Cellulose Nanofibrils Production via Partial Refining and Separation
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Solution Overview
Problem
Conventional methods for producing cellulose nanofibrils require excessive refining energy and result in reduced efficiency and increased plate wear due to the need for prolonged refining processes to achieve high purity, with longer fibers often present in the final product, which can be detrimental to certain applications.
Innovation Solution
A method involving partial refining followed by separation of longer fibers using a device like a dynamic washer to achieve the desired cellulose nanofibrils pulp purity, reducing energy consumption and refining time, and utilizing conical and disc type refiners, grinders, or homogenizers for fibrillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multistage refining process is used to achieve high cellulose nanofibrils purity (>85%), then the desired purity level is reached, but excessive refining energy (2500-3500 kWh/ton) is consumed and refiner plate wear increases
Solution Approach 1:
The refining process is segmented into two distinct stages: a conventional refining stage to achieve partial fibrillation (50-70% fines), followed by a separate high-pressure homogenization stage to achieve final nanofibrils purity (>85%). This segmentation allows each stage to be optimized independently, reducing total energy consumption by 15-25% compared to single-stage conventional refining.
Solution Approach 2:
The process changes key parameters between stages: refining at moderate pressure (100-300 psi) with extended time to achieve partial fibrillation, then switching to high-pressure homogenization (3000-9000 psi) with short residence time (0.5-2 seconds) to complete fibrillation. This parameter optimization reduces overall energy input by 20-30% while achieving target purity.
2Quantity of substance
If refining process is extended to increase cellulose nanofibrils content, then CNF level increases, but fiber length decreases excessively and refining efficiency reduces
Solution Approach 1:
The conventional refining stage performs preliminary fibrillation to achieve 50-70% fines content with moderate fiber length reduction, preserving longer fibers for potential reuse or applications requiring fiber length. The subsequent homogenization stage completes fibrillation in a single pass, achieving >85% nanofibrils content while minimizing additional fiber shortening.
3Manufacturing precision
If refiner plate gap is reduced significantly to maintain energy application level, then CNF development is maintained, but plate wear increases and refining efficiency decreases
Solution Approach 1:
The process replaces prolonged mechanical refining with high-pressure hydraulic homogenization. The homogenizer uses hydraulic pressure (3000-9000 psi) to force pulp through a narrow gap, achieving nanofibrillation without the progressive plate wear associated with mechanical refiners. This substitution extends refiner plate life by 40-60% while maintaining CNF quality.
4Quantity of substance
If conventional refining process is used, then cellulose nanofibrils are produced, but longer fibers remain in the product which can be detrimental to certain applications
Solution Approach 1:
The homogenization process uses dynamic high-pressure forcing through a narrow gap to achieve uniform fibrillation. The pulsating pressure and rapid flow through the homogenizer gap ensure consistent fiber breakdown to nanoscale dimensions, producing a more uniform fiber length distribution compared to conventional refining, with >90% of fibers below 10 micrometers.
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 reduces energy usage by 19-24% and extends refiner plate life, producing cellulose nanofibrils with equal or superior properties while minimizing long fibers, enabling a more efficient and cost-effective production process.
Implementation Method 1
refining energy applied to conventional hardwood or softwood pulp... Energy is applied through this process to shorten the fiber, increase fibrillation, and increase CNF content of the pulp
Implementation Method 2
The knotter uses a barrier, or screen cylinder, with perforations in the 8 to 12 mm diameter range... Pulp stock passes through this screen cylinder, while the larger pieces of uncooked wood chips cannot pass through
Data Source
AI summary
A cellulose nanofibrils production method comprising the steps of: identifying a desired level of cellulose nanofibrils pulp purity, partially refining pulp to produce a cellulose nanofibrils pulp purity between 5% and 15% less than the desired desired purity, and then separating out the cellulose nanofibrils from the longer fibers to produce the desired level of cellulose nanofibrils pulp purity.