JPH0587726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a direct-fired burner structure used in continuous annealing equipment for steel strips, and more particularly to a burner structure for direct-fired reduction heating for heating and reducing steel strips.

[Conventional technology]

As a method for heating a steel strip, a direct flame reduction heating method is known in which the steel strip is heated and reduced by causing high-temperature combustion gas to directly collide with the steel strip from a burner. For example, special public service in Showa 62
Publication No. 21051 discloses a technique in which a non-equilibrium combustion flame is caused to directly impinge on a steel strip using a swirling flow burner to perform reductive heating.

The feature of direct flame reduction heating is that the heating rate is significantly faster than indirect heating using radiant tubes, etc., and it is suitable for direct flame heating of steel strips in annealing equipment such as continuous annealing equipment and continuous hot-dip galvanizing equipment. Therefore, if it becomes possible to heat in a completely non-oxidized state, the post-processing following heating can be simplified and many advantages will be brought about. In other words, it is possible to omit a reduction furnace in continuous annealing equipment for steel strips and continuous hot-dip galvanizing equipment, which has the effect of reducing the amount of reducing gas such as hydrogen and fuel gas used, and the maintenance cost of radiant tubes. You can expect it.

[Problem to be solved by the invention]

However, the direct fire reduction heating using the swirling flow burner disclosed in the above-mentioned Japanese Patent Publication No. 62-21051 has the problem that the reducing power is weak and reduction occurs only in a narrow area. When designing a heating furnace for direct flame reduction, the reduction capacity is insufficient compared to the heating capacity.

[Means to solve the problem]

The present invention advantageously solves the above-mentioned problems of the prior art, and provides an inner diameter for the wall of a steel strip direct-fired reduction furnace.
A straight tube-shaped burner tile section with a length of 60 to 120 mm and a length of 50 to 130 mm is provided, and the open end of the burner tile section facing the inside of the direct-fired reduction furnace is expanded to 2 to 4 times the inner diameter of the burner tile section. The gist is a steel strip direct-fired reduction heating burner structure that is provided with a diameter section and a plurality of double-pipe discharge holes that discharge fuel gas and air in layers at the bottom of the burner tile section. .

[Effect]

The present inventors conducted research on the phenomenon in which reduction occurs when combustion gas (flame) with an air ratio of less than 1.0 is directly blown onto a steel plate, and found that this phenomenon occurs when the high-temperature combustion gas in the middle of the reaction is cooled by the steel plate. As a result, the flame structure changes and the surface of the steel strip becomes a strongly reducing atmosphere.The higher the combustion gas temperature to a certain extent, the greater the effect. It was found that this decreases.

Based on the results of this research, we conducted an experimental study on the most efficient way to utilize this phenomenon, and found that this phenomenon requires a nozzle structure that can uniformly mix fuel and air, and the shape of the burner tile. It was found that it was greatly influenced by The burner tile part is a cylindrical part (straight pipe part) that extends straight in the direction in which combustion gas and air are ejected from the double-pipe discharge hole of the burner, and one end thereof is opened to the direct-fired reduction furnace. This is what we are doing.

Figure 2 shows detailed test results. The figure shows the relationship between the diameter D ₁ and length L ₁ of the straight pipe part of the burner tile part and _the reducible range.
When the length L1 was set in the range of 60 to 120 mm and the length _L1 was set in the range of 50 to 130 mm, the result was that the combustion gas during the reaction could reach the steel plate while being kept at a high temperature. The best range for reduction reaction is diameter D ₁ : 60~100mm, L ₁ : 50~
The range was 130mm.

Figure 3 shows the results of an investigation into the effect of the length of the straight pipe section of the burner tile on the burner reduction degree. It is expressed as the ratio of burner reduction area to pipe length.

This diagram shows that the burner tile straight pipe length is 50
It can be seen that the reduction reaction is best in the range of ~130 mm. The longer the length of the straight pipe within the above range, the more preferable it is from a practical standpoint since it is not affected by the atmosphere in the furnace.

In addition, Figure 3 shows a burner tile diameter of 90 mm, a distance of 250 mm between the steel strip and the burner tile, and a combustion gas:
COG10Nm ³ /H, air ratio 0.8, burner discharge hole 20
This was determined under individual conditions.

The influence of the straight pipe section of the burner tile on direct flame reduction has been explained above, but when the value is outside the above range, that is, the diameter of the straight pipe section, the spread of the combustion flow is small when D ₁ is less than 60 mm, and If it exceeds 120 mm, the combustion flow will spread too much and the reduction reaction will be reduced. On the other hand, if the length _L1 is less than 50 mm, the combustion flow rectification effect will be small, and if it exceeds 130 mm, although the reduction reaction will be good, the reduction reaction will be reduced. It generates such intense noise that it becomes unusable.

Next, the enlarged diameter portion provided at the open end of the burner tile will be explained. Figure 4 shows the value of burner tile enlarged diameter part diameter/burner tile straight pipe diameter (diameter ratio value) and reduction area in burner tile enlarged diameter part/
This figure shows the relationship between the reduction area value (reduction area ratio value) in the straight pipe portion of the burner tile, and it can be seen that when the diameter ratio is 2 to 4, the reduction area ratio is approximately 2. That is, if the diameter of the enlarged diameter part of the burner tile is made 2 to 4 times the diameter of the straight pipe part, the reduction area can be approximately doubled compared to the case where the diameter of the burner tile is not enlarged.

The reason why such an effect is obtained is that enlarging the open end of the burner tile prevents surrounding exhaust gas from being drawn in, and also has the effect of preventing thermal shock destruction of the refractory material at the open end of the burner tile.

Figure 5 shows the results of an investigation into the relationship between the distance between the steel strip and the burner tile and the reduction area. The reduction area decreases as the distance between the steel strip and the burner tile increases, and this is thought to be due to the fact that when the distance between the tile and the steel strip increases, it becomes impossible to keep the combustion gas at a sufficiently high temperature. . This allows the distance between the steel strip and the burner tile to be at least 50mm.
It can be seen that it needs to be less than 300mm.

〔Example〕

The present invention will be further explained below based on the drawings. FIG. 1 shows the burner structure of a direct-fired reduction heating furnace used in the present invention, with FIG. 1A being a side sectional view and FIG. 1B being a front view thereof.

In the figure, a burner tile portion 1 is provided at an appropriate location on a wall 7 of a direct-fired reduction heating furnace, one end of which is open and in contact with the inside of the heating furnace, and a bottom portion 2 is provided at the other end. A suitable number of outer tubes 3 into which nozzles 10 are inserted are bored in the bottom 2. In the figure, burner tile section 1
An example is shown in which the tube is composed of a straight tube portion 5 and an enlarged diameter portion 6, and the diameter and length of each portion are as described above. An outer cylinder 4 is attached to the outer periphery of the burner tile bottom 2.
A cylinder 8 is disposed within the outer cylinder 4, a fuel diffusion chamber 9 connected to the inner cylinder 8, and a nozzle 10 protruding from the wall of the fuel diffusion chamber 9. As mentioned above, the nozzle 10 is connected to the outer tube 3 at the bottom of the burner tile.
The tip thereof is inserted into the nozzle 10 so that a space is provided between the outer surface of the nozzle 10 and the outer tube 3. In this way, the burner tile bottom 2 has 2
A double pipe type discharge hole 11 is configured.

Since the burner structure of the present invention is configured as described above, when air flows into the outer cylinder 4 and fuel gas flows into the inner cylinder 8, both of them are directed toward the burner central axis through the double pipe discharge hole 11. Flows in parallel layers,
By uniformly and thoroughly mixing within the straight pipe section of the burner tile and adjusting the air ratio to 0.7 to 0.9, high temperature combustion gas is generated during the reaction, and the surface of the moving steel strip is 50 to 300 mm away from the bottom 2 of the burner tile. The high-temperature combustion gas is blown onto.

In the present invention, the structure of the burner tile straight pipe part and enlarged diameter part is designed as shown in Figs. 2 to 4, so that the steel strip surface is heated to a high temperature and becomes a strongly reducing atmosphere. Heating is performed effectively.

Note that the above description shows one embodiment of the present invention, and the burner tile straight pipe part may be constructed and planted in the bottom of the burner tile in a pipe shape. A similar effect can be obtained by flowing combustion gas into the cylinder 8.

Next, the results of reduction heating of a steel strip using the above-mentioned apparatus will be shown.

The burner part has 25 double pipes 11 on the bottom part 2 of the burner tile, and the straight pipe part of the burner tile has a diameter of 85 cm.
Using a burner structure consisting of a burner tile section with a length of 85 mm and an open end enlarged to a diameter of 320 mm, fuel gas is flowed into the inner cylinder 8 and air is flowed into the outer cylinder 4, and the following combustion conditions are set. It was burned by

Combustion conditions: Fuel: Coke oven gas Air ratio: 0.8 Burning amount: 50000 Kcal/h As a result of setting the distance between the open end of the burner tile and the steel strip to 150 mm, a reduction area of 0.08 m ³ (per burner nozzle) was obtained. This value was almost the same as the value reduced in a normal reduction furnace.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to perform direct fire reduction heating of a steel strip in a completely non-oxidizing state, and the performance can be maintained even if the distance between the steel strip and the burner tile changes over a wide range. Because of this, it can be applied to continuous annealing equipment for steel strips and continuous hot-dip galvanizing equipment, and has the remarkable effect of omitting a reduction furnace in the subsequent process.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, in which FIG. Figure 3 is a diagram showing the relationship between the straight pipe length of the burner tile of the present invention and the reduction area;
The figure shows the relationship between the shape of the enlarged diameter part of the burner tile and the reduction area, and FIG. 5 shows the relationship between the distance between the steel strip and the burner tile and the reduction situation. DESCRIPTION OF SYMBOLS 1... Burner tile part, 2... Burner tile bottom part, 3... Outer pipe, 4... Outer cylinder, 5... Burner tile straight pipe part, 6... Burner tile enlarged diameter part, 7... Reduction furnace wall body, 8... Inner cylinder, 9... Fuel diffusion chamber, 10... Burner nozzle, 11... Double pipe discharge hole, A... Burner structure, B... Inside of reduction furnace.

Claims (1)

[Claims] 1. The wall of the steel strip direct-fired reduction furnace has an inner diameter of 60 to 120 mm,
An open flame of a steel strip, characterized in that a straight tube-shaped burner tile section with a length of 50 to 130 mm is provided, and a plurality of double-pipe discharge holes for discharging fuel gas and air are provided at the bottom of the burner tile section. Burner structure for reduction heating. 2. The burner structure according to claim 1, wherein a portion of the burner tile portion facing the inside of the direct-fired reduction furnace is provided with an enlarged diameter portion that is 2 to 4 times the inner diameter of the burner tile portion.