A microwave energy emitter (108) is positioned in a chamber within a vessel (106) that is transparent to microwave energy absorption that is further surrounded by a microwave reflective means to reflect the waves back into the vessel. The vessel (106) encloses a material that absorbs microwave energy through molecular vibration of its molecules. An inlet path (116) and outlet path (112) is provided for the material to flow in and out of the vessel upon predetermined conditions. Heated material can be condensed via a condensing means (124) into a collection vessel (120). A controller means (126) is provided to send control signals to switching means for controlling the material flow and receiving sensing signals for decision means.