Dewaxing Process in Refinery

Which oils need dewaxing?

Wax is a high molecular lipid with a high melting point and poor solubility in oil. It will affect the taste and transparency of edible oil and is not easily absorbed by the human body. Therefore, edible oil needs to be dewaxed.

However, not all oils need to be dewaxed. This process is mainly aimed at those oils that are easy to precipitate wax at low temperatures, such as sunflower oil, rice bran oil, corn germ oil, cottonseed oil, tea seed oil, etc. If these oils are not treated, they will become turbid at low temperatures, affecting transparency and taste.

Rapeseed oil, peanut oil, palm oil, sesame oil, etc., due to their own characteristics, rarely require this step.

What is the process of edible oil dewaxing?

The process flow of edible oil dewaxing is as follows:

Refined oil - heating - cooling - crystallization - crystal growth - filtering - heating - finished oil

1. Heating: 

At room temperature, some solid wax in the oil has precipitated crystals. In order to achieve a good dewaxing effect, it is necessary to use a steam heater to heat the oil before dewaxing to destroy the existing crystals. This will achieve a better crystallization effect, and this process can also be called crystal breaking.

2. Cooling: 

After crystal breaking, the oil needs to be cooled to a low temperature, usually below 0°C, depending on the type of oil and the melting point of the wax. The cooling process causes the wax to begin to crystallize.

3. Crystallization:

Under low temperature conditions, the wax will gradually form larger crystalline particles. In order to promote the formation of crystals, slow cooling and slow stirring can be used. The crystallization tank is equipped with a variable speed mechanical stirrer to ensure uniform stirring. When the oil appears in the liquid soft fat as semi-solid hard fat crystals (slurry), prepare to filter. If the crystallization effect is not good, send the slurry to the feed oil heater for re-crystallization.

4. Filtration: 

When the wax is fully crystallized, the crystallized wax is separated from the oil by filtration. Filtration usually uses a plate and frame filter.

5. Heating:

Finally, the dewaxed oil is heated to room temperature to restore it to liquid state for subsequent processing and use.

It should be noted that the temperature and time should be controlled during the dewaxing process to avoid excessive crystallization of wax or the influence of other components in the oil. At the same time, for different types of oils, the dewaxing process parameters will also be different and need to be adjusted according to actual conditions.

The purpose of oil dewaxing is to improve the transparency and stability of oils, change the quality of oils, make them clearer, and reduce precipitation and deterioration during storage and transportation.

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