US1254316A - Process of treating ores. - Google Patents

Description

ARTHUR S. DWIGHT, OF NEW YORK, Ni

vrnooEss or HEATING ones.

Specication of Letters Patent,

Patented Jan. 22,1918.

Application led June 17, 1911, Serial No. 633,760. Renewed J une 2, 1917. ySerial No. 172,522.

To all ajhom z't may concern.'

Be it knownk that I, ARTHUR S. DWIGHT, a citizen of the-United States, residing at New York, in `the county of New York and State of New York, have invented a certain new` and useful Improved Process of Treating Orcs, of which the following is a specification, reference being had therein to the .accompanying drawing.

This invention relates to processes for trentine: metal-bearing materials which are normally in an initially fine or pulverulent condition and which do not contain native combustible elements (such as sulfur,`or its equivalent) in sufficient quantities; it rclat ing particularly to a process for the treatment of metal-bearing materials which are characterized principally by the presence of the metal oxids.

The oxid bodies referred to are Well typified by the ores containing iron oxids, such as hematite, magnetite, limonite, etc.

The term oref as herein 'used,refers to mineral-bearing masses, (both those in their native conditions and those that are artificially formed) which include not only the metal oxid of one form or another, but include also other materials that are ordinarily found in these ores such av silica, earthy bodies. or the like, and also traces, or larger quantities, of other metalliferous materials.

Bv the iron oXid ores (tvpieally above mentioned) such as hematite Fe20fs magnetite Fe04, or limonite FeO3H6, etc., reference is made to those iron ores which are, respectively characterized more particularly by the presence of these oxids, even though accompanied in any given case by other ore components; and, as is Well known, these cxid ores are found in largevquantities in a fine or pulverulent condition. t

The reduction of any finelv divided ores in a blast furnace, or similar apparatus, Without preliminary treatment. involves considerable difficulty and loss` because of the tendency of the fine ore particles to settle into and choke the gas passages in the mass in the furnace and because of the tendency for laree quantities to becarried olf by the blast and deposited as flue dust or scattered to points outside of the furnace.

These pulverule'ntores may, for present purposes, be classified as those which are of the sulfid class, and those which are of the oxid class.

As concerns ores characterized by the presence of a vmaterial amount of sulfur or equivalent, combustible, I have heretofore (either solely or jointly with others) devised a process for, and have succeeded in, transforming them into agglomerated or sintered blocks or cakes which can be readily introduced into the blast furnace, 'and which there operate in an advantageous and economical manner.

In that process the agglomerating or sin tering of the fine ores is'eifected by means of heat derived from combustion of substances in chemical combination and contained therein; this combustion occurring Within the ore mass. The ore is distributed in a layer of stratum which is relatively thin or shallow, so that there is no material amount of Weight or pressure exerted at any region and so tha-t the air can be readily passed through the layer with great uniformity on all vertical lines. The sulfur component of.

the fine particles is ignited at the exposed surface and its combustion is supported by the air currents which are passed ,through the stratum from the plane of. ignitionto- Ward a plane of escape. And at the region of the latter plane and'throughout the mass .the particles are held against agitation, or

movement, in relation to each other; that is. agitation such as might be caused by the air currents or otherwise. i

The oxidizing of the sulfur (and an ac companying oxidizing of the metals) is carried on to the desired degree, some of the 4sulfur being generally allowed to remain, and more or less of metalllc oxids (as oxids of copper and iron) are produced. And, at the same time, the agglomerating is effected, this latter including the reaction of the silica upon `such hase materials as are initially present or are formed. The gases that are generated at the time of the reactions and at the time that particles are permitted to ,cr-here, act to form large cells or pores in the nascent and softened mass, and these are uniformly distributed through the stratum from the top to the bottom: and

hafter the instant of the forming and the cooling of thel silicated and agglomerated materials these cells or pores remain, and constitute important matters, during the stage of treatment in the blast furnace. The

p steps.

But when I undertook to agglomerate or' snter finely divided or pulverulent orcs of these other classes, to wit, those of the oxid class, or their equivalents, different conditions Were met and peculiar difficulties were experienced by me. I found that the agglomerating of the fine particles of the oxid ores must depend upon activities other than those which I found to be elicient in operating on the materials of the sulfid class, and that the cementing or binding of these particles must be secured by different causes. I found", particularly, that the silicating, or the hke, of the basic materials should not be depended on, and, in fact, should be avoided as far as possible. i

I further discovered that in order to prevent the temperature from being raised to the point of silicification, the oxid ore should be arranged in a relativel thin layer, so that the heat, after performing the necessary work, would readily escape by.

conduction through short paths, and by radiation. i

In place of the sulfur I employ carbonaceous material in pulverulent form, which is intimately and uniformly commingled with the ore oxid. This is ignited at the exposed surface and the combustion is carried through the mass by currents of combustion gas, such as the oxygen of the atmosphere. The carbon oXids peculiarly interact with the metal oxid and by properly controlling and regulating the different materials l am able to eii'ect a binding of the Iparticles together, not so much by an action like that of silicating a base material as by causing the union of one form of metal oxid with another the oxids'passing from one form` .to another in the presence and under the influence ofthe carbon oxids.

the line 4+-4 of Fig. 2.

Fig. 5l is a view of the preliminary mixing mechanism separate from the other parts of the apparatus. Y

Fig. y6 is a View showing the sintering mechanism separate from the Inizging mecha? nism and from the furnace. p

Fig. 7 shows a separate furnace into which may be fed material preliminarily treated by the mechanism shown in Fig. 4.

It will be understood that the forms of apparatus shown in the drawings have been selected merely as typical of the various` forms of apparatus which may be used for this purpose, and that my invention is not limited to any particular form of apparatus.

'I do not herein claim as a part of my present invention either of the forms of apparatus which I have shown for the sake of illustration'as these are shown and claimed in co-pending applications among which are certain applications filed by kme and serially numbered 440,404, 544,507 and 558,621.

In an apparatus for carrying out my improved process a suitable mechanism is provided for effecting the mixing of the ore t0 be treated with a combustible substance, and when desirable or necessary with a suitable fluxing material.

In the drawings, I have indicated by A one form of mechanism which may be used for` this purpose. 1 is a receptacle in which the ore to be treated is deposited. The receptacle 1 is preferably hopper-like in shape and is provided with a centrally located bottom opening. 2 and 3 are other hopperlike receptacles located adjacent the receptacle 1 and also provided with bottom openings.' Mounted beneath the bottom openings of the hoppers is an endless belt 1 which vis suitably mounted and connected for continuous movement inv the direction of the arrow in Fig. 2. By referring to the drawings, it will be observed that the bottom openings of the hoppers arey out of alinement with each other longitudinally of the belt, and thatmaterial from each hopper can be vdeposited on the belt without interference with material from either of the other. hoppers. sumed thatthe material to be treated, as for instance iron ore, has been deposited in vthe receptacle 1,'that a combustible substance,prefe`rably powdered coal, charcoal or coke when iron ore is to be treated, has been deposited in the receptacle 2, and that a fluxing material, such as crushed limestone, has been deposited, if needed, in the receptacle 3. As the belt 4 moves beneath the hoppers it draws lout from each of them a continuous stream of material. The thicknesses of these streams can be regulated by adj usting the positions of the doors or slides 5, 6 and 7 which are located adjacent the belts at the front sides of the respective receptacles.

In operation, let it be as` 8 is a box-like trou h mounted in position to receive at one en materials discharged from the moving belt 4. Inside of the trough is a .continually rotating stirrer 9 having spirally arranged blades which serve not only to mix the materials in the trough t but also to gradually work them toward the other end which is provided with an opening discharging into a chute l0. This chute communicates at its other end with the hopper 11 to which the thoroughly mixed materials are conveyed. Y,

B represents as a whole one form of mechanism which may be used for effectingthe sintering and agglomerating step of the process. Of this mechanism 12 is an air suction box from which air isexhausted by means of a fan 13. Upon the upper edges of the box are carefully planed. wearing strips 14 upon which slide cast iron pallets 15, the lower edges of which are likewise carefully planed so as to make an air tight joint with `the strips when the pallets are pushed along the top surface of the box.`

The pallets carry the grates 16 and are built with transverse members 17 which together with the sides of the pallets form four-sided boxes beneath the gra-tes.r Above the grates these transverse members are omitted soY that when a number of pallets are adjacent each other an uninterrupted grate surface is provided. These lower transverse members also serve as partitions to` cut offthe air at certain points in a manner which will be described. l y

Each of the pallets may be considered as an independent or individual car provided with four wheels 18-18 attached by suitable bearing pins so arranged that the axes of the wheels are in the same plane with the lower edges of the pallets,v each pallet being thus permitted to move around the curved track hereinafter described without inter ference with the other pallets. As the pallets are pushed across they suction Vbox they are guided by the flanges ofthe wheels 18-18 which are in engagement with the `longitudinal track rails 19-19, the weight of the pallets being sustained on the wearing strips 14.

At each end of the suction box there is arranged a dead plate 20, the upper surface of which is flat and in alinement with the upper surfaces of the strips 14. The pallets move with an air tight joint over the surface of one dead plate 20 just before theyv pass to a position over the suction box and pass with an air tight joint over the surface ofthe other dead plate 20 after they pass the suction box. Each of these dead plates has a length slightly greater than the length of a pallet so that there will be no leakage f of air during the time that a pallet is but partly over the suction box.

The pallets are elevated one by one and consecutively placed in position on the rails 19-19 by means of a pair of sprocket wheels 2l which are so designed that their teeth engage the treads of the wheels 18-18 in conl ward and backward incline at their lower on the pallet grates a uniform layer of thev materials which have been discharged from the mixing mechanism A..

As the pallets are pushed slowly forward by the sprocket wheels 21 the layer of material on them is carried away from the hopper 11 and beneath an igniting device such as is indicated at 24. This igniting device serves to fire the combustible sub-y stance, such as powdered coal which has been mixed with the ore, in the manner before described. `yThe igniting device 24 may be 4simply a perforated pipe adapted for supplying gas to support flames which con tinually play upon the top surface of the ore layer.

of the ore to become relatively softened at the time of nascency, and, as will be referred to more fully below, with the result that they unite and harden upon cooling to form a rigid integral cake. On account. of the continuous passage of the air and the formation of large quantities ofthe carbon oxids through the cake during the juocess of sintering, the cake is highly and uniformly porous, and on this account well adapted for the smelting action which will be hereinafter described. It will be 'understood that the rate of movement of the pallets along the upper track rails 19*19 is relatively slow and is so regulated, that when the combustion and sintering at any one point has progressed downward entirely through the layer, that point will have' moved beyond the suction box and substantially to the discharge end of the machine.

In the construction shown in Figs. 1 and 2, the sintering is moved continuously forward onto a shelf 25which is adjacent and in alinement with an aperture 26 in the Wall of a smelting furnace which is indicated as a whole by C. The pallets l5 after freeing themselves from the sinter cake return by gravity in the manner before described to be picked up and returned by the Wheels 21.

The furnace here selected for illustration is of a reverberatory form. It is provided with a hearth indicated at 27 and with a receptacle 28 adapted for the retention of molten metal or matte as indicated at 29 and a top layer of slag as indicated at 30. Tap holes 31 and 32 are provided for the metal and the slag respectively. Nozzles 33 are provided to direct Haines directly onto the incoming sinter cake at points immediately above the hearth 27. The fuel supplied to the nozzles 33 may be either gas or oil and is conducted through the pipes 34 and 35.V 36 is a flue for waste gases from the furnace, and in this flue are located pipe coils 37 and 38 which connect With the pipes 34 and 35 and serve to preliminarily heat the oil or gas which is supplied to the nozzles 33.

I have described the step of adding fluxing material to the ore, when'such materials are needed, as taking place in the preliminary mixing mechanism and I consider the introduction of fluxing materials at that point preferable, as they are in thatl way brought into more intimate contact with the ore particles. However, if desired, the hopper 39 may be used for the supplying of fluxing materials to the ore at points immediately adjacent the region of smelting. Obviously, if desired, fluxes can be supplied through both of the hoppers 3 and 39.

As the forward part of the advancing sinter cake passes within the heating zone of the flames from the nozzles 33 it is smelted into a metal or 'matte, while the earthen ingredients separate themselves into the form of slag. The molten metal or matte being the heavier is collected in the bottom part of the receptacle 28 as indicated and the slag collects in the upper part of the receptacle 28 on top of the metal. Because of the great and uniform porosity of the sinter cake it is readily attacked by the flames and is very quickly and sufficiently smelted.

While it is desirable that the incomingl sinter cake remain unbroken until smelted it is not essential, as it is obvious that any part of the sinter cake which may accidentally break ofl" will remain on the hearth 27 within the zone of the flames until smelted.

It will be observed that when the furnace the sinter cakes were allowed to cool before being smelted.

It is also to be borne in mind that the sinterlmg itself is a step in the prccess of smelting and that as a result of the sintering, the smelting is much more readily accomplished.

In the smelting of iron ores the presence of carbon is necessary. The required carbon can, if desired, be supplied, instead of flux, through the hopper 39. Preferably, how-4 ever, an excess of carbon beyond that necessary for sintering is added to the cre in the preliminary mixing mechanism. By properly regulating the quantity of carbon supplied and by properly adjusting the draft and the rate of movement of the sintering machine, a portion of the carbon may be retained in the sinter cake and carried by it into the furnace and intimately mixed with the ore and flux particles.

In Fig. 5, I have shown the preliminary mixing mechanism A separate from the sintering mechanism. The construction is similar to that hereinbefore described, with the exception that, the material is deliveredl to a suitable point of storage instead of being delivered directly to the sintering machine.

In Fig. 6,1 have shown a sintering machine separate from the mixing mechanism and from the furnace. similar to that hereinbefore described. The material from the mixing mechanism` which may be at a remote point, is conveyed to the sintering machine in any desired manner The construction is l and placed in the hopper 11. The forward portion of the sinter cake instead of being passed directly into the furnace is allowed to break off from time to time and to collect in a pile from which it may be removed from time to time to la region of storage or directly to a smelting furnace. n

In Fig. 7 I have shown a smelting furnace separate from the mixing mechanism and the sintering machine. This furnace may be located, if desired. at a remote point and the sinter cakes or blocks may be supplied to it in any desired manner. The con struction of the furnace is similar to that which has been hereinbefore described.

It is believed that the general nature and scope of my improved process will be apparentfrom the foregoing description ofthe construction and operation of the apparatus selected for purposes of illustration. However, it may be well to point out in detail the larly to the use of an oXid iron ore and a. car.-

Y bonaceous material' such as powdered coal or The temperature at which this occurs (from coke. For illustration, I 'will assume that the metal body to `be treated is the above mentioned magnetite iron ore.

The iron oxid after having been mixed with a proper quantity of powdered coal or coke and with a flux if desired, is deposited upon the moving grate of the .sintering machine and the coal or coke is ignited at the top surface in the manner which has been described. Airis drawn downward through the interstices of the mixture and causes the combustion of the coal or coke to progress downward and inward through the mass. 'v The actionwhich takes place is in some respects similar to the action which `takes place in ablast furnace. The carbon in burning generates, of course, the ordinaryy carbon oxids. The plane of combustion proceeds from the surface toward and through the interior. The atmospheric oxygen is supplied more slowly the farther the air travels inward and there tends to be a correspondingly large amount of carbon monoxid generated, but this, in turn, as more oxygen is taken up by it, passes into the dioXid form; and the mass of metalliferous particles are enveloped in these carbon oXids. The temperature which is generated raises that of the iron oxids to the points where "reactions can occur. The magnetite, in the presence of the carbon oxicls, manifests the tendency, largely from contact reaction, to adhere to neighboring particles, either those of its own constitution or those of Vother compositions. It is an instance of the phenomenon analogous to cementation of certain forms of iron. There is; also, a tendency for it, under certain conditions, to 4-pass into other lower oxid forms, and then lower and the higher oXids, in the presence of the carbon oXids, unite again to form a ferrite.

600 to 800 C.) is much lower than that at which siliciication occurs.

If in the reactions between the metal oXids and the carbon oxids any metallic iron is temporarily released, the particles of such metal tend to unite and assist in establishing the coherency of the mass.

If, instead of the iron oxid, ore being largely magnetite, it is of the lower oXid form, namely hematte: as soon as it is heated and enveloped in the bodies of carbon oxids more or less of it takes' on more oxygen and becomes relatively acid in character, and this part in turn unites with the lower oxid and produces a ferrite which, at the time of nascency, and as above described, produces a cohering analogous to cementation and at a temperature much lower than that at which the silicating of the iron occurs.

I am aware of the" fact that it has been heretofore proposed to mix carbonaceous material with iron ores and then place the mixture in a large pot or converter and with a powerful blast attempt to force air through it for the purpose of agglomerating it. .But1 so far as I have been able to learn, no success was attained and all such attempts have been abandoned.

It was discovered that in the case of most of the iron ore bodies the fineness for pul-` verulency was even greater than that incident to the sulid ores. To cause the air to pass upward through it required a powerful pressure, and this not only produced an intense agitation among the dusty particles, but lifted them awayfrom each otherand prevented the cementation which I attain.

The neness of the particles requires that the stratum should be thin; this also acting, as above described, to relieve the mass of heat before it rises to the degree wherehard indurated silicates are formed. Oresof the class referred to herein include iiue dust from iron blast furnaces and in many cases it will be found that there has passed from the furnace carbon with the ore dust.

After the combustion has ceased the sintered and partly smelted porous cake or vblock is subjected to externally applied heat diately after sintering while the cakes or blocks still retain the heat of the sintering combustion.

While I have/described my invention as especially adapted for the treatment of metal bearing ores, it will be understood that it is not necessarily so limited and that it may also be used in the treatment of non-metallic materials, as for instance, in the burning or roasting of cement clinkers.`

1. The herein described process of treatingmetal oxid ores which are initially in a line or pulverulent condition, to form uniformly porous coherent thin agglomerated or sintered masses for introduction to the blast `furnace, it consisting in forming a stratum or layer of such oXids together with commingled pulverulent carbonaceous matter, said' stratum being made thin to preyunite and cohere at the time of the oxid transformation, and at a` temperature below that of the silicilication of the metal.

2. The hcreln described process of formmass of pulverized carbonaceous material,

forming a relatively thin layer of substanf tially uniform depth of this mixture, igniting the carbonaceous ingredient thereof at the top of the layer, causing the zone of ignition to propagate,l downward through.

the layer by a current of air, causing reactions to take place between the carbon oxid formed by the combustion of the carbon and metallic oxid at temperatures maintained below the'temperature of formation of metal silicates, whereby the layer of material is transformed into cellular agglomerated masses united by the metal oxids contained, and free from metal silicates.

3. The herein described process of treating pulverulent iron ores containing oxids, lower in oxygen than ferrite to form uniformly porous solid coherent cakes or blocks,

it consisting in forming a relatively thin stratum of the iron oxids commingled with pulverulent carbonaceous material, igniting the carbon at the exposed surface of the said stratum, passing currents of air through the said stratum from the surface of ignition, causing thecombustion to pass to and through the interior of the said mass, causing the iron oxids to be oxidized to an extentl equivalent to that of ferrite, 'and lwhile the ferrite particles are in contact, permitting them to cohere at the time of reaction to form the agglomerated blocks or cakes as aforesaid.

4. The process of formingl uniformly porous blocks or cakes from pulverulent ironl oxid ore which consists in forming a relatively thin stratum of the said pulverulent ore while commingled with pulverulent carbonaceous material, igniting the carbon at the exposed surfaces, passing streams of air therethrough, forming bodies of carbon oxids in the mass, causing said carbon oxids to effect the deoxidizing and the oxidizing of the iron oxids and simultaneously causing the cementation of the oxids and commingled particles, substantially as described.

5. The herein described process of forming an agglomerated mass of metal oxids, which consists in commingling a mass of ine material carrying metal oxid and a mass of pulverized carbonaceous material, forming the resulting mixture into a relatively thin layer of substantially uniform depth, igniting the carbonaceous ingredient thereof, causing the resulting zone of fusion and reaction to propagate downward through the layer by a down-draft of air, causing reactions to take place between the carbon oxids formed by the combustion of the carbon and the metallic oxids during fusion at temperatures maintained below the formation temperature of metal silicates, whereby the layer of material is transformed into cellular agglomerat'ed masses united by the metal oxids contained, and free from metal silicates.

6. The herein described process of forming an agglomerated mass of iron ferrite, which consists in commingling a mass of iron oxids and a mass of pulverized carbonaceous material, then forming the resulting mixture into a relatively thin layer of uniform depth, igniting the carbonaceous ingredient at the top of the layer, causing the zone of ignition and reaction to propagate downward through the mass by a current of air, causing a` partial reduction of more or less of the oxids and a combining of the relatively lower with the relatively higher oxids into masses of iron ferrite, and maintaining the temperature of ignition and reaction at points below the formation temperature of iron silicates, whereby the layer of material is formed into cellular agglomerated masses free from iron silicates.

7. The process of treating metal ,bearing ore initially in a relatively fine condition and substantially free from combustible elements to prepare it for smelting, which consists in mixing with the ore a quantity of combustible substance, disposing the resulting mixture in a mass, igniting the combustible substance in the mass at one surface thereof, causing a supporter of combustion to pass from the surface of ignition to the interior and through the mass whereby combustion is made to progress into and through the mass to cause sintering thereof into a cake, holding all of the particles of the mass against agitation or movement in relation to each other during combustion and sintering,.and supplying to the ore before thesmelting action a quantity of fluxing may terial.

8. The herein described process of sinteringl a mixture of fine metal-bearing material and carbonaceous matter to prepare the metal for subsequent smelting, which consists in disposing the mixture in a thin layer permeable to air, igniting the carbonaceous constituent of the mixture at a surface of the mass, and causing combustion thereof to proceed entirely through the mass while the particles are ,held in a state of substantial quiescence among themselves, wherebyL there are formed uniformly cellular rigid masses containing the metal.

9. The method of sintering ine ore or material, consisting in mixing such material with fine carbonaceous fuel-,- disposing the 10.' The method of sintering fine ore moterial, consisting in mixing the same with fine culbonaceous fuel, feeding the mixture on to a bed or conveyor, and sintering` the ore by completecombustion of the inter- `mingled curbonaeeous fuel as the material lll is ca rried along.

11. `The method of sintering fine ore ma-v l12. The method of sinterng fine ore material, consisting in mixing it with fine carbon, feeding the mixture upon a moving conveyer, ignitin'g the carbonaceous fuel at one point in its travel, and drawing gases down and out of the layer as the mixture is carried Illongbeyond the ignition point.

In testimony whereof I aiiix my signature, in presence of two Witnesses.

ARTHUR S. DVIGHT.

Witnesses: Y l

CHARLES L. MONTAGUE, JOHN KNOX.

DISCLAIMER 1,254,316.-Arthur S. Dwight, New York, N. Y. Pnocsss 0F TnEA'rrNG Ones. Patent dated January 22, 1918. Disclaimer liled October 21, 1931, by the assignee, Dwi/q', ht d: Lloyd Sintering Company, Inc.

Hereb enteres this disclaimer to claims 4 and 8 of said Letters Patent, which are in the fo lowing words, to-wit:

4. The process of forming uniformly porous blocks or cakes from pulverulent iron oxid ore which consists in forming a relatively thin stratum o the said pulverulent ore while commingled with pulverulent carbonaceous material, igniting the carbon at the exposed surfaces, passing streams of air therethrough, forming bodies of carbon oxids in the mass, causing said carbon oxide to effect the deoxidizinv' and the oxidizing of the iron 'oxids and simultaneously causing the cementation of the oxids and commingled particles, substantially as described.

8. The herein described process of sintering a mixture of fine metal-bearing material and carbona/ceous matter to prepare the metal for subsequent smelting, which consists in disposing the mixture in a thin layer permeable to air, gniting the carbonaceous constituent of the mixture at a surface of the mass, and causin combustion thereof to proceed entirely through the mass while the particles are hel in a state of substantial quiescence `among themselves, whereby there are formed uniformly cellular rigid masses containing the metal.

[Oficial Gazette November 17, 1.931.}

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