Nowadays, the economic manufacture of high-quality soap supposes a fully-boiled process. The following procedures proved successful for continuous steam drying.
1. Vacuum Drying
Drying and expansion under vacuum with simultaneous cooling of the soap.
2. Atmospheric Drying
Drying with atmospheric expansion and subsequent cooling of the soap on a chill roll.
3. Combined Drying
Drying in an atmospheric stage and connected in series cooling by expansion under vacuum.
When selecting the drying process, besides aspects of soap quality partly depending on speed of cooling down during or after steam drying, questions of energy consumption and availability of low temperature cooling water become important to an increasing extent.
At atmospheric drying, the evaporated water is expanded to ambient pressure and drained off vaporously. A condensation of vapor and the requirement of cooling water connected therewith are not necessary. Then the dried soap has the boiling temperature of water of ab. 100°C and has to be cooled to a suitable processing temperature of 20 to 30°C by means of a chill roll.