Valmet S.p.a.

Olli Jaakko Antero Saikkonen

Ingvar B Klerelid

Klavdij Lasic

Luca Moscatelli

Lorenzo Simeoni

Luigino Furlan

Ingvar Klerelid

The invention relates to a Yankee drying hood arrangement () which is shaped to be fitted over a Yankee drying cylinder () such that the drying hood arrangement () can cover a part () of the circular cylindrical surface () of a Yankee drying cylinder (). The Yankee drying hood arrangement () comprises a plurality of nozzle boxes () distributed equidistantly around an imaginary axis (X) such that, when the Yankee drying hood arrangement () is fitted over a Yankee drying cylinder (), the nozzle boxes () are spaced from the circular cylindrical surface () of the Yankee drying cylinder () but form a curved structure () that follows the outer contour of the circular cylindrical surface () of the Yankee drying cylinder (). Each nozzle box () has a longitudinal extension in a direction parallel to the axial extension of the Yankee drying cylinder () and each nozzle box () has openings () distributed along the longitudinal extension of the nozzle box () through which openings () a fluid such as hot air can exit the nozzle boxes () and stream towards the circular cylindrical surface () of the Yankee drying cylinder () at different points at different points along the axial extension of the Yankee drying cylinder (). The Yankee drying arrangement further comprises a plurality of distributor conduits () for a fluid such as hot air and the distributor conduits () extend in the circumferential direction around the curved structure () formed by the nozzle boxes (). Each distributor conduit () is in communication with several nozzle boxes () such that a fluid such as hot air can stream from each distributor conduit () to several different nozzle boxes (). At least one main supply conduit () for a fluid such as hot air is in communication with the distributor conduits () such that a fluid such as hot air can stream to the distributor conduits (). The distributor conduits () are oriented around the curved structure () of the nozzle boxes () in such a pattern that, when one and the same distributor conduit () communicates with different nozzle boxes (), it does so at different points along the longitudinal extension of the different nozzle boxes (). The invention also relates to a Yankee drying cylinder fitted with the inventive Yankee drying hood arrangement and to a method of drying a fibrous web.

Yankee drying hood arrangement, a yankee drying cylinder fitted with a yankee drying hood arrangement and a method of drying a fibrous web

The invention relates to a process and a machine for making a tissue paper web (W) in which the tissue paper web W is passed through an extended nip N formed between an extended nip unit () and a Yankee drying cylinder () and in which the tissue paper web W is carried on a felt () through the extended nip N in such a way that, in the extended nip N, the tissue paper web W contacts the outer surface () of the Yankee drying cylinder (). The web W and the felt () are led over a suction roll () prior to the extended nip N in such a way that the felt () contacts the suction roll () and the tissue paper web W is separated from the suction roll () by the felt (). The suction roll () has a suction zone () over which the felt () and the tissue paper web W pass together, and a first hood () is arranged opposite the suction roll () and partially surrounds the suction roll (). The first hood () has an extension around the suction roll such the first hood () covers the entire suction zone (), and moist hot air is fed from the first hood () and sucked through the tissue paper web and the felt () by the suction roll (). The tissue paper web W is directly exposed to the first hood () such that the moist hot air reaches the tissue paper web W without passing through a fabric before reaching the tissue paper web W. The Yankee drying cylinder () is covered by a second hood () which is a Yankee hood which has an air heating and distribution system () and hot exhaust air from the second hood () is fed through a conduit () to the first hood () and used to supply the first hood () with moist hot air. The moist hot air has a temperature in the range of 130&#xb0; C.-300&#xb0; C. and a moisture content of 300 g/kg dry air-1000 g/kg dry air at a rate of 90-130 m/minute per square meter suction zone area. The moist air is then sucked through the tissue paper web W by the suction roll () such that moisture condensates on the tissue paper web W and thereby raises the temperature of the tissue paper web W before the tissue paper web W passes through the extended nip N.

Process and a machine for making a tissue paper web

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Gorizia, Italy

Olli Jaakko Antero Saikkonen