US1207881A - Process of smelting metallic ores. - Google Patents

Description

H. L. DOHERTY.-

PROCESS OF SMELTING METALLIC ORES. APPLICATION FILED JUNE2 2. 1909.

. fi fi l Patented Dec. 12, 1916.

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M 1 t? m I Q N a @Xkbvwooeo: H e n ry L. D0 h e r ty, 3 mm wl oz H. L. DOHERT'Y; PROCESS OF SMELTING METALLIC ORES.

' APPLICATION FILED JUNEZZ, 1909.

P0 1 OJ 1 2 1 0 e D d e t H e t a P am T E E H 4 S T E E H S 3 Henry L. Doherty,

S n00, wtoz HENRY L. DOHER'JLY, OF NEW YORK, N. Y.

PROCESS 0F SMELTING METALLIC ORES.

Specification of Letters Patent.

Patented Dec. I2, 1916.

Application filed June 22,1909. Serial No. 503,736.

To all whom it may concern Be it known that I, HENRY L. DOI-IERTY, a citizen of the United States, residing at New York city, in the county of New York and State of New York, have invented new and useful Improvements in Processes of Smelting Metallic Ores, of which the following is a specification.

This invention relates to processes of smelting metallic ores, and particularly to that kind of such processes in which the reduction of the metal from the ore is carried out in a rotating furnace divided into two sections, the lower section generating and being filled with a combustible gas formed by the semi-combustion of carbonaceous material in aerial suspension in said lower sec-v tion, the heat of this semi-combustion maintaining the ore in the lower section at a temperature that will permit of the reduc tion of the metal by the carbonaceous mates rial added to the ore upon its entrance to said lower section, and the fusion of the. resulting metal and slag. The upper section of the .furnace is subdivided into a plurality of chambers in which the combustible gas generated in the lower section is burned to superheat the charge.

The object of my process is to so carry out the smelting operation that, without inter? fering with the reducing character of the flame in the-actual region of reduction, the gases of incomplete combustion from'the reducing flame are fully oxidized in another region of the furnace, the heat so developed being applied to the superheating of the charge and the superheating of the primary and secondary air.

I am aware that it has beenpropose'd before to use a rotating furnace for the smelting of metallic ores, notably by the process set forth in the patent to Ellis, No. 839126, in which he heats the ore and flux in a rotating chamber and then reduces the ore mixed with carbonaceous material on an in clined hearth with a stratified flame, the under being. a reducing flame while the upper flame is a high temperature flame of highly oxidizing character, intended to heat the charge on the hearth. In my process, however, I make no attempt to use a stratified flame but instead subject the materials in the reducing chamber to a flame which is wholly reducing in character, while supplying to the ore the quantity of carbon necessary to effect the reduction of the metal, the

heat required in the reduction being supplied by the super-heat communicated to the charge in the heating chambers, and by the heat of the reducing flame, itself. I am also aware that it has been proposed to smelt ores in a rotating furnace by first heating said ores by an oxidizing flame in the upper section of said furnace and then subjecting the heated ore to reduction at a comparatively low temperature by hot producer gas generated in a separate producer chamber discharging into the lower end of said rotating furnacethe temperature of reduction being maintained at that point which will not render either the metallic iron or Slag producing constituents of the ore fluid.

This process is, also, obviously different from my invention, described in detail below, among other things, in that the inventor effects the reduction of the metal at a relatively low temperature (below the fusion temperature of both the iron and slag) by contacting with the ore a current of ignited producer gas. In my process, I depend upon added solid carbon to effect the reduction, and heat the charge during reduction by burning to carbon monoxid, in contact with the same, powdered carbonaceous matter in fluid-suspension. I

In carrying out my process, I first preheat the charge of ore and flux by the action of a high temperature flame formed by the secondary combustion of the gases from the reducing flame with the aid of preheated air, said high temperature flame burning in intimate contact with said charge, and I then introduce into the mixture of ore and fluxsuflicient carbonaceous material to effect the reduction of the metallic constituents of the charge, and, finally, subject the mixture of superheated ore, flux and fuel to the heat of a reducing flame burning in heat-radiating proximity thereto and of sufficient intensity to maintain the materials at a reacting temperature until the reduction of the metal is complete and fusion of metal and slag accomplished.

In the. accompanying drawings, I have shown in diagrammatic form an apparatus for applying my process, although any other form of apparatus that will accom plish the same ends may be used ins ad.

In the drawings Figure 1 shows a p an of the apparatus; Fig. 2 shows a part longitudinal section on the line A B of 1 and a part elevation of the furnace; Fig. 3 is a cross-section of the furnace on the line C D of Fig. 2; Fig. 4 is across-section of the furnace on the line E F of Flg. 2; Fig. 5 1s a top View (diagrammatic) ofthe air recuperator; Fig. 6 is a section through the secondary air recuperator on the line A B of Fig. 5.

The furnace, 1, of the apparatus, n the design shown, comprises a metal cylinder, 2, having a thick lining, 3,.of refractory material. This cylinder 2, rests on suitable roller-bearings 1, and has a driving mechanism 5, which causes it to rotate. The upper portion of the furnace contains a core 6, n which are formed a plurality of flues, 7. A passage, '8, occupies the axial portion of the core 6, and has located within it a separate flue or pipe, 9. This pipe 9 extends long tudinally of the furnace and has its upper 20 end extending through the housing 10, Which'incloses the upper end of furnace 1. The upper end of 9 works in a bearing, 11, which has a suitablepacking so as to form an air-tight joint with 9. Opening into.11 and communicating, therethrough, with 9 is a-conduit, 12, which conducts the hot secondary air from the secondary-air recuperator and discharges it into the flue 9. The flue 9 is supported in its position in passage 8 by suitable supports, 13. The portion of 9 VlthiIl the core 6 is preferably of some renace.

'kiln to project the portion of the walls of 7 nearest the lining 3 of the main shell 2,

fractory material since the temperature to which it will ordinarily be exposed is rather high. A chute, 14, provided with a screw,

conducts the charge of ore and flux from the conveyer 15 and discharges it onto the bottom of the rotating furnace The furnace being set with a decided inclination to the horizontal, the rotation of the furnace causes the mixed charge of ore and fiux to pass into the passages or flues 7. The continued rotation of 1 gives the charge a progressive motion through the flues 7, and causes it, finally, to discharge into the open barrel or reducing chamber 16, of the fur- The lower end of core 6 is cut away, as shown in its peripheral portion on a cylindricalsurfaceextending through the centers of fiues 7. This causes that portion of the walls of fines 7 nearest the axisof the beyond the termination of forming a lip 17, to eachflue 7. The object of these lips or prolongs is to intercept the discharge of material from the-fines 7 while they are passing through the upper segment of their rotary path. The length of the lips 17 should be about of the longitudinal travel of the charge in flues 7 for 1 revolution of the furnace. Thus, while the flues 7 are passing through the upper segment of their path the material discharging from them simply advances on the lips 17 and does not shower down across the'draft of the air current entering through 9, or-across the draft current entering such of the fiues 7 as, at the. time considered, occupy a position in the lower segment of rotation. When the fines 7, have entered the first of the lower two I conveyed to the furnace through the conveyer 18, and enters through the chute 19, discharging into the annular passage 8. As the furnace rotates the fuel works down through the annular passage formed in the flue 8 by the walls of flue 9, and discharges into thereducing chamber 16. As the fines, 7, pass through the lower segment of their travel the lips or prolongs 17 of the flues 7 in that position, of course, form overhangs over the discharge end of the fines. The fuel discharging from 8 falls onto the overhangs (17) and isdeflected to either side of the orifice of the flue which happens, at the particular time considered, to be occupying the lowest position, being carried into the fiues 7 by falling across the draft current entering the fiues. By the rotation-of the furnace the ore and flux and the fuel are thoroughly mixed and both being at a high temperature reduction immediately sets in.

The air discharging from flue 9 is, of course, immediately taken up by the gaseous current entering the flues 7, and drawn into the said fiues. Since the reducing operation takingplace in 16 requires that the atmosphere therein should be of a highly reducing character the gases passing from 16 to the fines 7 carry still a large portion of the potential heat of the fuel entered at the lower end of the chamber 16. The air entering through 9 should be in sufficient quantity to cause the complete combustion of the gases entering flues 7. There is thus developed in the fiues 7 a long flame which by reason of the small diameter of these lines is forced to burn in intimate contact 22, is the recuperator forthe primary air,

and is thus prevented from respective re,

23, the recuperator for the secondary air. These recuperators may be of any type preferred. In the design shown they consist of rectangular chambers inclosed in a metal shell'and having heavy walls of flrebrick or other refractory material. Bafile walls 24, 24., 24.", etc., and 25, 25', etc., divide the recuperators 22 and 23 into a series of compartments 26 and 27, respectively. These compartments communicate, alternately, at the top and bottom and thus form in each case a continuous passage through the re spective recuperator. The baffle walls 24, 24, 25, 25, etc., force the current of gases passing through the recuperator to take a serpentinecourse. Located in the compartments of the recuperators 22 and 23 are sets of return- bend flues 28 and 29,-respectively. The 'flues 28 are connected at their inlet ends with a c ross-flue 2 8 and at their discharge ends with a cross-flue 28". Opening out of 28" is the hot air conduit 28 which conducts the hot air to the blast nozzle 30 of the furnace 1. The return-bend flues 29 are connected at their inlet ends with the cross-flue 29 and at their dis charge ends with the cross-flue 29". Opening out of 29 is the hot air conduit 12 which conducts the hot air to the flue 9 of furnace 1. The flue 28' is connected by a pipe 32 with the discharge pipe 33 of blower 34. The fine 29- is also connected with 33 by a pipe 35. W

The hot primary air discharges through the nozzle 30, taking up and bearing into the furnace powdered coal or other fuel fed through the hopper 36, in the manner well known to those connected with the cement industry; i. 6., as a more or less axially presented flame of powdered coalburning in aerial suspension. A screw conveyer 37 delivers the requisite quantity of powdered fuel to the feed-hopper 36 A valve, 31, on the pipe 28 serves to regulate the-quantity of. air sup-plied to the blast nozzle 30. I aim to introduce through 30 only enough air to furnish suflicient heat by its combustion to maintain the temperature in the re ducing chamber, 16, at the point most favorable'to the reactions it is designed to bring about.

As before mentioned, it is not possible to completely burn the coal or other fuel introduced through 36, owing to the necessity of maintaining a strongly reducing atmosphere in the chamber. 16. In the case of iron: reduction there should not be any more air admitted through 30 than that reuired to form CO with the carbon of the uel borne in by the air blast. Should there be any excess of 0 over this amount there would be a formation of CO which would be immediately reduced again to CO at the expense of the metallic iron in chamber 16. This action could be compensated for by the introduction of an excess of the reducing carbon through the flue 8.

The metal reduced .by the reactions between the metallic ore, the flux and carbon introduced through 9, and the slag formed, runs to the end of the cylinder 2 and discharges through the passage 39, in the lions ing 38 mounted on trucks 40 closing the lower end of the furnace, and falls into the crucible .or hearth 41. Here the metal and fluid slag separate by gravity, the slag flowing away through the cinder notch 42, while the metal is tapped off at intervals through the tap-hole 43, into a pig mold or converter ladle according to the disposition to be made of the crude iron.

Taking the case of iron ore reduction for example of the working of my process,

I proceedas follows: The ore if not already crushed is reduced to about 20 mesh. The flux is also crushed to about the same size. The ore and flux are fed in, the proper proportion into the conveyer 15 and in their progress therethrough are thoroughly mixed. The mixed material, as before explained, is fed by the feed chute 14 to the flues 7. During its passage through the flues 7 the mixed ore and flux is highly heated by the secondary combustion taking place in the flues. In these narrow flues, the hot reducing gases'from the-lower zone of the kiln meet and burn with the superheated air coming through 9 from the regenerators, and there are produced intensely hot oxidizing flames burning in direct'and intimate contact with the hot granular charge coming down such fines. The high temperature prevailing in 7 causes the flux to unite with the siliceous material (gangue) of the iron ore. Owing to the presence of the iron oxids of the ore, however, the mass-does not become liquid but leaves the flues 7 in a pasty or semi-fluid condition. The fluxing reaction is that due to the reaction between f the SiO of the ore and the base (usually CaO) of the flux. 'This may be typified by the reaction although the reaction which actually takes place is usually more or less complex. When the superheated and partially fluxed ore enters the reducing chamber, 16, it comes into contact with the carbon entering 16 from the flue 8. The iron oxide are quickly reduced by the carbon with the formation of metallic iron and CO, the resultant reaction in the case of Fe O being Fe.,.o,+zaoiit asoo,

although it actually occurs in two stages+ the Fe O being first reduced to 2Fe0, and

this, in turn, to metallic iron. The reduction of the iron ore leaves the whole mass in a fluid condltion and, as explained above, the

iron and fluid slag flow away to the separate hearth 41, where they are separated in the usual manner.

, In the usual method of reducing iron in the blast furnace, itis not possible .to utilize more than about one-half of the total derived fromthe carbonates charged as flux.

Less than half of the total calorific power of the-fuel is actually developed in the blast furnace itself. Now, in my process of smelt ing as hereinbefore explained I secure the complete combustion of the fuel in the furnace, the heat developed in the secondary combustion being utilized to flux the impurities of the ore and to superheat the ore and flux to a high temperature. These materials are-thus brought to the reducing zone of my furnace in the best possible state of preparation for the reducing operation proper. The

gasesleave the furnace'still carrying a large amount of sensible heat, which, as explained, I utilize to preheat my air-currents. By thus carrying out the complete combustion of the fuel in my furnace without in any way interfering with the reduction process, I

secure many economies in operation. For

example, the necessity for compressing a great volume of air to a pressure of 1044: lb. per sq. inch, as is required in blast furnace practice, is entirely avoided. In my process theair is, as explained, introduced into the furnace at but little inexcess of atmospheric pressure by means of a fan of the ventilating type, requiring an insignificant amount of power to operate it, since in my furnace there is no resistance offered to the blast by the charge in the furnace, the passages for the gas current being comparatively free andunobstructed.

I tion, there is in such case no additional ex- As my process is designed particularly to handle the fine ore from magnetic concentrapense entailed for the crushing of the ore. On the contrary, in such case there is asaving of theexpense for briqueting, since such concentrates must invariably be briqueted before they can be treated in an ordinary blast furnac It is to be understood that in this specification and in the claims I use the expression superheating of the charge and equivalent expressions, to designate the heating of the charge to therelatively high temperature produced bythe combustioncf the combustible gas formed by'the semi-combustion in the reducing chamber, so that, 1n consequence thereof, a portion of the heat required to support the reduction of the metal of the, ore will be supplied by the sensible heat of the charge as it enters the reducing chamber.

- Having described my invention, what I claim is:

1. The process of smelting metallic ore which comprises superheating said ore with an oxidizing flame, the said oxidizing flame burning with the aid of superheated air and being in direct and intimate contact with said ore, continuously adding a reducing material to said superheated ore, and subjecting the mixture of ore and reducing material to the action of radiated heat from a reducing flame of carbonaceous material in aerial suspension burning with a limited amount of.

heated air to assist in the reduction of the metal of said mixture and to maintain the said mixture at a temperature suflicient to smelt reduced metal during the said reduction.

2. The process of smelting metallic ore which comprises superheating said ore and a suitable flux to a temperature above the temperature of reduction with a comparatively high temperature oxidizing flame burning in intimate contact therewith, adding to the superheated mixture of ore and flux a powdered carbonaceous material capable of reducing the metallic constituent of the ore to the metallic state, and agitating the resulting mixture while maintaining the temperature of the same above the fusing temperature of the reduced metal by exposing said mixture to radiated heat from a flame of burning carbonaceous material in suspension in only suflicient heated air to burn said material to carbon monoxid.

3. The process of. smelting metallic ore which comprises directly and intimately contacting metallic ore and a suitable flux with a flame burning with the aid of suflicient.

- superheated air to make it freely oxidizing to the metallic constituent of the ore, whereby said mixture of ore and flux is superheated and reaction caused to take place between gangue of said ore and said flux, mixing the superheated mixture of, ore and flux with a reducing material and maintaining the temperature of the mixture for'a time sufiioient for reduction by radiated heat from r a strongly reducing flame formed by burning powdered fuel with a proportion of heated air only suflicient to burn said fuel to carbon monoxid.

4:. The process ofsmelting metallic ores I which comprises directly and intimately contacting metallic ore mixed with a suitable flux with-a relatively high temperature flame which .is freely oxidizing to the. me,-

.tallic constituent of the ore to, superheat 'said ore and to bring about a partial reaction between the said flux and the gangue of said ore, continuously adding to the superheated materials powdered reducing material, and subjecting the mixture of superheated material and reducing material to heating to a temperature capable of liquefying the reduced material and fluxed gangue by burning powdered fuel in radiating relation to said materials but out of contact therewith by a proportion of air only suflicient to burn said fuel to carbon monoxid, removing the molten metal and fluxed gangue to a settling chamber, and separating said metal from said gangue in said settling chamber.

5. The process of smelting a metallic ore which comprises heating said ore and a suitable flux in a plurality of rotating chambers by direct contact with a flame of combustible gas and preheated air, whereby gangue of said ore is caused to combine with said flux, removing the fluxed ore to a rotating reducing chamber, substantially filled with a reducing atmosphere coming from powdered carbonaceous material burning to carbon monoxid in aerial suspension, mixing a reducing material with said fluxed ore at substantially its place of entrance to said reducing chamber, and subjecting the mixture of heated ore, flux and reducing material to heat in said reducing atmosphere to reduce the metallic constituent of the ore and to fuse the reduced metal and slag, conducting the hot reducing gases from. said reducing chamber to the said heating chambers, and mixing preheated air with said gases, at substantially their place of entrance to said heating chambers, to burn said gases in contact with the mixture of ore and flux in said heating chambers, to heat said mixture.

6. The process of smelting a metallic ore which comprises crushing said ore, crushing a suitable flux, mixing with said crushed ore sufficient of said flux to form a fusible compound with the gangue of said ore, in-

, troducing said mixture of ore and flux into a furnace chamber, introducing a combustible gas and preheated air into said furnace chamber, whereby said mixture of ore and flux is subjected to a temperature sufficient to cause the said flux to partially combine with a gangue of said ore, removing the partially fluxed ore to a second furnace chamber filled with a reducing atmosphere, adding to the partially fluxed ore suflicient reducing agent to reduce the metallic baseof said ore to the metallic state, introducing a fuel laden blast of preheated air into the second furnace chamber, the proportionof fuel and air in said blast being such that substantially no carbon dioxid is formed in said second furnace chamber, burning said mixture of fuel and preheated air in said second furnace chamber in proximity to said mixture of partially fluxed ore and reducing agent to heat the said mixture, during the said reduction of the metallic base of said mixture, to a temperature sufficiently high to fuse said metallic base and the compound formed by the gangue of said ore and the flux, and to convert the mix ture of fuel and air into a combustible gas, removing the fluid metal and fluxed gangue to a third chamber, separating said metal from said fluxed gangue by gravity, and in troducing the said combustible gas formed in the said second furnace chamber into the first furnace chamber together with preheated air to heat a fresh portion of ore and flux.

7. The process of smelting iron ore which comprises mixing the said ore with a suitable flux, subjecting the mixture of ore and flux in a rotating chamber to heating by intimate contact with an oxidizing flame burning with superheated air, such heating being to a temperature suflicient to cause a partial union of the gangue of said ore with said fiux, adding powdered carbonaceous material to said mixture of ore and flux in quantity sufiicient to effect the reduction of the metallic base of said ore, and subjecting the mixture of ore, flux and reducing material to radiated heat from reducing flame spaced away. therefrom and serving to maintain the temperature of said mixture above the fusing temperature of the reduced metal and the fluxed gangue of said ore.

Signed at New York city,in the county of New York and State of New York, this 21st day of June, 1909.

HENRY L. noHEn'rY.

Witnesses:

FRED B. Munoox, THos. I. CARTER.

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