Extraction Technologies For Medicinal And Aromatic Plants - Unido

7 DISTILLATION TECHNOLOGY FOR ESSENTIAL OILS
7.5.2 Proper Design of Equipment
Improper designing of tank, condenser or separators can lead
to loss of oil and high capital investments. The design of the furnace and
chimney affects the fi ring and heat control of the distillation rates. Tank
height:diameter ratio is important. Similarly the use of a condenser with an
improper design and without calculating the heat transfer areas based on
the steam generation areas will lead to improper condensation and loss of
oil.
7.5.3 Material of Fabrication of Equipment
Essential oils which are corrosive in nature should be preferably
distilled in stills made of resistant materials like aluminum, copper or
stainless steel. The tank still can be made from a cheaper metal like mild
steel or galvanized iron, and the condenser and separator can be made
from a resistant material like stainless steel. As only vapor is present in the
tank still, the rust and other products of corrosion may not be carried over
into the oil. This can result in considerable savings in the capital cost of the
equipment. Expensive, high-value essential oils like rose, agarwood, kewda,
sandalwood and lavender should be distilled in stainless steel systems.
Although copper was the most common material of fabrication of distillation
stills since ancient times, its availability is getting reduced and with the arrival
of superior alloys like stainless steel, it is slowly disappearing from the
scene.
7.5.4 Condition of Raw Material
The condition of the raw material is important because some
materials like roots and seeds will not yield essential oil easily if distilled in
their natural state. These materials have to be crushed, powdered or soaked
in water to expose their oil cells. Chopping of plants will also change the
packing density of the material when placed in the distillation still. One can
pack up to 50% more plant material in the same still after chopping of some
aromatic herbs like mint. Air drying and wilting the herb prior to distillation
also has considerable effect on distillation. If required, drying of the herbs
prior to distillation should be done in shaded areas and the dried material
should not be kept in heaps.
7.5.5 Time for Distillation
Different constituents of the essential oil get distilled in the
order of their boiling points. Thus, the highest boiling fractions will be last
to come over when, generally, very little oil is distilling. If the distillation is
terminated too soon, the high-boiling constituents will be lost. In many aromatic
plants, like vetiver, patchouli, chamomile, sandalwood and agarwood,
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