JPH0637659B2 - 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 for use in a smelting reduction method, a blast furnace method, etc. in a fluidized bed reduction furnace.

(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 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.

The smelting reduction method has been attracting attention as an alternative to such conventional hot metal production technology. 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 refining method, the present inventor has previously proposed a method constituted by the flow shown in FIG.
Proposed as an issue.

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 an oxygen-containing gas are blown into the preheated ore and the asbestos in a fluidized state. The coal 7 exchanges heat with the preheated ore in the fluidized bed reduction furnace 4 and is thermally decomposed by partial combustion due to reaction with oxygen. As a result, the coal 7 becomes a char 9 while generating a reducing gas.

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

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. The issue is how to achieve the promotion of the refining reaction.

However, if you use cheap raw materials such as steam coal and powdered ore,
A large amount of dust is generated during the treatment process. For this reason, the air permeability in the furnace deteriorates and a large amount of gas cannot be blown in,
It becomes difficult to increase productivity. Therefore, such powdered ore is agglomerated into briquettes or pellets, and processed into a raw material that does not generate dust before use.

Further, in the smelting reduction methods developed so far, the reduced iron discharged from the fluidized bed reduction furnace is merely heat-collected as necessary, and then put into charcoal in the smelting reduction furnace. In such a system, there is a limit in efficient heat recovery and promotion of the scouring reaction.

Therefore, the present invention, when obtaining hot metal from iron ore by the smelting reduction method, the use of steam coal with a large amount of endowment and fine ore with low present utility value as raw materials, aiming at expanding utilization of resources and reducing hot metal cost To do.

(Means for Solving Problems) In the iron ore fluidized bed reducing apparatus of the present invention, an external circulation device is provided in the fluidized bed reducing furnace 6 in a facility for producing reduced ore used in a smelting reduction method. A gas outlet 34 is provided in the particle descending pipe 33 of this external particle circulation device, and gas inlets 36, 38 are provided at the bottom and upper part of the fluidized bed reduction furnace 6.

(Function) The present invention is configured as described above, and the iron ore raw material such as iron ore and limestone preheated in the fluidized bed preheating furnace is also charged in the fluidized bed reduction furnace 6 together with the coal in the form of powder and granules, and the smelting reduction furnace The gas generated in 10 or the reducing gas 11 obtained by the decarbonation treatment is blown from the lower part of the fluidized bed reduction furnace 6.

With this reducing gas, high-temperature iron ore is brought into a fluidized state and reduced to produce reduced ore. The produced reduction ore is collected from the discharge part provided in the lower part of the fluidized bed reduction furnace 6. Reducing gas 11
By increasing the superficial velocity and the slip velocity with the fluidized particles, the reduction reaction is promoted and the productivity and the gas utilization efficiency are improved. At this time, most of the charged raw material particles are scattered along with the reducing gas from the fluidized bed reduction furnace 6.

An external particle circulation device is attached to collect the scattered raw material particles by a cyclone 31 provided at the outlet of the fluidized bed reduction furnace, and circulate and supply them again into the fluidized bed reduction furnace 6. The collected particles are circulated and supplied to the fluidized bed reduction furnace 6 via the particle descending pipe 33. Gas injection ports 34 and 34 'are provided in the middle of the particle descending pipe 33 to circulate the particles in the fluidized bed reduction furnace 6 while preventing the particles from hanging. It is possible to control the circulation amount by adjusting the amount of the gas blowing ports 34 and 34 '. Further, the gas blown from the gas injection port 36 provided at the bottom of the fluidized bed reduction furnace 6 acts to break the repose angle of the particles discharged from the particle downcomer pipe 33 at the bottom of the fluidized bed reduction furnace 6 and removes the particles from the furnace. Inflow and diffuse to the bottom. The level of this inflowing particle is transferred to the upper part of the furnace, and the particle level is raised above the gas blowing port 38. Then, the reducing gas is blown through the gas blowing port 38 so that the superficial gas velocity is equal to or higher than the final particle velocity Ut, and the particles are fluidized at high speed to efficiently proceed the reduction reaction. The fine-grained particles are entrained in the reducing gas and are reduced while flowing and scattering in the furnace, and scattered outside the furnace. Then, by the external particle circulation device, it is supplied again into the furnace and the reduction proceeds. On the other hand, coarse particles do not scatter and stay in the lower part of the furnace and are reduced. The reduced ore that has been reduced can be taken as coarse-grained reduced ore from the discharge part at the bottom of the fluidized bed reduction furnace 6 and fine-grained reduced ore from the external particle circulation device.

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

A cyclone 31 is connected to the outlet provided in the upper part of the fluidized bed reduction furnace 6 to capture particles that have been scattered along with the reducing gas 11.

A hopper 32 for temporarily storing the captured particles is connected to the lower portion of the cyclone 31, and the hopper 32 is connected to an appropriate position of the bottom of the fluidized bed reduction furnace 6 by a particle descending pipe 33. Carrier gas is supplied from a gas outlet 34 provided at an appropriate position in the particle downcomer pipe 33, for example, in the vertical pipe portion of the particle downcomer pipe 33 or in the vicinity of a connection portion to the fluidized bed reduction furnace 6 via a flow control valve 35. It's blowing. The shape of the gas outlet 34 is not particularly limited, and may be, for example, one point, a large number of pores, or a louver shape as shown in FIG.

A gas dispersion bed 36 is formed at the bottom of the fluidized bed reduction furnace 6. The gas dispersion bed 36 has, for example, a cylindrical nozzle 37 projectingly provided as shown in FIG. A gas inlet 38 is formed slightly above the outlet of the particle descending pipe 33 to the fluidized bed reduction furnace 6. The bottom blowing gas dispersion bed 36 and the gas blowing port 38 are provided with flow rate control valves 39 and 40, respectively, and the gas generated in the smelting reduction furnace or the reducing gas obtained by the decarbonation gas treatment
It is possible to adjust the amount of air blown into the fluidized bed reduction furnace 6 of 11.

In the figure, 41 is a cutoff valve for charging the raw material 25 such as powdered ore and limestone into the fluidized bed reduction furnace 6, 42 is a cutout valve for fine-grained reduced ore,
Reference numeral 43 is a coarse-grained reduction ore cutout valve.

Raw material 25 such as powdered ore and limestone is charged into the fluidized bed reduction furnace 6 from the cut-out valve 41, and the reducing gas 11 is blown from the furnace bottom blowing gas dispersion bed 36 and the gas blowing port 38 through the flow rate control valves 39 and 40. Blow,
The high-temperature reducing gas 11 reduces the high-temperature iron ore in a fluidized state to produce reduced ore. By increasing the superficial velocity of the reducing gas 11, the reduction reaction is promoted and the productivity is improved. At this time, most of the charged raw material particles are entrained and scattered in the reducing gas 11 from the fluidized bed reduction furnace 6, but the particles are collected by a cyclone 31 provided at the outlet of the fluidized bed reduction furnace 6, Store the particles in the hopper.

This particle circulates to the lower part of the fluidized bed reduction furnace 6 through the particle downcomer 33, but from the gas outlet 34 formed near the vertical pipe part of the particle downcomer 33 and the connection to the fluidized bed reduction furnace 6. The carrier gas is blown out and the particles are smoothly circulated in the fluidized bed reduction furnace 6 while preventing the phenomenon of the particles being suspended in the particle descending pipe 33.

Thus, the particles that have passed through the external particle circulation device are circulated to the bottom of the fluidized bed reduction furnace 6 and are generated in the vicinity of the particle downcomer 33 from the reducing gas 11 blown out from the cylindrical nozzle 37 provided in the gas dispersion bed 36. While reducing the angle of repose and performing reduction, the filling level of the particles at the bottom of the furnace is raised to raise the particles to the upper part of the gas blowing port 38, and the reducing gas 11 blown out from the gas blowing port 38 fluidizes the particles at high speed for efficient Make a reduction. As shown in FIG. 5, the gas injection port 38 is provided so as to penetrate the furnace in the horizontal direction.

Here, the reduction rate is controlled by controlling the flow rates of the flow rate control valves 39 and 40 and the circulation rate of the particles scattered in the fluidized bed reduction furnace 6 by the flow rate control valve 35.

The fine-grain reduced ore is collected from the cut-out valve 42, and the coarse-grain reduced ore is collected from the cut-out valve 43.

As described above, in the present invention, the fine particles of the reducing ore are relatively sized by the sieving effect of only the fine particles of the reducing ore from the particle circulation system including the cyclone 31, the hopper 32, and the particle downcomer 33. This discharged reduction ore can be gas-transported and can be blown into the smelting reduction furnace 10 with a nozzle. Further, the coarse-grained reduction ore stays and flows in the bottom of the fluidized bed reduction furnace 6, and is discharged from the cut-off valve 43 from the discharge port provided in the bottom of the fluidized bed reduction furnace 6. Since it is too large for gas transportation, it is mechanically processed by conveyors.

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, the circulation of the particles entrained and scattered in the gas in the fluidized bed reduction furnace into the fluidized bed reduction furnace is smoothly performed, and the circulation amount is easily controlled. As a result, stable high-speed circulation and flow characteristics can be secured and particle concentration in the furnace can be secured, efficient reduction reaction can be promoted, and high productivity and gas utilization rate can be improved. Further, since the powdered ore having a wide grain thickness distribution can be positively treated, inexpensive steam coal and powdered ore can be used, 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 view showing the basic structure of the present invention, FIG. 2 is an enlarged explanatory view of the main parts of the same as above, FIG. 3 is an explanatory view showing a gas outlet of this embodiment, and FIG. 4 is a fluidized bed reduction furnace. FIG. 5 is an enlarged cross-sectional view of the gas blowing nozzle at the bottom, FIG. 5 is an explanatory diagram showing the arrangement of the upper gas nozzle in the furnace, and FIG. 6 is an explanatory diagram showing the outline of the smelting reduction method previously proposed by the present inventors. . 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 particle downcomer, 34 is gas outlet, 35, 39, 40 Is a flow rate control valve, 36 is a gas dispersion bed at the bottom of the furnace, 37 is a cylindrical nozzle, 38 is a gas inlet, and 41 and 42 are cutoff valves.

Claims (1)

[Claims] 1. A facility for producing reduced ore, wherein a fluidized bed reduction furnace is provided with an external particle circulation device, a particle downcomer of this external particle circulation device is provided with a gas blowing port, and the fluidized bed reduction furnace is provided. An iron ore fluidized bed reduction apparatus characterized in that a gas injection port is provided at the bottom and the top of the iron ore.