CASTOR-OIL INDUSTRY. 25 



solution of oil in the solvent. Such extractors are made in various sizes 

 and may be from 5 to 8 feet in diameter and from 12 to 18 feet 

 long. The solvent and steam are introduced through openings in the 

 top ; the saturated solvent and steam are drawn off at the bottom. 

 Another type introduces steam and solvent through a journal bear- 

 ing in the axis at one side and discharges steam and saturated solvent 

 through a similar opening in the axis on the other side, first passing 

 through a perforated false head which divides the discharge end of 

 the tank, into a small compartment into which the filtered solvent 

 collects. The smallest of such units will hold about 3 tons of oleagi- 

 nous material to the charge, while the large ones may hold as much 

 as 6 tons. The total period of treatment from the time of the com- 

 mencement of loading back to the corresponding stage of the suc- 

 ceeding batch may be about 12 hours, enabling the units to be used 

 twice in 24 hours. The channeling of the batch is obviated by rotat- 

 ing the tank at intervals, thus breaking up pockets and other deter- 

 rents of good extraction. 



With the exception of the form of the extractor, the rest of the 

 solvent plant is quite standard and simple. The solvent-recovery 

 still may be provided with a steam jacket on the bottom with auxiliary 

 heating coils, or with a calandria somewhat similar to that used with 

 sugar pans (simulating an upright fire-tube boiler) where steam cir- 

 culates on the outside of the tubes while the evaporating charge 

 boils up inside the tubes and down wider openings provided for the 

 purpose. An open steam coil is also provided in the bottom of the 

 still for blowing off final traces of solvent at the end of the operation. 



The ou-finishing still is very similar in construction to the solvent- 

 recovery still, and where such installation is made its purpose is 

 to complete the operation of removing the solvent left unfinished in 

 the preceding solvent-recovery unit. Where the latter is used for 

 the preliminary separation of oil and solvent, these stills, particu- 

 larly the oil-finishing still, should be equipped for operating under 

 -vacuum. 



The solvent and water separator is usually a tank with a separate 

 compartment and overflow for drawing off the water which has set- 

 tled from the distilled mixture of solvent and water. Such separation 

 must be effected in a quiescent condition, because even a slight agi- 

 tation of the layers precludes quantitative recovery. It may be 

 necessary to install a preliminary water-solvent separator to take 

 up the pumping pulsations in order to obviate the churning effect 

 when the vapors and condensed liquor are discharged direct from the 

 vacuum pump during any part of the boiling-off operation. 



The other equipment of such a plant consists of storage tanks for 

 saturated solvent and oil, for solvent alone, and for oil; also a solvent 

 heater, boilers, and conveyors. All storage tanks should be pro- 



