large scale extraction

Question 1

circulatory extraction

Answer 1

 The efficiency of extraction in a maceration process can be improved by arranging for the solvent to
be continuously circulated through the drug, as indicated in the figure below.
 Solvent is pumped from the bottom of the vessel to the inlet where it is distributed through 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.

Question 2

procedure

Answer 2

 Fill extractor with drug, add solvent and circulate. Run off to receiver 1.
 Refill extractor with solvent and circulate. Run off to receiver 2.
 Refill extractor with solvent and circulate. Run off to extractor 3.
 Remove drug from extractor and recharge. Return solvent from 1 to extractor. Remove for evaporation.
 Return solution from 2 to extracture and circulate. Run off to receiver 1.
 Return solution from 3 to extractor and circulate .
 Run off to receiver 2.
 Add fresh solvent to extractor and circulate.
 Run off to receiver 3.
 Remove drug from extractor and recharge.
 Repeat cycle.

Question 3

where drug immersed in a solvent

Answer 3

 By agitating the mixture occasionally, local concentration of the solution is dispersed increasing the
concentration gradient.
 By agitating the drug and solvent continuously increases the concentration gradient by dispersion of
local concentration as well as reduces the thickness of the boundary layer.
 By suspending the drug in a cloth or above a perforated plate near the surface of the liquid. As the drug
dissolves, the density of the solution increases leading to the convection of the solution, increasing the
concentration gradient through the boundary layers

Question 4

if the drug is poistioned so that the solvent flows past the particles

Answer 4

 The flow replaces the solution by pure solvent causing the increase in the concentration gradient
 Flow of the solvent between the particles reduces the boundary layer increasing the concentration
gradient.
 This can be achieved by suspending drug in a cloth bag or above a perforated plate

Question 5

elevated temperature advantages

Answer 5

 Solubility of most of the material is higher at higher temperature.
 Viscosity of the solvent gets reduced decreasing boundary layer thickness
 Diffusion coefficient is proportional to the absolute temperature and inversely proportional to the
viscosity, so raising the temperature