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Anhydrous Alcohol
Fermentation Industry
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The composition of vapor in
equilibrium with liquid on horizontal
line
Alcohol cant not be made stronger
than 95% by rectification
Why?
Constant Boiling Mixture
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Constant Boiling Mixtures An azeotrope is a mixture of two or more liquids in such
a ratio that its composition cannot be changed by simple
distillation This occurs because, when an azeotrope is
boiled, the resulting vapor has the same ratio of
constituents as the original mixture.
Because their composition is unchanged by distillation,
azeotropes are also called (especially in older texts)
constant boiling mixtures.
Azeotropes consisting of two constituents are called
binary azeotropes.
Those consisting of three constituents are called ternary
azeotropes.
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Minimum and Maximum Boiling
Azeotropes
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Anhydrous Alcohol
Absorbing 4 to 5%water from 95%alcohol
by quicklime with subsequent distillation
Expensive Forms azeotrope
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Minimum constant boiling mixtures
Boiling at temp. lower than 95% alcohol or water
Using benzene as the third component
Two homogenous mixtures
A heterogeneous mixture
ternary
Same concept can be used for separation of
organic liquids such as propyl alcohol and for
removing water formed in sulfonation
(benznesulfonic acid) and esterification (ethyl
acetate)
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Ternary ( boiling at 64.85C) (F)
starting composition must lie on
line CF to ensure that removal
of cbm will leave alcohol in still.
If the starting mixture is made
of adding benzene to
95%alcohol , starting
composition must lie on line
EB. Hence G represents
starting composition
Ifenough benzene is added
tothe 95% alcohol,constant
distillation wouldgive
ternaryconstant boiling
mixtureattopofcolumnand
absolutealcoholatthe
bottom ofthecolumn
Mand N represents the separationofcondensate intotwoliquidlayesTheratiooftop N to bottom layerM is equaltoMF/FN or84:16
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New Concepts
Dual distillation requires
Much more energy, exception being vacuum
distillation
Aluminum oxide and silicon oxide
Use liquid carbon dioxide to extract alcohol and
then depressurizing to flash off carbon dioxide
Other solvents such as dibutyl phthalate underinvestigation due to their solubility in alcohol
Cellulose or corn meal to adsorb water
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Energy Demand Cutoff
Much favored because of gasohol production
Energy liberated by burning 1L of 100% alcohol
is about 23MJ
Fermentation processes consume more than
42MJ
To make production viable require process that
need less energy Recent processes cut off energy demand to 11-
1.5MJ
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Thanks
Good Luck