US Patent 7234247 Low pressure dryer

A low pressure dryer for granular or powdery material includes a plurality of canisters rotatable about a common vertical axis serially among material heating, vacuum drying and material inventory discharge positions; pneumatic piston-cylinder means for rotating the canisters about said axis among said heating, vacuum drying and inventory discharge positions; means for heating contents of a canister at said heating position; means for sealing and drawing vacuum within a canister at said vacuum drying position and means for selectably permitting downward flow of dried granular or powdery material out of a canister at said discharge position where said canisters move collectively and unitarily one with another.