US817414A - Process of reducing ores. - Google Patents

Description

No. 817,414. PATBNTED APR. 10, 1906. H. F. BROWN.

PROCESS 0F RBDUUING DRES.

APPLIUATIOH FILED OUT. 24. 1905.-

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PATENTED APR. 10, 1906.

H. F. BROWN. PROCESS 0F RBDUGING GRES.

APPLICATION FILED 00T.24,1905.

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' HORACE F. BROWN, OF CHICAGO, ILLINOIS.

PROCESS OF REDUGING CRES.

Specication of Letters Patent.

Appunti@ med amber 24,1905. serai No. 284,238.

Patented April 1o, 1906.

To all whom t may concern.-

Be it known that I, HORACE F. BROWN, a citizen of the United States, residing atCliicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Processes of .Reducing Ores, of which the following is a specification.

. My invention relates to the treatment of i granular or pulverulent metallic oxids, as

well as finely-divided ores, in which the values readily oxldize or are 1n Athe form of or are closely associated with metallic oxids, my-

objcct being to provide an improved method ot reducing and saving such values m the large way, which method for lts practlcal operation on a commercial scale requiresbut a comparatively simple and inexpensive equipment and can be carried on with peculiar economy-in the matter of fuel consumption, losses by volatilization, mechanical dust losses, and operating expenses, while producing eminently satisfactory results.

My invention has reference more especially to the treatment bysmelting of nely-divided ores of iron, copper, lead, and zinc, such as liuc-dust, mill-dust, ine concentrates, oxid oi iron sands, and the like,

In carryingr out my invention I feed the ore into the upper part of a vertical stack, there subjecting the particles while'in suspension and in a more or less segregated lstate to the action of a reducing atmoshpere moving in the same direction as the ore, which renders the latter iiuid or semiiluid. I then cause the deoxidized ore to enter beneath a protecting-covering of molten slag in a reverberatory furnace or forehearth, where the deoxidized values are subjected to further heating to complete their fusion, if necessary, and where iinal separation takes place out of contact with the oxidizing atmosphere necessarily'present in the reverberatory furnace. In practicing my invention oarbonating and slag-producing ingredients may be fed with the ore to the stack,i desired.`

In the accompanying drawings I show apparatus of one approved form suitable for carrying out my improved method.

Referring to the drawings, Figure 1 is a broken partly sectional elevation showin a stack with means for feeding, the ore an supplying the heat thereto, a reverbatory furnace or forehearth, and regenerating means through which air to support combustion in the stack and reverberatory furnace is preparatorily passed; Fig. 2, a broken section Athrough the lower part of the stack, the reverberatory chamber, and regenerating apparatus or stoves; and Fig. 3, a broken plan section taken on line 3 in Fig. 1.

A represents an ore-feeding hopper of an suitable form, means being rovided, suoi as the Wormfeed a indicated, for discharging the finely-divided ore from the hopper A into the to of the furnace-stack B at a predetermine rate. The stack B is constructed, to all intents and urposes, like the stack shown and described-1n Letters Patent ofthe United States No.. 774,930, granted to Ine November 15, 1904, though in the present drawings I show two combustion-chambers' b b, one below the other and each provided with a single hydrocarbon-burner c. The burners enter the chambers tangentially to produce a whirl of the hot products of combustion. Between the upper combustionchamber and to of the stack is a chamber d, through whic the Ore drops to the upper combustion-chamber through a substantially quiescent or non-whirling atmosphere in order that during the rst subjection of the ore particles to heat they may remain in a more or less segregated state. Thus, as explained in my aforesaid patent, the fine particles of ore pass rst through a non-whirling atmosphere and are then subjected to the action of a whirling heated atmosphere moving in the downward direction. In the chamber d the'particles of ore are therefore subjected to a preliminary highly-heating atmosphere, so that on reaching the first combustion-chamber b they may be in condition to be quickly deoxidized by the actionoi' the reducing-gases produced by the combustion of the carbonac'eous fuel. The action of the whirling reducing atmosphere upon the ore is to produce a vortex, which tends `to cause the ore particles to come into hysioal contact with each other, so that ciiemical reactions take place, producing the necessary slags for separating the waste material from the metal. This action is enhanced and continued in the present construction by the second or lower combustion-chamber b and its hydrocarbon-burner. The stack B is provided of a height and the ore-feeding mechanism and hydrocarbon-burners are so arranged With relation to each other that approximately complete reduction of the ore articles will take place before they reach the oWer end ofthe stack. y

C is a forehearth or reverberatory lfurnace,

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into one end or side portion of which in the present embodiment 'of my invention the stack discharges. At op osite sides of the lower end of the stack in tfie chamber e of the reverberatory furnace are hot-air inlets f, which may be supplemented by hydrocarbonburners g, as indicated. At the opposite end of the chamber e is a brid e-wall h, forming with the front and side wa ls of the chamber a basin or hearth. Gases from the chamber e pass over the bridge-wall h and through stoves or regenerators D D alternately in a common manner, valves i being provided at the lower ends of the stoves and valves k at the upper ends thereof, all suspended from a rocking pulley-and-arm device E. In the turning of the device the valves lc 'i of one stove are closed, while the same valves of the other stove are opened. Both of the stoves discharge the gases passin through them into acommon conduit Z, lea ing in a suitable g g with the hydrocarbon-burners c.

manner through the hopper A to preliminarily dry the ore stored therein. The stoves are provided at their lower ends With valved alr-inlets m, and at the upper ends of the stoves are air-outlet pipes n, provided with valves n', the said pipes leading to a common pipe p, communicating through branch pipes A pipe r extends'from the pipe to the air-inletsf It is a fact that the oxids of all metals when in a finely-divided state are deoxidized very quickly when subjected to a reducing atmoshere at a high temperature. It 1s also a act that deoxidized metal particles become instantly oxidized when subjected under a lngh temperature to an oxidizing atmosphere 1n any form. For this reason it is vitally necessary for the purpose of carrying out my method that during the period between reduction and final separation of the metal constituent from the gangue or matrix the metal shall be protected from contact or association with an oxidizing-atmosphere or agent. In carrying out my invention with the apparatus shown a bath of molten slag is maintained in the hearth of chamber e, and as the deoxidized ore enters the hearth from the stack it is caused to fall into the said bath. Bein of eater specific gravity than pure slag, t e eoxidized metal naturally sinks into the bath as it enters the ,hearth from the lower end of the stack, and the construction is ysuch that a suitable extension of the chamber or forehearth e of the full width of the forehearth or narrower, as shown, projects beneath the stack, in which the deoxi dized ore falls to become buried beneath the slag before flowing along the forehearth. En-y tering the'forehearth with the ore from the stack is naturally 'an excess of carbon with the gas, which passes overthe slag-level on entering the forehearth and there expands and becomes mingled with the excess of oxygen from the hot air inlets f. This action produces com lete combustion and high temperature in t e forehearth, which kee s the slag and metal beneath the slag in aV ighly fluid state while substantially complete se arationby gravity of the metal from t e slag-making impurities is taking place. In the lower part of the hearth in the position shown is a tap-hole t, and at a higher level is a tap-hole if. When the separated metal reaches the level of the opening il, the taps may be opened to draw off slag and metal, as desired, care being employed, of course, to leave a sufficient protecting layer of slag for the metallic contents of the bath.

It will be seen from the foregoing description and the construction shown that ore may be fed continuously to the stack and that the metal and slag may be withdrawn continuously or as desired from the forehearth, thus causing m invention to operate as a continuous metho of ore reduction.

Different ores capable of reduction in accordance with my improved method would naturally require variations in the matter of mixes and handling in the furnace. In the treatment of finely-divided oxid of iron ores, for example, the iron and silicon particles with an added excess of lime particles as they rain in a more or less segregated state downward through the preliminary heating atmosphere are raised to a temperature which causes the oxid of iron particles to be in a condition ready for deoxidation. The deoxidizing or reducing action may commence at the upper combustion-chamber, Where the particles first meet the reducing-flame of the upper burner. The space in the 4stack from the upper combustion-chamber to its lower end is,in fact, areducing-chamber, care being employed in the practice of this method to prevent any excess of oxygen from entering at the brners. The reduction of` the iron oxids should be made as com lete as possible in the stack by subjecting t em to a strong reducing atmosphere at a suitable high temperature, whereby in the descent of the ore the lime Will combine with the silica and alumina of the charge, forming a silicate of lime and alumina, and the iron will reach the lower end of the stack as metal. The excess of lime forms a basic slag, so that when the reduced iron is once beneath the surface of the bath it is protected more or less completely from all oxidizing action. The molten metal and slag impurities r iixed therewith rain into the bath, while the carbonaceous reducing gases, as aforesaid, flow from the lower end portion of the stack into the forehearth over the surface of the bath. Here the gases ex and and mingle with the or less complete combustion which tends to further heat the bath. The flow of reducing` gases from the stack into the forehearth prevents the deoxidized metal from meeting with any reoxidizing influence before it plunges into the bath, and before flowing outward beyond the air-inlets it will have sunk beneath the protecting-covering formed by the molten slag. Here separation by gravity takes place, and under proper conditions substantially all of the metal may be saved.

In the treatment of nely-divided lead and copper oxids by my improved method a much lower temperature should be maintained in the stack than for the treatment of iron oxids as described. While descending through the stack the impurities would be formed into slag ci which iron, silica, and lime would form the main constituents. The reducing gases and heat should be so regulated that the iron would not be deoxidized, but would be caused to unite With the lime and silica, forming a slag consisting of silicate of lime andl iron, while the oxids of lead or copper are being reduced to the metallic state. ln this operation, as in the case of the treatment of iron oxids, as described, the slag would form a rotecting-covering in the forehearth during nal separation by gravity of the lead or copper from the impurities.

The presence of two combustion-chambers, one above the other as shown and de* scribed, makes it possible, When desired, to,

carry a very high temperature in the upper combustion-chamber with little or no reducing-atmosphere and to develo an excess of ieducing-gas at the lower com ustion-cham lt will be understood from the foregoing description that the gist of my invention lies in a process of treating finely-divided ore or mixture containing metallic oxids or metal readily oxidizable in the molten state, the process consisting in subjecting the ore or mixture While in atmospheric suspension to a reducing fusing-atmosphere, or first to a highly-heating and then to a reducing-atmosphere, then causing the reduced metal to enter beneath the protecting-surface of a molten bath without subjection to an oxidizing or reoxidizing influence and causing the reducing-gas, which descends through the stack, to ex and and min le over the bath with a high y-heated oxidizing atmosphere to further combustion` and heat the bath While separation of the metal from its slag; producing impurities is taking placebeneat the said rotecting-covering.

Vihat l) claim as new, and desire to secure by Letters Patent, is-

1. The process of treatin finely-divided ore, containing a metal readi y oxidizable in the molten state, Which consists in subjecting the ore while in atmospheric suspension to a reducing-atmosphere, then causing the reduced metal to pass, Without subjection to an oxidizin influence, beneath the surface oit'y a molten ath Which protects the metal against oxidation While separating from the slag-making constituents of the ore.

2. The rocess of treating finely-divided ore, containing a metal readily oxidizable 1n the molten state, which consists in subjecting the ore While in atmospheric suspension to a preliminary heating atmosphere and then to a reducing-atmosphere, and at the same time bringin the particles of ore into a proximate physica contact, then causing t 1e reduced metal to pass Without subjection to an oxidizing influence beneath the surface of a molten bath which protects the metal against oxidation While separating from the slag-malring constituents of the ore. I

3. The process of treating a iinely-divided mixture of metallic oxids and slag-making impurities, which consists in subjecting thematerial While in atmospheric suspension to the action oi' a reducing-gas movin in the same direction, and during such su jection bringing the particles of the mixture into a proximate physical contact, then causing t e reduced material to pass Without subjection to an oxidizing influence into a molten slagcovered bath, and'at the same time causing the reducing-gas to mix over the surface of the bath With an excess of ox gen to further its combustion and heat the ath, then permittin se aration by gravity of the metal from t e s zig-making impurities While protected by the said slag covering from the oxidizing atmosphere.

HORACE F. BROWN. ln presence of- A. U. Tnoninu,

J. H. LANDES.

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