Drying device, rotary valve and drying method

A drying device for drying a product, the drying device comprising:

• a housing having a drying chamber defined therein, and having a product inlet at a first end and a product outlet at a second end;
• a drying rotor being arranged rotatable within the drying chamber, wherein the drying rotor comprises a plurality of helical grooves arranged at the outer surface thereof and adjacent to each other in the direction of the circumference;
• a screw having a flight with a flight channel there between, wherein the screw is arranged rotatable within the drying chamber and substantially parallel to the drying rotor;
• a driver operatively connected to at least the screw, the driver being configured to drive the screw in rotation around a screw axis;
• and
• a heater for providing thermal energy to at least a part of the drying chamber in order to dry the product present within the drying chamber,
• wherein the drying rotor and/or the screw at least are configured for moving the product from the first end to the second end,
• wherein the screw and the drying rotor are configured such that the flight of the screw engages into multiple helical grooves of the drying rotor,
• wherein the screw and the drying rotor are configured such that, during use, the screw scrapes over the surface of the multiple helical grooves.