Measurement of ferromagnetic particle concentration for characterization of fluidized bed fluid-dynamics

A method based on indirect measurement of magnetic properties of solids is proposed and investigated to be implemented in existing cold flow models of fluidized beds as a system for the determination of bed density and particle residence time distribution. The current work reports the fundamental principles for the measurement method and presents a first approach to the practical implementation which is based on inductance measurement of a simple coil. The characterization of the materials is reported and the fluid-dynamic suitability of the chosen ferromagnetic tracer particles is confirmed. The results clearly show the reproducibility of the measurement and evidence the capability to measure the concentration of tracer particles in an accurate way. The bed density of a fluidized bed was successfully determined using the designed apparatus. The method proposed appears promising and easily implementable for measurements of void fraction, residence time distribution of solids (RTD) and circulation rate in fluidized bed cold flow models.