Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS
and evaporation requirements for concentrated products are reduced. Reducing
the cost of evaporation has the further advantage of minimizing the heat
damage to thermolabile constituents. Some of the modified maceration procedures
used for large-scale extraction are described in the next paragraphs.
3.5.4.1 Circulatory Extraction
The effi ciency of extraction in a maceration process can be
improved by arranging the solvent to be continuously circulated through the
drug, as indicated in the Figure 1. Solvent is pumped from the bottom of the
vessel (through an outlet) and is distributed by spray nozzles over the surface
of the drug. The movement of the solvent reduces boundary layers and
the uniform distribution minimizes local concentration in a shorter time.
3.5.4.2 Multistage Extraction
Figure 1: Circulatory extraction
In the normal maceration process, extraction is incomplete,
since mass transfer ceases when equilibrium is reached. This problem can
be overcome using a multistage process. The equipment needed for this
method is a vessel for the crude drug, a circulating pump, spray distributors
and a number of tanks to receive the extracted solution. The extractor and
tanks are connected with piping and valves as shown in Figure 2, so that any
of the tanks may be connected to the extractor for transfer of the solution.
Each batch of drug is treated several times with solvent and, once a cycle
is in process, the receivers contain solution with the strongest in receiver 1
and the weakest in receiver 3.
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