Assembly for the extraction of water from a wet paper web has a rotating press surface with grooves, and an air flow through the groove recesses to strip away surface water to set the web moisture content profile

摘要

To extract water from a wet paper web, a grooved rotating press surface is used as the mantle of a rotating press roller or a press belt at a papermaking machine. An air flow is generated within the recesses of the press surface, which carries out any water which has not spun away, to strip surface water from the press surface. To extract water from a wet paper web, at a papermaking machine, the air flow at the press surface is formed at least partially by an underpressure or an overpressure. The air flow at the press surface is adjusted to set the lateral moisture profile, by altering the air flow volume and/or the air flow speed over the press surface width. A suction slit is formed between two bars, across the running direction of the press surface, to generate an underpressure at the press surface. The trailing bar in the running direction is in contact with the press surface and the leading bar is at a gap from the press surface of 0.2-1.0 mm. Both bars can be in contact with the press surface, with at least one of them pressed home against it by at least one air hose, and at least one air hose can be used to lift a bar clear of the press surface. The trailing bar can have a scraper blade, pressed against the press surface. The bar to be pressed against the press surface is of plastics. The water extraction from the grooves is supported by at least one blowing or suction pipe, and the water film in the recesses is destroyed before reaching the blowing or suction zone, using a needle scraper or an angled plate set at the press surface by an underpressure or overpressure. The grooves in the press surface are expanded by drillings and/or walls out of parallel at regular or irregular intervals. An Independent claim is included for an assembly (10) to extract water from a wet paper web, with a rotating press surface (14) fitted with grooves (12) on a press roller (16) or belt at a papermaking machine. An air flow (22) is generated within the groove recesses, and a scraper (20) strips away any surface water. Preferred Features: Bars (18,20), across the direction of roller rotation (L), form a suction slit (24) between them, with an underpressure. Stripped water and spray water are deflected towards a suction tube for extraction through a gutter.