US1594000A - Metallurgical furnace - Google Patents

Description

July 27,1926.

F. G. BREQYER METALLURGICAL FURNACE Fil ed Sept. 4, 1924 s Sheets-Sheet 1 INVENTOR flank @Bnyer ATTORNEYS July 27,1926. o 1,594,000 F. G. BREYER METALLURG I C AL FURNACE Filed Sept. 4, 1924 3 Sheets-Sheet 2 INVENTCR Fran/r C'lBre er QMZ TAWM- ATTOR NEY5 July 27 1926.

1,594,000 F. G. BRE YER METALLURGICAL FURNACE Filed Sept. 4,, 1924 3 Sheets-Sheet 3 INVENTOR Patented July 27, 1926.

UNITED STATES PATENT' OFFICE.

FRANK G. BREYER, OF PALMERTON, PENNSYLVANIA, ASSIGNOR TO THE NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

'. METALLURGICAL FURNACE.

Application filed September 4, 1924. Serial No. 735,760.

This invention relates. to metallurgical furnaces and particularly to furnaces for making metallic oxides, such as zincoxide. The invention has for its object the provision of an improved metallurgical furnace particularly adapted for the manufacture of zinc oxide, or other metallic oxides. A further omect of the invention isto provide an 1mproved construction of electrlc furnace and more especially an electric furnace adapted for the manufacture of zinc oxide.

The working or heating chamber of the improved furnace, of the invention, in its preferred form, is lined with graphite blocks having their contacting surfaces machined smooth to provide substantially perfect joints between adjacent blocks. Thegraphite block lining is preferably surrounded by a layer of tamped or rammed carbonaceous material, which in turn is surrounded by a layer of heat-refractory material. The heatrefractory material is preferably surrounded by a layer of heat-insulating material, and

the various layers are confined and maintained in their respective positions in the furnace structure by an outer metallic casing surrounded by heat-insulating material.

The furnace is preferably heated by electric energy and to this end an arcing hearth may advantageously be provided at one end of the heating chamber. The arcing hearth is preferably built of a solid mass of machined graphite blocks and has a substantially horizontal upper surface or shelf above the normal operating level of the working charge in the chamber. A pair of 1 electrodes extend into proximity with this horizontal surface. An electric current path of relatively high resistance is provided between the electrodes by granular electric conductive material, such as granules of carbon or graphite, supported on the horizontal surface of the arcing hearth and contacting with the electrodes.

As constructed for the manufacture of metallic oxides, such as zinc oxide, the furnace has a vapor conduit leading from the heating chamber, preferably through the top wall or roof thereof, to the exterior atmosphere. The outer end of the vapor conduit, preferably provided with a nozzle extension, is operatively associated with a compartment arranged to be supplied with relatively cool oxidizing gas, such as air, and hav ing an appropr ate opening oropenings for directing this gas against the stream of metallic vapor issuing from the vapor conduit or nozzle extension thereof.

The furnace, in its preferred construction, is further provided with a feed well of refractory material for introducing material into the heating chamber below the normal operating level of the working charge therein.

These and other novel features of the improved metallurgical furnace of the invention will be best understood from the acco1npanying drawings in which are represented three furnace structures embodying what I now consider the preferred modes of carrymg out various aspects of the invention.

In these drawings:

Fig. 1 is a sectional elevation of an electric furnace particularly adapted for the manufacture of zinc oxide from metallic zinc;

Fig. 2 is a sectional elevation of a slightly modified furnace construction particularly adapted for the manufacture of zinc oxide from zinc ore;

Fig. 3 is a sectional elevation of a modified furnace embodying certain features of the invention; and

Fig. 4 is a detail sectional elevation showing a modifiedconstruction of charge well.

Referring to Fig. 1 of the drawings, the furnace there represented is erected upon a concrete foundation 5. The bottom of this foundation is located some few feet below the floor line or ground level, and its vertical or side walls extend from the bottom to the floor line. A layer 6 (of appropriate thickness) of heat insulating material, for example, sil-o-cel brick, Quigley brick, or the like, is laid next to the bottom and vertical walls of the foundation.

An outer casing 7, of steel plate, is mounted adjacent the inner faces of the vertical walls of the heat-insulating layer 6 and extends on all four sides of the furnace from the bottom of the layer 6 to the top of the furnace structure. The casing 7 is supported and strengthened by vertical beams 8 and appropriate tie-rods (not shown) and horizontal beams 9. Within the casing 7 and appropriately spaced therefrom is an inner casing 10, of steel plate, preferably of box-like construction having a bottom securely united to the four vertical walls.

The space between the vertical walls of the casings 7 and 10 is filled with heat-insulating material 11, preferably powderedsil-o cel firmly tamped or rammed into the space. WVithin the casing 10, the furnace construction comprises an outer layer 12 of heat-refractory material, an intermediate layer 13 of carbonaceous material and an inner layer or lining 14 of machined graphite blocks.

The heat-refractory layer 12 may advantagcously consist of dry chromite or dry magnesite appropriately rammed or tamped into position. The intermediate layer 13 1s rammed or tamped into position in the form of a carbon paste, being essentially a paste made of anthracite coal, powdered carbon and pitch. The outer layer 12 of heat-refractory material extends over the top of the furnace, although somewhat thinner than in the vertical walls, and a'metal plate 7 secured to the casing 7, covers the top of the furnace structure.

The graphite blocks of the lining 14 are machined so that the contacting surfaces of adjacent blocks are perfectly smooth. In

this manner substantially perfect joints are formed between adjacent blocks, and the blocks as a whole form a substantially monolithic graphite lining. This machined graphite block lining covers the four vertical walls and the top and bottom of the heating chamber 15.

The graphite blocks may advantageously be about 4 to 6 inches square in section and from 3 to 4 feet in length. The contacting surfaces (sides and ends) of these blocks are machined and the blocks are fitted together with exacting care. I have found such a construction of particular advantage in providing eflicient heat-conductivity between adjacent blocks.

The machined contacting surfaces of the carbon blocks enable these blocks to be assembled so that a substantially perfect joint is provided between adjacent blocks. In this manner the block construction is made to closely approximate a solid monolithic graphite lining. As a result of this con struction, the substantially perfect joints between adjacent blocks offer practically negligible resistance to the conduction of heat from block to block. This is of especial importance in my improved furnace since the graphite lining serves to conduct heat into the sides and bottom of the charge in the chamber 15, and thereby insures a more uniform heat distribution than is usuallv obtained in electric arc furnaces.

The furnace structure is conveniently assembled by first constructing the foundation 5 and the adjacent layer of sil-o-cel brick, or the like, 6. The metal casings 7 and 10 are next fixed in position and the bottom of the heat-refractory layer 12 tamped into ed inside the casin 10 for the layer 13 of carbon paste. The furnace structure is then built u of the various layers hereinbefore descrlbed and the mold removed in due course to permit the completion of the top or roof of the furnace.

The heating or working chamber. 15 of the furnace illustrated in Fig. 1 of the drawings is approximately 7.5 feet lon 5 feet wide and 4 feet high. The grap ite block lining 14 is, for the most part, slightly under 6 inches in thickness, and the carbonaceous layer 13 and heat-refractory layer 12 are each about six inches thick, except on the top or roof where the thickness is somewhat greater. The space between the vertical walls of the casings 7 and 10 is about ten inches. It will, of course, be understood that these dimensions are given merely by way of example and are in no sense to be considered as any limitation of the invention.

A pair of spaced electrodes 16 extend through the top or roof of the furnace into proximity with the upper horizontal surface 17 of an arcing hearth 18. The arcing hearth is preferably built u of a solid mass of machined raphite bloc s extendin entirely across the width of the heating 0 amber at one end thereof. The horizontal surface 17 of the arcing hearth is above the normal operating level of the working charge in the chamber 15. Thus, in the furnace illustrated in Fig. 1, the surface 17 is approximately 26 inches above the bottom of the chamber 15, and in this furnace the arcing hearth 18 extends approximately 30 inches inwardly from the adjacent end wall of the chamber 15.,

The graphite blocks in the arcin hearth 18 are machined smooth on all su aces including the ends. In this manner the arcing hearth is made substantial] geneous mass of graphite of uniform heat conductivity throughout.

Appropriate openings are made in the roof of the furnace for the accommodation of the electrodes 16. A gland '19 of refractory material, such as carborundum or carbofrax, surrounds each electrode at the top of the furnace, and a ring 20, of carborundum, carbofrax, or the like, is mounted on top of the gland 19. A metallic hat 21 is mounted upon the ring 20. This gland construction is provided-to prevent the admission of air into the chamber 15 and the escape of vapor therefrom.

The electrodes 16 may be operated by any appropriate electrode-feeding mechanism for maintaining the proper space relation between the lower ends thereof. and the horizontal surface 17 of the arcing hearth. An electric current path of relatively high resistance is provided between the two eleca homo- Ill place. An appropriate mold is then mounttrodes by carbon granules 22 supported on the surface 17 and contacting with the electrodes.

A vapor conduit 23 extends through the roof or top wall of the furnace and permits the flow of metallic vapor from the chamber 15 to the exterior atmosphere. This conduit is formed bya circular opening in--the top wall of thegraphite block lining 14 and a material, such as carbofrax, carborundum, or thelike. Above the top of the furnace the vaporconduit 23 is continued by a nozzle extension 25, also of refractory material. In the furnace illustratedin Fig. 1, the the vapor conduit 23 is about 12 inches in diameter, and the nozzle 25 tapers from this dimension at the bottom to about 9 inches at the top.

Mounted on top of the furnace, and. sur-, rounding the nozzle 25, is a circular compartment 26 adapted to be supplied with compressed air, or other appropriate gas, from any suitable source through a supply pipe'27. The compartment 26 has a circular opening 28 in its top, which opening is slightly larger than and approximately at the level of the discharge opening of Fthe nozzle 25.

A charging well 29 extends through the roof of the furnace into one corner of the.

heating chamber 15. The charging well is preferably in the form of a tube of refractory material, such as graphite, carborundum, carbofrax, or the like. The well 29 terminates below the normal operating level of the working charge in the chamber 15.. Appropriate means are employed to keep the top of the well 29 closed, except at the times when charging material into the chamber 15.

The charging well 29 may, if desiredfbe built into the furnace structure, as illustrated in Fig. 4. Here the charging well 34 is built in one corner of the heating chamber 15, and may conveniently be constructed of refractory brick or the like. At or near its bottom, the charging well 34 is provided with one or more openings 34 permitting communication between the interior of the well andthe chamber 15.

A door 30 is preferably provided through the end wall of the furnace, opposite the arcing hearth end. The opening made through the wall of thefurnace for this door is cased with appropriate ,heat refractory brick-work. such as magnesite brick, carborundum brick, or the like. In the normal operation of the furnace this door is closed and the opening or hole through the wall is appropriately filled with suitable brick, or the like, to maintain the required heat-insulating and heat-refractory characteristics of the furnace. The door 30 is principally used for cleaning out the furmice whenhot in operation, or for inspec the combustion zone. t1cles thus formed are drawn into the lower tion of the condition of the interior of the furnace when shut down.

The electric furnace hereinbefore described is particularly adapted for the manufacture of the improved zinc oxide product described in the application of Frank G. Breyer, Earl C. Gaskill and James A. Singniaster, Serial No. 640,846, filed May 23, registering tube or tubes 24 of refractory 1923. The operation of the furnace in manufacturing this product is as follows: Metallic zinc, preferably in a molten condition, is introduced into the chamber 15, through the feed well 29, until the chamber is filled with molten zinc to about the level indicated by the line a, and this approximate level is maintained in the normal operation of the furnace. The passage of the electric current through the carbon granules 22, between the electrodes 16. produces enumerable arcs and develops suflicient heat to maintain the zinc in a molten condition and to produce sufficient metallic zinc vapor so that a steady stream of vapor escapes through the conduit 23. When desired sufficient heat may be developed to melt additions of solid metallic zinc introduced into the chamber 15.

The space between the top surface of the molten zinc in the chamber 15 and the roof or top of the chamber becomes filled with metallic zinc vapor and this vapor passes through and is discharged from the conduit 23 in a steady stream. As the zinc vapor issues from the nozzle 25, it comes in contact with the .surroun ding air arid if uninfluenced would burn or oxidize with the characteristic natural zinc flame. The opening 28 in the top of the compressed air compartment 26 directs an annular or circumferential blast or draft of relatively cool air inwardly against the escaping stream of zinc vapor and causes its intense combustion. The effect of this air blast is to radically reduce the size of the combustion or oxidizing zone from the size which it would have ifthe zinc vapor were burning free in the air in the absence of the air blast. The annular air blast has the further effect of lowering the temperature of the combustion zone and instantly chilling and removing the initially very fine particles of zinc oxide from the region of even slightly elevated temperature prevailing in The zinc oxide parllO flaredeend or hood of a flue 31 by means of a suction fan or the like (not shown) in the flue system, and are conveyed through the flue system to a bag-house or to other appropriatemeans for the collection of the zinc oxide.

Excellent results have been secured in the ditionsz-The' chamber 15 contained approximately 10,000 pounds of molten zinc.

The heating of the zinc was effected with an electric current of about 4000 amperes with an alternating potential across the electrode 16 of about 75 volts. About 500 pounds of metallic zinc were distilled oif and passed through the conduit 23 per hour. About 4500 cubic feet of air per minute at a pres sure of about ten inches of water were supplied to the compartment 26. The lower flared end or hood of the flue 31 was 36 inches in diameter and was mounted 2 feet above the discharge end of the nozzle 25. The ten'iperature of the gases entering the lower end of the flue 24; varied from about 5 60 C. near the middle to about 20 C. at the periphery.

In Fig. 2 of the accompanyimg, drawings, there is illustrated a slightly modified furnace construction embodying the principles of the invention. Similar parts and features in the two furnaces are indicated by the same reference character. In the furnace structure of Fig. 2, the inner steel plate casing of Fig. l is dispensed with, and the heat insulating layer 6 extends up the vertical walls of the furnace to the top thereof. The roof of the chamber is arched in the furnace of Fig. 2 rather than flat as in the furnace of Fig. 1. I

In the furnace of Fig. 2, the layers 6 and 12 are separated by an intermediate re atively thin layer of tamped dry chromite powder 32 and in other parts by a relatively thin layer of chromite mud 33. In this furnace structure, the layer 12 is preferably tamped dry magnesite, and the layer 6 is preferably Quigley brick.

A tapping tube 34 extends through the wall of the furnace (opposite the arcing hearth) and communicates with the chamber 15 near the bottom thereof. This tube 'is provided for the tapping of molten slag and the like from the chamber 15. Vhile the furnace is in normal operation, the tube 34:, which may conveniently be made of graphite, carborundum. carbofrax, or the like, is filled with powdered graphite and is closed by a plug of mud.

It will be understood that in the normal operation of the furnace, the door is closed and the opening in the wall of the furnace appropriately tilled or bricked-up as described in connection with Fig. 1. A charge of mixed oxidized zinc ore and anthracite coal is introduced through the feed well 29 into the chamber 15, from time to time, as requried to maintain the desired level of the working charge in the chamber. The zinc ore is reduced and metallic zinc is 'volatilized and flows through the conduit 23 in a steady stream as described in connection with Fig. 1. From time to time, the molten slag, matte, or the like. accumulating in the bottom of the chamber 15 is removed by tapping the tube 34.

The arcing hearth may, if desired, be dispensed with and the electrodes may extend into proximity with the surface of the charge in the arcing chamber (see Fig. 3). The passage of the electric current across the spaces or gaps between the electrodes and the surface of the charge, will then develop the required heat for the operation of the furnace. Such a construction may advantageously be used when making zinc oxide from high grade metallic zinc. since with such a charge the establishment and maintenance of the are between the electrodes and the surface of the molten zinc is not interfered with by the separation out of the molten bath of solid non-volatile materials like iron surrounding the electrodes where the temperature is highest.

A modified furnace construction embodying certain features of my invention is .illustrated in Fig. 3. The outer metal casing 7 of this furnace extends through the heat insulating brick layer 6 to the concrete foundation 5. The inner metal casing 10 rests on the layer 6 and the space between the two casings is filled with sil-o-sel, or the like. 11.

The working chamber 15 of the furnace shown in Fig. 3 is provided with a rammed or tamped lining of refractory material. Various refractory mixes may be used to form the lining 35. Excellent result-s have been secured with a mix containing 39 pounds of Baum water glass solution, 19 pounds of water, 150 pounds of furnace chrome and 150 pounds calcined magnesite. The dry materials of this mix are ground to a size completely through mesh; the greater part of the material being actually through 200 mesh. The ground materials are then mixed with the water glass and water for approximately one hour in a large rod mill. The resulting mixture is then rammed or tamped into position to form the chamber 15 and then appropriately dried.

A feed well or pipe 29', of carborundum, earbofrax, or other suitable refractory ma terial, extends into the chamber 15. The upper and outer end of the feed pipe 29 terminatesin a housing 36 of such form as to permit the convenient introduction of the charge into the pipe and at the same time permit the covering or closing of the open end of the pipe during the intervals between charging. The pipe 29 is sealed in position with respect to the chamber 15 by a mass 37 of refractory material similar to the refractory material of the lining 35.

The top of the chamber 15 is covered by a roof 38 preferably of slabs or blocks of graphite. A. thick layer 39 of refractory material, similar to that of the lining 36, is laid on top of the roof 38.

The electrodes 16 are disposed longitudimetallic oxides V chamber for conducting metallic vapor from fractory-mix lining may be entirely replaced by a graphite block lining with appropriate surrounding layers of heat-refractory and heat-insulating materials as illustrated in Figs. 1 and 2 of the drawings.

The insulated metal casing 10 of my furnaee construction is of peculiar and special advantage. This easing holds the lining and surrounding layers of refractory material tightly together during the early stages of heating up the furnace, but not so tightly as a cold metal casing would, because by my construction, the casing also heats up and will expand as the lining heats u If desired, this casing maybe made of sufficient section to assist in the transfer or conduction of heat from the upper part of the furnace to the bottom and lower portions of, the heating chamber.

I claim:

1. A metallurgical furnace comprising a heating chamber, a vaporconduit associated with said. chamber for conducting metallic vapor from the chamber to the atmosphere exterior of the furnace, and means for directing a blast of relatively cool gas against the metallic vapor issuing from said conduit.

2. A metallurgical furnace for making comprising a heating chamber for producing metallic vapor, a vapor conduit associated with said chamber for conducting the metallic vapor produced therein to an oxide-forming environment, and means for directing a circumferential blast of relatively cool oxidizing gas against the metallic vapor issuing from said conduit. I Y

3. A metallurgical furnace comprising a heating chamber, an upright vapor conduit extendin thi ough the roof of said chamber for conducting metallic vapor upwardly from the chamber to the atmosphere above and exterior thereof, and means for directing a blast of relatively cool gas againstthe metallic vapor issuing from said conduit.

, 4:. A metallurgical. furnace comprising a heating chamber, a vertically disposed vapor, conduit extending through the roof of said the chamber to the exterior thereof, and a gas compartment surrounding the upper end of said conduit and arranged to direct a blast of relatively 'cool gas against the metallic vapor issuing from the conduit. 5. A metallurgical furnace comprising a 1 zle and having a substantially heating chamber, a vertically disposed vapor conduit extending through the roof of said chamber for conducting metallic" vapor from said chamber to the exterior thereof, a nozzle mounted on the roof of said chamber above said conduit and registering therewith, a compartment surrounding said nozcircular opening near the top of the nozzle,and means for supplying gas to said compartment.-

6. A metallurgical furnace comprising a heating chamber, a vapor conduitassociated with said chamber for conducting metallic vapor from said chamber to the exterior thereof, .a gas compartment operatively associated with the outer end of said conduit and having an opening therein adapted'to direct a blast of relatively cool gas against the metallic vapor issuing from said conduit.

7. A metallurgical furnace comprising a heating chamber, a vapor conduit associated with said chamber for conducting metallic vapor from said chamber to the exterior thereof, a nozzle registering with said vapor conduit and forming an extension thereof, a compartment surrounding said nozzle-and having an opening adjacent the discharge end thereof, and means for supplying gas to said compartment. If

8. A metallurgical furnace comprising a heating chamber, a vertically disposed vapor conduit extending through the roof ofsaid chamber for conductingmetallic vapor from said chamber to the exterior thereof, a nozzle mounted above said conduit and registering therewith, a compartment surrounding said nozzle and having an opening adjacent the upper discharge end thereof, and means for supplying gas to said compartment.

In a zinc oxide furnace having a chamber and a vapor conduit associated therewith for conducting metallic zinc vapor from the chamber to a zinc-oxide-forming environment, a gas compartment operatively associated with the discharge end of said conduit and having an opening therein adapted to direct a blast of relatively cool oxidizing gas against the metallic zinc vapor issuing-from said conduit.

10. In a zinc'oxide furnace having a vapor from the chamber to a zinc-oxideforming environment, and means operatively related to the discharge end of said conduit for directing a blast of relatively cool oxidizing gas against the metallic zinc vapor issuing from said'conduit.

11. In a zii oxide furnace having a chamber and a vapor conduit associated therewith for conducting metallic zinc vapor from the chamber to a zinc-oxide-forming environment, a nozzle registering with said vapor conduit and'forming an extension thereof, a compartment surrounding. said nozzle and having an opening adjacent the discharge end thereof for directing a blast of gas against the metallic zinc vapor issuing from the nozzle. and means for supplying a relatively cool oxidizing gas to said compartment. I

12. An electric furnace comprising a heating chamber lined with blocks of graphite, the contacting surfaces of said blocks being n'iachined so as to provide substantially perfect joints between adjacent blocks.-

13. An electric furnace comprising a heating chamber lined throughout with blocks of graphite, "the contacting surfaces of said blocks being machined so as to provide substantially perfect joints between adjacent blocks, and a layer of carbonaceous material surrounding the graphite-block linin 14. In an electric furnace, a heating chamber having an inner lining of graphite blocks, the contacting surfaces of said blocks being machined so as to provide substantially perfect joints between adjacent blocks and whereby the blocks form a substantially monolithic graphite lining for the chamber, and a layer of carbonaceous material surrounding said graphite block lining.

15. In an electric furnace, a heating cham ber having an inner lining of graphite blocks, a solid mass of graphite extending across one end of said chamber to a height above the normal operating level of the working charge in the chamber and having a substantially horizontal upper surface, a pair of spaced electrodes extending into proximity with said horizontal surface, and granular electric conductive material supported on said surface and contacting with said electrodes for providing an electric current path of relatively high resistance between the electrodes.

16. In an electric furnace, a heating chamber having an inner lining of graphite blocks,'an arcing hearth within said chamber having a substantially horizontal upper surface above the normal operating level of the working charge in the chamber, a pair of spaced electrodes extending into proximity with said horizontal surface, and granular electric conductive material supported on said surface and contacting with said electrodes for providing an electric current path of relatively high resistance between the electrodes.

17. In an electric furnace, a heating chamber having an inner lining of graphite blocks, an arcing hearth within said chamber having a substantially horizontal upper surface above the normal operating level of the working charge in the chamber, a pair of spaced electrodes extending into proximity with said horizontal surface, granular electric conductive material supported on said surface and contacting with said electrodes for providing an electric current path of relatively high resistance between the electrodes, and a charging well of refractory material for introducing material into the heating chamber terminating below the normal operating level of the working charge therein.

18. In an electric furnace, aheating chamber having a lining of graphite blocks, an arcing hearth made of a solid mass of graphite blocks extending across one end of the furnace to a height above the normal operating level of the working charge in the chamber and having a substantially horizontal upper surface, the contacting surfaces of said graphite blocks being machined smooth so as to provide substantially perfect joints between adjacent blocks, a pair of spaced electrodes extending into proximity with said horizontal surface, and granular electric conductive material supported on said surface and contacting with said electrodes for providing an electric current path of relatively high resistance between the electrodes.

19. In a metallurgical furnace, a heat refractory lining, a metallic casing surrounding said lining for holding the same firmly in position in the furnace structure, and heat-insulating material surrounding said casing.

20. In a metallurgical furnace, a metallic casing having a bottom and side walls, a heat-refractory lining within said casing, and heat-insulating material surrounding said casing.

21. A metallurgical furnace comprising a heating chamber having an inner lining of carbonaceous material, heat-insulating material surrounding said lining, a metallic casing for holding the inner elements of the furnace structure firmly in their respective positions, and heat-insulating material surrounding said casing.

22. In a metallurgical furnace, a heating chamber having an inner lining of graphite blocks, the contacting surfaces of said blocks being machined smooth so as to provide substantially perfect joints between adjacent blocks, heat-insulating material surrounding said graphite block lining, a metallic casing surrounding said heat-insulat ing material for holding the inner elements of the furnace structure firmly in their respective positions, and heat-insulating material surrounding said casing.

23. A metallurgical furnace comprising a heating chamber having an inner lining of carbonaceous material, heat-refractory material surrounding said inner lining, heatinsulating material surrounding said heatrefractory material, a metallic casing for holding the inner elements of the furnace structure firmly in their respective positions, and heat-insulating material surrounding said casin cent blocks and whereby the blocks form a substantially monolithic graphite lining for the chamber, a layer of carbonaceous material surrounding said graphite block lining, a layer of heat-refractory material sur-' rounding said layer of carbonaceous material, a layer of heat-insulating material covering said layer of heat-refractory material,

a metallic casing for confining and maintaining the aforesaid various elements in their respective positions in the furnace structure, and heat-insulating material surrounding said casing.

25. In a metallurgical furnace. a heat refractory lining, heat-insulating I surrounding said lining, a metallic casing surrounding said heat-insulating material for holding the inner elements of the furnace structure firmly in their respective po sitions, and heat'insulating material surrounding said casing.

26. A metallurgical furnace comprising a heating chamber having a heat-refractory lining, a metallic casing surrounding said lining for holding the same firmly in position in the furnace structure, heat-insulating material surrounding said casing, a vapor conduit associated with said chamber, and means operaIt-ively related to the discharge end of said conduit for directing a blast of gas against the vapor issuing from the conduit.

27. A metallurgical furnace comprising a heating chamber having a heat-refractory lining, a metallic casing surrounding said lining for holding the same firmly in position in the furnace structure, heat-insulating material surrounding said casing, a vapor conduit associated with said chamber, and a gas compartment operatively related to the discharge end of said conduit and having an opening therein adapted to direct a blast of gas againstthe vapor issuing from the conduit.

28. A metallurgical furnace comprising a heating chamber having a heat-refractory lining, heat-insulating material surrounding said lining, a metallic casing surrounding said heat-insulating material for holding the inner elements of the furnace structure firmly in'their respective positions, heat-insulating material surrounding said casing, a vapor conduit associated with said chamber, and means operatively related to the discharge end of said conduit for directing a blast of gas against the-vapor issuing from the conduit.

29. A metallurgical furnace comprising a heating chamber having an inner lining of carbonaceous material, heat-refractory mamaterial terial surrounding said lining, heat-insulating material surrounding said heat-refractory material, a metallic casing for holding the aforesaid inner elements of the furnace structure firmly in, their respective positions, heat-insulating material surrounding said casing, a vapor conduit associated with said chamber, and means operatively related .to the discharge end of said conduit for directing a blast of gas against the vapor issuing from the conduit.

30. A metallurgical furnace comprising a heating chamber having an inner lining of graphite blocks, the contacting surfaces of said blocks being machined smooth's'o as i o provide substantially perfect joints between adjacent blocks, a layer of carbonaceous material surrounding said graphite block lining, a layer of heat-refractory material surrounding said layer of carbonaceous material, a layer of heat-insulating material surrounding said layer of heat-refractory material, a metallic casing for holding the aforesaid inner elements of the furnace structure firmly in their respective positions, heat-insulating material surrounding said casing, a vapor conduit associated with said chamber, and a gas compartment operatively related to the discharge end of said conduit and having an opening therein adapted to direct a blast of gas against the vapor issuing from the conduit.

31, A metallurgical furnace comprising a heating chamber having an inner lining of graphite blocks, the contacting surfaces of said blocks being machined smooth so as to provide substantially perfect joints between adjacent blocks. heat-insulating material surrounding said graphite block lining, a metallic casing surrounding said heatinsulating material for holding the inner elements of the furnace structure firmly in their respective positions, heat-insulating material surrounding said casing. a vapor conduit associated with said chamber, and

a gas compartment operatively related to the discharge end of said conduit and having an opening therein adapted to direct a blast of gas against the vapor issuing from the conduit. 7

32. A metallurgical furnace having an inner lining of graphite blocks, the contacting surfaces of said blocks being machined smooth so as to provide substantially perfect joints between adjacent blocks, heatrefractory material surrounding said graphite block lining, heat-insulating material surrounding said heat-refractory material, a metallic casing for holding the aforesaid inner elements of the furnace structure firmly in their respective positions, heat-insulating material surrounding said casing, a vapor conduit associated with said chamber, means operatively related to the dischar e end of said conduit for directing a blast a gas against the vapor issuing from the conduit, an arcing hearth Within said chamber having a substantially horizontal upper surface above the normal operating level of the Working charge in the chamber, a pair of spaced electrodes extending into proximity withsaid horizontal surface, and granular electric conductive material supported on said surface and contacting with said electrodes.

33. An electric furnace comprising a heating chamber having a lining of graphite blocks, an arcing hearth made of a solid mass of graphite blocks extending across one end of the furnace to a height above the normal operating level of the Working charge in the chamber and having a substantially horizontal upper surface, the contacting surfaces of said graphite blocks being machined smooth so as to provide substantially perfect joints between adjacent blocks, heat-refractory material sun rounding said graphite block lining, heatinsulating material surrounding said heatrefractory material, a metallic casing for holding the aforesaid inner elements of the furnace structure firmly in their respective positions, heat-insulating material surrounding said casing, a vapor conduit associated with said chamber, a gas compartment operatively' related to the discharge end'of said conduit and having an opening therein adapted to direct a blast of gas against the vapor issuing from the conduit, a pair of spaced electrodes extending into proximity with the horizontal surface of said arcing hearth, and granular electric conductive material supported on said surface and contacting With said electrodes for providing an electric current path of relatively high resistance between the electrodes.

In testimony whereof I aflix my signature.

FRANK G. BREYER.

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