JPH03188223A - Preheating furnace - Google Patents

Abstract

PURPOSE:To prevent the damage of the refractories of the preheating furnace of a continuous heat treating device for steel strips without abnormally increasing the temp. of the preheating furnace and to prevent the generation of oxide scale on the surfaces of a steel strip by causing the incomplete combustion of gaseous fuel in the preheating furnace, thereby heating the steel strip. CONSTITUTION:Plural oxygen burners 5 and secondary air supplying pipes 12 are provided on both surface sides of the steel strip W at the time of preheating the steel strip W with preheating furnace 4 prior to the heat treatment of the steel strip in the continuous heat treating furnace 1. Each oxygen burner 5 consists of a fuel supplying pipe 6 provided in the transverse direction of the preheating furnace 4, oxygen supplying pipes 7 on both sides thereof and a nozzle 8. Gaseous fuel supplying pipes 6 and oxygen supplying pipes 7 are communicated via through-holes 10a, 10b with plural mixing chambers 9 which are provided in the nozzles 8 and are opened at one end. The supply rate of the O2 to the mixing chambers 9 is set lower than the perfect combustion rate of the fuel to lower the combustion temp., by which the erosion of the refractory bricks of the preheating furnace by the abnormally high temp. is prevented and the formation of the oxide scale on the front surface and rear of the steel strip W is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a preheating furnace, and particularly to a preheating furnace equipped with an oxygen burner as a preheating burner.

(Prior Art and Problems to Be Solved) Conventionally, in order to shorten the processing steps in a continuous heat treatment furnace for steel strips, a preheating furnace is provided at the entrance of the heating zone of the continuous heat treatment furnace.

This preheating furnace is provided with an oxygen burner consisting of a fuel gas supply pipe and an oxygen supply pipe.

By the way, in order to increase the preheating efficiency of the steel strip, it is sufficient to completely burn the fuel in the oxygen burner at the theoretical amount of oxygen.

However, if you do this, the flame temperature will be 2500
℃ or higher, and expensive refractories must be used for the furnace walls, making equipment expensive. Further, even if such refractories were used, there was a problem that the lifespan was short.

An object of the present invention is to provide a preheating furnace that can solve the above problem by adding a simple mechanism.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a preheating furnace for continuous heat treatment of the belt, which uses a fuel gas supply pipe and a smaller amount of oxygen to completely burn the fuel gas. An oxygen burner consisting of an oxygen supply pipe, and an oxygen burner on the side of the flame forming part of the oxygen burner, which corresponds to the oxygen deficiency required for complete combustion of the flame.
This configuration includes a secondary air supply pipe that supplies secondary air.

(Example) Next, an example of the preheating furnace according to the present invention will be described with reference to the drawings.

In FIG. 1, 1 is a continuous heat treatment furnace equipped with a heating burner (not shown), and a preheating furnace 4 according to the present invention is provided on the upstream side thereof.
A seal roll 3 is provided at the charging port 2 of the continuous heat treatment furnace 1.

In the width direction of the preheating furnace 4, an oxygen burner 5 and a secondary air supply pipe 12, which will be described below, are arranged on the front and back sides of the steel strip W, respectively, and the exhaust gas generated in the preheating furnace 4 is The exhaust gas is discharged from the furnace through an exhaust gas passage 14.

As shown in FIGS. 2 and 3, the oxygen burner 5 consists of a fuel gas supply pipe 6 provided in the width direction of the furnace, oxygen supply pipes 7 provided on both sides of the fuel gas supply pipe 6, and a nozzle 8.
A plurality of mixing chambers (spout holes) 9 with one end open provided in the
The fuel gas supply pipe 6 and the oxygen supply pipe 7 communicate with each other via the through holes 10a and 10b.

Note that the mixing chambers 9 may be provided in one row in the nozzle 8,
Also, double rows may be provided.

The amount of oxygen supplied to the mixing chamber 9 is smaller than the amount required to completely burn the fuel gas.

On the other hand, the secondary air supply pipe 12 is rotatably disposed on both sides of the flame forming section 11 of the oxygen burner 5, and the secondary air supply pipe 12 is connected to the belt 1 based on the rotation of the motor 14.
By rotating with the drive of 5, the air injection angle from the ejection hole 13 can be varied. Note that the amount of air from the secondary air supply pipe 12 is the amount of air equivalent to the oxygen deficiency required for complete combustion of the flame.

Therefore, since the flame from the oxygen burner 5 does not burn completely, it becomes a high-temperature flame of 2,500° C. or less, collides with the front and back surfaces of the steel strip W, and heats the steel strip W. On the other hand, since secondary air is supplied from the side of the flame from the secondary air supply pipe 12, the flame after colliding with the steel strip W quickly burns its unburned portion and is cooled. .

(Effects of the Invention) As is clear from the above explanation, according to the preheating furnace according to the present invention, the amount of oxygen supplied to the oxygen burner is smaller than in the case of complete combustion (and the running cost is reduced accordingly). .°Moreover, the temperature is lower than in the case of complete combustion, and the combustion gas temperature after colliding with the steel strip is cooled by the air from the secondary air supply pipe, so it is not possible to make the furnace wall with conventional inexpensive materials. It can be constructed from refractory materials.In addition, since the unburned components in the incompletely combusted combustion gas are combusted by secondary air, exhaust gas treatment can be performed easily.Furthermore, the flame from the oxygen burner Since the flame is oxygen-deficient, it has the advantage of not causing uneven oxide scale (flame pattern) on the surface of the steel strip.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a preheating furnace and a continuous heat treatment furnace according to the present invention, Fig. 2 is a detailed view of an oxygen burner and a secondary air supply pipe, and Fig. 3 is a diagram indicated by the ■-■ line in Fig. 2. It is. DESCRIPTION OF SYMBOLS 1... Continuous heat treatment furnace, 4... Preheating furnace, 5... Oxygen burner, 6... Fuel gas supply pipe, 7... Oxygen supply pipe, 8... Nozzle, 12... 2 Next air supply pipe, 13.
...Blowout hole. Patent applicant Chugai Roko Kogyo Co., Ltd. Haka 1 person

Claims (1)

[Claims] (1) In a preheating furnace for continuous heat treatment of steel strips, an oxygen burner consisting of a fuel gas supply pipe and an oxygen supply pipe that supplies a smaller amount of oxygen than completely combusting the fuel gas;
A preheating furnace characterized in that a secondary air supply pipe is provided on the side of the flame forming part of the oxygen burner for supplying secondary air corresponding to the oxygen deficiency required for complete combustion of the flame.