Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

5 DECOCTION AND HOT CONTINUOUS EXTRACTION TECHNIQUES
5.5.1 Continuous Extraction
For continuously operating extraction, percolation and immersion
are used.
5.5.1.1 Percolation
The solvent passes through the non-moving solid material and
extracts the soluble active constituents. One advantage of this method is
that the solid material requires little mechanical treatment because it does
not need to move in the percolator while the product passes in the solution.
Moreover, since self-fi ltration takes place, there is minimum content of fi ne
solid particles in the extract.
5.5.1.2 Immersion
In this process, the solid material dips completely into the solvent
and is mixed with it. Therefore, no special percolation properties of the
solid material are necessary. The disadvantage is that no self-fi ltration of the
extract solution takes place. Therefore, a fi ltration step has to be added.
5.5.2 Continuous Extraction Equipment
5.5.2.1 Continuous Horizontal Extractor
The solid material is placed in baskets and comes in contact
with the solvent by percolation. The fl ow of solvent through the extractor is
counter-current to the fl ow of solid material.
Figure 5: Continuous horizontal extractor
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