US2051913A - Production of magnesium - Google Patents

Description

Patented Aug. 25, 1936 UNITED STATES PRODUCTION OF MAGNESIUM Robert Suchy, Bitterfeld, Germany, assignor, by mesne assignments, to Magnesium Development Corporation, a corporation of Delaware No Drawing. Application October 19, 1934, Serial No. 749,074. In Germany October 28, 1933 10 Claims.

means of carbon, the cooling of the magnesium vapours escaping from the furnace together with carbon monoxide is generally accompanied with a re-formation of magnesium oxide on the basis of the equilibrium reaction Mg+CO- MgO+C,

which hitherto presented great difliculties to a technical utilization of this process. It has been previously recognized that in order to condense the magnesium it is necessary to cool the gas mixture escaping from the furnace as rapidly as possible to low temperatures at which MgO reforms extremely slowly, if at all. Recently it has been proposed for this purpose that the magnesium be condensed in the furnace itself on cooled surfaces, a process which in its practical application, however, encounters great difliculties with apparatus and which cannot be used for large scale operations. Moreover, .it has been proposed to cool the highly heated gases escaping from the furnace by blowing in a cold inert gas and thus effecting a rapid condensation of the magnesium vapour into the form of powder. It has been found, however, that all these methods only inadequately prevent a re-formation of magnesium oxide. 'Upon condensation of the metal vapour, the surfaces of the particles .of metal powder are obviously reoxidized and a troublesome treatment of the powder in a vacuum is required to melt a metal regulus therefrom.

According to the present invention, rapid cooling of the gases escaping from the furnace is effected simultaneously with the condensation of the magnesium by means of solid anhydrous salts or salt mixtures inert to magnesium which fuse at temperatures below the boiling point of the magnesium. First of all, the process has the advantage that the heat of fusion of the salt is used for the intensive cooling of the gases. At the same time, the condensed magnesium is immediately'withdrawn from the action of the carbon monoxide gas by intimate contact with the fusing salt. However, since reoxidation of the magnesium cannot ,always be prevented even under these conditions, salts capable of dissolving or otherwise absorbing magnesium oxide, such, for example, as anhydrous magnesium chloride or carnallite, are appropriately used for cooling the vapours, which saves a special remelting .of the condensed metal powder in that the latter is immediately relieved of any oxide formed and in this manner is immediately produced in reguline form. 5 The intimate contact, over a large superficial area, of the furnace gases with the solid salt. which isd'esirable for the purpose of rapid heat exchange, may be attained in various ways. For example, one may with the aid of an inert carrier 10 gas blow solid salt in finely divided, e. g.. pulverulent form through nozzles into the stream of gas escaping from the furnace. the amount of carrier gas required for this purpose not being, by a long way, in itself sufficient to condense the 15 magnesium vapours, or even only to effect substantial cooling of the furnace gases. A method of practicing ,the invention which has proved to be especially suitable is one in which the highly heated furnace gases are conducted through a shaft in which large pieces of carnallite (for example, about the size of walnuts) are arranged loosely on a grate. While the carbon monoxide escapes at the top, the carnallite which melts in contact with the gases flows down through the grate and thus carries the condensed metal powder with it. It then passes into a collecting vessel which may, if desired, be heated and in which the metal rapidly separates from the fused-salt, whereupon it may be tapped off separately from the latter. In this connection it is advantageous, by suitably regulating the temperature of the saline metal melt and possibly also by addition of other salts having a low specific gravity to provide that the specific gravity of the saline melt is maintained at a lower level than that of the magnesium metal, in order to maintain a fused saline layer on the surface of the coagulated metal and thus to protect the latter from any subsequent action of the (IO-containing gases. 40

Moreover, separation of the metal from the cooling salts subsequent to the condensation of the magnesium vapours may be promoted by the addition, to the melt, of compounds such as metal oxides and/or fluorides acting as inspissating agents in known manner.

Of course, there is nothing to prevent one from carrying out the cooling of the furnace gases by chilling them with molten saltsialthoughthe advantage of an intensive cooling by utilizing the heat of fusion is thereby dispensed with.

I claim:--. 7

1. A process of recovering magnesium metal from magnesium vapours containing .carbon monoxide which comprises suddenly contacting the 55.

highly heated vapours with a salt inert ta magnesium and having a fusing point below the boiling point of magnesium, so as to condense the magnesium content of said vapours.

2. A process of recovering magnesium metal from magnesium vapours containing carbon monoxide which comprises suddenly contacting the highly heated vapours with a'salt inert to magnesium and having a fusing point below the boiling point of magnesium and capable of absorbing magnesium oxide, so as to condense the magnesium content of said vapours.

3. A process of recovering magnesium metal from magnesium vapours containing carbon monoxide which comprises suddenly contacting thehighly heated vapours with a solid salt inert to magnesium and having a fusing point below the boiling point of magnesium, so as to condense the magnesium content of said vapours.

4. A process of recovering magnesium metal from magnesium vapours containing carbon monoxide which comprises suddenly contacting the highly heated vapours with an inert salt comprising anhydrous magnesium chloride, so as to condense the magnesium content of said vapours. 5. A process of recovering magnesium metal from magnesium vapours containing carbon monoxide which comprises suddenly contacting the highly heated vapours with an inert salt comprising solid anhydrous magnesium chloride, so as to .condense the magnesium content of said vapours. 6. A process of recovering magnesium metal from magnesium vapours containing carbon monoxide which comprises suddenly contacting the highly heated vapours with a finely divided salt inert to magnesium and having a fusing pointbelow the-boiling point of magnesium, so as to condense the magnesium content of said vapours.

7. A process of recovering magnesium metal from -magnesium vapours containing carbon monoxide which comprises blowing by the aid of an inert carrier gas a finely divided salt inert to magnesium and having a fusing point below the boiling point 01' magnesium and capable of absorbing magnesium oxide, into the highly heated vapours, so as to condense the magnesium.

8. A process of recovering magnesium metal from magnesium vapours containing carbon monoxide which comprises'suddenly contacting the highly heated vapours with an inert salt comprising solid anhydrous magnesium chloride, so as to condense the magnesium content of said vapours, and adding inspissating agents to the mixture of salt and metal thus obtained so as to promote separation of the saline melt and the metal re ulus.

9. In a process for the thermal production of magnesium from magnesium oxide or materials containing magnesium oxide by reduction with carbon the steps which comprise suddenly contacting the reaction gases issuing from the furnace with a finely divided solid salt inert to magnesium and having a fusing point below the boiling point of magnesium and capable of absorbing magnesium oxide, so as to condense the magnesium, removing the carbon monoxide vapours while collecting the condensed magnesium with said condensing salt, and separating the condensed magnesium from said condensing salt.

10. In a process for the thermal production of magnesium from magnesium oxide or materials