Vacuum drying

Vacuum drying removes moisture from a material under reduced pressure, which lowers water’s boiling point and can enable drying at lower temperatures.

Vapor pressure: The pressure exerted by a vapor in equilibrium with its condensed phase at a given temperature. Lowering chamber pressure helps water evaporate from a material at a lower temperature.
Freeze-drying: A drying process that freezes a material and removes ice by sublimation under vacuum. It preserves delicate structures by freezing moisture before removing it under vacuum.
Evaporation: The conversion of a liquid into vapor from its surface, below or at its boiling point. Vacuum drying relies chiefly on moisture evaporating from the material.
Hot-air drying: A drying process that removes moisture by exposing material to heated, flowing air. Unlike vacuum drying, it uses heated gas at approximately atmospheric pressure.
Vacuum chamber: A sealed enclosure designed to maintain pressure below the surrounding atmospheric pressure. Its seals, ports, and structure must withstand the pressure difference during drying.
Boiling point: The temperature at which a liquid’s vapor pressure equals the surrounding pressure. Vacuum lowers the pressure water must reach to boil.
Vacuum oven: A heated chamber that dries or processes materials under reduced pressure. It is a common batch apparatus for laboratory and industrial vacuum drying.
Sublimation: The direct phase transition from solid to gas without passing through a liquid state. It distinguishes ordinary vacuum drying from freeze-drying, where ice sublimes.
Spray drying: A process that converts a liquid feed into powder by atomizing it into a hot drying gas. It dries droplets rapidly through hot gas rather than reduced pressure.
Condenser: A heat exchanger that converts vapor into liquid by removing heat. It can capture vapor removed from the chamber and protect the vacuum pump.

Linked from 8 pages