JPS62228870A - Out-of-core circulator for fluidized-bed spare reducing furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a fluidized bed pre-reduction furnace that reduces iron ore in a fluidized bed in order to obtain pre-reduced ore used in smelting reduction methods, etc. Regarding circulation equipment.

[Conventional technology]

In order to reduce iron ore to produce hot metal, methods such as using a blast furnace and melting iron ore reduced in a shaft furnace in an electric furnace have been 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 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 distilling highly caking coal and sintering equipment for producing sintered ore. Therefore, the blast furnace method requires a large amount of energy and labor as well as a large amount of equipment cost. For this reason, the blast furnace method has the disadvantage of high processing costs. Furthermore, the availability of strong coking coal is small worldwide, and its distribution is regionally uneven, making its supply unstable.

On the other hand, the method of reducing iron ore using a shaft furnace requires pre-treatment of turning the iron ore into pellets and pellets, and also has the drawback of consuming large amounts of expensive natural gas as a reducing agent and heat source. .

Therefore, the smelting reduction smelting method is attracting attention as an alternative to the conventional hot metal production technology. The smelting reduction furnace used in this method was developed for the purpose of producing molten iron-based alloys using smaller-scale equipment without being restricted by the raw materials used.

As one such melt reduction method, the present inventors previously proposed a method consisting of the flow shown in FIG. 5 in Japanese Patent Application No. 184056/1983.

According to this method, hot metal is produced as follows. That is, iron ore 1 and limestone 2 are placed in a fluidized bed preheating furnace 3.
It is heated by the heat generated by the combustion reaction between coal 4 and air 5 inside. As a result, the limestone 2 (CaCOs) becomes quicklime (Cab) and is supplied to the fluidized bed pre-reduction furnace 6.

In the fluidized bed pre-reduction furnace 6, coal 7 and oxygen or oxygen-containing gas 8 are blown into the preheated ore and quicklime in a fluidized state. Coal 7 is exchanged and thermally decomposed by partial combustion due to reaction with oxygen.As a result, coal 7 generates 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 decarboxylating the gas is reduced to 700 to 90% by heat exchange with the fuel gas 12 from the fluidized bed preliminary reduction furnace 6.
After being heated to 00°C, it is blown into a fluidized bed pre-reduction furnace 6. Reducing gas 11 blown into the fluidized bed preliminary reduction furnace 6
is mixed with the reducing gas produced by thermal decomposition of coal 7 to reduce the high temperature granular iron ore in a fluidized state and produce 13 in the reduction.

Moreover, the quicklime 14 produced in the fluidized bed preheating furnace 3 is charged into the fluidized bed prereduction furnace 6 together with the preheated ore, and the gas in the fluidized bed prereduction furnace 6 is desulfurized.

Next, the quicklime 14 is discharged from the fluidized bed preliminary reduction furnace 6 together with the reduced ore 13 and the char 9.

To the thus obtained reductions 11i, 13, char 9 and quicklime 14, carbonaceous materials such as coal and coke necessary for the heat balance in the smelting reduction furnace IO are added from the outside and kneaded. The mixture is formed into briquettes 16 by an agglomeration device 15 such as a briquette machine, and then charged into the melting reduction furnace 10 by a charging device 17.

In this melting 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 panel 20. Then, the carbonaceous material contained in the briquette 16, the bottom-blown surface 2
Carbon material being blown in with oxygen from 0, charging device 17
The carbonaceous material such as coke 21 supplied from the top blowing lance 18 reacts with the oxygen supplied from the top blowing lance 18, and generates a large amount of heat in the melting reduction furnace 10.

Due to this generated heat, reduced tfL1 in the briquette 16
3 melts and reduction progresses to become hot metal 22.

On the other hand, the gangue in the reduced ore 13 reacts with the carbon material and the quicklime 14, and slag 23 is generated. This slag 23 is stored in the melting reduction furnace IO, and its amount increases as time passes. Therefore, the slag 23 is discharged out of the furnace intermittently or continuously.

[Problem that the invention seeks to solve]

like this? In the 8 fusion reduction method, as is clear from the development process, it is a low grade fine ore.

It is assumed that steam coal, etc. will be used. Therefore, it is necessary to efficiently collect and reuse the dust generated during the treatment process.

For the purpose of collecting and reusing this dust, JP-A No. 56-1
In Publication No. 05409, floating dust contained in exhaust gas discharged from a fluidized bed pre-reduction furnace is collected by a cyclone installed at the furnace outlet, and the collected dust is cut into the furnace through a downcomer pipe by a gas trap installed below the cyclone. ing.

However, since the gas seal of the gas trap is metal-touch, the seal is incomplete. However,
In a fluidized bed pre-reduction furnace equipped with an external circulation device, reducing gas is blown into the furnace at a gas flow rate and pressure such that the iron ore filled in the furnace is scattered. For this reason, a large fluidization pressure m is generated in the fluidized bed pre-reduction reactor, and this comes to be applied to the gas trap of the external circulation device. Therefore, when the seal of this gas trap is incomplete, reducing gas blows out of the system. In addition, due to the high temperature atmosphere,
The gas trap is prone to deformation and the gas seal becomes more imperfect.

When reducing gas blow-through occurs in the Wj ring system in this way,
Particles are re-entrained in the cyclone, reducing the efficiency of collecting particles suspended in the exhaust gas. Moreover, the unreacted reducing gas in the lower part of the fluidized bed pre-reducing furnace directly leaks out of the system, resulting in a reduction in the reducing gas utilization rate. Furthermore, the fluidization state of the powder in the fluidized bed pre-reduction furnace becomes unstable. Therefore, the reduction reaction that effectively utilizes the fine ore cannot be carried out smoothly.

Therefore, an object of the present invention is to make the reduction reaction in the fluidized bed pre-reduction furnace smooth by completely sealing the external circulation path with gas.

[Means for solving problems]

In order to achieve the purpose of the extra-core circulation device of the present invention,
A cyclone is installed at the outlet of the fluidized bed pre-reduction furnace, and the 3-cycle cyclone is connected to a pneumatic feeder via a descending connecting pipe with a pressure equalization header installed in the middle, and a gas blowing header provided on the pneumatic feeder is connected to the cyclone. It is characterized by being divided into a plurality of headers whose carrier gas amount is independently adjusted.

[Effect]

In the fluidized bed pre-reduction furnace used in the smelting reduction method,
Fine ore with a large specific gravity is used as the raw material to be fluidized, and the fine ore is dispersed and fluidized at a high particle concentration. Therefore, the fluidization pressure drop of the raw material particles in the fluidized bed pre-reduction furnace becomes extremely large, ranging from several thousand to tens of thousands of columns of water. Therefore, since this large pressure difference is directly applied to the external circulation system, high sealing performance is required.

In the external circulation path of the fluidized bed pre-reduction furnace, fine ore floating in the exhaust gas is collected by a cyclone and then returned to the fluidized bed pre-reduction furnace by a pneumatic feeder. At this time, it is also conceivable to simply connect the cyclone and the fine ore return device located below it with a downcomer pipe, and perform powder sealing by the fine ore flowing down therein. However, in this case, a considerable length of downcomer tube is required in order to obtain the powder pressure necessary for sealing.

Therefore, in the present invention, a pressure equalizing header is provided in the middle of the descending connecting pipe, and by releasing the internal pressure of the pressure equalizing header into the fluidized bed pre-reduction furnace, the pressure necessary for sealing is built up, and the descending connecting pipe is This prevents it from becoming excessively long.

In addition, the blowing header that blows carrier gas into the pneumatic feeder in order to send the fine ore from the pneumatic feeder to the fluidized bed pre-reduction furnace has a split configuration. A flow rate adjustment valve is provided in each carrier gas blowing conduit so that the flow rate of the carrier gas supplied to each split header can be adjusted independently. By operating this flow rate adjustment valve, the amount of fine ore sent from the pneumatic feeder to the fluidized bed pre-reduction furnace is adjusted. Therefore, since the circulation amount can be adjusted, it is possible to maintain the reduction reaction in the fluidized bed pre-reduction furnace in a favorable manner.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained with reference to Examples.

FIG. 1 schematically shows the fluidized bed pre-reduction furnace in this example.

Reducing gas 11 is blown into the fluidized bed preliminary reduction furnace 6 at a superficial velocity increased to such an extent that the t51 ore is scattered within the furnace. The particles of fine ore scattered thereby are discharged from the outlet of the fluidized bed pre-reduction furnace 6 together with the exhaust gas. The discharged fine ore particles are collected by a cyclone 24 provided at the outlet of the fluidized bed pre-reduction furnace 6, and the cyclone 24
It is temporarily stored in a hopper 25 located below. Next, the fine ore particles are sent from the hopper 25 to a pneumatic feeder 26, and returned to the fluidized bed pre-reduction furnace 6 by the pneumatic feeder 26. In this way, the fine ore is pre-reduced while circulating between the fluidized bed pre-reduction furnace 6 and the external circulation path.

At this time, a descending connecting pipe 27 connecting the hopper 25 below the cyclone 24 to the pneumatic feeder 26
A and 27b are filled with powder flowing down and sealed with the powder. If this powder sealing were to be performed using a single downward connecting pipe, a considerably long downward connecting pipe would be required.

Therefore, in this example, the descending connecting pipes 27a, 27b
A pressure equalizing header 28 is provided in the middle, and this pressure equalizing header 28 and the free board of the fluidized bed pre-reducing furnace 6 are connected by a pressure guiding pipe 29.

Inside the pressure equalizing header 28, as shown in detail in FIG. 2fa), powder a remains at a predetermined angle of repose.

That is, a space 30 is formed between the powder a and the inner wall of the pressure equalizing header 28. Therefore, the reducing gas 11 that has passed through the lower descending connecting pipe 27b flows into the pressure equalizing header 28 and is collected in the space 30. However, since the impulse pipe 29 is opened in this space 30, the reducing gas 11 collected in the space 30 is returned to the freeboard above the fluidized bed pre-reduction furnace 6 through the impulse pipe 29, and the reducing gas 11 is returned to the freeboard above the fluidized bed pre-reduction furnace 6. It is reused in the furnace 6 to reduce iron ore.

On the other hand, in the descending connecting pipe 27a above the pressure equalizing header 28, only a pressure difference corresponding to the pressure loss of the cyclone 24, for example, a pressure difference of several hundred am of water column or less, is generated. Therefore, gas sealing in the descending connecting pipe 27a is almost completely performed, and the collection efficiency of the cyclone 24 is not adversely affected.

The pressure equalizing headers used here include those shown in FIG. 2(b) and +1. ) is also available in the format shown below. In other words, FIG. C1 indicates its internal state.

The pneumatic feeder 26 disposed below the pressure equalizing header 28 is shown in FIG.

A diffuser plate 33 is provided at the bottom of the pneumatic feeder 26 to disperse the carrier gas 32 into the internal space of the pneumatic feeder 26. In this example, a perforated plate is used as the diffuser plate 33. Further, as the carrier gas 32, the reducing gas 11 blown into the fluidized bed pre-reducing furnace 6 can be branched and used. When this reducing gas is used as a carrier gas, the atmosphere inside the fluidized bed pre-reduction furnace is not disturbed. Also,
Even in the external circulation system, reduction of fine ore can be expected to some extent.

The particles of fine ore are suspended and fluidized by the carrier gas 32 blown into the pneumatic feeder 26 through the diffuser plate 33 , creating a circulating flow toward the fluidized bed pre-reduction furnace 6 .

This v! ii In order to control the flow over a wide range, the third
As shown, a blow header 34 for carrier gas 32
is split into multiple split headers.

Next, with reference to FIG. 3, the circulation of fine ore from the pneumatic feeder 2G to the fluidized bed preliminary reduction furnace 6 will be explained.

In the example shown in FIG. 3, the blowing lid 34 is divided into the divided soda
It is divided into three parts: ~34c. A flow rate adjustment valve 3 adjusts the flow rate of the carrier gas 32 for each divided unit.
5a to 35c are provided. These flow rate adjustment valves 35
By individually controlling a to 35c, the amount of fine ore to be circulated is adjusted.

If only the carrier gas 32 is blown into the blowing via the ivy 34, the fine ore remains at rest in the pneumatic feeder 26 at an angle of repose, as shown in FIG. 3 la.

From this state, open the flow rate adjustment valve 35a to divide the ivy 34.
When the carrier gas 32 is blown into the carrier gas 32, as shown in FIG. On the other hand, when all the flow f! adjustment valves 35a to 35c are opened and the carrier gas 32 is blown into the split headers 34a to 34c, the fine ore above the entire blowing header 34 is fluidized and passes through the pipe 36 into a fluidized bed. It flows into the pre-reduction furnace 6. In this way, the flow rate of the fine ore flowing into the fluidized bed pre-reduction furnace 6 via the pipe line 36 can be adjusted depending on how many of the division headers 34a to 34c the carrier gas 32 is blown into. can.

In addition, when the carrier gas 32 is blown into the ivy 34a to 34c to all the divisions, if the amount of carrier gas 32 blown into the division header 34a on the fluidized bed pre-reduction furnace 6 side is increased, the carrier gas 32 will be blown into the pneumatic feeder 26. Since a flow toward the fluidized bed pre-reduction furnace 6 occurs in the fine ore, it becomes possible to send the fine ore to the fluidized bed pre-reduction furnace 6 effectively.

In addition, in order to generate a flow toward the fluidized bed pre-reduction furnace 6, as shown in FIG. 4 (8), the fluidized bed pre-reduction furnace 6
The air diffuser plate 33c of the split header 34c on the opposite side, that is, below the downcomer pipe 27, may be tilted, and the slit nozzle 37 directed in the horizontal direction may be formed there.
When using this horizontally directed slit nozzle 37,
The powdered ore falling down the downcomer pipe 27 is passed through the fluidized bed preliminary reduction furnace 6.
This will cause a horizontal flow towards
The fine ore can be smoothly fed into the fluidized bed pre-reduction furnace 6.

In the example described above, a perforated plate is used as the diffuser plate 33, but the diffuser plate 33 is not limited to this. For example, as shown in FIG. A cylindrical nozzle 39 having an opening 38 can also be attached to the diffuser plate 33. In this case, it is possible to prevent fine ore from falling into the blowing header 34 and clogging the carrier gas 27 supply pipe. be done.

Note that the opening 38 provided on the side of this cylindrical nozzle 39
The area of the downcomer pipe 27 is increased on the fluidized bed pre-reduction furnace 6 side
By making it smaller on the side, it is possible to give a flow toward the fluidized bed pre-reduction furnace 6 to the fine ore.

〔Effect of the invention〕

As explained above, in the extra-furnace circulation device of the present invention, there is a connection between the cyclone provided at the outlet side of the fluidized bed pre-reduction furnace and the pneumatic feeder that returns the collected ore to the fluidized bed pre-reduction furnace. , are connected by a descending connecting pipe equipped with a pressure equalizing header.

Therefore, the pressure necessary for sealing can be maintained in the downcomer pipe below the pressure equalizing header, and the pressure is not transmitted to the downcomer pipe above the pressure equalizing header.

Therefore, even if the pressure required for sealing is increased, the cyclone is not adversely affected, and the down-connection pipe can be shortened. Furthermore, since gas leakage to the cyclone can be reduced to almost zero, it is possible to maintain good collection efficiency of fine ore by the cyclone.

Furthermore, since the reducing gas sent into the descending connecting pipe at high pressure is sent into the fluidized bed pre-reduction furnace via the impulse pipe, it is possible to increase the utilization rate of the reducing gas while preventing leakage to the outside of the system. .

On the other hand, the fine ore collected by the cyclone is returned to the fluidized bed pre-reduction furnace by a pneumatic feeder that can adjust the delivery flow rate, so the powder passing through the fluidized bed pre-reduction furnace and the external circulation path is It becomes possible to smooth the flow of the ore and maintain an appropriate fluidization state in the fluidized bed pre-reduction furnace.

As described above, the extra-furnace circulation device of the present invention exhibits excellent effects in handling powder, making it easier to use low-grade steelmaking raw materials, and improving the productivity and economy of hot metal production by the smelting reduction method. It is intended to improve

[Brief explanation of drawings]

Figure 1 shows a fluidized bed preliminary reduction furnace equipped with an extra-furnace circulation device according to an embodiment of the present invention, and Figure 2 shows the outside of the furnace. Details of the pressure equalizing header provided in the a-ring device are shown, FIG. 3 also shows details of the pneumatic feeder, and FIG. 4 shows another example of the pneumatic feeder. Moreover, FIG. 5 is a diagram showing the flow of the smelting reduction method previously developed by the present inventors.

Claims (1)

[Claims] 1. An extra-furnace circulation device attached to a fluidized bed pre-reduction furnace for pre-reducing fine ore, which includes a cyclone at the outlet of the fluidized bed pre-reduction furnace and a descending connecting pipe with a pressure equalizing header in the middle. A fluidized bed reserve characterized in that the cyclone is connected to a pneumatic feeder, and a gas blowing header provided on the pneumatic feeder is divided into a plurality of headers whose carrier gas amount is independently adjusted. Extra-furnace circulation device for reduction furnace.