Patent GB-538155-A (GB)
Title: Improvements in or relating to processes of refining vegetable and animal oils containing free fatty acids
IPC: C11B3/06
Filed: 1939-05-23
Abstract: 538,155. Purifying oils. TENNANT, W. J. (Refining Inc.). May 23, 1939, No. 15344. Drawings to Specification. [Class 91] Animal or vegetable oils (including fish oils) are refined by the removal of free fatty acids and other impurities by mixing the oil with a non- saponifying neutralizing agent or agents (i.e. agents. which will not saponify neutral oil but will react with free fatty acids), in an amount at least three times and preferably 5-12 times that theoretically required to neutralize the fatty acid, and separating the soap stock from the oil. The preferred neutralizing agent is soda-ash but other non-saponifying neutralizing agents mentioned are trisodium phosphate, disodium phosphate, sodium silicate, equivalent potassium salts and other alkaline salts of alkali or alkaline earth metals, ammonia, triethanolamine. Sodium sulphate, sodium thiosulphate, sodium thiocyanate, and equivalent potassium salts, ammonium and alkaline earth metal salts may be used together with the basic substances mentioned above. Part of the neutralizing agent may be replaced by an alkali such as caustic soda if this is not used in an amount greater than is sufficient to neutralize the free fatty acids. A small amount of an acidic material such as naphthenic acid, and abietic acids such as those found in rosin may be employed. these have a softening effect on the soap stock. Petroleum solvents such as benzene, hexane, gasoline, and benzol may be present, also other vaporizable materials such as ethyl or isopropyl alcohol, or other fatty acid or soap solvent. The soap stock may be separated by gravity separation, but preferably it is separated by a continuous centrifugal separation. Elevated temperature is an aid to separation and a suitable range is from 160‹-200‹F. The addition of a large amount of neutralizing agent has been found to have a large influence on the softening of the soap stock. The neutralizing agent is preferably added as an aqueous solution containing a major amount of water. After the addition of the neutralizing agent the soap stock may be conditioned for continuous centrifugal separation by the addition of water or aqueous solutions of soap stock softening agents, or by the application of heat. The separation of the oil and the soap stock may be assisted by a dehydration treatment followed by a re-hydration treatment. This combination is stated to change the physical state of aggregation of the materials. The neutralizing agents may be added successively at different stages in the process, if desired in the form of powders or slurries. Dilute solutions may be added at a later stage to act as hydrating agents. A very small amount of caustic soda may be added to the oil or to the soap stock mixture to improve the colour. This addition is carried out at a low temperature. An apparatus is described in which the process of the invention may be carried out. Oils mentioned which may be treated by the process of the present invention include cottonseed, corn, sesame, soya bean, tung and linseed oils. The vegetable oils may either be crude oils containing gums or may be the so-called de-gummed oils. Animal oils mentioned include fish oils such as sardine, menhaden and herring oils. Specification 3164/02, [Class 91], is referred to.