Long Fine Mesh Wire for Nanofibrillated Cellulose Web Detachment
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Solution Overview
Problem
The use of nanofibrillated cellulose in papermaking is limited by its gel-like consistency, slow water removal, strong adherence to wire, low internal strength, and high drying shrinkage, leading to inefficient web detachment and reduced machine running speeds.
Innovation Solution
The method involves supporting the web with a long, fine mesh wire continuously from formation to the drying section, allowing for increased dry matter content and reduced drying shrinkage, enabling detachment without breaking and maintaining web integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nanofibrillated cellulose is added to the pulp suspension to achieve high content in the product, then the tensile strength and surface properties are improved, but the web adherence to wire increases and internal strength decreases
Solution Approach 1:
The patent changes the physical-chemical parameters of the nanofibrillated cellulose suspension by adjusting consistency, pH, and chemical composition to optimize the balance between achieving high tensile strength and maintaining sufficient web detachment reliability from the wire
Solution Approach 2:
The patent applies different treatments to different parts of the web formation process, using specific wire coatings or surface treatments in contact zones while maintaining high NFC content in the bulk material, thereby achieving local optimization of both strength and detachment properties
2Productivity
If the web is detached from the wire at early stage with low dry matter content, then the process speed is maintained, but the web breaks due to low internal strength
Solution Approach 1:
The patent applies preliminary strengthening treatments to the web before detachment, such as pre-drying zones or chemical strengthening agents, that enhance internal strength in advance without significantly reducing machine speed, allowing reliable detachment at lower dry matter content
3Strength
If dewatering is performed to increase dry matter content before detachment, then web strength is improved, but the process time increases and productivity decreases
Solution Approach 1:
The patent implements accelerated dewatering methods that rapidly increase dry matter content through enhanced drainage systems or pressure gradients, allowing the web to reach sufficient strength for detachment in reduced time, thereby maintaining productivity while improving web strength
4Device complexity
If a coarse wire is used for web formation, then the device complexity is reduced, but the retention degree of nanofibrillated cellulose decreases
Solution Approach 1:
The patent introduces intermediary substances such as retention aids or surface modifiers that facilitate the adhesion of nanofibrillated cellulose to coarse wire structures, enabling effective retention without requiring fine mesh wires, thus maintaining device simplicity while improving retention degree
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 allows for higher nanofibrillated cellulose content in the product, reduces web breaks, and controls drying shrinkage, enhancing the efficiency and cost-effectiveness of the papermaking process.
Implementation Method 1
The relative proportion of the surface of a piece with respect to the volume of the piece increases when the piece becomes smaller
Implementation Method 2
supporting said web with a long, fine mesh wire continuously from formation to at least the drying section
Implementation Method 3
nanofibrillated cellulose sticks easily to the wire used, because small particles of nanofibrillated cellulose adhere particularly strongly to the wire cloth
Implementation Method 4
The fibrous web tends to shrink when it dries
Implementation Method 5
the drying shrinkage takes place when the web dries
Data Source
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Figure 2
AI summary
The present invention relates to a method and system for producing fibrous material. In the method, fibrous suspension is supplied onto a wire in such a way that a web is formed and the formed web is dried. Further in the method, after the web formation, the web is kept at least partly in contact with said long wire continuously until the dry matter content of the web exceeds a predetermined limit value, in any case at least to the press section. A system for producing fibrous material in a web forming machine comprises fastening members for placing a wire in said machine in such a way that the wire runs continuously from at least the web forming section substantially to the press section.