Physical Refinery part 1

Crude vegetable oils contain a wide variety of materials including fatty acids, glycerides, phosphatides, sterols, tocopherols, hydrocarbons, pigments (gossypol and chlorophyll), stearol glucosides, protein fragments and mucilaginous material. Refinery process is designed to remove undesirable constituents in crude oils with minimal oil loss. Physical refinery usually refers to a process that removes FFA in the crude or degummed oil by evaporation rather than being neutralized in alkaline refining process.

            Deodorization is the major section in the physical refinery process. In the industry, the crude oil is usually pre-treated before entering deodorizer. The pre-treatment sections include degumming and bleaching. For seed oil with high FFA content, an alkaline refining process may be required. Degumming process is designed to remove phosphatides and mucilaginous material from the oil. Bleaching is the process to remove color bodies from the crude oil by adsorption onto the bleaching earth. Lastly, deodorization is designed to remove the relative volatile odoriferous compounds from the crude oil.

            Generally, the crude oil is heated to about 105 ^oC before sent to the drier or degasser to remove moisture and dissolved gas. The dried oil will be mixed with phosphoric acid before entering a retention vessel. This retention vessel is designed to provide time for the coagulation of gums to occur. Here is the place where degumming process occurs and it is accomplished by hydrating the phosphatides and similar materials to make them insoluble in oil. Then, the oil slurries are sent to bleacher where bleaching earth is added in to adsorb the color bodies in the oil. The degummed-bleached oil is sent to a leaf filter to separate the oil from bleaching earth. Pre-coating is done by circulating oil in pre-coat tank to the leaf filter. This is to provide better filtration of bleaching earth as the cake form on the surface of the filter. the filtered oil is sent to a buffer tank. From buffer tank, the filtered oil is further refined in the deodorizer.

            There are many type of deodorization plant available in the market including continuous packed column, semi continuous tray and many others type. Normally deodorization column will be design with heat recovery whereby the hot oil leaving from the column bottom will be used to pre-heat the oil feed into the Deodorizer column. Deodorization column temperature will be depending on type oil. During deodorization, FFA and other volatile component is vaporized and sucked out by the vacuum. The RBD oil is further cooled down by heat exchanger before sent to a polishing filter prior to storage. The vapor phase from deodorizer is sent to scrubber to recover the FFA and is collected as fatty acid distillate, FAD. Below is the simplified process flow diagram for a normal physical refinery plant.