JPH02173251A - Vertical type continuous heating furnace for steel strip - Google Patents

Abstract

PURPOSE:To make temp. distribution uniform in a furnace and to improve unit consumption of fuel by projecting plural pairs of parting walls in the prescribed interval from both inner side furnace wall to furnace center part at direct fired heating zone in a vertical type continuous heating furnace, parting plural zones vertical direction and also arranging a burner at each zone. CONSTITUTION:A hot dip galvanizing steel strip P treated in a hot dipped plating vessel S is introduced to the direct fired heating zone 2 and convection heating zone 3 in order through inlet side opening 4 in the vertical type continuous heating furnace 1, and after executing alloying treatment, this is discharged from the outlet side opening 5. Then, plural pairs of the parting walls 7 are projected from both inner side furnace wall to the furnace center part at the direct fired heating zone 2 and gap between tip parts of pair of the parting walls 7 has the interval, which does not come into contact with the steel strip P, and plural parting zones are demarcated to vertical direction, and the burner 8 and a furnace inner pressure detector 9 are arranged at each zone. By this method, the temp. distribution in the furnace is made uniform and the unit consumption of the fuel is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vertical continuous heating furnace for thin steel sheets, and in particular to a vertical continuous heating furnace for thin steel sheets suitable as a heating furnace for continuous alloying treatment of hot-dip galvanized steel sheets and the like. This relates to a type continuous heating furnace.

[Conventional technology]

As is well known, hot-dip galvanized steel sheets include alloyed hot-dip galvanized steel sheets in which a dip-plated steel sheet is heated and soaked to form a Pe-Zn alloy on the entire surface of the galvanized layer.

As a continuous heating furnace for alloying treatment applied to continuous hot-dip galvanizing equipment, it is movable so that it can be installed on the production line only when manufacturing alloyed hot-dip galvanized steel sheets. As shown in Figure 5, for reasons such as installation space and ease of heating control, an inlet opening (51) is placed at the bottom of the furnace, and an outlet opening (54) is placed at the top of the furnace. ), and a plurality of burners (55
) is provided with a direct flame heating zone (52) that heats the plated steel sheet (56) being passed from the front and back with flame from the direct flame heating zone (52). ,
A vertical continuous heating furnace equipped with a convection heating zone (53) for soaking the plated steel plate (56) is widely used.

On the other hand, in these vertical continuous heating furnaces, when the plated steel plate comes into contact with the furnace body when passing the plated steel plate, the plating layer of the plated steel plate is damaged and its quality is impaired. The heating furnace is required to have a structure that can strictly avoid contact between the plated steel sheet to be passed through and the furnace body.

For this reason, in these vertical continuous heating furnaces, the entrance opening at the bottom of the furnace and the exit opening at the top of the furnace are relatively large, making it easy for outside air to enter the furnace. In addition, the furnace is vertical, and the combustion waste gas from the direct-fired heating zone is guided to the convection heating zone above and discharged from the outlet opening at the top of the furnace, so there is a dotted line on the left side of Figure 5. As shown by the arrow, an upward gas flow is formed inside the furnace, and a draft is generated in the lower part of the furnace, just like a chimney effect.
If the furnace height is relatively large, the pressure inside the furnace at the bottom is -3 m.
It can even reach mAq, and due to this draft force,
As shown by arrow A in FIG. 5, a phenomenon occurs in which low-temperature air outside the furnace is sucked into the furnace through the inlet opening of the furnace bottom.

As a result, these vertical continuous heating furnaces have the problem of low-temperature air outside the furnace entering through the inlet opening at the bottom of the furnace, resulting in uneven temperature distribution inside the furnace and a decrease in fuel consumption. there were.

Therefore, conventionally, regarding these vertical continuous heating furnaces,
Discharge of combustion waste gas mainly from the outlet opening at the top of the furnace 2ff
Studies have been conducted to control the internal pressure of the furnace to a positive pressure by suppressing il, thereby suppressing air entering from the inlet opening of the furnace bottom.

However, for example, with a configuration in which a damper is provided at the outlet opening and the opening degree of the outlet opening is simply narrowed, vibrations caused when the plated steel sheet is passed through and deformation due to heating (warping in the length and width directions) can be avoided. As a result, in order to avoid contact with the plated steel plate, restrictions are placed on the aperture width, making it difficult to obtain the desired effect. As shown in the figure,
A pair of touch rolls (63) are provided directly above I), and by sandwiching the plated steel plate (64) to be passed between them, vibration and warping in the width direction of the plated steel plate (64) are suppressed and contact is avoided. The opening degree of the damper (62) provided in the outlet opening (61) can be further narrowed down.
As shown in Fig. 7, directly above the outlet opening (71),
A position detection device (74) for the plated steel plate (75) to be passed is provided, and a drive means (73) connected to the device adjusts the opening degree of the damper (72) provided at the outlet opening (71). As shown in Fig. 8, a static pressure plate (83) is installed directly above the outlet opening (81) to suppress the vibration of the plated steel plate (84) through which the plate is passed using air pressure. As shown in FIG.
A labyrinth (92) is provided at the top of the furnace to increase the gas flow resistance in this area, thereby suppressing the flow rate of combustion waste gas from the outlet opening (91) and adjusting the furnace pressure. It is also being put into practical use.

[Problem to be solved by the invention]

However, when the present inventors conducted a detailed study on these conventional vertical continuous heating furnaces, it was found that they had the following problems.

In other words, ■ a damper with a pair of touch rolls above the damper can narrow down the opening of the outlet opening more effectively, and is effective in controlling the furnace pressure; Because it is directly sandwiched between the touch rolls, problems related to product quality arise, such as the plating layer wrapping around the roll surfaces and surface flaws occurring on the plated steel sheet.

■If the damper opening degree is adjusted by detecting the position of the plated steel plate, the opening degree must be set in consideration of the occurrence of warpage in the width direction of the plated steel plate and the time lag from detection to activation. As a result, the aperture width is more restricted than necessary.

■For models equipped with static pressure butts, in order to obtain the vibration suppressing effect, the air injection part or static pressure surface must be brought extremely close to the plated steel plate surface, or the gas supply amount and pressure must be sufficiently high (secured). Furthermore, if the plated steel plate is warped in the width direction, the gap on the concave side will become larger and the effectiveness will be reduced, so the shape of the plated plate should be continuously grasped to avoid contact. However, it becomes necessary to add a function to adjust the gas supply amount and pressure according to the fluctuations, and the equipment becomes complicated and large-scale, leading to a rise in equipment costs.

In addition, ■ those with a labyrinth at the top of the furnace do not depend on the opening degree of the outlet opening, but increase the gas flow resistance at the relevant part and suppress the flow rate of the combustion waste gas flowing out, thereby reducing the furnace pressure. Although the structure is simple, it is difficult to adapt to changes in the type of plated steel sheet to be passed and the heating conditions, and it has the disadvantage that it is less effective in controlling the furnace internal pressure.

This is because the basic principle of furnace pressure control is that the fluid (in this case, the combustion waste gas) in the throttle section (in this case, the outlet opening at the top of the furnace)
, that is, the pressure loss Δ expressed by the following equation 1
The purpose is to adjust P, and Δp=(υ/C)” (r/
2 g) ----- Also, the pressure loss ΔP of 1 equation
can be adjusted by controlling the gas flow rate υ as indicated by ■2 below, and υ−F, ((273+T, )/27
3) l/3600A-If formula [However, in the above formulas 1 and 2, ΔP is pressure loss (mmAg), and υ is gas flow rate (
m/5ee), C is a constant, γ is the specific weight of gas (g/5ee),
m3), g is the acceleration of gravity (9,8-8 ec”), F,
is a gas flow! (Nm'/H), Tc is the gas temperature ('
C), A is the flow passage cross-sectional area (m”), ) In the conventional vertical continuous heating furnace equipped with the above damper, this gas flow velocity υ
is controlled by changing the flow passage cross-sectional area A of the throttle part, that is, by changing the opening of the outlet opening at the top of the furnace. Is this gas flow velocity υ controlled by flow path resistance? )I, but in such a configuration, as mentioned above, there are restrictions on the width of the opening, and in addition, the combustion waste gas temperature TG which affects the gas flow velocity υ at the top of the furnace This is thought to be because the effect of suppressing the gas flow velocity υ decreases in the upper part of the furnace because it decreases compared to the upper part of the direct-fired heating zone below due to heat exchange with the plated steel plate.

Therefore, as a result of further detailed study, the present inventors found that
In a structure in which a control means for controlling the furnace pressure is provided at the outlet opening at the top of the furnace, as in the conventional vertical continuous heating furnace described above, especially in a vertical continuous heating furnace with a relatively large furnace height, We came to the conclusion that it is difficult to expect effective furnace pressure control to suppress air entering from the inlet opening of the furnace bottom. Focusing on the pattern of the combustion waste gas flow rate FG and gas temperature T, which affect the gas flow velocity υ, when restricting the combustion waste gas flow in the lower part of the furnace, the internal pressure in the lower part of the furnace can be effectively controlled, and the inlet side of the furnace bottom can be effectively controlled. It can effectively suppress air entering from the opening, and further,
The present invention was completed based on the knowledge that the effect of stirring and mixing the low-temperature air that entered the furnace at the lower part of the furnace could also be obtained.

That is, the present invention can increase the pressure inside the furnace in the lower part of the furnace, effectively suppress air entering from the inlet opening at the bottom, and further direct air from outside the furnace that has entered through the inlet opening into the lower part of the furnace. The object of the present invention is to provide a vertical continuous heating furnace for thin steel sheets, which can be stirred and mixed in the furnace, and can uniformize the temperature distribution in the furnace and improve the fuel consumption rate.

[Means to solve the problem]

In order to achieve the above object, the vertical continuous heating furnace for thin steel sheets according to the present invention is provided with an entrance opening at the bottom, an exit opening at the top, and a direct heating zone at the bottom, and a continuous heating zone at the top. In a vertical continuous heating furnace for thin steel sheets, which is equipped with a convection heating zone, the direct-fired heating zone has a plurality of pairs of convex steps extending from both inner walls of the furnace to the center of the furnace, and with a predetermined interval between the tips. It is vertically divided into a plurality of zones by a partition wall, and each of these zones is provided with at least one burner.

One or more of the plurality of pairs of partition walls can be provided such that their leading ends can move forward and backward.

Further, the tip portions of the pair of partition walls provided so as to be movable back and forth can be connected to a drive means for controlling the furnace internal pressure, which is communicated with the furnace internal pressure detecting means.

[Effect]

In the vertical continuous heating furnace for thin steel sheets of the present invention, the lower direct-fired heating zone is provided in a plurality of pairs projecting from both inner walls of the furnace at the center of the furnace, and with a predetermined interval between the tips. Since the partition wall is vertically divided into multiple zones, the upward flow of combustion waste gas from the burners installed in these zones is
The pressure loss of the combustion waste gas stream is increased by throttling between the tips of the pair of partition walls narrowed at a predetermined distance, and the pressure loss can increase the internal pressure in the zone below each of the pair of partition walls, That is, the pressure inside the furnace in the lower part of the furnace can be increased, and the intrusion of outside air from the entrance opening in the bottom can be suppressed.

Furthermore, by constricting the upwardly flowing combustion waste gas between the ends of the plurality of pairs of partition walls, turbulence is formed in the combustion waste gas at the upper and lower parts of the ends of these partition walls, and the combustion waste gas is Due to the turbulent flow, the air outside the furnace that entered through the inlet opening at the bottom is quickly mixed with the combustion waste gas at the bottom of the furnace.
By mixing, the temperature can be raised and the high temperature can be made uniform.

In addition, since the combustion waste gas is divided vertically into multiple zones using multiple pairs of partition walls, the combustion waste gas can be throttled, stirred, and mixed in multiple stages in the vertical direction. The effect can be made more reliable.

Then, the tips of one or more of the pairs of partition walls are provided so that they can move forward and backward, and by moving the tips of these pairs of partition walls arbitrarily forward and backward, the interval between the tips can be changed and the number of effective zones can be changed. can be increased or decreased, thereby making it possible to control the furnace internal pressure in the lower part of the furnace to a predetermined positive pressure in response to changes in the type of FiE plate and heating conditions.

Furthermore, the tips of the pair of partition walls, which are provided so as to be movable back and forth, can be connected to a drive means for controlling the furnace pressure, which is connected to the furnace pressure detection means, so that the distance between the tips can be changed and the number of effective zones can be increased or decreased. can be automatically controlled in accordance with the furnace internal pressure.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a front sectional view showing the vertical continuous heating furnace for thin steel sheets of this example.

In FIG. 1, (1) is a furnace body, and the furnace body (])
is a flat rectangular shape whose horizontal cross section has a long side corresponding to the width of the thin steel plate P to be threaded, and is a vertically elongated rectangular cylinder having an outer shell of the steel plate and an insulating inner wall. A direct fire heating zone (2) is provided at the bottom of the furnace, a convection heating zone (3) is provided at the top, and an inlet opening (4) is provided at the bottom of the furnace, and an outlet opening (5) is provided at the top of the furnace. It is something.

The direct fire heating zone (2) and the convection heating zone (3) are provided horizontally and are divided vertically by a partition wall (6) having a slit-shaped opening in the center thereof, and The inlet opening (4) and the outlet opening (5) are provided in the shape of a slit that is as narrow as possible without contacting the front and back surfaces of the thin steel plate P being passed through.

On the other hand, the direct-fired heating zone (2) in the lower part of the furnace is arranged horizontally facing each other toward the center of the furnace from both inner walls of the furnace on the long sides of the horizontal cross section, and is threaded between the tips of each other. The heating zone is divided into four heating zones Nα1 to Magnetic 4 sequentially from the bottom by three pairs of partition plates (7) which are protruded at intervals narrow enough to avoid contact with the thin steel plate P to be heated. These heating zones are divided into dense sections at the bottom, and a pair of burners facing each other and facing the inside of the furnace is installed on both furnace side walls on the long side of the heating zone. (8
) and a furnace pressure detector (9).

In addition, the vertical continuous heating furnace of this example is installed in a continuous hot-dip galvanizing facility and used for continuous alloying treatment of plated steel sheets. It is located directly above the immersion plating tank S of the continuous hot-dip galvanizing equipment and is movable in the horizontal direction, with a total furnace height of 1.
The length of the direct heating zone (2) at the bottom of the furnace was 7 m.

Using the vertical continuous heating furnace of this example having the above configuration,
Continuous alloying treatment of plated steel sheets was performed by comparing this with an example using a conventional vertical continuous heating furnace with the same furnace height and heating capacity.

The graph of FIG. 2 illustrates the combustion exhaust gas temperature T and the combustion exhaust gas flow IFG pattern at each vertical position in the furnace during this continuous alloying process.

In addition, the solid line in the graph of FIG. 2 shows that of this example, and the dotted line shows that of a comparative example.

As is clear from the graph in FIG. 2, in the vertical continuous heating furnace of this example, in comparison with the comparative example, the combustion waste gas temperature T in the lower part of the furnace and the combustion waste gas flow ft F
The rise of c is much faster.

This means that there is less air entering from the inlet opening at the bottom of the furnace.
Furthermore, as shown by arrow A in FIG. 1, even if air enters from the inlet opening, the area near the tips of the three pairs of partition plates (7) as shown by the dotted arrows in the figure. This is because the intruding air is stirred and mixed with the combustion waste gas due to the turbulent flow of the combustion waste gas generated in the process, and the temperature rises quickly and the temperature becomes uniform.This is due to the vertical continuous heating of this embodiment. Although a small area of negative pressure was observed directly above the inlet opening of the lees 1 heating zone of the furnace, this effect was confirmed by the fact that it was completely eliminated in the Nα2 heating zone.

Also, in this way, the combustion waste gas temperature T at the lower part of the furnace
, and combustion waste gas! If the amount of Fe rises quickly, from the relationship shown in the above equation Become.

Furthermore, according to the vertical continuous heating furnace of this embodiment, for example,
No. at the bottom of the open heating zone! By supplying an excessive amount of preheated air for combustion to the pair of burners provided in the heating zone, specifically, at an air ratio of 1.2 or more, the internal pressure in the lowermost Nαl heating zone is reduced. Increase the pressure to positive,
It is possible to completely prevent air outside the furnace from entering through the inlet opening of the furnace bottom, thereby improving the thermal efficiency.

Note that the vertical continuous heating furnace of this example was installed in continuous hot-dip galvanizing equipment and used for continuous alloying treatment of galvanized steel sheets, but this is just an example, and contact with the furnace body is This is suitable for continuous heating of a thin steel plate having a surface texture that avoids it while passing it vertically upward.

In addition, in this example, the direct fire heating zone is divided into four heating zones.
In addition, although the lower section is densely divided, this can be increased or decreased or the density of the vertical divisions can be changed depending on the scale and purpose.

Furthermore, it is also preferable to provide a damper or the like at the outlet opening of the top of the furnace so that the degree of opening thereof can be adjusted.

Figure 3a is a front sectional view showing the main part of the vertical continuous heating furnace for thin steel sheets of this embodiment, and Figure 3 is a partial sectional view of Figure 3a.

The vertical continuous heating furnace of this embodiment is different from the vertical continuous heating furnace of the first embodiment, except for the structure of the partition plate that divides the direct-fired heating zone into a plurality of heating zones. They are the same, and only the differences will be briefly explained here.

In Figure 3a, (1) is the furnace body, (2) is the direct heating zone, (4) is the entrance opening, (6) is the partition wall, (8) is the burner, and (9) is the furnace pressure detection. These are the same as those in the first embodiment described above.

(37) is a partition plate, and the partition plate (37) is provided in three pairs of convex steps extending from the inner wall of the furnace on the long side toward the center of the furnace in the horizontal direction, with their tips facing each other. , in terms of dividing the open flame heating zone (2) into four heating zones in the vertical direction,
It is similar to the first embodiment described above, but these partition plates (37
) As shown in Fig. 3, each of them includes a base plate (37a) fixed to the inner wall of the reactor, and a base plate (37a) rotatably connected to the tip of the base plate (37a), as shown by the arrow in the figure. As shown,
The distal end is composed of a rotary plate (37b) that can be pivoted and retracted in the vertical direction, and this rotating mechanism allows the pair of rotary plates (37b) to move forward and backward in opposite directions. The degree of opening between the tips can be changed.

In addition, each of these rotating plates (37b) is configured to detect the furnace pressure.
It is connected to a furnace pressure regulator (not shown here) which is connected to the furnace pressure detector (9), and its rotation is controlled based on the set value corresponding to the furnace pressure detected by these furnace pressure detectors (9). The evacuation direction and angle are adjusted.

According to the vertical continuous heating furnace of this embodiment having the above configuration, the distance between the tips of the partition plates (37) and the effective heating zone can be changed according to the type of thin steel plate to be communicated and the heating conditions. By increasing and decreasing the furnace pressure in the lower part of the furnace, it is possible to automatically control the furnace pressure in the lower part of the furnace to a preset value, and also to control the furnace pressure and temperature pattern in the vertical direction in the direct-fired heating zone. In addition to suppressing intruding air, combustion efficiency can also be improved.

FIG. 4a is a front sectional view showing the main part of the vertical continuous heating furnace for iR steel plate of this embodiment, and FIG. 4 is a partial sectional view of FIG. 4a.

The vertical continuous heating furnace of this embodiment is the same as the vertical continuous heating furnace of the second embodiment described above, except for the difference in the structure of the partition plate of the direct-fired heating zone. Here, only the differences will be briefly explained.

In the vertical continuous heating furnace of this embodiment, as shown in Figure 4a, the direct flame heating (2) is controlled by three pairs of partition plates (47).
The heating zone is divided into four heating zones from below, and each heating zone is provided with a pair of burners (8) and a furnace pressure detector (9), which is the same as in the second embodiment described above. However, as shown in FIG. 4, each of these partition plates (47) is slidably supported on a base plate (47a) fixed to the inner wall of the furnace and the tip of the base plate (47a). As shown by the arrow in the figure, it is composed of a sliding plate (47b) that can move forward and backward in the horizontal direction toward the center of the furnace.

Each of these sliding plates (47b) is connected to a furnace pressure adjustment device (not shown here) that communicates with the furnace pressure detector (9), as in the second embodiment described above.
The distance between the pair of tips is adjusted by moving forward and backward based on the set value corresponding to the furnace internal pressure detected by these furnace pressure detectors (9).

According to the vertical continuous heating furnace of this embodiment having the above-mentioned configuration, similarly to the second embodiment described above, the partition plate (47) can be By changing the distance between the tips and increasing/decreasing the effective heating zone, it is possible to automatically control the vertical internal furnace pressure and temperature pattern in the direct-fired heating zone, suppress air entering from the inlet opening in the furnace bottom, and improve combustion efficiency. It is also possible to improve the In addition, since the sliding plates (47b) of the partition plates (47) move back and forth in the horizontal direction, even if these partition plates (47) are provided relatively densely in the vertical direction, the movement of these partition plates (47)
47) There is no grudge to block the flame directed toward the thin steel plate of the burner provided in the heating zone separated by .

〔Effect of the invention〕

As described above, according to the vertical continuous heating furnace for thin steel sheets of the present invention, it is possible to increase the pressure inside the furnace at the lower part of the furnace, and to effectively suppress air entering from the inlet opening at the bottom. The air that has entered through the inlet opening can be stirred and mixed in the lower part of the furnace, making it possible to equalize the temperature distribution in the furnace and improve the fuel consumption rate.

[Brief explanation of the drawing]

FIG. 1 shows 'g!' of the first embodiment of the present invention. A front sectional view showing a vertical continuous heating furnace for steel plates, FIG.
A graph showing the pattern of FIG. Fig. 4a is a front sectional view showing the main parts of a vertical continuous heating furnace for thin steel sheets according to the third embodiment of the present invention; Fig. 4 is a partial sectional view of Fig. 4a; Fig. 5 is a conventional A front cross-sectional view showing a vertical continuous heating furnace for thin steel sheets. Figure 6 is a front cross-sectional view showing the main parts of a conventional vertical continuous heating furnace for thin steel sheets. Figure 7 is a conventional vertical continuous heating furnace for thin steel sheets. A front sectional view showing the main parts of the furnace. Figure 8 is a front sectional view showing the main parts of a conventional vertical continuous heating furnace for thin steel plates. Figure 9 is a front sectional view showing the main parts of a conventional vertical continuous heating furnace for thin steel plates. FIG. (1)-furnace body, (2)-direct heating zone, (3) one convection heating zone, (4)-inlet opening, (5)-outlet opening, (
7) - Partition wall, (8) - Burner, (9) - Furnace pressure detector, P - thin steel plate. Patent Applicant Kobe Steel Co., Ltd. Agent Patent Attorney Akira Kanamaru - Figure 1: Planting Hori g, Fube Gate Rigi p Figure 5 Figure 6

Claims (3)

[Claims] (1) In a vertical continuous heating furnace of thin steel plate, which has an inlet opening at the bottom and an outlet opening at the top, a direct flame heating zone at the bottom, and a convection heating zone at the top, The heating zone is
The furnace is vertically divided into a plurality of zones by a plurality of pairs of partition walls that protrude from both inner walls of the furnace to the center of the furnace and have a predetermined interval between their tips, and each of these zones has at least one partition wall. A vertical continuous heating furnace for thin steel sheets, characterized by being equipped with a burner. (2) The vertical continuous heating furnace for thin steel sheets according to claim 1, wherein one or more of the plurality of pairs of partition walls are provided such that their leading ends can move forward and backward. (3) The thin steel sheet according to claim 2, wherein the tip ends of the pair of partition walls provided so as to be movable back and forth are connected to a drive means for controlling the furnace pressure, which is communicated with the furnace pressure detection means. Vertical continuous heating furnace.