At present, the relatively mature palm oil fractionation method is dry fractionation, which is a relatively economical method. This method slowly cools the dissolved oil to a certain extent, and then filters, separates and crystallizes to separate out the solid ester.

Basic process: palm oil → heating → cooling and crystallization → filtration → soft fat and hard fat

Heating: Palm oil is in a semi-solid state at room temperature, with saturated acid and unsaturated acid accounting for about 50% each. The triglyceride composition is GS3 accounting for 8%~10%, GS2U accounting for approximately 48%, and GSU2 accounting for 35%~ 39%, GU3 accounts for 7%~7.5%. The unique composition of palm oil determines its special crystallization process.

Palm oil is first dissolved into a liquid state by heating. Before crystallization, the palm oil is generally heated to about 70 degrees to destroy all existing crystals.
Cooling crystallization: The key to the dry fractionation process is cooling crystallization. If the crystallization is successful, the separation will be easy. Users set the cooling curve according to the season and temperature in order to obtain products that are in line with market sales.

During the processing, the cooling and crystallization conditions will determine the start of nuclear crystallization, the number of crystals, and the size of the crystals. Cooling efficiency and order are decisive factors in ensuring the unique formation and filterability of the crystals.

The specific operation is to control the cooling process by setting the temperature difference and cooling time between the oil and cooling water under the conditions of stirring and circulating water cooling, so that crystal nuclei are formed and grow slowly. When the required temperature is reached (depending on the desired soft fat quality, usually 20 degrees), stop cooling.

Filtration: After filtration, liquid oil and solid grease are obtained and stored separately. While it is important to control the conditions for cooling and crystallization, the selection of filtration equipment also has a great impact on the yield of liquid oil. The following types of filtration systems are currently used in industry: box filters and membrane filters.