JP4261328B2 - Molten metal chloride electrolyzer - Google Patents

Description

  The present invention relates to an electrolysis apparatus for molten metal chloride that is a high-temperature melt, and more particularly, to an electrolysis technique that suppresses a decrease in current efficiency.

  In the manufacturing technology of sponge titanium by the crawl method, molten magnesium is used as a reducing agent for titanium tetrachloride. The molten magnesium chloride by-produced by this reduction reaction is regenerated into magnesium and chlorine gas by molten salt electrolysis (hereinafter sometimes simply referred to as “electrolysis”).

  Therefore, when reducing titanium tetrachloride, it is necessary to frequently handle molten magnesium and molten magnesium chloride. However, molten magnesium easily reacts with oxygen gas and nitrogen gas in the atmosphere. Therefore, when handling these, care must be taken to avoid contact with the atmosphere.

  However, for example, when molten magnesium is pumped from the electrolytic cell to the transport container, or when molten magnesium is injected from the transport container into the reduction container, the molten magnesium may come into contact with the atmosphere to generate oxides and nitrides. is there. The generation of these oxides and the like (hereinafter sometimes simply referred to as “electrode stack”) causes a decrease in the yield of titanium.

  Moreover, when the electrolyzer is left standing, the generated electropile sinks to the bottom by gravity. However, when the electrolysis apparatus is operated, the raw material must be supplied into the bath of the electrolytic cell. For example, the bath is locally turbulent by the raw material at this time. For this reason, a part of the electric stack is wound up along the bath flow, reaches the electrolytic chamber, and may adhere to the carbon anode to inhibit generation of chlorine gas. In addition, the deposit that has reached the electrolysis chamber promotes the reverse reaction of the molten magnesium produced on the anode surface, which may lead to a decrease in current efficiency. For this reason, development of the technique which suppresses the production | generation of an electric pile or the technique which suppresses the fall of electric current efficiency even when the electric pile is produced | generated was requested | required.

  In response to such a request, a technique for discharging an electric pile from the bottom of the electrolytic cell to the outside of the system has been proposed (see Patent Documents 1 to 3). In addition, a technique has been proposed in which titanium tetrachloride gas is blown into an electrode stack accumulated at the bottom of the electrolytic cell to dissolve and extinguish the electrode stack (see Patent Document 4).

JP 50-001014 A JP 57-063687 A JP-A-63-219595 JP-A-60-187893

  In the techniques described in Patent Documents 1 to 4, the amount of the electric stack can be reduced. However, the electrolysis apparatus is usually provided with a heat exchanger in the molten salt bath, and when the heat exchanger is extracted from the electrolysis tank, the deposit or heat deposited on the lid of the dismantled electrolysis tank is removed. The deposit attached to the exchanger itself falls into the electrolytic bath. Since such a deposit is a relatively large lump, the dropped litter settles to the bottom of the electrolytic cell, and sometimes this lump accumulates the circulation path of the bath. In addition, accumulation of deposits that have settled down to the bottom of the electrolytic cell will result in pushing up the bottom of the electrolytic cell upward, and the fine deposits floating in the electrolytic bath will follow the bath flow. There is a risk of reaching the electrolytic chamber. For this reason, it is difficult to completely prevent the above-described problems with the anode and the cathode, and the reduction in current efficiency cannot be suppressed at a high level. Accordingly, there has been a demand for the development of an electrolyzer that can further suppress a decrease in current efficiency.

  This invention is made | formed in view of the said situation, and it aims at providing the electrolytic device of the molten metal chloride which can suppress the fall of the current efficiency by an electric stack at a high level.

  The inventors of the present invention diligently studied to solve the above-described problems. As a result, the plurality of branch pipes constituting the heat exchanger are parallel to the branch pipes at the top, the bottom, and at least one of them. By providing an impurity collecting member, the sedimentation of the deposit to the bottom of the electrolytic cell can be prevented, thereby preventing the accumulation of the deposit in the bath flow, and the decrease in current efficiency can be suppressed. And gained knowledge. The present invention has been made based on the above findings.

In other words, the molten metal chloride electrolysis apparatus of the present invention comprises an electrolytic cell and a partition wall suspended from the upper part of the electrolytic cell, wherein the product metal storage chambers are formed on both sides of the partition wall. An electrolytic chamber is formed on the opposite side of the two partition walls, a gas discharge nozzle is provided on the electrolytic chamber side above the electrolytic cell, a cathode and an anode are provided on the electrolytic chamber, and a lid is provided on the storage chamber side above the electrolytic cell. And two pipes extending from the outside through the lid to the storage chamber side in the electrolytic cell in the vertical direction and a plurality of branches extending in the horizontal direction from one of the two pipes to the other A range including a heat exchanger having a pipe and being sandwiched between the two pipes at the upper, lower, and at least one of the branch pipes in parallel with the branch pipe this provided the impurity collecting member so as to extend within It is characterized in.

  In such a molten metal chloride electrolysis apparatus, it is preferable to provide a plurality of through holes in the impurity collecting member in that particularly excellent current efficiency can be obtained. Moreover, such an apparatus can be used suitably when producing | generating magnesium from the molten salt bath containing magnesium chloride, sodium chloride, and calcium chloride.

  According to the molten metal chloride electrolysis apparatus of the present invention, impurities are trapped in parallel to the branch pipes at the upper, lower, and at least one of the branch pipes constituting the heat exchanger. Providing a collecting member, that is, adopting a technique that prevents the accumulation of the deposits into the bath flow without sinking the deposits at the bottom of the electrolytic cell, to suppress the decrease in current efficiency at a high level it can. Moreover, by providing a plurality of through-holes in the impurity collecting member, it is possible to appropriately flow down the electrolytic bath and to prevent sedimentation of the electrode stack, thereby further suppressing a decrease in current efficiency.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a front view showing a molten metal chloride electrolysis apparatus of the present invention, which has first and second partition walls. In the figure, reference numeral 1 is a magnesium chloride electrolytic cell, and 2 is a molten magnesium chloride container disposed in the upper part of the electrolytic cell 1. As shown in the figure, the electrolytic cell 1 includes an iron outer plate 3, a heat insulating brick layer 4, and a refractory brick layer 5, and a first partition wall 6 and a second partition wall 7 from an upper wall portion made of the heat insulating brick layer 4. It has a structure that hangs down. The interior of the electrolytic cell 1 is partitioned by a first partition wall 6 into a molten metal storage chamber 8 and an electrolytic chamber 9 connected to the storage chamber 8.

  The electrolytic bath 1 is filled with a high-temperature melt containing molten magnesium chloride up to an electrolytic bath level 10 in FIG. In addition, a lid 11 is disposed on the upper side of the electrolytic cell 1 on the storage chamber side of the electrolytic cell 1, and extends vertically from the outside to the storage chamber side in the electrolytic cell 1 through the lid 11. A heat exchanger 12 is disposed. The heat exchanger 12 is immersed in the electrolytic bath, and is used for adjusting the temperature of the electrolytic bath by passing cooling air or combustion gas therethrough. Furthermore, an iron cathode 13 and a graphite anode 14 are respectively inserted and arranged in the electrolysis chamber 9 from the outside.

FIG. 2 is a side view of the molten metal chloride electrolysis apparatus shown in FIG. 1 and shows only the electrolytic cell 1, the lid 11, and the heat exchanger 12 shown in FIG. 1 for convenience of explanation.
As described above, the lid 11 is disposed in the upper part of the electrolytic cell 1, and the heat exchanger 12 passes through the lid 11 from the outside and extends into the electrolytic cell 1 in the vertical direction 12 a. , 12b and three branch pipes 12c to 12e extending in the horizontal direction from the conduit 12a to the conduit 12b. Under such a configuration, the impurity collecting members 12f and 12g are provided with a plurality of through holes in the vertical direction between the branch pipe 12a and the branch pipe 12b and between the branch pipe 12b and the branch pipe 12c. Are arranged respectively.

Below, the case where the apparatus of the structure mentioned above is used is demonstrated. In addition, the example shown below is a case where a to-be-electrolyzed metal is molten magnesium and an electrolytic bath is comprised from molten magnesium chloride, sodium chloride, and calcium chloride.
As shown in FIG. 1, molten magnesium chloride produced as a by-product in the titanium sponge manufacturing process is injected into the electrolytic cell 1 from the container 2 through the supply / discharge port 15 of the electrolytic cell 1, and has an annular shape with arrows in FIG. Join the path.

  In this manner, the molten magnesium chloride injected from the container 2 contains an electric pile that is an impurity. As shown in FIG. 1, since the electric stack 16 has a specific gravity greater than that of molten magnesium chloride, it deposits and deposits on the impurity collecting members 12 f and 12 g of the heat exchanger 12.

  Thus, the molten magnesium chloride from which the electropile 16 is naturally separated by gravity changes the course along the circulation flow path of FIG. 1, passes under the first partition 6 and passes from the storage chamber 8 to the electrolysis chamber 9. To reach. In the electrolysis chamber 9, molten magnesium chloride is electrolyzed on the graphite anode 14 and separated into molten magnesium and chlorine gas.

  Next, the electrolyzed molten magnesium further changes its course along the annular path of FIG. 1, passes through the hole 6 a of the first partition 6, passes below the second partition 7, and enters the storage chamber 8. To reach. On the other hand, chlorine gas is discharged from the opening 17 to the outside. Finally, the molten magnesium that has reached the storage chamber 8 is taken out from the supply / discharge port 14. When molten magnesium passes below the second partition wall 7, the electrolytic bath (for example, sodium chloride and calcium chloride) that has not been electrolyzed settles down because of its higher specific gravity than molten magnesium, and circulates again. The electrolysis chamber 9 is reached along the flow.

The above is a series of flows until molten magnesium chloride is injected into the electrolytic cell 1 and the molten magnesium obtained by electrolysis is taken out. Hereinafter, the impurity collecting members 12f and 12g which are characteristic features of the present invention are described below. The effect of the will be described in more detail.
Below, the other effect of the impurity collection members 12f and 12g is described.

  Since it is necessary to maintain the heat exchanger 12 after a predetermined use time has elapsed, in addition to removing the lid 11 in FIG. 1, the heat exchanger 12 must also be taken out. At this time, when the lid 11 is moved upward in the figure, there is a possibility that the deposit attached to the back side of the lid 11 falls. Moreover, when moving the heat exchanger 12 upward and taking it out, there is a possibility that the deposit attached to the heat exchanger 12 may fall. However, since these electric piles are also collected by the impurity collecting members 12f and 12g of the heat exchanger 12, settling to the bottom of the electrolytic cell can be prevented.

  The size and number of through holes provided in the impurity collecting members 12f and 12g can be selected as appropriate. However, when the heat exchanger 12 is pulled up, the heat exchanger 12 above the impurity collecting members 12f and 12g. It is preferable that the electrode stack attached to each part of the battery can be prevented from falling, and the electrolytic bath can flow down appropriately. In addition, the impurity collecting members 12f and 12g can be arranged in a space surrounded by the conduits 12a and 12b and the branch pipes 12c to 12e constituting the heat exchanger 12, or the heat exchanger 12 It can also be arranged below.

  Further, the widths of the impurity collecting members 12f and 12g extending in the horizontal direction (the left-right direction in FIG. 1 and the direction perpendicular to the paper surface) are arranged to exceed the widths of the respective members 12a to 12e of the heat exchanger 12. You can also. However, when the width is excessively increased, the gap between the heat exchanger 12 and the electrolytic cell 1 is narrowed, which may hinder the flow in the electrolytic bath. For this reason, it is necessary to select the widths of the impurity collecting members 12f and 12g as appropriate so as not to cause such a problem. By adopting the structure of the heat exchanger 12 as described above, it is possible to effectively remove the deposits attached to the back side of the lid 11 located above the heat exchanger 12 and the deposits attached to the heat exchanger 12 itself. Can be collected. In addition, when the impurity collection member is arrange | positioned in the several places of an up-down direction, the said collection effect can be improved further.

(Experimental example 1)
Using the apparatus shown in FIG. 1, the impurity collecting members 12f and 12g were disposed, and molten magnesium electrolysis of molten magnesium chloride was performed for 24 months. As a result, almost no decrease in the current efficiency generated immediately after the injection of molten magnesium chloride was observed, and the current efficiency throughout the operation period was 80%.

(Experimental example 2)
The same device as in Experimental Example 1 was used. However, the impurity collecting members 12f and 12g were not provided, and molten salt electrolysis of molten magnesium chloride was performed for 24 months. As a result, a decrease in current efficiency generated immediately after injection of molten magnesium chloride was observed, and the current efficiency throughout the operation period was 75%.

  As described above, according to the present invention, it is possible to prevent the current efficiency from being lowered by adopting the technology for preventing the accumulation of the deposits into the bath flow without sinking the deposits at the bottom of the electrolytic cell. it can. Therefore, the molten metal chloride electrolysis apparatus of the present invention can be used for molten salt electrolysis typified by molten salt electrolysis of molten magnesium chloride by-produced in the production of sponge titanium by the crawl method.

It is a front view which shows the electrolytic device of the molten metal chloride of this invention. It is a side view which shows the electrolysis apparatus of the molten metal chloride shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrolytic cell 2 ... Container 3 ... Iron outer plate 4 ... Heat insulation brick layer 5 ... Fireproof brick layer 6 ... 1st partition 6a ... Hole 7 ... 2nd partition 8 ... Storage chamber 9 ... Electrolytic chamber 10 ... Electrolytic bath level 11 ... Lid 12 ... Heat exchangers 12a, 12b ... Conduit 12c, 12d, 12e ... Branch pipes 12f, 12g ... Impurity collecting member 13 ... Iron cathode 14 ... Graphite anode 15 ... Supply / discharge port 16 ... Electrode 17 ... Opening

Claims (3)

An electrolytic cell and a partition wall hanging from the upper part of the electrolytic cell are provided, and a storage chamber and an electrolytic chamber for the generated metal are formed on both sides of the partition wall, and a gas discharge nozzle is provided on the electrolytic chamber side above the electrolytic cell, The electrolysis chamber includes a cathode and an anode, and further includes a lid on the storage chamber upper side of the electrolysis cell, and extends from the outside to the storage chamber side in the electrolysis cell through the lid in the vertical direction. A molten metal chloride electrolysis apparatus comprising a heat exchanger having a plurality of branch pipes extending horizontally from one of the two pipes to the other of the two pipes,
Impurity trapping is performed so as to extend in a range sandwiched between the two pipes in parallel with the branch pipe at least at one of the top, bottom, and between the plurality of branch pipes. An apparatus for electrolyzing molten metal chloride, comprising a collecting member.   The molten metal chloride electrolysis apparatus according to claim 1, wherein the impurity collecting member is provided with a plurality of through holes.   3. The molten metal chloride electrolysis apparatus according to claim 1, wherein magnesium is produced from a molten salt bath containing magnesium chloride, sodium chloride and calcium chloride.

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