When choosing the installation we watch its price, but the only question that matters is: “What will be my profits over the years ??”. Many aspects must be considered and it can be done in various ways. Here some examples:

Yield : the quality specification of end product can be based on different basis. Seldom is only IV ( Iodine Value ), more often IV followed by specific CP (Cloud Point), or even IV as indication and CP plus CS (Cold Stability) requirements that prevail. Then the difference between two “apparently” similar installations to produce the required quality can reach few percent in yield. Per year this loss ( L) can be staggering…

Energy costs : the differences in energy consumption appear especially when double processing is “replacing” single processing. Indeed, some installations obtain bottling olein quality in single step, others must fractionate RBDPO in two steps to obtain satisfactory quality (mainly due to CP and CS problem). Reprocessing costs include: utilities (steam, electricity, air, water, chemicals,…), plant capacity, operational (staff, spares).

Estimation of re-processing steam costs:

Estimation of re-processing electricity costs:

The palm oil is mainly composed of 5 fatty acids, themselves grouped in monoglycerides, (0,2 - 1 %), diglycerides, ( 2-7 %) and triglycerides, (about 94 %), minor components (about 1% ). We find also there free fatty acids.

Due to their fatty acid composition, the triglycerides can be classified according to their degree of saturation. Palm oil composition as fatty acids saturated and unsaturated is in proportion 50 / 50.

Dry Fractionation is a physical process without any chemical change to the incoming oil. In opposition to other fractionation processes: Solvent Fractionation and Detergent Fractionation there is no use of chemical additives, no yield loss (no effluent) and no contamination.

The quality of fractionation plant lies in its ability to separate in selective way the different triglycerides, so we reach targeted composition of olein and stearin.Unfortunately the interaction among various component of palm oil (over 40 glycerides), design of the crystallizer (mechanical and thermodynamic), the process control, as well as the filtration influence drastically this operation.

The process can be described as follow: the hot oil, with fully melted di- and triglycerides we cool down until reaching super-saturation . When this one is sufficient, the super-cooled oil enters the phase of nucleation ( creation of crystal germs ), followed by crystals growing phase. One may think that the high melting point (MP) triglycerides (TAG) will crystallize first as nuclei, than the lower melting point TAG will join and so on, until we create slurry of so called “stearin” crystals, suspended in liquid “olein” . But is far from that simple.

We face very complex exothermic, polymorphic crystallisation process, where the dynamic of crystallisation is not fully related to the melting points. Furthermore, the inter-solubility of various triglycerides affects the selectivity of the crystals build-up. The temperature control of oil and water (but not only !) has a critical influence during nucleation stage, as well as during crystals growth.

Due to all these factors that make this process so fragile and sensitive, we can understand that the term of “art of crystallisation” is well justified.