DE1186002B - Device for magnetizing reduction of finely divided iron ores - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: B 03 c

German class

C 21b

lb-2

Number: 1186 002

File number: M 53084 VI a / l b

Filing date: June 1, 1962

Opening day: January 28, 1965

The invention relates to a device for reducing finely divided ores by means of fluid bed roasting for the purpose of subsequent magnetic separation.

It is well known that many ores, such as mesabi shale ore, cannot be melted in a blast furnace, since the silicon dioxide, the aluminum oxide and other compounds in the ore form a large volume of slag form, which increases the heat requirement of the furnace and lowers the yield of metallic iron. Furthermore, such ores are soft, so that they can be handled or shipped in small Particles disintegrate that are unsuitable for use in blast furnaces. Furthermore, one must obtain a given amount of iron due to the low iron content of such ores almost three times as much Send or process the weight of ore.

There are large quantities of poor iron ores available today, which as such have a large iron supply mean. In many of these ores the iron occurs in the form of the oxidic hematite or of oxide hydrates, such as goethite or limonite, which are unsuitable for the usual magnetic separation. By roasting these iron oxides in a reducing atmosphere, the oxides are converted into magnetite, which is magnetic and can be obtained by magnetic separation. As a reducing Gases commonly used are carbon monoxide, hydrogen, or mixtures thereof. In general, the gases are used in a mixture with other gases that are used in the partial combustion of fuels such as natural gas, oil, coal or the like.

If intimate contact is maintained between the reducing gas and the solid iron oxide at elevated temperatures, the reduction of the iron in the ore from hematite to magnetite proceeds rapidly. The surfaces of large ore particles therefore easily come into contact with the reducing gases and the gaseous reaction products are easily removed, so that the reduction of the surface oxides occurs rapidly. In the interior of a large ore particle, however, the iron oxides are not reduced as quickly as the reducing gas has to diffuse through the solid before it comes into contact with the iron oxide. To exit the reaction area, the gaseous reaction product then has to diffuse to the outside again through the solid and be replaced by reducing gas to continue the reaction. Therefore, it is mainly the magnetizing device for the reaction speed
Reduction of finely divided iron ores

Applicant:

W. S. Moore Co., Duluth, Minn. (V. St. A.)

Representative:

Dr.-Ing. W. Abitz, patent attorney,

Munich 27, Pienzenauer Str. 28

Named as inventor:

Richard E. King, Birmingham, Ala. (V. St. A.)

Claimed priority:

V. St. v. America May 31, 1961 (113 854) -

the speed at which the gas diffuses through the solid ore particles is decisive.

The devices previously used for roasting iron ore include the vertical shaft furnace, the rotary kiln, the multi-hearth furnace, the horizontal moving grate and the fluidized bed reactor.

With the exception of the fluidized bed reactor, the ore is generally used in all of these working methods a grain size much larger than 6.4 mm is used, and the reaction takes long periods of time from 30 minutes to several hours until the desired reduction is achieved. in the Fluidized bed reactor can indeed treat ore with a grain size of less than 6.4 mm, but the gas velocity must be so low that the solids are not carried out of the device will. In this case, the generating capacity of the plant is therefore limited by the speed with which the reducing gas can be supplied.

Although it is known per se, finely divided material in pneumatic lines with the aid of Venturi nozzles bring in; by combining the Venturi nozzle with the other features of the invention but the special effect achieved is that the downpipe is so dimensioned in its width and length lets that there is no pressure gradient in the downpipe, so that there is no driving force, which could drive the fresh gas supplied to the first riser into the downpipe.

In a known method for the production of metals, especially iron, from a finely divided reducible compound, e.g. B. oxidic iron ore, the compound in question is in

409 770/61

a zone kept at the reduction temperature below the softening point of the metal in suspended in a stream of reducing gas passed upward at such a rate, that the solids do not settle at the bottom of the zone, but essentially over the whole Cross-section of the zone with the flow, but at a slower speed, in the form of a dispersion are slowly moved upwards and after their reduction at least partly from the upper one Section of the zone. This process is preferably used as a cycle process carried out by circulating the finely divided solids for so long in suspension in the reducing gas until the reduction is complete, whereupon a flap is opened and the reduced material is deducted. The process therefore does not work really continuously and is also disadvantageous from a thermal point of view, because there is no way to save heat.

Another known method for smelting pulverulent or fine-grained ores with pulverulent or fine-grain fuels consists in that the fuel is coked in a first reaction chamber, preferably with the ore the fuel is mixed and prereduced that the coke and the ore and any powdery or fine-grain smelting aggregates together in a second, designed as a dust generator Reaction space, preferably a vortex chamber, in suspension in a gasification agent that if necessary mixed with a circulated part of the gases formed in the dust generator are caused to react with each other at the temperature generated by the coke burning so that the ore is completely reduced and the metal and slag are melted, that in the first reaction chamber and in the second reaction chamber designed as a dust generator formed gases are not mixed with one another and that the in the first reaction chamber for the coking of the fuel and the any pre-reduction of the ore required heat through partial gasification of the fuel is generated in the first reaction space and / or the first reaction space indirectly from the heat content the gases generated in the second reaction chamber, designed as a dust generator, are supplied. Apart from the fact that this process makes use of the reduction of solid fuels, which a oxygen-containing gasification agent is supplied, the gases used in the process immediately removed after crossing through the respective reaction space, and there is no possibility provided to utilize the heat of these gases to heat the fresh ore charge.

The device according to the invention is an important one compared to the known methods technical progress achieved. In particular, the multi-stage design of the device makes it possible full utilization of the reducing gas, both in terms of its heat content also with regard to its reducing power. The ore to be reduced comes first with hot, largely consumed reducing gas in contact and is through this at the same time on the Reaction temperature heated and already pre-reduced. The now completely exhausted gas occurs out of the device, while the hot, pre-reduced ore through the downpipe into a riser reaches, in which it comes together with fresh reducing gas and from this through the riser is promoted upwards. During this brief ascent through the riser, the full one takes place Reduction of the ore takes place and the reduced material is discharged from the device, while the hot, mostly consumed

ίο Reducing gas pumped into another riser where, as described above, it now comes into contact with fresh ore. The procedure works really continuously and achieves the in a very simple and heat-economical way Reduction of the starting material in a very short time and with full utilization of the gas. Neither the finely divided ore nor the gas passes through the device several times; the advanced Rather, the effect is achieved by the (one-time) circulation of the ore particles against the (also one-time) circulation of the gas is shifted by one phase.

Apart from the advantages in terms of heat and economy, the device according to the invention enables the finely divided ore to be conveyed by the reaction gas without the use of mechanical means, and consequently to work properly at high temperatures. It is of simple construction, can be produced economically and is suitable for the continuous processing of large quantities of ore.
In the drawing shows
F i g. 1 a two-stage system in the flow diagram,
F i g. 2 graphically shows that the gas pressure developed at the bottom of an upwardly extending pipe by the flow of solids is directly proportional to the length of the pipe and the pressure that develops increases with the flow of solids and with decreasing pipe diameter, and
F i g. 3 shows a complete treatment of the substances in a multi-stage system in the flow diagram.

The two-stage system according to FIG. 1 is provided with two upwardly extending risers 10 and 11 provided. At the lower end of the first riser 10, a gas inlet 12 is provided while the upper end is in communication with a cyclone separator 13, which removes the gas from the solid particles separates. The solid particles are discharged from the cyclone separator 13 through a line 14. With the gas discharge side of the separator 13 there is a downwardly extending line 17 in connection, which leads to the lower end of the second riser pipe 11, whereby the dashed line by the Arrows 18 indicated gas flow led up the second riser flows through. The upper end of the second riser 11 is connected to a cyclone separator 19, which has a gas outlet 21 and an outlet 22 for discharging solid particles. The risers 10 and 11 are provided at the lower end with Venturi parts 23 and 24, respectively with the venturi part 24 an inlet line for supplying the to be roasted, a small grain size containing substances. The substances introduced through line 26 in this way are carried upwards by the upwardly moving gas stream, the direction of the Particle movement is indicated by the solid arrows 27. While the same-

5 6

sensible flowing gases and solid particles denote the finer proportions, which means the coarser proportions Passing separator 19, the gases are exposed to the hot gases for a longer period of time and the outlet 21 and the solid particles down through the required roasting of the coarser Andurch the outlet 22 discharged. parts is effected.

With the solids discharge opening 22 is the 5 Without countermeasure, this shows at inlet 12 upper end of a line 28 in connection, the inclination at the introduced gas, the solids-fall lower end with the venturi part 23 in connection line 28 to the separator 19 in the upward direction stands, causing the solid particles to pass into the lower one and thereby the reaction zone »short-end the first riser 10 are introduced. to close ”and the separation efficiency of the Ab-Die hot gases are continuously reduced by the io separator 19 because of Inlet 12 is introduced and upward frictional losses in the system flow through the gas at the inlet the riser 10 and the separator 13 and then a higher pressure than in the separator 19. down the line 17 to the venturi part 24 at the Desired is a flow of the gas through the lower end of the second riser 11. The gases venturi part 23 and flow up through the first riser after passing the venturi part 24 the 15 line 10 to the separator 13 and then after Riser 11 up and are through the bottom through the line 17 to the lower end of the Outlet 21 of the separator 19 finally discharged. second riser 11 and further up and The finally drawn through the line 26 to the Venturi part 24 to the final discharge at 21. solids are carried out by the gas flow. from the separator 19 through the outlet 22 in the not solve, since such devices in the at Discharged line 28 and temperatures applied thereto in the venturi reducers of iron part 23 of the riser 10 introduced. They are not flowing enough.

then with the hot gases coming through the inlet. The invention allows proper flow

12 are introduced, in cocurrent upwards 25 of the gases and solids without the use of mechazum Separator 13 and are made of this by Nischer devices. When the plant of gas the outlet 14 discharged. The volume that is flowed through alone becomes the pressure drop of the Riser 10 introduced gases and the size of the desired path in the device through the riser 10 are chosen so that due to the gas flowing through the venturi parts Gas velocity the gas flow the fine-particle 3 ° pressure change had an almost completely balanced effect, gene substances suspended and to the separator 13 contributes. so that there is essentially no pressure that a This velocity depends in large part on upward flows of the gas through line 28 the particle size and density of the fine ore. causes. In practice it has been shown that when conveying In practice it has been shown that one usually of solids by means of gas in the device of a speed of more than 3 m / sec. 35 pressure drop is increased in the desired way, Necessary to a settling of parts of the iron part during the pressure difference that ore the venturi part from the gas stream under the action of there, due to the presence of solids not To prevent gravity. is significantly influenced. It has also been shown

The solid particles and gases thus flow when the correct choice of diameter and Passing the risers 10 and 11 in the 40 length of the solids downpipe 28 in this after upwards direction in the same direction, whereby the solid particles falling below the gas pressure at the Particles suspended in the moving gases increase the bottom of the pipe and become a short circuit. The total flow of solids, on the other hand, takes place away from the gas when conveying solids in the in countercurrent to the gases, d. i.e. the solids plant can be avoided, Particles are in the lower end of the second 45 Since the solid particles are down the downpipe28 Riser 11 introduced and then pass through before flowing through, is that of solids that are in discharging the first riser 10. The second dropping a standpipe, pressure developed Riser 11 thus serves as a preheater, while an important factor for the work of the multi-stage the first riser 10 serves as a reaction zone. Since the device according to the invention. It happened Downward flow of solids in line 5 ° shows that the at the bottom of a standpipe is through the 28 is essential to equalize pressure and the flow of solids developed pressure the length of the To maintain proper direction of gas flow, pipe is directly proportional. F i g. 2 shows that the one must introduce solids at 26 with developed pressure also with the solids flow start at a relatively low speed and increase with decreasing pipe diameter, and gradually bring it to operating value. Furthermore 55 where the figure can be based on if desired, a valve in line 28 values an iron ore with a grain size of 25 should be provided to the passage of the <C 0.84 mm was used. The curves show that Throttle the gas through the line 28 until the other pressure developed in the pipes larger bypass is in operation, the valve 25 gradually knife, as it is applied on a technical scale Open position is moved after finding the solids 60 manure is much less. A balancing factor feed speed is reached. The solidity, however, is that the resistance to the discharge opening 14 is with a solid discharge gas flow in the riser and other systems connected, which an influx of gas layer parts in pipes of larger diameter even the system and outflow from it decrease if necessary (cf. the dashed curve in FIG. 2). borders. While the is in the same direction as the gas stream 65 is the pressure developed by falling solids The upward movement of the solids is correspondingly similar in a large-scale inhibiting effect gravity on the upward technical system of value to an upward movement of the coarser material parts flow more strongly than gas through the solids downpipe 28

7 8

to prevent. The pressure developed is shown in Fig. 2 The movement of the finely divided ore through the

in units of 2V2 cm water column overpressure per riser 38 and 44 is used for a temperature

30 cm pipe length indicated. treatment, by which the ore before the Ein-F i g. 3 shows the complete treatment of the lead into the hot, reducing effects

Substances in a multi-level system. The broken riser pipe 46 carrying 5 gases is preheated. That

Ore is stored in a suitable bunker 29, and finely divided material to be roasted is

and on the generally shown dry grinding system speed through the device by

31 pulverized and dried at the same time. The grain - which the particles pass through the riser fineness to which the ore to achieve a 46 completely in the reducing gases must be brought about a rapid reaction, is directed to be suspended. The riser 46 thus serves according to the physical properties of the natural as a reaction zone through which the fine particles borrowed ore. So some natural ores have one not only to be suspended in this zone, but porous structure, which has a certain penetration of the same direction as the reducing ones Gas allowed into the particle interior. These ores flow to the separator 45 under gases. The volume are a rapid reduction at a much larger 15 that introduced into the riser 46 reducing ren grain coarseness than an ore with a dense structure-acting gases and the size of the riser 46 door. In practice it has been shown that the can be chosen so that the speed of the Device according to the invention many ores loading gas flow for suspending the finely divided material can act that decomposes to such a grain size and its promotion to the separator 45 leads. the have been reduced so that the largest particles become ore particles when passing through the separating test sieve of 2.00 mm sieve opening. ders 45 separated and discharged into a cooler 54

The finely powdered is carried by the grinding system 31.

Ore to an air classifier 32 and then from cooler 54 the reduced ore is fed to ge-cyclone separator 33, on which exhaust gases are suitable magnetic separators, which are generally removed at 56 as at 34. The powdered ore is shown, and is here stored in a bunker 36 with a separation of the main and then subjected to an upwardly extending line 37 through a magnetic line 37 from the non-magnetic components. The magnetic ore can then be fed in the riser 38, which is connected at the top to a suitable briquetting or cyclone separator 39 in a conventional manner. Which are fed into the pelletizing device 34.
Exhaust gases obtained from separator 39 are passed through a 30 Since the finely divided ore to be reduced and the line 41 are removed and the air classifying device 32 and the separator are passed through the grinding system 31, hot, reducing gases in cocurrent, it is desirable that the reducing 33 be passed , whereby they dry the gases acting in the grinding plant and the iron oxides at least in the guided ore. The fine-particle material fed into the line 38 to produce the desired chemical movement thus moves at the same rate. This makes sense with the gas flow carrying it to the discharge 10 and 46 occurs, the amount of in

The gas supplied to line 38 has a reducing effect introduced by these lines a cyclone separator 42 obtained. Those from the gas are enough to extract everything in the ore At the end of the cyclone separator 39, iron held out is reduced to the desired oxide fine ore particles enter the line 43 a decorate.

and are then discharged into a riser 44 to convert 0.45 kg of hematite into magne-

gen, which the gas discharge side of a cyclone ab- tit are about 22.71 carbon monoxide or

separator 45 connects to the cyclone separator 42. Hydrogen (dry basis, 16 ° C, 760 mm Hg)

The gas 45 flowing upward in the riser 44 is necessary. With a content of the reducing effect

absorbs the finely divided ore, which converts it into gas of 15%> of carbon monoxide or water

suspended in the gas and in cocurrent with this substance and at a temperature of approximately 760 ° C

the separator 42 is fed. and at atmospheric pressure are for 0.45 kg

With the cyclone separator 45, the top end of hematite is about 5301 of gas required. About this one

connected to the riser 46, while the lower 5 ° amount of gas is required to produce 0.45 kg of hematite and

End with a line 47 is in connection, the other substances assigned to it in the natural

which borrowed the gas stream from a gas generator 48 to suspend ore.

feeds. Solid discharged from the separator 42. As an example of the operation of the device The following experiment is used in the lower end of the riser 46 according to the invention: A introduced through a conduit 49, resulting in 55 iron ore with an iron content of 43.6 per cent as a suspension in the gas stream with this im crushed to such a grain size that there is a Direct current moved up to separator 45. Test sieve with a sieve opening of 1.41 mm To form the reducing gases in the passed, and in a two-stage, similar to FIG. 1 Gas generator 48 can be reduced by a line 51-designed device, the rising air and introduce natural gas through line 52, 60 lines of standard 3.2 cm pipe of approximately the two gases in the gas generator 48 were made before 2 m in length. That becomes more reducing Introduced into the riser 46 mixed and kende gas contained 16.5% carbon monoxide and partially burned. To direct the supply hydrogen; its measured temperature was on The composition and temperature of the generator kept it around 838 ° C. It became an essentially 48 Leaving gases can be a part of the 65 borrowed complete reduction of the iron oxide in the gas stream of magnetite obtained from the cyclone separator 42 at an ore throughput of approximately through line 53 in circulation to the air 85 kg / hr. and a gas velocity of Return feed line 51. 283 l / min. (16 ° C, 760 mm Hg).

The invention thus provides an improved device for treating iron ores Disposal. It is shown above on the basis of its particular suitability for the treatment of iron ores explained, but is also suitable for roasting other substances, such as pyrite and the like Roasting occurs during a state of complete suspension in the hot gases or reduction in a minimal amount of time. Furthermore, the structure and arrangement of the device depends such that the pressure drop flowing through the risers and the parts associated with them Gas is substantially equal to the pressure change occurring at the venturi part of the first riser and is obtained by flowing the solids down the downcomer, essentially No pressure drop at the solids downpipe leading to a direct inflow of gas the gas inlet into the separator associated with the second riser.

The device according to the invention is suitable for operation under a wide variety of conditions and is not limited to any particular ratio of gases to solids.

Claims (6)

Patent claims: 1. Device for the magnetizing reduction of finely divided iron ores by means of fluidized bed roasting, characterized by at least two risers (10, 11) attached to their upper ends open into solids separator (13, 19), one from the first separator (13) to the lower end of the second riser line (11) leading gas circulation line (18), a gas supply line (12) to the lower end of the first riser line (10), a solids feed line (26) to the lower end of the second riser (11), a lower end of the second Solids separator (19) with the lower end of the first riser (10) connecting Downpipe (28) of such width and length that that from the second separator (19) into the lower At the end of the first riser (10), fine-particle material falling, the gas flow from the first riser (10) throttled through the downpipe (28) to the second separator (19), and a line (14) for discharging the finely divided solids from the first separator (13). 2. Device according to claim 1, characterized by a third solids separator (36), a lower end of the third separator (36) with the lower end of the second riser (38) connecting second downpipe (37) of such width and length that the from the third separator (36) into the lower end of the second riser (38) falling fine-particle material the gas flow from the second riser line (38) to the third separator (36) throttles, one connecting the upper end of the second separator (39) to the third separator (36) third riser (41) and a feed line for finely divided solids to the lower part the third riser (41). 3. Apparatus according to claim 1 or 2, characterized in that a number of Risers (38, 44, 46), solids separators (39, 42, 45) and the corresponding downpipes (37, 43, 49) for the finely divided solids from the separators into the risers so with one another are connected that the finely divided solids the risers (38, 44, 46) in suspension in the heated gas must pass through one after the other. 4. Apparatus according to claim 1, characterized by one at the confluence point of the downpipe (28) in the first riser (10) located device (23) for generating a Pressure drop at this point of confluence, which is equal to the pressure drop in the from lower part of the first riser (10) through the first solids separator (13) to the second Solids separator (19) is gas flowing through the device. 5. Apparatus according to claim 4, characterized in that the means for generating of the pressure drop is a venturi nozzle (23) connected to the downpipe (28). 6. Apparatus according to claim 1 or 4, characterized in that the downpipe (28) Has such a cross-section and such a length that when the finely divided Solids through the downcomer (28) in the same a pressure rise from the second solids separator (19) to the point where it joins the first riser (10), which also is as large as that caused by the entrainment of the finely divided solids with the gas through the Device from the mentioned point of confluence through the first solids separator (13) to the second solids separator (19) generated pressure drop. Considered publications:
German Patent Nos. 849 710, 937 039;
German interpretative document No. 1024245;
German patent application F 5331 VI / 40a (published on April 21, 1955). 1 sheet of drawings 409 770/61 1.65 © Bundesdruckerei Berlin