US2018265A - Method of condensing magnesium vapor - Google Patents

Description

Oct. 22, 1935. F. R. KEMMER 2,018,265

METHOD OF CONDENSING MAGNESIUM VAPOR Filed Jan. 12, 1934 Patented Oct. 22, 1935 METHOD or conmmsmc mcnssmm VAPOR Frank R. Kemmer, Larchmont, N. Y., alsignor to American Magnesium Metals Corporation, Pittsburgh, Pa., a corporation of Delaware Application January 12, 1934, Serial No. 706,358

8 Claims. (01. 75-17) This invention relates to the condensation of magnesium vapors, and more especially to the condensation of metallic magnesium from a mixture of magnesium vapors and a gas reactive g therewith.

Probably the first procedure suggested for the production of magnesium was that of electrothermic reduction of its compounds with carbonaceous reducing agents. Such a procedure 10 has much to commend it from a theoretical standpoint, but electrothermic processes have not attained sustained commercial importance as applied to magnesium. In this process there is produced a mixture of magnesium vapor and carbon monoxide gas, in equimolecular proportions,

according to the equation At elevated temperatures, for example, above 30 about 2000 C., the reaction proceeds completely,

or substantially so, to the right, but as the temperature is lowered there is a progressively greater tendency for the magnesium, both in the vapor and solid states, to be reoxidized by the carbon monoxide, i. e., decrease of temperature causes the reaction to proceed toward the left in the foregoing equation. It is only when the solid has been cooled to quite low temperatures that the reoxidation becomes so slight as to be unimportant. This situation has engendered grave difilculties in the condensation of magnesium from the reaction products because the reoxidation of the magnesium vapor has been so serious as to prevent economical practice from a 85 commercial standpoint. Such reoxidation contaminates themagnesiumwith oxide,and it represents an added cost burden. In consequence of these and other factors magnesium has for many years been produced commercially by electrolytic methods.

It is among the major objects of this invention to provide a method of condensing magnesium vapor, especially from a mixture thereof with a gas reactive therewith, which provides satisfactory condensation of the vapor to the solid state,

effectively prevents reaction between the magnesium and accompanying gas, is simple and may be easily practiced in connection with desired electrothermic procedures and apparatus.

A further object is to provide apparatus suitable for the practice of the foregoing method, and which is simple, inexpensive and easily used.

The invention may be described in connection with the accompanying drawing which schematll ically represents 'a longitudinal sectional view through an apparatus suitable for use in the practice of the invention.

The present invention is predicated upon the fact that the prejudicial reaction of magnesium vapor with a reactive gas, for example, with carbon monoxide gas, may be effectively prevented by cooling the mixture of vapor and CO gas from a temperature at which such reaction does not occur, so rapidly to such a low temperature as substantially to preclude the reaction. In my 10 copending application Serial No. 664,932, filed April '7, 1933, I have described and claimed a method of condensing magnesium vapor according to which the vapor is impinged against a moving film, or curtain, of liquid inert to mag- 15 nesium, preferably a thin film of liquid flowing over a stationary cooled surface. The present invention makes use of the gist of that disclosed in my aforesaid copending' application, together with certain other features. go

In accordance with the present invention a stream of magnesium vapor is caused to impinge upon a cooled surface provided with a layer, e. g.,

a film, of liquid inert to magnesium and the surface is continuously moved to present fresh 25 cooled areas and fresh liquid for continuously maintaining condensation. The invention is applicable to the condensation of pure, or substantially pure, magnesium vapor, but particularly is it applicable to the condensation of magnesium 30 vapor from a mixture thereof with a gas reactive to magnesium, such as carbon monoxide. In the latter aspect of the invention the mixture is presented to the condensing operation at a temperature such that reaction does not occur, and 35 heat is abstracted from the cooled surface at a rate such as to cool the magnesium so rapidly through the critical temperature range as to prevent reaction of the vaporous and condensed magnesium and the gas and to bring the solid to a (0 temperature at which such reaction proceeds at a negligible rate.

In the preferred embodiment of the invention the stream of magnesium vapor is caused to impinge from a fixed point upon a surface of a ro- 5 tating metallic drum the lower portion of which rotates in a bath of suitable liquid. Advantageously the drum is mounted so that its ends rotate in a plane normal to the direction of flow of the Mg vapor, the end adjacent the vapor stream forming the condensing surface. The condensing surface of the drum is cooled interiorly thereof by any suitable means. Thereby there is continuously presented to the impinging stream of magnesium vapor a fresh, cooled condensing 66 surface with fresh liquid thereon, and by suitable provision for adequate abstraction of heat, through the interior cooling, and if desired by refrigeration of the liquid, the vapor and result- 5 ant solid magnesium are cooled substantially instantaneously to such a low temperature that the reactive gas is substantially innocuous.

The invention is particularly applicable to the production of magnesium by electrothermic reduction of-an oxygen compound of magnesium with carbon, for which reason it may be described further with reference thereto for purposes of illustration, but not by way of limitation. Having reference to the drawing, a mixture of magnesium vapor and CO issues in a stream from a port I in a wall of an electric reduction furnace 2, the mixture being produced at a temperature at which reoxidation does not occur, e. g., 2000 C. or higher, and it impinges against the end surface 3 of a drum 4 iournalled for rotation by any suitable means, not shown. As shown in. the

drawing, the drum is mounted to bring its condensing surface as close as practicable to the source of the vapor-gas stream, and if desired it may be adjustably mounted to vary the distance according to need.

The drum is cooled interiorly in accordance with the invention, and in the preferred embodiment this is accomplished by mounting the drum concentrically on the end of a hollow trunnion 5 of relatively large diameter through which there extends a conduit 6 for conveying water to a spray head -I facing condensing surface 3 against which it distributes cooling water. Trunnion 5 is conveniently mounted in bearings 8.

The water collects in the bottom of the drum and overflows through the trunnion 5 in the annular space surrounding conduit 6. The trunnion is rotated, to rotate the drum, by any suitable means, not shown.

The lower portion of the drum projects into a bath of a suitable liquid l0, so as to be continuously bathed therein, and as the drum rotates it carries a film of liquid I0 distributed on con- 5 densing surface 3 upwardly into the region of the impinging vapors; and likewise continuously returns the liquid to the bath, Any suitable liquid which is inert to magnesium under the conditions of operation may be used, although advantageously a hydrocarbon oil, such as kerosene or the like, is used. Such oils not only afford desirable properties for condensation, but also provide a protecting film over the condensed particles, and they also are adapted to provide effective protective atmospheres in other operations.

Access of air to the vapors is, of course, to be avoided. To this end the apparatus is enclosed in a housing I l whose bottom and side walls may,

if desired, cooperate to form, in effect, a tank for holding liquid Ill. The residual gas is withdrawn through a. pipe I! provided withja damper ii for regulating gas flow, to provide ajslight back pressure and thus prevent entry of air into the housing. To further exclude air, trunnion 5 is mounted in a suitable packing gland l4 associated with wall Ha of the housing.

In the practice of the invention the stream of Mg vapor and CO gas issues from port I and impinges against surface 3 where the magnesium is instantly condensed and cooled to a temperature at which CO has no effect upon it, e. g., 150 C. or lower. The necessary cooling may be effected wholly or primarily through the cooling 16 water projected against the inner side of the condensing surface from spray head I, the cooling effect being controllable through the volume of water used and by supplying it in a refrigerated state if need be. The cooling effect may be augmented by cooling liquid III, as by refrigerating 5 together with magnesium condensed on drum face 3. 5

The magnesium vapor is condensed to the solid state and in part falls into the bath and in part is carried into it by the film of oil adhering to surface 3, where it is washed off. The condensed metal collected 'in-the liquid bath is then re- 0 covered, for instance, by withdrawing the metal in suspension in the oil through a conduit l5 and separating the two materials, as by means of a filter press, not shown, the clean oil being returned for further use through another conduit 25 I6. If desired the oil may be refrigerated in this operation, for instance by passing it through suitable refrigerating means after it has been freed from the metallic magnesium which it carries.

Oxidation of the metallic vapor due to the oxy- 30 gen of the atmosphere is prevented by housing I l which acts to prevent air from reaching the hot vapor. The carbon monoxide gas remaining after condensation escapes through a pipe l2, the opening being controlled by damper [3 so 35 that there is always sumcient carbon monoxide pressure within the housing to prevent inward seepage of air.

It will be recognized that the invention is not restricted to the particular apparatus shown, nor 0 to the condensation of magnesium vapor in admixture with carbon monoxide gas, but that it is applicable not only to condensation of the metallic vapor from mixtures with other reactive gases, but also to the condensation of substan- 1,5 tially pure magnesium vapor, for example, derived from a distillation process.

No claim is made herein to the apparatus described hereinabove and shown in the drawing, this subject matter having been transferred to a 50 divisional application filed November 20, 1934, Serial No. 753,883.

According to the provisions of the patent statutes, I have explained the principle and operation of my invention, and have illustrated and 55 described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and 00 described.

I claim:

1. The method of condensing magnesium vapor, comprising causing said vapor to impinge against a cooled surface provided with a film of 65 liquid inert to magnesium, thereby condensing the magnesium to solid state, and continuously moving said surface to continuously present new cooled areas thereof and fresh liquid to the vapor to thereby maintain continuous condensation, 70

and preventing access of air during said step.

2. The method of condensing magnesium from a mixture of vapor thereof and a gas reactive with said vapor, comprising the steps of providing said mixture at a temperature at which reaction between magnesium and said gas does not occur and while at said temperature causing a stream thereof to impinge upon a cooled surface provided with a film of liquid inert to magnesium, abstracting heat from said surface at a rate such that the magnesium is condensed and cooled so rapidly that said reaction is substantially prevented, continuously moving said surface to continuously present new cooled areas thereof and fresh liquid to the vapor to thereby maintain continuous condensation, and preventing access of air during said steps.

3. The method of condensing magnesium from a mixture of vapor thereof and a gas reactive with said vapor, comprising the steps of providing said mixture at a temperature at which reaction between the magnesium and said gas does not occur and while at said temperature causin a stream thereof to impinge upon a cooled surface provided with a film of hydrocarbon oil, abstracting heat from said surface at a rate such that the magnesium is condensed and cooled so rapidly that said reaction is substantially prevented, continuously moving said surface to continuously present new cooled areas thereof and fresh oil to the vapor to thereby maintain continuous condensation, and preventing access of air during said steps.

4. The method of condensing magnesium from a mixture of vapor thereof and carbon monoxide, comprising the steps of providing said mixture at a temperature at which reaction between the vapor and carbon monoxide does not occur and while at said temperature causing a stream thereof to impinge upon a cooled surface provided with a film of liquid inert to magnesium, abstracting heat from said surface at a rate such that the magnesium is condensed and cooled so rapidly that said reaction is substantially prevented, continuously moving said surface to continuously present new cooled areas thereof and fresh liquid to the vapor to thereby maintain continuous condensation, preventing access of air during said steps, collecting the condensed magnesium in said liquid, and separating the magnesium from the liquid. 1

5. The method of condensing magnesium from a mixture of vapor thereof and a gas reactive with said vapor, comprising providing said mix- 5 ture at a temperature at which reaction between the vapor and gas does not occur and while at said temperature causing a stream thereof to impinge upon the end of a rotating drum mounted adjacent the source of said stream, con- 10 tinuously circulating a cooling fluid through the drum to abstract heat at a rate such that the magnesium is condensed and cooled so rapidly that said reaction is substantially prevented, continuously maintaining on said end a film of liquid 15 inert to magnesium, continuously rotating the drum to continuously present new cooled areas thereof and fresh liquid to the vapor to thereby maintain continuous condensation, and preventing access of air during said steps.

6. A method according to claim being a hydrocarbon oil.

7. A method according to claim 5, said liquid being refrigerated and thereby augmenting condensation and cooling of the magnesium.

8. The method of condensing magnesium from a mixture of vapor thereof and a gas reactive with said vapor, comprising providing said mixture at a temperature at which reaction of the vapor and said gas does not occur and while at 30 said temperature causing a stream thereof to impinge upon the end of a drimi mounted for rotation coaxially with the source of said stream and having its lower end rotating in liquid inert to magnesium, circulating water through the 5 drum to abstract heat from said end surface at a rate such that the magnesium is condensed and cooled so rapidly that said reaction is substantially prevented, continuously rotating the drum to continuously present new cooled areas thereof and fresh liquid to the vapor to thereby maintain continuous condensation, and preventing access of air during said steps.

FRANK R. KEMMER.

20 5, Said liquid

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