This ppt is about the process of supercritical fluid extraction of oils from oilseeds

1. Presented by:
Neha Jaiswal (11)
Urmi Sarkar (23)
Aurik Bairagi (05)

2. CONTENT
 Introduction
 What are super critical fluids?
 Most commonly used SCF
 Advantages
 Limitations
 Applications of SFE
 SFE process
 Pumps
 Pressure vessels
 Precaution
 Pressure maintenance
 Collection
 Concentration profiles during typical SFE
 Explanation
 Essential steps in SFE
 Concentration profiles for diffusion limited &
solubility limited extraction
 Explanation
 Extraction profiles & explanation
 Optimization

3. INTRODUCTION
SUPERCRITICAL FLUID EXTRACTION(SFE) is the
process of separating one component(the extractant) from the
another( the matrix) using supercritical fluids as the extracting
solvent.
Extraction was usually done from a solid matrix, but can also be
done from liquids.

4. WHAT ARE SUPER CRITICAL FLUIDS ?
 A supercritical fluid (SCF) is any
substance at a temperature and pressure
above its critical point, where distinct
liquid and gas phases do not exist. It can
effuse through solids like a gas, and
dissolve materials like a liquid
 “Supercritical fluids are suitable as a
substitute for organic solvents in a range
of industrial and laboratory processes.
 Carbon dioxide and water are the most
commonly used supercritical fluids,.

5. MOST commonly USED SCF:
 Carbon dioxide(co2)is the most
commonly used SCF sometimes
modified by co-solvents such as ethanol
or methanol.
 Extraction conditions for supercritical
carbon dioxide are
1.Above the critical temperature 31°C
2.Above critical pressure 74 bar.

6. ADVANTAGES:
 SELECTIVITY:
 The properties of a SCF can be altered by varying the temperature and pressure ,allowing
selective absorption.
 SPEED:
1. Diffusivities are much faster in supercritical fluids than in liquids.
2. Also there is no surface tension and viscosities are much lower in liquids.
3. As a result of both ,the speed of the extraction process becomes faster.

7. LIMITATIONS:
 It’s a costly procedure than conventional liquid extraction.
 Requirement for high pressure
 Co2 has limited dissolving power so cannot be always used as a solvent
alone, particularly for polar .
 The use of modifiers increases the range of materials which can be
extracted.

9. SUPERCRITICAL FLUID EXTRACTION PROCESS
Requirements For A Supercritical Fluid Extraction System

10. PUMPS
 CO2 usually pumped as a liquid.
 Temperature:- below 50
C
 Pressure:- 50 bar
 Pumped in incompressible form.
 If pumped in supercritical form, most of pump stroke would be used in
compressing the fluid rather than pumping it.
 Small scale extractions:- reciprocating CO2 pumps/ syringe pumps.
 Large scale extractions:- diaphragm pumps.
 Pump head requires cooling.

11. PRESSURE VESSELS
 Range from simple tubing to more sophisticated purpose built vessels with
quick fittings.
 Pressure requirement:- 74 bar(minimum)
 Pressure required for most extractions:- under 350 bar
 Pressure requirement for vegetable oils:- 800 bar (complete miscibility of two
phases)
 Should be equipped with means of heating
 Small vessels:- placed inside an oven
 Larger vessels:- oil or electrically heated jacket

12. PRECAUTION(in pressure vessels)
In case rubber seals are used on the vessels care should be taken as because:-
 Supercritical CO2 may dissolve in rubber
 It may cause swelling
 Rubber ruptures on depressurization

13. PRESSURE MAINTENANCE
 Smaller systems( up to about 10ml/min):- simple restrictor can be
used
 Larger systems:- back pressure regulator will be used
 Heating must be supplied because adiabatic expansion of CO2
results in significant cooling.
 This is problematic because:- water or other extracted material
peresnt in sample will freeze in valves creating blockage.

14. COLLECTION
 Density and dissolving power of supercritical fluids varies with
pressure.
 Solubility of low density CO2 is lower as compared to
supercritical fluids.
 From extraction vessel it is passed through lower pressure vessels
 Solubility decreases and extractant precipitates.
 Solvent may be recycled or depressurized to atmospheric pressure
and vented

15. CONCENTRATION PROFILES DURING A TYPICAL SFE
EXTRACTION

16. EXPLANATION OF CONCENTRATION PROFILES
Figure a)
At the start of
extraction the
level of extractant
is equal across
the whole sphere
Figure b)
As extraction
commences the
material is extracted
from the edge of the
sphere and the level
of extractant in the
centre is unchanged
Figure c)
As extraction
progresses the
concentration in the
centre drops as
extractant diffuses
towards the edge of
the sphere

17. ESSENTIAL STEPS IN SFE

18. CONCENTRATION PROFILES FOR DIFFUSION LIMITED
AND SOLUBILITY LIMITED EXTRACTION

19. EXPLANATION
Figure (a) (diffusion limited
extraction)
 Dissolution is fast relative to diffusion
 Extractant is carried away from the edge
faster than it can diffuse from the center, so
conc. At center drops to 0.
 Extraction is completely diffusion limited.
 Rate of extraction increases with increased
diffusion rate ( eg-raising temperature)
 The rate is independent of flow rate of
solvent
Figure (b)(solubility limited
extraction)
 Dissolution is slow relative to diffusion.
 Extractant is able to diffuse to edge to the
faster than it can be carried away by the
solvent. Hence, conc. Profile is flat.
 Extraction rate increases with increased
dissolution rate.
 Extraction rate depends on the flow rate of
solvent.

20. EXTRACTION PROFILE FOR DIFFERENT
TYPES OF EXTRACTION
Extraction curve of %recovery
against time is used to
elucidate the type of extraction
occurring

21. EXPLANATION FOR EXTRACTION
PROFILES
Curve (a)
 Diffusion controlled curve
Initially the extraction is
rapid until the concentration
at the surface drops to zero
and then the rate becomes
much slower.
%extracted eventually
approaches to 100%
Curve(b)
Solubility limited extraction
Extraction rate is almost
constant and only flattens off
towards the end.
Curve(c)
There are significant matrix
effects.
There are some sort of
reversible interaction with the
matrix, such as desorption from
an active site.
Recovery flattens off and is
100% recovery is not known,
then it is hard to tell that
extraction is less than complete.

22. OptimizatiOn:
 Maximizing Diffusion:
 By increasing the Temp of the Super Critical Extraction Fluid.
 By swelling the Matrix or reducing the Particle size.
 Matrix swelling can be done by increasing the pressure of the solvent.
 Also can be done by the addition of the Modifier to the solvent.
 Some Polymers & Elastomers can be used as they can increase the diffusivity
several times as they swollen rapidly in contact with CO2.

23. OptimizatiOn:
 Maximizing Solubility:
 Higher Pressure increase the Solubility.
 The effect of temperature is less certain as close to the critical point.
 Increase in temperature causes decrease in density hence dissolving capacity.
 At pressure well above the critical pressure increase in temperature increase the
Solubility.
 Addition of low level Modifiers can increase the Solubility of the fluid. Eg.
Methanol, Ethanol etc.
 These are called Entrainers.

24. OptimizatiOn:
 Optimizing Flow rate:
 Flow Rate of Super Critical Extraction Fluid is measured in terms of Mass Flow Rate,
because the CO2 changes its volume according to temperature.
 Coriolis Flow meters are the best to achieve flow confirmation.
 To maximize the Rate of Extraction the Flow rate should be high enough that extraction to
be completely Diffusion limited.
 But this will be very wasteful of solvent.
 To minimize the amount of solvent, the extraction should be completely Solubility limited.
 But it will a take a very Long time.
 So the flow rate should be determine by the factors of Time, Solvent Cost, and also the
capital cost of Pumps, Heaters & Heat Exchanger.
 The Sweet point will be in the region where Solubility & Diffusivity both are significant
factors.