Microfibrillated Cellulose Stepwise Fibrillation Energy Reduction
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Solution Overview
Problem
Conventional methods for producing microfibrillated cellulose face challenges such as high energy consumption, low productivity, difficulty in scaling up, and fiber cutting, leading to a low aspect ratio and increased costs due to dilute suspensions and high energy requirements in low and high consistency refining processes.
Innovation Solution
A method involving stepwise fibrillation, starting with low consistency (less than 12.5% pulp suspension) followed by dewatering to increase consistency for further high consistency fibrillation, optimizing energy use and fiber friction to achieve high aspect ratio microfibrillated cellulose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low consistency refining is used to fibrillate cellulose, then the process runs smoothly without clogging, but large amounts of energy are consumed for continued fibrillation and the resulting suspension is dilute requiring expensive transportation
Solution Approach 1:
The fibrillation process is divided into two distinct stages: first low consistency fibrillation to initiate fiber separation and create a runnable suspension, then high consistency fibrillation to complete the fibrillation process. This segmentation allows each stage to operate under optimal conditions, reducing overall energy consumption while maintaining process smoothness.
Solution Approach 2:
Low consistency fibrillation is performed as a preliminary action to pre-separate the fiber bundles and create a suspension that can be easily pumped and processed. This preliminary separation reduces the energy required for subsequent high consistency fibrillation, as the fibers are already partially separated and more accessible.
2Manufacturing precision
If high consistency refining is used to obtain high aspect ratio microfibrils, then fiber friction is enhanced and aspect ratio improves, but the process becomes difficult to scale up and productivity decreases
Solution Approach 1:
The refining process is segmented into low consistency and high consistency stages. The low consistency stage prepares the suspension for scalable processing, while the high consistency stage is applied selectively to achieve the desired aspect ratio. This segmentation allows the process to be scaled up more easily while maintaining product quality.
Solution Approach 2:
Instead of applying high consistency fibrillation throughout the entire process, the invention applies it partially after the low consistency stage has done the preliminary work. This partial application of high consistency fibrillation achieves the necessary aspect ratio improvement without the full productivity penalty that would result from applying it throughout the entire process.
3Ease of manufacture
If mechanical disintegration by refining and milling is used, then microfibrillated cellulose is produced, but fiber cutting occurs leading to reduced aspect ratio and increased costs
Solution Approach 1:
The invention changes the key parameter of consistency throughout the process. By maintaining low consistency during initial fibrillation and only increasing to high consistency later, the process minimizes fiber cutting while achieving adequate fibrillation. This parameter change strategy preserves fiber length and aspect ratio while still producing MFC.
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 overall energy consumption, enhances productivity, and produces microfibrillated cellulose with a high aspect ratio, improved mechanical properties, and reduced fiber cutting, making it suitable for composites and paper products with enhanced strength and reduced transportation costs.
Implementation Method 1
dewatering fibrillated pulp obtained from step (a) to a consistency of at least 12.5%
Data Source
AI summary
The invention relates to methods of producing microfibrillated cellulose (MFC). According to the invention a fibrous pulp suspension is fibrillated mechanically at a consistency of less than 12.5%, dewatered to raise the consistency of the fibrillated suspension to at least 12.5%, and then subjected in the dewatered condition to further fibrillation. Alternatively an initially fibrillated fibrous pulp suspension may be dewatered and fibrillated in the dewatered condition, after which these dewatering and fibrillating steps are repeated one or more times so that pulp consistency is increased for each fibrillation step. The goals of raising the consistency between subsequent fibrillations are energy saving and an increased aspect ratio in MFC. The invention even comprises uses of the MFC product, e.g. as an additive for papermaking furnish or injection molded plastic composites.