JPS639563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heating furnace for uniformly heating steel materials, such as slabs and billets, to a target rolling temperature.

(Prior art) Conventionally, this type of heating furnace has a combustion chamber with direct burners arranged above and below the material to be heated, and heats the material directly while conveying it from the charging side to the extraction side. Fire-burning heating furnaces were generally used.

In this type of direct combustion type heating furnace, 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 volatile flames, gas radiation and the furnace wall. Radiation is used to heat the material to be heated, but in general, in this type of direct combustion, even if the jet energy of the fluid supplied from the burner is sufficiently large, the flame length is at most 3 to 4 meters. In addition, during low-load combustion, the ejection energy of the burner supply fluid also decreases, which reduces the straightness of the flame, resulting in flame soaring due to buoyancy and flame bending due to the gas flow in the furnace. Due to this problem, the furnace was made larger (furnace width is 10 mm) like recent heating furnaces.
~15m, furnace length 30-50m) and diversification of operations (950m
Conventional direct-fire combustion methods have the disadvantage that it is difficult to achieve the desired goal (uniform heating over a wide temperature range up to 1250°C).

In addition, recently, as furnaces have become larger, there has been a general tendency to adopt a walking beam method as a means of conveying the heated material.In this walking beam method, the heated material is supported by a fixed and movable skid with an insulated and water-cooled structure. Because of the conveyance method, the heated material directly above the skid pipe is in the shadow of the skid pipe (shadow effect), which impedes heat transfer and has the disadvantage that it is difficult to heat compared to other parts of the heated material. There is. In order to uniformly heat the material to be heated, it is possible to locally and intensively heat the skid shadow area at the initial stage of heating. It is desirable to form a furnace temperature distribution having a so-called peak temperature, but in conventional direct-fired heating furnaces, it has generally been impossible to create a peak temperature at an arbitrary point, that is, at a skid portion.

On the other hand, it is generally known that there are three types of direct-fired heating furnaces of this type, depending on how the burners are arranged in the combustion chamber: side burners, axial burners, and roof burners. The side burner system, as disclosed in Japanese Patent Application Laid-Open No. 57-32321, has a structure in which burners are placed on both side walls of the furnace. This method has a simple furnace structure and relatively low equipment cost, and generally it is easy to obtain a relatively uniform furnace temperature distribution in the furnace length direction, but it is not uniform in the furnace width direction due to flame soaring and bending. It has the disadvantage that it is difficult to obtain furnace temperature distribution.

On the other hand, axial flow burner systems such as those in JP-A-57-82424 have a structure in which the burners are arranged in the longitudinal direction of the furnace, so unlike the side burner system, the furnace temperature is generally relatively uniform in the width direction. Although it is easy to obtain a uniform temperature distribution in the furnace length direction, it has the disadvantage that it is difficult to obtain a uniform furnace temperature distribution in the furnace length direction. Since it is necessary to provide a partition section (hereinafter referred to as a partition section) across the entire width of the hearth, this method has disadvantages in that the utilization rate of the hearth is poor and the equipment cost is high.

On the other hand, the roof burner method has a structure in which the burner is placed on the ceiling furnace wall of the upper combustion chamber, so it has the advantage of being able to obtain a relatively uniform furnace temperature distribution over the entire width and length of the furnace. However, compared to the other two methods, the number of burners is larger, so the equipment cost is generally higher, and the disadvantage is that it can only be applied to the upper combustion chamber due to the nature of the burner arrangement.

As described above, conventional heating devices have fundamental drawbacks in meeting the needs of larger furnaces and diversified operations.

(Objective and Summary of the Invention) The present invention focuses on improving the uniform heating property of the heated material, which is a drawback of the conventional direct flame combustion method, and improves the heating capacity and quality by preventing uneven heat of the heated material. The objective is to achieve this improvement using the side burner method, which has low equipment costs.

In the present invention, burners are arranged on both walls in the furnace length direction of the lower part of the furnace, with gas jet ports facing in a direction perpendicular to the traveling direction of the heated material, and burners on the gas jet port side of some burners on each side wall are arranged. A cylindrical heat radiating tube with both ends opened in the axial direction is installed, and semi-cylindrical heat radiating tubes are installed in the burner axial direction on the gas jet port side of the remaining burners and in the burner axial direction on the opposite burner side of the cylindrical heat radiating tube. A heat radiating tube is arranged with the chord facing downward, and at the bottom of the semi-cylindrical heat radiating tube there is a tube perpendicular to the semi-cylindrical heat radiating tube at an appropriate interval. The present invention provides a heating device for a heating furnace characterized by disposing a gas dispersion wall having an appropriate gap therebetween.

(Embodiments of the Invention) The present invention will be described below with reference to embodiments shown in the drawings. FIGS. 1 and 2 show an embodiment of a steel heating furnace according to the present invention. 1 is a furnace wall having 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;
3 is a side burner arranged on both lower side walls of the furnace wall 1 in the furnace length direction; 4 is a partition wall for partitioning the heating furnace into each combustion chamber; 5 is a steel material as a material to be heated;
6 is a preheating zone, 7 is a heating zone, and 8 is a soaking zone. 9
1 is a fixed skid for supporting the steel material 5, and 10 is a movable skid for conveying the steel material 5. The outer surface of the water-cooled skid pipe has a heat insulating structure. Reference numeral 11 indicates a cylindrical heat radiating tube having heat resistance and thermal conductivity and having a required length, which is arranged on the axis of the inside of the furnace of the side burner 3, 12 indicates a support frame for the cylindrical heat radiating tube 11, and 13 indicates a side burner. 3, a semi-cylindrical heat radiating tube having the required length of heat resistance and thermal conductivity and arranged with the chord facing downward;
14 is a support frame for the semi-cylindrical heat radiating tube 13.

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 from the side burner 3.
The combustion gas flows from the soaking zone to the heating zone, from the heating zone to the preheating zone, and is finally discharged from the flue 16 to the outside of the furnace.

The relationship between the cylindrical heat radiating tube and the semi-cylindrical heat radiating tube and the support frame is shown in FIGS. 3 and 4, respectively. As shown in FIG. 4, the support frame 14 for the semi-cylindrical heat radiant tube supports and fixes the radiant tube 13, and at the same time has heat resistance to disperse and supply the combustion gas released from the side burner 3 into the furnace. A plurality of combustion gas dispersion walls are usually provided at the bottom of the semi-cylindrical heat radiation tube 13 at predetermined intervals in a direction perpendicular to the heat radiation tube. 15 is a semi-cylindrical heat radiating tube 1 on the upper end surface of the combustion gas distribution wall 14 on the semi-cylindrical heat radiating tube 13 side.
This is a combustion gas passage groove provided opposite to No. 3, and the opening area is usually determined depending on the purpose of heating.

Next, the operation of the heating device of the present invention will be explained. The material to be heated 5 inserted 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 being transported, the upper surface of the material to be heated 5 is heated by the roof burner 2, and the lower surface 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 cylindrical heat radiation tube 11 or the semi-cylindrical heat radiation tube 13, and their support frame, the fuel and combustion air supplied from the side burner 3 are Mixed combustion takes place within the heat radiating tube, and is therefore less affected by buoyancy and in-furnace gas flow than conventional direct-fire combustion methods, ensuring a stable furnace temperature distribution regardless of the amount of combustion. It is possible to do so.

Further, since a combustion gas distribution wall 14 is provided at the bottom of the semi-cylindrical heat radiation tube 13, some combustion gas passes through the gas passage groove 15 formed by the gas distribution wall and the heat radiation tube. The combustion gas then passes in the direction away from the burner in the furnace, but the flow direction of the combustion gas that collides with the gas distribution wall 14 changes at that position, and it is possible to blow out into the furnace and form a local high temperature area. Here, by aligning this high-temperature part with the so-called skid shadow part between the fixed skid 9 and the movable skid 10, the shadow part can be actively heated. Uniform heating of the material to be heated 5 can now be performed stably.

An example of a gas dispersion wall is shown in Fig. 4, and in places where a so-called flat temperature distribution is required without blowing out gas, gas passage grooves 1 are installed as shown in Fig. 4A.
It is sufficient to arrange a large gas dispersion wall 14 with a diameter of 5 and a small gas dispersion wall 14 with a small gas passage groove 15 as shown in FIG. . Furthermore, if you want to create a peak furnace temperature near the burner near the furnace wall, you can use a semi-cylindrical heat radiation tube from near the burner, but you can also create a peak furnace temperature near the furnace center, that is, at a location far from the burner. If desired, a cylindrical heat radiation tube 11 is used near the burner to prevent the combustion gas from being dispersed, and a semicylindrical heat radiation tube 13 and a gas distribution wall 14 are used near the area where the peak furnace temperature is to be generated to disperse the combustion gas. What is necessary is to disperse the temperature and form the desired furnace temperature pattern. Based on this idea, there are two
FIG. 5 shows a specific example of a heating furnace having several shadow parts, in which heat radiation tubes and gas distribution walls are arranged, and a schematic diagram of its effects.

In Fig. 5, figure A shows the arrangement of the material to be heated and the skid in the width direction of the furnace in a 1/2 section in the width direction of the furnace. A shadow portion S2 is formed near the center of the furnace. Figure B is a diagram in which a heat radiation tube and a gas distribution wall are arranged for the purpose of forming a peak furnace temperature in a portion of the shadow portion S1 near the furnace side wall. Since the shadow part is close to the furnace side wall, all the heat radiation tubes 3 are semi-cylindrical, and for (a) where a large amount of gas dispersion is required as a gas dispersion wall, the type shown in Fig. 4B is used. However, other (a), (c),
As the gas dispersion wall (d), the type shown in FIG. 4A is used because it is desirable that the gas is not dispersed as much as possible.

The furnace temperature pattern obtained by the heat radiating tube and distribution wall arrangement of FIG. 5B is shown by a in FIG. 5D. The shadow portion S1 is actively heated by the dispersion and ejection of gas by the dispersion wall in (a). On the other hand, FIG. 5C is a diagram in which a heat radiation tube and a gas distribution wall are arranged for the purpose of forming a peak furnace temperature in the shadow portion S2 near the furnace center. In this case, since the shadow part is far from the burner, a cylindrical heat radiation tube is used near the burner to suppress gas dispersion, followed by a semicylindrical heat radiation tube and a gas distribution wall. The shape of the gas distribution wall is based on the same idea as in Figure 5B, so the type shown in Figure 4B is used for the part (F), and the type shown in Figure 4A is used for parts (E) and (G). . Figure 5C
The furnace temperature pattern obtained by the arrangement of the heat radiation tube and the gas distribution wall is shown in FIG. The shadow portion S2 is actively heated by the dispersion and ejection of gas by the dispersion wall (f). Therefore, for a heating furnace with skid arrangement as shown in Fig. 5A, the heat radiation tubes and gas distribution walls shown in Fig. 5B and C are arranged alternately with respect to the burners in the furnace length direction. Therefore, it is possible to avoid the adverse effects of the shadow portion.

The furnace temperature patterns a and b shown in Fig. 5D are as follows:
As mentioned above, since the combustion of gas takes place inside the heat radiation tube, the combustion gas is not affected by buoyancy or the gas flow throughout the furnace, and is extremely stable regardless of the amount of combustion. .

Experimental Example Next, we will demonstrate the effect of the present invention in a combustion experimental furnace (height 1.8 x width
3.0 x length 6.4 m). In order to confirm the effect of the present invention, the experiment was conducted with a diameter of 1.7 mm in the furnace width direction.
2 burners with a combustion rate of 1.5 million Kcal/H at a pitch of m
In this installation, water-cooled heat-absorbing pipes are arranged on the ceiling furnace wall to simulate heat absorption by the heated material 5, coke oven gas is used as the fuel, hot air at 300°C is used as the combustion air, and the common conditions are an air ratio of 1.1. Figures 6 to 8 show the results of a comparison between the conventional direct-fire combustion system and the combustion system of the present invention under the following conditions.

FIG. 6 shows a measurement example of the furnace temperature distribution of a gas two-flow burner, which is highly rated as having the best temperature distribution characteristics in the burner axial direction in an actual furnace, as an example of a conventional direct-fire combustion method.

Moreover, FIG. 7 shows an example of measuring the furnace temperature distribution when the semi-cylindrical heat radiating tube 13 and the combustion gas distribution wall 14 of the present invention are arranged in combination. Cylindrical heat radiation tube 1
3 is a 400φ semi-cylindrical SiC tube.
This is the result of using a length of m. Here, the results are obtained when the opening area ratio of the dispersion wall (gas passage groove area ratio) gradually decreases from the burner side to 240, 240, 60, 20, and 20%.

FIG. 8 shows an example of measuring the furnace temperature distribution when the cylindrical heat radiating tube 11, semi-cylindrical heat radiating tube 13, and combustion gas distribution wall 14 of the present invention are arranged in combination. The diameters and materials of the burner and heat radiation tube are the same as those shown in FIG. 7, but both the cylindrical heat radiation tube and the semi-cylindrical heat radiation tube have a length of 1.6 m. Moreover, the results are obtained when the opening area ratio of the gas dispersion wall of the semi-cylindrical heat radiating tube section gradually decreases from 110% to 70% to 70% from the burner side.

In Figures 6 to 8, 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 range of ~100% are shown in the shaded range in the figure.

As a result, in the conventional direct-fire combustion method, the flame peak temperature is approximately 1.5 m from the burner, and the furnace temperature rapidly decreases beyond that point, showing a so-called temperature distribution trend at the burner side height. Moreover, the temperature distribution changes significantly due to the difference in combustion amount.

On the other hand, in the present invention in which the cylindrical heat radiating tube 11, the semi-cylindrical heat radiating tube 13, and the gas distribution wall 14 are appropriately combined and arranged, it is necessary to appropriately select the above combination and position and the opening area of the combustion gas passage groove. This shows that it is possible to form a furnace temperature distribution with a peak point at a predetermined position within the furnace, regardless of the amount of combustion.

(Effects of the Invention) As described above, the heating device for a heating furnace according to the present invention improves the furnace temperature distribution in the longitudinal direction of the burner, which was a problem with conventional direct combustion type heating furnaces. By arranging a semi-cylindrical heat radiating tube, or a cylindrical heat radiating tube and a semi-cylindrical heat radiating tube at the tip of the fire combustion burner, and arranging a combustion gas distribution wall at the bottom of the semi-cylindrical heat radiating tube, Since it is possible to form a furnace temperature distribution with a required peak point at a predetermined position in the furnace, it is possible to actively heat the skid shadow area, which is the cause of uneven heat of the material to be heated in the heating furnace. This heating device for a heating furnace has the feature that it is possible to increase heating capacity and improve quality by uniformly heating the material to be heated, that is, by preventing unbalanced heat, using a side burner method with low equipment cost.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an example of a steel heating furnace equipped with the heating device of the present invention, FIGS. 2A and B are cross-sectional views taken along lines - and -, respectively, of the furnace in FIG. 1, and FIG. 4 is a cross-sectional view of the cylindrical heat radiating tube and the support pedestal, and FIG. 4 is a cross-sectional view of the semi-cylindrical heat radiating tube and the gas distribution wall that also serves as the support pedestal. A and B in FIG. 4 are the shapes of the gas distribution wall. Examples of types of FIG. 5 is a diagram showing a specific example and effect of applying the heating device of the present invention. FIG. A cross-sectional view of the furnace shown in FIG. Figure 6 shows an example of measuring the temperature distribution inside the furnace in a conventional direct-fire combustion method in an experimental furnace, and Figure 7 shows a furnace using the semi-cylindrical heat radiating tube of the present invention and the gas distribution wall that also serves as a support frame. Figure 8 shows an example of measuring the internal temperature distribution in an experimental reactor using the cylindrical heat radiating tube, semi-cylindrical heat radiating tube, support frame, and gas distribution wall of the present invention. 3 is each graph showing measurement examples of . 1... Furnace wall, 2... Roof burner, 3... Side burner, 4... Partition wall, 5... Material to be heated (steel material), 6... Pre-heating zone, 7... Heating zone, 8... Soaking zone , 9... Fixed skid, 10... Movable skid, 11... Cylindrical heat radiating tube, 12... Support frame for the cylindrical heat radiating tube 11, 13... Semi-cylindrical heat radiating tube, 14... Semi-cylindrical Gas dispersion wall that also serves as a support frame for a shaped heat radiation tube, 15... Gas passage groove, 16... Flue.

Claims (1)

[Claims] 1. Burners are arranged on both walls in the furnace length direction of the lower part of the furnace with the gas outlet facing perpendicular to the direction of movement of the material to be heated, and some of the burners on each side wall are arranged in the burner axial direction on the gas outlet side. A cylindrical heat radiation tube with both ends open is installed, and a semi-cylindrical heat radiation tube is installed in the burner axis direction on the gas outlet side of the remaining burner and in the burner axis direction on the opposite burner side of the cylindrical heat radiation tube. is arranged with the chord facing downward, and at the bottom of the semi-cylindrical heat radiating tube, a suitable space is provided perpendicularly to the semi-cylindrical heat radiating tube, and between the semi-cylindrical heat radiating tube and the semi-cylindrical heat radiating tube. A heating device for a heating furnace, characterized in that a gas distribution wall having an appropriate gap is provided.