US1733419A - Continuous copper-melting furnace - Google Patents

Description

Oct. 29, 1929. H. s. LUKENS ErAL 1,733,419

CONTINUOUS COPPER NELTIHG FURNACE Original Filed Dec. 19, 1925 2 Sheets-Sheet 1 j, 1 I J6 4 Oct 2 1929. H. s. LUKENS ET m. 1,733,419

CONTINUOUS COPPER HELTING FURNACE Original Filed Dec. 19, 1925 2 Sheets-Sheet 2 flawiowa IYLZIM zzdifi'amz dim NN \N .i' aieiiie d @ct. 29, 1929 UNITED STATES PATENTOFFICE HIBAM S. LUKENS AND RUSSELL P. HEUER, OF PHILADELPHIA, PENNSYLVANIA CONTINUOUS COPPER-MELTING FURNACE Application filed December 19, 1925, Serial No. 76,440. Renewed August 16, 1929.

Our invention relates to methods and apparatus for refining copper and is suitable for use in founding operations attending copper refining.

A purpose of our invention is to continuously melt copper with a minimum of sulphur contamination and of oxidation subsequently as part of the continuous operation to deoxidize the molten copper.

A further purpose is to use ,waste heat from fuel combustion to preheat copper masses (which may be cathode masses) to a temperature near to their melting point and then to drop the massesinto a molten pool of copper and melt them while submerged in order to keep them from taking up sulphur during the melting.

A further purpose is to prevent a 001- of molten copper from absorbing sulp ur by protecting its surface with a layerof slag and maintaining a somewhat oxidizing atmosphere above the slag.

A further purpose is to operate the founding of copper as a continuous operation.

A further purpose is to deliver cathodes to a melting furnace in practically a'continuous stream, and to preheat the stream of cathodes by passing it into the furnace throu h a-flue carrying waste gases of combustion rom the furnace.

A further purpose is to continuously feed to and tap from a copper melting furnace.

Further purposes will appear in the specification and in the claims.

- In illustrating our invention we have elected to show one form only and have ,selected a form that is efficient in operation and inexpensive in manufacture and which illustrates particularly well the principles involved.

All of the figures are to a considerable extent diagrammatic.

Figure 1 is a top plan assembly view illustrating structure for operating our invention.

Figure 1 shows a portion of Figure 1 arranged to pour into moulds upon a casting wheel. v

Figure 2 is a side elevation of Figure 1.

Figure 3 is an end elevation of Figure 1.

' wide, which are so irregular'and rough as Figure 4 is an enlarged portion of Figure 1 showing the continuous melting furnace.

Figure 5 is a section of Figure 4 taken upon line 55.

Figure 6 is a sectional elevation of our fur- 5 nace for removing oxide from thecopper.

Figure 7 is a section of Figure 6 taken upon line 7-7.

Like numerals refer to like parts in all figures.

Describing in illustration and not in limitation, and referring to the drawings,-

The present invention is to some extent a development of the subject matter of our application No. 703,122, method of removing copper oxide from copper, filed March 31, 1924, and our application No. 758,723, method of freeing copper from copperoxide,. filed December 29, 1924:.

We antici ate that one of the widest applications 0 our invention will be that of working up the cathode product from electrolytic refining of copper, and for this reason illustrate it in this application.

The cathode raw material is usually substantially pure copper, but copper that is physically unsuited for commercial use.

Usually the cathodes comprise sheets about one inch thick, three feet long and two feet to be wholly unadapted to use without remelting.

Prior to our present invention in common practice the cathodes have been remelted withinlar e. reverberatory furnaces which are intermittent in operation. A customary charge has been about 250 tons. This is fired for about 12 hours before it is completely melted and during melting takes up some oxygen and considerable sulphur. The sulphur is burned out by blowing air into the molten bath. It goes 01f eventually with gaseous products of combustion as SO during the blowing.

The blowing operation, necessary to burn out the sulphur, greatly increases the oxide content of the molten'bath so that after the blowing is over the metal contains perhaps six percent of Cu O. an amount altogether too much for commercial copper, and the bath is now poled to remove the greater part of this copper oxide.

. At some time before poling, slags formed with the silica of the hearth and with other silicious materials are removed. This is necessary to prevent introduction of impurities from the slag into the pool during the polings.

The polin operation is tedious, expensive and wastefu The poles, usually are trees often eight or ten inches in diameter and forty feet long and as many as twenty of them are used on one charge.

Poling usually lasts about two hours and reduces the copper oxide content to a value never much less than one-half of one percent, which has for this reason hitherto been the oxide content of commercial copper.

After poling the charge is poured off into wire bars, ingot bars, cakes, etc., as desired, about five hours usually being required to empty the furnace. Such a furnace customarily makes one heat in 24 hours.

We may use the same raw material, the cathode product of electrolytic refining, but operate continuously, using Waste heat from the melting furnace to preheat the piles of cathodes to nearly melting temperature. We deliver the preheated piles of cathodes in a stream whic is not in heat-conductive relation with the bath and drop the end piles into the molten bath before they begin actually to melt. They here sink beneath the surface and melt out of contact with the gaseous combustion products of the furnace.

We protect the surface of the bath by a floating layer of the slag and maintain slightly oxidizing conditions above the slag, and melt while submerged, in this way being able to avoid the very material contamination with the sulphur that takes place when melting copper is in contact with products of combustion, as in the reverberatory furnace. We thus avoid or greatly reduce the need for blowing the bath to take out sulphur, by greatly reducin ing the oxide produced in blowing.

In our process some oxide is present in the metal after melting since we deem it desirable to maintain a slightly oxidizing atmos-' phere within the furnace to prevent absorption of sulphur through the slag, but the amount is much less than the six percent usually present from blowing the bath and we eliminate whatever amount there is to to 3, comprises the melting furnace15, slagging furnaces 16 and 17, pourin ladle 18 and casting wheel 19 with a ram 20 or delivering absorption of sulphur .and we avoid the su sequent necessity of remova stream .of piles 21, (preferably cathodes from electrolytic refining), into the melting furnace. The melting furnace is shown with a combustion chamber 22, hearth 23 and exit flue 24 to any suitable use or stack.

Fuel, desirably pulverized coal, and air for combustion, are delivered into the combustion chamber at 25 and the combustion products passing over the bridge 26 heat a molten pool 27 upon the hearth, leaving the furnace by means of the flue 24.

The hearth tapers downwardly toward the rear making the pool relatively deep in the rear where the cathodes are to be dropped into it and shallow in the front portions of the hearth. The exit fiue leaves the furnace from a point28 some distance above the surface of the pool within the hearth. The puroses of droppin the cathode piles into the bath are two-fol This protects from loss of heat from the pool by conduction of heat from mass to mass back through the line of cathodes. Such losses would have the cf fect of chilling the pool. Our invention also makes sure that the melting takes place below the slag.

The exit flue serves a double purpose, that of leading away the gaseous products of combustion, and that of providing a runway 29 in which to preheat the piles before they enter the pool. It is shown as sloping upwardly away from the furnace, so that the runway, carrying in fresh piles, slopes downwardly to the furnace. This downward slope of the runway toward the furnace makes easier the workof pushing in the piles.

The runwa is the sloping bot-tom of the flue 24 and t e inwardly progressing piles are shown covering it throughout its length and most of its breadth. The copper may be raised somewhat on runway 29 to permit the hot gases to surround the copper if desired.

The piles are pushed into the flue at the rear through any suitable opening 30 by the reciprocating plungers 31 of the ram 20.

Rows of piles are placed successively in I front of the plungers upon a suitable feed table 32 and are pushed forward into the flue successively-by the forward strokes of the plungers. In movin forward successively they push ahead of t em the layers of piles already in the fiue. With each stroke of the plungers a row of cold piles is thus pushed into the flue, those piles already in the flue are progressed forwardly one step, and a front row, now preheated by its progressive passage throughout the whole length of the hot flue, falls into the pool, to sink and melt while submerged. Three rows of iles are shown side by side on the runway. With the usual dimensions of copper cathodes this would-mean a total runway width of about nine feet, and if one such row falls into the pool, with each stroke gle plunger.

of the plunger the effective stroke of the plunger will be about two feet. Three plungers are shown in the figure. These may act from the gases of combustion, and yet as near to this temperature as is practicable. In practice this means with piles of copper cathodes a temperature just below melting.

The depth of the pool at 33 where the piles enter is suflicient to permit the piles to sink below the surface of the pool before they begin to melt, and, with the available heat of the furnace to secure substantially complete melting of each charge before the next charge comes in with the next stroke of the ram. The temperature of the molten metal at this part of the pool is near but somewhat above the melting temperature to continually supply the latent heat of fusion.

As is best seen in Eigurefi, the bottom is desirably sloped so as to become progressively more shallow toward the front of the hearth, and the molten metal is continuously.

discharged from a suitable delivery spout 34 near the front of the furnace. It is well to have the metal somewhat superheated above its melting temperature when delivered, and the progressively smaller depth toward the delivery door lends itself to superheating the metal near the point of delivery notwithstanding that the temperature at the rear ofsthe hearth is nearer the melting point.

The slag upon the surface of the bath is normally that which forms of itself, due to oxidizing some of the metal with perhaps deposition of more or less ash from the fuel of combustion.

The furnace operates continuously day and night and we show a door 35 at which excess slag due to gradual accumulation over a considerable period of time, may be removed as found desirable.

The melting furnace is shown as delivering its superheated metal continuously through its spout 34 into the deoxidizing furnace 16.

The deoxidizing or slagging furnace has already been described and explained in detail in our applications above referred to.

The molten copper within the furnace 16 is covered with a 'deoxidizing slag 36, the slag being so chosen that under operating conditions the partial free energy of copper oxide in it is less than the partial free energy of copper oxide in the incoming copper.

tpen passes from the molten copper into the s ag. c

To prevent undue increase in the partial free energy of the copper oxide in slag which would result in the slag becoming ineffective for the removal of copper oxide from the copper, we provide means chemically or/and electrolytically for reducing the oxide of the slag, so that the slag may be maintained continuously operative or may be used over and over.

This revivification of the slag may be per formed in place, if desired, continuously or intermittently as illustrated in Figure 6, or

some of the slag may be removed continuous- 'ly or intermittently for treatment to reduce its oxide content with a corresponding delivery into the furnace of fresh slag.

In the structure shown in Figure 6 the molten copper is covered with a layer of slag 36. Above this is shown a thick layer of carbon 37; and electrodes 38 and 39 make contact with theslag. They are adapted for use either in electrolytic deposition of copper from copper oxide absorbed by the slag or in electrica ly heating the furnace interior.

The molten stream from-the melting furnace enters the slagging furnace through a suitable door 40. Doors 41 and 42 in the roof of the slagging furnace may be used for the charging of slag or carbon, or one may be used as an inlet for hot gases to heat the furnace interior and the other as an outlet for these gases.

The furnace is shown mounted upon suitable trunnions 43 and 44 for use in emptying the furnace when it is to be shut down, as for repairs. In normal operation, molten copper purified to any desired degree from its dissolved copper oxide is delivered through a seal 45 and spout 46 into the pouring ladle 18 feeding the moulds 47 of the casting wheel 19.

It is often desirable to provide more than one slaging furnace. This has an advantage in that a poorer slag may be used in the first slagging furnace than is adapted for complete elimination of copper oxide from the metal. The elimination of final traces of copper oxide is then performed in the second slagging furnace in which the partial free energy of copper oxide which is attained in the slag should be relatively lower than that attained in the slag within the first slagging v furnace.

Lower partial free energy of copper oxide in the slag of the second furnace will mean lower copper oxide content in the slag of the second furnace as compared to that in the first furnace if the two slags be otherwise chemically the same.

In the figures we have illustrated the use of two slagging furnaces, which, as above,

As explained in detail in our other appli makes available for use in the first furnace cations above referred to, the copper oxide a slag that would be unavailable for use at 130 all if but one furnace were used. Even if the same slag be used, the higher-concentration of copper oxide in the first'furnace would cause reduction to take place more rapidly in it than in the second furnace.

The pouring ladle, casting wheel and moulds are all shown conventionally and in themselves form no part of the present invention.

In operation, the piles of cathodes are slowly progressed through the hot flue 24 by the ram 20. Theytravel in any desired number of transverse rows covering the whole floor ofthe flue and ultimately drop into the molten bath, having been preheated in the flue to a temperature preferably just below that of incipient melting. When they take their plunge into the molten bath the piles sink beneath the surface of the molten co per, and the layer of slag upon the top of the ath and the somewhat oxidizing conditions main tained above the slag largely protect the bath from sulphur.

The drop deliver of the piles into the bath prevents heat con uction between the bath and the layer of piles in the flue, with 1ts attendant cooling of the bath.

Normally the product will contain so little sulphur that this may be neglected but any objectionable sulphur content may be re moved by blowing. l

The molten product containing copper oxide is delivered in a continuous stream through the spout 34 into the first slagging furnace. l

- When leaving the melting furnace and en- 1 tering the slagging furnace the metal is preferably preheated sufliciently to avoid the need of adding additional heat within the slagging furnace.

It is to be noted that the slag used should. be one in which copper oxide has a relatively.

, lower partial free energy than copper oxide would have in" the copper bath.

The copper oxide from the molten co per flows into the supernatant slag. This oating slag is maintained effective for removal of copper oxide from the metal either chemically by carbon or hydro-carbon or electrol ically or both. The revivification of this s ag, continuously'or intermittently has been slagging furnace.

described in "detail in the applications above referred to. w

The first slagging furnace is shown delivering continuously through'a trap45 and spout 46 into a second slagglng furnace and the second slaging furnace is shown as delivering continuously into the ladle 18 feeding the moulds 47 of the casting wheel 19.

. The casting wheel is operated continuously.

The pouring ladle does not move away from beneath the delivery spout 46 of the second The man who ours successively advances the wheel to ring successive moulds to position to be filled and at the end of a week to mend furnace linings and when this is done the slag furnaces are turned on their trunnions to empty the s out traps 45 and 45. This prevents metal rom freezing and closing ofl' the spouts.

While we regard our invention as most widely applicable at the present state of the art for founding the cathode product from electrolytic refining, we recognize that the invention is applicable to founding other raw material than cathodes and within limits other metals than copper.

Obviously the specific structure used may be widely varied to meet individual need and particular whim and in view of our invention and disclosures such variations and modifications will doubtless become evident to others skilled in the art. We therefore claim all such in so far as they fall within the reasonable spirit and scope of our invention.

Having thus described our invention, what we claim as new and desire to secure by Let- .ters Patent is p 1. In apparatus for melting a stream of copper masses, a furnace adapted to contain a pool, a hearth, an exit flue for gaseous products of combustion of the furnace,'

adapted to receive the masses fed, flat for gravity feed of copper masses andspaced at the furnace end above the pool, means for positively advancing a stream of copper masses'along the bottom of the flue and dropping them at the spacing, preheatedinto the pool and means for continuously delivering molten copper from the furnace.

'3. A furnace for melting copperv cathodes adapted to contain a pool of molten copper, a fuel inlet, an exit flue for the gaseous products of combustion, positively step by step means for passing a stream of masses of copper relatively slowly toward the pool and means separating the stream from the pool and-for discharging the copper abruptly into the pool.

4. The process of preheating copper and of melting it free from attack by sulphur while melting by the gaseous products of combustion in a furnace adapted to contain a furnace pool and having a flue leading off from said furnace pool, which consists in feeding the copper masses through the flue relatively slowly to preheat the copper, in dropping them into the bath to submerge them quickly therein and to avoid continuous heat conduction from the pool to the masses and maintaining a covering above the pool to protect the surface from gaseous products of combustion.

5. The process of melting copper in conjunction with a furnace adapted to contain a pool ofmolten copper, which consists in preheating the copper in its path to the furnace pool by moving it through a preheated flue at a relatively slow speed and in plunging it beneath the surface of the furnace pool quickly by dropping it into the pool, thus preventing heat conduction from the pool masses further from the furnace pool, giving heat transferring contact between the adj oining masses in the line pushed and in plunging the end masses adj oining the pool successively quickly into the pool to avoid continuity of contact between molten and solid copper and prevent heat conduction from the molten bath to the stream of copper masses.

HIRAM S. LUKENS.

RUSSELL P. HEUER.

back through the plungingscopper to other copper which is being moved through the flue.

6. In the art of founding copper from masses within a furnace, the steps which consist in relatively slowly advancing the solid masses through a space traversed by hot gases from the furnace, to preheat the masses, and in suddenly wholly submerging the masses in'molten copper while they are still solid, thus avoiding continuous heat conduction between the molten copper and the masses.

7. In the art of founding copper from masses within a furnace, the steps which consist in relatively slowly advancing the solid masses through a space traversed by hot gases from the furnace to preheat the masses, in submerging the masses in molten copper by dropping them into a pool of molten copper while they are still solid so that heat conduction between the molten copper and the masses is avoided, in protecting the molten copper from sulphur contamination by covering its surface with a layer of slag and in maintaining an oxidizing atmosphere over the slag.

8. The steps in the continuous founding of copper from a stream of copper. masses entering a furnace along a flue carrying gases of combustion away from the furnace, which consists in relatively slowly advancing the masses toward the furnace, to preheat them and in dropping the masses successively into a bath of molten copper within the furnace and thus avoiding heat conduction from the molten bath to the stream of copper piles.

9. The steps in the continuous founding of copper from a stream of copper masses fed into a furnace al'on a flue carrying gases of combustion away om the furnace, which consist in feeding the masses through the flue relatively slowly by pushing the masses nearer to the furnace pool by means of the

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