EP3788313B1 - Process for drying a substrate, air drying module and drying system - Google Patents

Description

Technical background

1. (a) Erzeugung einer auf das Substrat gerichteten Zuluftströmung, die eine Zuluftströmungsrichtung aufweist, die eine Richtungs-Komponente in Transportrichtung oder in Gegenrichtung dazu hat, und
2. (b) Erzeugen einer vom Substrat wegführenden Abluftströmung.

The invention relates to a method for at least partially drying a substrate, comprising the method steps:

1. (a) generating a supply air flow directed towards the substrate, which has a supply air flow direction that has a directional component in the transport direction or in the opposite direction thereto, and
2. (b) Generating an exhaust air flow away from the substrate.

1. (a) eine Zulufteinheit, umfassend eine Zuluft-Düse zur Erzeugung einer auf das Substrat gerichteten Zuluftströmung, die eine Hauptausbreitungsrichtung hat, die mit der Oberfläche des Substrats einen Winkel zwischen 10 und 85 Grad einschließt, und
2. (b) eine Ablufteinheit zum Erzeugen einer vom Substrat aus dem Trocknungsraum wegführenden Abluftströmung.

The invention also relates to an air dryer module for drying a substrate moved in a transport direction through a drying room, comprising

1. (a) a supply air unit, comprising a supply air nozzle for generating a supply air flow directed towards the substrate, which has a main direction of propagation that forms an angle between 10 and 85 degrees with the surface of the substrate, and
2. (b) an exhaust air unit for generating an exhaust air flow leading away from the substrate from the drying room.

Furthermore, the invention is about an infrared dryer system for drying a substrate moved in a transport direction through a process space, comprising an infrared dryer module which, viewed in the substrate transport direction, has a sequence of the following components: a front air exchanger unit, one with several in parallel Irradiation room equipped with mutually arranged infrared radiators, and a rear air exchanger unit.

Such air dryer modules and drying processes are used, for example, for drying water-based dispersions, inks, paints, varnishes, adhesives or other solvent-containing layers on substrates or for drying moist material sheets made of fleece and other textile materials are used. Infrared dryer systems are used in particular for drying printed products such as paper and cardboard and products made from them.

State of the art

Offset printing machines, lithographic printing machines, rotary printing machines or flexographic printing machines are used to print sheet-shaped or web-shaped printing materials made of paper, cardboard, foil or cardboard with printing inks. Typical ingredients of printing inks and inks are oils, resins, water and binders. For solvent-based and especially water-based printing inks and varnishes, drying is required, which can be based on both physical and chemical drying processes. Physical drying processes include the evaporation of solvents (especially water) and their diffusion into the printing material. Chemical drying refers to the oxidation or polymerization of printing ink ingredients.

In addition to infrared radiators, common infrared dryer systems have other functional modules such as cooling, supply air and exhaust air, which are linked and regulated in various forms in an air management system. For example, this describes DE 10 2010 046 756 A1 a dryer module and a dryer system composed of several dryer modules for printing machines for printing sheet or roll material.

The dryer system consists of several infrared dryer modules arranged transversely to the transport direction, each of which has an elongated infrared radiator aimed at the printing material to be dried, the longitudinal axis of which runs perpendicular to the transport direction of the printing material. An adjustable ventilation system creates an air flow that acts on the infrared radiator and the printing material. The infrared radiator is arranged within a process space for the printing material. The supply air is fed to a supply air collection room and heated there by a heating device. In addition, the air heated by the infrared heater is removed by means of a fan, added to the heated supply air and the infrared heater is thereby cooled.

From the supply air collection room, the heated supply air reaches the process room via gas outlet nozzles in the form of slot nozzles. The gas outlet nozzles are arranged on both sides of the infrared radiator, with the front slot nozzle in the transport direction for the printing material running obliquely to the printing material plane with an orientation opposite to the transport direction, and the rear slot nozzle in the transport direction also running obliquely to the printing material plane with an orientation in the transport direction. The degree of inclination of the slot nozzles can be changed using a motor.

The moisture-laden supply air is removed from the process room as exhaust air via an intake duct and partly fed to a heat exchanger, and another part is added to the supply air collection room.

In the well-known infrared dryer module, the process gas is heated using a specially designed heating device. The heated process gas exits via the slot nozzles in the direction of the printing material as a heated air flow and acts on the printing material to be dried locally and otherwise in a more or less undefined manner until it is sucked out again elsewhere as moisture-laden air. The effectiveness of the drying air in terms of moisture removal from the substrate surface is therefore not exactly reproducible.

The CA 2 748 263 C describes a method and a device for drying using heated air flow and ultrasound. The ultrasonic transducers used for this generate ultrasonic waves with a power level in the range of 120 to 190 dB at the interface of the material to be dried and thus contribute to the breakdown of a diffusion boundary layer. In one embodiment, the ultrasonic transducers are designed with compressed air support, with a housing being used with a central air outlet, which is surrounded on both sides by an inclined compressed air outlet with an additional ultrasonic transducer and two return air inlets.

From the WO 01/02643 A1 a nozzle arrangement in an air-assisted web drying device for drying a coated paper web is known, in which an overpressure nozzle is arranged so that it blows drying air both in the running direction of the web and against the running direction of the web. The Nozzle arrangement also includes an impingement nozzle which is combined with the overpressure nozzle, a plurality of nozzle slots being formed in the impingement nozzle in order to blow drying air largely perpendicular to the web. When using several nozzle arrangements arranged one behind the other in the transport direction of the paper web, a common suction channel for extracting the exhaust air is arranged between adjacent nozzle arrangements.

The DE 10 2016 112 122 A1 describes an LED curing device for UV printing inks, which includes an LED lamp holder with a cooling device and a housing. A partition plate extends from the top of the cooling device of the LED lamp holder to a housing upper wall, which divides the interior of the housing on both sides of the LED lamp holder into a gas suction chamber with a plurality of gas suction openings and into a gas blow-out chamber with a plurality of gas blow-out openings. Both the gas intake opening and the gas exhaust opening are angled so that they form an angle of 45° with the vertical center line of the LED lamp holder.

The DE 10 2016 112 122 A1 shows a drying device for a material web moving in the transport direction, with a pressure chamber which is closed at the bottom by a plate, with several openings being provided in the plate for the supply of hot air to the material web. A special feature of the hot air supply is that the axes of the supply air openings are inclined against the direction of movement of the material web. Several extraction channels are arranged in front of and behind the supply air openings.

DE 2203621 A1 and US 5606805 A disclose various methods for drying a substrate,

Technical task

The invention is based on the object of specifying a drying process that is reproducible and effective and, in particular, leads to an improved result in terms of homogeneity and speed of drying of the substrate. In addition, the invention is based on the object of providing an energy-efficient air dryer module and an infrared dryer system, which are improved in terms of homogeneity and speed of drying, particularly for the drying of solvent-containing and in particular water-based dispersions.

Summary of the invention

With regard to the method, this object is achieved according to the invention, starting from a method of the type mentioned at the beginning, in that the exhaust air flow is divided into several partial flows by supplying each of the partial flows to an individual intake duct, and that in the case of a supply air flow with a directional component in the direction the movement of the substrate, the supply air flow is spatially arranged upstream of the exhaust air flow, and in the case a supply air flow with a directional component in the opposite direction of the movement of the substrate, the supply air flow is spatially arranged downstream of the exhaust air flow, and wherein the intake channels each have an intake channel suction opening facing a drying room, with adjacent suction openings differing in their position and orientation in the drying room.

The supply air flow is not diffuse, but has a main direction of propagation in which, depending on the air throughput and flow speed, it penetrates the substrate surface and hits it at a preset angle, where it has a drying effect on the coated substrate. Action here means that the supply air flow dries the substrate, for example by absorbing solvents from the surface layer into the gas phase. Preferably, the main direction of propagation of the supply air flow forms an angle between 10 and 85 degrees with the surface of the substrate.

Each supply air flow directed towards the substrate is spatially assigned an exhaust air flow leading away from the substrate and divided into several partial flows, via which the moisture-laden process gas and other gaseous components emerging from the substrate are removed from a drying room as exhaust air. The flow of exhaust air is generated by suction via an intake duct.

1. (i) Mittels der auf die Substrat-Oberfläche gerichteten Zuluftströmung werden die am bewegten Substrat mitgezogenen und hängenden Strömungsgrenzschichten durchbrochen. Insbesondere wird dabei in einem vorgelagerten Heizprozess verdampftes Wasser mit der Zuluftströmung mitgerissen und vom Substrat entfernt. Das Durchbrechen der Strömungsgrenzschichten gelingt am besten, wenn die Zuluftströmungsrichtung eine Hauptausbreitungsrichtung mit einer Richtungs-Komponente in Richtung der Fortbewegung des Substrates oder in Gegenrichtung dazu hat, also schräg zur Substrat-Oberfläche verläuft. Vorzugsweise liegt der zwischen der Hauptausbreitungsrichtung der Zuluftströmung und der Substrat-Oberfläche eingeschlossene Neigungswinkel zwischen 10 und 85 Grad. Dadurch wird eine Störung, Verkleinerung oder sogar Ablösung der fluiddynamischen laminaren Strömungsgrenzschicht und damit einhergehend eine Verbesserung des Stofftransports und insbesondere der Abführung von Feuchtigkeit aus dem Substrat bewirkt.
   Im Fall einer schräg in Transportrichtung austretenden Zuluftströmung trifft diese mit einer Auftreffgeschwindigkeit auf das Substrat auf, die um die Bewegungsgeschwindigkeit des Substrats vermindert ist. Im anderen Fall addieren sich die in Transportrichtung weisenden Geschwindigkeitsvektoren von Zuluftströmung und Substrat-Bewegung in der Auftreffgeschwindigkeit.
2. (ii) Der schräg zur Substrat-Oberfläche verlaufenden Zuluftströmung ist eine Absaugung zugeordnet, die je nach Transportrichtung des Substrats entweder räumlich vor oder nach dem Ort der Zuluftströmung liegt. Die schräg zur Substrat-Oberfläche verlaufende Zuluftströmung weist somit stets in Richtung auf die Abluftströmung. Die räumliche Zuordnung von Zuluftströmung und Abluftströmung bewirkt auf der Substrat-Oberfläche eine Interaktion der jeweiligen Gasströmungen miteinander und gewährleistet, dass die Luft der von der Zuluftströmung aufgerissenen Strömungsgrenzschicht unmittelbar abgesaugt werden kann.
   • Im Fall einer Zuluftströmung mit einer Richtungs-Komponente in Gegenrichtung der Fortbewegung des Substrates ist die Zuluftströmung der Abluftströmung räumlich nachgeordnet. Dadurch und infolge der schräg zur Substrat-Oberfläche verlaufenden Zuluftströmungsrichtung besteht jedoch die Gefahr einer Wirbelbildung. Der Drehsinn des sich dabei bildenden Luftwirbels wird durch die schräge Orientierung der Zuluftströmungsrichtung bestimmt und verläuft im gegebenen Fall im Uhrzeigersinn.
   • Im anderen Fall mit einer Zuluftströmung mit einer Richtungs-Komponente in Richtung der Fortbewegung des Substrates ist die Zuluftströmung der Abluftströmung räumlich vorgeordnet und es besteht die Gefahr einer Wirbelbildung in der Abluftströmung mit einer Drehrichtung entgegen dem Uhrzeigersinn.
3. (iii) Eine ausgeprägte Wirbelbildung führt zu einer örtlichen Stabilisierung und Bindung der verwirbelten Luft, einhergehend mit austauscharmen, sogenannten toten Zonen, was ein effektives Absaugen erschwert. Die Erfindung sieht daher vor, dass die Abluftströmung in mehrere Teilströme aufgeteilt wird, indem jeder der Teilströme einem individuellen Ansaugkanal zugeführt wird. Jedem Teilstrom ist genau ein Ansaugkanal zugeordnet; jeder Teilstrom wird über genau einen Ansaugkanal abgesaugt.
   Es hat sich gezeigt, dass die Wirbelbildung durch eine Aufteilung der Abluftströmung in mehrere Teilströme vermindert werden kann. Ein sich bildender Luftwirbel wird in den Ansaugkanälen kanalisiert und dadurch mindestens teilweise aufgelöst. Dadurch wird ein effektives und energiesparendes Absaugen ermöglicht und der Luftverbrauch sinkt.

The drying process according to the invention is characterized in particular by the combination of the following aspects:

1. (i) By means of the supply air flow directed towards the substrate surface, the flow boundary layers that are pulled along and suspended on the moving substrate are broken through. In particular, evaporated water is carried along with the supply air flow in an upstream heating process and removed from the substrate. Breaking through the flow boundary layers is best achieved if the supply air flow direction has a main direction of propagation with a directional component in the direction of the substrate's movement or in the opposite direction, i.e. runs obliquely to the substrate surface. Preferably, the angle of inclination included between the main direction of propagation of the supply air flow and the substrate surface is between 10 and 85 degrees. This causes a disruption, reduction or even separation of the fluid dynamic laminar flow boundary layer and thus This results in an improvement in mass transport and in particular in the removal of moisture from the substrate.
   In the case of a supply air flow exiting obliquely in the transport direction, it hits the substrate at an impact speed that is reduced by the movement speed of the substrate. In the other case, the velocity vectors of supply air flow and substrate movement pointing in the transport direction add up to the impact velocity.
2. (ii) The supply air flow running obliquely to the substrate surface is assigned a suction which, depending on the transport direction of the substrate, is either spatially before or after the location of the supply air flow. The supply air flow, which runs obliquely to the substrate surface, always points in the direction of the exhaust air flow. The spatial assignment of supply air flow and exhaust air flow causes the respective gas flows to interact with one another on the substrate surface and ensures that the air from the flow boundary layer torn open by the supply air flow can be sucked out immediately.
   • In the case of a supply air flow with a directional component in the opposite direction to the movement of the substrate, the supply air flow is spatially downstream of the exhaust air flow. However, as a result of this and as a result of the supply air flow direction running obliquely to the substrate surface, there is a risk of vortex formation. The direction of rotation of the air vortex that forms is determined by the oblique orientation of the supply air flow direction and in this case runs clockwise.
   • In the other case, with a supply air flow with a directional component in the direction of the movement of the substrate, the supply air flow is spatially arranged upstream of the exhaust air flow and there is a risk of vortex formation in the exhaust air flow with a counterclockwise direction of rotation.
3. (iii) A pronounced formation of vortices leads to local stabilization and binding of the turbulent air, accompanied by poor exchange, so-called dead zones, which makes effective suction more difficult. The invention therefore provides that the exhaust air flow is divided into several partial streams by supplying each of the partial streams to an individual intake duct. Each Partial flow is assigned to exactly one intake channel; Each partial stream is extracted via exactly one intake channel.
   It has been shown that the formation of vortices can be reduced by dividing the exhaust air flow into several partial streams. An air vortex that forms is channeled into the intake ducts and is thereby at least partially dissolved. This enables effective and energy-saving suction and reduces air consumption.

In the method according to the invention, due to these measures, rapid and effective drying of the substrate is achieved with at the same time low energy consumption. In addition, by controlling the volumes of supply air and exhaust air, the degree of gas turbulence can be controlled and the effectiveness of the drying can therefore be adjusted reproducibly.

By dividing the exhaust air flow, the formation of zones with little exchange in a pronounced exhaust air flow vortex is counteracted. It has proven to be advantageous if the exhaust air flow is divided into at least three partial streams.

At the local positions in the drying room where the exhaust air flow is divided, partial streams are branched off from the “exhaust air flow vortex”. In the preferred case, these positions are located where the said exhaust air flow vortex would otherwise form in a pronounced manner.

In view of this, the suction channels each have a suction channel suction opening facing a drying room, with adjacent suction openings differing in their position and orientation in the drying room. As a result, partial streams are tapped from the “exhaust air flow vortex” at different positions and directions.

Structurally, this is preferably achieved by delimiting and defining the suction openings by air baffles protruding into the drying room. Through the position and orientation of the air baffles, intake openings are defined and partial flows are branched off from the exhaust air flow vortex and a new flow direction is imposed on them, which is referred to below as the "inflow direction" of the respective partial flow.

Each of the suction openings defines its own inflow direction, with the suction openings preferably being oriented so that their respective suction directions differ from one another. With regard to effective drying, it has proven to be advantageous if several suction openings, particularly preferably all suction openings, are oriented in such a way that their individual inflow direction and the main propagation direction of the supply air flow are almost opposite, for example including an angle between 0 and 45 degrees.

In a particularly preferred method variant, it is provided that the supply air flow flows out of a longitudinal slot-shaped nozzle opening and acts in strips on the substrate to be dried, and that the exhaust air flow is discharged via several slot-shaped suction channels.

The drying air emerges from a slot-shaped inlet opening into the drying room in the direction of the substrate surface. The slot-shaped inlet opening is designed, for example, as a continuous gap or as a series of a large number of individual openings. It acts on the substrate to be dried in a strip-shaped surface area. If necessary, the intake channels are also slot-shaped and thus the exhaust air partial streams are each preferably strip-shaped and are discharged through a corresponding number of slot-shaped intake channels. The strip-shaped supply air flow is therefore preferably spatially assigned a plurality of parallel strip-shaped exhaust air partial flows.

The drying space is arranged transversely to the direction of substrate travel and extends over the entire width of the substrate moving underneath. This means that the entire width of the substrate can be treated and dried homogeneously using the dynamic air.

A particularly advantageous embodiment of the method according to the invention is characterized in that the gas volume V in introduced into the drying room is set to _be smaller than the gas volume V _out sucked out of the drying room by means of a process gas quantity control, whereby the following preferably applies: 1.2 x V _in <V _out < 1.5 x V _in .

Using simulations, it could be shown that in a pronounced air vortex within the drying room, high flow velocities of the exhaust air flow would be generated, which could lead to exhaust air escaping in significant quantities via the inlet and outlet sides of the substrate, which would lead to disruptions in the upstream process stage can lead to contamination of the environment.

As a result of dividing the exhaust air flow into partial streams, the formation of a pronounced air vortex within the drying room is avoided, as explained above. Instead of letting the drying air escape from the drying room, it is preferably sucked into the drying room with a slight tendency. The air balance between the exhaust air flow on the one hand and the quantities of air flowing into the drying room via the supply air flow and on the substrate inlet and outlet sides is preferably adjusted so that a volume ratio between 1.2 and 1.5 results. Ideally, this prevents any drying air from escaping outside of the drying room. The drying module has a neutral effect on the outside in terms of air quality, which means that the environment is not contaminated by escaping hot and moisture-enriched air; the module is pneumatically sealed.

With regard to the air dryer module, the above-mentioned task is solved according to the invention, starting from an air module of the type mentioned at the outset, in that the exhaust air unit comprises a plurality of intake channels, so that the exhaust air flow is divided into several partial streams, and in that the supply air nozzle has a nozzle opening which corresponds to the exhaust air unit is facing, and wherein the suction channels each have a suction channel suction opening facing a drying room, with adjacent suction openings differing in their position and orientation in the drying room.

The supply air flow exits through the supply air nozzle at an angle towards the substrate surface. The nozzle opening of the supply air nozzle thus points towards the substrate surface and at the same time points towards the exhaust air unit.

In the drying room, the partial drying of the substrate and the air exchange between supply air and exhaust air take place. The aim is to maximize the drying room to keep it small and to avoid leakage of air from the drying room as far as possible

1. (i) Mittels der auf die Substrat-Oberfläche gerichteten Zuluftströmung werden die am bewegten Substrat mitgezogenen und hängenden Strömungsgrenzschichten durchbrochen. Das Durchbrechen der Strömungsgrenzschichten gelingt am besten, wenn die aus der Düse austretende Zuluftströmung eine Hauptausbreitungsrichtung hat, die mit der Substrat-Oberfläche einen Winkel zwischen 10 und 85 Grad einschließt. Durch das effektive Durchbrechen der Strömungsgrenzschichten kann der Trocknungsraum kompakt gehalten werden. So schließt beispielsweise bei einer schlitzförmigen Zuluft-Düse mit einer in Richtung der Zuluftströmung verlaufenden Düsen-Längsachse, die Längsachse mit der Oberfläche des Substrats einen Winkel zwischen 30 und 90 Grad ein.
2. (ii) Der Zuluftströmung ist eine Ablufteinheit zugeordnet, die je nach Transportrichtung des Substrats entweder räumlich vor oder nach dem Ort der Zuluftströmung liegt. In jedem Fall weist die Düsenöffnung der Zuluft-Düse in Richtung auf die Ablufteinheit (und nicht von der Ablufteinheit weg). Die schräg zur Substrat-Oberfläche ausströmende Zuluftströmung hat somit stets eine Richtungs-Komponente in Richtung der Ablufteinheit.
   Im Fall einer Zuluftströmung mit einer Richtungs-Komponente in Gegenrichtung der Fortbewegung des Substrates ist das Trocknungsmodul so orientiert, dass die Zulufteinheit der Ablufteinheit räumlich nachgeordnet. Im anderen Fall mit einer Zuluftströmung mit einer Richtungs-Komponente in Richtung der Fortbewegung des Substrates ist das Trocknungsmodul so orientiert, dass die Zulufteinheit der Ablufteinheit räumlich vorgeordnet.
3. (iii) Um eine ausgeprägte Wirbelbildung und damit eine örtliche Stabilisierung und Bindung der verwirbelten Luft im Trocknungsraum zu erschweren , sieht die Erfindung vor, dass die Ablufteinheit mehrere Ansaugkanäle umfasst, mittels denen die Abluftströmung in mehrere Teilströme, vorzugsweise in mindestens drei Teilströme, aufgeteilt wird, indem jeder der Teilströme einem individuellen Ansaugkanal zugeführt wird. Jedem Teilstrom ist genau ein Ansaugkanal zugeordnet; jeder Teilstrom wird über genau einen Ansaugkanal abgesaugt.

The drying module according to the invention is characterized in particular by the combination of the following aspects:

1. (i) By means of the supply air flow directed towards the substrate surface, the flow boundary layers that are pulled along and suspended on the moving substrate are broken through. Breaking through the flow boundary layers is best achieved when the supply air flow emerging from the nozzle has a main direction of propagation that forms an angle of between 10 and 85 degrees with the substrate surface. By effectively breaking through the flow boundary layers, the drying room can be kept compact. For example, in the case of a slot-shaped supply air nozzle with a nozzle longitudinal axis running in the direction of the supply air flow, the longitudinal axis forms an angle between 30 and 90 degrees with the surface of the substrate.
2. (ii) The supply air flow is assigned an exhaust air unit, which, depending on the transport direction of the substrate, is either spatially in front of or after the location of the supply air flow. In any case, the nozzle opening of the supply air nozzle points towards the exhaust air unit (and not away from the exhaust air unit). The supply air flow flowing out obliquely to the substrate surface therefore always has a directional component in the direction of the exhaust air unit.
   In the case of a supply air flow with a directional component in the opposite direction to the movement of the substrate, the drying module is oriented such that the supply air unit is spatially downstream of the exhaust air unit. In the other case, with a supply air flow with a directional component in the direction of the movement of the substrate, the drying module is oriented such that the supply air unit is spatially arranged upstream of the exhaust air unit.
3. (iii) In order to make it more difficult for pronounced vortex formation and thus local stabilization and binding of the swirled air in the drying room, the invention provides that the exhaust air unit comprises several intake channels by means of which the exhaust air flow is divided into several partial streams, preferably into at least three partial streams by feeding each of the partial flows to an individual intake channel. Each partial flow is assigned exactly one intake channel; Each partial stream is extracted via exactly one intake channel.

It has been shown that the formation of vortices can be reduced by dividing the exhaust air flow into several partial streams. This creates an effective and energy-saving suction within a small drying room volume, and air consumption decreases. The air dryer module according to the invention is therefore suitable for use in the method according to the invention.

The subdivision of the exhaust air unit into suction channels is preferably carried out in a constructive manner by air baffles protruding into the drying room, which delimit and define at least part of the suction openings of the suction channels.

Due to the position and orientation of the air baffles, the partial flow is diverted at different points in the drying room. Each of the suction openings is defined by an individual surface normal, whereby the directions of the surface normals can differ from one another. It has proven useful if the respective individual surface normal forms an angle between 90 and 200 degrees with the supply air flow direction.

This means that the respective intake opening is oriented in such a way that the inflow direction of the respective partial flow of the exhaust air flow and the supply air flow direction are almost opposite.

In a particularly preferred embodiment of the air dryer module according to the invention, it comprises an air supply box in which the supply air unit and the exhaust air unit are integrated.

In the air supply box in this sense, for example, the supply air unit, comprising a supply air chamber with a supply air connection and the supply air nozzle, as well as the exhaust air unit, comprising a suction chamber with an exhaust air connection and the suction channels are combined in such a way that they form an independent component that is used in systems for substrate processing as a drying module can be inserted without the need for structural redesign of other areas of the system. The air supply box can also contain a fan that can be assigned to the supply air unit or exhaust air unit. The lateral dimension of the air supply box - viewed in the transport direction of the substrate - is less than 100 mm in preferred embodiments.

In a further advantageous embodiment of the air dryer module according to the invention, the drying space is delimited by a first surface in which the supply air nozzle is formed, by a second surface in which the suction channels are formed, and by the substrate.

The drying space is essentially delimited by three surfaces and has an approximately triangular shape when viewed in a cross section along the substrate transport direction. It facilitates air circulation in which the supply air flowing out of the supply air nozzle can rise again after contact with the substrate, initially forming a partial vortex, where it can be efficiently captured and sucked out by the intake channels. With the dryer module according to the invention, due to this measure, rapid and effective drying of the substrate is achieved with at the same time low energy consumption. Given the efficient air management, the air module represents a compact drying unit that saves space in the machine. The distance between the supply air nozzle and the surface of the substrate is preferably adjustable to less than 10 mm.

The dryer module according to the invention can be part of a dryer system in which several identical or different dryer modules are combined.

With regard to the dryer system for drying a substrate moved in a transport direction through a process space, the above-mentioned technical problem is solved according to the invention in that the front and/or the rear air exchanger unit each contain at least one air dryer module according to the invention.

The dryer system according to the invention is designed, for example, as an infrared dryer module, in which the actual process space comprises an irradiation chamber which is equipped with one or more infrared radiators. The actual process space, for example the irradiation chamber, is delimited by at least one air dryer module according to the invention. In a particularly preferred embodiment, the actual process space is delimited by several air dryer modules according to the invention, which are in the transport direction can be arranged next to each other and/or one behind the other. Three air dryer modules are preferably arranged one behind the other in the transport direction.

In each rear drying module arranged downstream of the process chamber in the transport direction, the direction of the air flow from the nozzle is directed opposite to the transport direction of the substrate. For each front drying module located upstream of the process chamber in the transport direction, the direction of the air flow from the nozzle corresponds to the transport direction of the substrate.

The front and rear air dryer modules take on the function of air curtains at the inlet and outlet of the dryer system in addition to the functions of separating the flow boundary layer and drying the substrate and thus pneumatically seal the dryer system from the outside. The interaction of the irradiation chamber with the air dryer modules reduces the risk of contaminants, and especially water, entering the process space and outgassing from the dryer system. This enables a particularly low-water process space and improves and optimizes the drying effect.

Definitions

In the simplest case, “supply air” is the air taken from the atmosphere. It can also include synthetically produced gases and gas mixtures that are suitable for physically absorbing water. It can also contain reactive substances for chemical drying of the substrate. To improve drying efficiency, the supply air is preferably preheated to a temperature in the range between 70 and 90 °C.

The exhaust air flows out of the drying room via the “intake ducts”. The “intake opening” of an intake duct is the area delimited by a duct edge through which the sucked-in exhaust air enters the intake duct. The suction channels can open into a common suction chamber.

The terms “spatially downstream” or “spatially upstream” refer to the arrangement seen in the transport direction of the substrate.

A supply air flow with a directional component in the substrate transport direction has a main propagation direction with a directional component in the substrate transport direction. Accordingly, a supply air flow with a directional component greater than zero against the substrate transport direction is one whose main direction of propagation has a directional component greater than zero against the substrate transport direction. The main direction of propagation is the flow direction of the supply air flow (still uninfluenced by the flow conditions in the drying room) immediately after entering the drying room. At the in Figure 2 In the embodiment shown schematically, the direction is predetermined by the longitudinal axis 25a of the supply air nozzle 25.

Examples of embodiments

Figur 1

eine Ausführungsform des erfindungsgemäßen Lufttrocknermoduls in einem Querschnitt entlang der Transportrichtung eines zu behandelnden Substrats,

Figur 2

einen Ausschnitt des Lufttrocknermoduls mit Einzelheiten zum Strömungsverhalten innerhalb des Trocknungsraums,

Figur 3

eine weitere Ausführungsform des erfindungsgemäßen Lufttrocknermoduls in einem Querschnitt entlang der Transportrichtung eines zu behandelnden Substrats, und

Figur 4

ein Infrarot-Trocknersystem, ausgerüstet mit Lufttrocknermodulen gemäß der Erfindung in einem Längsschnitt in Bedruckstoff-Transportrichtung.

The invention is explained in more detail below using exemplary embodiments and a patent drawing. The drawing shows a schematic representation in detail:

Figure 1

an embodiment of the air dryer module according to the invention in a cross section along the transport direction of a substrate to be treated,

Figure 2

a section of the air dryer module with details of the flow behavior within the drying room,

Figure 3

a further embodiment of the air dryer module according to the invention in a cross section along the transport direction of a substrate to be treated, and

Figure 4

an infrared dryer system, equipped with air dryer modules according to the invention in a longitudinal section in the printing material transport direction.

At the in Figure 4 In the schematically shown embodiment of an infrared dryer module 1, a housing 2 encloses a treatment room (=process room) for a printing material 3 (=substrate) with the following components (seen in the transport direction 5): a front air exchanger unit 6 with a own housing 10 and an additional air baffle 6a, an infrared irradiation chamber 9 equipped with eighteen infrared radiators 8, the longitudinal axes 8a of which run approximately in the transport direction 5 and which are arranged parallel to one another, and a rear air exchanger unit 7 with its own housing 10. The one in the irradiation chamber 9 directional arrows 20 indicate an air flow directed towards the surface of the printing material 3, and the directional arrows 21 indicate an air flow leading away from the printing material 3, as well as an interaction 22 of these air flows with one another.

In a dryer system, for example, several of the dryer modules 1 are arranged in pairs next to and behind one another when viewed in the transport direction 5. The pair of dryer modules 1 arranged next to each other covers the maximum format width of a printing press. Depending on the dimensions and color of the printing material, the dryer modules 1 and the individual infrared radiators can be electrically controlled separately from one another.

The air exchanger units 6; 7 are each equipped with their own housing 10 and releasably inserted into the housing of the dryer module 1. The air exchanger units 6; 7 are identical in construction, but in the air exchanger unit 6 the supply air side is in front of the exhaust air side, and in the air exchanger unit 7 it is the other way around. At the outlet of the dryer module 1, three air exchanger units 7 are combined into a group, and the last air exchanger unit 7 is provided with a final air baffle 7a. The air exchanger unit 6; 7 also form air dryer modules in the sense of the invention. You will be informed below using the Figures 1 to 3 explained in more detail. If the same reference numbers are used in these figures as in Figure 4 are used, this refers to structurally identical or equivalent components and components, as explained above based on the description of the infrared dryer module 1.

The in Figure 1 Cross section shown of a single air dryer module 6 comprises a two-part, box-shaped housing 1010, which has an upper supply air chamber 13, a middle supply air chamber 14 and a lower supply air chamber 15 on a supply air strand (supply air duct), and a lower exhaust air chamber on an exhaust air strand (intake duct). 16, a middle exhaust air chamber 17 and an upper exhaust air chamber 18 encloses.

The upper supply air chamber 13 is connected to a fan 19, by means of which dry supply air with the volume V _in is introduced into the supply air line in a controlled manner. Likewise, the upper exhaust air chamber 18 is connected to a fan (not shown in the figure), by means of which the moist exhaust air with the volume V _out is removed from the exhaust air line in a controlled manner. The process gas quantity control for the drying module 6; 7 is designed so that: 1.2 x V _in < V _out < 1.5 x V _in . This means the drying module 6; 7 is pneumatically neutral in the sense that it nominally does not release any other volume of gas into the environment other than via the suction. On the contrary, a certain volume of external air (around 20 to 50% based on the supply air volume) is sucked into the drying module from the environment. The effect of the incoming external air is in Figure 2 indicated by the flow arrows 37.

There is a front perforated plate 23 between the upper and middle supply air chamber (13; 14), and a rear perforated plate 24 between the middle and lower supply air chamber (23; 24), the front perforated plate 23 having a first number N1 of supply air passage openings, which have a have a first average opening cross section A1, and wherein the rear perforated plate 24 is provided with a second number N2 of supply air passage openings which are uniformly distributed over the perforated plate 24 and which have a second average opening cross section A2, where: N2>N1 and A1 >A2. The front perforated plate 23 causes a uniform distribution of the supply air volume along the rear perforated plate 24, which in turn serves to distribute the supply air evenly along the slot-shaped air outlet nozzle 25.

The lower supply air chamber 15 is connected to a slot-shaped air outlet nozzle 25, the longitudinal axis 25a of which forms an angle α of 30 degrees with the surface of the substrate to be dried (printing material 3). A supply air flow with a main direction of propagation in the direction of the longitudinal axis 25 reaches the substrate surface via the slot-shaped air outlet nozzle 25 and has a drying effect on the substrate (3) in the drying space 26.

From the drying room 26, the moisture-laden process air reaches the lower exhaust air chamber 16. There is a second front perforated plate 28 between the lower exhaust air chamber 16 and the middle exhaust air chamber 17, and between the middle ones and upper exhaust air chamber (17; 18) a second rear perforated plate 29, wherein the second front perforated plate 28 has a first number N3 of exhaust air passage openings which have a first average opening cross section A3, and wherein the second rear perforated plate 29 with a second number N4 is provided with exhaust air passage openings which are evenly distributed over the perforated plate 29 and which have a second average opening cross section A4, where: N4>N3 and A3>A4. The perforation in the second front perforated plate 28 is designed so that an internal pressure that is as uniform as possible is established over the length of the lower exhaust air chamber 16.

By means of the supply air flow directed towards the substrate surface, the flow boundary layers that are pulled along and suspended on the moving substrate (3) are broken through. Because the supply air flow direction has a directional component in the direction of the movement of the substrate (3) or in the opposite direction, there is a disruption, reduction or even separation of the fluid dynamic laminar flow boundary layer and, as a result, an improvement in the mass transport and in particular the removal of moisture from the substrate (3) and the drying room 26.

What is important for this is the flow direction of the supply air, which runs obliquely to the substrate 3 (main propagation direction in the direction of the longitudinal axis 25a), and also a division of the exhaust air flow by a suction, which, depending on the transport direction of the substrate, is either spatially before or after the location of the supply air flow. In any case, the supply air flow, which runs obliquely to the substrate surface, points towards the exhaust air side. The drying chamber 26 has a substantially triangular shape in the cross section shown.

Figure 1 shows the case of a supply air flow with a flow direction component opposite to the transport direction of the substrate 3. The supply air flow is spatially subordinate to the exhaust air flow in the transport direction. As a result of the inflow angle α and the opposite suction, a vortex formation of the inflowing and outflowing drying air begins, which is indicated by the directional arrow 27. The direction of rotation of the air vortex 27 that forms is clockwise. In order to prevent pronounced vortex formation, the exhaust air flow is controlled with the help of air baffles 30; 31 in several Partial streams divided. The air baffles 30; 31 are angled in the opposite direction to the direction of rotation of the air vortex that forms and form individual intake channels 41 for a total of three partial flows; 42; 43 out, like out Figure 2 recognizable.

The formation of vortices is reduced by dividing the exhaust air flow into several partial streams and an air vortex that initially forms is channeled into the intake channels 41, 42, 43. The flow behavior within the drying chamber 26 is indicated schematically by the flow arrows 37, 38 and 39, with the supply air flowing into the drying chamber 26 being designated with the reference number 38 and the exhaust air after reversal of direction with the reference number 39. The external air flowing in independently is designated by reference number 37.

The channeling of the exhaust air flow in the intake channels 41, 42, 43 is achieved by the angled air baffles 30; 31 causes which protrude in different positions into the initially and partially forming air vortex 27. They define suction openings 41a, 42a, 43a of the suction channels 41, 42, 43 (marked by dashed lines in the drawing). Adjacent suction openings 41a, 42a, 43a differ in their position and orientation in the drying space 26. As a result, partial flows are tapped from the exhaust air flow vortex 27 at different positions and directions. Each of the suction openings 41a, 42a, 43a is defined by an individual surface normal. The respective surface normal indicates approximately the inflow direction of the relevant partial flow into the intake channel 41; 42, 43 again. The directions of the surface normals and thus the inflow direction differ from one another and form an angle of 180 degrees +/- 30 degrees with the supply air flow direction (longitudinal axis 25a).

The local positions in the drying room 26 at which the exhaust air flow is divided are located where the said exhaust air flow vortex 27 would otherwise form in a pronounced manner. This is at least partially resolved, so that the formation of a pronounced exhaust air flow vortex is counteracted by the division of the exhaust air flow, and effective and energy-saving suction is made possible. In the method according to the invention, due to these measures, a quick and effective drying of the substrate 3 is achieved with low energy consumption at the same time.

Figure 3 shows schematically a series arrangement of three air dryer modules 7 according to the invention Figure 1 . This arrangement occurs, for example, at the output of an infrared dryer module 1 Figure 4 for use. This ensures that when the printing material 3 exits the infrared dryer module 1, as far as possible no toxic or otherwise undesirable substances in gaseous and liquid form leave the process space unfiltered and uncontrolled.

Claims (15)

1. A method for at least partially drying a substrate (3) moved in the transport direction (5) through a drying space (26), comprising the method steps of:

   (a) generating a supply air flow (38) directed onto the substrate (3), which flow has a supply air flow direction which has a directional component in the transport direction (5) or in the opposite direction thereto, and

   (b) generating an exhaust air flow (39) leading away from the substrate (3),

   wherein the exhaust air flow (39) is divided into a plurality of sub-flows by each of the sub-flows being supplied to an individual intake channel (41; 42; 43), and in that, in the case of a supply air flow (38) having a directional component in the substrate transport direction (5), the supply air flow (38) is arranged spatially upstream of the exhaust air flow (39) in the transport direction (5), and in the case of a supply air flow (38) having a directional component counter to the transport direction (5), the supply air flow (38) is arranged spatially downstream of the exhaust air flow (39) in the transport direction (5),

   characterized in that the intake channels (41; 42; 43) each have an intake channel suction opening (41a; 42a; 43a) facing the drying space (26), with adjacent suction openings differing in their position and orientation in the drying space (26).
2. The method according to claim 1, characterized in that the exhaust air flow (39) is divided into at least three sub-flows.
3. The method according to claim 1, characterized in that the suction openings (41a; 42a; 43a) are delimited by air baffles (30; 31) projecting into the drying space (26), and each suction opening (41a; 42a; 43a) specifies an individual inflow direction for the inflowing sub-flow in each case, the inflow directions of adjacent sub-flows differing from one another.
4. The method according to claim 1, characterized in that a plurality of suction openings (41a; 42a; 43a), particularly preferably all of the suction openings (41a; 42a; 43a), are oriented such that their individual inflow directions run approximately opposite to a main propagation direction (25a) of the supply air flow (38).
5. The method according to any of the preceding claims, characterized in that the supply air flow flows out of a slot-shaped nozzle opening (25) and acts in a strip-shaped manner on the substrate (3) to be dried, and in that the exhaust air flow (39) is removed via a plurality of slot-shaped intake channels (41; 42; 43).
6. The method according to any of the preceding claims, characterized in that, by means of process gas quantity control, the gas volume V_in introduced into the drying space is set so as to be smaller than the gas volume V_out sucked out of the drying space, wherein preferably 1.2 x V_in < V_out < 1.5 x V_in.
7. An air dryer module for drying a substrate (3) moved in a transport direction (5) through a drying space (26), comprising

   (a) a supply air unit (13; 14; 15; 25) comprising a supply air nozzle (25) for generating a supply air flow (38) directed onto the substrate (3), which flow has a main propagation direction (25a) that encloses an angle of between 10 and 85 degrees with the surface of the substrate (3),

   (b) an exhaust air unit (16; 17; 18; 41; 42; 43) for generating an exhaust air flow (39) leading away from the substrate (3) out of the drying space (26),

   wherein the exhaust air unit (16; 17; 18; 41; 42; 43) comprises a plurality of intake channels (41; 42; 43), such that the exhaust air flow (39) is divided into a plurality of sub-flows, and in that the supply air nozzle (25) comprises a nozzle opening which faces the exhaust air unit (16; 17; 18; 41; 42; 43),

   characterized in that the intake channels (41; 42; 43) each have an intake channel suction opening (41a; 42a; 43a) facing the drying space (26), with adjacent suction openings differing in their position and orientation in the drying space (26).
8. The air dryer module according to claim 7, characterized in that the exhaust air unit (16; 17; 18; 41; 42; 43) comprises at least three intake channels (41; 42; 43).
9. The air dryer module according to claim 7 or claim 8, characterized in that a plurality of suction openings (41a; 42a; 43a), particularly preferably all of the suction openings, are oriented such that their individual inflow directions run approximately opposite to a main propagation direction (25a) of the supply air flow (38).
10. The air dryer module according to any of claims 7 to 9, characterized in that it comprises an air supply box in which the supply air unit and the exhaust air unit are integrated.
11. The air dryer module according to any of the preceding claims 7 to 10, characterized in that the distance between the supply air nozzle (25) and the surface of the substrate (3) is less than 10 mm.
12. The air dryer module according to any of claims 7 to 11, characterized in that the drying space (26) is delimited by a first surface, in which the supply air nozzle (25) is formed, and by a second surface, in which the intake channels (41; 42; 43) are formed.
13. A dryer system for drying a substrate (3) moved in a transport direction (5) through a processing space (9; 26), comprising an infrared dryer module (1), which, viewed in the substrate transport direction (5), comprises a sequence of the following components: a front air exchanger unit (6), an irradiation space (9) equipped with a plurality of infrared emitters (8) arranged in parallel with one another, and a rear air exchanger unit (7), characterized in that the front and/or the rear air exchanger unit each contain at least one air dryer module (6; 7) according to any of claims 7 to 12.
14. The dryer system according to claim 13, characterized in that the rear and/or the front air exchanger unit comprises a plurality of air dryer modules (6; 7) arranged next to one another and/or one behind the other.
15. The dryer system according to either of claims 13 or 14, characterized in that at least one air dryer module (6) is arranged upstream of the irradiation space (9) and at least one air dryer module (7) is arranged downstream of the irradiation space (9).

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