Fibrous Web Formation Control via Charge Concentration Feedback
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Solution Overview
Problem
The formation of fibrous webs, such as paper or cardboard, is prone to fluctuations due to changes in raw material composition and basis weight, leading to instability in the water management system and requiring excessive energy and retention agents, which destabilizes the entire process.
Innovation Solution
Incorporating a charge concentration sensor to measure and control the charge concentration of the fibrous suspension as a controlled variable, allowing for targeted adjustments of manipulated variables like retention agent addition and vacuum levels to maintain formation stability at a predefined setpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If mechanical adjustment of the headbox lip opening is used to counter formation changes, then the basis weight can be kept constant, but the energy use increases and retention decreases
Solution Approach 1:
The patent implements automatic formation control using online formation measurements as feedback to dynamically adjust process parameters. The formation controller continuously monitors formation quality and automatically adjusts the headbox lip opening and retention agent addition, replacing manual mechanical adjustment with a closed-loop control system that optimizes energy use while maintaining basis weight stability
Solution Approach 2:
The patent changes the control approach by introducing charge concentration as an additional controlled variable alongside formation. By measuring and controlling charge concentration of the fibrous suspension, the system can adjust retention agent addition and vacuum levels to maintain formation stability without requiring excessive energy input or retention agent volumes
2Stability of the object's composition
If the lip opening is enlarged to improve formation, then the throughput volume increases, but the overall ash-retention decreases
Solution Approach 1:
The patent controls charge concentration as a key parameter to optimize the balance between formation quality and ash retention. By measuring charge concentration online and using it as a controlled variable, the system can adjust retention agent addition precisely, maintaining adequate ash retention even when lip opening is enlarged for improved formation and higher throughput
Solution Approach 2:
The automatic formation control system uses online measurements of both formation and charge concentration as feedback signals. This dual-parameter feedback enables the controller to make coordinated adjustments to lip opening and retention agent addition, improving formation while maintaining ash retention through optimized control rather than simple parameter enlargement
3Quantity of substance
If increased volumes of retention agents are added to compensate for retention loss, then the formation deteriorates due to stronger flocculation, but the retention is maintained
Solution Approach 1:
The patent introduces charge concentration as a new controlled variable to replace simple retention agent volume control. By measuring charge concentration online and using it as feedback, the system can precisely control the chemical state of the suspension, maintaining retention effectiveness at lower retention agent volumes and avoiding the flocculation problems that occur with excessive retention agent addition
Solution Approach 2:
The patent replaces mechanical/chemical trial-and-error adjustment of retention agent volumes with an automated control system based on online charge concentration measurements. This substitution of manual chemical dosing with instrumented control enables precise retention management that maintains formation quality while achieving required retention levels
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 stabilizes the formation of fibrous webs by enabling precise control of charge concentration, reducing the need for excessive retention agents and minimizing process fluctuations, thereby improving the efficiency and stability of the water management system.
Implementation Method 1
the charge concentration of the fibrous suspension forming the fibrous web is measured as a controlled variable
Implementation Method 2
the formation of the fibrous web is measured online as a controlled variable
Implementation Method 3
vacuums in the forming unit
Data Source
AI summary
A method regulating the formation of a fibrous web, such as a paper, cardboard, or tissue web, in which method the formation of the fibrous web is measured online as a controlled variable and is held at a predefinable setpoint level via automatic formation regulation. In addition to the formation, the charge concentration of the suspension is measured as a controlled variable and is taken into consideration during the formation regulation.