De-oiling of Raw Lecithin by High Pressure Extraction ... - ISSF 2012

De-oiling of Raw Lecithin by High Pressure Extraction Processes
Volkmar Steinhagen 1 , Dr. Christoph Lütge 1 , Michael Bork 1 , Maša Knez Hrnčič 3 , Željko Knez 2,3
1 Uhde High Pressure Technologies GmbH, 58093 Hagen, Germany
2 CINS d.o.o, SI 2000 Maribor, Slovenia
3 University of Maribor, Faculty of Chemistry and Chemical Engineering, Laboratory for Separation Processes
and Product Design, SI 2000 Maribor, Slovenia
Corresponding author: volkmar.steinhagen@thyssenkrupp.com; Ph.: +49 2331 967-381; Fax: +49 2331 967-370
ABSTRACT
The development of a new process for de-oiling of raw lecithin (dried degumming residue) is presented.
Research on laboratory scale was later verified on a pilot scale plant and in next step in a small scale production
plant. In each scale the target concentration of minimum 95% of phospholipids was reached in a free flowing
powderous product. A production plant for the continuous supercritical de-oiling of soy raw lecithin with carbon
dioxide was designed, engineered, assembled, started up and it is in operation since middle of the year 2007.
INTRODUCTION
Separation and formulation of products by supercritical fluids and production of substances and composites with
unique properties and characteristics for the use in different applications are now days intensively studied. One
of the most important advantages of the use of supercritical fluids is the design of solvent free products with
special product properties.
Lecithin is a natural emulsifier, which is found in high concentrations in soy beans and it is a by-product of the
soy bean oil production. It is used as a nutraceutical, as emulsifying agent in the food industry and as a source for
phosphatidylcholine (PC) in the pharmaceutical industry. Soy lecithin is mainly used in the food industry.
Lecithin is not a single substances but a mixture of different phospholipids: phosphatidylcholine (PC),
phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatoic acid (PA) and others [1]. The raw lecithin,
with a typical content of 50% of phospholipids, is conventionally de-oiled by acetone to form a pure lecithin in
powderous or granular shape with phospholipids content of approx. 97%. Supercritical CO2 processing of raw
lecithin is an alternative to overcome the problems of acetone residues in the de-oiled lecithin and extracted oil.
The conventional process need solvent recovery and processing plants have to be explosion-proof. The demand
of green products requires the use of green solvents - like CO2 [2-7]. De-oiling of lecithin using supercritical
fluids was investigated by several research groups [8-14] but up to our new developed process no application on
industrial scale was carried out. The development of a new process was started to establish a feasible process
leading to a production scale plant, which produces lecithin powder with a minimum content of 95% of
phospholipids. Fundamental thermodynamic data as well as mass transfer, mechanical design of industrial-scale
equipment, influence of process parameters on lecithin particle size and particle size distribution, particle shape
and modeling of extraction process was studied.
PROCESS DEVELOPMENT
Thermodynamic data
For the process design solubility measurements and phase equilibrium observations were performed for the
system raw lecithin (50% phospholipids)/CO2 in a variable volume high pressure view cell which was supplied
by NWA (Lörrach – D) presented on Figure 1.
CO 2
PI
TI
TIC
(a)
(b)
Figure 1: High pressure view cell: flow sheet (a) and photo (b) of the apparatus (60 mL, max. operating pressure
700 bar and max. operating temperature 250°C)

Solubility measurements were performed in a pressure range up to 600 bar and at temperatures of 40°C and 60°C.
Results are presented in Figure 2.
P (bar)
700
600
500
400
300
200
100
40°C 60°C
0
0 10 20 30 40 50 60 70 80 90 100
wt.% CO2
Figure 2: Phase diagram for the system raw lecithin (50% phospholipids)/CO2
Influence of pressure, temperature and stirring rate on:
• distribution of liquid and gaseous phases – possible phase inversions,
• qualitative evaluation of viscosity of mixtures,
• separation of phases after intensive stirring,
was observed.
In the range of applied pressure and temperature (up to 520 bar at 62°C and 700 bar at 40°C) the distribution of
phases was such that the phospholipids rich phase (liquid phase) was the bottom phase and the CO2 rich phase
containing dissolved oil (gaseous phase) was the upper phase.
Lab-scale extraction experiments
Tests were carried out in a 10 litre laboratory scale plant at 400 bar and 500 bar at a constant temperature of
60 °C. The specific CO2 flow rate, which is defined as kilogram of CO2 per kilogram of raw material, was varied
between 75 and 225 kg/kg and it is shown in Figure 3. As could be seen from Figure 3 the phospholipids content
in the de-oiled product is widely independent from the specific CO2-demand at the tested condition.
AIM [%]
100
90
80
70
60
50
40
30
20
10
0
0 50 100 150 200 250
Spec. CO2 [kg/kg]
Figure 3: Phospholipids content (AIM) vs. specific CO2 flow rate
Pilot scale extraction experiments
The tests were carried out at 400 bar and 60 °C with specific CO2 flow rates ranging from 100 kg/kg to 200
kg/kg. During each test run totally 200 kg of raw lecithin were extracted resulting in approx. 100 kg of
powderous de-oiled lecithin. As it was found out during the lab-scale tests, also the pilot scale up tests shows that
the de oiling efficiency is independent from the specific CO2 flow rate in the range between 100 kg/kg and 200
kg/kg.

Production plant design, construction and start up
As the result of the experimental studies a production plant was designed, based on the parameters, which were
obtained and verified in different scale tests. Beside the degree of de-oiling and the powdery shape it is essential
to prevent oxidation of phospholipids in the final product. The basic process flow diagram of the unit is
presented in Figure 4a and a photo of the unit is presented in Figure 4b. Because de-oiled lecithin is a powderous
product (electronic microscope picture of lecithin particles could be seen on Figure 5) the extractor has to be
emptied batch-wise during the process without interruption of feeding. This has the advantage of a more
effective and economic operation of the de-oiling process and ensures that the sensible product will not come
into contact with oxygen from air.
a
b
Figure 4: a) basic process flow diagram of industrial plant, b) photo of industrial plant
Figure 5: View of lecithin particles produced in industrial scale plant

CONCLUSIONS
A green process for processing of the highly viscous raw lecithin was developed from laboratory scale up to
industrial plant scale. The main advantages using supercritical CO2 instead conventional solvents (which
contaminate lecithin with organic solvents which can not be easily removed) are presented.
Examples on selective extraction and further fractionation of components of lecithin from raw lecithin are
presented. Fundamentals, like phase equilibrium data for the system oil/SCF as well as mass transfer data will be
given in the presentation. Mechanical design of industrial-scale equipment, influence of process parameters on
lecithin particle size and particle size distribution, particle shape, modeling of extraction procedure of the process
will be presented.
REFERENCES
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