JP4658053B2 - Method and apparatus for producing metal by molten salt electrolysis - Google Patents

Description

【Technical field】
[0001]
The present invention relates to the recovery of metals from metal chlorides, and more particularly to a method and apparatus for producing metals by electrolysis of molten salts containing metal chlorides.
[Background]
[0002]
Conventionally, single metal titanium has been produced by a crawl method in which titanium tetrachloride is reduced with molten magnesium to obtain sponge titanium, and production costs have been reduced by accumulating various improvements. However, since the crawl method is a batch process that repeats a series of operations discontinuously, there is a limit to the efficiency.
[0003]
For the above situation, a method of directly producing titanium metal by reducing titanium oxide with metallic calcium in a molten salt (for example, see Patent Documents 1 and 2), an active metal such as calcium or an active metal alloy There has been proposed an EMR method (see, for example, Patent Document 3) in which a reducing agent containing is produced and a titanium compound is reduced by electrons emitted from the reducing agent to obtain metallic titanium. In these methods, calcium oxide by-produced by the electrolytic reaction is dissolved in calcium chloride, and then metal calcium is recovered and reused by performing molten salt electrolysis. However, since the calcium metal produced by the electrolytic reaction is in a liquid state, it has a high solubility in calcium chloride and easily dissolves, and there is no disclosure of a technique for recovering the solid state calcium metal in a simple manner.
[0004]
In addition, a technique for depositing metallic calcium on a cathode in a solid state by performing molten salt electrolysis at a lower temperature than conventional using a molten salt having a melting point lower than that of metallic calcium is disclosed (for example, Patent Document 4). reference). However, in this method, it is necessary to specially prepare the composite molten salt, and it is necessary to consider the cost.
[0005]
As described above, the conventional method has a problem that it is difficult to recover the active metal such as metallic calcium alone or the cost is high even if it is possible.
[Prior art documents]
[0006]
[Patent Literature]
[Patent Document 1]
WO99 / 064638 [Patent Document 2]
JP 2003-129268 A [Patent Document 3]
JP 2003-306725 A [Patent Document 4]
US3226311 Summary of the Invention
[Problems to be solved by the invention]
[0007]
The present invention has been made in view of the above situation. For example, the metal used for reducing the oxide or chloride of metal titanium can be recovered in a solid state, and it is an inexpensive method. It aims at providing the manufacturing method of the metal by molten salt electrolysis which can be implemented.
[Means for Solving the Problems]
[0008]
That is, in the method for producing a metal by molten salt electrolysis according to the present invention, an electrolytic bath equipped with an anode and a cathode is filled with a metal chloride, and the metal chloride is heated and melted to form an electrolytic bath. In a method for producing a metal by molten salt electrolysis in which a metal is deposited on the cathode in a solid state, the temperature of the electrolytic bath used for molten salt electrolysis is maintained at or above the melting point of the metal, and the temperature of the cathode is maintained below the melting point of the metal. It is characterized by that.
[0009]
According to the present invention, the metal can be deposited on the cathode in a solid state with low solubility in the molten salt and recovered. In addition, metal recovery can be performed at low cost.
[0010]
In addition, the present invention fills an electrolytic cell equipped with an anode and a cathode with metal chloride, heats and melts the metal chloride to form an electrolytic bath, electrolyzes the electrolytic bath, and deposits the metal in a solid state on the cathode. An apparatus for producing metal by molten salt electrolysis, in which an electrolytic bath is divided into an electrolytic chamber and a melting chamber by partition walls, an anode is disposed in the electrolytic chamber, and a cathode is circulated through the electrolytic chamber and the melting chamber. The metal deposited and adhered to the cathode in the electrolysis chamber is separated and collected in the melting chamber.
[0011]
According to the present invention, when the cathode passes through the electrolytic chamber, electrolysis of the metal chloride proceeds to deposit the metal on the cathode, and when the cathode passes through the melting chamber, the deposited metal can be recovered. In addition, since the cathode revolves and periodically moves back and forth between the electrolysis chamber and the melting chamber, the metal can be deposited and recovered automatically and efficiently.
[Brief description of the drawings]
[0012]
FIG. 1 is a schematic view showing a method for producing metallic calcium in an embodiment of the present invention.
FIG. 2 (a) is a schematic view showing a method for producing calcium metal in another embodiment of the present invention, and FIG. 2 (b) is a schematic view of a scraper at the cathode when (a) is viewed from the direction A. FIG.
FIG. 3 (a) is a schematic view showing a method for producing metallic calcium in another embodiment of the present invention, (b) is a schematic view of (a) seen from direction A, and (c) is a schematic view. It is the schematic diagram which looked at (a) from direction B.
BEST MODE FOR CARRYING OUT THE INVENTION
[0013]
Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an example of an apparatus configuration for carrying out the present invention. Hereinafter, a case where the electrolytic bath is calcium chloride and the generated metal is calcium metal will be described as an example.
[0014]
In FIG. 1, reference numeral 1 denotes an electrolytic cell, which is filled with an electrolytic bath 2 made of calcium chloride and is heated to a melting point of calcium chloride or more by a heating means (not shown) and kept in a molten state. . Reference numeral 3 denotes an anode, and reference numeral 4 denotes a cathode, which is immersed in the electrolytic bath 2.
[0015]
When the anode 3 and the cathode 4 are connected to a DC power source (not shown) and electrolysis of the electrolytic bath is started, chloride ions in the electrolytic bath 2 are attracted to the anode 3 to release electrons, and become chlorine gas outside the system. Released. Calcium ions are attracted to the cathode 4 to receive electrons and become metal calcium 5 and are deposited on the surface of the cathode 4.
[0016]
The temperature of the electrolytic bath 2 can efficiently carry out the present invention in any temperature range above or below the melting point (845 ° C.) of the metallic calcium 5. In particular, when the temperature of the electrolytic bath 2 is equal to or lower than the melting point of the metal calcium 5, the metal calcium 5 can be deposited in a solid state on the surface of the cathode 4. On the other hand, even when the temperature of the electrolytic bath 2 is equal to or higher than the melting point of the metal calcium 5, the solid metal calcium 5 can be deposited around the cathode 4 by incorporating the cooling structure in the cathode 4.
[0017]
Even when electrolysis is performed at any temperature, the metal calcium 5 produced by the electrolytic reaction is precipitated in a solid state, and therefore the solubility in calcium chloride in contact with the produced solid metal calcium 5 is almost negligible. Therefore, metallic calcium can be recovered with high efficiency.
[0018]
After depositing a predetermined amount of metallic calcium 5 on the cathode 4, the cathode 4 is taken out from the electrolytic bath 2, and is collected in a recovery tank 7 holding a molten salt 6 held at a temperature higher than the melting point (845 ° C.) of the metallic calcium 5. Soak. The metal calcium 5 deposited on the cathode 4 is partly dissolved in the molten salt 6 held in the recovery tank 7, and the rest melts and floats from the cathode 4 and is concentrated near the liquid surface of the recovery tank 7, This is separated and recovered. At this time, the molten salt 6 promotes the evaporation loss of the metallic calcium 5 as the temperature increases, so it is practical to keep the molten salt within 900 ° C.
[0019]
In this way, calcium can be melted and floated and recovered in a liquid state, but may be cooled below the melting point of metallic calcium within a range where the molten salt 6 does not solidify. By performing such a cooling operation, the floating metal calcium 5 becomes a solid state and can be efficiently recovered. Since the melting point of calcium chloride is around 780 ° C. and the melting point of metallic calcium is around 845 ° C., the metallic calcium 5 dissolved in the molten salt 6 is in a solid state by reducing the temperature of the recovery tank 7 to around 800 ° C. It can be recovered.
[0020]
The cathode 4 from which the precipitated metallic calcium 5 has been detached and recovered can be returned from the recovery tank 7 to the electrolytic tank 1 and again subjected to molten salt electrolysis. By repeating the above series of operations, metallic calcium can be efficiently recovered. Thus, the metal calcium 5 produced | generated in the collection tank 7 can be utilized for the calcium reduction | restoration of the titanium tetrachloride using molten salt, for example.
[0021]
It is also possible to recover the metal calcium concentration in the molten salt 6 without increasing the metal calcium in the recovery tank 7 and use it in the reduction reaction of titanium tetrachloride together with the molten salt.
[0022]
The chlorine gas 8 generated at the anode 3 of the electrolytic cell 1 can be separately collected and reused for the chlorination reaction of titanium ore. Or you may utilize for another use.
[0023]
The material of the anode 3 is preferably one that has conductivity, does not dissolve in the electrolytic bath, and does not react with chlorine gas. Such a material is preferably carbon.
[0024]
The cathode 4 may be made of a conductive material, and may be made of any material such as carbon steel, stainless steel, copper, or aluminum. It is preferable that the cathode 4 has a structure in which a cooling medium can flow therethrough. By taking such a structure, precipitation of metallic calcium on the cathode 4 can be promoted.
[0025]
Although arbitrary things can be used as the molten salt 6 in the collection tank 7, it is preferable to use calcium chloride. Since calcium chloride is also produced as a by-product in the molten salt electrolysis step of titanium chloride and metal calcium, if the molten salt 6 is used as calcium chloride, the concentrated metal calcium is used in the molten salt electrolysis step of titanium chloride. There is no need to remove calcium chloride. In addition, after the molten salt electrolysis step of titanium chloride, it can be recycled to the electrolytic cell 1 together with calcium chloride which is a by-product of this step.
[0026]
The melting point of the electrolytic bath can be lowered by adding potassium chloride to calcium chloride constituting the electrolytic bath 2. The potassium chloride added to the calcium chloride is preferably in the range of 20 wt% to 80 wt%. By adding potassium chloride in such a range, even if the temperature of the electrolytic bath 2 is lowered by 150 ° C. to 250 ° C. below the melting point of metallic calcium, stable operation can be performed without worrying about freezing of the electrolytic bath.
[0027]
The temperature of the electrolytic bath 2 can be controlled to a target temperature range by using a heating burner with a cooling function immersed in an electrolytic bath (not shown). The temperature of the electrolytic bath 2 may be controlled by other means.
[0028]
FIG. 2 represents another aspect of the present invention. The electrolytic bath 1 of FIG. 2A is filled with an electrolytic bath 2 made of calcium chloride, and is heated to a melting point of calcium chloride or more by a heating means (not shown) and kept in a molten state. Further, an anode 3 and a cylindrical cathode 4 are immersed in the electrolytic bath 2. The cathode 4 is configured to be capable of rotating, and a scraper 9 is disposed adjacent to one end of the cylindrical side surface of the cathode 4. FIG. 2B is a schematic view of the cathode 4 and the scraper 9 viewed from the direction A. As shown in the figure, when the cathode 4 rotates, the metallic calcium 5 deposited on the cathode surface can be efficiently scraped by the scraper 9.
[0029]
The solid metallic calcium 5 scraped from the cathode 4 has a lower density than calcium chloride, and therefore floats on the bath surface of the electrolytic bath 2. The metal calcium 5 floating on the bath surface of the electrolytic bath 2 is appropriately recovered from the electrolytic bath 2. The solid metallic calcium recovered from the electrolytic bath 2 can be used as a reducing agent for titanium oxide by molten salt electrolysis.
[0030]
At this time, a net-like ridge may be provided around the scraper 9. The precipitated solid metal can be efficiently recovered by pulling up the soot from the electrolytic bath at an appropriate time.
[0031]
Moreover, it is preferable to arrange the partition wall 10 in the vicinity of the bath surface of the electrolytic bath 2. The calcium metal deposited on the cathode 4 is scraped off, floats up, diffuses to the bath surface, reaches the vicinity of the anode 3, and tends to cause a reverse reaction with the chlorine gas generated at the anode 3. By providing, it is possible to prevent the levitated metal calcium 5 from diffusing and to effectively suppress the reverse reaction.
[0032]
A heater may be immersed in the vicinity of the scraper 9 so that the temperature of the electrolytic bath in the vicinity of the scraper 9 is limitedly maintained above the melting point of metallic calcium. By doing in this way, the metallic calcium scraped off from the cathode 4 can be recovered in a molten state. A part of the molten calcium metal is dissolved in calcium chloride and floats in the electrolytic bath 2. For this reason, calcium chloride enriched with metallic calcium is in a state of floating on the bath surface of the electrolytic bath 2 through the partition wall 10. Calcium chloride enriched in metallic calcium in a floating state can be extracted and used for, for example, a reduction reaction of titanium tetrachloride.
[0033]
3A to 3C show another aspect of the present invention. 3B is a schematic view of FIG. 3A viewed from the direction A, and FIG. 3C is a schematic view of FIG. 3A viewed from the direction B. The electrolytic bath 1 of FIG. 3 is filled with an electrolytic bath 2 made of calcium chloride, and is heated to a melting point or higher of calcium chloride by a heating means (not shown) and kept in a molten state. Further, an anode 3 and a cathode 4 are immersed in the electrolytic bath 2. The electrolytic cell 1 is divided into an electrolytic chamber 1a in which the anode 3 is immersed and a dissolution chamber 1b by a partition wall 10 provided in the vicinity of the bath surface of the electrolytic bath 2. However, only the vicinity of the bath surface of the upper part of the electrolytic bath 2 is divided by the partition wall 10 and is integrated in the lower part of the electrolytic bath 2. As shown in FIG.3 (c), the some cathode 4 is arrange | positioned so that it can circulate through the electrolytic chamber 1a and the melting | dissolving chamber 1b. These cathodes 4 can pass through a cutting portion provided in a part of the partition wall 10 to circulate through the electrolytic chamber and the melting chamber and revolve.
[0034]
The cathode 4 has a heating function and a cooling function. That is, a flow path through which a heater and a cooling medium can flow is provided inside the cathode 4, and the temperature of the cathode 4 can be arbitrarily controlled from the melting point of the metallic calcium 5 to the melting point or more. Yes.
[0035]
In the apparatus configuration as described above, when the cathode 4 is on the electrolysis chamber side, the temperature of the cathode 4 is maintained below the melting point of metallic calcium, and metallic calcium is deposited on the surface of the cathode 4 in a solid state. On the other hand, when the cathode 4 revolves and reaches the melting chamber side, the temperature of the cathode 4 is maintained above the melting point of metallic calcium, and the precipitated metallic calcium is brought into a molten state. A part of the metal calcium 5 melted and separated from the cathode 4 is dissolved in calcium chloride and floats in the electrolytic bath to form a metal calcium concentrated layer. The metal calcium concentrated layer formed on the dissolution chamber side bath surface of the electrolytic bath 2 is appropriately extracted and can be used as, for example, a reducing agent for titanium oxide by molten salt electrolysis.
[0036]
Thus, by controlling the temperature of the cathode 4 below the melting point and above the melting point of the metal calcium according to the position of the cathode 4 revolving inside the electrolytic bath 2, the metal calcium can be efficiently recovered.
【Example】
[0037]
[Example 1]
Using the electrolytic cell and the recovery cell shown in FIG. 1 together, molten salt electrolysis of calcium chloride was performed. The temperature of the electrolytic bath composed of calcium chloride was controlled to 800 ± 5 ° C. to deposit metallic calcium on the cathode. As a result, it was possible to recover metallic calcium corresponding to 85% of the theoretical weight calculated from the amount of current applied to the anode and the cathode.
[0038]
[Example 2]
Using the apparatus shown in FIG. 2, calcium chloride is used in an electrolytic bath, and this is melt-electrolyzed to deposit metallic calcium continuously on the cathode, which is scraped off by a scraper to obtain solid-state metallic calcium. Was recovered. The production amount of metallic calcium per unit time increased about twice as compared with Example 1.
[0039]
[Example 3]
Using the apparatus shown in FIG. 3, calcium chloride was used as an electrolytic bath, and this was melt-electrolyzed to continuously deposit metallic calcium on the cathode, and recovered as molten metallic calcium partially including the electrolytic bath. . The production amount of metallic calcium per unit time increased about twice as compared with Example 2.
[Industrial applicability]
[0040]
According to the present invention, calcium metal can be efficiently produced by electrolysis of calcium chloride.
[Explanation of symbols]
[0041]
DESCRIPTION OF SYMBOLS 1 Electrolysis tank 1a Electrolysis chamber 1b Dissolution chamber 2 Electrolytic bath 3 Anode 4 Cathode 5 Metal (calcium)
6 Molten salt 7 Recovery tank 8 Chlorine gas 9 Scraper 10 Bulkhead

Claims (6)

  An electrolytic cell equipped with an anode and a cathode is filled with metal chloride, and this metal chloride is heated and melted to form an electrolytic bath. This electrolytic bath is electrolyzed, and metal is deposited on the cathode in a solid state by molten salt electrolysis. In a metal production method, the temperature of the electrolytic bath used for the molten salt electrolysis is maintained at a temperature equal to or higher than the melting point of the metal, and the temperature of the cathode is maintained below the melting point of the metal. Metal manufacturing method.   The method for producing a metal by molten salt electrolysis according to claim 1, wherein the solid metal deposited on the cathode is scraped off by mechanical means.   2. The metal by molten salt electrolysis according to claim 1, wherein the metal is recovered by immersing the cathode on which the solid metal has been deposited in a recovery tank filled with a metal chloride that is maintained at a melting point of the metal or higher. Manufacturing method. An electrolytic cell equipped with an anode and a cathode is filled with metal chloride, and the metal chloride is heated and melted to form an electrolytic bath. The electrolytic bath is electrolyzed, and metal is deposited on the cathode in a solid state by molten salt electrolysis. A method for producing metal,
The electrolytic bath is divided into an electrolytic chamber and a melting chamber by partition walls, an anode is disposed in the electrolytic chamber, a cathode is disposed so as to be capable of revolving through the electrolytic chamber and the melting chamber, and the cathode is electrolyzed. when passing through the chamber maintains the temperature of the cathode below the melting point of the metal, the molten salt when the cathode passes through the melting chamber, characterized in that the holding temperature of the cathode above the melting point of the metal A method for producing metal by electrolysis.   5. The method for producing a metal by molten salt electrolysis according to claim 4, wherein the cathode comprises a plurality of cathodes and is disposed on a revolution orbit of the cathode.   The metal production method according to claim 1, wherein the metal chloride is calcium chloride and the metal is calcium metal.

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