116
8 Scaling-Up Enabling the Full Potential of Industrial …
with. A similar design with two counter spinning rotors was published by Petkovšek
et al. (2013), which like all the other machines presented, needs an extra pump for
operation. The same authors improved the system making it more energy efficient
thanks to an extremely compact generator and pump used in wastewater treatment
(Dular et al. 2016). Moreover, Cravotto’s group experimented the rotor/stator apparatus made by E-PIC S.r.l. (Turin, Italy) successfully applied in biodiesel production
(Crudo et al. 2016) and in the oxidative polymerization of waste cooking oil with air
(Rinaldi et al. 2017).
The ultrasonic cavitation scale-up is mostly performed with piezoelectric technology compared to magnetostrictive transducers. The latter nevertheless benefit from
a good coupling coefficient, strain performance, thermal and mechanical resistances
superior to piezoelectric transducers. However, the magnetostritive devices have the
drawback of being more expensive and difficult to manoeuvre because heavier and
bulky. These are the main reasons why the development of ultrasonic cavitation is
almost exclusively with piezoelectric transducers. Otherwise, one of the factors limiting the development of ultrasound is related to high power transducers and the
limit that can reach the unit probes. Although advances have been made in recent
years, the current maximum power of a single device is of the order of 3–4 kW eff . At
the industrial scale, it is therefore necessary to multiply the number of transducers
to obtain the desired power and to rely on an adequate optimization of the reactor.
Finally, the impact of ultrasonic noise, especially when using low frequencies, cannot
be neglected in the case of exposure to operators in a work environment (Smagowska
2013). Thus, the sonochemical devices must be adapted to limit sound emission and
propagation with specific noise protection.
8.3 Design Considerations
Critical examination of the numerous publications of the literature makes it possible
to work out an operational strategy for scaling-up. Thus, once the benefits are established and the technology chosen, the reactor development stage can begin. First, we
must consider that due to the introduction of large powers over large volumes, the
control of temperature and pressure is crucial to ensure the expected effects on the
chemical process, which highlights the preponderant aspect of chemical engineering. Among all the technical specifications of an industrial operation of the cavitation
phenomenon, the following points should be carefully considered:
• Type and number of probes for ultrasonic cavitation and choice of venturi and
orifices (number, size) for hydrodynamic cavitation,
• Intrinsic properties of the medium and its evolution over time,
• Temperature and pressure,
• Solid particles and dissolved gases,
• Geometry and sizing of reactor,
• Velocity of flow or agitation,
• Surfacing of the transmission system and erosion.
8 Scaling-Up Enabling the Full Potential of Industrial …
with. A similar design with two counter spinning rotors was published by Petkovšek
et al. (2013), which like all the other machines presented, needs an extra pump for
operation. The same authors improved the system making it more energy efficient
thanks to an extremely compact generator and pump used in wastewater treatment
(Dular et al. 2016). Moreover, Cravotto’s group experimented the rotor/stator apparatus made by E-PIC S.r.l. (Turin, Italy) successfully applied in biodiesel production
(Crudo et al. 2016) and in the oxidative polymerization of waste cooking oil with air
(Rinaldi et al. 2017).
The ultrasonic cavitation scale-up is mostly performed with piezoelectric technology compared to magnetostrictive transducers. The latter nevertheless benefit from
a good coupling coefficient, strain performance, thermal and mechanical resistances
superior to piezoelectric transducers. However, the magnetostritive devices have the
drawback of being more expensive and difficult to manoeuvre because heavier and
bulky. These are the main reasons why the development of ultrasonic cavitation is
almost exclusively with piezoelectric transducers. Otherwise, one of the factors limiting the development of ultrasound is related to high power transducers and the
limit that can reach the unit probes. Although advances have been made in recent
years, the current maximum power of a single device is of the order of 3–4 kW eff . At
the industrial scale, it is therefore necessary to multiply the number of transducers
to obtain the desired power and to rely on an adequate optimization of the reactor.
Finally, the impact of ultrasonic noise, especially when using low frequencies, cannot
be neglected in the case of exposure to operators in a work environment (Smagowska
2013). Thus, the sonochemical devices must be adapted to limit sound emission and
propagation with specific noise protection.
8.3 Design Considerations
Critical examination of the numerous publications of the literature makes it possible
to work out an operational strategy for scaling-up. Thus, once the benefits are established and the technology chosen, the reactor development stage can begin. First, we
must consider that due to the introduction of large powers over large volumes, the
control of temperature and pressure is crucial to ensure the expected effects on the
chemical process, which highlights the preponderant aspect of chemical engineering. Among all the technical specifications of an industrial operation of the cavitation
phenomenon, the following points should be carefully considered:
• Type and number of probes for ultrasonic cavitation and choice of venturi and
orifices (number, size) for hydrodynamic cavitation,
• Intrinsic properties of the medium and its evolution over time,
• Temperature and pressure,
• Solid particles and dissolved gases,
• Geometry and sizing of reactor,
• Velocity of flow or agitation,
• Surfacing of the transmission system and erosion.