US1492086A

US1492086A - Electbical smeiiting furnace

Info

Publication number: US1492086A
Authority: US
Publication date: 1924-04-29
Anticipated expiration: 1941-04-29

Description

April 29. 1924. 1,492,086

J. F. SHAWHAN ELECTRICAL SMELTING FURNACE Filed April 15 1920 4 Sheets-Sheet 1 mwbui April 29, 1924. 1,492,086

J. F. SHAWHAN ELECTRICAL SMELT ING FURNACE Filed April 15 1920 4 Sheets-Sheet 3 Apri! 29, 1924. 1,492,086

J. F. SHAWHAN ELECTR I CAL SMELT I NG FURNACE Filed Aril 15 1920 4 Sheets-Sheet 4 dAazA F. JAM n l/A A) agnum.

Patented Apr. 29, 1924.

UNITED STATES PATENT OFFICE.

JABEA F. SHAWHAN, F DAYTON, OHIO, ASSIGNOR O'F ONE-HALF TO PERLE L. SAGEBIEL, OF DAYTON, OHIO.

ELECTRICAL SMEIi-TING FURNACE.

Application filed April 15, 1920. Serial No. 874,080.

To all whom it may concern:

Be it known that I, JABEA F. SHAWHAN, a citizen of the United States, and residing at Dayton, county of Montgomery, an State of Ohio, have invented the new and useful Improvement in Electrical smelting Furnaces, of which the following is a specification.

This invention relates to smelting furtraces, and more particularly to that type of furnace used for smelting pyritic ores.

In the process of pyritic' smelting, the heat required for the smelting process is obtained by combustion of materials contained in the ores themselves, particularly sulphur and iron in the case of pyritic ores. In order to carry on such a process, pure air in a heated condition must be supplied to the charge to and iron. The charge can, of course, first be brought to a sufiiciently high temperature so that the oxidation will be carried on automatically, by rapid oxidation of the iron and sulphur, but once this condition has been attained, the process itself so long as the proper supply of heated air and ore is maintained. a

One of the objects of this invention, therefore, is to providea smelting furnace adapted to carry on such a smelting process continuously by providing an; adequate supply of properly heated air upon the charge.

In a great many cases, facilities for smelting by ordinary methods are hot on hand at themine and ores must be shipped to a distance to .be smelted.- As the ores' in the mine usually carryonly about 10% of their weight in valuable metals, a great saving canbe efiected by carrying on the smelting operation at the mine,-thereby saving the cost of transporting the bulky ores and the necessary fuel for heating is and the charge. As water wer is usually available in mining districts, and when transformedinto electrical energy, can be used for heating purposes, this invention provides means for carrying on a smelting process at the mines.

Another object of this invention, therefore, is to provide means for utilizing materials and sources of energy available at or near the mine location for the smelting process.

cause oxidation of the sulphur 4 goes on of e air I at the sides are Another object of this invention is to provide electric means for heating the air used in such a process.

Further objects will appear from the detailed description taken in connection with the accompanying drawings in which:

Figure 1 is an elevation in cross section of a smelting furnace embodying this invention;

Figure2 is a section taken on the line 2-2, Fig. l;

Figure 3 shows the electrical connections for the air heating furnace, having two heating elements, when used on a two phase system of electrical distribution;

Figure 4 shows the electrical connections for a furnace having three heating elements when. used on a three phase system;

Figure 5 shows the connections for a-fu'rnace with two heating elements when used on aisingle phase system.

Figure 6 shows the electrical connections for a furnace having one heating element when used on. a three phase. system;

Figure 7 shows. the connections fora furnace having one heating element when used 'on a'single phase system;

I Figure 8 1s a cross sectional view'showing another arrangementof the air heating furnace; i

Figure 9 is a sectional view inelevatio'n of a smelting furnace showing another embodiment of this invention; and

. Fi ure 10 is a sectional view in elevation showing-still another embodiment of this invention, 7, i

Referring to Figs. and 2, 1 designates the ore stack, 2 is the contracted portion. thereof or smelting chamber, and 3 is the crucible. Theicruciblet is provided 'withanfoutlet 4 for the slag and an outlet '5 for tli'ma tte. Opening into the crucible I miners. These maybe all of the usual construction. The lower part of the furnace', including the crucible, and the smelting chamber are usually constructed ofbrick and lined with refractory material, while. theore st'ack 1 may be of cast iron and may be provided with awater jacket 8 to keep. it cool;

The tuyeres 6 communicate with heating chambers 7. Each chamber 7 comprises a bed formed in the brick worlgwhich may be lined with refractory material, and s filled with granulated carbon, chrome ore or other suitable resistance material 9. Electrodes 10 afe introduced into this bed suitably insulated by means of refractory materm 11 and provided with connectors 12 for connection to the electric circuit.- By means of the electrodes 10, electric current may be passed through the beds of resistance material for the purpose of heating them.

The beds are filled with granulated resistance material nearly to the top and over this are placed ii'isulating layers v 3 to separate the hot carbon from the air in the heat ing chamber 7 so as to prevent both oxidation of the resistance material and the extraction of oxygen from the air. It is, of course: evident that to extract a portion of the oxygen from the air while it i'sijn' the he ting chamber would seriously reduce its e ciency as a supporter of combustion in the smelting chamber. The insulating layer 13' is preferably composed first of a layer of pure silica quartz crushed to a size of about one-fourth ii'ich,. then a layer of quartz sand and then a second layer pure silica q'iiartz crushed; to aboutone-half inch size The grains of this top layer are sulficiently lar e that theywill not be disturbed bytlie air last passing owfer them..

When the resistance bed: is heated up, the temperature will usually reach a sufliciently high value to melt the layer of silica on top, thus forming a complete coating over the top of the resistance material o prevent contact of the air therewith, and providing at the same time av high1y'heated surface against which the air impinges. The air will, therefore, be heated to a high temperature in the heating chamber 7 so as to be ready for combustion when it reaches the smelting chamber 2.

The air enters from the outside of the furnace into the chamber 14..passing thence through the ducts 15 into the chamber 16 where it is warmed by contactvwiththe hot electrodes 10, thence through the ducts 17 into the heating chamber 7, and then out through the tu yhres 6' into the smelting chamber. Openings 18- are provided for access to the heating chamber- 7 for cleaning. and similar purposes. )i1tlets 19' are provided for drawing off the molten layer of quartz 13 whenthe furnace is shut down. Upon resuming operation, the quartz may again be broken up and replaced. to form a newlayer l3.-

v Each chamber 7: may have a separate heatingelement comprising a resistance bed 9 and a pair of electrodes 10 These may be connected to the electrical circuit in any suitable manner a number of alternative arrangemcntsbeing shown in Figures 3 to 7 inclusive. In Figure 3, in a furnace haressee-e ing two heating elements each element is connected across one leg of a two phase ClICll'li tlle' secondary winding oi the usual transformer being represented at 20. In Figure 4, the three beds of the furnace are arranged for connection to a three phase circuit. In Figure 5, two elements are connected in series on a single phase circuit. In Figure 6, :r heating element having three electrodes arranged in the same resistance bed is arranged for connection to a three phase circuit. In Figure 7, a single heating element is arranged for connection to a si'n le phase circuit.

*ig'ure 8 shows another arrangement of the heating chamber and resistance bed, which may be used, for instance in a furnace having three heating elements using the connection shown in Figure }V In this furnace, the ducts 17 are formed by metal caps attached to the side of the brick work,

Figure 9 shows another embodiment of this invention, iniwhich the heating chamber 7 is located underneath the smelting furnace, The arrangement is otherwise similar to that described except that the air passes from the heating chamber 7 to the tuyere's 6' through additional air ducts 21; and exr-ept that the air enters at the ends of the chamber 14, passes in contact with the elect-r'odb san'd is led from chambb'r 16 to charm her 7 by vertical ducts rising vertically outside of the layer 9 of resistance material.

In this figure is also shown an" arrangement for condensing the flue gases: Connected with the u er end of the stack 1 underneath thefho per 22, is a downwardly directed flue 23'. is flue is surrounded by a water jacket 24 adapted to" cool the flue 23, thereby condensing any volatiliaed metal in the flue gases, which metal is deposited in the form of dust at the bottom of the chamber 25 into which the fine 23 opens. Such gases as are not condensed pass out of the chamber 25 upwardl through the s'tac'k 26. The clean out door 27 is provided for access to the chamber" 25 for removal of the deposited metal which can be recovered by any suitable treatment, suchas by sintering and subsequent resmelting.

Figures 10, illustrates another embodimerit in which the air is liat'ed by mean's'of an electric arc furnace. O'nlythe lower part of the smeltin fiirn'a cc is shown, namely, crucible 3 with the outlets 4 and 5 and the tuyeres 6. The upper portion of the furnace which is broken away may however, be the same as that illustrated in Fig ure 1.

Underneath the smelting furnace is a chamber 30 in which are mounted

electrodes

38, 34. and 36, ad'apted to form in this case. two arcs for heating this chamber. One. hm or more arcs may be used, accordinf! to cir mnF an -cs. These electrodes pass through the walls of the chamber and are insulated by bushings of

refractory mate rial

37 and 38. The lower electrodes 33 and 35 are provided with connectors 12 for connection to the electric circuit. The

upper electrodes

34 and 36 are each provided with an elevating device 39 including a rack and pinion movement. These electrodes are further equipped with connectors, not shown, for connection to the circuit.

Surrounding the heating chamber 30 is a series of air passages 40 communicatingat the lower end with the air heating chamber 41 and at the upper end with the tuyeres 6. The air supply enters the chamber 14 at the inlet 42 and passesthrough the ducts 43 to the heating chamber 41 where it is heated by contact with the hot electrodes 33 and 35, assing thence up through the passages 40, eing heated by contact with the hot walls 44 of the heating chamber 30 to the tuyeres 6. This arc-heated chamber may be put to double use by using it as a refining furnace. To this purpose it may be provided with an inlet 31 and an outlet 32. The material tobe operated upon'is spread over the floor to be acted upon by the are heat. If said material is a conductor of electric current it may be heated by passing the current directly throu h it.

The electrical connections 0 the furnace to the supply circuit may be made as shown in Figure 10. "The el'ectrodes are connected through the double throw'switch 45 to the secondary of an adjustable transformer 46 connected to the supply line. 'With this arrangement, the furnace can be used either as an arc furnace or as a resistance furnace. By throwing the switch 45 to the upper position, the electrodes 33 and 35 are connected to one side of the circuitand-the electrodes 34*and 36 to the other side of? the circuit. It is evident that-withthis connection either or both of the electrodes may be used as an arc furnace by. touching-and separating the electrodes by meansofthe controlled device It is convenient to use a furnace in this way item are furnace when starting up on a new charge, as heat can be generated more rapidly. When the charge has melted down, the switch 45 may e thrown to the lower position whereby the electrodes 33 and 35 are connected to oppo site sides of the circuit. With this connec' tion, the furnace operates as a resistance furnace establishing a circuit through the molten charge. With this connection, it is immaterial whether the upper electrodes are or are not in contact with the lower electrodes, since each pair is short circuited by the switch 45.

It will, therefore, be seen that the invention accomplishes its objects. The electrical resistance is entirely enclosed and covered with a refractory material, which is nonoxidizable by air. Accordingly, an ordinary granular material (which, while economical, is ordinarily rendered unfit for use on account of being readily oxidizable) can be used. Accordingly, the furnace is not only economical in requiring renewal of the resistance material only at long intervals, but it is also-efficient in that the entire oxygen in the air can be utilized for smelt ing purposes. The resistance material electrodes or heating elements are entirely enclosed and the air is circulated therearound, so that subsequently all of the heat generated by the current is utilized, thereby resulting in maximum economy of electrical energy used.

It is obvious that various changes may be made in the details of construction without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details shown and described.

Having thus described this invention, what is claimed is:

1. A pyritic smelting furnace, comprising, a furnace chamber adapted to receive a charge to be oxidized, tuyeresada'pted to deliver air to saidv chamber in order to oxidize the charge, a heating passage through which the air passes preparatory to delivery, an oxidizable electric heat generating medium, and a heat conducting envelope for: said medium adapted to provide a wallflfor said passage'iniorder to heat the air but protect said medium against-oxidation thereby.

2. A pyritic smelting furnace, comprising, a furnace" chamber adaptedtoreceive a charge to be: oxidized, tuyeres adapted to deliver air-to said chamber in order to oxidize the charge, a'heating passage through which the air :passesprparatory to delivery,

a bed of-granulated and oxidizable. resistance material, and a heatconducting envelope for said medium adapted to provide a wall for said passagerm order 'to heat the air but protect said medium against oxidation thereby. Y? D 1 3. A pyritic smelting furnace, comprising, a furnace chamber adapted to receive a charge to be oxidized, tuyeres adapted to deliver air to said chamber in order to oxidize the charge, a heating passage through which the air passes reparatory to delivery, an oxidizable e1ectr1c heat generating medium, and a non-oxidizable heat conducting envelope for said medium adapted to provide a wall for said passage in order to heat the air but protect said medium against oxidation thereby.

. 4. A pyritic smelting and refining furnace, comprising, a smelting chamber adapted to receive the charge and provided with tuyeres, a refining chamber, an oxidizable electric heat generating medium for said refining chamber, a heat conducting envelope for said medium, and means for passing the air over said envelope preparatory to its delivery tosaid tiuyeres.

5. A pyritic smeltin and refining fur nace, comprising, a sme ting chamber adapted to receive the charge and provided with tnyeres, a refining chamber, an oxidizable electricheat generating! medium for said rcfining chamber, a heat conducting. envelope for said medium, and means whereby the air is heated as generated by saidmedium before passing to said tu yres.

6. A pyriti'c smelting and refining. furnace', comprising, a smelting chamber adapted to' receive the charge andprovidedwith tuycres, means for delivering air to said tuyeres, a= refining chamber adjacent said smelting chamber, heating means therefor including cooperating electrodes, means for controlling said electrodes in order to adapt them selectively for are or resistance heating, and means for utiliiingi the heat of said refining chamberto heatthe air delivered to said tuyeres.

7. A pyritic smelting and refining turnace, comprising, a smelting chamber adapted to" receive the charge and provided with tuyeres, means for delivering. air to said Buyer-es; arefining chamber adjacent said smelting chamber,- heating means therefor including cooperating electrodes, means for selectively connecting said electrodes in order to adapt themselectively for are or resistance heating, and means for utilizing the heat of said refining chamber to heat the air delivered to said tuyeres.

8. A-pyri tic'smeltin furnace, comprising, a furnace chamber a aptd to receive the charge and provided wi-tir tujveres, means for delivering. air to said tiryeres, and means for heating said air including a heating chamber, and means for circulating said air over the walls of said chamber adapted to heat said air.

9. A pyritic' smelting furnace, comprising, as smelting chamber adapted to receive a charge and provided with tuyres; means for delivering air to said tuyeres, and means for heating said air including a horizontally disposed bed of granulated resistance material and electrodes entering said bed from the bottom thereof.

10. A pyritic smelting furnace, compris ing, a smelting chamber adapted to receive a charge and provided with tuyeres, means for'delivering air to said tuyeres, and means for heating said air including a horizontally disposed bed of granulated resistance material covered with a layer of refractory material and electrodes entering said bed from the bottom thereof.

11. A pyritic smelting furnace, comprising, a smelting chamber adapted to receive a charge and provided with tuyeres, means for delivering air tosaid tuyeres, and means for heating. said" air including a chamber containing a horizontally disposed bed of gramllated resistance material and electrodes entering said bed from the bottom thereof.

12L A pyritic smelting furnace, comprising, a smelting chamber adapted to receive a; ch'a'lge and provided with tuyeres, means for delivering air to said tuye-res, and means for heating said air including, a chamber containing a horizontally disposedbed of granulatedresistance materialcovered with a layer of refractory material, and electrodes entering said bedfrom the bottom thereof. 7

13.- A pyritic smelting'furnace, comprising, a smelting chamber adapted to receive a charge and provided with tuyeres means for delivering. air to said tuyere's, and means for heating; said air including a chamber containing, ahorizontally disposed bed of granulated resistance; material coveredwith a layer of refractory material, adapted to form a part of the lining of said chamber, and means for passing an" electric'cu-rrent thaoug'h said resistance material to heat said be a In testimony whereof, I afiixmy signature this 27th day of February, 1920.

JABEA F. SHAWHAN.