• A spray dryer, as the name implies, is a device for drying, utilizing a spray.
• A spray dryer mixes a heated gas with an atomized (sprayed) liquid stream within a vessel (drying chamber) to accomplish evaporation and produce a free flowing dry powder with a controlled average particle size.

The unit operation of spray drying includes the following key components:

• A method for atomizing a solution or slurry
• An air/gas heater, or a source of hot air such as a waste flue gas
• A gas/spray mixing chamber with adequate residence time and droplet trajectory distance for achieving the heat and mass transfer
• A means for recovering the solids from the gas stream
• A fan to induce the required air/gas through the spray drying system

The unique feature of a spray dryer is the surface area per unit weight generated by atomization of the liquid feed. It is this fact that enables a spray dryer to work. For example, feed atomized to 100 micron average droplet size generates approximately 15,400 ft2/lb of surface area. The same feed atomized to an average of 20 micron generates approximately 77,021 ft2/lb! This is like spreading one gallon of feed over 14 football fields!