. The feed mass flow
rate was calculated multiplying the volumetric flow rate by the
feed density. The feed volumetric flow rate was controlled every
10 min by observing the level of a graduate glass vessel (feed reservoir).
If the measured volumetric flow rate differs from the desired
value, the motor rpm must be regulated until the desired value is
achieved. At the beginning of the experiment the column operates
without reflux in order to collect a reasonable amount of liquid in
the bottom of the separator. When the liquid level in the bottom
of the separator reaches the upper part of the view cell, the reflux
pump is turned on and the extract is recycled into the top of the
column with the desired reflux flow rate. This can be viewed as the
beginning of the extraction experiment. In the following 3 or 4 h,
the raffinate and extract are collected every 30 min and both the
overall mass balance and gas load are checked. The extraction column
is said to reach the stationary state when gas load reaches a
constant value. The gas load is measured by taking sample at the
top of the column as follows. A special glass tube (cold trap) is connected
to a high pressure valve at the tubing line leaving the top
of the column. After opening the high pressure valve, the supercritical
carbon dioxide containing the solubilized light fraction of
palm fatty acids distillates is expanded into the atmosphere and
the precipitated condensates trapped in the glass tube. The weight
of condensates was determined by weighing in an analytical balance
(Sartorius GmbH, Göttingen, Germany, Model: R 300 S-D) the
glass tube before and after sampling. The volume of the expanded
carbon dioxide was measured with a gas flow meter.