JPS6360207A - Smelting reduction furnace and its operation - Google Patents

Abstract

PURPOSE:To prevent over-heating of the inner wall in a combustion chamber by setting plural of tuyeres around the furnace wall as sloping downward and toward tangential direction at plural steps and arranging nozzles, so as to swirl supplied metallic oxide flow along the side wall. CONSTITUTION:At each part around side wall in the smelting reduction furnace 21, the nozzles 22 are arranged slightly sloping downward at their tips and in plural steps. The tip of nozzle 22 is set toward tangential direction, so as to form the swirling flow. At the time of giving the supplied ore powder the swirling flow, the centrifugal force is applied to the ore powder, and so falling action is imparted against the ascending current of combustion gas generated in the furnace 21 and also the raw material supply is stably maintained. Oxygen is blown into the furnace 21 from a lance 23, such as double pipes, etc. At the time of operating by using the furnace having such a construction, the furnace lining at the inside of combustion chamber is protected by curtain effect of the ore powder and so the service life of the furnace lining is lengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical summary to which the invention pertains] The present invention relates to a smelting and reducing furnace for metal oxides, which is used to prevent overheating of the inner wall of a combustion chamber, and a method of operating the same.

[Prior Art] Melting reduction methods have rapidly attracted attention in recent years, and various improvements have been made.

When metal oxides are smelted and reduced using this technique, the reaction proceeds by a combination of steps: carbonization of the metal bath, decarburization of the metal bath, and heat transfer to the metal bath.

Inside this metal bath, there are parts that are in an oxidized state and parts that are in a reduced state, and carbon monoxide generated by reduction combines with oxygen above the metal bath to become carbon dioxide gas. The heat generated at this time is returned to the metal bath as a source of heat required during the reduction and decarburization reactions.

The three types of reactions mentioned above, namely carburization, decarburization and heat conduction, are carried out in the process by using carbon materials such as coke, coal, gas and oil, and oxygen and carbon monoxide such as metal oxides. This is done with oxygen to burn the gas into carbon dioxide.

In the generally known smelting reduction method, it is said that the reduction reaction of the carbon material proceeds in a granular layer of coke which is supplied in excess and floats on the slag and iron bath.

This reaction takes place in a rotating reactor, which allows for good mixing, and radiant heating transfers heat directly from the furnace to the iron bath.

Charcoal material is put into the iron bath in this state, but oil or gas is used instead of coal or coke. It can also be used directly.

Iron oxide, which has the function of a decarburization agent and is usually a source of iron, is desirably made as fine as possible, and the higher the grade of iron ore, the better the results can be expected.

As mentioned above, the heat generated by the oxidation of carbon monoxide is conducted to the iron bath by radiation and heats it, but in some cases it is also used to preheat the ore, and at this time the ore is placed in the iron bath. This radiant heat is also absorbed until it is moved, and the amount of heat transferred to the iron bath is approximately 1 to 1.56 cal/l·n to the material.

Most of this heat is generated by radiant heat from the high-temperature region, which can heat the ore to its melting temperature.

By the way, the molten iron oxide that is the subject of this study has the property of easily corroding the lining material in the smelting reduction furnace, so if effective measures for extending the life of the furnace are established, this tumor can be eliminated. This will be a major contribution to the industry.

On the other hand, for example, when obtaining 1 ton of granulated iron from 1.5 ton of ore that has been preheated to 1000°C, the
It is said to absorb the heat of Mcal.

Therefore, if the ore is heated to 1500°C, which is higher than the melting point of the oxide, the amount of absorbed heat is about 500 Mcal, and in this case, the amount of heat transferred by the ore to the iron bath is approximately the total amount of heat transferred to the iron bath. It becomes 25-40%.

It is said that the rate of heat transfer by radiation is proportional to the fourth power of the temperature difference between the combustion zone and the pig iron bath, so the iron bath temperature should be kept as low as possible and the carbon content in the iron bath should be high. At the same time, it is desirable to maintain the combustion zone temperature as high as possible.

In order to achieve this purpose, pure oxygen is sometimes used during combustion, and if pure oxygen is used, the temperature will reach approximately 2500°C, and at this time, this pure oxygen must be preheated. This will cause the temperature to rise further.

By the way, as the combustion temperature increases, extremely large stress acts on the lining inside the furnace, and in reality, there is no material that can follow such operating conditions.

As a specific measure to make the lining able to withstand such harsh environments, there is a method of cooling the lining.

As a specific means, for example,
A technique as described in Publication No. 1 has been proposed.

This technology uses a reactor having the configuration shown in Figure 4, where 1 is a combustion chamber, 2 is a slag, 3 is a molten metal, 4 is a refractory brick, and 5 is an airtight 6 is an ore supply pipe, 7 is an ore flow path, 8 is a tuyere for introducing carbonaceous material, 9 is a pipe for oxygen introduction, and 10 is a discharge route for combustion exhaust gas (carbon dioxide gas).

It is believed that this device can perform the following functions:

That is, the carbonaceous material supplied from the tuyere 8 for introducing carbonaceous material becomes carbon monoxide when it exits the molten metal 3 onto the surface of the submerged slug 2, but it is supplied from the upper part in the space of the combustion chamber 1. When it encounters oxygen, it becomes carbon dioxide gas.

By the way, as this oxidation reaction of carbon oxide progresses, the surrounding inner wall will naturally be exposed to high temperatures, leading to damage to the furnace wall material.

In order to eliminate such inconveniences, this device is characterized by covering the periphery of the porous refractory bricks 4 with an airtight cover 5, and supplying low-temperature oxygen into the refractory bricks 4 at appropriate rIIJ intervals. Then, the refractory bricks 4 are cooled.

In addition to adopting such a configuration, ore is introduced from above along the furnace wall near the inner wall of the combustion chamber 1 to form a curtain, thereby effectively transmitting the heat in the combustion chamber 1 to the ore and melting it. Another feature is that it is intended to recover the heat generated within the reduction furnace.

[Problem that the invention seeks to solve]

However, when trying to actually implement this, providing oxygen at such a position has the opposite effect, and contact with the oxygen that is sufficiently supplied to the voids of the refractory bricks occurs, causing Combustion of carbon monoxide will occur, which will lead to additional overheating of the furnace walls.

Also, looking inside the smelting reduction furnace, the metal oxide curtain is actually created by combustion inside the furnace, and the heated updraft disturbs the curtain state of the ore and maintains the curtain. In the end, this requirement was found to be meaningless.

[Means for solving problems]

The present invention has been arrived at as a result of various studies to solve the above-mentioned conventional problems. A smelting reduction furnace consisting of a plurality of tuyeres installed in multiple stages at a downward angle and tangentially, and a nozzle arranged so that the metal oxide supply flow rotates along the side wall, and such a configuration. Using a smelting reduction furnace with This relates to a method of operating a smelting reduction furnace, which comprises ejecting the tuyere at a downward angle and rotatingly in contact with the side wall due to the jet flow from a multi-stage tuyere ring installed in a tangential shuffle. It is.

[Structure and operation of the invention]

Specifically, the method of operating a melting reduction furnace according to the present invention can be explained with reference to conceptual diagrams of the reduction furnace shown in FIGS. 1 and 2.

That is, FIG. 1 shows the front of the melting and reduction furnace, where 21 is the melting and reduction furnace, and 22 is a nozzle for giving a swirling flow to the ore. As is clear, the nozzles 22 are arranged in multiple stages in the height direction of the melting reduction furnace 21, with their tips facing slightly downward.

This nozzle 22 is typically approximately 10
The tip of the nozzle 22 is oriented tangentially as shown in FIG. 2 to form a swirling flow.

In addition, this nozzle, in the height direction of the melting reduction furnace,
It goes without saying that when changing the height and providing multiple stages, the phase of the nozzle may be shifted little by little each time the height changes.

Naturally, the nozzle 22 provided in the melting reduction furnace 21
It goes without saying that the number and degree of deflection can be changed as appropriate depending on the scale and equipment capacity of the melting reduction furnace.

In this way, by applying a swirling flow to the ore powder to be supplied, a centrifugal force is applied to the ore, giving it the effect of falling against the upward current of combustion gas generated in the smelting-reduction furnace 21, and at the same time, supplying the raw material. This makes it possible to maintain stability.

Furthermore, the lance 23 that is weighted inside the smelting reduction furnace 21 may be of a double-pipe composite pipe type as shown in FIG.
Oxygen blown into 1 can be widely dispersed.

〔Example〕

Hereinafter, the structure and effects of the present invention will be further explained by specifically showing examples.

Example 1 In a smelting reduction furnace with a capacity of 100 tons equipped with a bottom blowing lance, an upper lance, and 4 x 3 stages of ore blowing nozzles as shown in Figs. 1 and 2, the amount of bottom blown carbon material was 120
0 kg/min, ore blowing is 4 N per nozzle
m 100 kg with carrier gas (air) at a speed of 7 minutes
/min of powdered ore was introduced while swirling.

The ore blowing nozzle was of a configuration facing downward at an angle of 20°.

The upper lance 1 is of a double pipe type as shown in Fig. 3, and has three holes in the center and eight holes in the outer part. 61
Oxygen was introduced at 6Nrn'/min and from the outer part at 67ONm''/min.

By implementing this method, the ore could be placed along the inner wall of the smelting reduction furnace, thereby reinforcing the curtain effect.

The conditions of 100 tons of seed water, 4.5% carbon content, 0.5% silicon, and temperature of 1300°C were maintained, and ore was not injected until the carbon content reached 3.5%, and the temperature reached 1500°C. At that time, a melting reduction operation was performed based on the following specifications, and the amount reached 200 tons in 62 minutes, which was then melted into steel in a decarbonizing converter.

The iron yield (%) at this time was 95%, but it remained at 70% in the method described in Japanese Patent Publication No. 1983-6561, which was used for comparison.

Example 2 Under operating temperature conditions of 1,300 to 1,650°C, when using ore particle size 1-, the method described in Japanese Patent Publication No. 44-6561 and the method described in Japanese Patent Publication No. 44-6561, and when the curtain operation in this was not performed, When the furnace life of the invention method (the internal lining in this case is Mg0-C type) was compared, the following results were obtained.

Processing method Furnace life (times) Furnace temperature (°C) Normal converter 2000 1300-1650 No curtain 500 Method of the present invention 2500 [Effects of the invention] By rotating the ore, centrifugal force acts on the ore. The curtain effect of the ore powder acts against the upward airflow of the combustion exhaust gas generated in the smelting reduction furnace, and the furnace material inside the combustion chamber can be protected.

This also extends the lifespan of the furnace materials in the melting reduction furnace, and has the effect that the equipment can be used stably over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a front view of the equipment according to the present invention, Fig. 2 is a plan view of Fig. 1, Fig. 3 is a front view of the lance, and Fig. 4 is a front view of the smelting reduction furnace of the prior art. be. 1 Combustion chamber, 2...Slag, 3 Molten metal, 4 Refractory brick, 5-Airtight cover, 6-Ore supply pipe, 7-Ore channel, 8 Tuyere for introducing carbonaceous material, 9-Oxygen introduction pipe,
10...Emission route of combustion exhaust gas (carbon dioxide gas), 21...
- Melting reduction furnace, 22... Nozzle, 23 - Lance.

Claims (5)

[Claims] (1) In a metal oxide smelting reduction furnace, a plurality of tuyeres are installed at various points around the side wall at a downward angle and tangentially in multiple stages as metal oxide supply nozzles, and the metal oxide supply flow is directed to the side wall. A melting reduction furnace consisting of nozzles arranged to rotate along the (2) Install one metal oxide supply nozzle on the side wall of the smelting reduction furnace.
The melting reduction furnace according to claim 1, which is installed with an angle of depression of 0° to 45°. (3) In a smelting reduction furnace in which a combustion chamber is formed by spraying pure oxygen through a lance inserted into the container from the top in a molten metal container that is a cylinder with a circular or elliptical cross section, metal oxide powder is produced. and one or more selected from the group of coal, coke, oil and gas in an amount corresponding to the chemical equivalent of the metal oxide powder thereof, and a plurality of tuyeres at downward angles around each part of the side wall, and A method of operating a smelting reduction furnace, which comprises ejecting a jet stream from multiple stages of tuyere rings installed tangentially in a rotating manner in contact with a side wall. (4) The operating method according to claim 3, which uses a smelting reduction furnace in which a metal oxide supply nozzle is installed at an angle of depression of 10° to 45° from the side wall of the smelting reduction furnace. (5) Claim 3 in which pressurized air is used as a jet source
Operating method described in section.