(571d) Low-Order Modeling for the Effective Cleaning Radius of a Pulse Jet Mixer

Pulse Jet Mixers are designed at the Hanford Site Waste Treatment Plant to keep radioactive solids in suspension prior to vitrification for permanent storage. These systems must operate dependably and without maintenance for 40 years or more. The existing design database for pulse jet mixing of slurries like those at Hanford is meager. Verified/validated low-order design tools do not exist that can be used to reliably predict the operating conditions under which the Hanford slurry will successfully achieve suspension.

This study presents the results of a coupled CFD/analytical effort to develop a low-order design tool to support the design/evaluation of pulse jet mixers. The modeling begins with the Eulerian-Granular 2-phase flow equations governing the suspension, transport, and deposition of particulates in a carrier fluid. The equations are simplified based on observations from CFD pertinent to the zone-of-influence for the pulsed jet flow leading to a reduced set for which the solution relating the wall shear-stress to the radial distance from the pulse jet impingement point is known. By evaluating this expression at the critical shear stress for solid suspension, a model for the effective cleaning radius is evolved.

The model is validated using comparisons to CFD results and by comparisons to empirical correlations derived from experimental data.