Ethanol Distillation FOR bSC STUDENT 2012 -...
Transcript of Ethanol Distillation FOR bSC STUDENT 2012 -...
Distillation of Ethanol
Keikhosro Karimi
Department of Chemical Engineering
I f h U i it f T h lIsfahan University of Technology
Content
- Why purification?y p
- What is distillation?
- A short review on distillation?
Eth l Di till ti- Ethanol Distillation
- Ethanol Dehydration- Ethanol Dehydration
Fe mentationFermentation
C6H12O6 2 C2H5OH + 2 CO2C6H12O6 2 C2H5OH + 2 CO2
Fermented broth or “mash” typically t icontains:
- Ethanol (2-12%)
- Microbial biomass
- Fusel oil
- Volatile components
Stillage- Stillage
Fusel oil
Fusel oil is a mixture of primary methylbutanolsd th l l f d f k t id dand methylpropanols formed from ketoacids and
derived from or leading to amino acids. Depending on the resources used, important
components of fusel oil can be isoamylalcohol, n-propylalcohol, sec-butylalcohol, isobutylalcohol, n-butlyalcohol, active amylalcohol, and n-amylalcohol.
Amount and Application of Fusel Oil
The amount of fusel oil in mash highly depends on the pH of the fermentor. Typically,depends on the pH of the fermentor. Typically, 1–5 L of fusel oil are produced per 1000 L of ethanolethanol
F l il i d i l t f i t Fusel oil is used in solvents for paints, polymers, varnishes, and essential oils.
Aldehyde and other volatile components
Acetaldehyde and trace amounts of Acetaldehyde and trace amounts of other aldehydes and volatile esters are usually produced.usually produced.
Typically, 1 L of acetaldehyde are produced per 1000 L of ethanolproduced per 1000 L of ethanol
Odor of ethanol
Stillage- Stillage consists of nonvolatile fraction of materials
remaining after alcohol distillation. - Composition: depends on the type of feedstock used for
fermentation. Stillage generally contains: Solids (Originated from feedstock proteins and spent Solids (Originated from feedstock proteins and spent
cells) Residual sugars, residual ethanol, glycerol Waxes Fats
ib Fibers Mineral salts
Microbial biomass
Mash is usually centrifuged or gsettled in order to separate the pmicrobial biomass from the liquid and qthen the liquid sent to the ethanol recovery system.
Purification of ethanol
Mash
95% - 99%- Ethanol (2-12%)-Water-Fusel oilVolatile components
Ethanol-Volatile components-Stillage
95%, E10, E30, …
Distillation process
- Distillation is the king of separation process, and the most important and most visible pseparation technology.
- Basis: difference in volatilities or separationBasis: difference in volatilities or separation of more volatile materials from those less volatile or non-volatile materialsvolatile or non volatile materials.
- Distillation is typically used for the separation of ethanol fusel oil aldehydes and stillageof ethanol, fusel oil, aldehydes, and stillage.
Ethanol distillation
Various industrial distillation systems f h l ifi ifor ethanol purification are- Simple two-column systems- Three- or four-column Barbet- Three- or four-column Barbet- Three-column Othmer system- Vacuum rectificationacuu ect cat o- Vapor recompression- Multieffect distillation- Six-column reagent alcohol system.
Parameters in selection of the industrial distillation systems:
Energy consumption (e.g., steam and cooling water consumption)-Quality of ethanol (complete separation of fusel oil and light components).- How to deal with the problem associated with clogging of the first distillation column- Simplicity in controlling the system- Simplicity in opening column parts and cleaningthe columns.- Of course, lower capital investment
Simple two-column system
Othmer system
Barbet system
Thermodynamic ofThermodynamic of Ethanol-Water Mixture
- Ethanol-Water mixture (EWM) is a non-ideal mixtures and show a large positive deviation from Raoult's Law.
- EWM has a high vapour pressure it means that it will have a low boiling point. This means that the molecules are escaping easily and it is not necessary to heat the mixture much to overcome theis not necessary to heat the mixture much to overcome the intermolecular attractions completely.
- The boiling point / composition curve have a minimum value lower g p / pthan the boiling points of either water or ethanol.- This minimum occurs with 95.6% by mass of ethanol in the mixture. - The boiling point of this mixture is 78.2°C, compared with the boiling point of pure ethanol at 78.5°C, and water at 100°C.
http://www.chemguide.co.uk/physical/phaseeqia/nonideal.html
References
- MJ Taherzadeh and K Karimi “Bioethanol: MarketMJ. Taherzadeh and K. Karimi, Bioethanol: Market and Production Processes”, In “Biofuels Refining and Performance” by Ahindra Nag, Mc Graw Hill, 2008.
- B. L. Maiorella. Ethanol, In: Comprehensive Biotechnology, Moo-Young, M. (Ed.), First ed., gy, g, ( ), ,Oxford: Pergamon Press Ltd., 1985.
Dehydration ProcessDehydration Process
Ethanol (90-95%) Ethanol (99%)
Pressure swing adsorption (PSA) with molecular sieve is selected for ethanol dehydration. PSA is a modern technology for ethanol dehydration that is commercialized in h 1980the 1980s.
This process uses the adsorption and d ti t f i l l l idesorption nature of special molecular sieve toward the water
Why Molecular Sieve? Low operating cost and energy consumption It can produce fuel ethanol with water content less
than 0.01% (v/v). PSA for ethanol dehydration is just a physical
process with no addition of chemical components toprocess, with no addition of chemical components to the system and no discharge to environment.
High yield of recovery for ethanol. Less capital investment. Advanced and proven technology with sate and
reliable operationreliable operation.
Process Principle
Molecular sieve: Absorb water vapor from ethanol vapor
M l l i Molecular sieve: A type of white clay Manufactured in granule form Manufactured in granule form Synthetic zeolite of type 3Å is used for this application
The pores are 3Å in diameterpWater molecules are 2.8ÅEthanol molecules are 4.4Å
Therefore, water molecules are strongly attracted into the pores but ethanol molecules are excluded.
http://www.alibaba.com/product-gs/208496770/Molecular_Sieve_3A.html
Good luckGood luck