Method and Device for Applying a Material to a Moving Web

Abstract

In a method for applying a substance to a moving web (4) of a product, an air-vapor mixture is supplied to at least one nozzle (13) in which the substance is propelled by means of the air-vapor mixture as propellant in an application zone (32) on the web (4) is applied. Excess air-vapor mixture and excess material are removed from the application zone (32). In order to improve the energy efficiency of such a process, it is proposed that at least part of the excess air-steam mixture discharged from the application zone (32) be recycled and returned to at least one nozzle (13). In addition, a device (1) for carrying out the method described above is proposed.

Claims

1-11. (canceled)

12. A method for applying a substance to a moving web, the method comprising: supplying an air-vapor mixture to at least one nozzle; applying the substance through the at least one nozzle to the web in an application zone by the air-vapor mixture acting as a propellant; discharging excess air-vapor mixture and excess substance from the application zone; and recycling at least a first portion of the excess air-vapor mixture from the application zone and feeding the first portion of the excess air-vapor mixture back to the at least one nozzle.

13. The method according to claim 12, further comprising: dehumidifying the first portion of the air-vapor mixture through a cyclone or a mist eliminator during recycling.

14. The method according to claim 12, further comprising: dehumidifying a second portion of the excess air-vapor mixture through the cyclone; and discharging the second portion of the excess air-vapor mixture downstream of the cyclone into an ambient.

15. The method according to claim 14, further comprising: adding ambient air to the first portion of the excess air vapor mixture after discharging the second portion of the excess air-vapor mixture downstream of the cyclone into an ambient.

16. The method according to claim 15, further comprising: transferring heat energy from the second portion of the excess air-vapor mixture to the ambient air added to the first portion of the air vapor mixture downstream of the cyclone.

17. An apparatus for applying a substance to a moving web, the apparatus comprising: a first conduit that feeds an air-vapor mixture to at least one nozzle arranged in an enclosure that envelops an application zone; a propellant that is formed by the air-vapor mixture and applies the substance to the web in the application zone; a second conduit that discharges excess air-vapor mixture and excess substance from the application zone; a third conduit that feeds a first portion of the excess air-vapor mixture into the first conduit.

18. The apparatus according to claim 17, further comprising: a fourth conduit through which steam from a vapor source is introduced into the first portion of the excess air-vapor mixture, wherein the fourth conduit is arranged at the first conduit downstream of a junction of the third conduit and the first conduit.

19. Apparatus according to claim 17, wherein the excess air-vapor mixture is vacuum extracted by a side channel blower from the enclosure that envelops the application zone, and wherein the side channel blower is arranged downstream of a cyclone that separates water from the excess air-vapor mixture.

20. The apparatus according to claim 17, further comprising: a rotary compressor that compresses the first portion of the excess air-vapor mixture and that is arranged in the first conduit upstream of a junction of the first conduit and a sixth conduit.

21. The apparatus according to claim 20, further comprising: a mist eliminator that is arranged in the first conduit downstream of a junction of the third conduit and the first conduit; and a filter that is arranged in the first conduit downstream of the mist eliminator and upstream of the rotary compressor.

22. The apparatus according to claim 14, further comprising: a heat exchanger that extracts heat from a second portion of the excess air-vapor mixture, exhausts the second portion of the excess air vapor mixture into an ambient, wherein the heat exchanger transfers the heat to ambient air that is fed through a fourth conduit and the first conduit to the at least one nozzle.

Description

EMBODIMENT

[0021] The method according to the invention will be explained in more detail below with reference to an exemplary embodiment of a device for its implementation, which is illustrated in the drawing figure. The drawing figure shows a schematic process diagram which explains the procedure according to the invention.

[0022] A device 1 for applying a substance, namely a starch suspension, to a moving web 4 of a product, namely a paper web, has an enclosure 2 which, together with a web 4 moving in the direction of an arrow 3, defines an interior space 5. In the upper part of the drawing figure are both guide rollers. 6 as well as the web 4 of the paper and the housing 2 and an applicator 7 are shown in a cross-section, The housing 2 has a cuboid shape and extends over the entire width of the web 4 of the paper extending perpendicular to the plane of the drawing. Two longitudinal sides 8 and a narrow side 9 of the enclosure 2 form together a U, which is closed at an open side of the passing web 4 of the paper, so that a rectangle is formed in cross-section. The end faces of the housing 2 which are not visible in the drawing figure are also closed, so that the interior 5 of the housing 2, except for gap areas 10 between the paper-side ends of the longitudinal sides 8 and the web 4 of the paper, are hermetically closed.

[0023] Within the cuboid housing 2 is also the cuboid application device 7, which extends transversely to the direction of the web 4 of the paper above the entire web width. The application device 7 comprises a cuboidal housing 11, to the web 4 of the paper facing top 12 a plurality of vanes arranged in series behind one another 13 is arranged. The nozzles 13 are two-substance nozzles, to each of which a first line 14, an air-steam mixture, and above a further line 15, a starch suspension is fed, Serving as propellant air-vapor mixture is homogeneously mixed in the nozzles 13 with the starch suspension and sprayed uniformly on the facing top of the passing web 4 of the paper. The individual lines 14 for supplying in each case a nozzle 13 with air-steam mixture are supplied by a common manifold 16, which is led out of the housing 2 and connected to an air-steam mixture supply. Similarly, the individual lines 15 are connected to the power supply to a common starch manifold, not shown, which leads to a reservoir 33 for the starch suspension. To that

[0024] Reservoir 33 also performs a return line 34 for excess starch suspension, which drains from a sump area of the housing 2.

[0025] Via a second line 17, the excess air-vapor mixture from the interior 5 of the housing 2 is removed. The air-vapor mixture also contains a proportion of excess starch suspension and that of less than 1%, The temperature of the air-vapor mixture exiting the interior 5 of the enclosure 2, i.e. when entering the second line 17 is about 70 to 100 C., the relative humidity is about 80 to 100%.

[0026] The excess air-vapor mixture then passes into a cyclone 18, and is deposited in the water droplets. The air-steam mixture flows after the cyclone 18 through a process air fan 19, with which the required negative pressure for suction from the housing 2 is generated. When the air-vapor mixture from the process air fan 19 exits, it has a relative humidity of 80% to 100% and a temperature between 70 C. and 100 C.

[0027] At a branch 20, a partial volume flow of the air-steam mixture is then discharged via a fifth line 21. The proportion of this volume flow to the total volume flow in the second conduit 17 is about 15 to 20%. The other part of the air-steam mixture is fed via a third line 22 in the circulation. Not in the Circuit-guided, the fifth line 21 flowing part of the air-steam mixture passes before being discharged to the environment a heat exchanger 23, which is also integrated in a fourth line 24 and withdrawn by means of which the exhaust air flowing through the fifth line 21 their heat and fresh air, preferably outside air flowing in the fourth conduit 24, is transferred. At a junction 25, the current flowing through the fourth line 24 and the current flowing through the third line 22 combine with each other. After this junction 25, the relative humidity of the partially recycled and partially rejuvenated air-vapor mixture is about 85% to 100% and the temperature about 70 C. to 80 C. This mixing volume flow is now in one first line 26, which extends to the housing 2 located in the application device 7. The above-described mixing volume flow arrives at the passage of a mist eliminator 27 and a filter 28 into a rotary compressor 29. The relative humidity falls after the rotary compressor 29, since the temperature rises very high by the compression heat. At a further junction 30, the third line 26 and a sixth line 31 meet, being supplied by the latter pure steam at a temperature of 105%, i.e. a pressure of 1.2 bar (abs), from a steam generator or steam tank. By means of live steam and optionally condensate injection into a mixing chamber 35, the temperature of the created mixing volume flow behind junction 30 in the third conduit 26 is increased to about 95%. In this state, the partially recycled fresh air-vapor mixture mixed with preheated outside air and fresh live steam enters the collection tube 16 of the applicator and then mixes in the nozzles 13 with starch and is sprayed onto the web 4 of the paper.

LIST OF REFERENCE NUMBERS

[0028] 1 contraption

[0029] 2 housing

[0030] 3 arrow

[0031] 4 web

[0032] 5 Interior

[0033] 6 guide roller

[0034] 7 applicator

[0035] 8 long side

[0036] 9 narrow side

[0037] 10 gap region

[0038] 11 casing

[0039] 12 top

[0040] 13 jet

[0041] 14 line

[0042] 15 line

[0043] 16 manifold

[0044] 17 second line

[0045] 18 cyclone

[0046] 19 Side-channel blower

[0047] 20 branch

[0048] 21 fifth line

[0049] 22 third line

[0050] 23 heat exchangers

[0051] 24 fourth line

[0052] 25 junction

[0053] 26 first line

[0054] 27 Droplet

[0055] 28 filter

[0056] 29 Rotary compressor

[0057] 30 junction

[0058] 31 sixth iine

[0059] 32 application zone

[0060] 33 reservoir

[0061] 24 Return line

[0062] 35 mixing chamber