US 6,584,703 B1Granted

Method for controlling the moisture of a web in machine direction on a coating machine and calender

AssigneeMetso Paper, Inc.

InventorsTapio Mäenp{umlaut over (aa)}, Vesa Ijäs

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Abstract

The invention relates to a method by means of which the machine-direction moisture of a web being calendered or coated and calendered can be controlled in an optimal manner that takes into account moisture content changes along the entire path of the coating and drying process. Advantageously, all the dryers and the calender of the coater section are controlled in an integrated manner in order to obtain a controlledly processed product which is optimized in regard to energy consumption and product quality. Each process section and unit contributing to the drying of the web is identified by means of a mathematical submodel describing the specific evaporation rate in the respective process section/unit and, by chaining these submodels, a composite model is compiled for the entire process, whereby the composite model makes it possible to manage the drying operation in the process so that the individual units are controlled as a portion of the overall process. In its simplest form, the composite model of the overall process comprises a submodel describing the behavior of the calender and at least one partial submodel describing the web processing unit preceding the calender.

Claims32

Dependent claims

A method for controlling a drying effect of an equipment layout used in making a calendered web of paper or board, the equipment layout comprising at least one calender unit and at least one web-processing unit preceding the at least one calender unit, the method comprising:

processing a web on at least one web-processing unit capable of affecting a moisture content of the web;
passing the web directly from the at least one web-processing unit to the calender unit;
calendering the web on the calender unit;
compiling, for each unit of the equipment layout wherein the moisture content of the web changes, an evaporation rate submodel capable of describing an amount of moisture change during web travel within the respective unit of the equipment layout, wherein at least one evaporation rate submodel is linked into a composite evaporation rate model;
determining a needed overall moisture evaporation effect of the equipment layout;
determining, by employing the composite evaporation rate model, a needed moisture evaporation effect for each unit of the equipment layout that is controllable in terms of a moisture evaporation rate;
and
controlling the moisture evaporation rate for each controllable unit of the equipment layout in accordance with the determined needed moisture evaporation effect.

5 more elements

Dependencies are inferred from the claim text.