Measurements of microwave transmission characteristics through various configurations of fluidized bed materials

The feasibility of developing a microwave diagnostic system for measurement of bubbles in a fluidized bed combustion system was experimentally investigated. Experiments were performed in a simple waveguide geometry using microwave frequencies from 2.4 to 3.9 GHz. Styrofoam spacers were used to simulate bubbles in bed materials, such as Greer limestone. The results show that it is feasible to develop a diagnostic system based on microwave transmission through a system consisting of gaps in a limestone media, such as a fluidized bed. The gap is shown to perturb the transmitted power, and to be very sensitive to bubble and bed material dimensions. Resonance effects are shown to occur when dimensions are integer multiples of a quarter wavelength.