A process and a machine for making a tissue paper web

摘要

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 2 and a Yankee drying cylinder 1 and in which the tissue paper web W is carried on a felt 3 through the extended nip N in such a way that, in the extended nip N, the tissue paper web W contacts the outer surface 4 of the Yankee drying cylinder 1. The web W and the felt 3 are led over a suction roll 5 prior to the extended nip N in such a way that the felt 3 contacts the suction roll 5 and the tissue paper web W is separated from the suction roll 5 by the felt 3. The suction roll 5 has a suction zone 6 over which the felt 3 and the tissue paper web W pass together, and a first hood 7 is arranged opposite the suction roll 5 and partially surrounds the suction roll 5. The first hood 7 has an extension around the suction roll such the first hood 7 covers the entire suction zone 6, and moist hot air is fed from the first hood 7 and sucked through the tissue paper web and the felt 3 by the suction roll 5. The tissue paper web W is directly exposed to the first hood 7 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 1 is covered by a second hood 8 which is a Yankee hood which has an air heating and distribution system 9 and hot exhaust air from the second hood 8 is fed through a conduit 10 to the first hood 7 and used to supply the first hood 7 with moist hot air. The moist hot air has a temperature in the range of 130 °C - 300 °C and a moisture content of 300 g/kg dry air - 1000 g/kg dry air at a rate of 90 - 130 m 3 /minute per square meter suction zone area. The moist air is then sucked through the tissue paper web W by the suction roll 5 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.