Distillation dehydrations sieves

1. Dehydration
(Sieves)

2. Molecular Sieve Overview
• Absolute or anhydrous alcohol generally refers
to purified ethanol, containing no more than one
percent water.
• Alcohol as manufactured in a distillation column
is rectified spirit, It is not possible to obtain
absolute alcohol by simple fractional distillation,
because a mixture containing around 95.6%
alcohol and 4.4% water becomes a constant
boiling mixture (an azeotropic mixture).

3. Molecular Sieve Overview
• Therefore a special process for removal of
water is required for manufacture of
absolute alcohol.
• In order to extract the remaining water
from alcohol it is necessary to use some
dehydrate, which is capable of separating,
water from alcohol.

4. Molecular Sieve Overview
• To remove this final percentage of water
we use a Molecular Sieve system.
• The final process is the dehydration of
the alcohol to less than 1% water.
• This process is a stand-alone system,
able to startup and stop with minor
effects on the rest of the system.

5. Molecular Sieve Overview
• Using adsorbent
desiccant which
consists of small
granular substances
(beads) that are
manufactured from
clay like materials
such as potassium
aluminosilicates, to
remove the
remaining water from
the 190 proof alcohol
to produce 200 proof
ethyl alcohol.
(Audio pronunciation
for ”aluminosilicate”
hear it

6. Molecular Sieve Desiccant (Beads)
• An Angstrom is a unit of measure for
length. It is sometimes used expressing
the size of atoms, and lengths of chemical
bonds.
• Sieve beads are manufactured to a very
precise pore size such as 3 Angstrom.
• Water molecules have a diameter of 2.5
Angstrom ethanol has a diameter of 4
Angstrom.

7. Molecular Sieve Desiccant (Beads)
• Molecules small enough to pass through such as
water are adsorbed while larger molecules like
alcohol are not adsorbed and pass around the
bead.
• It is different from a common filter in that it
operates on a molecular level. For instance, a
water molecule is small enough to pass through
while larger alcohol molecules are not. Because
of this, they function as a desiccant.
• Molecular sieve can adsorb water up to 22% of
its own weight in water.

8. Molecular Sieve Desiccant
Regeneration Overview
• The adsorbent desiccant contained in the molecular
sieve beds must be regenerated, thus removing the
water that it has collected from the 190 proof vapor while
that bed was online.
• During the regeneration process, the bed is operated
under a vacuum, which favors the de-adsorption
(release) of water from the beads back into the vapor
phase. The vapor leaving the regenerating bed is
approximately 145 proof ethanol. A stream of 200 proof
vapor from the “online” sieve bed is used to pass through
(sweep) in a backward direction the bed that’s being
regenerated in order to flush out any remaining water in
the bed

9. 190 Proof Sieve Vaporizer
• The 190 proof vaporizer, uses direct 135# steam
from the boiler to boil the 190 proof back to
vapor form.
• The 190 proof enters the bottom of the tube side
of the exchanger and is heated by the steam on
the shell side.
• The 190 proof is vaporized and superheated to a
temperature of 300 degrees F at 30 to 35 psi.
and flows to the sieve bottles. As the steam is
condensed, it flows through a stream trap and
travels to the Distillation Condensate Tank.

10. Molecular Sieves
• The Sieve feed pump (P-702) is used to
pump 190 ethanol from the 190 surge tank
through the 702 filter pot and into the
sieve vaporizer.
• The 702 filter pot uses a 10 micron bag filter to
remove any solids before they can be feed into
the sieve beds.
• There are two molecular sieve “Beds” (vessels
containing desiccant).

11. Molecular Sieves
The sieves can be ran is several different modes:
– Auto time – This means that all the sequences will
use timers to control the system.
– Auto event – This means that all the sequences will
use some timers and some pressure differentials to
switch the sequence.
– Manual step mode – This means you can step the
sieve sequence to check valves etc.

12. Sieve Operation
Step #1,Bed A
is in on-line or
“Adsorb” mode.
Bed B is

13. Sieve Operation

14. Sieve Operation

15. Sieve Operation
BED A
EAST
BED B
WEST
EV-766A
EV-767B
EV-766B
EV-765B
EV-768BEV-768A
EV-765A
EV-740
EV-769
EV-767A

16. Sieve Operation
BED A
EAST
BED B
WEST
EV-766A
EV-767B
EV-766B
EV-765B
EV-768BEV-768A
EV-765A
EV-740
EV-769
EV-767A

17. Dehydration Operations

18. Dehydration Operations

19. Dehydration Operations

20. Dehydration Operations

21. Dehydration Operations

22. Dehydration Operations

23. Dehydration Operations

24. Dehydration Operations

25. Molecular Sieves
• As the hot 190 proof vapor from the vaporizer
goes to the bed on line the bed that is in regen
mode has hot 200 proof vapor brought through it
to remove all the water.
• Then the two beds switch and the other bed is
online while the other is in regen.
• The product from the bed that is online then
goes to the 1501 or 1502 heat exchangers.

26. Molecular Sieves
• These Sieve vapor/beer heat exchangers
are used to both cool the 200 proof vapor
and also to pre-heat the beer before it
goes to the Binary column.
• After the cross flow heat exchanger, the
200 product flows into the 200 product
surge tank.
• From the 200 product surge tank the
product is pumped through the 751 filter
pot by the 751 pump (P-751).

27. Molecular Sieves
• This 751 filter is used to filter out any solids that
might be in the product, such as sieve bead dust
from the sieve beads decomposing.
• The final stage is further cooling of the 200 proof
alcohol, after the filter pot, the flow goes through
the 200 product final cooler which is a water
cooled plate and frame heat exchanger.
• The final product is a minimum of 99% ethanol
and is sent to one of two shift tanks.

28. Molecular Sieves
• Once in Shift Tanks a sample is pulled and
tested in the quality assurance lab to insure that
our specifications are meet.
• Shift tanks are tested for the purity of the
alcohol.
• Our 200 proof alcohol has maximum moisture
content of .99%.
• The next test is to determine the level of acidity,
our maximum allowable amount is 70 parts per
million (PPM).

29. Molecular Sieves
• When the shift tank results are in and have met
specifications the shift tank can be sent to
storage.
• Part of the process of transferring the product to
storage is rendering it unfit for consumption.
• This is achieved by adding, “denaturant” such as
unleaded gasoline.

30. Regeneration
• The adsorbent desiccant contained in the
molecular sieve beds must be regenerated, thus
removing the water that it has collected from the
190 proof vapor.
• During the regeneration process, the water
adsorbed into the bed from the 190 proof vapor
stream is removed.
• A slipstream of 200 proof vapor from the “online”
sieve bed is used to pass back through, in a
backward direction, the bed that’s being
regenerated.

31. Regeneration
• During the regeneration process, the bed
is operated under a vacuum, which favors
the de-adsorbtion of water from the bed
back into the vapor phase.
• The vapor leaving the regeneration bed is
approximately 145 proof ethanol.

32. Regeneration
• The 145 proof ethanol vapor stream is
condensed in the regeneration condenser and
then collected in the regeneration tank where it
is pumped through the regen scroll heat
exchanger and back into the regen tank.
• To control the level in the regen tank a portion of
the liquid is removed and sent to the rectifier
feed tank.

33. Mole Sieve Vacuum System
• Regenerating the Mole Sieve under vacuum
favors the desorbtion of water from the
desiccant.
• The vacuum for the regen system is pulled on
the regen tank by a liquid ring vacuum pump.
• The liquid for the ring is supplied from regen
pump.
• The liquid used for the vacuum pump is then
sent to Rectifier Feed tank.
• The vacuum on the system is around 2 PSIA.

34. Storage and Denaturant Addition
• The final step in this process is transferring the
final product to the main storage tanks.
• As stated before, this 200 proof ethyl alcohol
must be rendered unfit for human consumption
before it can be loaded for shipment.
• The amount of gallons transferred from a Shift
tank to storage is measured via the totalizer on
the shift tank to storage flow meter.
• The control room operator will calculate the
amount of gallons of Denaturant that is to be
pumped into the storage tank.

35. Storage and Denaturant Addition
• In the field an operator will open the denaturant
to storage valve and pump the calculated
amount of Denaturant into the storage.
• The denaturant being pumped is measured via
the denaturant flow meter.
• The unleaded gasoline (Denaturant) is added at
a rate of 4.5 to 5 gallons per every 100 gallons
of alcohol, or 4.5% to 5%.
• The final proof of the ethanol in the main storage
tanks is 201 to 203 proof. The higher proof is
due to the difference in density between the
ethanol and denaturant.