JP2009019250A - Method and apparatus for producing metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal production method for producing an alkali metal, an alkaline earth metal or a rare earth metal (particularly Ca metal) by an electrolytic method, and a metal production apparatus used for carrying out the method. <P>SOLUTION: Electrolysis is performed while circulating an electrolytic bath 12 at the side of a cathode 11 in an electrolytic cell 10. In order to extract the metal while continuing electrolysis, the electrolytic bath at the side of the cathode is introduced into an adjusting tank 15 for adjusting the metal concentration in the electrolytic bath, a necessary concentration of the metal 18 is extracted from the adjusting tank 15, and the electrolytic bath 20 is returned into the electrolytic cell. Preferably, an electrolytic flow cell capable of carrying out electrolysis while flowing the electrolytic bath in the vicinity of the surface of the cathode in one direction. The method can be carried out using the metal production apparatus including the electrolytic cell, a circulating path 13 for circulating the electrolytic bath at the side of the cathode and the adjusting tank. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an alkali metal, an alkaline earth metal or a rare earth metal by an electrolytic method, and more particularly to a metal production method applicable to the production of metal Ca and a metal production apparatus used for carrying out the method.

  In the production of alkali metals and alkaline earth metals such as Na, Li, Be, and Mg, the raw material ore of each metal is refined through various processing steps, and then converted into a metal chloride, which is subjected to molten salt electrolysis. The method is used. In addition, molten salt electrolysis is also used for producing La, Ce, and the like of rare earth metals.

On the other hand, Ca, which is an alkaline earth metal, is mainly manufactured by a volatile reduction method in which purified Ca carbonate and Al are mixed, heated and reacted to condense the generated Ca vapor. Not used. However, a technique for producing Ti by reducing TiCl ₄ with Ca has been proposed, and in the production process, the step of generating Ca by electrolysis of molten CaCl ₂ is an industrial Ti production method. It is positioned as an important process in establishing.

As an industrial method for producing metal Ti, a crawl method in which TiCl ₄ is reduced with Mg is generally used. However, since this method is a batch type, there is a problem that the product price becomes very high. On the other hand, the Ti production method by the above-mentioned Ca reduction is, for example, as described in Patent Document 1, a reduction process in which Ti particles are generated by reacting TiCl ₄ with Ca in molten CaCl ₂ in which Ca is dissolved. and wherein the step of separating the resulting Ti particles, the electrolysis step to increase the Ca concentration in the molten CaCl ₂ by the Ca concentration in association with formation of Ti particles to electrolytic molten CaCl ₂ was reduced, it was produced in the electrolysis step This is a Ti production method using Ca for reduction of TiCl _{4 in} the reduction step, and has an advantage that the operation can be continuously performed by reusing Ca as a reducing agent.

Furthermore, the present inventors have studied the electrolytic process of molten CaCl ₂ , and as described in Patent Document 2, the electrolytic cell container that is long in one direction holding the molten salt, and the longitudinal direction of the electrolytic cell container The molten salt supply port is provided at one end in the longitudinal direction of the electrolytic cell container, and the Ca concentration generated by electrolysis of the molten salt is at the other end. An electrolytic cell provided with a molten salt outlet for extracting the molten salt out of the electrolytic cell was proposed.

JP 2005-133195 A JP 2007-63585 A

As described above, the electrolytic method is used for the production of metals such as Na, Li, and Mg. On the other hand, in the production of Ti by Ca reduction, in order to circulate and use Ca as a reducing agent, molten CaCl is used. Used to generate Ca from ₂ .

  The object of the present invention is to make an epoch-making improvement to the basic structure of the electrolytic cell used in this electrolysis method, and to target alkali metals, alkaline earth metals or rare earth metals (particularly, metal Ca). An object of the present invention is to provide a metal production method using an electrolysis method and a metal production apparatus used in carrying out the method.

In order to achieve the above-mentioned object, the present inventors have repeatedly studied the generation of Ca by electrolysis of molten CaCl ₂ . As a result, by continuing the electrolysis while circulating the electrolytic bath on the cathode side (using molten CaCl ₂ ) in the electrolytic cell, the Ca concentration in the electrolytic bath on the cathode side is increased and further exceeds the saturation concentration. It has been found that electrolysis can be continued in a molten state or precipitated state of metal Ca in the electrolytic bath.

  If an adjustment tank for extracting a part of the electrolytic bath to be circulated is arranged in the middle of the circulation path of the electrolytic bath, the electrolytic bath in which Ca is concentrated is extracted while the electrolysis is continued, or the metallic Ca is taken out. Can do.

  This method can also be applied to metals other than Ca produced by the electrolytic method.

  The present invention has been made on the basis of such findings, and the gist of the present invention resides in the following metal production method (1) and the metal production apparatus (2) used for carrying out this method.

  (1) A method for producing an alkali metal, alkaline earth metal or rare earth metal by electrolysis, wherein electrolysis is carried out while circulating an electrolytic bath on the cathode side in an electrolytic cell.

  The term “alkali metal, alkaline earth metal, or rare earth metal” as used herein specifically refers to a metal that can be collected and produced by electrolyzing a molten salt containing a chloride or fluoride of each metal. And Na, Li, Be, Ca, Mg, La, Ce and the like.

  In this metal production method, the electrolytic bath on the cathode side is introduced into an adjustment tank for adjusting the metal concentration in the bath, and after removing a metal having a required concentration from the adjustment tank, the electrolytic bath is returned to the electrolytic tank. If this is the case, it is desirable because an electrolytic bath containing a metal or a high concentration of metal can be taken out while continuing electrolysis (this is referred to as “Embodiment 1”).

  Furthermore, in this metal production method, if the electrolysis is performed in a state where the metal in the electrolytic bath on the cathode side exceeds the saturation concentration, the metal can be obtained as a melt or a solid, which is desirable.

  In this metal production method, as an electrolytic cell, an electrolytic bath is supplied continuously or intermittently from one end of the electrolytic cell between the anode and the cathode, thereby giving a one-way flow rate to the electrolytic bath near the cathode surface. It is desirable to adopt an embodiment using a fluidized electrolytic cell that can be electrolyzed while flowing in one direction near the cathode surface. In general, as the fluidized electrolytic cell, one having a partition wall or a diaphragm for separating the cathode side electrolytic bath and the anode side electrolytic bath is used. (This metal production method is referred to as “Embodiment 2”).

  Further, in this metal production method, the above-described fluidized electrolytic cell is used as an electrolytic cell, and the electrolytic bath returned to the fluidized electrolytic cell from the adjusted tank is taken out (that is, the electrolytic bath containing metal or metal is taken out). If an electrolytic bath having a lower metal concentration than the electrolytic bath in the adjustment tank is mixed in the adjustment tank or between the adjustment tank and the fluidized electrolytic tank and returned to the fluidized electrolytic tank, the cathode side The electrolytic bath can be replenished, and electrolysis can be continued for a long time.

  Furthermore, in this metal production method, using the fluidized electrolytic cell as an electrolytic cell, the electrolytic bath after adjusting the metal concentration in the electrolytic bath by introducing the electrolytic bath is returned to the cathode chamber of the fluidized electrolytic cell, It is desirable to supply an electrolytic bath having a metal concentration lower than that of the electrolytic bath in the adjustment tank after the adjustment to the anode chamber of the fluidized electrolytic tank because the electrolytic bath on the anode side can be directly replenished. Here, the “cathode chamber” refers to a region where the cathode is disposed in the electrolytic cell, and the “anode chamber” refers to a region where the anode is disposed.

  Further, in this metal manufacturing method, if the anode chamber side is pressurized with respect to the cathode chamber side, the metal generated on the cathode chamber side can be prevented from flowing into the anode chamber side and the current efficiency can be prevented from decreasing. .

  In the metal manufacturing method of the second embodiment, if the fluidized electrolytic cell uses a porous ceramic body as a diaphragm or a partition wall, it is effective to allow the metal generated on the cathode chamber side to flow into the anode chamber side. Can be suppressed.

  Moreover, it is also possible to use a metal net cheaper than the porous ceramic body as the diaphragm, and in that case, it is desirable to flow the electrolytic bath at a high speed.

  In the metal production method of the present invention, an embodiment using a metal halide as an electrolytic bath can be adopted. In addition, if an embodiment in which a molten material such as calcium (Ca) salt or mixed salt containing Ca salt is used as an electrolytic bath to obtain metallic Ca or molten salt containing metallic Ca is employed, the above-described Ca reduction is achieved. Thus, it becomes possible to continuously produce Ca to be circulated in the Ti production method according to (referred to as “Embodiment 3”).

  In this case, the metal Ca can be obtained as a melt or as a solid.

  (2) A metal production apparatus used for producing an alkali metal, alkaline earth metal or rare earth metal by electrolysis, wherein an electrolytic cell, a circulation path for circulating an electrolytic bath on the cathode side in the electrolytic cell, and the circulation A metal manufacturing apparatus comprising means for causing the metal to be produced.

  In this metal manufacturing apparatus, if an embodiment having an adjustment tank for adjusting the metal concentration of the electrolytic bath is employed in the middle of the circulation path, it becomes possible to take out the metal or the like during the electrolysis.

  Furthermore, in this metal manufacturing apparatus, the electrolytic cell has an electrolytic cell container holding an electrolytic bath, an anode and a cathode disposed along the longitudinal direction of the electrolytic cell container, and the longitudinal direction of the electrolytic cell container An electrolytic bath in which an electrolytic bath supply port is provided at one end so as to supply an electrolytic bath between the anode and the cathode, and the concentration of metal generated by electrolysis of the electrolytic bath is increased at the other end It is desirable to employ an embodiment that uses a fluidized electrolytic cell provided with an electrolytic bath outlet for extracting water from the electrolytic cell (this is referred to as “Embodiment 4”).

  According to the metal production method of the present invention, an anode of alkali metal, alkaline earth metal or rare earth metal produced on the cathode side is obtained by adopting a method in which electrolysis is performed while circulating the electrolytic bath on the cathode side in the electrolytic cell. It is possible to produce these metals continuously while preventing the shift to the side and maintaining high current efficiency. This method can be carried out using the metal production apparatus of the present invention.

  The metal production method of the present invention is a method for producing an alkali metal, an alkaline earth metal or a rare earth metal by an electrolysis method, and electrolysis is performed while circulating the electrolytic bath on the cathode side in the electrolytic cell.

  In this metal production method, when electrolysis is performed in a state where the metal in the cathode-side electrolytic bath exceeds the saturation concentration, the metal can be obtained as a melt or a solid. 1 is a preferred embodiment of the present invention.

  When the metal is collected by electrolysis, the electrolytic bath in the tank is usually kept stationary, but in the metal production method of the present invention, the electrolytic bath on the cathode side in the electrolytic tank is circulated. Thereby, the dissolution of the metal deposited on the electrode into the electrolytic bath or the flow of the metal as it is is promoted, and the metal concentration in the electrolytic bath on the cathode side gradually increases as the electrolysis time elapses.

For example, in the case of electrolysis of molten CaCl ₂ , Ca generated by electrolysis is dissolved in CaCl ₂ by about 1.5 mass% (that is, dissolved up to a saturated concentration of Ca at the temperature during electrolysis). Until this value is reached, the Ca concentration in the electrolytic bath on the cathode side increases. When the saturation concentration is exceeded, precipitation of Ca begins to occur in the electrolytic bath, and when the temperature of the electrolytic bath is higher than the melting point of Ca, Ca becomes a melt and the Ca content of the electrolytic bath increases.

Therefore, at the end of electrolysis, the molten CaCl _{2 in} which the concentration of contained Ca is increased, or when the Ca concentration in the electrolytic bath exceeds the saturation concentration, the molten state or solid metal Ca is replaced with the molten CaCl ₂ . It can be obtained in a state of being floated and separated on the liquid surface. In this case, the operation is batch-type.

  Hereinafter, a case where a metal (for example, Ca) obtained in a molten state or a precipitated state (solid matter), which is an object of the present invention, will be described.

  The circulation of the electrolytic bath on the cathode side in the electrolytic cell may be either continuous or intermittent. Moreover, the flow velocity at that time is not particularly limited. Depending on the operating conditions (temperature of the electrolytic bath), Ca in the electrolytic bath may be precipitated, so that the circulation is performed at a flow rate that does not cause problems such as blockage of the circulation path.

  There is no limitation on the shape of the electrolytic cell. Although it is possible to use a general electrolytic cell that holds the electrolytic bath in a stationary state and circulate the electrolytic bath on the cathode side, it is desirable to use a fluidized electrolytic cell. This will be described in detail later.

In order to circulate the electrolytic bath, a commonly used centrifugal pump or the like may be used, which is made of a material resistant to high-temperature molten CaCl ₂ or other molten salt (or melt) to be handled, and a required flow rate. As long as it can be secured.

  The method of the first embodiment is the metal production method of the present invention, wherein an adjustment tank for adjusting the metal concentration of the electrolytic bath is provided in the circulation path, and the cathode-side electrolytic bath is introduced into the adjustment tank. In this method, a metal having a necessary concentration is taken out from the electrolytic bath, and the electrolytic bath is returned to the electrolytic cell.

  The “regulating tank” may be any tank that has a function of temporarily storing the electrolytic bath being circulated and taking out the metal present in the molten or precipitated state in the electrolytic bath. In this way, the adjustment tank is provided in the circulation path, and the metal is taken out there, thereby suppressing an unnecessary increase in the content of the metal present in the molten state or in the deposited state in the electrolytic bath. Excessive mixing in can be suppressed.

  The term “removing a required concentration of metal” as used herein usually means that a metal that does not include an electrolytic bath (that is, a concentration of 100%) is in a molten state (melt) or a precipitated state (solid). To take out as. However, depending on the application, for example, a metal that has reached a saturation concentration or a predetermined predetermined concentration may be taken out together with the electrolytic bath, so the expression “necessary concentration of metal” is used.

  Thus, by providing the adjusting tank, it is possible to take out the molten or precipitated metal while continuing the electrolysis, although it is a batch operation.

  The method of the second embodiment is a method using a fluidized electrolytic cell as an electrolytic cell in the metal production method of the present invention. It is good also as providing an adjustment tank in a circulation path.

As the fluidized electrolytic cell, for example, an electrolytic cell proposed by the present inventors described in Patent Document 2 described above can be used. This electrolytic cell was originally developed as an electrolytic cell capable of continuously electrolyzing a large amount of, for example, molten CaCl ₂ to obtain a molten salt with an increased Ca concentration. It is also possible to take out the molten or precipitated metal by taking into consideration such as widening the gap between the electrode and the partition wall, or maintaining the temperature of the electrolytic bath at a high level so that the generated metal such as Ca is molten. It is.

  FIG. 1 is a longitudinal sectional view showing a configuration example of a main part of a fluidized electrolytic cell used when the metal production method of Embodiment 2 is carried out.

The fluidized electrolytic cell includes a cylindrical electrolytic cell container 1a that holds an electrolytic bath (for example, molten CaCl ₂ ), and a cylindrical shape that is disposed in the container 1a along the longitudinal direction of the electrolytic cell container 1a. The electrolytic bath container 1a is provided with an electrolytic bath supply port 6 at one end (bottom plate 4) in the longitudinal direction of the electrolytic cell container 1a, and at the other end (upper lid 5). Is provided with an electrolytic bath outlet 7. The anode surface and the cathode surface are opposed to each other and arranged in a substantially vertical direction, and a diaphragm 8 is provided between the anode 2 and the cathode 3 to suppress the passage of Ca generated by electrolysis. A cooler 9 is attached to the outer surface of the anode 2. In addition, in the example shown in FIG. 1, molten CaCl ₂ is supplied from below the electrolytic cell and extracted from above, but conversely, it is supplied from above the electrolytic cell 1 and extracted from below. It is also possible to do.

  In the flow type electrolytic cell, as illustrated in FIG. 1, one having a partition wall or a diaphragm for separating the cathode side electrolytic bath and the anode side electrolytic bath is generally used. In addition to the “partition or diaphragm” that has been used in the past, the “metal partition” described later and other concepts beyond the conventional “partition” and “diaphragm” may be used. Any material that is disposed between the electrolytic baths and has an effect of suppressing the migration of Ca generated by electrolysis to the anode side is included.

If the fluidized electrolytic cell shown in FIG. 1 is used, molten CaCl ₂ is supplied to one of the electrolytic baths near the cathode surface by continuously or intermittently supplying molten CaCl ₂ between the anode 2 and the cathode 3 from one end of the electrolytic cell. Directional flow rates can be applied and electrolysis can be performed while flowing the electrolytic bath in one direction near the cathode surface.

  The fluidized electrolytic cell is not limited to such a cylindrical electrolytic cell, and a flat plate electrolytic cell in which a flat anode and a cathode are arranged in parallel can be used as described later.

  In the metal production method of Embodiment 2 in which a regulating tank is provided in the circulation path and the fluidized electrolytic cell is used, the electrolytic bath in the regulating tank after taking out the metal is used as an electrolytic bath for returning from the regulating tank to the fluidized electrolytic cell. Alternatively, an electrolytic bath having a low metal concentration can be mixed and returned to the fluidized electrolytic cell. Mixing may be performed in the adjustment tank, or may be performed between the adjustment tank and the fluidized electrolytic tank. According to this method, since the electrolytic bath on the cathode side can be replenished with an electrolytic bath that does not contain a metal present in a molten state or a deposited state, electrolysis can be continued for a long time.

  Further, in the metal production method of Embodiment 2, the electrolytic bath after being introduced into the adjusting tank and taking out the metal in the electrolytic bath is returned to the cathode chamber of the fluidized electrolytic bath, and the metal concentration is higher than the electrolytic bath in the adjusting bath. A method of supplying a low electrolytic bath to the anode chamber of a fluidized electrolytic cell can also be employed. This method is desirable because it can directly replenish the electrolytic bath on the anode side.

  In the metal production method of the present invention, it is desirable to perform electrolysis while maintaining the anode chamber side pressurized against the cathode chamber side.

  The “state in which the anode chamber side is pressurized with respect to the cathode chamber side” means a state in which the liquid level of the electrolytic bath is higher on the anode side, or the pressure in the cathode chamber is equal to the pressure in the anode chamber. On the other hand, it refers to a state that is set relatively low. In the latter case, the pressure inside the anode chamber may be increased, or the pressure inside the cathode chamber may be decreased.

When electrolysis is performed in this state, movement of the electrolytic bath on the cathode side in the electrolytic cell to the anode side is suppressed, and movement of Ca generated on the cathode side is also suppressed, so that Ca reacts with chlorine generated on the anode side. Therefore, the back reaction that returns to CaCl ₂ hardly occurs, and electrolysis can be performed with high current efficiency.

  If the diaphragm or partition provided between the anode and the cathode of the fluidized electrolytic cell used in the metal production method of Embodiment 2 is a porous ceramic body, the flow of the metal generated on the cathode chamber side into the anode chamber side is effective. Can be suppressed.

As the diaphragm, for example, a porous ceramic body containing yttria (Y ₂ O ₃ ) can be used. A porous ceramic body obtained by firing yttria has a selective permeability that allows Ca and chlorine ions dissolved in an electrolytic bath (for example, molten CaCl ₂ ) to pass but does not allow metal Ca to pass therethrough. It has excellent calcium reduction resistance that is not reduced even by Ca having a reducing power, and is suitable as a diaphragm.

  If an electrolytic cell in which such a diaphragm is provided between the anode and the cathode is used, it effectively acts to suppress the inflow of metal (for example, Ca) generated on the cathode chamber side to the anode chamber side, and back reaction Therefore, electrolysis can be performed with high current efficiency.

  Instead of the diaphragm, a partition configured to allow the molten salt to flow may be used. The partition wall itself does not allow molten salts such as Ca and chlorine ions as well as metal Ca, but by providing slits or holes through which molten salt can pass in a part of the partition wall, electrolysis is possible, while metal Ca The back reaction can be suppressed by restricting the passage of the air to some extent.

  A metal net can be used as the partition wall of the fluidized electrolytic cell used in the metal production method of the second embodiment.

  The metal net is advantageous in that it is less expensive than a porous ceramic body and is not easily damaged. However, as compared with the porous ceramic body, the mesh is coarse and the metal Ca easily passes. Therefore, when using a fluidized electrolytic cell using a metal mesh partition, use a metal mesh that is as fine as possible. Consideration is necessary.

  When the electrolytic bath on the cathode side in the electrolytic cell is flowed at a high speed, the movement of the electrolytic bath from the cathode chamber side to the anode chamber side is considerably suppressed. In particular, the fluidized electrolytic cell using metal mesh partition walls Is used, it is effective to suppress the movement of the electrolytic bath by flowing the electrolytic bath at a high speed.

As a material of the metal net, it is necessary not to be dissolved in a high-temperature electrolytic bath, and in the case of molten CaCl ₂ , iron, stainless steel, titanium, or the like can be used.

In the metal production method of the present invention, the case where a metal halide is used as an electrolytic bath is defined as one embodiment. When metals such as Na, Li, Mg, and Ca, which are conventionally used, are produced by an electrolytic method (molten salt electrolysis), these metal chlorides are used to lower the melting point of the electrolytic bath and lower the viscosity. In general, binary and ternary molten salts to which KCl, CaCl ₂ , NaCl, and the like are added are used as an electrolytic bath. Adopted.

  The method of the third embodiment is a method for obtaining metal Ca by using a melt such as calcium (Ca) salt or a mixed salt containing Ca salt as an electrolytic bath in the metal production method of the present invention. If necessary, a molten salt containing metal Ca at a high concentration can be obtained.

As the Ca salt, CaCl ₂ is preferable, and a melt such as a mixed salt obtained by adding CaF ₂ , KCl or the like to this is generally used. If this is used as an electrolytic bath, metal Ca is obtained as described above. In this case, since the melting point of Ca is 839 ° C., if the electrolysis is performed while maintaining the temperature of the electrolytic bath higher than this, the metal Ca can be obtained in a molten state, and if lower than this, it can be obtained as a solid. it can.

  According to the method of the third embodiment, it is possible to continuously produce Ca that is circulated and used in the Ti production method by the above-described Ca reduction.

  The metal production apparatus of the present invention is a metal production apparatus used for producing alkali metal, alkaline earth metal or rare earth metal by electrolysis, and circulates between an electrolytic cell and an electrolytic bath on the cathode side in the electrolytic cell. It is a device having a path and means therefor.

  There is no limitation on the shape of the electrolytic cell. The cylindrical electrolytic cell shown in FIG. 1 may be used, or an electrolytic cell equipped with a flat plate electrode shown later.

  There is no limitation on the circulation route. Any path (pipe, etc.) may be used as long as the cathode-side electrolytic bath can be taken out of the electrolytic cell and returned to the electrolytic cell again. A feature of the metal production apparatus of the present invention is that this circulation path is provided.

As a means for circulating the electrolytic bath, as described above, a centrifugal pump made of a material resistant to high-temperature molten CaCl ₂ or other molten salt to be handled may be used.

  If the metal production apparatus of the present invention has an adjustment tank for adjusting the metal concentration of the electrolytic bath in the middle of the circulation path, it is possible to take out the metal and the like during the electrolysis.

  The apparatus of the fourth embodiment is a desirable form of the metal production apparatus of the present invention, and has an adjustment tank in addition to an electrolytic cell and a circulation path for circulating an electrolytic bath on the cathode side in the electrolytic cell. It is an apparatus in which a fluidized electrolytic cell is used as a tank.

  FIG. 2 is a longitudinal sectional view schematically showing a configuration example of the metal manufacturing apparatus according to the fourth embodiment. 2A shows a case where the electrolytic bath is not replenished in the cathode chamber, and FIGS. 2B and 2C show a case where the electrolytic bath is replenished in the cathode chamber. The apparatus shown in (a) is slightly different in the shape of the electrolytic bath supply port of the anode chamber, but the apparatus shown in (b) and (c) is not different in configuration.

  As shown in FIG. 2, this metal manufacturing apparatus has an electrolytic cell 10, a circulation path 13 for circulating the electrolytic bath 12 on the cathode 11 side in the electrolytic cell, and a pump 14 as a means therefor, An adjustment tank 15 is provided.

  The electrolytic cell 10 is a fluidized electrolytic cell, and is different from the cylindrical fluidized electrolytic cell shown in FIG. 1 in that the planar cathode 11 and the planar cathode 11 are arranged facing each other across the partition wall 17a. It is a tank. Note that the electrolytic cell of the apparatus shown in FIG. 2A has an opening below the partition wall 17a to ensure conductivity between both electrodes. Further, in the electrolytic cell of the apparatus shown in (b) and (c), a large number of small holes (not shown) through which the electrolytic bath can pass are provided on the entire surface of the partition wall 17b.

  The adjustment tank 15 temporarily stores a portion (metal separation portion) where a molten metal 18 (for example, metal Ca) floated and separated in a molten state is extracted by a pump 19 and an electrolytic bath 20 after the molten metal 18 is extracted. It is divided into a part (electrolytic bath storage part), and both parts are connected below. If the adjustment tank 15 having such a shape is used, even if the circulation rate of the electrolytic bath is high, the molten metal 18 can be prevented from being mixed into the electrolytic bath 20 and can be floated and separated at the metal separation portion.

In the case of using molten CaCl ₂ as an electrolytic bath in FIG. 2A, for example, chlorine 21 is generated on the anode 16 side of the electrolytic cell 10 and Ca is generated on the cathode 11 side by electrolysis. . When the electrolytic bath 12 on the cathode side is extracted in the direction indicated by the white arrow and electrolysis is continued while circulating, molten Ca is generated in the molten CaCl ₂ and floats as molten Ca in the metal separation portion of the adjustment tank 15. To be separated. Molten Ca is appropriately taken out by the pump 19, and the electrolytic bath 20 from which the molten Ca has been separated and removed is returned to the cathode 11 side of the electrolytic cell 10 via the circulation path 13 by the pump 14. In this example, an electrolytic bath is replenished on the anode 16 side.

  In the apparatus shown in FIGS. 2B and 2C, the electrolytic bath is replenished to the cathode chamber. In the apparatus shown in (b), the electrolytic bath is replenished to the electrolytic bath storage part of the adjustment tank 15. On the other hand, in the apparatus shown in (c), the circulation path 13 is directly replenished between the adjustment tank 15 and the electrolytic tank 10. On the other hand, in both apparatuses (b) and (c), the electrolytic bath is replenished on the anode side. Thus, by replenishing the electrolytic bath, it becomes possible to perform electrolysis continuously for a long time.

  As described above, the metal production method of the present invention can be easily carried out by using the apparatus of the present invention.

  FIG. 3 is a longitudinal sectional view schematically showing another configuration example of the metal manufacturing apparatus according to the fourth embodiment. The difference from the metal manufacturing apparatus shown in FIG. 2 is the shape of the adjustment tank. The adjustment tank 15 illustrated in FIG. 3 is a single tank, and a portion for extracting the molten metal 18 that has been levitated and separated by the pump 19 (metal separation unit) ) And a part (electrolytic bath storage part) for temporarily storing the electrolytic bath 20. Since it is small in size and does not require a large installation space, it is effective when the circulation rate of the electrolytic bath is not so high and there is no fear that the molten metal 18 is mixed into the electrolytic bath 20.

  Below, the electrolytic cell (fluidized electrolytic cell) which comprises the principal part of the metal manufacturing apparatus of this invention is illustrated.

  FIG. 4 is a perspective view conceptually showing a plate-type electrode used in the electrolytic cell of the metal production apparatus shown in FIGS. 2 and 3, and also shows a vertical section perpendicular to the electrode plate. FIG. 3A shows a case where the plate-like anode 16 and the cathode 11 are arranged in parallel with the partition wall 17b interposed therebetween, and FIG. 3B shows a case where the anode 16a is further provided. By providing the anode 16a, the electrolytic cell itself becomes somewhat larger, but there is an advantage that the anode surface area is large and Cl ions are easily discharged.

  FIG. 5 is a longitudinal sectional view schematically showing a configuration example of the fluidized electrolytic cell having the flat plate-type electrode shown in FIG. Both (a) and (b) are electrolytic cells having the electrode arrangement shown in FIG. 4 (b). In the electrolytic cell shown in (a), the electrolytic bath is replenished to the anode side from below. On the other hand, the electrolytic cell shown in (b) is different in that an opening is provided below the partition wall 17a and the electrolytic bath is replenished to the anode side from the lower side.

  FIG. 6 is a longitudinal cross-sectional view schematically showing another configuration example of the fluidized electrolytic cell, in which (a) is a cylindrical electrolytic cell (representing a surface including the central axis), and (b) is a flat plate type. It is an electrolytic cell which has the electrode of. The electrolytic cell shown in (a) employs a configuration in which the anode 16 is disposed at the center and the entire inner surface of the outer peripheral portion functions as the cathode 11. The cathode area is wide. The electrolytic cell shown in (b) has a configuration in which a flat cathode 11 is arranged at the center, and anodes 16 are arranged on both sides in parallel with the cathode 11.

  FIG. 7 is a longitudinal sectional view schematically showing still another configuration example of the fluidized electrolytic cell, in which (a) is a cylindrical electrolytic cell (representing a surface including the central axis), and (b) is a flat plate. An electrolytic cell having a mold type electrode. The overall configuration of the electrolytic cell shown in FIG. 7A is similar to the electrolytic cell shown in FIG. 6A, but a plurality of anodes 16 are arranged in the center. On the other hand, the electrolytic cell shown in (b) is similar in overall configuration to the electrolytic cell shown in (b) of FIG. 6, but the anode 16 a is arranged on one side of the anodes 16 arranged on both sides. Is provided.

  Each of the electrolytic cells shown in FIGS. 5 to 7 has its own characteristics. Which of them is used depends on the type of electrolytic bath, the fluidity and solubility of the metal to be produced, and the generation of gas on the anode surface. It may be determined as appropriate in consideration of ease of operation, partition performance, overall layout of the apparatus, and the like.

Next, taking as an example the case where metal Ca is produced at a production rate of 100 kg / h in a continuous electrolysis facility using molten CaCl ₂ as an electrolytic bath and using flat electrodes in which both electrodes are arranged in parallel. Verify the effect.

  The electrolysis conditions are as follows.

Cathode current density: 0.5 A / cm ²
Current efficiency: 90%
Ca concentration at the outlet of the electrolytic cell: 50% by mass or 5% by mass
Ca concentration at the electrolytic cell inlet: 1.0% by mass
Distance between diaphragm and electrode: 5 mm
The required current (I ₀ ) when producing metal Ca at 100 kg / h is about 150 kA in consideration of the current efficiency (90%) (see the following formula (i)). In the formula (i), 40 g is the atomic weight of Ca, and 96500 C (Coulomb) is the amount of electricity required to deposit (or decompose) 1 g equivalent of the substance.

  As Example-1, a case where the Ca concentration at the outlet of the electrolytic cell is 50% by mass will be examined.

In this case, the flow rate (V _out ) at the outlet of the electrolytic cell is 200 kg / h (3.33 kg / min) (see the following formula (ii)). Note that 1.0% by mass (1 kg) of Ca is melted in the molten salt.

On the other hand, the flow rate (V _in ) at the inlet of the electrolytic cell is 381.1 kg / h (see the following formula (iii)). That is, the total amount of CaCl ₂ (277.5 kg / h) that generates Ca and Cl ₂ by electrolysis and CaCl ₂ that passes through the electrolytic cell without being electrolyzed. The latter CaCl ₂ is equal to the molten CaCl ₂ amount (100 kg / h) obtained by subtracting the electrogenerated metal Ca (100 kg / h) from the outlet flow rate (200 kg / h) of the electrolytic cell. In the formula (iii), it is considered that 1.0% by mass of Ca is melted. In the formula (iii), 111 g is the molecular weight of CaCl ₂ .

  Here, as a comparative example, the case where 100 kg / h of metallic Ca is produced without continuously supplying an electrolytic bath to the continuous electrolysis equipment and circulating it will be considered. In this case, since it is necessary to regulate the Ca concentration at the outlet of the electrolytic cell, the Ca concentration is set to 50% by mass as described above.

The cathode surface area needs to be 30 m ² (required current 150 [kA] × 10 ³ ÷ cathode current density 0.5 [A / cm ² ]). Here, the shape of the plate electrode is simply 5 m × 6 m. Further, since the distance between the diaphragm and the electrode is 5 mm, the volume of the cathode chamber is 0.15 m ³ = 150 l (liter).

The amount of molten CaCl ₂ obtained by the above formula (iii) is charged into this cathode chamber at a flow rate of 381.1 kg / h (about 180 liters / h = 3 liters / min), and the flow rate obtained by the formula (ii). It is taken out at 200 kg / h (about 95 liters / h = 1.56 liters / min).

That is, in order to increase the Ca concentration at the outlet of the electrolytic cell, it is necessary to perform the electrolysis by introducing molten CaCl ₂ very slowly at a low flow rate. Considering simply taking the average at the inlet and outlet of the electrolytic cell, the average flow rate is 2.28 liters / min. Therefore, it is necessary to perform electrolysis for about 60 minutes at this flow rate. In that case, in the case of a vertical electrolytic cell, the shape of the flat plate electrode (5 m × 6 m) requires a head pressure of 5 m or more in terms of pumping capacity. However, there is no pump that can be used at low flow rates.

On the other hand, when the metal production method of the present invention is applied and metal Ca is produced at a production rate of 100 kg / h by the above-mentioned continuous electrolysis equipment, molten CaCl ₂ is circulated. There is no need to specify. It is sufficient that the Ca concentration at the outlet of the electrolytic cell is equal to or higher than the Ca saturation solubility so that the metal Ca is obtained as a melt or a solid.

The flow rate of molten CaCl ₂ at the electrolytic cell inlet is also unrelated. 100 kg / h of metallic Ca can be produced by introducing molten CaCl ₂ into the cathode chamber and performing circulation for 1 hour at 150 kA determined by the equation (i) while circulating.

Since the current density is fixed at 0.5 A / cm ² , the size of the equipment does not change and the required cathode surface area is 30 m ² . The shape of the plate electrode is 5 m × 6 m, which is the same as in the comparative example.

  A pump with a head pressure of 5 m or more is necessary, but with a margin, a pump with a head pressure of 6 m has a discharge capacity of about 20 liters / min or more. Therefore, the metal manufacturing method of the present invention uses this pump. And if the operation which circulates a bath salt at 20 liters / min and takes out metal Ca with an adjustment tank is performed, the target quantity of metal Ca can be produced.

  Furthermore, as Example-2, the case where metal Ca is produced at 100 kg / h under the same conditions as the other electrolytic conditions with the Ca concentration at the electrolytic cell outlet being 5% by mass will be similarly examined.

The required current (I ₀ ) for producing 100 kg / h of metallic Ca is about 150 kA, as described above, but the flow rate (V _out ) at the electrolytic cell outlet is 2000 kg / h (33.3 kg / min). ) And the flow rate (V _in ) at the inlet of the electrolytic cell is 2199 kg / h.

The size of the equipment remains the same, the cathode surface area is 30 m ² , and the volume of the cathode chamber is 0.15 m ³ = 150 liters. The shape of the plate electrode is 5 m × 6 m.

In the case of a comparative example in which metallic Ca is produced at 100 kg / h without circulating the electrolytic bath, molten CaCl ₂ is 2199 kg / h (about 1037 liters / h = 17.3 liters / min) in this cathode chamber. It is introduced at a flow rate and taken out at a flow rate of 2000 kg / h (about 952 liter / h = 15.9 liter / min). Since the average flow rate is 16.6 / min, electrolysis is required at this flow rate for 60 minutes.

  In that case, if it is a vertical electrolytic cell, a head pressure of 5 m or more is required in terms of pump capacity, but a pump having a head pressure of 6 m has a discharge capacity of about 20 liters / min or more, and the above-mentioned 16.6 liters. The flow rate of about / min is included in the flow rate in the region where it is difficult to adjust the flow rate of the pump. Therefore, even if the Ca concentration at the outlet of the electrolytic cell is reduced to 5% by mass, it is difficult to produce metallic Ca at a production rate of 100 kg / h without circulating the electrolytic bath in a continuous electrolysis facility using parallel plate electrodes. It is.

On the other hand, when the metal production method of the present invention is applied and metal Ca is produced at a production rate of 100 kg / h by the above-mentioned continuous electrolysis equipment, what is necessary is that the Ca concentration at the electrolytic cell outlet is equal to or higher than the Ca saturation solubility. %. Regardless of the flow rate of molten CaCl ₂ at the inlet of the electrolytic cell, molten CaCl ₂ is charged into the cathode chamber and electrolyzed at 150 kA for 1 hour while circulating, so that metallic Ca can be produced at 100 kg / h. .

When the required cathode surface area is 30 m ² and the shape of the plate electrode is 5 m × 6 m, a pump with a head pressure of 5 m or more is required, but a pump having a discharge capacity of about 20 liters / min can be used.

  When applying the metal production method of the present invention, this pump is used to circulate the bath salt at 20 liters / min and produce the target amount of Ca by performing the operation of taking out the metal Ca in the adjustment tank. it can.

As a result of the above examination, when performing electrolysis without circulating the electrolytic bath, when the target Ca concentration at the outlet of the electrolytic cell is increased, molten CaCl ₂ must be supplied to the continuous electrolysis equipment at a very small flow rate, Although it is difficult to implement because there is no pump that can handle this, if the method of the present invention is applied, the Ca concentration at the outlet of the electrolytic cell is not related (however, more than the saturated concentration), and it matches the pump with the required head pressure. It has been found that it is possible to produce metallic Ca while circulating molten CaCl ₂ at a high flow rate.

  As described above, according to the metal production method of the present invention, it is possible to produce metal continuously from Ca, alkali metals such as Na, Mg, La, alkaline earth metals, or rare earth metals. . It is possible to effectively prevent the metal generated on the cathode side from moving to the anode side and to ensure high current efficiency.

  The metal production method of the present invention is a method of performing electrolysis while circulating the electrolytic bath on the cathode side in the electrolytic cell. According to this method, Na, Ca, Mg, La, etc. produced by the electrolysis method are used. The alkali metal, alkaline earth metal or rare earth metal can be continuously produced with high current efficiency. This method can be carried out using the metal production apparatus of the present invention.

  Therefore, the metal production method and production apparatus of the present invention can be effectively used in the fields of refining and production of these metals.

It is a longitudinal cross-sectional view which shows the structural example of the principal part of the flow type electrolytic cell used when implementing the metal manufacturing method of this invention. It is a longitudinal cross-sectional view which shows the structural example of the metal manufacturing apparatus of this invention typically. It is a longitudinal cross-sectional view which shows the other structural example of the metal manufacturing apparatus of this invention typically. It is a perspective view which shows notionally the flat type electrode used with the electrolytic vessel of the metal manufacturing apparatus of this invention. It is a longitudinal cross-sectional view which shows typically the structural example of the fluidized-type electrolytic cell which has a flat electrode. It is a longitudinal cross-sectional view which shows the other structural example of a fluidized-type electrolytic cell typically. It is a longitudinal section showing still another example of composition of a fluid type electrolytic cell.

Explanation of symbols

1: Electrolyzer 1a: Electrolyzer vessel 2: Anode 3: Cathode 4: Bottom panel 5: Upper lid 6: Molten salt supply port 7: Molten salt outlet 8: Separator 9: Cooler 10: Electrolyzer 11: Cathode 12: Electrolysis Bath 13: Circulation path 14: Pump 15: Adjustment tank 16: Anode 17a, 17b: Septum 18: Molten metal 19: Pump 20: Electrolytic bath 21: Chlorine

Claims (18)

  A method for producing an alkali metal, an alkaline earth metal or a rare earth metal by an electrolytic method, wherein electrolysis is carried out while circulating a cathode-side electrolytic bath in an electrolytic cell.   The electrolytic bath on the cathode side is introduced into an adjusting tank for adjusting the metal concentration of the bath, and after removing a metal having a necessary concentration from the adjusting tank, the electrolytic bath is returned to the electrolytic tank. The metal production method according to 1.   The metal production method according to claim 1 or 2, wherein the metal in the electrolytic bath on the cathode side exceeds a saturation concentration.   As an electrolytic cell, an electrolytic bath is supplied continuously or intermittently from one end of the electrolytic cell between the anode and the cathode to give a flow rate in one direction to the electrolytic bath near the cathode surface. The metal production method according to claim 1, wherein a fluidized electrolytic cell that can be electrolyzed while flowing in a direction is used.   The metal production method according to claim 4, wherein the fluidized electrolytic cell includes a partition wall or a diaphragm that separates the cathode side electrolytic bath and the anode side electrolytic bath.   The electrolytic bath according to claim 4 or 5 is used as an electrolytic bath, and an electrolytic bath having a metal concentration lower than that of the electrolytic bath in the adjusted tank is adjusted to the electrolytic bath returned from the adjusted tank to the fluidized electrolytic tank. The metal manufacturing method according to claim 2 or 3, wherein the metal is mixed in the adjustment tank or between the adjustment tank and the fluidized electrolytic tank and returned to the fluidized electrolytic tank.   The fluidized electrolytic cell according to claim 4 or 5 is used as an electrolytic cell, and the electrolytic bath after being introduced into the adjusting tank and adjusting the metal concentration in the electrolytic bath is returned to the cathode chamber of the fluidized electrolytic cell, and after adjustment 4. The method for producing metal according to claim 2, wherein an electrolytic bath having a metal concentration lower than that of the electrolytic bath in the adjustment bath is supplied to the anode chamber of the fluidized electrolytic bath.   The metal production method according to any one of claims 1 to 7, wherein the anode chamber side is pressurized with respect to the cathode chamber side.   9. The metal production method according to claim 5, wherein the fluidized electrolytic cell uses a porous ceramic body as a diaphragm or a partition wall.   9. The metal production method according to claim 5, wherein the fluidized electrolytic cell uses a metal net as a diaphragm.   The metal production method according to any one of claims 5 to 8, wherein the fluidized electrolytic cell uses a metal net as a diaphragm, and causes the electrolytic bath to flow at a high speed.   12. The metal production method according to claim 1, wherein a metal halide is used as the electrolytic bath.   The metal production method according to any one of claims 1 to 12, wherein calcium salt or a molten salt containing calcium salt is used as an electrolytic bath to obtain metallic calcium or molten salt containing metallic calcium.   The metal production method according to claim 13, wherein the obtained metal calcium is a melt.   The metal production method according to claim 13, wherein the obtained metal calcium is a solid.   A metal production apparatus used for producing an alkali metal, an alkaline earth metal or a rare earth metal by an electrolytic method, comprising: an electrolytic cell; a circulation path for circulating an electrolytic bath on the cathode side in the electrolytic cell; A metal manufacturing apparatus comprising means.   The metal manufacturing apparatus according to claim 16, further comprising an adjustment tank for adjusting a metal concentration of the electrolytic bath in the middle of the circulation path.   The electrolytic cell has an electrolytic cell container for holding an electrolytic bath, and an anode and a cathode disposed along the longitudinal direction of the electrolytic cell container, and an electrolytic bath is provided at one end in the longitudinal direction of the electrolytic cell container. An electrolytic bath provided with a supply port so as to be able to supply an electrolytic bath between the anode and the cathode, and extracting the electrolytic bath having an increased concentration of metal generated by electrolysis of the electrolytic bath at the other end. The metal production apparatus according to claim 16 or 17, wherein the metal production apparatus is a fluidized electrolytic cell provided with an extraction port.

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