Continuous Saponification
- Continuous Saponification Type KVN
The continuous SELA saponification process for production of laundry or toilet soap using neutral fat is shown by scheme.
Compared to common kettle boiling the continuous process offers essential savings of utilities, higher yields, lower product losses and recyling of spent lye and niger.
The process starts with constant level vessels to be fed from storage tanks or constant level vessels for recycled concentrated glycerin lye.
The four process stages are controlled by dosing pump groups with individual adjustment of the dosing components.
Saponification
By introducing fat and caustic soda solution in a loop formed by saponification reactor and recycling pump, the saponification takes place in a reactor at 110° to 125°C. The reactor and the loop are heated to also allow stop and start. Excess saponification heat can be removed by loop cooling.
Cooling and Neutralization
The saponified product is mixed with spent lye which in a heat exchanger is cooled to a temperature of about 35°C. The soap leaves this stage at about 90°C and is fed to the following washing column.
For control of saponification manual sampling to adjust the alcali content is absolutely adequate for common purpose. If requested automatic control device of the electrolyte content via pH-measurement in the soap discharge pipe of the saponification loop with automatic metering device of lye are available.
Glycerin Extraction
The separation of soap and glycerin by countercurrent liquid/liquid extraction with brine takes place in the washing stage. The washed soap is discharged at the top of the extraction column and fed into the fitting stage.
The glycerin spent lye is discharged from the bottom of the column in the spent lye constant level feeding vessel. A dosing pump element recycles a part of the spent lye into the saponification stage.
By overflow the excessive spent lye is separated and fed to the following spent lye evaporation plant by a circulation pump.
Fitting
By adding a small quantity of caustic soda the curd soap is fitted. This addition is done by a separate metering pump in the metering tank and takes place directly after the washed soap leaves the extractor. If requested also an additional static or dynamic mixer can be used for better homogenization.
Separation of Neat Soap and Spent Lye
The soap being fitted with a small quantity of soap and leaving the extractor is fed to a separating centrifuge. Here the two phases neat soap and spent lye are completely separated from each other and are separately discharged from the centrifuge. The spent lye is fed to the metering tank together with the spent lye coming from the extractor. The neat soap reaches the storage tank and in the following drying plant can be dried to the requested drying degree.