Örjan Johansson, Head of the Department of Civil, Environmental and Natural Resources Engineering at Luleå University of Technolgy, is working on the project.
– The potential of this new technology is potentially very wide - in Sweden alone paper mills stand for about three percent of the total energy use, says Örjan Johansson.
Photo: Taraka Rama Krishna Pamidi
Above: Cavitation reactor developed for fibrillation of cellulose fibers. The above example shows how a sheet of aluminium foil is perforated within seconds of cavitation bubbles generated and collapsed by ultrasound.
The get a fibrillation effect on the cellulose fibers a type of ultrasonic reactor has been developed and optimized. The generated sound waves creates high enough amplitudes to collapse cavitation bubbles, usually formed by small bubbles of gas that occurs naturally in water.
– Ultrasound is used to create something called transient cavitation. In this case a pulp suspension is put under huge pressure variations to generate and collapse cavitation bubbles of various sizes on the fiber surfaces. This technology aims to save energy in an otherwise very energy consuming process, says Örjan Johansson.
The project "Improved Energy efficiency by hydrodynamically induced cavitation controlled by resonance amplified ultrasound" is conducted in collaboration with ÅF, Innventia, Mittuniversitetet, SCA, Holmen and Stora Enso and financed by the Swedish Energy Agency.
Wikipedia: Cavitation is the formation of vapour cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shock wave.