US2156420A - Metal vaporizing furnace - Google Patents

Description

2 Sheets-Sheet' A1- RIzING FURNACE..

.Filed May 2 8, 1937 G. ANDERSON ET A1.

METAL VAP lllllllllllll May 2,- 1939.

May 2,1939.

G. ANDERSON ET AL METAL vAPonIzING FURNAcE:

'2 Sheets-Sheet 2 Filed may 2a, 1937 A [req F915 f 7 f INVENToRsl ATTORNEYS Patented May 2, 1939 UNITED STATES PATENT OFFICE METAL VAPOBIZING FURNACE George Anderson, Hammond, Ind., and Rang'- wald S. Olsen, Chicago, Ill., assignors to International Smelting & Refining Company, New York, N. Y., a corporation of Montana Application May as, 1937, sen-a1 No. 145,251

ov claims.

Our invention aims to provide an improved furnace for the vaporizing more particularly of zinc, and a method of operation by which there is a lessening of .the tendency to vaporize certain impurities which may be in the zinc.

The accompanying drawings illustrate an em bination of rebrick and plastic insulating re' fractories. The method and materials used depend on the amount of heat calculated to be conducted through it to the monolithic container orr hearth, hereinafter referred to. The fact that molten zinc is vhard to hold in a structure of refractory materials on account of the hydrostatic pressure has been taken into consideration and providedl for by encasing the lower part of the furnace, the part which carries the molten bath, in a steel shell comprising a bottom 4, sides 5 and ends 6. The furnace is braced on the bottom by any usual or suitable steel structure such as cross-beams 1 and longitudinal girders 8; at

the sides by upright buckstays 9 and across the top by tie rods I0. The top of the completed structure comprises, an arch II of rebricks with a cover I2 of plastic insulation. On the bottom wall I of the complete structure is a. hearth or container I3 for the molten charge of zinc or other metal.` It is preferably a monolith with sides I4, Fig. 2, and ends I5, Fig. 1, ofa height suicient to contain the molten bath. It mayY be of various refractory materials, such for example as silicon carbide.

Above the container or hearth is a horizontal roof I6. 'I'he space Il above the roof I6 is a heating or combustion chamber. The heat therefrom is transmitted through the roof I6 to the surface of the bath. The 4roof I6, therefore, is closely spaced above the bath and the outer cover II is sufficiently high to leave an abundant space Il for combustion of the fuel. Burner openings -are indicated at I8 and combustion gas outlets- I9. Gas, oil or powdered coal may be used. At 20 are located openings for pyrometers so as to indicate and record the temperature within the heating chamber and to direct the control thereof as far as necessary.

The arch I2 illustrated is built of blocks of refractory material of high heat conductivity such, for example, as silicon carbide; the joints being made substantially vapor-tight by using a suitable refractory cement.

A stack 2I is located at one end of the struc- Fig. 3 is van end elevation.'

ture, up which the vapor is drawn and burned to oxide or conducted to a chamber in which it is sublimed to zinc dust or condensed to cakes of solder, or treated in any usual or suitable way.

Through one of the end walls 3, there is an opening 22 leading into the vaporizing chamber vbetween the roof thereof and the upper edge of the hearth or container. It communicates through anopening 23 with the stack and also ducing any inert or reducing gas into the vaporizing chamber whenever this may be desired.

In ordinary operation these openings are plugged with clay. When the introduction of -such gases is not desired, the openings 25 can be used as exits for metal vapors orinlets for charging similarly to the opening 22 at the opposite end. and `they may be made of the same size as the opening 22 for that purpose, although here shown of smaller size. Of course, where the openings 25 are to be used as an exit for the vapor, they must be connected to a stack or other means for treating or utilizing the vapor.

At one side, and inclined downward from the bottom I3 of the container, is a .tap hole 26 leading to al chute 2l. It is normally plugged with clay or the like and is opened as necessary for the drainageof residual non-volatile metals or for removal of molten charge. On the opposite side and leading downward into the top of the container is an opening 28 through the Wall connecting with a vessel 29. This opening too is normally plugged. When the plugis withdrawn it may be used as a charging spout through which molten metal is run into the furnace for treatment without access of oxidizing gases.

direction. In cross-section itl is arch shaped as preferably through the charging spout when molten metal is used.

Heat transmitted through the arch or top it,

after first melting the charge if it shall have been introduced in solid form, is radiated to the below and a more turbulent vaporizing operation maintained.

The improved furnacehas several advantages over the type commonly used in zinc distillation, in which the zinc has been carried in cylindrical pots of ceramic material or large graphite bottles with a maximum capacity of about one ton of zinc. Such furnaces require frequent recharging, with attendant high labor cost. They also involve great expense for the maintenance of the numerous pots.

The furnace of the present invention is not subject to any such limitation of size as the 'old' furnaces, involves a smaller labor charge and eliminates the old charge for replacement of pots or bottles.

The present furnace also is Well designed for receiving a molten charge. Such charging on a large scale is simple and quick, resulting in drossfree metal within the furnace chamber. Compared witha maximum of about one ton capacity for the older type, a furnace of this invention has operated satisfactorily with a charge of seven and one-half tons.

The arch i5 is much less expensiveto maintain than the old structures. It bears no load. Its construction permits it to yield to changes in temperature and thus avoid breakage. The arch tends to seal itself since it is under pressure of Zinc vapor from the inside which tends to ll in all crevices with zinc vapor Whenever such crevices may occur. Any small leaks that may occur through sudden cooling, permit passage of zinc vapors into the combustion chamber above where they are oxidized. The leaks quickly disappear through formation of an oxide coating at the point of leakage. This keeps the volatilizing chamber air-tight at all times, which is essential to successful operation. Such vaporizing chambers are generally operated under vapor pressure in order to prevent the entrance of air.

The large amount of zinc vaporized in one ves- Sel permits of better control than in the case of small pots provided with a number of openings.

Continuous operation can be effected by intro-- ducing a constant stream of molten metal through the port opening 28 at such a rate as to compensatey for the rate of vapor discharge through the opening 22. Any non-volatile metals remaining behind in the chamber l0 can bey tapped out through the tapzholes 26; so that there is no dimculty in treating charges of zinc containing metal impurities.

Various modifications in the design and operation` of the furnace may be made by those skilled in the art without departingfrom the invention as donned in the -following claims.

WhatweclaimisV 1. A metal vaporizing furnace which comprises aioaaac a monolithic container for molten metal, a furnace structure having a bottom and side and end walls supporting and enclosing said container and having a roof and a partition arch sprung from the sides and sealed to the en d walls of said furnace to provide a combustion chamber thereabove and a vaporizing chamber therebelOW.

2. A metal vaporizing furnace which comprises a hearth for holding molten metal, a furnace structure having a bottom and side andend walls supporting and enclosing said hearth, an arch sprung from the side walls of said furnace and extending to the end walls and having a layer of sealing bricks closely overlapping the ends of said arch and cemented into the end wall of said furnace.

3. A metal vaporizing furnace whichcomprises a metal holding hearth having upturned side and end Walls to hold molten metal, a furnace structure having a bottom and side and end walls supporting and enclosing said hearth, an arch sprungfrom the ,-side Walls of said furnace and sealed to the end walls thereof to provide a combustion-chamber above said arch and a vaporizing chamber therebelow and a metal shell en closing the bottom of said furnace and the side wallsthereof `to the level of said hearth. 4. A metal vaporizing furnace which comprises a metal holding hearth having a bottom and upturned sides and ends to contain molten metal enclosed in the Walls of said furnace and a furnace structure of metal having a bottom and side and end walls supporting and enclosing the bottom, side and end walls-of said furnace to approximately the height of said hearth walls, a roof spaced above said metal holding hearth and a partition arch sprung from the side walls of said furnace between said hearth and said roof and sealed to the end wallsthereof to provide a heating chamber Vthereabove and a vaporizing chamber therebelow. 1

5. A metal vaporizing furnace which comprises an outer shell of material impervious to metal and having a bottom, side and end walls, a furnace structure having a bottom, side and end walls enclosed by the bottom, side and end walls respectively of said shell and having a bottom lining with upwardly extending side and end Walls structure having a bottom, side and end walls enclosed by the bottom, side and end walls respectively of said shell and having a bottom lining vwith upwardly extending side and end walls to form a metal holding` hearth in the lower part of said furnace, said furnace having a-roof and a partition arch between said roof and said hearth sprung from the side Walls of said furnace and sealed to the end walls thereof to enclose a va- Yporizing space above said hearth and a separate combustion chamber between said arch and said' roof, means to supply metal to said hearth and means to remove metal vapors therefrom.

GEORGE ANDERSON. RANGWALD S. OLSEN.

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