US1775591A - Electrothermic zinc furnace - Google Patents

Description

82-29%. 5%, 1930., E. c. GASKBLL EJ575591 ELEGTROTHERMIG ZINC FURNACE Filed Sept. 1'7, 1928 4 Sheatsiheat l ELECTROTHERMIC ZINC FURNACE Filed Sept. 17, 1928 1 Shuts-Sheet 2 Filed Sept. 1'7, 1928 4 Sheets-Sheet 3 Ill/II III! Sept 9,, 1930. E. c. GASKILL 1,775,591

ELECTROTHERMIC ZINC FURNACE Filed Sept. 17, 1928 4 Shuts-Sheet 4 Patented Sept. 9, 1930 EARL C. GASKILL, OI IBONNE TERRE, MISSOURI ELECTROTHERMIC ZINC FURNACE I Application filed September 17, 1928. Serial No. 306,583.

This invention relates to a furnace of the shaft type in which ores mixed with a reducing agent are continuously or intermittently fed through the furnace, and are heated to Jhe temperature necessary-for the reduction of the ores by the passage of an electric current through the charge which acts as a resistor.

The invention particularly relates to a fur- 1 ziace for the electrothermic reduction of zinc ores with the production of either speltcr or zinc oxide, and is so designed as to obviate in practice difficulties which have heretofore prevented or interfered with the successful reduction of zinc in electrically operated furnaces of this type.

The furnace is formed of suitable refractory materials and the charge is continuously fed in at the top and continuously removed at the bottom, and is, during its passage through the shaft, heated to a temperature sufficient to effect the reduction of the zinc oxide to the metal 'vapor which is continuously removed, at suitable points, from the furnace and either condensed as metallic zinc or burned to form zinc oxide.

An essential feature of the invention is the arrangement of the electrodes in such manner as to secure uniform heating of the charge by passage of current thcrethrough.

Another novel feature isthe construction of the shaft in a superposed series of independently supported annular bodies of refractory material.

In the accompanying drawings:

Fig. 1 is a sectional elevation of the furnace;

Fig. 2 is a horizontal section on plane 22 of Fig. 1; Fig. 3 is a horizontal sectional plan on the broken plane 33 of Fig. 1;

Fig. 4 is a horizontal sectional plan on plane 44 of Fig. 1 showing the arrange ment when the furnace is used to produce zinc oxide; v

Fig. 5 is a vertical section on plane 55 of Fig. 6, showing a detail of the means for supporting the furnace sections;

Fig. 6 is a plan of Fig. 5

Fig. 7' is aside elevation of a modified form of supporting means as applied to the upper section of the furnace;

- Fig. 8 is a plan view of an arrangement like that shown in Fig. 4 except that a series of condensers are shown;

Fig. 9 is a diagrammatic showing of the electrical circuits; and

Fig. 10 is a detail, partly in section, showing one of the electrodes and its mounting.

As shown in Fig. 1, the furnace is of the shaft type, and has a circular interior crosssection.

The body of the furnace is made up of a series of sections A, B, C, D and E, each inde-- pendently supported, and is preferably provided at its top with a similarly supported preheater section, designated as F. This preheater has a central tube 10 made of refrac tory material, which is externally heated by products of combustion from a burner 11 (Fig. 2), which pass upwardly in a spiral or tortuous path through flue 11, suitable bafiles 12' being provided for this purpose. The charge of ore and carbon is delivered to this tube 10, by any suitable delivering device such as a spout 13, arranged to be rotated by the gear mechanism 14, the spout being connected to a hopper 15, to which the charge is delivered from traveling belt 16 and elevator 17.

As stated above, the shaft is formed in sections, each separately supported from columns 18 of structural steel (three being shown in Fig. 3), by means of brackets 19. Carried by each bracket are depending rods 20, which, as shown in Fig. 5, are insulated from the horizontal web of the bracket by suitable insulating plates 21 and bushings 22'. At the upper ends of the rods are provided nuts 22, which rest upon a supporting channel piece, 23, between which and the insulating plates are strong springs, 24 (see Fig. 5).

As shown in Fig. 7, the nuts may rest directly on the insulating plates carried by the brackets, without the interposition of springs, and this construction may be used on the sections B, C, D. Both constructions provide means for adjustment of the sections.

As shown in Figs. 5 and 7, the rods 20' screw-threaded at their lower ends, pass through and support by nuts skew rings 25, which in turn support an annular ring 26, of brick-work, which in turn supports the cylindrical masonry 27, and annular ring 28. The rings 26 and 28 are frusto-conical at their lower and upper edges, so that there is provided between adjacent sections an annular opening of the tapering shape shown. The brick work used in forming the parts 26, 27 and 28 is preferably made of fused magnesia brick, which has the characteristics that it is not only highly refractory, but is resistant to the penetration of zinc vapors.

As shown in connection with sections B, C, E and F, I prefer to provide a shell or cas ing 29, supported on the skew ring 25 and extending upwardly to the outer periphery of the ring 28 and spaced from the masonry tube 27 The intervening space, I pack with powdered chrome ore, which is highly refractory and is also an efiective means for preventing the passage of zinc vapor or metal.

It will thus be seen that the furnace shaft 3 is made upof a series of separately supported spaced sections, thereby providing for expansion or contraction of the sections, and also providing a space or spaces, through which zinc vapor may have its exit directly into the condensers, if spelter is to be made,-

or into the oxidizing flues, if zinc oxide is to be manufactured. Through this annular space also project the pyrometers 30.

Located in the annular spaces between the sections are the means for removing the zinc vapors from the furnace. As shown in Figs.

7 1 and 4, pipes 31, having sector shaped ends 32, are located around the furnace, with suitable brick-work between the pipes. The inner ends of these pipes and the brick-work of the rings 26 and 27 of adjoining sections are so shaped that tight oints are provided, suitable luting, such as a cement which may be made of fused magnesia and a binder, being used, if necessary.

1 The outerends of these pipes extend into the conduits 33, in which the zinc vapor is oxidized by air admitted through suitable openings. These conduits are connected to a bag-house, or other suitable collecting means. In case metallic zinc or spelter is to be made, a series of condensers 34* (see Fig. 8) are located around the shaft, the inner ends of the condensers being secured between the adjacent rings 26 and 28. of adjoining sections and luted into place in the m'anenr above described in connection with the pipes 32.

In order that the workmen may haveready access to the shaft, for tapping the spelter or making repairs and adjustments, I provide a cage 34, mounted on a frame-work or car 35, mounted on a circular track extending around the furnace, suitable means, preferably electrically operated, being provided for raising and lowering the cage.

At the bottom of the shaft is provided a fected is an important part of my invention.

The arrangement of the electrodes is shown diagrammatically in Fig. '9, in which A represents the shaft of the furnace.

Near the top of the furnace are three electrodes G, H and I, of carbon or graphite, spaced about tending, as shown in Figs. 1 and 3, within the periphery of the shaft so that they come into contact with the furnace charge.

At the lower portion of the furnace are located a corresponding set of electrodes G, H, I, which, as shown, are displaced 180 with respect to the corresponding electrodes G, H and I, so that the upper and lower electrodes of each pair are located at opposite sides of the shaft. As will be apparent, the

current passes from G to G diagonally through the charge, as does the current from C to C, and from D to D. Each one of these circuits has its own separate source of electrical energy here shown as three transformers G H I each connected to alternating current power mains, each circuit being provided with suitable control devices M, N, 0, preferably automatic, for controlling the voltage and amperage of each circuit.

Either alternating current or direct current may be used, preferably single phase alternating current, and obviously independently generated currents may be used for each circuit. a i

.The paths of the currents, generally indicated by the dot and dash lines (Fig. 9),

'cross each other somewhere about the middle point of the charge between the electrodes.

The result of this arrangement is that, as the charge passes downwardly through the furnace, each portion is subjected to the action of one or the other of these currents, so that the whole mass is uniformly raised to and maintained at any desired temperature. The electrodes .are. preferably square or rectangular in cross-section and are arranged with one of their edges up, as shown in Figs. 1 and 3, so that they offer no substantial obstruction to the downward passage of the charge through the furnace.

As shown in Fig; 10, the electrodes may be mounted in holders50 carried on posts 51,

or tapered, and having 120 apart, with their ends exsections A'and D is so built as to provide suitable apertures for the electrodes.

The operation of the furnace is as follows Assuming that the furnace has been brought to the proper temperature, as by the passage therethrough of a preliminary charge of coke, the charge of ore and carbon is continually fed in at the top of the furnace and continually removed at the bottom. In its downward descent through the furnace, the

charge, preheated in section F, passes between the electrodes, and is maintained at the reducing temperature by the heat electrically generated by the passage of the several currents through the electrically resistant charge.

Because of the fact that the furnace is heated by separate current flows, the current density through any particular path can be separately controlled, thus providing for not only the maintenance of a uniform temperature but also the maintenance of a uniform rate of reduction at such temperature.

In the .reduction of zinc ore in particular,

. it is important that the reduction take place between rather narrow temperature limits, because if the temperature is low, the rate of reduction is diminished, while if the temperature is above the maximum limit, impprities such as zinc sulfide, silica, etc., will volatilized, the production of which is deleterious in that it interferes with the condensation of the metallic zinc vapor and contaminates the product when zinc oxide is being produced.

When the furnace is being used for the reduction of zinc ore, the zinc vapors formed are afforded a ready exit from the charge, either through the pipes 31, 32 to the zinc oxide flues 33, or directly into the condensers 34*, when it is desired to collect metallic zinc.

As shown, the lower and upper walls of the parts 26 and 28 are converging, so that by the use of correspondingly shaped bricks or other devices, the annular openings between the parts 26 and 27 may be readily sealed by inward or outward movement of the inserted parts. 1

The construction of the furnace in inde pendently supported sections is particularly advantageous from a metallurgical standpoint in that it provides annular spaces ,between the sections, through which ready egress of the zinc vapors is provided at a number of zones, and is mechanically advan-- tageous in that the sections can be vertically adjusted to compensate for contraction and expansion, are easily accessible for repairs, and permit access to the charge duringopertion.

Further, the use of pyrometers at a large number of points is made possible, and according to the indications of the pyrometers, the voltage and current strengths can be regulated to secure the desired operating conditions.

The use of a shaft furnace, in which the charge itself, acting as a resistor, is directly heated by electrically generated heat, has the great advantage that such furnaces may be made of relatively large dimensions, as compared with externally heated retorts.

The furnace illustrated has an internal diameter of four feet, as compared with the usual retorts which are about eight inches in diameter.

I have shown three pairs of electrodes, but a greater or less number of pairs may be used, but I prefer to use not less than three pairs.

My invention is not limited to the use of the particular number of'sections ,of the furnace, as a greater or less number may be used.

While the furnace shown and described was designed for and is particularly applicable to the reduction of zinc ore and the production of spelter or zinc oxide, it may obviously be useful in the reduction of other ores.

I claim:

1. A shaft furnace consisting of a series of independently supported sections, a plurality of spaced electrodes at the upper portion of the shaft and a corresponding number of spaced electrodes at the lower portion of the shaft, and means for supplying electrical energy to each pair of electrodes.

2. A shaft furnace consisting of a series of independently supported sections, a plurality of spaced electrodes at the upper portion of the shaft and a corresponding number of spaced electrodes at the lower portion of the shaft, and separate means for supplying electrical energy to each pair of electrodes. 3. A shaft furnace consisting of a series of independently supported sections, a plurality of spaced electrodes at the upper portion of the shaft and a corresponding number of spaced electrodes at the lower portion of the shaft, and means for supplying electrical energy to each pair of electrodes, the electrodes of each pair being located at opposite sides of the shaft.

4. A shaft furnace consisting of a series of independently supported sections, a plurality of spaced electrodes at the upper portion of the shaft and a corresponding number of spaced electrodes at the lower portion of the shaft, and separate means for supplying electrical energy to each pair of electrodes, the electrodes of each pair being located at opposite sides of the shaft.

5. A furnace for electrothermic reduction of ores comprising a shaft-like structure made up of a series of independently sup ported annular sections, means located be tween such sections for permitting egress of gases or vapors from the furnace, and electrodes located at the upper and lower portion of the shaft.

6. A furnace for electrothermic reduction of ores comprising a series of independently supported annular sections, each section consisting of 'a body of refractory material hav- 5 ing a cylindrical bore and a supporting ring for said body, pillars located about said shaft, and means for supporting the rings from said pillars.

, 7. A furnace as claimed in claim 6 in which 0 the upper and lower surfaces of each body are inclined and correspondingly shaped apertured parts are located-between said bodies.

8. A furnace as claimed in claim 6 in which the supporting rings are insulated from the pillars.

9. A furnace as claimed in claim 6 having an independently supported preheater section located at the top of the furnace.

10. A shaft furnace for electrothermic reduction of ores by the passage of electric current through aconductive charge, said furnace having a plurality of vertical pairs of electrodes com rising a plurality of electrodes spaced about the upper portion of the shaft, and a corresponding number of electrodes spaced about the lower portion of the shaft and angularly displaced about the vertical axis of the shaft relative to the upper electrodes, said electrodes contacting with the conductive charge.

11. A shaft furnace for electrothermic reduction of ores by the passage of electric current through a conductive charge", said fur-, .nace having a plurality of vertical pairs of electrodes comprising a plurality of electrodes spaced about the upper portion of the shaft, and a corresponding number of electrodes spaced about the lower portion of the shaft and angularly displaced about the vertical axis of the shaft relative to the upper electrodes, said electrodescontact'ing with the conductivecharge, and separate means for supplying electrical energy to each pair of electrodes.

12. A shaft furnace for electrothermic reduction of ores by the passage of electric current through a conductive charge, said furnace having a plurality of vert cal pairs of electrodes comprisin a plurality of elec- 1 trodes spaced about t e upper portion of the shaft, and a corresponding number of electrodes spaced about the lower portion of the shaft, said electrodes contacting with the conductive charge, and separate means for.;sup-

plying electrical energy to each pair of electrodes, the electrodes of each pair being located at opposite sides of the shaft.

In testimony whereof, I aflix my signature.

EARL Q. GASKILL.

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