(553a) A Multiple-Radioactive-Particle Tracking Technique for Mixing Applications
AIChE Annual Meeting
2013
2013 AIChE Annual Meeting
Particle Technology Forum
Mixing and Segregation of Particulates II
Wednesday, November 6, 2013 - 3:15pm to 3:35pm
Radioactive Particle Tracking (RPT) is a powerful and nonintrusive measurement technique to track particles in a multiphase system. In particular, the high penetrating power of gamma rays makes RPT an appealing technique that overcomes the limitations of other conventional methods (e.g. LDA and PIV) in the case of opaque particulate systems. RPT has been successfully used to investigate flow dynamics and mixing in a variety of blenders and stirred tanks (cylindrical drum, V-blender, Rushton turbine) as well as fluidized bed reactors.
Although RPT has shown efficient non-invasive tracking abilities in different flow situations, it is limited to one single tracer and relies on the so-called ergodicity assumption (the time average of one tracer is equal to a population average) to investigate mixing characteristics in a system. However, tracking more than one particle simultaneously is of interest because it could then yield direct information on both the relative translational and rotational motions of these particles. In particular, such rotational motion may play a role for instance on the lift force exerted on particles and then have an impact on their distribution. In systems where heat transfer is involved, the rotational movement of solid particles may change the rate of heating or cooling by increasing the interphase heat transfer coefficient. Moreover, tracking more than one particle could be used to assess the accuracy of a simulation model based for instance on the discrete element method (DEM).
This work presents a multiple-radioactive-particle tracking technique (MRPT) for the tracking of two (free or linked) tracers in a system. First, the proposed method is presented in detail. Its accuracy and precision are then investigated on the basis of experiments that have involved stationary or moving tracers in a cylindrical drum. Finally, the application of MRPT to mixing systems and other processes will be discussed.