US2399180A - Sublimation apparatus - Google Patents

Description

pr 30, E946., M v D. GIRVIN ET AL",

SBLIMATION APPARATUS I Fild Aug. 18, 1943 I N V EN TOR.

L eo .Q/fred y Dervio/7e.

Patented Apr. 30, 1946 ElcE SUBL'IMATION APPARATUS Murray D. Girvin, Manteca, and LeolAlfred'Dentone. Stockton, Calif., assignors. by mcsne assignments, to The remanente Metals Corporatloma corporationof Delaware Application August 18, 1943, Serial No. 199, ll86 4 Claims. (Cl. 26S-22) This invention relates to an apparatus for subliming metals from their ores and for refining impure metals by sublimation and has particularly in view an apparatus adapted for the reduction of magnesium-oxide containing raw material with .the aid of reducing agents that do knot form gaseciusL products of oxidation, for instance with the aid of silicon or alloys thereof, especially ferro-silicon, aluminum or a mixture of both,v silicides, and carbides.

If it is intended to recover magnesium from its ores by reduction at a temperature above the boiling'point of the metal, which requires even under very low absolute pressures relatively high temperatures, and by causing the vapor levolved to condense directly from'the vapor state in the solid state, without intermediate liquefaction, the rate oflsublimation, Within limits, will depend under appropriate temperature and pressure conditions upon the quantity of heat applied to the initial material; hence, in the parts of the apparatus forming the reduction chamber a material with high thermal' conductivity will be necessary. On the other hand, it is necessary that the temperature in the condensing area should be markedly below lthat of the metal being sublimed since the difference in the vapor pressure due to this difference in temperature is the driving forcecausing the rapid transfer of the magnesium vapor from the subliming to the condensing end of the system; hence, a minimum transmission of heat from the subliming'to the condensing' area is desired. This problem is further complicated by the necessity of disposing the condenser in near proximity to the heated part of the apparatus for the purpose of causing the crystalline condensate to -be densely deposited on restricted sections of the condenser area; hence the type of sublimation apparatus employed for the purpose usually consists `of van elongated retort aportion ofwhich is 40 kept cool to serve as a condenser, or within which a condenser with internal cooling is Suspended so -as to extend downward closely to the heated part of the'retort. It is the main object of the inventionitoA satisfy these partially conflicting conditions by providing a retort in the heated part of which the evolution of vapor Will be rapid enough to allow industrial application and in the condenser part of which there is, in spite of the close proximity of the heated and cooled areas in the apparatus, the possibility of establishing a very satisfactory temperature control.

To this end, there is according to the invention between the heated part and the condenser part of the sublimation apparatus a partition body insorted, which is made of a material of low heat conductivity and provided with one or more, pref-VY erably a plurality, of ducts which are fairly large and form together a large-diameter communicatiorrcapable of allowing the free passage of vapor, the Said partition being however adapted to prevent the vapor from proceeding in perpendicular direction from the retort side to the condenser side thereof. According -to a preferred embodiment of the invention the holes of the partition are arran-ged to-run in diagonal direction across the partition body. The said partition is preferably made of a refractory material of high temperature resistivity. u l v In this manner a very satisfactory quantity of heatcan be applied to the heated parts of the apparatus, Without provoking an undesired rise in temperature Within .the condenser. This is of crucial importance since if the condenser is run at too high atemperature this results in considerable loss of metal through burning. ,Moreover by the use of a partition of such kind the loss of heat due to transmission of heat from the retort Side to the condenser side is minimized. Besides,

25 in this mannerv a very exact temperature control by appropriate means .can be accomplished in the condenser. This is desired since the condensation of the metal should be performed Within narrow temperature limits in order to obtain a Wellcrystallized condensate t for being discharged without undergoingl undesired alterations. If the condenser is kept too cool the metal condenses in a micro-crystalline condition and the crystals catch re or combine slowly with the oxygen and the nitrogen of the air 'on being discharged.

In the drawing there isa concrete 'exemplication of the invention' diagrammatically illustrated showing, by way.v of example, a Sublimation apparatus of the horizontal vretort type destined for batch or discontinuous operation. Figure 1 is a top view of the partition according to the invention on the retort side thereof, Figure 2 a vertical section on line A-B in Figure 1; Figure 3 is a sectional view of a retortk equipped with the partition, Figure'4 atop 'view' ofa slightly modified form of the partition on the retort side thereof.

I designates part of the retort which is made from heat-resisting metallic material, preferably steel, and comprises an elongated receptacle of substantially tubular shape, hermetically closed at the bottom end and provided with aV removable cover on the opposite end (Fig. 3) The said retort is adapted to be heated by means of any convenient kind, for instance horizontally supported within an appropriate furnace structure equipped with appropriate means (not shownl adapted to be connected with a conduit 3b 'for creating and maintaining during operation a` suitably reduced absolute fp ressiur'e 'Within Lthej system. i f

The retort I and the condenser 2 are separated; for the purpose of thermal insulation, by a trans- Though specifically described in connection with the recovery of sublimable metals, such as in particular of magnesium, from their ores, the present apparatus is equally applicable to the refining of crude metals, particularly magnesium, by sublimation.

We claim: 1,15 Sublimation:apparatus comprising in combination a retort part and a condenser part ad- .jacent to the retort part, which parts are separated, by thermal insulation, and connected, by `vapor passages, through a partition body made of a material-,voith louheat conductivity and providedvvith@plurality of ducts forming together a verse vertically-disposed partition #made from refractory material in which holes 5 are arranged so as to run in a diagonal direction from the retort side to the-condenser side of the partition. In the embodiment shown in Figures. 1 andf`2' of the Vdrawing' there are fourof suchfholes: 5' provided that form-ducts lstarting ad'joined at the center of the retort side; running across the depth of the partition in adiagonally-inclined arrangement, and opening on the condenserside of the partition-dispersed at regular intervals around-v the periphery thereof;A According" tothe alterna-'- tive embodiment shown inlFigure L the ducts 5 sta-rt on theretort side ofthe partition body disposed at regularintervalsf near the periphery thereof, proceed, regularlylwidening, inA an oblique direction but substantially straight-'linedito the condenser side and terminatel thereA `Qvitlopenings symmetrically arrangedalong the periphery thereof. i

Refractorymaterialswellz adapted for the purpose are rebricks, magnesite refractories, carbon stones and the like materials inert to magnesium vapors and capable of enduring high temperatures Without damage.y

It is self-evident that less orr more than four ducts for the passage'of the Vapor can be pro'- vided, butit has been found that four holes give advantageous results under otherwisefavorable conditions. The partition cairbe situated eitherv in the condenser part 2 adjacent to ,the retort part I or in the. head end of the retort part l (Fig. 3). In the former embodiment the partition may be rxed in its position with the 'aid of a heat resistant cement. If Vthe partition is placed in the retort part,V it suiices tov arrange the outer diameter ofthe partition so that the partition b odyclosely iits,l the retort tubeand no uniting by cement'is needed'. It would appear as if a partition bodyo'iZto `3linches thickness gives the most'satisiactoryresults;"y

The securingoiY al minimum-loss 4 oi heat by heat exchange `on Ythe one hand and of aminmum loss of metal'l by burning; oxidation'and nitridation on 'the other hand, results obtaining a higher yield,.whi'ch` increasefmay amoun4 to from 5to 8 pounds ofmetallpen unit. Y

{large-diameter communication capable of allow- ;ing-.freerescapeiof. vapor from the retort part of the condenser part, the said ducts being so arrangedthat they'start adjoined at the center of the retort side of the partition body, run across the depth of the said body in a diagonally inclined direction and` open Aon 'they condenser' side of the said body dispersed' at regular intervals around thefp'eriphery thereof,V

Sublimation f apparatus comprising in 'combinationj aretort partand' acond'enser part" adjacent to the retortpartg'which parts areseparated', thermal" insulatim and connected, by vapor passages, through a partitionbod'y made' of' a material with low heat conductivity and4 provided with a plurality of duets forming together a largediametercommunicatin capable of allowing free escapev o f vapor from the retort part to the condenser part,' the said ducts being solarranged that*they start on the retort sideV of the partition body' disposed-` at regular. intervals near the periphery thereof, runj l'regularly Widening'l in oblique ,direction acrossV the partition body, and terr'ninateonthe condenser side' ofthe vpartition body with.openingssymmetrically'arranged along the'periphery. thereof. A

3. Sublimation'apparat'us comprising in combination'a retort part,l a condenser part, `and a member of heat, insulating material forming a partition between said parts, said partition member having a plurality of ducts providing for, the free lpassage of vapor from' the retort part to the condenser part, and arranged to extend regularly, wideningin an oblique direction through the paititionnember to prevent directtransmission offheat'fromthe retort to the condenser part.

il. Sublimation apparatus comprising inv combinationan elongated. tubular inclosure, a partition of heat'kinsulating materialdisposed transversely within the inclosure to divide. the same into 'a rtcrt'iiart and a condenser part, said partition having a. plurality of openingsA to permit the free 'passage' of vapor `from the retort to the condenser" part andi said openings extending obliquely through the partition to prevent -the direct transmission yof heat 'from'the retort tothe condenser in ardirecti'on vparallel to they length of the `inclosure.

. MURRAY D.;G1R.vn\r.

LEO vALFRED DENTONE.

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