Bleached oil is continuously pumped from the feed tank by the deareator feed pump. The oil is pre-heated in the deaerating economizer by outgoing deodorized oil followed by the deaerating heater (if necessary) before entering the deaerator. The vessel is under full vacuum, so that residual air is reduced to an absolute minimum. The deaerator discharge pump sends the oil through a heat economizer where the temperature is increased by hot deodorized oil. The oil is heated to full processing temperature in the vacuum heater by thermal fluid from the thermal oil heater. A portion of the free fatty acids in the oil will be flashed off as the oil temperature increases.
Stripping : The hot oil enters the packed column, which is filled with special structured packing so that the oil is distributed into a thin film and is evenly agitated by stripping steam flowing counter currently from the bottom of the column. As a result, free fatty acids and other remaining volatile impurities in the oil are evaporated and removed with the steam. The residence time in the column is only a few minutes. The bulk of the free fatty acids along with aldehydes, ketones etc. In the oil are quickly stripped off before any heat induced permanent damage has been done.
Deodorizing : The stripped oil from the column flows into the deodorizer where it flows through the channels of a series of vertically stacked compartments (trays) while agitated by stripping steam. The prolonged thermal action breaks down carotene and other color bodies, resulting in a lighter oil color. Also, the amount of remaining free fatty acids in the oil is reduced to an absolute minimum. The stripping steam passes through the packed column and no separate steam is required in the stripping column. The maximum retention time in the deodorizer is 70 minutes.
Cooling : The deodorized oil is discharged into the deodorizing economizer and cooled by incoming oil. The oil is then discharged by the product pump and further cooled to storage temperature in the deaerating economizer and product cooler. The anti-oxidant is mixed with oil in the deodorizing economizer. The finished oil is finally sent to storage via one of the alternating product filters.
Distillate recovery : fatty acids and other materials, evaporated from the oil, are condensed by contact with recycled and cooled distillate in the vapor scrubber. The distillate is circulated by the distillate pump via the distillate cooler where it is cooled by cooling water. Accumulated distillate is discharged from the scrubber to storage.
Trans and tocopherol : the high efficiency (low amount of stripping steam) and short retention time of the stripping column, combined with the possibility to reduce the heat bleaching time or temperature, ensure optimum conditions for controlling the process. The oil can thereby be properly deodorized without the creation of trans fatty acids while also controlling the amount of tocopherol removed from the oil.
Protection against air contamination : for optimum quality, especially when processing unsaturated oils, the oil should be protected from air contamination during the entire deodorizing process. The packed column type deareator ensures maximum removal of dissolved air before high temperature heating. This also helps minimize polymerization of the oil on the inside of the heat exchange coils of the heat economizer.
Process control: the control, operation and supervision of the plant can be handled by one operator per shift. All main process parameters, if required, e. G. Flow rates, temperatures, liquid levels etc. Are automatically maintained from a control panel or, as an option, with the help of pid/pc based controls.