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Observing particle concentrations and velocities inside a fluidized bed

| By Gerald Ondrey

Fluidized beds are used in a variety of industries for combustion, drying, catalytic cracking and other processes. However, the process that occurs inside a fluidized bed is extremely complex and — due to a lack of effective measurement techniques — has remained largely unknown. Now, researchers from Chalmers University of Technology (Gothenburg, Sweden; have developed a high-frequency radar technique that can measure exactly how particles behave in fluidized beds with unrivaled precision.

The radar transmitter and receiver convert lower frequencies into extremely high frequencies (up to 340 GHz), which can then be transmitted through the horn antenna. A gold mirror (an off-axis parabola) is used to redirect the beam toward the fluidized bed, enabling very precise measurements with high resolution in space and time.

As described is a recent issue of Fuel, this new terahertz-radar technology was demonstrated in a 3-m-high circulating fluidized-bed boiler. The technique can penetrate the reactor from the outside and measure the behavior of the particles inside it without disturbing the flow. The radar technique can also measure the velocity and concentration of the solid particles simultaneously with great precision and high resolution in time and space. This means that even minimal changes in the flow can be detected in real time, which is important when monitoring and controlling industrial processes.