Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

7 DISTILLATION TECHNOLOGY FOR ESSENTIAL OILS
within permissible limits, the process is carried out under vacuum or with
the help of steam distillation.
7.6.1 Continuous Steam Distillation
Steam distillation units involve manual charging and discharging
of plant material from the tank still. These operations are labor intensive
and time consuming. To overcome these problems, continuous steam
distillation plants have been developed in the Soviet Union and have been
in operation since the last couple of decades. These units are being used
for distillation of lavender and require negligible manual handing. Capacities
of 2 tonnes per hour are quite common. Incoming plant material is fi rst
chopped with special ensilage cutters and then conveyed to the top of a tall
distillation column by means of a belt conveyor. The movement of material
inside the column is by gravity or by special helical screw conveyors. Sometimes
two columns in series are used for complete removal of oil. Steam
is injected at multiple points in the column. Spent material is continuously
ejected out of the bottom of the distillation column by special screw conveyors
with a vapor lock which does not allow steam to escape.
Fabrication and operation of continuous distillation columns is
rather complicated and these have not yet gained acceptance and popularity
outside the former Soviet Union. In another development, containerized
distillation is also being used for the distillation of Mentha piperita and
lavender in some parts of the United States. In this method, large capacity
containers mounted on wheels are attached to a harvester which directly
loads the plant material into the containers from the fi elds (these containers
have inbuilt steam coils); these are then taken to the distillation area
where steam is directly connected to the coils and the top is closed and
connected through a vapor line to the condenser and subsequently to the
oil separator.
7.7 Conclusions
Distillation is the most widely used method for the extraction
of essential oils. Proper selection of the distillation technique, design and
material of fabrication of the equipment, and processing parameters all play
vital roles in determining the quality and yield of an essential oil.
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