6.4 Oscillatory Baffled Reactor
Oscillatory baffled reactor (OBR) consists of equally spaced orifice plate baffles
arranged in a tube operating with an oscillatory or pulsed flow with generation of
re-circulating flow pattern. This reactor provides enhanced mixing and inter-phase
contact within sufficiently long residence time suitable for the reaction when
employed in transesterification reaction. It can be established from the data
available on transesterification reaction with OBR that the molar ratio in the range
of 1:6–1:9 with flow rate of 0.12–3.12 L/h and residence time ranging from 20 to
40 min is able to yield 99% conversion in almost all the studies (Harvey et al.
2003; Zheng et al. 2007). OBR can also work with heterogeneous system and
their scale up for effective operation at commercial scale is possible. It is
important to understand that no direct work has been still reported for utilization
of algal oil in biodiesel production with OBR, though the reported trends for
other similar systems do induce a confidence for possible success.
6.5 Reactive Distillation
Reactive distillation (RD) combines the chemical reaction and product separation
in a single unit. RD column boosts the conversion with improvement in selectivity by breaking the reaction equilibrium conditions (Estrada-Villagrana et al.
2006). The application of this reactor in biodiesel production can be very helpful
as demonstrated by He et al. (2006). In the study, the canola oil and methanol
feed were made to enter through an in-line static mixer into the RD column.
Downward flow of reactant from the top of the RD column across the plate
ensured efficient contact with vapors of methanol (produced in reboiler from
product mixture) providing uniform mixing at each plate. Virtually, a series of
“mini- reactors” were created in the reaction zone of RD column. Methanol from
the distillate could be recycled and was combined with the feed methanol and
then refluxed back to the RD column. This made the reactor to give 94.4% of
yield with methanol: oil molar ratio of 4:1. From this study, it was also established that there is drastic decrease in quantity of methanol required and reaction
time as compared to the conventional reactors. The requirement of extra unit
operation required for recovery of solvent is also not present in RD giving lower
capital costs. It is important to understand that not much work could be seen for
the use of algal oil in the reactive distillation approach. More investigation needs
to be carried out to employ this reactor for the algal oil with a detailed study on
parameter optimization and also establish scale up strategies so that the
commercial-scale biodiesel production from algal oil is a possibility.
80
S. Joshi and P. Gogate
Oscillatory baffled reactor (OBR) consists of equally spaced orifice plate baffles
arranged in a tube operating with an oscillatory or pulsed flow with generation of
re-circulating flow pattern. This reactor provides enhanced mixing and inter-phase
contact within sufficiently long residence time suitable for the reaction when
employed in transesterification reaction. It can be established from the data
available on transesterification reaction with OBR that the molar ratio in the range
of 1:6–1:9 with flow rate of 0.12–3.12 L/h and residence time ranging from 20 to
40 min is able to yield 99% conversion in almost all the studies (Harvey et al.
2003; Zheng et al. 2007). OBR can also work with heterogeneous system and
their scale up for effective operation at commercial scale is possible. It is
important to understand that no direct work has been still reported for utilization
of algal oil in biodiesel production with OBR, though the reported trends for
other similar systems do induce a confidence for possible success.
6.5 Reactive Distillation
Reactive distillation (RD) combines the chemical reaction and product separation
in a single unit. RD column boosts the conversion with improvement in selectivity by breaking the reaction equilibrium conditions (Estrada-Villagrana et al.
2006). The application of this reactor in biodiesel production can be very helpful
as demonstrated by He et al. (2006). In the study, the canola oil and methanol
feed were made to enter through an in-line static mixer into the RD column.
Downward flow of reactant from the top of the RD column across the plate
ensured efficient contact with vapors of methanol (produced in reboiler from
product mixture) providing uniform mixing at each plate. Virtually, a series of
“mini- reactors” were created in the reaction zone of RD column. Methanol from
the distillate could be recycled and was combined with the feed methanol and
then refluxed back to the RD column. This made the reactor to give 94.4% of
yield with methanol: oil molar ratio of 4:1. From this study, it was also established that there is drastic decrease in quantity of methanol required and reaction
time as compared to the conventional reactors. The requirement of extra unit
operation required for recovery of solvent is also not present in RD giving lower
capital costs. It is important to understand that not much work could be seen for
the use of algal oil in the reactive distillation approach. More investigation needs
to be carried out to employ this reactor for the algal oil with a detailed study on
parameter optimization and also establish scale up strategies so that the
commercial-scale biodiesel production from algal oil is a possibility.
80
S. Joshi and P. Gogate