Supercritical Fluid Extraction
Andrew DeMartini
Brooks Hurd
Chris Petry
Amanda Walker
Supercritical Fluids
• Supercritical fluid is
one that is above
critical temperature
and critical pressure.
• Possess properties of
both gases and liquids.
• Density, diffusivity,
and viscosity are vital
properties to SCF.
General Process
• Basis: the more volatile component will
partition into the supercritical phase
• Pump liquid solvent from a reservoir and
adjust to supercritical conditions
– CO2 is the most common solvent
• Remove solute and solvent from extractor
• Separate extract from CO2
Equipment
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Heat exchanger
Pump or compressor
Extraction chamber
Collection trap
Separator
Compressor
Governing Equations
• Liquid Extraction can be modeled as a
regular stripping column
– Number of Equilibrium Stages
– Size of Equilibrium Stages
• Solid Extraction is controlled by Mass
Transfer of Supercritical Fluid through solid
• Mass Transfer Equation: Ca  v  Ca  DAB 2Ca
t
SFE Application: Extraction of
Vitamin E from Olive Oil
• Vitamin E is extracted from olive oil via
counter-current supercritical extraction
• CO2 is brought to supercritical state before
entering the column
• Fenske rings are used as the column packing
• Cascade decompression takes place after the
extraction to separate the CO2 from the
product
Olive Oil Extraction Schematic
Column Schematic
• Column operates at
313 K and 20 MPa
• Column used is 17.6
mm I.D. and 1.8 m in
height
• Extraction is 50%
efficient with no
raffinate recycle
streams
Alternative Methods
• Aerosol Solvent Extraction System
– Solution sprayed through small nozzle
– Small droplets of the solution are mixed with the
supercritical fluid and the liquid droplets dissolve into
the supercritical fluid
• Solution Enhanced Dispersion Process
– Supercritical fluid is mixed with the solution.
– Then the mixture is put into a chamber and is followed
by change in temperature and change in pressure.
Solvent Variations
• Water could be used as the supercritical fluid
– Critical water works well for aqueous streams with a
low concentration or organic materials, but it is a poor
solvent for many inorganic compounds.
• A mix of carbon dioxide and a light hydrocarbon
may be used.
– Ethane and propane mixtures are ones that have been
used successfully.
– Hydrocarbons cost more than carbon dioxide, but work
better as a solvent.
Pros and Cons of SFE
Pros
• Non-Toxic Solvent
• Low Heating Cost
• Inexpensive Solvent
• Easy Separation after
Extraction
• High Efficiency
Cons
• High Pressure System
requires High Pressure
Vessel
• High Pumping Cost
– High Initial Cost