WO2018228661A1

WO2018228661A1 - Nozzle for a hot-dip coating system and method for operating same

Info

Publication number: WO2018228661A1
Application number: PCT/EP2017/064289
Authority: WO
Inventors: Michael Peters; Sridhar Palepu; Marc Blumenau; Florian Spelz; Andreas WESTERFELD; Heinrich Meyring
Original assignee: Thyssenkrupp Steel Europe Ag; Thyssenkrupp Ag
Priority date: 2017-06-12
Filing date: 2017-06-12
Publication date: 2018-12-20
Also published as: CN110741104A; EP3638823A1; CN110741104B; EP3638823B1

Abstract

The invention relates to a nozzle (9) for a hot-dip coating system for a flat product (11), said nozzle extending from the outlet of a continuous furnace (10) into a melt (13) below the coating bath level (12) and isolating the flat product (11) from the surroundings. At least one suction unit (3) and a blowing unit (1) are provided, and the at least one suction unit (3) is arranged between the at least one blowing unit (1) and the coating bath level (12). The invention is characterized in that a pressure equalizing unit (7) is arranged between the blowing unit (1) and the outlet of the continuous furnace (10), and a first pressure sensor (14.1) is provided at the outlet of the continuous furnace (10) and a second pressure sensor (14.2) is provided between the coating bath level (12) and the pressure equalizing unit (7).

Description

Probes for a hot-dip coating plant and methods of operation thereof Technical Field

The present application describes a so-called "snout" construction typically used as an essential piece of equipment for a hot dip or fire coater in industrial practice, which is previously heat-treated in a metallic manner Flat product, such as steel, as a strip in a coating bath of molten metal (eg, Zn or Al-based alloys) passed over, so that contact between the heat-treated surface and the environmental atmosphere is avoided.

Technical Background (Background Art)

For example, a system for continuous fire-coating of steel strip consists inter alia of a continuous annealing furnace, a molten bath, a device for adjusting the coating thickness and a subsequent cooling device. In the continuous furnace, the steel strip is continuously annealed, the continuous furnace being divided into several chambers where different treatments are performed. These treatments include, for example, the adjustment of the desired mechanical properties of the base material by recrystallization of the steel. In addition, iron oxides formed in a preheating zone are thereby reduced. In a cooling zone following the continuous annealing furnace, the strip is cooled under inert gas (HNX) to a temperature close to the molten bath temperature. The shielding gas is intended to prevent the annealed strip from oxidizing prior to fire coating, thereby reducing the adhesion of e.g. Zinc layer would be significantly deteriorated. Due to the different treatments, therefore, sometimes different gas atmospheres in the chambers are required. The protective gas-containing connector or lock between annealing furnace and molten bath is called proboscis.

Coating faults whose causes can be found in the trunk represent a significant challenge for any operator of such a hot-dip coating system. It is known that metal evaporates from the molten pool of molten metal inside the trunk and can precipitate on the steel strip or the trunk inner wall, for example. This observation is reinforced when using measures to produce a directed flow in the melt in the trunk, for example by the use of zinc pumps. Both can cause qualitative failures of the flat steel product to be produced, eg also by falling of condensed and agglomerated metal dust from the trunk inner wall to the flat steel product. Simple and well-established countermeasures are, for example, the targeted sowing of the trunk atmosphere to reduce the evaporation rate or the heating of the trunk. However, the former has the negative side effect of increased slag formation on the surface of the molten bath or coating bath level, which also produces quality failures. Furthermore, a trunk heating itself does not prevent the presence of the metal dust, so that it can continue to be harmful to the process.

It was recognized that the steel strip moved in the direction of the zinc bath entrains protective gas downwards in the trunk, whereby the entrained protective gas absorbs zinc vapor on the zinc bath surface, which condenses and resembles there when the entrained protective gas ascends on the colder inner walls of the trunk as dust settles. The prior art therefore describes a variety of technical solutions to avoid or remove metal dust in a proboscis.

From JP H07-157853 (A) a device for removing zinc vapor in a trunk of a continuous strip galvanizing plant is known. In order to remove the zinc vapor produced on the zinc bath surface, the trunk is provided with injection openings (circulation openings) and suction openings arranged vertically underneath. In a first exemplary embodiment, a single injection opening is arranged in the trunk wall facing the upper side of the steel strip and a single suction opening is arranged vertically below it. Accordingly, in the underside of the steel strip facing trunk wall also a single injection opening and vertically below a single suction opening arranged. In a second embodiment, a single injection port is disposed in a side wall of the spout, while vertically thereunder are provided two exhaust ports formed as longitudinal slots in pipes penetrating the side wall of the spout and extending over the entire top and bottom of the steel belt Steel strip width extend. A disadvantage of such designs, however, is an insufficient sealing of the gas atmospheres with and without zinc dust. From industrial practice is further disadvantageous to note that no effective decoupling takes place between the inert gas atmospheres of the trunk and the actual continuous furnace. Episodes are, for example, a heightened Gas consumption of the stove by extraction of the furnace atmosphere via the trunk or a metal dust contamination of the furnace, with too weak suction in the trunk.

From DE 10 2012 106 106 AI another example from the field of the trunk of a galvanizing plant is known. In this case, an area with a plurality of injection openings adjacent to a region with a plurality of suction openings, wherein the areas mesh at least partially in a comb-like manner. As a result, a relatively good sealing of ascending zinc vapors is achieved with respect to the overlying gas atmosphere. However, such a device is relatively expensive to manufacture and is associated with a high space requirement. Due to the high saturation of the gas atmosphere resulting from the sealing before immersion with zinc vapor, the product quality may continue to be impaired.

SUMMARY OF INVENTION The invention is thus based on the object of providing an apparatus and method which effectively prevents interference of adjacent gas atmospheres, in particular achieves separation of proboscis and furnace atmosphere to avoid unnecessary protective gas consumption or contamination of the furnace, as well as effectively Quality failures due to metal dust caused by evaporation from the coating bath avoids. Other objects of the invention are a favorable manufacturability, a small footprint and ease of assembly or is suitable for retrofitting existing systems and to realize with the least possible technical effort to allow.

This object is achieved by a device according to the features of claim 1, in particular when it is used by a method according to the features of claim 7.

According to the invention, a proboscis is for a hot-dip coating installation for a flat product which extends from the outlet of a continuous furnace into the melt below the coating bath level and isolates the flat product from the environment, wherein at least one suction unit and one blowing unit are provided and the at least one suction unit between the at least one injection unit and the Beschichtungsbadspiegel is arranged, characterized in that a pressure compensation unit between the injection unit and the outlet of the continuous furnace is arranged, and that a first pressure sensor are provided at the outlet of the continuous furnace and a second pressure sensor between the coating bath and the pressure compensation unit. Inert gas, for cost reasons ideally N ₂ or alternatively N ₂ and H ₂ , is injected at a temperature of> 500 ° C to <650 ° C through the injection unit into the trunk and sucked back through the suction unit, resulting in the lower part of the trunk On both sides of the steel strip to be produced results in a directed gas flow. This directed gas flow describes a vortex, starting from the blowing unit, to the flat product, along the belt run towards the coating bath mirror, which corresponds to the material flow direction, across the coating bath to the suction unit. As a result, a good seal ascending vapor is achieved from the melt and sucked this effectively. Furthermore, both the proboscis atmosphere and the furnace area near the transition to the proboscis are pressure-monitored, so that the amount of gas injected into the proboscis and sucked off can be controlled so that the difference between the pressure of the proboscis and the pressure of the furnace atmosphere is never <0 mbar. In order to achieve this pressure decoupling, additional inert gas is blown into the trunk at a pressure compensation unit, wherein the amount of inert gas to be injected here is regulated in such a way that no negative pressure in the trunk is created in relation to the furnace. Preferably, on both sides of the flat product pressure equalization units are provided, which are the same or similar to the injection units formed. Embodiments of a trunk according to the invention are characterized in that the suction unit is arranged at a distance of 50 mm to 200 mm from the coating bath level. The suction unit for removing metal dust contaminated trunk atmosphere is like the injection units positioned transversely to the tape direction and acts at least over the max. Width of the flat product to be produced. The suction unit is installed below the lower injection nozzle and above the coating bath. The distance to the coating bath is at least 50 mm, since if this distance is below the risk of premature failure, and is a maximum of 200 mm, otherwise the effectiveness of the suction decreases in a deficient area, because the desired gas vortex or the circulating flow is not sufficient forms.

Furthermore, embodiments of a proboscis according to the invention are characterized in that the injection unit is arranged at a distance of 200 mm to 800 mm away from the coating bath level, or more precisely that the distance between the suction unit and injection unit is at most 750 mm. A necessary minimum distance between Blowing unit and suction unit results only by their structural design. However, the maximum distance is 750 mm, because if this distance is exceeded only a lack of effectiveness is achieved because the forming vortex flow deteriorates.

In further embodiments, proboscis according to the invention is characterized in that a dew point unit is provided, via which humidified protective gas can be supplied for dew point control. By monitoring the oxygen (0 ₂ ) and hydrogen content (H ₂ ) in the trunk atmosphere by appropriate sensors, the dew point can be monitored and adjusted by supplying eg humidified inert gas. Furthermore, the moisture reduces the evaporation rate from the coating bath.

In preferred embodiments of the trunk, the dew point unit is arranged between the coating bath level and the suction unit. The added moisture promotes the agglomeration of the metal dust particles, so that the extraction result is improved. Thus, addition at this point is most effective.

According to further embodiments, probes according to the invention are characterized in that the at least one injection unit and a suction unit extend on both sides of the flat product over the transverse extent of the trunk to opposite walls, that the injection units are provided directly opposite one another, that the injection units each comprise at least two Rows of a plurality of slot nozzles with intervening intersections, the slot nozzles of the rows being offset from each other, and wherein the breaks are shorter than the slot nozzles of the adjacent row to overlap the slot nozzles of the rows in the material flow direction, and the slot nozzles of a sparger each opposite to an interruption of the opposite injection unit. Thus, the injection units are located on both sides of the flat product guided through the trunk, preferably a continuous material web, such as steel strip. The arrangement in rows and the interruptions in the rows slot machines can be used optimally, since the occurring beam expansion of emerging from adjacent slot nozzles protective gas flows do not interfere with each other and forms a closed curtain of gas through the arrangement. Due to the likewise staggered arrangement of the slot nozzles of a blow-in unit with respect to the slot nozzles or interruptions of the opposite injection unit, the center area also forms in the middle area Sluice where the injected gas flows meet, a dense gas curtain. As a result, a very good separation of the gas atmospheres is also achieved outside the material web. Further embodiments of the trench according to the invention are characterized in that the suction units have main openings provided over the transverse extent, the main openings being aligned in the material flow direction in order to produce a circulating flow. Thus, the main openings are located on the side facing away from the injection unit, whereby a entrainment of the injected gas is favored in the material flow direction and a circulation of the gas atmosphere takes place. In this way, for example, zinc dust in a trunk can be sucked off and then filtered to obtain a largely "clean" gas atmosphere.

In preferred embodiments of the trench, the injection units and suction units are each connected to at least one centered line for the supply and removal of gas. As a result, the flow conditions over the width of the injection and suction units can be kept largely the same.

In particularly preferred embodiments of the trunk, the main openings in the region of the centered line have a greater height. By such a design, the flow conditions over the width are kept uniform, which improves the suction effect.

Further embodiments of the trunk are characterized in that the suction units comprise additional openings which are aligned perpendicular to the material flow direction. These additional openings improve the pressure conditions in the trunk and reduce the flow velocities at the openings of the suction unit, which has advantages in terms of noise and wear.

In embodiments of the trench, the slot nozzles are characterized in that the slot nozzles have a width b, that the distance a between the rows is in the range of b <a <2 * b, and that the overlap u of the slot nozzles in the material flow direction in the range of b <u <3 * b, where additionally a <u. In order to achieve the best possible separation of the gas atmospheres, the slot nozzles must not be too far away from each other. Here it has been shown that, based on the width of the slot nozzles, a minimum distance between the rows in the same width achieved good results and at a distance of more than twice the width increases the risk of deterioration in separation.

Preferred embodiments of the snout are characterized in that the slot nozzles have a length I in the transverse direction, wherein the length I is in the range of 20 * b <I <50 * b, preferably in the range of 30 * b <I <35 * b ,

In further embodiments of the trench, the blow-in units and / or suction units are divided transversely into several sections, each section comprising its own centered line for supplying or removing inert gas. By this division into preferably equal-width sections, the flow conditions over the width of the trunk are further improved and in addition the required power per line is reduced.

Embodiments of the trunk are characterized in that the injection units and / or suction units have a semicircular cross-section. Rounded cross-sections have aerodynamically advantageous geometries. Furthermore, the cross-section of the snout to be sealed is reduced by a blowing or suction unit placed on the trunk wall. The proboscis according to the invention is preferably operated with a method which is characterized in that inert gas is introduced by the injection unit at an injection rate of 10Nrr h to 500 Nm ³ / h (Nm ³ / h = standard cubic meter per hour) through the aspiration unit 150Nm ³ / h to 700Nm ³ / h is subtracted that the condition suction amount is greater than the injection volume is met, and that by the pressure compensation unit a compensation amount is introduced in order to achieve a pressure decoupling of continuous furnace and trunk. For the formation of a dense gas curtain, a Einblasmenge of 100Nm ³ / h to 500Nm ³ / h has been found to be practicable, since there is no sufficient seal and above turbulent flows increase, which degrades the effectiveness and possibly leads to band vibrations.

Processes according to the invention are characterized in that a larger amount of suction than the injection quantity is sucked off by at least 50 Nm ³ / h. This ensures that a stable vortex flow is formed in the lower area of the trunk and accumulating metal dust is reliably sucked off. Method according to embodiments of the invention are characterized in that the compensation quantity is regulated on the basis of the difference of a first pressure sensor at the outlet of the continuous furnace and a second pressure sensor between coating bath level and pressure equalization unit, and that the difference is in a range of greater than 0 mbar, preferably greater than 0, 1 mbar, to 0.7 mbar, is maintained. As a result, it is largely prevented that a negative pressure is created in the trunk relative to the pressure prevailing in the continuous furnace, as a result of which removal of the furnace atmosphere is avoided. In principle, an equal pressure is sufficient, as practicable as a controlled variable for the lower threshold of a pressure difference of 0, lmbar exposed. As the upper limit of the control 0.3 mbar or 0.5 mbar have proved favorable. Ideally, the pressure difference is below 0.2 mbar. If the pressure difference becomes too low, proboscis is forced into the continuous furnace due to the overpressure in the trunk, which adversely affects the furnace atmosphere.

Embodiments of inventive method are characterized in that the protective gas is inflated with 4m / s (m / s = meters per second) to 10m / s on the flat product. If the inert gas to be injected into the trunk via the blow-in units is inflated directly onto the steel strip at a speed of> 4 m / s and <10 m / s, the most advantageous setting for removal of metal dust from the trunk atmosphere and thus avoiding qualitative failures results , If these limits are exceeded or undercut, the measure loses effectiveness because, for example, insufficient gas vortex builds up or the atmosphere becomes too turbulent. Inventive embodiments of the method are characterized in that the protective gas is injected at a temperature of 500 ° C to 650 ° C. As a result, the flat product is brought to a bath immersion temperature or maintained in order not to disturb the temperature control or heat treatment of the materials and to avoid condensation of components of the trunk atmosphere.

Processes according to the invention are further characterized in that nitrogen or a nitrogen-based mixture is used as protective gas. As a neutral shielding gas, nitrogen offers cost advantages. Embodiments of methods according to the invention are characterized in that hydrogen is added to the protective gas in a range from 0.5% by volume to 10% by volume. In particular, if a limit of 10 ppm for the oxygen content in the trunk is exceeded, this measure is provided. The selective addition of hydrogen (H ₂ ) (eg via the injection unit) can be selected if the oxygen (0 ₂ ) concentration in the trunk exceeds> 10 ppm. Otherwise there is a risk of deterioration in product quality due to unwetted areas or poor zinc adhesion on the steel strip to be produced. In the case of H ₂ feedpoint of the H ₂ content is ideally> 0.5% by volume to <10.0% by volume to ensure an effective work, but to avoid unnecessary costs.

Processes according to embodiments of the invention are characterized in that the dew point in the trunk is set to a range of -10 ° C to -40 ° C. It has proven to be advantageous for the product quality, depending on the steel alloy to be produced to set a dew point of <-10 ° C to> -40 ° C in the trunk, which can be done via a controlled supply of humidified inert gas (eg: N ₂ ) , In this case, the inventive solution provides that the humidified protective gas is fed directly above the coating bath level and below the suction device. The added humidity supports the agglomeration of the metal dust particles, so that the extraction result is improved. Furthermore, the moisture reduces the evaporation rate from the coating bath.

Further embodiments of the method according to the invention are characterized in that at least part of the suction quantity is cleaned in a cleaning unit and returned to the blowing unit, equalizing unit and / or the continuous furnace as protective gas. In order to increase the environmental compatibility and (cost) efficiency, it is proposed to free the sucked off metal dust contaminated metal dust from the metal dust and to recirculate the inert gas injection according to the invention. As an alternative return feed the continuous furnace of the coating plant offers itself. The cleaning can be done for example by a cold trap, a cyclone separator or a filter device, or by combining these options. Depending on the H ₂ concentration of the extracted trunk environment, dilution may be necessary to meet the applicable occupational safety and explosion protection requirements. That the trunk is heated or at least insulated in order to minimize the metal dust deposit on the trunk inner wall, corresponds to the prior art and is taken for granted. Short description of the drawings (Brief Description of Drawings)

In the following the invention will be explained in more detail with reference to schematic drawings, wherein similar components are provided with the same reference numerals. In detail show:

1 shows a trunk in a schematic, inventive embodiment,

Fig. 2: a schematic injection unit viewed perpendicular to the material flow direction and

3 shows an embodiment of a suction unit. Description of the Preferred Embodiments (Best Mode for Carrying Out the Invention)

Fig. 1 shows a schematic side view of an embodiment of a trunk (9). The trunk (9) extends from the outlet of a continuous furnace (10) into the melt (13) of a coating bath. The flat product (11) to be coated is in this case passed from the continuous furnace (10) through the trunk (9) into the melt (13). The leadership of the flat product (11) through the continuous furnace (10) and the melt (13) is not shown here. In order to avoid sealing of the flat product (11) heated in the continuous furnace (10) with the environment, the proboscis (9) extends below the coating bath level (12). In the lower part of the spout (9) there is provided a blowing unit (1) and a suction unit (3) arranged downstream in the material flow direction (M) and thus arranged between the blowing unit (1) and the coating bath mirror (12). The injection unit (1) and the suction unit (3) are each provided on both sides of the flat product (11) in transverse extent across the width of the spit (9) and arranged opposite one another. Through the injection units (1), a defined injection amount of protective gas is introduced into the trunk (9) and through the suction unit (3) a suction amount which is greater than the injection volume deducted. This forms a dense gas curtain which seals off the trunk atmosphere below the injection unit (1) towards the remaining trunk atmosphere. By the moving flat product (11) and the suction unit (3) is in the lower a circulating flow respectively on both sides of the flat product (11) generated. By this flow contained in the trunk atmosphere metal vapor from the flat product (11) is held and withdrawn through the suction unit (3).

In order to achieve a decoupling of pressure to the continuous furnace (10) so that the Ofenatmos- is not in the trunk (9) is pulled, in the region of the upper end of the spout (9) or at the outlet of the continuous furnace (10), a pressure compensation unit (7) intended. This pressure compensation unit (7) is also preferably provided on both sides of the flat product (11) extending across the width of the spit (9). The construction is further similar in preferred embodiments or equal to the injection unit (1). By the pressure equalization unit (7) a compensation amount of inert gas in the trunk (9) is introduced to compensate for the difference between injection quantity and suction.

To control the compensation amount, at least one first and one second pressure sensor (14.1, 14.2) are provided in the trunk. The first pressure sensor (14.1) is arranged in the upper region between the pressure compensation unit (7) and the outlet of the continuous furnace (10) in order to detect the pressure in this area. Of course, the first pressure sensor (14.1) may also be arranged instead of the spout (9) in the outlet region of the continuous furnace (10) or may be formed by possibly existing sensors of the continuous furnace (10). The second pressure sensor (14.2) is arranged in the material flow direction (M) downstream of the pressure compensation unit (7) to detect the pressure in the trunk (9). For the best possible detection of the difference, in preferred embodiments, as shown, the second pressure sensor (14.2) is arranged downstream of the injection unit (1). However, the position of the first and second pressure sensors (14.1, 14.2) is not limited to the variant shown, but rather the sensors can be arranged as desired in the specified range. It is also possible to use a plurality of first and / or second pressure sensors (14.1, 14.2) in order, for example, to have redundancy with regard to process reliability or to be able to work with an average value of a plurality of measuring points. Due to the difference between the pressures determined by means of the first and second pressure sensors (14.1, 14.2), the compensation quantity supplied via the pressure compensation unit (7) is regulated. In order to avoid influencing the atmosphere in the trunk (9) by the atmosphere in the continuous furnace (10) and vice versa the furnace atmosphere through the trunk atmosphere, the pressure difference should never be less than 0 mbar. As practicable, a controlled variable for the pressure difference of greater than 0, 1 mbar has been found. In Fig. 1, a dew point unit (15) is further provided. In embodiments of the invention, one or more dew point units (15) may be provided to adjust the dew point of the atmosphere in the trunk (9). To set the dew point humidified protective gas can be introduced into the trunk. The introduction can in principle take place at at least one arbitrary position of the spout (9), wherein the dew point unit (15) is preferably arranged, as shown, in the lower region between the suction unit (3) and the coating bath mirror (12). As a result, the evaporation rate from the melt (13) is reduced and at the same time supports the agglomeration of the metal vapor particles in the trunk atmosphere, whereby the extraction of these particles is improved. As an alternative to a separate dew point unit (15), it is also possible to humidify the protective gas supplied to the injection unit (1) and / or pressure compensation unit (7).

Not shown in Fig. 1, the lines (6) for supply and removal of inert gas to the individual injection units (1), suction units (3), pressure compensation units (7) and optionally dew point unit (15).

2 shows a schematic representation of an injection unit (1) according to the invention perpendicular to the material flow direction M, more precisely perpendicular to the plane of the flat product (11) to be conveyed through. In this case, two rows of slot nozzles (2) are shown, which each have interruptions or gaps between the slot nozzles (2). The slot nozzles (2) each have a width b and a length l. The two rows of slot nozzles (2) are removed from each other with a distance a in the material flow direction M. The slot nozzles (2) of adjacent rows are offset from each other, so that an interruption of a row is associated with a slot nozzle (2) of the adjacent row. The slot nozzles (2) are designed to be longer than the intervening interruptions, so that an overlap u of the ends of the slot nozzles (2) arises in the material flow direction M. The overlap u is formed uniformly along the injection unit (1).

In Fig. 3, a portion is shown, which shows the lower injection unit (1) and suction unit (3) and parts of the upper injection unit (1) and suction unit (3) in the trunk (9) of an embodiment. The two opposite injection units (1) on the upper and lower wall of the spout (9) are shown, as well as the suction units (3) located downstream of the material flow direction M, ie downstream. In this illustration, it can be seen that the slot nozzles (2) of the injection units (1) are arranged offset from each other. Next to the Offset between the rows on a blowing unit (1), as already shown in Fig. 2, in Fig. 3, the offset of the slot nozzles (2) relative to the opposite blowing unit

(I) shown. In the example shown, the outermost slot nozzle (2), seen in the width direction of the spout (9), lies in the front row, that is to say in the upstream row, and the rear row, that is to say in the downstream row, begins with an interruption in the lower injection unit (1). Accordingly, in the upper blowing unit (1), the outermost slot nozzle (1) is arranged in the rear row and the front row starts with an interruption. As a result of this arrangement, the protective gas emerging from the slot nozzles (2) passes unhindered in the main extent to the opposite trunk wall, more precisely to the opposite blowing unit (1) or the material surface of the flat product

(I I) and a contact of the protective gas flows takes place only in the region of the unavoidable areas of the beam expansions. By this embodiment, a gas curtain is achieved, which is very stable and has a very good sealing effect. In the example shown in FIG. 3, both the suction units (3) and the injection units (1) are divided into several areas by intermediate walls (8) in the width direction. For the removal or supply of protective gas to the suction units (3) or blowing units (1), these each have lines (6), which are indicated in Fig. 3 respectively by round connection openings for the lines (6). Furthermore, in the illustrated example, the blowing units (1) and the suction units (3) are each formed with a semicircular cross-section which has flow-related advantages due to the avoidance of sharp edges.

Further, Fig. 3 shows a preferred embodiment of a suction unit (3). Here, the main openings (4) in the material flow direction M are aligned to produce a circulating flow behind the injection unit (1). The main openings (4) in the region of the lines (6) are in this case formed with a greater height in order to achieve relatively homogeneous flow conditions over the width. The height of the main openings (4) may change continuously or, as in the example shown, can jump. At the top of the suction units (3), additional openings (5) are preferably provided. Through this, in addition to an improvement of the suction also a shortening of the area of the circulating flow allows, which reduces the required space in the trunk (9) and favors the circulating flow. The additional openings may be formed with a uniform height across the width of the suction unit, or also analogously to the main openings (4) with different heights. For the example in a proboscis of a fire-coating plant, the injection units (1) and suction units (3) may be formed, for example, with a radius of 40mm, and the height of the main openings (4), for example in the range of 10 to 15mm and the height of the additional openings (5) are at about 8mm. The lines (6) can then be formed in this example with a diameter of about 60mm.

The various features of the invention can be combined with one another as desired and are not limited to the described or illustrated examples of embodiments.

LIST OF REFERENCE NUMBERS

1 injection unit

2 slot nozzles

3 suction unit

4 main opening

5 additional opening

6 line

7 pressure compensation unit

8 intermediate wall

9 proboscis

10 continuous furnace

11 flat product

12 coating bath level

13 melt

14.1 first pressure sensor

14.2 second pressure sensor

15 dew point unit a distance

b width

I length

u overlap

M material flow direction

Claims

claims

A trunk (9) for a hot-dip coating installation for a flat product (11) which extends from the exit of a continuous furnace (10) into a melt (13) below the coating bath level (12) and isolates the flat product (11) from the environment, wherein at least one suction unit (3) and one blowing unit (1) are provided and the at least one suction unit (3) is arranged between the at least one blowing unit (1) and the coating bath mirror (12), characterized in that a pressure compensation unit (7) between the blowing unit (1) and the outlet of the continuous furnace (10) is arranged, and that a first pressure sensor (14.1) at the output of the continuous furnace (10) and a second pressure sensor (14.2) between the coating bath (12) and pressure compensation unit (7) are provided ,

2. proboscis according to claim 1, characterized in that the suction unit (3) at a distance of 50mm to 200mm from the coating bath (12) is arranged away.

3. proboscis according to claim 1 or 2, characterized in that the distance between the suction unit (3) and injection unit (1) is a maximum of 750mm.

4. proboscis according to one of claims 1 to 3, characterized in that a dew point unit (15) is provided, via the humidified protective gas for dew point control can be fed.

5. proboscis according to claim 4, characterized in that the dew point unit (15) between the coating bath (12) and suction unit (3) is arranged.

6. proboscis according to one of claims 1 to 5, characterized in that the at least one injection unit (1) and a suction unit (3) on both sides of the flat product (11) each extend over the transverse extent of the trunk (9) on opposite walls in that the injection units (1) are provided directly opposite one another, in that the injection units (1) each comprise at least two rows of a plurality of slot nozzles (2) with interruptions therebetween, the slot nozzles (2) of the rows being offset from one another, and the Interruptions are shorter than the slot nozzles (2) of the adjacent row, so that the slot nozzles (2) of the rows in the material flow direction (M) overlap, and that the slot nozzles (2) of a blowing unit (1) each opposite to an interruption of the opposite blowing unit (1) ,

7. A method for operating a trunk (9) according to any one of claims 1 to 6, characterized in that inert gas is introduced with an injection of lOONrr h to 500Nm ³ / h by the injection unit (1) that by the suction unit (3) a suction volume of 150Nm ³ / h to 700Nm ³ / h is deducted, that the condition suction amount is greater than the injection volume is met, and that by the

Pressure equalization unit (7) is introduced a compensation amount to achieve a pressure decoupling of continuous furnace (10) and trunk (9).

8. The method according to claim 7, characterized in that a relation to the injection quantity by at least 50Nm ³ / h larger suction is sucked off.

9. The method according to claim 7 or 8, characterized in that the compensation amount due to the difference of a first pressure sensor (14.1) at the output of the continuous furnace (10) and a second pressure sensor (14.2) between coating bath (12) and pressure compensation unit (7) is controlled , And that the difference in a range of greater than 0 mbar, preferably greater than 0, 1 mbar, is held to 0.7 mbar.

10. The method according to any one of claims 7 to 9, characterized in that the protective gas with 4m / s to 10m / s is inflated onto the flat product (11).

11. The method according to any one of claims 7 to 10, characterized in that the protective gas is injected at a temperature of 500 ° C to 650 ° C.

12. The method according to any one of claims 7 to 11, characterized in that is used as the protective gas nitrogen or a nitrogen-based mixtures.

13. The method according to any one of claims 7 to 12, characterized in that the shielding gas hydrogen in a range of 0.5% by volume to 10% by volume is mixed, especially when a limit of the oxygen content in the trunk (9) of 10 ppm is exceeded.

14. The method according to any one of claims 7 to 13, characterized in that the dew point in the trunk (9) is set to a range of + 30 ° C to -40 ° C.

15. The method according to any one of claims 7 to 14, characterized in that at least a portion of the suction amount is cleaned in a cleaning unit and as inert gas back to the injection unit (1), compensation unit (7) and / or the continuous furnace (10) is supplied.