SOAP STOCK SPLITTING
SOAPSTOCK from vegetable oil refining usually presents either a disposal problem for the refiner or a processing problem for the user, and frequently both conditions prevail. Typical soap stock coming from chemical neutralizing of vegetable oils and fats mixture contains soap, neutral oil, water (approx. 80% ) and traces of free alkali.
Soap stock is not a waste and shouldn’t be discharged directly because of environmental conditions. The soap stock should be splitted into acid water and acid oil which is known as “Soap Stock Splitting”.
Acid Oil is generated by Sulphuric acid which splits the fatty acids and un-reacted glycerides from mixture. The quantity of acid addition depends on the TFA – Total Fatty Acid present in the soap stock. Feeding acid range could be between 10 to 14%.
The soapstock is collected in feed tank and it is heated by steam. Via pump it conveys to heat exchanger to heat up to the required temperature. Then a certain amount of recycled waste water is added into the mixture in order to reduce fresh water consumption. The acid water is treated with wash water to decrease the pH level of the acidic water.
Soapstock is mixed with concentrated sulphuric acid under pH control and then the reaction will be completed in reaction vessel.
The acidulated soapstock drops by gravity into the reaction vessels, where separation into acid oil and acid water occurs. After the separation is completed into reaction vessels acid waters are discharged into settling vessel. Acid oil is collected in vessel and controlled automatically by a level switch.
The acid waters coming from vessel are partially recycled in system and partially flow into tank waste water tank where are agitating by compressed air and neutralized by means of sodium hydroxide, the flow of which is automatically controlled by a pH-meter.
In this way, the waste waters flowing out of the plant are neutralized and they contain just sulphates: so, it is possible to discharge water diluted with the other liquid effluents from the factory, or, if requested by local regulations, to send them to a treatment plant.
The exact quantities of sulphuric acid and acid water are added by means of the dosing pumps under control of a pH-meters.
The acid vapours coming from reactors are sucked by fan and scrubbed in scrubber by means of circulating water. With this scrubbing system there are no acid gaseous effluents in the waste air coming from the plant.