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Energy Efficient Fibrillation of Cellulose Fibers using an Ultrasound Reactor
Contact: Taraka Pamidi ([email protected])Örjan Johansson ([email protected]), Torbjörn Löfqvist([email protected]) Funded by:
Motivation• Minimizing electrical energy use by 50% is essential for a
cost efficient and competitive operation of modern pulp &paper mills.
• Hydrodynamic and acoustic cavitation has the potentialto be an energy efficient alternative to modify theproperties of cellulose fibers.
Results
Future Work• Increasing flow rates, process temperature and static
pressure in an up-scaled reactor• Find optimal balance between process parameters related
to the fiber suspension characteristics and flow inducedcavitation.
Problem Description• Swedish paper mills combined consumes about 19 %
of the Swedish industry’s total energy use.• In the refining process, fibrillation is one of the essential
unit operation that count for up to 80% of the total energyuse.
Effect on fibers due to cavitation“Development of an energy efficient flow reactor for
treatment of cellulose fibers”• Separate the wood fibers from each others• Retain or reduce fiber length• Swelling and shrinking occurs• The fibers will be delaminated (internal fibrillation)• Fibrillation of the secondary wall (external fibrillation)• Creation of fines occur
MethodsAcoustic modeling coupled to structural interaction andCFD are used to optimize an ultrasound controlled reactorusing FEM, CFD.and experimental investigation
Scanning Electron Microscopy images of untreated and ultrasound treated cellulose fibers
Background
Micro jets and shockwaves effects the fiber surfaceFrequency dependent bubble size –– Optimized with respect
to pulp characteristics
Taraka Pamidi, Örjan Johansson, Torbjörn LöfqvistEngineering Acoustics
Experiment have been performed on both mechanical andchemical pulp fibers. The fibers did not receive any pre-treatment prior to ultrasound exposure. After ultra-sonication the samples was characterized with respect tomodification of fiber properties and the energy supplementby sonication. Test 4 and 3b give the best results.
The reactor is driven with nine sonotrodes mounted radiallyon the reactor wall. Three in the center, top and bottompositions at 120° spacing. The sonotrodes are excited withdouble frequencies, at 22.6 and 38.8 kHz. Both bottom upand top down flow through a venturi nozzle to initiatebubbles give a significant impact on fiber properties.
(a) Fiber absorption properties (b) fiber mean length with distribution