US2109841A - Production of metallic magnesium - Google Patents

Description

March 1, 1938. F. HANSGIRG PRODUCTiON 0F METALLIC MAGNESIUM Filed Dec. 1 1934 4 Sheets-Sheet l INVENTOR.

' kwnvessss 8 ATTORNEYS March 1, 1938. F. H ANSGIRC-S PRODUCTION OF METALLIC MAGNESIUM Filed Dec. 1, 1934 4 Sheets-Sheet 2 INVENTOR aw, 9%; QAITQRNEYJ WITNESSES March 1, 1938. F. II-IANSGIRG 2,109,841

PRODUCTION OF METALLIC MAGNESIUM Fi led Dec. 1, 1934 v4 sheets-sheet 3 ATTORNEYS March 1, 1938. F. HANSGIRG PRODUCTION OF METALLIC MAGNESIUM Filed INVENTOR. r r

, @900, 3.4a LQATTORN YS Patented Mar. 1, 1938 UNITED STATES PATENT OFFICE 2,109,841 rnonnc'rron or METALLIC MAGNESIUM Delaware Application December 1, 1934, Serial No. 755,574

16Cla1ms.

This invention relates to the production of metallic magnesium, more particularly by the thermal reduction of its compounds by means of carbon. i

In the thermal reduction of magnesium compounds with carbon the reduction proceeds, taking magnesium oxides as an example, according to the equation At sufliciently high temperatures that reaction proceeds to the right with production of a mixture of magnesium vapor and carbon monoxide;

If the mixture is kept at a sufliciently high temperature the reverse reaction (from right to left) does not proceed to any substantial extent, but

if the reaction products are cooled progressively the reverse reaction occurs to such an increasing extent that the starting materials are reformed substantially completely and no material amount .of magnesium is recovered.

In accordance with the invention disclosed and claimed in Patent No. 1,884,993 granted October 25, 1932, on an application filed by me, the reversal of the reaction, with reformation of magnesium oxide and carbon, may be avoided substantiall; completely by maintaining the mixture of magnesium vapor and carbon monoxide up to the point at which it leaves the furnace at such a high temperature that the reaction proceeds practically to the right, and then chilling the mixture at this point by admixture with a nonoxidizing gas down to a temperature at which under the dilution conditions existing, magnesium and carbon monoxide are stable when'in contact with one another. Advantageously the chilling is effected by introducing a gas which is inert with respect to magnesium, such as hydrogen in a cooled state, into the mixture of highly heated reaction products as they issue from the furnace. As stated in my aforementioned patent, the process may be practiced satisfactorily by contacting the stream with a cooled surface and introducing into the stream of magnesium vapor and carbon monoxide cool or cold hydrogen in sufficient quantity to rapidly cool the gases from a temperature of at least about 2000 to a temperature in the vicinity of 200 C.

Patent No. 1,884,993 likewise discloses and claims an apparatus for the practicing of that process. It consists, essentially, in a furnace capable of reducing magnesium compounds and pro-.

vided with a reaction product exit within which there is centrally a water-cooled no z e avi g a circumferential series of ape tures for injecting the cool chilling gas into the efliuent gases.

The meth'od described in the foregoing patent operates completely satisfactorily, and through extensive practice it has been found to be the only method known by which metallic magnesium can be produced commercially and economically by thermal carbonaceous reduction of magnesium compounds. In the use of the apparatus shown in'my aforementioned patent, however, it has been found that under some conditions there may be a tendency for solid material to build up between the nozzle and the wall of the exit opening from the reduction furnace, which is, of course, a serious difficulty when itoccurs.

It is among the objects of this invention to provide an improved method of practicing the process disclosed and claimed in my aforementioned patent, which provides for particularly efficient, rapid and thorough mixing of the efiiuent gases from the furnace and the chilling gas, so that consequently the chilling is effected so quickly as substantially to inhibit reoxidation of the magnesium vapor by the carbon monoxide.

A further object of the invention is to provide an apparatus for practicing the method provided by the invention.

Still another, and a major, object of the invention is to provide apparatus for producing magnesium by thermal reduction of its compounds with means for avoiding the consequences of deposition of solid matter in the exit opening from the furnace.

The invention may be described with reference to the accompanying drawings, in which Fig. 1

is a sectional view taken longitudinally through the center of a condensing apparatus constituting the preferred embodiment of the invention and'adapted for the practice of the method which it provides; Fig. 2 an enlarged view of a portion tion of the chilling means shown in Fig. 1; Fig. 3a cross-section through the apparatus shown inFig. 1, taken on line III-III thereof; Fig. 4 a sectional view taken on line IV--IV of Fig. 1; Fig. 5 a development view of a portion of the condenser shown in Fig. 1; and Fig. 6 a longitudinal central sectional View through a collecting chamber and condenser showing the preferred means provided by the invention for maintaining the outlet from the furnace and the condenser free from deposited material.

In the practice of the invention a magnesium compound, such as magnesia or calcined or dead burned magnesite, is reduced with carbon at a sufiiciently high temperature in a suitable furnace to produce a mixture of magnesium vapor and carbon monoxide, and, in accordance with the method covered by my aforementionedpatent, this mixture of reaction products up to the time it leaves the furnace is kept at a temperature such as to avoid substantial reconversion of the metallic magnesium into magnesium oxide by the carbon monoxide present; the effluent mixture of reaction products is then suddenly chilled to a point at which no mutual reaction between magnesium and carbon monoxide takes place under the dilution conditions existing.

A major feature of. this invention resides in introducing the chilling gas into the stream of reaction products circumferentially thereof at a plurality of points and in a plurality of zones disposed longitudinally of the path of the mixture. Most suitably the zones of introduction of chilling gas are disposed closely adjacent to each other and immediately succeedingthe outlet end of the opening in the furnace through which the reaction products move, which leaves the furnace opening entirely free for movement of the reaction products.

In order to obtain the most rapid and complete mixing of the chilling gas with the eflluent gases from the furnace, the chilling gas is introduced in each zone from a'plurality of points, advantageously in such manner that the gas is introduced from. each zone at an angle to but in the direction of movement of the eflluent gases. I have found, moreover, that particularly desirable mixing, and consequent chilling, is obtained by effecting introduction of the chilling gas in theseparate zones at angles which, from the furnace outwardly, diverge progressively, most suitably decreasing progressively from an acute angle, relative to the axis of the moving eilluent gases, in the zone adjacent to the furnace exit, to an angle substantially parallel or tangential to the direction of movement of the eifluent gases in the zone farthest removed from the furnace outlet.

Through the present invention I am able,

' therefore, to provide means for chilling the reaction products in which .the outlet from the furnace'is unobstructed, whereby the 'eifect of deposition of solid matter thereat is minimized, and by which especially eflicient repression of reoxidation of the magnesium is provided. In a further feature of the invention, means is provided for periodically removing solid matter, if any, deposited on; the walls of the condenser, with consequent advantages which will be understood in the art.

Having reference now to the drawings, Fig. 1 shows the wall I of an electric furnace provided with an outlet 2 for the reaction gases, which advantageously is lined with graphite 3. Connected to the outer end of outlet 2 in gas-tight relationship therewith is a condenser 4 having its outer end opening into a collecting chamber 5, Fig. 6. The condenser is provided with means for introducing the chilling gas immediately adjacent outlet 2. This condenser is shown as being of truncated conical form, 1. e., tapering, or flaring, outwardly from the outlet, but it may, of course, assume other forms. The condenser is advantageously covered with refractory 6 in the region of the furnace, as seen in Fig, 1.

The chilling means comprises a plurality of nozzles or the like adapted to introduce chilling gasinto the effluent gases in a plurality of zones longitudinally of their movement. In the embodiment shown this comprisesa succession of in solid matter.

9, II), II and I2 situated in the condenser wall immediately adjacent the outlet from the furnace. Each of these rings is' provided in its inner wall with a plurality of small openings l3 through which chilling gas is introduced into the con- 5 I denser.

The gas may be introduced into the rings in a variety of ways. In the preferred embodiment shown in the drawings condenser 4 is of doublewalled construction, as shown in Figs. 1 to 4, and the chilling gas, such as hydrogen, is supplied to the rings through pipes extending longitudinally of the structure, between the walls forming the jacket, from a manifold It provided with inlet connections I5 connected by pipes, not shown, leading to a source of chilling gas. Two pipes lead through the jacket from the manifold to each of the chilling rings. Thus, having reference to Figs. 1 and 4, a pair of diametrically oppositely positioned pipes l6 extend from manifold ll between the double walls of the condenser to ring l2. Similarly, a pair of pipes I! lead to ring ll, pipes l8 to ring it, pipes 19 to ring 9, pipes 20 to ring 8, and pipes 2| to ring I.

In order to compensate for expansion and contraction of gas feed pipes Hi to 2|, they are bent into sinuous form, as indicated schematically in the development view of Fig. 5. Advantageously they are cooled by circulating a cooling medium, such as cooled oil, through the jacketed portion of the condenser 4. In the embodiment shown the jacket is divided into a plurality of sections by metallic diaphragm members 22 extending from end to end and connected to the walls of the condenser. Each of the sections thus formedis subdivided by alternately disposed diaphragm members 23 and 24 connected respectively to opposite ends of the condenser within the jacketed portionand terminating, respectively, short of the other end, th'us dividingeach section into a plurality of chambers connected at their opposite ends, as appears clearly in Fig. 5. Each section is provided with an inlet 25 for cooling liquid and an outlet 26 at the opposite end of the group.

As described hereinabove, the openings I3 are preferably positioned to project jets of the chilling gas at an angle to but in the direction of the movement of the eifluent gases from the furnace, the angle of the outlets in each zone, or ring, being the same, and the angles decreasing progressively in successive zones, so that the streams of chilling gas diverge progressively from zone to zone in the line of movement of the ellluent gases. This may be seen particularly clearly in Fig. 2, in which the openings IS in ring 1 are adapted to inject the gas at an angle of approximately 30 to the axis of movement of the efliuent gases. It may be seen also that the inclination of the openings I 3 changes progressively in successive rings up to and including ring l2 the openings l3 in which are such that the jets of gas move 'in a direction substantially parallel, or tangential, to the eiiluent gases.

Although in, the apparatus just described the outlet from the furnace is entirely unobstructed, there being no cooling or other members disposed in it, deposition of condensed solid may take place on the wall of the condenser. The invention contemplates a simple and efficient mechanism for preventing the accumulation of such deposited In this aspect of the invention the condenser is provided with scraping mechanism, suitably mounted reciprocably in the collecting chamber for insertion into the condenser, and for rotation therein for removal of such solid matter to prevent it from building up undesirably on the walls.

Having reference to Fig. 6, collecting chamber 5 is shown provided with a screw-type scraper 21 carried by a hollow shaft 28 supported in bearings 29 carried by bracket members 38 and end wall 3i of the collecting chamber. Shaft 28 may be rotated continuously, as by means of a sprocket wheel 32 keyed on shaft 28 and actuated by a sprocket chain drive, not shown, or it may be rotated by any other suitable means. The edge of screw 21, whichmay be provided with a brush if desired, is adapted to move continuously against the wall of the collecting chamber and thus acts to continuously remove powdered metallic magnesium from the wall and simultaneously to move all of the magnesium produced by the chilling action longitudinally of the collecting chamber to an outlet where the metal powder falls into a trough 33 and is removed through a second screw conveyor 34 actuated in any desired manner.

A second shaft 35 journalled in bearings 36 provided in shaft 28 is mounted within the latter for rotation therein and reciproca ion relat ve thereto. At its forward end shaft,35 is provided with a cutting scraper 31 .the scraner kn ves of which are disposed toconform closely to the wall of condenser 4. as may be seen from Fig. 6. The forward end 31a of the scraper is likew se adapted to act on the wall of outlet 2. to clean it of deposited matter. In the use of this dev ce the furnace is normally onerated wi h the scraper retracted as shown in Fig. 6. At intervals. when sol d material may have dep sited on the inner wall of condenser 5. the scra er shaft 35 is moved forwardly in shaft 28 to bring scrapers 31 and 31a into contact with the condenser and out et walls, and it is thereupon rotated. thus d slodgng any material that may have depos ted. and causing it to be carried away by screw conveyor 21. Thereupon the scraper is a ain retracted to the pos tion shown. Scraper shaft 35 may be rotated by any suitable means. as by a hand wheel 38. In addition to providing adequate cleaning action, it w ll be observed that by this construction the operation of the furnace and condenser is not interfered with.

Thecondenser and collecting chamber are, of course. of gas-ti ht construction, to avoid losses through seepa e from the condenser. and to avmd entry of air, which would cause oxidation of the metal powder, which in the finely div ded form in which it is deposited is highly reactive in the presence of oxygen. To these ends. shafts 28 and 35 are sealed by stuffing boxes 39 and 40, respectively.

In order to increase the ch lling action collecting chamber 5 may likewise be of jacketed construction, as seen in Fig. 6, and a cooling liquid, such for example as oil, may be circulated therethrough from an inlet 4!, to an outlet Q2. The

walls may be spaced and supported by I-members 43, and in such caseto permit circulation of the oil they are provided with openings 44, preferably staggered relative to each other to cause the cooling liquid to circulate in a tortuous path.

In the practice of the invention a charge of magnesium compound, suitably burned magnesite, and carbonaceous material, advantageously in an amount sufiicient to reduce all of the reducible constituents of the ore used, is brought up to reaction temperature in furnace I, The furnace is operated so that the reaction products,

a mixture of magnesium vapor and carbon monoxide gas, are kept, while in the furnace, at a temperature sumeiently high to substantially avoid oxidation of the metal vapor by the CO gas. The reaction products flow through outlet 2 to condenser 4, and while at their initial high By sudden chilling a powder is formed which is then continuously removed by conveyors 21 and 3 6, and the walls of condenser 4 and outlet 2 are periodically cleaned by scrapers 31 and 31a. The uncondensed gases, carbon monoxide and hydrogen are removed through an outlet 45, and the hydrogen may be recovered and cooled for reuse.

The metal powder produced is extremely reactive in the presence of oxygen, and because of its finely divided condition there is always some powder in the collecting chamber. If the collecting chamber were opened there would accordingdy be present the danger of inflammation of the powder upon the entry of air, it being possible for the combustion to be exceedingly violent. For this reason means are provided to -make it possible to open the apparatus, for example to make repairs, without such danger. To this end the collecting chamber and condenser are provided with nozzles for spraying oil into the apparatus. Having reference to Fig. 1, a nozzle 46 supplied with oil under pressure through a pipe 41 projects downwardly into condenser 4 through a flanged conduit 48 which is sealed by a cover 49 to exclude air. Oil sprayed, suitably as a fine mist, from nozzle 46 reaches all parts of the condenser, as indicated by the broken lines proceeding from the nozzle. The collecting chamber 5 is likewise provided with conduits 48a for receiving similar spray nozzles, not shown. In this manner the entire condenser and apparatus may be drenched with oil, the excess of which may be drained from a normally sealed syphon member 50. After such spraying the apparatus may be opened safely, for the film of oil on the particles of magnesium prevents their rapid reaction with air.

Pyrometer wells 5| may be provided in the apparatus to receive pyrometers for measuring the temperature if desired.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have illustrated and 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 described.

I claim:

1. In a process of making metallic magnesium in which a mixture of magnesium vapor and carbon monoxide gas is chilled suddenly from a high temperature at which the reaction MgO CzMg+ C0 proceeds practically from left to right, to a low temperature at which the magnesium formed is not substantially oxidized by the carbon monoxide present, that step comprising introducing cool hydrogen into the said mixture as it leaves the furnace at said high temperature, said hydrogen being introduced at a plurality of points in each of a plurality of zones disposed circumferentially of said mixture and longitudinally of its axis of movement, the gas from the zone adjacent the furnace being introduced at an acute angle to the direction of movement of said mixture, and the angle of gas entry decreasing progressively from zone to zone outwardly from the furnace.

2. In a process of making metallic magnesium in which a mixture of magnesium vapor and carbon monoxide gas is chilled suddently from a high temperature at which the reaction proceeds practically from left to right, to a low temperature at which the magnesium formed is not substantially oxidized by the carbon monoxide present, that step comprising introducing cool hydrogen into the said mixture as it leaves the furnace at said high temperature,said hydrogen being introduced at a plurality of points in each of a plurality of zones disposed circumferentially of said mixture and longitudinally of its axis of movement, the gas from each zone being introduced at an angle to but in the direction of movement of said mixture, and the angle of gas entry decreasing from an acute angle in the zone adjacent the furnace to an angle approaching said axis in the zone most remote from the furnace.

3. In a process of making metallic magnesium in which a mixture of magnesium vapor and carbon monoxide gas is chilled suddenly from a high temperature at which the reaction MgO+ C2Mg+ co proceeds practically from left to right, to a low temperature at which the magnesium formed is not substantially oxidized by the carbon monoxide present, that step comprising introducing cool hydrogen. into the said mixture as it leaves the furnace at said high temperature, said hydrogen being introduced at a plurality of points in each of a plurality of zones disposed circumferentially of said mixture and longitudinally of its axis of movement, the gas from each zone being introduced at an angle to but in the direction of movement of said mixture, and said angles decreasing progressively from about 30 to said axis in the zone adjacent the furnace to 0 to said axis in the zone farthest from the furnace.

4. In a process of making metallic magnesium in which a mixture of magnesium vapor and carbon monoxide gas is chilled suddenly from a high temperature at which the reaction proceeds practically from left to right, to a low temperature at which the magnesium formed is not substantially oxidized by the carbon monoxide present, that step comprising introducing cool hydrogen into the said mixture as it leaves the furnace at said high temperaturesaid hydrogen being introduced at a plurality of points in each of a plurality of zones disposed circumferentially of said mixture, the jets of a zone converging conically toward the axis of movement of said mixture, and the conical angle of the jets decreasing from zone to zone outwardly from the furnace.

5. An apparatus for making metallic magneu'um comprising an electric furnace for reducing magnesium from its compounds, the furnace being provided with an outlet for the magnesium vapor, and means associated with said outlet for chilling said vapor rapidly to convert it to metallic magnesium, said means comprising a condenser having one end associated with and flaring outwardly from said outlet, a plurality of circumferential gas nozzle rings arranged successively relative to each other and each provided with a plurality of openings for directing gas into the condenser, and connections between said nozzles and a source of chilling gas.

- 6. An apparatus for making metallic magnesium comprising an electric furnace for reducing magnesium from its compounds, the furnace being provided with an outlet for the magnesium vapor. and means associated with said outlet for chilling said vapor rapidly to convert it to metallic magnesium, said means comprising a condenser having one end associated with and flaring outwardly from said outlet, a plurality of circumferential gas nozzle rings arranged successively relative to each other, said rings being provided with a plurality of jet openings disposed at an angle to the ring axis and said angle decreasing from ring to ring outwardly from said,

outlet, and connections between said nozzles and a source of chilling gas.

7, An apparatus for making metallic magnesium comprising an electric furnace for reducing magnesium from its compounds, the furnace being provided with an outlet for the magnesium vapor, and means associated with said outlet for chilling said vapor rapidly to convert it to metallic magnesium, said means comprising a condenser having one end associated with and flaring outwardly from said outlet, a plurality of circumferential gas nozzle rings arranged successively relative to each other, each of said rings having a plurality of jet openings for directing chilling gas conically into said vapor, the conicity of the openings diverging progressively from ring to ring outwardly from said outlet, and connections between said nozzles and a source of chilling as.

8. An apparatus for making metallic magnesium comprising an electric furnace for reducing magnesium from its compounds, the furnace being provided with an outlet for the magnesium vapor, and means associated with said outlet for chilling said vapor rapidly to convert it to metallic magnesium, said means comprising a condenser having one end associated with and flaring outwardly from said outlet, a plurality of circumferential gas nozzle rings arranged successively relative to each other, each of said rings being provided with a plurality of jet openings disposed at an angle to the axis of movement of said vapor, said angle decreasing from about 30 in the ring adjacent said outlet to about 0 in the ring most remote from said outlet, and connections between said nozzles and a source of chilling gas.

9. In an apparatus for producing metallic magnesium the combination of a furnace adapted to reduce magnesium from its compounds, the' furnace being provided with an outlet for magnesium vapor, and means for condensing said vapor and collecting the condensate including a condenser having a conical end portion associated with said outlet and provided with means for suddenly chilling the vapor as it leaves the furnace, and a collecting chamber connected to the other end of said condenser, and a scraper rotatably and reciprocably disposed in the collecting chamber for insertion into said conical end portion and outlet for removing magnesium deposited on the walls thereof.

'10. In an apparatus for producing metallic magnesium the combination of a furnace adapted tov reduce magnesium from its compounds, the furnace'belng provided with an outlet for magnesium vapor, and means for condensing said vapor and collecting the condensate including a collecting chamber having a cylindrical body portion, and a. conical condenser associated with said outlet and opening into said collecting chamber and provided with means for suddenly chilling the vapor as it leaves the furnace, a screw conveyor rotatably mounted in said collecting chamber, and a scraper rotatably and reciprocably disposed in the collecting chamber iorinsertion into said end portion for removing mag nesium deposited on the wall thereof.

11. In an apparatus for producing metallic magnesium, the combination of a furnace adapted to reduce magnesium from its compounds, the furnace being provided with an outlet for magnesium vapor, and means for condensing said vapor and collecting the condensate including a collecting chamber having a cylindrical body portion continuous with a conical condenser having its extended end associated with said outlet, said condenser being provided with means for suddenly chilling the vapor as it leaves the furnace, a screw conveyor rotatably mounted in said collecting chamber, and a scraper rotatably and reciprocably disposed in the collecting chamber proceeds practically from left to right, to a low temperature at which the magnesium formed-is not substantially oxidized by the carbon monoxide present, that combination of steps comprising passing said mixture at said high temperature from the furnace into a condenser flaring outwardly from the furnace, and as said mixture enters said condenser introducing cool chilling gas which is inert withrespect to magnesium into said mixture at a plurality of points and in fine jets circumferentially of the mixture in each of a pinrality of zones disposed longitudinally of the path of said mixture.

13. In a process of making metallic magnesium I in which a mixture of magnesium vapor and carbon monoxide gas is chilled suddenly from a high temperature at which the reaction of a plurality of zones disposed longitudinally of the path of said mixture. g

14. In a process of making metallic magnesium in which a mixture of magnesium vapor and carbon monoxide gas is chilled suddenly from a high temperature at which the reaction mo t-Calumet) proceeds practically from left to right, to a low temperature at which the magnesium formed is not substantially oxidized by the carbon monoxide present, that combination of steps comprising passing said mixture at said high temperature from the furnace into a condenser flaring outwardly from the furnace, and as said mixture enters said condenser introducing cool hydrogen into said mixture at a plurality of points and in line jets circumferentially of the mixture in each of a plurality of closely adjacent zones disposed longitudinally of the path of said mixture.

15. An apparatus for making metallic magnesium comprising an electric furnace for reducing magnesium from its compounds, the furnace being provided with an outlet for the magnesium vapor, and means associated with saidoutlet for chilling said vapor rapidly to convert it to metallic magnesium, said means comprising a condenser having a conical end portion associated with said outlet and flaring outwardly therefrom, a plurality of gas nozzles disposed in said end portion and arranged circumierentially thereof and adapted to produce fine jets of gas, said nozzles being arranged successively relative to each other, and connections between said nozzles and a source of chilling gas.

16. An apparatus for. making metallic "magnesium comprising an electricfurnacefgr reducing magnesium from its compounds, the furnace being provided with an outlet for the magnesium vapor, and means associated with said outlet for chilling said vapor rapidly to convert it to metallic magnesium, said means comprising a condenser having a conical end portion associated with said outlet and flaring outwardly therefrom, a plurality of circumferential gas noz zle rings arranged successively relative to each other within said end portion, said rings being provided with a plurality of jet openings disposed at an acute angle to the condenser axis, and connections between" said-nozzles and a source of chilling gas.

- FRITZ HANSGIRG.

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