EP2166299A2 - Web of material drying device - Google Patents

Abstract

The arrangement has an air dryer provided with an air supply pipe and an air discharge pipe in an air guidance system. A radiation dryer has another air guidance system provided with a suction- and/or air circulation channel (30) and another air discharge pipe that is connected to the suction- and/or air circulation channel. The latter air discharge pipe is connected with the former air supply pipe of the former air guidance system of the air dryer. The suction- and/or air circulation channel of the radiation dryer is completely surrounded with a thermal insulation (35).

Description

The invention relates to a web dryer arrangement with at least one radiation dryer and at least one air dryer, wherein the air dryer in a first air duct system at least a first air supply line and preferably a first exhaust duct, and wherein the radiation dryer has a second air duct system, which at least one suction and / or recirculation duct and at least one connected to this second exhaust duct, which is connected to the at least one first air supply line of the first air duct system of the air dryer.

A web dryer assembly of this type is used, for example, in the manufacture of a paper web to dry it. The radiation dryer has a relatively high power density, i. he can transfer a relatively large amount of heat to the web, so that the water contained therein can evaporate well. Although the air dryer transmits a smaller amount of heat to the web. But he is able to support the web contact.

A web dryer arrangement of the type mentioned is, for example WO 2005/085729 known. The radiation dryer is connected upstream of the air dryer. Several such arrangements of radiation dryer and air dryer can be arranged one behind the other. Heated air from the radiation dryer is collected by the air dryer and optionally blown after reheating on the web.

A similar embodiment is made EP 1 169 511 known. Here, too, heated air from the radiation dryer reaches a capture device of the Air dryer, where it is taken up, circulated and blown back onto the web.

Out DE 39 10 898 B4 is a combination dryer with a radiation dryer and an air dryer is known in which the radiation dryer is heated with air, which is branched off from a feed stream for the air dryer. Heated air from the radiation dryer is fed to the housing of the air dryer, sucked there, mixed with fresh air and circulated again, the combination of already heated air and fresh air is heated by a heater again.

The process of drying a material web is energetically more favorable, the lower the fresh air mass supplied or the lower is the discharged into the environment hot exhaust mass. Ideally, therefore, one would completely switch off the supply of fresh air or exhaust air discharge. However, this has the disadvantage that set a high air temperature and a high moisture content.

In order to achieve a higher efficiency with the least possible impairment of the quality of the material web is according to the unpublished application DE 102007051962.3 been tried with success, the radiation dryer to assign a second air duct system with supply air and exhaust air, both air ducts each with a connection of supply air and exhaust air to provide and connect both air ducts only in the region of their respective exhaust air.

It is an object of the present invention to further increase the efficiency of the material web dryer arrangement mentioned above.

The object is achieved in that the suction and / or recirculation channel of the radiation dryer is substantially completely surrounded by a thermal insulation.

It is the endeavor to bring the exhaust air from the radiation dryer and the hot air generated between the radiation dryer and the material web with the highest possible temperatures to the air dryer in order to use there with the highest possible efficiency as blowing air for further drying. For this it seems obvious to completely isolate the radiation dryer thermally, so to speak "pack". The invention is a different, on the first appearance much more complicated way and isolates primarily only the existing suction and / or recirculation channels.

In this way, some disadvantages of prior art web dryer arrangements are overcome.

This firstly, that the radiation-generating elements, so for example, as in dependent claims, infrared modules are protected at their temperature-sensitive points from overheating.

Furthermore, significantly less heat of the discharged hot air is lost to the housing walls of the radiation dryer, the heat-emitting surface is smaller.

Due to the insulation of the at least one suction and / or circulating air channel, it is possible to dispense with thermal insulation on the rear side of the radiation dryer. This increases the ease of maintenance of the system.

In advantageous embodiments, it can be ensured that by omitting a suction channel in the inlet region of the material web in the effective range of the radiation dryer also significantly less cold, is discharged through the run of the web as a boundary layer with entrained air over the first air duct system before it is heated, which the efficiency further improved.

In addition, it has become possible by the thermal insulation of the at least one suction and / or recirculation channel to cool the radiation dryer from the inside, without exerting an effective negative impact on the desired high temperature of the exhaust air.

The subclaims contain even further advantageous embodiments. A further description of the advantages will be made in the explanation of the embodiments according to the figures.

Figur 1

eine schematische Darstellung einer Material-bahntrockneranordnung vorwiegend in Hinblick auf die Strömungspfade,

Figur 2

eine schematische Darstellung eines Strah-lungstrockners vorwiegend in Hinblick auf erfin-dungsgemäße Isolierung und Dichtung

Figur 3

eine schematische Darstellung eines Strah-lungstrockners vorwiegend in Hinblick auf erfin-dungsgemäße Anordnung von Saugkanälen

Figur 4

ein Diagramm, dass die Beziehungen von Luftmas-senströmen, Isolierungen und Wirkungsgraden ver-deutlicht

The invention will be described below with reference to a preferred embodiment in conjunction with the drawings. Herein shows the

FIG. 1

a schematic representation of a material web dryer arrangement mainly with regard to the flow paths,

FIG. 2

a schematic representation of a radiation-drying mainly with regard to inventive insulation and seal

FIG. 3

a schematic representation of a radiation-drying mainly with respect to inven tion proper arrangement of suction channels

FIG. 4

a diagram that illustrates the relationships of air mass flows, isolations and efficiencies

A web dryer assembly 1 according to FIG. 1 is used to dry a material web 2, which passes in a marked by an arrow 3 direction of the web dryer assembly 1.

In the running direction, the material web 2 first passes through a radiation dryer 4, which is designed as an infrared dryer and then an air dryer. 5

The radiation dryer 4 is supplied via an inlet 6 air. If it is an electrically powered radiation dryer, then this dryer requires cooling air. If it is a gas-powered radiation dryer, then this radiation dryer additionally requires combustion air. Because it is important to the invention, it is in Fig.1 to a cooling air supply, which ensures within the radiation dryer 4 that cables, gaskets o. Ä. Not excessively stressed by heat. In this case, a motor 7 drives a fan 8.

On the one hand, the radiation dryer 4 emits radiant heat to the material web 2, on the other hand, it heats the air introduced with the material web. The heated air is removed together with the evaporated water from the material web and - in gas-heated infrared radiators - the combustion exhaust gases via an exhaust duct 9, which is connected to at least one suction and / or recirculation duct 30, the radiation dryer 4. A portion of the exhaust air, for example, 15 to 30%, in particular about 20%, as a mass air flow m ₅ via a compound 10 of a supply air line 11 are supplied. In the connection 10, a fresh air connection 12 is provided. A conveying device having a motor 13 and a fan 14 conveys the supply air via the supply air line 11 into the radiation dryer 4. By admixing the air from the fresh air connection 12, this supply air is cooled to about 120 to 140 ° C., for example. This partial cycle is of importance for the invention insofar as that the quantitatively possible air mass flow, which is dissipated to the air dryer, is reduced by the air mass flow m ₅ . In the embodiment according to the invention only the remaining ratio of m ₁ to m _{2 is} important.

It should be noted in general that the term air mass flow is to be understood as meaning a unit in weight / time unit and in this case preferably kg / h.

The air dryer 5 has an air supply line 16 and an exhaust air line 17. Between the exhaust duct 17 and the supply air line 16, a connection 18 is arranged. In the connection 18, a conveyor 19 having a motor 19 and a fan 20 is arranged. Further, a Abschottklappe 21 is arranged in the connection. Finally, optionally in the connection 18, a heating device 22 may be arranged. The heater 22 may be formed, for example, as a combustion chamber. If such a heating device 22 is arranged in the connection 18 or in the supply air line 16, then it is expedient to provide a fresh air connection 23 which, just like the fresh air connection 12, is designed to be controllable. If necessary, this fresh air connection 23 serves to rinse the circuit through the air dryer 5.

The air dryer 5 thus has a first air guidance system 24 and the radiation dryer 4 has a second air guidance system 25. Both Air duct systems have a connection 18, 10 of supply air line 16, 11 and exhaust duct 17, 9 on. Both air ducts 24, 25 are connected to each other in the region of their exhaust duct 17, 9, that is, there is a node 26 where the lines leading the exhaust air 17, 9 meet.

In the exhaust duct 17 of the first air duct system 24, ie between the air dryer 5 and the node 26, an exhaust outlet 27 for the exhaust air mass flow m _{4 is} arranged, which has a motor 28 and a fan 29 having conveyor. This conveyor has an even lower capacity than the other two conveyors 13, 14 and 19, 20. For example, a pressure rating of only 20 mbar is sufficient here. The exhaust outlet 27 is disposed in the first air duct system 24 where the drying air is coldest and has the highest moisture content. The laden exhaust air mass flow m ₄ is withdrawn at the exhaust outlet 27 with the lowest energy losses.

The web dryer arrangement 1 operates as follows: a small portion, for example 20%, of the exhaust air 9 of the radiation dryer is mixed with fresh air and thereby cooled to about 120 to 140 ° C and fed back to the radiation dryer 4 as supply air or blowing air. This serves, for example, for the purpose of boundary layer destruction at the place of radiation drying. The largest part of the exhaust air 9 of the radiation dryer 4 is fed into the air duct system 24 of the air dryer 5. As an air mass flow component (m ₂ ), which is supplied to the air mass flow m ₁ , it already ensures heating of the air required in the air dryer. If this is not the case to a sufficient extent, additional heat can be introduced via the heating device 22. As the air in the air dryer 5 loads with moisture, a portion of this air is removed via the exhaust outlet 27.

It is preferred that all conveyors 14, 20, 29 are independently controllable. One can therefore control the air flow in the first air duct system differently than in the second air duct system. In order to further increase the efficiency, the ratio of the total air mass flow m ₁ supplied to the air dryer 5 to the air mass flow m ₂ taken as exhaust air from the radiation dryer 4 to the air dryer 5 is considerably increased compared with the prior art. It is therefore the ratio of the total air mass flow, which is supplied via the at least one first air supply line 16 to the air dryer 5, to the at least one second exhaust duct 9 at the air dryer 4 extracted air mass flow, which is not returned to the radiation dryer 4.

This ratio has a value between 1 and 2 in known web dryer arrangements of this kind. According to the invention it is provided to increase this value to 3 to 10, preferably 4 to 8.

The air mass flow m ₂ , which is discharged at the radiation dryer, compared to the prior art, a significantly larger air mass fraction m ₃ from the first exhaust duct 17 is mixed in order to achieve the desired air mass flow m ₁ . This leads to a considerable increase in the efficiency, which will be explained by the following example.

For example, a prior art web dryer assembly had m ₁ at 14000 kg / h and 400 ° C, m ₂ at 10000 kg / h and 500 ° C, and m ₃ at 4000 kg / h and 230 ° C. Such a constellation leads to a discharged via the exhaust outlet 27 air mass flow of 13800 kg / h at 230 ° C.
According to the invention, for example, the following distribution would result: m ₁ with 34000 kg / h and 260 ° C, m ₂ with 10000 kg / h and 500 ° C and m ₃ with 24000kg / h and 180 ° C. Such a constellation leads to an air mass flow of 14,100 kg / h discharged through the exhaust air outlet 27 at 180 ° C.

Energetically, the efficiency of the web dryer arrangement 1 increases from 53 to 64%. It has not yet been considered that air derived from the air dryer in the prior art has hitherto been used, for example, to return it to the place of radiation drying for the purpose of the destruction of boundary layers. As a result, the effectiveness of the web dryer arrangement 1 but substantially less increased than with the inventive utilization of the prior art greatly increased air mass flow m ₃ , which combines with the air mass flow m ₂ which also significantly increased air mass flow m ₁ forms. As far as possible, no air is returned from the air dryer to the radiation dryer. The exhaust air mass flow remains about the same compared to conventional web dryer arrangements, but with reduced temperatures, which causes the higher efficiency.

The increased air mass m ₁ can be used to increase, for example, the drying surface 37 of the air dryer 5 over the prior art. This has the consequence that the material web can be subjected to more drying air.

The radiation dryer 4 is according to FIG. 2 infrared modules 32 suspended from a support 36. The carrier or attached to it Guides also carry the supply lines and cables needed by the infrared module. The infrared modules 32 are known per se and will not be described further here. For example, we refer to the DE 19901145 A1 ,

Usually, infrared modules 32 are combined in one or more rows under a hood 31. At the edges there are usually suction and / or circulating air channels 30, via which the heated by the combustion in the infrared modules 32 and the heat radiation air and the emerging from the web 2 water vapor can be removed. In the material web dryer arrangements used in the prior art, the hood 31 is insulated at best on the rear side facing away from the material web side so that assembly personnel do not burn themselves when working on the infrared modules 32 accessible from there. However, in order that the electrical supply lines, seals and other parts inside the hood 31 do not suffer from the high temperatures that develop therefrom, in the prior art the outer walls of the hood have not been isolated as a rule. Accordingly, they consciously accepted to lose thermal energy to the environment. In many cases, the interior had to be additionally supplied with a very high amount of cooling air,

In the execution according to FIG. 2 If you go now another way and insulated the hood 31 completely around and in particular the suction and / or recirculation channels 30 are - except, of course, at the air inlets and outlets - substantially completely isolated, even to the interior 38 of the hood 31 out in which the infrared modules 32 are located. By isolating the at least one hot suction and / or recirculating air channel 30 against the interior 38, the need for cooling air, which is supplied via the cooling air connection, in favor of a higher Efficiency can be minimized. In this way, the rear wall is not overheated, which facilitates maintenance of the infrared modules 32. Almost the entire back of the hood remains in this way in the range of only 50 ° C.

The infrared modules 32, which are located in a row, for example, can not be close to each other due to their thermal expansion and expandability. Through the gaps in between, the cooling air would be able to escape in a counterproductive manner into the region between infrared modules 32 and material web 2, which should have very high temperatures for drying the fibrous web. For this reason, the gaps between the infrared modules 32 are closed by seals 33. Only at the edges of the hood 31, exactly where inlet openings in a suction and / or recirculation duct 30 are present (in Fig.2 indicated by arrows), column 34 are provided, through which the heated after a short time cooling air from the interior 38 can be discharged into a suction and / or recirculation duct 30. In this way, a disturbing influence of the cooling air on the hot center between the infrared module 32 and material web 2 is avoided.

According to Fig. 3 It should be particularly pointed out that a suction and / or recirculating air duct 30 should only be arranged in the direction of web travel 3 at the end and possibly laterally of a hood 31. In the inlet region 39 of the effective range of a radiation dryer 4, therefore, no suction is installed. In this way, less unwanted cold ambient air is drawn through the material web 2 in the inlet area 39 in the radiation dryer 4. The friction on the material web 2 ensures that the hot air, which is located between the infrared modules 32 and the material web is taken undisturbed by environmental influences in a suction and / or recirculating air duct 30 at the end of the hood 31st can escape. This configuration according to the invention is particularly true in an inclined position or even a vertical installation of the radiation dryer 4. Because by the inclination of the negative intake of cold ambient air in the inlet region 39 of the radiation dryer 4 is still supported by the natural thermals.

Fig. 4 illustrates the advantages of the material web dryer assembly 1 according to the invention with reference to a diagram. The abscissa shows the quotient from m ₁ to m ₂ . The ordinate indicates the thermal efficiency of the material web dryer assembly 1. The two curves K1 and K2 stand for the cases
K1: Radiation dryer with non-insulated suction and / or recirculating air duct 30 K2: Radiant dryer with insulated suction and / or circulating air duct 30 as described above.
It can be seen from the graph when K1 pursues that in a conventional web dryer assembly by increasing the air dryer 5 supplied air mass flow m ₁ in relation to the extracted from the radiation dryer 4 air mass flow m _2, an efficiency improvement of about 54% to 62% is possible when the ratio m ₁ / m _{2 is increased} from about 2 to 8.

Due to the additional insulation even efficiencies of 74% can be achieved with the same m ₁ / m ₂ value. Above an abscissa of 10, no increase is expected.

LIST OF REFERENCE NUMBERS

1

Web dryer arrangement

2

web

3

Running direction (arrow)

4

radiation dryer

5

air dryer

6

Cooling air connection

7

engine

8th

Fan

9

second exhaust duct

10

connection

11

second supply air line

12

Fresh air connection

13

engine

14

fan

15

Abschottklappe

16

first supply air line

17

first exhaust pipe

18

connection

19

engine

20

fan

21

Abschottklappe

22

heater

23

Fresh air connection

24

first air distribution system

25

second air distribution system

26

junction

27

exhaust outlet

28

engine

29

fan

30

Suction and / or recirculation channel

31

Hood

32

infrared module

33

poetry

34

gap

35

thermal insulation

36

carrier

37

drying surface

38

inner space

39

entry area

m ₁

Air mass flow

m ₂

Air mass flow

m ₃

Air mass flow

m ₄

Air mass flow

m ₅

Air mass flow

K1

Curve

K2

Curve

Claims (7)

Material web dryer arrangement with at least one radiation dryer (4) and at least one air dryer (5), wherein the air dryer (5) in a first air duct system (24) at least a first air supply line (16) and preferably a first exhaust duct (17), and wherein the radiation dryer (4) has a second air duct system (25) which comprises at least one suction and / or recirculating air duct (30) and at least one second exhaust duct (9) connected thereto, which is connected to the at least one first supply air duct (16) of the first duct system (16). 24) of the air dryer (5) is connected,
characterized in that the at least one suction and / or circulating air channel (30) of the radiation dryer (4) is substantially completely surrounded by a heat insulation (35). Material web dryer arrangement according to claim 1, characterized in that in the entry region (3) of the material web (2) in the effective range of the radiation dryer no suction and / or recirculation air duct is provided. Material web dryer arrangement according to claim 1 or 2, characterized in that the radiation dryer comprises infrared modules (32) which are arranged under a hood (31). Material web dryer arrangement according to claim 3, characterized in that the hood (31) has a cooling air connection (6). Material web dryer arrangement according to one of claims 3 to 4, characterized in that seals (33) are provided between the infrared modules (32). Material web dryer arrangement according to one of claims 3 to 5, characterized in that at least between a suction and / or recirculating air channel (30) and at least one infrared module (32), a gap (34) is provided without seal. Material web dryer arrangement according to claim 1, characterized in that an air mass flow (m ₁ ) in the at least one first air supply line (16) of the first air duct system (24) of the air dryer (5) during operation of the web dryer assembly 3 to 10, preferably 4 to 8 times is large, such as an air mass flow (m ₂ ) in the at least one second exhaust duct (9) of the second air duct system (25) of the radiation dryer (4).

Images