JPS62228869A - Fluidized bed furnace with out-of-core circulating mechanism - 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 [Field of Industrial Application] The present invention relates to a fluidized bed furnace used when drying, heating, and reducing treatments are performed on powder particles maintained in a fluidized state under high pressure.

[Conventional technology]

BACKGROUND OF THE INVENTION Conventionally, powdered materials such as coal and lime have been treated in a fluidized bed furnace. In order to speed up the processing inside the fluidized bed furnace, a method has recently been adopted in which the inside of the furnace is maintained in a high-pressure fluidized state and the powder and granules scattered outside the furnace are treated separately. There is.

Further, the use of such a method of processing raw materials in a high-pressure fluidized state for preliminary reduction of iron ore is also being developed.

Until now, in order to reduce iron ore to produce hot metal,
Conventional methods include using a blast furnace and melting iron ore reduced in a shaft furnace in an electric furnace.

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 installation II 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 supply of highly coking coal is unstable because there is little production equipment available throughout the world, and its distribution is regionally uneven.

On the other hand, the method of reducing iron ore using a shaft furnace requires pretreatment to pelletize the iron ore, and has the disadvantage that it consumes a large amount of reducing agent and expensive natural gas as a heat source.

As an alternative to such conventional hot metal production technology, the smelting reduction smelting method is attracting attention. The melting reduction furnace used in this method is not limited by the raw materials used.
It was developed for the purpose of producing molten iron-based alloys using smaller-scale equipment.

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 lffi 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 the coal 7, reduces the hot powdery iron ore in a fluidized state, and produces the reduced ore 13.

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.

Reduced ore thus obtained 13. Carbon materials such as coal and coke necessary for the heat balance in the smelting reduction furnace 10 are added to the char 9 and quicklime 14 from the outside and kneaded. The mixture is then processed through an agglomeration device such as a briquette machine. 15 into a brigette 16, the charging device i! 17, it is charged into the melting reduction furnace IO.

In this melting and reduction process 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 slat 20. Then, the charcoal material contained in the briquette 16, the bottom blowing tuyere 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.

This generated heat melts the reduced ore 13 having six widths of Bricella, and the reduction progresses to become hot metal 22.

On the other hand, the gangue in the reduced ore 1-3 reacts with the carbon material and quicklime 14, and slag 23 is generated. This slag 23 is
It is stored in the melting reduction furnace 10, and its amount increases as time passes. Therefore, the slag 23 is intermittently or i
! l! Discharge to the outside of the furnace.

[Problem that the invention seeks to solve]

In this type of smelting reduction method, as is clear from the development process, low grade fine ore is produced.

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. Therefore, a large fluid pressure drop occurs in the fluidized bed pre-reduction reactor, which is 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 the reducing gas blows through in the circulation system in this way, the particles are re-scattering in the cyclone, reducing the efficiency of collecting particles floating in the exhaust gas. In addition, unreacted reducing gas in the lower part of the fluidized bed pre-reduction reactor directly leaks out of the system.
The reduction gas utilization rate will also decrease. 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.

This problem is not only a problem of pretreatment of iron ore in the iron ore melt reduction method, but also applies to the case of treating powder or granules in general in a high-pressure fluidized state.

Therefore, an object of the present invention is to process powder and granular materials in a fluidized bed furnace smoothly and quickly by completely sealing the gas in the external circulation path.

[Means for solving problems]

In order to achieve the objective, the fluidized bed furnace of the present invention is provided with a cyclone at the outlet of the fluidized bed furnace for collecting powder particles floating in the exhaust gas discharged from the fluidized bed furnace, and a descending connection equipped with a pressure equalizing header. The cyclone is connected to a granular material return device by a pipe, and the pressure equalizing header is connected to the inside of a fluidized bed furnace by a pressure pipe.

[Effect]

The operation of the present invention will be explained below with respect to the smelting reduction method. However, the present invention is not limited to this (also when processing powder or granules in a high-pressure fluid state,
Of course, this effect is exhibited.

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 loss of the raw material particles in the fluidized bed pre-reduction furnace becomes extremely large, ranging from several thousand meters of water to several tens of thousands of meters 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, the fine ore floating in the exhaust gas is collected by a cyclone and then returned to the fluidized bed pre-reduction furnace by a fine ore return device such as a pneumatic ivy 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, the downcomer pipe is required to be considerably longer 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.

〔Example〕

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

FIG. 1 schematically shows the fluidized bed (Li reduction furnace) in this example.

A reducing gas 11 is blown into the fluidized bed preliminary reduction furnace 6 at a superficial velocity high enough to scatter the fine ore inside 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 are temporarily stored in a hopper 25 located below the cyclone 24.
Next, the fine ore particles are sent from the hopper 25 to a pneumatic ivy feeder 26, and returned to the fluidized bed pre-reduction furnace 6 by the pneumatic ivy 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 conduit 29.

Inside the pressure equalization ladder 28, as shown in detail in FIG. 2, the 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 rising inside the lower descending connecting pipe 27b flows into the pressure equalizing header 28 and is collected in the space 30.

However, since the pressure impulse pipe 29 is opened in this space 30, the reducing gas 11 collected in the space 30 flows through the pressure impulse pipe 29.
The iron ore is then returned to the freeboard above the fluidized bed pre-reduction furnace 6 and reused in the fluidized bed pre-reduction 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 or less water columns 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.

In addition to the pressure equalizing headers used here, in addition to those shown in FIG. 1 in which the descending connecting pipes 27a and 27b have different diameters, there are also types shown in FIG. 3+al and fb). That is, FIG. 3 (al) is an example in which a constriction part 31 is provided in the middle of the descending connecting pipe 27, and the pressure impulse pipe 29 is opened into the space 30 created in the descending connecting pipe 27 by the constricting part 31. fbl indicates its internal state.

Further, in FIG. 1, a pneumatic feeder 26 is employed as a fine ore return device for feeding fine ore in the external circulation path into the fluidized bed preliminary reduction furnace 6. However, this fine ore return device is not limited to the pneumatic feeder, and for example, a rotary feeder as shown in FIG. 4 can also be adopted.

〔Effect of the invention〕

As explained above, in the external circulation system of the fluidized bed furnace of the present invention, a pressure equalizing header is provided in the middle of the descending connecting pipe that connects the cyclone and the powder return device. This allows the pressure required for the seal to be maintained in the downcomer pipe below the pressure equalizing header, without transmitting that pressure to the downcomer pipe above the pressure equalizing header. Since the cyclone is not adversely affected by increased pressure, the down-connection pipe can be shortened. Further, since gas leakage to the cyclone can be reduced to almost zero, the efficiency of collecting powder and granular materials by the cyclone can be maintained at a good level. In addition, in the smelting reduction method, the reducing gas sent into the descending connecting pipe at high pressure is sent into the fluidized bed preliminary reduction furnace through the impulse pipe, so the reducing gas can be utilized while preventing leakage outside the system. rate can be increased.

[Brief explanation of drawings]

FIG. 1 shows an outline of a fluidized bed furnace equipped with an external circulation device according to an embodiment of the present invention, FIG. 2 shows details of a pressure equalization header in the external circulation device, and FIG. 3 shows other details related to the pressure equalization header. FIG. 4 shows another example of the powder return device, and FIG. 5 shows the flow of the smelting reduction method previously developed by the present inventors.

Claims (1)

[Claims] 1. A cyclone is installed at the outlet of the fluidized bed furnace to collect the powder floating in the exhaust gas discharged from the fluidized bed furnace, and the cyclone is connected to the powder return device by a descending connecting pipe equipped with a pressure equalizing header. A fluidized bed furnace equipped with an extra-furnace circulation device, characterized in that the pressure equalizing header is connected to the inside of the fluidized bed furnace by a pressure guiding pipe.