US2348194A - Metal vapor condensation - Google Patents

Description

May 9, 1944- R. G. CRANE ETAL 2,348,194

METAL VAPOR CONDENSATION Filed June 5, 1942 hi n f i W5S;

Il @w l l| f! I I l w QI gm l\ l il; I l f INVENTOR ioland rane BY Melville Per/fia.;

lPutente'l'l May9, I l Y w condenser and vmethod of condensing zinc 0, Whi ch is supDOrted horizontally .on roller.

Marax. varon coNnENsArroN y f Roland G.V Crane, .-Woodbrid'ge, and Melville L/ff Perkins, Barber, Nfl., assixnorato American Smelting and 'Refining Company. New York, z N. Y.; a corporation olNcw J rsey f' Application June l3, 1a4z,l'seri'a1i\i. 445,514 I 'sclaims. fletes-:14) a l Thisinvention relates to the metallurgy` of.,l I' denseryas illustrated in Figure.V 1, consists o faf zinc and more particularly to an improved .hollow cylindrical member,generallydesignated UNITED As'A-TAE'S 1PA-rear vapors formed by smelting zinc containing sub means-l I.' `Duringthe processing treatment, the' stances. The invention is adapted for use with- 5- condenser is rotated.- .Mechanism suitable for any of the conventionalfurnaces but is espe#V eiectingthisis shown inFlgure 1 andcomprisesf cially useful in condensingmetal vaporsjfrom aringjgeariz which-is' attached to the-condenelectric arc smelting furnaces.` I se'r and arranged to` be driven A-by` afmotor I3` In the recovery of metallic zinc by thermal through' theinterconnecting chain -means M, l reduction ofzincy substances 'with carbonace' jl0 "Hot metal `Vaporsare conductedfromy a -smeltous reducing agents, zinc is vaporized and conf- V ing furnace'generally designatedat- I5 into fthe? ducted to a condenser whereitis condensed tof con'clen'serflty"15s/ ay of the conduit I6.. 'I his con# liquid metal. Many different types of condensersf duit is preferablymade ofrre'fractory material; and smelting arrangements have vbeen proposed andforms'fan extension of the-furnaceilue I 1." heretofore, including` rotary devices, but suoli l5 Toform a gas'tight connectionbetween the devices have been primarily designed and used Ato outer end of the conduit IB andthe condenser. recover metallic zinc from blue -powder..- f the x'n`e' mbe'r I6 is -telescopicallynt 'into the ther, prior to our invention, in' spite 'or' all iprecylindrical f vextension I8 of the condenser, -as' l cautions, it has been practically impossibleV to shown in Figure 1.` l Asbestos packing'-is corn-4 condense metal vapors, such as zinc, from an'arc. 20 pressed-into the space between the outer walli furnace without formingjexcessive amounts of of the conduitl andthe circumjacentextension blue powder which requires resmelting or special J I 8 offthe condenser and isljleld` inplace by,I a treatment for the recovery -ofits metallic zinc retaining ringflnemberfzz. Suiijztblev meansis", content. a also'. pro vi ded` -for '-1 'I lowing cooling; Water over It isv the principal object of this invention to 25' the outer surface o'ffthe memberlikasfillus-fI overcomethese dllculties andprovide af con-1v tratedfin Figure 1,-.tfo improvethe'sealjbetween denser and method of treating `zinc vapors wherel C the` parts graphite disc 2l of' suitable 'thick- -i by they can be condensed vdirectly to metallic nessisinterposedbetweenthe outerend'ofthefg, zinc While avoiding the formation: of a high, Jjonduitfl'and the condensertoassist in forming. ,1 proportion of'blue powder.`l 3 0"agastight" jointf Another object is to providev an improve'dro- -condIlSr 'f'comprises v`'armetal shell-25? tary condenser whicnis' operable to eiectsub- :f havingv At 1'1e' jen iiclosing,plates-'21." The shell-isi: stantially instantaneous 'condensation o f the equippedfwith tiresli'orengaging the 'supportmetal vapors upon enteringthecondenser-.f2 v. ing rollerfmeansujI'jduringfrotation ofth 'con= Another object is to devise a' method iofcool- :zadensen-jrlofprftyfhf metaf she11,-- i|j 1s'=1inedi ing zinc metalvapors as-emittedfrorn'- en -arc: gmconcalrbideor smelting furnace with ysuch rapidity that oxif th- 'jike' maf-,gal ,whfhsbgtaau'y. `in; dation of thezinc to form'bluepowder in ap permebilgt:thfmtlvpo-S.beigcodensei preciable amountsis avoidet'l-v v u i Wherefurther-'protection i".-z d`e'sired, al'ay'er of. f; other ObJectS and advantages ofthe inventien 4!! micaor' asbesto'rs not shown; may be placed m E Wm become apparent fffelihe follpwng'detiled: afweer-1. usf 'Quiet nie-ar steunend-stas fe: f l lrpti vtfin -cn-'z-cion' mhp??? a?" .frefforrfl-1inms,e2.iA bafhfof P601.' efrliquid' p ny g g"1 W 1 metal- 3551smamtameazmtneiower portion o'ftion of a condenser. constructed'in accordance; l f, f. -1 with the'present invention, the condenser being denser'fliguid ,metalli-s '-cgminuauyfsplas'hd' shown connected toan arc smelting furnace fnfted-and-hurled ffom'tthebg'thmtothgspa which is illustrated diagrammatically andshown ftherapoye''produmg anatmospher med with partly broken away; Y 1 mvmg, droplesy'finqud'f-metal ITO.. pr`` Figure 2-is avertical cross-sectional view taken; lit)y Vide, means for: acgmpnshmgimsf the' Gln-:ula: substantially on the line 2-2 of- Figure 1:7; Sid? Wan-@f thefondnser L1 5 m9419119 of spaced Figure 3 is an enlarged perspective .view of I'WS 0 5 bamelblQQkS .fajuwhch'ldw Shped`-t9 I we f the bames which are shaped tothe 'fitted f splash and dip up- 11qu1.d"mew1fromthebotwm together to form a lining for the. condenser.' part of the condenser as it ls-rotated Referring to the drawing in detail, the cpud6, The cames'-arelcnstructedffromggrdradby material, shaped and fitted together. as illustrated in Figures 2 and 3, to form a substantially continuous limer wall. 'Ihis baille wall construction preferably extends throughout the entire length of the condenser inasmuch as we have found by-tests that where the condenser is made up oi' plain unbamed sections the resultant emciency of the 'condenser is lowered. Each baille member qomprises a shoulder or abutment 4l which protrudes inwardly and is inclined to the curved backing wall portion l2. Tongue and groove sections 4I and Il respectively are provided at the opposite ends of the curbed backing portions to form tight joints between the bane blocks.A An elongatedcup or trough I8 is formed on the outer sloping side of the abutment part 4I of each baille which, during rotation of the condenser, is vfilled with liquid metal from the pool 36. In this manner, as the condenser rotates, liquid metal is picked up from the bath and carried into the upper part of the condenser where the metal is discharged producing a series of liquid metal cascades to which the incoming hot metal vapor is subjected.

To eliminate end-to-end surging of the metal bath resulting in excessive discharge of, `liquid metal therefrom w hich would lower the eiliciency of the process, the inner end wall sections of the condenser are corbelled, as shown at 4l in Figure 1. This improved construction efi'ectively inhibits surging of the liquid metal bath permitting the condenser to be rotated at high speed while the amount of the liquid metal in the bath remains substantially constant.

Heat is dissipated rapidly by our rotary condenser arrangement, so that, in most installations, it is necessary to supply heat to the exterior of the condenser -to maintain the liquid metal bath at the proper temperatin'e. Suitable means may be provided for supplying heat, such as by the use of a burner, as shown at Il. Where the temperature ofthe metal vapors entering the condenser is such as to require cooling of the condenser, conventional means such as shown at Il, may be utilized in place of the burner for inches and a length of seven feet was directly connected to la top-arc smelting furnace. The condenser which was partially filled with liquid 'metal zinc was rotated at a speed of 45 R. P. M. Approximately 1600 pounds of zinc metal was recovered per day using a charge assaying about 60% zinc. This charge consisted of a mixture by weight of 100 parts brass furnace dust calcined and screened to -5/4". 16 parts coke of and 5 parts calcareous slag material. Suflicient heat was supplied to maintain the liquid metal bath at about 500 C. Metal vapor at a temperature of around 1000 C. was condensed with about 6 to 12% of the zinc entering the condenser emerging in the form of blue powder. This represents a decided improvement over results attained heretofore using the conventional conapplying a spray of water or the like coolingv j medium to the outer walls of the condenser.

In smelting zinc `materials in an arc furnace. there is a tendency for many compounds of moderately low vapor pressure, such as PbC, PbS, SnO, ZnO and the like, to volatilize in the intense heat of the arc. The more reducible of these are immediately acted upon by the hot metal vapors and by carbon monoxide Awith the resultant formation, either directly or indirectly, yof C02. The carbon dioxide gas which does not Example A condenser, constructed as illustrated and described, having an inside diameter' of twenty densing mechanism wherein from 30 to 75% of the zinc is recovered as blue powder.

To initiate the process, the condenser is heated to around 500 C. and the lower part of the condenser is filled with molten zinc 36. As metal vapor passes into the condenser and is recovered as liquid metal increasing the size of the metal bath 36, a like amount is drawn of! through the openingv 52 or is intermittently tapped from the condenser. During the process the lcondenser is continuously rotated at a substantially coxfstant R. P. M. Preferably, the condenser is rotated at between and 5 4, of the critical rotational speed or that at which the liquid metal would centrifuge. This critical rotational speed for any given size rotary drum-like member has been authoritatively represented by the following formula:

54.19 1/ Internal radius of the drum in feet Rotation of the condenser at this relatively high lspeed during the process has been found to be a salient factor in obtaining the improved results. The metal vapors which leave the arc furnace at a temperature of about 1100" C. enter the condenser at considerable velocity and are forced to take a twisting, spirally extended path therethrough. Intimate intermixing of the va` pors with liquid metal zinc at a temperature below the dew point of the metal vapor is effected by subjecting the vapor to a torrential shower of liquid zinc falling in cascades from the top portion of the condenser. This enveloping and uniform intermixing of the metal vapor phase with the liquid zinc combined with the vigorous splashing and sloshing created by the bailles travelling into and out of the pool of metal in the lower part of the condenser, produces an intense scrubbing action on the metal vapors and mechanically disrupts the metal condensate fllms on the droplets of zinc causing the same to coalesce to liquid zinc and decreasing to a minimum the metallic zinc content of the small amount of blue powder formed. In order to secure the best results, it is necessary that suiiicient amount of liquid-metal zinc is kept in the condenser so that the maximum effect of the moving. bales can be obtained at all times.

Although the improved condenser and method is particularly useful in connection with the production' of zinc metal, it will be obvious that the invention may be advantageously employed to condense other metal vapors, such as magnesium and the like, toliquid metal form as well as vapors comprising a mixture of different metals for example, lead, zinc, tin, etc.

While the preferred form of apparatus and method of practicing the invention has been described in detail, it is to be understood that the procedure and form of condenser may be modified by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. An improved condenser for condensing zinc metal vapors formed in an electric arc smelting furnace comprising a rotatable chamber into which the hot metal vapors from the furnace are conducted, means for rotating said chamber, a bath of liquid zinc metal lling the lower portion of said chamber, means comprising spaced interlocked baille blocks forming the inner wall of said rotating member for splashing and hurling liquid metal from said bath into the space thereabove to maintain the same filled with falling droplets of liquid zinc metal and to produce an intense scrubbing and substantially instantaneousquenching action on the metal vapors upon their entry into said chamber, said chamber having corbelled end-wall sections to inhibit endto-end surging and premature discharge of liquid metal from said bath as said chamber is rotated.

2. In the art of producing zinc by reducing zinc bearing substances in an electric arc furnace and condensing the metal vapors emitted therefrom,`

that improvement which consists in directly subj`ecting the zinc vapor from the reduction operation without intermediate conditioning treatment to substantially instantaneous quenching by intimately intermixing said zinc vapor with a torrential shower of moving droplets of liquid zinc while intimately contacting it with a vigorously agitated bath of liquid zinc.

3. The process of producing zinc which consists in heating a charge comprising zinc containing material and carbonaceous reducing agent in an electric arc furnace, conducting the zinc vapors formed in the arc furnace directly withoutintermediate treatment into a rotary condenser comprising a cooling shower of liquid zinc which is maintained over a bath ofl liquid zinc metal to thereby quench the zinc vapor and condense the same to liquid zinc metal without ap-v 4. The process of cooling and condensingzlnc Vmetal vapor at a temperature of approximately vaporinto a chamber lled with moving droplets l of molten liquid zinc maintained over a bath of liquid zinc metal contained in said chamber, and subjecting said droplets to attrition by intimately contacting the same with said bath of liquid zinc while it is vigorously agitated to thereby mechanically disrupt the films formed on the droplets to recover zinc as liquid metal and controlling the temperature of said molten zinc so as to quickly absorb the heat of condensation whereby the zinc vapor is condensed to the liquid phase in such a short period of time that oxidation of the zinc to form 'substantial amounts of blue powder is inhibited.

5. An improved condenser for condensing zinc vapors formed in an electric arc smelting furnace to liquid zinc metal comprising a rotary chamber into which hot zinc metal vapors are introduced directly from said arc furnace, said chamber being adapted to contain a bath of liquid zinc in the lower portion thereof, spaced inner baflle wall means protruding inwardly and extending substantially throughout the length of said chamber, said baffle means having an integral backing wall which is curved to flt the circular wall of the chamber, said backing walls being interlocked in such a manner to form a continuous lining wall for said chamber, mean for rotating said chamber at a relatively high uniform rotational speed to cause portions of the liquid zinc to be picked up from the bath and carried to the uppermost part of the rotating chamber by said baille wall means and.cascaded through said zinc metal vapors in the form of droplets as said vapors are conductedv into said chamber,

said zinc vapors being cooled to the dew point with such rapidity that oxidation of the zinc to form blue powder in appreciable amounts is avoided, said chamber having corbelled end-wall sections to inhibit end-to-end surging and premature discharge of liquid metal from said bath as said chamber is rotated.

RCLAND G. CRANE. MELVILLE F. PERKINS.

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