Summary,Extraction
New knowledge
Triangle phase equilibrium diagram
cross flow process
mass balance in triangle diagram
Old method
theoretical stage model
differential contact model
minimum solvent/feed ratio
engineering considerations
– Exercise 1 of week 9
– Exercise of this week
When to use extraction?
Distillation is preferential.
When distillation is difficult (azeotropic
or relative volatility is close to 1)
When distillation is inefficient (eg 1%
HAc water)
When the component is heat sensitive (eg
bioproduct,penicillin)
Limitation of extraction
AB should be miscible;
B and S should be immiscible or partially
miscible;
Solvent should be regenerated either
through distillation or other methods
Apparatus for extraction
Performance of commercial extraction equipment
type Liquid
capacity
com bine d
streams,
ft3/f t2 - h
HTU
/ft
plate
or
stage
ef ficie ncy
(%)
spacing between
plates
or stages,
in,
typical
applications
mix er - settle r 75 - 100 Duo - Sol
lube - oil
process
spray
colu mn
50 - 250 10 - 20 amm onia
extraction of
salt from
caustic soda
packed
colu mn
20 - 150 5 - 20 phenol
recove ry
perforat ed
- plate
colu mn
10 - 200 1 - 20 6 - 24 30 - 70 furfural
lube - oil
process
agitated
tower
50 - 100 1 - 2 80 - 100 12 - 24 pharm aceut ica
ls and o r gani c
chem ical s
Leaching
When AB is a solid mixture
Solid extraction or leaching
Equilibrium is different from
liquid extraction
How?
Without chemical reaction
With chemical reaction
Equipment is different from
liquid extraction
How and why?
stationary solid beds
moving-bed leaching
dispersed solid leaching
stationary solid beds
similar to the cleaning of filtration cake
moving-bed leaching
similar to the countercurrent extraction in
spray column
How is the solid moving?
dispersed solid leaching
similar to mixer-settlers
mechanical agitation
settling
filtration