US1951836A - Process and apparatus for the production of magnesium by electrolysis - Google Patents

Description

March 20, 1934. v QBIEDOFF 1,951,836

PROCESS AND APPARATUS FOR THE PRODUCTION OF MAGNESIUM BY ELECTROLYSIS Filed Feb. 15, 1932 Patented Mar. 20, 1934 UNITED STATES PATENT OFFICE rnocsss AND APPARATUS ron run PRO- DUCTIGN 0F TROLYSIS MAGNESIUM BY ELEG- Vladimir Obiedoif, Paris, France, assignor to Soclete de Produits Chimiquea des Terrcs Bares,

Paris, France Application February 15, 1932, Serial No. 593,188

Germany February 19, 1931 9 Claims.

- such that the metal is enabled to collect in a compact homogeneous liquid mass, and when the magnesium is allowed to accumulate for several hours instead of being removed from the vat as fast as it is formed. This lengthy accumulation aids the collecting of the metal into globules and also the elimination of impurities due to the bath, such as the chlorides forming the electrolyte itself and the traces of oxides and other solid materials carried in suspension in the electrolyte, which canthus be separated from the metal.

For this purpose, when proceeding according to the invention, a suitable space or chamberis formed in which the magnesium will collect, this chamber being given the greatest possible depth which will not unduly raise the voltage of the vat, by means of a relatively deep immersion of the vertical partitions which form the sides of the said chamber in which the magnesium collects, and in the lower extremity of which the cathode is situated. The chamber thus formed serves for the accumulation of a rather large quantity of magnesium, this, quantity having a relatively considerable thickness, for instance 10 centimeters, and the depth to which the said partitions may descend is limited only as stated above, by the electrical design of the vat. The metal will thus collect in the chamber so provided, sufliciently removed from the chlorine to be protected from its action, and free from all disturbances whiclymay take place in the anode chamber, and the metal may remain polarized in this chamber, if desired. The magnesium may be removed for instance twice a day, as this gives the metal a sufliclent time to collect and for the impurities tosettle out.

The invention has further for its object a particular method for the removal of the magnesium which is formed, due to the fact that the apparatus now contains a certain quantity .of-

magnesium in the form of a thick layer. According to this method, the magnesium is drawn oil by a conduit or tube, leading from the mass of magnesium.

For this purpose, the electrolytic vat comprises a discharge conduit provided with means for closing the same, controlled from the exterior, said conduit being located in a region which is sufficiently hot to prevent all obstruction by solidiflcation of the magnesium in the conduit. This method of removal by direct outflow has the advantage of affording a marked saving of labor.

The following description, together with the accompanying drawing, given by way of example, shows a particular embodiment of the invention.

Figure 1 is a vertical section along the line 1-1 of Figure 2, of an electrolytic vat according to the invention.

Figure 2 is a corresponding section along the line II-II of Figure 1.

It is to be observed that in the said vat, thepartitions which (in plan view) bound the space in which the magnesium accumulates, descend into the bath to a considerable depth, and thus the magnesium accumulates in the form of a layer 2 of relatively great thickness, for instance 10 centimeters. The cathode 3 issituated at the bottom of the vat, and hence the partitions 1 can be lowered to the proper point without reducing the efliciency of the apparatus, as the region of electrolysis is thus maintained at the lower part of the bath. I

The magnesium deposited on the cathode collects in small spherical particles which slide upwards along the sides of the cathode and collect in a compact mass in the cathodic space or chamber.

This accumulation in a thick layer also permits drawing of! of the metal by direct outflow, siphon discharge or the like, by means of a suitably placed conduit, which has hitherto been found impracticable, the metal being removed from the vat in the hitherto known processes as soon as possible after its formation, and thus only existing in the vat in the state of separate globules, or at the most, in a thin continuous layer which cannot be drawn oil? by a fixed conduit without bringing with it a considerable portion of the electrolyte. Q In the construction here represented, the metal is evacuated by gravity by means of a tube conduit leading from the mass of metal and so arranged that the temperature therein shall be sumcient to avoid all serious obstruction owing to solidification of the metal.-

. In the example shown the conduit 4 is a metallic conduit which is placed against the cathode and-ends at 5 in the upper portion of the accumulated layer of magnesium. As it is in contact with the cathode, the said conduit has the same polarity as the latter, and it may further participate in the cooling oi. the cathode if this In the particular case shown in Figure 2, the discharge conduit or tube extends along the cathode 3 for its whole lower length, and until it emerges out of the vat, and thus, as the said conduit has the same polarity as the cathode, it is certain that the metal deposited on the conduit will collect with the rest of the metal in the cathodic space or chamber.

In this form of construction, the said conduit is stopped at the outlet of the furnace by a plug 6 of refractory material. The plug might be situated at the other end of the conduit, means being provided for controlling it from the exterior.

Obviously, instead of a single tube 5, it is feasible to employ a plurality of such tubes, suitably distributed in the cathodic chamber. Or again the discharge might be so arranged as to take place at the upper level of the mass of magnesium, in which case it would not be necessary to employ a special tube.

The intake 5 of the said conduit should be situated as high as possible in the layer 2 of magnesium, as in the first place the impurities are greater in amount in the lower portion of the layer, and in the second place, when the metal is run oif, owing to the hydrostatic effect produced by the flow of the electrolyte around the partitions the upper level 0-4) will vary but little, while the lower level rises from c-d to c'd'.

I claim:

1. Process for the production of magnesium by the electrolysis of magnesium chloride, which consists in maintaining the resulting magnesium free from all agitation, and in allowing it to accumulate in a refractory walled chamber which constitutes no part of the electric circuit, in the form of a homogeneous mass having a substantial depth, whereby the impurities in the magnesium will be separated from'this latter.

2. Process for the production of magnesium by the electrolysis of chloride, which consists in maintaining the resulting magnesium free from all agitation, and in allowing it to accumulate in a refractory walled chamber which constitutes no part of the electric circuit, in the form of a homogeneous mass constituting the product of at least several hours, whereby the impurities in the magnesium will be separated from this latter.

3. Electrolytic vat for the electrolysis of molten MgCla, said vat containing a cathode and an anode, and a cathodic chamber wherein magnesium liberated at the cathode can accumulate, said cathodic chamber being made of refractory material and forming no part of the electric circult of said cell, the entire cathode being posi-' tioned within the plan of the interior of such chamber and below the bottom thereof, said chamber being bounded by partitions of refractory material extending down into the electrolyte to a depth suflicient to ensure that-the metal is able to accumulate in a layer of sufficient thick ness to permit of the depodtion of impurities.

4. Electrolytic vat according to claim 3, characterlzed by the fact that the cathode is situated in the lower portion of the vat, in such a manner that the top of the cathode is situated at a lower levelthan the bottom of the partitions forming the cathodic chamber, all ofhe cathode area being beneath the plan of said cathodic chamber.

5. Electrolytic vat according to claim 3, in which the partitions bounding said cathodic chamberextenddownintothebathtoasomewhat greater depth than said anode, whereby the gas given off at the anode is all given off at a height above the bottom of said cathodic chamber, and at a higher level than the zone of communication of the part of the bath in the anodic magnesium chamber and the part of the bath in the cathodic chamber.

6. Improvement in processes for the production of magnesium according to claim 1, characterized by the fact that the magnesium formed by the electrolysis is drawn off from. the cell in a liquid state by means of a conduit having its upper orifice in the homogeneous layer of molten magnesium, and near the upper level of this molten layer.

7. In the production of metallic magnesium, the herein described steps which comprises maintaining a bath of molten magnesium chloride in an electrolytic cell, maintaining inter-communicating portions in such bath, which communicate with each other only below the level of the bottom of an inner compartment of said cell, all of the cathode surface being positioned below the interior of said compartment, the anodes being positioned outside said compartment and wholly away from the bottom thereof, whereby gases liberated at said anodes cannot flow toward the bottom of said compartment nor toward the zones of communication between the anode compartment and said inner compartment, allowing a considerable depth of metallic magnesium to accumulate in said inner compartment, and allowing sufllcient time of quiescent storage of said in said irmer compartment for particles of magnesium chloride to settle out of the upper portion of said body of molten magnesium, and finally withdrawing molten magnesium from well above the bottom of. said body of metallicmagnesium.

8. In an apparatus for the electrolysis of magnesium chloride, an electrolytic cell having anodes which enter the same at the top, a cathode entering the bottom of the cell from below, an interior compartment defined by walls of refractory material, closed at the top, and open at the bottom, covering the entire cathode surface in the cell, such interior compartment being of considerable depth, to allow the molten magnesium to rise into said interior compartment, said interior compartment communicating with the compartment containing the anode only at its bottom, whereby the molten material in said interior compartment is not materially agitated by gas evolved at the anode, and entry of any of such gas into said interior compartment is prevented.

9. In an apparatus for the electrolysis of magnesium chloride, an electrolytic cell having anodes which enter thesame at the top, a cathode entering the bottom of the cell from below, an

interior compartment defined by walls of refractory material, said interior compartment bein closed at the top and open at the bottom and covering the entire cathode surface in the cell and being of suillcient size to hold all of the metallic magnesium which the cell can produce- ,during a period of at least several hours, said inby gas evolved at the anode, and entry of any of such gas into said interior compartment is prevented.

VLADIMIR QBIEDOFI".

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