To improve the efficiency of treatment while preventing deterioration in quality due to drying and to realize a safe drying process by measuring the electric field strength and/or potential in a fluidized layer in a drying process and controlling the drying conditions according to the measurement.
An electric field strength meter 14 and/or potentiometer 15 is disposed in a fluidized layer drying machine 1 to measure the electric field strength and/or potential in the fluidized layer. Further, the obtd. measured values are inputted in a personal computer 16 for controlling to control the drying conditions according to the measured values. By measuring the electric field strength and/or potential, the time when the wet toner is excessively dried to decrease its water content which causes a hazard of dust explosion and oxidation of the toner can be indirectly judged. Thereby, at this time, an inert gas is introduced through an inlet 10 and mixed with a fluidizing gas so that the oxygen concn. of the fluidizing gas can be controlled to a degree not to cause dust explosion or oxidation of the toner.
KANDA HITOSHI
NAKAMURA TATSUYA
