US2494551A - Zinc condenser - Google Patents

Description

j., Il?, R5@ E. c. HANDWERK fr AL 2,494,55

ZINC CONDENSER 2 Sheets-Sheet l Filed Oct. 30, 1948 MAME@ 1a Lm/m ATTORNEYS j 37 i950 E. c. HANDWERK Er Ax. 2,494,55l

ZINC CONDENSER 2 Sheets-Sheet 2 Filed Oct 30, 1948 INVENTORS {RW/A1 C HANDWERK G50/vae 7T MAH/fp? ATTORNEYS Patented Jan. 17, 1950 ZIN C CDNDENSER Erwin C. Handwerk, Lehighton, and George T. Mahler, Palmerton, Pa.. assignors to The New Jersey Zinc Company, New York, N. il., a corporation of New Jersey Appneationociober so, 194s, sei-iai No. 57,588

e claimt. (ci. 26e-i5) This invention relates to the condensation oi' zinc vapor and contemplates novel apparatus for condensing zinc vapor into liquid zinc.

In the cri-pending application of ourselves and Harry C. Haupt. Serial No. 626,508, filed November 3, 1945, and now Patent No. 2,457,545 there is described a. splash-type condenser comprising a condensing vessel adapted to hold a body of molten zinc and a cylindrical rotor .provided with peripheral pockets disposed for rotation within the vessel. The cylindrical rotor in this apparatus is mounted on a horizontal shaft with the lowermost pocket of the rotor positioned beneath the level of molten zinc so that upon rotation of the rotor the successively ascending pockets pick up and hurl upwardly into the vessel a substantially continuous shower of molten zinc. The shower of molten zinc thus produced within the condensing vessel splashes against the confining walls thereof and provides such intimate contact between the molten zinc and zinc vapors passing through the condensing vessel that substantially all of the `zinc vapor is condensed. Although the apparatus described in the above-identified application is capable of effecting condensation of zinc to an extraordinary degree, it is difficult to repair in the event of any accidental or mechanical breakdown. The horizontal rotor shaft extends through bearings mounted in opposite side walls of the condenser, and the only feasible procedure for removing a damaged rotor from the condenser is to remove the side wall panels and roof section above the rotor so that the rotor can be lifted out therethrough.

We have now devised a splash-type zinc condenser which will condense zinc as effectively as the apparatus described in the above-identied application. The improved apparatus of our present invention requires only one shaft opening in one wall of the condensing vessel and this shaft opening may readily be made of such size that the rotor may be withdrawn therethrough if necessary. The position of the ,rotor shaft opening is also such as to minimize the tendency of condenser products getting into and interrotatable shaft extends obliquely through a wall of the vessel and into the interior thereof. A rotor is mounted on the shaft within the vessel and is adapted when rotated to dip into the body of molten zinc and hurl a shower` of molten zinc upwardly into the interior of the vessel. The entire rotor assembly is supported by a bearing removably disposed in said wall of the vessel. The dimensions of the rotor normal to the axis of its shaft are advantageously no greater than the corresponding dimensions of the removable bearing support so that the shaft and rotor may be withdrawn from the vessel through the opening provided by removal of the bearing support from the wall of the vessel. The rotor shaft is so positioned with respect to the zinc vapor inlet and gas outlet that zinc vapor-bearing gases trave ersing the interior of the vessel pass through the Vshower of molten zinc thrown upwardly by the rotor. The resulting intimate contact between the shower of molten zinc and the zinc vapor effects substantially complete condensation of the zinc vapors so that the gases emerging from this shower contain such a negligible amount of zinc vapor that there is very little tendency for blue powder to form in that portion of the condenser adjacent the shaft bearing.

These and other novel features of our invention will be more fully understood by reference to the accompanying drawings in which Fig. 1 is a plan view of the zinc condenser of our invention:

Fig. 2 is a sectional longitudinal elevation taken along lines 2-2 in Fig. 1;

Fig. 3 is a sectional transverse elevation taken along lines 3-8 in Fig. 1;

Fig. 4 is a partial cross-sectional view of the rotor assembly including its bearing support taken along line I-l in Fig. 2; and

Fi. 5 is an end view of the rotor shown in Fig.

As shown in Figs. 1 and 2, the zinc condenser of our invention comprises a closed vessel 6 of generally rectangular shape except for one sloping end wall 'I through which the rotor shaft projects. The vessel 6 is provided with ay zinc vapor inlet 8 located at a position remote with respect to the sloping end wall 1., and the vessel is further provided with an exhaust or waste gas outlet 9 positioned adjacent the sloping end wall 1. The vessel is constructed with sufficient strength to hold a body of molten zinc I0 in the bottom thereof and is lined with an appropriate refractory material. The end wall of the vessel opposite the sloping wall 1 is provided with a clean-out opening Il having a closure I2 through which solid impurities such as ore dust introduced with the zinc vapor-bearing gases and 3 any small amount of blue powder formed within the condenser may be removed.

As shown clearly in Figs. 1 and 3, one side wall of the condenser vessel 8 is provided with an opening I3 positioned below the normal level of the molten zinc within the vessel. The opening I3 permits communication between the body of molten zinc in the vessel 6 and a body of molten zinc maintained in a discharge well I4. The discharge well is provided with an overfow spout I5 which determines the normal level of the molten zinc within the discharge well and within the condensing vessel. Molten zinc produced during condensation within the vessel 6 causes the molten metal in the discharge well to overflow the spout I5 whence it is collected in a trough I6 which delivers the molten metal to a casting machine or other metallurgical equipment.-

The rotor assembly, as shown in Fig. 2, com prises a suitable drive mechanism such as a motor I'I and a gear drive I8 connected, through a coupling I9, to a graphite rotor shaft 20. A rotor 2I is mounted on the inner end of the shaft within the interior of the condenser vessel. The rotor shaft extends obliquely into the interior of the condenser vessel, although the entire rotor assembly is mounted in a position normal to the sloping end wall 'I.

The rotor assembly is mounted in such manner that only one bearing support is required in one of the walls of the condenser vessel. The motor II and gear box I8 are advantageously constructed as a unit which will be referred to herein as the gear motor. The gear motor is provided with a mounting frame 22 which is secured to the rotor assembly frame. The rotor assembly frame comprises a base portion 23a adapted to support the gear motor and an end portion 23h adapted to be secured to the rotor shaft bearing. The two portions of the frame 23a and 23h may be constructed integrally or they may be separate portions connected together by angle straps 24, as shown in Fig. 2. It will be seen, accordingly, that the gear motor and shaft are secured to the rotor shaft bearing as a single unit. The rotor shaft bearing to which the supporting frame is secured comprises a graphite bearing block 25 appropriately mounted in an opening in the sloping end wall l. The bearing block is provided with a central opening 26 of such size as to accommodate the rotor shaft 20 with close tolerance. Rotation of the graphite rotor shaft 20 in the graphite bearing block 25 requires no lubrication and permits such close tolerance as to eliminate the necessity for a packing gland.

The rotor assembly is constructed advantageously in such manner as to facilitate separation of the rotor and rotor shaft therefrom and to minimize heat transfer between the rotor within the condenser vessel and the remainder of the rotor assembly positioned exteriorly of the vessel. Thus, as shown in Fig. 4, the coupling I9 permits rapid connection or disconnection of the gear motor drive shaft 21 and the exterior end of the graphite rotor shaft 20. One side of the coupling I9 is secured to the end of the motor driven shaft 21 by means of a tapered pin 28 or the like. The other side of the coupling is provided with a threaded interior adapted to be screwed onto a threaded exterior end 29 of the graphite rotor shaft. The two sections of the coupling I3 are separated by a suitable heat insulating disc 30 and are secured together by bolts 3I engaging the flanges of the coupling. At the innermost end of the rotor shaft 28, the shaft is advantageously threaded so that it can be screwed into an internally threaded hub 32 of the graphite rotor 2l. It will be seen, accordingly, that the graphite rotor shaft may be readily disconnected from the motor driven shaft 21 and that the rotor 2| may be readily disconnected from the inner end of the rotor shaft. The heat insulating disc 30 separating the two halves of the coupling joining the motor driven shaft 21 and the graphite rotor shaft 20 prevents heat transfer from the rotor to the windings and bearing of the gear motor.

Heat loss through the rotor shaft bearing is also minimized. Thus, the graphite bearing block 25, which is positioned within an opening 33 in the sloping end wall "I of the condensing vessel, is provided with externally positioned heat insulation. This heat insulation may be provided advantageously by an appropriate heat-insulating medium such as one or more layers of a heat insulating board. two of such layers 34 being shown in the drawing (Fig. 4). The layers of heat insulating material 34 are advantageously shaped in the form of discs having a central opening of su'cient size to permit free rotation of the graphite rotor shaft 20. The heat insulating discs 34 are also provided with a plurality of radially disposed holes through which bolts 35 may be inserted to clamp these discs between the outer surface of the bearing block 25 and the end portion 231; of the rotor assembly frame. The heads of the bolts 35 are advantageously countersunk in the inner face of the graphite bearing block 25 and are covered by a suitable protective material such as graphite cement 36 to prevent exposure of the metal bolts to the atmosphere Within the condenser vessel.

The mounting of the rotor assembly is'such that the assembly may be secured in position or removed therefrom in a matter of minutes. For this purpose, the graphite bearing block 25 is advantageously provided with a tapered periphery 31 of somewhat smaller diameter than that of the opening 33 in the sloping side wall 1. The bearing assembly is readily mounted in the opening 33, which is also advantageously tapered inwardly, by applying an appropriate refractory cement 38 to the surface of the wall opening 33 and by then inserting the bearing block assembly. The annular space remaining between the outer portion of the wall opening 33 and the heat insulating discs 34 and the frame end portion 23h is then lled with an appropriate cement 40. It will be seen that the rotor assembly can be removed readily from the sloping end wall I by removing the cement 40 and then pulling the assembly out of the wall opening 33. The refractory cement 38 effectively closes the space between the tapered periphery 31 of the bearing block and the tapered wall opening 33`but does not provide such a tenacious mechanical bond therebetween as would interfere with removal of the rotor assembly for cleaning or for replacement of the graphite rotor. Whenever the rotor needs cleaning or replacement, the entire assembly is removed and is replaced by another rotor assembly which has previously been assembled and aligned. Thus, replacementf a rotor requires only a minimum of time and labor; no further assembling or aligning of parts is required after the new rotor assembly has been mounted in position.

The graphite rotor 2I may be of any appropriate shape capable, when the rotor is rotated. of

dipping into the body of molten zinc within the I condenser vessel and of hurling molten zinc upwardly into the interior of the vessel. We have found that such a rotor can be machined readily from a section of a graphite electrode so as to provide a central hub Il having vanes or blades l2 extending radially outward therefrom. Although these blades may be straight, we have found it to be advantageous to provide them with a curved shape like turbine blades, as clearly shown in Fig. 5. Rotors having such a construction have been .found to be mechanically strong and capable of long life. They areadmirably suited for dipping into the body of molten zinc and hurling molten zinc upwardly into the interior of the condenser vessel when rotated in the -direction indicated by the arrow in Fig. 5.

The level of the molten zinc in the bottom of the condenser vessel is maintained at a height which will insure adequate immersion of the rotor therein by means of an appropriate dam 39 Fig. 1 positioned in the overflow spout l5. The dam is readily fashioned from blue powder mud or the like and can be altered at will to change the level of molten metal within the condenser vessel.

The molten zinc hurled upwardly by the rotor 2l leaves the rotor in adirection substantially normal to the axis of the rotor shaft. The angle of entry of the rotor shaft into the condenser vessel is so chosen with respect to the shape of the condenser vessel that the molten zinc hurled upwardly bythe rotor will bathe the major portion of the interior of the vessel. The rotor is rotated at such a speed, correlated to the size of the rotor, as to insure hurling of molten zinc against the upper inner surface of the vessel with sufllcient force to splash thereagainst and bathe as much of the interior as possible with molten zinc. With rotors having diameters ranging from 8 to 15 inches, rotor speeds of 250 to 500 R. P. M. are `generally adequate. For example, we have found that when a rotor provided with six blades or vanes 21/2 inches deep and having a diameter of approximately l2 inches is rotated at a speed of about 350 R. P. M., the resulting shower of molten zinc effects such a thorough condensation of the incoming zinc vapors that the exhaust gas from the condenser contains only that amount of zinc vapor which corresponds to the vapor pressure of the molten zinc within the condenser vessel. Thus, the resulting low concentration of zinc vapor in the gases which emerge from the shower of molten zinc makes it of little importance whether the sloping end wall 1 of the condenser is bathed with molten zinc to prevent blue powder formation. Moreover, the low concentration of zinc vapor in the gases adjacent the rotor shaft entry into the condenser vessel decreases the tendency for the formation of blue powder in the shaft bearing to the point where it is negligible. The formation of blue powder in the rotor shaft bearing by ingress of atmospheric air is also minimized by the fact that close tolerance between the shaft and the bearing block 26 can be maintained and by the fact that the downward inclination of the shaft insures drainage away from the bearing of any molten metal which may be splashed on the shaft or bearing. The low temperature of the gases in the neighborhood of the rotor shaft bearing (only slightly above the temperature of the molten metal at this end of the condenser) minimizes burning of the graphite bearing and shaft and extends the life thereof.

It will be noted that the rotor 2i is so positioned in the condenser vessel that the zinc vapor-bearing gases traversing the condenser must pass 6 through the shower of molten metal hurled upwardly by the rotor. This result is obtained by so positioning the rotor that the molten zinc hurled upwardly thereby strikes the upper portion of the condenser vessel at a point between the zinc vapor inlet 8 and the exhaust gas outlet l. If the zinc vapor supply line communicating with the vapor inlet 8 is not sufficiently inclined to insure the return ilow into the condenser oi' any molten metal which may be thrown into this inlet, the inlet may be shielded from the shower of molten zinc by the interposition of a baille Where such a baille 43 is used. it serves to provide a downwardly directed stream of molten zinc which scrubs the incoming zinc vapor in addition to the scrubbing provided by the shower of molten metal thrown upwardly by therotor. The baille 43 also shields the cleanout opening Il from molten metal thrown upwardly by the rotor sothat cleaning out may be effected while therotor is still in operation. When the baille I3 is not present, it is necessary to shut down the rotor when the clean-out closure is removed. We have found that a shower of molten zinc thrown up' wardly in this manner by they aforementioned l2-inch diameter rotor rotated at a speed of about 350 R. P. M. will condense incoming zinc vapor at the rate of 6 to 8 tons of zinc metal condensed per 24 hours. The capacity of the con` By maintaining the inner surface of the vessel bathed with molten zinc, it will be understood that the incoming zinc vapors cannot come into contact with any surface having a temperature below that at which zinc remains molten, with the result that the zinc vapor condenses into droplets which are afforded adequate opportunity to coalesce into a body of molten zinc rather than being chilled to such an extent that the small droplets are solidified with the resulting production of blue powder.

As previously indicated, we prefer at present to construct the rotor, the rotor shaft and the rotor shaft bearing of graphite. The rotor may, however, be made of corrosion-resistant metal not readily attacked by molten zinc, or of any satisfactory metal protected by a coating of vitreous enamel or the like. The rotor shaft may also be made of such a corrosion-resistant metal in which case it may, if desired, be further protected by a graphite sleeve. The lubricating quality of graphite, however, recommends the use in all instances of a graphite bearing block, or at least a graphite liner for the shaft opening in the bearing block.

Although some cooling is elected by heat dissipation through the walls of the condenser vessel, additional cooling of the condenser is advantageously provided by articial ,cooling means. For example, a water-cooled shell may be positioned within the condensing vessel in the path of the incoming zinc vapor-bearing gases as described in our co-pending application Serial No. 633,004, led December 5, 1945, now Patent No. 2,457,547. This internal direct articial cooling element is bathed by the molten zinc thrown into the condensing vessel by the screw lift and serves to withdraw heat both from the molten metal and from the incoming gases. The artidcial cooling means may also comprise a bayonetshaped water-cooled shell immersed in4 the molten zinc in the discharge well I4, as described in our co-pending application Serial No. 678,540, filed June 22, 1946, now Patent No. 2,457,548. In this latter type of direct artificial cooling, the cooling element withdraws heat from the molten metal in the discharge well. 'I'he violent agitation of the molten metal within the condensing chamber prevents the existence of any objectionable temperature gradient therebetween. As will be noted upon reference to Fig. 3, the motion imparted to the body of molten zinc by the rotor 2l, and the position of the discharge well with respect thereto, is such as to forcibly circulate the molten metal from the condensing vessel into the discharge well where the desired heat transfer with a cooling shell positioned in the well takes place. As a result, it is possible to control the temperature of the molten metal and gases in the condenser with exceptional accuracy and with virtually no time lag.

We claim:

1.` A condenser for zinc vapor comprising a closed vessel having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc in the bottom thereof, a rotatable shaft extending obliquely through a wall of the vessel and into the interior thereof, a rotor mounted on said shaft within the vessel and adapted when rotated to dip into the body of molten zinc and hurl a shower of molten zinc upwardly into the interior of the vessel, and means for rotating said shaft.

2. A condenser for zinc vapor comprising a closed vessel having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc in the bottom thereof, a rotatable shaft extending obliquely through a wall of the vessel and into the interior thereof, supporting means for said shaft comprising a bearing support disposed in said wall of the vessel and a supporting element disposed exteriorly of the vessel, a rotor mounted on said shaft within the vessel and adapted when rotated to dip into the body of molten zinc and hurl a shower of molten zinc upwardly into the interior of the vessel, and means for rotating Said shaft.

3. A condenser for zinc vapor comprising a closed vessel having a zinc vapor inlet and a vessel and adapted when rotated to dip into the body of molten zinc and hurl a shower of molten zinc upwardly into the interior of the vessel, the dimensions of the rotor normal to the axis of said shaft being no greater than the corresponding dimensions of the removable bearing support whereby the shaft and rotor may be withdrawn from the vessel. through the opening provided upon removal of said bearing support from the wall of the vessel, and means for rotating said shaft.

4. A condenser for zinc vapor comprising a closed vessel having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zine in the bottom thereof, a rotatable shaft extending obliquely through a wall of the vessel and into the interior thereof, a rotor mounted on said shaft within the vessel and adapted when rotated to dip into the body of molten zincM and hurl a shower of molten zinc upwardly into the interior of the vessel, said shaft being so positioned with respect to the zinc vapor inlet and gas outlet that zinc vapor-bearing gases traversing the interior of the vessel pass through said shower of molten zinc, and means for rotating said shaft.

5. A condenser for zinc vapor comprising a closed vessel having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc in the bottom thereof, a rotatable shaft extending obliquely through a Wall of the vessel and into the interior thereof, a rotor mounted on said shaft within the vessel and adapted when rotated to dip into the lvady of molten zinc and hurl a shower of molten zinc obliquely upwardly into the interior of the vessel, said shaft being so positioned with respect to the zinc vapor inlet and gas outlet that zinc vapor-bearing gases traversing the interior of the vessel pass through said shower of molten zinc and that said shower of molten zinc bathes substantially all of interior surfaces of the vessel with which the zinc vaporbearing gases come into contact, and means for rotating said shaft.

6. A condenser for zinc vapor comprising a closed vessel having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc in the bottom thereof, a rotatable shaft extending obliquely through a wall of the vessel and into the interior thereof, a rotor mounted on said shaft within the vessel, said rotor being provided with blades disposed radially with respect to the axis of the shaft and being adapted to dip into the body of molten zinc and hurl a shower of molten zinc upwardly into the interior of the vessel, and means for rotating said shaft.

ERWIN C. HANDWERK. v GEORGE T. MAKLER.

No references cited.

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