CASTOR-OIL INDUSTRY. 23 



expeller indicated a possible thousand pounds, or an hourly rate 

 of 21 bushels. In the expeller plant at Gainesville, the machines 

 were not set to yield more than about 15 pounds of oil per 46-pound 

 bushel. 



The relative quality of expeller castor oil compared with that 

 of hydraulic pressed oil will be considered later. 



SOLVENT EXTRACTION. 



On account of the large proportion of residual castor oil left in 

 the cake from the pressing or expelling operation, namely, from 12 

 to 20 per cent, or about 5 pounds per 46-pound bushel, solvent 

 extraction of the cake is universally practiced in this country, follow- 

 ing the methods generally applicable to oleaginous products. The 

 units comprising a complete extraction plant consist of the extractor 

 and the solvent-recovery still, the oil-finishing still, the condenser, 

 the solvent and water separator, pumps, and storage tanks. 



Two general types of equipment are used, namely, the stationary 

 extractor and the rotary extractor. The former is primarily an 

 English development, while the latter is American, having found 

 extensive application in the extraction of garbage and other waste 

 materials where the great problem is to handle in an economical 

 manner bulky products with small oil content. 



The iron stationary extractors vary in dimensions, but may have 

 a diameter of 6 to 8 feet and a height of 10 to 12 feet, entirely inclosed, 

 with, however, apertures for loading and discharging and also stirrers 

 and vapor pipes. The extractor is provided with a false bottom, 

 perforated over its entire surface with small openings, varying in 

 size with the character of the material to be extracted. These 

 openings may be over an inch in diameter, but if finer materials 

 are to be extracted auxiliary plates with smaller perforations may 

 be laid on. 



In order to obviate channeling in castor-pomace extraction, 

 attempts have been made to operate a stirrer, but owing to the 

 tendency of such material to pack during extraction it has been 

 found impracticable to operate such stirrers when the extractors 

 are charged to anything like their capacity. Accordingly, recourse 

 is had to auxiliary methods of breaking up channeling in extraction, 

 as well as in "steaming off" the solvent in the final treatment. 

 Another difficulty of stationary extractors is that there is a tend- 

 ency for materials containing large quantities of nonfibrous albu- 

 minous material to pack on the bottom, which very effectively 

 precludes the circulation of the solvent, so essential to the efficiency 

 of extraction. Among the methods which have been used to 

 obviate this packing tendency of castor beans is that of lajdng 

 burlap between quarter-inch chicken wire over the floor, spreading 



