JPH0792343B2 - Iron ore preliminary reduction device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for reducing iron ore in a fluidized bed preliminary reduction furnace for use in a smelting reduction method.

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

In the method using a blast furnace, a large amount of coke is used as a heat source and a reducing agent. Further, iron ore, which is an iron source, is usually sintered in order to improve air permeability and reducibility in the furnace, and is charged into a blast furnace as a sintered ore. For this reason, the blast furnace method requires coke oven equipment for dry distillation of strong coking coal and sintering equipment for producing sinter. Therefore, the blast furnace method requires a large amount 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 is high. Moreover, 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 the shaft furnace has a drawback that it requires pretreatment for pelletizing the iron ore and consumes a large amount of reducing agent, expensive natural gas and the like as a heat source.

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 one of such smelting reduction methods, the inventors of the present invention have applied for a method including the flow previously shown in FIG.
Proposed as 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 by the heat generated by the combustion reaction between the coal 4 and the air 5 in the fluidized bed preheating furnace 3. As a result, the limestone 2 (CaCO ₃ ) becomes quicklime (CaO) and is supplied to the fluidized bed preliminary reduction furnace 6.

In the fluidized bed preliminary reduction furnace 6, coal 7 and oxygen or oxygen-containing gas 8 are blown into the preheated ore and quicklime in a fluidized state. The coal 7 exchanges heat with preheated ore in the fluidized bed preliminary reduction furnace 6 and is thermally decomposed by partial combustion due to reaction with oxygen. As a result, the coal 7 generates a reducing gas and 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 is the fluidized bed preliminary reduction furnace 6
After being heated to 700 to 900 ° C. by heat exchange with the fuel gas 12 from the above, it is blown into the fluidized bed preliminary reduction furnace 6. The reducing gas 11 blown into the fluidized bed preliminary reduction furnace 6 is mixed with the reducing gas generated by the thermal decomposition of the coal 7, and reduces the high temperature powdery 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 preliminary reduction furnace 6 together with the preheated ore to desulfurize the gas in the fluidized bed preliminary reduction furnace 6. Then the quicklime 14
Is discharged from the fluidized bed preliminary reduction furnace 6 together with the reduction ore 13 and the char 9.

Reduced ore 13, char 9 and quicklime 1 thus obtained
4, coal materials such as coal and coke necessary for heat balance in the smelting reduction furnace 10 are added from the outside 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 17
Is charged into the smelting reduction furnace 10.

In the smelting reduction furnace 10, oxygen 19 is blown toward the bath from the top blowing lance 18, and oxygen and carbonaceous material are blown into the bath from the bottom blowing tuyere 20. The carbonaceous material contained in the briquette 16, the carbonaceous material blown together with oxygen from the bottom blowing tuyere 20, the coke 21 supplied from the charging device 17 and the like are supplied from the top blowing lance 18. And reacts with oxygen to generate a large amount of heat in the smelting reduction furnace 10.
The generated heat melts the reduction ore 13 in the briquette 16 and the reduction proceeds to form hot metal 22.

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
It will be stored within 10 and its amount will increase 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, how to expand the range of usable raw materials, improve the efficiency of heat recovery, promote the smelting reaction in the smelting reduction furnace, etc. It is a future issue whether to achieve it.

However, if cheap raw materials such as steam coal and powdered ore are used,
A large amount of dust is generated during the treatment process. Therefore, the air permeability in the furnace is poor and a large amount of gas cannot be blown in,
It becomes difficult to increase productivity. Therefore, such a powdered ore or the like is used by being processed into a raw material that does not generate dust, by lumping briquettes or pellets.
Further, in the smelting reduction methods developed so far, the reducing ore discharged from the fluidized bed preliminary reduction furnace is merely charged into the smelting reduction furnace after heat recovery as necessary. In such a system, there is a limit in efficient heat recovery and promotion of the smelting reaction.

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

[Means for solving problems]

Iron ore pre-reduction apparatus of the present invention, in order to achieve the object, in a facility for producing a pre-reduction ore used in the smelting reduction method, a cyclone is provided at the outlet of the fluidized bed pre-reduction furnace, the cyclone lower part, The lower part of the fluidized bed preliminary reduction furnace
An external particle circulating device is formed by connecting through a pneumatic feeder provided with a carrier gas blowing port, and an outlet for taking out fine granular reduced ore is provided in the external particle circulating device, and the fluidized bed preliminary reducing furnace is also provided. It is characterized in that a discharge part for taking out coarse-grained reduction ore is provided at the bottom part of.

[Action]

That is, in the present invention, the exhaust gas discharged from the fluidized bed preheating furnace and the iron ore raw materials such as iron ore and limestone are supplied to the fluidized bed preliminary reduction furnace, and coal in the form of granules is also charged to the smelting reduction furnace. The gas generated in 1 or the reducing gas obtained by the decarbonation treatment is blown from the lower part of the fluidized bed preliminary reduction furnace. This reducing gas is mixed with the gas generated by the partial combustion reaction of the carbonaceous material with oxygen. And this gas makes high temperature iron ore into a fluid state and reduces it, and produces | generates a reduction ore. The produced reduction ore is collected from the discharge part provided in the lower part of the fluidized bed preliminary reduction furnace. By increasing the superficial velocity of the reducing gas and increasing the slip velocity with the fluidized particles, it is possible to accelerate the reduction reaction and improve the productivity. At this time, most of the charged raw material particles are scattered together with the reducing gas from the fluidized bed preliminary reduction furnace. In order to circulate and supply the scattered charged raw material particles, an external particle circulation device is attached so as to collect particles by a cyclone provided at the outlet of the fluidized bed preliminary reduction furnace and circulate and supply them again into the fluidized bed preliminary reduction furnace. . The circulation reduction of fine ore improves the reduction rate and the reducibility and controllability of the reduction rate.

In this way, it is possible to collect coarse-grained reduction ore from the discharge part in the lower part of the fluidized bed preliminary reduction furnace and fine-grained reduction ore from the external particle circulation device.

〔Example〕

 Hereinafter, the features of the present invention will be specifically described with reference to examples.

FIG. 1 is a schematic diagram showing the basic configuration of the present invention. In the figure, a fluidized bed preliminary reduction furnace 6 is provided with a raw material 25 such as powdered ore and limestone sent from the fluidized bed preheating furnace 3 (see FIG. 4).
Are charged through the cut-out valve 41. The fluidized bed preliminary reduction furnace 6 is also charged with powdered coal 7 through a cut-off valve 43, and gas generated in the smelting reduction furnace 10 (see FIG. 4) or decarbonated gas is discharged. The reducing gas 11 obtained by the treatment is blown from the bottom of the fluidized bed preliminary reduction furnace 6 through the control valve 45. The reducing gas 11 is mixed with a gas generated by causing the coal 7 charged through the cutoff valve 43 to partially burn with oxygen. This reducing gas brings the high temperature iron ore into a fluid state and reduces it to produce reduced ore. By increasing the superficial velocity of the reducing gas and increasing the slip velocity with the fluidized particles, the reduction reaction is promoted and the productivity is improved. At this time, since most of the charged raw material particles are scattered along with the reducing gas from the fluidized bed preliminary reduction furnace 6, the particles are collected by the cyclone 31 provided at the outlet of the fluidized bed preliminary reduction furnace 6 and the particles are collected. Stored in hopper 32, pneumatic feeder 33
It is circulated and fed into the fluidized bed preliminary reduction furnace 6 via. As the gas for circulating and supplying the particles, the reducing gas 11 whose flow rate is adjusted via the adjusting valve 46 is used. Circular reduction of fine ore improves the reduction rate and improves the uniform reduction rate and control of the reduction rate. Coarse-grained reduction ore 26 is continuously sampled from the lower discharge part of the fluidized bed preliminary reduction furnace 6, and fine-grained reduction ore 27 is continuously sampled from the pneumatic feeder 33. The amount of reduction ore 26, 27 to be collected is determined by the cutoff valves 42 and 4
Adjust the opening to adjust the amount appropriately.

The pneumatic feeder 33 is used to circulate and feed the collected particles into the fluidized bed preliminary reduction furnace 6 for the following reason. That is, the circulation system composed of the cyclone 31, the hopper 32, and the pneumatic feeder 33 is several hundred mm in the portion of the cyclone 31 and the lower part of the fluidized bed preliminary reduction furnace 6.
There is a pressure difference above the water column. For this reason, it is difficult to seal the gas during the circulation of particles, and the circulating particles are at a high temperature, and a cutting device having heat resistance and wear resistance is required. For this reason, a pneumatic feeder that combines powder seal and gas transportation is used. As a result, the sealing property can be improved, and since there is no rotating mechanical part, heat resistance and wear resistance are also good.

As described above, in the present invention, the outlets of the reducing ores 27 and 26 from the fluidized bed preliminary reduction furnace 6 are provided with the particle circulation system including the cyclone 31, the hopper 32 and the pneumatic feeder 33 and the fluidized bed preliminary reduction furnace. Provided at the bottom of 6. From the particle circulation system, fine particles of the reduced ore scattered in the fluidized bed in the fluidized bed preliminary reduction furnace 6 are relatively sized by the air sieving effect. Therefore, the discharged reduction ore 27 can be transported by gas, and nozzles can be blown into the smelting reduction furnace 10. On the other hand, in the lower part of the fluidized bed preliminary reduction furnace 6, a relatively small-sized reducing ore is retained and fluidized, and this relatively coarse particle of the reduction ore 26 is provided in the lower part of the fluidized bed preliminary reduction furnace 6. Eject more. This is too large for gas transport,
It is mechanically conveyed and processed by conveyors.

If the raw material has a wide particle size distribution and a large amount of iron ore is charged, or if there is a material that is sintered and granulated in the fluidization reduction process to become a large grain, the fluidized bed reserves as shown in Fig. 2. The gas dispersion plate 6a provided on the hearth of the reduction furnace 6 is shaped like a squirrel to discharge coarse particles from the central portion. Further, since the reduction rate of the coarse particle ore is much slower than that of the fine powder, the particles are temporarily stored in the coarse particle discharge pipe 47 as shown in FIG. 3, and the reducing gas 11 is discharged through the control valve 48. Run from the bottom of tube 47. With this configuration, the reduction of the coarse particles in the discharge pipe 47 is promoted, and the rising particles of the reducing gas 11 cause the fine particles and the large particles to be air-sieved. The particles in the discharge pipe 47 are discharged into the hopper 49 by listening to the cutoff valve 42, and are collected as the reduction ore 26 by opening the cutout valve 50.

〔The invention's effect〕

As described above, in the present invention, the fine powder generated in the fluidized bed preliminary reduction furnace is collected and circulated in the fluidized bed preliminary reduction furnace, and the reducing ore is fed from the fluidized bed preliminary reduction furnace and its circulation system. I try to collect it. For this reason, it has become possible to use inexpensive steam coal and powdered ore even in the smelting reduction method. Therefore, it becomes possible to expand the use of resources,
Moreover, the cost of hot metal can be reduced. further,
Compact reduction equipment due to high reaction rate and improved gas utilization rate.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the basic constitution of the present invention, FIGS. 2 and 3 are schematic diagrams showing another constitutional example of the present invention, and FIG. 4 is a smelting reduction previously developed by the present inventors. The flow of the method is shown.

 ─────────────────────────────────────────────────── --Continued front page (56) References Japanese Patent Publication Sho 60-46354 (JP, B2)

Claims (1)

[Claims] 1. A facility for producing pre-reduced ore used in a smelting reduction method, wherein a cyclone is provided at an outlet of a fluidized bed pre-reduction furnace, and a lower portion of the cyclone and a lower portion of the fluidized bed pre-reduction furnace are provided with a carrier gas blowing port. To form an external particle circulation device, and the external particle circulation device is provided with a discharge part for taking out fine-grained reduction ore, and at the bottom of the fluidized bed preliminary reduction furnace. An iron ore pre-reduction device, characterized in that it is provided with a discharge part for taking out granular reduction ore.