Methods for drying a paper web

Method for drying a paper web in a dryer section situated after a press section of a paper machine, in which dryer section the paper web is dried in a plurality of successive dryer groups with a single-wire draw, each of said dryer groups comprising contact-drying cylinders arranged in a first row, reversing suction cylinders arranged in a second row spaced from said first row of contact-drying cylinders and a drying wire for supporting the paper web in a run alternatingly in pressing contact with heated faces of each of said contact-drying cylinders and over an outside curve of one of said reversing suction cylinders situated between adjacent ones of said contact-drying cylinders, comprising the steps of:

• drying a first face of the web across the entire length of the dryer section by arranging said drying wire in each of said dryer groups to press the first face of the web against the heated faces of said contact-drying cylinders,
• providing a pressure difference extending over the entire inner circumference of said reversing suction cylinders, said pressure difference maintaining the web in constant contact with said drying wire in each of said dryer groups against the effect of centrifugal forces acting upon the web as the web runs on the outside curve of said reversing suction cylinders, and
• directing a liquid-containing medium at the first face of the web to control and equalize the moisture profile of the web in a cross-machine direction transverse to a running direction of the web, said medium comprising moist air and/or water mist.

Method for drying a paper web in a dryer section situated after a press section of a paper machine, in which dryer section the paper web is dried in a plurality of successive dryer groups with a single-wire draw, each of said dryer groups comprising contact-drying cylinders arranged in a first row, reversing suction cylinders or suction rolls arranged in a second row spaced from said first row of contact-drying cylinders and a drying wire for supporting the paper web in a run alternatingly in pressing contact with heated faces of each of said contact-drying cylinders and over an outside curve of one of said reversing suction cylinders situated between adjacent ones of said contact-drying cylinders, and wherein the web is held on the drying wire by a pressure difference against the effect of centrifugal forces when the web runs at the side of the outside curve on the drying wire, comprising the steps of:

• drying a first face of the web across the entire length of the dryer section by arranging said drying wire in each of said dryer groups to press the first face of the web against the heated faces of said contact-drying cylinders,
• drying a second face of the web opposite to said first face in at least one of said dryer groups by removing said drying wire from contact with the second face of the web to expose the second face on at least one draw of the web and blowing dry, hot air at the web on said at least one draw to intensify evaporation of water from the second face of the web and equalize the drying profile of the web in the direction of thickness of the web.

Method for drying a paper web in a dryer section situated after a press section of a paper machine, in which dryer section the paper web is dried in a plurality of successive dryer groups with a single-wire draw, each of said dryer groups comprising contact-drying cylinders arranged in a first row, reversing suction cylinders or suction rolls arranged in a second row spaced from said first row of contact-drying cylinders and a drying wire for supporting the paper web in a run alternatingly in pressing contact with heated faces of each of said contact-drying cylinders and over an outside curve of one of said reversing suction cylinders situated between adjacent ones of said contact-drying cylinders, and wherein the web is held on the drying wire by a pressure difference against the effect of centrifugal forces when the web runs at the side of the outside curve on the drying wire, comprising the steps of:

• drying a first face of the web across the entire length of the dryer section by arranging said drying wire in each of said dryer groups to press the first face of the web against the heated faces of said contact-drying cylinders,
• drying a second face of the web opposite to said first face in at least one of said dryer groups by at least one of
• removing said drying wire from contact with the second face of the web to expose the second face on at least one draw of the web;
• and
• applying a flow of drying air to the second face of the web through said drying wire;
• and
• removing said drying wire from contact with the second face of the web to expose the second face of the web on at least one draw of the web and applying a flow of drying air to the second face of the web on said at least one draw, and
• directing a liquid-containing medium onto the first face of the web when the web runs over said reversing suction cylinders to equalize the moisture profile of the web in the direction of thickness of the web, said medium comprising moist air and/or water mist.

Method for drying a paper web in a dryer section situated after a press section of a paper machine, in which dryer section the paper web is dried in a plurality of successive dryer groups with a single-wire draw, each of said dryer groups comprising contact-drying cylinders arranged in a first row, reversing suction cylinders or suction rolls arranged in a second row spaced from said first row of contact-drying cylinders and a drying wire for supporting the paper web in a run alternatingly in pressing contact with heated faces of each of said contact-drying cylinders and over an outside curve of one of said reversing suction cylinders situated between adjacent ones of said contact-drying cylinders, and wherein the web is held on the drying wire by a pressure difference against the effect of centrifugal forces when the web runs at the side of the outside curve on the drying wire, comprising the steps of:

• drying a first face of the web across the entire length of the dryer section by arranging said drying wire in each of said dryer groups to press the first face of the web against the heated faces of said contact-drying cylinders,
• drying a second face of the web opposite to said first second face in at least one of said dryer groups by at least one of
• removing said drying wire from contact with the second face of the web to expose the second face on at least one draw of the web;
• and
• applying a flow of drying air to the second face of the web through said drying wire;
• and
• removing said drying wire from contact with the second face of the web to expose the second face of the web on at least one draw of the web and applying a flow of drying air to the second face of the web on said at least one draw, and
• directing a liquid-containing medium at the first face of the paper web to control and equalize the moisture profile of the paper web in a cross-machine direction transverse to a running direction of the web, said medium comprising moist air and/or water mist.

Method for drying a paper web in a dryer section situated after a press section of a paper machine, in which dryer section the paper web is dried in a plurality of successive dryer groups with a single-wire draw, each of said dryer groups comprising contact-drying cylinders arranged in a first row, reversing suction cylinders or suction rolls arranged in a second row spaced from said first row of contact-drying cylinders and a drying wire for supporting the paper web in a run alternatingly in pressing contact with heated faces of each of said contact-drying cylinders and over an outside curve of one of said reversing suction cylinders situated between adjacent ones of said contact-drying cylinders, said first and second rows being horizontal, diagonal or vertical rows, and wherein the web is held on the drying wire by a pressure difference against the effect of centrifugal forces when the web runs at the side of the outside curve on the drying wire, comprising the steps of:

• drying a first face of the web across the entire length of the dryer section by arranging said drying wire in each of said dryer groups to press the first face of the web against the heated faces of said contact-drying cylinders,
• drying a second face of the web opposite said first face of the web in at least one of said dryer groups by removing said drying wire from contact with the second face of the web while the first face is in direct contact with one of said contact-drying cylinders in said at least one dryer group to expose the second face of the web on a sector of said one of said contact-drying cylinders and applying heat from a source other than said one of said contact-drying cylinders to the exposed second face of the web as the web runs over said sector of said one of said contact-drying cylinders.

Method for drying a paper web in a dryer section situated after a press section of a paper machine, in which dryer section the paper web is dried in a plurality of successive dryer groups with a single-wire draw, each of said dryer groups comprising contact-drying cylinders arranged in a first row, reversing suction cylinders arranged in a second row spaced from said first row of contact-drying cylinders and a drying wire for supporting the paper web in a run alternatingly in pressing contact with heated faces of each of said contact-drying cylinders and over an outside curve of one of said reversing suction cylinders situated between adjacent ones of said contact-drying cylinders, said first and second rows being horizontal, diagonal or vertical rows, comprising the steps of:

• drying a first face of the web across the entire length of the dryer section by arranging said drying wire in each of said dryer groups to press the first face of the web against the heated faces of said contact-drying cylinders,
• providing a pressure difference extending over the entire inner circumference of said reversing suction cylinders, said pressure difference maintaining the web in constant contact with said drying wire in each of said dryer groups against the effect of centrifugal forces acting upon the web as the web runs on the outside curve of said reversing suction cylinders, and directing a liquid-containing medium onto the first face of the web when the web runs over said reversing suction cylinders to equalize the moisture profile of the web in the direction of thickness of the web, said medium comprising moist air and/or water mist..