Valmet Paper Machinery Inc.

Valmet Corporation

Ilkka Jokioinen

Pertti Heikkila

Raimo Rajala

Antti Kuhasalo

Antti I Ilmarinen

Heikki Ilvespaa

Jouko Yli-Kauppila

Mikko Karvinen

Vaino Sailas

Bertel Karlstedt

Matti Korpela

Pekka Taskinen

Henrik Petterson

Reijo Ruottu

Dick Parker

Sture Ahlskog

Jukka Parvinen

A method and device for drying a paper web wherein the paper web is supported on a drying wire without long open draws of the web. The paper web is contact-dried by pressing it with the drying wire onto a face of a contact-drying cylinder whose diameter is greater than about 1.5 m on a sector b whose magnitude is greater than about 180.degree.. The web is evaporation-dried as blowing-on drying and/or as through-drying by means of high-velocity drying-gas jets applied to the web on the drying wire on the face of the following large-diameter cylinder whose diameter is greater than about 2 m on a sector a having a magnitude greater than about 180.degree. while the web is on the side of the outside curve. The web to be dried is passed over a sector c of the suction roll which is subjected to negative pressure while the web is supported on the drying wire at the side of the outside curve. The magnitude of the sector of the suction roll has a magnitude greater than about 160.degree. and the diameter of the suction roll is less than the diameter of the contact-drying cylinder.

Drying method and drying module as well as dryer sections that make use

The invention relates to a method for air-drying material webs, in particular material webs of relatively high grammage such as pulp webs. The invention also relates to a nozzle-blow-box and a pulp dryer that make use of the method. Air blowings in a direction substantially perpendicular to the web and air blowings in a direction substantially parallel to the plane of the web are applied to the web to be dried from underneath the web. By means of these blowings, both heat is transferred to the web and the web is supported by the air free of contact, and the run of the web through the dryer is stabilized. In order to improve the transfer of heat in comparison with a planar carrier face, the air flow velocity parallel to the plane of the web is initially kept substantially invariable. The air flow velocity is lowered in the lateral areas of the carrier face by employing lateral areas of the nozzle-carrier face that become rampwise and/or stepwise lower in the air-flow direction.

Method in contact-free air-drying of a material web as well as a

A device for contact-free supporting, turning, and spreading of a paper web, comprises a face (K) curved in accordance with the turning of the web (W), in connection with which face (K) the web (W) runs supported by air blown in between the face (K) and the web (W). The nozzle members in the device comprise guide faces (28a, 28b) and carrier faces (27, 37) placed in connection with the guide faces, air being blown through nozzle slots (26a,26b,36) in the nozzle members, transverse to the direction of running of the web (W), onto the carrier faces (27,37). The nozzle slots (26a,26b,36) are, from one side, defined by the guide faces (28,28b,38). The air-supported face (K) in the device is defined by carrier faces (27,37) substantially parallel to the run of the web (W) to be supported, provided at float-nozzle boxes (20) and at foil-nozzle boxes (30). In the direction of running of the web (W), the first nozzle box and the last nozzle box are float-nozzle boxes (20), in which the nozzles (26a,26b) that flow (F.sub.1) against each other produce pressurized carrier faces (K+). Between the float-nozzle boxes (20), there are one or several foil-nozzle boxes (30). Between the nozzle boxes (20,30), there are pressure equalization pockets (18).

Device for supporting, turning and spreading of a web

Apparatus for drying a moving web includes a first infrared dryer unit having a first infrared treatment gap, a gas-support unit situated substantially immediately after the first infrared dryer unit and having a gas-support unit gap into which web-supporting gas blowings are directed, and a second infrared dryer unit situated after the gas-support unit and having a second infrared treatment gap. The gas-support gap has a width which is less than the width of the first infrared gap and the width of the second infrared treatment gap is less than the width of the first infrared treatment gap and greater than the width of the gas-support gap. In accordance with the method, the web is passed through the first infrared treatment gap so that upon exiting from the gap, its temperature has preferably been raised only to a point where evaporation of water from the web is imminent but has not begun, whereupon the web is passed through the gas-support gap in which web-supporting gas blowings, preferably heated, are directed in regions of both sides of the web, whereupon the web is passed through the second infrared treatment gap where evaporative drying is accomplished.

Method and apparatus for drying a moving web

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Lieto, Finland

Ilkka Jokioinen