Tracking Individual Particles in a Fluidized Bed using a Medical PET-Camera

This paper describes a series of experiments tracing a single radioactive particle in a fluidized bed in an ECAT EXACT HR+ PET camera in order to obtain 3-D paths for an actual bed particle – i.e. a particle typical for the bed material – with a high spatial and temporal resolution. The paper describes how "lines of response" (LORs) were calculated from the binary list-mode files from the camera, and how particle positions (1 per ms) were computed from the LORs. It also gives a condensed account of how the data were analyzed further. The particle movement in the bed is shown graphically, and the findings interpreted in light of the theories o­n mechanisms behind particle movement in fluidized beds. Among other things the issue of fast, short-range movement of particles in fluidized beds is discussed. The findings are consistent with the notion of upward particle motion in the wakes of fluidization bubbles, and downward motion in the bulk. The vertical motion is rather structured and is cyclical, vertical paths often spanning most of the bed. The lateral motion is less structured. A close analysis of the spread in the millisecond positions both for the fixed and fluidized bed does not reveal any fast, short-range motion of the particles in the fluidized condition.


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