Through-Air Drying Cylinder Fabric Conditioning Loop
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Solution Overview
Problem
In papermaking machines using through-air drying (TAD), the permeability of the fabric is reduced due to fiber residue and chemicals, leading to uneven drying and potential web transfer issues, necessitating effective fabric conditioning to maintain fabric performance.
Innovation Solution
A drying section with rotatable through-air drying cylinders, a permeable fabric loop divided into web-carrying and conditioning parts, incorporating a cleaning section with showers, dewatering sections with suction devices, and an applicator for release agents, ensuring thorough removal of contaminants and efficient dewatering to maintain fabric permeability and facilitate web transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If through-air drying cylinders are used to dry the fibrous web, then drying efficiency is improved, but fabric permeability is reduced due to fiber residue and chemicals
Solution Approach 1:
The fabric is cleaned and dewatered before re-entering the drying section. The cleaning section removes fiber residue and chemicals from the fabric surface, and the dewatering section removes excess water, preparing the fabric to maintain its permeability during the drying process
Solution Approach 2:
The fabric loop creates a continuous cycle where the fabric is constantly being cleaned and dewatered as it passes through the conditioning section, ensuring that permeability is maintained throughout the drying process without interruption
2Reliability
If the fabric is cleaned to remove fiber residue, then fabric permeability is maintained, but additional equipment and process complexity are introduced
Solution Approach 1:
The cleaning section and dewatering section are combined into a single conditioning section that processes the fabric in sequence. The cleaning section with showers and the dewatering section with suction devices work together as an integrated system to maintain fabric permeability
Solution Approach 2:
The conditioning section serves multiple functions: it cleans the fabric surface, dewateres the fabric, and prepares it for re-entry into the drying section. This multi-functional approach consolidates several operations into one system
3Ease of operation
If the fabric is dewatered to remove excess water, then web transfer is facilitated, but energy consumption increases
Solution Approach 1:
The dewatering section uses suction devices that create negative pressure to draw water through the fabric. This pneumatic approach is more energy-efficient compared to mechanical pressing or heating methods, as it utilizes pressure differentials rather than mechanical force or thermal energy
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 effectively removes contaminants and water from the fabric, maintaining its permeability and ensuring uniform drying and proper web transfer, addressing the issues of reduced fabric performance and uneven drying.
Implementation Method 1
The dewatering section comprises one or several suction dewatering devices including but not limited to suction dewatering boxes and/or air knives
Implementation Method 2
a cleaning section that comprises at least one shower arranged to act on the fabric to wash away contaminants such as fibre residue and chemicals from the fabric
Implementation Method 3
a drying section of a paper making machine which drying section comprises one or more through air drying cylinders (TAD cylinders)... air (usually hot air) is blown or drawn through the fibrous web
Data Source
Figure 1
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AI summary
The invention relates to a drying section and comprises one or more through air drying cylinders 3, 5 and a permeable fabric 9 that runs in a loop and wraps part of the circumference of each through air drying cylinder. The loop of the fabric 9 is divided in a web-carrying part 10 and a conditioning part 11. The web-carrying part extends from a receiving point 12 to a transfer point 15 where a fibrous web is transferred to a further component. The conditioning part extends from the transfer point 15 to the receiving point 12. The conditioning part has a cleaning section 19 comprising a shower 20 to wash residue from the fabric. A dewatering section 21 is arranged to act on the fabric 9 after the cleaning section and comprises one or several suction dewatering devices 22. An applicator section 23 is arranged in the conditioning part 11 after the dewatering section. The applicator section comprises an applicator 24 for applying release agent on the fabric 9. The dewatering section 21 of the fabric loop comprises a substantially vertical run VR of the fabric which does not deviate more than 30˚ from a vertical plane and a suction dewatering device 22 is placed along the vertical run of the fabric 9 on the web-contacting side of the fabric 9. The dewatering section either comprises a further suction dewatering device placed along the vertical run of the fabric on the side of the fabric 9 that is opposite the web-contacting side or it has room for installing a further suction dewatering device of the same size as the suction dewatering device 22 that is located on the web-contacting side of the fabric.