JPS5873727A - Preheating method of strip in continuous heat treatment equipment - Google Patents

Abstract

PURPOSE:To preheat a strip by use of a through-plate roll without exerting bad influence on a quality of the strip, by constituting so that a high boiling point organic heating medium which has utilized sensible heat of waste combustion gas of a heating furnace flows in the through-plate roll provided on the entry of the heating furnace. CONSTITUTION:A spiral heating medium flow course 102 is provided so as to contact with the inside of a shell 101 of a through-plate roll 1 provided on the entry of a heating furnace 2 of a continuous heating furnace, or a reheating furnace 5. By a circulating pump 13, a high boiling point organic heating medium is made to circulate in a circulating duct system 8, and the heating medium which has become a high temperature by collecting sensible heat of waste combustion gas from the heating furnace 2 by a heat exchanger 10, on the way of the system is made to pass through the heating medium flow course 102 a pair of through-plate rolls 1a, 1b. By utilizing this temperature, preheating of a strip is executed effectively through through-plate rolls 1a, 1b. In this way, a unit of of fuel of the heating furnace 2 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preheating a strip in a continuous heat treatment facility.

In continuous heat treatment equipment for strips such as a continuous annealing furnace, it is necessary to heat the air-temperature IJ tube to several hundred degrees, and for this reason, an extremely large amount of heat is introduced into the heating furnace.

However, of the combustion heat in such a heating furnace, the heat actually used for heating the strip is only about the entire amount, and the combustion heat of 40 to sob becomes heat loss due to combustion exhaust gas. is normal. For this reason, conventionally, in order to effectively utilize the combustion heat in the heating furnace and reduce the fuel consumption rate, the strip is preheated by applying the combustion exhaust gas of the heating furnace to the strip surface KvK at the front of the heating furnace. A method is proposed. However, although this method can be expected to have a certain effect in terms of heat utilization efficiency, in order to implement this method, another (C) furnace must be installed in front of the heating furnace. O
Another problem is that if the exhaust gas is directly blown onto the strip surface, the properties of the 971 surface deteriorate.

The present invention was devised to solve the above-mentioned conventional problems, and it is possible to process strips using sensible heat of combustion exhaust gas from a heating furnace with compact equipment and without adversely affecting the quality of the strips. The purpose is to provide a method for preheating. The present invention circulates a high boiling point organic heating medium in which the sensible heat of the combustion exhaust gas of the heating furnace is recovered by a heat exchanger through a passing roll installed in the heating furnace. The strip is preheated through the threading roll, thereby eliminating the need for expensive equipment and without causing any negative effects on the quality of the strip. It is possible to preheat nine strips using the sensible heat of the combustion exhaust gas.

Figures 1 to 3 show an example in which the method of the present invention is applied to continuous annealing of strips, in which (2) is a heating furnace, (stage is a soaking furnace, and (4) is a rapid cooling equipment. , (5) is a reheating furnace, (6) is an overaging furnace, (η is a quenching furnace, and strip 2 (S) is these facilities, ′.

The inside can be transferred sequentially and continuously. In such equipment, the present invention configures the passing roll (1) on the entry side of the heating furnace (a) and further the reheating furnace (5) as a heat roll,
A heating furnace (2) and a reheating furnace (5) are placed inside this threading roll (1).
) A heating medium is circulated through which the sensible heat of the combustion exhaust gas is recovered, and the sensible heat is used to preheat the tubes passing through the passing board roll (1).

As the heating medium, an organic heating medium with a negative boiling point is used, and among these, an aromatic heating medium having good thermal stability is mainly used.

The conditions required for a heating medium include a high boiling point and excellent thermal stability.Water, which is normally used as a refrigerant, has a usage limit of about 200°C at most under high pressure, whereas the above-mentioned high boiling point Organic heating media are thermally stable up to about 400'O, and have properties that are not inferior to water in terms of freezing point, corrosivity, toxicity, explosion resistance, ease of handling, etc.

Figure 2 schematically shows the '11 method of the present invention, (8)
(9) is a heating medium O circulation pipe system, (9) is a heat exchange exhaust gas discharge pipe system, and the ring is a heat exchange device. ) (lb) is present. Threading roll (1) used in this example
As shown in FIG. In this embodiment, in order to increase the amount of heat given to the strip (S), it is equipped with a heating furnace (2) (or reheating furnace). (5)) A set of two entry-side type pipes are provided. In addition, in other drawings, (c) is an air separator, (b) is a swelling tank, o4 is a circulation pump, o4 is a booster fan, and (g) is a chimney. In the present invention, the heat medium is circulated in the circulation pipe system (8) by the circulation pump (2), and in the middle of the circulation, it is passed through the heat exchanger (G) to the heating furnace (2) (or reheating furnace). 5
)) by recovering the sensible heat of the flue gas from the combustion exhaust gas, and by passing the heating medium through the plate rolls (1a) and (1b), the strip is passed through the mail order rolls (la) and (lb). (S) is preheated by applying heat. Here, the combustion exhaust gas discharged from the heating furnace (2) etc. is normally at a temperature of about 400° 69, and this temperature can be used to effectively preheat the strip (8).

Such a preheating effect reduces the sensible heat recovery rate of the heating medium,
Number of rolls (1), strips (S) and mail order rolls (1)
Although it differs depending on conditions such as the contact area (winding angle) with the
A 1.2-thick strip was treated at a capacity of 7°t/H by passing an aromatic organic heating medium from which the sensible heat of the heating furnace (2) had been recovered using a heating furnace (lb). case, 70-10
It was confirmed that the preheating effect of G'0 can be increased.

Thus, such a preheating effect results in a fuel savings of approximately 15-20. FIG. 4 shows a thermal cycle of continuous annealing, and according to the present invention, it is possible to reduce the heat load in the portion O indicated by diagonal lines in the figure. As described above, in the present invention, an appropriate preheating effect can be obtained by selecting the number of threading rolls (1) and the contact area (wrapping angle) of the strip (S) therewith.

Additionally, in general, in a heating furnace, when a low-temperature (room temperature) strip comes into contact with a high-temperature furnace passing roll, a concave thermal crown is formed on the roll due to the temperature difference between the P1 furnace temperature and the strip temperature. However, in the present invention, since the strip is preheated, this temperature difference is small, and the resulting thermal crown is made small, which improves the ability to pass the strip through the furnace. It can be improved.

Example 1 Two sheet passing rolls on the heating furnace entry side of continuous annealing equipment were used as heat rolls, and a high boiling point organic heating medium that recovered the sensible heat of the combustion exhaust gas of the heating furnace was passed through them to perform preheating. . The conditions are as follows.

Strip size Thickness: 0.8 ■ Width: 1000 ■ Line speed: 160 centimeters/min 2 heat rolls x 1050 φ ■ Strip winding angle: approx. 400° (for 2 rolls) As a result, the conventional The temperature was about 14
A preheating effect of about 100°C was obtained even when the temperature was preheated to 0°C.

Additionally, as a result, we were able to save about 20 cents of fuel.

Example 2 Three sheet passing rolls on the heating furnace entry side of continuous hot-dip galvanizing equipment were used as heat rolls, and preheating was performed in the same manner as in the above example. The conditions are as follows.

Strip size thickness = 1.3 ■ Width: 117S - Line speed: 50.7 minutes Heat rolls: 3 x 1200φ ■ Strip winding angle: Approx. 600° (for 3 rolls) As a result, conventional approx. 20'O @ Rarely, at a temperature of about 20 degrees
When the temperature was preheated to 0'O, a preheating effect of about 180°C was obtained.

'1. Also, as a result, we were able to save about 1 son of fuel.

According to the above-described method of the present invention, the sensible heat of the flue gas discharged from the heating furnace is effectively used to produce strips without requiring any major equipment and without adversely affecting the quality of the strips. It has the excellent effect of being able to perform preheating, lowering the fuel consumption rate of the heating furnace, and performing economical and appropriate heat treatment.

[Brief explanation of the drawing]

Figures 1 to s21 show an example in which the method of the present invention is applied to a continuous annealing process, Figure M1 is an explanatory diagram showing the entire line, and Figure 2 schematically shows the method of the present invention. Explanatory drawing, FIG. 3d is an explanatory drawing schematically showing the passageway 11ia used in the present invention. FIG. 4 shows the thermal cycle in the continuous annealing line shown in FIG. 41 and the heat load reducing effect of the present invention on this. In the figure, (1) (1m) (lb) indicates a mail order roll, (2) a heating furnace, (5) a reheating furnace, and (8) a strip.

Claims (1)

[Claims] A high boiling point organic heating medium, which has recovered the sensible heat of the combustion exhaust gas of the heating furnace to a heat exchange device, is passed through a passing roll installed on the inlet side of the heating furnace of continuous heat treatment equipment for strip. A method for preheating a strip in a continuous heat treatment facility, which is characterized by nine methods of preheating the strip and the whelk using a removing plate roll.