Vacuum Drying Plants
- Scheme of a Vacuum Drying Plant
SELA vacuum driers are built in series for capacities of 300 up to 6000 kgs/hr. The process of vacuum drying is shown in the scheme. The base soap resulting from saponification is filtered and pumped into a feeding tank by means of a level control. Then the soap is supplied to the drier continuously by speed regulation of the proportioning pump. The pumps are especially suited for viscous mediums and the shaft sealings are insensitive against steam and easy to maintain.
- Vacuum spraying chamber - internal view
The heat exchangers are designed for a heating steam pressure of 9 bar abs. and a feeding temperature of the base soap of 80°C. They are reconciled to the special demands of soap drying where the evaporation of water already starts in the heat exchanger.
In the evacuated spraying chamber the soap is cooled down to the boiling temperature of vapor corresponding to the vacuum and sprayed on the inside wall of the chamber by means of a rotating spraying shaft with spraying nozzle. The sprayed soap is removed from the inside wall of the chamber by scraping knives being fastened at the spraying shaft. In order to produce a perfect soap quality without overdried soap particles, the inner face of the spraying chamber is machined exactly. Thus, a safe and maintenance-free removal of the dried soap is possible by means of springy scrapers.
- Condensation plant with vapor compression
The vacuum-tight discharge of the soap out of the spraying chamber is effected by means of a noodle plodder. Driers for laundry soap usually discharge in form of a soap bar by means of a duplex-vacuum plodder. For drying laundry soap the spraying chamber is operated with a pressure of ab. 20 - 25 mbar and for toilet soap with ab. 40 - 50 mbar. A control of the spraying chamber can be made through the above mounted sight glass with corresponding lighting.
The evaporated water is led via centrifugal dust separators in order to separate the soap dust sucked in and is condensed afterwards in the barometric condenser or surface condenser.
The costs for condensing vapor essentially depends on available cooling water temperature and local conditions of the plant. In case of high cooling water temperatures, a vapor compression by means of steam ejector is necessary prior to condensation in order to reach the equilibrium pressure of vapor in the condenser.
Evacuation of noncondensable gas and leak air can be made by means of steam ejectors or mechanical vacuum pumps at choice.