US2657990A - Feeding furnaces - Google Patents

Description

C. R. KUZELL FEEDING FURNACES Nov. 3, 1953 4 sheets-sheet 1 Filed March 29, 1949 ATTORNEY C. R. KUZELL FEEDING FURNACES Nov. 3, 1953 4 Sheets-Sheet 2 Filed March 29. 1949 INVENTOR M t w K. R... m, M pHv B ATTORNEY Nov. 3, 1953 c. R. KuzELl. 2,657,990

FEEDING FURNACES i Filed March 29. 1949 4 Sheets-Sheet 5 INVENTOR CHARLES R. KUZELL Nov. 3, 1953 c. R. KuzELL 2,657,990

FEEDING FURNACES Filed March 29. 1949 4 Shee'Ls-Sheetl 4 INVENTOR CHAR/.Es R KuzELL ATTORNEY Patented Nov. 3, 1953 Charles R. Kuzell, Douglas', Ariz., assignor to Phelps Dodge Corporation, New York, N. Y., a

corporationof N ew York Application Marchas, 1949, serial No. 84,166

9 Claims. (Cl. 'I5-74) `This invention relates to a method of feeding tween charges but a molten bath is maintained the furnace at all times between the time of starting up the furnace and shutting it down for repairs or some other reason.

One method of feeding such a furnace that has been used was the `introduction of the 'charge through holes or. ports in the center of the furnace roof or arch, allowing the charge to fall by gravity down into the bath. This center feed method could be used only for dry material however, and in more'recent years has been largely superseded by the side feeding furnace.

The charging openings in the side feed furnaces are located at the edge of" the arch along the skewback so that the charge piles up in sloping heaps along the interior side walls ofthe furnace. This was adoptedwith a'view to protecting the sidewalls of Y' the furnace and-in an effort to approach continuous feeding and smelt- However, this method has the disadvantage of producing accumulations of solidified material on the floor or hearthof the furnace which gradually build up and reduce the size of the molten bath. Such solid accumulations include charged material that has never been melted but that has been forced down through the bath'to a'point K where the temperatures are too low fory melting,

and other material which has separated out'of the bath as a refractory substance.

rilhe so-called gun-feed bath furnace has also been used with hot dry raw materials, and in this case the hot dry feed is introduced by gravity through retractable inclined conduits `or pipes inserted through the side walls of the furnace so that they discharge at an elevationlonly a few inches above the surface of the bath and cause the calcine to spread over the surface-of the bath. Such a feeding method;A however, could not be used for moist orwet material. i.

In recent years, there has been considerable use of the reverberatory furnace to melt down.

concentrates froml copper ore, thesefconcentrates being unroasted and oftenl moist, andin some cases even wet. This developmentwas brought about byfprogress in the ore dressing field and the upgrading of concentrates from copper ore to such an extent that it became no longer necessary to roast the concentrates preliminary to smelting in order to make a copper matte of the desired high copper content for converting directly to blister copper.

By this procedure the three-step process of roasting, melting and converting hasbeen reduced to a two-step process of melting and converting. However, because wet materials in contact with molten matte produce violent explosions` it has been apparent that the old center feed or gun feed type of furnace could not be used, and the charging of such material has had to be confined to the side feed furnace with its attendant disadvantages. However, even with this method of feeding, operators are troubled by the fact that explosions do occur unless the greatestv of vcare is exercised to prevent any substantial quantity of wet material from slipping down or rolling olf the inclined heap of charge along thev sides ofthe furnace and plunging into the bath. f l

Also, such moist or Wet unroasted concentrates are not providedwith adequate flux for the silicious matter, such as the iron oxide which is present in a roasted ore or concentrate, and this necessarily makes diicult the practice of smeltingraw or Wet sulfide concentrates in the reverberatory furnace. The iluxing of the non-sulfide or silicious portion of the charge is very haphazard with the side feeding method. In the two-stage melting-converting process al1 of the iron sulfide in the reverberatory furnace charge must beoxidized in the final or converting step and all of the iron oxide produced in the converter is returned at infrequent intervals to the reverberatory furnace in the form-of molten converter slag. 1- v .For the Ibest metallurgical results, such converter slag must not only be combined with additional silicious material to increase its silicate contentto the point where'it can be economically disposed of as reverberatoryfurnace slag, but also the condition of super-oxidation in which it arrives at the reverberatory furnace must be reducedV by proper high temperature contact with sulphide or other reducing agent. These results vare not properlyr accomplished in the side feed reverberatory' furnace'and the converter" slag is `likely to flow forwardly in the furnace more or less along the center line thereof'and thus pick up only in a haphazard fashion the needed silica and sulde material with which it should react.

Y hnotherfdificulty inherent in the sidefeed'fur- ,trates is that it does 3 nace for the treatment of raw or wet concennot lend itself to steady continuous feeding. All sulfide concentrates contain some volatile sulfur, and if substantial amounts of pyrite are present, this sulfur has substantial fuel value which should be utilized. The side feed furnace does not permit uniform control of the combustion of the sulfur as shown by the fact that even under the best operating conditions, sulfur vapor is usually present in the furnace exit during part of the cycle while free oxygen is present in other parts of the cycle. In attempting to proportion combustion air to the regular furnace fuel plus the irregular sulfur supply, the furnace operator is compelled to operate with appreciable thermal inefficiency. This in turn means that it is not possible to melt nearly as much solid charge as the furnace is theoretically capable of smelting.

One object of my invention is the provision of a method of feeding a reverberatory furnace which makes bath smelting applicable to raw moist charges without explosion hazards and without the necessity of expensive and laborious pre-mixing or bedding the Acharge of raw materials.

A further object of this invention is the provision of a reverberatory furnace feeding method for the direct melting of sulfide concentrates which provides better fluxing ofthe charge, better reduction and treatment of converter slag, less iron in the matte and less copper loss in the reverberatory furnace slag.

Another object of my invention is to provide such a furnace feeding method for moist concentrates which improves the utilization asfuel of the volatile sulfur content of the concentrates.

A still further object is the provision of such a feeding method which permits the charge to be fed more continuously and makes possible a reduction in labor and in fuel consumption as well as an increase in the smelting capacity of the furnace.

These objects and advantages will be more readily understood from the following description of my invention in conjunction with the accompanying drawings, in which:

Fig. l is a general plan view of a copper reverberatory furnace equipped for operation according to my invention.

' Fig. 2 is a side elevational view of such a copper reverberatory furnace.

Fig. 3 is a transverse sectional view through such a furnace, taken approximately'on the line 3,-3 of Fig. 2.

Fig. 4 is a side elevational view, partly in -section, showing one form of charging device mounted for use according to my invention.

Fig. 5 is a sectional view through such a charg-l ing device, taken approximately alongA the offset line 5-5 of Fig. 4.

Fig. 6 is a plan view of the charging device illustrated in Figs. 4 and 5.

Figs. 7, 8, 9 and 10 are side elevational views, partly in section, showing other forms of charging devices that can be utilized for feeding a furnace according to my invention.

I have found that the foregoing objectives and advantages can be accomplished by forming a molten bath. in a reverberatory furnace, and spreading or distributing over the surface of the bath the raw materials charged into the furnace to produce a layer that will not submerge, sink or plunge so as tobring wet or moist materials in contact with the molten matte.

which floats on or near the surface of the bath, is preferably maintained at such a thickness that rapid smelting will be promoted by the exposure of its upper surface to the flame in the furnace and its under surface to the stored up heat in the molten bath. Moist or wet concentrates can thus be charged into a furnace as well as iiuxing and other materials. The charge may be premixed, although it does not have to be and the different materials can be charged in separately. Suitable uxes, reducing agents or other materials may be introduced as separate layers when needed and the entire layer or blanket of the charge may be continuously or intermittently replenished at the will of the operator, thus making the method unusually flexible.

rIg'his method also permits much more efficient handling of the molten converter slag since a layer of appropriate silicious flux with or without a sulfide or carbonaceous reducing agent may be established on the surface of the bath in the area near the port through which the molten converter slag is introduced into the furnace.

Referring n ow to Figs. 1, 2 and 3 of the drawings, numeral II indicates generally a reverberatory furnace for smelting copper ores or concentrates in accordance with my invention. This furnace may be constructed with the concrete and cast slag foundation I2 and I3 reinforced as necessary by suitable tie rods. The furnace may also be provided with the crucible I4 and formed with refractory side walls I5, arch or roof I6, and end walls I'I made and lined with any desired type of refractories.

One end of the furnace is provided with ports I8 for the burners used to fire the furnace, and provision may be made for one or more uptakes I9 at the other end of the furnace to carry off the exit gases.

The furnace may also be provided with the customary slag skimming launder 20. to deliver the reverberatory furnace slag directly into a. slag pot 2-I, the usual matte tapping spouts 22 for drawing off matte directly into the ladles 23, and the launder 24 for the. introduction of converter slag into Vthe reverberatory furnace.

In accordance with my invention, the side walls of the furnace are preferably provided at appropriate intervals with charging ports 25, and if desired an additional charging port 26 may be provided in the end Wall of the furnace near the charging the furnace.

port communicating with the converter slag launder 24. Vertically sliding doors 25a may be usedto cover theseports when they are not being employed for charging the furnace.

Platforms 2.1 supported by-suitable superstructure 28; may be arranged along. the walls of` the furnace opposite these charging ports 25 and 26, so that charging'devicessuch as shown at v2.9 may be properly positioned; adjusted and operated for Raw materials to be introduced into the furnace may be handled in portable containers` SII; which can be positioned on platformsA 21a aboveV the feeding hoppersl` used with variable-speed conveyors 3Ia for delivering the raw materials to the charging devices 29.

The portable containers 30 may be readily shifted fromone position to another as desired by meansof an overhead crane and eachindividual container may, if desired, be iilled'with different material tobe charged, suchas moist concentrates, silica, crushed lime rock, or Whatever is to be fed intothe furnace fromtime to time.

Referenceis now, madelparticularly to Figs. 4,

This layer, 15 5 and 6 which illustrate one form of charging device 29 suitable forfeeding afurnace'infaccordance with my method. YThis slinging-type of charging device may consist of a carriage 32 mounted on wheels 33 so that it can be moved up into position adjacent the charging ports 25 or 26 for feeding material into the furnace, orl can be retracted to a position back some distance from the furnace side wall when it is notl being used for feeding. The Icarriage 32 may have an upper plate 34 which supports similar plate y35 for rotation about the central axis or spindle 36. Plate 35 in turn has bolted thereto the vertical arms 31 which'supportthe frame 38 of the slinging device for rotation on trunnion about a horizontal axis.

The slinging device itself may consist ofan endless belt 39 driven by the motor 40 and supported by the pulleys or rollers 40a, 4| and 42 to hold the belt in contact with the distributing Wheel 43.

The distributing wheel 43 is preferably lconstructed with radially extending side flanges 44 centrally Iconnected by a -cylindrical hub 45 ofA smaller diameter. The outer ends of the side flanges 44 are provided with flat surfaces 46 which 'bear directly against the outer edges of the belt 39, thus leaving an arcuate space bounded by the side flanges 44, the belt 39 and hub 45 Where the belt is in contact with this wheel. A hopper or chute 41 is mounted above and to one side of the axle of the distributing wheel in such a manner as to deliver the raw materia1 48 into the upper end of this arcuate space. Thus, as the raw material is brought into Icontact with the rapidly moving belt, it is formed into a, compact stream and propelled by the belt into the furnace along a very at trajectory.

The frame 38 of the charging device which carries the motor 40, the belt 39, pulleys 4| and 42, distributing wheel 43 and hopper 41, is arranged to be rotated or tilted as a unit about a horizontal axis by reason of the support of this frame on trunnions by the arms 31.' In this manner the angle which the delivering portion of the belt 39 makes with the horizontal can be varied by tilting the charging device so that the pulley 42 is lowered or raised the required amount.

In addition, the entire charging device being supported on the rotatable plate 35 can be swung about a vertical axis so that the direction of the belt 39 is changed laterally. The charging device itself thus can be readily swung in a horizontal direction or tilted vertically by the operator using the handle 50 which is fixed to the frame 38 to direct the raw material as may be desired. Y

The motor 40 is preferably designed to operate the belt at a fairly high speed so that a more or less compact ribbon of raw material, as illustrated at may be delivered continuously from the end of the belt and propelled or projected through the charging ports 25 or 26, into the furnace. Vertica1 tilting of the charging device will of course change the angle and therefore the distance that this raw material is thrown into the furnace. Dot-dash lines 52 indicate a position in which the material is projected a considerable distance into the furnace, whereas the stream 5| is illustrated as being delivered onto the surface of the molten bath at a point fairly close to the side wall |5.

In any case the materials charged preferably are thrown so as to hit the surface of the bath at .a low angle and in the form of a more or less compact stream. 'Ihis avoids submersion or of the molten bath." -i i 1,

Insteadcf the sunging device mutated'inf Figs. 4,'5l and 6,! other devices maybek used to.

feed moist yor wet concentrates and other moist or dry raw materialsinto a reverberatory furnaceto spread or "distribute these raw materials over the surface of the molten bath in accordance with my invention.

Fig; 7 illustrates a rotary disc typev of slinging device which may be used for moist or dry materials and is shown mounted upon a retractable wheeled carriage 55. In this case the device consists essentially of a rotatable disc 56 mounted on a frame 51 that is arranged to tilt about a horizontal axis. Disc 56 may be rotated at a reasonably highk speed by the motor y53. Mounted above the disc 56 so that its lower edge just clears the disc surface is a stationary cylindrical shell v59 supported by the shaft 60. The shell 59 preferably has an opening 6| :adjacent the charging port 25 in the furnace side wall |5 and is provided with a fixed plow element 62 at .one side of the opening 6I. Thus, as wet concentrates or other raw material are delivered onto the surface of the disc 56 from the spout 63, the rotating disc brings this material around at high speed to a point Where'it'fis caught'by the plow 62 and directed out through the opening 6|. Centrifugal force thus serves to project the material into the furnace. L

If desired, the cylindrical shell 59 may be made adjustable to swing the opening 6| to one side or the other and thus provide some lateral adjustment under the control of the operator, and of course tilting the disc 56 about a horizontal axis provides the operator with some fiexibility of control in the distance that the raw material is projected or propelled into the furnace.

Another form of charging device which is i1- lustrated in Fig. 8 consists of a frame 65 mounted on a retractable carriage 66, the frame 65 being rotatable about a verticalfaxis. vFrame 65 supports on trunnions for vertical tilting a pneumatic discharge tube 61 which is provided at its upper portion with a feed hopper 68 to receive the wet concentrates or other raw materials from the delivery hopper 69.V Compressed air or other gas may be supplied to the device through the hose 16 controlled by the valve 1|. The inner end of the hose 10 may be provided with a tapered nozzle 12 to serve as an injector for entraining and forcing the raw materials out the end of the tube 61. The operator may easily adjust the vertical angle of throw or lateral angle of dist'iibution of the charge by means of the handle Another form of charging'device is illustrated in Fig. 9 and consists essentially of a motor driven centrifugal pump-15 supported on a suitable retractable carriage"16. AA pumpable mixture of slurry of the raw material to be charged into the furnace is 'delivered' toA the pump Vthrough the inlet 11 and is discharged through the flexible hose 18 and a rigid nozzle 19 of any vsuitable length. Thus, byv moving Vthe nozzle 19v around to different positions, and preferably by ,holding the end of the nozzle close to the surface of the molten bath of the furnacef` the operatorA can deliver a continuous compact stream of raw material onto the surface ofthe bath and distribute or spread this material V'around at will.

A still further form of charging device is illustrated in Fig.' 10 'and' consists essentiallyof -an extruding chamber: 80 mounted on airetra'ctablelrcerriager Mii and. driven.: through suitable reduction gearing by the motorrll;A The; extnuding machinemaybe provided uiternally-With; a feed.screw:-83.1of suitable sizesand pitchp. andthe wet materialv to: be :extnudedcinz pasteflikef conf-v sistency'isiediinto the extrusion! chamber through. a= suitable hopper. or; intaregsuchas; shown at; 84; The outlet of theextrudingmachine may also. be provided with a flexiblefhose 85,'- havingatits outerV end .an rigid; delivery; nozzle 86;-which the operator can move. around as neededfto deliver an extrudedribbon off moist rawmaterial directly onto. the. surface of* the'fmolten'bath in; the furnace.

In accordancewithi. my invention; the raw maf terials, whether-'theyl be moistfor dryV ores., concentrates, fluxesrorrother material, are projected, or' propelled...1aterally.:V into .the'f furnace onto the surface. of: thefmoltenbath of. theV furnace, in such af. manner that :theimaterial delivered will not submerge, sinleorfplunge intoy the' molten bath but' will .be established. and maintained, as` a floating. layerV having. its4` upper surface 'ex-posed* to the flamerin .the furnace;- and fits. under surface exposed. taz thefstored'iup: heat in-the molten bath.` This. procedure. makes'. unnecessary the pre-mixeing or Abedding of 'rawfmaterials to' be charged into. the. furnace sincereachz-material. can be sepa.- rately'ichargediand" proportioned as desired. In addition, ofcourse, concentrates .to be smelteci can be delivered directly to the furnace from thefllters or.. concentratorsi: without. intermediate treatment, and` such.. delivery.` can be made Vby.- means of portablevcontainers, conveyorI belts or. other suitable means.. By,.'cl'elivering` the. charged. materials.ontozvthe; surface: of. thefbath at'. aflow; preferably almosthorizontal angle, I have found thatit is: possible: to: charge wet raw materials into the furnaceiwithout any serious. hazard of explosions;

I prefer tduseza charging: device; whichI iseasy for. the operatorA to regulate-and adjust, and. for this; purpose the; slinging-.device illustrated iin Figs. 4,. 5.` and 6, isparticularlyi suitable., By swinging..thezmachinelaterallyV4 as well as upv and Vdown,.th `e operatori canA deposit afan-like. thin blanket of concentrates. or yrawcharge on the surface ofthehetzbath." Spreading action caused by .the heatexchangeandeliminationof moisture and other; gases; cause further spreading of the blanket so that it can-.be readily made to. cover substantially` :the whole area of the smeltingA zone of the furnacegthus presenting a maximum sur face; areazto the flame and. to the. hot. bathv and promoting rapiditynof smelting andi eiiicientuse of thefurnace'fuel;v

The feeding method of my invention may be carried out. continuously .by the operatori if; desired, or it can be made continuous-only for certain periods of time..

When the operator i is: about rto; receive. molten slag from .the converter departmentfit'. issa .simple nratterV for; him td Aprepare*l the bathilto'.: receive this: slag; so that.4 theV properfreactionsi take)A place and are controlled.

It is most desirable toi-retluce"the-higherl iron -oxideslsuchal as magnetite in the'\converter slag toferrousoxide.V The latterr can them-'easily be combinedwith hot silica; to produceiar` reverberatory furnace slag suitable for= disposal'.I Just-before .the converter: slag is received; the;I operator may spreadioverI thepbath mearrthe Iconverterfslag launder.; a suitable layer; of silicai and reducing agent: Eon' example;` in. `the :furnace illustrated,

aslniing device-maebeaoperatedtdeliverrsilica.

reaction withebullition of the bath which prop v erly stirs andmixes the various ingredients and thusipromotesstheqbest metallurgical result at or close-to the surface ofthe bath. Such treatment minimizes `the amountof unconverted heavy oxides'ofiron.V which re-enter the matte-and are re-cycled unnecessarily back to the converter department. y

Also, .such aitreatmentreduces to a minimum the amount of/oxides that separate out and freeze as solid'accretionson the hearth of the crucible l and which eventually cut down its capacity for holdingjfluidmatte and slag. More complete metallurgical-reactions at this point in the process alsol reduce` the amount of copper which otherwise wouldberetained by the slag and lost when the 'reverberatory furnace slag is taken to the slag dump.

The feeding method of my invention also makes possible the introduction of crushed lime rock or otherc fluxes and the'kspreading of such material overthebath at any time that such correction may beneeded.V In accordance with my invention,.such additions can be madequickly and are almost immediately effective, whereas such corrective measures-.arenot possible with the standardside feed.v furnace as. heretofore operated. The feedingmethodofmy invention further cuts down the surgeswhich-otherwise necessarily take placein the ratefofliberation of sulfur. With the sulfur-liberated at amore uniformrate in accordancezwith `myx feeding method, it is far easier for the.- operator to regulate combustion air in the-furnace andthus-produce more eicient useof available fuel.

The termsand' expressions which I have employed are. used. asvterms of description and not of limitation, and I. have no intention, in the use of such-termsand expressions, of excluding any.; equivalents` ofthe features shown and describedforl portions thereof,lbut recognize that various.- modifications are possible within the scope. oftheinvention claimed.

1` A..metliod offeeding a reverberatory smelting furnacecontaininga molten bath of metalliferous materials Whichcomprises propelling moist concentrates laterally into the furnace in the form 'ofI a compact stream unmixed with air so. thatsaid.- stream strikes the surface of the moltenbath ata low angle to avoid plunging moist surfacesf-into. thebath incontact with moltenimattefand toform andmaintain a floating layer of solid materialcovering at least a substantiallarea of the molten bath.

2. A. method.as-deiined in` claim l in which thecompact. stream ofmoistconcentrates is introducedthrough. anzopening in asidewall of the furnace andz'thedirection in which the stream` isfpropelled into l the furnace is changed from time to time to spread the concentrates around over different areas of the molten bath surface.

BMA method'assdeiined` in claim 1 iny which fluxing :materialsfareseparately charged into the furnace from. time; totime: in theA same manner that'. thefmoist concentrates are: charged.

ll. A method as dened in claim 1 in which the raw materials charged into the furnace are propelled through a port in the furnace Wall by a slinging device.

5. A method as defined in claim 1 in which the raw materials charged into the furnace are propelled through a port in the furnace Wall by a pneumatic device.

6. A method as defined in claim 1 in which the moist concentrates are mixed with fluxing material before being propelled into the furnace.

7. A method of operating a copper smelting reverberatory furnace which comprises forming a molten bath of matte and slag extending substantiallil` the full width of the furnace, establishing a layer of solid materials to be smelted floating or near the surface and covering a substantial area of said molten bath, and maintaining said solid layer by propelling laterally into the furnace at least one ribbon-like stream of moist copper concentrates unmxed with air so that the stream strikes the surface of said molten bath or said layer at a low angle to avoid plunging moist solids below the surface of the bath and into contact with the molten matte.

3. A method as dened in claim 7 in which from time to time silica is distributed over one 10 area of the molten bath where converter slag is normally received, and molten converter slag is then introduced to flow over said area for reaction therewith.

9. A method as defined in claim 7 in which the direction in which the ribbon-like stream of concentrates is propelled into the furnace is varied from time to time to spread the concentrates over a substantial area of the molten bath.

CHARLES R. KUZELL.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 871,477 Charles Nov. 19, 190'? 895,939 Baggaley Aug. 11, 1998 1,164,653 Klepinger et al. Dec. 21, 1915 1,240,409 Black -eptl i8, 1917 1,286,652 Kirsebom Dec. 3, 1918 1,378,223 Garr May 17, 1921 1,759,078 Wilkinson May 20, 1930 1,915,540 Krejci .lune 27, 1933 1,940,977 Simpson Dec. 26, 1933 2,307,459 Greenavvalt Jan. 5, 1943 2,438,911 Gronningsaeter Apr. 6, 1948

Claims (1)

1. 7. A METHOD OF OPERATING A COPPER SMELTING REVERBERATORY FURNACE WHICH COMPRISES FORMING A MOLTEN BATH OF MATTE AND SLAG EXTENDING SUBSTANTIALLY THE FULL WIDTH OF THE FURNACE, ESTABLISHING A LAYER OF SOLID MATERIALS TO BE SMELTED FLOATING ON OR NEAR THE SURFACE AND COVERING A SUBSTANTIAL AREA OF SAID MOLTEN BATH, AND MAINTAINING SAID SOLID LAYER BY PROPELLING LATERALLY INTO THE FURNACE AT LEAST ONE RIBBON-LIKE STREAM OF MOIST COPPER CONCENTRATES UNMIXED WITH AIR SO THAT THE STREAM STRIKES THE SURFACE OF SAID MOLTEN BATH OR SAID LAYER AT A LOW ANGLE TO AVOID

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