Through-Air Drying Fabric Segmentation for Moisture Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional through-air drying methods struggle with non-uniform tissue webs, leading to variable moisture content and physical properties due to differences in airflow resistance caused by the supporting fabric, which amplifies existing differences or creates new ones during the drying process.
Innovation Solution
The use of at least two noncompressive through-air driers, each encircled by a separate fabric, allows for optimized drying performance and tissue product properties by adjusting airflow and temperature conditions between the driers, enabling more efficient drying and improved tissue web quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single fabric is used to support the tissue web during through-air drying, then the web is supported throughout the drying process, but the fabric creates differences in flow resistance that amplify moisture distribution differences and create non-uniform drying
Solution Approach 1:
The drying process is divided into multiple stages with different fabrics. The first fabric (molding fabric) has lower air permeability and is used for initial drying, while the second fabric (drying fabric) has higher air permeability and is used for final drying. This segmentation allows each fabric to be optimized for its specific function, preventing the single-fabric flow resistance problem from affecting the entire drying process.
Solution Approach 2:
The system dynamically transitions from one fabric to another during the drying process. The web is transferred from the first fabric to the second fabric at an intermediate moisture content level, allowing the airflow characteristics to change dynamically rather than being constrained by a single static fabric configuration.
2Productivity
If the fabric air permeability is increased to improve drying efficiency, then drying performance improves, but the fabric creates greater flow resistance differences that worsen non-uniform drying of non-uniform webs
Solution Approach 1:
Different regions of the drying process use fabrics with different air permeability characteristics. The first fabric provides lower permeability for controlled initial drying, while the second fabric provides higher permeability for efficient final drying. This local optimization allows high permeability to be used where it benefits productivity without compromising moisture uniformity in the overall web.
3Loss of time
If high temperature airflow is used to reduce drying time, then drying speed increases, but energy consumption increases and the fabric's flow resistance effects are amplified
Solution Approach 1:
The first fabric performs preliminary drying at lower temperatures to remove a portion of the moisture before the web is transferred to the second fabric. This preliminary action reduces the moisture load that would otherwise require high-temperature, high-energy processing in the final drying stage, thereby reducing overall energy consumption while maintaining efficient drying time.
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
This approach reduces the residence time and energy required for drying, enhances drying efficiency, and results in tissue webs with consistent moisture content and improved physical properties, addressing the challenges of non-uniform drying and fabric-induced airflow issues.
Implementation Method 1
Hot air flow passes through the web, then through the permeable fabric or vice versa. The air flow principally dries the embryonic web by evaporation.
Implementation Method 2
Because airflow directed towards the web is transferred through the supporting fabric during manufacture, the fabric itself creates differences in flow resistance through the tissue web.
Data Source
Figure 1
Figure 2
AI summary
Unlike conventional through-air drying processes the instant invention utilizes at least two through-air driers where the first dyer is at least partially encircled by a first through-air drying fabric and the second dyer is at least partially encircled by a second through-air drying fabric. By providing each through-air dryer with its own fabric the overall drying performance may be increased. Additionally, in certain embodiments, the first and second fabrics may be different to optimize both the drying performance and/or tissue product properties.