Vacuum Drying

VACUUM DRYING is a process in which drying is carried out at reduced pressures and lower relative humidity compared to ambient pressure, enabling faster drying which lowers the heat required for rapid drying. This is the mass transfer operation in which the moisture present in a substance, usually a wet solid, is removed by means of creating a vacuum.

Vacuum drying is based on the principle of creating a vacuum to decrease the chamber pressure below the vapor pressure of the water, causing it to boil. With the help of vacuum pumps, the pressure is reduced around the substance to be dried. This decreases the boiling point of water inside that product and thereby increases the rate of evaporation significantly. The result is a significantly increased drying rate of the product. As reduced pressure is maintained in vacuum drying system, the boiling point of water is 25-30 °C.

Vacuum Drying Consists of 3 Phases: Evacuation, Evaporation & Final Drying.

About Vacuum Dryer

  • VACUUM DRYER is the equipment with the help of which vacuum drying is carried out.
  • The dryer is divided into hollow trays which increases the surface area for heat conduction. The dryer door is locked air tight and is connected to vacuum pump to reduce the pressure.
  • The materials to be dried are kept on the trays inside the vacuum dryer and pressure is reduced by means of vacuum pump.
  • The dryer door is tightly shut and steam is passed through the space between trays and jacket so that the heat transfer occurs by conduction.
  • Water vapour’s from the feed is sent into the condenser and after drying vacuum pump is disconnected and the dried product is collected from the trays.