Chemical refining - Neutralization of the free fatty acids
If the chemistry is right..
... free fatty acids don't stand a chance. The caustic soda added to the crude oil reacts with the FFAs to form sodium soaps. Centrifugal separators then remove the soaps from the crude oil. The neutral oil is subsequently bleached and deodorized. This method can be used for reliably refining virtually all crude oils, including oils of low quality, with the exception of castor oil.
Neutralization
In chemical refining caustic soda is used to neutralize free fatty acids.
The standard neutralization process is called exactly this, Standard Neutralization. It is the most common method to neutralize pre-degummed oils or oils with only a low phosphatide content.
Feedstock: Virtually all oils, including and especially low quality oils, except castor oil.
What to consider:
- In order to condition the NHPs (non-hydratable phosphatides), a small quantity of concentrated phosphoric acid is added and intensively mixed with the oil. Only then neutralization takes place by adding caustic soda.
- Crude oils with a relatively high phosphatide content require a reaction tank after mixing, oils with lower phosphatide contents can be conveyed directly to the first separator that removes the sodium soaps.
- After the first separator stage the residual soap content in the neutralized oil is still too high for subsequent process stages. So a washing stage is required, in most cases one stage will suffice.
- Cottonseed oil is the only exception here: in order to eliminate most of the gossypol we recommend a second caustic treatment. Cottonseed oil should always be neutralized in 3-stage installations.
Benefits:
- Most reliable process, also and especially for low-quality oils
- Better oil quality than with physical refining
- All oils except castor oil can be processed
Cold refining
Cold refining
Feedstock: for oils that contain waxes and have relatively low FFA contents, e.g. sunflower oil
What to consider
- The oil's residence time in the crystallizers is several hours
- Before removing the soapstock in the separator the crude oil has to be gently heated to reduce viscosity
- Also in cold refining an additional washing stage is required
Benefits:
- Effective removal of FFAs and waxes
- Compact installation
Soapstock splitting
Soapstock splitting
