8.3 Design Considerations
117
The operating conditions largely affect the cavitation physics and control some
parameters such as the number of cavities, the magnitude of the collapse pressure,
the intensity of the cavitation and its distribution of activity in the reactor (Gogate
et al. 2011). In this section, only a few considerations are summarized in order to
allow the understanding of the main lines of the optimization of parameters of the
scaling-up of the cavitation phenomenon.
8.3.1 Optimization of Sonoreactor
As we have mentioned, the prerequisites for scaling-up are to obtain a high power on
a maximum irradiation surface while taking into account the time required to enable
the chemical process. The best solution to get ultrasonic high power is to use a horn
system directly immersed in the solution. However, it also presents major drawbacks
like the strong erosion of the tip, weak irradiative surface and a decreasing intensity as
one move away from the device. In order to overcome these disadvantages, rod-type
transducers can be used.
The most common devices use the transducers placed outside the sonochemical
reactor. According to the required irradiation time to achieve the chemical process,
the continuous flow systems and the loop reactors can be distinguished.
If the required cavitation collapse time is relatively short, a flow rate system can
be selected. The generation of a continuous flow passing through venturi devices or
orifices produces hydrodynamic cavitation phenomenon. To avoid pressure losses
and cavitation energy, the process intensification requires a pumping system that can
provide a high level of power. Otherwise, ultrasonic cavitation is produced either by
the addition of transducers along the pipe (of tubular or hexagonal forms) or by the
use of a vibrating bar whose useful length can be several tens of centimetres.
When a greater ultrasonic irradiation time is required, a reactor is added to form
a loop with the continuous flow system. It has both the advantage of being able to
conduct long irradiation times as well as control and adjust the medium during the
transit of the treated material through the reactor.
8.3.2 Processing Parameters
Optimizing operating parameters when implementing a sonochemistry experiment
is a crucial phase before scaling-up. Thus, among the input variables having the
most influence on the cavitation during the intensification of the process are power
dissipation, frequency, operating mode and the intensity of the irradiation as well as
the geometry of the reactor.
117
The operating conditions largely affect the cavitation physics and control some
parameters such as the number of cavities, the magnitude of the collapse pressure,
the intensity of the cavitation and its distribution of activity in the reactor (Gogate
et al. 2011). In this section, only a few considerations are summarized in order to
allow the understanding of the main lines of the optimization of parameters of the
scaling-up of the cavitation phenomenon.
8.3.1 Optimization of Sonoreactor
As we have mentioned, the prerequisites for scaling-up are to obtain a high power on
a maximum irradiation surface while taking into account the time required to enable
the chemical process. The best solution to get ultrasonic high power is to use a horn
system directly immersed in the solution. However, it also presents major drawbacks
like the strong erosion of the tip, weak irradiative surface and a decreasing intensity as
one move away from the device. In order to overcome these disadvantages, rod-type
transducers can be used.
The most common devices use the transducers placed outside the sonochemical
reactor. According to the required irradiation time to achieve the chemical process,
the continuous flow systems and the loop reactors can be distinguished.
If the required cavitation collapse time is relatively short, a flow rate system can
be selected. The generation of a continuous flow passing through venturi devices or
orifices produces hydrodynamic cavitation phenomenon. To avoid pressure losses
and cavitation energy, the process intensification requires a pumping system that can
provide a high level of power. Otherwise, ultrasonic cavitation is produced either by
the addition of transducers along the pipe (of tubular or hexagonal forms) or by the
use of a vibrating bar whose useful length can be several tens of centimetres.
When a greater ultrasonic irradiation time is required, a reactor is added to form
a loop with the continuous flow system. It has both the advantage of being able to
conduct long irradiation times as well as control and adjust the medium during the
transit of the treated material through the reactor.
8.3.2 Processing Parameters
Optimizing operating parameters when implementing a sonochemistry experiment
is a crucial phase before scaling-up. Thus, among the input variables having the
most influence on the cavitation during the intensification of the process are power
dissipation, frequency, operating mode and the intensity of the irradiation as well as
the geometry of the reactor.