KR100333065B1 - Nozzle attached device for drying and heating ladle - Google Patents

Abstract

PURPOSE: A nozzle attached device for drying and heating ladle is provided to uniformly heat the ladle by adhering various typed nozzles onto the end part of a conventional ladle burner so that flame of the ladle burner gets to the bottom of the ladle. CONSTITUTION: In a burner(3) for drying and heating a ladle where the burner is installed at the central part of a ladle cover(2) and consisted of fuel supply port(4), air supply port and flame guide(6), the nozzle attached device for drying and heating the ladle is characterized in that the nozzle attached device uniformly dries and heats upper and lower parts of the inside of the ladle(1) by adhering a long nozzle formed of Ni/Cr steel or Cr/Co steel based heat resisting alloy steel, silicon nitride, sialon or silicon carbide based ceramic material onto the flame guide(6).

Description

Drying and heating device of ladle with nozzle

The present invention relates to a ladle drying and heating apparatus having a nozzle attached to a conventional ladle burner end by attaching various types of nozzles so that the flame of the ladle burner reaches the bottom of the ladle to be uniformly heated.

The ladle is a container that holds a molten metal of high temperature (above 1500 ℃), and the inside is made of various kinds of refractory, and the outside is made of iron plate.

Refractories in conventional ladles have been constructed mainly as refractory having a certain form (hereinafter referred to as orthogonal refractory).

However, in recent years, construction methods for constructing ladles with irregular refractory materials such as castables have been expanded due to problems in construction due to construction and economic reasons.

The amorphous refractory material is added to the wall and bottom of the ladle by adding a large amount of moisture during construction.

Therefore, after the refractory is installed inside the ladle, a large amount of crystalline water and adsorbed water included in the amorphous refractory should be removed through drying and heating.

In addition, the temperature inside the ladle is not heated above a certain temperature (1100 ℃) before receiving the hot melt in the ladle, and the hot melt is scattered or solidified, causing problems such as heating. Should be.

1 is a schematic view showing the shape of a ladle and a burner used in a conventional steel mill.

The burner 3 for heating the conventional ladle 1 is combusted by mixing the coke oven gas supplied through the fuel supply port 4 and the air supplied through the air supply port 5, and the flame guide 6. The combustion stream is formed by

The interior of the ladle (1) used in the steel mill of the steel mill is constructed of castable (7), an amorphous refractory, and the amount of moisture in the castable (7) is 6% by weight, which includes 1.5 to 1.7 tons. have.

The ladle 1 constructed of amorphous refractory material is dried and dried in the castable 7 in a temperature rising process for 72 hours up to 1000 ° C. based on the temperature measured by the reference thermocouple 50. Heating will be performed.

Ladle (1) during the drying and heating process, the moisture in the castable (7) is initially supplied by a small amount of fuel and air is removed by heating at a slow rate of heating, since the flame formed only acts on the upper portion of the ladle (1) Due to this, a shape in which the flame hardly reaches the bottom of the ladle 1 occurs.

Therefore, the water in the amorphous amorphous refractory at the top is removed, but the water at the bottom is not evaporated, but the amount of fuel and air is increased so that the flame reaches the bottom and thus cannot be evaporated in the castable 7 below the ladle 1. Residual water expands rapidly and vapor pressure suddenly increases, causing the refractory to thermal explosion.

Such explosion of amorphous refractory material is mainly generated at a temperature of 400-500 ° C. or lower, which is the temperature of the initial heating in which small amounts of fuel and air are supplied.

However, even if the inside of the ladle is heated in a predetermined temperature raising process to remove such moisture, the crystal water and the adsorbed water contained in the amorphous refractory material are constant due to the temperature difference between the upper and lower ladles when heated by a conventional burner. It is not removed at a rate and often causes the refractory to thermal explosion.

Thus, the ladle 1 conventionally used in steel mills was dried by raising the ladle 1 to a predetermined temperature by the burner 3 attached to the ladle cover 2, and thus the flame to the bottom of the ladle 1 This was not sufficiently reached and had problems such as non-uniform heating and explosion of refractory due to poor combustion inside the ladle 1, temperature difference between the upper and lower parts.

The present invention has been invented to solve the above conventional problems, by installing a nozzle in the drying and heating burner of the ladle to raise the ladle, through which the flame inside the ladle to reach the bottom enough during the drying process By drying the refractory uniformly by reducing the temperature difference between the upper and lower part of the field, it prevents the explosive phenomenon of amorphous refractory and can be heated at a high speed even when the ladle is heated, thereby saving fuel and improving productivity. It is an object of the present invention to provide an apparatus for drying and heating a ladle with a nozzle.

1 is a schematic diagram showing the shape of the ladle and the burner used in the conventional steel mill,

2a, 2b and 2c are cross-sectional views showing various shapes of the nozzle according to the present invention, respectively,

3 is a graph showing the temperature distribution and the reference temperature and the temperature difference in the bottom of the ladle by a conventional burner for the ladle,

4, 5 and 6 are graphs showing the temperature distribution in the ladle and the temperature difference between the reference temperature and the bottom, respectively, according to one embodiment of the present invention;

Figure 7 is a front sectional view showing a ladle drying and heating apparatus with a nozzle of the present invention.

<Explanation of symbols for main parts of drawing>

1: ladle 2: ladle cover

3: burner 4: fuel inlet

5: air inlet 6: flame guide

7: castable 10: nozzle

50: reference thermocouple 51-59: thermocouple

The present invention for achieving the above object, is installed in the center of the ladle cover (2) burner for ladle drying and heating consisting of a fuel supply port (4), air supply port (5) and flame guide ( 3) The ladle (1) is attached to the flame guide (6) by attaching a long nozzle (10) formed of a nickel / chromium steel or chromium / cobalt-based heat-resistant alloy steel or a silicon nitride, sialon or silicon carbide-based ceramic material. It is characterized in that it is configured to uniformly dry and heat the upper and lower portions of the interior.

Hereinafter, with reference to the accompanying drawings, the drying and heating apparatus of the ladle with a nozzle of the present invention will be described in detail.

Figure 7 is a front sectional view showing a ladle drying and heating apparatus with a nozzle of the present invention.

In the present invention, in order to reduce the temperature difference between the upper part and the lower part of the ladle 1, as shown in FIGS. 2a, b, and c, a long nozzle 10 of various forms is installed in the burner 3, and fuel In the initial stage of heating and low air volume, the flame was sufficiently reached to the bottom of the ladle 1 to facilitate evaporation of moisture contained in the refractory to prevent thermal explosion.

The nozzle 10 is made of a heat resistant alloy steel such as nickel / chromium steel or chromium / cobalt steel having a low strain rate at the operating temperature of the ladle 1 or a ceramic material of silicon nitride, sialon and silicon carbide having excellent strength and toughness at high temperature. It is preferable to produce.

Hereinafter, a ladle drying and heating apparatus with a nozzle of the present invention will be described in detail by comparing a working condition using a burner with a nozzle according to the present invention and a burner for ladle heating according to the present invention.

First, the inside of the ladle 1 was heated with a conventional ladle burner 3 and heated.

The combustion conditions used at elevated temperature are maintained at a constant condition of 120 Nm3 / h of air flow rate, and the coke oven gas (COG) flow rate is 6 Nm3 / h from the beginning of heating to 3 hours, and 12 Nm3 from 3 hours to 7 hours. / h, ladle was heated to 14 Nm 3 / h from 7 hours to 9 hours and 15 Nm 3 / h from 9 hours to 12 hours.

In order to measure the reference temperature inside the ladle 1 and the temperature at each position, the reference thermocouple 50 is placed on the ladle cover 2 at a temperature of 190 mm from the upper side of the ladle 1 and below it. Eight thermocouples 51, 52, 53, 54, 55, 56, 57, 58, and 59 were provided at intervals of 180 mm each in the direction.

All of the thermocouples 51 to 59 were installed at a position of 100 mm from the wall surface, and the temperature of each part was measured at 30 minute intervals.

Reference thermocouple 50, average temperature of the three thermocouples (51, 52, 53) located at the top, average temperature of the three thermocouples (54, 55, 56) located at the center, three thermocouples (57, 58) located at the bottom (59), and the difference in temperature between the average temperature and the reference temperature and the floor are shown in FIG.

As can be seen in FIG. 3, the temperature of the upper part of the ladle 1 tended to be significantly higher than the temperature of the lower part during the entire heating process.

The average temperature of the reference temperature and the bottom part showed a difference of 100 ° C from the beginning of heating. At the reference temperature of 300 ° C, the difference was reduced to about 180 ° C with the largest temperature difference of 228 ° C and the increase of the reference temperature to 500 ° C.

As such, the temperature difference between the reference temperature and the lower portion of the ladle 1 causes the adsorbed water and the crystallized water contained in the amorphous refractory body constructed in the ladle 1 to not evaporate slowly, causing the refractory heat-expanding phenomenon.

<Inventive Example 1>

Next, a nozzle 10 made of a heat-resistant alloy steel having an inner diameter of 130 mm, a tip diameter of 100 mm, and a length of 500 mm was attached to the flame guide 6, and the inside of the ladle 1 was heated to be heated.

The combustion conditions used at the time of temperature increase were the same as before, the temperature of the same position was measured, and the result is shown in FIG.

As can be seen in FIG. 4, the temperature difference between the upper and lower parts of the ladle 1 as the heating time elapsed was significantly lower than that of the conventional ladle burner 3 in which the nozzle 10 was not installed.

The difference between the reference temperature and the average temperature at the bottom was increased to 67 ° C by increasing the temperature at 55 ° C at the beginning of heating, and when the reference temperature increased to about 350 ° C, the temperature difference decreased to 30 ° C.

The low temperature difference between the upper part and the lower part of the ladle 1 prevents the thermal expansion of the refractory by uniformly evaporating various moisture contained in the refractory constructed in the ladle 1.

<Inventive Example 2>

Next, as in Inventive Example 1, a nozzle 10 made of a heat-resistant alloy steel having an inner diameter of 130 mm, a diameter of 100 mm and a length of 500 mm is attached to a conventional flame guide 6 to heat up the inside of the ladle 1. Heated. The combustion conditions used for the temperature increase were used as the same conditions as above, a total of 10 thermocouples were installed at the same temperature as above to measure the temperature of each part continuously.

Reference temperature and the average temperature of the top, center and bottom, and the temperature difference between the reference temperature and the bottom in the example of the present invention are shown in FIG.

However, unlike Inventive Example 1, a nozzle 10 having a reduced diameter of the end portion of the nozzle 10 was used.

The difference between the standard temperature and the average temperature at the bottom was significantly lower than the conventional temperature difference of 150 ° C. at 15-20 ° C. at the beginning of heating, and the temperature difference was about 40 ° C. even when the reference temperature increased to 250 ° C.

The composition of the heat-resistant alloy steel used in Inventive Example 1 and Inventive Example 2 was carbon (C) 0.35-0.45, silicon (Si) ≤ 1.75, manganese (Mn) ≤ 1.5, molybdenum (Mo) ≤ 0.5, chromium (Cr) 24 -27, nickel (Ni) 19-22% by weight nickel / chromium steel, its strain rate is 0.06% or less, even under loads of 2,3,4 and 6 kg / 까지 up to 200 minutes holding at 1000 ℃ It is suitable for the nozzle 10 for a ladle.

<Inventive Example 3>

Next, a ladle (1) was attached to the flame guide 6 by attaching a silicon carbide (SiC) -like nozzle 10 having an inner diameter of 130 mm, a diameter of 100 mm and a length of 500 mm, the same as that used in Inventive Example 2 above. The internal temperature was measured.

The same combustion conditions and a total of 10 thermocouples were installed to measure the temperature of each part, and the reference temperature, the average temperature of the upper, middle and bottom of the ladle 1, the temperature difference between the reference temperature and the bottom are shown in FIG. 6.

In the initial heating with the nozzle 10 of the same type as Inventive Example 2, the difference in temperature between the reference temperature and the bottom is 20-30 ° C, the reference temperature is 270-360 ° C, and the temperature difference is 30-50 ° C and the reference temperature is 360 ° C or higher. The temperature difference then decreased below 40 ℃.

The room temperature strength (four point bending strength) of the silicon carbide used in the present invention has a strength of 34.7 kg / mm 2, 48.5 kg / mm 2 at 1000 ° C. and 47.2 kg / mm 2 at 1200 ° C., which is suitable for the ladle nozzle 10. In addition, sialon and silicon nitride ceramics having similar properties to silicon carbide can be used.

As described above, by using the ladle drying and heating apparatus equipped with the nozzle of the present invention, the temperature deviation of the upper and lower portions of the ladle can be significantly reduced to improve the combustion state by uniform heating of the ladle, and included in the amorphous refractory material. It is possible to prevent economic losses due to the reconstruction by preventing the refractories of refractories by the gradual heating and evaporation of the moisture, and has a useful effect such as cost reduction by increasing the lifetime by uniform heating of the ladle.

Claims (1)

In the burner 3 for ladle drying and heating, which is installed at the center of the ladle cover 2 and composed of a fuel supply port 4, an air supply port 5, and a flame guide 6, the flame guide 6 is provided. Elongate nozzle 10 formed of nickel / chromium steel or chromium / cobalt steel based heat-resistant alloy steel, or silicon nitride, sialon or silicon carbide based ceramic material to uniformly dry and heat the upper and lower parts of ladle 1 Ladle drying and heating apparatus with a nozzle, characterized in that configured to enable.

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