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Comparison of Two Different Ultrasound Reactors for the Treatment of Cellulose Fibers
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. (Engineering Acoustics)ORCID iD: 0000-0002-4657-6844
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. (Engineering Acoustics)ORCID iD: 0000-0003-2955-2776
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. (Engineering Acoustics)
2019 (English)In: Ultrasonics Sonochemistry, ISSN 1350-4177Article in journal (Refereed) Epub ahead of print
Abstract [en]

The pulp and paper industry is in continuous need for energy-efficient production processes. In the refining process of mechanical pulp, fibrillation is one of the essential unit operations that count for up to 80% of the total energy use. This initial study explores the potential and development of new type of scalable ultrasound reactor for energy efficient mechanical pulping. The developed reactor is of continuous flow type and based on both hydrodynamic and acoustic cavitation in order to modify the mechanical properties of cellulose fibers. A comparison of the prototype tube reactor is made with a batch reactor type where the ultrasonic horn is inserted in the fluid. The pulp samples were sonicated by high-intensity ultrasound, using tuned sonotrodes enhancing the sound pressure and cavitation intensity by a controlled resonance in the contained fluid. The resonant frequency of the batch reactor is 20.8 kHz and for the tube reactor it is 22.8 kHz. The power conversion efficiency for the beaker setup is 25% and 36 % in case of the tube reactor in stationary mode. The objective is to verify the benefit of resonance enhanced cavitation intensity when avoiding the effect of Bjerkenes forces. The setup used enables to keep the fibers in the pressure antinodes of the contained fluid. In case of the continuous flow reactor the effect of hydrodynamic cavitation is also induced. The intensity of the ultrasound in both reactors was found to be high enough to produce cavitation in the fluid suspension to enhance the fiber wall treatment. Results show that the mechanical properties of the fibers were changed by the sonification in all tests. The continuous flow type was approximately 50% more efficient than the beaker. The effect of keeping fibers in the antinode of the resonant mode shape of the irradiation frequency was also significant. The effect on fiber properties for the tested mass fraction was determined by a low-intensity ultrasound pulse-echo based measurement method, and by a standard pulp analyzer

Place, publisher, year, edition, pages
Elsevier, 2019.
Keywords [en]
ultrasound reactor, hydrodynamic and acoustic cavitation, cellulose fiber properties
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Fluid Mechanics and Acoustics Paper, Pulp and Fiber Technology
Research subject
Electronic systems; Engineering Acoustics
Identifiers
URN: urn:nbn:se:ltu:diva-76606DOI: 10.1016/j.ultsonch.2019.104841PubMedID: 31806547OAI: oai:DiVA.org:ltu-76606DiVA, id: diva2:1367645
Funder
Swedish Energy Agency, 166518Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-12-16

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Pamidi, Taraka Rama KrishnaJohansson, ÖrjanLöfqvist, TorbjörnShankar, Vijay

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Pamidi, Taraka Rama KrishnaJohansson, ÖrjanLöfqvist, TorbjörnShankar, Vijay
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Operation, Maintenance and AcousticsEmbedded Internet Systems Lab
Other Electrical Engineering, Electronic Engineering, Information EngineeringFluid Mechanics and AcousticsPaper, Pulp and Fiber Technology

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