Oils, caustic soda and water are fed into the pan equipped with direct steam heating system. Steam is fed in order to bring the content to the boiling temperature and to facilitate the mixing action required to start the saponification reaction.

When the reaction starts, as saponification is an exothermic reaction, steam feeding can be reduced or completely eliminated.

When the saponification is completed, brine is added into the pan to separate the content into two phases: an upper phase containing soap, and a lower phase containing salt, caustic soda, impurities and glycerine. The lower phase is discharged into a vessel and can be sent to a glycerine recovery plant.

After further washing by dilution with water and separation with brine, the soap is drawn out of the pan and is pumped to a Vacuum Cooling and Drying Plant.