with similar reaction parameters as that of US but the reaction time required may be
higher (45–60 min) than US (Ghayal et al. 2013). It is important to understand that
the cavitational yield (amount of product per unit energy) of HC is also typically
higher than US.
6.2 Microreactors
Miniature reaction systems have proven to provide sustainable and innovative
solutions and have been utilized at both laboratory level and industrial level with
good degree of intensification benefits. Intensified heat and mass transfer are
achieved with these reactors as they have a small characteristic dimension and high
surface-to-volume ratio offering proper temperature control. Immiscible liquid–liquid reactions can be carried out with higher efficiency with this reactor as it provides
very high interfacial area between phases which further improves the rate of mass
transfer (Kashid and Kiwi-Minsker 2009). Transesterification reaction consists of
two immiscible reactants, that is, triglycerides and methanol. There are reports in
which homogenous transesterification reaction have been performed using
microreactor with significant reduction in reaction time (Mazubert et al. 2013; Wen
et al. 2009). Typical operating conditions consist of methanol-to-oil molar ratio at
1:4–1:9 and catalyst loading in the range of 1–4.5% w/w of oil with a flow rate varied
from 8 to 15 mL/h which can give yield of biodiesel up to 99% in very less reaction
time of 1–6 min. More work is required to be performed to establish the design and
scale up strategies for application of micro-reactors at the commercial scale of
operation for the specific application of biofuel production from microalgae.
6.3 Microwave Reactor
Microwave reactors work on the principle of intensification based on the effects of
dipolar polarization and ionic conduction. The dipolar polarization occurs when the
alignment of the dipoles occurs in the direction of electric field imposed with help
of microwave irradiation. Oscillation of the charged dissolved particles due to
microwave results in the ionic conduction. Transesterification reaction performed
using these reactors shows significant increase in reaction rate. Also it has been
reported that intensification in the transesterification reaction is more sensitive for
the use of methanol than ethanol due to low gyration radius and molecular inertia
(Terigar et al. 2010). Intensification trends have been reported with different
heterogeneous and homogenous transesterification reactions for the use of microwave reactors (Mazubert et al. 2013). It can be seen from the studies reported in the
literature that the important reaction parameters are molar ratio (1:6–1:12), catalyst
loading (0.15– 5 wt% of oil), temperature (40–60 °C), and power (300–1600 W)
with required reaction time varying from 0.5 to 20 min.
4 Process Intensification of Biofuel Production …
79
higher (45–60 min) than US (Ghayal et al. 2013). It is important to understand that
the cavitational yield (amount of product per unit energy) of HC is also typically
higher than US.
6.2 Microreactors
Miniature reaction systems have proven to provide sustainable and innovative
solutions and have been utilized at both laboratory level and industrial level with
good degree of intensification benefits. Intensified heat and mass transfer are
achieved with these reactors as they have a small characteristic dimension and high
surface-to-volume ratio offering proper temperature control. Immiscible liquid–liquid reactions can be carried out with higher efficiency with this reactor as it provides
very high interfacial area between phases which further improves the rate of mass
transfer (Kashid and Kiwi-Minsker 2009). Transesterification reaction consists of
two immiscible reactants, that is, triglycerides and methanol. There are reports in
which homogenous transesterification reaction have been performed using
microreactor with significant reduction in reaction time (Mazubert et al. 2013; Wen
et al. 2009). Typical operating conditions consist of methanol-to-oil molar ratio at
1:4–1:9 and catalyst loading in the range of 1–4.5% w/w of oil with a flow rate varied
from 8 to 15 mL/h which can give yield of biodiesel up to 99% in very less reaction
time of 1–6 min. More work is required to be performed to establish the design and
scale up strategies for application of micro-reactors at the commercial scale of
operation for the specific application of biofuel production from microalgae.
6.3 Microwave Reactor
Microwave reactors work on the principle of intensification based on the effects of
dipolar polarization and ionic conduction. The dipolar polarization occurs when the
alignment of the dipoles occurs in the direction of electric field imposed with help
of microwave irradiation. Oscillation of the charged dissolved particles due to
microwave results in the ionic conduction. Transesterification reaction performed
using these reactors shows significant increase in reaction rate. Also it has been
reported that intensification in the transesterification reaction is more sensitive for
the use of methanol than ethanol due to low gyration radius and molecular inertia
(Terigar et al. 2010). Intensification trends have been reported with different
heterogeneous and homogenous transesterification reactions for the use of microwave reactors (Mazubert et al. 2013). It can be seen from the studies reported in the
literature that the important reaction parameters are molar ratio (1:6–1:12), catalyst
loading (0.15– 5 wt% of oil), temperature (40–60 °C), and power (300–1600 W)
with required reaction time varying from 0.5 to 20 min.
4 Process Intensification of Biofuel Production …
79