A drum dryer is a rotating cylinder that uses steam or hot air to heat feedstock and reduce the moisture content during a manufacturing process. The configuration may include one or more drums. A drum dryer may use atmospheric pressure or function under a vacuum. Drum dryers have many applications in the food industry because they are very efficient for drying pastes or gelatinous materials.
In the simplest configuration, a single drum dryer is supported on a frame so it can rotate on its axis. Steam is forced through the inside. A thin layer of feedstock is then applied to the outside of the drum. As the temperature rises, the moisture in the feedstock reaches boiling point, begins to evaporate, and leaves the feedstock. The dried layer of feedstock is removed from the drum with a scraper.
Depending upon the products it will be processing, a drum dryer is typically made from cast iron or stainless steel. The length of time the feedstock remains on the drum depends on the original moisture content and the desired ending moisture content. The range is usually between a few seconds and half a minute. Feedstock may be applied to the drum dryer by rollers, dipping the lower edge of the drum into a tray of feedstock, or spraying it on to the drum surface.