EP2047991A2 - Thermal air drying device and method for drying a printed item - Google Patents

Abstract

Drying device comprises a preheating heat exchanger (6) for preheating the dry air stream using a heat stream in the region of a guiding or curved path through a cooling unit (5) and a heating unit (3) arranged in an air section in the air stream path of the heat exchanger. An independent claim is also included for a drying method using the above device. Preferred Features: The cooling unit is formed as a guiding or curved cooler. Heat is removed from the guiding or curved path using a heat carrier. The heat carrier is guided through the cooling unit and forms a working medium.

Description

The invention relates to a thermo-air drying device according to the preamble of claim 1.

Such drying devices are suitable for a sheet-fed or web-fed printing press and can be arranged there, in particular following a paint or inking unit in the area of the printing press or the rising of a jib. The drying effect is brought about by subjecting the printing material to a heated gas, in particular dryer air, here also frequently referred to as thermolust.

In order to minimize the possible occurring as a result of the heating of the printing material deformations thereof, it is known to cool the substrate in the region of its back side facing away from Trockenluftbeaufschlagungsseite by cooling a sheet path arranged here.

From the DE 33 24 130 A1 For example, a method and apparatus for drying printed or dyed webs by means of heat is known. The process of drying printed or dyed webs with heat is characterized by subjecting the printed web to a non-contact heat shock in a first stage, then contact heating in a second stage at a lower temperature than in the first stage, and then in one third stage is cooled via direct contact. In this case, the energy obtained during cooling is transferred by means of a cooling unit in other parts of the system.

From the DE 202 06 407 U1 is a printing machine with a drying station known. The printing machine is equipped with several arranged in series construction and traversed by a printing material printing units. Each Printing unit is arranged downstream of a drying station. Each of the drying stations is in each case arranged on the circumference of a single, the printing material web-supporting temperature control. It is envisaged here that the heat dissipated by the tempering roller is used for the preheating of drying air.

Furthermore, in the DE 298 19 202 U1 a device for drying and cooling freshly printed paper webs described. The apparatus for drying and cooling of freshly printed paper webs is provided with a dryer, a downstream in the direction of the dryer cooler along the passage line arranged nozzles for blowing hot drying gas or cold air to the continuous paper web; a Nachbrennkammer provided with a suction for enriched with volatile oil or resinous substances drying gas from the interior of the dryer and with supply lines for clean gas to the nozzles and an exhaust passage for excess clean gas. An absorption refrigeration system with refrigerant is thermally linked to the dryer and the radiator in such a way that heat is supplied to the refrigerant, which is withdrawn from the clean gas flowing through the exhaust duct. In addition, heat is supplied to the evaporator of the refrigeration system, which is withdrawn from the cold air in the cooler or the fresh air flowing to the cooler.

The known devices have complex designs in order to reuse thermal energy obtained during the cooling of system parts in other parts of the system, such as a dryer.

The invention has for its object to provide solutions by which a required drying effect can be achieved in a simple manner in a procedural and in particular in terms of machine operating costs over previous approaches more advantageous manner.

This object is achieved according to the invention with the features of claim 1.

It is envisaged to use a working with thermal air drying device for a printing press. This has an inflator for directing a dry air flow to a substrate, a conveyor for promoting the drying air flow through the inflator, a heater for heating the dry air flow or thermoluftstromes, a control device for adjusting the temperature of the drying air flow, and a cooling device for cooling a for guiding the Substrate by the thermo-air drying device provided arc path.
The working with thermo-air drying device is characterized in that a preheating heat exchange device is provided, which serves to preheat the dry air flow using a picked up in the arc of the arc path through the cooling device heat flow.

As a result, it is advantageously possible to use a heat flow tapped from the arc cooling directly for preheating the dry air directly in the area of the drying device operating with thermo-air. Overall, this results in a significant reduction in the waste heat accumulation of the printing press as well as the energy consumption of the drying device and thus the machine itself.

In particular, it becomes possible to use the intense heat output generated by any IR / TL dryer installed in the area of the cantilever, which also has an effect on the very intensive heating of the underlying arc path for preheating the dry air flow. The heater provided for heating the dryer air is arranged downstream of the preheating heat exchanger device in the air flow path. The heater thus only has to make the energy required to heat the dryer air to the required final temperature in the already preheated dryer air.

The cooling device is preferably designed as a sheet-web cooler, wherein the withdrawal of heat from the sheet career is preferably carried out by means of a liquid heat transfer medium. This heat transfer medium is preferably performed by a circulating device by the preheating heat exchanger according to the invention used for preheating the dry air stream.

It is possible to continue to guide the heat transfer medium through another cooling grid or a cooling unit. In the further guidance of the heat transfer medium by a cooling unit, it is in particular possible to use the waste heat arising in the region of the cooling unit for preheating the dry air flow. The heating of the dry air stream is preferably carried out according to the principle of a heat pump, wherein the heat carrier medium guided through the sheet web cooler preferably also forms the working medium of the cooling unit.

The drying device according to the invention is preferably largely thermally encapsulated. This thermal encapsulation can be achieved, in particular, by a cladding device which, as such, shields the inflator, and preferably also the arc track cooler, from the wider surroundings of the printing press, as far as possible. For further support of the dryer effect, a radiator device is preferably also provided for acting on the printing material with a radiation supporting the drying process. This radiation can be generated in particular by an IR emitter or a UV emitter.

In particular, for the derivation of the incurred in the drying device, emissions laden with exhaust air, a discharge device is preferably provided. This exhaust air discharge device is preferably designed so that in this case there is a further guidance of the exhaust air via a heat exchanger device, wherein the heat flow tapped here from the exhaust air can also be used to preheat the dryer air.

The nozzle arrangement provided for inflating the heated dryer air onto the printing substrate can be formed, in particular, by a blow box, wherein this blow box preferably comprises an outlet nozzle plate, through which a sufficiently uniform inflation of the heated air is achieved on the substrate. In particular, in the realization of the inflator using a blow box, it is possible, according to the invention for preheating the dryer air provided Vorwärmwärmauschereinrichtung and possibly also integrated, for example, designed as an electric heating coil heater in this blow box.

According to a further aspect of the present invention, the object stated at the outset is also achieved by a method for effecting the drying of a printing material guided by a printing machine, in which a drying air stream is fed onto a printing material by means of an inflator, and a sheet path intended for guiding a printing material is cooled is, wherein the dry air stream is preheated using the picked up in the arc path heat.

It is possible to operate the dryer in such a way that the air blown off through the blowing nozzles onto the printing material is picked up again in the vicinity of the inflation region, ie still in the region around the blow box, and circulated through a substantially closed air circulation circuit. In order to prevent excessive loading of this "closed" circulated dryer air with vaporized media, a partial air stream can be withdrawn from this closed circuit and passed through a dryer air scrubber, in particular low-temperature condenser to separate condensable fractions of the dryer air. The generated, washed and frozen cold air stream can be introduced into the sheet-web cooler and thus used for cooling the sheet-web, if necessary filtered and returned to the circulation. The dryer can be operated in this respect as a largely emission-neutral sheet treatment module.

Figur 1

eine Schemadarstellung des Aufbaus einer erfindungsgemäßen Trocknungseinrichtung zur Bewerkstelligung der Trocknung eines vorzugsweise bogenförmigen Bedruckstoffes und

Figur 2

eine Variante zur Schemadarstellung nach Figur 1.

Further details and features of the invention will become apparent from the following description taken in conjunction with the drawings. It shows:

FIG. 1

a schematic representation of the structure of a drying device according to the invention for effecting the drying of a preferably sheet-shaped substrate and

FIG. 2

a variant of the schema representation after FIG. 1 ,

In the FIG. 1 As shown drying device serves as the drying of a guided through the drying means printing material. The drying device comprises an inflator 1, which is designed in this embodiment as a combined IR / dry air dryer and is suitable for generating a so-called thermo air for drying. About this inflator, it is possible to inflate a here indicated by the arrow symbols dry air flow to the substrate. For feeding the dry air flow into the inflator 1, a conveyor 2 is provided, which is designed in the embodiment shown here as a blower device. The heating of the dry air stream to the required drying temperature is effected by a heater 3. The heating power of this heater 3 is controlled by a control device 4.

As printing material webs or sheets of different materials are known and suitable. In this case, the printing material is guided in each case in the field of drying devices of guide surfaces, which can be designed as a guideway or as a curved path. In the following, the design for sheet-shaped substrates will be described.

The drying device accordingly also comprises a cooling device 5 designed as a sheet-web cooler or guideway cooler, which as such serves for cooling the sheet path intended for guiding the printing material in the region of the drying device.

The drying device according to the invention is characterized in that a preheating heat exchanger 6 is provided for preheating the Dry air flow using a tapped from the arc path heat flow. The cooling effect generated via the cooling device 5 is regulated by a radiator control device 7.

In the exemplary embodiment shown here, the heating device 3 is located in an air path section arranged downstream of the air flow path of the preheating heat exchanger device 6. In this way, it is ensured that the heating device 3 can heat the air which has already been preheated by the preheating heat exchanger device 6, if still necessary, to the required end temperature.

The cooling device 5, which is embodied here as a sheet-fed track cooler, is structurally designed so that the withdrawal of heat from the sheet course takes place using a guided through a pipe system 8 heat transfer medium. This heat transfer medium may be a preferably liquid heat transfer medium, or in particular a refrigerant, which circulates through the sheet course cooler and the preheating heat exchanger 6 used for preheating the dryer air. This heat transfer medium can still be performed by an additional cooling unit to ensure, if necessary, particularly low cooling temperatures. This cooling unit can be designed so that the heat generated in the region of the cooling unit waste heat is also used to preheat the dry air flow. Otherwise, it is also possible to dissipate the waste heat, which is not yet adequately removed from the heat transfer medium as part of the preheating of the drying air, via the additional heat exchanger 9 exemplified here. In the embodiment shown here, the inflator 1 is in the immediate vicinity of a sheet travel path and is arranged for this purpose between the side frames 10, 11 of the printing press or possibly also a cantilever.

In FIG. 2 is a very useful addition to the embodiment of the drying device according to Fig. 1 shown, which relates to the pretreatment of the air to be provided for the drying.

Here it is provided that the air supply for the thermal air to be generated can be additionally conditioned at the entrance to the drying device. The basic aim of this treatment is that to increase the achievable drying effect, a dehumidification of the thermal air to be extracted for drying is carried out.

• Die Luftversorgung erfolgt nicht mehr direkt durch einfachen Bezug von unbehandelter Außenluft, sondern wird über eine Konditioniereinrichtung 12 durchgeführt. Die Konditioniereinrichtung 12 ist in Verbindung mit einem mit Kondenswasserabscheider ausgebildet. An dieser Stelle des Aufbereitungsprozesses der Trocknungsluft bzw. Thermoluft sinkt die Temperatur T ab, da die Feuchtigkeit ψ über Kältezufuhr bzw. Wärmeabfuhr zum Kondensieren gebracht wird. Ebenso sinkt die die Feuchtigkeit ψ der Trocknungsluft bzw. Thermoluft, da Wasser abgeschieden und entsorgt wird. Dieser thermodynamische grundlegende Prozess ist dem Mollier-Diagramm zu entnehmen.

Therefore, the following is in FIG. 2 Model provided for the drying device:

• The air supply is no longer directly by simple reference of untreated outdoor air, but is carried out via a conditioning device 12. The conditioning device 12 is formed in conjunction with a condensate separator. At this point of the preparation process of the drying air or thermo air, the temperature T decreases, since the moisture ψ is brought to condensation via the supply of cold or heat removal. Likewise, the moisture ψ of the drying air or thermo-air decreases because water is separated and disposed of. This thermodynamic basic process is shown in the Mollier diagram.

The associated with the conditioning temperature losses of the drying air or the thermal air in the primary air supply can be supplemented in a relatively simple manner in the context of the already described system for heat recovery through the heat exchanger 6, 9 through the transfer of excess heat energy.

• von der Kühleinrichtung 5 (z.B. einer Wasserkühlung) an der zu kühlenden Bogenführungsbahn
  oder
• als abzweigenden Teilluftstrom der Warmluftversorgung an der Trocknereinrichtung 1 für die Trockenstrecke
• oder
• von einer Warmluftabsaugung 13 überschüssiger Warmluft an der Trocknerstrecke als Nachwärmeeinrichtung 14 abgeführten Energie

wieder zu gewinnen und in der Trocknungsluft zu ergänzen.For this it is possible to use the heat energy required for increasing the temperature of the raw air

• from the cooling device 5 (eg a water cooling) on the sheet guide path to be cooled
  or
• as a branching partial air flow of the hot air supply to the drying device 1 for the drying section
• or
• from a hot air extraction 13 excess hot air at the dryer section as Nachwärmeeinrichtung 14 dissipated energy

recover and supplement in the drying air.

In this case, the temperature T rises again to the supplied and meanwhile dried drying air or thermo air again. The humidity ψ remains constant.

The air heating to the optimal for each respective drying operation temperature T _Optimum then takes place in a commercial and simple heating register 3 directly in front of the drying nozzle 1. The air outlet from the drying nozzle 1 is carried out on the drying result and on the sheet flow flow optimized tuned outflow.

• Zum Einen ist eine auf einen Standard bezogen unveränderte und hoher Thermolufttemperatur vorhanden und
• es ist zusätzlich eine deutlich vergrößerte Feuchtigkeitsaufnahmefähigkeit vorhanden als zuvor.

The advantages of such a device are, above all, that the dry and hot air produced has the following properties:

• On the one hand, a standard air intake temperature is unchanged and high
• In addition, there is a significantly increased moisture absorption capacity than before.

• Betrieb bei hohen Maschinenlaufgeschwindigkeiten,
• veranschlagtes sehr breites Produktionsspektrum oder
• die Ausführung von Druckaufträgen, bei denen Prozessstabilität von besonders großer Bedeutung ist.

In this way, the performance of the dryer device can be additionally increased. This is especially true for applications in which no further influenceable parameters would be able to achieve even more performance. In this connection are to be mentioned by way of example

• Operation at high machine speeds,
• rated very wide production spectrum or
• the execution of print jobs where process stability is particularly important.

Equally simple is the advantage that compared to the values in standard processes with a constant air humidity, a significantly lower necessary air temperature is made possible.

Here, at lower temperatures, sensitive materials or paints can be dried efficiently. Under both approaches, it is possible to save a large part of the heating energy by the means described in a relatively simple manner.

Generally, it will be through use of in conjunction with Fig. 2 described device with a conditioning device 12 possible to achieve constant process parameters, since ultimately both the temperature T and the humidity ψ are kept constant.
This statement applies to the device shown both in relation to any installation site of a press equipped therewith anywhere in the world, as well as for the production process during a production layer.

Thus, the heat energy used, including the energy recovery, is used in a more precise and efficient manner. This means a significant energy saving and the use of the dryer system according to the invention makes a contribution to the design and operation of an energy and thus also cost-saving printing press. Since the drying system has a modular structure and can be parameterized, it enables a flexible and cost-effective optimization of the drying results for various fields of application right from the development stage and even more so during the application.

It is possible to thermally decouple the dryer device shown here by cladding elements not shown here in detail from the environment of the printing press, so that the Abwärmeaustrag from the thermal air drying device according to the invention in the surrounding area of the printing press is as low as possible.

The modules provided for the thermal conditioning of the dryer air, in particular the preheating heat exchanger 6 and the heating register 3, can be arranged in the side area of the printing machine. The inflator 1 and the Bogenbahnkühler 5 can be designed as a plug-in modules that can be easily inserted into the machine, or removed from this, with the integration of these modules in the system shown here preferably interfaces are prepared on the machine either a functional combination of the modules by simply plugging in ("plug and play"), or in other ways, quickly and without special installation effort developable way.

The inventive concept, the ambient air is preheated in the preheat heat exchanger from the cooling circuit of the arc. The operating temperature of the thermo-air dryer is then further increased in the heating register and adjusted to the required temperature value. So that this temperature TL reaches a certain setpoint value, the heating register 3 is regulated by the controlled variable TL. As the operating temperature in the machine increases, the performance of the heat exchanger also increases. The air preheating is thus becoming more intense. The heating register is then preferably regulated in terms of power down. The supplied electrical power is thus reduced

The heater and the heat exchanger are preferably installed directly on the dryer, so that the path for the thermal air from the heater to the dryer and the path for the cooling medium from the arc to the heat exchanger can be kept as short as possible, whereby the efficiency of the system is improved.

The object of the thermal air box according to the invention is to produce the required in its properties hot air flow (uniformity, intensity, profile, direction) and to apply the bow accordingly with dryer air. This box is preferably designed as a sheet metal construction and can thus be made relatively inexpensive.

The embodiment of the dryer system according to the invention can be designed as a combined IR / UV lamp drying system with integrated hot air extraction. Overall, the Blaskastensystem invention can be made universally and inexpensively in cassette form.

The inventively provided Vorwärmwärmetauscher should at least ensure that the temperature in the arc cooling duct TB is less than the maximum temperature T max. Optionally, the heat exchanger 6 can be connected via a control member 7 with the control variable T _B.

The inventive design of the dryer system makes a significant contribution to the design of an energy-saving printing press. The inventive system can be modular and allows the flexible and inexpensive optimization of the drying results. The dissipated in the context of cooling the sheet running plane heat output is used according to the invention for preheating the dryer air. By the inventive concept, the consumption of necessary for the heating of the thermal air electrical energy is reduced by preheating the supplied to the heater ambient air thanks Vorwärmwärmetauscher in the cooling circuit of the arc. Thanks to this measure, a large part of the energy supplied to the system for drying can be recovered, the efficiency is improved.

The invention can be used in conjunction with dryers in which IR emitters, UV emitters or microwave emitters are used for energy conversion.

LIST OF REFERENCE NUMBERS

1

inflator

2

Conveyor

3

heater

4

control device

5

cooling device

6

Vorwärmwärmetauscher

7

Cooler controller

8th

Piping

9

Additional heat exchanger

10

side frame

11

side frame

12

conditioning device

13

hot air exhaust

14

reheating

T _L

Temperature of the air

T _B

Temperature of the substrate

T _max

maximum temperature in the dryer

Claims (15)

Thermo-air drying device for a web or sheet-fed printing press, comprising: an inflator (1) for directing a dry air flow onto a printing substrate and a conveying device (2) for conveying the dry air flow through the inflator (1), a heating device (3) for heating the dry air stream, - A control device (4) for adjusting the temperature of the drying air flow, and a cooling device (5) for cooling a guiding or arc path provided for guiding the printing material by the drying device, characterized, in that a preheating heat exchanger (6) is provided for preheating the dry air flow using a heat flow picked up by the cooling device (5) in the region of the guide or curved path and in that the heating device (3) is arranged in a downstream air section in the preheating heat exchanger device (6) is. Drying device according to claim 1, characterized in that the cooling device (5) is designed as a guideway or sheet course cooler, and that the withdrawal of heat from the guideway or sheet career takes place using a heat transfer medium. Drying device according to claim 2, characterized in that a fluid is used as the heat transfer medium which is guided by the guideway or sheet course cooler and the preheating heat exchanger (6). Drying device according to claim 2 or 3, characterized in that the heat transfer medium is passed through a cooling unit and forms its working medium. Drying device according to one or all of claims 2 to 4, characterized in that the waste heat generated in the region of the cooling unit is used to preheat the drying air flow. Drying device according to at least one of claims 1 to 5, characterized in that a covering device is provided for thermal foreclosure of the inflator (1) and / or the Bogenbahnkühlers from the environment. Drying device according to at least one of claims 1 to 6, characterized in that a radiator device is provided for acting on the printing material with a drying process supporting the radiation and that the radiator device is designed as IR or as a UV or microwave radiator. Drying device according to at least one of claims 1 to 7, characterized in that an exhaust air discharge device is provided. Drying device according to at least one of claims 1 to 8, characterized in that the exhaust air is also passed through a heat exchanger device for preheating the dryer air with a tapped from the exhaust air heat exchanger heat flow. Drying device according to at least one of claims 1 to 9, characterized in that the inflator comprises a blow box. Drying device according to at least one of claims 1 to 10, characterized
that the Vorwärmwärmetauschereinrichtung is involved in this blow box. Drying device according to at least one of claims 1 to 11, characterized in that the preheating heat exchanger (6) is associated with a device (12) for conditioning the dryer air. Drying device according to claim 12, characterized in that the device (12) for conditioning the dryer air has a device for reducing the humidity of the air and that the device comprises a water separator. Method for accomplishing the drying of a printing material guided by a printing press, in which: - By means of an inflator a dry air stream is fed onto a substrate, and a sheet path intended to guide a printing material is cooled, wherein the dry air stream is preheated using the heat picked up in the region of the arc path. Method according to claim 14,
characterized,
that the dry air flow - Dehumidified under cooling effect and - Then reheated using the picked up in the arc or the waste heat of the drying device heat and then further preheated and brought to operating temperature.

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