US2457547A - Internally cooled zinc condenser - Google Patents

Description

Dec. 28, 1948.

E. C. HANDWERK ET AL INTERNALLY COOLED ZINC CONDENSER Filed Dec. 5, 1945 2 Sheets-Sheet l A xnxx-:

. INVENTORS BY ,317ml 'c/ITIHM f" ATTORNEYS Dec. 28, 1948. E. c.,HANDwERK ETAL 2,457,547

INTERNALLY COOLED ZINC CONDENSER 2 Sheets-Sheet 2 Filed Deo. 5, 1945 lllllllllllllllllllll|l|l advantageously Patented Dec. 28, 1948 UNITI-:D STATE 2,457,547 INTERNALLY COOLED ZINC CONDENSER Erwin C. Haupt, Palmerton,

Jersey Zinc Company,

C. Handwerk, Geolrge a., New York, N. Y., a corporation of New Jersey Application T. Mahler, and Harry assignors to The New December 5, 1945, Serial No. 633,004

2 claims. (c1. 26e-15) This invention relates to condensing zinc vapor, and has for its object an improved apparatus for condensing zinc vapor.

In the customary pyrometallurgical practices of smelting zinc ores, the zinc is recovered as molten metal by condensing the zinc vapor contained in the gaseous products of the smelting operation. The condensers ordinarilyl used for condensing the zinc vapor produce a considerable amount of zinc dust or blue powder which usually is returned to the smelting operation. For example, the condensers heretofore use'd with modern externally-heated vertical zinc retorts commonly produce blue powder or zinc dust amounting to 7 to 15% of the output of zinc. It is ordinarily necessary to recirculate this blue powder through the vertical retorts, since it is usually not in the form of salable zinc dust and is difficult to melt down to liquid zinc with the use of the heretofore available equipment. A particular object of the invention is the provision of an improved apparatus; for condensing zinc Vapor diluted with ordinary smelting gases, such as carbon monoxide and the like, with the formation of only a minimum amount of blue powder. The invention is particularly adapted for use with smelting equipment of relatively large capacity such as modern externally-heated vertical zinc retorts or electro-thermally heated retorts.

The condenser of the invention comprises a condensing chamber having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc. Artificial cooling means are positioned within the condensing chamber, in the path of the gaseous stream containing zinc vapor passing through the chamber, and a rotor within the chamber is adapted when rotated to dip into the molten zinc and throw a substantially continuous shower of molten zinc upwardly into the chamber in the, region of the artificial cooling means. The rotor may advantageously be generally cylindrical with circumferentially spaced peripheral pockets that successively dip into the molten zinc as the rotor is rotated, such as described in our copending patent application Ser. No. 626,508, liled November 3, 1945. The artificial cooling means is adapted to directly cool the gaseous stream containing zinc Vapor passing through the condensing chamber, and means are provided for controlling the heat dissipated from the condensing chamber by the artificial cooling means. The artificial cooling means may be a metal shell depending into the condensing chamber from the roof thereof, and through which a cooling medium is circulated. The rate of flow of cooling medium through the shell may be regulated, to control the heat dissipated from the condensing chamber, by a temperature responsive means operatively associated therewith and with the molten zinc in the chamber.

The foregoing and other novel features of the invention will be best understood from the following description taken in conjunction with the accompanying drawings, in which Fig. l is a longitudinal sectional elevation of the condenser of the invention,

Fig. 2 is a transverse sectional elevation on the section line 2-2 of Fig. 1, and

Fig. 3 is a top plan View of the condenser.

The condenser of the invention as illustrated in the drawings comprises-a generally rectangular condensing chamber 5 having a zinc vapor inlet 6 approximate. one end and an exhaust or waste gas outlet 1 approximate its other end. The condensing chamber is lined with suitable refractory material and is interiorly provided with artificial cooling means. While the artificial cooling means may be of any suitable type, satisfactory results are secured with a bayonet water-cooler depending from the roof of the chamber. As illustrated in the drawings, a metallic (e. g. iron) cooling shell 8 having water inlet and outlet pipes 9 and I0, respectively, is operatively supported in the roof of the condensing chamber, and depends into the chamber to a short distance above the normal molten Zinc level (a) therein. The shell 8 should preferably not dip into the bath of molten zinc in the chamber, in order to avoid freezing the zinc bath if the supply of zinc vapor should be cut oil:',or, alternatively, any portion of the shell (or cooler) that traverses the zinc bath should be heat insulated. The portion of the shell adjacent the roof of the chamber is surrounded with heat insulation I I zinc will not bind the shell to the roof and thereby prevent its removal.

The condensing chamber 5 communicates, beneath the lower edge of its end wall I2, with a discharge well I3 having an overflow spout I4 determining the level (a) of the body of molten zinc in the condensing chamber. A collecting trough I5 receives the molten metal overflowing the spout I4 and conveys it to casting equipment or the like. The lower portion of the end wall I2 dips "into the molten metal between the condensing chamber and the discharge well and seals the condensing chamber from the atmosphere at this point. The volume of molten zinc in the condensing chamber is thus maintained subso that frozen to the bore at one end of the stantially constant by continuously withdrawing molten zinc from the chamber as zinc vapor is condensed therein.

A generally cylindrical rotor I6 is mounted within the condensing chamber 5. The rotor is carried by a hollow or axially-bored metal shaft I1 mounted in bearings The shaft I1 is horizontally disposed and extends through the side Walls of the condensing chamber between the zinc vapor inlet and the gas outlet in a direction generally transverse to the direction of gas ow through the chamber. The rotor may be constructed of graphite, silicon carbide or other suitable refractory, and ,is separated from direct contact with the shaft I1 by a sleeve I9 of insulating cement. The shaft I1 has a plurality of circumferentially spaced peripheral ribs embedded in the cement sleeve, and the bore of the rotor has a plurality of spaced recesses 2| lled with the cement of the sleeve, so that the shaft, sleeve and rotor are effectively keyed together. The shaft I1 is cooled by the flow of a cooling medium, such as water, through its axial bore, the cooling medium being supplied shaft by a pipe 22 and discharged from the other end through a pipe 23.

The peripheral surface of the rotor I6 has a plurality of circumferentially spaced pockets or cups 24. The shaft I1 is positioned at a level substantially above that of the molten zinc adapted to be held in the chamber 5, and the rotor I6 is of such outside diameter that its lowermoslt pocket is beneath the molten zinc level The rotor is rotated by means of a pulley secured to the shaft I1 and operatively connected to a suitable source of power, such as an electric motor (not shown).

The condenser is provided with effective seals for preventing the leakage of zinc vapor through and the freezing of molten zinc in the apertures in the side walls through which the shaft I1 extends. Thus, the rotor I6 has a laterally extending sleeve 26 at each end thereof surrounding the cement sleeve I9 where the latter extends through the wall of the condenser. The rotating sleeves 26 extend through stationary sleeves 21. Each stationary sleeve ance with the rotating sleeve 26, and is elsewhere spaced from the rotating sleeve to provide an elongated inner annular space 29. The outer ends of the concentric sleeves I9, 26 and21 are enclosed in a gas seal comprising a tight fitting cap or housing 3| having a gland bushing 32 through which the shaft I1 extends. A suitable non-oxidizing gas, such for example as a portion of the exhaust gas exiting from the condenser through the outlet 1, is pumped into the caps 3| through the inlet pipes 33 to maintain a sufficiently high gas pressure within the caps to prevent zinc vapor and diluting gas from flowing outwardly between the stationary sleeves 21 andl the rotating sleves 26.

. The sleeves 26 and 21 are so shaped that molten metal does not accumulate in the elongated annular space 29 between the sleeves, but on the contrary runs out by gravity into the molten zinc at the bottom of the condensing chamber. Thus, the ends of the stationary sleeves 21 extend into annular grooves 34 in the ends of the rotor I6, and the lower portions of these ends are internally beveled or thinned to form spouts 35 for discharg ing by gravity any molten metal entering the space 29 -between the sleeves. The annular I8 outside the condenser.`

21 has a constricted por-v tion 28, near its outer end, to provide a close cleartion of the end of each sleeve 21 is beveled or thickened to form a backwardly sloping spout 36 for guiding any molten metal falling on or wetting the upper surface of the sleeve towards the condenser wall and thence downwardly over the sleeve to the body of molten metal.

lIn the operation of the condenser illustrated in the drawings, a continuous stream of gas containing zinc vapor enters the condensing chamber beneath a depending baille 31 of the inlet 6, and ows in a generally horizontal direction through the chamber and beneath a depending baille 38 to the exhaust gas outlet 1. Where the entering gas is derived from a'vertical retort smelting operation it will have a temperature of around 820 to 900 C. and will generally contain around 30 to 50% zinc vapor diluted for the most part with carbon monoxide gas. Dissipation of heat from the condenser is controlled by regulating the water, or other cooling medium, owing through the interior cooler 8, the operating temperature within the condensing chamber being thereby maintained at about 500 to 550 C. Since the operating temperature of the condensing chamber is indicated by the temperature of the moltenzinc in the chamber, the articial cooling may advantageously be regulated and controlled by that temperature as obtained from a suitably positioned pyrometer or other temperature measuring instrument. The contemplated condenser temperature is preferably maintained automatically by means of a pyrometer 39 positioned in the bath of molten condensed zinc (preferably near the discharge end of the condenser) and operatively associated with a valve 48 of the inlet pipe 9. The rate'of flow of the cooling medium through the cooler 8, and hence its cooling effect is automatically controlled by the pyrometer so that the temperature of the body of molten zinc in the condensing chamber is held within a desired predetermined range, thus controlling the operating temperature of the condensing chamber.

The rotor I6 is rotated at a relatively high speed, say around 100 to 150 R. P. M., clockwise as viewed in Fig. 1, so that the pockets 24 in rapid thrown laterally of molten zinc into the entering gas stream. The pockets 24 have a generally scoop-like section with a relatively long advancing fiat section and a shallow semi-circular depression at the inner end or bottom of the pocket. The pockets terminate short of the circumferential peripheral ends of the rotor, so that little or no molten zinc is against the side Walls of the condensing chamber, although the shower of molten zinc is thrown upwardly substantially completely transversely of the chamber. The upwardly-directed and rapidly succeeding sheets or showers of molten zinc splash into the shower or rain of molten zinc particles falling through the chamber. and also splash against the cooler 8, the bullies 31 and 38, and the roof of the chamber, with the result that the condensing chamber is substantially filled with sheet-like showers and lmoving particles of molten zinc which form ideal anzu? about 5,000 B. t. u.s per minute from th condenser, a relatively small cooler is adequate for condensing large amounts of zinc.' Instead of the automatic control -hereinbefore described, the ilow of cooling medium through the cooler may be manually controlled from pyrometer readings.

Cooling of the shaft I1 permits the use of a metal shaft, and the sleeve I9 of'insulating cement inhibits appreciable cooling of the condensing chamber by the cooling medium flowing through the shaft, and eliminates any thermal stresses in the rotor` I6. The special conflguration of the stationary sleeve 21 prevents the co1- lection and freezing of zinc metal :in .the close clearance between the sleeves 26 and 21, and consequent stoppage of the drive shaft. The gas seals prevent the iniltration of air and the escape of zinc vapor through the 'rotating contact between the sleeves 26 and 21, and thus insure free relative movement of these sleeves.

While the invention is particularly applicable to' the condensation of zinc vapor from the gaseous products of zinc smelting operations carried out in externally or electrically heated retorts, where the zinc vapor content is relatively high, itis also applicable to the condensation of zinc vapor from larger relative amounts oi.' diluting gases. For example, the invention may be advantageously applied to condensing zinc vapor from the gases iproduced in zinc smelting' operations carried' out in blast or cupola furnaces, where the zinc vapor 3 condensing chamber provided with top, wall and bottom members and having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc, a cooling shell depending into said chamber from the roof thereof, a horizontally disposed shaft extending through the' walls of said chamber and mounted in bearings outside the chamber, means providing zinc vapor and molten metal seals where said shaft extends content of the gas may'be as low as 2 to 5%, provided the carbon dioxide content of such gases is low enough and if the temperature is sumlclently below the zinc dew point. In all cases,

lshowers of molten zinc throughout the entire. gas stream and thus` splashes molten zinc on the cooling means wherever located between the bames 31 and 38 above the metal bath. We claim: y L A condenser for zinc vapor comprising a through the walls of the chamber, va generally cylindrical rotor having peripheral surface pockets secured to said shaft within the chamber with the lowermost pocket beneath the level ofthe molten zinc adapted to be held in the chamber, and means for rotating said shaft so that the successively ascending pockets of the rotor are caused to throw an upwardly-directed shower of molten zinc into and substantially completely transversely of the chamber in the region of said cooling shell.

2. A condenser for zinc vapor comprising a condensing chamber provided with top, wall and `bottom members and having a zinc vapor inlet and a gas outlet and adapted to holda body of molten zinc, a cooling shell depending into `said -chamber from the roof thereof, means for circulating a cooling medium through said shell, a rotor provided with peripherally disposed pockets capable. when the rotor is rotated of dipping into the body of molten zinc'and of throwing a substantially continuous shower of moltenzinc upwardly and substantially completely transversely of the chamber in the region ofsaid cooling means, and'means for rotating said rotor.

HARRY C. HAUPT.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 1,530,154 Casparl Mar. 17, 1925 1,955,269 Anetsberger Apr. 17, 1934 2,060,070 Hansgirg Nov. 10, 1936 2,091,159 Persons Aug. 24, 1937 2,117,410 Y Erbach May 17, 1938 2,219,826 Swinburne Oct. 29, 1940 2,288,819 Nevel Apr. 15, v194:1 2,348,194 Crane May 9, 1944 OTHER. REFERENCES The Chem. Age. Nov.- 4, 1944. pages 447 and 448.

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