—The “yellow oil” of trade has a decided flavor which it is desirable to remove, and this process is accomplished by deodorizing. (See [Fig. 155].)
Treating Tank.
—This tank is equipped for heating the oil to a very high temperature by the introduction of a large coil surface, preferably rings, one within the other and arranged so that each ring is accessible. The kettle coils, etc., should be made extra heavy. The top of the kettle must also be hooded and as the oil boils violently the steam must be given free opportunity to escape. The escape pipe should be at least sixteen to twenty inches in diameter in a tank six feet in diameter, and should be provided with a goose neck, so that the steam rising which condenses, does not drip back into the tank. [Fig. 155] show the construction of an oil treating tank.
The exhaust pipe extends into the atmosphere a short distance above the deodorizing tanks. On account of the extreme agitation caused by the heat, the oil is likely to boil over and waste. Special attention is called to the crook or neck in the exhaust pipe with two-inch outlet at the lowest point. This is done so that the condensation will not run back into the oil, but can be taken out at this point.
Process For Oil.
—The tank is filled with oil to about half its capacity. The oil is then heated to a temperature of 320° to 360° F. After being held at this temperature for an hour to an hour and a half, it is ready for the washing process. This is done by means of a two-inch perforated pipe at the top of the kettle, through which is sprinkled cold water on the oil. The extreme temperature evaporates the water very rapidly and at the same time causes a precipitation. The water should be allowed to run for five minutes, and then the body of oil should stand for from one to two hours. The cone, or bottom of the kettle, will be found to have a sediment which has been precipitated from the oil. This “bottom” should be drawn off, and the steam again turned on the coils.
FIG. 155.—DEODORIZING TANK FOR COTTON SEED OILS.
Blowing.
—The oil is heated to the original temperature and steam of high pressure and temperature introduced into the body of the oil. The length of time required for treating the oil depends largely upon its nature, some oils being more neutral and more nearly odorless than others, consequently no exact rule can be laid down that would fit all cases; it must be left to the judgment of the person handling the oil.