It prepared for Undergraduate students teaching purpose

1. 4.3 PRODUCTION OF
GLYCERINE
R E C O V E R Y F R O M S O A P P L A N T S
R E C O V E R Y F R O M FAT T Y A C I D P R O D U C T I O N
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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2. GLYCERINE
• Glycerine is a tribasic alcohol occurring in nature in the form of triglycerides which are
glyceryl esters of fatty acids.
• It is an important high value by-product obtained from the processing of oils and fats.
• Also can be synthesized from petrochemical.
• Over the years, the demand for glycerine in the world, has continued to grow, far
outstripping the supply.
• It's a highly strategic chemical, used in the manufacture of explosives, pharmaceuticals,
foods, paints, chemicals and dyes.
• All-out efforts are therefore being made to bridge this gap between supply and
demand by increasing the present fatty acid industry capacity, and also to step up the
production of glycerine in globally.
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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3. PRODUCTION OF GLYCERINE
• The glycerol is derived from the direct saponification of fats and oils with caustic soda
and recovery as a by-product from the soap production unit.
• During saponification process glycerol is liberated and then extracted by the counter
current washing of soap to obtain spent lye which contains maximum concentration of
glycerol in water and impurities such as, soap, fatty acids, color bodies, insoluble
materials and phosphorus and nitrogen compounds.
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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Triglyceride + Caustic Soda ---- Glycerol + Soap

4. The process of recovering glycerol from soap lyes can be divided into the
following stages:
• Chemical treatment (Purification of soap lye)
• Evaporation (concentration of lye to crude glycerine)
• Separation of salt
• Refining of crude glycerine (to produce marketable grades)
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RECOVERY FROM SOAP PRODUCTION

5. CHEMICAL TREATMENT
• The chemical treatment of soap lye is designed to maximize the removal of dissolved
soap and other organic impurities prior to evaporation and distillation.
• The most common method for the purification of soap lyes consists of two stages.
• The addition of HCl (acid) and Alum (coagulant) followed by filtration.
• The addition of caustic soda to the filtrate to precipitate the excess of coagulant
followed by filtration.
• Then the final filtrate is used as the feed to the evaporators.
(Filtration: plate and frame type filter is commonly used)
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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6. EVAPORATION
• Purified soap lye are concentrated by evaporation under reduced pressure (vacuum) to
produce crude glycerine containing 80-85% glycerol.
• Concentration of glycerol is accomplished by boiling out water. With soap lye liquors
the evaporation must be carried out in such a way that the salt, as it crystallizes from
hot liquors, it can be removed without allowing it to be deposited on the heating
surfaces of the evaporator.
• Evaporation may be achieved by two stages: (a) single effect evaporation lead to 40%
half crude, (b) double effect evaporators leads to finishing product with 80-85%
concentration.
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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7. SINGLE EFFECT
EVAPORATION
• Steam is used as a heating medium in an internal shell and tube
heat exchanger. The liquor goes through the tubes by natural
circulation. Salt is removed from the system using a salt box.
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8. DOUBLE EFFECT
EVAPORATION
• This type consists of two evaporators coupled in series. Live steam
is admitted to the first effect (evaporator). The resultant vapour is
used as a heating medium in the second effect.
• The transfer of process liquor between effects is achieved by
utilizing the difference in pressure in each effect.
• Effective condensate removal is necessary between each effect.
• The second effect usually operates at about 760 mm of Hg of
vacuum, and the first effect about 300 mm of Hg lower.
• Salt is continuously removed from the system along with glycerol
liquors.
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9. SEPARATION OF SALT
• During the evaporation process, as water evaporates, salts and glycrol concentration
increases and solid salt starts crystallizing.
• The solubility of salt is seldom effected by temperatures, and is principally controlled
by the concentration of glycerol present. Salt can be removed by using salt box.
What is salt box?
• This fitted to the bottom of the evaporator. It is designed to steam the glycerol out of
the salt, and return the liquor to the evaporator.
• After salt removal the crude glycerine is stored into large conical tanks to allow a large
amount of salt to settle down for at least six hours (its recommended time for salt
crystallization)
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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10. REFINING OF CRUDE GLYCERINE
• Refining of glycerol is accomplished by steam distillation to separate high boiling, heat
sensitive substances like glycerol from water soluble and other impurities. The
distillation process utilizes two principles: steam distillation coupled with fractional
condensation, followed by fractionation to produce extra pure refined glycerine.
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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11. DISTILLATION
• The concentration of glycerol in the crude feed is around 85-88%.
• To purify glycerol, it must be heated to a temperature where its
vapour pressure is greater than the partial pressure of the glycerol
vapour.
• The vapour pressure of pure glycerol is 760 mm of Hg at 270 °C.
• Since glycerol can polymerizes at 160 °C, the partial pressure of
glycerol is reduced by creating vacuum in the system, and thereby
allowing the glycerol to vaporize at a lower temperature.
N.B. :At room temperature glycerol molecules polymerizes in the
presence of caustic soda to form polyglycerols which adversely affect
the glycerine yield.
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12. CONDENSATION OF VAPOURS
• Glycerol vapours contains water vapour as well as volatile impurities.
• Therefore, quality of the glycerine can be improved through partial condensation.
• During distillation, as the vapour passes through the condensers partial condensation
takes place, because vapour pressure of glycerol is much higher than that of water..
• Volatile substances close tot the boiling point of glycerol will condense along with
pure glycerine, which act as an impurity needing either redistillation, fractionation, or
bleaching deodorization.
• Products removed from the condenser are subjected to a continuous carbon
bleaching.
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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13. DE-ODOURIZATION
• Impurities found in the crude glycerine, especially organic matter of non-glycerol can
cause odour, taste, color in the refined product.
• Trimethyl glycol, a constituent of non-glycerol organic matter, often effects the color
of the product.
• In the de-odourizer (carbon bleaching system), 3-5% charcoal (Activated carbon) is
introduced in the bleacher to improve the colour.
• Through carbon bleaching high quality of CP (chemically pure) grade glycerine (with
nearly 99.5% purity.
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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14. RECOVERY FROM FATTY ACID
PRODUCTION
• Triglycerides are hydrolysed to fatty acid chains and glycerol by adding water at a
temperature of 250 C under a pressure of 55 bar.
• The hydrolysis products are glycerol and three fatty acids
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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Triglyceride + 3 water ---- Glycerol + 3 Fatty acid

15. PROCESS FLOW DIAGRAM OF FATTY ACID AND GLYCEROL PRODUCTION
29/2/2020
CPB30303 Oil & Fat Technol
Dr. Mohammed Danish
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16. FATTY ACIDS
• Fat and oils can be hydrolyzed into
corresponding fatty acid and
glycerol.
• Hydrolysis is the reversible reaction
whereby a molecule of steam breaks
a fatty acid off the glycerol backbone
of a triglyceride, resulting in a free
fatty acid and glycerol.
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Danish 29/2/2020 16
Vegetable oleic acid
Animal oleic acid
High purity oleic acid

17. SINGLE STAGE COUNTER
CURRENT SPLITTING OF
FAT & OIL
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18. STEPS OF
GLYCERINE
RECOVERY
• During hydrolysis reaction, a light phase which contains fatty acids
and the heavy phase , which consists of glycerol and other
impurities are obtained.
• This glycerol rich solution called sweetwater.
• The glycerol by-product must be withdrawn continuously to force
the reaction to completion.
• During the hydrolysis rection, each molecule of fat and oils will
yield one mole of glycrol and three moles of fatty acids.
• For every 100 g of fat and oil with 6.1 g of water will produce 95.7
g of fatty acid and 10.4 g of glycerol.
• Glycerol recovered from the hydrolysates of fat and oil contains a
mixture of water impurities such as free fatty acids. Thus need to
go for purification techniques.
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19. PURIFICATION OF GLYCERINE
The purification of crude glycerine used following methods:
• Neutralization: removal of fatty acids & simultaneous removal of non-
glycerol products via precipitation.
• Evaporation: concentrate the solution & remove alcohols
• Filtration/centrifugation: to separate the different coagulants form in the
solution.
• Vacuum distillation: purification and refining process achieved to the
desired degree through vacuum distillation or ion exchange, membrane
separation and adsorption.
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20. SLIDE ENDS HERE
T H A N K S F O R Y O U R AT T E N T I O N !
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Dr. Mohammed Danish
Senior Lecturer, Food
Technology Section, UniKL-
MICET, Alor gajah 78000,
Melaka, Malaysia