US2477420A

US2477420A - Apparatus for cooling gaseous media by interchange of heat with cooling gases

Info

Publication number: US2477420A
Application number: US585884A
Authority: US
Inventors: Donald A Rhoades
Original assignee: Permanente Metals Corp
Current assignee: Permanente Metals Corp
Priority date: 1945-03-31
Filing date: 1945-03-31
Publication date: 1949-07-26
Anticipated expiration: 1966-07-26

Description

July 26, 1949. D. A. RHoADEs 2,477,420

APPARATUS FOR COOLING GASEOUS MEDIA BY INTERCHANGE OF HEAT WITH COOLING GASES Filed March 51, 1945 3 Sheets-Sheet 1 m N .N m v. m

BY "a,

D. A. RHOADES 4 OLI July 26, 1949. v 2,477,420

APPARATUS FOR co NG GAsEoUs MEDIA BY INTERCHANGE I oF HEAT wITH COOLING GAsEs Filed March 31, 1945 July 26, 1949. D. A. RHoADl-:s 2,477,420

APPARATUS FOR COOLING GASEOUS MEDIA BY INTERCHANG'E OF HEAT WITH COOLING GASES Filed March 51, 1945 3 sheets-sheet s l N V EN TOR. a/vzu @#04055 BY fama/6%? Patented July 26, '1949 `APPAIm'rUs FOR COOLING GAsEoUs MEDIA` BY INTERCHANGE OF HEAT WITH COOL.-

ING GASES Donald A. Rhoades, Palo Alto, Calif., assignor to ThePermanente Metals Corporation, Calif., a corporation of Delaware i Oakland,

Application March 31, 1945, Serial No. 585,884

. claims. (o1. 26e- 15) ihave a tendency to react chemically with theV said vapors. However the invention will be described, for purposes of illustration, with particular reference to the manufacture of magnesium from magnesia or magnesia-containing ores while using a carbonaceous material as the reducing agent.

In the thermal reductionV of magnesium oxide with carbon the reaction proceeds according to the equation Mg0|C 2Mg+CO with production of amixture ofmagnesium vapor and carbon monoxide. At a sufliciently high temperature the reversion of the reaction from rightto left is eiliciently repressed, but if the reaction products are` allowed to cool gradually the reverse reaction progresses so rapidly that the starting materials MgO and C are reformed substantially completely and no material amount of magnesium is recovered.

It is now well known that the reversion of the reaction can be minimized by keepingthe 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 suddenly cooling (shock-chilling) the mixture at this Very point, by the injection of fine `jets of a non-oxidizing gas, down to a temperature at which under the dilution conditions existing magnesium and carbon monoxide are `stable in the presence of each other. Since that temperature lies below the solidication point of metallic magnesium, the metal is condensed in this way in the form of a nely divided dust. i Usually shock-chilling is effected by introducing into the escaping mixture of highly heated reduction products a cooled gas, which is inert or substantially inert to magnesium, such as hydrogen or a noble gas, particularly helium, or an industrial hydrocarbon, or natural mixtures of hydrocarbons such as natural gas.

As large quantities of the chilling gas are required in commercial operations of any appreciable scale, with coolants other than natural gas, it is unavoidable to return the coolant in cycles, and this can notbe done without removal of carbon` monoxide before recirculation. However, it is already known that it is not necessary to reclaim the entire volume of gas employed for chilling, but it suliices to remove an amount of carbon monoxide corresponding to the increment due to CO formation in the reduction stage. For that purpose it has been proposed to divide the gas mixture left behind after separation from the powdery condensate, into two portions,iof which a smaller one is detached for reuse in an unchanged condition, whereas the other portion is subjected to a treatment capable of reducing the carbon monoxide content therein; eventually these two fractions are united to lead back into the circuit the gas mixture thus obtained (cf. U. S. Pat-ent No. 2,200,772). l i i It is a particular object of the invention to provide a method in which a portion of the chilling gas used is recirculated in a cooled but otherwise unchanged condition, and a quantity of fresh gas or recirculated gas substantially freed from carbon monoxide, which are referred to as make-up gas in the following, is added to the vapor-gas mixture to be chilled at a point and in a manner to obtain the greatest shock-chilling eciency.

Another principal object of the invention is to provide an apparatus that renders it possible to increase the shock-chilling efficiency by admixing an economical quantity of cooling gas turbulently with the Vapor gas mixture to be chilled without undue restriction to the ow of the gaseous reduction products from the furnace and without there being the danger of plugging.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings.

To accomplish these objects the |invention essentially contemplates that the recirculated gas and the make-up gas are maintained separately and separately Iintermingled with the gas vapor mixture to be chilled while introducing the makeup gas into the flow of the hot reduction products to be chilled at a zone in advance of the introduction of the gas that is recirculated in a cooled but otherwise unchanged condition. The recirculated gas then enters the flow to supply the balance of the required Volume and supplement the cooling eifect of the make-up gas.

Natural gas which is available in large quantities and inexpensive enough to be subsequently burned as a fuel, is most attractive for use as a chilling agent in the practice of the carbothermic method of producing magnesium. For these reasons the present method, too, is particularly adapted to be applied in connection with chilling the vapor-gas mixture escaping from the reduction furnace by means of natural gas, of which than natural gas as coolants, the portion introduced as fresh gasin the case of natural'gas has to consist ofv recirclated coolant which had previously been Vsubjected to a treatment for eliminating or materially reducing the CO currM tent thereof, and which has been cooled down to an adequately lower` temprature' and ,elevated to an adequately higher pressure; Yet in doing so, the make-up gas may also consist of, or contain, a portion of fresh gas, vinn which case ari amount of gas escaping from: the reduction furnace equivalent to the portion of fresh gas" f troduced would have to be rejected.

Thus the make-up gas e'ztlilL-rV low in, orl

free from, carbon monoxide and also in a'coolei state and available under higher pressures and hence' a more efficient chilling agent than the recirculated gas. Consequently inA this way the initial impingement and intermingling of chilling gas and reductionproducts to be cooled takes place between the hottestvapors and the cold.- est gasunder highest pressure. The rate of back reaction is evidently greatest at elevatedV tempeiatures which are only' slightly lower thank the equilibrium temperatures for the operating conditions of the particular partial pressures involved Therefore the lower the percentage of CO in the coolant initially introduced and the more rapidthe initial cooling rate, the more effestive the shock-chilling operation. Whether the make-up gas consists offresn gas `or of ap propriately reclaimed recirculated gas,- all in; all this arrangement results ina saving inl volume as well as in pressure and cooling of the total quantity of gas necessary tegainrthe desired end.

No matter what gas is used, it must enter the chilling cone at a temperature sufficiently below the final shock-chilling temperature, that is approximately `at 206 @LtoA effect acooling without resorting toY circulating impractical quantities of gas. The proportions of chilling ga-scir- Yculated. and make-up gas' introduced on the one hand, andthe entering temperaturesvon the other, havetofbe balanced against each other to arriveV atl favorable' economicall working conditions. The pressure at which. the make-up gas and the recirculated gas, respectively, are elevated. is likewise'y a function of economics to achieve rapid mixing in a limited distance" from the: outlet portithout resorting to excessive horsepower for compression. It is obvious that this,` too, tiesY in with the quantities of gas to be circulated which on1 their part are a functiony of the temperature.

An apparatus which may be used according to the invention for carryingv out Vthe process described' is illustra-tedV by way of example` in the accompanying drawings. y

Fig. l is a longitudinal sectional View taken`v through a chillingldevice: which embodies' the present inventief-ii4 Fig. 2 is: anenlarged fragmentary detail in section of a part eti the rriiier end of tlie device shown in: Fig.` 1'.

Fig. 3f is an elevational view', witnl'parts; in section,l of the device' shown Fig. l as viewed' freni. the right hand end', and.'

Pigna is. a fragmentary isometric' view cf spor tion' of the device showny Fig. 1f, the outer' Shelli part thereof being. removed` to disclose thearu rangementy of partsilii'dden thereby.

'.lfh'el apparatus lshown'. comprises ani shell member I0.

acting in the manner of. nozzles in directing the gas to the interior of the frusto-conically shaped While the nozzle openings herein shown are in the form of slots milled through the 'nozzleY liilat'e,f they may be of any desired shape consistent with their function which is to admit chilling gas' to the interior of the shell l0 so as to cause the gas to' mix violently with the hot vapors passing therethrough. A plurality of circular' ori'ces may be preferable in the zone where theel-ugh pressure make-up gas is introduced, while economically milled slots appear to be entirely` adequate for the introduction of the recirculated gases at relatively lower pressures, which latter mayl contain a small amount of solidv particles owing to-.mperfector damaged dust filters. It appears that dustthatcollects' at the edges ofthe openingstendsV to breakaway and free itself` more readily from the longVv edges of the slots than it does from-circular openings..

The nrembersiK l0 andv il are sin'rounded by' a frustoconical outer shell member;V lf2 spaced fromv the member Hi to form: aA channel or passag-e of conical contour' throughwhich gas may be delivered to-'the nozzle plate Hs The mem v bers l0, Il, and l2 are connected togetherby means present-ly togibe described to form ai unit or inner jacket which is inscrtable in asuitable" recess in the Wall" lisci the ful-nace sotha-t the4v Crucible while thev outer end: thereof projects to a point outside the wal-l of the furnace where it l it connected; with a clust collecting chamber or other dust collecting` and separating device.

As shown in: Figure l the outlet of the walll t3 Y of. the furnace cruoibleisv lured with an annular replaceable insert I4 of graphite or other materi'al resistant tothe erosive effects of the hot reductionv productsV escaping from the furnace. The furnace usually has" an outer metallic sheil 5 spaced from theY cruciblefand'the spacebetween the shellv andthe crucible is -lled with a heat insulating material- 6 which: may be lamp black or other nely divided caritaonac'eous substance- In the present instance' an openingfor the reception. of the chilling cone is definedVV throughfthe furnace insulating material by a, double-walled.truste-conical member 5 or outer jacket whichy is cooled by'a liquid2 coolant suchas oily for itsL own protection and also, for the'E protection of .the chilling cone againstV the fural nac heat. .liev connection is madel between the member F51 andthe furnace wall 5 by means of a .pair of flanges 1;. one' carried Iby the: furnaceY wall; and` the other; bail-ref merrlbe'rY t5. The ine ner endfcf the-member lisis spaced at a short distance from the outer wall or the furnace and'V of the :finely divi-died insulating material' to the interior of the space' occupied byY the' .chilling cone. This loose 'connection between the cene isl Vand crucible permits the' crumble to expand' 'th rsdiallyanu vertically without contacting or dstcrtmgv the cone. The inner end or. the member i! is sumcieritly largeirr `discrete'r' to? permitremcvsl'anc replacement of! the: gra-puits insert .M which; may' becomei eroded or otherwise defective after long-continued service due to the temperature and nature of the vapor which passes through it.

The cooling fluid may be introduced to the interior of the member I5` through `an annular manifold pipe I6 adjacent to its outer end and communicated to its inner end through a plurality of longitudinally extending pipes, one of which is shown at I1 in Figs. 1 and 2. The cooling fluid enters the manifold I6 through a supply pipe I8 and is conducted through the pipes I1 t0 the innermost end of the space through which it is circulated, then flows back around the outside of the pipes I1 and passes out through adischarge pipe I9. The inner ends of the pipes I1 are preferably cut at an angle, as illustrated. to cause the cooling iluid delivered through the pipes to sweep the interior of the space to be cooled with a sort of circular motion and thus maintain a constant movement of the coolant against the surfaces as it flows back toward the discharge pipe I9. The outer end of the double walled member I5 is provided with a flange 20. A gastight connection between this flange and a manifold housing 2I, which is carried by the outer shell I2 of the inner jacket of the chilling cone, is formed by an expansion plate 9 which is in the form of -a flexible metal ribbed annulus fastened `at both edges by cap screws and suitable `gaskets or the like (not shown) for forming a perfect o seal. This expansion plate 9 provides suilicient flexibility to absorb movement due to expansion and contraction between the member I5 and the enclosed inner jacket of` the chilling cone. The inner end of the chilling cone assembly is, as will presently appear, also spaced slightly from the crucible i. e., graphite insert I4, to permit movement in all directions resulting from Vexpansion and contraction. l

The chilling gasis delivered to the outside of the outermost end of the nozzle plate II through the manifold 2l which surrounds the outer shell I2 adjacent to its right hand end and communicates with the space between the shells Ill and I2. To introduce the portions of the recirculated gas and make-up gas separately and at different points in the flow of the gaseous reduction products to be chilled, the supply manifold2l through which the` chilling gas is introduced is divided by an annular wall 22 to form an outer manifold 23 for make-up gas, and an inner manifold 24 for recirculated gas. As shown in Fig. 3 a supply conduit 25 for recirculated gas extends through the outer manifold and communicates with the inner manifold 24, while a supply conduit 26 for make-up gas communicates directly with the outer manifold. The recirculated gas entering through the manifold 24 flows inwardly through -a chamber or outermost compartment between the conical shells I0 and I2 in cooling contact with the exterior of shell Ill and then passes through the slots of the nozzle plate II into the interior of the chilling cone where it mingles with the hot furnace products. On the other hand, the make-up gas which enters the manifold 23 is communicated by pipes such as indicated at 2.1, to the left hand end of the space between the members Il) and I2 andthrough a wall 28 which forms the inner boundary of the main portion of this space and which separates the inner portion of the nozzle member Il from the outer portion thereof. Thus the make-up gas is supplied to a small annular chamberor innermost compartment 29 and escapes through openings in he inner end of the nozzle plate II to mix viostantially unobstructed lently With, and chill, the furnace vapors immediately as they emerge from the Crucible at a point in advance `of the introduction` of the rei circulatedgas. The inner portion of the chamber 29 is dened by a double walled flange 3l) the interior of which provides a casing for the circulation of a cooling fluid and thus protects the entire inner face of the chilling cone from the heat of the furnace. Cooling uid is supplied to the protecting flange 3D through a plurality of small pipes 3| which communicate with an annular manifold ypipe 32 disposed within an exhaust manifold chamber 33 that is formed by a Wall 34 defining the right hand end of the space between the shells I0 Iand I2. The cooling fluid is furnished to the supply manifold through a pipe 35 and flows from the manifold through the pipes 3l, which penetrate the wall 34 and also the wall 28 and terminate, as best shown in Fig. 2, adjacent the innermost end of flange 30 where they are preferably cut diagonally to `induce a circular or sweeping flow within the flange. This coolant discharges through pipes 36 one of which is shown in the lower part of Fig. 1 and which, as` also illustrated in Fig. 4, communicate `with the interior of the flange 30 and with the exhaust chamber 33, from which the fluid escapes through a discharge pipe 31. It is an advantage of the arrangement herein shown that the chilling gas enters through what may be likened to a very large conduit so that a lower initial gas pressure will sullice to deliver a large volume of gas and produce a high nozzle velocity at the nozzle plate II. While the space between the members I0 and II includes the make-up gas pipes 21 and the cooling gas supply and discharge pipes 3l and 36, all as illustrated in Fig. 4 of the drawings, there still remains an unusually large area for the transmission of recirculated gas to the nozzle.

In Fig. 4 the relative positions assumed by the

pipes

21, 3|, and 36 are indicated and the pipes 3| and 36 are shown as provided with expansion bends 40 which serve to absorb any distortion resulting from variations in temperature. Such a bend is preferably eliminated from the p'pe 21, the inner end of which is loosely fitted in a suitable perforation in the wall 28 so that i-t is free to move lineally when subjected to temperatures different from that of the parent member. The sliding t of the pipe 21 where it pierces the wall 28 may -permit leakage of a small quantity of make-up gas through this wall, but this leakage is of no consequence because the escaping gas simply enters the area loccupied by the recirculated chilllng gas.

Fig. 4 also illustrates one of a plurality of spacer plates 4I which may be disposed between the inner and outer shells I0 to brace and maintain them in their concentric positions. The spacer plates and -pi-pe occupying this area may be as numerous as required by `the functions which they perform and yet leave the space subfor the passage of a very large volume of a chilling gas which serves as a coolant in contact with the inner shell I0 and which eventually enters through the nozzles the interior of 'the cone where it chills the furnace vapors by direct contact.

The form of the apparatus herein disclosed permits the use of Scrapers for maintainingthe inside surfaces of the conically shaped chilling chamber free of undesirable deposits. Likewise, spray devices may Ibe employed for wetting and rendering inactive lpyrophoric materials within the cone prior to itsbeing opened to the atmose ousmedia Iemeuging from fai `furnacewhereinY the i :convergent end of lsai-iifcone is positionewadja- 'cent the furnace opening :comprising ani inner lc-:enfically "shaped I:jacket and "an A"outer conicaliy shapedjaeket, V'said- Vinner iacketecomprising independent innermost-and" outermost compartmerits; said 'innermost HVc'ompartmentA "being Cloicated :at the 'convergent -iportion^^offnthe inner A"ra'e'lret said -`outermost`compartmentcomprising ai 4rsubstantially -hollow '-"chambe-rextendingmth'e length oil the cone exceptor 'they nd-thereofadiacentfthe-"convergent portion" of 's'aid`-cone, a

'manifold and conduit yarrangement "for supplying chilling media to said outermost-compartment, a ==pluraiity of conduitsconnected` to Asaid 4innermost compartment Varid-'runningE throughi lsaid buterrnost*compartmentf'atapted to 'supply independent chilling -mecliato said "innermost compart/ment, rsaid outermost and innermost" 'compartments having slots adjacent the -'convergent vfend 'of said fconefor passage of chillingrnediaiinto contact 'with gases v 'emerging from 'the' `ifurnacle, and separate supply and ldischarge conduits' extending through said innermost fandoutermost compartments "and-1 ext-'endingy `'inwarrily- V'to form the @convergent end voftheufchilling cone `vand adaptedI to l'carrycooling --iiiiiid forremovirijgheat treinl fthewconi-z,v andfmeans for @supplying cooling fluid to :said `outer'jacket.

1 l2. A chilling-cone for-use irrchilling-hotgaseous fined-ia- .emerging trom *ai turna-cef wherein the convergentiend of said-'teorie is ps'itionedadjacent ithe Iturnacejfopeningcomprisingfan inner coni'eally 'shaped Vgacket and y an "outer f-conically shapedlijacket, :said: :inner ljacketcomprising independentv :innermost and `:outermost Y'cormciartgmentswgsaid xinn'er-most compartment-beinglocatedifaat the :convergent portionV of Ithe vinner gacketxsaiol@outermost fcompartment comprising aws'uhstant'ially hollow v.Jch'am'loer extending-the length of the cone except for sheend thereofladf jacentsthe'rconvergent portieri 'of lsaid KHKcone, a manifold Shousing at theidiverg'ent -endoisafii innerajacketf and :extendingsexteriorlythereof como uprisingeconcentrically,arrangedI manifolds, `errev of said manifolds terminating, in and lying linfoperr communication with fsaid outermost compartment for supplying chilling emedia thereto, a 51plurality ofyconduitsaconnected to the futher et isaid-fmanifolds @aesing .through fsaifdgnut'ermost' compartment fvarrdeconnecting:'with aicliinnermostcemparti-nent- ;.toat-hereby 'supply independent fchilili-n'g medi-a .ethereto `said @utenm'ost l and inner-most compartments having slots-,:adjacentivthe acenverg-ent vend ofi fsaidiconeforpassage :of chilling media into feontact iwith gases enlargingl "from the tui-nace, and:separateisnppiiyiand dseharge'fcondui-tsrentend-ingl ithroughfsaidiinnermost an'dcutentrust-.compartments and:l extemiingrinwardiy to form the fcontergent fend of/the chiliing :cone-and adapted :to: carry coolingxidzfor reni-aviri'gfheeit ftieillwhollowchamloer extending-*the iengthef `the corre except lfor theend'thereoi adjacent` theconvergent portion of said cone' andenes/'ing stiffeningr-member's-fvfor lsupporting' the wallsthereof, amanifold andconduitarrangement for supplylin'g"=ehil'1ing`media to the second compartment, I,a plurality 'of conduitsI connected tothe Tirst'icompartment vand running through 'the vsecond Icompartrrientl adapted `to supply independent chill# fing tired-ia to the -rst compartment, 'sad rst'and 'second'compartments having slots adjacent *the Y convergent endo'f the cone iurpassa'ge of' chill ingfm'edia in-to contacty with gases vemerging from the furnace, and `separate supply :and :discharge conduits :extending through 'the tfirst i' and :second compartmentsand 7extending 4'inwart'ily to form the of-ltlre `con-e at ithe`convergent Aien'd Lthereoi and adapted to carry; cooling lfluid for removing heat therefrom.

"4; -Achilling-cone for usein chilling hot gaseous rnediaemerging *froma furnace'wherein the .convergentend yofsaidconeispositioned 'adjacentthe 'furnace openingcomprising a Vclinically'.shaped' iacket having two 'independent `iirst.A and second compartments, the `iirst compartment 'being 'located -'at the convergent end -otthe 'jacket,the second compartment Acomprising a 'substantially hol- .lowchamber' extending the length" oi the A.cone except for the end thereofadjac'ent the ,convergent*portion loi "said ycone andhaving .stiffening-membersfor 'supporting theiwalls thereof, .a maniild-housing atthe'divergentend:of the -.cone comprising a pair. `oi maniiolds, onefotfwlfiich communicates wwith the second "compartment .for supplying chil-ling media thereto, a plurality. ,of conduits connected 'to' the l,other manifold which paSsf-through'the second' compartment .taconnect'with the 'first compartment and Aarel-ladap'ted toSupply chilling media thereto, said i'lrst .and secondcompartm-ents having slotsl adjacent ithe eonvergent'end Aof the cone for ypassage ot chillirrg'media into Contact With Agases emergingfrom th'efurnace, and separate .supply and discharge conduits extending through` the .rst and second compartments and extendinginwardly -tofiorm the tip of the cone at .the.convergentgenelthereof andY adapted to carry coolingmflud for :removing heat therefrom.

f5.' In Aa furnace oi vthe .type employed ine-high temperature operations wherein-.thefturnacegpruducts" are Ladap'ted to Y heacted -onimmediately upon their emergence from ,the iurnacevthelcomhinatiorrl including, a .furnace wall; having fan opening therein, fa `graphite-:linerringnadtmted to be'ins'erted in the .portion ofatheturnacefopenin'g "adjacent thefurnace .crzuciblez rand. to serve as'th channel through which .the furnace prod-- uctsL pass, a conical Aunimpositioned :in-:the` onen-v ing 4and occupying the. remainingtportionathereef comprising an yinner conicall-y. shapedijacketrand an 'outer' conically .shapeeljacket saidinnerijanket comprisingindependent innermost and outermost compartments, said innermostcompartmentabe- .ingfflocated a'tjthe convergent `portionelointhe inner vjacket, said outermost compartment comprising a substantially hollow chamber extending? the length oi the cone except ior the end thereof adjacent the convergent portion of said cone, a manifold and conduit arrangement for supplying chilling media to said outermost compirtment, a plurality of conduits connected to said innermost compartment and running through said outermost compartment adapted to supply dependent chilling media to said innermost mpartment, said outermost and innermostcoml artiients having slots adjacent the convergent 'gend of said cone forv passage ot chilling media ,into contact with products emerging frornthe iurnace through said graphite ring, separate sup- Aply and discharge conduits extending through {said innermost and outermost compartments and extending inwardly to form the convergent lend foi the chilling cone and adapted to carry cooling uid for removing heat trom the confegfsaid outer conically shaped jacket having an Ainside diameter at the convergent end thereof greater than the outside diameter of saldgraphite liner ring whereby removal of said outer jacket is rendered unnecessary upon removal of said ring, and means for supplying cooling iluid to said outer jacket.

DONALD A. RHOADES.

REFERENCES CITED The following references are of record in the