DE2510116A1 - PROCESS AND EQUIPMENT FOR THE REDUCTION OF MATERIAL CONTAINING IRON (III) OXYDE - Google Patents

Description

DR. BERG DI? ·, .- · NG.
DIPL.-ING. SCHWABE DR. DR. SANDMAIR

8 MUNICH 86, POST BOX 86 02 45

Attorney's file: 25 879 ₇ . _March

Stora Kopparbergs Bergslags AB, Falun / Sweden

Process and device for the reduction of iron (III) oxide

• 4

containing material

The invention relates to a method and a device for the complete or partial reduction of pulverized material with iron (III) oxides, which are mixed with finely divided, solid carbonaceous material are mixed at a temperature lower than the melting point of iron is. Here, solid, carbonaceous material is understood to mean coke, which consists of a fuel and a reducing agent containing carbon such as anthracite, coal or oil. Under VII / XX / Ktz

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powdered iron (III) oxide containing material becomes concentrated iron ore, burnt pyrite or others Iron (III) oxide-containing material understood, where the Material has a particle size of up to 1 mm.

It has already been proposed to reduce pulverized material containing ferric oxides mixed with pulverized, solid, carbonaceous material, for example in rotary kilns or in fluidized beds (fluidized beds) of conventional design. ^x _m j_t

In the invention, however, a fluidized bed of the conventional type is not used, but a so-called circulating one instead or circulating fluidized bed is used, the nature and mode of operation, for example, by L. Reh in "Chem. Engineering Progress "of Feb. 1971, Vol. 67, No. 2, pages 58-63.

In most of the attempts that have been made to date to use the fluidized bed process for reducing Material containing iron (III) oxides is to be used the conventional fluidized bed process has been used, whereupon difficulties have arisen due to the gas, which was only retained in the fluidized bed for a short time is or is present. Attempts to increase the efficiency or the yield in such a process by increasing the To improve the reaction temperature also have difficulties with regard to the "sticking or sticking together" guided, i.e. the small particles or particles of material

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in the fluidized bed have agglomerated to larger particles and structures, so that finally a so-called "Fluidization" or an application of the fluidized bed process has become impossible.

By using a circulating fluidized bed, the contact time can be increased, which also reduces the tendency to to glue or to stick together. due to the strong internal circulation or overturning of the material has decreased. The gluing and tacking together decreases with increasing Temperature, with the degree of metallization and with the fineness of the fluidized bed material increases and increases with increasing Turbulence, with the content of gangue, with the total pressure as well as with the addition of powdered dilution material, such as coke.

Attempts have also been made to compare the pulverized material, which contains ferric oxides, with pulverized, solid, carbonaceous material are mixed, in a circulating fluidized bed by reducing that the carbonaceous material is partially burned with the aid of a molecular oxygen-containing gas, which is introduced as fluidizing gas into the fluidized bed. As a result of the addition of solid, powdered, carbonaceous Material, the risk of sticking or sticking together has become less and it has become possible to To increase the temperature, which then also increases the rate of reaction. However, if that is molecular oxygen

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containing gas for fluidization is blown in via distribution devices at the bottom of the reaction vessel, then consists in this case, probably as a result of local overheating, a certain tendency towards agglomeration or agglomeration. Agglomeration at the distribution facilities.

The invention therefore relates to a method for reducing pulverized material, which contains iron (III) oxides mixed with pulverized, carbonaceous material, in a circulating or revolving fluidized bed, in which the particles stick together or stick together completely is avoided, and also relates to a device for carrying out this method.

According to the invention, a circulating fluidized bed of pulverized material, which contains iron (III) oxides mixed with pulverized, carbonaceous material, maintained in a reaction zone elongated in the vertical direction. The circulating fluidized bed is maintained by that it is with appropriate flow rates or streams of the powdered, ferric oxides containing Material, from powdered, solid, carbonaceous material and possibly liquid, carbonaceous Material together with a 'containing molecular oxygen Gas is supplied. A mixture of gas and solid material then leaves the reaction zone and then becomes separated, whereupon the solid material is returned to the reaction zone.

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The iron (IIl) -aiyde-containing, fed to the fluidized bed, pulverized material has a particle size that is less than 1mm, preferably less than 0.5mm. That supplied, finely divided, solid, carbonaceous material can be coke slag, anthracite or coal dust and should have a particle size of less than 3mm, preferably less than 1mm.

The reaction zone can be divided into an upper, lower and a middle part. In the procedure according to of the invention is the powdered, ferrous oxide-containing material, the carbonaceous material as well the molecular oxygen-containing gas is introduced into the central portion. By partially burning the carbonaceous material in this section, the heat necessary for the process or the process is generated. In the upper part of the reaction zone there is coking and degassing of the carbonaceous material as well a reduction with the carbon of the carbon dioxide and of the water formed during the combustion takes place, whereby Hydrogen gas and carbon monoxide is formed. There is also a certain reduction in iron (III) oxides Materials instead. This reaction takes place at a temperature of 850 to 1000 ° C. The flow rate of solid, carbonaceous Material must be controlled in such a way that it is always sufficient in the fluidized bed to be impaired and to prevent disturbance of the fluidization or the fluidized bed process due to agglomeration.

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From the upper part of this generated gas is discharged or discharged, which with solid material'von the fluidized bed is mixed. The latter is then separated from the gas and returned to the central section.

It has also been found that the solid, carbonaceous Depending on the material sticking or sticking together can be prevented by the temperature and the properties of the ferric oxide-containing material. At a temperature of 900 ° C and using normal Iron ore concentrate has also been found to be the weight ratio between solid, carbonaceous material (Coke) and the concentrate in the reaction zone should be at least 0.5: 1.

Part of the discharged gas is used for an additional dust separation subjected, making most of COp and EUO is removed, is then withdrawn and returned to the lower part of the reaction zone as fluidizing and reducing gas fed. In this way a strongly reductive atmosphere is obtained in the lower part and it continues to find one Reduction of the ferric oxides-containing material instead.

Solid material is discharged from the lower part of the reaction zone if necessary, so that the amount of solid material is kept constant in the reaction zone. The pure supply of solid material is then countercurrent to the in maintain the lower part of the introduced gas. The heat-

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However, transfer from the central portion of the reaction zone to the lower part thereof is mainly due to the internal material circulation or the internal material circulation in the reaction zone. This inner circulation or the circulation is relatively large, so that the temperature equalization is promoted in this way. The carried out, solid material consists of coke and completely or partially reduced ferric oxides, is preferred among the C.urie point of the iron is cooled and is magnetically converted into an essentially coke-free iron component and an essentially iron-free coke content separated. The cooling is expedient ^ in that the material is a conventional, through the fluidized bed formed by the material itself, and also takes place with the help of built-in cooling surfaces. That Molecular oxygen-containing gas is accordingly used as a coolant and is thereby preheated.

^x to control ^

Also is convenient and advantageous for the flow of the gas containing molecular oxygen, for example air, which one (s) may COp and / or EUO is mixed, so ^X that the heat required to keep up with the required temperature in the circulating or rotating fluidized bed, is covered. The heat is generated through partial combustion of the carbonaceous material. It is also possible to supply heat either alone or exclusively or partly indirectly from an external heat source, as for example from a nuclear reactor. In this case, the heat can be applied to heating surfaces provided in the reaction zone with the aid of hot gas

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be transmitted.

To prevent excessive heat generation per unit volume in the reaction zone, causing local overheating and the risk of some agglomeration of the fluidized bed material would result, the flow of molecular oxygen-containing gas preferably divided into several substreams, which then at separate points are fed at different heights to the middle section of the reaction zone.

The solid, carbonaceous material is accordingly the central portion of the reaction zone in the form of several Blasting, preferably with the aid of reducing and / or neutral gas blown in via nozzles. With carbonaceous Material with a low content of volatile components, such as anthracite, it is possible to use molecular oxygen containing gas, such as air ^ to be used, which is then preferably not preheated in this case, to avoid the risk of local overheating. Depending on the shape of the blower nozzles, this is a total of a gas flow required, which is ΊΟ to 3O # of the total flow or the total flow rate of the carbonaceous material having.

It is also possible to introduce the carbonaceous material via a small additional makeshift reaction zone, which is separated from the actual reaction zone, in which a

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Fluidized bed is maintained with the help of a partial flow of the molecular oxygen-containing gas. In this case it will be then the gas and material from the additional makeshift reaction zone via a common pipe into the central section passed the reaction zone. In the additional makeshift zone there is a certain partial combustion of the carbonaceous Material instead, and agglomeration around the manifold openings can as a result of the be avoided for a short time during which the carbonaceous material is distributed there; this only means few particles have time to be burned to ashes. At too high concentrations and in the event of local overheating however, agglomeration and crusting can easily occur.

Some of the solid, carbonaceous material can be replaced by liquid, carbonaceous material, such as oil. In this case the material is preferably sprayed into the central portion of the reaction zone by a number of jets. So-called atomization of the oil, as is carried out in connection with complete combustion, is not necessary. A _relatively: coarse dispersion of the oil, which is obtained when it is fed into ■ partial flows through pipes together with a non-oxidizing gas is sufficient. A volume ratio of 100: 1 for the gas and the oil used is adequate and. -practical. If an additional makeshift reaction zone is used, the oil is preferably fed to this zone and the

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Height or the level at which or at which the oil is supplied should be about 0.5 m above the distributor plate for the molecular oxygen-containing gas.

The gas discharged from the reaction zone can be at least to the Part for preheating the ferric oxides containing "feed material be used by bringing it into direct contact with it. After that, this part of the Gas is returned to the lower part of the reaction zone after most of the COp and HpO are known per se Way has been removed, and is then called iTuidierungs-and Reaction gas, used in the lower part of the reaction zone.

A partial flow of the discharged or discharged gas, which is essentially free of COp and HpO, is accordingly used as fluidizing gas in the cooling and magnetic separation of the material discharged from the lower part of the reaction zone. Since the entire process is carried out above atmospheric pressure, for example 1 to 10 atm _/ , the dimensions required for the device can be reduced considerably. The heat content (physical and chemical) of the discharged or expelled gas is accordingly used to generate electrical energy with which, for example, the reduced ferrous material can be melted and possibly finally reduced.

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The following is the method and the device according to the Invention based on a preferred embodiment with reference explained on the attached drawing.

in
The device has a vertically elongated reaction vessel 1, the upper part 2 of which encloses the upper part of the reaction zone, the central part 3 of which encloses the central section of the reaction zone and the lower part 4 of which encloses the lower part of the reaction zone. A cyclone 5 is connected to the upper part 2 of the reaction vessel 1 and has a return line 6 which leads to the middle part 3 of the reaction vessel. One or more inlets for carbonaceous material 7 are also provided in this zone. The gas containing molecular oxygen is fed to the middle part 3 of the reaction vessel in the form of a number of partial flows via nozzles 8, while the partial flow of the gas returned to the circuit is fed to the lower part of the reaction vessel via a corresponding distributor 9. Correspondingly treated, solid material is discharged via an outlet 10 in the lower part of the reaction vessel, cooled in a cooling device 11 and passes through a magnetic separating device 12 in which it is separated into an essentially coke-free iron component 13 and an essentially iron-free coke component 14.

The gas 15 containing molecular oxygen, preferably air ₇ , is at the point 16 via the cooling device 11, where it is preheated, and then via a pipe 17 to nozzles 8

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blown. The cooling device 11 preferably has the form of a conventional fluidized bed with built-in cooling elements on, over which the molecular oxygen-containing gas is passed for preheating.

A portion of the vented gas (for example 50%) is passed via the outlet pipe 18 from the cyclone 5 to a venturi device 19, where it preheats the pulverized material containing ferrous oxides, for example an ore concentrate 20, possibly with mixed with the coke returned from the magnetic separator. The gas and material flow is then transported to a cyclone 21 and then to a fine cleaning cyclone 22, in which the solid material is separated off _and fed back to the central part of the reaction vessels, preferably via the return line 6 y. The gas cleaned of solid material is then fed along a line 23, where it is possibly cooled indirectly at the point 24 by boiling water, and via a heat exchanger 25 to gas scrubbing devices 27, where it is essentially freed of COp and HpO. Cooling by means of boiling water may be necessary in order to prevent the temperature in the heat exchanger from becoming too high for the materials used. HpO can be removed by direct or indirect cooling. COp is washed out, for example with the aid of alkaline solutions, in which case the stream 28 from the vessel or boiler 24 can then be used in this pail to regenerate these solutions again. If the pressure in the system is sufficiently high, C0 _p

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be washed out with water. Much of the gas from the gas scrubbing device, which is moved by means of a compressor, experiences a heat exchange at point 25 gas flowing into the gas scrubbing devices and is then used as fluidizing and reducing gas in the lower part 4 of the reaction vessel initiated. This creates a strongly reducing zone through which the solid material, before it is discharged, is passed through. In view of the smaller gas flow, this part of the reaction vessel faces accordingly has a smaller diameter than the upper part. A substream 31 of the freed from COp and HpO Gas is, without a heat exchange taking place, as fluidizing gas in the cooling device 11 for the discharged solid material and used in the magnetic separating device 12 and is then via lines or via corresponding Means 32 and 33 to the lower part of the reaction vessel promoted. The remainder of the gas 34 discharged from the cyclone 5 is, possibly together with a partial flow of the coke content from the magnetic separator, preferably used as fuel in a thermal power station, while the remainder of the coke stream is fed back into the reaction vessel, possibly with the ferric oxides containing Material is mixed, and / or is used as a reducing agent in a smelting reduction stage for the iron content of the magnetic separator used.

Claims

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Claims (14)

Claims 1. Process for the reduction of pulverized material, which iron (IIl) oxide mixed with carbonaceous material contains, characterized in that a circulating fluidized bed in a stretched in the vertical direction Reaction zone is maintained by using it with appropriate amounts of pulverized material containing ferric oxides, of powdered, solid, carbonaceous material and possibly liquid, carbonaceous material as well is supplied with molecular oxygen-containing gas that the gas and the solid material which the reaction zone are left, separated, the solid material is returned to the reaction zone, that the pulverized, Material containing iron (III) oxides that contains carbon e Material and the molecular oxygen-containing gas in a central, intermediate section of the reaction zone is fed that thereupon the fed stream of carbonaceous material is controlled so that always sufficient Coke is present in the fluidized bed to interfere fluidization as a result of sticking or sticking together to prevent the gas and solid material exiting the reaction zone from being carried out from the upper part be, the solid material separated from the gas and again the middle, intermediate section of the Reaction zone is fed that then part of the discharge after the dust has been separated and the largest part of. CO and HpO is eliminated, is fed to the lower part of the reaction zone as fluidizing and reducing gas, and that closing 509837/0711 borrowed the solid material which wholly or partially contains reduced iron (III) oxides, is discharged at the lower part of the reaction zone. 2. The method according to claim 1, characterized in that that the flow of molecular oxygen containing gas possibly mixed with GOyu / or HpO, is controlled so that the heat requirement to maintain the required temperature in the reaction vessel is covered. 3. The method according to one of claims 1 or 2, characterized g ekennz indicates that the solid material discharged from the lower part of the reaction zone is below the Curie point of the iron is cooled and magnetically into an essentially coke-free iron content and an essentially iron-free one Coke is separated. 4. The method according to claim 3, characterized net that part of the gas fed back into the circuit which is essentially free of GOp and H _? Is 0 is used as a siuidation gas in the magnetic separation. 5. The method according to one or more of claims Λ to 4, characterized in that the solid, carbon-containing material is introduced into an additional reaction zone which is separated from the actual reaction zone, where it is treated with the aid of the fluidized bed process and with the aid of a partial flow of the containing molecular oxygen 509837/0711 Gas is partially burned, whereupon the gas and solid material in the central section of the reaction zone be introduced. 6. The method according to one or more of claims 1 to 4-, characterized in that the carbonaceous material, which may be divided into partial flows, is blown into the central portion of the reaction zone by means of a non-oxidizing gas. 7- Method according to one or more of the preceding claims , gekennz eichnet that the molecular oxygen-containing gas in the central portion of the Reaction zone is introduced, where it is divided into a number of smaller substreams. 8. The method according to one or more of the preceding claims, characterized in that the solid, discharged from the lower part of the reaction zone material is cooled in that it is passed through a fluidized bed with built-in cooling surfaces, which is formed by the material itself, the is fluidized by a partial flow of the gas recirculated, which is essentially free of CO ₂ and H _{2 O.} 9. The method according to claim 8, characterized in that that the molecular oxygen-containing gas is used as a coolant. -17-509837 / 0711 10. The method according to one or more of the preceding claims, characterized in that part of the discharge from the circulating fluidized bed is brought into direct contact with the supplied, ferric oxides-containing material in order to preheat the material, and that it is thereafter is returned to the lower part of the reaction _{zone after most of the CO 2} and HpO has been removed. 11. The method according to one or more of the preceding claims, characterized in that the whole process is carried out above atmospheric air pressure. 12. The method according to one or more of the preceding claims, characterized in that the Heat content (the physical and the chemical) of the discharge is used to generate electrical energy. 13. The method according to one or more of the preceding claims, characterized in that a partial flow of the coke content obtained in the magnetic separation is returned to the reaction zone, possibly mixed with ferric oxide-containing material is, and that the remainder of the coke portion in some other way, for example as a reducing agent in a Melting reduction stage for the magnetic separation Preserving iron content and / or as fuel, in a thermal power station is used. · " 509837/0711 14. Device for performing the method according to claim 1, characterized by a reaction vessel (1) stretched in the vertical direction with a cyclone (5)? which is connected to the upper part (2) of the reaction vessel, through a to the middle part (3) of the reaction vessel (8th) leading return line (6), through inlets l'for carbonaceous Material (7) and for molecular oxygen-containing gas, through a pipe (23). around the discharge from the cyclone (5) to convey to gas scrubbing devices (27) to get out of the gas COpUnd HpO to remove, and through a line (30) to to feed the gas back to the lower part (4) of the reaction vessel (1), which has an outlet (10) for the solid Material is provided.