Bleaching earths of various types in combination with activated carbon and/or filter aids are extensively used for removal of colour and suspended material from vegetable oils and fats which are used for making Vanaspati or edible refined oil. Spent bleaching earth removed from the filter bed after filtration of bleached oil contains 20-40% absorbed oil which constitutes the major part of the bleaching loss.
An estimate 120 Million MT of oil are processed with bleaching earth globally and 2.5 Million MT of spent bleaching earth is released.
Assuming an average oil retention value of 30% for the bleaching earths normally used, approximately 75,000 MT of oil is lost in the bleaching process constituting a significant economic loss. Prevention of this loss would be of immense importance in view of the huge deficit between supply and demand of vegetable oils in the global market. Serious fire and pollution hazards arising during stocking and disposal of spent earths also call for appropriate technical solutions for recovery of oil from spent earth. In view of these, Mecpro developed a method to extract the oil from spent bleaching earth economically and safely.
The first continuous plant in the world with a non-flammable solvent was established for Wilmar, Indonesia with a processing capacity of 150 MT per day.
Besides the importance of oil recovery, treatment of bleaching clays is also important for safety.
- For security reasons, because fatty clays are prone to catching fire,
- The environmental aspect, with the hazard of pollution of ground water because of the draining of fat by rain causing a fire hazard in the dumping grounds.
- Self-ignition in case of storage near the processing plant.
The present method of disposal of spent bleaching earth is environmentally unfriendly. After extraction of the oil it can be disposed safely or it can be converted to useful products to make fertilizers, cement, bricks etc. Without such extraction disposal of spent bleaching earth has a bad impact on the environment.
The technology would thus transform what was hitherto waste into a valuable material and provide a more environmentally friendly method of dealing with spent earth disposal. Besides, extracting oil in an affordable manner will help to enhance the profitability of the plant.