soap drying plant

Drying plant diagram - Soap factory

Drying is a crucial stage in bar soap manufacturing as it affects the physical properties of the soap. The optimum moisture content at the end of the drying stage determines better performance and productivity on the finishing line.

As a rule, liquid soap at the end of the saponification process contains between 42% and 44% moisture content (MC). In drying plant, it can be dried to different degrees of MC:

  • Toilet soap: 12% – 15% MC
  • Translucent soap: 18% – 22% MC
  • Laundry soap: 22% – 30% MC

Another way to measure the quality of soap at the end of the drying plant is with the Total Fatty Matter (TFM) variable. This variable determines the total amount of fatty matter that can be extracted from a sample of soap. A low TFM is associated with lower quality.

  • Toilet soap: 77% – 80% TFM
  • Translucent soap: 70% – 72% TFM
  • Laundry soap: 62% – 70% TFM

The drying process consists of four steps:


The liquid soap from the saponification step is pumped by the Filtration Pump through the soap filter to the feed tank.

The saponification step can be made using three different process: by boiler, by continous saponification plant or by Soap Crutchers.

The Soap Filter guarantees that the liquid soap wich come from saponification process comes out without any kind of impurities and other things which could contaminate the soap. We also protect the rest of the machines after this step.

The Soap Feed Tank is used to accumulate filtered liquid soap before it is pumped into the heating step.

Crutcher for the soap saponification step


Filtration Pump for the soap drying plant to pump liquid soap to the filter soap


Soap filter for the soap drying plant to filter liquid soap



After the soap feed tank, the liquid soap is fed by the Feed Pump into the Heat Exchanger where it is heated. In this way the water evaporates and the soap starts to dry before to vacuum spray Chamber.

Feed pump to feed the liquid soap into the heat exchanger and vacumm spray chamber in a soap drying plant


Heat exchanger to heat the liquid soap in the soap drying plant



The liquid soap is splashed into the Vacuum Spray Chamber through the feed pump. The controlled combination of temperature and vacuum allows the water to evaporate obtaining the desired degree of humidity in the soap. The steam separated from the soap is sucked in and condensed in the barometric group.

The soap is scraped from the internal walls of the vacuum spray chamber by means of spatulas precipitates until it falls into the Plodder.

To recover and recycle the soap particles produced in the vacuum spray chamber we use cyclones. Cyclones allow to separate the soap particles from the vapours produced inside the vacuum spray chamber.

Vacuum spray chamber to evaporate water and dry liquid soap in a soap drying plant


Cyclone to separate the soap particles from the vapours produced inside the vacuum spray chamber


Plodder to refine the soap - Refining process



All the steam produced in the drying plant are sucked from the inside of the vacuum spray chamber and cyclone by the vacuum group and are condensed in the Barometric Condenser. The condenser continuously transforms the steam produced during the soap drying process into water.

Barometric condenser for soap drying plant to use in the steam condensation step


Vacuum pump for soap drying plant to use in the steam condensation step


There are different possibilities of drying plant configuration, depending on the level of production (Kg/h) and type of soap (laundry or toilet soap bars).  

We design, make and sell to you a complete drying plant taking into account your requirements. Contact with us to start with your project.