JPH0222634Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to the improvement of a catenary type continuous annealing furnace. Direct-fired catenary-type continuous annealing furnaces are used in the stainless steel manufacturing process. Recently, improvements have been made to improve the efficiency of furnaces in hopes of saving energy. FIG. 1 is a vertically cut side view showing an example of a conventional catenary-type continuous annealing furnace, in which a radiant preheating zone 3 is arranged in front of a direct-fire heating zone 2 equipped with a burner 1, and a radiant preheating zone 3 is placed on a feed plate roll 4. A steel strip 5 passed in the direction of the arrow is preheated by high-temperature waste gas that is sent from an open heating zone 2 through a radiant preheating zone 3 without a burner to an exhaust gas duct 6 (specially (See Publication No. 52-26723). FIG. 2 is a vertically sectioned side view showing another example of a conventional catenary type continuous annealing furnace. Components that are the same or substantially the same as those in FIG. The device shown in FIG. 2 is a combination of a radiation preheating zone 3 and a convection preheating zone 7 (see Japanese Patent Publication No. 42804/1983). Here, the convection preheating zone 7 receives the waste gas sent from the direct heating zone 2 via the radiant preheating zone 3.
Upper and lower gas blowers 11, 1 by convection fan 10
The waste gas is sprayed onto both the upper and lower surfaces of the steel strip 5 through the gas pipe 2, and the steel strip 5 is circulated and heated by the sprayed waste gas (see Japanese Patent Publication No. 54-42804). The conventional devices shown in FIGS. 1 and 2 have the following drawbacks. That is, in the continuous annealing furnace shown in FIG. 1, when the waste gas temperature approaches 900°C, the radiation preheating effect deteriorates, and if the waste gas is not to be used effectively, the furnace length of the preheating zone becomes undesirably long. In order to compensate for this drawback, the system shown in FIG. 2, which combines a radiation type and a convection type, was proposed. However, even in the combination of radiant preheating zone 3 and convection preheating zone 7 shown in Fig. 2, the convection temperature range is set from the allowable heat-resistant temperature of the convection fan 10 to around 900°C, but in a higher temperature range. If convection preheating is performed, the transfer will occur even more quickly and the length of the furnace can be shortened, which will not only reduce equipment costs but also have the effect of improving thermal efficiency. However, as mentioned above, the exhaust gas temperature is 900℃.
If the temperature exceeds the limit, the life of the convection fan 10 will be extremely shortened, and economical operation will not be possible. In the present invention, in order to solve this problem, all of the preheating zones are made into convection preheating zones 7, the length of the furnace is shortened, and a furnace with better energy saving performance is obtained. FIG. 3 is a vertically cut side view showing one embodiment of the present invention, and FIG. 4 is a booster 16 schematically shown in FIG. 3, which exhibits the most desirable Coanda effect. FIG. 2 is a detailed vertically cut enlarged side view of a type booster. Third
An embodiment of the present invention will be described based on FIGS. 1 and 4. Components that are the same or substantially the same as those in FIGS. 1 and 2 are given the same reference numerals, and their explanations will be omitted. In the present invention, the convection preheating zone 7 is divided into an out-of-furnace treatment type convection preheating zone 8 near the direct-fired heating zone 2 and an in-furnace treatment type convection preheating zone 9 closer to the steel strip inlet. Reference numeral 13 denotes a blower, whose suction side is connected to the waste gas duct 6 via a pipe 14, and whose discharge side is connected via a pipe 15 to at least one Coanda type booster 16.
is connected to. The booster 16 has an inlet 17 and a throat 1
9, and the pipe 15 on the discharge side of the blower 13 communicates with an annular outlet 20 which is arranged around the entire inner wall or substantially the entire inner wall of the throat section 19. There is. Outlet 18 of booster 16
is communicated with a wind box 22 via a pipe 21, and an air outlet 25 or a group of air outlets 25 provided in this wind box 22 is used to cool the steel in the out-of-furnace convection preheating zone 8 of the convection preheating zone 7. They are arranged opposite to each other so as to sandwich the band 5 from above and below to constitute an injection device. On the other hand, the inlet 17 of the Coanda booster 16 connected to the air outlet 25 closest to the direct flame heating zone 2 is connected to the direct flame heating zone 2 which is the closest to the convection preheating zone 7 via a pipe 26. ing. In addition, when a plurality of Coanda type boosters 16 are arranged, at least one Coanda type booster 16 communicating with the direct flame heating zone 2 as described above is provided.
Separately, the inlet 17 of the Coanda booster 16 connected to the n+1st air outlet 25 (where n≧1) in the direct fire heating zone 2 is connected to the n+1st air outlet 25 and the The convection preheating zone 7 located between the nth air jet ports 25 communicates with the out-of-furnace treatment type convection preheating zone 8 . In such a configuration, the Coanda type booster 1
A pipe 26 and a convection preheating zone 7 that draw the waste gas from the direct fire heating zone 2 by the pressurized waste gas produced by the pipe 26
A group of pipes 27 are arranged to induce waste gas from the out-of-furnace treatment type convection preheating zone 8 to constitute an induction device. Therefore, when the blower 13 is turned, a part of the waste gas in the waste gas duct 6 flows through the air passage, that is, the pipe 14 and the pipe 15, to the throat 1 of the Coanda booster 16.
Sent to 9th. Then, from the throat 19 to the exit 18
This waste gas flows towards. At this time, the waste gas in the direct fire heating zone 2 and the out-of-furnace treatment type convection preheating zone 8 of the convection preheating zone 7 is transferred to the corresponding pipes 26 and 2.
7 from the inlet 17 of each booster 16 to the suction outlet 18. Although this Coanda type booster 16 itself is well known,
By applying this, approximately 5 to 15 times the amount of waste gas ejected from the throat 19 is sucked in from the inlet 17 in the direct fire heating zone 2 and the out-of-furnace treatment type convection preheating zone 8. Then, it can be sent out to the exit 18. The present invention is an annealing furnace configured to convey a steel strip 5 in a catenary form from a convection preheating zone 7 to a direct-fire heating zone 2. a booster 16 that induces and boosts the pressure of each waste gas in the direct heating zone 2 and (= and/or) convection preheating zone 7 by the waste gas boosted by the blower 13; Therefore, an induction device having pipes 26 and 27 that induces each waste gas from the direct flame heating zone 2 and the convection preheating zone 7, and an injection device that sprays the waste gas that has passed through the induction device onto the steel strip 5 in the convection preheating zone 7. It is characterized by comprising the following. In other words, the focus of the present invention is to forcefully convect the waste gas as high as possible in the direct flame heating zone 2 and the convection preheating zone 7 and to blow it onto the steel strip 5 in order to increase the thermal efficiency of the catenary type continuous annealing furnace. It is necessary to transfer the thermal energy of this high-temperature waste gas to the steel strip 5, and for this purpose, it is necessary to determine how to increase the pressure of the high-temperature waste gas. The pressure is increased in the gas body, and the high-temperature waste gas in the direct heating zone 2 and convection preheating zone 7 is induced to move by the pressure energy of the gas body. The high-temperature waste gas pressurized in this way is transported to the wind box 2.
2 and is blown onto the steel strip 5 through an injector which injects the air from its air outlet 25. By repeating such forced convection several times, the thermal energy of the high-temperature waste gas can be easily transferred to the steel strip 5, and the temperature of the waste gas can be lowered. Next, the results of Examples will be listed. However, heating zone waste gas temperature 1250℃ Preheating zone waste gas temperature 200℃ Pressure after preheating zone pressure increase 2000mm (underwater) Air volume 20% of waste gas

[Table] As shown in the above example, by performing convection preheating three times, the temperature of the waste gas in the direct fire heating zone, which was initially 1250°C, decreased to 890°C, and after the fourth time, the temperature of the waste gas decreased to 820°C. It was about ℃. As described above, even if the exhaust gas is in a high temperature range, the heat transfer effect by forced convection is very good, and the exhaust gas temperature can be sufficiently lowered by repeating the process several times. This means that a large amount of thermal energy possessed by the waste gas was transferred to the steel strip 5. After the temperature drops, it is only necessary to increase the pressure with the direct convection fan 10, and this convection fan 10 has a great advantage in that there is a big difference in life and performance between waste gas temperatures of 900°C and 800°C. . Comparing the effects of the above embodiments in terms of the length of the furnace that can achieve the same efficiency as the conventional method, the length of the furnace using the conventional radiant preheating method is 48 m, and the length of the furnace using a combination of radiant preheating and convection preheating is 17 m, while the length of the furnace using the present invention is 12 m.
This made it possible to shorten the time. In the embodiment shown in FIG. 3, the convection preheating zone 7 is composed of an out-of-furnace treatment type convection preheating zone 8 and an in-furnace treatment type convection preheating zone 9, but the in-furnace treatment type convection preheating zone 9 is omitted. It is also possible to provide only the out-of-furnace treatment type convection preheating zone 8. Furthermore, although the embodiment shown in FIG. 3 shows that the wind box 22 is provided within the convection preheating zone 7, it can also be provided outside the convection preheating zone 7 as shown in FIG.

[Brief explanation of the drawing]

FIG. 1 is a vertically cut side view showing an example of a conventional catenary type continuous annealing furnace, and FIG. 2 is a vertically cut side view showing another example of the conventional catenary type continuous annealing furnace.
Fig. 3 is a vertical cut side view showing an embodiment of a catenary type continuous annealing furnace according to the present invention, Fig. 4 is a vertical cut side view of a Coanda type gas booster, and Fig. 5 is a catenary type continuous annealing furnace according to the present invention. FIG. 7 is a vertically cut side view of main parts in a modified embodiment of the annealing furnace. 1... Burner, 2... Direct flame heating zone, 3...
...Radiation preheating zone, 4...Feed plate roll, 5...Steel strip, 6...Waste gas duct, 7...Convection preheating zone, 8...Out-of-furnace treatment type convection preheating zone, 9...In-furnace treatment type Convection preheating zone, 10... Convection fan,
11... Gas blower, 12... Gas blower, 13
... Blower, 14 ... Pipe, 15 ... Pipe, 16 ... Booster, 17 ... Inlet, 18 ... Outlet, 19 ... Throat, 20 ... Annular outlet, 21
...pipe, 22 ... wind box, 25 ... air outlet, 26 ... pipe, 27 ... pipe.

Claims (1)

[Claims for Utility Model Registration] In an annealing furnace configured to convey a steel strip 5 in a catenary form from a convection preheating zone 7 to a direct-fire heating zone 2, a part of the waste gas in the convection preheating zone 7 is guided. A booster 16 that induces and boosts the pressure of each waste gas in the direct fire heating zone 2 and the convection preheating zone 7 by the waste gas boosted by the blower 13 installed in the channel; Equipped with an induction device having pipes 26 and 27 that induce each waste gas from the direct-fire heating zone 2 and the convection preheating zone 7, and an injection device that sprays the waste gas that has passed through the induction device onto the steel strip 5 in the convection preheating zone 7. A catenary type annealing furnace characterized by: