US2503555A - Ore conditioning and reduction process - Google Patents

Description

April 11, 1950 H. G. LYKKEN 2,503,555

ORE CONDITIONING AND REDUCTION PROCESS Filed Sept. 25, 1945 Y 5 Sheets-Sheet 1 [V VE N TOE /7ENE Y GIL YKKEN' m Fm! FWW A T TOENS v61 April 11, 1950 H. G. LYKKEN 5 5 ORE CONDITIONING AND REDUCTION PROCESS Filed Sept. 25, 1943 5 Sheets-Sheet 2 N VEN TOE HENRY G. L YKKEN ivfaufi, pubq YWM flTTORNEYJ April 1950 H. G. LYKKEN 2,503,555

ORE CONDITIONING AND REDUCTION PROCESS Filed Sept. 25,1943 5 Sheets-Sheet 3 COLD WATER HOTW/ITEE LET Ol/TLFI' /NVEN7'0E HENRY G. L YKKEN fi6'4 rfawflfaufl {WM/11 Patented Apr. 11, 1950 ORE CONDITIONING AND REDUCTION PROCESS Henry G. Lykken, Minneapolis, Minn. U V Application September 25, 1943, Serial No. 503,795 1 12 Claims. (01. 75-39)" This invention relates to a process and apparatus for the heat treatment and processing of finely divided or pulverized ores such as carbonates, sulphides and sulphates to the oxides, but more particularly the invention relates to methods and apparatus for the partial deoxidation or partial reduction of finely divided iron ore for the purpose of concentration and, in a variation of the methods and apparatus, the invention provides for the complete reduction and smelting of such ores. The invention relates particularly to the metallization of iron ores having a percentage iron content below that which can be shipped economically to and utilized in blast furnaces. The invention provides for the reduction of such ores directly to the metallic state. It is an object of the invention to provide such methods and apparatus.

More particularly it is an object of the invention to provide improved apparatus and processes for treating finely divided ores, particularly low grade ores and more specifically to provide apparatus and processes for smelting or reducing such finely divided ores. It is a further object ofthe invention to provide apparatus and processes wherein finely divided ore is conditioned for concentration or smelting by utilizing radiant heat under reverberatory conditions. Other and further objects of the invention are those inherent in the apparatus and processes herein illustrated, described and claimed.

The invention is illustrated with reference to the drawings in which Figur 1 is an elevational View representing a cross section through one form of furnace of the present invention utilized in carrying out the processes of the invention;

Figure 2 is a composite cross-sectional view of the furnace apparatus shown in Figure 1 at five diiferent levels Thus, the angular segment between the lines A-X and E--X is taken along the level A-A, th segment between the lines A-X and B-X is taken at the level B-B, the segment between the .lines B-X and CX is taken at the level C-C, the segment between the lines C-X and DX is taken at the level D al) and the segment between the lines DX and E X is taken at the level E -E, all with reference to Figure 1;

Figure 3 is an enlarged fragmentary elevational view of the ore-feeding mechanism shown in.

Figure 2 Figure fl is: an elevational, cross-sectional view through another form of apparatus of the in vention utilized for smelting ore; and

' of ore particles downwardly into the'furnaceh The illustrated form of apparatus for accom-.

Figure 5 is acomposite, cross-sectional vie wherein the segment shown around the arc" FG--H is taken at the level G--G of Figure 4 and the section around the arc HKF is taken at the level K-K-of Figure 4. view of the lower portion of Figure 4 is along the, lines 4-4 of Figure 5;

ORE TREATING FURNACE illustrated is for the'purpose of treating finely; divided ores without causing any agglomeration of the finely divided particles, and for example may be used for converting finely divided hematite ores to the magnetite condition, prior to electromagnetic concentration, forthe metalizing of iron ores, reduction of iron ore, partially or completely, to metallic iron, or may be used for the treatment of carbonate, sulphide or sulphate ores to oxidize them.

The apparatus of Figure 1 consists of a base generally designated I 0 on which there is mounteda plurality of upright columns HH which serve as the basic framework of the furnace. The; framework serves to support a hopper generally designated l9, and ore-feeding mechanism 25, reverberatory furnace section 4!), heat exchanger section 44 and ore-withdrawal apparatus l2.

At the top of the columns ll, there is a roof top of a hopper I!) which is formed by the wall plates l4 and the hopper bottom plates l5, l6, l1 and IS. The hopper inner plates l6 and I! constitute a cone and with the downwardly converging conically shaped outer plates I5 and it serve to cause the ore generally designated 0 to be di-- rected to a plurality of spouts 2|] arranged inv a circle at the bottom of the hopper. Any number of spouts 20 may be used around the circular bottom of the hopper and they deliver the ore into the hopper portion 22 of the ore-feeding mechanism generally designated 25.

The ore-feeding mechanism may be of any desirable type capable of feeding a thin curtain plishlng this process consists of a plurality of vane-type feeders illustrated between the lines A-.X and EX of Figure 2 and in detail in.

Figure 3. Thus, as illustrated in Figure 3, the

The sectional 3 each of the circular bottoms 26 there is a thin narrow slit 24 in chute 3!] which may be from one-half to one inch in width and of a length equal to the width of the hopper 22 in a radial direction. Each of the shafts 21 is provided with a gear 32 and the adjacent gears 32 are geared together by idlers 33. A motor generally designated 35 is shown in Figure 2 and is provided with a built-in or external gear box, and is attached to one of the shafts 21 for slowly rotating the shaft. The gear 32 on the motor-driven shaft serves to drive the adjacent gears 32" through the connected idler 33, and adjacent gears 32 in turn serve to drive still the next ad jacent gears 32 through their connecting idlers, and so on for all of the shafts 21in the'group. This may be continued all-around the entire circumference of the furnace ore feeder, but it is preferred to install the motor drives in"segmerits so that the failure or clogging of one segmentwill not entirely interrupt the furnace. The ore fecdersmay=be arranged circumferentially end to end so asto form a continuous or nearly continuous circle rather thana circle of radial slits, o1 thcy maybe arranged along successive'chords of the circle,'one feeder overlapping the next to form a circlearound'the axis of the furnace.

The action of the ore feeder is as follows: The 'finely granulated ore drops into" the space betweenthe vanes28 on shafts '21 and is then carrie'd around by the'vanes as 'theshafts are rotated. As the ore=then"reaches the thin slit 24in the chute 30,"theore'isbrushed through the slit of each spout '30 until all of the ore between those particular vanes has been dropped, and then the ore'between the next pair of vanes is similarly brushed'through the slit 24 and drops into the furnace. 'This goes on continuously and as a result a curtain o'f o're particles 'falls continuously down through the furnace under the circle of spouts 30. 'I'he'ore-feeding mechanism 25 is supported on'the framework 23 as is also the upper portion orthe reverberatory furnace'section, generally designated 40.

The reverberatory furnace section 40 consists of a vertical cylinder 4! whlchmay be of any suitable horizontal'an'd vertical dimensions'supported on the trusswork 23 and upon suitable brackets '42. nace section 4:: is'intended to designate variations in heightto'accommodate the. heating requirements o'fdifferent sizes of ores. The height ofthe "reverberatory'radiant heat furnace section 40 depends upon the size of Itheore being treated, theflame temperature of operation and. the reaction temperature tto which the furnace feed particles (ore and carbonaceous material) are heated. A sufiicient height of portionv 46 is provided so asto'allow'theparticlesof ore and other 'materialconstituting the furnace feed to be heated to the required .reaction temperature by radiant reverberatory energy while the par ticles are falling downwardly around the heat source 75. Where'the particles are larger, or where'a higher reaction temperature .of the particles-is sought, the furnace height is increased. Similarly, for fihenparticles. or.lower temperatures', the height may bedecreased. Thefurnace is thusidesi'gne'd forum or a particular size.

'The heat'source, illustrated as flame I5, radiates heat .energy in all directions, and this is reflected by the walls. of thefurnace repeatedly, thus'setting'up;a conditionof reverberating heat energy within section 40. As each particle of In' Figur 1, the break in the furabsorber section 44. 'mensions of the cylinders and 4! may be idenfurnace charge falls downwardly, the reverberating energy is impinged against it, and heating of the particle thus results. As the particles are small and the amount of reverberating energy is large, heating is almost instantaneous. Energy Waves that do not impinge upon the particles are not wasted, because they simply reflect from the refractory walls 46, top 48 and cone 52.

A shoulder is provided in the furnace at 43 where the diameter is reduced and from the shoulder 43 there extends another cylindrical section 45 which forms the outer wall of the heat If desired, the outer ditical, although the shoulder 43 provides a convenient ledge'for' supporting the refractory brickwork of the furnace.

Within the section 4| there is provided a refractory brickwork 4B and the brickwork is extended across the top of the furnace as shown at '48. Suitable "radial openings are provided 2 in the brickwork to receivethebottom ends of each of the 'Spouts fill-40 and 'a' central opening is provided at 49 for receiving the heat source burner nozzle generally designated-'50 and steam:

is formed intoaconverging 'cone 52'which ter'-' minates atthe'circular bottom'opening 53. Sup portifor' the refractory lining '52 is'provided by a plurality of boiler tubes constituting tubebank 54 of the heat absorber, generally designated 44. The tubes 54- extend E tromra circular steam drum '55 radially inwardly at 5'1, and thence downwardly and inwardly at 58. The tubesthen continue downwardly" at 59 until they reach the pointEO at which they 'diverge outwardly'at 6| to the water drum"62. A sufiicient number of boiler tubes 54 are provided so' that at'the vertical'portion 59'-theyare spaceduniformly several inches apart as shown in the section between the lines 0 X and D-X oiFigure 2.

The'lower portion of each boiler tube'in bank 54 is provided with a fin'64 which extends'from the boiler tube in the directionofthe adjacent boiler'tube as shown in the cross section between the lines D--X and EX of Figure 2. The fins 64 are of sufficient width so' that they close off the space between adjacent boileritubes', and thus the tubes and the fins 64 forms. continuouswall (see Figure 2) at the levelE-E of Figure 1.

Under certain conditions of operation the gases passing out between tubes at. 59, contain combustibe constituents andhave a .sufliciently high temperature .to ignite in the presence of oxygen. By increasing the distance between'the inner bank of tubes54 and the next bank of tubes 83,.space is allowed'for combustion of.such.

At theilevels 11-1) and; E- E.ofI'Figure=1 the tubes of bank 54fare spaced apart and. hence the hot gases may pass -outwardly between .them has at. 59. At the,portion.58.ofttube 54, the spacing increases, but they are sufficiently close together to provide adequate supportforthe refractory cone 52. Likewisaatthe, portiontfilof. the tubes of bank 54, thetubes spreadoutand anymortionof ore which is carried by the gases and falls between the tubes at 59 (level D-D) may again fall back between the tubes at 6|, near the bottom of the furnace. This is indicated by the arrows 66. At the level E-E the boiler tube portion 59 and the fin 64 serve to retain the main body of ore which collects at the column as shown at 68. The angle of the cone shape formed by portion GI of tubes 54 is less than the angle of' repose of the hot ore within the bottom I0, and hence facilitates passage of the ore between the tubes at the bottom of the furnace.

At the lower end of the tube section45 of the furnace, there is a converging bottom "I which serves to close the bottom of the furnace and at the central point of the conical bottom 'Ifl-there is provided a treated-ore outlet generally designated I2 consisting of a delivery tube I3 provided with a worm I4 for gradually drawing out of the furnace the finished ore which collects in column 68 over the conical bottom I0.

The hot gases of the furnace result from the flame I5 projecting downwardly from nozzle 50 and the gases travel downwardly through the central opening "I6 and thence outwardly between the tubes of bank 54, as indicated by the arrows II. The combustion of residual gases may be caused to take place just outside tube bank 54,

as previously noted. The hot gases then blow over a plurality of additional tubes which may contain either water or air, depending upon process requirements. Thus, for example, in the illustrated embodiment of the invention, there is provided a hot air manifold 80 which is attached to the cylindrical side wall 45 of the furnace and a cold air manifold 8| which is attached to the conical bottom. From the hot air manifold 80 lie alternately in spaced relation with the tube' 82 in the bank 83, whereas the remaining banks of steam tubes 88 and 89 are arranged in circles of successively greater diameter. A baiiie is arranged as illustrated at 90 for causing the hot gases to flow downwardly as indicated by the arrows 'I'I so as to traverse the steam and air tubes and thence upwardly as indicated by the arrows 9|, 92, 93 and 94 into the stack manifold 95.

The number, spacing and character of tubes in the several banks depend upon the process requirements. Thus, suflicient tube area isprovided so as to furnish all hot air needed for the burners, combustion, drying etc. and sufiicient steam surface is then provided to recapture the heating values remaining, any surplus steam,

above process requirements being used for power.

ORE REDUCING SMELTING FURNACE The furnace apparatus, illustrated inFigures 4 and 5, is essentially the same asthat illustrated in Figures 1-3 except that theheat exchanger section 44 of the latter is not used andthe reverberating furnace portion 40 is superimposed upon an annular open hearth or annular ring of open hearths. Thus, the furnace section above line G-,G of Figure 4 correspondsto the reverberating furnace section 40 of,.'the apparatus shown in Figure 1, and is used for the pre-heating and reduction of ore to the metallic state,-

which then falls into the lower open hearth sec-- tion illustrated in Figure 4 for reducing the metal and gangue to the fluid state so these components may be withdrawn separately.

The furnace illustrated in Figure 4 consists of a base I00 and supporting framework of I-beams IOI. At the top of the I-beams there is a roof I02 over a hopper generally designated I05 which may be of any suitable construction, for example of the type illustrated and described with reference to the furnace of Figure 1. An ore introduction pipe I06 is provided in the roof and serves to deposit the ore, generally designated 0, into the hopper I05. The hopper I05 delivers the ore through a plurality of spouts I0'I to an ore-feeding mechanism of any suitable design, for example such as illustrated and de-' scribed at in the apparatus of Figure 1. Connected to the columns ilJI is an intermediate truss I09 which serves to stiffen the framework and support intermediate columns I I0 upon which the furnace proper is built.

The furnace consists of a brick or masonry base generally designated H2 having a built-in circular flue H3 which is connected by breeching II4 to a flue gas exhaust fan or stack (not illustrated) Extending upwardly at the center of the base, there is a masonry pillar I I5 havingan outwardly diverging under surface I I6, an area of maximum diameter II! and an upper conical dome I I8. A water drum H0 may be included centrally within the pillar so as to cool it, and

thus keep the pillar from disintegration. An outer wall I20 is built up around the periphery of v the base IIZ and an intermediate wall I22 extends upwardly to support the roof I23, which is provided with a central opening for the powdered fuel or liquid fuel burner I25. The wall I22 forms the enclosure in which reverberatin radiant energy from flame I28 serves to heat the ore and furnace charge particles, as they fall. The height of the wall I22 is accordingly varied in accordance with the temperature conditions sought to be produced on the ore and size of the ore being treated. The roof I23 which may be supported by any suitable structural steel framework (not shown) is provided with openings for receiving the spouts 30 of the ore-feeding mechanism, all

is a hearth generally designated I28, the second identical hearth I29. a third hearth I30 and a fourth hearth I32. Only a portion of hearth I30" and none of hearth I32 show in Figure 5 Each of the hearths has a curved bottom surface I34, Figure 4, extending from the inner wall I35 of the pillar II5, to the outer wall I20. Hearth I29,

Figure 5, is representative of all of the hearths'.

Hearth I29 is in the form' of a segmental basin,

having upwardly sloping edge walls I36 and,I3 I, back wall 130 and front wall I39. Similarly," hearth I28 has upwardly sloping walls' l40, I4I,-, I42 and another upwardly sloping wall, not illustrated in Figure 5, opposite wall .I4I. Likewise, Figure 5 illustrates a portion of hearth I30, wherein the front upwardly sloping .wall is designated I44 and the upwardly sloping side wall is designated I 45. The side wall I31 of hearth I29 and,

the side wall I45 'of hearth I30 blend into each other'at the elevated land. I48 which extends-from the. inner surface. I of the pillar I I5 to the opposite: inner surface I49 of the pier. of wall I22. Walt 122 extends downwardly to meet the hearth refractory at that" point, as illustrated by the pillars in section in Figure 5.

Between the outer surface I59 of the furnace wall I22 and the inner surface'of' the outer furnace wall I520? and between sidewalls I and I3! of adjacenthearths I 29 and I30, there is an annular spaceacross. which there extends a flue opening, generally designated I51, Figure 4. Space I51 joins with vertical fiue I5I. There is a similar flueopening I52 between the slopin side walls I35 and I4I of hearths I29 and I28 respectively, and a similar elevated land I53 lies between these walls: (between the center pillar Miami the furnace wall I22). are between each of the remaining hearths (see Figure 5 wherein the flues are designated I54 and I55).

The hearths are covered by the furnace top illustrated at I69, the top preferably being curved over each hearth for strength and also to assist in establishing a condition of reverberatingheat energy in the hearth. The flue. gases flow through the space I5! and thence downwardly into the fines I51, I52, I54 and I55 as the case may be and thence into circular flue H3, from which they are withdrawn. at breeching H4. The gases thence flow into heat exchangers, boilers-and the like, not illustrated. Each of the hearths is provided with a tapopening IBI' and a spout I62 as illustrated in Figure 4., One or more burner nozzles I64 is provided above the bath of melted ore and slag in each hearth.

OPERATION OF ORE TREATING FURNACE To place the furnace, illustrated in Figures 1-3, into operation, the ore is first introduced into the hopper generally designated I9 by means of inlet pipe I3, and the feed mechanism 25 is placed in readiness for operation. The burner isthen lighted and the furnace brought up to temperature.

The furnace may be used for the heat treatment and processing of various ores such as the reduction of finely ground carbonate, sulphide or sulphate. ores to the oxides, in a neutral or oxidizing atmosphere and in any required temperature range. The use of thefurnace for the reduction of iron ores will be described in detail and may be-taken as typical of the operation of the furnace.

A. Low temperature reduction 0 iron ore For. low temperature reduction of iron ores, the furnace flame and height of the furnace-are adjusted so that the ore particles are heated to a relatively low temperaturev in the range of 650 to-800 F. Such temperature sufiices for the reduction of weakly magnetic or. non-magnetic oxides to themagnetic oxides, preparatory tomagnetic concentration of the oxide.

Carbonaceous material, preferably lignitic material, which is finely pulverized is added to the finelypulverized oreas provided for in my Patent Nor. 2,269,465 and in my co-pending application Serial No. 410,474, now Patent, No. 2,333,111 dated November 2,1943... The carbonaceous. material supplies the reducing influence.

The furnace is first brought up to the required temperature by flamev I5 which isoperated with a minimum air supply to obtain complete combustion, the air being, Dre-heated. by exhaust gases.

or the furnace so. as to provide as high, aflame.

Similar flue openings and lands temperature as possible. In this waythere is produced a high radiant energy potential between the. flame and the ore processed in the furnace. The ore feeders 25 are then started and the ore mixed with carbonaceous material is dropped in a thin and tenuous curtain around the flame 15 through the reverberatory furnace zone 40. The falling material is exposed to the radiant energy of the flame and reverberatory action in the. furnace and is brought up to the reaction temperature by the exposure of the particles to the radiant energy. This is accomplished practically instantaneously. In addition, some heat isimparted to the, particles by the hot atmosphereof' the furnace. The lignitic carbon or new carbonaceous material is oxidized by the oxide components of the ore, yielding carbon monoxide which in itself acts as a reducing agent as outlined in my patent and my copending application, previously referred to, to reduce or partially'reduce the ore and thus make it susceptible to magnetic separation. The ore drops through the conical section, outlet 53 and to the bottom of the furnace in the direction of the arrow 68 where it is slowly withdrawn from the column of ore supported by boiler tubes 59 and the intervening fins 64 between the tubes.

The hot gases pass. outwardly between the boiler tubes, above the baflle B4 and thence pass downwardly over the banks of tubes 83, 81, 89 and 39, and thence upwardly between the baffle 90 and the outer refractory line wall 45 of the heat exchanger. The thus cooled gases pass to the flue breaching and may then be carried to further heat exchange apparatus recovering the heat values of the gases, or may be passed over the incoming ore for somewhat pre-heating and drying the ore. The proportion of tube surface in the heat exchanger 44, which is devoted tosteam generation and pre-heating of air, may be' varied as desired. Thus, one or more of the banks of tubes 81, 88 and 89 may be given over to the heating of air if the process requirements so indicate.

The flow of hot gases through section 59 of boiler tubes 54 carries some finer particles of ore into the space between baflie 99 and the tubes. Such portions of ore tend to fall downwardly rather than to be carried up by the fiue gases and. the ore particles thus fall upon the lower conical bottom I0 and fall between portions SI of the tube bank 54 onto the treated ore cone collected in the conical bottom I0. The rotation of screw 7-4 serves to Withdraw the treated ore from the: bottom III, and the speed of withdrawal is adjusted so that a solid column of ore is at all times maintained below level E-E of Figure 1, with the result that the furnace gases are compelled: to pass outwardly between the tubes above the fin 64. After withdrawal from the furnace, the. ore may be separated by any conventional magnetic or other types of separators for removingthe magnetite ore from the accompanying gangue, where the furnace is used for preparing iron ore for magnetic separation. For other uses, the. treated. one. follows appropriate melting procedures in subsequent steps.

' B, High temperature reduction ofiron ore core.

estates state. The apparatus and operation is the same as that outlined under low temperature reduction except that the heat input of flame 15, the size of particles fed and furnace height are selected so as to allow the particles of furnace charge to be heated to a much higher temperature, viz. in

excess of 1700 F., preferably 1800 to 2200 F.

Under such conditions the exit gas temperature at breeching 95 will be correspondingly higher, admitting of a correspondingly higher air preheat to the flame 15 and much higher radiant energy potential between the flame and falling particles of charge fed into the furnace. At this higher temperature there is a reaction between the carbon introduced with the ore and any moisture in the furnace entering with the air, fuel and ore, or that may be introduced as steam. The water vapor reacts with the carbonaceous material present, liberating hydrogen and carbon monoxide in any desired and regulated amounts.

Heating to such a higher temperature, viz. in excess of 1700 F., preferably 1800 F. to 2200 F., causes the finely divided iron oxide particles to be subjected to a hot and highly reducing atmosphere, and the ore particles are reduced to the metallic state almost instantaneously, well within the time needed for such particles to fall the height of the furnace which, of course, is adjusted to the required height for any given size ore being processed. For many purposes of the invention, it is not necessary that the particles be completely reduced to the metallic state. Thus it is suiiicient for magnetic separation and other uses to only partially metallize the oxide, thus in effect forming a metallic shell with an oxide Such partially metallized material can then be concentrated magnetically or by other methods of concentration. Such concentrates may also have an increased iron concentration, the iron content being adjusted to any concentration desired. Such concentrates may be used for blast furnace charges and can also be used directly or indirectly in the open hearth furnace or a modification of same, thus by-passing the blast furnace.

The increased heat in the exit gases can be completely utilized. Some of the available heat is required for the preheating of combustion air used in the apparatus and the remaining heat may be used to generate power for the grinding of the ore and fuel and other power purposes and the pro-drying of the ore, if required. It is contemplated that the heating value of any oombustibles in the flue gases shall be recovered by adding superheated air to oxidize the residual combustibles in an enlargement of the space between tube bank 54 (at 59) and the tube row 83, where the gases are still above the temperature of ignition.

Among the advantages of high temperature treatment of the iron ore is the increased value of the product, the generation of hydrogen as well as CO as reducing gases, vastly increased reaction rate (due to the presence of the hydrogen and the increased temperature), and the production of a product which is much more readily separated from the gangue.

While the high temperature process is least usable for ores having very low softening-point gangue material, the gangue in most ores, for example silicious ores, will not be seriously affected or soften at the temperature indicated.

The method of heating by radiant energy provides in addition a differential rate of heating of ore and gangue, the ore heating faster than the 10 gangue material because of the difference in absorptive values of the surfaces of such diverse materials. This causes the gangue to drop to the relatively cooler section of the furnace before attaining a temperature that will produce softening and consequent agglomeration.

, It will be noted that the top of the reaction chamber will be substantially hotter due to stratification with the hotter and lighter gases at the top, and due to the radiant energy reverberating effects which are obtained in this zone. For a similar reason the lighter hydrogen and CO will tend to remain in the reaction chamber While the heavier inert gases flow out at the bottom.- This is a major advantage of the invention.

OPERATION OF REDUCING SMELTING FURNACE In operating the apparatus of Figures 4 and 5 for the reduction of iron ore, the process and reactions are as described with reference to Figures l-3 except that higher temperatures and higher concentrations of reducing gases may be used to obtain complete reduction of the oxides. It will be noted that in reduction of iron ore by the combined process carried out in the apparatus of Figures 4 and 5, the full utilization of the heat values in the fuel is provided for, including the recovery of the heat values in the residual combustible gases from the reducing section I22 of the furnace. By utilizing high temperatures, viz. from 1800 to 2200 F. for the charge, and an adequate amount of carbonaceous material as described in my Patent No. 2,269,465 and my copending application Serial No. 410,474 or other carbonaceous material, the ore particles falling through chamber I22 are completely reduced prior to their entry into the open hearth section at the bottom of the furnace.

Due to the higher temperatures of operation and the heat input by way of the hearth burners I64, the gases at flue I I4 contain a large amount of heat, which may be recovered for the heating of the combustion air and generation of steam and power. This is accomplished in an independent heat exchanger section not indicated.

With most ores, flux is required to obtain sufiicient fluidity of the slag. The flux may be mixed with the ore, preferably as a finely divided powdered oxide of lime, which is dropped through the furnace along with the ore and carbonaceous material.

While the furnace apparatus of Figures 4 and 5 may be employed in direct reduction of higher grade iron ores and concentrated ores, it is also adapted for the utilization of low grade ores, particlularly making possible smelting and utilization of iron ores with 30% or less of iron content Without concentration. The furnace is thus adaptable for installation adjacent low grade ore deposits, the only freight charges involved being against the fuel, flux and metallic product, minor items in most cases. The furnace thus makes possible the working of smaller deposits and wider distribution of steel-making, and the products of the furnace are available for small open hearth and furnace installations, variously located.

In placing the furnace in operation, the burner I25 and the several burners I64 over the hearths arelighted and the furnace brought up to temperature. At the same time Water circulation through the drum I I9 is started so as to maintain the interior of the column H5 relatively'cool'. The ore is then introduced into the hopper I05 by means of inlet pipe H16, and after the hopper slightly oxidizing) has been filled sufficiently, the ore-feedingmech- ,anism 25 is started, whereupon the ore, together .with any flux material fallsas a curtain around the intensely hot, brilliant flame I26 projected downwardly from the burner I25. As the ore and flux falls, it absorbs radiant energy from the flame and is heated almost instantaneously. In this connection, it should be borne in mind that conduction is not required for the transmission of heat energy from the flame I26 to the curtain .surface of the wall I22 and any ore particles which fall upon the slope of cone II8 likewise slide or, if fluid, drip downwardly into this space and into the hearths below. The gases procluced by flame I26 likewise pass downwardly through space I65 and into the hearths, where any residual combustible is oxidized, imparting additional heat to the material. Additional heat is supplied by the flame or series of flames from burners I64, combustion conditions being adjusted to a relatively neutral (slightly reducing or atmosphere, in accordance with the requirements of the metal and slag bath .and the amount of oxygen required to oxidize the combustibles in the gases from the reducing furnace section I22 above the hearths. Within the hearths the ore particles are meLted, if not already melted due to the radiant heat energy absorbed in section I22, and the ore is then ren- .dered:fluid and the ore smelted by the reverberating heated gases above the ore. The resultant :metal collects at I66 in the bottom of the hearth. Periodically the ore and slag are drawn off through the tap holes IEI of each of the hearths, and after each tapping the tap hole is plugged .in the conventional manner. Separate tap holes .for ore and slag may be provided.

The spent gases from the hearths are drawn .out .through ports I51 on each side of each hearth TdOWIl into duct I I3 and through heat exchangers, not indicated, where part of the heat is utilized .forpre-heating the air for the various burners and for making steam for furnishing power to grind the ore and fuel, and other purposes .ineluding pre-drying the oreif required, thus'effec- 'tively utilizing all the heat.

With this process, ore having an iron content of 30% can be reduced to a metallic iron with less total fuel per ton of metal than is required in standard blast furnace practice for the blast furnace alone, operating on high grade ores, and permits a much higher heat recovery, more than ample for all power purposes including the grinding of ore and fuel. In addition, the total fuel for the burners as well as for the carbonaceous reducing agent mixed with the ore, can be any low'sulphur coal and/or lignite. The metal produced is available for electric furnace and open hearth use and refining.

It provides a means for the economical utilization of low grade ores and scattered .deposits of same on a competitive basis with high grade ores.

,By finely divided ore, as used herein, there is meant a fineness of particle sizesufficient, on the average, completely to free the particles of oxide from associated particles ofgangue, so that concentration may be accomplishedby customary processes .such as magnetic separation, flotation .orthe like. For example, a-finenesszof IOU-mesh or finer is suitable for most ores, although larger sizes are frequently permissible for utilization in the processes herein. The invention is not limited to any particular degree of fineness, for the criteria .is the time element required for heating the ore particles by reverberatory radiant heat energy while theparticles are falling through a given height'of furnace. The furnace height is therefore selected, in any particular installation, vso as to allow sufficient time of fall for heating particles of the size being processed.

Ores ,of the required fineness may be those occurring naturally or theremay be used theore dumps from previous concentration processes or ore ground andgraded to the selected sizes suitable, for a particular furnace.

As .many apparently different embodimentsof this invention may .be made without departing from thespirit and scope thereof, it is to be understood that I do not'limitmyself to-the specific embodiments herein except as defined by the appended claims.

What I claim is:

1. In an orc treating process wherein ore is heated to an elevated temperature, the improvement which .comprises projecting a luminescent flame downwardly along a vertical axis of an enclosed vertical space and substantially continuously dropping ore particles downwardly in a mannerso as .to form a curtain of falling particles around said flame for absorbing heat radiated therefrom and simultaneously projecting flame jiets transversely through said curtain of falling particles to consolidate .them.

2. The process .Of smelting iron ore fines which comprises projecting a flame along the vertical axis of an enclosed vertical furnace to produce a condition of .reverberating radiant-heat .energy in said space, substantially continuously dropping a furnace charge mixture of iron ore fines, finely divided solid reducing agent 'and finely divided .flux downwardly in said space around said flame in a manner so as to form a .curtainof falling particles of the-furnace charge around the flame and ,in direct View thereof ,for absorbing heat radiated therefrom, collecting the so .treated and.heated furnace charge mixture ,in .a lower refining furnace hearth and thereinfur- ,therheating the charge torender the ,ironand resultant slag fluid.

'3. An ore reducing furnace comprising a vertical space connected at its lowerendto a lower ;reverberating furnace located beneathsaid yer.- ..tical space, a burner for projecting-a flame ,downwardly along a ,central axis ,of said vertical space, .means for feeding a finelydivided furnace charge into the upper part of said space in aposition .to allow said charge to fall vertically around said flame, and additional burner means for heating :said lower reverberating furnace.

4. An ore reducingrfurnace comprising a rela- .tively tall cylindrical space {enclosed .at its. upper end and having an ,-annu-lar bottom opening at its lower end leading into aireverberating furnace space located directly :beneath said cylindrical space, burnermeansmounted on the upper end of said cylindricalspace and positioned for projecting a flame downwardly along a centralvertical axis thereof, means positioned on the upper end of said cylindrical space for substantially continuously dropping finely divided ore-particles of ore chargeinto the cylindrical space substantially over said annular-opening, means in the reverberating furnace space for supplying heat thereto and for withdrawing the so treated ore charge at a rate sufficient to prevent any substantial accumulation of ore charge in the cylindrical space.

5. An apparatus of the type described in claim 4 wherein the reverberating furnace space is annular.

6. An apparatus of the type described in claim 4 wherein the reverberating furnace space is composed of a plurality of segmental arcuate hearths having outlet flue openings therebetween.

7. An ore reducing furnace comprising a closed-top vertical space forming a reaction zone, a burner for projecting a flame downwardly along a central axis of said zone, ore-feeding means at the top of said zone for dropping fine ore particles downwardly around the central axis in a manner so as to form a curtain of falling ore particles around the flame along said axis, and a plurality of radial segmental hearths beneath said reaction zone, each being provided with a heat burner, draw-off port and exhaust flue, said hearths being positioned to catch the reacted ore particles after they have fallen in a curtain through said reaction zone.

8. The method of reducing iron ore comprising establishing a central flame source of high radiant energy potential in a reverberatory space, se lecting a finely divided ore, mixing said ore with finely divided carbonaceous material to form a furnace charge, dropping said charge as a curtain of particles around said flame source of high radiant energy potential and subjecting said ourtain of particles directly to said radiant energy potential so as to heat the charge to reaction temperature principally by means of radiant energy while said charge remains dispersed, said temperature being sufficient for the reduction reaction by radiant and reverberatory heat energy while the furnace charge falls by gravity freely dispersed in the atmosphere of said heated reverberatory furnace space.

9. The method of preparing finely divided iron ore for subsequent concentration comprising establishing a central flame source of high radiant energy potential in the reverberatory space, mixing said ore with a minor percentage of finely divided carbonaceous matter to form a furnace charge, dropping said charge as a curtain of particles around said flame source of high radiant energy potential and subjecting said charge to direct radiant energy from said flame source of high radiant energy potential so as to heat said charge principally by radiant energy to a reaction temperature in excess of 1700 F. for the reduction reaction by radiant and reverberatory heat energy while the charge falls by gravity freely dispersed in a reducing atmosphere in said heated reverberatory furnace space at least partially to metallize the ore.

10. The method of utilizing low-grade, finelydivided ore which comprises establishing a central flame source of high radiant energy potential in a reverberatory space, mixing said ore with finely-divided carbonaceous material, to form a furnace charge, dropping said. charge as a curtain of particles around said flame source of high radiant energy potential, subjecting'sa id curtain of particles to direct radiant energy from said flame source of high radiant energy potential so as to heat said charge principally by radiant energy to a temperature sufiicient to allow reduction of the orewhile the particles of furnace charge fall freely by gravity dispersed from each other in a reducing atmosphere in a heat reverberatory furnace space, collecting the heated and reduced ore in a reverberatory heated hearth below said furnace space to complete the reduction and smelting of the ore of the furnace charge.

11. In an ore treating process wherein ore is heated to an elevated temperature, the improvement which comprises projecting a luminescent flame downwardly along a vertical axis of an en-- closed space to maintain a high temperature zone in the uppermost portion of said space and progressively cooler zones in the lower portion of said space, introducing a mixture of ore particles and a finely divided solid reducing agent substantially continuously into said high temperature zone at the top of said enclosed space, thereby maintaining a body of reducing gases in said high temperature zone and dropping said ore particles downwardly in a manner so as to form a curtain of falling particles around said flame and in direct view thereof for absorbing heat radiated therefrom whereby said ore particles are heated to an elevated temperature and reduced in said high temperature zone.

12. In an ore treating process wherein ore is heated to an elevated temperature, the improvement which comprises projecting a luminescent flame downwardly along a vertical axis of an enclosed space to maintain a high temperature zone in the uppermost portion of said space and progressively cooler zones in the lower portion of said space, introducing a mixture of ore particles and a finely divided solid reducing agent substantially continuously into said high temperature zone at the top of said enclosed space, thereby maintaining a body of reducing gases in said high temperature zone, dropping said ore particles downwardly in a manner so as to form a curtain of falling particles around said flame and in direct view thereof for absorbing heat radiated therefrom to heat said ore particles to an elevated temperature in said high temperature zone and reduce said particles, collecting the heated and reduced ore below said enclosed space, and smelting said heated and reduced ore.

HENRY G. LYKKEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 244,408 Weimer July 19, 1881 285,462 Canavan Sept. 25, 1883 555,680 Cunningham Mar. 3, 1896 806,774 Brown Dec. 12, 1904 817,414 Brown Apr. 10, 1906 1,278,180 McDonald Sept. 10, 1918 1,283,515 Hill Nov. 5, 1918 1,618,011 Isenberg et a1 Feb. 15, 1927 2,052,928 Harris Sept. 1, 1936 2,194,454 Greenwalt Mar. 19, 1940 2,365,194 Hodson, Dec. 14, 1944 2,418,394 Brown Apr. 1, 1947 FOREIGN PATENTS Number Country Date 663,942 France Aug. 27, 1929 268,793 Great Britain Mar. 31, 1927 (Not accepted) Certificate of Correction Patent No. 2,503,555

April 11, 1950 HENRY G. LYKKEN It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 36, for plates 15 and l6read plates 15 and ]8,'col11mn 6, line 53, for the Word hearts read hearths; and that the said Letters Patent should be read with these corrections therein that e same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 18th day J 1950.

[sun] JOE E. DANIELS,

.ssz'stant Commissioner of Patents.

Claims (2)

1. 3. AN ORE REDUCING FURNACE COMPRISING A VERTICAL SPACE CONNECTED AT ITS LOWER END TO A LOWER REVERBERATING FURNACE LOCATED BENEATH SAID VERTICAL SPACE, A BURNER FOR PROJECTING A FLAME DOWNWARDLY ALONG A CENTRAL AXIS OF SAID VERTICAL SPACE, MEANS FOR FEEDING A FINELY DIVIDED FURNACE CHARGE INTO THE UPPER PART OF SAID SPACE IN A POSITION TO ALLOW SAID CHARGE TO FALL VERTICALLY AROUND SAID FLAME, AND ADDITIONAL BURNER MEANS FOR HEATING SAID LOWER REVERBERATING FURNACE.
2. 8. THE METHOD OF REDUCING IRON ORE COMPRISING ESTABLISHING A CENTRAL FLAME SOURCE OF HIGH RADIANT ENERGY POTENTIAL IN A REVERBERATORY SPACE, SELECTING A FINELY DIVIDED ORE, MIXING SAID ORE WITH FINELY DIVIDED CARBONACEOUS MATERIAL TO FORM A FURNACE CHARGE, DROPPING SAID CHARGE AS A CURTAIN OF PARTICLES AROUND SAID FLAME SOURCE OF HIGH RADIANT ENERGY POTENTIAL AND SUBJECTING SAID CURTAIN OF PARTICLES DIRECTLY TO SAID RADIANT ENERGY POTENTIAL SO AS TO HEAT THE CHARGE TO REACTION TEMPERATURE PRINCIPALLY BY MEANS OF RADIANT ENERGY WHILE SAID CHARGE REMAINS DISPERSED, SAID TEMPERATURE BEING SUFFICIENT FOR THE REDUCTION REACTION BY RADIANT AND REVERBERATORY HEAT ENERGY WHILE THE FURNACE CHARGE FALLS GRAVITY FREELY DISPERSED IN THE ATMOSPHERE OF SAID HEATED REVERBERATORY FURNACE SPACE.

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