Patent ID: 6662468
Filing Date: 2003-12-16
Classification: D21F

Abstract:
A method of drying a paper web in a dryer section of a paper or board machine comprising the steps of:passing a paper web from a pressing section to a first cylinder drying group of the dryer section at a web velocity of at least 1000 meters per minute; wrapping a first heated dryer cylinder, having a dryer cylinder surface, with the web so that the web is in contact with the dryer cylinder surface, and simultaneously wrapping a drying wire to overlie and travel with the paper web; wrapping the web and the drying wire about a reversing roll positioned below the first drying cylinder, and below a second heated drying cylinder forming part of the first drying group of dryers, so that the drying wire is positioned against the reversing cylinder; wrapping the web and the drying wire about the second heated drying cylinder so that the drying wire overlies and travels with the paper web; positioning a runnability component within a pocket space defined between the first dryer, the second dryer, and the reversing roll; and in like manner wrapping at least three more heated dryer cylinders and two more reversing rolls to form at least three more pockets in which runnability components are positioned; operating the runnability components to draw an under-pressure of 1000 to 8000 Pa at selected areas defined where the web and drying wire leave each drying cylinder, and drawing an under-pressure of 100 to 500 Pa, on at least a part of a space defined by the pocket but excluding the selected areas defined where the web and drying wire leave each drying cylinder; drying the web on the first cylinder drying group of the dryer section until the solids content of the web is 50 to 60 percent; feeding a portion of the web to a broke conveyor, during threading of downstream drying groups, the broke conveyor being placed under the first cylinder drying group of the dryer section; and passing said portion of the web on the broke conveyor into a pulper of the pressing section.