6.6 Centrifugal Contact Separator
Centrifugal contact separator (CCS) employs the chemical reaction, and centrifugal
separation in a single apparatus. Preheated oil is fed into the reactor, and
the reaction is started by adding the methanol and the catalyst. The dispersion of the
immiscible liquids takes place in the annular gap between the static housing and the
rotating centrifuge. Further this mixture is transferred to the hollow centrifuge
through a hole at bottom and separation into heavy and light layers take place via
centrifugation. The optimum conditions reported by Kraai et al. (2009) for this
system, though not for algal oil, were rotational frequency of 30 Hz, oil flow rate at
12.6 mL/min, sodium methoxide catalyst concentration of 1% w/w of oil, and
reaction temperature of 75 °C. The FAME yield of 96% was reported in time period
of 30 min. It was also reported that further increase in temperature and catalyst
beyond optimum leads to excessive evaporation of methanol and soap formation
which affects the overall reaction rates. The higher flow rates of oil also were
reported to have a negative effect on the mean residence time of mixture lowering
the yield of FAME. Again similar to the reactive distillation, more investigations
are needed for the application of centrifugal contact separators for the specific feed
stock of algal oil before firm conclusion can be made.
6.7 Membrane Reactor
In order to overcome the limitations of conventional biodiesel production processes,
the development of membrane reactor can be a potential solution. Reaction and
separation occur in a single chamber, and this ensures that the reversible reaction
proceeds in the forward path with efficient removal of desired products from
reaction mixture which leads to increase in yield (Cao et al. 2008, 2007; Dube et al.
2007). Membrane reactor works on the principle of utilizing the immiscibility of
methanol with oil and miscibility of products (FAME and glycerol) in methanol.
During the transesterification process, oil exists in the form of emulsion in methanol
and reaction occurs at the surface of oil droplets. FAME produced via transesterification is soluble in methanol and is able to pass through the membrane with the
by-product glycerol. The oil droplets being larger in size cannot pass through the
membrane and remain in the reactor vessel. The simultaneous removal of product
from a reversible reaction helps in the improvement of the reaction rates, and the
permeate obtained is in pure form which requires less processing. Cao et al. (2008)
have investigated the transesterification reaction using different feedstocks (soybean
oil, canola oil, a hydrogenated palm oil/palm oil blend, yellow grease, and brown
grease) having varied FFA presence. With efficient purification and separation
process, membrane reactor was demonstrated to give high efficacy for different
feedstocks making it a energy efficient, and environmental friendly reactor.
4 Process Intensification of Biofuel Production …
81
Centrifugal contact separator (CCS) employs the chemical reaction, and centrifugal
separation in a single apparatus. Preheated oil is fed into the reactor, and
the reaction is started by adding the methanol and the catalyst. The dispersion of the
immiscible liquids takes place in the annular gap between the static housing and the
rotating centrifuge. Further this mixture is transferred to the hollow centrifuge
through a hole at bottom and separation into heavy and light layers take place via
centrifugation. The optimum conditions reported by Kraai et al. (2009) for this
system, though not for algal oil, were rotational frequency of 30 Hz, oil flow rate at
12.6 mL/min, sodium methoxide catalyst concentration of 1% w/w of oil, and
reaction temperature of 75 °C. The FAME yield of 96% was reported in time period
of 30 min. It was also reported that further increase in temperature and catalyst
beyond optimum leads to excessive evaporation of methanol and soap formation
which affects the overall reaction rates. The higher flow rates of oil also were
reported to have a negative effect on the mean residence time of mixture lowering
the yield of FAME. Again similar to the reactive distillation, more investigations
are needed for the application of centrifugal contact separators for the specific feed
stock of algal oil before firm conclusion can be made.
6.7 Membrane Reactor
In order to overcome the limitations of conventional biodiesel production processes,
the development of membrane reactor can be a potential solution. Reaction and
separation occur in a single chamber, and this ensures that the reversible reaction
proceeds in the forward path with efficient removal of desired products from
reaction mixture which leads to increase in yield (Cao et al. 2008, 2007; Dube et al.
2007). Membrane reactor works on the principle of utilizing the immiscibility of
methanol with oil and miscibility of products (FAME and glycerol) in methanol.
During the transesterification process, oil exists in the form of emulsion in methanol
and reaction occurs at the surface of oil droplets. FAME produced via transesterification is soluble in methanol and is able to pass through the membrane with the
by-product glycerol. The oil droplets being larger in size cannot pass through the
membrane and remain in the reactor vessel. The simultaneous removal of product
from a reversible reaction helps in the improvement of the reaction rates, and the
permeate obtained is in pure form which requires less processing. Cao et al. (2008)
have investigated the transesterification reaction using different feedstocks (soybean
oil, canola oil, a hydrogenated palm oil/palm oil blend, yellow grease, and brown
grease) having varied FFA presence. With efficient purification and separation
process, membrane reactor was demonstrated to give high efficacy for different
feedstocks making it a energy efficient, and environmental friendly reactor.
4 Process Intensification of Biofuel Production …
81