Method Of Production: The Glycerol is derived from the direct Saponification of Fats & Oils with Caustic Soda and recovery as a By-product from the resulting Soap. During the Saponification Process, glycerol is librated and then extracted by the counter current washing of soap to obtain Spent Lye which contains maximum concentration of glycerol in water and impurities i.e. Soap, fatty acids, color bodies, insoluble materials and phosphorous and nitrogen compounds.
Saponification Reaction:Triglyceride + Caustic Soda ---- Glycerol + Soap
Glycerine Manufacturing Process: 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 And Preparation Of Brine• Crude Glycerine To Produce marketable Grades
1. Purification Of Soap Lye: 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 consist of two stages.• The addition of Hcl (acid) and a Alum (coagulant) followed by filtration• The addition Alkali (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: Filtration is important in the Chemical treatment. When the well agitated mixture is pass through the filter a clear filtrate is produce. Plate & Frame type filter is commonly used.
2. Concentration Of Glycerol Liquors: Purified soap lye are concentrated by evaporationunder reduced pressure (vacuum) to produce crude glycerinecontaining 80-85% glycerol. Evaporation may be achieved bytwo stages.i.e Single Effect Evaporator(40% half crude) andthen followed by finishing to 80-85% concentration at DoubleEffect Evaporators.Operation: In the evaporation process, Concentration of glycerol isaccomplished by boiling out water. With soap lye liquors theevaporation must be carried out in such a way that the salt, asit Crystallizes from hot liquors,can be removed withoutallowing it to be deposited on the heating surfaces of theevaporator.
Single Effect Evaporation: Steam is used as a heating medium in an Internal Shelland tube heat exchanger.The liquor goes through the tubes bynatural circulation.Salt is removed from the system using a saltbox.Double Effect Evaporation: This type consists of two evaporators coupled in series.Live steam is admitted to the first effect (evaporator). Theresultant vapour is used as a heating medium in the Secondeffect. The transfer of process liquor between effects isachieved by utilizing the difference in pressure in each effect.Effective condensate removal is necessary between eacheffect.The second effect usually operates at about 760 mm Hgof vacuum,and the first effect about 300 mm Hg lower. Salt iscontinuously removed from the system along with glycerolliquors.
Salt Crystallization: During the evaporation process,as water evaporates, saltand glycerol concentration increases and solid salt startscrystallizating. The solubility of salt is seldom effected by temperatures,and is principally controlled by the concentration of glycerolpresent. Salt can be removed by using Salt Box.Salt Box: This is fitted to the bottom of the evaporator. It isdesigned to steam the glycerol out of the salt, and return theliquor to the evaporator.Storage and Handling Of Crude: After that, Crude glycerine is stored into large conicaltanks to allows a large amount of salt is settle down for at leastsix hours is recommended that.
3. Refining Of Glycerine: Refining Of Glycerol is accomplished by Steamdistillation to separate high boiling, heat sensitive substanceslike glycerol from water soluble and other impurites.Thedistillation process utilizes two principles, Steam distillationcoupled with fractional condensation, followed by fractionationto produce extra pure refined glycerine.Distillation: The concentration of glycerol in the crude feed to thestill is around 85-88%. To distill glycerol, it must be heated to atemperature where its vapour pressure is greater than thepartial pressure of the glycerol vapours in the still. The vapourpressure of pure glycerol is 760 mm (atmospheric) at 270Centigrade. Since glycerol polymerizes at 160 Centigrade, thepartial pressure of glycerol is reduced by Vacuum System,maintaing the same total pressure, and thereby allowing theglycerol to vaporize at a lower temperature.Chemical Reactions: At the Still temperature, glycerol polymerizes in thepresence of caustic soda to form polyglycerols whichadversely effect the yield.
Condensation of Vapors: After the vapors leave the still, they must be condensed.Vapors contain water vapor and volatile impurites as well as theglycerol. Success in producing good quality of refined glycerine lies inthe effectiveness of partial condensation. As the vapors pass throughthese condensers, partial condensation takes place. Since the vaporpressure of glycerol is much higher than that of water, relatively pureglycerol is condensed at higher temperatures. Volatile substancesclose to the boiling points of glycerol will condense along with puregkycerine, which acts as an impurity needing either redtisllation,fractionation, bleaching deodorization. Product removed from the condenser (99.5% wt. percent) aresubjected to a continuous Carbon Bleaching.Deodorization: Impurities found in crude Glycerine, especially MONG (MatterOrganic Non Glycerol), it can cause odor, taste, color problems in therefined Product. Trimethylene glycol, a constituent of MONG, ofteneffects the color of the product. In the Deodorizer (Carbon Bleaching System), 3-5% Charcol(Activated Carbon) is introduced in the Bleacher to improve the color. Such an effectiveness system to produces a product of 99.5%high quality of CP (Chemically Pure) Grade Glycerine.