JPH06147777A - Exhaust gas cooling equipment for ladle refining - Google Patents

Abstract

PURPOSE:To obtain equipment dispensing with a dust collector of a large capacity in the case of treating an exhaust gas produced in a conventional simple refining method based on a rise in the temperature of molten steel in a ladle, by disposing a water-cooled duct and a multitube type exhaust gas cooler in the rear of an exhaust gas suction tube of refractory construction, by providing the water-cooled duct with an air port for combustion and by other means. CONSTITUTION:While molten steel 2 is agitated by an inactive gas blown in from the bottom of a ladle 1, an immersion tube 3 is inserted into the ladle 1 and an oxidative gas is blown against the surface of the molten steel 2 in the ladle 1 through top-plown lance 6 so as to raise the temperature of the molten steel 2 in the ladle 1 to be refined. In this case, an exhaust gas suction tube 5 connected to the upper part of the immersion tube 3 is constructed to be refractory and a water-cooled duct 9 and a multitube type exhaust gas cooler 11 are disposed in the rear of the exhaust gas suction tube 5. The water-cooled duct 9 is provided with an air port 10 for combustion and the cooling capacities of the water-cooled duct and the exhaust gas cooler 11 are so designed as to enable cooling of the exhaust gas to the heat resistance temperature of a dust collecting device 15 positioned behind the exhaust gas cooler 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas cooling device for ladle refining, which is used for heating and refining molten steel in a ladle.

[0002]

As a ladle refining method having a molten steel heating function in a ladle, processes such as LF using electric energy, RH-OB using oxygen under reduced pressure, and VOD method have been put into practical use. However, due to the drawbacks such as treatment cost and long treatment time in the treatment, recently, a simple method for raising molten steel in a ladle can be easily applied and the equipment cost is low Has been done.

The above-mentioned simple method for raising the temperature of molten steel in a ladle is as follows: An inert gas is blown from the bottom of the ladle to stir the molten steel while inserting a dip tube into the ladle to melt the molten steel in the dip tube. A method in which an oxidizing gas is blown onto the surface through an upper blowing lance (see Japanese Patent Laid-Open No. 61-235506), the lance is deeply immersed in the molten steel in the ladle to stir the molten steel, and the snorkel is immersed to the top. A method of blowing oxygen with a blowing lance (JP-A-1-56)
No. 816) are known. Although there is a difference in the method of raising the temperature of the molten steel in the ladle described above, there is a difference in the stirring method in the ladle, but a heat-generating agent such as Al is added on the surface of the molten steel bath, and the mixture is burned with oxygen supplied from the top blowing lance. It is used to heat molten steel with combustion heat.

At this time, the oxygen supplied from the top blowing lance is C, Si, M in the molten steel depending on the steel type such as high carbon steel.
Reacts with n, etc. That is, a large amount of CO due to the decarburization reaction
Gas is generated, and it is necessary to treat the toxic CO gas. As a method of treating CO gas, for example, in a converter, since the CO gas ratio in the exhaust gas is high and combustible, there is also a method of recovering and using it as it is in an unburned state. If it is applied to refining of molten steel by the heating method, the equipment cost will increase and it will not be industrial. Therefore, as the exhaust gas treatment method, conventionally, CO gas is completely combusted to form CO ₂ gas, but since the exhaust gas temperature becomes high due to the combustion heat of CO ₂ gas, a large amount of dilution air is introduced into the dust collection duct to collect dust. The bag filter of the equipment was cooled to the heat resistant temperature of the furnace cloth and the exhaust gas was treated.

[0005]

The exhaust gas treatment method shown in the prior art described above uses a simple exhaust gas for refining by raising the temperature of molten steel in a ladle when the dust collector equipment of the entire steelmaking plant has a sufficient reserve capacity. Although it is not impossible to treat, it is usually inconvenient in terms of equipment cost and running cost of operation because it has no spare capacity and it is necessary to install a large-capacity dust collector.

In view of the above-mentioned conventional problems, the present invention provides an exhaust gas cooling device which does not require a large-capacity dust collector, for processing the exhaust gas of a conventional simple refining method by raising the temperature of molten steel in a ladle. With the goal.

[0007]

Means for Solving the Problems The present invention is to solve the above problems, in which an immersion gas is blown from the bottom of a ladle to agitate molten steel, and an immersion pipe is inserted into the ladle. In spraying an oxidizing gas on the surface of the molten steel in the dip pipe through an upper blowing lance to heat and refine the molten steel in the ladle, the smoke exhaust suction pipe connected to the upper part of the dip pipe has a fireproof structure, A water cooling duct and a multi-pipe type exhaust gas cooler are arranged behind the smoke exhaust suction pipe, a combustion air port is provided in the water cooling duct, and the exhaust gas cooling capacity of the water cooling duct and the exhaust gas cooler is located after the exhaust gas cooler. This is an exhaust gas cooling device for ladle refining, which is capable of cooling to a heat resistant temperature of a dust collector.

[0008]

As a result of intensive studies, the inventors of the present invention provided a water cooling duct and a multi-pipe type exhaust gas cooler in the upper part of the dipping pipe and behind the smoke exhaust suction pipe to completely burn the CO gas in the water cooling duct. We have found that it is extremely economical and effective in industry to cool the exhaust gas to the heat resistant temperature of the dust collector by introducing only the required amount of air and combining the water cooling duct and the multi-tube exhaust gas cooler. The present invention has been completed. In particular, in order to be able to cool the exhaust gas cooling capacity of the water cooling duct and the exhaust gas cooler to the heat resistant temperature of the dust collector, the number of heat transfer tubes in the exhaust gas cooler, the diameter, the length, or the amount of cooling water flowing around it must be controlled. To be adjustable,
In addition, this can be achieved by making it possible to adjust the amount of cooling water flowing through a water cooling duct (having a double pipe structure, exhaust gas flows inside, and cooling water flows outside).

In the exhaust gas cooling device thus constructed, when the molten steel in the ladle is heated, the smoke exhaust suction pipe above the dip pipe is lined with a heat resistant castable to have a fire resistant structure, and the high temperature exhaust gas treatment portion is Since it is water-cooled, burnout of the exhaust gas duct system is prevented. In addition, the amount of air required to completely burn the CO gas in the water cooling duct is introduced, and the exhaust gas is cooled to the heat resistant temperature of the dust collector by the combination of the water cooling duct and the multi-tube type exhaust gas cooler. You can use the dust collector.

[0010]

The present invention will be described in more detail with reference to the drawings. An embodiment of the exhaust gas cooling device according to the present invention is shown in FIG. In the figure, a cap type immersion pipe 3 (hereinafter simply referred to as an immersion pipe) is installed on the upper surface of the molten steel 2 in the ladle 1,
A sub-material feeding pipe 4 and a smoke exhaust suction pipe 5 are connected above the immersion pipe 3 in a structure that follows the vertical movement of the immersion pipe 3, and an upper blowing lance 6 that moves up and down independently of the immersion pipe 3. And a porous plug 7 is embedded in the bottom of the ladle 1 for the purpose of stirring the molten steel 2 (Japanese Patent Laid-Open No. 61-23550).
No. 6 publication). As an elevating device (not shown) for the immersion tube 3, there is a device (see Japanese Utility Model Publication No. 63-13229) for holding the immersion tube 3 by a gripping arm on an elevating table. Behind the smoke exhaust suction pipe 5, a water cooling duct 9 and an exhaust gas cooler 11 are provided.
Are connected.

Oxygen is blown onto the surface of the molten steel in the dipping pipe 3 through the upper blowing lance 6, and an oxidizing reactant such as Al is injected into the auxiliary material feeding pipe 4.
Exhaust gas generated by heating the molten steel in the ladle by adding from above is water-cooled through the smoke-exhausting suction pipe 5 lined with fireproof castable, high alumina brick, or high alumina lining. Air is introduced from the combustion air port of the duct 9, and the water cooling duct 9 and the exhaust gas cooler 1
The exhaust gas cooled by the combination of 1 is sent to the dust collector 15 by the suction fan 14 through the dust collection duct 13, and is dusted and then diffused to the atmosphere.

In the exhaust gas cooling apparatus for ladle refining according to the embodiment thus constructed, when the steel species such as high carbon steel is subjected to the sublimation heat treatment, the exhaust gas from the dip tube 3 generated by the sublimation is not burned. Contains CO gas. An amount of air ratio (λ) of about 1 to 1.5 required to completely burn CO gas by opening a water cooling damper (not shown) provided in the combustion air port 10 in the water cooling duct 9. Is introduced to produce CO ₂ gas. At this time, since the exhaust gas temperature becomes high due to the combustion heat of the CO ₂ gas, the water cooling duct has a double tube jacket structure, and the exhaust gas cooler 11 has a multi-tube structure having many heat transfer tubes 12. As a result, the hot exhaust gas is heated by the combination of the water cooling duct and the exhaust gas cooler by the heat exchange of the gas / water by the cooling water (the water supply pipe and the discharge pipe are not shown) supplied to these devices, and the heat resistance of the dust collector 15 is reduced. Cooled to temperature. Therefore, the burnout of the exhaust gas duct system including the smoke exhaust suction pipe 5 having the fireproof structure is prevented,
CO gas can be processed into harmless CO ₂ gas, and C
There is no external leakage of O 2 gas.

When the decarburization amount of C in the molten steel such as low carbon steel is small, the generation of CO gas is so small that it is not necessary to completely combust it. In such a case, the combustion air in the water cooling duct 9 is required. A water-cooled damper (not shown) provided at the mouth 10 is closed and used. Since the amount of exhaust gas to be treated is smaller than that in the case of treating high carbon steel, the rotation speed of the electric motor (not shown) of the suction fan 14 is controlled by controlling the water cooling damper and the suction fan 14. Energy consumption can be reduced.

In the present invention, regardless of the above embodiment, CO gas is burned by combining a water cooling duct and an exhaust gas cooler with refining, etc., in which CO gas is generated in a reaction vessel such as ladle refining, and the exhaust gas is discharged. A cooling system is applicable. Further, when the dust collector of the existing factory has an excess capacity, the system after the dust collecting duct 13 is not required.

[0015]

Since the present invention is constructed as described above, burnout of the exhaust gas duct system is prevented and CO
Since the gas can be treated as harmless CO ₂ gas, there is no external leakage of CO gas and the facility is highly safe. In addition, compared with the method of cooling exhaust gas with a large amount of diluted air, the amount of exhaust gas processed is smaller, so there is a feature that it does not require a large-capacity dust collector and leads to reduction of equipment cost and running cost, which is an industrial advantage. However, it is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an exhaust gas cooling device of the present invention.

[Explanation of symbols]

 1 Ladle 2 Molten Steel 3 Immersion Pipe 4 Secondary Material Input Pipe 5 Smoke Suction Pipe 6 Top Blowing Lance 7 Porous Plug 8 Slag 9 Water Cooling Duct 10 Combustion Air Port 11 Exhaust Gas Cooler 12 Heat Transfer Pipe 13 Dust Collection Duct 14 Intake Fan 15 Collection Dust device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukinori Shigeyama 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corp. Technology Development Division

Claims (1)

[Claims] 1. An inert gas is blown from the bottom of the ladle to agitate the molten steel, and a dip pipe is inserted into the ladle so that the oxidizing gas is passed through the upper blowing lance to the surface of the molten steel in the dip pipe. Spray,
When heating and refining the molten steel in the ladle, the flue gas intake pipe connected to the upper part of the dip pipe has a fireproof structure, and a water cooling duct and a multi-pipe type exhaust gas cooler are arranged behind the flue gas intake pipe. For ladle refining, characterized in that a combustion air port is provided in the water cooling duct, and the exhaust gas cooling capacity of the water cooling duct and the exhaust gas cooler can be cooled to the heat resistant temperature of the dust collector located after the exhaust gas cooler. Exhaust gas cooling device.