Metso Paper Inc.

Hannu Lätti

Antti Heikkinen

Pekka Linnonmaa

Markku Kyytsönen

Heikki Kettunen

Harri Kuosa

Markko Jaakkola

The moisture profile and/or moisture gradient of a paper web of at least SC quality paper is controlled in a paper machine comprising a calender () which has at least two roll stacks (), one stack has at least three rolls and another has at least five rolls. The web is moisturized to a desired pre-moisture content Mby a pre-moisturizer () before the calender. At least one intermediate moisturizer () is arranged between two roll stacks moisturizes the web to a desired intermediate moisture content Mbefore the last roll stack (), in which the web is dried to a desired final moisture value M. For continuously controlling and optimizing the moisture profile and/or moisture gradient of the web, the pre-moisturizing Wof the web is controlled by a pre-moisturizer () control parameter which corresponds to the final moisture value Mof the web.

Method, system and calendar for controlling the moisture profile and/or moisture gradient of a paper web, and a web

A paper web moistened in a paper machine and reeled on a machine reel is calendered in a multinip calender arranged apart from the paper machine, whose roll assembly is formed of a first set of rolls and a second set of rolls in the travel direction of the paper web. At least one surface of the paper web is moistened with at least one pre-moisturizer, whereafter the paper web is guided to the first calender nip of the first set of rolls and one surface of the paper web is moistened with at least one intermediate moisturizer, whereafter the paper web is guided to the first calender nip of the second set of rolls, wherein a paper web having a roughness of 1.0-1.1 &#x3bc;m and/or gloss of 54-57% or 56-60% is produced as a result of calendering.

Method and apparatus for producing calendered paper

A method for controlling the moisture profile of a paper web or board web processed in a heated multi-roll calendar to optimize the qualities of the paper or board, especially gloss. The method is characterized in that the moisture measurement is carried out both on either surface of the web and as a through-measurement, and the measurement results thus obtained are specified by a thermodynamic model which calculates the moisture of the web in three layers, and that the results thus obtained are used for controlling the supply of moisture to the web.

Method for controlling the moisture profile of a paper web

Tension variations in the paper web on a paper machine are caused by successive draws and moisture fluctuations. Good strength properties require optimization of the draws. In addition, the tension variation induced by moisture must be minimized. The analysis of local modulus and the strain components can be used for determining optimal locations for profiling actuators in order to achieve good tension profile. Longitudinal strain components of the web, i.e. reversible elastic strain, permanent plastic strain and frozen-in strain relievable with water are continuously measured and determined and the variation of said longitudinal components is minimized by correcting the moisture content of the paper web in a dryer section of the paper machine and/or by optimizing the draws between dryer groups in the dryer section.

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Järvenpää, Finland

Hannu Lätti