JPWO2006115027A1 - Molten salt electrolytic bath and method for producing metal using the same - Google Patents

Abstract

  Provided is an electrolytic cell for extracting calcium chloride containing calcium used for reducing an oxide or a chloride of titanium, which is capable of efficiently recovering calcium chloride by molten salt electrolysis. A container in which a molten salt bath is held and a lid is provided on the upper portion, an anode and a cathode which are arranged by being immersed in a molten salt bath through the lid from above the container, and a decompression device connected to the cathode, A gas introduction nozzle for introducing gas from the outside of the container to the inside, a gas discharge nozzle for discharging gas from the inside of the container to the outside, and a molten salt supply nozzle for supplying molten salt from the outside of the container to the inside, and the cathode is hollow. The fin member is joined to the outer surface of the cathode, and the through hole is provided in the cathode just above the joining portion between the cathode and the fin member.

Description

  The present invention relates to a molten salt electrolysis cell and a method for producing a metal using the same, and more particularly to a molten salt electrolysis technique used for extracting calcium chloride containing calcium used as a reducing agent when producing titanium from a titanium compound. ..

  Titanium sponge has been conventionally manufactured by the Kroll process, and the manufacturing cost has been reduced by stacking various improvements. However, since the crawl method is a batch process, its efficiency is beginning to reach its limit.

  As a technique for pursuing the efficiency of titanium production by the Kroll method, a technique of directly producing titanium by reducing titanium oxide with calcium in a molten salt is known (see, for example, Patent Document 1). Further, as a technique similar to that of Patent Document 1, a step of storing a mixed sample of calcium chloride and calcium oxide inside a reduction container, heating the mixed sample to prepare a molten salt, and the step of electrically converting the molten salt The step of producing a strongly reducing molten salt by decomposing and generating calcium ions and electrons in molten calcium chloride, and supplying titanium oxide to the inside of the strongly reducing molten salt to convert the titanium oxide to the calcium ions and electrons. Discloses a method for refining titanium, which comprises the steps of reducing, deoxidizing and producing titanium (see, for example, Patent Document 2). The technique described in Patent Document 2 is to generate titanium by reducing titanium oxide with calcium in a molten salt, dissolve by-produced calcium oxide in calcium chloride, and electrolyze the calcium chloride in which the calcium oxide is dissolved. It produces calcium and reuses it as a reducing agent.

  Furthermore, a method for producing titanium by using a titanium compound containing titanium halide or titanium oxide as a raw material and reducing these titanium compounds, wherein the molten salt is electrolyzed in an electrolytic bath containing a molten salt of an active metal. A method for producing titanium is disclosed, in which a reducing agent composed of an active metal or an active metal alloy is decomposed to produce a reducing agent, and the titanium compound immersed in the electrolytic bath is reduced by electrons emitted from the produced reducing agent. (For example, see Patent Document 3).

  In addition, a technique of depositing calcium on the cathode in a solid state using a complex molten salt having a melting point lower than that of calcium has been disclosed (see, for example, Patent Document 4). This technique requires a step of peeling calcium deposited in the solid state from the electrode.

  In each of the techniques described in Patent Documents 1 to 4 described above, calcium is used as a reducing agent used when titanium is produced, and it is industrially required to regenerate calcium by-produced in the reduction reaction into calcium. However, since calcium generated by molten salt electrolysis dissolves in calcium chloride, it is difficult to separate calcium as a simple substance.

  In order to solve such a problem, there is disclosed a technique in which calcium carbide is added to a molten salt to effectively suppress redissolution of produced calcium in the molten salt (see, for example, Patent Document 5). .. However, this technique is not necessarily suitable for the production of high-purity titanium because the carbon in calcium carbide contaminates calcium.

  However, in the above-mentioned technology for directly producing titanium by reducing titanium oxide with calcium in molten salt, calcium does not necessarily have to be a simple substance, and even if calcium partially dissolved in calcium chloride is reduced. It can be used as an agent.

  In this way, a technique for efficiently producing calcium chloride in which calcium is mixed or in which calcium is dissolved (hereinafter, may be simply referred to as "calcium chloride containing calcium") by electrolyzing molten salt of calcium chloride. Development is desired.

WO99/064638 JP, 2003-129268, A JP, 2003-306725, A US3226311 Publication JP-A-49-70808

  The present invention has been made in view of the above circumstances, and is an electrolytic cell for extracting calcium chloride containing calcium used to reduce oxides or chlorides of titanium, which is particularly efficient by molten salt electrolysis. It is an object of the present invention to provide a molten salt electrolytic cell capable of recovering calcium chloride well.

  The inventors have conducted extensive studies on the molten salt electrolyzer in view of the above circumstances. As a result, it was found that calcium chloride can be efficiently extracted by making the cathode hollow. Also, by arranging the anode and the hollow cathode in a molten salt bath and arranging a fin member on the cathode surface, calcium chloride containing calcium generated at the cathode is affected by the difference in specific gravity between the bath flow and the surroundings. It was discovered that calcium chloride could be efficiently introduced into the hollow part, and that the calcium chloride could be more efficiently extracted and recovered through this hollow part by the pressure reducing device installed outside, and the following invention was completed. Came to do.

  That is, the first molten salt electrolytic cell of the present invention is characterized by including a container holding a molten salt bath, in which an anode and a cathode are immersed and arranged, and the cathode is hollow. A second molten salt electrolyzer of the present invention is the same as the first molten electrolyzer, in which a container with a lid holding the molten salt bath and a container from above the container penetrates through the lid and melts. An anode and a cathode immersed in a salt bath, a decompression device connected to the cathode, a gas introduction nozzle for introducing gas from the outside of the container to the inside, and a gas discharge nozzle for discharging gas from the inside of the container to the outside, A molten salt supply nozzle that supplies molten salt from the outside of the container to the inside, a fin member is provided on the outer surface of the cathode, and a through hole is provided in the cathode just above the joint with the fin member. Is preferable (second molten salt electrolytic cell).

  Further, the inventors have further made earnest studies, placing importance on the efficiency of calcium production at the cathode. As a result, by immersing all the cathodes in the molten salt bath, the calcium chloride generated at the cathodes can be efficiently extracted and recovered with the influence of the difference in specific gravity between the bath flow and the surroundings minimized. The present invention has been completed and the following inventions have been completed.

  That is, in the first molten electrolytic cell, a container with a lid holding the molten salt bath, an anode penetrating the lid from above the container and immersed in the molten salt bath, and the anode Underneath, is immersed in a molten salt bath and expands upward, a bath extraction pipe connected to the cathode and extending to the outside of the container, and a decompression connected to the bath extraction pipe outside the container. An apparatus, a gas introduction nozzle for introducing gas from the outside of the container to the inside, a gas discharge nozzle for discharging gas from the inside of the container to the outside, and a molten salt supply nozzle for supplying molten salt from the outside of the container to the inside may be provided. Desirable (third molten salt electrolyzer).

  Next, the method for producing a metal of the present invention is characterized by using the above first to third molten salt electrolyzers, and according to such a production method, molten calcium or molten magnesium can be obtained. ..

  According to the present invention, the cathode is hollow, or in addition to this, the fin member is joined to the cathode, and the through hole is provided in the cathode immediately above the joining portion, whereby calcium deposited on the cathode surface is calcium chloride. The effect of being able to efficiently collect the calcium or calcium chloride in which calcium is partly dissolved and to extract it to the outside prior to dissolving or diffusing in the entire bath. Further, according to the present invention, by disposing the entire cathode under the anode, in addition to the above effects, it is possible to avoid recombining chlorine gas generated in the anode and calcium generated in the cathode, As a result, the current efficiency can be improved.

It is a side sectional view showing a suitable molten salt electrolyzer of the present invention. It is a side sectional view showing other suitable molten salt electrolyzers of the present invention. It is a side sectional view showing other suitable molten salt electrolyzers of the present invention. FIG. 4 is a side sectional view showing a cathode obtained by improving the cathode used in the electrolytic cell shown in FIGS. 2 and 3. It is a schematic diagram of the vertical groove of the anode which is one embodiment of the present invention.

Explanation of symbols

B... Molten salt bath 10... Container 10a... Lid
11... Anode 12... Cathode 13... Pressure reducing device 14... Gas introduction nozzle 15... Gas discharge nozzle 16... Molten salt supply nozzle 17... Fin member 18... Through hole 28... Straightening plate 51... Vertical groove

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the molten salt electrolyzer of the present invention and a metal manufacturing method using the same will be described with reference to the drawings.
FIG. 1 is a side sectional view showing a preferable molten salt electrolytic cell of the present invention. As shown in the figure, this electrolytic cell is arranged so that a molten salt bath B is held and a lid 10a is provided on an upper portion of the container 10, and a lid 10a is penetrated from above the container 10 to be immersed in the molten salt bath B. In addition, the anode 11 and the cathode 12 and the decompression device 13 connected to the cathode 12 are provided. Further, the lid 10 a of the electrolytic cell has a gas introduction nozzle 14 for introducing gas from the outside of the container 10, a gas discharge nozzle 15 for discharging gas from the inside of the container 10 to the outside, and an outside of the container 10. A molten salt supply nozzle 16 for supplying molten salt is provided inside.

  In this molten salt electrolytic cell, the cathode 12 has a hollow shape, and a fin member 17 is joined to the outer surface of the cathode 12. Further, a through hole 18 is provided in the cathode 12 just above the joint between the cathode 12 and the fin member 17.

  By providing the through hole 18 in the cathode 12, the molten calcium generated on the surface of the cathode 12 can be efficiently collected in the hollow portion of the cathode 12 before being dissolved or diffused in the molten salt bath B.

  When the molten salt electrolysis cell shown in FIG. 1 is used, the anode 11 and the cathode 12 are immersed in the molten salt bath B held in the container 10, and the container 10 is sealed with the lid 10a. Next, it is preferable to introduce the inert gas into the space of the container 10 from the gas introduction nozzle 14 connected to the lid 10a, and to discharge the inert gas to the outside through the gas discharge nozzle 15 for circulation.

  By circulating the inert gas in the space of the container 10 as described above, it is possible to effectively suppress the invasion of the atmosphere into the space of the container 10 and efficiently discharge the chlorine gas generated in the anode 11 to the outside. be able to. This is because when the atmosphere enters the space of the container 10, calcium chloride forming the molten salt bath B is oxidized and the molten salt electrolytic reaction may be delayed.

  The material of the above-mentioned anode 11 is preferably made of a material such as carbon. With such a material, stable electrolytic operation can be continued without being corroded by chlorine gas generated from the surface of the cathode 11. On the other hand, it is preferable that the anode 12 in which calcium is generated is made of stainless steel or titanium material that is not easily corroded by calcium generated in the surfaces of the electrolytic bath B and the cathode 12.

  As described above, the cathode 12 used in the electrolytic cell shown in FIG. 1 has a hollow interior, and the fin member 17 may be disposed and joined to the surface of the portion of the cathode 12 to be immersed in the molten salt. preferable. Further, it is preferable that the fin member 17 is arranged in a state where the fin member 17 is expanded upward and a through hole 18 that communicates with the inside of the fin member 17 is provided at a joint portion of the fin member 17 to the cathode 12. The expansion angle of the fins forming the fin member 17 is preferably selected from the range of 30° to 45°.

  The number of fin members 17 is practically about 2 to 5 for the electrolytic cell shown in FIG. 1 according to the present invention. Further, it is preferable that the size of the through holes 18 that are formed at equal intervals on the surface of the cathode 12 is set within a range of 10 to 30% of the inner diameter of the cathode 12. By forming the through holes 18 having such a size, calcium chloride containing calcium generated on the surface of the cathode 12 can be efficiently extracted to the outside.

  The inventors tried various experiments in the process of completing the molten salt electrolytic cell shown in FIG. As a result, when molten salt electrolysis was performed by immersing the cathode and the anode, which do not have fin members joined to the outer surface, in a calcium chloride bath, the molten salt bath of calcium (hereinafter, simply “metal fog”) was formed around the cathode. It may be referred to as “.”) was diffused throughout the molten salt bath B in a short time.

  This metal mist tends to diffuse throughout the bath in a short time due to the influence of the convection of the bath due to the generation of chlorine gas at the anode and the difference in specific gravity from the surroundings. However, it has been confirmed that at the beginning of the formation of calcium on the surface of the cathode 12, a part of the calcium described above tends to settle in the molten salt bath B and accumulate at the bottom of the container 10. Therefore, in the present invention, it is preferable not only to join the fin member 17 to the cathode 12 in a state where the fin member 17 is widened upward, but also to arrange the fin member 17 as close to the lower end as possible. By arranging in this way, calcium generated on the entire surface of the cathode 12 immersed in the molten salt bath B can be efficiently recovered.

  The calcium generated on the surface of the cathode 12 passes through the through hole 18 formed on the surface of the cathode 12 along the fin member 17 arranged in the upper opening due to the difference in specific gravity from the surroundings, and enters the hollow portion of the cathode 12. Guided efficiently. In this way, by efficiently guiding the calcium generated on the surface of the cathode 12 to the hollow portion, it is possible to suppress the contact reaction between the calcium generated at the cathode 12 and the chlorine gas generated at the anode 11. As a result, it is possible to effectively prevent a decrease in current efficiency.

  The calcium chloride containing calcium introduced into the hollow portion of the cathode 12 can be relatively easily extracted to the outside by engaging the other end of the cathode 12 with the decompression device 13. The calcium generated on the surface of the cathode 12 is dissolved in the molten salt bath B, guided to the hollow portion of the cathode 12 through the through hole 18 provided on the surface of the cathode 12, and sucked upward by the decompression device 13. Then, it can be discharged to a tank (not shown) provided in the middle of the decompression pipe.

  When the above operation is performed, the level of the molten salt bath B is lowered according to the amount of the molten salt bath B discharged from the container 10, but a new amount of the corresponding molten calcium chloride was installed in the lid 10a. By supplying the molten salt from the nozzle 16 into the container 10, the level of the molten salt bath B can be kept constant. By adopting such an operation form, it becomes possible to continuously operate calcium chloride.

  A new calcium chloride bath may be used as the calcium chloride to be supplied to the container 10. However, the calcium chloride containing calcium oxide by-produced by the calcium reduction of titanium oxide described in the prior art is chlorinated to chlorinate the entire amount. You may use what changed into calcium.

  Calcium chloride containing calcium extracted through the hollow portion of the cathode 12 can be used as a reducing agent used in the direct reduction of titanium from titanium oxide as cited in the prior art. At this time, even if a portion of the calcium dissolved in the calcium chloride is deposited by cooling the calcium chloride containing calcium extracted through the hollow portion of the cathode 12 to near the melting point of calcium. Good.

  The temperature of the molten salt bath B is preferably maintained above the melting point of calcium chloride. Further, it is preferable to maintain this temperature within a range not exceeding 100° C. higher than the melting point of calcium. This is because if the temperature of the molten salt bath B becomes higher than the melting point of calcium by more than 100° C., the evaporation of the molten salt bath B is promoted and the yield is lowered, which is not preferable.

  Further, by adding potassium chloride to calcium chloride forming the molten salt bath B, the melting point of the molten salt bath B can be lowered. By lowering the melting point of the molten salt bath B in this way, it is possible to give the electrolytic operation temperature a degree of freedom. The potassium chloride added to calcium chloride is preferably in the range of 18 wt% to 67 wt %. By adding potassium chloride in such a range, the melting point of the molten salt bath B can be lowered to 600° C. to 760° C., and the operating temperature of the molten salt bath B can be stably lowered. As a result, the amount of produced calcium dissolved in calcium chloride can be suppressed.

  FIG. 2 is a side sectional view showing another preferable molten salt electrolytic cell of the present invention. As shown in the figure, this electrolytic cell is arranged so that the molten salt bath B is held and the lid 20a is provided on the upper portion of the container 20, and the lid 20a is penetrated from above the container 20 to be immersed in the molten salt bath B. An anode 21, a cathode 22 that is disposed below the anode 21 in the molten salt bath B and expands upward, and a bath withdrawal pipe 23 that is connected to the cathode 22 and extends to the outside of the container 20. A decompression device 24 connected to the bath withdrawing pipe 23 is provided outside the container 20. Further, in the lid 20 a of the electrolytic cell, a gas introduction nozzle 25 for introducing gas from the outside of the container 20 to the inside, a gas discharge nozzle 26 for discharging gas from the inside of the container 20 to the outside, and the outside of the container 20. A molten salt supply nozzle 27 for supplying a molten salt is provided inside.

  As described above, among the components of the electrolytic cell shown in FIG. 2, the container 20, the anode 21, the gas introduction nozzle 25, the gas discharge nozzle 26, and the molten salt supply nozzle 27 are the same as those of the electrolytic cell shown in FIG. It is the same as the component. On the other hand, of the components of the electrolytic cell shown in FIG. 2, the cathode 22 which is completely immersed in the molten salt bath B and the bath withdrawing pipe 23 arranged between the cathode 22 and the decompression device 24 are This is a structural difference from the electrolytic cell shown in FIG.

  As shown in FIG. 2, by completely immersing the cathode 22 in the molten salt bath B and further arranging it below the anode 21, chlorine gas generated on the surface of the anode 21 and calcium generated on the surface of the cathode 22 are formed. Immediately after the production of calcium, contact with can be effectively suppressed. For this reason, most of the generated calcium can be guided to the bath withdrawing pipe 23 with the influence of the surrounding specific gravity being minimized, so that the molten salt bath B can be efficiently withdrawn to the outside via the withdrawing pipe 23. be able to.

  Further, the cathode 22 does not need to be arranged with high precision on the downward extension of the anode 21 as shown in FIG. 2, and the centers of the anode 21 and the cathode 22 may be displaced from each other. Further, in the embodiment shown in FIG. 2, the cathode 22 is expanded upward, and the expansion angle can be selected in the range of 30 to 45° upward with respect to the horizontal plane. The expanded cathode 22 has the same effect as that of the fin member 17, which is a component in the electrolytic cell shown in FIG. 1, that is, the influence of the difference in specific gravity from the surroundings is minimized. And functions to efficiently extract the generated calcium to the outside.

  The back surface of the cathode 22 (the surface of the cathode 22 not facing the anode 21 in FIG. 2) and the surface of the bath withdrawal tube 23 should be coated with a highly insulating ceramic such as silica or alumina by means of thermal spraying or the like. Is preferred. By performing such an insulation treatment, not only the site where calcium is generated can be limited to the inner surface of the cathode 22, but also the inner surface of the bath extraction tube 23 can be efficiently used as a calcium deposition surface. ..

  It is preferable that the end of the bath withdrawal tube 23 opposite to the cathode 22 is engaged with the decompression device 24, and that end together with the decompression device 24 is engaged with a tank (not shown). With such a device configuration, calcium can be extracted to the outside more efficiently. Further, as shown in FIG. 2, the bath withdrawing pipe 23 is not limited to the arrangement in which the molten salt bath B is sucked upward to penetrate the lid 20a and extend to the outside of the container 20 or the bottom of the container 20 or It is also possible to provide a through hole in the side portion so as to extend through the bottom portion or the side portion to the outside. With such an arrangement, it is possible to effectively suppress contact between chlorine gas generated at the anode 21 and calcium generated at the cathode 22.

  FIG. 3 is a side sectional view showing another preferable molten salt electrolytic cell of the present invention. Since the electrolytic cell shown in the figure is an improved example of the electrolytic cell shown in FIG. 2, description of the same components as the electrolytic cell shown in FIG. 2 will be omitted. The electrolytic cell shown in FIG. 3 differs from the electrolytic cell shown in FIG. 2 in that a rectifying plate 28 extending from the inner wall of the container 20 between the anode 21 and the cathode 22 is provided.

  As shown in FIG. 3, the current plate 28 is preferably arranged so as to be inclined upward with respect to the horizontal plane. The inclination of the straightening vane 28 with respect to the horizontal plane is preferably selected in the range of 10° to 45°. By selecting such a range, the upward flow of the molten salt bath B generated near the cathode 22 can be efficiently suppressed.

  Further, it is preferable that a bent portion facing downward is provided at the tip of the current plate 28. By providing such a bent portion, the rising flow of the molten salt bath B containing calcium can be directed toward the central portion of the cathode 22.

  When chlorine gas is generated on the surface of the anode 21, the chlorine gas rises in the molten salt bath B. Therefore, in the molten salt bath B below the anode 21, a bath flow from the lower side to the upper side in FIG. 3 is generated, and chlorine gas generated at the anode 21 and calcium generated at the surface of the cathode 22 come into contact with each other so that both flow. This is because there is a risk of re-reaction.

  On the other hand, in the case where the flow straightening plate 28 is provided as shown in FIG. 3, when the bath flow containing a part of calcium generated in the cathode 22 reaches the flow straightening plate 28, the bath flow moves toward the center of the container 20. The diversions and the flows from the respective directions influence each other to form a downward bath flow indicated by an arrow in FIG. As a result, the molten salt bath B containing calcium is guided toward the center of the cathode 22 and can be efficiently withdrawn from the system via the bath withdrawing pipe 23.

  FIG. 4 is a side sectional view showing a cathode 30 obtained by improving the cathode 22 used in the electrolytic cell shown in FIGS. 2 and 3. The cathode 30 has two upwardly expanding portions 31 and 32, and a through hole 33 is provided between the expanding portions 31 and 32. By adopting such a structure of the cathode 30, compared with the case of the cathode in which the fin member (corresponding to reference numeral 17 in FIG. 1) and the through hole (corresponding to reference numeral 18 in FIG. 1) shown in FIG. 3 is formed. It is possible to bring out the effect of recovering calcium. As a result, the productivity of calcium can be further improved as compared with the electrolytic cells shown in FIGS.

  In the electrolytic cells of FIGS. 1 to 3 shown above, graphite is preferably used for the anodes 11 and 21 from the viewpoint of corrosion resistance because chlorine gas is generated. Further, in the example shown in FIG. 1, the lower end of the anode 11 is preferably processed into a hemispherical shape or a tapered pencil shape. By processing the lower end portions of the anodes 11 and 21 in such a shape, it is possible to suppress the growth of bubbles due to the retention of chlorine gas, and as a result, between the anodes 11 and 21 and the cathode 12. The convection of the molten salt bath B can be minimized. Further, as shown in FIG. 5, vertical grooves 51 are preferably formed in the longitudinal direction at the lower ends of the anodes 11 and 21. By providing such a vertical groove, the rise of chlorine gas generated on the surfaces of the anodes 11 and 21 can be promoted more smoothly.

  The number of vertical grooves 51 provided at the lower ends of the anodes 11 and 21 is preferably arranged at intervals of 4 to 10 equal parts in the circumferential direction of the anodes 11 and 21. The width and depth of the groove are preferably selected from the range of 5% to 20% of the diameter of the anodes 11 and 21. For example, when the diameter of the anode 12 is 15 mm, it is preferable to select the width and depth of the vertical groove from the range of 1 mm to 3 mm. By selecting the width and depth of such vertical grooves, it is possible to set the diameter larger than the bubble diameter of chlorine gas generated on the surfaces of the anodes 11 and 21, and as a result, the tips of the anodes 11 and 21 are generated. The effect that the rising behavior of chlorine gas can be smoothly advanced is exhibited.

  The fin member 17 shown in FIG. 1 and the cathodes 22 and 30 shown in FIGS. 2 to 4 can be made of carbon steel or stainless steel because the generated calcium exhibits a reducing property. However, since chlorine gas generated at the anodes 11 and 21 exists in the space portions of the containers 10 and 20, ceramics or the like which can withstand chlorine gas are formed on the surfaces of the cathode 12 of FIG. Is preferably coated.

  The calcium produced by the present invention can be used in the step of directly producing titanium by calcium reduction of titanium oxide using a molten salt. When manufacturing high-purity titanium, it is preferable to use carbon steel having a low nickel or chromium content for the cathodes 12, 22, and 30 shown in FIGS. This is because the above metal has a strong tendency to dissolve in calcium or a molten salt bath, and as a result, there is a risk of contaminating the metal titanium produced by the above-described calcium reduction of titanium oxide.

  The present invention can also be applied to the case where the molten salt bath B is changed to calcium chloride and the molten salt electrolysis of magnesium chloride is performed. In this case as well, molten magnesium is produced at the cathode, but unlike the case of calcium chloride described above, magnesium has almost no solubility in magnesium chloride. Therefore, the magnesium simple substance can be recovered by allowing the magnesium with the magnesium chloride extracted from the bath withdrawing pipe 23 to stand and separate outside the system. As a result, there is an effect that the reduction reaction of titanium tetrachloride can be efficiently advanced.

  As described above, by using the molten salt electrolyzer according to the present invention, calcium chloride containing calcium can be efficiently extracted to the outside, and as a result, high current efficiency can be achieved.

Hereinafter, the present invention will be described in detail with reference to examples.
Using the electrolytic cell shown in FIG. 1, an electrolytic test of calcium chloride was carried out under the following conditions.
1) Molten salt bath
Molten salt: anhydrous calcium chloride
Weight: 1kg
2) Anode Material: Graphite Dimensions: Diameter 15 (mm) x Length 600 (mm)
3) Cathode Material: Stainless steel
Dimensions: Inner diameter 6 (mm) x Outer diameter 9 (mm) x Length 600 (mm)
Fin member: conical, three-stage arrangement
Through hole: Immediately above each connection point of the conical fin member to the cathode
6 through holes of 3 mmφ are formed in the cathode 4) Container material: transparent quartz Dimensions: diameter 70 (mm) x length 500 (mm)
5) Extraction tube Material: Transparent quartz
Dimensions: Diameter 6 x Length 200 (mm)
6) Heating furnace output: 1kW (rated)
Heater: Nichrome wire

  Anhydrous calcium chloride is supplied to the container 10 shown in FIG. 1, the anode 11 and the cathode 12 are immersed and placed in the anhydrous calcium chloride, and then the entire container 10 is sealed with a lid 10a, and a gas introduction nozzle connected to the lid 10a. While supplying a small amount of argon gas from 14, while exhausting from the gas discharge nozzle 15 connected to the lid 10a, the space above the supplied anhydrous calcium chloride is maintained in a slightly pressurized state so as to surround the container 10. A heater (not shown) arranged was energized to heat and heat the anhydrous calcium chloride to maintain the temperature at 800°C ± 5°C.

Then, a direct current voltage was applied between the anode 11 and the cathode 12 to start the electrolysis of anhydrous calcium chloride. The applied voltage was adjusted so that the current density at the cathode 12 was 0.2 A/cm ^{2 to} 0.5 A/cm ² . The chlorine gas by-produced by the electrolytic reaction was discharged to the outside from the gas discharge nozzle 15 connected to the lid 10a.

  After the start of energization, coloring due to the formation of calcium was confirmed near the surface of the cathode 12, so the decompression device 13 was operated and the calcium chloride in which calcium was dissolved was extracted from the lower end of the cathode 12 to the outside. During this time, the inside of the container 10 was visually inspected, but the calcium generated at the cathode 12 did not diffuse to the anode 11. In addition, the generated calcium did not stay at the bottom of the cathode 12.

  The above test was carried out 7 times in total, and after the test was completed, the amount of calcium in the calcium chloride extracted from the container 10 was analyzed, and the current efficiency was calculated based on the amount of electricity passed. It was confirmed that the current efficiency achieved by the present invention is at a high level as shown in Table 1.

  In Example 1, molten salt electrolysis of calcium chloride was performed under the same conditions as in Example 1 except that the cathode 12 was changed to the cathode 22 which was expanded as shown in FIG. 2, and the current efficiency was calculated. As a result, high current efficiency as shown in Table 2 could be achieved.

    In Example 2, molten salt electrolysis of calcium chloride was performed under the same conditions as in Example 2 except that the outer surface was changed to the cathode 12 sprayed with silica, and the current efficiency was calculated. As a result, high current efficiency as shown in Table 3 could be achieved.

  As described above, according to the present invention, the cathode is made hollow, or in addition to this, the fin member is joined to the cathode, and the through hole is provided immediately above it, so that chloride containing calcium deposited on the cathode surface can be formed. Calcium can be efficiently extracted to the outside. Therefore, the present invention is particularly promising in that it can be applied to extraction of calcium chloride containing calcium, which is a reducing agent used in producing titanium from a titanium compound.

Claims (15)

  A molten salt electrolytic cell comprising a container holding a molten salt bath, wherein an anode and a cathode are immersed in the bath and the cathode is hollow.   A container with a lid holding the molten salt bath, an anode and a cathode penetrating the lid from above the container and immersed in the molten salt bath, a decompression device connected to the cathode, and a container outside A gas introduction nozzle for introducing gas into the inside of the container, a gas discharge nozzle for discharging gas from the inside of the container to the outside, and a molten salt supply nozzle for supplying molten salt from the outside of the container to the inside, and a fin on the outer surface of the cathode. The molten salt electrolyzer according to claim 1, wherein a member is provided, and a through hole is provided in the cathode immediately above a joint portion with the fin member.   The molten salt electrolytic cell according to claim 2, wherein an end of the cathode on the side immersed in the molten salt bath is closed, and an end on the side not immersed in the molten salt bath is engaged with a decompression device.   A container with a lid that holds the molten salt bath, an anode that penetrates the lid from above the container and is immersed in the molten salt bath, and is immersed in a molten salt bath below the anode, and , An upwardly expanded cathode, a bath withdrawing pipe connected to the cathode and extending to the outside of the container, a decompression device connected with the bath withdrawing pipe outside the container, and introducing gas into the interior from the outside of the container The molten salt electrolysis according to claim 1, further comprising a gas introduction nozzle, a gas discharge nozzle for discharging gas from the inside of the container to the outside, and a molten salt supply nozzle for supplying molten salt from the outside of the container to the inside. Tank.   The molten salt electrolytic cell according to claim 4, wherein an insulating layer is provided on a surface of the cathode not facing the anode and an outer surface of the bath withdrawal tube.   The molten salt electrolytic cell according to claim 4 or 5, wherein a rectifying plate extending obliquely upward from a horizontal surface from the inner wall of the container toward the cathode and the anode is arranged.   The molten salt electrolyzer according to any one of claims 4 to 6, wherein the bath withdrawal pipe penetrates the lid of the container and extends to the outside of the container.   The molten salt electrolytic cell according to any one of claims 4 to 6, wherein the bath withdrawing pipe extends through the bottom or side of the container to the outside of the container.   The molten salt electrolytic cell according to any one of claims 1 to 8, wherein the anode is made of graphite and the cathode is made of carbon steel or stainless steel.   The molten salt electrolytic cell according to claim 9, wherein a vertical groove having a width larger than a bubble diameter of chlorine gas generated at the anode is formed on the surface of the anode.   The molten salt electrolytic cell according to any one of claims 1 to 10, wherein the molten salt is composed of calcium chloride, magnesium chloride, or a mixture of calcium chloride and potassium chloride.   A method for producing a metal, comprising using the molten electrolytic bath according to claim 1.   A method for producing a metal, comprising using the molten electrolytic bath according to claim 2.   A method for producing a metal, comprising using the molten electrolytic bath according to claim 4.   The method for producing a metal according to claim 11, wherein the metal is molten calcium or molten magnesium.

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