The genus Cinnamomum

The condenser is the most bulky and troublesome unit of the conventional camphor
distillation unit. Since camphor oil partly crystallises at ordinary temperatures, the
conventional spiral condensers cannot be used for the distillation of camphor. The low
price of camphor prevents the growers from high investment in distillation units.
Hence relatively crude condensers are still used for camphor distillation. The vapours
coming out from the distillation chamber (Koshiki) goes through a pipe to three wooden
barrels or boxes, connected in a series. The first condenser serves for preliminary cooling,
where the heavier high boiling fractions are condensed. This condenser is smaller
than the other two. The second condenser is the main part where most condensation
takes place. The barrel type condensers are covered with a V-shaped copper basin, which
is fed with running water throughout the operation. Prior to distillation the barrel
is half filled with water. In the box type (called the Tosa type) the condenser consists
of a big box constructed of heavy wooden planks (about 1.8 m long, 1.2m wide and
0.85m deep). The inside chamber is divided into interconnected compartments. Prior
to distillation the box is half filled with water. The lid of the box consists of a shallow
tray of the same length and width and about 10 cm deep, and the bottom is made of
copper. Water flows through this shallow lid during the distillation period to keep the
lower box cool. The third condenser is similar to the second one, but smaller.
Distillation
Camphor Tree 217
The flow chart of camphor extraction is given in Fig. 9.4. This chart indicates the
various products (camphor and the different types of camphor oil) obtained in the
industrial distillation of camphor wood and fractionation of the distillate.
Chipped wood material is charged tightly into the wooden retort (koshiki), through the
opening at the top, and water in the kettle is brought to a boil. Steam passes through wood
chips carrying vapours of camphor and camphor oil and passes to the condenser where the
vapours condense. Camphor separates in the form of white crystals along the walls of the
condensers. The distillation water is returned into the retort and redistilled (cohobated)
during distillation. The duration of the distillation process depends upon the quantity
of chips charged and the type of wood. Roots require more time than wood (15 hours
compared to 8–10 hours). The optimum rate of distillation is attained when 700–800 ml
of distillate per minute is produced from a 500 kg charge of wood material. The ratio of
oil and water in the distillation is 1:25. On completion of the distillation, the exhausted
chips are discharged through the man-hole in the side of the retort and are used as fuel.
The camphor and camphor oil accumulating in the condensers are usually removed
once a month, after about 40 distillations. The semi-crystalline camphor is first separated
from the camphor oil by crude filtering. The oil is poured into cans, the camphor
packed into barrels and the two products are then carried to the collection centres of
camphor manufacturing companies. Final purification of camphor oil by fractionation
is done by such companies.
Advanced camphor distillation factories were established in Japan, Taiwan and in
China. In such factories, an integrated production process for camphor and fractionated
camphor oil is employed. Continuous vacuum fractionation is used for separating the
various commercially useful fractions. A continuous vacuum fractionation unit consists
of a series of distillation towers where distillation and fractionation take place as
a continuous process. Such units separate camphor and linalool containing fractions and
produce a rectified Ito oil that contains more than 85% linalool.