84 



The Supplement to the Tropical Agriculturist 



EXTRACTION OF OIL FROM SEEDS. 



A New Method. 

 Referring to the various articles on oil ex- 

 traction from seeds which have appeared from 

 time to time in the Indian Trade Journal, 

 Mr. Louis Hoffmann, Chemist and Oil Mill 

 Engineer, who is interested in oil extraction 

 by chemical solvents and whose Calcutta address 

 is care of Messrs. MacBeth Bros. & Co., writes 

 to say that the present methods employed 

 in the milling of seeds are not only quite 

 out of date but result in a poor return, great 

 waste, and an unnecessarily heavy bill for 

 labour. After dilating on the loss India sus- 

 tains by shipping her oil-seeds to be worked 

 in other countries, the writer proceeds : — 



The manufacture of oil seeds and the treat- 

 ment of oils for various purposes is still in its 

 infancy in India. I will not go as tar into anti- 

 quity as to dwell upon the "Checkao " mills of 

 the Coromandel Coast, but point at the plants 

 in working operation in Calcutta, called qhan- 

 nies. What a waste of money, material, labour, 

 steam ! We see a large area covered with some 

 hundreds of revolving pots, each holding but a 

 few pounds of seed. Apart from the considera- 

 ble cost of such a large plant, the repairing and 

 labour runs into large figures. A powerful (of 

 course non-condensing) engine is the moving 

 spirit in the show. The whole place is dirty 

 and greasy and looks anything but like a mill. 

 The oil oozing out at the bottom of the grinding 

 pots is led into a small tank to be sold in its 

 crude state. I have seen one native concern 

 called an oil mill ; I do not yearn to see another. 



There are also mills worked by Europeans 

 for the purpose of crushing linseed. Even in 

 these I noticed a great indifference as regards 

 saving labour, cleanliness, and working on 

 modern lines. It seems to me that it is rather 

 a question of getting through a larger quantity 

 than the plant is supposed to do, than of making 

 a profit by careful work. No wonder that lin- 

 seed crushing does not pay ! What a difference 

 between the plants at present in use as com- 

 pared to the latest extraction plant by chemical 

 solvents ! This plant— suitable for treating oil- 

 seeds, oil-cakes, fish bones, etc., say 400 tons per 

 week— consists of 



A U BATTEKY ; ' OF 5 EXTRACTING POTS, 



each capable of holding about 3 tons of 

 the material to be dealt with. The shape 

 of those pots is cylindrical and they are 

 arranged vertically in one line. The seed passes 

 through a pair of horizontal rollers and is car- 

 ried up by an elevator and thence conducted 

 by a conveyor over the "battery''. It drops 

 through the open manhole into the pot and, 

 when full, the former is tightly closed and the 

 operation begins. In order to ensure perfect 

 extraction, it is paramount that the material 

 to be separated from the oil is perfectly dry. 

 Fresh seed or cake always contain a certain 

 amount of moisture, which must be removed 

 as the tiny water-cells prevent the benzine from 

 attacking andsohing the oil-bearing cells. Some 

 makers of extraction plants of ancient date 

 dry the material in a drying apparatus, which, 

 apart from the cost of the plant, increases the 



cost of steam, and yet seldom secures perfect 

 drying because the size of the drying plant is 

 generally inadequate to deal with large quanti- 

 ties in a short time. Hence this money is mostly 

 thrown away. Other makers do not even attempt 

 to dry and the result is unsatisfactory extrac- 

 tion. This difficulty has been solved by a new 

 patent (Middleton-Hoffraann's) in a very inge- 

 nious and yet simple way and the drying and ex- 

 tracting proceed at the same time. 



From an elevated benzine tank the solvent is 

 led down into the bottom of the extracting pots. 

 Inside each pot is a steam coil. As soon as the 

 liquid benzine touches the pipes, it evaporates 

 and the gas penetrates the crushed seed. In 

 about an hour the vapour works its way right 

 through the whole pot continuously condensing 

 and evaporating the whole time until the whole 

 of the contents is uniformly heated from 105c to 

 110 u C. During the condensing a certain per- 

 centage of oil is solved which collects at the 

 bottom of the extractor; and while the 

 heated vapour rushes through the seed, every 

 trace of moisture is removed and carried up 

 with the solvent vapour to be liquified again in 

 the condenser and separated from the solvent 

 by means of a separator acting upon the diffe- 

 rent specific gravities of water and benzine. 

 In this single operation about 80 per cent, of oil 

 is extracted. As soon as the condensing of the 

 vapours begins, which is a certainty that the 

 drying is complete, the liquid benzine-pipe, 

 leading to the bottom of the extractor, is closed 

 and the solvent tank is connected with the top 

 of the extractor letting the solvent run down 

 through the warm crushed seed. The oil left 

 in the seed is rapidly and completely solved and 

 carried down towards the bottom of the ex- 

 tracting pot. Other makers of ancient plants 

 now draw off the solution and distil the ben- 

 zine until the extraction is finished. The great 

 fault in this system is that during the greater 

 portion of the process 90 to 98 per cent, of 

 benzine has to he distilled in order to obtain a 

 few per cent, of oil. Loss of benzine and steam 

 is the natural consequence. 



Another feature of this new plant is that the 

 solution is conducted from the first pot into the 

 second, where the benzine is allowed to be 

 thoroughly saturated before it is drawn into the 

 still for distillation. This concentrating process 

 is continued by coupling on the third and fourth 

 pots. Meantime (for about three hours) fresh 

 benzine having continuously been playing on 

 the first pot, there is practically no oil left in 

 the seed. In order to get the liquid benzine out 

 of the seed, the steam coil is again heated and 

 forces the liquid benzine to evaporate. Then 

 live steam is introduced which carries along the 

 benzine vapour ; and, as the seed is above 100 

 C, the steam passes through without conden- 

 sing. This finishes the process. The manhole 

 above the bottom plate is then opened and the 

 perfectly dry, odourless meal is removed. The 

 other pots are treated in the same way and an 

 ideal extraction is obtained. 



The extracting process lasts from four to six 

 hours according to the oily contents of the seed. 

 The principal matter is the selection of the right 

 quality of solvent, as many failures are traced to 

 the purchase of cheap and unsuitable benzine, 



