Paper Drying Section Web Curl Control via Inverted Cylinder Contact
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Solution Overview
Problem
Dryer sections with single-tier dryer groups tend to cause fibrous webs to curl due to uneven drying, leading to production issues and increased risk of web damage during high-speed processing, especially at high basis weights.
Innovation Solution
Incorporating a last dryer group where the upper side of the fibrous web contacts heated drying cylinders, with a downward orientation of the drying cylinder row and a transfer device for efficient web guidance and removal, ensuring continuous support and minimizing curling tendencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-tier dryer groups are used to simplify construction and ease web removal, then device complexity is reduced and ease of operation is improved, but the fibrous web develops strong curling tendency due to uneven drying
Solution Approach 1:
The dryer section is divided into multiple single-tier dryer groups arranged in sequence, with the last group specifically configured to dry the upper side of the web. This segmentation allows each group to have a focused function while collectively solving the curling problem without requiring a complex multi-tier structure throughout.
Solution Approach 2:
Instead of having drying cylinders contact the underside of the web (conventional approach), the last dryer group is configured with drying cylinders that contact the upper side of the web. This inversion of the drying contact side balances the moisture distribution and eliminates the curling tendency caused by conventional single-tier drying.
2Shape
If the fibrous web is moistened to reduce curling tendency, then web shape stability is improved, but the drying result is impaired
Solution Approach 1:
The last dryer group is specifically designed to dry the upper side of the web before the web leaves the dryer section. This preliminary action of drying the upper side prevents curling development downstream without requiring intermediate moistening steps that would compromise drying efficiency.
3Shape
If two-tier dryer groups are used at the end of the dryer section to reduce curling, then web shape stability is improved, but device complexity and cost increase
Solution Approach 1:
Rather than making the entire dryer section complex with two-tier groups, the invention segments the solution by using simple single-tier groups for most of the drying section and only configures the last group differently to handle the upper side drying, achieving curl control with minimal added complexity.
4Productivity
If high-speed processing is implemented to increase productivity, then output is improved, but mechanical stress on the fibrous web increases and web damage risk increases
Solution Approach 1:
The drying belt continuously supports the web throughout the dryer section, including during high-speed operation. This constant support system allows the web to withstand mechanical stresses at high speeds without damage, enabling productivity increases while maintaining web integrity.
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
Significantly reduces web curling, improves web guidance, and facilitates easy removal of web remnants and dirt, enhancing production efficiency at high speeds and basis weights, while maintaining a simple and cost-effective structure.
Implementation Method 1
the upper side of the fibrous web comes into contact with the heated drying cylinders
Implementation Method 2
drying the upper side of the fibrous web, which has not been directly dried up to that point
Data Source
Figure 1
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AI summary
The invention relates to a drier section for drying a paper, cardboard, or other fiber material web (1) in a machine for producing the same, having at least two drying groups (7,8,9) wherein the fiber material web (1) is supported by an endless circulating drying belt (2) and guided alternately over heated drying cylinders (3) disposed in a row adjacent to each other and over guide rollers (4), wherein the drying belt (2) presses the fiber material web (1) against the jacket surface of the drying cylinder (3) and only one particular side of the fiber material web (1) comes into contact with the drying cylinders (3) in each of the drying groups (7,8,9). The curl of the fiber material web (1) should thereby be reduced in an improved manner with good web guidance, in that the upper side of the fiber material web (1) comes into contact with the heated drying cylinders (3) in the last drying group (9), and the lower side of the fiber material web (1) comes into contact with the heated drying cylinders (3) in all preceding drying groups (7,8), and the row of drying cylinders of the last drying group (9) runs downward in the running direction of the web (12).