Solids motion in a Gas-Solid two-phase mixture flowing through a packed bed

This paper reports the first study on solids motion at the single particle scale in a gas-solid two-phase mixture flowing through a packed bed, a process of great importance to a number of industrial processes. A solids circulating system and the non-intrusive Positron Emission Particle Tracking (PEPT) technique were used, which enabled steady-state measurements for a prolonged period thus also allowed the macroscopic solids behaviour to be analysed. The results show that the single particle scale velocity fluctuates with both radial and axial positions, but the average (macroscopic) solids velocity changes periodically with radial position, and the periodicity does not correspond exactly to the packed particle diameter. The residence time and tortuosity of the suspended particles show an approximately Gaussian distribution. The occupancy data suggest that particles spend more time in a region close to the wall.