The palm oil fractionation process strives to obtain lipid crystals with high stability and good filtration performance. Since crystallization occurs in the eutectic system of solid fat and liquid oil, the complexity of components and operating conditions directly affect the fractionation of palm oil.
1. Oil products and their quality Different types of oils and fats have different triglyceride components, coupled with the influence of the technology in the process of oil production and refining, there are differences in the difficulty of oil separation.
2. Seed crystal and heterogeneous crystal nucleus The so-called crystal seed refers to the crystal nucleus formed first in the process of cooling and crystallization, and can induce solid fat to precipitate and grow around it. In the process of palm oil fractionation, solid fatty acids that are similar in structure to fatty acids in solid fats are generally added, and sometimes the oils are not subjected to deacidification pretreatment, and the free fatty acids contained are used as crystal seeds to facilitate the growth of lipid crystals. Inhomogeneous crystal nuclei refer to the crystals that are precipitated due to the temperature being lower than the freezing point of the solid fat during the refining and transportation of the oil.
3. Crystallization temperature and cooling rate In palm oil fractionation, since the three acyl carbon chains in the triglyceride molecule are all long, there will be serious supercooling and supersaturation during crystallization, and the crystallization temperature is often much lower than Freezing point of solid fat. The cooling rate depends on the temperature difference between the cooling medium and the grease and the heat transfer area. Excessive temperature difference will form crystal nuclei on the surface of the heat exchanger, affecting heat transfer and delaying the fractionation process.