454631 The Influence of Squeeze Films in Particle-Impeller Breakage Events

Thursday, November 17, 2016: 8:30 AM
Bay View (Hotel Nikko San Francisco)
Rory Tyrrell, MABE, University of Limerick, Limerick, Ireland and P.J. Frawley, Mechanical, Aeronautical and Bio-medical Engineering, SSPC, MSSI, University of Limerick, limerick, Ireland

Existing theories surrounding secondary nucleation mechanisms in stirred batch crystallisations predominantly include varying forms of breakage kernels for particle-impeller collisions. The foundations of such theories lie with the assumption that high impeller tip-speeds are linked to the fragmentation of crystals as they come into contact with the blade surface. What will be outlined here is a mechanism by which crystals near the impeller may not even contact its surface due to a squeeze film boundary layer at the impeller blade's surface. Through the use of an impingement-jet particle impactor, direct imaging and tracking of particle-plane collisions was captured outlining the behaviour of crystals as they approach a target surface with initial velocities of up to 10m/s. Furthermore, A theoretical description of the squeeze film is detailed alongside its implications for future secondary nucleation kinetics dealing with breakage or attrition events near reactor surfaces.

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