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In the processing of any oil material with a fairly high soiled content, the greatest yield of oil can be realizes only by extraction with solvents. How-ever, solvent extraction is much more advantageous in the case of some material than others. At the present time this process finds its most important application in the recovery of oil from Rice Bran, any seed &.
The large scale extraction of soyabean originated in Germany, and has been used there and in other European Countries almost to the exclusion of other method of processing. |
In the United States extraction of soyabeans is the less generally practiced, although it was estimated 32 that in 1939, 20.2% of a total 1,712,152 tons was processed by this method, as compared with 74.4% processed in expellers, and 5.4% handled in Hydraulic mills? The solvent extraction process, in its relation to both technical and economic factors, has recently been discussed in some detail , who point out the following circumstances as having encouraged its development in Europe and hindered its general adoption in the United States. The soyabean has only recently become a major American oil seed crop (Since about 1935), Whereas Manchurian soyabean became plentiful available in Germany a good many years ago. Solvent extraction has been commercially successful only in relatively large installation; the fact that European oil seed are largely important has United State is for the most part decentralized. Because of general domestic deficiencies in oil production, there has been a greater need in European Countries for attaining the highest possible yield of oil. |
The total capacity of oil all contains solvent extraction plants in the United State; in Comparison with the total world capacity of such plants (as of 1941) was estimated by Goss to be as follows: U.S. capacity, 1,555 Short tons per 24 hours; world capacity, 6,475 short tons pre 24 hours.
Solvent extraction is relatively more advantageous the processing of Rice Bran than other oil seeds because of the low oil content of this particular seeds. The oil content to which oilcake can be reduced by mechanical expression is approximately the same for all oil seed, I.e., about 4-5% consequently, the oil unrecoverable by mechanical expression, in term of percentage of the total oil increase content of the seed decrease. Comparative yields of oil from rice bran & seed of low, medium, and high oil content by the two method of processing are shown approximately It will be seen that the substitution of solvent extraction for pressing methods may increase the yields of oil from Rice bran by 20%. |
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In some cases the application of solvent extraction to specific oil limited by mechanical considerations. The most efficient extraction is obtained only in continuous counter-current systems, in which the solvent and the seeds make contact with each other in streams moving continuously in opposite directions. Most of these are system is operated satisfactorily only if the Rice Bran & seed/cake substantially retain their original form during extraction. If the flakes are inclined to disintegrate under the influence of the solvent, the fine particles will not only be difficult to separate from the miscella, but will also impede its uniform circulation through the raw materials mass. Rice Bran can be formed in pellets, which are excellently adapted to solvent extraction. Whole cottonseed meats also form flakes which are suitable for extraction; such meats have bees satisfactorily processed in experimental lots in raw materials. However, disintegrate to a virtual powder in extraction, and hence can probably not to be handled except in special types of equipment, such as that designed.
It is possible, by extracting the hydraulic- or expeller-pressed oil cake, to recover almost all the oil from oil seeds which cannot be satisfactorily extracted in their original form. The solvent extraction of mechanical press residue is not general practiced in the United States, except in the case of castor bean pomace, but is common in Europe. The oil obtained from the cake is invariably inferior in quality to that expressed from the seeds, since it contains a disproportionate amount of the pigments, Phosphatides, and other non oil constituents of the seed.
In addition to its use in processing oil Rice Bran of low oil content solvent extraction may be peculiarly advantages in the recovery of oil which are scare or expensive. Castor been reduce from hydraulic cold pressing are customarily solvent extracted in batch extractors. Solvent extraction may also be resorted to in order to obtain a fat free residue, or a residue proposes of improving yield of oil Solvent extracted in order to produce a residue which may serve as a source of, solvent extracted meal is preferred for the manufactured of protein adhesive, fibers, plastics, since there is much less denaturation of the protein in this meal then in that pertained cooking and mechanical pressing.
The recovery of fat from garbage is often carried out by means of solvent extraction, since the low fat content of this material makes other method of recovery difficult. Garbage is extracted in Continuous equipment of special design.
A rather elaborate cost analyze of solvent extraction, in comparison with mechanical expression, is presented in the economics of solvent extraction by the Hildebrandt system have been discussed in some detail by Meyerweissflog.
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