JPWO2008102520A1 - Metal production apparatus by molten salt electrolysis and metal production method using the same - Google Patents

Abstract

An apparatus for producing a metal by molten salt electrolysis and a method for producing a metal using the same, particularly a metal producing apparatus and a production method capable of efficiently producing and recovering a metal having solubility in an electrolytic bath. In a method for producing a metal by molten salt electrolysis performed by filling an electrolytic bath in an electrolytic bath and immersing and arranging an anode and a cathode, a metal is deposited in a solid state on the cathode configured to allow a refrigerant to flow inside, and the cathode A method for producing a metal, characterized in that a solid metal is melted in an electrolytic bath by cutting off electricity to the electrolysis bath, and the melted metal is immediately extracted outside the electrolytic cell.

Description

  The present invention relates to a metal production apparatus using molten salt electrolysis and a metal production method using the same, and more particularly, to an efficient production technique of a metal having solubility in an electrolytic bath.

  As for titanium metal, demand for civilian use has increased significantly in recent years as well as in the aircraft industry, and expectation for supply of sponge titanium as a raw material has also increased.

  The sponge titanium is industrially produced by a so-called crawl method in which titanium tetrachloride is reduced with a reducing metal such as magnesium. However, since the crawl method is based on a batch operation that repeats a series of steps discontinuously, there is a limit in improving productivity. In addition, although efforts are being made to improve costs, significant cost improvements are difficult.

  With respect to these points, a technique for producing titanium metal by continuously reducing titanium oxide or titanium tetrachloride with molten calcium in molten salt has been attracting attention and studied (for example, see Patent Documents 1 and 2). ). These methods are methods for producing titanium metal by reducing with calcium metal using titanium oxide or titanium tetrachloride as a raw material. In these methods, calcium chloride produced as a by-product in the reduction reaction is subjected to molten salt electrolysis to obtain metallic calcium for recycling.

  Since the metallic calcium has a certain degree of solubility in molten calcium chloride, it is difficult to efficiently recover metallic calcium with high purity by molten salt electrolysis. Since the reaction proceeds without any problem even when the calcium chloride electrolytic bath is mixed somewhat, it is disclosed in the above-mentioned patent document that metallic calcium can be recovered and used in a state where calcium chloride remains.

  However, considering the reduction efficiency and material handling, it is desirable that the metallic calcium produced by molten salt electrolysis can be recovered as simple as possible.

  In this regard, in a molten salt electrolysis apparatus for calcium chloride as shown in FIG. 3, after depositing solid metallic calcium 8 on the cathode 3 cooled below the melting point of metallic calcium, then in another container 11. Although the method of melting and recovering the solid metallic calcium by heating after transferring is considered, it is necessary to prepare another device for recovery in addition to the electrolytic cell, and the equipment becomes complicated as a whole process, and the improvement It was sought after.

  Thus, a technique for efficiently producing high purity metallic calcium by molten salt electrolysis of calcium chloride is desired.

JP-T-2002-517613 JP 2005-133195 A

  An object of the present invention is to provide a method for producing a metal by molten salt electrolysis, and in particular, to provide a method for producing a metal capable of efficiently producing and recovering a metal having solubility in an electrolytic bath.

  In the apparatus and method for producing a metal by molten salt electrolysis, in view of such circumstances, in the apparatus and method for producing a metal, the cathode in which a cathode in which a flow path capable of circulating a refrigerant is formed is immersed in an electrolytic bath. Then, the solid metal deposited on the cathode is melted in the electrolytic bath by cutting off the current to the cathode, and the molten metal is continuously electrolyzed. It has been found that the metal can be efficiently recovered by extracting it to the outside, and the present invention has been completed.

  That is, the present invention relates to a method for producing a metal by a molten salt electrolysis apparatus in which an electrolytic bath is filled with an electrolytic bath and an anode and a cathode are immersed, and a solid is formed on the cathode in which a flow path capable of circulating a refrigerant is formed. After the metal is deposited in a state, the molten metal is continuously melted in the electrolytic bath by cutting off the current to the cathode, and the melted metal is continuously extracted outside the electrolytic cell. is there.

  The present invention is characterized in that the surface temperature of the cathode is not less than the melting point of the electrolytic bath and not more than the melting point of the deposited metal, and the temperature of the electrolytic bath is not less than the melting point of the deposited metal.

  The invention of the present application is characterized in that a cathode partition wall and an anode partition wall are immersed and disposed around the cathode and the anode.

  Furthermore, this invention arrange | positions several electrodes in an electrolytic bath (henceforth "multipolar electrolytic cell" may be called), and by combining the cycle of electricity supply and stop about each of several electrodes, While the energization of one electrode is stopped and the molten metal is extracted, the other electrode is energized to continue the molten salt electrolysis and continuously extract the molten metal from the multipolar electrolytic cell. .

  By producing the metal by the molten salt electrolysis method according to the present invention described above, the apparatus is simpler than the prior art, and the metal can be produced efficiently, and as a result, high current efficiency can be achieved. Is.

It is a schematic cross section which shows the molten salt electrolysis and metal collection | recovery process in embodiment of this invention. It is a top view in other embodiments of the present invention. It is a schematic cross section which shows the conventional recovery process of molten salt electrolysis and a metal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolysis tank 2 Electrolytic bath 3 Cathode 4 Anode 5 Cathode partition 6 Anode partition 7 Refrigerant 8 Solid metal 9 Extraction pipe 10 Molten metal 11 Heating vessel

  The best embodiment of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 show a preferred apparatus configuration example for carrying out the present invention, and a preferred embodiment of the present invention will be described below with reference to FIG.

  FIG. 1 shows an apparatus outline of a molten salt electrolysis apparatus M used in the present invention. The left side of FIG. 1 is a schematic diagram during electrolysis of the molten salt electrolysis apparatus M. The molten salt electrolysis apparatus M includes an electrolytic cell 1, and the electrolytic cell 1 is filled with an electrolytic bath 2, heated to a melting point or higher by a heating unit (not shown), and held in a molten state. Moreover, this electrolytic bath 2 makes it a preferable aspect to be hold | maintained at the temperature higher than melting | fusing point of the metal to precipitate.

  In addition, a cathode 3 and an anode 4 are immersed in the electrolytic bath 2, and a cathode partition 5 and an anode partition 6 are immersed around the cathode 3 and the anode 4, respectively. The lower part of these partition walls is in an open state, and the electrolytic bath 2 can flow therethrough. Here, the inside of the cathode 3 in FIG. 1 is depicted as a perspective view, and the inside of the cathode 3 has a structure in which a refrigerant 7 for temperature control of the cathode itself can flow. The cathode 3 is cooled by the refrigerant 7 to keep the temperature of the cathode surface below the melting point of the metal, and the metal can be efficiently deposited in a solid state.

  When a predetermined voltage is applied between the cathode 3 and the anode 4 using this device to conduct electricity and molten salt electrolysis is started, the cathode 3 is kept at a temperature lower than the melting point of the deposited metal. Thus, it can be deposited as solid metal 8. Next, when the flow of the refrigerant 7 in the cathode 3 is stopped after the molten salt electrolysis is terminated by cutting off the current between the cathode 3 and the anode 4, the electrolytic bath 2 is maintained at a temperature higher than the melting point of the deposited metal. 1 As shown on the right, the molten metal 10 can float on the electrolytic bath surface. The molten metal 10 can be extracted out of the system by using an extraction tube 9.

  When the metal to be deposited by molten salt electrolysis is calcium metal and the electrolytic bath is calcium chloride, the metal deposited on the cathode 3 is melted in the electrolytic bath and immediately extracted outside the electrolytic cell 1. It is preferable.

  After the metallic calcium deposited on the cathode 3 in this way is melted in the electrolytic bath 2, it is immediately taken out of the system, thereby effectively dissolving and diffusing the metallic calcium in the calcium chloride constituting the electrolytic bath. There is an effect that it can be suppressed.

  The right side of FIG. 1 is a schematic diagram of a process of extracting the metal melted and generated in the electrolytic bath 2 after the molten salt electrolysis. In the figure, reference numeral 9 denotes a molten metal extraction pipe, which is provided for recovering the generated molten metal.

  The electrolytic bath 2 used in the present invention preferably uses a metal chloride deposited on the cathode 3. When the metal is calcium metal, calcium chloride or a composite salt containing calcium chloride is used for the electrolytic bath 2. Is preferred. When the composite salt composed of calcium chloride and potassium chloride is used as an electrolytic bath, the decomposition voltage of potassium chloride is in a high voltage range with respect to calcium chloride, so the voltage applied to the electrode when practicing the present invention is It is preferable that the decomposition voltage is not less than the decomposition voltage of calcium chloride and not more than the decomposition voltage of potassium chloride.

  In the present invention, the surface temperature of the cathode 3 immersed in the electrolytic bath 2 is set to be equal to or higher than the melting point of the electrolytic bath 2 and equal to or lower than the melting point of the deposited metal. It is preferable to set it above the melting point. For example, when the metal is calcium, the surface temperature of the cathode 3 is preferably not higher than the melting point (845 ° C.) of metallic calcium, and the temperature of the electrolytic bath 2 is preferably maintained not lower than the melting point (845 ° C.) of metallic calcium. By taking such a temperature setting, the molten salt electrolysis is interrupted in the middle, so that the metallic calcium once deposited in the solid state on the cathode 3 can be melted into the electrolytic bath 2, and the molten metallic calcium in the molten state. Can be efficiently extracted out of the system.

  The composite salt used in the present invention is preferably a composite salt obtained by adding potassium chloride to calcium chloride. By appropriately blending the potassium chloride with calcium chloride, the melting point of the electrolytic bath 2 can be lowered as compared with a calcium chloride single bath. In this invention, it is preferable to add the said potassium chloride only in the range of 5-75 mol% with respect to calcium chloride.

  As a result, the control range of the cathode temperature is widened, the operation is facilitated, and the operation temperature of the cathode can be set in a lower temperature range than the conventional one, so that the metallic calcium can be efficiently deposited on the cathode 3. It is. Further, by using a composite salt composed of calcium chloride and potassium chloride as the electrolytic bath 2, the solubility of metallic calcium in the electrolytic bath 2 can be reduced, and as a result, the metallic calcium can be efficiently recovered. It plays.

  For example, solid metallic calcium can be deposited on the cathode 3 by setting the temperature of the electrolytic bath 2 to 870 ° C. and the surface temperature of the cathode 3 to 750 ° C. The temperature of the cathode 3 is preferably as large as the temperature difference from the melting point of the calcium metal, and the temperature of the cathode 3 can be increased by using a composite salt having a lower melting point as compared with the case of calcium chloride alone as described above. There is an effect that can be reduced.

  In the present invention, it is preferable to deposit a certain amount of solid metallic calcium on the cathode 3 and then insert the molten metal calcium extraction tube 9 into the electrolytic bath 2 between the cathode 3 and the cathode partition wall 5. The other end of the extraction tube 9 is preferably engaged with a decompression device (not shown) so that the molten metal in which the tip end of the extraction tube 9 is immersed can be extracted.

  Next, the calcium metal deposited on the cathode 3 can be melted in the electrolytic bath 2 by cutting off the current supply to the cathode 3 and the anode 4. Along with this, metallic calcium melted in the electrolytic bath 2 can be extracted out of the system by the extraction tube 9. At this time, by stopping the flow of the refrigerant 7 circulated inside the cathode 3, there is an effect that the solid metal 8 deposited on the cathode 3 can be suitably dissolved.

  Since molten metal calcium has a specific gravity smaller than that of the electrolytic bath 2 and tends to float on the surface of the electrolytic bath 2, it is preferable to dispose a cathode partition 5 around the cathode 3. By disposing the partition walls 5 described above, diffusion of molten metal calcium 10 melted from the cathode 3 can be effectively suppressed.

  Note that a part of the electrolytic bath 2 may be mixed into the molten metal calcium 10 extracted from the extraction tube 9, but the reduction reaction is used when used as a reducing agent for titanium tetrachloride or titanium oxide in a later step. It is not an obstacle.

  However, it is preferable that the electrolytic bath 2 to be mixed in is as small as possible. For this purpose, the immersion depth of the extraction tube 9 immersed in the electrolytic bath 2 is shallower than the depth predicted from the amount of metallic calcium deposited on the cathode 3. It is preferable to immerse and arrange. With such an arrangement, it is possible to efficiently extract high-purity metallic calcium melted in the electrolytic bath.

  FIG. 2 shows another preferred embodiment according to the present invention. In the present embodiment, the multi-electrode molten salt electrolysis apparatus P is configured by arranging one anode 4 and ten cathodes 3 surrounding the anode 4 inside the electrolytic cell 1. Here, FIG. 2 is a plan view of the electrolytic cell 1 as viewed downward from the bath surface toward the bottom surface.

  The anode 4 and the plurality of cathodes 3 are preferably connected in parallel. By taking such an electrical connection form, it is possible to easily set the electrolysis period and the electrolysis rest period of each cathode. The above electrolysis period means the time when metallic calcium is deposited and grown in the solid state on the surface of the cathode 3 as described above, and the electrolysis rest period is the disconnection between the cathode 3 and the power source to perform molten salt electrolysis. This represents a step of stopping, melting the solid metal calcium 8 deposited and grown on the cathode 3 in the electrolytic bath, and simultaneously extracting the metal calcium from the electrolytic cell 1 through the extraction tube 9 and transferring it to the reduction step.

  By combining the cycle of the electrolysis period and the rest period of each cathode 3 described above, it is possible to continuously produce metallic calcium from the multipolar molten salt electrolysis apparatus P. The manufactured calcium metal can be efficiently used as a direct reducing agent for titanium oxide or a reducing agent for titanium tetrachloride.

  The calcium chloride by-produced in the reduction step can be recycled to metallic calcium as a reducing agent by returning it to the electrolytic cell 1 as shown in FIG. In addition, the chlorine gas produced | generated by the anode 4 can be used for the chlorination reaction of a titanium oxide, and can manufacture the titanium tetrachloride which is a raw material of a titanium reduction reaction.

  Next, the preferable apparatus aspect of the molten salt electrolysis apparatus used for this invention is described. The cathode 3 on which the metal calcium 8 is deposited is preferably composed of a conductive metal, and is preferably composed of stainless steel or titanium metal. By configuring the cathode 3 with the above-described material, high-purity metallic calcium can be deposited.

  The cathode 3 is preferably configured so that the cooling medium 7 can flow therethrough. By taking such a configuration, the surface temperature of the cathode 3 can be efficiently maintained below or above the melting point of metallic calcium.

  That is, when depositing metal on the cathode 3, the refrigerant 7 is circulated inside the cathode 3 to keep the surface temperature of the cathode 3 below the melting point of metallic calcium, and the solid metal 5 deposited on the cathode 3 is electrolyzed. In the case of dissolving in 2, the surface temperature of the cathode 3 can be kept above the melting point of metallic calcium by stopping the flow of the refrigerant 7 to the cathode 3. As the refrigerant flowing to the cathode 3, air or inert gas is preferable.

  On the other hand, the anode 4 is preferably made of carbon or graphite that can withstand high-temperature chlorine gas since chlorine gas is generated. By comprising with such a material, there exists an effect that chlorine gas can be collect | recovered effectively, maintaining the damage of the anode 4 low.

  The cathode partition 5 and the anode partition 6 disposed around the cathode 3 and the anode 4 are preferably made of ceramic, and in the present invention, it is more preferably made of silicon nitride. The silicon nitride has corrosion resistance against not only metallic calcium and calcium chloride but also chlorine gas, and is suitable as a device constituent material used in the present invention.

  The electrolytic cell 1 may be made of a material that can withstand high-temperature calcium chloride or potassium chloride, and stainless steel or titanium metal can be suitably used.

  The extraction tube 9 of the electrolytic bath 2 may be made of a corrosion-resistant metal material such as stainless steel that can be easily replaced when worn out.

  By following the present invention described above, molten metal calcium can be produced effectively. As a result, by using the metal calcium, titanium tetrachloride or titanium oxide can be efficiently reduced to produce metal titanium.

1. Apparatus configuration 1) Reaction vessel Size: inner diameter 150 mm × total length 500 mm
Material: Titanium Shape: Bottomed cylindrical container 2) Cathode Size: Outer diameter 10 mm x Length 60 mm
Material: Stainless steel (SUS304)
Shape: Column Refrigerant: Air (kept at 300 ° C)
Surface temperature: 750 ° C
3) Anode Size: outer diameter 15mm x length 60mm
Material: Carbon Shape: Cylinder 4) Cathode partition Size: Inner diameter 80 mm x Thickness 5 mm x Length 200 mm
Material: Silicon nitride Shape: Cylinder 5) Anode partition Size: Inner diameter 30 mm x Thickness 3.5 mm x Length 1000 mm
Material: Silicon nitride Shape: Cylindrical

2. Electrolytic bath 1) Composition: calcium chloride: potassium chloride = 85: 15 (mol%)
2) Electrolysis temperature: 870 ° C
3) Melting point: 713 ° C

[Example 1]
After depositing metallic calcium on the cathode 3 using the electrolysis apparatus shown in FIG. 1, the current between the cathode 3 and the anode 4 is cut off, and the metallic calcium deposited on the cathode 3 is placed in the electrolytic bath 2. The molten metallic calcium 10 was extracted out of the system while being melted. The metallic calcium contained 5% by weight electrolytic bath. However, the ratio of the recovered metal calcium amount to the metal calcium calculated from the energization amount was 85%, indicating high current efficiency. During this time, the electric power necessary for dissolving the metallic calcium deposited on the cathode was 6.4 KWH per 1 kg metallic calcium.

[Example 2]
Molten metal calcium was produced by molten salt electrolysis of calcium chloride using a multipolar electrolytic cell in which 10 cathodes were arranged in parallel to one anode 4 shown in FIG. In FIG. 2, the left half of the electrolytic cell is energized to perform molten salt electrolysis, and the right half of the electrolytic cell is turned off and the solid metallic calcium deposited on the cathode is melted and extracted from the electrolytic cell. Feeded to the reduction process.

  As a result, it was apparent that the molten metal calcium could be continuously supplied to the Ti reduction step from the electrolytic cell shown in FIG. Moreover, compared with the case where 10 molten salt electrolyzers were comprised individually, the initial investment could be suppressed to 90%.

[Comparative Example 1]
As shown in FIG. 3, the solid metallic calcium deposited on the cathode 3 was once extracted out of the system and then transferred into the heating container 11 to obtain molten metallic calcium. At this time, 52.7 KWH of dissolution power was required per 1 kg of calcium metal, which was unnecessary in Example 1.

  By producing metallic calcium according to the present invention from the above examples and comparative examples, the apparatus is simpler than the conventional method, and the melting energy of metallic calcium deposited on the cathode can be reduced by about 88%. This is an effect.

Claims (11)

  An electrolytic device for metal production, the electrolytic device comprising: an electrolytic cell; an electrolytic bath filled with the electrolytic cell; an anode and a cathode placed immersed in the electrolytic bath; and a partition wall disposed between both electrodes; An electrolysis apparatus for metal production, comprising a generated metal extraction tube, wherein a flow path through which a refrigerant can flow is formed inside the cathode.   2. The electrolytic apparatus for metal production according to claim 1, further comprising an anode partition and a cathode partition surrounding each of the anode and the cathode.   The electrolytic apparatus for metal production according to claim 1, wherein a plurality of cathodes are arranged so as to surround the anode.   It is a metal manufacturing method using the electrolytic device for metal manufacture in any one of Claims 1-3, Comprising: Depositing a metal in the solid state on the said cathode, and cutting off the electricity to the said cathode, The said solid A method for producing a metal, wherein the molten metal is continuously extracted outside the electrolytic cell while melting the metal in the electrolytic bath.   5. The metal production according to claim 4, wherein the surface temperature of the cathode is not lower than the melting point of the electrolytic bath and not higher than the melting point of the deposited metal, and further the temperature of the electrolytic bath is not lower than the melting point of the metal. Method.   The method for producing a metal according to claim 4, wherein an electrolytic bath is contained in the molten metal extracted outside the electrolytic cell.   The metal manufacturing method according to claim 4, wherein a partition wall is immersed around the cathode.   By holding a plurality of electrodes in the electrolytic bath (hereinafter, sometimes referred to as a “multi-electrode electrolytic cell”), each of the plurality of electrodes has a difference in the energization and stop cycles. The current supply is stopped and the molten metal is extracted while the other electrode is energized to continue the molten salt electrolysis, and continuously extract the molten metal from the multipolar electrolytic cell. The manufacturing method of the metal in any one of 4-7.   The method for producing a metal according to claim 4, wherein the molten metal extracted out of the system is used as a reducing agent for titanium tetrachloride or titanium oxide. The method for producing a metal according to any one of claims 4 to 9, wherein the molten salt is a composite salt composed of calcium chloride and potassium chloride. The method for producing a metal according to any one of claims 4 to 9, wherein the metal is calcium metal.

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