JPS63109113A - Heating device in heating furnace - Google Patents

Abstract

PURPOSE:To increase the coefficient of heat transfer and to enable rapid heating by arranging combustion gas injection part at suitable position in combustion gas guiding pipe supplying the combustion gas from a burner and injection the combustion gas against heating material at high speed. CONSTITUTION:Heating devices 20, 21 are arranged at upper and lower parts of preheating zone 2. In this heating devices 20, 21, the combustion gas of burners 31, 32 is supplied from both ends of the guiding pipe 30 and injected against the heating material, such as steel plate 5, etc., from plural combustion gas injecting part branching from the guiding pipe 30 at high speed. And, the heating device having almost same construction as this is arranged at end part of the heating zone 3, to eliminate the development of skid mark. Then, the combustion gas is injected at >=50m/s speed. The heating in the above preheating zone 2 is executed by the collision heat transfer and the efficiency of heat transfer is high and the preheating is completed in a short time.

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention is mainly used for preheating a steel billet or for local heating of a skinned mark in a heating furnace that heats a steel billet for hot rolling of steel. This invention relates to a heating device for.

<Prior Art> A conventional heating furnace for steel billets has a configuration as shown in FIG. 10 or FIG. 11. The heating furnace 1 shown in Fig. 10 is formed into a long and narrow furnace with a --like furnace width, and the area indicated by the length Ll is the preheating zone 2) The area indicated by the length L2 is the heating zone 3, and charging is carried out from the inlet 4. The heated objects (steel pieces) 5.5, . It is heated to a temperature of 100% and then sent out from outlet 1. 12 in the figure is the flue.

The heating furnace 13 shown in FIG. 11 differs from the heating furnace 1 in that side burners 14 and 15 are provided in the preheating zone.

Since most of the other parts are the same as those of the heating furnace 1, the same parts will be designated by the same reference numerals and the explanation will be omitted. In addition, the length L
The area indicated by 4 is the preheating zone 2) The area indicated by the length L5 is the heating zone 3. Heat transfer to the object to be heated 5 in these heating furnaces 1 and 13 is mainly due to radiation and some convection between the burner flame and wall.

Furthermore, in the conventional heating furnace, since the object to be heated is placed on a skid, skid marks occur, which causes many problems in terms of quality and energy saving.

The solution to this problem is Utility Model Application No. 58-4214.
There are techniques described in Japanese Patent Publication No. 8 and Japanese Patent Application Laid-Open No. 60-200908. This technology locally eliminates skid marks by installing a radiant tube with flame radiation holes close to the skid, or by attaching combustion radiant tubes with multiple combustion gas injection holes on both sides of a skind pipe. It is heated to

<Problems to be Solved by the Invention> In conventional heating furnaces, heat transfer to the object to be heated 5- is mainly due to the burner flame, radiation from the wall, and some convection. Even in this case, the furnace gas and furnace wall temperatures must be kept fairly high. For example, if the object to be heated 5 is a steel piece formed by continuous casting and has a temperature of about 800'C, the temperature in the preheating zone 2 needs to be about 1000 to 1100C. Also,
When manufacturing a heating furnace to satisfy predetermined heating conditions, it is desirable to shorten the furnace length as much as possible.
and 8.9.10.11.1 as shown in FIG.
4.15 There is a certain limit to the heat transfer coefficient from the burner flame and the furnace wall to the heated object 5, and in order to meet the requirements, the furnace length must be shortened because there is a problem with the heat transfer coefficient. I can't smell it. In addition, Japanese Utility Model Application Publication No. 58-42148 and Japanese Patent Application Publication No. 60-2 are installed in high-temperature furnaces to eliminate skid marks.
There is no inside of the radiant tube or combustion radiant tube according to No. 00908,
If there is a large amount of oxygen contained, there is a drawback that local oxidation of the object to be heated occurs. Another problem is that the radiant tube and the combustion radiant tube have a short service life. Because combustion of fuel gas takes place in a radiant tube or combustion radiant tube, the temperature is partially 1400 to 1500℃.
This significantly shortens the service life in terms of heat resistance and oxidation resistance.

Means for Solving the Problems> The means of the present invention provides a heating furnace with a combustion gas guide pipe provided to pass near a predetermined heating position in the furnace, and a method for supplying combustion gas to the guide pipe. The apparatus is equipped with a burner provided in the guide tube, and a combustion gas jetting section provided at an appropriate position in the guide tube so as to inject the combustion gas in the guide tube at a high speed of 50 m/s or more toward the object to be heated.

According to this method, the combustion gas is a high-velocity gas of 50 m/s or more from the ejection part, and the heat transfer coefficient is is 1.5 ~
This increases the temperature by a factor of two, and enables rapid heating, especially in the preheating zone.

In addition, if a burner with a pre-combustion chamber is connected directly to the guide tube, combustion will be completed quickly from the part where the combustion gas exits the burner, and combustion will not occur within the guide tube. There is no high-temperature peak in the middle, and it is possible to reduce 02 to zero in the combustion gas, making the temperature distribution of the ejected combustion gas uniform and preventing oxidation due to collision flames. In addition, if non-oxidizing ceramic or heat-resistant steel is used for the guide tube and the ejection part, oxidative wear and tear of the material can be prevented.

<Example> A first example is shown in FIGS. 1 to 3. This embodiment is a billet heating furnace similar to that shown in FIG. 1O, and the same parts as those in FIG. The difference from the one in FIG. 10 is that heating devices 20 and 21 are provided in the preheating zone 2, and a heating device 22 is provided in the heating zone 3.

The heating device 20 is provided above the preheating zone 2, and is connected to the combustion gas guide pipe 30. Burner 31.32) Combustion gas jetting part 33
There are three sets of these.

The guide tube 30 is provided horizontally across both side walls 34, 34 of the furnace along the furnace width direction, and is appropriately supported at both ends and in the middle. The burners 31, 32 are configured to combust a mixture of gaseous fuel and combustion air exiting through the porous body, and have a pre-combustion section 35 for combustion. For technical details regarding burners 31.32,
For example, Utility Application No. 58-21560, Utility Application No. 58-987
No. 64, Jitsugan No. 58-98'765, Jitsugan No. 58-9
8766 and Japanese Patent Application No. 58-412633. The key point is that fuel gas and combustion air are premixed at a stoichiometric air-fuel ratio and then completely combusted, and the feature is that the distance from the burner tile exit to the completion of combustion is very short. In this embodiment, combustion is completed at about 200 at after the burner tile 36, and since the 400 mm thick area of the side wall 34, 34 of the furnace is used as the pre-combustion section 35, it is ensured that the combustion is completed in the pre-combustion state. It is completed within section 35. The guide pipe 300 is arranged so that the combustion gas of the burners 31 and 32 is supplied from both ends of the guide pipe 30.
Both ends are connected to a pre-combustion section 35. Combustion gas blowout part 3
3 is one in which several short tubes are attached downward so as to branch from the guide tube 30. Its mounting position is appropriately determined so that the temperature of the comparatively cold part of the steel billet inserted into the furnace can be effectively raised so that the entire billet is preheated.

The heating device 21 has the same configuration as the heating device 20, and has a preheating zone 2.
Guide pipes 30 are provided at the bottom of the guide pipes 30 so that the combustion gas ejecting portions 33 are directed upward and are located below the passage of the steel piece 5, and three sets of guide pipes 30 are also provided.

The heating device 22 is for eliminating skid marks, and is provided at the end of the heating zone 3, that is, at the lower side of the passage of the steel billet 5 before the lower exit of the furnace, and is approximately the same as the heating device 20.21. The structure is slightly different in the shape of the combustion gas ejection part 33g. The tip of the short tube forming the combustion gas ejection part 33g is directed toward the part where the skid 6 and the steel piece 5 are in contact. The guide tube 30, burners 31, 32 are the same.

In the billet heating furnace provided with the heating devices 20, 21, and 22 in this manner, the billet 5 is mainly heated in the heating device 20.21 in the preheating zone 2.
21. The heating is achieved by collision heat transfer in which the combustion gas that has been completely combusted is blown through the guide pipe 30 and the combustion gas jetting section 33. Therefore, since the heat transfer efficiency is high, preheating can be completed in a short time, and therefore, the length of the preheating zone 2 in the furnace length direction can be made shorter than in conventional furnaces. Further, since the heating device 22 is also based on collisional heat transfer, skid marks are eliminated very effectively.

FIG. 4 shows a cross section of the preheating zone 2 in a modification of the first embodiment, in which the burner indicated by 40 and 41 uses liquid fuel. The general structure of the burner 40, 41 is a liquid fuel ejected in the form of mist, such as heavy oil or heavy oil droplets H20.
is completely combusted in a preheating chamber 42 together with combustion air. The vertical cross-sectional shape of the preheating chamber 42 is a streamlined concave curved surface, and this technique is disclosed in Japanese Patent Laid-Open No. 126510/1983.

Note that the guide tube 30 is divided in the middle and closed at one end.

Even if such a burner using liquid fuel is used, it is possible to preheat the steel billet or eliminate skid marks by collision heat transfer, as in the first embodiment.

FIG. 5 shows a modification of the ejection part of the preheating zone heating device in the first embodiment, in which a combustion gas ejection part 33 made of a short tube and a restricting wall 50 are provided on this ejection part 33.
This is a mixture of 3b and 3b, in which the degree of heating is partially varied.

In FIG. 6, the degree of heating is partially varied, and for this purpose, the inner diameters d1, d2), d3, d4, and d5 of the ejection portions provided in the guide tube 30 are made different.

The combustion gas ejection portions shown in FIGS. 5 and 6 both change the amount of combustion gas ejected depending on the size of the opening area of the combustion gas ejection port. In this case, as mentioned above, the combustion gas has completed combustion, and its temperature is at the guide pipe 30.
Since there is not much difference between the various parts of the heat exchanger, the amount of heat transfer can be controlled fairly accurately using such means. In particular, it is easy to create a peak portion of the heat transfer amount by simply increasing the amount of combustion gas ejected.

7 and 8 show a second embodiment. The only difference from the first embodiment is the configuration of the heating device for the preheating zone 2, and the rest is the same. The heating devices 20a, 21a are connected to a guide tube 3o in the furnace width direction and sub-guide tubes 60a, 6 in the furnace length direction.
0b, 60c, etc. are provided to branch and extend the guide tube,
A short pipe is provided in the sub guide pipe to form a combustion gas ejection part 33c. As a result, the combustion gas ejection part 3
3a is a smaller number of burners 31.3 than in the first embodiment.
2, a burner with a larger capacity is required to supply the same amount of heat, but it is not convenient to make the temperature and composition of the combustion gas ejected from each combustion gas ejection part 33c uniform. Good.

In addition, as shown in FIG.
The configuration in which point c is located directly above the skid 6 is effective in eliminating skin marks. Therefore, this configuration is effective when applied to the heating zone 3.

FIG. 9 shows a modification of the combustion gas jetting section, in which a slit is provided along the longitudinal direction of the sub guide tube 60n to form a combustion gas jetting section 33d.

<Effects of the Invention> According to the present invention, the object to be heated can be heated by collision heat transfer with the combustion gas injected at a high speed of 50 m/s or more, so that the heat transfer of the combustion gas to the object to be heated is 1.5～
This increases the heating capacity by two times, allowing rapid heating and shortening the length of the heating furnace. Furthermore, by applying this invention to the preheating zone, even if cold steel billets are mixed into a heating furnace for charging hot steel billets, it has become possible to heat them without significantly changing the heating capacity.

When heating objects by collision heat transfer in the preheating zone, it is easy to heat the top surface from the ceiling, but it is difficult to install many upward burners on the bottom surface due to falling and accumulating steel. This problem can be solved by the present invention, and effective collisional heat transfer is now possible.

Furthermore, by applying the present invention to the heating zone, skin marks could be alleviated by locally applying collisional heat transfer.

Furthermore, by changing the burner directly connected to the end of the guide tube to a burner with a pre-combustion section or a pre-mixing section, the temperature distribution of the combustion gas inside the guide tube becomes uniform, and the object to be heated can be heated evenly. It became so. It is possible to equalize the temperature distribution of combustion gas inside the guide tube and suppress O2 inside the guide tube to nearly 0,
We were able to greatly extend the life of the guide tube and the ejection hole.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of a heating furnace schematically showing a first embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 is a sectional view taken along the line B-B in FIG. FIG. 4 is an enlarged sectional view corresponding to the lower half of FIG. 2 showing a modification of the first embodiment, and FIG. 5 is a combustion gas jetting part of the preheating zone heating device of the first embodiment. FIG. 6 is a vertical cross-sectional view of the main part showing a modification of the combustion gas ejection part that is different from FIG. 5;
FIG. 7 is a vertical sectional side view of a heating furnace showing an outline of the second embodiment;
Fig. 8 is an enlarged partial cross-sectional view taken along the line Q-Q in Fig. 7, Fig. 9 is an enlarged cross-sectional view of the sub-guide tube showing a modified example of the combustion gas ejection part in the second embodiment, and Fig. 10 is an enlarged cross-sectional view of the conventional heating furnace. FIG. 11 is a vertical side view showing the general structure of another conventional heating furnace. 1... Heating furnace, 30... Combustion gas guide pipe, 31, 3
2.40 X41...burner, 33.33a,
33b, 33c, 33d... Combustion gas ejection part. Patent applicant: Nippon Sailing Co., Ltd. Hiroshitsuki Co., Ltd.

Claims (4)

[Claims] (1) In a heating furnace, a combustion gas guide pipe provided to pass through a predetermined position in the furnace, and a burner provided directly connected to the guide pipe so as to supply combustion gas from both ends or one end;
A heating device comprising: a combustion gas jetting section provided at an appropriate position of the guide tube so as to jet combustion gas inside the guide tube at high speed at 50 m/s or more toward an object to be heated. (2) The heating device according to claim (1), wherein the burner has a pre-combustion section that completes combustion on the burner side. (3) The heating device according to claim (2), wherein the burner burns a premix of gas fuel and combustion air through a porous body. (4) In the heating device according to claim (2), the burner is for burning liquid fuel, and the pre-combustion section has a streamlined concave inner surface between the inlet and the outlet. A heating device that is a chamber formed by a curved surface.