JPH11314151A - Heating and heat retention method and equipment for metallurgical equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus capable of raising or keeping the temperature in a metallurgical facility by using an inert gas, having extremely high thermal efficiency and maintaining a highly reducing inside of a furnace, without using an inert gas. . SOLUTION: When heating and maintaining heat of a metallurgical facility using a plurality of regenerative heat exchangers that alternately alternate between a radiating state and a heat storage state, the plurality of regenerative storage methods are used. The fuel gas is heated by one of the heat exchangers in a heat-dissipating state, and the temperature of the metallurgical equipment is raised or kept while keeping the metallurgical equipment in a reduced state by the heated fuel gas. The gas is introduced into the other heat storage type heat exchanger in the heat storage state together with the gas to be burned, and the heat is stored in the heat exchanger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for heating and keeping metallurgical equipment such as a ladle for casting steel, a tundish for continuous casting, and a heating furnace, and more particularly to a metal ingot existing inside these equipment. Also, the present invention relates to a method and an apparatus for heating or keeping the inside of a metallurgical facility without oxidizing an intermediate product to maintain and improve the quality of a product produced thereafter.

[0002]

2. Description of the Related Art In producing steel, metallurgical equipment such as a tundish for continuous casting and a heating furnace is used. Although these facilities are used continuously in principle, their use may need to be interrupted due to circumstances such as changes in the type of steel to be treated. In such cases,
Heat or keep the above equipment ready for the next use,
Alternatively, once cooled, it is necessary to raise the temperature and reheat. Taking the continuous casting of steel as an example, in so-called continuous continuous casting of different types of steel (called continuous casting), the tundish is exchanged when changing the steel type, and the tundish continuously casts the same steel type as the previous time. It is necessary to wait while maintaining the heat retention state.

In such a case, the inside of the waiting tundish is generally at a high temperature exceeding 1500 ° C., and the metal remaining in the inside is oxidized to produce iron oxide. When the tundish is subjected to the next use in this state, Al ₂ O _{3 and the} like are formed by a reaction between the generated iron oxide and Al in the molten steel injected, and when this flows into the continuous casting mold, the continuous casting slab is formed. It remains as a non-metallic inclusion in the steel and has various effects on the quality of the steel product.

As means for preventing such oxidation of the metal in the tundish, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-155599, a heating means outside the tundish (in this case, a regenerative heat exchanger) is used. Means have been proposed for keeping the inside of the tundish heat by using an inert gas heated to 850 ° C. or higher and using it for the next use. In this case, it has also been proposed to introduce a small amount of reducing gas below the explosion limit in addition to the inert gas.

[0005]

However, the above-mentioned proposal heats an inert gas such as nitrogen (N ₂ ) by an external heat source, thereby keeping the inside of the metallurgical equipment warm. However, there is a drawback that extra heat energy is required to perform the process, and the cost increases. In particular, when reheating a relatively low temperature tundish, or when heating or heating large metallurgical equipment such as a heating furnace used in the hot rolling process or an annealing furnace, the above excess heat is used. Energy also increases. An object of the present invention is to solve the problems of the prior art described above, without using an inert gas, with extremely high thermal efficiency and maintaining the inside of the furnace highly reducible, to maintain the inside of the metallurgical equipment. It is an object of the present invention to propose a method and a device capable of raising or maintaining the temperature.

[0006]

In order to solve the above-mentioned problems, the present invention provides a method for raising and keeping heat of metallurgical equipment by using a plurality of heat storage type heat exchangers which alternately alternate between a heat radiation state and a heat storage state. When raising the temperature and keeping the heat of the metallurgical equipment, the fuel gas is heated by one of the plurality of regenerative heat exchangers in a radiating state, and the heated fuel gas raises the temperature while maintaining the metallurgical equipment in a reduced state. After warming or keeping the heat, the heated fuel gas and the supporting gas are introduced into the plurality of regenerative heat exchangers to be burned, and the heat is stored in the heat exchangers.

In the above method, it is preferable that the fuel gas is guided to a heat exchanger in a radiating state together with a thermal decomposition accelerator of the fuel gas and heated, thereby promoting the thermal decomposition of hydrocarbons in the fuel gas. At the same time, it is possible to prevent carbon deposition on the heat storage body of the heat storage type heat exchanger.

[0008] Further, the amount of the supporting gas for burning the fuel gas discharged from the metallurgical equipment in the regenerative heat exchanger is made slightly larger than the theoretical value, so that the exhaust gas discharged from the regenerative heat exchanger remains. It is desirable that oxygen be supplied in a volume ratio of 0.1 to 1.0. By doing so, the deposition of carbon on the heat storage body can be prevented.

Further, the present invention provides a heat-up and heat-retention device for metallurgical equipment for carrying out the above-mentioned method, comprising: a plurality of regenerative heat exchangers which alternately alternate between a radiating state and a heat storing state; A switching valve that guides the combustion gas to the heat exchanger in the heat radiation state of the heat exchanger, and guides the gas discharged from the heat exchanger in the heat storage state to the radiation system, and the heat exchanger in the heat radiation state. A lid for introducing the heated fuel gas into the metallurgical equipment and guiding the fuel gas discharged from the metallurgical equipment to a heat exchanger in a heat storage state; And a switching valve that leads to a heat exchanger in a heat storage state.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described based on embodiments. FIG. 1 shows an arrangement of an example of an apparatus for carrying out the present invention, in which two regenerative heat exchangers 1, 2
Are connected to the fuel gas supply device 7 via the switching valve 3 and to the metallurgical equipment 4 (for example, a heating furnace) via the lid 5 by piping. A switching valve 6 is provided on the rear surface of the regenerative heat exchangers 1 and 2, and is connected to a combustion supporting gas supply device 8.

Therefore, the fuel gas passes through the switching valve 3 and
It is heated by the heat exchanger 1 in the heat radiation state, enters the metallurgical equipment 4 via the lid 5 having the gas passage 11, and heats the inside of the equipment by sensible heat. The fuel gas that has heated the inside of the facility is guided to the heat exchanger 2 in a heat storage state via the lid 5 and the gas passage 12. At that time, the supporting gas is introduced into the heat exchanger 2 via the switching valve 6, whereby the fuel gas burns in the regenerative heat exchanger 2 and heats the heat storage body. The gas discharged from the regenerative heat exchanger is released to the atmosphere via the switching valve 3. After a lapse of a predetermined time, the switching valve is switched from the state shown by the solid line to the state shown by the broken line in FIG.
Is used in a heat storage state.

Each equipment element such as a regenerative heat exchanger used in the above-mentioned apparatus of the present invention is not particularly limited as long as it is used for processing high-temperature gas.
For example, a ball-shaped or pipe-shaped one made of ceramics or heat-resistant metal can be used as a heat storage body which is a main part of the heat storage type heat exchanger in consideration of an electric heating area, a heat storage amount (heat capacity), and the like. Further, the lid 5 that connects the metallurgical equipment 4 and the heat exchangers 1 and 2 only needs to have a shape capable of introducing a heating gas into the equipment according to the shape of the metallurgical equipment. However, lid 5
And the metallurgical equipment should be completely sealed
Leakage of fuel gas, and thus gas explosion, must be avoided.

In the present invention, the fuel gas itself is used to raise or keep the temperature inside the metallurgical equipment 4. As fuel gas, hydrocarbon fuel gas (LNG, LPG, etc.)
However, other fuel gases, such as blast furnace gas, coke oven gas, etc. may also be used. These gases may be selected or mixed according to the heat energy required for raising or maintaining the temperature of the metallurgical equipment.

In the present invention, only the fuel gas is used,
The feature is that no inert gas is used.However, if a small amount of oxidizing gas is added to the fuel gas as a thermal decomposition accelerator, the deposition of carbon on the heat storage body of the regenerative heat exchanger that is in a radiating state can be prevented. It is possible to prevent a decrease in pressure loss when operating the apparatus of the present invention for a long time. As such a thermal decomposition accelerator, CO ₂ , H ₂ O (steam), O _2, or air can be used, and the addition amount is preferably 1 or less in terms of volume ratio with respect to the fuel gas. In this case, a pipe for introducing the pyrolysis promoting gas into the pipe 13 between the fuel gas supply device 7 and the switching valve 3 or the pipe 14 between the switching valve 3 and the first and second heat exchangers is provided. Good.

The supporting gas introduced together with the fuel gas into the heat exchanger in the heat storage state is a gas containing oxygen and capable of burning the fuel gas, such as air and oxygen-enriched air. In general, the amount required for stoichiometric combustion is sufficient. However, if this amount is slightly increased so that the amount of residual oxygen (O ₂ ) in the exhaust gas becomes 0.1 to 1 in volume ratio, the same as above The deposition of carbon on the heat storage body can be prevented. If it is less than 0.1, the effect of preventing the deposition of carbon on the heat storage body is not remarkable,
On the other hand, if the residual amount exceeds 1.0, the effect of preventing the deposition of carbon is not improved much, and the fire temperature of the combustor is lowered, so that the thermal efficiency deteriorates, which is not preferable.

[0016]

【Example】

Embodiment 1 An example in which the present invention is applied to heat retention of a tundish for continuous casting having a capacity of 70 tons will be described below. The used tundish is covered with a heat retention lid having two gas passages, and the two regenerative heat exchangers and the gas passage of the heat retention lid are connected to form a gap between the lid and the tundish, a gas passage and the heat exchanger. Was sealed with an irregular-shaped refractory, and the temperature of the tundish was raised and the heat was kept.

The heat storage body of the heat storage type heat exchanger at the start of heat retention was 1300 ° C. on the heat dissipation state side and 1100 ° C. on the heat storage state side. The coke oven gas is supplied to the heat-exchanger side heat exchanger at a flow rate of 200 Nm ³ / h, and the coke oven gas is heated to 1350 ° C. and the internal temperature becomes 10
It was sent into a 00 ° C tundish. Coke gas discharged from the tundish was introduced into the heat exchanger on the heat storage state side. At that time, 250 Nm ³ / h of air was used as a supporting gas.

This state was continued for 30 minutes. As a result, the temperature of the coke oven gas supplied from the heat-exchanger side heat exchanger dropped to 1000 ° C. Then, when the gas flow was reversed by switching the switching valve and the state of the heat exchanger was changed, the temperature of the coke oven gas returned to 1300 ° C. About 3h
And the same operation as above was repeated. as a result,
The temperature in the tundish rose from 1000 ° C to 1100 ° C. In this case, since it was not necessary to use nitrogen gas as a heat medium as disclosed in Japanese Patent Application Laid-Open No. 8-155599, it was possible to save about 70,000 kcal of heat energy.

[0019]

Example 2 The same operation as above was performed by adding 1 steam as a thermal decomposition accelerator to the coke oven gas to the heat exchanger on the heat radiation state side, and supporting the heat exchanger on the heat exchanger on the heat storage state side. The supply amount of the reactive gas was adjusted so that the residual oxygen in the exhaust gas became 0.5. As a result, even when used for a cumulative period of 200 hours, deposition on carbon in the accumulator was hardly observed, and no increase in pressure loss was observed as shown in FIG. On the other hand, when the thermal decomposition accelerator was not added and the supporting gas was not excessive, a slight increase in pressure loss was observed as shown in FIG. 2B.

In the description of the above embodiment, the number of storage heat exchangers is two, but more heat exchangers, for example, three
It is also possible to provide two storage heat exchangers, two of them being in a heat-dissipating state and the other being in a heat-storing state.

[0021]

Since the present invention is constructed as described above, it is possible to raise the temperature and maintain heat of the metallurgical equipment with high thermal efficiency while maintaining the inside of the metallurgical equipment in a highly reducing atmosphere as compared with the conventional method. . In addition, during the operation of the present invention, since no carbon is deposited, it is possible to reduce the maintenance cost of the heat storage body.

[Brief description of the drawings]

FIG. 1 is a layout view of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the accumulated use time and the heat storage element pressure loss when the present invention is implemented.

[Explanation of symbols]

 1,2: regenerative heat exchanger 3: switching valve 4: metallurgical equipment 5: lid 6: switching valve 7: fuel gas supply device 8: combustible gas supply device 11, 12, 13, 14: conduit

Claims (4)

[Claims] 1. A method for raising and keeping heat of metallurgical equipment by using a plurality of regenerative heat exchangers, wherein a fuel gas is heated by one of the plurality of regenerative heat exchangers in a radiating state. Then, after the metallurgical equipment is heated or heat-retained while maintaining the inside of the metallurgical equipment in a reduced state by the obtained heated fuel gas, the heated fuel gas and the combustion-supporting gas are in a heat storage state among the plurality of regenerative exchangers. A method of raising the temperature and keeping heat of metallurgical equipment, wherein the method is performed by introducing into a regenerative heat exchanger, burning the heat, and storing heat in the heat exchanger. 2. The method according to claim 1, wherein the fuel gas and the thermal decomposition promoter of the fuel gas are led to a heat exchanger in a heat radiation state and heated. 3. The combustion supporting gas according to claim 1, wherein the combustion supporting gas is supplied such that the residual oxygen of the exhaust gas discharged from the regenerative heat exchanger has a volume ratio of 0.1 to 1.0. Heating and heat retention method for metallurgical equipment. 4. A plurality of regenerative heat exchangers, and fuel gas is guided to a heat exchanger in a heat radiation state among the plurality of regenerative heat exchangers, and is discharged from the heat exchanger in a heat storage state. A switching valve that guides the gas to the diffusion system, and introduces the fuel gas heated by the heat exchanger in the heat radiation state into the metallurgical equipment, and transfers the fuel gas discharged from the metallurgical equipment to the heat exchanger in the heat storage state. And a switching valve that guides the combustible gas to the heat exchanger in the heat storage state among the plurality of heat storage type heat exchangers. Thermal equipment.