Patent ID: 6732453
Filing Date: 2004-05-11
Classification: D21F,Y02P

Abstract:
A method in a papermaking machine or the like for exhausting air and supplying air to a drying section covered with a hood, wherein the drying section has at least a plurality of drying cylinders wrapped by a web, the dryer section having a plurality of negative pressure devices operated by negative pressure which draw air from the vicinity of the web, and a plurality of first devices operated by positive pressure which first devices are runnability components which create negative pressure at desired points of the web, and a plurality of second devices operated by positive pressure which do not create negative pressure, the method comprising the steps of:drawing air by a first blower from the negative pressure devices which draw air from the vicinity of the web and exhausting all said air directly to a first heat recovery tower drawing substitute air by a second blower from the first heat recovery tower and discharging said air to the plurality of first devices operated by positive pressure, thereby creating a negative pressure at desired points of the web, the negative pressure attaching the web to a wire and stabilising its run; supplying by a third blower substitute air from a second separate heat recovery tower to the plurality of second devices operated by positive pressure; and drawing by a fourth blower between 20 percent and 60 percent of all air exhausted from an air space formed by the hood, said air being drawn directly from the hood, and not from the vicinity of the web, and exhausting said drawn air directly from the air space to the second separate heat recovery tower.