Third Stage of Vegetable Oil Refining Process
Bleaching Process is the third step in vegetable oil refining which commences after complete of effective neutralization process. Bleacher Pressure Vessel is used to carry out the Bleaching Process. A Bleacher is careful designed equipment based on design parameters to ensure perfect bleach-ability of the crude oil. The process has its own importance.
The purpose of Bleaching is to remove the color pigments contained inside Vegetable Oils. The neutralized oil is heated at additional temperature through thermic boilers to ultimately raise the temperature of oil upto 120 C to 130 C. The oil is then treated with Bleaching Clays that adsorb the color pigments. The addition amount for bleaching clay varies from oil to oil. It also depends on the color content of the crude oil and the desired quality oil color index.
Following parameters are crucial while performing the Bleaching Process:
- Selection of Clay Type
- PH and Free Moisture Content in the Clay
- Activated or Non-Activated
- Surface Area and Porosity
- Surface Acidity
- Particle Size Distribution
- The Dosage Quantity
- Bleach-ability Index
The process variables such as moisture levels, temperature, contact time, vacuum are reliant parameters in oil purification process to determine achieve high quality refined oil product.
The activated bleaching clays have increased bleaching efficiency and impurity removal rate as compared to normal one.
Factors affecting adsorption
If one desires to obtain good quality RBD oil, then he must perform bleaching process with shear excellence. It should be regarded with care and attention. The following are the important stages in bleaching process:
- Temperature Raise to Limit Level
- Process Control of Clay Dosing
- Continuous Agitation for Uniformity
- Understanding Desired Color and Chlorophyll
- Total Contact Time
- Vacuum Pressure
- Final Filtration Method
Once the bleaching process is completed, filtration is done to the crude oil. The purpose of filtration is to remove the spent chemicals. The clay is filtered either on Plate Type Conventional Filter Presses or on Vertical Pressure Leaf Filters. Clean bleached oil is stored in Bleached Oil Tanks for subsequent processing.