Transcript Distillation and Alcohol Production Application

Distillation and Alcohol
Production Application
Distillation and Alcohol
Production Applicaiton
Distillation and Alcohol
Production Application
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Distillation process
Types of distillation
Distillation equipments and properties of
them
Alcohol production
Distillation of alcohol
Types of alcohol distillation
Distillation
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Distillation is a kind of seperation technique of two or
more volatile liquid compunds by using the difference in
boiling points and relative volatility.
The process takes place in a column, and two heat
exchangers.
In the column two phases, liquid and gas, are
distributed to enrich the vapor in more volatile
compounds and enrich the liquid phase on less volatile
compounds.
Mass transfer is the key to a successful distillation.
Advantages & Disadvantages
Advantages
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It has simple flowsheet, low
capital investment, and low
risk. If components to be
separated have a high
relative volatility difference
and are thermally stable,
distillation is hard to beat.
Disadvantages
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Distillation has a low
energy efficiency and
requires thermal stability of
compounds at their boiling
points. It may not be
attractive when azeotropes
are involved or when it is
necessary to separate high
boiling components,
present in small
concentrations, from large
volumes of a carrier, such
as water.
Types of Distillation
Continous Distillation
 Batch Distillation
 Semi-Batch Distillation
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Continous Distillation
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The mixture which is to be
seperated is fed to column
at one or more points.
Liquid mixture runs down
the column while vapor
goes up.
Vapor is produced by
partial vaporisation of the
mixture which is heated in
reboiler.
Then vapor is partially
condensed to earn back the
less volatile compounds to
the column to seperate as
bottom product. (reflux)
Batch Distillation
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The oldest operation
used for seperation of
liquid mixtures.
Feed is fed from
bottom,where includes
reboiler, to be
processed.
Numbers of
accumulator tanks are
connected to collect the
main and the
intermediate distillate
fractions.
Semi-batch Distillation
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Semi-batch distillation
is very similar to batch
distillation.
Feed is introduced to
column in a continous
or semi-continous
mode.
It is suitable for
extractive and reactive
distillations.
Comparsion of Distillation
Types
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For batch distillation, it
is enough to use only
one column to seperate
multicomponent liquid
mixture.
One sequence of
operation is enough to
seperate all the
components in a
mixture.
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For continous
distillation, to seperate
multicomponent liquid
mixtures, more than
one columns are
necessary to be used.
One column is
dedicated to seperate a
specific mixture and
specific operation.
Equipment Designs
Plate Columns (Tray Columns)
 Packed Beds
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Plate Columns (Tray Columns)
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It is the most widely used kind of
distillation column.
Trays are shaped to maximize the
liquid-vapor contact and increase the
mass transfer area.
Tray types include sieve, valve and
bubble cap.
Advantages & Disadvantages
Advantages
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Least expensive colum for
diameters greater than 0.6m
The liquid-vapor contact in the
cross-flow of plate columns is
more effective than
countercurrent-flow in packed
columns.
Cooling coils can be easily
added to the plate column
Can handle high liquid flow
rates.
Disadvantages
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Higher pressure drops than
packed columns
Foaming can occur because
the liquid is agitated by the
vapor flowing up through it.
Packed Beds
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Packings can be provided either as dumped
or stacked.
Dumped packing consistutes of bulk inert
materials.
Stacked packing is includes meshwork which
has the same diameter with the column.
Important criterias for packings are efficent
contact (liquid-vapor), resistence to flow, flow
capacity, resistance of packing against
corrosion.
Advantages & Disadvantages
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When the diameter is
less than 0.6m it is less
expensive than the
plate column.
Packing is able to
handle corrosive
materials.
Lower pressure drop
than in plate columns.
Good for thermally
sensitive liquids.
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Can break during
installation or due to
thermal expansion.
Not cost efficient for high
liquid flow rates.
Contact efficiencies are
decreased when the
liquid flow rate is too low.
Making of Alcohol
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Alcohols, generally can
be created by reduction
of aldehydes or twice
reduction of ketones.
Ethanol (C2H5OH) can
produced by
fermantation of
molases.
Fermantation is done in
a tank and it is cleaned
and sterilized before
the fermantation
begins.
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Molases have strong concentration of sugar which
doesn't provide the adequate conditions for
fermantation. Consequently it must be dilluted to
concentration of %17 sugar.
Optimum enviromental pH range is between 4.0 and
5.0; and optimum temperature is 76°F(25°C).
Fermantated molases is called beer and it contains
%6.5 to %11 alcohol by volume.
Distillation of Alcohol
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Under 1 athmosphere
pressure boiling points of
water and alcohol are 100°C
and 78.3°C.
Water and ethyl alcohol
mixture forms an azeotrope in
athmospheric pressure at a
mole fraction of %89.4 of ethyl
alcohol which means that by
simple distillation of ethyl
alcohol, it cannot be purified
more than %95.6 w.
As distillation equipments,
bubble cap trays and tray
columns are mostly used in
alcohol distillation.(Figure on
left)
Pot Distillation Process (Batch
Distillation)
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Entire batch of beer is
heated in a large container
and alcohol/water vapors
are chanelled into a
distillation column.
After all the boiling and
reflux operations, when
almost all alcohol is boiled,
process is stopped and
stillage is removed.
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The basic advantage of pot distillation is its
simplicity. It has simple equipment system.
Fermantation and boiling for distillation can
take place at the same pot, which makes it
more practical
The disadvantage of the pot distillation is low
distillation efficiency. It requires about three
times more energy comparing to continous
distillation.
Continous-Feed Distillation
Process
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Typically it is also known as
continous distillation.
Alcohol/liquid mixture is fed
to column and it flows.
Flow rate is decreased by
trays.
Mixture boils up in the
reboiler and goes up of the
column to condenser as it
contacts with the
condensed liquid.
The vapor with high alcohol
percent leaves the
condenser to be collected
in accumulator.
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The advantage of the continous feed distillation
process is it's high energy efficiency comparing
to the pot distillation process. Eventually
amount of energy required for per liter of
alcohol is less than in pot distillation. On the
other hand it can operate for long hours (almost
8000 hours per annum)
The disadvantage of continous feed distillation
is it needs a little more complicated equipment
system comparing to the batch distillation.
Vacuum Distillation
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Low temperature allows us
to achieve higher alcohol
concentrations.
At a pressure below 0.1
athmosphere azeotrope
disappears and enables to
distillate to almost 100
percent alcohol.
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Because of the high
operation and
installation costs,
low energy
efficiency, vacuum
distillation appears
to be uneconomical
in the commercial
applications.
Azeotropic Distillation
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This type of distillation is used for processes that
produce almost 100 percent alcohol with help of an
organic solvent and two additional distillations.
A solvent (pentane, gasoline etc.) is added to distillation
product comming out of the usual distillation column.
Mixture is fed to another distillation column which
seperates it into a top product and a bottom product.
Distillate of this column is fed to a third column which
distills out the solvent leaving the mixture of alcoholwater.
Solvent is recycled and never gets out.
System is hard to design and it is more complicated
comparing to ordinary distillation system.