KR20030018823A - Device for heating ladle uniformly - Google Patents

Abstract

PURPOSE: A device for heating stainless steel casting ladle uniformly is provided to heat the ladle uniformly by adhering various shaped nozzles to the longitudinal part of burner of the ladle so that flame of the burner of the ladle reaches the bottom of the ladle. CONSTITUTION: In a ladle drying device comprising a ladle cover(2) covered on the upper part of the ladle(1), a burner installed at the center of the cover, and fuel supply pipe(4) and air supply pipe(5) for supplying coke oven gas and air to the burner(3), the device for heating stainless steel casting ladle uniformly further comprises a pipe shaped nozzle having a certain length installed at flame guide(6) of the burner, wherein the upper part of the nozzle has the same diameter as the lower part thereof, wherein the nozzle has a structure in which inner diameter of the nozzle is being decreased as it goes from the upper side to the lower side, wherein observation holes are formed on the outer circumferential surface of the nozzle with being spaced apart from each other in a certain distance to check flame inside the ladle, wherein the nozzle is a heat resistance alloy steel comprising 38 to 42 wt.% of cobalt, 25 to 32 wt.% of chromium and 15 to 25 wt.% of nickel, and wherein the nozzle is formed of silicon nitride, sialon and silicon carbide based material.

Description

Device for heating ladle uniformly

The present invention relates to a heating apparatus for heating the interior of a stainless steel casting ladle, and more particularly, by attaching various types of nozzles to the burner end of the ladle, the flame of the ladle burner reaches the bottom of the ladle so that the ladle is uniform. It relates to a uniform heating device of the ladle to be heated.

A stainless steel casting ladle is a container for high temperature (1500 ℃ or more) molten metal. The inside is mainly made of fixed refractory material and the outside is made of iron plate. Ladles used in general steel mills have recently been applied to irregular refractory materials such as castables due to problems in construction and economic reasons. Since a large amount of crystallized water and adsorbed water contained in the amorphous refractory material must be removed through the heating process, heating is generally performed at about 1000 ° C. for 36 to 65 hours.

However, since the interior of the stainless steel casting ladle is mainly made of orthogonal refractory, and its capacity is about 100 tons smaller than that of the general steel ladle (300 tons), the ladle is heated for 18 to 30 hours shorter than the ladle heating time of general steel. Done.

In addition, if the ladle temperature is not heated above a certain temperature before receiving the hot melt in the ladle, problems such as high melt of the metal are scattered or solidified. Therefore, ladles of general steelmaking are usually dried and heated to about 1000 ° C. Casting ladles are used by heating at 1200 ° C, which is about 200 ° C higher than the heating temperature of ladles in general steelmaking.

Figure 1 is a schematic diagram showing the shape of the casting ladle and the burner generally used in stainless steel mills.

According to the above figure, drying of the ladle 1 is performed by the burner 3 installed in the ladle cover 2 which is covered on the upper ladle, and the coke oven gas and the air supply pipe 5 supplied to the fuel supply pipe 4 are Air supplied to) is mixed and burned in the burner attached to the ladle cover, and the burned flame is flowed into the ladle by the flame guide 6.

Here, the inner wall of the casting ladle used in the stainless steel mill is mainly made of orthogonal refractory, and part of the floor is made of amorphous refractory.

The cast ladles constructed with the standard and amorphous refractory materials are thus heated by a predetermined temperature raising pattern up to 1200 ° C. without the reference thermocouple.

However, even if the inside of the ladle is heated by a predetermined temperature raising process for drying and heating the casting ladle, the flame formed in the burner does not sufficiently reach the bottom of the ladle when heated by a conventional burner. In addition to spurious phenomena due to uneven heating and refractory of the fire, the complete combustion of the fuel does not occur, resulting in high fuel consumption, energy loss and environmental problems.

In other words, ladle drying uses a burner attached to a cover used in a stainless steel mill where the flames of the burner do not reach the bottom of the ladle sufficiently, causing uneven heating of the ladle and spalling of the refractory due to rapid heating. In addition, the flame formed in the burner does not cause complete combustion, so a large amount of fuel is consumed, causing problems such as energy loss and pollutant discharge into the atmosphere.

Therefore, the present invention has been made to solve the above problems, by installing a nozzle of a certain length in the burner for drying and heating the casting ladle to raise the ladle, the flame of the burner evenly reaches the bottom of the ladle ladle It is an object of the present invention to provide a uniform heating device of a ladle for casting stainless steel, which is to uniformize the temperature distribution and thereby suppress the spalling phenomenon of the refractory and to completely burn the fuel.

It is also an object of the present invention to provide a uniform heating device of a stainless steel casting ladle to reduce the fuel consumption to enable cost reduction.

1 is a schematic drawing generally showing a stainless steel ladle and a burner for heating the ladle;

2 is a cross-sectional view showing a state in which the ladle heating apparatus according to the present invention is installed on the ladle,

3a and 3b show a nozzle of the ladle heating apparatus according to the present invention,

4 is a graph showing the temperature distribution in the hydrophobic ladle heated by the ladle heating apparatus according to the present invention,

5 is a graph showing the temperature distribution in the heavy repair ladle heated by the ladle heating apparatus according to the present invention,

Figure 6 is a graph showing the temperature distribution of the ladle according to the heating time of the hydrophobic ladle according to the prior art.

Explanation of symbols on the main parts of the drawings

20: nozzle

In order to achieve the object as described above, the present invention, in the burner for drying and heating the casting ladle which is installed in the center of the ladle cover and composed of a fuel supply pipe and an air supply pipe, a nozzle of various types is attached to the flame guide of the burner. It is characterized in that the flame to reach the bottom of the ladle.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic drawing showing a ladle for ladle casting and a burner for heating the ladle in general, FIG. 2 is a cross-sectional view showing a ladle heating apparatus installed in the ladle according to the present invention, FIGS. 3b shows a nozzle of a ladle heating apparatus according to the present invention.

According to the above drawings, the present invention has a structure in which a flame spray nozzle 20 having a predetermined length is mounted on the flame guide 6 of the burner 3 installed inside the cover 2 of the ladle 1. have.

The nozzle 20 has a pipe shape, and the flange 21 is integrally formed at the top of the nozzle 20, and a bolt fastening hole is formed along the flange to be bolted to the flame guide of the burner.

The nozzle may have a structure having the same diameter as the top and the bottom as shown in FIG. 3A, and may have a structure in which the diameter decreases toward the bottom as shown in FIG. 3B.

In addition, an observation hole 22 is formed in the outer surface of the nozzle 20 so that the flame can be observed. The observation holes are arranged at regular intervals along the outer circumferential surface of the nozzle, and six observation holes are preferably formed at 60 degree intervals.

On the other hand, looking at the material of the nozzle 20, the nozzle can not be used for heat-resistant alloy steel, such as nickel / chrome steel, nickel / cobalt steel that can be used in a general steel mill that heats the ladle to about 1000 ℃, instead of skid of the heating furnace Cobalt / chromium (25 to 32 wt%) / nickel (15 to 25 wt%) heat-resistant alloy steel with cobalt (Co) content of 38 to 42 wt% used for rails, and high strength and toughness at high temperatures It is preferable to fabricate a ceramic material of silicon nitride, sialon, and silicon carbide, but considering the economics of nozzle manufacturing and ease of nozzle installation, alloy steel of cobalt / chromium / nickel type is effective.

Hereinafter, a method and apparatus for uniform heating of the present invention stainless casting ladle will be described in detail by comparing a working condition using a burner for heating a conventional casting ladle and a nozzle according to the present invention.

Comparative Example 1

First, the inside of the ladle was heated by heating the conventional ladle burner.

The combustion conditions used at elevated temperatures are generally used by the operators. The air flow rate is fixed and the COG opening rate is heated to 30% at the start of heating and up to 60% after 8 hours to heat the ladle. Four (11, 21, 31, and 41) and the top of the ladle wall at an interval of 1050 mm from the top of the center of the ladle to 200 mm from the center of the burner to measure the temperature at each position inside the ladle at elevated temperature A total of eight thermocouples (51, 61, 71, 81) were installed at intervals of 1050 mm in a downward direction, and the temperature of each part was measured at 10 minute intervals.

As such, by measuring the internal temperature of the hydrophobic casting ladle for 14 hours by the conventional burner, the results are shown in FIG. 4.

As can be seen in Figure 4, unlike the ladle of the general steel mill, the temperature of the ladle bottom (thermocouples 41 and 81) was higher in the upper temperature (thermocouples 11 and 41), this phenomenon is the ladle of the general steel mill (burner capacity: normal It is due to the large burner capacity (3 million kcal / h) of the stainless steel mill, despite the small capacity compared to 2 to 2.2 million kcal / h. From the beginning of heating, the flow rate of COG was artificially manipulated, indicating that the atmospheric temperature of the ladle increased rapidly. In addition, the ladle cover was not equipped with a reference thermometer so that the operator could not perform standard operations, and it was impossible to check whether the ladle was heated to an appropriate reference temperature.

Due to the excessive burner capacity, a large amount of energy is wasted during heating of the ladle, and the rapid heating of the ladle causes the spalling phenomenon of the fixed refractory structure constructed in the ladle and the collapse of the irregular refractory formed in the second part.

Invention Example 1

A nozzle 20 made of a heat-resistant alloy steel having an inner diameter of 220, a thickness of 12, and a length of 945 mm was attached to the flame guide 6 of the burner for the ladle, and the inside of the hydrophobic casting ladle 1 was heated to heat.

Unlike the comparative example 1, the combustion conditions used for heating were heated at the initial stage of heating by adjusting the COG opening rate to 20%, 30% after 1 hour 30 minutes, and 50% after 7 hours, and the temperature of the same position was measured. The results are shown in FIG.

As can be seen in FIG. 5, the ladle is not heated rapidly by setting the COG opening rate to 20% at the beginning of heating, and the temperature distribution by the nozzle shows a temperature distribution similar to that of a conventional burner, but the flame of the burner is the center of the ladle. It can be seen that it is concentrated at and heated. In the ladle heating by the nozzle at 60% by the conventional burner, the ladle could be heated above the same temperature even if the COG opening rate was reduced by 50%.

In this way, when the hydrophobic ladle is heated by the nozzle, the COG opening ratio can be appropriately controlled to suppress the rapid heating of the refractory material installed in the ladle, and the burner's flame is concentrated at the center of the ladle to heat the ladle uniformly. And even a small amount of fuel can heat the ladle above the same temperature, resulting in significant energy savings.

Invention Example 2

Like the invention example 1, the nozzle 20 was attached to the flame guide 6 of the ladle burner, and the inside of the repair ladle 1 which was repaired was heated up and heated.

The heating conditions used for heating were heated at the initial stage of heating to adjust the COG opening rate to 20%, 30% after 2 hours, and 55% after about 4 hours, and the temperature was measured at the same position. The results are shown in FIG. It was.

As can be seen in FIG. 6 the temperature of the ladle bottom (thermocouples 41 and 81) was heated to the same temperature of this, and the temperature of the ladle top (thermocouples 11 and 51) was heated somewhat lower than the bottom. In the heating of the heavy repair ladle by the conventional burner, the COG opening rate is adjusted to 30% at the start of heating, and after 3 hours, the opening rate is adjusted to 60%. In the heating of the heavy repair ladle by the nozzle according to the present invention, the heating of the ladle is controlled by adjusting the COG opening ratio, thereby suppressing the rapid heating of the refractory, the flame of the burner is concentrated in the center, and the uniform heating of the ladle and the small amount of COG fuel. The ladle could be heated above the same temperature in a shorter time than the heating period.

In this way, the nozzle suppresses the rapid heating of the refractory material installed in the ladle by adjusting the COG opening degree in the same way as the heating of the hydrophobic ladle, and by heating the flame of the burner to the center of the ladle, heating the ladle uniformly and Significant energy savings could be achieved by heating the ladle above the same temperature with fuel.

According to the method and apparatus for uniformly heating the ladle for a stainless steel casting according to the present invention as described above, the suppression of rapid heating of the refractory material installed in the ladle by the control of the COG opening ratio, and focusing the burner flame in the center of the ladle A substantial amount of energy savings could be achieved by uniform heating of the ladle by heating the same and by heating the ladle above the same temperature with a small amount of fuel.

Claims (6)

In a ladle cover that covers the upper ladle, a burner installed in the center of the cover, a ladle drying apparatus including a fuel supply pipe and an air supply pipe for supplying coke oven gas and air to the burner, The uniform heating device of the ladle for casting stainless, characterized in that the nozzle of the pipe length is further installed in the flame guide of the burner. The method of claim 1, wherein the nozzle is a uniform heating device of the ladle for casting stainless, characterized in that the top and the bottom has the same diameter. The apparatus of claim 1, wherein the nozzle has a structure in which an inner diameter decreases toward a lower end thereof. According to any one of claims 1 to 3, wherein the nozzle is a uniform heating device for a stainless steel ladle, characterized in that the observation hole is formed at a predetermined interval along the outer surface to check the internal flame. The stainless steel casting according to any one of claims 1 to 3, wherein the nozzle is a heat-resistant alloy steel made of 38 to 42% by weight of cobalt, 25 to 32% by weight of chromium, and 15 to 25% by weight of nickel. Heating device. The apparatus of claim 1, wherein the nozzle is made of a ceramic material of silicon nitride, sialon, and silicon carbide.