Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Numerical and experimental design of ultrasonic particle filters for water treatment
    Cappon, H.J. - \ 2014
    Wageningen University. Promotor(en): Gerrit van Straten, co-promotor(en): Karel Keesman. - Wageningen : Wageningen University - ISBN 9789461738592 - 202
    waterzuivering - terugwinning - ultrasone behandeling - geluidsleer - scheidingstechnologie - wiskundige modellen - water treatment - recovery - ultrasonic treatment - acoustics - separation technology - mathematical models

    Due to limited water resources available in the world and the ever growing world population, there is an increasing need for water recycling, recovery and multi-sourcing strategies. One of the new physical process technologies being investigated for water purification and/or constituent recycling is ultrasonic particle separation. This technology is especially interesting for harvesting particles with an almost neutral buoyancy. An ultrasonic particle filter does not use a filter medium, like sand or a membrane, but filters on a basis of acoustic forces in ultrasonic standing waves, which are able to immobilise particles in flowing water.

    The objective of this study was to develop an ultrasonic separation device for particle recovery and water purification. This separator should be fit for industrial applications treating cubic meters of water per hour. In order to reach this objective, a combined numerical-experimental approach was proposed to develop a model-based design of an ultrasonic separator. Each individual component of this separator was modelled using a finite element (FE) approach. The numerical simulations were continuously cross-checked with experiments in order to find the best solution possible.

    In this thesis, the source of the acoustic wave is a piezoelectric transducer attached to a glass matching layer of the acoustic cavity, which couples the transducer to the fluid inside the cavity, forming an acoustic resonator/separator. In order to obtain a valid FE transducer model, a limited set of material parameters for the piezoelectric transducer were obtained from the manufacturer, thus preserving prior physical knowledge to a large extent. The remaining unknown parameters were estimated from impedance (admittance) analysis combined with a numerical optimisation routine using 2D and 3D FE models. Thus, a full set of physically interpretable material parameters was obtained. The approach provided adequate accuracy of the estimates of the material parameters, near 1%.

    A similar approach as used for the transducer was applied to an existing ultrasonic separator, again preserving known physical parameters and estimating the remaining unknown or less certain parameters. The results showed that the approach led to a fully calibrated 2D model of the emptyseparator, which was subsequently validated with experiments on a filledseparator chamber. The large sensitivity of the separator to small variations indicated that either such system should be made and operated within tight specifications to obtain the required performance. Alternatively, the operation of the system should be adaptable to cope with a slightly off-spec system, requiring a feedback controller.

    Starting from a fully characterised existing separator with all material parameters found so far, the subsequent step was the actual design of, or extrapolation to, a new separator. A basic design for an industrial scale acoustic separator was obtained based on simulated flow characteristics inside the separation chamber, on acoustic analysis within the chamber and simulated particle trajectories combining these two analyses. Results showed that positioning the piezoelectric transducer surfaces perpendicular to the flow direction and introducing chamber partitioning with multiple flow lanes to enforce laminar flow, resulted in high particle retention. The average particle displacement was found to be related to acoustic pressure in the fluid, showing large retention at peak pressures above 1 MPa or average pressures above 0.5 MPa for small (10 µm), near buoyant (1100 kg/m3) particles at a flow speed of 3.5 cm/s, thus providing comprehensible criteria for subsequent optimisation.

    This basic ultrasonic standing wave separator design was optimised with respect to separation efficiency, throughput and energy consumption. The methodology, using a design of experiments (DOE) approach, showed that it was possible to improve system performance based on acoustic pressure profiles, separation efficiency and flow robustness. Compromising the energy consumption and aiming for maximum separation efficiency with a laminar stable flow up to 5 ml/s resulted in a separator with inner dimensions of 70 mm length, 20 mm width and 28.5 mm height using two transducers perpendicular to the direction of flow and three parallel flow lanes with 9.5 mm height each. The lowest power consumption (with an average of 30 W) with adequate pressure to trap the particles was obtained when it was not operated at the main eigenfrequency.

    Finally, this new ultrasonic particle filter was built and evaluated experimentally. The particle filter was a three channel device, manufactured from glass with four in/outlet ports made of ABS. It was operated in sequenced batch mode and the separation efficiency was determined at three flow rates ranging from 1 to 3 ml/s, using a stock suspension of insoluble potato starch of 1 g/l (1000 ppm). Concentrations of stock, filtrate and concentrate were measured using a turbidity meter and significant effects of acoustic particle concentration were measured at both outlets of the process. The maximum filtration efficiency and concentration efficiency were 54% and 76%, respectively. The performance found was lower than the 100% that was expected for 10 µm particles from the model based design study. The deviation in performance is mainly a result of (i) the pulsation of the feed pump, (ii) differences between the model and the actual prototype, (iii) the limited power supply of only 10 W used and (iv) (too) small particles, below 10 µm, occurring in the starch suspension.

    The best dimensions for an acoustic separator were obtained, but thus far operational characteristics were not yet studied. Operational characterisation and optimisation is the last step in the process of obtaining the best possible solution for operation. With the aim to achieve a high separation efficiency with minimal energy consumption, a model-based open-loop switching control strategy was designed for the commercially available BioSep, using a numerical-experimental approach. Firstly, a dynamic BioSep model structure was derived from mass balances and its system properties were studied. Then, the unknown system parameters were estimated from steady state and dynamic experimental data and subsequently, the switching times of the control input were determined. The model with switching control outputs was then validated by experiments. Finally, the control strategy was implemented in an experimental setup and tested using suspended potato starch. Results showed that the optimal control strategy reached a mass separation efficiency of 96%, which was an improvement of 4% with respect to the initial settings, while using less energy.

    Concluding, a stepwise numerical-experimental approach to acoustic separator design was presented in this study. The minimum power required was estimated to be 22-34 W, resulting in an average electric energy consumption of 1-1.5 kWh/m3. The practical concentration efficiency obtained was 76% at a flow rate of 2 ml/s and a filtration efficiency of 54% at 1 ml/s with a real power input of 8.8 W. An optimal open loop control strategy showed that it is possible to operate an acoustic separator with high separation efficiency using the least power possible. Parallelisation, instead of enlarging the separator, is recommended to scale this system up to larger, industrial flows.

    Ontwikkeling van veilige toepassingen voor gewasbehandelingen met electrolysewater in de glastuinbouw
    Hofland-Zijlstra, J.D. ; Vries, R.S.M. de; Blok, C. ; Boer-Tersteeg, P.M. de; IJdo, M.L. ; Bosch, C. ; Ayik, A. ; Bruning, H. - \ 2013
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten WUR GTB 1240) - 50
    water - elektrolyse - glastuinbouw - gewasbescherming - milieubescherming - arbeidsomstandigheden - plantenvoeding - biociden - ultrasone behandeling - verneveling - druppelbevloeiing - nederland - water - electrolysis - greenhouse horticulture - plant protection - environmental protection - working conditions - plant nutrition - biocides - ultrasonic treatment - nebulization - trickle irrigation - netherlands
    Dit onderzoek had als doel om de werking van electrolysewater te verbinden met de chemische eigenschappen en op zoek te gaan naar veilige toepassingen als gewasbehandeling voor de glastuinbouwsector. Vijf producenten hebben voor dit onderzoek de gewenste samenstelling van electrolysewater aangeleverd. Alle producten met daarin 36-65 ppm vrij chloor waren binnen vijf minuten 100% effectief tegen de bacterie, Erwinia chrysanthemi en de schimmel, Botrytis cinerea. De grenzen van gewasschade in de kiemplantentest werden sterker bepaald door de hoeveelheid natriumzout en EC gehalte van de electrolysevloeistof dan de hoeveelheid vrij chloor. In een korte meedruppelproef met tomaat zijn verschillende concentraties vrij chloor (0, 4, 8, 20 ppm) gedoseerd aan het voedingswater. Er werd geen gewasschade gevonden of negatief effect op de wortelkolonisatie van Trianum door de geringe chloorwaardes (vrij en totaal) die na vier weken bij de druppelaar werden teruggemeten. Testen met gewasbehandelingen laten zien dat éénmalige behandelingen tot 300 ppm geen gewasschade geven. Bij meerdere toepassingen is groeiremming te voorkomen door lagere concentraties te gebruiken of blootstellingstijd te beperken. Electrolysewater kan een veilig en bruikbaar alternatief bij het terugdringen van het fungicidegebruik.
    Kennisinventarisatie naar de achtergronden en toepassingen van electrochemisch geactiveerd water in de agrarische sector
    Hofland-Zijlstra, J.D. ; Vries, R.S.M. de; Bruning, H. - \ 2011
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1087) - 38
    elektrochemie - water - toepassingen - landbouw - tuinbouw - ultrasone behandeling - verneveling - teelt onder bescherming - ziektebestrijdende teeltmaatregelen - elektrolyse - electrochemistry - water - applications - agriculture - horticulture - ultrasonic treatment - nebulization - protected cultivation - cultural control - electrolysis
    Wageningen UR Greenhouse Horticulture, with funding of Dutch Horticultural Board, has described the history and background of electrochemically activated water and explored possibilities for applications within the agricultural sector. In the Netherlands, the use of activated water as a biocide is allowed since 2009. Active ingredients of activated water are chlorine gas, hypochlorous acid and hypochlorite. Together with a high oxidation-reduction potential (ORP 750-1100 mV) there is a broad activity against bacteria, fungi, viruses, algae, protozoa and nematodes. Agricultural applications of activated water are described for seed disinfection, cleaning equipment and packing materials, removal of biofilms from pipes, disinfection of flowers, fruits and vegetables. The recent development of ultrasonic atomization of activated water created new possibilities to treat crops and harvested products against pathogens without excessive volumes of water and disinfect air from pathogens. For applications in protected crops it is desirable that the corrosive properties of the activated water should be minimized and capacities of dispensing equipment must be enlarged.
    Voorstudie ultrasone geluidsgolven tegen zuur in tulp : werkt de Bulbsweep tegen Fusariumbesmettingen?
    Duyvesteijn, R.G.E. ; Breeuwsma, S.J. ; Dam, M.F.N. van; Boer, M. de - \ 2010
    Lisse : PPO Bloembollen en Bomen
    ultrasone behandeling - behandeling na de oogst - tulipa - tulpen - fusarium - schimmelziekten - bloembollen - landbouwkundig onderzoek - nederland - ultrasonic treatment - postharvest treatment - tulipa - tulips - fusarium - fungal diseases - ornamental bulbs - agricultural research - netherlands
    Er is vanuit de KAVB gevraagd om de effectiviteit van de ultrasone geluidsgolven tijdens het spoelen van tulpen te onderzoeken. Er is gekeken of ultrasone geluidsgolven in staat zijn besmetting met Fusarium te voorkomen. Hiervoor is in samenwerking met ArcaZen de Bulbsweep uitgetest onder praktijkomstandigheden. De Bulbsweep is een apparaat dat ultrasone geluidsgolven opwekt. Een vellenbak met daarin een Bulbsweep werd besmet met Fusarium sporen. Vervolgens zijn er tulpenbollen door getransporteerd. Het was niet mogelijk een verschil vast te stellen tussen het aantal zieke bollen met of zonder een ultrasone behandeling. In een tijdreeks is getest of ultrasone geluidsgolven ook daadwerkelijk schimmelsporen van Fusarium doden. Hieruit bleek dat er na 5 minuten een effect te zien was. Dit effect is echter marginaal en zal geen groot effect hebben op het voorkomen van besmettingen.
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