JPH0135896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating furnace with a radiation tube,
Specifically, the invention relates to a metal heating furnace for heating slabs, billets, blooms, etc. to rolling temperature in front of a metal rolling mill.

Conventional metal heating furnaces have used a direct heating method in which fuel is directly combusted in a burner. In this case, the gas ejected from the burner and the combustion air are mixed and combusted in the space inside the furnace, so if the furnace is large, like modern furnaces with a length of 30 meters or more and a furnace width of 10 meters or more, the following For these reasons, it has become difficult to equalize the temperature inside the furnace in the lower part of the furnace.

In other words, when side burners are installed on both sides of the furnace, even if a conventional direct-fired burner provides a high ejection velocity (for example, 50 meters per second or more),
The flame length is at most about 1/4 of the furnace width, and there is a temperature difference of more than 100℃ between the sides and the center of the furnace (the center is colder), and this tendency becomes more pronounced as the combustion rate is reduced. Getting worse. Furthermore, when the combustion amount is reduced, the energy ejected from the burner is reduced, which causes the flame to flow due to the flow of gas in the furnace, buoyancy, etc., and the flame only heats the ends of the material to be heated. As a result of the above, the material to be heated is heated non-uniformly, resulting in deterioration in quality and the need to use extra fuel.

On the other hand, in order to improve the drawbacks of side burners, an axial burner system has also been adopted in which direct-fired burners are arranged in the longitudinal direction of the furnace. In this case, the temperature distribution in the width direction of the furnace was improved, but because the axial burner was installed, it was necessary to create peaks and valleys in the hearth, making the lower structure of the furnace extremely complex and difficult to maintain. At the same time, heat from the burner accumulated in the peaks and valleys, significantly deteriorating workability and safety. Furthermore, in the direct-fired axial flow type, the temperature distribution becomes uneven especially in the lower part of the furnace in the longitudinal direction of the furnace due to floating of the flame.

The present invention has been made in order to eliminate the above-mentioned drawbacks, namely, the present invention facilitates maintenance of the hearth of a metal heating furnace and reduces heat accumulation in the hearth. The purpose of the present invention is to provide a heating furnace with a radiant tube, which improves safety, maintains a good temperature distribution in the furnace, and increases the amount of heat transfer, thereby avoiding the need to input excess fuel. It is something to do.

For this reason, the configuration of the heating furnace with a radiation tube of the present invention is a metal heating furnace that has a flat hearth,
and a burner provided in the hearth, which is coaxial with the axis of the burner and oriented in the longitudinal direction of the furnace, and has an open end at the end of the furnace to direct combustion flame and combustion gas from the burner into the furnace. It is characterized by being equipped with a combustion device consisting of a guiding radiant tube.

An embodiment of the present invention will be described below with reference to the drawings.

In the drawings, reference numeral 1 denotes a metal heating furnace, which has a flat hearth 2 and an in-furnace beam 3 in which a metal material to be heated 4 is placed and moved. Further, 5 is a hearth burner, and 6 is a radiant tube. That is, the radiation tube 6
is provided so as to be coaxial with the axis of the hearth burner 5 and is oriented in the longitudinal direction of the furnace, and has an open port 7 at the end of the furnace to allow combustion flames and flames from the burner 5 to flow out. It is designed to guide combustion gas into the furnace. The radiant tube 6 is placed at a higher position than the hearth 2 by a radiant tube support 8 in order to reduce damage caused by foreign matter that accumulates on the hearth 2.
In addition, 9 is an upper burner, 10 is the material to be heated 4
This is an arrow indicating the direction of movement.

In the metal heating furnace 1 configured in this way, the material to be heated 4 is placed on the in-furnace beam 3 and moves in the direction of the arrow 10, while the upper part of the material is placed on the burner 9.
The lower part is heated by a hearth burner 5 and a radiant tube 6.
Heated by a combination combustor. The burner 5
As shown in an enlarged view in FIG. 3, the fuel and combustion air introduced into the burner 5 are combusted within the radiant tube 6 and are ejected from the open port 7 at the end of the furnace. Flame and combustion gases are ejected. Therefore,
The flame and combustion gas pass through the radiant tube 6, thereby heating the radiant tube 6, and are discharged through the open port 7 to any desired position within the furnace. For the radiation tube 6, it is preferable to use heat-resistant steel when the temperature is below 1000°C, and to use ceramic material such as silicon carbide when the temperature exceeds 1000°C, and the length can be selected freely depending on the conditions of the furnace. be able to. In addition, as shown in FIG. 1, the burner 5 and the radiant tube 6
Since the burners can be arbitrarily arranged in one zone in two or more rows instead of in one row as in a conventional furnace, a large number of small burners can be provided. Furthermore, the radiant tube 6 preferably has a shape bent at an angle of 90 degrees or less as shown in the figure, but if necessary, a straight tube may be installed inclined toward the inside of the furnace. Also, as seen in Figure 3,
By oriented the opening 7 horizontally and by making the upper part of the opening 7 an extended cut, it is possible to prevent foreign matter falling from above from falling into the radiation tube 6 and into the burner 5.

As described above, according to the present invention, the flow of the combustion flame and combustion gas from the hearth burner is guided in the radiation tube oriented in the longitudinal direction of the furnace, so that there are no peaks or valleys in the lower part of the furnace. Since the burner can be installed without the need for a conventional hearth, the hearth is simplified into a flat one, making maintenance easier, reducing heat accumulation, and improving safety. Since there is no need to form peaks, there is no problem of the temperature of the heated material decreasing at the peaks, and since the flame is guided within the radiation tube,
It is possible to prevent the flame from hitting the beam in the furnace, and the risk of burnout of the beam in the furnace is greatly reduced. In addition, since not only the flame but also the combustion gas flows inside the radiation tube, the combustion gas can reach any desired position in the furnace without being affected by the gas flow or buoyancy in the furnace, so even if the combustion amount is small, Not only can the temperature distribution inside the furnace be maintained well, but the heat from the radiant tube becomes solid heat radiation, and because the radiation activity is high, the amount of heat transfer increases.
Excess fuel input is avoided. In particular, since the in-furnace end of the radiant tube is an open port, combustion gas is discharged to an appropriate location within the furnace, improving convective heat transfer and effectively utilizing exhaust gas. Furthermore, since the number of hearth burners can be increased depending on the hearth structure, the temperature distribution in the lower part of the furnace can be made uniform, and the direction of the radiation tubes can be adjusted to the same level as in the axial flow burner system. obtain.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention.
The figure is a side view showing a part of the hearth in cross section, Fig. 2 is a cross-sectional front view showing an enlarged cross section of Fig. 1, and Fig. 3 is a cross-sectional side view showing a part of the hearth further enlarged. It is a diagram. DESCRIPTION OF SYMBOLS 1... Metal heating furnace, 2... Hearth, 3... Furnace beam, 4... Material to be heated, 5... Hearth burner, 6...
...Radiation tube, 7...Open port, 8...Radiation tube support, 9...Upper burner.

Claims (1)

[Claims] 1 A metal heating furnace with a flat hearth,
and a burner provided in the hearth, which is coaxial with the axis of the burner and oriented in the longitudinal direction of the furnace, and has an open end at the end of the furnace to direct combustion flame and combustion gas from the burner into the furnace. characterized by comprising a combustion device consisting of a guiding radiant tube,
Heating furnace with radiant tube.