Dry
fractionation is the simplest and cheapest separation technique. This is
because no post treatment of the finished product is required as there is no
chemical added in the process. The slurries will be fed into a membrane filter
press to separate into olein and stearin. Some products need to fractionate in
a special way. For example, palm kernel oil is solidified into cakes in the
static crystallizer before feed into the membrane filter press.
Solvent fractionation
The
crystallization is performed in dilute solutions with usually acetone or hexane
is used as solvent. This process only requires a short crystallization time and
provides rather easy separation. Hence, solvent fractionations give higher
yield and higher purity of the finished products. As solvent fractionation
required a very high production costs and capital investment, it is becoming
less interest to the industry and only used in specialty fats production.
Detergent fractionation
In detergent
fractionation, an aqueous detergent solution is added to the crystallized oil.
The wetting agent, usually sodium lauryl sulfate, in combination with an
electrolyte, usually magnesium sulfate allows the crystals to be suspended
easily in the aqueous phase. The water phase and the oil phase are separated by
means of centrifuge. The water phase is subsequently heated to melt the stearin
which will be recovered in a second centrifugation step. After separation, the
olein and stearin fractions are washed and dried to remove the detergent added.
The high production costs and contamination with the detergent are the main
disadvantages of this fractionation technique.
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