and cathodes are arranged in a vertical direction and molten metal is collected into the receiving vessel above the cell bottom. The space between the electrodes is not affected by the accumulation of molten metal, but nevertheless is changed by the continuous electrolytic consumption of the carbon anode surfaces. The cathodes typically consist of an inert metal such as molybdenum or tungsten.

Since the anodes are consumed, there is no effective means to keep the anode cathode separation distance uniform. Since much of the process heat is carried by the ohmic resistance of the electrode gap, the process temperature is very variable and is generally controlled by the reduction of the current supplied to the cell. This is impractical in larger scale operations where multiple cells are connected in electrical series. Moreover, reduction of current throughout the electrolytic process is also undesirable because it reduces the production capacity of the cell. Most importantly, failure to strictly control the process temperature results in reduced process yield, or Faraday efficiency, and formation of insoluble sludge that builds up on the bottom of the cell. As a result, electrolysis is interrupted periodically to remove sludge from the cell, thereby preventing continuous electrolysis.

Insufficient control of process temperature also increases vapor release from the cell, which is detrimental to the working atmosphere and environment if they are not suppressed.

In addition, as the anodes are consumed, the volume replaced 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, impairing process efficiency, including power consumption, and increasing the likelihood of the 'anode effect' of generating high pollutant gases.

Moreover, the product rare earth metal is reactive with carbon at the process temperature. Carbon is a very undesirable impurity in certain rare earth metal production applications. Reducing the possibility of contact between fugitive carbon and metal in the cell and / or the residence time of the product metal in the cell is not a clear design of current commercial cell designs, but is a desirable design attribute. This particular problem is not a factor in the design of electrolytic cells for aluminum production, since aluminum does not react with carbon under these conditions.

In addition, in current electrolytic cell designs for rare earth metals, it is difficult to keep the product rare earth metal in the molten state, since the operating temperature is usually only 10-30 ° C. above the freezing point of the product rare earth metal. This problem is not an issue and is not mentioned in the electrolytic cell for electrolytic production of aluminum because the process temperature is about 300 ° C. above the freezing point of aluminum.

At present, commercial activities for the electrolytic production of rare earth metals are small, labor intensive and run in a semi-batch manner. Some deficiencies hinder the scaling of the process to allow higher productivity to be reached, continuous delivery, high standards of environmental improvement, occupational health and safety.

First, electrolytic cells typically operate in a limited current range of 5-10 kiloamps, which corresponds to low production capacity.

The control of the rare earth oxide feed material to the cell is poor, which accumulates insoluble sludge, requiring frequent clean-out of the cell, thus preventing subsequent electrolysis. In addition, the feed material is manually supplied to the cell without a known criterion for the current oxide concentration in the cell.

Existing techniques use vertical electrode arrays. This arrangement is not suitable for achieving high Faraday efficiency. For example, bubbles that rise and rise at the anode surface are entrained in the electrolyte flow and come into contact with the product metal formed on the cathode plate, thereby back-oxidating the product metal to reduce process yield.

In US Pat. No. 5,810,933 Keller describes a process for producing neodymium in an electrolytic cell designed to operate without the occurrence of an anode effect and thus to prevent the generation and release of highly contaminated perfluorinated carbon (PFC) gases. In this invention, the first anode provides a multiple anode plate such that the current density stays far below what an anode effect can occur, and the second cathode is removed from the vertical anode using an inert barrier material that remains porous to neodymium ions. This object is achieved by physically separating and thereby allowing a higher concentration of dissolved neodymium oxide to be maintained in the anode region than in the cathode region. However, this disclosed invention has several drawbacks and impracticalities. There is no demonstration in the cited embodiments that the barrier material (boron nitride) is actually permeable to neodymium ions as required for the continuous electrolytic process. Furthermore, it can be expected that the proposed anode design is complex and the wear rate of the anode plate is very non-uniform and wasteful. The compartmental separation of the anode region and the cathode region further leads to a large separation distance between electrodes and consequently inefficient energy consumption. The invention also proposes the use of carbon as an inert cathode material, which is well known to react with and contaminate product metals.

Therefore, there is a need for an alternative or improved electrolytic cell and process for the production of rare earth metals.

Reference to the background art above is not an admission that the technology forms part of the common general knowledge of those of ordinary skill in the art. The above reference is also not intended to limit the electrolytic cells disclosed herein.

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

A cell housing, comprising: at least one inclined channel disposed at the bottom of the cell housing, wherein the cell housing is capable of draining molten rare earth metal produced in the electrolytic cell along the channel (s);

One or more cathodes suspended in the cell housing and arranged substantially perpendicular to the one or more channels, wherein each opposing surfaces of the one or more cathodes are angled downwardly and vertically; The at least one cathode inclined outwardly;

At least one pair of anodes suspended within the cell housing, wherein each of the at least one pair of anodes is inclined from vertical and spaced apart from each other in an array in parallel with respective opposing sloping surfaces of the at least one cathode; Said at least one pair of anodes having facing surfaces defining a substantially constant anode cathode distance; And

A sump separate from the at least one cathode and the at least one anode and spaced apart from each other and for receiving molten rare earth metal from the channel.

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

A cell housing for containing an electrolyte bath;

One or more cathodes suspended within the cell housing;

One or more pairs of consumable anodes suspended within the cell housing, each anode of the one or more pairs of the one or more pairs of consumable anodes spaced apart from each other opposing sides of the cathode; And

Displacement device for controlling the height of the electrolyte bath contained in the cell housing.

In one embodiment, the displacement device adjusts the height of the electrolytic cell included in the cell housing in response to anode consumption and the volume of the rare earth metal product contained in the cell housing.

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

Cell housing;

One or more cathodes suspended within the cell housing;

One or more pairs of consumable anodes suspended within the cell housing, each anode of the one or more pairs of the one or more pairs of consumable anodes spaced from respective opposing faces of the cathode; And

And operatively associated with the at least one pair of consumable anodes to control the distance between the anode and the opposing faces of the cathode in response to anode consumption.

In another aspect, a system for the electrolytic production of rare earth metals is disclosed that includes:

An electrolysis cell consistent with any one of the first, second or third aspects as defined above;

A feed material comprising at least one rare earth metal compound capable of being electrolyzed to produce a rare earth metal;

A molten electrolyte in which the feed material can be dissolved; And

A direct current power source configured to pass a current between an anode and a cathode in the electrolysis cell to electrolyze the feed material to produce a molten rare earth metal product in the electrolysis cell.

In another aspect, a process for the electrolytic production of rare earth metals is disclosed, including:

Providing an electrolytic cell consistent with the second aspect;

Filling said electrolytic cell with an electrolyte bath comprising a feed material comprising at least one rare earth metal compound that can be electrolyzed to produce a rare earth metal and a molten electrolyte in which the feed material can be dissolved;

Passing a direct current between at least one consumable anode and cathode in the electrolysis cell to electrolyze the feed material to produce a molten rare earth metal product over the cathode; And

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

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

In another aspect, a process for the electrolytic production of rare earth metals is disclosed that includes:

Providing an electrolytic cell consistent with the third aspect;

Filling said electrolytic cell with a feed material comprising at least one rare earth metal compound that can be electrolyzed to produce a rare earth metal and a molten electrolyte in which the feed material can be dissolved;

Passing a direct current between at least one consumable anode and cathode to electrolyze the feed material to produce a molten rare earth metal product over the cathode; And

Translating the or each consumable anode toward the cathode in response to an anode consumption rate to maintain a constant cathode anode distance in the electrolysis cell.

The disclosed embodiments provide improved control of the anode cathode distance (ACD) and consequently the process temperature, improved control of the electrolyte bath height and anode immersion in the electrolysis cell, better mixing of the electrolyte to improve dissolution of the feed material, and anode It allows for a higher Faraday efficiency by limiting the chance of back reaction of the gas and the metal produced.

Notwithstanding other forms that may fall within the scope of the disclosure as set forth in the solution to the subject matter, specific embodiments will be described by way of example only with reference to the accompanying drawings.
1 is a side view of an electrolysis cell according to one specific embodiment.
2 is a cross-sectional view of the electrolytic cell shown in FIG. 1.

The present technology broadly relates to electrolytic cells arranged to produce rare earth metals by an electrolytic process in an electrolytic salt bath.

Rare earth metals produced in the electrolytic cells disclosed herein include rare earth metals having a melting point lower than 1100 ° C. Exemplary rare earth metals include, but are not limited to, Ce, La, Nd, Pr, Sm, Eu, and their alloys such as didymium, Mischmetal. The electrolytic cells disclosed herein are also suitable for the production of alloys of rare earth metals and iron.

The molten electrolyte salt bath acts as a solvent for the feed material. The electrolyte for use in the molten electrolyte salt bath may comprise a halogen salt, in particular a fluorine salt. Examples of 'fluoride salts' include metal fluorides including rare earth metal 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 Salts, including but not limited to.

The choice of feed material for the electrolysis process will depend on the desired rare earth metal product and the composition of the electrolyte. If the electrolyte contains a fluoride salt, the feed material to be subjected to the electrolytic process may comprise an oxide of a rare earth metal.

The term 'rare earth metal oxide' broadly refers to all oxides of rare earth metals or all precursors of such oxides of rare earth metals, including hydroxides, carbonates or oxalates of rare earth metals. Rare earth metals are a set of seventeen elements in the periodic table, in particular fifteen lanthanides, scandium and yttrium. Scandium and yttrium tend to occur in ore deposits such as lanthanides and are considered rare earth metals because they have similar chemical properties. Lanthanum elements include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, euroopium, gadolinium, terbium, and dysprosium dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

Suitable examples of feed materials for electrolytic production of neodymium or praseodymium include neodymium oxide (Nd ₂ O ₃ ) or praseodymium oxide (Pr ₆ O ₁₁ ). If an alloy, such as didymium, is the desired product, the feed material is an oxide of two or more rare earth metals (eg, Nd ₂ O _{3) at} the desired stoichiometric ratio of the desired alloy. And Pr ₆ O ₁₁ ). Mischmetal can be prepared from oxides of several rare earth metals such as Ce, La, Nd, Pr, with the proportion of rare earth metals in the micrometal corresponding to the ratio of rare earth metal oxides in the feed material.

Alternatively, if the electrolyte consists of chloride salts, the feed material may comprise chlorides of rare earth metals.

In one embodiment, the electrolyte comprises one or more rare earth metal fluorides and lithium fluoride. One or more rare earth metal fluorides may be present in the electrolyte with the remainder of lithium fluoride in the range of about 70-95 weight percent. Optionally, the electrolyte may further comprise up to 20% by weight calcium fluoride and / or barium fluoride.

It will be understood by those skilled in the art that the operating temperature of the electrolytic cell will depend on the target rare earth metal product or the rare earth metal alloy, the composition of the electrolyte and consequently the freezing point of each 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. higher than the freezing point of the electrolyte, preferably in the range of 10-20 ° C. higher than the melting point of the electrolyte. The composition of the electrolyte is chosen such that the liquidus of the electrolyte can be in the range of 5-50 ° C. above the freezing point of the metal.

In some embodiments, if the target rare earth metal product is a micrometal (a mixture of cerium, lanthanum, neodymium and praseodymium), the freezing point may vary depending on the composition of the micrometal and the relative proportion of the rare earth metal therein, nevertheless Around 800 ° C. In these embodiments, the electrolyte may comprise barium fluoride or calcium fluoride, as described above, to obtain an electrolyte liquidus range of 5-50 ° C. above the freezing point of the micrometal.

In other embodiments, when the freezing point of the rare earth metal alloy or mixture is 800 ° C. or less, the electrolyte can optionally include one or more rare earth metal chlorides and lithium chloride salts.

1 and 2, the same reference numerals consistently refer to the same member, and shows an embodiment of the electrolytic cell 10 for rare earth metal production. The cell 10 includes a housing 12 having a bottom 14, a sump 16, one or more cathodes 18 and one or more pairs of anodes 20.

The housing 12 is formed from an anti-corrosive material that is inert in terms of electrolyte composition and operating conditions as described previously herein. In particular, the anticorrosive material used to lining the interior of the housing 12 should be resistant to forming alloys with the rare earth metals produced therein. In one embodiment, the housing 12 may be padded with a refractory meterial. Suitable refractory materials may include, but are not limited to, carbon, silicon carbide, silicon nitride, boron nitride or certain stainless steels as is well known to those skilled in the art.

The inclined bottom 14 has one or more inclined channels 22 disposed therein and through which molten rare earth metals produced in the electrolytic cell 10 can be discharged along. In one embodiment, the one or more sloped channels 22 are inclined from horizontal at an angle α of about 10 degrees or less.

In the embodiment shown in FIG. 2, the channel 22 has a rectangular cross section. However, it will be appreciated that in alternative alternative implementations, the cross section of the channel 22 may have other shapes, such as V-shaped or U-shaped.

In some forms of the invention, the floor 14 may have one or more sloped channels 22 as shown in FIG. 2. In these particular forms the channels 22 may be configured in side-by-side parallel arrangement adjacent to each other. In general, the channels 22 may be arranged along the longitudinal axis of the center of the bottom 14 in the housing 12 or spaced apart by an equal distance therefrom. In this arrangement, the channel (s) 22 in the bottom 14 proximal to the bottom face 24 of the one or more cathodes 18 to receive the molten rare earth metal produced on the one or more cathodes 18. ) Can be located.

The bottom 14 or top surface of the bottom 14 may be formed from a corrosive material similar or identical to the material selected for lining the cell housing 12. All surfaces in direct contact with the rare earth metal product, including channel (s) 22 and outlet 16, should be resistant to forming alloys with the rare earth metals produced in the electrolysis cell. Suitable lining materials for channel (s) 22 and outlet 16 are, but are not limited to, metals such as tungsten, molybdenum or tantalum.

A sump 16 is configured to receive molten rare earth metal that is generated over one or more cathodes 18 in use and collected in the channel 22 and discharged toward the lower end 26 of the channel 22. . The discharge vessel 16 is isolated from one or more cathodes 18 and one or more anodes 20 apart from one another.

Discharge tank 16 may be provided with a heater to maintain the temperature above the liquidus of molten rare earth metal. Discharge tank 16 may also be provided with a port (not shown) to tap molten rare earth metal therefrom, if necessary. The discharge vessel 16 may be formed from an inert metal similar to that used for the housing 12.

This arrangement allows for continuous removal of the molten rare earth metal product from the bottom 14 of the cell 10, which prevents the molten rare earth metal product from collecting and consequently provides several advantages. In conventional electrolytic cells that allow the molten rare earth metal product to gather at the bottom or cathode surface of the cell, in particular, the 'sludge' includes the molten rare earth metal product containing undissolved and partially molten rare earth metal feed materials, reaction intermediates and by-products. It is common to be contaminated with '. In the electrolytic cell 10 disclosed herein, in the absence of molten rare earth metal products, the sludge is maintained in contact with the molten electrolyte, thereby providing an opportunity for re-dissolution in the molten electrolyte.

The molten rare earth metal product collected in the discharge vessel 16 is isolated from one or more cathodes 18 and one or more anodes 20 apart from one another. As a result, the molten rare earth metal is protected from reaction with and / or contamination with fugitive carbon generated from one or more anodes 20 and back reaction with gases released from one or more anodes 20. Can be.

One or more cathodes 18 are suspended in an array substantially perpendicular to the channel 22 in an electrolyte bath 11 contained within the cell housing 12. In the form as shown, the cathode 18 comprises a plate of cathode material having an upper surface 28 and opposing extended surfaces 30 together with a lower surface 24 disposed over the channel 22. The molten rare earth metal produced on the opposing surface 30 can then fall directly into the lower channel 22 by gravity. Opposing surfaces 30 of the cathodes 18 are supported by an inert, refractory filler material 32 that further prevents the formation of an inert electrolyte region in the cell 10.

The cathodes 18 are arranged in an arrangement adjacent to each other, whereby the opposing elongated surfaces 30 of the adjacent cathodes 18 are each arranged longitudinally with each other and each opposing of the adjacent cathodes 18 The end surfaces face each other. It will be understood by those skilled in the art that the spacing between opposing opposite end surfaces of adjacent cathodes 18 is as narrow as possible.

The plates of cathode material are correspondingly sized such that in an arrangement as described above, the effective length of the adjacently disposed cathodes 18 is substantially equal to or slightly shorter than the length of the channel 22.

Alternatively, a single cathode 18 having a length similar to the channel 22 can be employed within the electrolytic cell 10 as disclosed herein.

The opposing elongated surfaces 30 of the cathodes 18 are angled from the vertical and inclined downward and outward so that the cross-sectional shape of the cathode 18 is substantially triangular. Opposing elongated surfaces 30 may be inclined at an angle β of about 45 ° or less, preferably 2 ° to 10 °, from the vertical.

The angle of inclination is selected based on the flow of the bubble-driven electrolyte and the maintenance of high Faraday yields optimized to achieve good mixing with the feed material. Preferred angle β can be determined by computer modeling for a particular cell geometry.

In embodiments where a single rare earth metal or alloy of rare earth metals is the desired electrolytic product, the cathode 18 has sufficient resistive heat properties to ensure that the molten rare earth metal flows freely at a temperature higher than its melting point. It can be formed from an electrically conductive material having. Such materials must be resistant to forming alloys with rare earth metals produced in the electrolytic cell. Suitable materials include, but are not limited to, metals such as tungsten, molybdenum, or tantalum.

In alternative embodiments where an alloy of iron and one or more rare earth metals is desired, cathode 18 may be formed from iron. It will be understood by those skilled in the art that in this particular embodiment the cathode 18 will be consumed during the electrolytic process for the production of the iron rare earth metal alloy.

In the embodiment shown in FIGS. 1 and 2, a plurality of pairs of anodes 20 are suspended within cell housing 12. Each anode 20 in the pair is spaced apart from each opposing elongated surfaces 30 of the cathode 18. In the form as shown, the anode 20 has an upper surface 32, a lower surface 34, opposing distal and proximal elongated surfaces 36a, 36b and opposing ends. (ends) 38 and plates of consumable anode material. The distal extended surface 36a of each anode 20 may be substantially vertical or inclined from vertical. The proximal elongated surface 36b is inclined from vertical. The proximal opposing elongated face 36b can be tilted towards the lower surface 34 of the anode 20 at an angle β 'of about 45 ° or less, preferably 2 ° to 10 °, from vertical. have.

Proximal extended surfaces 36b of the anodes 20 face each opposing extended surfaces 30 of the cathodes 18. Both surfaces 36b and 30 are inclined at a corresponding angle β 'from vertical to be spaced apart from each other in an array parallel to each other to define a substantially constant anode-cathode distance therebetween.

The anodes 20 are configured in an arrangement adjacent to each other such that the opposing elongated surfaces 36a, 36b of the adjacent anodes 20 are each arranged longitudinally with each other, and each opposing end of the adjacent anodes 20. The fields 38 face each other. It will be understood by those skilled in the art that the spacing between opposite opposing ends 38 of adjacent anodes 20 is as narrow as possible.

The plates of anode material are sized correspondingly so that, in the arrangement as described above, the effective length of the adjacently disposed anodes 20 is substantially equal to or shorter than the length of the channel 22.

Alternatively, a single pair of anodes 20 having a length similar to the channel 22 can be employed within the electrolytic cell 10 as disclosed herein.

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

The anode is consumed as the electrolytic process progresses, and the tilt angle β of the proximal extended face 36b remains substantially constant. The bubbles emitted from the anode 20 are therefore proximal extended surface 36b as the bubbles rise to the electrolyte surface by an inclined profile of the proximal extended surface 36b as shown in FIG. 2. Stay close to. Advantageously, this reduces the chance of the gas generated in contact with the metal formed above the cathode 18, thus improving Faraday efficiency and preventing the formation of insoluble sludge by back reaction therewith.

Under most operating conditions, the ACD in the electrolytic cell may be from about 30 mm to about 200 mm, although disclosed herein is about 50 mm to about 100 mm. Those skilled in the art will readily be able to determine the appropriate ACD depending on the desired heat generation in the electrolyte region, electrolyte flow for optimal solubility of the feed material, and optimization of process yield (Faraday efficiency).

The anode is consumed during electrolysis and consequently the ACD can increase as the electrolysis proceeds. The electrolytic cell 10 described herein is provided with an apparatus 40 operatively connected with one or more anodes 20 to control the ACD, in particular to maintain a substantially constant ACD. The device 40 includes a horizontal positioning device in operative communication with one or more anodes 20. In use, the horizontal positioning device may laterally move one or more anodes 20 in the direction of the cathodes 18 corresponding to the speed at which the anodes 20 are consumed such that the ACD is substantially constant. The anode consumption rate can be determined with reference to the current flow. Alternatively, the horizontal positioning device may move one or more anodes 20 in response to a change from a predetermined value of the cell resistance.

As the anode is consumed, the volume occupied by the anodes 20 in the electrolytic cell 10 decreases, thereby lowering the height of the electrolyte bath in the housing 12. Similarly, intermittent cell operation such as replacement of the used anode with a new anode, removal of the rare earth metal product from the cell will result in significant and undesirable variations in the height of the electrolyte bath and the electrode immersion depth. The electrolytic cell 10 disclosed herein includes a displacement device 42 to control the height of the electrolytic cell in the housing 12, in particular to maintain a substantially constant height of the electrolyte bath in the housing 12. Can be provided. Displacement device 42 may include an inert body suspended within housing 12 and capable of being positioned in a vertical direction. In use, the inert body can move downward or upward in response to certain cell operations such that the height of the electrolyte bath remains substantially constant. The inert body can have any suitable form, for example a rod form as shown in the figures.

The displacement device 42 may be formed from a refractory material similar to the inner lining of the housing 12 as described above.

In use, the electrolytic process may be performed by charging the molten electrolyte into electrolytic cell 10 as described herein. Alternating current can be supplied between the cathode 18 and the anode 20, and the resistance of the electrodes 18, 20 raises the operating temperature of the electrolytic cell 10 to a predetermined temperature. The feed material is then charged into the electrolysis cell 10 and dissolved in the molten electrolyte. Direct current in the range of 5-100 kiloamps is supplied to the anode 20, whereby electrolysis of the dissolved feedstock begins. In the electrolysis reaction the feed material is reduced to molten rare earth metal (s) on the opposing elongated surfaces 30 of the cathode 18. The molten rare earth metal (s) then falls into the channel 22 and is discharged along the channel 22 to the discharge vessel 16 and tap if necessary. The feed material may be regularly charged into the electrolytic cell 10 in a region of high electrolyte flow, at a rate approximately corresponding to the rate of consumption. Those skilled in the art will understand that the feed rate can be finely controlled to achieve the target cell resistance corresponding to the desired feed concentration in the electrolyte.

The electrolysis process may be performed under an inert or low oxygen atmosphere in the electrolysis cell 10. An inert atmosphere can be established and maintained by supplying an inert gas or gas mixture to the electrolytic cell 10 to exclude air therefrom, thereby undesirable reaction with the molten electrolyte and / or the electrodes 18, 20. Can be prevented. Suitable examples of inert gases include, but are not limited to, helium, argon, and nitrogen.

Numerous variations and modifications, in addition to those already described, will be suggested to those skilled in the art without departing from the basic inventive concepts. All such modifications and variations are considered to be within the scope of this invention, and the nature of the invention will be determined from the foregoing description of this specification.

In the claims that follow and in the foregoing description, the terms "comprise" and variations such as "comprising" are inclusive meanings unless required to be interpreted otherwise due to an explicit language or essential meaning. That is, it is used to specify the presence of the stated features but not to exclude the presence or addition of additional features in various embodiments of the apparatus and method as described herein.

Claims (17)

As an electrolytic cell for rare earth metal production,
A cell housing, comprising: at least one inclined channel disposed at the bottom of the cell housing, wherein the cell housing is capable of draining molten rare earth metal produced in the electrolytic cell along the channel (s);
At least one cathode comprising molybdenum or tungsten, suspended in the cell housing and arranged substantially perpendicular to the at least one channel, each opposing surfaces of the at least one cathode being The at least one cathode angled from vertical and inclined downward and outward;
At least one pair of consumable carbon anodes suspended within the cell housing, wherein each anode of the at least one pair is inclined from vertical and spaced apart from each other in an array in parallel with respective opposing sloping surfaces of the at least one cathode. The at least one pair of consumable carbon anodes having facing surfaces defining a substantially constant anode cathode distance therebetween; And
A sump for receiving molten rare earth metal from the channel, the sump being spaced apart from each other from the at least one cathode and the at least one pair of consumable carbon anodes, whereby the molten rare earth metal is separated from the channel. A discharge tank protected from reaction with and / or contamination with fugitive carbon arising from the anode and back reaction with gases emitted from the anode;
And an apparatus operatively connected with the at least one pair of anodes to control a distance between the anode and the opposing faces of the cathode in response to anode consumption. According to claim 1,
Electrolytic cell for rare earth metal production further comprises a displacement device for controlling the height of the electrolyte bath contained in the cell housing. delete The method of claim 2,
And the displacement device is suspended in the housing and comprises an inert body which can be positioned in a vertical direction. According to claim 1,
And said device operatively connected with said at least one anode comprises a horizontal positioning apparatus. The method of claim 5,
And the horizontal positioning device is configured to move the at least one anode laterally toward the cathode in response to a rate at which the anode is consumed during use. According to claim 1,
Electrolytic cell for the production of rare earth metal in which the one or more channels therein are inclined at an angle of 10 degrees or less from the horizontal. According to claim 1,
Electrolytic cell for rare earth metal production wherein the at least one channel has a rectangular, V-shaped or U-shaped cross-sectional shape. According to claim 1,
Electrolytic cell for the production of rare earth metal in which the opposite faces of the cathode and the opposite faces of the anode are inclined at less than 10 ° from vertical. The method of claim 9,
Electrolytic cell for the production of rare earth metal in which the opposite sides of the cathode and the opposite sides of the anode are inclined from 2 ° to 10 ° from the vertical. An electrolysis cell as defined in claim 1;
A feed material comprising at least one rare earth metal compound capable of being electrolyzed to produce a rare earth metal;
A molten electrolyte in which the feed material can be dissolved; And
And a direct current power source configured to pass a current between an anode and a cathode in the electrolysis cell to electrolyze the feed material to produce a molten rare earth metal product in the electrolysis cell. Providing an electrolytic cell as defined in claim 1;
Filling said electrolytic cell with an electrolyte bath comprising a feed material comprising at least one rare earth metal compound that can be electrolyzed to produce a rare earth metal and a molten electrolyte in which the feed material can be dissolved;
Passing a direct current between at least one consumable anode and cathode in the electrolysis cell to electrolyze the feed material to produce a molten rare earth metal product over the cathode; And
Disposing the molten electrolyte in the electrolytic cell to maintain the height of the electrolyte bath in the electrolytic cell. Providing an electrolytic cell according to claim 1;
Filling said electrolytic cell with a feed material comprising at least one rare earth metal compound that can be electrolyzed to produce a rare earth metal and a molten electrolyte in which the feed material can be dissolved;
Passing a direct current between at least one consumable anode and cathode to electrolyze the feed material to produce a molten rare earth metal product over the cathode; And
And translating the or each consumable anode toward the cathode in response to an anode consumption rate in order to maintain a constant cathode anode distance in the electrolysis cell. delete delete delete delete

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