EP3916150A1

EP3916150A1 - Nozzle system of a device for contact-free treatment of a running fiber web

Info

Publication number: EP3916150A1
Application number: EP21170077.8A
Authority: EP
Inventors: Richard Solin; Pertti Heikkilä
Original assignee: Valmet Technologies Oy
Current assignee: Valmet Technologies Oy
Priority date: 2020-05-26
Filing date: 2021-04-23
Publication date: 2021-12-01
Also published as: CN113718553B; CN113718553A

Abstract

The invention relates to a nozzle system of a device for contact-free treatment of a running web, which nozzle system (10) comprises an overpressure nozzle part (20) and at least one direct impingement nozzle part (25A; 25B) arranged on either side of the overpressure nozzle part (20) and in which nozzle system (10) the direct impingement nozzle part (25A, 25B) is combined with the overpressure nozzle part (20) such that no discharge passage for discharging gases is formed between the direct impingement nozzle part (25A; 25B) and the overpressure nozzle part (20), in which nozzle system (10) the overpressure nozzle part (20) has a carrier surface (24) and on both sides of the carrier surface (24) a nozzle orifice row formed of nozzle orifices (18A, 18B) and extending in length direction of the nozzle system (10) and which nozzle orifices (18A, 18B) are configured to blow gas flows, which are guided against each other with the aid of curved Coanda-surfaces (22A, 22B) formed on each side of the carrier surface (24), in which nozzle system (10) the direct impingement nozzle part (25A; 25B) comprises at least one nozzle orifice row formed of nozzle orifices (16A, 16B) configured to blow gas flows mainly perpendicularly in view of upper surface of the direct impingement nozzle parts (25A, 25B). The overpressure nozzle part (20) comprises on the carrier surface (24) at least one row of direct impingement nozzle orifices (21) configured to provide direct impingement blowing by gas flows directed mainly perpendicularly in view of the upper surface of the overpressure nozzle part (20).

Description

The invention relates to fiber web technology. More especially the invention relates to a nozzle system of a device for contact-free treatment of a running fiber web according to the preamble of claim 1.
As known from the prior art fiber web making processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in the process line. A typical production and treatment line comprises a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other devices and sections for finishing the fiber web, for example, a sizer, a calender, and a coating section. The production and treatment line also comprises at least one slitter-winder for forming customer rolls as well as a roll packaging apparatus. In this description and the following claims by fiber webs are meant for example paper and board webs.
As is known in the prior art, in some applications of drying, carrying, supporting etc. of a fiber web, for example a paper or board web, a device is needed which is capable of by gas flows, typically by air flows to dry, cool, support, carry etc. a running fiber web without contacting the fiber web.
With regard to the prior art related to nozzle systems for devices for contact-free treatment, such as drying, cooling, supporting, carrying etc., of running fiber webs, reference is made to publication EP 1218589 B1 , which is disclosed an airborne web-drying apparatus for drying a travelling coated fiber web, such as a paper or board web, which apparatus comprises a nozzle arrangement including: an overpressure nozzle extending across the web and having on both sides of the nozzle, i.e. on the entrance and exit sides of the nozzle as seen in the web travel direction, a nozzle orifice arrangement extending across the web and comprising one nozzle slot or a row of successive nozzle orifices extending across the web, and which nozzle orifice arrangements are arranged to blow drying air jets obliquely against each other, or which nozzle orifice arrangements are arranged to blow drying air jets which are guided against each other with the aid of curved Coanda-surfaces, and at least one direct impingement nozzle extending across the web, in which direct impingement nozzle a plurality of nozzle slots or nozzle orifices are formed for blowing drying air mainly perpendicularly against the web, wherein said direct impingement nozzle is combined with said overpressure nozzle on the exit side or on the entrance side thereof in order to form a nozzle assembly such that no discharge passage for discharging wet air is formed between said direct impingement nozzle and said overpressure nozzle; the apparatus comprises on each side of the web two or more of said nozzle assemblies spaced-apart from each other in the web travel direction, wherein the gap between two adjacent nozzle assemblies on each side of the web forms a discharge passage for discharging wet air; and the nozzle assemblies are arranged on opposite sides of the web so that opposite each discharge passage between two adjacent nozzle assemblies on one side of the web there is on the other side of the web a nozzle assembly. In this patent publication is disclosed a nozzle system comprising of overpressure nozzles combined with direct impingement on either side of the overpressure nozzles so that no passage for return air is formed between said overpressure nozzle and direct impingement nozzle.
The aim is to continuously improve the effect of the airborne web-drying for instance in order to be able to make the drying faster and/or to reduce the size of the dryer and to increase the heat transfer capability of the nozzle system.
An object of the invention is to provide a nozzle system of a device for contact-free treatment of a running fiber web, in which the disadvantages of prior art are eliminated or at least minimized.
It is a further non-limiting object of the present invention to provide a new and improved nozzle system, in which the heat transfer capability of the nozzle system is increased.
In order to achieve the above objects and those that will come apparent later the nozzle system according to the invention is mainly characterized by the features of claim 1. Advantageous aspects and features of the invention are presented in the dependent claims.
In this description and the claims, the word upper have been used as assuming that the nozzle system is below the fiber web. It should be noted that the location can also be vice versa or oblique in respect of the fiber web and the word upper should be understood correspondingly. By longitudinal direction of the nozzle system is meant direction crosswise in respect of the main travel direction of the fiber web. It should be also noted that instead air other gaseous substances can be used as the flow medium.
According to the invention the nozzle system of a device for contact-free treatment of a running web, which nozzle system comprises an overpressure nozzle part and at least one direct impingement nozzle part arranged on either side of the overpressure nozzle part and in which nozzle system the direct impingement nozzle part is combined with the overpressure nozzle part such that no discharge passage for discharging gases is formed between the direct impingement nozzle part and the overpressure nozzle part, in which nozzle system the overpressure nozzle part has a carrier surface and on both sides of the carrier surface a nozzle orifice row formed of nozzle orifices and extending in length direction of the nozzle system and which nozzle orifices are configured to blow gas flows, which are guided against each other with the aid of curved Coanda-surfaces formed on each side of the carrier surface, in which nozzle system the direct impingement nozzle part comprises at least one nozzle orifice row formed of nozzle orifices configured to blow gas flows mainly perpendicularly in view of upper surface of the direct impingement nozzle parts, wherein the overpressure nozzle part comprises on the carrier surface at least one row of direct impingement nozzle orifices configured to provide direct impingement blowing by gas flows directed mainly perpendicularly in view of the upper surface of the overpressure nozzle part.
By the invention the heat transfer capability of a nozzle system is increased due to the direct impingement section on the carrier surface of the overpressure nozzle.
According to an advantageous feature of the invention the nozzle system comprises two direct impingement nozzle parts arranged symmetrically on both sides of the overpressure nozzle part and the direct impingement nozzle parts are combined with the overpressure nozzle part such that no discharge passage for discharging gases is formed between the direct impingement nozzle part and the overpressure nozzle part.
According to an advantageous feature of the invention the carrier surface is recessed in respect of the level of upper ends of the curved Coanda-surfaces.
According to an advantageous feature of the invention the carrier surface is at the same level as the upper ends of the curved Coanda-surfaces.
According to an advantageous feature of the invention the nozzle system is an integrated structure and comprises an inlet gas channel and at least one side gas channel and the gas to be blown through the nozzle orifices is guided from the inlet gas channel through openings in a partition wall formed between the inlet gas channel and the side gas channel for the direct impingement nozzle orifices and for the overpressure nozzle orifices, correspondingly, and the gas to be blown through the nozzle orifices of the carrier surface of the overpressure nozzle part is guided directly from the inlet gas channel.
According to an advantageous feature of the invention the nozzle system is an integrated structure and comprises an inlet gas channel and at least one side gas channel and the gas to be blown through the nozzle orifices is guided from the inlet gas channel through openings in a partition wall formed between the inlet gas channel and the side gas channel for the direct impingement nozzle orifices and for the overpressure nozzle orifices and for the nozzle orifices of the carrier surface of the overpressure nozzle part.
According to an advantageous feature of the invention the nozzle system is an integrated structure and comprises an inlet gas channel and at least one side gas channel and the gas to be blown through the nozzle orifices is guided from the inlet gas channel through openings in a partition wall formed between the inlet gas channel and the side gas channel for the direct impingement nozzle orifices and for the overpressure nozzle orifices, correspondingly, and that the gas to be blown through the nozzle orifices of the carrier surface of the overpressure nozzle part is guided via a pressure balancing chamber from the inlet gas channel through pressure balancing orifices.
According to an advantageous feature of the invention in the nozzle gas distribution between the direct impingement nozzle orifices, the direct impingement nozzle orifices of the carrier surface and the overpressure nozzle orifices is such that of the total gas amount 25 - 55% is blown through the direct impingement nozzle orifices and through the overpressure nozzle orifices is blown 30 - 60% of the total gas amount and through the direct impingement nozzle orifices of the carrier surface is blown 10 - 25 % of the total gas amount.
According to an advantageous feature of the invention temperature of the gas used in the nozzle system is up to 500 °C and velocity of the gas flow at the nozzle orifice is up to 100 m/s.
According to an advantageous feature of the invention diameter of the direct impingement nozzle orifices and the direct impingement nozzle orifices of the carrier surface and the overpressure nozzle orifices is in the range of 2-10 mm, advantageously 3-8 mm.
According to an advantageous feature of the invention distance between the overpressure nozzle orifices and the next row of the direct impingement nozzle orifices in the cross direction of the nozzle system, i.e. in web travelling direction, is over 15 mm, but less than 100 mm, advantageously 40-60 mm.
According to an advantageous aspect of the invention the nozzle system comprises the overpressure nozzle with the direct impingement blowing on the carrier surface of the overpressure nozzle section combined with direct impingement on either side, advantageously on both sides, of the overpressure nozzle, so that no passage for return air is formed between the overpressure nozzle and the direct impingement nozzle(s). Preferably, the direct impingement orifices are round holes, however other orifice shapes are also possible.
According to an advantageous aspect of the invention the direct impingement carrier surface is flat.
According to an advantageous aspect of the invention the direct impingement carrier surface is recessed. By this the nozzle orifices can be located at more optimal distance in respect of heat transfer and less prone to plug, which provides more stable run of the fiber web, in cases where it tends to run very close to the nozzle system.
According to an advantageous aspect of the invention the direct impingements orifices are in one row or in several rows. The number of rows on the different sides of the overpressure nozzle can be same or different.
The device in accordance with the invention can be utilized in such nozzle system constructions used for contact-free web treatment, which are supposed to be substantially straight in view of the virtual plane of the passing fiber web and also in cases, where, the nozzle system constructions are supposed to be bent to a curved form in the cross direction of the machine. The device in accordance with the invention is particularly suitable for use in various airborne and/or impingement nozzle systems and especially when the fiber web is to be dried by contact-free drying in connection with two-sided and/or one-sided coating and/or sizing.
By the invention and its advantageous features is achieved: The heat transfer capability of the nozzle system is increased 10 - 20 %, when same amount of air used is used, and even up to 25%, if air amount to be used is increased. By the more efficient nozzle system faster drying is achieved. Further, energy savings can be achieved as the heat consumption is lower for same drying capacity. An improved nozzle system with higher heat transfer and evaporation capacity, compared to existing nozzle technology, is achieved. Thus, the nozzle system provides improved performance of air dryer technology.
Aspects of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of some example embodiments when read in connection with the accompanying drawings and in the following the invention is described in more detail referring to the accompanying drawing, in which
In figure 1 is schematically shown an advantageous example of a nozzle system according to an advantageous aspect of the invention as a partial, three-dimensional, cross-sectional view,
In figure 2 is schematically shown another advantageous example of a nozzle system according to an advantageous example of the invention as a partial, three-dimensional, cross-sectional view,
In figure 3 is schematically shown yet one advantageous example of a nozzle system according to an advantageous aspect of the invention as a partial, three-dimensional, cross-sectional view,
In figure 4 is schematically shown yet another advantageous example of a nozzle system according to an advantageous aspect of the invention as a partial, three-dimensional, cross-sectional view,
In figure 5 is schematically shown yet another advantageous example of a nozzle system according to an advantageous aspect of the invention as a cross-sectional view and
In figure 6 is schematically shown further another advantageous example of a nozzle system according to an advantageous aspect of the invention as a cross-sectional view.
During the course of this description like numbers and signs will be used to identify like elements according to the different views which illustrate the invention. Repetition of some reference signs have been omitted in the figures for clarity reasons.
In the example of figure 1 the nozzle system 10 comprises an overpressure nozzle part 20 and direct impingement nozzle parts 25A, 25B arranged symmetrically on both sides of the overpressure nozzle part 20. The direct impingement nozzle parts 25A, 25B are combined with the overpressure nozzle part 20 such that no discharge passage for discharging gases is formed between the direct impingement nozzle part 25A; 25B and the overpressure nozzle part 20.
The overpressure nozzle part 20 has a carrier surface 24 and on both sides of the carrier surface 24, a nozzle orifice row formed of nozzle orifices 18A, 18B and extending in length direction of the nozzle system 10 and which nozzle orifices 18A, 18B are arranged to blow gas flows, which are guided against each other with the aid of curved Coanda- surfaces 22A, 22B formed on each side of the carrier surface 24. The overpressure nozzle part 20 comprises on the carrier surface 24 a row of direct impingement nozzle orifices 21 configured to provide direct impingement blowing by gas flows directed mainly perpendicularly in view of the upper surface of the overpressure nozzle part 20. In the example of the figure 1 the carrier surface is planar between the upper ends of the curved Coanda- surfaces 22A, 22B and at the same level as the upper ends of the curved Coanda- surfaces 22A, 22B.
The direct impingement nozzle parts 25A, 25B extending in length direction of the nozzle system 10 comprise at least one nozzle orifice row formed of nozzle orifices 16A, 16B formed for blowing gas flows mainly perpendicularly in view of the upper surface of the direct impingement nozzle parts 25A, 25B. The direct impingement nozzle parts 25A, 25B according to figure 1 have planar nozzle surfaces with the nozzle orifices 16A, 16B in three adjacent rows.
The nozzle system is an integrated structure and the gas to be blown through the nozzle orifices 16A, 16B, 18A, 18B, 21 is guided from the inlet gas channel 11 through openings 13A, 13B in partition walls 12A, 12B between the inlet gas channel 11 and side gas channels 14A, 14B for the direct impingement nozzle orifices 16A, 16B and for the overpressure nozzle orifices 18A, 18B, correspondingly. The gas to be blown through the nozzle orifices 21 of the carrier surface 24 of the overpressure nozzle part 20 is guided directly or through side gas channels 14A, 14B (fig. 5) from the inlet gas channel 11. In the figure the direction of the gas travel and flows is shown by arrows.
The example shown in figure 2 corresponds to the example shown in figure 1 but instead of the carrier surface 24 being planar at the same level as the upper ends of the curved Coanda- surfaces 22A, 22B, the carrier surface 20 is recessed in respect of the level of the upper ends of the curved Coanda- surfaces 22A, 22B. The carrier surface 24 being located in the recess 23 provides benefits in cases where the passing fiber web tends to run very close to the upper surface of the nozzle system 10 as the direct impingement nozzle orifices 21 are at more optimal distance in respect of heat transfer and less prone to plug.
The example shown in figure 3 corresponds to the example shown in figure 2 but the recess 23 is wider and deeper than in the example of figure 2.
The example shown in figure 4 corresponds to the example shown in figure 1 but instead of one row of the direct impingement nozzle orifices 21 on the carrier surface 24 there are two rows of the direct impingement nozzle orifices 21A, 12B. Also, more than two rows of the direct impingement nozzle orifices 21 can be located on the carrier surface.
In figure 5 shown example corresponds to the example shown in figure 4 but the gas to be blown through the nozzle orifices 16A, 16B, 18A, 18B, 21 is guided from the inlet gas channel 11 through openings 13A, 13B in partition walls 12A, 12B between the inlet gas channel 11 and side gas channels 14A, 14B for the direct impingement nozzle orifices 16A, 16B and for the overpressure nozzle orifices 18A, 18B and for the nozzle orifices 21A, 21B of the carrier surface 24 of the overpressure nozzle part 20.
In figure 6 is shown an example, which corresponds to the example shown in figure 1 but instead the gas to be blown through the nozzle orifices 21 of the carrier surface 24 of the overpressure nozzle part 20 is guided via a pressure balancing chamber 26 from the inlet gas channel 11 through pressure balancing orifices 27. In the figure the direction of the gas travel and flows is shown by arrows.
In the nozzle system 10 according to the invention and to the examples of the figures the gas distribution between the direct impingement nozzle orifices 16A, 16B, the direct impingement nozzle orifices 21 of the carrier surface 24 and the overpressure nozzle orifices 18A, 18B is such that of the total gas amount 25 - 55% is blown through the direct impingement nozzle orifices 16A, 16B and through the overpressure nozzle orifices 18A, 18B is blown 30 - 60% of the total gas amount and through the direct impingement nozzle orifices 21 of the carrier surface 24 is blown 10 - 25 % of the total gas amount. The variation between the distribution in respect of the gas amounts for different nozzle orifices is selected depending on the use purpose of the nozzle system 10.
The diameter of the direct impingement nozzle orifices 16A, 16B and the direct impingement nozzle orifices 21 of the carrier surface 24 and the overpressure nozzle orifices 18A, 18B is in the range of 2-10 mm, advantageously 3-8 mm.
The distance between the overpressure nozzle orifices 18A, 18B and the next row of the direct impingement nozzle orifices 16A, 16B, 21 in the cross direction of the nozzle system 10, i.e. in web travelling direction is over 15 mm, but less than 100 mm, advantageously 40-60 mm.
The upper surface levels of the overpressure nozzle part 20 and the direct impingement nozzle part/- s 25A, 25B can be on same height level or at a different height level depending on the use purpose of the nozzle system 10. Advantageously the upper surface level of the overpressure nozzle part 20 is at a higher height level than the upper surface level of the direct impingement nozzle part/- s 25A, 25B.
The total nozzle orifice area of the direct impingement nozzle orifices 16A, 16B, 21 is typically about 40 to 150 % of the total nozzle orifice area of the area of the overpressure nozzle orifices 18A, 18B.
In drying applications, the temperature of the gas used in the nozzle system 10 is up to 500 °C and the velocity of the gas flow at the nozzle orifice 16A, 16B, 18A, 18B, 21 is up to 100 m/s.
The nozzle system 10 is configured to be located over or under a passing fiber web (not shown) for drying, cooling, carrying and/or supporting etc. of the fiber web, for example a paper or board web. The nozzle system is capable of by gas flows blown through nozzle orifices of the overpressure nozzle part 20 and the direct impingement nozzle part 25A, 25B, typically by air flows, to dry, cool, support and/or carry etc. the passing fiber web without contacting the fiber web. The nozzle system 10 is configured to be located in a fiber web production line, advantageously in a sizing or a coating section of the fiber web production line. The nozzle system 10 is very advantageously located directly after sizing or coating equipment of the sizing or the coating section of the fiber web production line. The device for contact-free treatment of a running fiber web can be formed of one or more nozzle systems 10 and thus the nozzle system 10 can be combined with other nozzle systems, similar or different, to form one or more devices for contact-free treatment of a running fiber web configured of one or more nozzle systems located on one or both sides of the passing fiber web.
The nozzle system can be manufactured as a single beam-like structure, which is completely ready for installation. Further, it can be clearly seen from the figures that the nozzle system has a simple structure and that its manufacture and installation is easy.
The nozzle system solution provides a more efficient heat transfer with the same volume of drying air per square metre, which is an important advantage of the invention. On the other hand, compared to conventional drying using overpressure nozzles, substantially higher heat transfer effects can be achieved with the same blowing velocity but using a larger air volume per square metre, which is another important advantage of the invention.
In the description in the foregoing, although some functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments or examples, those features may also be present in other embodiments or examples whether described or not. Above the invention has been described by referring to some advantageous examples only to which the invention is not to be narrowly limited. Many modifications and alterations are possible within the invention as defined in the following claims.

Claims

Nozzle system of a device for contact-free treatment of a running web, which nozzle system (10) comprises an overpressure nozzle part (20) and at least one direct impingement nozzle part (25A; 25B) arranged on either side of the overpressure nozzle part (20) and in which nozzle system (10) the direct impingement nozzle part (25A, 25B) is combined with the overpressure nozzle part (20) such that no discharge passage for discharging gases is formed between the direct impingement nozzle part (25A; 25B) and the overpressure nozzle part (20), in which nozzle system (10) the overpressure nozzle part (20) has a carrier surface (24) and on both sides of the carrier surface (24) a nozzle orifice row formed of nozzle orifices (18A, 18B) and extending in length direction of the nozzle system (10) and which nozzle orifices (18A, 18B) are configured to blow gas flows, which are guided against each other with the aid of curved Coanda-surfaces (22A, 22B) formed on each side of the carrier surface (24), in which nozzle system (10) the direct impingement nozzle part (25A; 25B) comprises at least one nozzle orifice row formed of nozzle orifices (16A, 16B) configured to blow gas flows mainly perpendicularly in view of upper surface of the direct impingement nozzle parts (25A, 25B), characterized in, that the overpressure nozzle part (20) comprises on the carrier surface (24) at least one row of direct impingement nozzle orifices (21) configured to provide direct impingement blowing by gas flows directed mainly perpendicularly in view of the upper surface of the overpressure nozzle part (20).
Nozzle system according to claim 1, characterized in, that the nozzle system (10) comprises two direct impingement nozzle parts (25A, 25B) arranged symmetrically on both sides of the overpressure nozzle part (20) and the direct impingement nozzle parts (25A, 25B) are combined with the overpressure nozzle part (20) such that no discharge passage for discharging gases is formed between the direct impingement nozzle part (25A, 25B) and the overpressure nozzle part (20).
Nozzle system according to claim 1 or 2, characterized in, that the carrier surface (24) is recessed in respect of the level of upper ends of the curved Coanda-surfaces (22A, 22B).
Nozzle system according to claim 1 or 2, characterized in, that the carrier surface (24) is at the same level as the upper ends of the curved Coanda-surfaces (22A, 22B).
Nozzle system according to any the previous claims, characterized in, that the nozzle system (10) is an integrated structure and comprises an inlet gas channel (11) and at least one side gas channel (14A; 14B) and that the gas to be blown through the nozzle orifices (16A, 16B, 18A, 18B, 21) is guided from the inlet gas channel (11) through openings (13A, 13B) in a partition wall (12A, 12B) formed between the inlet gas channel (11) and the side gas channel (14A, 14B) for the direct impingement nozzle orifices (16A, 16B) and for the overpressure nozzle orifices (18A, 18B), correspondingly, and that the gas to be blown through the nozzle orifices (21) of the carrier surface (24) of the overpressure nozzle part (20) is guided directly from the inlet gas channel (11).
Nozzle system according to any the previous claims, characterized in, that the nozzle system (10) is an integrated structure and comprises an inlet gas channel (11) and at least one side gas channel (14A; 14B) and that the gas to be blown through the nozzle orifices (16A, 16B, 18A, 18B, 21) is guided from the inlet gas channel (11) through openings (13A, 13B) in a partition wall (12A, 12B) formed between the inlet gas channel (11) and the side gas channel (14A, 14B) for the direct impingement nozzle orifices (16A, 16B) and for the overpressure nozzle orifices (18A, 18B) and for the nozzle orifices (21) of the carrier surface (24) of the overpressure nozzle part (20).
Nozzle system according to any the previous claims, characterized in, that the nozzle system (10) is an integrated structure and comprises an inlet gas channel (11) and at least one side gas channel (14A; 14B) and that the gas to be blown through the nozzle orifices (16A, 16B, 18A, 18B, 21) is guided from the inlet gas channel (11) through openings (13A, 13B) in a partition wall (12A, 12B) formed between the inlet gas channel (11) and the side gas channel (14A, 14B) for the direct impingement nozzle orifices (16A, 16B) and for the overpressure nozzle orifices (18A, 18B), correspondingly, and that the gas to be blown through the nozzle orifices (21) of the carrier surface (24) of the overpressure nozzle part (20) is guided via a pressure balancing chamber (26) from the inlet gas channel (11) through pressure balancing orifices (27).
Nozzle system according to any the previous claims, characterized in, that in the nozzle system (10) gas distribution between the direct impingement nozzle orifices (16A, 16B), the direct impingement nozzle orifices (21) of the carrier surface (24) and the overpressure nozzle orifices (18A, 18B) is such that of the total gas amount 25 - 55% is blown through the direct impingement nozzle orifices (16A, 16B) and through the overpressure nozzle orifices (18A, 18B) is blown 30 - 60% of the total gas amount and through the direct impingement nozzle orifices (21) of the carrier surface (24) is blown 10 - 25 % of the total gas amount.
Nozzle system according to any the previous claims, characterized in, that temperature of the gas used in the nozzle system (10) is up to 500 °C and velocity of the gas flow at the nozzle orifice (16A, 16B, 18A, 18B, 21) is up to 100 m/s.
Nozzle system according to any the previous claims, characterized in, that diameter of the direct impingement nozzle orifices (16A, 16B) and the direct impingement nozzle orifices (21) of the carrier surface (24) and the overpressure nozzle orifices (18A, 18B) is in the range of 2-10 mm, advantageously 3-8 mm.
Nozzle system according to any the previous claims, characterized in, that distance between the over pressure nozzle orifices (18A, 18B) and the next row of the direct impingement nozzle orifices (16A, 16B, 21) in the web travelling direction is over 15 mm, but less than 100 mm, advantageously 40-60 mm.