US2457545A - Condensing zinc vapor - Google Patents

Description

INVENTOR 5 ATTORNEYS Dec 28, 1948 E. c. HANDWERK ET AL CONDENSING ZINC VAPOR Filed Nov. s, 1945 2 shams-sheet 1 fsw/N C. #Amon/RH Gama E' MAH/ E@ Ha Rm C. HAL/P7 Dc. 28, 1948. E. c. HANDWERK ETAL 2,457,545

CONDENSING ZINC VAPOR 2 Sheets-Sheet 2 K..` R@ M EE s W L T R @Hpm NAUFN; AMAV 1 f/.J/.Hm f@ vm NGV. Y. /RR B i w. .l l A. x L m |m. Hmmm F ATTORNEYS Patented Dec. 1948 A UNITED STATES PATENT OFFICE CONDENSING ZINC VAPOR Application November 3, 1945, Serial No. 626,508

11 claims. l

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 Arecovered as molten metal by condensing the zinc vapor contained in the gaseous products of the smelting operation. The condensers ordinarily 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 used with modern externally-heated vertical zinc retorts'commonly produce blue powder or zinc dust amounting to 7 to 15% of the output of zin-c. It is ordinarily necessary to reclrculate this blue powder through the Vertical retorts, since it is usually not in the iorm of salable zinc dust and is diiiicult 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 smeltnig 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. A generally cylindrical rotor having peripheral surface pockets is rotatably mounted Within said chamber with its axis substantially horizontal and with its lowermost pocket beneath the level of the molten zinc adapted to be held in the chamber. Means are provided for rotating the rotor so that its successively ascending pockets lare adapted to pick up in rapid succession and throw into the chamber in a substantially continuous and upwardly-directed shower small amounts of the molten zinc held in the chamber. The rotor is mounted on a power driven horizontal shaft transversing the condensing chamber at such a. level that its peripheral pockets successively dip into the molten metal as aforementioned. In the preferred construction of the condenser, the rotor shaft is artificially cooled and is mounted in bearings outside the condenser proper, and novel sealing means are provided where the shaft passes through the Walls of the condensing chamber.

The foregoing and other novel features of the invention will be best understood from the fol- 2 lowing description taken in conjunction with the accompanying drawings, in which Fig. 1 is a longitudinal sectional elevation of the condenser of the invention,

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

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

yThe 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 lend. The condensing chamber is lined with suitable refractory material and is exteriorly equipped with air or water-cooling jackets 8 having appropriate inlets and outlets for the cooling medium as conventionally indicated by the arrows on the drawings. The zinc vapor inlet 6 is connected by a pipe 9 to the source of zinc vapor, such as a. vertical zinc smeiting retort. The zinc vapor inlet 6 and the gas outlet 1 are shielded by depending refractory bailles I0 and II, respectively, to prevent splashing or spraying of molten zinc into the inlet and outlet. The condensing chamber 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 oi 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 substantially constant by continuouslywithdrawing 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 I'I mounted in bearings I8 outside the condenser. 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 flow 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 -20 embedded inthe cement sleeve, and the bore of the rotor has a plurality of spaced recesses 2| filled with the cement of the sleeve, so that the sha'ft, sleeve and rotor'are effectively keyed together. The shaft I1 is cool-ed by the flow of a cooling medium, such as water, through its axial bore, the cooling medium being supplied to the bore at one end of the 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 circumfrentially spaced pockets or cups 24. The shaft I1 is positioned at a level substantially above that of the molten zin: adapted to be held in the chamber 5, and the rotor I6 is of such outside diameter that its lower-most pocket is beneath the molten zinc level a. The rotor is rotated by means of a pulley 25 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 21 has a constricted portion 28, near its outer'end, to provide a close clearance 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 and 21 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 vexample as a portion of the exhaust gas exiting from the condenser through the outlet 1, is pumped into the caps 3l through the inlet pipes 33 to maintain a suiciently high gas pressure within the caps to prevent zinc vapor and diluting gas from flowing outwardly between the stationary sleeves 21 and the rotating sleeves 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 exftend 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 discharging by gravity any molten metal entering the space 29 between the sleeves. The annular grooves 34 are outwardly flared to facilitate the fiow of molten metal therefrom. The upper portion of the end of each sleeve 21 is beveled or thickened to form a backwardly sloping surface 36 for guiding any molten metal falling on or wetting the upper surface of the sleeves towards the condenser wall and thence downwardly over the sleeve to the body of molten metal.

In the operation of the condenser illustrated in the drawing, a continuous stream of gas containing zinc vapor enters the condensing chamber beneath the baille IIl of the inlet 6, and ows in a generally horizontal direction throughthe chamber to the exhaust gas outlet 1. Where the entering gas is `derived from a vertical retort smelting operation it will have-a temperal the most part with carbon monoxide gas. yDis-- spation of heat from the condenser is controlled A by regulating the cooling medium flowing through the jackets 8 to maintain Within the condenser an operating temperature of about 530 to 550 C. The rotor I6 is rotated at a relatively high speed, say around to 150 R. P. M., clockwise as viewed in Fig. 1, so that the pockets 24 in rapid I succession pick up and throw sheets or showers of molten zinc into the entering gas stream. The pockets 24 have a generally scoop-like section with a relatively long advancing flat surface and a shallow semi-circular depression at the inner end or bottom o1' the pocket. The pockets terminate short of the circumferential peripheral ends of the rotor, so that little or no molten metal is thrown laterally against the side walls of the condensing chamber. iected and rapidly succeeding sheets or showers of molten metal splash into the shower or rain of molten zinc particles falling through the chamber, and also splash against the baffle I0 and the roof of the condensing chamber, with the result that this area of the condensing chamber is substantially lled with sheet-like showers and moving particles of molten zinc which form ideal nuclei for the condensation and subsequent coalescence of the zinc vapor. Formation of blue v powder or zinc dust is practically negligible, and whatever particles are formed are dissolved n the splashing and showering molten zinc or carried thereby into the bath of moltenv'zinc and there melted.

Cooling of the shaft I1 permits the use of a metal shaft, and the sleeve I9 of insulating cement inhibits appreciable vcooling of the condensing chamber by the cooling medium flowing through the shaft, and eliminates any thermal stresses in the rotor I6. The special configuration of the stationary sleeve 21 prevents the collection 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 escape of zinc vapor through the rotating contact between the sleeves 26 and 21, and thus insure free relative movement of these sleeves. y

While the invention is particularly'applicable to the condensation of zinc vapor from the gaseous productsvof zinc smelting operations carried out in externally or electrically heated re torts, where the zinc vapor content is relatively high, it is also applicable to the condensation of zinc vapor from larger relative amounts of diluting gases. For example, the invention may be advantageously applied to condensing zinc vapor from the gases produced in zinc smelting opera u little o r noyblue 'Y powder fis otherwise formed.` While the upwardly-'directed and splashing sheets or showers offj molten Zinc are preferably thrown `into the gaseous v stream-:in the initials't'ageof its passage throughthe chamber,- byrotation of the l rotor I6 clockwiseas viewed in Fig. 1,the1rotor may be arranged to throw the splashing sheets vor showers of moltenfzinc into the gasfstream at any passage ythrough the condensing stage in its chamber.,-

The upwardly-di- We claim:

1. A condenser for zinc vapor comprising a condensing chamber provided with top, wall and bottom members and having a zinc vapor inlet approximate one end and a gas outlet approximate its other end and adapted to hold a body of molten zinc, a horizontally disposed shaft extending through the walls of said chamber between said inlet and said outlet in a direction generally transverse to the direction of gas flow through the chamber and at a level substantially above that of the molten zinc adapted to be held in the chamber, a generally cylindrical rotor having peripheral surface pockets secured to said shaft within the chamber with the lowermost pocket beneath the level of the molten zinc adapted to be held in the chamber, means providing zinc vapor and molten metal seals where said shaft extends through the walls of the chamber, and means for rotating said shaft so that the successively ascending pockets al' the rotor are caused to throw an upwardly-directed shower of molten zinc into the chamber.

2. A condenser for zinc vapor comprising a condensing tom members and having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc, 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 through the walls of the chamber, a generally cylindrical rotor having peripheral surface pockets secured to said shaft within the' chamber with the lowermost pocket beneath the level of the 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 metal into the chamber.

3. The condenser denned in claim 2 `.lurther characterized in that the peripheral surface pockets of the rotor terminate short of the circumferential peripheral ends of the rotor.

4. The condenser defined in claim 2 further characterized in that the horizontally disposed shaft is axially bored and means are provided for passing a cooling medium through the axial bore.

5. The condenser defined in claim 2 further characterized in that the horizontally disposed shaft is hollow and thus adapted to be artificially cooled by the passage therethrough of a cooling medium, and a heat insulating sleeve is disposed between the shaft and the rotor.

6. The condenser denned in claim 2 further characterized in that the horizontally disposed shaft is surrounded by a gas seal where it extends through the walls of the condensing chamber.

7. The condenser denned in claim 2 further characterized in that the rotor has at each end a sleeve surrounding the shaft where the shaft-extends through the walls of the condensing chamber, and a stationary sleeve surrounds each rotor 'sleeve in spaced relation therewith except for a constricted portion :forming a close clearance between the sleeves.

8. The condenser characterized in that the rotor has defined in claim 2 further at each end chamber provided with top, wall and bota sleeve surrounding the shaft where the shaft -extends through the walls of the condensing chamber, and a stationary sleeve surrounds each rotor sleeve in spaced relation therewith except for a constricted portion forming a close clearance between the sleeves, the lower inner -end of the stationary sleeve being shaped to' promote inward now of any molten metal in the space between the sleeves, and the upper inner end of the stationary sleeve being shaped to promote outward flow towards the condenser wall of any molten metal on the top surface of the stationary sleeve.

9. The condenser defined in claim 2 further characterized in that the rotor has at each end a sleeve surrounding the shaft where the shaft extends through the walls. of the condensing chamber and further has an annular groove in each end surrounding the sleeve, and a stationary sleeve surrounds each rotor sleeve in spaced relation therewith except for a constricted portion forming a close clearance between the sleeves, the inner end of each stationary sleeve extending into the annular groove in the adjacent end oil' the rotor,

10. The condenser defined in claim 2 further characterized in that the horizontally disposed shaft is surrounded where it extends through the walls of the condensing chamber by a cap tightly fitted to the exterior of the condenser, each cap carrying a bushing for the shaft and having a gas supply means.

11. 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 hold a body of molten zinc, a generally cylindrical rotor having peripheral surface pockets rotatably mounted UNlTED STATES PATENTS Number Name Date 619,094 shedlock Feb. 7, 1899 1,530,154 Caspar! May 17, 1925 1,649,428 Waring Nov. 15, 1927 1,790,012 Mahler Jan. 27, 1931 1,884,088 Miller Oct. 25, 1932 2,238,819 Neve Apr. 15, 1941 2,348,194 Crane May 9, 19M

FOREIGN PATENTS Number Country Date 55,473 Sweden May 24, 1922 within said chamber with its axis substantially horizontal and with its lowermost pocket beneath the level of the molten zinc adapted to be held in the chamber, and means rotor so that its successively ascending pockets are caused to pick up in rapid succession and throw into the chamber in a substantially continuous and upwardly-directed shower small amounts of the molten zinc held in the chamber.

ERWIN C. HANDWERK. GEORGE T. MAHLER. HARRY C. HAUPT.

REFERENCES CITED ille of this patent:

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