Patent GB-538156-A (GB)
Title: Improvements in or relating to processes of and apparatus for refining vegetable andanimal oils containing free fatty acids
IPC: C11B3/06
Filed: 1939-05-23
Abstract: 538,156. Purifying oils. TENNANT, W. J. (Refining Inc.). May 23, 1939, No. 9936/40. Divided out of 538,155. Drawings to Specification. [Class 91] Animal and vegetable oils which contain impurities such as fatty acids, colouring matter and gums are purified by a process of mixing the oils with a refining agent which combines with the impurities to form a residue and which forms a mixture in which water or vaporizable solvents or vaporizable impurities are present, characterized by subjecting the mixture to a dehydration treatment to remove a major portion of the water or vaporizable solvents or impurities and then rehydrating said mixture and separating the residue from the oil. The preferred refining agent is soda-ash, but other non- saponifying agents may be used. The impurities are preferably continuously centrifugally separated while the soap stock is heated. In the case of those oils where there is considerable acidity, caustic soda may be added in an amount not more than sufficient to neutralise the fatty acids, the balance of refining agents required being made up by some non-saponifying refining agent such as soda-ash. Alternative materials to sodaash which are mentioned include tri-, and disodium phosphate, sodium silicate and equivalent potassium and alkaline earth salts, amines such as ammonia and triethanolamine, neutral salts such as sodium sulphate, thiosulphate and thiocyanate and equivalent potassium and alkaline earth salts. A small amount of some acidic materials such as naphthenic and abietic acids may be present as these have a strong softening action. Sufficient neutralizing agents must be employed to neutralize all the free fatty acid present, but the diluting and rehydrating agent may consist in whole or in part of substantially neutral salts which have a softening effect on the soap stock. The invention may be carried out by mixing the oil and refining agent in one zone and releasing a stream of the mixture thus formed into a dehydration zone to remove a major portion of the impurities which are removed and then the stock is rehydrated and the remainder of the impurities removed. The dehydration is preferably carried out with the aid of heat under vacuum conditions. It is preferred when using soda-ash to use as much as three times the theoretical amount necessary to neutralize free fatty acid in order to suppress carbon dioxide formation and give a good separation of the soap stock. If solvents such as hexane, benzine, gasolene, benzol and other petroleum solvents have been used in extracting the oils, they need not be removed before performing the process of the present invention but are removed in the vapour state along with water and vaporizable impurities in the dehydration stage. Oils mentioned to which the process of the present invention may be applied include vegetable oils such as cottonseed, corn, sesame, soya bean, tung and linseed, also animal oils such as sardine, menhaden and herring oils. Fats are also included.