Numerical validation of microwave heated fluidised bed calcination of waste containing ceramic powders

Abstract

This study corresponds to the first phase of the development of a microwave heated fluidised bed for calcination of waste (metal nitrate salts) containing ceramic powders under H 2 /N 2 reducing atmosphere. The power is delivered through the top end of the calciner at 2.45 GHz. Apart from the experimental investigations, the study also involved microwave analysis to approximately predict the mode numbers corresponding to specific solutions of the characteristic field equations in the cavity as a function of powder bed height. The calculations reveal the dominant modes expected to propagate in the calciner. Here, a finite-volume time-domain technique simulates the electromagnetic phenomena inside the empty and loaded calciner. Because of the geometry of the calciner, special stair-case type boundary conditions ensure accurate calculations of the fields at the cylindrical conducting walls of the cavity. The simulation results confirm the experimentally observed mode structure inside the calciner. Thus the numerical technique can capture the nature of the modes in the case when the calciner is empty and loaded with a ceramic powder.