JPH0213011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel heating furnace that uniformly heats steel materials such as slabs and billets to a target rolling temperature.

Conventionally, this type of heating furnace was heated on the heated material (steel material).
Direct-fire combustion type heating furnaces are generally used, which have a combustion chamber with a direct-fired burner placed on the bottom and heat the material while transporting it from the charging side to the extraction side. It is generally known that there are three types of burner arrangement methods: side burners, axial burners, and roof burners.

The former side burner method has a structure in which burners are placed on both side walls of the furnace, so it is generally easy to obtain a relatively uniform furnace temperature distribution in the furnace length direction, but it is not possible to obtain a uniform furnace temperature distribution in the furnace width direction. However, since the furnace structure is simple, the equipment cost is low.

On the other hand, the middle axial flow burner method has a structure in which the burners are arranged in the longitudinal direction of the furnace, so contrary to the side burner method, a relatively uniform furnace temperature distribution is generally obtained in the width direction of the furnace. However, it has the disadvantage that it is difficult to obtain a uniform furnace temperature distribution in the furnace length direction, and in terms of equipment, it is necessary to provide a nose section in the furnace width direction due to the burner arrangement, which reduces the hearth utilization rate. It has the drawbacks of low cost, high equipment cost, and poor workability and maintainability.

On the other hand, the latter roof burner method, due to its characteristics,
Because the burners are placed on the ceiling wall of the upper combustion chamber, a relatively uniform furnace temperature distribution can be obtained over the entire width and length of the furnace. Since the number of burners is larger than that in the conventional method, the equipment cost is generally high, and due to the nature of the burner arrangement, it has the disadvantage that it can only be applied to the upper combustion chamber.

Also, when looking at this type of direct combustion method from the combustion function point of view, the fuel supplied from the burner and the combustion air are mixed and burned directly in the free space inside the furnace (combustion chamber), and the combustion gas emits a bright flame. , which uses gas radiation and furnace wall radiation to heat the material to be heated, but in general, in this type of direct combustion method, even if the ejection energy of the fluid supplied from the burner is sufficiently large, the The flame length is only 3 to 4 m at most, and in addition, during low-load combustion, the ejection energy of the burner supply fluid is also reduced, which reduces the straightness of the flame, resulting in flame soaring phenomena due to buoyancy and flame bending due to gas flow in the furnace. Because of the basic problem of the occurrence of this phenomenon, the furnace was made larger (10 to 15 m in width and 30 to 50 m in length) like recent heating furnaces.
Conventional direct-fire combustion methods were not able to adequately cope with the growing demand for heat treatment and diversification of operations (uniform heating over a wide temperature range from 950 to 1,250 degrees Celsius).

In addition, recently, as furnaces have become larger, there has been a general tendency to adopt a walking beam method as a means of transporting heated materials, but in this walking beam method, heated materials are supported by a fixed and movable skid with heat insulation and a water-cooled structure. Due to the conveyance method, heat transfer to the heated material directly above the skid pipe is inhibited by the shadow effect of the skid pipe, so it has the disadvantage that it is difficult to heat compared to other parts of the heated material. In order to uniformly heat the heated material, actively heat this skid shadow part in the initial stage of heating.
It is desirable to form a furnace temperature distribution with a so-called peak temperature, but in conventional direct-fire combustion type heating furnaces, it is generally impossible to create a peak furnace temperature at any point, that is, at the skid part. .

The present invention focuses on improving the uniform heating of the heated material, which is a problem with conventional direct-fired combustion heating furnaces, and aims to increase heating T/H and improve quality by preventing uneven heat of the heated material. In order to use the side burner method, which has low equipment costs, we arranged multiple semi-cylindrical radiant tubes with their cross sections facing downward, with one end located inside the furnace.
A combustion device is disposed at the furnace wall tube end of each radiant tube, and
A plurality of combustion gas distribution walls are disposed below each radiation tube at a predetermined interval perpendicular to the radiation tube, and a cross section of a semi-cylindrical radiation tube is formed on the upper end surface of the combustion gas distribution wall on the radiation tube side. This is a steel heating furnace characterized by having a combustion gas passage groove in opposition to the combustion gas passage groove.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

In the figure, 1 is a furnace wall with fireproof insulation and airtightness, 2 is a plurality of roof burners arranged in the furnace length direction and furnace width direction on the ceiling of the furnace wall 1, and 3 is a furnace wall on the furnace wall 1 in the furnace length direction. Side burners are arranged on both lower side walls, 4 is a partition wall for partitioning the inside of the heating furnace into each combustion chamber, 5 is a material to be heated, that is, steel material, 6 is a preheating zone, 7 is a heating zone, and 8 is an equalization zone. It is tropical.

9 is a fixed skid for supporting the heated material 5;
Reference numeral 10 denotes a movable skid for conveying the heated material 5, and the outer surface of the water cooling pipe has a heat insulating structure.

Reference numeral 11 denotes a semi-cylindrical radiant tube with a required length of heat resistance and thermal conductivity provided at the tip inside the furnace of the side burner 3 with the cross section facing downward; 12 the semi-cylindrical radiant tube 11 It is a combustion gas dispersion wall that has heat resistance to support and fix the combustion gas emitted from the side burner 3 into the furnace at the same time, and is usually installed orthogonally at the bottom of the semi-cylindrical radiant tube 11. It has multiple stages.

Reference numeral 13 denotes a combustion gas passing rod that is provided on the upper end surface of the combustion gas distribution wall 12 on the side of the radiation tube 11 so as to face the cross section of the radiation tube 11.

Further, the broken line arrows in the figure indicate the flow of combustion gas from the roof burner 2, and the solid line arrows indicate the flow of combustion gas distributed and supplied into the furnace from the side burners.

Next, the operational functions of the present invention will be explained.

The material to be heated 5 charged into the heating furnace is directed from the preheating zone 6 on the charging side to the soaking zone 8 on the extraction side by means of a fixed skid 9 and a movable skid 10, which are supporting and conveying devices for the heated material 5. While the material to be heated 5 is transported, the upper surface of the material to be heated 5 is heated by the roof burner 2, and the lower surface of the material to be heated 5 is heated by the side burner 3.

In this case, since the lower part of the heating furnace is composed of the side burner 3, the semi-cylindrical radiant tube 11, and the combustion gas distribution wall 12, the fuel and combustion air supplied from the side burner 3 are transferred to the semi-cylindrical radiant tube 11. Because mixed combustion takes place inside the furnace, it is less susceptible to the effects of buoyancy and gas flow in the furnace than conventional direct-fire combustion systems, and it is possible to ensure a stable furnace temperature distribution regardless of the amount of combustion.

Furthermore, this combustion gas is designed to flow through the semi-cylindrical radiant tube 11 to near the center of the furnace, and an appropriate number of combustion gas distribution walls 12 are provided at required positions of the semi-cylindrical radiant tube 11. Since the combustion gas distribution wall 12 is provided with a combustion gas passage groove 13 having a required opening area, a part of the combustion gas jet at the bottom of the semi-cylindrical radiant tube 11 is The gas collides with the gas distribution wall 12 and is distributed and supplied into the furnace.

Therefore, by appropriately combining the opening area of the combustion gas passage groove 13 and the mounting position and number of the combustion gas distribution walls 12, it is possible to ensure a temperature distribution that matches the heating purpose. Before the heat is raised, in the heating zones 6 and 7, the combustion gas distribution wall 12 is arranged so that the opening area is successively reduced from the side burner 3 side in the order of A, B, and C in Fig. 4. A peak furnace temperature is formed in the width direction of the furnace, and the so-called skid shadow area between the fixed skid 9 and the movable skid 10 is actively heated. 4
Combustion gas dispersion wall 1 with a wide opening area as shown in A in the figure
2 over the entire area, it is possible to form a uniform furnace temperature distribution in the width direction of the furnace.
It has become possible to stably and uniformly heat the heated material 5 over a wide heating temperature range of 950 to 1250°C.

Next, we will demonstrate the effects of the present invention in a combustion experimental furnace (height 1.8 x width 3.0).
x length 6.4m).

The experiment was conducted in the width direction of the furnace to confirm the effect of the present invention.
Two burners with a combustion rate of 1.5 million Kcal/h are installed at a pitch of 1.7 m, and a water-cooled heat-absorbing pipe is placed on the ceiling furnace wall to simulate heat extraction by the heat-receiving material 5. The fuel is coke oven gas, combustion Figures 5 and 6 show the results of a comparison between the conventional direct flame heating system and the heating system of the present invention under the common conditions of using hot air at 300°C as the air and an air ratio of 1.1.

FIG. 5 shows a measurement example of the furnace temperature distribution of a gas two-flow side burner, which is highly rated as having the best temperature distribution characteristics in the furnace width direction in actual furnaces, as an example of the conventional direct-fire combustion method.

Moreover, FIG. 6 shows an example of measuring the furnace temperature distribution when the semi-cylindrical radiant tube 11 and the combustion gas distribution wall 12 of the present invention are combined. 400φ for pipe 11
This is the result of using a half-split SiC tube with a length of 3.2 m. The diagonal line A in the figure shows the combustion gas distribution wall 12 arranged in all stages in the shape of A in Figure 4, and the combustion gas passage groove 13. The area of is the opening area ratio (400φ
(ratio to the cross-sectional area of These are the results when the opening area ratio gradually decreases from the burner side to 240, 240, 60, 20, and 20%.

In Figures 5 and 6, the horizontal axis shows the distance from the burner, and the vertical axis shows the furnace temperature. It is shown as the difference between the combustion amount 20~
The results of experiments conducted in the 100% range are shown in the shaded area in the figure.

In other words, in the conventional direct combustion method, approximately
There is a peak temperature of the flame at a point of 1.5 m, and beyond that point, the furnace temperature rapidly decreases, showing a so-called temperature trend at the burner side. Therefore, in large furnaces with a wide furnace width, the furnace temperature at the center of the furnace decreases rapidly. This indicates that the temperature becomes lower and the uneven heat of the heated material 5 becomes larger.

On the other hand, the semi-cylindrical radiation tube 11 and the combustion gas distribution wall 1
In the present invention, which is a combination of the above two, by appropriately selecting the position of the combustion gas distribution wall 12 and the opening area of the combustion gas passage groove 13, as shown in FIG. It is possible to freely create a furnace temperature distribution that has a peak point, and the furnace temperature distribution, which in conventional direct combustion methods was determined primarily by the burner type and combustion amount, can be freely created to suit the heating purpose. Now you can choose.

In the above embodiment, the roof burner 2 and the side burner 3 are combined, but the upper part of the furnace is an axial flow burner, and the lower part is an axial flow burner in which a semicylindrical radial tube 11 and a combustion gas distribution wall 12 are combined. Furthermore, it is also possible to combine these.

As described above, the steel heating furnace of the present invention has a semi-cylindrical radiant tube at the tip of the direct-fired combustion burner in order to improve the furnace temperature distribution in the burner length direction, which was a problem with conventional direct-fired heating furnaces. This heating method distributes and supplies combustion gas to desired locations within the furnace by arranging combustion gas distribution walls and a combustion gas dispersion wall, allowing for a greater degree of freedom in the variability of furnace temperature distribution than with conventional direct-fire heating systems. ,
Since it is possible to arbitrarily form a furnace temperature distribution suitable for the heating purpose, it is possible to uniformly heat the material to be heated, that is, to improve quality.

Because combustion occurs in a semi-cylindrical radiant tube, it is less affected by buoyancy and gas flow in the furnace, and it is possible to maintain a substantially constant furnace temperature distribution regardless of the amount of combustion, making it suitable for low-temperature heating.

Since the upper surface of the semi-cylindrical radiation tube facing the heated material becomes a solid radiation surface, the amount of heat transfer increases, that is, the heating T/
H up is possible.

Because the lower part of the semi-cylindrical radiant tube has an open structure, the radiant tube is not extremely overheated due to the entrainment of gas in the furnace from the open surface compared to when a cylindrical radiant tube is used. It is possible to extend the service life of
Regarding the NOx problem, it is also possible to reduce NOx.

The side burner system provides a uniform furnace temperature distribution, which simplifies the lower furnace type, improves workability and maintainability, and reduces equipment costs.

This is a steel heating furnace with many features.

[Brief explanation of drawings]

In the drawings, FIG. 1 is a longitudinal sectional view of the steel heating furnace of the present invention, FIG. 2 is a side sectional view taken along the - line in FIG. Figures 4A, 4A and 4C are enlarged cross-sectional views of the semi-cylindrical radiation tube and the combustion gas dispersion wall provided with combustion gas passage grooves used in the present invention, and Figure 5
The figure shows an example of measuring the temperature distribution inside the furnace in a conventional direct-fire combustion method, and Figure 6 shows an example of measuring the temperature distribution inside the furnace when the semi-cylindrical radiant tube of the present invention and the combustion gas distribution wall are combined. It is a diagram. 1 is a furnace wall, 2 is a roof burner, 3 is a side burner, 4 is a partition wall, 5 is a heated material (steel material), 6 is a preheating zone, 7 is a heating zone, 8 is a soaking zone, 9 is a fixed skid, 10 is a 11 is a semi-cylindrical radiation tube, 12 is a combustion gas distribution wall, and 13 is a combustion gas passage groove.

Claims (1)

[Claims] 1 A plurality of semi-cylindrical radiant tubes with their cross sections facing downward are arranged so that one end is located inside the furnace, a combustion device is placed close to the end of each radiant tube on the furnace wall side, and the radiant A plurality of combustion gas distribution walls are disposed below the tube at predetermined intervals and perpendicular to the radiation tube, and the upper end surface of the combustion gas distribution wall on the radiation tube side faces the cross section of the semi-cylindrical radiation tube. A steel heating furnace characterized in that it is configured to have a combustion gas passage groove in the shape thereof.