JPH10140247A - Steel material heating furnace and method for controlling combustion in it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently eliminate skid marks by arranging plural heat-storage type burners at the upper part of a soaking zone in a heating furnace. SOLUTION: Since the heat-storage type burner 3 is the burner, by which the combustion gas in the furnace is absorbed and the other burner is fed and burnt by preheating and circulating the air with a heat exchanger 4, the merit, in which the heat efficiency is good and comparatively high temp. combustion gas is obtd., is used, and about 10 pieces of the burners 3 are parallel arranged in the width direction of the furnace at the upper part 2 of the soaking zone in the heating furnace 1. Then, the burners executing on and off, are arranged as the zigzag state, and the combustion cycle repeates the combustion and the suction of the gas in the furnace in the interval of 1-2mm. Therefore, the temp. compensation with the burner can be supplied to the temp. of the combustion load or higher, and the heating is executed in the condition near the preset heating temp. curve without bringing about the lowering of the temp. in the soaking zone. As a result, the temp. at the position bringing a cast slab into contact with a skid rail is made to raise, too and the combustion load at the skid part is drastically reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel heating furnace provided with a plurality of regenerative burners, of an axial combustion type or of a soot tropical type, and a combustion control method therefor.

[0002]

2. Description of the Related Art Slabs, blooms, billets and other cast slabs are heated to a predetermined temperature before hot rolling, in the range of about 1150 to 1250 ° C. for ordinary steel. When heating the above slab, a pusher type or walking beam type heating furnace is used, but in the case of the former pusher type heating furnace, a portion in contact with a heated slab bottom and a water-cooled skid rail. In the same way, in a walking beam type heating furnace, a skid mark is formed at a part of the fixed support part and the movable support part which mainly comes into contact with the water-cooled fixed support part and the slab bottom part. A temperature drop called a mark occurs. This skid mark causes a problem such as cracking caused by a decrease in product thickness accuracy and a lack of strength elongation in subsequent rolling or the like, and lowers the yield. Therefore, much effort has been made to eliminate the skid mark.

FIG. 1 shows a temperature distribution in the longitudinal direction of a slab heated by a heating furnace. It can be seen that the temperature drop is remarkable in a portion having a skid mark. This temperature difference reaches 50 ° C. at the maximum, and compensating for this temperature difference appears as a heating load. Therefore, how to reduce this temperature difference and reduce the heating load is a major issue. The simplest and general method for eliminating this skid mark is a method of changing the arrangement direction of the skid rail provided in the heating furnace and constantly changing the contact point between the slab and the skid rail, Skid marks are hardly eliminated. For this reason, in addition to the above method, or in addition to the above method, there is an example in which a normal combustion burner or a regenerative burner is provided in the former stage of the heating furnace to improve the performance of the heating furnace and to perform heat compensation. Has not been resolved. Further, Japanese Patent Application Laid-Open No. 3-111513 discloses a combustion apparatus for generating a combustion gas for heating a skid mark on a slab extraction side of a heating furnace, and a metal or ceramic conduit for introducing the combustion gas into the heating furnace. It has been proposed to separately provide a heating device to be used. But,
This device is a multi-layered device with a metal or ceramic conduit and a cooling air, combustion air and fuel pipes inside it independently near the lower part of the skid rail in the heating furnace. It is a complicated structure and very expensive. Further, there is a disadvantage that the maintenance of this apparatus must be constantly performed.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method and apparatus for controlling combustion in a steel heating furnace, which efficiently eliminates skid marks generated when a slab is heated in the heating furnace, which has been regarded as a problem. To provide.

[0005]

SUMMARY OF THE INVENTION The present inventor has focused on a commercially available regenerative burner having a high heating effect to eliminate skid marks. This regenerative burner is a type of burner in which the combustion gas in the heating furnace is sucked, the air is preheated by a heat exchanger, circulated, and sent to another burner for combustion. Is obtained. Therefore, it was examined how to arrange the regenerative burner in which part in the heating furnace and in what form to improve the skid mark. As a result, it was found that the soaking zone in the heating furnace, that is, the slab extraction side of the heating furnace did not reach the relatively desired soaking temperature even though it was in the ripening zone. It has been found that arranging the regenerative burners according to the predetermined requirements is most effective for eliminating skid marks.

The present invention has been made based on the above findings, and the gist is as follows. That is, the first invention is a steel heating furnace characterized by installing a plurality of regenerative burners in the upper part of the soaking furnace of an axial combustion or soaking furnace of an axial combustion type. In a steel heating furnace of axial combustion type or axial flow combustion type, a regenerative burner is installed in the soaking zone, and the combustion load of the burner near the skid is controlled according to the temperature information obtained from the heating temperature history of the steel product Combustion control method in a steel material heating furnace, characterized in that,
It is.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A skid mark heating apparatus and a heating method according to the present invention will be described below with reference to FIG. FIG.
(A) is a regenerative burner 3 in the upper part 2 of the heating furnace 1
FIG. Although the regenerative burners 3 are commercially available, these regenerative burners inhale the combustion gas in the heating furnace and remove the air in the heat exchanger 4 as shown in FIG. Because it is a burner of the type of preheating, circulating and sending to another burner for combustion, it positively utilizes the advantages of obtaining thermal efficiency and relatively high temperature combustion gas, and uses about 10 regenerative burners. As a roof burner, it is arranged in parallel with the furnace width direction on the upper ceiling of the soaking zone of the heating furnace. Since these regenerative burners have the functions described above, the burners that are turned on and off are arranged in a zigzag pattern. Repeat inhalation. Therefore, the number of regenerative burners that are operating at all times is about 1/2 of that. In addition, the temperature compensation by these regenerative burners makes it possible to supply a sufficient amount of temperature to compensate for the above-mentioned combustion load.
In other words, since heating can be performed in a state close to a preset heating temperature curve without causing a temperature drop in the solitary zone, the temperature of the part where the slab and the skid rail come into contact necessarily increases. Thus, the combustion load at the skid portion is greatly reduced.

In actual heating, the composition of the slab to be heated, the heating temperature and soaking temperature required for the slab, the slab size, the contact area and time between the slab and the skid rail,
Factors such as the amount of cooling water for the skid, the temperature of the skid, and the heating time are all computer-processed, the amount of heat taken by the skid portion is integrated, and the amount of heat compensation in the regenerative burner is determined to control combustion.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Ten regenerative burners are arranged side by side in the furnace width direction on the upper ceiling of a soaking furnace of an axial-flow or axial-burning steel heating furnace of the axial-flow combustion type. I let it. Slab size is 10m long, 1m wide, 0.2mm thick
5 mm. The combustion was controlled according to the flowchart shown in FIG. Table 1 shows the combustion load of the skid when 10 conventional roof burners were installed and heated.
The comparison is shown.

FIG. 4 is a view showing the temperature distribution in the longitudinal direction of the slab, the position of the regenerative burner corresponding thereto, and the combustion load pattern. When the temperature distribution in the furnace width direction (slab longitudinal direction) as shown in FIG. 4 exceeds the upper and lower limits of the target temperature range (shaded area in the figure), the heat storage type closest to the position By controlling the combustion load of the burner, it is possible to make the temperature distribution flat and converge within the target range. The bar graph in the figure schematically shows the amount of combustion load according to the skid mark. still,
The regenerative burner used has the same structure as that shown in FIG. In addition, since the solitary zone is a zone in which the temperature in the slab is generally uniformly adjusted, even if the combustion load is slightly changed in the furnace width direction as in the present invention, the operation can be performed regardless of the baking time of the slab.

[0011]

[Table 1]

By employing the method of the present invention, the unit energy consumption of the entire heating furnace can be reduced by about 2%, and by eliminating the skid mark, the steel material yield has been improved by about 0.2%.

[0013]

As described above, according to the present invention, it is possible to exchange heat between high-temperature exhaust gas and combustion air by installing a regenerative burner in the upper part of the soaking zone where the furnace temperature is high, thereby achieving energy saving. In addition, the burn load of the burner in the high-temperature part near the skid part where the temperature drops sharply in accordance with the preset slab heating temperature pattern in the solitary zone is reduced, and the burn load in the low-temperature part is slightly increased to make the skid mark. Can be eliminated.

Further, the life of the ceiling refractory of the heating furnace is improved by providing the regenerative burner in the upper part of the soaking zone.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature distribution in a slab longitudinal direction heated by a heating furnace.

FIG. 2 (a) is a diagram in which a regenerative burner is installed in a steel material heating furnace according to the present invention, and FIG. 2 (b) is a schematic diagram of a regenerative burner.

FIG. 3 is a flowchart when the fuel control method of the present invention is performed.

FIG. 4 is a diagram showing an example in which a combustion load is changed in accordance with a slab longitudinal temperature pattern using the combustion control method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heating furnace 2 ... Equilibrium upper part 3 ... Regenerative burner 4 ... Heat exchanger 5 ... Switching valve

Continued on the front page (72) Inventor Hideki Murakami 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Toshiaki Saito 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division

Claims (2)

[Claims] 1. A steel heating furnace characterized in that a plurality of regenerative burners are installed in an upper part of a soaking furnace of an axial combustion or soaking furnace of an axial combustion type. 2. A steel heating furnace of an axial combustion type or a soaking zone is an axial combustion type, wherein a regenerative burner is provided in the soaking zone.
A combustion control method in a steel heating furnace, wherein a combustion load of a burner near a skid is controlled according to temperature information obtained from a heating temperature history of a steel material.