US1219194A - Electric zinc-distilling furnace. - Google Patents

Description

J. THOMSON & F. A. J. FITZ GERALD. ELECTRIC ZINC DISTILLING FURNACE.

APPLICATION FILED JUNE 21, 1916.

1,21 9,1 94. Patented Mar. 13, 1917.

3 SHEETS-SHEEI I.

J. THOMSON & F. A. J. FlTZ GERALD.

ELECTRIC ZINC DISTILLING FURNACE.

APPLICATION FILED JUNE 21, 1916- 3 SHEETSSHEET 2.

Patented Mar. 13, 1917.

v1 00 mfo'zs J. THOMSON & F A. I. FITZ GERALD.

ELECTRIC ZINC DISTILLING FURNACE.

APPLICATION FILED IUNEZI, I916.

Patented Mar. 13, 1917.

3 SHEETSSHEET 3L UN Y UNITED STATES PATENT OFFICE."

JOHN THOMSON, OF NEW YORK, AND FRANCIS A. J. FITZ GERALD, OF NIAGARA FALLS, NEW YORK, ASSIGNORS TO JOHN THOMSON PRESS COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC ZINC-DISTILLING FURNACE.

Application filed June 21, 1916.

To all whom it may concern:

Be it known that we, JonN Thomson and FnANcis A. J. Frrz GnnALn, citizens of the United States, and residents, respectively, of the borough of Manhattan, city of New York, county and State of New York, and of Niagara Falls, county of Niagara, State of New York, have invented certain new and useful Imprm'ements in Electric Zinc-Distilling Furnaces, of which the following is a specification, reference being made to the accompanying drawings, forming a part hereof.

This is an invention relating to the metallurgy of zinc, and it particularly pertains to an apparatus for the purification of spelter containing deleterious metals, such as lead, iron and cadmium, by distillation in an electric furnace. The objects of the invention are to construct an apparatus in a manner to minimize the cost of transforming metal into fu-me or gaseous vapor, to retain cer-- tain elements of the fume within the furnace and to then evacuate and conduct other portions of the fume, viz., portions which are at the lowest permissible temperature, to any suitable means for liquid condensation, or for precipitation as dust, or for burning to an oxid.

In the accompanying drawings, which constitute a part of this specification there is illustrated a preferred but not necessarily an exact detail mode of realizing the invention.

Figure 1 is a vertical transverse center section, viewed as denoted by the arrow on line A of Figs. 2 or 3; Fig. 2 is a vertical longitudinal center section, viewed as denoted by the arrow on line B of Figs. 1 or 3; Fig. 3 is a top plan, the cover and several of the upper septum-plates being omitted, and Fig.

I 4 is a detail showing a feature of construction less clearly shown in the necessarily smaller scale of the assembled drawings.

The heating system of the furnace needs only be here described in so far as will incorporate it as an element in combination with the novel features of the invention. Thus, it is comprised in a suspended carbon resistor, C, shown as the zig-zag type, attached by a connector, 5, for electrification Specification of Letters Patent.

Patented Mar. 13, 1917. Serial No. 104,838.

in series, when incited through the terminals, (5, 7, from the diagrammatically illustrated source of energy 8.

Beneath the resistor is a trough, or tank 9, which contains the bath of molten metal, as 10, usually supplied through a spout, indicated by the dotted lines, 12, Fig. 2.

In furnaces having a zig-zag type of resistor as hitherto constructed, the operation and result were such that the fume flowed directly upwardly from the bath, through the zig-zag slots and around the sides of the resistor and thence through superhuposed slotted or ported septums, the latter acting to somewhat conserve the heat emitted by the upper surface of said resistor. But as the area of the bath was relatively large and as the rate of fumeflow was also correspondingly low or sluggish, the fume became super-heated, its temperature in fact approximating that of the resistor. However, some portions of this super-heat were dissipated by causing the fume to pass along horizontal septum-spaces and in contact with the walls and roof of the furnace.

It will here be noted that while the temperatures at which various metals will boil have been rather accurately determined, as, say, the conventional figures of 930 for zinc and 1800 C. for lead, various conflicting phenomena are observable when the fume of several metals are combined, as in the instance of combining metals as an alloy. Thus, a large volume of zincfume may carry with it a minor volume of lead-fume although the ten'iperature of the resistor may not exceed 1,300 to 1,400" C- ()u the other hand, given two metals. that having the higher fuming temperature will also condense at the higher temperature.

It has been proven in practice. as was primarily theoretically predicated, to be of the highest importance not only to avoid hot-spots on the bath, due to the direct action of the resistor, but that the flow of fume from is surface must be uniformly distributed. In other words it is important that a constant amount of fume be emitted from each square inch of the exposed surface of the bath. If not, those portions of the furnace walls, as shown.

the bath from which fume passes off most slowly will absorb an excess of heat-units and thus become in fact hotter than other portions from which fume escapes more freely.

Again, the facility with which zinc-fume can be rapidly condensed, in large volume, is considerably a function of its tempera ture. Thus, if fume enters the condenser at a temperature of, say, 1,300 C., about 350 must be emitted to atmosphere before the critical point is approximated, whereas if the fume enters at about 950 the initial condensing temperature may be almost immediately reached.

The foregoing premises are to be kept in mind as relates to the construction and functioning of the remaining features of the furnace now to be described.

The resistor and is connector is ineased, or boxed-in, except at the lower side, by two vertical aprons or septumplates. 13, 1 supported on struts, 15, 1(3, anchored in the furnace walls, and an over-lying horizontal septum, 17, which rests upon the side septums. The latter are set so as to leave vertical spaces, or fines, 18, 19, along the side walls of the furnace and also to provide spaces, or ports, 20, 21, beneath their lower edges and contiguous to the space between the top of the trough and the surface of the bath. Upon the horizontal septum, 17, is preferably laid a layer of granular charcoal or petroleum coke, Again, above the coke is an upper septum, composed of plates, as 23, which may be supported by One end of these plates is partially cut away to form a series of ports. as 24, overlying either set of the vertical fiues, or whichever set that is opposite from the exit to the condenser. Over the upper-septum is a large fume chamber, P, inclosed by a relatively thin cover, formed of plates, 25, and leading from the said chamber is a throat, 26, through which fume eventually passes to any suitable means for condensing, not shown but indicated by the dotted outline, J.

It will now be perceived that the fume within the resistor-boxing is imprisoned, dead, serves as a blanket or envelop" for the resistor, and cannot flow therefrom; the only escape for the evolved bath-fume being right and left along its surface, as arrows a, thence vertically through fine 18 and the ports, as arrows c, 2', also vertically through flue 19, thence horizontally along the intermediate space, R, between the horizontal septums, as arrows d, e, h, and finally again vertically through the ports, 24, whereat it commingles with the fume from fine 18. v

The coolest fume is that first rising from the bath, thence escaping to the side flues and this, at its liberation, is probably not over 950 C.

In flowing across the bath, however, and thence. up through the fines, additional heat is absorbed.

The hottest fume is that immediately in contact with the resistor and surrounding boxing; which, being a gas, is perfectly transparent to the radiant heatfrom the resistor and also being a very poor thermal conductor gives little heat to the fume rising from the bath but prevents that fume from coming in contact with the resistor, whereat it would become superheated.

N0 heat directly radiated from the resistor reaches the furnace side-walls, as the impingement is upon the inner surfaces of its casing; hence the heat imparted to the furnace walls is largely confined to that contained in the up-fiowing fume.

The areas of the side-fines and the intermediate horizontal septum chambe are to be such that a relatively rapid flow of fume must occur therein.

As is well known, granular charcoal or coke is a good non-conductor of heat. Hence, this acts to insulate the septum; energy is thereby conserved in the resistor. Due to the layer of granular charcoal or coke the horizontal space, R, can become a cooling chamber for the fume which passes through said space. The heat imparted to the upper septum plates, 23, is largely that conveyed by the fume. The charcoal or coke, as the case may be, also serves another desirable purpose. At the starting of a green furnace, a certain quantity of CO, or water-gas, H,O+C:H,+(70, will be formed and the charcoal or coke will serve to wash out any contained. air thus preventing or minimizing the formation of ZnO.

As will be observed, the ports, '24:, are located along the side of the furnace opposite from the condenser or the ports leading to the condenser; the upper fume-chamber is of large volumetric capacity, relative to the lower spaces and chambers, and the primary cover is quite thin relatively to the furace walls. In this wise, by a proper selection, and application thereon, of heat-insulating bricks, as 27, two advantageous conditions are obtained; first, a very slow displacement of the fume from this upper cooling chamber and, second, the opportunity to control, by means of the cover, the temperature of fume at its exit through the throat,

as arrow m.

The consequences of the foregoing construction, and the conditions thereby ensuing, are that any lead-fume entrained with the zinc-fume is subjected both to a condens ing temperature and also, which is of equal importance, it is brought into physical contact with an ample coalescing surface, whereby liquefied lead is entrained within the furnace and drips back into the bath. To facilitate the flow of condensed lead, the upper surfaces of the horizontal septums may be given a slight slope, downwardly toward its ports, 24, as is shown in Fig. 1.

The greater the difference of temperature between the resistor and the bath, the higher will be the thermal efficiency. This axiomatic statement points to important contingent advantages, namely: the rate of fuming may be carried on at a rate which would not otherwise be permissible; the residuum need not be so frequently withdrawn, through the tap-opening 28, Fig. 2, as if the primary fuming of lead had to be more carefully safe-guarded, and the capacity and endurance of any given condenser is substantially enhanced.

Zinc-fume is exceedingly penetrative and effective heat insulating bricks are very porous. As a consequence, in starting up a green furnace, much spelter is lost by absorption, even to the extent of tons of metal. Many unsuccessful efforts have been made. to minimize or avoid this. A satisfactory, simple and inexpensive solution has been found in the expedient of applying between the chamber wall or walls, as 29, and outer courses of bricks, as 30, and also beneath the bottom of the trough. relatively thin plates of molded crucible mixture (graphite and clay) or amorphous carbon, as 31, 32, of as large surface as can conveniently be manufactured, their contiguous edges being joined by a system of, or analogous to that of shipq'oints. By forming the laps of these joints at a slight angle, as 33, Fig. 4, to the axis of the faces of the plates, as also the end-joints, 34, they are thus caused, when confined by the brick-courses, to firmly interlock, while any contraction Within the plates serves to tighten the laps on their bevels and any expansion also tightens by the direct pressure of the transverse abutting ends. This or any similar form of ship-joint can be easily molded or machined with a considerable degree of accuracy, thereby realizing a very effective barrier to the escape of both fume or liquid metal. The advantage of this barriersheathing is not confined to the metal primarily saved, as a furnace so provided can be more quickly put into full operation.

Various of the details, as illustrated in the drawings, may be modified without evasion of the essential functions. Thus, for example, baffle-plates may be set in the upper chamber, whereby to effect a sinuous flow of fume from the ports to the throat, and vertical fines might also be provided at either or both of the end-Walls as Well as at the side-walls of the furnace. So, too, under certain circumstances, as by the use of a thicker layer of granular or powdered carbon on the top of the resistor-casing, the upper septum may be omitted.

What is claimed is:

1. In an electric furnace, a suspended resistor embraced by an overhead horizontal and vertical side septums, so disposed within the main chamber as'to provide fume-passages between the furnace walls and along the top of the horizontal septum.

2. In an electric distilling furnace, a suspended resistor facing a volitizable bath, a suspended trough or casing surrounding the top and sides of the resistor, vertical uprising fiues between the sides of the casing and the furnace-walls and connecting spaces beneath the lower edges of the casing, whereby vaporized products are trapped in the casing but are otherwise free to escape.

3. In an electric. furnace, a suspended rcsistor whose top and sides are incascd by a horizontal and two vertical septums, vertical fume-fines between the. side-septunls and the furnace walls and a Sll])Ollll'l[)()S0(l horizontal ported septum forminga fume-chamber between it and the roof of the. furnace, whereby the. rising fume passes from the lines through the septum ports and thence into said chamber.

4. In an electric furnace, an open bottomed septum casing, suspended within the main furnace chamber, within which is a. suspended resistor. and an underlying volatilizable charge, whereby the gases or fumes collected in the said septum-casing cannot be displaced.

5. In an electric zinc distilling furnace, a resistor casing, open at its bottom and having an overlying layer of granular carbon, such as charcoal or petroleum coke.

6. In an electric zinc. furnace, a resistor casing surrounding the top and sides of a downwardly radiating resistor, an underlying bath, spaces beneath the lower edges of the casing and open fiues between the sides of the casing and the furnace walls which communicate with the upper portion of the furnace chamber, the latter having a throat leading to a condenser.

7. In an electric furnace for distilling zinc, a resistor enveloped by non-displaceable fume contained in a casing open at its bottom, above a bath of metal, and having spaces below its edges and fines along its outer sides, whereby the evolved fume traverses across the lower zone of'trapped fume and thence rises vertically through the fines.

8. An electric furnace for refining zincfume contaminated with lead-fume, comprised in a bath over which a resistor is suspended and enveloped by undisplaceable fume, a system of vertical uprising side flues contiguous to the furnace walls leading to over-head enlarging spaces, whereby there is a cumulative reduction in the velocity of flow and the temperature of the fume prior to its entering the condenser.

9. In an electric furnace, means for securing the envelopment of a resistor with un-- displaceable zinc-fume, means for permitting a free upward escape of evolved fumes or gases from an underlying charge and means for progressively reducing the velocity of flow and also the temperature of the volatilized matters, whereby that substance which has the highest condensing temperature will be retained within the furnace.

1(). In an electric furnace, a resistor septum-casing for enveloping the resistor with undisplaceable fume or vapor which rises from an underlying charge, said casing be ing mounted upon a plurality of spaced struts or supports .in such manner as to provide free spaces along its lower edges and between its sides and the furnace walls, and through which the evolved vaporous products are evacuated.

11. In an electric zinc distilling furnace, a horizontal septum or septums disposed between the roof of the furnace and a resistor, and beneath the resistor a trough containing the charge, the said septum or septums being sloped toward a vertical flue o'r llues, whereby any condensed metal collected thereon will flow to the charge.

12. An electric. zinc distilling furnace having a trough containing the charge, a resistor above the charge, a ported horizontal septum or septums above the resistor, a fume chamber above the septum or septums and an inclosing cover whose rate of heat-radiation to atmosphere is controllable, whereby to increase or decrease the tempe'ature of the fume prior to its entering the condenser.

13. In an electric furnace, a chamber at whose bottom is a charge, a suspended radiating resistor above the charge and a suspended septum-casing within the chamber,

surrounding the top and sides of the resistor,whereby the resistor is free to directly transmit heat to the charge but is enveloped by trapped volatilized matter evolved therefrom.

14. An electric furnace having therein an open receptacle containing a charge which is being vaporized by radiant heat from an overlying resistor, means for entrapping vapor whereby to envelop the resistor and not be displaceable therefrom, and means for permitting the vapor evolved from the charge to flow horizontally along the lower portion of the trapped vapor and thence pass vertically upward through side-fines disposed along the furnace.

15. An electric furnace having a radiating resistor enveloped in non-displaceable vapor directly received from an underlying open receptacle containing the charge, and means for permitting the continuously evolved vapor to freely escape along the lower zone of said envelop and thence upwardly.

This specification signed and witnessed the 14th day of June, A. l)., 1916, in the city of New York, borough of Manhattan, State of New York, by

JOHN THOMSON, and the 16 day of June A. 1)., 1916, at Niagara Falls, county of Niagara, and State New York, by

FRANCIS A. J. FITZ GERALD.

\Vitnesses for John Thomson:

\V. (l. MARGESON, M. F. Kna'rixo. 'itnesses for Francis A. J. Fitz Gerald:

R. H. \VARREN, H. M. VVARD.

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