JPS5940437Y2 - Furnace with radiant tube - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a heating furnace with a radiation tube, and more specifically, to a metal heating furnace that heats 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 burned in the furnace air, so the furnace length is 3
When the furnace size is increased to 0 meters or more, or the furnace width is 10 meters or more, it becomes difficult to equalize the temperature inside the furnace in the lower part of the furnace for the following reasons.

In other words, if side burners are installed on both sides of the furnace,
In conventional direct-fired burners, even if a large ejection velocity (for example, 50 meters per second or more) is applied, the flame length is at most one width of the furnace, and near the sides and center of the furnace,
There is a temperature difference of 100°C or more (lower temperature at the center), and this tendency becomes worse as the combustion amount is reduced.

Furthermore, when the combustion amount is reduced, the energy emitted 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 excess fuel.

On the other hand, in order to improve the drawbacks of side burners, an axial flow burner system, which is a direct-fired burner and is arranged in the longitudinal direction of the furnace, has also been adopted.

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 accumulated in the peaks and valleys, significantly deteriorating workability and safety.

Furthermore, in the direct-fired axial flow type, in the longitudinal direction of the furnace,
In the lower part of the furnace, the temperature distribution becomes uneven, especially due to the rising flame.

The present invention provides a combustion device consisting of a lower side burner provided on the furnace wall and a plurality of radiant tubes arranged in the furnace coaxially with the burner, and a By providing a gap between the radiant tubes and by making the in-furnace end of the radiant tube an open port that opens into the furnace, the above-mentioned drawbacks of the conventional radiant tubes are skillfully solved, and one embodiment thereof. will be explained with reference to the drawings.

In the drawings, reference numeral 1 denotes a metal heating furnace, which has a hearth 2 and an in-furnace beam 3 in which a metal material to be heated 4 is placed and moved.

5 is a lower side burner, and 6j, - and 6' are radiant tubes.

That is, as seen in the second rotation and FIG. 3, the burner 5 is provided relatively below the side furnace wall 9,
The radiant tube 6 is provided so as to be coaxial with the axis of the burner 5 and has a gap 7 between it and the side furnace wall 9, and the radiant tube 6I is coaxial with the axis of the burner 5. In this way, it is provided to be an extension of the radiation tube 6, and moreover, the radiation tube 6
There is a gap 7 between and 6', and the inner end of the furnace is an open port 8 that is open into the furnace.

The radiant tubes 6 and DA are supported by a radiant tube support 10 and separated from the hearth 2 so as not to be damaged by foreign objects hitting the hearth 2.

Additionally, 11 is an upper burner, and 12 is an arrow indicating the moving direction of the heated material 4.

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 12, while its upper part is heated by the burner 11 and its lower part is heated by the lower part. It is heated by a combination combustor of a side burner 5, a radiant tube 6, and a radiant tube.

The burner 5 and the radiant pipes 6 and 6' are arranged so that, as shown in an enlarged view in FIG. Then, flame and combustion gas are ejected from the open port 8 at the inner end of the furnace.

The flame and combustion gases thus pass through the radiant tubes 6 and V, thereby heating the radiant tubes 6 and 6', and are discharged via the opening 8 to any desired location within the furnace.

In addition, each gap 7a, the radiation tubes 6 and 6 due to the temperature change inside the furnace.
The change in thermal expansion of I serves to prevent damage caused by collisions between the radiant tubes 6 and the furnace wall 9. In addition, due to the effect of the high-speed flame from the burner 5, the gas in the furnace The purpose is to reduce nitrogen oxidation by lowering the flame temperature by recirculating the gas in the furnace, and to improve the temperature distribution in the radiant tubes 6 and 6'.

In other words, since the gap 7 also serves as a suction port for the gas in the furnace, the gap T is 5 30 The length of one radiant tube is 18 to 10,000. When an experiment was conducted, nitrogen oxides were reduced by 20 to 30 times, and the temperature distribution was as shown in FIG. 4.

In other words, in Fig. 4, the horizontal axis represents the radiation tube length l (meters).
and the vertical axis is the temperature t ec).If no gap is provided, the temperature distribution is shown by the dotted line curve, but if the gap 7 is provided, the temperature distribution is shown by the solid line curve a. Temperature distribution was improved.

For the radiation tubes 6 and 6', heat-resistant steel may be used at temperatures below 1000°C, but when the temperature exceeds 1000°C, it is preferable to use ceramic materials such as silicon carbide! L<,
-! The length should be selected as appropriate depending on the furnace conditions.

As mentioned above, the present invention has a plurality of radiant tubes arranged in the furnace coaxially with the lower side burners, so that the flame button and combustion gas from the burners flow through the radiant tubes, so that the flame The gas and combustion gas are not affected by the gas flow or buoyancy in the furnace, and go to any desired position in the furnace, which not only improves the temperature distribution but also prevents the adverse effects of the gas in the furnace. The side burner method can be used, and a large number of small-capacity burners are arranged to match the furnace structure, improving the temperature distribution inside the furnace.The lower furnace structure is also simplified, which improves maintenance and safety. will improve.

Moreover, since the radiant tube has an open port at the end inside the furnace, the combustion gas is discharged to an appropriate location within the furnace, sufficient convection heat transfer is carried out, and thermal efficiency is improved.

In particular, since an appropriate gap is provided between the radiant tube and the furnace wall and between each other before the radiation, even if the radiant tube undergoes thermal expansion due to temperature changes inside the furnace, it will not be damaged. First, the gap also serves as a suction port for the furnace gas, which is sucked into the radiant tube through the gap and recirculated, which prevents local heating of the radiant tube and greatly improves the temperature distribution. improved and reduced nitrogen oxidation.

[Brief explanation of drawings]

Fig. 1 is a partially sectional side view showing one embodiment of the present invention, Fig. 2 is a sectional front view showing an enlarged cross section of Fig. 1, and Fig. 3 is a side furnace of Fig. 2. FIG. 4 is a partially cutaway sectional front view showing a further enlarged part of the wall, and a curve diagram showing the temperature distribution of the radiant tube. DESCRIPTION OF SYMBOLS 1... Metal heating furnace, 2... Hearth, 3... Furnace beam, 4... Material to be heated, 5... Lower side burner, 6
, 6'-... Radiation pipe, 7... Gap, 8... Opening port, 9... Side furnace wall, 10... Radiation tube support, 11
...Top burner.

Claims (1)

[Claim for Utility Model Registration] From a lower side burner installed relatively below the side wall of a metal heating furnace, and a plurality of radiant tubes arranged coaxially with the axis of this burner in the furnace. and a gap is provided between the radiant tube and the furnace wall, and the in-furnace end of the radiant tube is an open port that opens into the furnace. It is characterized by Heating furnace with radiant tube.