Pretreatment & Bleaching

Process description

The process of removing visible impurities and colour pigments from vegetable oils is known as bleaching. Traces of gums, soaps are removed as an added advantage. This process is typical to both physical and chemical refining - the only difference is that crude oil is pre-treated in physical refining, whereas, in chemical refining, neutralized oil can be directly fed into the bleacher.


Pretreatment is used as part of the physical refining process to remove traces of gums and impurities, ideally to process oils like palm, palm kernel and coconut. Incoming oil is heated and mixed with phosphoric or citric acid. The mixture is then transferred to the conditioning reactor, where retention is provided for a predetermined period to complete the reaction, where bleaching earth absorbs the phosphatides.


Bleaching removes colour pigments and traces of soap by adding bleaching earth under vacuum at bleaching temperature and providing optimum retention time. Oil is then filtered in a pressure leaf filter to remove bleaching earth from the oil followed by the polishing filter. Bleached oil is either stored or sent for further processing. The spent cake is dried with steam blowing to recover more oil.

Kumar’s Bleachers are equipped with an efficient mechanical agitator and sparging steam arrangement that allows the oil to adsorb the bleaching earth completely. Coils are provided to increase the temperature if additional heating of the oil is called-for.

The Kumar advantage
  • Automated cleaning of filters by steam blowing.
  • Special vibrator assembly to discharge spent earth from pressure leaf filters.
  • Highly efficient Dutch weave filter leaves made in SS 316.
  • Optional pneumatic conveying system for bleaching earth.
  • Kumar offers several bleaching processes using bleaching clay singly or in combination with silica and activated carbon.
  • Kumar Bleachers can be used in various bleaching process configurations.

Kumar's Oil Refining range

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