Multi-Stage Paper Web Rewetting for Uniform Moisture Uptake
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Solution Overview
Problem
Paper webs face challenges in re-moistening due to limited water absorption capacity, leading to defects like wrinkling and roping during processing and winding, which are not adequately addressed by existing methods.
Innovation Solution
A multi-stage re-moistening process involving pre- and secondary wetting stages with a wetting agent, utilizing a minimum residence time to enhance absorption rates, allowing for increased moisture reintroduction without excess wetting agent accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-stage re-moistening process is used, then the process is simple and quick, but the paper web cannot absorb sufficient moisture leading to defects
Solution Approach 1:
The re-moistening process is divided into multiple stages: a first re-moistening stage applies initial moisture to the paper web, followed by a second re-moistening stage that applies additional moisture after a residence time has elapsed. This segmentation allows the paper to absorb moisture more effectively in increments rather than attempting to absorb all required moisture in a single application, thereby resolving the contradiction between absorption capacity and process complexity.
Solution Approach 2:
The first re-moistening stage performs preliminary moistening of the paper web before the second stage. This preliminary action prepares the paper structure to receive and absorb subsequent moisture applications more effectively, allowing greater total moisture uptake without requiring an overly complex single-stage process.
2Quantity of substance
If excessive wetting agent is applied to achieve high moisture content, then moisture absorption increases, but defects like wrinkling and roping occur
Solution Approach 1:
The total wetting agent application is segmented into two separate stages with different quantities. The first stage applies a controlled initial amount, and the second stage applies an additional amount after the paper has had time to absorb the first application. This prevents the paper from becoming oversaturated in one location, thereby avoiding wrinkles and roping while still achieving the desired high moisture content.
Solution Approach 2:
The re-moistening process uses periodic application of wetting agent rather than continuous or single application. The paper web is allowed to reside and absorb moisture between applications, creating a periodic rhythm of wetting and absorption that ensures uniform moisture distribution throughout the web, preventing localized oversaturation that causes defects.
3Productivity
If the paper web is processed quickly through the system, then productivity is high, but insufficient moisture absorption occurs
Solution Approach 1:
The system implements periodic re-moistening stages separated by residence time intervals. During these intervals, the paper web moves through the system at normal speed but is temporarily held in a re-moistening zone where moisture is applied and absorbed. This periodic approach allows sufficient absorption time to be embedded within the continuous production flow, maintaining high overall productivity while ensuring adequate moisture uptake.
Solution Approach 2:
The multi-stage re-moistening process ensures continuous moisture absorption action throughout the paper web's journey. Rather than interrupting production for separate wetting operations, the system continuously applies and re-applies moisture in staged fashion as the web moves through, ensuring absorption occurs throughout the entire processing sequence without sacrificing productivity.
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 multi-stage process significantly enhances moisture absorption, reducing defects and ensuring uniform moisture distribution, enabling high machine dynamics and precise processing of paper webs.
Implementation Method 1
a pre-moistened web subsequently absorbs further moisture significantly better than a web that is not pre-moistened
Implementation Method 2
the web is pre-humidified with a first humidification unit and then, after a minimum residence time, by re-humidifying the web with a second humidification unit
Data Source
Figure 1~2
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Figure 4
AI summary
A method is specified, for rewetting a web (4) made from paper, wherein the web (4) is guided through a plant (2), wherein the plant (2) comprises a processing unit (10), by way of which the web (4) is processed, wherein, downstream of the processing unit (10), the plant (2) comprises a drying unit (12), for drying the web (4), wherein, downstream of the drying unit (12), the plant (2) comprises a plurality of wetting units (18, 20), by means of which the web (4) is rewetted in multiple stages using a wetting agent, by pre-wetting of the web (4) taking place by way of a first one of the wetting units (18), and post-wetting of the web (4) taking place after a minimum dwell time (T) by way of a second one of the wetting units (20), wherein the minimum dwell time (T) is selected in such a way that the web (4) has an increased absorption speed for the wetting agent in the second wetting unit (20) on account of the pre-wetting. Furthermore, a plant (2) is specified, for processing a web (4) made from paper.