US1545582A - Process of and apparatus for the reduction of ores - Google Patents

Description

' July 14, 1925.

v 1,545,582 B. G. COBB PROCESS OF AND APPARATUS FOR THE REDUCTIONOF ORES Original Filed July 17, 1920 4 Sheets-Sheet 1 avian/r02 B. G; COBB IROGESS"OF AND APPARATUS FOR THE REDUCTION OF ORES Jul -14, 1925 7 Original Filed July 17. 1920 v 4 s s 't 2 B. s. COBB PROCESS-' 0! AND APPARATUS FOR THE REDUCTION OF ORES July '14, 1925. 1,545,582

Original FiledJJuly 1 1920 4 Sheets-Sheet 3 July 14, 1925.

B. G. COBB PROCESS OF AND APPARATUS FOR THE REDUCTION OF ORES 4 Sheets-Sheet 4 Original Filed July 17. 1920 A T-TORNEYS.

Patented July 14, 1925.

UNITED'STATES PATENT OFFICE.

BAYARD GEEKIE COBB, OF TORONTO, ONTARIO, CANADA,.ASSIGNOB T COBB ELECTRO REDUCTION CORPORATION OF CANAD PoRATI'oN or CANADA.

A, LIMITED, or romnro, CANADA, A coaraocnss or AND APPARATUS non THE anniro'rron or onus.

Continuation of application Serial No. 398,88l, filed July 17, 1820. Thisappltcatlon filed August 5,1922.

Serial No. 579,804.

To all whom it may concern.

Be it known that I, BAYARD GEEKIE COBB. a subject of the King of'Great Britain, and

a resident of Toronto, county of York, Prov ince of Ontario, and Dominion of Canada, have invented a certain new and. useful Process of and Apparatus for the Reduction of Ores, of which the following is'a specification. i

The invention relates to the reductionof ores by the passage of an electric current through the ore while the latter is in a fluid state.

The objects of the invention are to provide a process of ore reduction partly, at least, by electrolysis in which the ore'is not only smelted but is refined; in which arcing is prevented; in which the electric current is controlled; wherein metal of a great purity may be produced; which will require low power consumption; in which the loss in flue dust will be small; in which crusting and freezing due to sudden variations in temperature will. be prevented or at least minimized; in which the heat will be evenly distributed; in which there will be a complete absence of dusting losses; which wil have a high efficiency factor and low radiation and flue losses of heat energy; in which electrode consumption will be low, in which the quantity of reducing agent necessary for carrying out the process will be very much reduced and in which the processes of the blast and reverberatory furnaces may be carried out in a single apparatus.

Further objects are the production of anapparatus in which the process may be economically carried out; which will be simple and relatively cheap of construction: in which all portions of the charge may be uniformly heated; which will be more or less automatic in operation, and which will have great capacity relatively to its size.

These and further objects will more fully appear in the following specification and accompanying drawings considered together or separately.

One embodiment of the invention is illustrated in the accompanying drawings, in which like parts in all of the several figures are designated b similar characters of-reference, and in. w ich- Fig. 1 is a longitudinal sectional View embodying the invention.

Fig, 2 is a fragmentary sectional view of the same, taken at right angles to F i 1.

Fig. 3 is a diagrammatic sections. view of the'mechanically and electrically operated portions of the control apparatus.

Fig. 4 is a longitudinal sectional view of the preferred form of current regulating device.

Fig. 5 is a sectionon the dot and dash line of Fig. 4, looking in the direction of the arrow 5. I

Fig. 6 is a section on the same line looking in the direction of the arrow 6.

Fig. 7 is a side elevation of a portion of the current regulator.

Fig. 8 is a detail View of the preferred form of pole changer.

F Fig. 9 is a view taken at right angles to ig. 8. Fig. 10 is a sectional view of a buggy for receiving theproduct of the retort, and in which a part of the process is carried out, and

Fig. 11 is a diagrammatic view of the entire apparatus.

The process of the invention may be carried out in any suitable form of retort, but the type of apparatus illustrated in Figs. 1, 2 and 10 is preferred. The retort comprises a chamber 1 bounded by walls 2 of suitable insulating and heat resisting material such as brick. The retort is provided with a lining as is common, and said. lining may be either, acidic, basic or neutral as the nature of the ore, reducing agent, or flux may require. The flOOr 3 and arch 4 may be composed of the same material as the lining of the sides of the retort, or said floor and arch may be lined with such material. A charging bosh 5 pierces the arch 4 as is common in smelting apparatus of the type illustrated, and the bosh is closed by the usual cover (not shown). The retort is pro- IOO with, or slightly lower than, the floor sur face, and preferably in the center thereof. A conductor 9 of proper cross section is secured to, or forms part of, the electrode 8 and extends horizontall then vertically and then again horizontally out of the Wall 2 as shown. All of the electrode 8, except one end surface thereof, and all of the conductor 9 except the extreme outer end thereof, are embedded in the masonry .of the structure, and that portion of the conductor which pierces the wall of the retort is above the predetermined level of the fused metal contents of the chamber, whereby there will be no danger of leakage of molten material along the conductor and out of the retort, as is likely to be the case when the conductor extends through the wall below the level of the moltenmetal contents of the retort.

Piercing the arch 4 is a positive electrode preferably in the form of two carbon cylinders 10, 10 movable through the arch (by mechanism not shown) toward and away from the cathode 8. The members 10, 10 are so positioned that when at their lowest posi tions they will contact with the exposed surface of the cathode. The electrodes 8 and 10 are connected by suitable conductors 11 and 12 to a source of direct current electricity, as

indicated by the leads of the line marked" plus and minus in Figs. 1 and 11. The cir-. cuit in which the electrodes 8 and 10 are included will hereinafter be referred to as the main circuit.

For controlling the main circuit, a plural ityof electrodes 13 and 14 (hereinafter referred to as the balancing electrodes) are connected by conductors 15 and 16 to the leads plus and minus (Figs. 1 and 11) through an automatically controlled switch 17, in what will be hereinafter termed the control circuit.- In the embodiment of the invention illustrated the balancing electrodes project through the side walls of the retort,

andlmay be movable toward and away from the -"central vertical line of the chamber 1, by any suitable mechanism (not shown). The balancing electrodes preferably pierce' the walls at an angle-;.whereby the openings in the outer faces of the walls will be above the level of the fused'contents of the chamber 1. 4

In the drawing one negative and two positive main electrode members and two balancing electrodes are illustrated, but it is desired to have it understood that the invention is not limited to the exact construction shown. Any number of such electrodes may be employed. If. a single main electrode 10 be used it will be arranged vertically above the cathode 8, and the bosh 5 will enter the chamber at one side of the center of the arch. Any number of balancing electrodes may be used, but it is desirable, however, that the number of openings in the walls of the retort be as few as possible, for mechanical reasons.

The balancing electrodes 13 and 14 are so "connected to the line that their polarities contact members being connected in pairs by conductors 22 and 22", as shown in Figs. 1 and 11. Carried by the top 19 of the casing 18 are four contacts 23, 23*,"23 and 23 so arranged that they may be engaged sigigultaneously 'by the contacts 22, 22, 22 -and The conductors-15 and 16 ofthe balancing electrodes are secured to oppositely disposed contacts 23 and 23", and the other two contacts 23 and 23 are connected by wires 24 and-25 to the line leads plus and minus as shown in Figs. 1 and 11. The wire 25 may be provided with a switch 26 by means of which the control circuit may be cut out. The element 21 is rotated by means of the shaft 20, and it will be plain from an inspection of Figs. 1 and 11 that the electrode 13 is negative while the electrode, 14 is positive and current will flow between 13 and 14 or between 13 and 10, and 14 and 8 as depends upon the positions of the balancing electrodes relatively to the main electrodes. When the element 21 is rotated a quarter turn the polarity of the balancing electrodes will be reversed, the electrode 13 will become positive and 14 negative.

The shaft 20 may be rotated in any desired manner preferably by means of an-electric motor 27 enclosed in the casing 18, and connected across the line.

The automatic switch 17 may be, and preferably is, operated by fluctuations in the main circuit, and such fluctuations act to change the polarity of the controlcircuit.

The switch may be operated by fluctuations of the voltage of the main circuit, but is preferably operated by fluctuations in the amperage on said circuit.

Mounted in proximity to the exposed end of the conductor 9, or the bus bar for feeding the said conductor, is a switch lever 28 pivoted at 29 as shown. Carried by one end of the lever is a double contact pin 30 which is insulated from the lever, or said lever may, if desired, be formed of insulating material. Suspended from the opposite end of the lever is a horse-shoe shaped member 31 of soft iron, which member straddles the conductor 9 or its bus bar as shown. Each leg of the member 31 carries a roller, preferably of non-conductive material whereby the member is positioned from the bus bar 9.

The normal position of the lever 28 is horizontal, and a s ring 32, or other balance may be em loye to counterbalance the member 31. I desired an auxiliary balance 33 may be employed to regulate the equilibrium of the lever.

The contact pin is adapted to be engaged with either a contact 34 or a contact 35 as the opposite end of the lever is moved toward or away from the conductor 9. i

The end of the lever 28 is rovided with a double headed detent mem Jet" 28 which is adapted to engage on the upward movement of the lever with a spring catch 34, and on the downward movement of the lever with a similar catch 35. The contact 30 is connected by a wire 36 with the motor 27. The contact 34 is connected by a Wire 37 to a binding post 40 and the contact 35 is connected by a wire 39 to a binding post 38 both of said binding posts being mounted on a disc 41, through which a shaft 42 extends, said shaft being supported on the underside of the top plate 19 of the casing 18. The disc 41 is provided on the side opposite binding posts 38 and 40 with a contact 43 Secured to the post 38, and a similar contact 44 is secured to the post 40.

The shaft 42 carries loosely mounted thereon a spur pinion 45 which meshes with a spur gear 46 on the shaft 20 whereby said pinion may be rotated-relatively to said shaft 42, and carried by the pinion, and rotatable therewith, is a disc 47 of insulating material in which is mounted a double contact member 48 which extends through the disc. The member 48 is composed of two separate plugs each adapted to be moved in the direction away from the member by means of a spring but being in electrical connection one with the other. The upper plug of the contact 48 is held by its spring into intimate engagement with the lower face of a metallic annulus 49 mounted on the lower face of a disc 50 also positioned by and on the shaft 42. The ring 49 has a bindinglpost 51, and a wire 52 connects the said annulus 49 with the opposite pole of the motor 27. The wires 37 and 39 are connected to opposite sides of the power line 53 through the binding posts 40 and 38 and the Wires 55 and 54.

When current is passing through the circuit of the electrodes 8 and 10 the currentin the member 9 will magnetize the member 31, and when the currentis normal the lever 28 will be in its horizontal position being balanced by the spring 32. When fiuctuat-ions in the main circuit occur they will be reflected in the bus bar 9 and the member 31 will be drawn down by the increase in amperage or be raised by the spring when the 35 and current from the line 53 will ener-' gize the motor 27 to operate the reversing switch 17.

When the pin 30 is in contact with either of the contacts 34 or 35 the detent 28 will be held by one of the spring catches a sufiicient length of time to insure operation of the motor. The springs 34" and 35* are so tensioned that the force required to break the circuit at 34 or 35 will be small.

In carrying out the process of the invention, a bath is built up in the retort, by fusing a silicious material, because of its resistance to the passage of the current, be tween the electrodes 8 and 10. The bath may be acidic or basic as depends upon the character of the ore, and of the lining of the retort. If a basic ore be used the bath and the lining should be acidic, and with an acidic ore the lining and bath should be basic.

When the fused bath has been built up to such a level that those portions of the balancing electrodes which project into the chamber 1 dip into the bath, the ore mixed with old slag and a suitable reducing agent, is introduced into the retort through the bosh 5, and the charge will be fused by the heat of the bath.

The active portions of the balancing electrodes are arranged at such a distance above the floor 3 that the heat of the side currents will penetrate through the fused mass to the bottom thereof and effectually prevent.

freezing, and are so posit'oned relatively to the surface of the ma s as to prevent crusting.

By reduction herein, is meant the thermal separation of a metallic compound into 7 its constituent parts, i. e., the separation of the metal or metals from the non-metallic substances of an ore, andparticularly of a complex ore.

The reducing agent employed in carrying out theprocess in the smelting of tin i carbon, preferably in the form of coke or culm.

The operation is as follows For convenience the operation herein described is that carried out in a furnace having a capacity of five tons of metal ,per 24 hours, and in the smelting of a rough concentrate of cassiterite from the Caracoles mine situated in the Quinsacruz district, Province of Inquisivi; Bolivia. The material had been subjected to previous ore dressing and considerable of the impurities, i. e., Bi, As and Sb, had been removed, as is good standard milling and ore treatment. It is possible to remove all of the impurities, with the exception of bismuth, from the ore in the process of the application, but it is desirable, and good practice to roughly concentrate the ore before smelting.

A rough analysis of the ore above described, is as follows Percent. Tin (Sn) 60 Iron (Fe) 8 Bismuth (Bi) t 2 Sulphur (S) .6 Arsenic (As) j 4 Antimony (Sb) insoluble 5 Oxygen (O 15 the cathode. A typical flux may consist of approximately coke; 10% fluorspar;

and 65% old slag, One or both of the carbons forming the anode is lowered into the powdered material but not into actual contact with the cathode, and adirect current sufficient to fuse the flux, the resistance of which is high, is turned on until the flux is melted to form the starting bath. i Y

When the anode is lowered into the powdered fluxing material a short are will be struck. The flux in the vicinity of the arc will be fused by'the heat of the same. When the fused flux submerges the lower end of the anode the are will be extinguished, and thenceforth the fusion will be accomplished by resistance heating. Old slag, ferrous silicate and calcium silicate (CaO) w (SiO.

y (FeSiO in crushed condition is now poured into the retort and the anode is gradually raised as the mass is fused by the resistance of the bath to the passage of the current, care being taken to always keep the anode partially submerged in the molten mass. This operation is continued by the introduction of more slag until the chamber 1 is about three-fourths full of the fused bath, and the balancing electrodes project into thebath. The amount of slag neces sary to form the bath is approximately 1000 pounds. By the time the bath is formed the coke in the starting flux will have been consumed and passed out of the furnace in the form of carbon monoxide, and the bath will be composed almost entirely of ferrous and calcium silicates, and be non-electrolytic. When the bath is completely fused, as indicated by steadiness of an ammeter in the main circuit or in both the main and control circuits, the retort is ready for the ore charge.

The ore, preferably mixed with old slag and a carbon reducing agent such as charin finely divided formx' the amperage is lowered or raised, and contact 30 will be at either point 35 or 34 as the casemay be. If the amperage be increased the circuit between30 and 34 will be made, the parts being in the position 'i'llustrated in Fig. 11. The current of the balancing circuit will be through wire 24, contacts 23* -22 conductor 22 contacts 22-23, wire 16, (making electrode 14 positive andelectrode 13 negative), wire 15 contacts 23"22"-, conductor 22 contacts 2223 and wire 25 to line.

The switch operating current will take the following path, wire 55, wire 37, contacts 3430, wire 36, motor, wire 52, contacts 49. 48, 43, wire 54, to line. The motor will operate'a'nd rotate the switch member 47 and, through the gears 45 and 46, the element 21 will berotated a quarter turn which will reverse the polarities of the balancing electrodes making 13 positive and 14 negative. When the contact 48 leaves the contact 43, due to the rotation of the armature of the motor, the circuit will be broken, but the momentum of the parts will carry. the contact 48 over the gap-between 43 and 44, and while in motion the motor, being shorted on, itself, acts as a dynamic brake, and the polarities of the electrodes 13 and 14 will remain the same until there is sulficient change in current of main circuit to cause circuit to be completed between 30 and 35.

The main circuit will always. be through Wire 12, electrode 10, electrode 8 and wire 11.

When a fluctuation occurs between the electrodes 8 and 10 to cause a drop in the amperage, the spring on the lever 28 will raise the horseshoe, and contact between 30 and 35 will be made, the current will flow through wire 55, contacts 44'48-4951, wire 52, motor, wire 36, contacts 3035, Wire 39, contact 58, wire 54, to line. This will energize the motor and move the contact 48 back to engagement with the contact 43, and the element 21 will be rotated a quarter turn whereby the balancing circuit will be brought to the position shown Pounds. ,Ore (SnO i 1,000 Coke or culm (C) 90 Limestone (Ow-0,) 65 Silica (SiO, 100 Slag (FeSi 100 There isno reducing agent in the'bath except the carbon which forms part of the ore charge.

The additionof the ore charge changes the bath to an electrolyte, and the ore is reduced by electrolysis and the comparatively small amount of chemical reducing agent mixed with the ore. The silica is the gangue of the ore, and the limestone, if not in the gangue,

may be added as a flux to act in conjunction with unconsumed starting flux to cause the silicious gangue to form a chemical compound. In addition the flux is desirable, when the furnace lining is of an acid character, to produce a slag, which will be either neutral or acid, in order to avoid damage to such lining, and to accomplishthe necessary metallurgical operations. If a basic bath is to be used the lining should be either neutral or basic.

The batch of ore is made up and fluxed, and is charged at regular intervals in amounts of about 150 to 200 pounds. There are no reducing agents in the bath before or after the introduction of the ore charge, except the carbon which forms part of the charge, and the direct current which has a reducing effect in the electrolytic bath. The temperature of the fused mass varies somewhat, but a heat of from 1,500 to 1,800 C. is desirable. The ideal temperature is that which will be high enough to hold the silico stannates '(SnO )w(SiO y, undecomposed but without being high enough to reduce all of the impurities.

After blowing in the furnace, slag taps should be taken in about one hour after the first ore charge, and the metal should be tapped about two hours later, and subsequently every forty-five minutes. When the metal is tapped a certain amount of slagis drawn ofi'. I

The discharge is received in a buggy '56 of any desired form, and the slag, by reason of its low specific gravity, will cover the surface of the metal 'in the buggy, and will hardmolten metal.

en, because of its exposure to the atmosphere,

and forma crust or skull 57 on the surface of the metal. The hardening of the skull will act to prevent rapid solidification of the Before the skull hardens .a hook or. bail 58is inserted therein, and when the skull has hardened sufiiciently to support its weight, a tackle is attached to the bail and the skull is removed. .This operation is performed before the greater bulk of the metal in the bu gy has solidified.

In wor mg an ore such as that above des scribed some of the ingredients such as bismuth; arsenic, and antimony will be par 'tially volatilized and sulphur will be partially, at least, vaporized and pass out of the retort and may, if desired, 'be collected in a 1 bag house. The greater part of the impurities above mentioned, forming dross, Will'be in the skull or adhering to the underside thereof in crystalline and tendril form, prob ably by capillarity, and will be removed with the skull. A considerable proportion of the metal removed with the skull will be tin which is carried with the skull and the dross by adhesion, and the skull is preferably crushed and added to the new ore charge, or .0

the crushed hardhead and dross of the skull may be charged into the retort, Without the addition of a reducing agent or of fresh ore, and be reduced in the bath by electrolysis. The skull is a metallic compound of tin In the fused bath the cassiterite (SnO 0 goes Wholly or partly into solution with a formation of silico-stannates and possibly tin silicate. These latter bodies are electrolyzed producing metallic tin at the cathode and silica and oxygen at the anode. The silica will combine with the iron oxides, with the production of one or more of the silicatesof iron.

By regulating the quantity of the reducing agent introduced into the charge, and care being taken that there is not sufficient carbon to extract all of the tin in a given period during which the direct current is passing through the fused mass, it follows that on account of the greater afiinity of iron oxides for silica than of tin oxide for silica, practically all of the iron will remain in the slag as ferrous silicate, and will chemically replace the tin of the silico-stannates, and liberate the metallic tin. For this reason it is chemical structure. The result of charging proximately 9 to 10% of the tin will remain in the slag. Thus by allowing chemical action to predominate at certain times the iron, which would be otherwise electrolyzed and found alloyed with the tin, will remain in the slag, and be slagged off with the other impurities. The amount of tin to be left in the slag is proportioned to the amount of iron in the ore, and the presence of the tin in the slag is an indication that the iron is also there. The skull which forms on the surface of the mass in the buggy will be slag su er-imposed above the tendril formation, w ich is largely composed of iron stannide, and which adheres to the base of the skull. The latter is a complex crystalline structure containing tin, iron, arsenic and antimony.

In the absence of iron in the ore a quantity of limestone sufficient to take up the silica, and form silicates of calcium, may be added.

If desired the excess of the silica may be retained in the bath, and by varying the fluxes in the charge, close temperature regulation ma be obtained owing to the fact that the richer the bath is in free silica the greater is the resistance to the passage of the current, and a higher temperature may be secured.

As the charge slag and metal monkeys fresh ore, reducing agents and fluxes are supplied through the bosh, and the operation is continuous.

The slag, and the dross metals or impurities, will float on the surface of the metal both in the retort and in the buggy with the slag above the dross, and the slag covering will act to prevent oxidation of the metal or metals.

As already explained the iron, when present, will combine with the silica to form a ferrous silicate, and the dross metals present being less electropositive than tin, the latter metal will be attracted to the cathode,

and because of the lower electropositiveness of the slag and dross the direct current, in conjunction with gravity, will cause a more or less clear point of demarkation between the tin on the one hand and the slag and dress on the other, and tin of great purity ,will be recovered.

As the skull is removed from the buggy before the contents have time to lose their more or less polarized conditions, the contents of the buggy will retain their more or less stratified condition and there will be little or no tendency for the metals to alloy.

It is desired to have it understood that with some ores, at least, the reducing agent may be omitted from the ore charge, and the process be carried out by electrolysis alone, but the use of a proper reducing agent is preferable.

is withdrawn through the This application is a continuation of an application for patent entitled Method of and apparatus for reduction of ores, filed by me on or about July 17, 1920, and numbered serially 396,891.

In accordance with the provisions of the patent statutes the rinciple of the invention has been descri d,toge-ther with the apparatus which is now considered to represent the best embodiment thereof, but it is desired to have it understood that the apparatus shown is merely illustrative and that the invention may be carried out in other ways.

The invention having been described what is claimed and desired to be secured by Letters Patent is 1. A process of. reducing metallic compounds, which comprises forming a bath by fusing a nonelectrolytic flux by the passage'of an electric current therethrough, maintaining the bath in the fused state by the passage therethrough of direct current electricity and charging the compound to be reduced into the fused bath.

2. A process of reducing metallic ores, which comprises forming a neutral bath by fusing a nonelectrolytic flux of high resistance material by the ,passage of an electric current therethrough, maintaining the bath in the fluid state by the passage therethrough of direct current electricity, and charging the ore and a reducing agent into the bath during the passage of the direct current.

3. A process of reducing metallic ores, which comprises forming a fused, shallow bath by the passage of direct current electricity through a nonelectrolytic flux of.

high resistance materials, adding to the bath a neutral. material, said neutral material being fused by the heat of the melted flux, charging theore into the bath to fuse the ore and render the fused mass electrolytic, the metallic constitutent of the ore being reduced by electrolysis.

4. A process of reducing metallic ores which comprises placing a fiuxing material in a retort and in contact with a cathode electrode and an anode electrode, passing direct current electricity between the electrodes to fuse the flux to form a relatively shallow bath, feeding a silicious material to the bath whereby the said material will be fused by the heat of the flux bath and the passage of the current, separating the electrodesas the depth of the fused mass increases, said electrodes being at all times submerged in part at least in the molten mass, charging the ore and a reducing agent to the fluid bath whereby the ore will be. fused by the heat of the bath and the latter will be rendered electrolytic by the ore,

whereby the ore will be reduced by electrol- -ysis and the reducing agent.

5. A process of reducing metallic ores, which comprises placing a fiuxing material in a retort and in contact with a cathode electrode and an anode electrode, passing direct current electricity between the electrodes to fuse the flux to form a relatively shallow bath, feeding a silicious material to the bath whereby the said material will be fused by the heat of the flux bath and the passage of r the current, separating the electrodes as the depth of the fused mass increases, said electrodes being at all times submerged in part at least in the molten mass, charging a mixture of ore, slag, and a reducing agent to the fluid bath whereby the ore will be fused by the heat of the bath and the latter will be rendered electrolytic by the ore, whereby the ore will be reduced by electrolysis and the reducing agent.

6. A process of reducing a complex metallic ore, which comprises forming a fused, neutral, silicate bath of high electrical resistance and maintaining the samein the liquid state by the passage therethrough of direct current electricity, directing a charge of ore and a suitable reducing agent into the bath whereby the ore will go into solution due to the heat causing said bath to be-' come an electrolyte whereby the ore will be reduced by electrolysis and the reducing agent.

7. A process of reducing a complex metallic ore,.which comprises forming a fused,

neutral, silicate bath of high electrical resistance and maintaining the same in the liquid state by the passage'therethrough of direct current electricity, directing a charge of ore and a suitable reducing agent into the,

bath whereby the ore will go into solution due to the heat causing said bath to become an electrolyte whereby the ore will be re duced by electrolysis and the reducing agent, tapping a charge of fused metal and slag, and separating the slag from the metal.

8. A process of reducing a complex metallic ore, which comprises forming a fused, neutral, silicate bath of high electrical resistance and maintaining the same in the liquid state by the passage therethrough of direct current electricity, directing a charge of ore and a suitable reducing agent into the bath whereby the ore will go into solution due to theheat. causing said bath to become an electrolyte whereby the ore .will be reduced by electrolysis and the reducing agent, tapping a charge of fused metal and slag, cooling the slag, and separating the slag from the metal.

9. A process of reducing a complex metallic ore, which comprises forming a fused,

neutral silicate bath of high electrical resistance and maintaining the same in the liquid state by the passage therethrough of direct current electricity. directing a charge of ore and a suitable reducing agent into the ties will adhere, and removing the skull.

10. A process of reducing a complex me tallic ore, whichcomprises forming a fused, neutral silicate bath'of highelectrical resistance and maintaining thesame in. the

liquid state by the passage therethrough of direct current electricity, directing a charge of ore and a suitable reducing agent into the bath whereby the ore will go into solution due to the heat causing said bath to become an electrolyte wherebythe ore will be reduced by electrolysis and the reducing agent, forming a slag having a chemical aflinity for undesirable minerals in the ore, removing the fused mass from the influence of the current until the slag forms a skull over the molten mass and to which impurities will adhere. and removing the skull and adhering materials. e

11. A process of electrically reducing ores, which comprises building up a fused neutral bath by heating a nonelectrolytic flux, passingtdirect current electricity between electrodes and through the bath in which the electrodes are immersed but separated one from the other, placing the ore in the bath whereby the ore will be fused and the bath will become electrolytic, passing a second direct current between electrodes of a second circuit through the fused mass, said second electrodes being immersed in the mass, and causing changes in the polarity 'ofthe electrodes of the second circuit.

12. A process of electrically reducing ores, which comprises building up a fused neutral bath by heating a non electrolytic flux, passing direct current electricity between electrodes and through the bath in which the electrodes are immersed but separated one from the other, placing the ore in. the bath whereby the ore will be fused and the bath will become electrolytic, passing a second direct current between electrodes of a second circuit through the fused mass, said second electrodes being immersed in the mass, and automatically causing changes in the polarity of the electrodes of the second circuit, as conditions in the first circuitv vary.

13. A process of reducing metallic ores, which comprises forming a neutral non-elcc trolytic silicate bath by fusionby the passage of direct current electricity between opposed electrodes, charging the ore into the bath whereby the ore will be dissolved and the bath will be rendered electrolytic, and preventingoxidation of the metal.

14. A'process of reducing metallic ores, which comprises forming a neutralnon-electrolytic silicate bath by fusion by the passage of direct current electricity between opposed electrodes, charging the ore into the bath whereby the ore will be dissolved and the bath will be rendered electrolytic, and covering the metal with the non-metallic substances in the fused mass to prevent oxidation of 'the metal.

15. A process of reducing cassiterite ore, which comprises forming a neutral bath rich in free silica by resistance heating by the passage of direct current electricity between vertically arranged and separated electrodes, the cathode electrode being at the bottom, said cassiterite ore containing an ingredient which Will chemically unite with the silica, introducing cassiterite ore, silica and a reducing agent such as carbon into the bath whereby the charge will be dissolved and the fused mass will become electrolytic, and maintaining the temperature of the fused mass suflicient to cause some of the silica of the silicostannates to unite with some of the ingredients.

16. A process of reducing cassiterite ore, which comprises forming a neutral bath rich in free silica by resistance heating by the passage of direct current electricity between vertically arranged and separated electrodes, the cathode electrode being at the bottom, said cassiterite ore containing iron oxide which will chemically unite with the silica, introducing cassiterite ore, silica and areducing agent such as carbon into the bath whereby the charge will be dissolved and the fused mass will become electrolytic, and maintaining the temperature of the fused mass sufficient to cause some of the silica of the silicostannates to unite with some of the iron oxide'to form iron silicates, removing the fused mass from the influence of the electric current, cooling the surface of the said cassiterite ore containing iron oxide which will chemically unite w1th the silica,

introducing cassiterite ore, silica and areducing agent such as carbon into the death whereby the charge will be dissolved and the fused mass will become electrolytic, passing direct current electricity in a second circuit through the molten mass, means for changing the polarity of the second circuit,

and maintaining the temperature of the fused mass sufiicient to cause some of the silica of the silicostannates to unite with some of the iron oxide to form iron silicates,

removing the fused mass from the influence of the electric current, cooling the surface of the mass to make a skull of slag and impurities, and removing the skull and adhering im urities.

F 18. process of reducing cassiterite ore, which comprises forming a neutral bath rich in free silica by resistance heating by the passage of direct current electricity between vertically arranged and separated electrodes, the cathode electrode being at the bottom, said cassiterite ore containing iron oxide which will chemically unite with the silica, introducing cassiterite ore, silica and a reducing agent such as carbon into the bath whereby the charge will be dissolved and the fused mass will become electrolytic, passing direct current electricity in a second circuit through the molten mass, means for changing the polarity of the second circuit, and maintaining the temperature of the fused mass sufiicient to cause some of the silica of the silicostannates to unite with some of the iron oxide to form iron silicates, removing the fused mass from the influence of the electric current, coolingthe surface of the mass to make a skull of slag and impurities, and removing the skull and adhering impurities, removing the skull, and mixing the material of the skull with a new ore charge.

19. A process of reducing a complex tin ore, which comprises forming a fused, neutral, silicate bath of high electrical resistance and maintaining the same in the liquid state by the passage therethrough of direct current electricity, directing a charge of the ore and a suitable reducing agent into the bath whereby the heat of the bath will fuse the ore and change the bath to an electrolyte, whereby the ore will'be reduced by electrolysis and the reducing agent, the amount of reducing agent being insufiicient to extract all of the tin.'

20. A process of reducing a complex tin ore, which comprises forming a fused, neutral, silicate bath of high electrical resistance and maintaining the same in the liquid state by the passage therethroughof direct current electricity, directing a charge of the ore and carbon into the bath whereby the heat of the bath will fuse the ore and change the bath to an electrolyte, whereby the ore will be reduced by electrolysis and the reducing agent, the amount of carbon being insuflicient to extract all of the tin.

21. A process of reducing a complex tin ore, which comprises forming a fused, neutral, silicate bath of high electrical resistance and maintaining the same in the liquid state by the passage therethrough of direct current electricity, directing a charge of the ore and carbon into the bath whereby the heat of the bath will fuse the ore and change the bath to an electrolyte, whereby the ore will be reduced by electrolysis and the reducing agent, the amount of carbon being insuflicient to extract all of the tin in a given period during which the current is passing through the fused mass. 3

22. A process of reducing a complex tin ore, which comprises, forming a charge comprising the mineral, a reducing agent, silica, a substance having a greater affinity for silica than the mineral has for silica, and a flux, directing the charge into a fused neutral bath whereby the charge will be dissolved, and passing direct current electricity through the fused mass.

23. A process of reducing a complex tin ore, which comprises, forming a charge comprising the mineral, carbon, silica, iron oxide, and a flux, whereby the charge will be dissolved, and passing direct current electricity through the fused mass whereby the ore will be reduced by electrolysis and the carbon, and the iron in the form of ferrous silicate will replace the tin of'the silico-stannates and liberate metallic tin.

24. A process of reducing a complex tin ore, which comprises forming a charge comprising the mineral, a reducing agent, silica, oxide of iron and a flux, directing the charge into a fused neutral bath whereby the ore will be dissolved, passing direct current electricity through the fused mass whereby the ore will be reduced by the reducing agent and electrolysis to form metallic tin and slag, and so proportion'ing the heat of the current and the quantity of reducing agent that a portion of the tin will remain in the sla 2%. A process of reducing a complex tin ore, which comprises forming a charge comprising the mineral, a reducing agent, silica, oxide of iron and a flux, directing the charge into a fused neutral bath whereby the ore will be dissolved, passing direct current electricity through the fused mass whereby the ore will be reduced by the reducing agent and electrolysis to form metallic tin and slag, and so proportioning the heat of the current and the quantity of reducing agent and flux that a portion of the tin and the 5 iron will remain in the slag.

26. A process of reducing a complex tin ore, which comprises forming a charge comprising the mineral, a reducing agent, silica, ironoxide, and a flux, introducing the charge into a retort carrying a fused, neutral, silicate bath of high electrical resistance whereby the charge will be dissolved, passing di rect current electricity through the fused mass to reduce the ore by electrolysis and the reducing agent, removing the fused mass from the influence of the current, cooling the mass until a skull of slag and impurities is formed, removing thecskull from the mass,

dissolving-tho materials of the skull in a fused neutral silicate bath, and passin direct current electricity through the used mass whereby the charge will be electrolytically reduced.

27. An apparatus of the character described, comprising a retort, a main circuit anode in the retort and removed from the bottom thereof, a main circuit cathode in the bottom of the retort, means for introducing a silicious material of high resistance into the retort whereb a molten bath will be produced by the resistance heating of direct current electricity between the main electrodes, a portion at least of said elec trodes being at all times submerged in said bath, a secondary circuit of direct current electricity comprising positive and negative electrodes each being partly submerged in the bath, and means for reversing the current in said secondary circuit.

28. An apparatus of the character described, comprising a retort, a main circuit anode in the retort and removed from the bottom thereof, a main circuit cathode in the bottom of the retort, means for introducing a silicious material of high resistance into the retort to submerge the cathode and partially, at least submerge the anode whereby a molten bath will be produced, by the resistance heating of direct current electricity between the main electrodes, a secondary circuit of direct current electricity comprising positive and negative electrodes each being partially at least submerged invthe bath,

and means for automatically reversing the current in said secondary circuit.

29. An apparatus of the character described, comprising a retort, means for build ing up a bath of molten material of high resistance, a plurality of main circuit anodes in contact with the bath, a main circuit cathode in the bottom of the retort and covered by the bath, the lead of said cathode projecting through the wall of the retort above the bottom of the retort, a secondary circuit comprising positive and negative electrodes in contact with the bath, a magnetic switch in the main circuit, a reversing switch in the secondary circuit, and means operated by fluctuations in the main circuit for operating the magnetic switch and operating the switch in the secondary circuit.

30. An apparatus of the character described, comprising a retort, means for buiding up a bath of molten silicious material of high resistance in the retort, a pluralityof main circuit anodes in contact with the bath, a main circuit cathode in the bottom of the retort and covered by the bath, the lead of said cathode projecting outwardly through the wall of the retort above the bottom of; the retort, a secondary circuit comprising positive and negative elecwhereby the secondary circuit will be controdes in contact with the bath, a magnetic. tinuous- 10 switch in the main circuit, a reversing switch This specification signed and witnessed in the secondary circuit, means 0 erated by this 28th day of July, 1922.

5 fluctuations in the main circuit or operat- BAYARD GEEKIE COBB. ing the magnetic switch and operating the Witnesses: secondary circuit switch, and means for cut-' F. A; BOHNE,

ting the secondary switch out of the circuit WM. VOLKMANL.

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