Refining Technologies Targeting Specific Oil...
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Refining Technologies Targeting Specific Oil Qualities Steen Balchen Alfa Laval
Transcript of Refining Technologies Targeting Specific Oil...
Refining Technologies
Targeting Specific Oil Qualities
Steen Balchen
Alfa Laval
www.alfalaval.com
Outline
The objective of refining
• Common understanding of the term…
• Refining versus modification
The “process tool box”
• Oil refining unit operations from a chem. eng. view point
• Tendencies within each process step
Options for FFA removal
• Re-esterification: Alternative to saponification / vaporisation
• Case: Rice Bran Oil
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Why refining?
Closing the GAP between quality of crude
oil and desired end product
Oil crop type
Extraction process etc
Spec as ingredient in
food, cosmetics, pharma
Process costs
Product safety / artifact formation
Plant configuration (bulk / flexible, etc)
By-product valuation
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Refining definition
Refining to be perceived as the total oil purification process
(in opposition to “RBD” oil term)
Glyceride oil refining comprises, besides from separation of
“impurities” (can be valuable components) also provoked
reactions (and separation of the formed products).
Refining vs. modification – no clear distinction
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Undesired components in oils Present in oil crop, co-extracted
• Phosphatides (of various hydratability)
• Waxes
• Colorised components (chlorophyll, carotenes)
• Natural flavour – related to origin
• Contaminants/POP (Pesticides, PAH, Dioxine/PCB, etc)
Derived by reactions (hydrolysis / oxidation) in oil matrix
• FFA
• Hydroperoxides
• Odorous break-down components (short chain aldehydes etc)
• Trans-FA, MCPD, other…
Contaminants derived from processing itself
• Metals (Fe, Cu), accidental (thermal oil, glycol, …)
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Gum content in various crude oils
Oil type
Phosphatides
(%)
Phosphorus
(ppm)
Coconut
Corn
Cottonseed
Groundnut
Palm
Rapeseed
Soya
Sunflower
0.02 – 0.05
0.7 – 2.0
1.0 – 2.5
0.3 – 0 .7
0. 03 – 0.1
0.5 – 3.5
1.0 – 3.0
0.5 – 1.3
10 – 20
250 – 800
400 – 1000
100 – 300
15 – 30
200 – 1400
400 – 1200
200 – 500
Data collected from various sources
Gum content varying
100+ times among
mentioned feed stocks –
and up to 5 times within
same feed stock type…
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Upstream (1) Oil crop quality
• Species type (bean origin, GMO varieties, etc)
• Harvesting timing (chlorophyll, wax, oil content)
• Storage conditions (burnt, moulded,…)
• Physically damaged crop (cell rupture initiates enzymatic degradation
reactions)
Extraction method
• Bulk oil cost effectiveness: Mechanical pressing and/or hexane solvent
extraction dependent on oil content in crop
• Seed pretreatment (mostly enzyme inactivation), extraction
temperature
• Some olive, rapeseed, specialty oils: Cold pressed and only water
degummed before sold in retail
• CO2 / entrainer (supercritical), ethanolic
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Upstream (2)
Knowledge about (and even better influence on) upstream
process can be utilised to tailor the oil refining process by
which obtain a competitive advantage.
However, tailoring the refining process and creating
proprietary knowledge requires
• In depth knowledge about the impurities, their physical and
chemical properties;
• Experimental facilities for testing processes;
• Analytical capabilities
Can proprietary benefits be identified which can justify the
cost burden of related R&D? A business choice between
standard bulk processing or proprietary processing…
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Downstream Examples of end spec variation for a specific oil type
Customer specs:
Oil for bottling Brand A requires a higher Tocopherol content
than Brand B
- requiring milder deodorisation conditions
Regional food standards:
Bottled oil colour requirements China / Western hemisphere
- typical deodorising time >60 / <45 minutes
Ingredient in bulk food or infant formula:
Difference in acceptable MCPD content
- various changes in CPO refining process
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Refining process (unit operations) The history shows tailoring just a few unit operations to
process a glyceride oil matrix
• Aqueous extractions (pH variation alkali / acid / neutral)
• Adsorption
• Crystallisation
• Filtration (+/- filter aid)
• Steam distillation
Chemical refining route
• ~150 years old
Physical refining route
• ~40 years old for low-P oils like CPO, <25 years old for high-P oils.
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Bleached Oil
Crude Oil
Neutralised/Refined, Bleached, Deodorized Oil
Chemical
refining
High-P
seed oil
Crude
Gums
Soap
Stock
Fatty Acid
Distillate
Spent
Earth
Wet physical
refining
Dry physical
refining
Low-P
palm oil
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3 edible oil refining routes Chemical refining with alkali-neutralisation Often initial separate water degumming step. Acid conditioning followed by aqueous alkali
extraction step with main function to remove FFA and phosphatides.
High neutral oil loss, but very robust for feed quality variation and in general producing
“best” refined oil quality.
Wet Physical refining of seed oils with deep degumming Deep degumming removing phosphatides (and other components) to ~ 5 ppm level by
various methodologies (all comprising aqueous extraction).
Thermal deacidification: Deodorisation with enhanced stripping efficacy
Lower overall oil losses than in chemical refining (mostly due to thermal deacidification),
but higher requirement to feed quality and process control.
Dry Physical refining of palm / exotic oils / tallow (low P oils) Combined degum/bleach (no separate degum step) with concentrated acid dosing.
Thermal deacidification: Deodorisation with greatly enhanced stripping efficacy by
structured packing bed.
Simplest process setup and lowest operating costs.
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Refining unit operations (1) Solids removal / Clarification
• Removal of residual solids/fines from oil crop
• Removal of added adsorbents (part of Bleach process)
• Removal of precipitated lipid crystals (part of Frac process)
• Removal of precipitated (overdosed) Citric Acid
• Centrifugation / filtration
Tendencies
• Crude oil clarification: Large scale operations using decanters instead
of filters
• Deeper filtration by going towards 5 micron filter bags or substituting
bag filters with cartridge filters
• More thorough (pressure) monitoring combined with auto switch-over
to prevent bag rupturing
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Refining unit operations (2) Degumming
• Hydration of phosphatides (acid assisted breakage of “salts”)
• Aqueous extraction (neutral/acidic condition)
• Lecithin by-product determines if a neutral water degumming step is
applied
• Deep degumming (<10 ppm P) necessary for physical refining of seed
oils
Tendencies
• CPO refining: Separation of acid conditioned gums from oil before
entering bleaching step (equals deep degumming of seed oils)
• Change of extraction process conditions to affect the content of Non-
Hydratable-Phospholipids (NHP)
• Enzymatic degumming: New types/combinations of enzymes, now
also offering deep degumming
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Refining unit operations (3) Neutralisation
• Acid pretreatment (if prior pure WDG)
• Alkali assisted saponification of FFA
• Aqueous extraction (alkali condition)
• Variant: Cold neutralisation for simultaneous bulk dewaxing
Tendencies
• Reduced consumption of wash water (recycle, evaporation,
substitution of wash step with Silica treatment)
• Intensified mixing by introduction of “nano” cavitation reactor –
reducing chemicals consumption and residence time.
• Ongoing improvement of High Speed Separator design (direct driven
etc)
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Refining unit operations (4) Bleaching
• Catalysed decomposition of hydroperoxides (and other components)
• Adsorption of polar components
• Selection of appropriate adsorbent
Tendencies
• 2 stage contact - reduction of adsorbent consumption
• Using combinations of silica and traditional clay adsorbents for more
cost effective process
• High temperature bleaching for reducing aldehydes (Anisidine Value
contributing components)
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Refining unit operations (5) Deodorisation
• High temperature provoked decomposition of unstable components
• Steam stripping (distillation) to remove volatile components present in
feed and formed
Tendencies
• Dual temperature process (high temp stripping / lower temp holding) -
to enhance stripping effect while reducing artifact formation
• Moving towards integration of structured packing bed into all kinds of
deodoriser designs – lowest cost option for enhanced stripping
• Dual stripping (introduce post-stripping) - to enhance removal of
decomposition products
• Double scrubbing technology – to improve yield or produce Toco-rich
stream as well as increase FFA purity of distillate
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Large capacity Dual Strip Deodoriser
Features
• Dual oil strip - prestrip for removing
reactive volatiles before entering holding
section, - poststrip for effectively
removing formed volatiles.
• Strip and Holding functions split up into
separate vessels due to capacity and
ease of vessel fabrication / installation
• Dual temperature process would require
intermediate cooling in top tray
• Double scrubbing of vapours
Continuous deodoriser of the future ?
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Refining unit operations (6)
Tendencies
• Enhanced crystallisation environment – moving HEX arrangement for
stirring
• Continuous crystallisation equipment – questionable benefit for
processes requiring several hours residence time…
Process
name
Dry Dewaxing
Dry Fractionation /
Winterisation
Solvent
Fractionation
Crystallisation
step
from a melt
(wax esters)
from a melt
(TAGs)
Solvent dilution
(10-20% oil)
Separation
step
Filtration
with filter aid
Filtration
w/o filter aid
(non-contaminated
cake)
Filtration
w/o filter aid
(non-contaminated
cake)
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Refining control strategies Typical control of a unit operation
Degum recipe = ƒ [ oil type, heavy phase appearance ]
Neutral recipe = ƒ [ oil type, FFA ]
Bleach recipe = ƒ [ oil type, (colour), end spec ]
Dewax/Wint/Frac recipe = ƒ [ oil type, end spec ]
Deo recipe = ƒ [ oil type, end spec ]
Tendencies
• Adjust B.E. dosing according to obtained colour
• Seems to be room for improvement…
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Modification unit operations (1) Blending of different oil stocks
• Change phys. properties (affect melting curve, eutecticum etc)
Hydrogenation
• Saturation of FA - partial, selective, full (increase solidification point /
melting curve)
• Solid metal catalyst + hydrogen
Interesterification
• TAG randomisation (reduce solidification point, change crystallisation
properties - prevent sandiness)
• Alkali catalyst (NaMe), enzymatic
Tendencies?? Not much news – and outside scope of this presentation…
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Modification unit operations (2) Specific TAG production (POS/SOS, OPO, MCT, etc)
• enzymatic1,3-specific reaction, often combined with Dry Frac
• Possible by esterification reaction (acyl donor FFA while releasing
water) or transesterification reaction (ester / ester) process
• Differs from enzymatic interesterification by acyl donor type and the
position specificity…
Tendencies
• Only a few niche markets – does not seem to grow a lot
• Related to enzyme development (mostly production cost focused)
• Apparently moving towards using esters as acyl donor instead of FFA
(easier control of water balance)…
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Modification unit operations (3) Glyceride recombination: FFA reduction by esterification with
glycerol / partial glycerides) into glycerides
Tendencies
• Glycerolysis using “excess” glycerol (only little emphasis on resulting
MAG/DAG content) is growing for pre-treatment for biodiesel
• Non-catalytic route currently for non-food only
• Enzymatic concept synergy to enzymatic biodiesel process leading to
increased innovation
Glyceride recombination: Recombine purified alkane esters (FAEE) +
glycerol into glycerides by trans-esterification
• Very limited market: O3 concentrates only
Under-utilised process as part of refining ?
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Removing FFA from high FFA oils
Alkali neutralization (saponification / aqueous extraction) Robust and proven process
High losses ~ 2+*FFA content - partial glycerides (especially MAG) emulsify the TAG with
aqueous phase.
De-acidification by stripping (separation by vaporization) Limited loss ~ 1.1*FFA content
High thermal exposure – formation of contaminants
Color fixation
De-acidification by esterification with partial glycerides / glycerol Net reaction conversion of FFA into TAG
Increased yield, no loss
Optional A) enzymatic or B) non-catalytic, high-temperature route
Required feed pretreatment
Current concerns about edible applications (GRAS status)
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Ester cleavage / synthesis
+ OH_
+
+ +H2O
R O H
O
CR OH R O H
O
CR O
O
CR O R
O
CR O R
H+
FFA Glyceride Glycerol /
partial glyceride
Normal situation is oil being in contact with ambient air/moisture:
The equilibrium water conc. in pushes towards increased hydrolysis,
which can be catalyzed by enzymes.
The water solubility increases with increasing FFA conc., creating
an autocatalytic effect.
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Removal of water
Options to remove water to drive reaction rate / push equilibrium
Simple vaporization from the liquid surface to vacuum head space
Stripping off water by sparging with nitrogen, combined with vacuum head space
Forced circulation of liquid through spray nozzle into vacuum head space (Dryer)
Adsorption by mol sieve or similar (requires regeneration of adsorbent)
Chosen combination for prototype plant :
1) Spray circulation during bulk period
2) Adding sparge nitrogen in last period of reaction
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Rice Bran Oil study
Concept:
Provide net conversion from
FFA to TAG, thus providing
unchanged MAG/DAG levels
Concept:
Net conversion from FFA to
TAG, thus providing
unchanged MAG/DAG levels
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Non-catalytic Hi-temp process Simple heat feed to desired reaction temperature and deploy
efficient water removal
Reaction condition range: 180-220C / 8-24 hrs
Water removal concept: Recirculation and spray into vacuum chamber
Surprisingly no significant
color increase over 8 hrs
reaction period @ 180C
- but bleachability was not
investigated
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Non-catalytic Hi-temp process Min 180C in 20 hrs was required to reach 4% residual FFA
Problematic to maintain unchanged MAG/DAG content, but probably
doable
Typical trial:
Change in FFA, MAG,
DAG and Tag during a
time course
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FFA remediation enzyme recycle BW RBO 200gr scale
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Lab testing enzyme reusability
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FFA remediation enzyme recycle BW RBO 200gr scale
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Flowchart prototype batch plant
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