JPS61217527A - Operating method for soaking pit burnt unidirectionally at upper part - Google Patents

Abstract

PURPOSE:To heat steel slab in a furnace to uniform temp., by completing heating of steel slab for hot rolling under preset burning pattern, then circulating forcedly atmosphere gas in furnace in inverse direction against burning gas flow, in heating the slab by the title furnace. CONSTITUTION:Materials M to be heated such as plural materials are mounted in the title furnace, heated by fuel combustion due to a burner 2 based on heat pattern preset in a computer 10, and exhaust gas is released in air from a flue gas hole 7. In th is case, since combustion gas flows from upper to lower part in furnace, temp. of upper steel material becomes higher than that of lower part steel material. When heating is ended once, combustion at burner is stopped, flue 11 of the hole 7 is closed and a circulating fan 8 is revolved, gas in the furnace is circulated from lower to upper inversely in arrow direction to circulate high temp. gas at upper part in furnace from lower to upper part of the material M and whole of the material M is heated uniformly to hot rolling temp.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a method of operating an upper one-way firing soaking furnace used for heating continuously cast slabs to rolling temperature.

Conventional technology and its problems In the upper one-way soaking furnace, a burner is attached to the upper side wall of the furnace body, a smoke exhaust port is provided at the lower part to discharge combustion exhaust gas, and the material to be heated is placed in the furnace in one stage. It is heated by stacking 4 pieces of wood in 4 to 5 tiers, but due to its structural characteristics, the temperature of the heated materials after baking is highest on the top tier and lowest on the smoke exhaust side of the bottom tier, and is usually heated to 60°C. A temperature difference of ~120°C occurs.

The reason why such uneven heating occurs in the furnace is that the gas flow in the furnace is set at K as shown by the broken line in Figure 5. This is because heat is taken away by the material to be heated (CM) or the furnace wall (1), and the gas temperature is lowest near the smoke exhaust port (3).

In the case of continuously cast slabs (hereinafter referred to as "CC7'room"), the heating temperature of the material in such a soaking furnace is such that the temperature of the CC plume near the smoke exhaust port at the lowest stage in the furnace is the temperature required for rolling. It has been decided that it will be. Therefore, the CC pump in the upper stage of kneading, which has a large uneven heat in the furnace, is heated to a high temperature, which leads to deterioration of thermal efficiency and creates a difference in rolling temperature conditions, which is not preferable. moreover,
The fuel consumption rate is also high.

Therefore, conventional methods for reducing the uneven heat in the furnace include, for example, installing an auxiliary burner at a low temperature position, or recirculating a part of the high-temperature combustion exhaust gas into the furnace (Japanese Patent Application No. 128807/1982). In addition, methods have been proposed in which the pressure inside the furnace is lowered mid-combustion (Japanese Patent Application No. 59-225488), but all of these methods have the problem that a large amount of heat is dissipated into the atmosphere as exhaust gas, resulting in poor heating efficiency.
It was not possible to significantly reduce fuel consumption.

Purpose of the Invention This invention was made to solve the above-mentioned conventional problems, and provides a method for operating an upper one-way soaking furnace that can further reduce uneven heat in the furnace and significantly reduce the total amount of fuel used. The purpose is to propose the following.

Structure of the Invention The operating method of the upper one-way firing soaking furnace according to the present invention is to provide a furnace atmosphere gas circulation duct via a fan on the side wall of the furnace body where the burner and the smoke exhaust port are provided, and to control the preset combustion. Immediately after completion of heating in the pattern, the smoke exhaust port is closed, and the furnace atmosphere gas is forcibly circulated in the opposite direction to the flow of combustion gas using the fan.

That is, the method of this invention aims to equalize the temperature inside the furnace by completely sealing the exhaust gas outlet during non-combustion and forcibly circulating the atmospheric gas in the furnace from the high temperature side to the low temperature side. .

The method of this invention will be explained below with reference to all the drawings.

FIG. 1 is a schematic diagram showing an example of the configuration of an apparatus for carrying out the method of the present invention, and FIG. 2 is a longitudinal sectional front view taken along line 1--2 in FIG.

In Figures 1 and 2, (5) is the smoke exhaust port (3) e
It is a damper for closing, and is opened and closed by a cylinder (5-1). (6) (7) are the suction duct and discharge duct for the furnace atmosphere gas, (8) is the circulation fan for the furnace atmosphere gas, (9-1) (
9-2) is the furnace temperature gauge, QO is the combustion burner (2), damper opening/closing cylinder (5-1), circulation fan (8)
and nine computers connected to the furnace thermometers (9-1) and (9-2), αη is the flue.

To explain the method of operating a soaking furnace using the above device, first, the burner fuel flow rate and combustion air amount are determined based on a uniform pattern preset in the computer α0 (based on a predetermined air-fuel ratio), and combustion begins. The heated material CM) is heated for a predetermined period of time. During burner combustion, the smoke exhaust port (3) is fully opened and the combustion exhaust gas is discharged from the flue I.

When heating of the material to be heated (M) is completed, combustion is stopped and the smoke exhaust port (3) is closed by the T-damper (5). Smoke exhaust port (3
) is fully closed, the circulation fan (8) is immediately driven to forcefully circulate the atmospheric gas in the furnace in the direction opposite to the flow of combustion gas, as shown by the arrow in FIG. At this time, the side wall of the furnace body (1
) is installed in the upper part of the furnace.The high-temperature furnace atmosphere gas is sucked in through the suction duct (6) and guided into the furnace through the discharge duct (7) installed at the lower part of the side wall of the furnace body. 3
) The nearby ambient temperature begins to rise.

Therefore, if this forced circulation of the furnace atmosphere gas continues, the temperature difference between the top (high temperature) and bottom (low temperature) inside the furnace will inevitably disappear. Then, the atmospheric temperature V near the smoke exhaust port at the lowest stage of the furnace measured by the furnace thermometer (9-2) and the atmospheric temperature X at the top stage of the furnace measured by the furnace thermometer (9-1). When V≧X is established, the circulation fan (8) is stopped and the material to be heated (M) is extracted.

Note that it is also possible to carry out a method in which secondary scale is suppressed by blowing N gas into the circulating atmospheric gas to create a non-oxidizing atmosphere.

Example @ 4.4 m + 7.5 m in length, 4.86 m in height, and two internal mixing low NOx burners are installed. As surface temperature 620℃
Charge 160 tons of CC plume (immediately before charging) with 9 pieces of 16 wood, and stop combustion after heating at a set temperature of 1220℃ for 10 hours. Immediately after that, completely close the smoke exhaust port with a damper and The post-circulation fan was driven to suck in the furnace atmosphere gas through the suction duct and introduce it into the furnace through the discharge duct, and the furnace atmosphere gas was circulated for a total of 1.5 hours. The experimental results are shown in FIG. In addition, the relationship between the circulation time and the material temperature at the lowest stage in the furnace in this example (circulation flow rate 5500 Nrrl/H) was
As shown in the figure.

As is clear from Figure 3, the uneven heat 8 at the end of heating
We were able to reduce the temperature from 0°C to around 40°C by about 40°C. In particular, the maximum effect is achieved when circulating for 1.5 hours at a circulation flow rate of 550 ONm'/H, with a fuel savings of 12 x 10"
It was kcaI2/T. As is clear from FIG. 4, this is because the temperature of the material at the lowest stage in the furnace was raised by circulating the atmosphere gas in the furnace.

Effects of the Invention As is clear from the above embodiments, according to the method of the present invention, the minimum temperature in the furnace can be increased simply by forcing the atmosphere gas in the furnace to circulate in the opposite direction to the flow of combustion gas after heating is completed. Therefore, it is possible to lower the set temperature by the amount that the minimum temperature has increased, and the amount of fuel used can be significantly reduced. Further, since the circulation of the furnace atmosphere gas to reduce this uneven heat is carried out by closing the smoke exhaust port during non-combustion, the heating efficiency does not decrease.

[Brief explanation of drawings]

Figure 1 shows the method of this invention in 5! FIG. 2 is a schematic front view taken along the line ll-Tl in FIG. FIG. 4 is a diagram showing the relationship between circulation time and material temperature in the same example as above, and FIG. 5 is a schematic diagram showing the state of gas flow in the upper one-way firing soaking furnace. 1... Side wall, 2... Burner, 3... Smoke exhaust port, 5...
Damper, 6 Suction duct, 7 Discharge duct, 8 Circulation fan, 9-1.9-2 Thermometer, 10 Computer, 11 Flue ,M...
・Heated material. Applicant: Sumitomo Metal Industries, Ltd. Figure 1 Figure 2 Figure 3 Circulating flow Q (Nd/H) Circulating time (Hr)

Claims (1)

[Claims] In the operating method of an upper one-way firing soaking furnace, which has a burner in the upper part of the furnace side wall and a smoke exhaust port in the lower part, a furnace atmosphere gas circulation duct is installed on the furnace side wall through a fan, and a preset A method for operating an upper one-way soaking furnace, characterized in that the smoke exhaust port is closed immediately after heating is completed in a combustion pattern, and the atmosphere gas in the furnace is forcedly circulated in the opposite direction to the flow of combustion gas using the fan.