JPH075950B2 - Preheating device in iron ore preliminary reduction facility - Google Patents

Description

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

[Conventional technology]

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 reducing property 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 in that it requires pretreatment for pelletizing the iron ore and consumes a large amount of 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 smelting method has been attracting attention. The smelting reduction furnace used in this method is not restricted by the raw materials used,
It was developed for the purpose of producing a molten iron-based alloy by a smaller-scale facility.

As one of such smelting reduction methods, the inventors of the present invention have proposed a method including the flow 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 coal stone 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 raw coal 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 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 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. 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.
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 in particular, 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 you use cheap raw materials such as steam coal and powdered ore,
Since a large amount of dust is generated during the treatment process and the gas permeability cannot be increased due to poor air permeability in the furnace, the powder and granules are lumped and used as in the blast furnace operation.

As a fluidized bed calcining device for limestone, Japanese Patent Laid-Open No. 57-63
There is one proposed in the 128 publication. This apparatus burns and calcines limestone, dolomite, etc. in a fluidized bed using a solid fuel such as coal and coke powder, and uses an out-of-reactor pipeline incorporating a cyclone group for preheating of raw materials.
That is, a so-called suspension preheater is used that preheats the input material in the process of conveying the input material to the cyclone by the exhaust gas discharged from the flue of the fluidized bed preheating furnace. Then, the preheated raw material is separated from the exhaust gas by a cyclone and sent to the fluidized bed preheating furnace through the hopper.

In the device described in JP-A-57-63128, a gas trap is provided in the middle of the pipe connecting the lower cyclone and the fluidized bed preheating furnace, and the gas trap causes the high-pressure gas to flow from the fluidized bed preheating furnace to the raw material inlet. It prevents it from passing through.

However, when attempting to preheat iron ore using this apparatus, it is necessary to blow a carrier gas into the fluidized bed preheating furnace at high pressure because the iron ore has a large specific gravity. That is, the flow pressure loss of the fluidized bed preheating furnace in the case of iron ore preheating is much larger than that in the case of firing lime, dolomite, or the like.

This fluid pressure loss appears as a pressure difference between the fluidized bed preheating furnace and the lower portion of the cyclone. Therefore, the method of sealing by the gas trap provided in the lower part of the cyclone cannot completely prevent the gas leak. For example, the high-pressure gas in the fluidized bed preheating furnace blows backward through the raw material supply pipe from the lower part of the cyclone to the fluidized bed preheating furnace, and the efficiency of collecting the granular material by the lower cyclone deteriorates. In addition, fine iron ore, limestone, etc. float in the connecting pipe, making it difficult to descend, and the supply of raw materials becomes unstable.

Therefore, the present invention enables the use of inexpensive raw materials such as steam coal and powdered ore and the effective utilization of waste heat by connecting the suspension preheater and the fluidized bed preheating furnace via a pneumatic feeder. The objective is to secure a stable supply of raw materials to the preheating furnace and improve the productivity of the smelting reduction method.

[Means for solving problems]

In order to achieve the object, the preheating apparatus of the present invention is a fluidized bed preheating furnace for preheating iron ore used in a smelting reduction method prior to reducing it in a fluidized bed prereduction furnace. And, a coal supply port and an opening for blowing air for fluidized combustion are provided in the hearth, respectively, and an iron ore supply port is provided in the middle of the exhaust gas flue extending from the fluidized bed preheating furnace to the cyclone, and the iron ore is collected by the cyclone. In order to load the iron ore into the lower part of the fluidized bed preheating furnace, a pneumatic feeder is arranged in a pipe line connecting the cyclone and the lower part of the fluidized bed preheating furnace.

[Action]

That is, in the present invention, the exhaust gas discharged from the fluidized bed preheating furnace is brought into countercurrent contact with the iron-making raw material such as iron ore, limestone or the like, so that the heat held by the exhaust gas is given to the iron-making raw material. Further, the dust contained in the exhaust gas is separated from the exhaust gas by the cyclone and is again charged into the fluidized bed preheating furnace together with the iron-making raw material. In this way, by using the cyclone in the fluidized bed preheating furnace, the use of powdered and granular raw materials,
Effective use of heat and reuse of particulate dust are possible.

Then, the ironmaking raw material containing dust separated from the exhaust gas by the cyclone is temporarily stored in the hopper and then charged into the fluidized bed preheating furnace by the pneumatic feeder. This pneumatic feeder stably supplies the iron-making raw material to the fluidized bed preheating furnace regardless of the pressure difference between the cyclone and the fluidized bed preheating furnace.

That is, the pneumatic feeder has no mechanically moving parts, and the powder filled in the conduit from the hopper to the pneumatic feeder can be used as a gas seal. Therefore, sufficient sealing is possible even with a large fluid pressure loss in the fluidized bed preheating furnace, and the cyclone powder collecting function is not adversely affected.

〔Example〕

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

1 to 5 show examples of a raw material supply system in which particulate dust floating in exhaust gas discharged from a fluidized bed preheating furnace is returned to the fluidized bed preheating furnace together with raw materials such as iron ore and limestone.

FIG. 1 shows an example in which two cyclones are provided.

In this example, raw materials such as iron ore 1 and limestone 2 are put into the supply hopper 24. On the other hand, the exhaust gas discharged from the fluidized bed preheating furnace 3 is discharged from the third flue 29 via the first flue 25, the first cyclone 26, the second flue 27 and the second cyclone 28.

At this time, as shown in the figure, it is preferable to connect the pipe 30 from the supply hopper 24 to the portion after the second flue 27 is bent from the vertical direction to the horizontal direction. When the pipe 30 is connected to the second flue 27 in this way, most of the raw material sent from the supply hopper 24 in the form of powder is sent to the second cyclone 28 along with the flow of exhaust gas. Then, the powdery raw material is separated from the exhaust gas by the second cyclone 28, and falls into the first flue 25 through the pipe 31.

Among the dropped raw materials, coarse particles fall vertically in the first flue 25 and are fed into the fluidized bed preheating furnace 3. On the other hand, the fine-grained raw material is sent to the first cyclone 26 along with the flow of exhaust gas. The coarse particles of the raw material supplied from the supply hopper 24 are sent to the first cyclone 26 by dropping through the second flue 27. Then, the powder particles collected by the first cyclone 26 fall through the pipe 32 into the hopper 33, and are temporarily stored therein.

That is, the raw material of the fine particles is the second flue 27, the second cyclone.
28, a pipe 31, a first flue 25 and a first cyclone 26 are circulated. In this circulation path, it is heated by the exhaust gas discharged from the fluidized bed preheating furnace 3.

A pneumatic feeder 35 is provided below the hopper 33 via a pipe 34. When the carrier gas 36 is blown into the pneumatic feeder 35 from its bottom, the raw material stored in the pneumatic feeder 35 is blown into the fluidized bed preheating furnace 3 through the pipe 37 according to the amount of the blown carrier gas. Be done. At this time, the hopper
It is preferable to control the blowing amount of the carrier gas 36 while monitoring the raw material level in 33 with a level meter. In this way, the preheated raw material is supplied to the pneumatic feeder 35 while maintaining the raw material level in the hopper 33 at an appropriate level.
Is sent to the fluidized bed preheating furnace 3.

As the carrier gas 36, one obtained by branching from a pipe 38 for blowing fluidized air into the fluidized bed preheating furnace 3 can be used. In this way, the reducing atmosphere in the furnace is not adversely affected.

As seen in this example, since the space from the hopper 33 to the pneumatic feeder 35 through the pipe 34 is filled with the granular material, sufficient gas sealing can be achieved against the pressure in the fluidized bed preheating furnace 3. It can be performed. Therefore, the pressure in the fluidized bed preheating furnace 3 does not adversely affect the first cyclone 26.

FIG. 2 shows an example of operating the fluidized bed preheating furnace 3 under a high load in order to obtain high productivity.

In this case, the exhaust gas containing a large amount of char is discharged from the fluidized bed preheating furnace 3. This exhaust gas is the first flue 25
a, first cyclone 26a, second flue 27a, second cyclone 2
8a, 3rd flue 29a and 3rd cyclone 39a and then 4th flue
It is released from the system from 40a.

On the other hand, the raw material supplied from the supply hopper 24 is the pipe 30a.
Through the 3rd flue 29a. Among them, the raw material of fine grain is
The exhaust gas flow is sent to the third cyclone 39a, separated from the exhaust gas by the third cyclone 39a, and then the pipe 3
Drop 1a. In this way, the fine-grain raw material circulates through the third flue 29a, the third cyclone 39a, the pipe 31a, the second flue 27a, the second cyclone 28a, and the third flue 29a, and the exhaust gas is circulated in this circulation path. It is heated by the heat of.

The raw material separated from the exhaust gas in the first cyclone 26a and the second cyclone 28a is temporarily stored in the hopper 33a via the pipe 32a. The raw material in the hopper 33a is appropriately cut into the fluidized bed preheating furnace 3 by the pneumatic feeder 35a in the same manner as in the example of FIG.

At this time, if air is used as the carrier gas, since a large amount of char is mixed in the exhaust gas discharged from the fluidized bed preheating furnace 3, abnormal combustion may occur in the pneumatic feeder 35a. Therefore, in order to prevent this abnormal combustion, part of the exhaust gas discharged to the outside of the system is piped.
It is sent back to the pneumatic feeder 35a via and used as a carrier gas. Others are the same as the example of FIG.

Fig. 3 shows the reducing gas with high residual CO partial pressure after reducing the ore in the fluidized bed preliminary reduction furnace 6
An example of using it as a carrier gas for 35b is shown. In FIG. 3, the reducing gas is also sent to the lower portion of the fluidized bed preheating furnace 3 and mixed and burned with the coal 7. That is, the carrier gas is sent to the lower portion of the fluidized bed preheating furnace 3 and the pneumatic feeder 35b through the pipe 42.
The raw material that has descended through the pipe 34 is further heated by this reducing gas. Others are the same as in the case of FIG.

FIG. 4 shows an example in which the feed port for the raw material is provided above the fluidized bed preheating furnace 3. At this time, the raw material falling from the supply hopper 24c in the pipe 30c comes into countercurrent contact with the exhaust gas rising from the fluidized bed preheating furnace 3, and is classified by the wind screen in the exhaust gas flue 25c. Of the classified raw material, the fine-grained portion is sent to the cyclone 26c together with the exhaust gas, and the coarse-grained portion which is not suitable for the air current transportation falls directly into the fluidized bed preheating furnace 3.

The raw material which has been heat-exchanged with the exhaust gas due to this countercurrent contact and has been heated is temporarily stored in the hopper 33c and then sent to the distribution pneumatic feeder 35c. The raw material for collection is
It is divided into a plurality of sections by the distribution type pneumatic feeder 35c and charged into the fluidized bed preheating furnace 3.

Further, FIG. 5 shows an example in which the raw material is charged into the cyclone 28d arranged in the upper part of the fluidized bed preheating furnace 3 by the oblique pipe 43. The exhaust gas discharged from the fluidized bed preheating furnace 3 is
Flue 25d, first cyclone 26d, second flue 27d, diagonal pipe 4
3, it is discharged to the outside of the system through the second cyclone 28d and the third flue 29d.

On the other hand, the raw material supplied from the supply hopper 24 rides on the flow of the exhaust gas and reaches the second cyclone 28d via the oblique pipe 43. In this process, the raw material is fed through the oblique pipe 43, so that the one having a large particle size rolls inside the oblique pipe 43. Therefore, the inside of the oblique pipe 43 is not blocked by the input material.

The raw material separated from the exhaust gas in the second cyclone 28d is the first
Similar to the example of the figure, the pipe 31, the first flue 25d, the first cyclone 26d, the second flue 27d, the oblique pipe 43, and the second cyclone 28d are circulated, and are heated by the exhaust gas in this circulation process. Then, it is sequentially separated from the exhaust gas by the first cyclone 26d and fed into the fluidized bed preheating furnace 3 by the pneumatic feeder in the same manner as in the example of FIG.

As seen in each of the above examples, the raw material charging part is provided in the middle of the exhaust gas flue 27 connected to the outlet of the fluidized bed preheating furnace 3. Thereby, the charged raw material exchanges heat with the high temperature exhaust gas from the fluidized bed preheating furnace 3. Then, the dust contained in the exhaust gas is separated from the exhaust gas by a cyclone together with the raw material. The separated collection materials are hoppers 33, 33a-33.
While being quantitatively stored in d, they are successively supplied to the fluidized bed preheating furnace 3 by the pneumatic feeders 35, 35a to 35d.

In this case, there is a pressure difference of several hundred mm or more between the lowermost cyclone 26, 26a, 28a, 26c, 26d and the lower part of the fluidized bed preheating furnace 3 due to fluid pressure loss, cyclone pressure loss or the like. Therefore, when the gas seal in the pipe 31 is incomplete, gas leaks from the fluidized bed preheating furnace 3 to the cyclones 26, 26a, 28a, 26c and 26d. This leak caused a cyclone 2
The gas flow in 6,26a, 28a, 26c, 26d will be disturbed, and the collection efficiency of the raw material particles by the cyclones 26, 26a, 28a, 26c, 26d will be drastically reduced, which will cause the product yield to deteriorate.

In order to avoid this gas leak, a method of providing a rotary feeder in the middle of the pipe 31 to control the gas seal and the amount of raw material particles cut out can be considered. However, since the raw material particles to be cut out are high in temperature and have high wear resistance, it is necessary to water-cool the rotating part of the rotary feeder. As a result, there is a drawback that the raw material particles are cooled, and wear of the rotating body also poses a problem.

On the other hand, pneumatic feeders 35, 35a to 35c
When is used, gas sealing is performed by the raw material particles with which the hoppers 33, 33a, 33c and the pipe 34 are filled. The raw material particles are pressurized by the carrier gas and cut out toward the fluidized bed preheating furnace 3.

The pneumatic feeder 35 has a structure as shown in FIG. A gas blowing header 44 is provided on the bottom of the pneumatic feeder 35, and the carrier gas 36 blown into the pneumatic feeder 35 feeds the granular material that has descended through the pipe 34 into the fluidized bed preheating furnace 3 through the pipe 37.
In the example of FIG. 6, this gas blowing header 44 is divided into a plurality of divided headers 44a to 44c. Then, the carrier gas supply pipe 45 is branched so that the flow rate of the carrier gas 36 sent to each of the divided headers 44a to 44c can be adjusted,
Flow control valves 46a to 46c are provided on the respective branch pipes 45a to 45c.

When cutting a small amount of powdery granular material into the fluidized bed preheating furnace 3, the carrier gas 36 is blown into the divided header 44a through the flow rate adjusting valve 46a as shown in the figure. This allows the split header 44
Only the granular material on the top of a is fluidized and flows into the fluidized bed preheating furnace 3 from the pneumatic feeder 35 through the pipe 37. In order to increase the flow rate of the powdery granular material, the carrier gas 36 may be sequentially blown into the divided headers 44b and 44c, and the blowing amount may be increased.

As described above, since the pneumatic feeder 35 has no rotating portion, problems caused by water cooling, abrasion, etc. do not occur. In addition, by controlling the blowing conditions of the carrier gas,
It is possible to adjust the cut-out amount of the powdery granular material accurately and over a wide range.

Coal 7 is supplied to the lower part of the fluidized bed preheating furnace 3, and the hearth of the fluidized bed preheating furnace 3 is provided with an opening for blowing fluidized air through a pipe 38. The fluidized air causes the coal 7 to mix and flow with the raw material fed from the pneumatic feeder 35 in the fluidized bed preheating furnace 3. Then, in the fluidized bed preheating furnace 3, the coal 7 burns to heat the raw material. Combustion air may be separately supplied to the freeboard section as secondary air.

〔The invention's effect〕

As described above, in the ore preheating device of the present invention, the raw material charging mechanism is incorporated in the exhaust gas flue extending from the fluidized bed preheating furnace. Therefore, it becomes possible to effectively recover the heat of the exhaust gas, and the dust floating in the exhaust gas is reused as an iron source. As a result, it is possible to use low-grade raw materials such as powdered ore and steam coal that easily generate dust, and it is possible to reduce fuel consumption in the fluidized bed preheating furnace. Furthermore, since the raw material heated by heat exchange with the exhaust gas is introduced into the fluidized bed preheating furnace through the pneumatic feeder, the gas in the fluidized bed preheating furnace does not blow through the introduction path in the opposite direction, and the fluidized bed preheating furnace does not blow. The raw material is put into the preheating furnace under stable conditions, and the cyclone collection efficiency does not decrease. In this way, the yield is improved, and the productivity and economic efficiency of the smelting reduction method are improved.

[Brief description of drawings]

1 to 5 each show a raw material supply system incorporated in an exhaust gas flue extending from a fluidized bed preheating furnace in an embodiment of the present invention. Further, FIG. 6 shows an example of a pneumatic feeder used in the present invention, and FIG. 7 is a schematic view of the smelting reduction method previously developed by the present inventors.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Riki Katayama 1-1-1, Emitsu, Hachiman-to-ku, Kitakyushu, Kitakyushu, Fukuoka Japan Nippon Steel & Co., Ltd. Yawata Works (56) Reference JP-A-61-64807 ( JP, A)

Claims (1)

[Claims] 1. A fluidized bed preheating furnace in which iron ore used in a smelting reduction method is preheated prior to being reduced in a fluidized bed preliminary reduction furnace. An opening for blowing air for combustion is provided, an iron ore supply port is provided in the middle of an exhaust gas flue extending from the fluidized bed preheating furnace to the cyclone, and iron ore collected by the cyclone is provided at a lower portion of the fluidized bed preheating furnace. A preheater in an iron ore pre-reduction facility, characterized in that a pneumatic feeder is arranged in a pipe line connecting the cyclone and a lower part of the fluidized bed preheating furnace for charging into the iron ore pre-reduction facility.