Smoothing Press for Paper Web Surface Dewatering
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Solution Overview
Problem
Conventional web-forming machines face issues with surface densification and oil absorption reduction leading to degraded print quality, along with complications in maintaining symmetry and potential delamination when heating paper or board, which affects brightness, opacity, and drying efficiency.
Innovation Solution
A new arrangement combining a press nip and a smoothing press with a metal belt and steam-heated rolls, allowing efficient heating without delamination and improving surface smoothness for enhanced drying, featuring a long nip area with smooth heat-carrying means and adjustable heating to achieve high dry content without moisturizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a press nip is used to rapidly remove water from the web, then water removal efficiency is improved, but surface densification occurs and oil absorption reduction appears leading to degraded print quality
Solution Approach 1:
The press section is divided into multiple press nips with different functions. The first press nip (with press felt) removes water efficiently, while the second press nip (without press felt) provides a smoothing action that improves surface quality. This segmentation allows each press nip to optimize for its specific function rather than trying to do both simultaneously.
Solution Approach 2:
Different regions of the press section are given different qualities: the first press nip uses a press felt configuration suitable for water removal, while the second press nip operates without press felt to provide smoothing. This local differentiation of press nip characteristics allows simultaneous optimization of water removal and surface quality in different locations.
2Manufacturing precision
If a smoothing press with two rolls forming a nip is used to smooth both surfaces of the wet web, then surface smoothness is improved, but water is not removed from the web and heating causes water to turn to steam leading to delamination
Solution Approach 1:
Water removal is performed as a preliminary action in the first press nip before the web enters the smoothing press. By removing excess water beforehand, the web can subsequently be heated in the smoothing press without the risk of rapid steam generation that would cause delamination. The smoothing press then focuses solely on surface smoothing without the complicating factor of water removal.
3Use of energy by moving object
If conventional heating methods are used in the smoothing press, then heating efficiency is achieved, but water turns to steam with sudden heat impulse causing delamination and reducing brightness and opacity
Solution Approach 1:
Water removal is performed beforehand in the press section before the web reaches the smoothing press. This preliminary dehydration allows subsequent heating in the smoothing press to proceed without causing sudden steam generation, thereby maintaining web integrity and optical properties while still achieving efficient heating.
4Manufacturing precision
If complicated structures are used in the press section and smoothing press to maintain symmetry of both web surfaces, then surface symmetry is improved, but device complexity increases
Solution Approach 1:
The press section is segmented into two distinct press nips, each with a simple, well-defined function. The first press nip handles water removal with press felt, while the second press nip provides smoothing without press felt. This segmentation into functional modules achieves surface symmetry through a relatively simple and maintainable structure rather than a single complex system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in improved initial smoothness and stiffness of the paper or board, enabling efficient drying with reduced drying shrinkage and lower investment costs, while maintaining symmetry and surface properties, thus improving production capacity and product quality.
Implementation Method 1
smooth heat carrying means (14), such as a belt (14)... the web is heated efficiently without any risk of delamination
Implementation Method 2
at least one press nip for dewatering the web manufactured on a web-forming machine... Dry content of 60% or more enables smoothing with lower nip loads
Data Source
AI summary
The invention relates to an arrangement in connection with the press section of a web-forming machine. The arrangement includes at least one press nip for dewatering the web manufactured on a web-forming machine. The arrangement also includes a smoothing press including a smoothing roll arranged after the press nip. The smoothing press includes smooth heat carrying devices arranged as a loop around at least two guide rolls. The smoothing roll is arranged into contact with the devices between two guide rolls. The smoothing roll and/or at least one of the guide rolls is a steam heated drying cylinder or a steam heated roll modified thereof. The invention also relates to a board or paper produced in such arrangement.