JPH0774368B2 - Iron ore fluidized bed reduction device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an iron ore reducing apparatus for reducing iron ore in a fluidized bed reducing furnace for use in a smelting reduction method, a blast furnace method and the like.

(Prior Art) In order to reduce iron ore to produce hot metal, a method of using a blast furnace and a method of melting iron ore reduced in a shaft furnace in an electric furnace have been conventionally adopted.

In the method of using a blast furnace, a large amount of coke is used as a heat source and a reducing agent, and iron ore, which is an iron source, is usually sintered to improve the air permeability and reducing property in the furnace, and is used as a sintered ore. It is installed in the blast furnace. For this reason, the blast furnace method requires coke oven equipment for dry distillation of strongly caking coal and sintering equipment for producing sinter. Therefore, the blast furnace method requires a lot of energy and labor as well as a large amount of equipment cost. Therefore, the blast furnace method has a drawback that the processing cost becomes high. Furthermore, the supply of strong coking coal is unstable because the amount of endowment is small worldwide and the distribution is unevenly distributed locally.

On the other hand, the iron ore reduction method using a shaft furnace requires a pretreatment for pelletizing the iron ore, and has a drawback that it consumes a large amount of a reducing agent, expensive natural gas as a heat source, and the like.

As an alternative to such conventional hot metal production technology, the smelting reduction refining method has been drawing attention. The smelting reduction furnace used in this method was developed for the purpose of producing a molten iron-based alloy by a smaller-scale facility without being restricted by the raw material used.

As an example of the above-mentioned smelting reduction method, the present inventor has previously proposed a method constituted by the flow shown in FIG. 3 as Japanese Patent Application No. 59-184056.

According to this method, hot metal is manufactured as follows. That is, the iron ore 1 and the limestone 2 are heated in the fluidized bed preheating furnace 3 by the heat generated by the combustion reaction of the coal 4 and the air 5. As a result, limestone 2 (CaCO ₃ ) becomes quicklime (CaO) and is supplied to the fluidized bed reduction furnace 6.

In the fluidized bed reduction furnace 6, coal 7 and oxygen or oxygen-containing gas are blown into the preheated ore and quicklime in a fluidized state. The coal 7 exchanges heat with the preheated ore in the fluidized bed reduction furnace 6 and is thermally decomposed by partial combustion due to reaction with oxygen. Thereby, the coal 7 generates a reducing gas and
It becomes Char 9.

On the other hand, the gas generated in the smelting reduction furnace 10 or the reducing gas 11 obtained by decarbonating the gas was heated to 700 to 900 ° C. by heat exchange with the fuel gas 12 from the fluidized bed reduction furnace 6. Then, it is blown into the fluidized bed reduction furnace 6. Fluidized bed reduction furnace 6
The reducing gas 11 blown into is mixed with the reducing gas produced by the thermal decomposition of the coal 7, and reduces the high temperature powdery granular iron ore in a fluidized state to produce the reduced ore 13.

The quicklime 14 produced in the fluidized bed preheating furnace 3 is charged into the fluidized bed reduction furnace 6 together with the preheated ore, so that the fluidized bed reduction furnace 6
Desulfurize the gas inside. Next, the quicklime 14 is discharged from the fluidized bed reduction furnace 6 together with the reduction ore 13 and the char 9.

Reduced ore 13, char 9 and quicklime thus obtained
Carbon materials such as coal and coke necessary for heat balance in the smelting reduction furnace 10 are externally added to 14, and kneaded. Next, the mixture is molded into a briquette 16 by an agglomerating device 15 such as a briquette machine, and then a charging device.
The smelting reduction furnace 10 is charged by 17.

In this smelting reduction furnace 10, oxygen 19 is blown toward the bath from a top blowing lance 18, and oxygen and carbonaceous material are blown into the bath from a bottom blowing tuyere 20. Then, the carbonaceous material contained in the briquette 16, the carbonaceous material blown together with oxygen from the bottom blowing tuyere 20, the carbonaceous material such as the coke 21 supplied from the charging device 17 is supplied from the top blowing lance 18. And reacts with oxygen to generate a large amount of heat in the smelting reduction furnace 10. Due to this heat generated, the reduction ore 13 in the briquette 16 is melted and the reduction proceeds to form hot metal.

On the other hand, the gangue in the reduced ore 13 reacts with the carbonaceous material and the quick lime 14 to generate the slag 23. This slag 23 is a smelting reduction furnace 10
It is stored inside and increases in quantity over time. Therefore, the slag 23 is discharged out of the furnace intermittently or continuously.

(Problems to be Solved by the Invention) In such a smelting reduction method, as is clear from the development process, the range of usable raw materials is expanded, the efficiency of heat recovery is improved, and the smelting reduction furnace is used. How to achieve the promotion of the refining reaction in the future is a future task.

However, when raw materials such as powdered ore and coal having a wide particle size distribution are used, it is very difficult to secure fluidity in the fluidized bed reduction furnace 6 and there is a problem in operability. That is, in order to obtain a stable state, it is good to increase the superficial velocity of the reducing gas until coarse particles are scattered, but even in this case, the particle concentration in the fluidized bed reduction furnace becomes too thin, The reaction efficiency, that is, the gas utilization rate decreases. On the other hand, when the empty velocity of the reducing gas is reduced, coarse particles are retained in the lower part of the fluidized bed reduction furnace, so-called slugging flow occurs, and fluctuations in the header pressure of the fluidized bed reduction furnace become large, making operation impossible.

In addition, the size of the particle generally affects the reduction rate,
There is an empty space velocity of reducing gas suitable for each of fine and coarse particles. Therefore, when reducing fine ore with a wide particle size distribution, fine grain ore is reduced more than coarse grain ore and has a higher degree of reduction, resulting in increased adhesion of the reduced ores and aggregation by fine grains or There is a risk that aggregation into coarse particles may occur, the fluidity may be deteriorated, and a trouble of stopping fluidization may occur.

Therefore, in the present invention, reducing gas blowing nozzles for performing reduction in the fluidized bed reduction furnace are arranged in several stages in the furnace height direction, and it is difficult to increase the speed by changing the blowing rate of the reducing gas from each blowing nozzle. Particles of iron ore or coagulated particles produced in the reduction step are separated from fine particles in a bubbling fluidized bed in the lower part of the furnace, settled, reduced in a packed bed located under the same, and discharged from the lower part.

(Means for Solving Problems) The iron ore fluidized bed reducing apparatus of the present invention is an apparatus for producing reduced ore used in a smelting reduction method, wherein an external particle circulation device is attached to a fluidized bed reducing furnace, Moreover, the gas injection nozzles are arranged in several stages in the furnace height direction in the furnace of the fluidized bed reduction furnace.

(Function) The present invention is configured as described above, and when raw materials such as powdered ore and coal having a wide particle size distribution are charged into the fluidized bed reduction furnace and the reducing gas is blown from the gas blowing nozzle, the uppermost gas is blown. Above the nozzle, the amount of air blown out from all the gas injection nozzles is added, and the final velocity Ut of the fine-grained raw material particles is exceeded, and the fine-grained raw material particles fly upward in the fluidized bed reduction reactor while reacting with the reducing gas. . That is, a high-speed fluidized bed is formed. In this case, some of the coarse-grained raw material that has not reached the terminal velocity Ut may be scattered upward due to the entrainment effect of the fine grains, but most of it stays in the fluidized bed. A reducing gas 11 is blown from a gas blowing nozzle located in the lower part of the furnace to form a fluidized bed. In this fluidized bed, raw materials with a wide particle size distribution are fluidized.
Since f is large and the fluidity is poor, it settles in the lower part of the fluidized bed while flowing, and is separated from fine particles. On the other hand, the fine-grained raw material is scattered to the upper part of the fluidized bed reduction furnace 6 by the above-mentioned upper blowing nozzle. The coarse-grained raw material settled in the lower part of the fluidized bed reduction furnace 6 forms a packed bed. That is, the gas injection nozzles arranged in several stages in the furnace height direction form a fluidized state of the packed bed, fluidized bed, high-speed fluidized bed and raw material to prevent slugging in the high-speed fluidized bed region and stabilize The fluidized state can be secured, and the particle concentration in the fluidized bed reduction furnace can be controlled to an appropriate concentration, so that the reaction efficiency and the gas utilization rate can be improved, while the coarse particles are packed in the packed bed. Reduction is surely performed by an appropriate flow rate of reducing gas from a furnace bottom blowing nozzle provided at the bottom of the furnace. Therefore, the uniformity of the reduction is improved by sizing the particles into fine and coarse particles and performing the reduction, and it becomes possible to avoid the aggregation trouble of the iron ore due to the progress to the high reduction degree.

(Embodiment) An embodiment of the present invention will be described in detail below with reference to the schematic diagram of the basic configuration shown in FIG.

An external particle circulation device is attached to the fluidized bed reduction furnace. In the structure of this external particle circulation device, a cyclone 31 is connected to the outlet provided in the upper part of the fluidized bed reduction furnace 6 to capture fine particles entrained with the reducing gas 11 and scattered. And cyclone
A hopper 32 for trapping and temporarily storing particles is connected to the lower part of the 31 and the hopper 32 temporarily stores and circulates a predetermined amount of a circulating cutting device 33.
And is returned to the fluidized bed reduction furnace 6.

On the other hand, in the furnace of the fluidized bed reduction furnace 6, a plurality of gas outlets 34,
35 are formed. A bubbling fluidized bed 36 is formed in the middle of the gas outlets 34, 35.
A circulation outlet of the external particle circulation device is provided in the inside of 36. Further, a packed bed 37 is formed at the bottom of the fluidized bed reduction furnace 6, and a furnace bottom blowing nozzle 38 is provided in the packed bed 37. In the figure, 39 is a cutoff valve for charging the raw material 25 such as powdered ore and limestone into the fluidized bed reduction furnace 6, 40, 41, 42 are flow rate control valves for adjusting the amount of reducing gas blown out, and 43 is A fine-grained reduction ore cutoff valve, and 44 is a coarse-grained reduction ore cutout valve.

Next, the raw material 25 such as powdered ore and limestone is charged into the fluidized bed reduction furnace 6 from the cut-out valve, and the reducing gas 11 is blown from the gas blow-out ports 34, 35, 38 through the flow rate control valves 40, 41, 42. And, above the uppermost gas blowing nozzle 34, the blowing amount of all the gas blowing nozzles is added, and the speed becomes higher than the terminal velocity Ut of the fine granular raw material particles, and the fine granular raw material particles react with the reducing gas. However, since the coarse-grained raw material has a higher terminal velocity Ut than the fine-grained raw material, the coarse-grained raw material does not scatter at the gas outlet 34, but between the two gas outlets 34, 35. Further sieving is performed in the bubbling fluidized bed 36 located, and the coarse particles descend to the fluidized bed 37 in the lower part of the furnace. Coarse particles in the packed bed 37 are reliably reduced by a reducing gas at a proper flow rate by a furnace bottom blowing nozzle 38 located in the lower part of the furnace, and coarse particles of reducing ore are discharged from the cut-out valve 44 and sent to the next step. . FIG. 2 shows the arrangement of the nozzles 34, 35 in the horizontal sectional view of the furnace. Nozzle headers 34 ', 35' are located through the furnace.

On the other hand, the fine particles are scattered in the fluidized bed reduction furnace 6, captured by the cyclone 31 from the outlet at the upper part of the furnace, the hopper 32, the circulation cutting device.
It is circulated to the bubbling fluidized bed 36 via 33, and reduction is performed again. Then, the fine-particle reduction ore from which the desired reduction has been obtained is discharged from the cutoff valve 43 and sent to the next step.

Note that this equipment is not limited to that used for the production of reduced ore for smelting reduction, and for example, reducing gas 11 such as converter gas or coke oven gas or an improved reducing gas is used. It is also possible to reduce the iron ore with and supply it to the blast furnace for use.

(Effects of the Invention) As described above, in the present invention, a stable high-speed fluidized bed, a bubbling fluidized bed, and a packed bed are formed by the reducing gas blown into the fluidized bed reduction furnace. Circulating flow characteristics can be obtained, and even in a raw material having a wide particle size distribution, the uniformity of reduction can be improved and an efficient reduction reaction can be promoted. Further, since the powdered ore having a wide particle size distribution can be positively treated, the powdered ore and steam coal can be used as raw materials, and the cost of hot metal can be reduced. Further, it has an excellent effect such that a compact reduction facility can be provided by a high reaction rate and an improvement in gas utilization rate.

When used in the blast furnace method, it is possible to improve productivity of the blast furnace and downsize auxiliary equipment such as sintering equipment and coke oven equipment.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the basic configuration of the present invention, FIG. 2 is an explanatory diagram showing the arrangement of nozzles, and FIG. 3 is an explanatory diagram showing the outline of the smelting reduction method previously proposed by the present inventors. Is. 1 is iron ore, 2 is limestone, 6 is fluidized bed reduction furnace, 11 is reducing gas, 25 is raw material, 31 is cyclone, 32 is hopper, 33 is circulating cutting device, 34 and 35 are gas outlets, 36 is Bubbling fluidized bed, 37 packed bed, 38 furnace bottom injection nozzle, 39 cutout valve, 40, 41 and 42 flow control valves, and 43 and 44 cutout valves.

Claims (1)

[Claims] 1. An iron ore fluidized bed reduction, wherein in a facility for producing reduced ore, gas injection nozzles are arranged in several stages in the furnace height direction in the fluidized bed reduction furnace. apparatus.