JP3094793B2 - Direct fire furnace preheating furnace inlet sealing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for sealing an inlet of a preheating furnace for preheating a steel strip in a continuous annealing facility having a direct-fired heating furnace.

[0002]

2. Description of the Related Art In order to improve furnace efficiency and save energy, a continuous annealing equipment for a thin steel sheet having a direct-fired heating furnace is provided with a preheating furnace for preheating a steel strip using exhaust gas from the direct-fired heating furnace. I have. Exhaust gas of the heating furnace sent from the heating furnace to the preheating furnace is discharged out of the furnace through a seal provided at the entrance of the preheating furnace or an exhaust port provided in the preheating furnace.

[0003] Even in the case of a vertical annealing furnace, the preheating furnace 1 may be installed as a horizontal type as shown in FIG. The furnace pressure at this time is always positive compared to the atmospheric pressure. In addition, preheating furnace 1
In the case where is a vertical type, the inlet of the preheating furnace 1 is often located at the lower part as shown in FIG. At this time, the furnace pressure ranges from negative pressure to positive pressure depending on the amount of combustion gas in the direct fire furnace 2. The method for sealing the furnace inlet of the steel strip changes depending on whether the pressure at the inlet of the preheating furnace is positive or negative with respect to atmospheric pressure.

Conventionally, a pair of seal rolls are arranged at the entrance 4 of a horizontal preheating furnace to prevent outside air from entering for the reason of preventing oxidation in the furnace. In this case, the seal roll alone is not enough to prevent outside air from entering, and since the furnace pressure is as high as several tens of mm H ₂ O or more, the furnace gas is constantly blown out from the inlet to compensate for the insufficientness. I have.

[0005] However, in the seal roll system, if the pair of roll gaps is too narrow, the steel strip is easily damaged. For this reason, a soft material or a lining material is provided for the rolls.However, the rotation speed of both rolls is deviated due to abrasion, and the gap becomes large. Rolls need to be replaced, and there are many problems in terms of maintenance.

Further, since the combustion gas to be blown out has a high temperature, the seal roll and its devices need to be heat-resistant. In addition, since the combustion gas contains a large amount of water, water condensed in the sealing device may fall on the surface of the steel strip and impair its quality. Further, in the case of providing a steel strip inlet at the lower part of the furnace in a vertical preheating furnace, Japanese Patent Laid-Open No. 4-141529 discloses, in addition to the seal roll method, a method for coping with a case where the furnace internal pressure becomes negative. Have been. This is achieved by installing a gas seal device at the lower atmosphere communication port of a vertical continuous steel strip heat treatment furnace (steel band outlet of a direct fire type heating furnace). And detects the furnace pressure in the vicinity of the atmosphere communication port, and operates the furnace pressure control damper in the exhaust gas duct with a pressure controller based on the detected value to control the furnace pressure to the set pressure. On the other hand, the amount of exhaust gas supplied to the gas sealing device is controlled by the differential pressure controller based on the detected value.

[0007]

However, in the method disclosed in Japanese Patent Application Laid-Open No. 4-141529, a gas sealing device is provided at the outlet of the direct heating type heating zone, so that the gas sealing device can reduce radiant heat from a high-temperature steel strip. Exposure and the use of high-temperature exhaust gas as a seal gas require heat-resistant measures, and this exhaust gas contains a large amount of moisture, which condenses at the gas seal and corrodes the equipment. There is. In addition, it is necessary to take heat-resistant measures for the blower that sends the exhaust gas from the preheating furnace to the gas sealing device.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for sealing a preheating furnace of a direct-fired furnace, in a continuous annealing equipment having a direct-fired heating furnace, a gas sealing portion connected to a preheating furnace for preheating a steel strip.
The pair of front and rear seal rows located at the steel plate inlet of the preheating furnace
The outside air suction section on the steel sheet entry side and the outside air blow on the preheating furnace side
If the internal pressure of the preheating furnace is higher than the outside air pressure,
Aspirate the seal gas from the pulling part and release the sucked seal gas to the outside air.
The internal pressure of the outside air blow section is blown into the blow section,
If the pressure is lower than the outside air pressure, suck the seal gas from the outside air suction section.
A method for sealing an inlet of a preheating furnace in a direct-fired furnace, characterized in that the suction gas is drawn into the atmosphere and the internal pressure of the outside air suction section is increased by ₂ to 6 mmH2O than the internal pressure of the preheating furnace.

[0009] The direct-fired furnace preheating furnace inlet sealing device of the present invention comprises:
In the continuous annealing equipment having a direct-fired heating furnace, a gas seal portion comprising an outside air suction portion and an outside air blowing portion provided between a pair of front and rear seal rolls located at a steel plate inlet of the preheating furnace, and An outside air blowing pipe system for sending the sucked gas to the outside air blowing unit via a first pressure regulating valve;
An outside air discharge piping system for releasing outside air sucked from the outside air suction unit to the atmosphere via a second pressure regulating valve, pressure detecting means provided in the gas seal unit and the preheating furnace, the gas seal unit and the preheating It is characterized by comprising valve opening control means for controlling the opening of the first pressure regulating valve and the second pressure regulating valve based on the internal pressure difference of the furnace.

[0010]

In the method for sealing a direct heating furnace preheating furnace of the present invention,
In continuous annealing equipment having a direct-fired heating furnace, in order to increase the internal pressure of the gas seal portion connected to the preheating furnace for preheating the steel strip by _{2 to} 6 mmH2O higher than the internal pressure of the preheating furnace, Because hot gas does not flow into the gas seal,
It is not necessary to use a heat-resistant material for the gas seal as a measure against the problem that moisture contained in the high-temperature gas is dewed at the gas seal and the high-temperature gas.

The reason why the differential pressure is set to ₂ to 6 mmH ₂ O is that if the differential pressure is within this range, the amount of air entering the preheating furnace inlet should be about 1% of the amount of combustion exhaust gas passing through the preheating furnace. Because it can be. For example, if the amount of combustion exhaust gas passing through the preheating furnace is 30,000 Nm ³ / H,
m ³ / H, and even if the amount of flue gas passing through the preheating furnace changes, the amount of air entering the preheating furnace inlet can be reduced to about 1%.

In the direct-fired furnace preheating furnace inlet sealing device of the present invention, when the internal pressure of the preheating furnace is higher than the external pressure, the second pressure regulating valve is fully closed, and the first pressure regulating valve is opened based on the differential pressure. The degree is controlled, and the first pressure regulating valve is controlled so that the difference between the internal pressure of the outside air blowing unit and the internal pressure of the preheating furnace is within a predetermined value, and the amount of outside air blown into the outside air blowing unit is controlled. When the internal pressure of the preheating furnace is lower than the outside air pressure, the first pressure regulating valve is fully closed, and the opening degree of the second pressure regulating valve is adjusted so that the internal pressure difference between the outside air suction unit and the preheating furnace becomes a predetermined value. Is controlled, and the outside air is released to the atmosphere.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of the device of the present invention. In the figure, reference numeral 1 denotes a preheating furnace, and a first side of the preheating furnace 1 immediately before the preheating furnace 1 on the side where the steel plate 20 enters the preheating furnace 1, that is, on the entrance side.
Is provided with a second seal roll 6 at a predetermined distance upstream from the seal roll 5. The outside air suction unit 7 is located upstream between these seal rolls.
However, an outside air blowing portion 8 is provided on the downstream side, and forms a sealing device 9. The second seal roll 6, the outside air suction unit 7, the outside air blowing unit 8 and the first seal roll 5 are respectively formed in a continuous cylindrical duct 10 surrounding a steel strip (strip) moving in the center thereof. The rear end of the cylindrical duct 10 is hermetically attached to the wall surface of the steel plate inlet of the preheating furnace 1.

The outside air suction part 7 is formed in a bulged section and is connected to a suction pipe 12 a of the blower 11. The outside air blowing part 8 is also formed in a bulged section,
The outside air blowing slit 8a is provided vertically above and below. The discharge pipe 12b of the blower 11 is connected to the outside air blowing slit 8a. A first pressure regulating valve 13a is mounted in the middle of the discharge pipe 12b. Discharge pipe 12
The outside air diffusion pipe 12c is provided to branch off from a position before the first pressure regulating valve 13a of b. A second pressure regulating valve 13b is attached in the middle of the outside air diffusion tube 12c.

Further, pressure sensors 14a, 14b and 14c for detecting respective pressures are provided inside the outside air suction section 7, outside air blowing section 8 and preheating furnace 1.
First pressure regulating valve 13a and second pressure regulating valve 13b
Are connected to valve opening controllers 15a and 15b for controlling the respective valve openings. The valve opening controller 15a is connected to the pressure sensors 14b and 14c, and the valve opening controller 15b is connected to the pressure sensors 14a and 14c.

With the above configuration, the outside air entering the outside air suction section 7 from the gap between the seal roll 6 and the steel plate 20 is sucked by the blower 11 and is passed through the first pressure regulating valve 13a. The air can be blown into the outside air blowing unit 8. Further, the outside air sucked by the blower 11 can be released into the atmosphere via the second pressure regulating valve 13b.

Next, the control operation of the apparatus of the present invention will be described. Table 1 summarizes the control operation of the first pressure regulating valve 13a and the second pressure regulating valve 13b corresponding to the pressure value in the preheating furnace 1. If the pressure inside the preheating furnace is outside pressure (or
When the pressure is higher than the atmospheric pressure (in the table, the pressure is indicated as positive pressure), the exhaust gas in the preheating furnace blows out from the inlet of the steel sheet through the gap between the seal rolls 5. In this case, the second pressure regulating valve 13
The b is fully closed, the first pressure regulating valve such that the [Delta] P ₁ 1
While controlling the opening of 3a, the sucked outside air is supplied to the outside air blowing unit 8
Blow into. As a result, the pressure in the outside air blowing section is maintained higher than the internal pressure of the preheating furnace by ₂ to 6 mmH ₂ O, the exhaust gas is prevented from flowing out of the furnace, and the temperature inside the outside air blowing section 8 and dew condensation do not occur.

[0018]

[Table 1]

On the other hand, the pressure in the preheating furnace is changed to the outside pressure (or
If the pressure is lower than the atmospheric pressure (in the table, the pressure is indicated as negative pressure), a large amount of outside air may flow into the furnace from the inlet of the steel plate of the preheating furnace. In order to prevent this, the first pressure regulating valve 13a is fully closed, and while controlling the opening degree of the second pressure regulating valve 13b so as to be ΔP ₂ , the sucked outside air is released to the atmosphere through the outside air diffusion pipe 12c. Dissipate in Thereby the pressure of the outside air suction portion 7 is kept high by about 2 mm H ₂ O than the pressure in the preheating furnace, the outside air amount is suppressed to a small amount flowing into the preheating furnace.

The pressure difference between the preheating furnace inlet and the outside air blowing section is 2
In the range of ６6 mm H ₂ O, the inflow of outside air is about 300 Nm ³ , depending on the shape of the opening between the seal roll and the steel plate.
/ H, which is the amount of flue gas passing through the preheating furnace 30
Only 1% of 000 Nm ³ / H. At such an amount of inflow of outside air, it reacts with unburned components in the combustion exhaust gas or is exhausted from an adjacent exhaust gas port (not shown), so that the steel sheet may be oxidized due to the low temperature of the steel sheet. Not at all.

FIG. 2 shows an example of the pressure distribution in the outside air suction section, outside air blowing section and the like when the method of the present invention is carried out. In the case of the pattern (I), the internal pressure of the outside air blowing unit 8 is controlled to be higher than the internal pressure of the preheating furnace 1 by ₂ to 6 mmH ₂ O, and in the case of the pattern (II), the internal pressure of the outside air suction unit 7 is adjusted to the internal pressure of the preheating furnace. About 2mm
Only H2O is controlled high.

FIG. 3 shows the pressure sensors 14a (internal pressure of the outside air suction section) and 14b (internal pressure of the outside air blowing section) and the pressure sensors (of the preheating furnace) when the apparatus of the present invention is applied to a vertical continuous hot-dip galvanizing facility. 5 shows a time transition of the measured value of the internal pressure). When the internal pressure of the preheating furnace is positive (pattern (I)), the internal pressure of the outside air blowing unit 8 is controlled within a set pressure range, and when the internal pressure of the preheating furnace becomes negative, the outside air suction unit 7 The internal pressure drops accordingly, but it is maintained above the preheat furnace internal pressure by a set value. Although the hunting of the pressure value is observed instantaneously, it is understood that the favorable differential pressure control is generally performed.

In the above example, the present invention is applied to a horizontal preheating furnace, but it goes without saying that the present invention can be applied to a vertical preheating furnace as it is.

[0024]

According to the present invention, the internal pressure of the outside air blowing section is always slightly higher than the internal pressure of the preheating furnace so that a small amount of outside air flows in from the inlet of the steel strip of the preheating furnace. can get. Since the combustion exhaust gas in the preheating furnace does not blow out to the seal portion, the use of heat-resistant equipment and the need for a water-cooled structure are not required, and the seal device can be inexpensive. As in the conventional device, the moisture in the exhaust gas does not condense in the sealing device and drop into the steel strip, so that the quality of the steel strip is not impaired. Since outside air can be used as it is as a seal gas,
Operating costs can be reduced. The differential pressure between the preheating furnace internal pressure and the gas seal is ₂ to 6 mm H ₂ O
In the range, the inflow of outside air can be reduced, and the steel sheet is not oxidized at all.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the device of the present invention.

FIG. 2 is a diagram illustrating an example of a pressure distribution of an outside air suction unit, an outside air blowing unit, and the like when the method of the present invention is performed.

FIG. 3 is a graph showing changes in the internal pressure of each part when the apparatus of the present invention is applied to a continuous hot-dip galvanizing facility.

FIG. 4 is an explanatory diagram of equipment having a horizontal preheating furnace.

FIG. 5 is an explanatory diagram of equipment having a vertical preheating furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preheating furnace 5 Seal roll 6 Seal roll 7 Outside air suction part 8 Outside air blowing part 9 Sealing device 10 Cylindrical duct 11 Blower 13a First pressure regulating valve 13b Second pressure regulating valve 14 Pressure sensor 15a Valve opening controller 15b Valve Opening controller

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-19682 (JP, A) JP-A-1-273991 (JP, A) JP-A-5-9592 (JP, A) JP-A-4- 285116 (JP, A) JP-A-60-238426 (JP, A) JP-A-1-153357 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21D 9/56 101 C21D 1/00 112 C21D 1/74 F27D 7/06

Claims (2)

(57) [Claims] 1. A gas sealing portion connected to a preheating furnace for preheating a steel strip in a continuous annealing facility having a direct-fired heating furnace.
The pair of front and rear seal rows located at the steel plate inlet of the preheating furnace
The outside air suction section on the steel sheet entry side and the outside air blow on the preheating furnace side
If the internal pressure of the preheating furnace is higher than the outside air pressure,
Aspirate the seal gas from the pulling part and release the sucked seal gas to the outside air.
The internal pressure of the outside air blow section is blown into the blow section,
If the pressure is lower than the outside air pressure, suck the seal gas from the outside air suction section.
A method for sealing an inlet of a pre-heating furnace of a direct-fired furnace , wherein the suction gas is drawn to the atmosphere and the internal pressure of an outside air suction part is increased by ₂ to 6 mmH2O than the internal pressure of the pre-heating furnace. 2. A continuous annealing facility having a direct-fired heating furnace, wherein a gas seal section comprising an outside air suction section and an outside air blowing section provided between a pair of front and rear seal rolls located at a steel plate inlet of the preheating furnace; An outside air blowing pipe system for sending out the gas sucked from the outside air suction unit to the outside air blowing unit via a first pressure regulating valve, and a second air system for sucking the outside air sucked from the outside air suction unit.
An outside air discharge piping system that discharges to the atmosphere via a pressure regulating valve of
A pressure detecting means provided in the gas seal portion and the preheating furnace, and a valve for controlling an opening degree of the first pressure regulating valve and the second pressure regulating valve based on an internal pressure difference between the gas seal portion and the preheating furnace. A direct-fired furnace preheating furnace inlet seal device comprising: an opening control means.