VEGETABLE OIL REFINING PLANTS
Vegetable oil refining plant is an integral part of oil mill machinery and it helps to refine vegetable oils from gums, waxes, phosphatides and free fatty acid (F.F.A) from the oil. In addition, specialized pigment is being used to give a uniform color to the oil and also it remove unpleasant odor by removing all odiferous matter. In most edible oil refining plants the refining is carried out by batch operation or as continuous operation. The refining also depends on properties of oils and therefore, sometimes physical refining can be carried out instead of chemical.
Normally batch process is recommended when oil refining is less than 30 tonnes of oil per day and F.F.A content is 1% or less. The batch process cost less because it is simple and require less maintenance, making refining economically a viable proposition even at the capacity as low as 10 tonnes per 24 hours. The equipment is needed in the batch processing includes neutralizer, bleacher, deodorizer, heat exchanger, high and low vacuum equipment and filters.
Continuous line processing an expensive and complicated process that has the capacity to refine oil higher than 30 tonnes in 24 hours. It is recommended for the organizations who have a huge requirement of oil processing. Continuous refining comprises of following steps:
Pretreatment / Degumming Section - The oils are treated under specific acids by which gums are precipitated and separated out by centrifugal separation. And when the gum content is low the conditioning is still carried out and separated in subsequent neutralizing process.
Neutralising Section - This is the second step of continuous oil refining where the pretreated oil is carried out by alkali treatment. The Free Fatty Acids (F.F.A) in the oil reacts with caustic soda and form soap stock. The soap stock is then separated by centrifugal process with the help of centrifugal separator and finally washed with water for complete removal of soap stock. The remaining water from the oil is again removed by centrifugal separator.
Bleaching & Deodorization Process - The neutralized oil is then treated with bleaching earth for removal of coloring pigment. The bleaching agent is filtered out in vertical pressure leaf filters. The deodorization process involves removal of odiferous matter. The operation is carried out at high temperature by injecting open steam and maintaining high vacuum at which time all odoriferous matter is distilled off and carried away to barometric condensors through vacuum system.
Dewaxing and Physical Refining - Some oils like sunflower oil or maize germ or corn oil have waxes and those need to be removed because of hazy appearance to oil. Some oils like palm oil do not require physical refining and need to refined only by high temperature and high vacuum.