Neutralization
Oil Neutralization & Cold Refining
The neutralization process typically treats cottonseed oil to remove most degummed oils and gossypol. This oil requires neutralization and low phosphatide content. In the process, free fatty acids saponify with caustic soda or sodium, depending on the subsequent bleaching method. Afterward, operators separate the soap. They then wash and vacuum dry the neutralized oil.
Neutralization Process Steps
- First, operators heat the oil to the optimal process temperature.
- To condition non-hydratable phosphatides, they add a small amount of concentrated phosphoric acid and blend it thoroughly with the oil.
- After a brief reaction, they add dilute caustic soda to neutralize the free fatty acids and phosphoric acid.
- Then they process the oil through a separator and into another reaction tank. This step is recommended for oils with high phosphatide content.
- Operators use self-cleaning separators to remove the sodium soap.
Soap Removal & Washing
However, the remaining soap content in the neutral oil is still too high for the next stages. Therefore, they refine the oil through one or two additional washings. To ensure efficiency, they add hot water and mix it with the oil. They then remove the soapy water using an additional separator.
Typically, one wash stage is enough. If small amounts of residual soap remain, a second wash is common. To reduce soap content further, they acidify the wash water with a citric or phosphoric acid solution. Finally, a second caustic treatment may be applied, particularly for crude oil, steam trouble, or lye.
Cold Refining Overview
Cold refining offers a sustainable alternative to winterization and usually follows neutralization. Oils with high FFA levels can lead to excessive oil losses, making cold refining less effective. In this process, operators add a small amount of acid to the crude oil without heating. The oil mixes thoroughly. After a short retention period, the acid infuses into the oil. Once infused, operators cool the oil. Afterward, they add caustic soda to neutralize the free fatty acids. The oil then flows through crystallizers for up to seven hours.
Once crystallization is complete, operators gently heat the oil to reduce its thickness. A centrifuge separates soap stock and waxes from the dewaxed neutral oil. Next, they wash the oil to remove the remaining soap content. They add the required wash water and mix the oil thoroughly. The oil and water then separate in a second centrifuge. Finally, they dry the oil in a vacuum dryer to remove any remaining moisture.
Process Images
Also check out, “Soap Stock Splitting“