Advanced Dewatering System for Tissue Web Moisture Control
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Solution Overview
Problem
Conventional wet pressing methods and Through Air Drying (TAD) processes in paper manufacturing are inefficient and costly, with TAD systems requiring high capital and operational expenses and producing suboptimal moisture profiles, while existing advanced dewatering systems do not support high-speed operations effectively.
Innovation Solution
An Advanced Dewatering System (ADS) utilizing a permeable Extended Nip Press (ENP) belt with a spiral link fabric, applying pressure and negative pressure to dewater the web around a suction roll, enhancing airflow and mechanical pressing to achieve high dryness levels without compromising sheet quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Through Air Drying (TAD) process is used to achieve high dryness levels and high bulk, then web quality (bulk and water holding capacity) is improved, but capital cost and operational cost increase significantly
Solution Approach 1:
The dewatering process is segmented into multiple zones along the belt path: initial pressing zone, capillary dewatering zone through the felt, and final drying zone. This segmentation allows each zone to perform a specific function efficiently, achieving high bulk and water holding capacity without requiring the entire system to be as complex as TAD
Solution Approach 2:
A permeable felt acts as an intermediary medium between the web and the suction roll. The felt facilitates capillary dewatering by drawing water from the web through its porous structure, enabling efficient moisture removal while maintaining web bulk and quality without direct contact drying mechanisms
2Device complexity
If conventional wet pressing methods are used to dewater the web, then capital cost is reduced, but dewatering efficiency and achieved dryness level are insufficient
Solution Approach 1:
A suction roll creates a negative pressure field that draws water from the web through the permeable felt. This pneumatic mechanism significantly enhances dewatering efficiency compared to conventional mechanical pressing alone, achieving higher dryness levels without proportionally increasing capital cost
Solution Approach 2:
A permeable felt with controlled porosity is used as the press belt. The porous structure enables capillary action to draw water from the web while maintaining mechanical strength for pressing. The porosity is optimized to balance water removal efficiency with web quality preservation
3Duration of action of moving object
If impermeable ENP belt is used to extend pressing dwell time, then mechanical pressing efficiency is improved, but airflow through the web is blocked preventing effective dewatering
Solution Approach 1:
The press belt is made from a permeable felt material with controlled porosity instead of an impermeable solid belt. This allows air and water vapor to pass through the belt during the extended pressing dwell time, enabling simultaneous mechanical compression and pneumatic dewatering to occur without mutual interference
4Manufacturing precision
If TAD process dries the web to high dryness level before Yankee Cylinder, then web quality is improved, but energy consumption and operational expense increase
Solution Approach 1:
The system performs preliminary dewatering and drying actions before the web reaches the Yankee cylinder. The permeable felt and suction roll remove the bulk of moisture early in the process, so that subsequent Yankee drying only needs to handle residual moisture, significantly reducing energy consumption while maintaining final web quality
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 ADS enables higher machine speeds, achieves dryness levels comparable to TAD processes, reduces operational costs, and maintains high-quality tissue or hygiene paper production with improved bulk and water holding capacity.
Implementation Method 1
a permeable press fabric... a suction roll... to dewater the web
Implementation Method 2
applying pressure and negative pressure to dewater the web
Implementation Method 3
In a wet pressing operation, a fibrous web sheet is compressed at a press nip to the point where hydraulic pressure drives water out of the fibrous web
Implementation Method 4
enhancing airflow and mechanical pressing to achieve high dryness levels
Data Source
AI summary
System for drying a tissue or hygiene web. The system includes a permeable structured fabric carrying the web over a drying apparatus. A permeable dewatering fabric contacts the web and is guided over the drying apparatus. A mechanism is used to apply pressure to the permeable structured fabric, the web, and the permeable dewatering fabric at the drying apparatus. This Abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.