JPS62230922A - Operating method for vertical type melt reduction furnace - Google Patents

Abstract

PURPOSE:To effectively prevent damage to the wall of a vertical type melt reduction furnace by providing gas supply ports to the cylindrical circumference of the furnace wall and cooling the furnace wall with a cooling gas at the time of producing a molten metal in said furnace. CONSTITUTION:A carbon solid reducing agent (powder coke, etc.) is charged from a supply device 4 into the vertical type melt reduction furnace 3. An oxygen-contg. gas is blown from plural tuyeres 5 into the furnace to form a fluidized bed 9 and a packed bed 11. Powdery ore is supplied from tuyeres 1 into the fluidized bed 9 and the powdery ore is heated to form the molten metal 13 and molten slag 12. A generated exhaust gas 2 is taken out of a discharge port 7. The fluidized bed part 9 forms a high-temp. region of about 1,500-1,600 deg.C and therefore cooling gas supply ports 6a, 6a are installed to the cylindrical circumference of the wall of the furnace 3. The exhaust gas 2 cooled to an ordinary temp. by a cooler 15 is introduced into said ports. The cooling gas ascends mostly along the furnace wall and therefore the inside wall of the furnace is effectively cooled. The volume of the cooling gas to be introduced is adjusted to about 1-5vol% of the volume of the gas in the furnace. The consumption of the inside wall of the furnace is, thus considerably reduced.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method of operating a vertical melting reduction furnace.

In particular, by achieving effective cooling of the high-temperature exhaust gas in the vertical furnace, it is intended to realize smooth operation of the vertical furnace.

[Conventional technology]

In recent years, raw material ores containing various metal oxides, including iron ore, have become more granular ore than lumpy ore.
This ratio is expected to continue to increase in the future. Conventionally, a common method for refining powdery ore is to agglomerate the powdery ore and then melt and reduce the agglomerated ore in an electric furnace, converter, or other melting furnace. However, this method not only requires processing costs such as equipment and materials for agglomeration and processing energy, but also requires additional processing costs when firing is required after agglomeration. However, there is a disadvantage in that the cost for treating NOx, SOx, dust, etc. in the gas discharged from the firing furnace is high.

In addition to the above-mentioned methods, methods have also been proposed in which powdery pre-reduced ore is melted and reduced without agglomeration or calcination using an arc furnace, a furnace that uses plasma, or pure oxygen. However, the method using an arc furnace or plasma furnace not only consumes a huge amount of electricity, but also has locational requirements, and the method using a furnace using pure IV element
Although it is easy to obtain a high-temperature atmosphere, there are problems such as a large amount of oxygen being used.

The present inventors previously proposed in Japanese Patent Application No. 11707/1987 that the above-mentioned problems could be solved advantageously by charging powdered ore into a fluidized bed of a carbon-based solid reducing agent and removing oxygen. We proposed a method for producing molten metal from powdered ore by blowing the containing gas into a packed bed of carbon-based solid reducing agent.

In the above method, the preheated charge charged into the vertical furnace is melted and reduced while dropping through the high temperature region of a fluidized bed of carbon-based solid reducing agent formed in the lower part of the furnace. It is stored in the hearth and taken out from the hearth as appropriate. The development of the smelting reduction method using such a vertical furnace has made it possible to refine granular ores extremely effectively.

[Problem that the invention seeks to solve]

However, in the above-mentioned smelting reduction method, since the inside of the vertical furnace is exposed to a high temperature atmosphere, there is a lot of wear and tear on the furnace inner wall.
Therefore, the furnace operation may be affected by changes in the furnace profile, and there remains a problem in that the number of repairs will increase.

[Means for solving problems]

The present invention advantageously solves the above problems by forming a fluidized bed of a granular solid reducing agent inside a vertical furnace, and by introducing oxygen through a group of panels provided on the lower body wall of the vertical furnace. In a vertical smelting reduction furnace, the granular ore is smelted and reduced by blowing a gas containing it into the vertical furnace and charging the granular ore which has been pre-reduced or not pre-reduced into the vertical furnace. By introducing cooling gas into the furnace from multiple gas supply ports provided along the furnace wall circumference of the mold furnace and cooling the furnace wall,
This is a means of solving the problem of furnace inner wall wear.

As the cooling gas used in the present invention, any gas may be used as long as it is at a low temperature of about room temperature and does not have an extremely adverse effect on the reaction in the furnace, and preferable examples include pre-4a reduction furnace exhaust gas or nitrogen gas. , and the supply amount is 1 to 1 at the exhaust gas field.
About 5% by volume is sufficient. Steam can also be used as the cooling gas.

[Effect]

The present invention will be specifically explained below along with its operation.

FIG. 1 schematically shows a vertical melting reduction furnace suitable for carrying out the present invention.

In the vertical smelting reduction furnace 3, raw material powdered atsushi is supplied from a powdered ore supply tuyere 1 to a fluidized bed of a carbon-based solid reducing agent, and a carbon-based solid reducing agent 1 is supplied from a carbon-based solid reducing agent supply device 4, for example. Coke powder is charged to form a fluidized bed 9 and a packed bed 11 inside the furnace. Further, a plurality of tuyeres 5 are arranged at the lower part of the circumference of the vertical melting reduction furnace 3, and gas containing oxygen is blown into the tuyeres 5. This gas is also the fluidizing gas for the fluidized bed 9. A cooling gas supply port 6 is provided in the vertical furnace over the circumference of the body.

By blowing gas containing oxygen through the wall group 5, a fluidized bed is formed in the upper part thereof, and the exhaust gas 2 generated in the vertical furnace 3 is discharged from the exhaust lower.

The packed bed 11 formed in the vertical furnace 3 generates a raceway similar to that at the tip of the tuyere of a blast furnace near the tip of the siding 5, and a high temperature region of 2500°C or more is formed, and the upper part of this packed bed 15 by creating a fluidized bed of carbon-based solid reducing agent.
A high temperature region of 00-1600°C is formed, and powdered ore such as preliminary ores charged into this region is immediately heated.
It melts easily and is reduced while dropping into the lower part of the vertical furnace 3, producing molten metal 13 and molten slag 12.

The molten metal 13 and slag 12 stored in the hearth are discharged from the tap 1
0, and is taken out of the furnace in a timely manner.

As the carbon-based solid reducing agent, granular coke is suitable, but granular char or coal may be used instead, or they may be used in combination.

Further, the pre-reduced ore is advantageous because it is heated in the fluidized bed section and its retained heat is brought into the vertical furnace 3.

The reduction rate varies depending on the type of ore, etc.
Best results can be obtained within the range of 30-80%.

By the way, as mentioned above, in the fluidized bed section in the vertical furnace 3, 15
Because a high temperature range reaching 00 to 1600 degrees Celsius is formed,
Inevitably, hot gas is generated in this region. Therefore, as this high-temperature gas rises inside the furnace, the furnace wall undergoes significant erosion, and in severe cases, the profile inside the furnace changes, causing fluctuations in furnace operation, as well as other negative effects such as increased heat loss. was occurring.

Therefore, in the present invention, in order to prevent the inner wall of the furnace from being eroded by this high-temperature gas, as shown in FIG.
Similar to the tuyere group 5, cooling gas supply ports 6 are provided along the circumference of the furnace wall.
．． A cooling gas such as a pre-reduction furnace exhaust gas 7 cooled to room temperature in a cooling bag 15, an inert gas, or steam is introduced into the furnace through the supply ports 6 and 6a. In the furnace, most of this cooling gas rises along the furnace wall, so even if the amount of cooling gas is small, the furnace inner wall is effectively cooled, and the furnace wall can be cooled without interfering with furnace operation. wear and tear can be advantageously prevented.

Note that the cooling effect is further improved by using a porous refractory 14 that also serves as a furnace wall as illustrated in FIG. 2 as a cooling gas supply port.

Incidentally, when the average gas temperature in the furnace is 1500°C, when cooling gas of 1 to 5% by volume is introduced into the furnace based on the amount of gas in the furnace, the gas temperature near the furnace inner wall is 1340°C to 900°C.
℃, and wear and tear on the inner walls of the furnace was significantly reduced compared to before.

If the amount of cooling gas supplied is too small, the effect of cooling the inner wall of the furnace will be poor, while if it is too large, the temperature of the top gas of the vertical furnace will drop and it will be difficult to introduce it into the pre-reduction furnace. It is desirable that the amount is about 1 to 5% by volume based on the amount of gas.

〔Example〕

Next, examples of the present invention will be described.

The test furnace of the example shown in FIG. 1 was operated under the following operating conditions.

■) Ore brand: MBR Ore particle size: 2 mm or less Supply rate + 48 kg/H 2) Carbon-based solid reducing agent brand - Steam coal (FC75, 1%) Particle size: 20 mm or less Supply rate: 36 kg/H 3) Vertical type Blow gas to the reduction furnace: 90% oxygen, 10% nitrogen Air volume: 18Nrn'/H 4) Pre-4Ia reduction rate of ore: 65% 5) Pig iron production: 27kg/H 6) Slag discharge amount: 8kg/H 7 ) Cooling gas type: Pre-reduction furnace exhaust gas temperature = 70℃ Supply amount: 0.5 Nm'/H (1 for exhaust gas amount
．． 5%) When operating under the above conditions, the gas temperature in the furnace, which was approximately 1490°C when no cooling gas was introduced as in the past, decreased to approximately 1230°C near the furnace inner wall, and the furnace We were able to reduce the number of wall repairs to 1/3 compared to conventional methods.

〔Effect of the invention〕

As described above, according to the present invention, the temperature of the gas in the furnace near the inner wall of the vertical furnace can be effectively lowered, and the erosion of the inner wall of the furnace due to the gas can be significantly reduced, without causing any hindrance to the operation of the smelting reduction furnace. Therefore, it is possible to prevent fluctuations in furnace operation due to changes in the furnace profile due to wear and tear on the furnace inner walls, and to reduce the number of repairs.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a vertical melting reduction furnace used for carrying out the present invention, and FIG. 2 is a vertical cross-sectional view of another preferred vertical furnace. 1... Powdered ore supply tuyere 2... Exhaust gas 3... Vertical melting reduction furnace 4... Carbon-based solid reducing agent supply device 5... Tuyere 6.6a... Cooling gas supply port 9... Fluidized bed lO... Tap port 11... Filled bed 12... Molten slag 13... Molten metal 14... Porous refractory 15... Cooling device

Claims (1)

[Claims] 1 Using a vertical smelting reduction furnace, maintaining a packed bed of a carbon-based solid reducing agent and a fluidized bed above it in the same furnace, charging powdered ore into the fluidized bed of the carbon-based solid reducing agent, In a method for producing molten metal from powdered ore in which a gas containing oxygen is blown into a packed bed of a carbon-based solid reducing agent, a cooling gas is introduced into the furnace from a gas supply port provided over the circumference of the furnace wall of the vertical furnace. A method of operating a vertical smelting reduction furnace characterized by cooling the furnace wall.