Oil+refining-2 - www.alfalaval.com Basics of Alkali...

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Unformatted text preview: www.alfalaval.com Basics of Alkali Refining & Water Washing of Vegetable Oils Andrew Logan Alfa Laval Copenhagen A/S Physical Refining Crude Oil Chemical Refining Water Water Degumming Degumming Acid Gums To meal or feed lecithin Gums Gums drying drying Crude Lecithin Special Special Degumming Degumming Alkali Refining Alkali Refining & Washing & Washing Soapstock Soapstock splitting splitting Acid Oil Dewaxing Dewaxing Dewaxing Dewaxing Bleaching Bleaching Bleaching Bleaching Deacidification/ Deacidification/ Deodorisation Deodorisation Deodorisation Deodorisation Hydrogenation Hydrogenation Fatty Acid Distillate Edible Oil Edible Oil www.alfalaval.com Purpose of Alkali Refining • Removing of impurities from oil – Phospholipids (gums) – Colour bodies – Metal Ions - Pro-oxidants • Iron • Copper – Free Fatty Acids – Solids - meal fines www.alfalaval.com Oil Impurities • Phospholipids – cause emulsions – darken oil with heat – interfere with crystallization • Colour Bodies – Some have nutritional value – Remove to add consumer appeal & functionality in industrial uses (not heat stable) • Metal Ions – act as pro-oxidants degrading the oil quality & stability www.alfalaval.com Alkali Refining Process Steps Crude Oil H3PO4 NaOH Acid Mixing Acid Mixing Lye Mixing Lye Mixing Heating Heating Heating Heating Water Addition Water Addition Hot Water Separation Separation Separation Separation Vacuum Drying Vacuum Drying Soapstock to waste treatment Refined & Dried Oil www.alfalaval.com Alkali Refining Plant - ca. 1892 www.alfalaval.com Neutralization Reaction O R - C - OH Fatty Acid + NaOH O R - C - O-Na + H2O Caustic Soda Soap Other mechanisms • colour bodies adsorbed onto soap • phosphatides hydrated by water in lye • chelated metal ions removed in soap www.alfalaval.com Amount of Neutralization Lye Amount of lye = A * FFA * 1000 * k l/h 100 * M * N where A = oil flow (kg/h) FFA = content of free fatty acids (%) * k = factor for lye excess M = molecular weight of the fatty acids (kg/mol) ** N = normality of the lye (mol/l) www.alfalaval.com Amount of Neutralization Lye (cont.) * Content of free fatty acids has to be adjusted for addition of gum conditioning acid (0,1 % Phosphoric Acid corresponds to approx. 0,8 % FFA) ** Molecular weight of the fatty acids: - Coconut/Palm kernal 200 - Palm 256 - High Erucic Acid Rapeseed 304 - Most other oils 282 www.alfalaval.com Effect of Lye Excess • Groundnut oil with 2,5 % FFA refined with 4,25 N lye Lye excess (%) FFASS (%) Refining factor (excl. saponification) Real refining factor (incl. saponification) 5 55 1,82 1,86 40 75 1,33 1,61 80 80 1,25 1,81 www.alfalaval.com Effect of Acid Conditioning Oil Amount of acid % w/w Soap content (ppm) P – content (ppm) Neutralised oil Washed oil Crude oil Washed oil Rapeseed 0 1900 1200 250 180 ” 0,15 1500 80 250 5 Sunflower 0 1600 500 320 90 ” 0,05 1400 50 320 2 Corn 0 2100 1500 540 120 ” 0,10 1100 80 540 4 Soybean 0 700 120 90 20 ” 0,10 600 40 90 2 www.alfalaval.com Washing and Drying • Washing - Hot soft process water should be used - 5 -10 % of oil flow • Drying - 70 mm Hg vacuum www.alfalaval.com Refining Process - Selection P - content < 200 ppm < 1,5 % FFA > 200 ppm Long-Mix or Multi-Mix Long-Mix Multi-Mix (2-stage) Multi-Mix (3-stage) 1,5 – 3 % >3% www.alfalaval.com Long-Mix Process Steps • • • • • • • • • Acid pre-treatment Lye mixing Retention mixing Emulsion break heating Centrifugal separation of soapstock Heat Water addition and mixing Centrifugal separation of wash water Vacuum drying of refined and washed oil www.alfalaval.com Long-Mix Process Neutralization Mixer Retention mixers Washing Mixer To drying/ bleaching or storage Steam Steam Crude oil Heater Heater Acid Lye Steam Separator Soapstock Heater Separator Process water www.alfalaval.com Long-Mix – Lye Treat Conditions Strength (°Bé) Excess (%) Reaction time (min) Crude seed oils 14 - 22 70 - 100 3–6 Degummed seed oils 16 - 26 35 - 70 2–5 Cottonseed 18 - 36 70 - 200 6 – 10 Corn 18 - 20 35 - 100 1-2 www.alfalaval.com Long-Mix Target Results • • Phosphorous in oil after S1 - 8 to 12 ppm, 20 ppm max. • • • • • Phosphorus in oil after S2 – max. 4 ppm Soap in oil after S1 - 200 to 300 ppm, 400 ppm max. Soap in oil after S2 – max. 50 ppm FFA in oil – 0,02 to 0,04 %, 0,05 % max. Moisture in oil – max. 0,5 % or 0,05% if dried Loss = max. 0,8 + 1,25 x TL www.alfalaval.com Multi-Mix Process Steps • • • • • • • • • Heat Acid pre-treatment Lye mixing Centrifugal separation of soapstock Lye or water mixing Centrifugal separator of soapstock or wash water Water addition and mixing Centrifugal separation of wash water Vacuum drying of refined and washed oil www.alfalaval.com Multi-Mix Process Acid conditioning Neutralisation Mixer Mixer Mixer Rerefining or washing Washing Mixer Neutralised oil to drying/storage or bleaching Steam Crude oil Heater Separator Acid Lye Soapstock Separator Spent water Make-up water Separator Process water www.alfalaval.com Multi-Mix – Lye Treat Conditions Strength (°Bé) Excess (%) Reaction time (sec) Crude seed oils 20 - 28 30 - 60 15 - 30 Degummed seed oils 20 - 28 10 - 30 1-3 Cottonseed 20 - 28 10 - 50 >1 Anaimal & Fish 20 - 28 10 - 30 1-3 www.alfalaval.com Multi-Mix Target Results • • Phosphorous in oil after S1 - 8 to 12 ppm, 20 ppm max. • • • • • Phosphorus in oil after S3 – max. 4 ppm Soap in oil after S1 - 500 to 700 ppm, 1000 ppm max. Soap in oil after S3 – max. 30 ppm FFA in oil – 0,02 to 0,04 %, 0,05 % max. Moisture in oil – max. 0,5 % or 0,05% if dried Loss = max. 0,3 + 1,25 x TL (+ 0,3 % if re-refining) www.alfalaval.com Multi-Wax Process Steps • • • • • • • • • • • • • Heat Acid pre-treatment Lye mixing Centrifugal separation of soapstock Lye mixing Cool Crystallization Heat Centrifugal separator of waxes and soapy water Heat Water addition and mixing Centrifugal separation of wash water Vacuum drying of refined and washed oil www.alfalaval.com Multi-Wax Process Mixer Regenerative heater/cooler Crude oil Dewaxing Neutralisation Acid conditioning Mixer Washing To drying/ storage or bleaching Mixer Mixer Steam Steam Heater Acid Separator Soapstock Crystallising tank Wax/ soap Separator Electrolyte/ lye solution Heater Separator Waste water Crystallising tank Process water Mixer Lye Cooling water Coolant Heater Steam www.alfalaval.com Multi-Wax Target Results • Soap in oil after S1 - 1500 to 2000 ppm, 2500 ppm max. • • • • • • Phosphorus in oil after S3 – max. 4 ppm Soap in oil after S3 – max. 50 ppm Wax removal – min. 85 % FFA in oil – 0,02 to 0,04 %, 0,05 % max. Moisture in oil – max. 0,5 % or 0,05% if dried Loss = max. 0,7 + 1,25 x TL for 600 ppm wax content or max. 1,2 + 1,25 x TL for 1500 ppm wax content www.alfalaval.com Other Refining Process • Cold neutralization - combined neutralization and dewaxing • Miscella refining - neutralization in the miscella phase • Modified Caustic Refining (MCR) www.alfalaval.com Dry Refined Oil Quality Targets • • • • • • Soap - < 30 ppm Phosphorous - < 2 ppm Iron - < 0.2 ppm Copper - < 0.01 ppm FFA - < 0.05% Moisture - < 0.05% www.alfalaval.com ...
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This note was uploaded on 01/28/2011 for the course CHEMICAL E 160 taught by Professor Blanche during the Spring '10 term at Berkeley.

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