What is drying and what are the common drying methods?

Drying is a mass transfer operation that removes moisture (usually water) from a solid, liquid, or semi-solid material by evaporation. Common methods include: tray drying (batch, for heat-sensitive materials), rotary drying (continuous, for granular materials), spray drying (for liquid feeds to produce powders), and fluidized bed drying (excellent heat/mass transfer for particles). Selection depends on material properties and production scale.