JPH01319620A - Method of operating smelting reduction furnace - Google Patents

Abstract

PURPOSE:To assure the high-temp. necessary for smelting reduction of a metal and to improve productivity by heating powder coal to a specific temp. to lump the coal, then charging the lumped coal into the furnace at the time of blowing the powder coal from the furnace wall charge ports provided to the side wall between furnace top charge ports and tuyeres. CONSTITUTION:A packed layer 2 of a solid carbon reducing agent is formed in the lower part in the vertical reduction furnace 1 and a fluidized bed 3 of the solid carbon reducing agent is formed above the same. Powder ore 5 is blown from the tuyeres 4 provided along the outer circumference of the side wall of the reduction furnace 1 to effect the smelting reduction of the metal oxide. The wall charge ports 8 are provided to the side wall between the furnace top charge port 7 and the tuyeres 4 and the powder coal to constitute the solid carbon reducing agent 6 is charged from these ports 8 and is lumped while the coal is heated to 500-1200 deg.C by the sensible heat and/or latent heat of the in furnace gas flowing into the ports 8. The adequate packed layer 2 is formed by using the powder coal prepd. by mixing the powder coal having a high viscosity and low viscosity. The packed layer 2 of the coarse- grained solid coal reducing agent 6 is positively formed in this way at the low initial cost and the productivity of a molten metal 11 is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of operating a vertical smelting reduction furnace, and relates to an improvement in technology for producing molten metal from powdered ore. More specifically, in order to secure the high temperature necessary to melt down the metal,
The smelting reduction furnace is used to agglomerate and charge powdered coal so that a packed bed of relatively coarse carbon-based solid reducing agent can be sufficiently formed in the furnace.

[Prior art 1] As a method for producing molten metal (e.g., pig iron) in a vertical furnace using powdered ore and a carbon-based solid reducing agent directly, for example, molten metal production from powdered ore containing metal oxides is used. Method(
JP-A-62-56537) has been proposed.

This method maintains a packed bed of carbon-based solid reducing agent in a furnace and a fluidized bed above it, and charges powdered ore together with oxygen-containing gas into the fluidized bed of carbon-based solid reducing agent. Gas is blown into a packed bed of carbon-based solid reducing agent.

When using pulverized coal here, once a month from a vertical reduction furnace
The coal is carbonized by pre-treating it in a separate coal pre-treating furnace that introduces the high-temperature gas that is released, turning it into powdered coke or char, which is then charged from the coal pre-treating furnace to a vertical reduction furnace. It has become. Alternatively, powdered coal may be charged directly into the furnace without undergoing the above-mentioned pretreatment.

[Problem to be solved by the invention 1: When charging pulverized coal into a vertical reduction furnace, the method of pre-treating the pulverized coal requires a carbon material pre-treatment furnace, resulting in high equipment costs. There are problems in that it is difficult to maintain the equipment, and extra work is required to maintain the equipment.

On the other hand, there is a consensus that the method of directly charging raw coal into a vertical reduction furnace without coking the powdered coal does not require a carbon material pretreatment furnace, making the equipment cheaper. In the method of charging coal from the furnace top or from the furnace wall charging port above the tuyeres, the temperature inside the furnace reaches a high temperature of 1400°C, so the coal is rapidly heated and cracks are formed due to vaporization and expansion of its volatile matter, causing it to become powder. There is a tendency to become Therefore, coarse grained coal is difficult to remain, making it difficult to form a sufficient packed bed, making it difficult to maintain the high temperature necessary for melting and reducing metals, and making it difficult to improve productivity. be.

The present invention has been made to solve the above problems, and has a method of reducing the installation cost and actively forming a packed bed of coarse-grained carbon-based solid reducing agent to increase the productivity of molten metal. The purpose of this invention is to provide a method for operating a smelting reduction furnace from powdered ore that can be processed.

Further, in this method of operating a smelting reduction furnace, the dust recovered from the gas generated in the vertical reduction furnace can be mixed with other powdered coal to be used as a carbon-based solid reducing agent for the packed bed in the furnace.

[Means for Solving the Problems] A method of the present invention for achieving the above object will be explained with reference to the drawings. FIG. 1 schematically shows a melting reduction furnace. A packed bed 2 of a carbon-based solid reducing agent is formed in the lower part of the vertical reduction furnace 1, a fluidized bed 3 of a carbon-based solid reducing agent is formed above it, and Powdered ore 5 is blown into the vertical reduction furnace 1 through the provided tuyere 4 to melt and reduce metal oxides.

In the present invention, a furnace wall charging port is provided on the side wall between the furnace top charging port and the siding of a vertical reduction furnace, and powdered coal to be a carbon-based solid reducing agent is supplied from the furnace wall charging port to a temperature of 500°C to 1200°C. It is characterized by being turned into lumps while being heated, and then charged into a vertical reduction furnace.

In this case, sensible heat and/or latent heat of the furnace gas flowing into the furnace wall charging port can be used to heat the powdered coal charged from the furnace wall charging port. In addition, a suitable packed bed is formed by charging powdered coal, which is a mixture of strongly coagulated powdered coal and weakly coagulated powdered coal, from the furnace wall charging port. Furthermore, by mixing the dust collected from the exhaust gas of the vertical reduction furnace with the powdered coal charged from the furnace wall charging port, it is possible to make effective use of Tus 1 to 1.

Note that the term pulverized coal here refers to coal with a particle size of less than 50 mm.

The first section is pulverized coal 6 (6b, 6
This figure shows an example of the charging position to the vertical furnace 1 in c).

Inside the vertical furnace 1, a packed bed 2 is formed at the bottom by a carbon-based solid reducing agent with a relatively large particle size, and a fluidized bed 3 is formed at the top by a carbon-based solid reducing agent with a relatively small particle size. ing. The fine ore 5 is blown into the furnace through the tuyere 4, melted and reduced by the high-temperature carbon-based solid reducing agent and gas in the furnace, and accumulates as molten metal 11 and molten slag 12 in the lower part of the furnace. Molten metal and molten slag are discharged out of the furnace continuously or intermittently depending on the operation of the vertical furnace.

A free board 9 is formed at the top of the vertical furnace 1 to prevent the carbon-based solid reducing agent having a relatively small particle size forming the fluidized bed 3 from flying out of the vertical furnace. A certain amount of the carbon-based solid reducing agent is not discharged to the outside of the vertical furnace 1 together with the generated gas 10, but is collected as a dust 1 by a cyclone or the like (not shown).

The charging position of the powdered coal 6 (6a, 6b, 6c) is selected and the charging amount is controlled depending on its particle size, properties such as composition, furnace internal conditions, amount of dust generated, and the like. Coal with a relatively large particle size is charged through the furnace top lower and furnace wall charging port 8, and coal with a relatively small particle size is charged or injected through the tuyere 4. The collected dust, which has a generally small particle size, is charged or blown into the furnace through the tuyere 4. The reason why the charging position is selected based on the particle size is that even if a carbon-based solid reducing agent with a small particle size is charged into the furnace, the rising gas flow inside the furnace will cause it to be returned to the outside of the vertical furnace. This is because they tend to be discharged into
This is because when charging from the tuyere 4, the fuel is combusted by the air and/or oxygen blown into the tuyere at the same time, so it can be effectively used as fuel.

Coal with a relatively small particle size, e.g. 3 mm or less, and dust collected from the gas generated in a vertical reduction furnace (containing a carbon-based solid reducing agent with a fine particle size) are collected at the top of the furnace with four or more tuyeres. When charging coal from the charging lower or furnace wall charging port 8 and making effective use of it, it is necessary to be creative.6 In other words, coal softens, melts, or cakes within a certain temperature range. Utilizing this property, we can agglomerate carbon-based solid reducing agents and collection dust 1~ with small particle size (
By charging the carbonaceous solid reducing agent into the furnace, the packed layer of carbon-based solid reducing agent can be enlarged, which promotes melting and reduction.
(6) Increased production of molten metals is expected.

In order to coarsen this pulverized coal having a small particle size, in the present invention, a furnace wall charging port 8 for pulverized coal is formed in the furnace wall without using a pretreatment furnace, and a charging passage of this furnace wall charging port is formed. is used as a pre-processing passage, where the powdered coal is heated by the sensible heat of the gas in the furnace and is agglomerated while being moved by a busher 15 or the like.

As a heating source for the coal charged through the furnace wall charging port 8, it is wise to use the sensible heat of the gas in the furnace.

The temperature, especially around 500°C, can be adjusted through the furnace wall charging port 8.
It can be controlled by the amount of gas flowing into the furnace and the coal charging speed. For more flexibility, coolant from outside the furnace (gas, liquid, solid, etc.) may be used.

When heating and charging coal from the furnace wall charging port, it is preferable to apply an appropriate mechanical load to the coal during temperature rise in order to produce a relatively strong carbon-based solid reducing agent. This increases the packing density of coal particles, reduces voids, and promotes bonding between particles. The mechanical load is 50-200 kg/crn per unit area of coal seam.
' is better. In the case of normal coal molding, a binder is added, but in the case of this method, the softened and molten material generated from the coal by heating functions to fuse the coal particles themselves and other coal, so a binder cannot be used. It is possible to produce a carbon-based solid reducing agent of suitable strength that can be used in this process. Of course, if a stronger carbon-based solid reducing agent is required, a small amount of binder may be added.

[Function] When charging coal with large particle size into a vertical furnace, if atmospheric temperature coal is directly charged into a high temperature furnace, the temperature inside the furnace is high, so rapid heating will cause thermal cracking. The carbon-based solid reducing agent has a relatively small particle size, which may make it difficult to form a packed bed in the lower part of the furnace.

FIG. 2 is a graph showing the particle size of coal produced after the volatile matter has been generated at that temperature when coal is subjected to rapid heat treatment. From Figure 2, the rapid heating temperature that can avoid powdering is 500℃~1.200℃.
It can be seen that the range of ``C'' is appropriate.Also, in the case of strongly caking coal, the particle size is relatively small at 500℃, so
Appropriate steepness depending on the viscosity (brand) of the coal! ! J! I can see that the temperature is different.

When the IB degree is too low than 500° C., both the strongly coking coal and the weakly coking coal tend to soften and melt, making it difficult to maintain their shape.

On the other hand, when the rapid heating temperature was set to 1250° C. to 1400° C., many cracks appeared in the coal due to the rapid heating, and most of the coal became fine particles.

Therefore, based on such data regarding various types of coal, when charging coal into a furnace, it is necessary to heat it in the pre-treatment passage of the furnace wall charging port 8 at a temperature in the range of 500°C to 1200°C and to lump it while charging. It was found that this method is effective in preventing powdering due to rapid heating and forming a packed bed of coarse carbon-based solid cyclic agent.

Next, we will discuss the caking properties of the coal used. When producing coke for use in the blast furnace ironmaking process, a total amount of 33
It is crushed into pieces smaller than mm, which are then carbonized and baked in a coke oven. In the case of the process of the present invention, that is, a process in which a fluidized bed of a carbon-based solid reducing agent is formed above a vertical reduction furnace and a packed bed of a carbon-based solid reducing agent is formed below, the carbon-based solids forming the packed bed are A reducing agent with lower strength than in the case of blast furnace iron making can be used.

Coal (for example, with a particle size of 3 mm or more) can be used as it is without coking, but in that case, if only weakly caking coal is used, the strength of the carbon-based solid reducing agent produced will be weak, and it will not cause strong caking. If only carbonaceous coal is used, the resulting carbon-based solid reducing agent may be weakened. Therefore, for example, by combining powdered coal 6b with weak caking property and coal 6c with strong caking property, it is possible to produce a carbon-based solid reducing agent with stable strength and particle size. Note that a classification device 14 may be provided to separate coal of 1 mm or less and transport it to the tuyere.

When a fluidized bed is formed above a vertical furnace, a certain amount of dust (mostly carbonaceous) is generated, so it is possible to separate and collect the generated dust using a separation device such as a cyclone and reuse it. Such tasses 1~ are generally tuyeres 4
It is reused by being blown into the furnace, but if there is a restriction on the amount of blown coal, it is mixed with coal from the furnace wall charging port 8 and used. By mixing with coal, the caking properties of coal can be utilized and a coarse carbon-based solid reducing agent is produced. At this time, if the ratio of TAS1- is too high, as illustrated in FIG. 3, the coarse grains will not be sufficiently coarsened due to the lack of caking content, so it is important to adjust the ratio.

[Example 1 A vertical test furnace with a configuration as shown in Fig. 1 (hearth diameter 1.2 m)
φ) produced pig iron using iron ore and coal. In the example, coal was charged from the furnace wall charging port 8 while being heated. The comparative example did not use a furnace wall charging port.

Example 1) Powdered iron ore MBR ore 2 particle size 2 mm or less Preliminary reduction rate = 51% Supply amount 607 kg/H 2) Coal Witbank ° weak caking, particle size 30 mm or less, 800
kg / I-1 Saus Yakut, strong caking, particle size 20 mm or less, 40
kg / H 150 kg of coal with a diameter of 10 mm or more from the furnace top charging lower
/ +( was charged. From the two furnace wall charging ports 8, 1.
658 kg/H of coal of less than 0 mm was heated to 500° C. to 1100° C. for about 6 minutes by the sensible heat of the gas in the furnace.

32 kg/H was blown into the tuyere.

3) Air flow rate 1.4.80 N m' / HO2a degree 3
0% Temperature 580°C 4) Tuyere injection (injection from the upper opening) Coal injection amount Particle size 1. mm or less 32 kg/H Dust injection amount 59 kg/H Particle size: 2 mm or less Main component C72% 5) Pig iron production: 10.4 t/d 6) Slag generation amount 4.9 t/d Comparative example All as before of coal was charged from the top of the furnace.

1) Powdered iron ore MBR ore 2 grain size 2 mm or less Preliminary reduction rate = 50% Supply amount 558 k, g / + (2) Coal Witbank 2 grain size 30 mm 1u 980 kg/l-1 Sausyakut, grain size 20 m m or less 50 kg
/ H 3) Air flow rate 148 ONn/t IO2 concentration, 30
% Temperature 585℃ 4) Damage 1-Blowing (Blowing from the upper tuyere) Blow rate: 95
kg/l (particle size: 2 mm or less, main component C: 71%) 5) Pig iron production: 9.5 t/d 6) Slag generation: 4.8 t/d The coarsening rate increased, the pulverized carbonaceous material decreased, and the proportion discharged outside the smelting reduction furnace decreased, so the amount of charged coal decreased accordingly. In addition, as the amount of coal charged decreased, the amount of heat for the decomposition of volatile matter in the coal and the amount of heat that became sensible heat due to an increase in heat content also decreased, and the amount of pig iron produced increased.

[Effects of the Invention] As described above, according to the present invention, powdered coal charged into the furnace from the furnace wall charging port is heated and lumped without installing a carbon material pretreatment furnace separately from the vertical reduction furnace. Therefore, it is possible to secure a sufficient high temperature necessary for melting and reducing the metal. As a result, the productivity of molten metal increases, resulting in an excellent effect of reducing manufacturing costs.

[Brief explanation of the drawing]

Fig. 1 is a flow sheet of a melting reduction furnace explaining an example of the method of the present invention, Fig. 2 is a graph showing the rapid heating temperature and the weight fraction of the produced carbon-based solid reducing agent with a particle size of 10 mm or more, and Fig. 3
The figure is a graph showing the influence of the dust mixing ratio. 1- Vertical falling smelting reduction furnace 2... Packed bed of carbon-based solid reducing agent 3... Fluidized bed of carbon-based solid reducing agent 4... Tuyere 5... Fine ore 6... Carbon-based solid reducing agent 7 Furnace top charging inlet 8 Furnace wall charging inlet 9 Free board 10 Generated gas 11 Molten metal 12 Molten slag 13 Air and/or oxygen 14...classifier 15...butsusha

Claims (1)

[Claims] 1. A packed bed of a carbon-based solid reducing agent is formed in the lower part of the vertical reduction furnace, a fluidized bed of the carbon-based solid reducing agent is formed above it, and the outer periphery of the side wall of the vertical reduction furnace is In a method for melting and reducing metal oxides by blowing powdered ore into a vertical reduction furnace through a tuyere installed along the A melting process characterized in that a wall charging inlet is provided, and from the wall charging inlet, powdered coal to be used as a carbon-based solid reducing agent is lumped while being heated to 500°C to 1200°C and charged into a vertical reduction furnace. How to operate a reduction furnace. 2. The method of operating a smelting reduction furnace according to claim 1, wherein sensible heat and/or latent heat of furnace gas flowing into the furnace wall charging port is used to heat the powdered coal charged from the furnace wall charging port. 3. The method of operating a smelting reduction furnace according to claim 1 or 2, characterized in that powdered coal, which is a mixture of strongly caking powdered coal and weakly caking powdered coal, is charged from a furnace wall charging port. 4. The method for operating a smelting reduction furnace according to any one of claims 1 to 3, characterized in that dust collected from the exhaust gas of the vertical reduction furnace is mixed into powdered coal charged from a furnace wall charging port.