THE GUARDED CAPACITANCE PROBE - A TOOL FOR THE MEASUREMENT OF SOLIDS FLOW PATTERNS IN LABORATORY AND INDUSTRIAL FLUIDIZED-BED COMBUSTORS

Although fluidized bed reactors at elevated temperatures (up to 1000 d egrees C) have a wide field of application, there is still a lack of m easurement techniques for the key entities: local solids volume concen tration and velocity. In this paper, a measurement technique which rel ies on the measurement of the local dielectricity is described. Throug h the application of a guard circuit and specially designed probes, an extremely high resolution and stability has been achieved. The system has been successfully operated under high-temperature conditions in a circulating fluidized bed where the local time-averaged solids volume concentration was as low as 0.1%. Measurements of local time-averaged particle velocities and solids volume concentrations in laboratory an d industrial fluidized bed combustors demonstrate the wide applicabili ty of the measurement system. (C) 1997 Elsevier Science S.A.