Deodorization and Physical Refining ( Wim De Greyt )

IUPAC-AOCS Workshop on Fats, Oils & Oilseeds Analyses & Production December 6-8, 2004 Tunis, Tunesia DEODORIZATION AND PHYSICAL REFINING DEODORIZATION AND PHYSICAL REFINING Wim De Greyt De Smet Group Belgium

Crude Oil Crude Oil P h Soybean oil g y Palm oil Soybean oil n s Palm oil i i n c i a f l e r r l e a f i c n i i m n e g h C Degumming GUMS Degumming Neutralisation SOAPS Bleaching SPLITTING Bleaching Steam refining- Steam refining- FFA Deodorisation Deodorisation Deodorisation Deodorisation Refined Oil Refined Oil

Physical versus chemical refining 108 Direct refining cost 107 Chemical 106 Cross-over 105 point Physical 104 103 3% 102 101 1% 100 Palm 99 Soybean %FFA 98 0 0.5 1 1.5 2 2.5 3 3.5 4

Deodorization conditions Typical deodorization conditions Chemical Refining Physical Conditions U.S. Europe Europe Temperature (°C) 250-260 230-240 230-250 Pressure (mbar) 3-4 2-3 2 Sparge steam (%) 0.5-2.0 0.5-1.0 1-2 Time (min.) 20-40 40-60 60-90 Final FFA (%) 0.03-0.05

Deodorization principle Stripping FFA, volatile odoriferous components, Valuable minor components (tocopherols,sterols,…..) Contaminants (pesticides, light PAH, PCB, dioxins,…) Odor and taste removal (actual Deodorization) Hydrolytic/thermolytic degradation : f (steam/ time) Temperature effect Heat bleaching, cis-trans isomerisation, Polymerisation, interesterification,

Distillation-Determining Factors • VOLATILITY of the components – Vapour pressure (at a given temperature) – General:heavier components are less volatile – FFA > Tocopherols > Sterols • CONCENTRATION of the components – Partial pressure – Depends on vapour pressure and concentration

Vapor pressure – temperature relationship for different components in oils 260ºC 260ºC Component Mol. Weight Relat. volatility Fatty acid 280 2.5 Squalene 411 5 Tocopherol 415 1 Sterol 410 0.6 Sterol ester 675 0.04 Oil 885 <small>

Stripping agent • Total pressure gas phase = S partial pressures – S partial pressures is low (mainly triglycerides) • Distillation will only occur if : – S partial pressures > applied system pressure Necessary to add stripping agent (steam, nitrogen)

Stripping agent Required amount of stripping agent – directly proportional to its molecular weight – low molecular weight is required (steam/nitrogen) Nitrogen – inert and non-condensable gas – lower losses (no hydrolysis) and higher distillate quality – more powerful vacuum system required – profitability is very uncertain Steam – most ‘evident’ choice

Distillation Simplified ‘Bailey’ Equation (initial FFA low) P V S = t .ln a E.p0 V i 0 S = Total Moles of steam P = Total deodorization pressure t o p = Vapour pressure of a given volatile component i V = Initial molar concentration of the component a V = Final molar concentration of the component o E = Vaporization efficiency

Stripping P V S = t .ln a E.p0 V i 0 – Impossible to eliminate all volatile components (V = 0 would require an infinite amount of steam) 0 – Halving the concentration of a given volatile requires same amount of steam irrespective of its absolute level

Refined Oil Quality • Deodorization is a crucial refining stage • Deodorizer design and process conditions have a determining effect on the refined oil quality • Control of ‘unwanted’ and ‘desired’ effects : – trans fatty acid formation – positional isomerisation of PUFA unwanted – polymerisation (dimers) – controlled stripping of tocopherols, sterols desired – complete stripping of contaminants

Trans Fatty Acids • Unsaturated fatty acids with one or more double bond in trans configuration • Structure similar to saturated fatty acids – Higher melting point than cis isomers – Negative nutritional properties : unwanted in food fats • Renewed interest because of stricter legislation – trans labelling in USA from 2006 – very strict Danish regulation : max. 2% in food fats – Canada considers to adopt same regulation

Trans Fatty Acids • Mainly formed during partial hydrogenation – depending on hydrogenation process conditions – typical levels : 10-50% (high in Cocoa Butter Replacers) • Trans formation during bleaching – 0.1-0.2% trans formation with acid activated BE • Deodorisation – % trans = f (time, temperature) – T > 220°C detectable; T > 250°C exponential – No significant influence of sparge steam and pressure

Trans Fatty Acids C18 : xtrans Degree of isomerization (DI) DI 18:x = ×100 C18 😡 (cis + trans) General rule : TFA= 10% of C18:3 + 1% of C18:2 For C18:3 rich oils : max. TFA = 1%; for other oils : max. TFA = 0.5%

Tocopherols Losses during bleaching – Limited degradation (5-10%) – Affected mostly by type and amount of BE Losses deodorisation/deacidification – Higher ‘losses’ possible (15…..> 60%) – Tocopherol removal = f (steam, temp., pressure) Distillation Thermal breakdown Oxidation

Controlled tocopherol stripping Relative tocopherol retention during deodorization P = 2 mbar P = 4 mbar 2.5 2.5 30 15 40 25 2.0 35 2.0 50 ) ) 60 % 45 45% % 58% ( ( m 1.5 55 m 1.5 70 a a e e t 80 t 65 S S 1.0 1.0 90 75 0.5 0.5 230 240 250 260 230 240 250 260 Temperature (°C) Temperature (°C) Higher retention/more stripping at higher P, lower T and less steam

Contaminant removal • Adsorption on specific adsorbens (activated carbon) – Heavy polycyclic aromatic hydrocarbons – Dioxins and furans from Fish Oils – PCB (only partially, less efficient than dioxins) • Deodorization (only ‘volatile’ contaminants) – Pesticides (organo-chlorine) – Light polycyclic aromatic hydrocarbons (coconut oil) – PCB,dioxins, brominated flame retardants (fish oil)

Pesticides – Today * Contamination usually below limit of detection (20-50 ppb) * Occasionally : 1-2 ppm (improper post-harvest treatment) – Efficient removal during deodorization if T >230°C, p< 4 mbar and steam > 1% Distillation Thermal decomposition Pesticides can be removed efficiently during deodorization Monitoring at regular intervals remains necessary (especially for mild refined oils)

PAH Removal during Refining – Heavy PAH * Adsorption on activated carbon * 0.1-0.4% added together with bleaching earth or separately – Light PAH * Stripped under conventionally applied deodorizer conditions T >220°C, p <4 mbar and steam > 1% Levels > 25 ppb can still be detected in refined oils in case of highly contaminated crude oils

Deodorization Technology Process stages – Oil deaeration Prevention oxidation – Heating Heat recovery Final heating – Deodorization Deacidification Injection of stripping steam Low pressure (vacuum) Condensation of volatiles – Cooling Heat recovery final cooling – Polish filtration + AO dosing

Heating Two stage process – preheating followed by final heating Preheating – heat recovery step – oil/oil heat exchanger (incoming oil/finished oil) Final heating – High pressure steam (most used & recommended today) – Thermal oil (avoided for food safety reasons) – Electrical heating (rarely used)

Heating Temperature of high pressure steam Pressure Steam temperature Latent heat Specific volume 3 (bar) (°C) (kJ/kg) (m /kg) 1 99.6 2258 1,694 2 120.2 2202 0,8853 3 133.5 2163 0,6056 5 151.8 2108 0,3747 7 164.9 2065 0,2762 10 179.9 2014 0,1943 15 198.3 1945 0,1316 20 212.4 1889 0,09952 30 233.8 1794 0,06663 40 250.3 1713 0,04975 50 263.9 1640 0,03943

Heat recovery oil-steam heat exchanger plate spiral Internal heat exchangers shell & tube oil-oil heat exchanger External heat exchanger

Heat recovery : Thermosyphon

Vaporization efficiency Steam distribution – sparge coils with very fine holes (Ø = 0.5-2.5 mm) – steam lift pumps Deodorizer design – Deep bed deodorizer (steam lift pumps) – Shallow bed deodorizer (sparge coils) – Continuous refreshing of the oil at vapor-liquid contact zone (lowest pressure)

Deodorizer design STEAM LIFT PUMPS STEAM SPARGE COILS Deep bed Deep bed deodoriserdeodoriser Shallow bed Shallow bed deodoriserdeodoriser

Vapor scrubbing system Composition of vapor phase – Volatile components (FFA, odor components) – Stripping steam – Non condensable gases (air,…) Condensation of volatile components – intimate contact between vapor and recirculating distillate – series of sprayers or packed bed in vacuum duct – Distillate is recirculating at the lowest possible temp. – Installation of demister at the top – Designed to have a minimal pressure drop

Vapor scrubbing system Deaerator Deodoriser Vapor scrubber Vacuum unit heating deodorising cooling

Deodorizer distillates Composition of industrial deodorizer distillates Soybean Corn Sunflower Component chemical physical physical chemical physical Squalene (%) 1-2 0.5 0.5-1.0 0.5 0.5 Tocopherols (%) 16-20 5-7 2-4 5-7 1-2 Sterols (%) 19-23 11 3-6 12-14 4-5 Triglycerides (%) 5-6 4 1-2 2-3 1-2 FFA (%) 33 75 77-81 39 70 Concentration of contaminants (pesticides, PAH)

Vacuum systems Conventional vacuum system – Combination of steam jet ejectors (boosters), vapor condensers and mechanical (liquid-ring) vacuum pump – High motive steam consumption (60-85% of total steam) Pressure kg motive steam per kg strippng steam Booster Deodorizer 30°C (1) 10°C (2) 2.5 3 mbar 4.5 1.6 1.5 2 mbar 6.2 2.5 Note: (1) Barometric condenser water inlet temperature: 24°C; outlet temperature: 30°C (2) Barometric condenser water inlet temperature: 5°C; outlet temperature: 10°C;

Vacuum systems

Dry condensing – Ice condensing – Sublimation of steam (into ice) on surface condensers – Low pressure can be reached (< 2 mbar in deodorizer) – Strongly reduced odor emission – Nearly no motive steam but higher electricity consumption – Higher investment cost (compared to boosters) – Operating cost (and ROI) will depend on ratio between cost of steam and electricity Generally shorter ROI in Europe

Dry condensing vacuum system with horizontal condensers Refrigerant Separator

Dry Condensation Systems with vertical condensers Dry Condensation Systems with vertical condensers Condenser Cooling water From FA scrubber Freeze condenser Compressor To de-aeration Separator Valve, open Valve, closed LP steam Vapour (vacuum) Refrigerant (ammonia) Condensate Non-condensable gases Melt vessel process vapor water ammonia

Deodorizer design Batch deodorization Continuous deodorization – Horizontal deodorizer – Single vessel vertical deodorizer – Packed column technology Semi-continuous deodorization

Continuous Deodorization Limited feedstock changes Advantages Low utilities cost (high heat recovery) Short residence time Excellent control of all parameters Disadvantage Contamination during feedstock change

Continuous Deodorization Continuous deodorizer types – Horizontal multi-vessel deodorizer -Vertical deodorizer most common all operations integrated in single vessel – Thin film deodorizer packed column + retention vessel

Continuous horizontal multi-vessel deodoriser

gas phase To FAD scrubber + vacuum unit Packed column Packed column stripper stripper liquid phase (oil) DP : 0.1 -0.5 mbar/m DT : min. 1.3ºC / %FFA H : 3-5 m D : f (vapor load) StructuredStructured packingpacking vapor phase (steam) F= Vvap * r* A liquid phase To deodorizer (stripped oil)

PACKED COLUMN TECHNOLOGY • Specific Process conditions 2 3 – Structured packing : 100 – 300 m /m – Efficient stripping : Counter-current contact oil/steam – Short residence time : Few minutes at high temperature • Applications – Stripping of valuable minor components or contaminants from heat sensitive oils – Preferably only in continuous operation – No deodoriser (too short residence time)

Future challenges in deodorization Lower ‘heat load’ – Low trans and polymer formation – No positional isomerisation of PUFA – Preservation of natural character (color, aroma,…) combined with Efficient and controlled stripping – Controlled stripping of tocopherols and sterols – Complete removal of contaminants

Improved Deodorization Technology • Dual temperature deodorization – Deodorization at two different temperatures • Integration of packed columns – for specific application only – efficient stripping – lower steam consumption • Dual condensation – Condensation at two different temperatures – Higher added value of deodorizer distillate (physical refining) • Dry-Ice condensing – Lower deodorizing pressure (1 mbar) – Allows milder refining (lower temp)

ONLY ONLY EFFICIENT EFFICIENT QUALITY QUALITY PAYS PAYS


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