AIChE General Meeting
12/10/2013
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General Announcements
o Senior Design Presentation Today
o Christmas Party
 Thursday, December 12
 4:00 pm in CBEC 212
 Jeopardy
 Dodgeball
 The Hobbit
 Cookie Bake-Off
 Taco Dinner
Senior Design Project
o ABE Fermentation
 Introduction
 Acetone, butanol, ethanol
 Fuel in internal combustion engine
 Butanol advantages vs. ethanol
o Better blending with gasoline
o Less likely to separate from water contaminated fuel
 History
 Past: Bio-butanol was first commercialized in 1914
 Present: petroleum production of butanol became cheaper
 Process
 Improvements
o Recovery improvement
o Research
 Heuristics
 Mass Balance
 Energy Demand
 Separation Sequence
 Equipment sizing
 Chemistry
 Acetone, butanol, and ethanol in a 3:6:1 ratio
 Anaerobic process (no oxygen)
 Conversion of 99%
 Kinetics limited by:
o Glucose inhibition
o Butanol inhibition
 Difficulty in controlling metabolism
 Must account for heat of reaction
 Separation limits due to azeotropes
 Objectives
 Requirements:
o 99.5% butanol and ethanol
o At least 90% aceton purity
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PFD
 Fermenter to flash to 3 distillation columns
Process Description
 Purchase corn
 Grind corn
 Mix with water
 Cooked to fertilize
 Sent to fermenter
o ABE produced
 Separated
o Non dissolved solids: centrifuge
o “Syrup” goes to evaporators
Fermenter
 Batch vs. Continuous
o Batch: easy to model, limited upset loss, easy to clean
o Continuous: faster rates
 In Situ Gas Stripping
o Strip ABE from the fermenter while it’s running
o Removes product as its formed
o Requires extremely high gas flow rates
 Product Recovery
o Partial condenser to remove non-condensables
o Remove excess water
o Extra stages allow for increased purity, which saves money
o Series of decants allows for separation of butanol-water
o Adsorber columns to separate ethanol and water
 Heat Generation
o Equation to determine the eat being generated
o Total rate: 3.27*10^9 kJ/hr
o Result verification conducted
Safety
 Low to moderate temperatures
 Atmospheric pressure
 Fire hazard
o Volatile organics
o Hydrogen gas
 Safety valves
o Over the fermenter
o On the distillation columns overheads
Economic Analysis
 Become profitable after year 4
 Major costs come from towers and solids handling
 Operating costs mainly from heat exchanger
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 To reduce costs: less water
Conclusions
 Separating out water reduces costs
 Azeotropes cause significant difficulty
 Safe design at low temperatures and pressures
 In-situ stripping not feasible
Recommendations
 Alternative separations
 Different substrates
 Different types of bacteria
Questions
 What’s an azeotrope?
o 2 components form a different boiling point than the
separate components
 Biggest challenge?
o Separating butanol and water
o Gas stripping
o Working with Aspen and azeotropes
o Determining heat inside of the fermenter
 Why only 90 g/L of substrate?
o Any higher and reached the value where the
microorganisms were destroyed
 How long is the cycle on the molecular sieves?
o Analyzer in the outlet stream
 Why heating so much water?
o Condenser
o Keep ABE out of the water
 Water utilization target?
o 2.5 gallons water for every 1 gallon butanol produced
 Operating Costs for how many years?
o One year: lots of low pressured steam
 Products in fermenter vapor stream?
o Everything came off but didn’t add another adsorber
column because of additional water
 Burn off acetone. What to do with ethanol?
o Sell both ethanol and butanol