ABSTRACT
The physical refining route can offer important advantages to the refiner. These are becoming ever more significant as concerns for the environment lead to increasingly stringent limits on the quality, and quantity, of water discharged from refineries. The primary objective of the neutralization (or refining) step is the removal of almost all the free fatty acids present in the crude oil. As already stated, an alkali solution reacts readily with free fatty acid to produce soap and water. Neutral refined oil leaving the primary separator typically contains 500–1000 mg soap/kg oil. This soap must be removed from the oil before further processing. Batch refining is carried out in open or, preferably, closed tanks. These are usually vertical cylindrical vessels fitted with conical bottoms. Silica hydrogel has a much higher capacity than bleaching clays for soaps and in particular, trace metals. A silica-based process has also been developed for acid refining high phosphorus oils such as canola and soybean oils.
