The outlet of the inlet screw conveyor dumps the material into a bin fromwhich it
is metered onto a moving conveyor belt which passes the material into a chamber where the water in the material is heated to its vapor state by the microwave energy. For lossy or thick materials, means may be provided along the belt to stir thematerial as it is subjected to the microwave energy and the vacuum dryer simultaneously. The speed of the belt is controlled so that the material is at its desired moisture content when its passes out of the microwave chamber and into a second bin where it isconveyed out of the pressure vessel by an outlet screw conveyor similar to the inlet screw conveyor. Since the process is conducted at reduced pressure, the temperature necessary to vaporize the moisture in the material need not be higher than theambient temperature thereby greatly reducing heat loss and enhancing efficiency of the overall apparatus. In addition, the present dryer does not needlessly pollute the air in the vicinity of the dryer since no blown air is circulated.