Valmet Corporation

Valmet Paper Machinery Inc.

Jouko Yli-Kauppila

Reima Kerttula

Antti Kuhasalo

Antti I Ilmarinen

Heikki Ilvespaa

Pertti Heikkila

Mikko Karvinen

Pekka Taskinen

Matti Korpela

Henrik Petterson

Dick Parker

Allan Liedes

Vaino Sailas

Ville Korhonen

Ilkka Jokioinen

Iikka Jokioinen

Mikko Siiteri

Va/ Ino/ Sailas

A method and device for drying a paper web in a dryer section having a number of successive dryer groups with a single-wire draw, and being situated after a press section of the paper machine. Each dryer group includes contact-drying cylinders arranged in a first row and reversing suction cylinders or equivalent suction rolls arranged in a second row, the rows being horizontal, diagonal or vertical rows. The paper web is dried by contact-drying cylinders from the side of its lower face across the entire length of the dryer section. The paper web is passed as a closed draw from one dryer group to the next group, and the paper web is guided, while it runs on the drying wire at the side of the outside curve, by the reversing suction cylinders having a curve radius selected in a range from about 250 mm to about 1000 mm. The paper web is kept in constant contact with the drying wire as it is placed at the side of the outside curve, against the effect of centrifugal forces by a pressure difference which preferably extends over the entire inner circumference of the reversing suction cylinders. In addition to the above, or as an alternative, the paper web is dried from the side of its upper face on a draw or draws of the paper web that is/are free from the wire and/or a flow of drying air is applied to the upper face of the paper web through the drying wire and/or on the draws of the paper web that are free from the wire.

Paper machine and methods for drying a paper web

Dryer sections of a paper machine

A method and device for contact drying a paper web, wherein the paper web is dried initially in a number of successive groups with single-wire draw by pressing the paper web via drying wires of each groups against the heated faces of the drying cylinders and by guiding the paper web on support of the same drying wire from one drying cylinder onto the next drying cylinder over the reversing suction cylinders or rolls in each group with single-wire draw. In the groups with single-wire draw, the paper web is dried to a first dry solids content, after which the paper web is dried directly further by a single group with twin-wire draw to a second dry solids content, after which the paper web is dried further to its final dry solids content by a single normal group with single-wire draw. The limits of the first and second dry solids contents are selected so that, in the middle or in the beginning of the range, the tear strength index and the breaking strength index of the web are at their maximum.

Method for drying a paper web

Dryer section of a paper machine

A method and device for drying a paper web wherein the paper web is supported on a drying wire without long open draws of the web. The paper web is contact-dried by pressing it with the drying wire onto a face of a contact-drying cylinder whose diameter is greater than about 1.5 m on a sector b whose magnitude is greater than about 180.degree.. The web is evaporation-dried as blowing-on drying and/or as through-drying by means of high-velocity drying-gas jets applied to the web on the drying wire on the face of the following large-diameter cylinder whose diameter is greater than about 2 m on a sector a having a magnitude greater than about 180.degree. while the web is on the side of the outside curve. The web to be dried is passed over a sector c of the suction roll which is subjected to negative pressure while the web is supported on the drying wire at the side of the outside curve. The magnitude of the sector of the suction roll has a magnitude greater than about 160.degree. and the diameter of the suction roll is less than the diameter of the contact-drying cylinder.

Drying method and drying module as well as dryer sections that make use

Methods for drying a paper web

A dryer section of a paper machine including cylinder groups provided with single-wire draw having smooth-faced heated drying cylinders against which a web to be dried enters into direct contact, and reversing rolls. The groups with single-wire draw have a drying wire which is guided in a loop by guide rolls as well as by the drying cylinders and the reversing rolls so that the drying cylinders are placed outside the wire loop, and the reversing rolls are situated in gaps between the drying cylinders inside the drying-wire loop. In order to optimize the drying capacity calculated per unit of length of the dryer section in the machine direction, as the drying makes progress, a different ratio of the drying cylinder diameter to the reversing roll diameter is employed, so that, in the first group or groups in the initial end of the dryer section, the ratio is higher than the corresponding ratio in the groups in the middle area of the dryer section. In the group or groups in the final end of the dryer section, a diameter ratio is used that is higher than the ratio in the middle area of the dryer section.

Dryer section of a paper machine including cylinder groups with

Drying module and dryer sections that make use of same, in particular

Dryer section of a paper machine having so-called normal drying groups with a single-wire draw, heated contact drying cylinders arranged in an upper row and leading cylinders or rolls arranged in a lower row. At least one drying module is arranged between and/or inside the normal drying groups and in which the opposite side of the web, in relation to the side of the web placed against the contact-drying cylinders, is placed against the heated cylinder face of a single large drying cylinder or cylinders in the drying module. The web is placed in direct contact against the heated cylinder face of the large drying cylinders. The drying module includes a separate loop of a drying wire which guides the web and presses its opposite side against the heated face of the large cylinders over a sector which is greater than about 180.degree.. The diameter of the large drying cylinder(s) is larger than the diameter of the contact drying cylinders in the normal drying groups.

A dryer section in a paper machine for drying a paper web, having normal dryer groups with a single-wire draw in which drying cylinders are arranged in an upper row and reversing cylinders in a lower row. The dryer section has at least one inverted dryer groups in which drying cylinders are arranged in a lower row and reversing cylinders are arranged in an upper row. In view of making the dryer section more compact, intensifying the evaporation, reducing the transverse shrinkage of the web, and/or improving the runnability of the web, the drying cylinder and/or the reversing cylinder or roll placed in connection with the transfer over the gap between the groups is/are placed so that its/their height position is displaced as compared with the other cylinders in the same group. In an inverted group, an upper reversing cylinder is arranged in connection with blower devices for drying air for the web. The blowings directed from the blower devices increase the evaporation from the web and/or control the transverse moisture profile in the web.

Dryer section in a paper machine

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Muurame, Finland

Jouko Yli-Kauppila