(68c) Measuring Particle Dynamics of Fluidized Bed Using Digital in-Line Holography
The quantification of three-dimensional (3D) particle behavior in a fluidized bed is crucial for updating the basic knowledge and thus implementing better designs for such complicated multiphase system. Current work reports recent development and application of digital in-line holography (DIH) on the in situ measurement of (a) solid circulation rates, (b) particle size distributions, (c) 3D location, and (d) velocity distributions in a dense particle fields. A Hough-transform-based hologram processing algorithm have been developed and tested over a wide range of flow conditions, solid fractions, and particle characteristics. The performance of the processing algorithm is firstly benchmarked using synthetic holograms with varying particle size and shape, generated using known particle trajectories from DEM-CFD simulations. Then, using a hopper system, real-time solid flow rates and particle size distributions are measured using DIH and are compared to high-precesion balance and QIPIC results, respectively. Finally, DIH is employed to measure the standing pipe (12.7 mm ID) particular flows in a mini-CFB system. Solid circulation rates evolution are measured and its mean value agrees reasonably well with pressure-based estimations. Moreover, DIH is demonstrated to be capable of resolving fine particle trajectories resulting from attrition (~10 µm, with Stokes number, St<<0). The motion of these fine particles is useful in determining flow conditions around large particles, and estimate the slip velocities.