A Continuous Fluidized Bed Microwave Paddy Drying System Using Applicators with Perpendicular Slots on a Concentric Cylindrical Cavity

Abstract

This article presents a continuous fluidized bed microwave drying system that provided a higher drying capacity than that provided by comparable conventional hot air drying systems. Its applicator consists of perpendicular slots over a concentric cylindrical cavity that is excited by perpendicular waveguides. The paddy to be dried was dropped vertically into the center of the applicator while hot air at 60°C, heated by magnetron ventilation, was injected from the opposite direction. Statistical data on the temperature distribution of the paddy, which scattered over the whole volume of the applicator, were collected and analyzed together with the probability of its orientation, position, and density. A suitable system was proposed, constructed, and tested. It provided good quality dried paddy, similar to that from a fluidized bed drying system. The system's maximum leakage power of 4.8 mW/cm2 was well within the safety standard. With only 5.2 kJ of energy consumption, this system reduced the moisture content of a large quantity of paddy from 24 to 14% (wb) with a capacity of 3.1 kg/h. The energy cost for drying was US$47.7/ton.