JPS62267429A - Continuous heat treatment line for metallic strip - Google Patents

Abstract

PURPOSE:To control the waste hot wind after a heat exchange within the range of acid condensation temp. and the heat resistant temp. of a blower by providing a duct with said blower for the purpose of supplying the waste hot wind in a preheating chamber to a dryer in a pretreatment stage and providing a furnace pressure control valve and vent hole thereto. CONSTITUTION:The waste hot wind subjected to the heat exchange with a strip in the preheating chamber 14 is supplied through the duct 21 to the dryer 23 of the pretreatment installation for the strip by the blower 25. The hot wind to be fed into the preheating chamber 14 is kept under about the pressure under which the intrusion of the outdoor air into the preheating chamber 14 is prevented. The opening degree of the furnace pressure control valve 24 provided to the end of the duct 21 on the preheating chamber 14 side is automatically increased and a large amt. of the waste hot wind flows when the pressure in the preheating chamber 14 increases too large. However, the excess waste hot wind is discharged from a vent port 26 provided on the upper stream of the blower 25 of the duct 21 to the outdoor air when the flow rate thereof is larger than the prescribed flow rate at which the wind is supplied to the dryer 23. Conversely, the deficient air is taken in through the vent port 26 when the opening degree of the valve 24 is narrowed and the flow rate to the duct 21 decreases to the rate smaller than the prescribed flow rate mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a continuous heat treatment line for metal strips that can effectively utilize waste gas heat from a continuous heat treatment furnace.

[Prior Art] Generally, a metal continuous heat treatment furnace is provided with a large number of rotating hearth rolls 4 in a heating chamber 1, a soaking chamber 2, and a cooling chamber 3 arranged as shown in FIG. The metal strips 5 are sequentially wound around the hearth roll 4 and passed through the heat treatment furnace from the heating chamber 1a to the outlet 3a of the cooling chamber 3 to perform a predetermined heat treatment.

In addition, the method of heating in the above heat treatment furnace is, for example, when bright annealing of tinplate, automobile steel plate, stainless steel, etc. that requires a glossy surface, a radiant tube 6 etc. is used in a reducing atmosphere. It is done by indirect heating.

Then, high-temperature waste gas generated from a combustion device such as the radiant tube 6 is blown directly onto the metal strip, or
Alternatively, a method of preheating the metal strip by spraying air, atmospheric gas, etc. that has undergone heat exchange with the waste gas has been widely adopted. FIG. 6 shows a method for preheating a metal strip disclosed in Japanese Utility Model Application Publication No. 57-158754, in which the preheating chamber 7 and the heating chamber 1 are provided in the same heat treatment furnace, and the reducing atmosphere in the preheating chamber 7 is shown. The gas is sent from the conduit 8 to an exchanger coil lO provided in the waste gas flue 9, where it exchanges heat with the waste gas and is sprayed onto the metal strip 5 with a nozzle 11;
It is configured to preheat this.

[Problem that the invention seeks to solve]

However, in such a conventional heat treatment line, when the metal strip is preheated as described above,
Because it is difficult to control the temperature of the waste gas after heat exchange, the waste gas blower and its surrounding components must be able to withstand acid condensation and high temperatures, which poses the problem of requiring high equipment costs. there were.

This invention was made in view of these conventional problems, and it recovers sufficient heat from waste gas and adjusts the temperature of the waste gas after heat exchange between the acid condensation temperature and the heat resistance temperature of the waste gas blower. The aim is to solve the above problems by creating a continuous heat treatment line that can be adjusted within a range.

[Means for Solving the Problems] The present invention provides a waste hot air system that is equipped with a blower between the preheating chamber and the dryer in order to supply the waste hot air in the preheating chamber to the dryer in the pretreatment process for metal strips. A duct is provided, and a furnace pressure control valve for adjusting the internal pressure of the preheating chamber is provided at the end of the duct on the preheating chamber side, and a vent for adjusting air volume is provided between the blower and the furnace pressure control valve of this duct. , a continuous heat treatment line for metal strips provided respectively.

[Effect]

Air or reducing atmosphere gas that has sufficiently exchanged heat with the combustion waste gas of the radiant tube by the heat exchange means is sent into the preheating chamber as hot air. This hot air is blown by a nozzle etc. onto the metal strip passing through the preheating chamber, exchanges heat with the metal strip, and becomes waste hot air, which passes through the waste hot air duct and is supplied by a blower to the dryer in the metal strip pre-treatment process. and will be put to good use again here.

Moreover, the hot air constantly sent into the preheating chamber is maintained at a pressure that does not allow air to enter through the seals at the entrances and exits of the metal strip. This pressure is adjusted by adjusting the opening degree of the furnace pressure control valve provided at the end of the waste hot air duct on the preheating chamber side. In other words, when the pressure in the preheating chamber is too high, the opening degree of the furnace pressure control valve increases and a large amount of hot air is sent to the waste hot air duct, but if the amount of air exceeds the certain amount supplied to the dryer. When the amount is high, excess hot air is discharged to the outside air from the vent provided upstream of the blower, and if on the other hand, the opening degree of the furnace pressure control valve is small, the amount of air from the waste hot air duct is supplied to the dryer. When the amount is less than a certain amount,
The draft effect of the blower draws outside air through the vent, mixes it with the waste hot air, and sends it to the dryer to dry the metal strip.

[Example] The present invention will be described below based on the drawings. Fig. 1.2 shows an embodiment of the present invention, and Fig. 3.4 is a diagram showing the effects of this embodiment. Note that the configuration of the continuous annealing furnace except for the preheating chamber is the same as that of the conventional example shown in FIG. 5, so a redundant explanation will be omitted.

First, to explain the configuration, 12 is a blower, which exchanges heat of air or atmospheric gas in the heating chamber 1 with high-temperature waste gas from the radiant tube 6 in the heat exchanger 3 to turn it into hot air. supply to The waste gas after heat exchange is discharged to the outside of the furnace by the blower 15.

The metal strip 5 is passed from the entrance looper 16 to the seal roll 1
7 into the preheating chamber 14 from the entrance side seal part 18,
It is wound around a hearth roll 4, passes through the chamber, and is sent to the heating chamber 1 from the exit side seal portion 19 via a seal roll 20.

11 is a nozzle header for blowing the hot air supplied to the preheating chamber 14 onto both sides of the metal strip 5. Reference numeral 21 denotes a waste hot air duct, in which the hot air that has undergone heat exchange with the metal strip 5, that is, the waste hot air, is transferred to the pretreatment equipment 2.
This is provided to send the water to the dryer 23 of No. 2.

Reference numeral 24 denotes a furnace pressure control valve, which is provided at the end of the waste hot air duct 21 on the preheating chamber side and controls the pressure in the preheating chamber to such an extent that air does not enter the preheating chamber 14 from the inlet and outlet seals 18 and 19. The opening degree of the valve is controlled so that it is always maintained.

25 is a blower installed in the waste hot air duct 21,
Waste hot air is supplied to the dryer 23 at a constant air volume. Reference numeral 26 denotes a vent, which is provided between the furnace pressure control valve 24 and the blower 25 to branch from the waste hot air duct 21, and when the waste hot air passing through the waste hot air duct 21 is larger than a predetermined flow rate. Excess hot waste air is discharged from here, and conversely, when the flow rate is smaller than a predetermined flow rate, the draft effect of the blower 25 causes air corresponding to the shortage to be sucked in from here.

Next, the effect will be explained.

The blower 12 exchanges heat between the air or the reducing atmosphere gas in the heating chamber 1 and the high-temperature waste gas from the radiant tube 6 in the heat exchanger 13, and then turns it into hot air and sends it into the preheating chamber 14. This hot air is blown to both sides of the metal strip 5 passed through the preheating chamber 14 by the flange 11 to the nozzle, exchanges heat with the metal strip 5, becomes waste hot air, passes through the waste hot air duct 21, and blows into the blower. 25 to the dryer 23 of the pretreatment facility 22 for the metal strip 5, where it is used again to dry the metal strip 5 wetted by washing.

Further, the hot air sent into the preheating chamber 14 is maintained at a pressure that does not allow outside air to enter the preheating chamber 14 through the inlet and outlet seal portions 18 and 19. This pressure adjustment is performed by automatically adjusting the opening degree of the furnace pressure control valve 24. That is, when the pressure in the preheating chamber 14 becomes too high, the opening degree of the furnace pressure control valve 14 increases and a large flow rate of waste hot air is sent from the duct 21 to the blower 25, but the flow rate is not supplied to the dryer 23. If the amount exceeds the specified amount,
Excess hot air is discharged to the outside air from a vent 26 provided upstream of the blower 25, and the opening degree of the furnace pressure control valve 24 is narrowed, so that the flow rate to the duct 21 is reduced from the predetermined amount. At this time, due to the draft effect of the blower 25, the amount of air that is insufficient than the predetermined amount is sucked in from the vent 26, and is added to the gradually decreasing waste hot air and supplied to the dryer 23.

As mentioned above, the high-temperature waste gas from the radiant tube 6 is
Since the atmospheric gas is sent unidirectionally from the preheating chamber 14 to the dryer 23 without being circulated as in the conventional example, heat is sufficiently exchanged in the heat exchanger 13. It can be easily maintained within the range of dew condensation and the heat-resistant temperature of the waste gas blower 15.

〔Effect of the invention〕

As explained above, according to the present invention, in order to supply the waste hot air in the preheating chamber to the dryer, a waste hot air duct equipped with a blower is provided between the preheating chamber and the dryer, Furthermore, a metal strip is provided with a furnace pressure control valve for adjusting the internal pressure of the preheating chamber at the end of the duct on the preheating chamber side, and a vent for adjusting the flow rate between the blower and the furnace pressure control valve. Because it is a continuous heat treatment line, the temperature of the waste gas after heat exchange can be easily maintained within the range of acid condensation and the heat-resistant temperature of the waste gas blower, so there is no need to use an expensive waste gas blower that is particularly resistant to acid and heat. Furthermore, by sufficiently recovering heat from the waste gas generated in the heating chamber, it is possible to effectively use the atmospheric gas not only for preheating the metal strip but also for drying it.

Furthermore, in actual operation, as shown by the solid line in Fig. 3, the preheating effect of the metal strip was greater than that of the conventional example shown by the dotted line, and as shown by the solid line in Fig. 4, the waste temperature was Effects such as maintaining a stable constant supply of air to the dryer can also be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment according to the present invention, Fig. 2 is a schematic diagram of the arrangement in the line of the embodiment, Fig. 3 is a comparison diagram between the embodiment and a conventional example of preheating effect, and Fig. 4 5 is a schematic sectional view of a continuous heat treatment furnace common to this embodiment and the conventional example, and FIG. 6 is a preheating chamber and heat recovery device in the conventional example. FIG. 5... Metal strip, 13... Heat exchanger, 14... Preheating chamber, 21... Duct for waste hot air, 23... ...Dryer, 24...
... Furnace pressure control valve, 25 ... Blower for waste hot air, 26 ... Vent. Patent Applicant Kawasaki Steel Corporation Agent Patent Attorney Tetsuya Mori Attorney Yoshiaki Uchi Patent Attorney Tadashi Shimizu Figure 1 Figure 2

Claims (1)

[Claims] In a continuous heat treatment line having a preheating chamber for preheating the metal strip by recovering waste gas heat from the continuous heat treatment furnace by heat exchange means, for supplying the waste hot air in the preheating chamber to the dryer in the pretreatment process of the metal strip. A waste hot air duct equipped with a blower is installed between the preheating chamber and the dryer, and a furnace pressure control valve for adjusting the internal pressure of the preheating chamber is installed at the end of this duct on the side of the preheating chamber. A continuous heat treatment line for metal strip, characterized in that vents for flow rate adjustment are provided between the blower and the furnace pressure control valve.