Multilayer Fiber Web Headbox Dilution Control
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Solution Overview
Problem
Existing methods for optimizing the cross-directional strength properties of multilayer fiber webs, such as those used in liner machines, face challenges in achieving even strength profiles without excessive raw material usage, as they often require complex headbox designs and adjustments that can lead to increased costs and material loss.
Innovation Solution
The method involves using two or more headboxes with parallel feed zones to feed stock suspensions with different properties, where the basis weight profile is adjusted by dilution water in the cross direction, allowing for independent adjustment of dilution in each stock suspension to achieve an even cross-directional basis weight and strength profile across the fiber web.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the basis weight of the fiber web is increased on the edges to improve cross-directional strength, then the strength of the edge rolls is improved, but expensive raw material is lost when the required basis weight is exceeded
Solution Approach 1:
The patent applies local quality by varying the fiber composition in different zones of the headbox. Specifically, the edges of the fiber web receive a higher proportion of long fibers (which provide strength) while the center receives a higher proportion of short fibers. This is achieved by dividing the headbox into multiple feed zones and controlling the distribution of different fiber fractions to specific zones, thereby optimizing strength where needed without wasting material across the entire web.
Solution Approach 2:
The patent changes the compositional parameters of the stock suspension in different zones of the headbox. By adjusting the ratio of long fibers to short fibers in each feed zone, the system optimizes the strength properties of the edge rolls while controlling material usage. The parameter change involves controlling the consistency and fiber length distribution in specific cross-directional zones rather than using a uniform composition throughout.
2Strength
If different fiber fractions are mixed in the headbox to achieve even strength profile, then the cross-directional strength is optimized, but the headbox design becomes complicated and the adjustment system becomes complex
Solution Approach 1:
The patent segments the headbox into multiple parallel feed zones that operate independently. Each feed zone has its own control system for regulating the flow of different fiber fractions. This segmentation allows for simplified control of fiber distribution - each zone can be adjusted independently to achieve the desired strength profile without requiring a complex integrated mixing system throughout the entire headbox.
Solution Approach 2:
The patent performs preliminary action by pre-separating and pre-positioning different fiber fractions before they enter the forming section. The fiber suspension is prepared with distinct long fiber and short fiber fractions that are routed to specific feed zones in advance. This preliminary arrangement of fibers according to their intended location simplifies the overall headbox design by eliminating the need for complex in-situ mixing mechanisms.
3Strength
If the headbox is divided into parallel feed zones with different stock suspensions to optimize edge strength, then the cross-directional strength profile is improved, but the system complexity and adjustment difficulty increase
Solution Approach 1:
The patent simplifies operation by focusing on controlling a single key parameter - the ratio of long fibers to short fibers in each feed zone - rather than managing multiple complex variables. Each feed zone's adjustment mechanism is designed to control this primary parameter independently, making the system easier to operate. The parameter change approach allows operators to achieve desired strength profiles by adjusting fiber ratio settings in each zone without needing to coordinate multiple interdependent variables.
Data Source
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AI summary
The invention relates to a method for the optimization of the properties of a multilayer fiber web (10) in the manufacture of a fiber web (10), in which method the multilayer fiber web (10) is formed by feeding at least two stock suspensions that form a layer (16) of the fiber web (10) to a forming section (50) from two or more headboxes (12) divided into parallel feed zones (18), where those properties of said stock suspensions that affect the strength of the finished fiber web differ from each other, and the basis weight profile of said stock suspensions is adjusted in two or more headboxes (12) by feeding dilution water in zones in the cross direction of the fiber web machine into each stock suspension. In the method, the cross-directional basis weight profile and strength of the formed fiber web (10) are adjusted in the cross direction of the fiber web machine by adjusting the amount of dilution water in zones separately in each stock suspension fed. The invention also relates to a corresponding system.