High Yield Fiber Blend Pulping Process
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Solution Overview
Problem
Current wood pulping processes face challenges in achieving a significant yield increase while maintaining high strength and stiffness in paperboard, with conventional methods only achieving 2-5% yield improvement and resulting in higher raw material and production costs due to increased basis weight requirements.
Innovation Solution
A novel pulping process involving chemical pulping to high kappa numbers, followed by mechanical processing of rejects to enhance fiber strength and stiffness, allowing for a higher rejects component integration back into the pulping process, resulting in a fiber blend that improves paperboard stiffness and strength at lower basis weights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If chemical pulping is used to remove lignin, then pulp strength and bleachability are improved, but yield is reduced to 45-53%
Solution Approach 1:
The invention segments the pulping process into two distinct stages: a chemical pulping stage to separate lignin and achieve high strength/bleachability, and a mechanical pulping stage to process rejects and maximize yield. This segmentation allows each stage to optimize for its specific function, resolving the contradiction between strength and yield.
Solution Approach 2:
The invention recovers and reprocesses the rejects from chemical pulping (which would normally be discarded) through mechanical pulping. This recovery process transforms low-value rejects into usable pulp fiber, significantly improving overall yield while maintaining the quality benefits of the original chemical pulping.
2Productivity
If mechanical pulping is used to separate pulp fibers, then yield is high (85-98%), but fiber strength is poor
Solution Approach 1:
The process is segmented into chemical pulping first (to achieve strength and remove lignin), followed by mechanical pulping of the rejects (to maximize yield). This reversal and segmentation allows each process to operate in its optimal performance range.
Solution Approach 2:
The final pulp product is a composite blend combining high-strength fibers from chemical pulping with high-yield fibers from mechanical pulping of rejects. This composite approach leverages the strengths of both processes to achieve both high strength and high yield.
3Productivity
If rejects are recooked in the digester, then fiber yield is extremely low, but this is the only way to process rejects
Solution Approach 1:
The invention replaces chemical cooking (thermal-chemical process) with mechanical pulping for reject processing. This substitution allows the rejects to be processed mechanically rather than chemically, dramatically improving fiber yield while maintaining effective reject processing.
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 process achieves an 8-20% yield increase over conventional methods, providing paperboard with enhanced stiffness and strength at reduced basis weights, comparable to multi-ply boards but with the economic benefits of single-ply production, and maintains tear and tensile strength.
Implementation Method 1
Chemical pulping reacts wood chips with chemicals under pressure and temperature to remove lignin that binds pulp fibers together
Implementation Method 2
Mechanical pulping primarily uses mechanical energy to separate pulp fibers from wood without a substantial removal of lignin
Implementation Method 3
Thermomechanical pulping (TMP) grinds wood pulps under steam at high pressures and temperatures
Implementation Method 4
hydrogen peroxide as an impregnation chemical and as a chemical directly applied to a high consistency refiner treatment for CTMP pulping
Data Source
AI summary
The present disclosure relates to producing paper or paperboard having improved stiffness and strength, compared to the conventional paperboard at the same basis weight. It also discloses a method of wood pulping having a significantly increased yield and providing fiber pulps with enhanced properties such as strength and stiffness. Wood chips are chemically pulped to a high kappa number, providing a rejects component and an accepts component. The rejects component is subjected to a substantially mechanical pulping process, optionally in a presence of bleaching agent, prior to blending back into the accepts component. The resulting fiber blend is washed, optionally bleached, and subjected to a papermaking process to provide paper or paperboard with enhanced strength and stiffness at low basis weight.