Solvent extraction process
Solvent extraction is a process which involves extracting oil from pressed cake. The method of solvent extraction process recovers almost all the oils and leaves behind only 0.5% to 0.7% residual oil in the raw material. In the case of mechanical pressing the residual oil left in the oil cake may be anywhere from 6% to 14%.But after solvent extraction process the residual oil left in the oil cake will less than 1%.
The method of solvent extraction can be applied directly to any low oil content raw materials. It can also be used to extract pre-pressed oil cakes obtained from high oil content materials. Because of the high percentage of recovered oil, solvent extraction process has become the most popular method of extraction of oils and fats. Fat is one of the essential components of the human diet, therefore the demand for oils and fats are increasing with the in-crease in population and standards of living. Today large quantities of oil cakes such as peanut, cottonseed, sunflower,soybean,rapeseed,palm kernel etc.
The prepared material enters the solvent extractor through the rotary air seal.The solvent extractor is the key equipment in solvent extraction process.The extractor consists mainly of a very slow moving articulated band conveyor inside a totally enclosed chamber. The band is lined with perforated sheets and porous stainless steel cloth. The mass of the material moving on this band forms a slow moving bed. During the movement of the bed through the extractor it is washed continuously at various points with miscella of decreasing concentrations and finally with a fresh solvent in a counter current manner by means of sprayers kept in a line over the meal bed. The miscella percolates through the perforated bottom and collects in various hoppers kept below the bed. The miscella from the last hopper, which is concentrated, is taken off for distillation.
One of the most widespread industrial uses of this solvent extraction technique is in the petrochemical refining industry. As petroleum products are processed, impurities remain in the raw products. Using suitable solvents, the useful material can be separated from the unwanted substances, and then further extraction can be used to separate out the different grades of hydrocarbons according to their uses, which may be as fuels, lubricants, or as raw materials for the chemical industry. Solvent extraction process is also used in the refining of uranium for nuclear reactors.
This method is also employed in the production of essential oils, which are used in perfumes, aromatherapy, and as flavorings, from plant material. The technique is often preferred where distillation is not suitable. Where soil has been contaminated by pollutants, solvent extraction process may be used to remove some of them as part of an environmental remediation project. This can be an effective method where the contaminants are themselves solvents. In the laboratory, the technique is much used in the analysis of samples to determine what substances are present, and in what amounts.