Method and apparatus for low temperature continuous drying of temperature sensitive materials (granular agricultural pesticides) at atmospheric pressure using radio frequency energy

摘要

The present invention provides a method and apparatus for agitation- free, low temperature drying of fragile, temperature sensitive, granular materials at atmospheric pressure using Radio Frequency (RF) energy to provide the heat of evaporation. A relatively low velocity flow of purge air through either a continuously moving or stationary product bed provides means for removing moisture from the product at atmospheric pressure. The purge air is maintained at a controlled humidity, temperature and velocity, and the intensity of the RF field is controlled in response to temperature sensing means to control the temperature of the product. For the case of a continuously moving product bed the RF applicator is preferably divided into multiple zones, which may be independently controlled, to effect control of the moisture and temperature profile of the product as it passes through the apparatus. The total air flow is kept to the minimum necessary to remove the moisture, which minimizes agitation of the product, minimizes fracturing of the granules and maximizes first pass yield.