JPS5918453B2 - Method for producing molten metal from powdered ore containing metal oxides - Google Patents

Description

[Detailed Description of the Invention] Various methods have been put into practical use as smelting methods for iron ore and metal oxides, but new smelting methods have been developed to cope with constraints from resources, energy, the environment, etc. expected in the future. development is desired.

The shape of ores containing iron oxide or various metal oxides tends to be less lumpy and more powdery.

Particularly in order to improve the quality of low-grade ore, ore beneficiation such as flotation and magnetic separation is performed, and it is expected that the proportion of powdered iron will increase in the future.

Currently, many smelting furnaces in operation require lump ore or pre-processed agglomerated ore as raw material, and powder ore is agglomerated into pellets, sinter, briquettes, etc. .

Agglomeration requires extra raw materials such as solvents and binders, and extra energy such as fuel and power.

Furthermore, when a firing furnace is used for hot agglomeration, NOx, SOx, and dust are normally generated, and if these are emitted as they are, they can cause air pollution, so facilities must be constructed to prevent them. However, this requires a large amount of cost.

On the other hand, as a technology that can directly use powdered ore, roasting or reduction technology using a fluidized bed has been put into practical use in some areas.

However, when the generated powdery prereduced ore is used in an electric furnace, converter, or other melting furnace, a binder is often added and agglomerated into briquettes or the like.

Methods have also been proposed in which the powder is used in powder form using an arc furnace or plasma, but this method consumes a huge amount of electricity and is inferior to international competitiveness in regions like Japan where electricity costs are high.

As a method of supplying the amount of heat necessary for reduction and melting, there is a method that mainly uses air to burn coke without using electricity or pure oxygen, and uses the combustion heat.
Blast furnaces for smelting copper and other materials use this method.

In particular, iron-making blast furnaces are known to be extremely efficient as smelting furnaces due to advances in operating technology and larger furnaces.

However, the blast furnace for steelmaking is a high shaft furnace, and in order to ensure ventilation inside the furnace, lump ore or agglomerated ore as mentioned above is required, and the lump ore and coke are layered in the furnace. Since the coke is deposited, high strength coke is required.

In order to produce high-strength coke, it is necessary to use strong coking coal, which is expected to be in short supply in the future and is expensive, or to use modified coking coal when using weakly coking coal or steam coal. This method requires a high-quality binder, leading to an increase in manufacturing costs.

By the way, Japanese Patent Publication No. 34-2103 or Japanese Patent Application Publication No. 54
According to No. 142313, a method is proposed in which powdery pre-reduced ore obtained by pre-reducing fine ore is melted and reduced in its powder form, and according to the former method, the combustion improver for burning fuel is 85% The latter method uses pure oxygen.

In addition, in order to maintain the sump of the smelting reduction furnace at a high temperature, according to the former method, CO2/co
By generating a gas that has an oxidizing effect on Fe with a ratio of 1, the latter method maintains a high temperature by burning the carbon attached to the pre-reduced ore with pure oxygen. .

Furthermore, according to the former method, since the gas is oxidizing, the iron oxide is easily turned into slag in an unreduced state and discharged outside the furnace. Since non-uniformity tends to occur, there is a drawback that it is difficult to set the operating conditions of the melting furnace.

The object of the present invention is to provide a manufacturing method that eliminates and improves the various drawbacks of conventional or proposed methods of manufacturing molten metal from powdered ore containing metal oxides, This object can be achieved by providing the method according to the claims.

Next, the present invention will be explained in detail.

According to the present invention, a powdery carbon-based solid reducing agent is supplied to a pretreatment furnace, and a part of the high temperature gas generated in the vertical reduction furnace is introduced into the pretreatment furnace to fluidize the reducing agent. , perform pretreatment by heating.

On the other hand, powdered ore is charged into a pre-reduction furnace, and part of the gas generated in the vertical reduction furnace and the pre-treatment furnace is introduced to carry out fluidized reduction.

Furthermore, high-temperature gas containing oxygen is supplied into the vertical reduction furnace through a plurality of channels provided at the lower part of the vertical reduction furnace.

Then, the pre-reduced product pre-reduced in the pre-reduction furnace, the pre-treated product heated in the pre-treatment furnace, and flux if necessary are supplied into the vertical reduction furnace, and the pre-treated product is kept in a fluid state. The preliminary reduction products are melted and reduced by the heat and reducing gas generated by the combustion to form molten metal and molten slag, which are then discharged from the hearth to the outside of the furnace in a timely manner.

Next, the present invention will be explained with reference to the drawings.

Powdered carbon-based reducing agent is supplied from the carbon-based solid reducing agent supply device 1 to the pretreatment furnace 2, and part or all of the generated gas generated in the vertical reduction furnace 3 is introduced into the generated gas discharge device 4. The reducing agent is introduced into a pretreatment furnace 2 through a device 5, and is fluidized and heated in the pretreatment furnace 2 to perform a pretreatment of heating or carbonization to a required degree.

For example, when using powdered coal, the coal is carbonized by being pretreated in the pretreatment furnace 2 and discharged from the furnace 2 as powdered coke or char.

Incidentally, the powdered carbon-based reducing agent may be directly supplied to the vertical reduction furnace 3 without being treated using the pre-treatment furnace 2, but in the pre-reduction furnace 3 and other facilities, the carbon-based reducing agent containing hydrocarbons may be If gas or tar is required, or if the reducing agent needs to be preheated in order to facilitate combustion of the powdered carbon-based solid reducing agent in the vertical reduction furnace 3, the reducing agent may be preheated. Pretreatment using a pretreatment furnace 2 is particularly advantageous.

On the other hand, ore containing powdered metal oxides is supplied from the ore supply device 6 to the pre-reduction furnace 1, and part or all of the gas generated from the vertical reduction furnace 3 and/or the gas generated from the pre-treatment furnace 2 is supplied. Gas introduction device 8, 9 that generates part or all of the gas
The powdered ore is fluidized and heated in the furnace 1 to be pre-reduced to a required level.

The gas generated from the vertical reduction furnace 3 is N2. CO2CO2,N
2. N20, among others, reducing C09H
2 content is high, and from vertical furnace 3 900 to 1500
On the other hand, the gas generated from the pretreatment furnace 2 is discharged at a high temperature of N2. CO2CO2,N
2゜) (20, CnHm (CnHm represents hydrocarbon), among others, reducing C09H2 or C
It has a high content of nHm, and is discharged from the generated gas discharge device 2a of the pretreatment furnace 2 at a temperature of 300 to 800°C.

Therefore, in the preliminary reduction furnace 7, the powdered ore is subjected to fluid preliminary reduction by the reducing gas.

The pre-reduced product is discharged from the pre-reduction furnace 7 in a high temperature state by the discharge device 10, passes through the induction device 11, and if necessary, flux is added to the pre-reduced product supply devices 12, 13 and 14. The wastes are transported to one, two or three devices selected from among them, and then charged into the vertical reduction furnace 3.

Although the gas is transported to the supply devices 13 and 14, the gas generated in the vertical reduction furnace 3 is used as the transport gas, and in some cases, the pressure of the transport gas may be increased using the pressure booster 15 as a preliminary reduction. This is advantageous because it facilitates gaseous transport of the product.

On the other hand, the pretreated product pretreated in the pretreatment furnace 2 is discharged from the discharge device 16, passes through the induction device 17, and is optionally pressurized by the pressure booster 17a to supply the gaseous carbon-based solid reducing agent generated in the vertical reduction furnace. Devices 18, 19, 20
At least one device selected from the following is supplied into the vertical reduction furnace 3, and is burned in the furnace 3 by reacting with high temperature gas containing oxygen supplied from the supply device 21, or The metal oxide is brought into contact with the metal oxide in the pre-reduction furnace product that is supplied to the mold reduction furnace 3 and turned into a molten state, and the metal oxide is reduced to produce metal.

As the high-temperature gas containing oxygen, high-temperature air of 80° C. to 1300° C. heated using a gas heating furnace 22 such as a hot blast stove or oxygen-enriched air can be used.

By the way, in the upper region above the tip of the tuyere-shaped pretreated product supply device 20 in the furnace 3, the product is pretreated with a powdery carbon-based solid reducing agent or in a pretreatment furnace with a high temperature gas containing oxygen. As the powdered carbon-based solid reducing agent burns and generates high temperature, the pre-reduction product is heated and melted in this high temperature region, and is reduced and separated into molten metal and molten slag. It is stored in two layers in the lower part of the reduction furnace 3, and is discharged from the furnace from the discharge device 23 at a timely manner.

According to the present invention, as the carbon-based solid reducing agent supplied to the pretreatment furnace 2, any one of powdered coke, char, and coal, or two or three thereof, can be used.
Furthermore, when coal is used, inexpensive non-caking steam coal can also be advantageously used, and when coke is used, coke breeze generated when producing lump coke can be advantageously used.

Powdered ore supplied to the vertical reduction furnace 3 needs to be pre-reduced and quickly melted and reduced in the high temperature area inside the vertical reduction furnace 3. It is advantageous to preheat the material to a high temperature and charge it in a state with a high reduction rate, since this facilitates melting and reduction.

The optimal preheating temperature and prereduction rate will naturally vary depending on the type of metal oxide, the properties of the ore containing the metal oxide, and the system configuration used, but the preheating temperature and prereduction rate are approximately 400 to 1000°C, respectively. Good results can be obtained at 80%.

According to the present invention, a high-temperature gas of 800 to 1300°C containing oxygen is blown into the vertical reduction furnace 3 through the tuyere 21, so around the inner end of the tuyere-shaped carbon-based solid reducing agent supply device 20. reaches 2000-2500°C.

The shape of this tuyere 21 can be similar to the shape of the ironmaking blast furnace tuyere, but the temperature of the hearth sump can be set to 1400~
Since it is necessary to maintain the temperature at 1700°C, it is desirable that the inclination angle of the tuyere 21 at which it enters the furnace is within a range of 45° downward from the horizontal so that the high temperature gas directly hits the sump.

By the way, around the inner end of the supply device 20 is 2000 to 2500
In order to maintain the temperature at a high temperature of .degree. C., it is necessary to supply excess oxygen to this vicinity from the tuyere 21 as a high temperature gas containing oxygen.

However, this maintains the high temperature and at the same time increases the oxygen partial pressure in this area, which in turn causes re-oxidation of the molten pre-reduced ore and iron oxide contained in the discharged slag. concentration increases, which is unfavorable from the point of view of reduction.

In order to avoid such disadvantages, the carbon-based solid reducing agent supply device 2 is located below the tuyere 21 for supplying high-temperature gas containing oxygen.
By supplying the powdered reducing agent directly onto the surface of the molten slag from zero, the vicinity of the internal tip of the supply device 20 can be maintained at high temperature and in a reducing atmosphere.

Next, the present invention will be explained with reference to examples.

EXAMPLE The present invention was carried out using a test furnace using the following raw materials under the following conditions, and the results were as follows.

■) Powdered iron ore brand: MBR Ore particle size: 2 dragons or less Supply rate: 2610 kf/hr 2) Type of carbon-based solid reducing agent supplied to the pretreatment furnace Steam coal (F, C: 74.8% ) Particle size: 3mm or less Supply rate: 1110kf/hr 3) Airflow rate to the vertical reduction furnace: 2350 Nm3/11
r Blowing temperature: 900°C 4) Preliminary reduction rate of fine ore near 1% 5) Pig iron production: 1710kf/hr6) Slag discharge: 364 to 9/hr.

As described above, according to the present invention, (a) Since powdered ore is used without agglomerating, energy and expense for agglomeration are unnecessary, and NOx, which may be generated during agglomeration, is eliminated. Measures against SOx and dust are no longer required, and the gas generated in the vertical reduction furnace and pre-treatment furnace is used as a preliminary reduction gas for the ore, so there is no need to separately install reducing gas production equipment, and the reduction rate is relatively low. Pre-reduced ore with a reduction rate of 40-80% can be used without any problems, and an inexpensive carbon-based solid reducing agent can be used as a heat source, and in particular, non-caking coal powder can be used as a heat source. (e) The gas blown into the smelting reduction furnace is primarily preheated air, and expensive oxygen is not necessarily necessary. (e) Since the preliminary treatment, preliminary reduction, and smelting reduction are all performed in a fluidized state, there is no need to limit the supply location of the preliminary reduced ore to the vertical reduction furnace, and melting and reduction are easily performed.

It was found that it has many excellent characteristics.

Although iron ore is shown as an example, the present invention can also be practiced using nickel ore, manganese ore, chromium ore, or the like as a raw material.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view of an apparatus used to carry out the invention. 1...Carbon-based solid reducing agent supply device, 2...
... Pretreatment furnace, 2a ... Generated gas discharge device,
3... Vertical reduction furnace, 4... Generated gas removal device, 5, 8, 9... Generated gas introduction device, 6.
...Ore supply device, 7...Preliminary reduction furnace,
10...Preliminary reduction product discharge device, 11...
...Induction device, 12,13,14...Preliminary reduction product supply device, 15,17a...Pressorizing device, 18.19,20...Carbon-based solid Reducing agent supply device, 21...Tuyere for high temperature gas supply, 22...
... Gas heating furnace, 23 ... Molten metal discharge device.

Claims (1)

[Claims] 1. A method for producing molten metal in which a powdered ore containing a metal oxide is pre-reduced and then the pre-reduced ore is melted and reduced in powder form, in which a high-temperature gas containing oxygen is blown into the lower part. A pre-reduction furnace is used in which the supplied powdery ore is fluidized and reduced using a reducing gas that is generated from a vertical reduction furnace that has tuyeres and forms a fluidized bed of carbon-based solid reducing agent. Then, the powdered pre-reduced ore pre-reduced in the pre-reduction furnace is charged into the vertical reduction furnace in the form of a mixture with flux. A metal oxide-containing powder characterized in that a carbon-based solid reducing agent is additionally added into the furnace at a lower position and higher than the furnace sump, and high-temperature gas containing oxygen is blown from the tuyere. A method for producing molten metal from shaped ore. 2. The carbon-based solid reducing agent is obtained by carbonizing powdered coal in a pretreatment furnace using the gas generated in the vertical reduction furnace. 3. The method according to claim 1 or 2, wherein part or all of the generated gas is used as part of the reducing gas supplied to the preliminary reduction furnace.