distillation dehydration (sieves)5
TRANSCRIPT
Dehydration(Sieves)
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).
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.
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.
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
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.
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.
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
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.
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).
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.
Sieve Operation
Step #1,Bed A is in on-line or
“Adsorb” mode.Bed B is
Sieve Operation
Sieve Operation
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
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
Dehydration Operations
Dehydration Operations
Dehydration Operations
Dehydration Operations
Dehydration Operations
Dehydration Operations
Dehydration Operations
Dehydration Operations
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.
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).
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.
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).
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.
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.
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.
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.
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.
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.
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.