Session: 10-07-01: Fluid Mechanics and Rheology of Nonlinear Materials and Complex Fluids

Paper Number: 110897

110897 - Comparing Experimental Results for Large Particle Separation From Non-Newtonian Slurries Using Full and Tapered Bump Arrays 

The removal of large particles from slurries is an important general problem in industry and, more specifically, at the Hanford site in Washington state where millions of gallons of radioactive waste slurries are stored in million gallon tanks for eventual processing. Industrially, large particles can clog downstream unit operations, and at Hanford large particle removal or treatment may be required to meet production requirements. In addition to slurries that exhibit Newtonian rheology, separating large particles from non-Newtonian slurries presents additional intricacies. These non-Newtonian slurries may support a yield stress with a stress-strain curve that exhibits power law-like curvature

 

Research on mesofluidic separation at PNNL has shown promise for eventual use when applied to the particle sizes and rheologies exhibited at the Hanford site.  PNNL’s mesofluidic separation technique uses staggered arrays of inline pins to create flow fields to move larger particles to one side. This migration results in two exiting process streams: one enriched in particles and the other depleted in particles. 

 

Traditionally bump arrays consist of staggered pin arrays that span the entire flow channel. The pins are staggered to create flow fields that direct larger particles out of the main slurry flow stream while permitting the smaller particles to pass through the pin array. The array extends for a finite distance in the direction of flow to permit larger particles to concentrate in the express lane and leaving the permeate stream comparatively enriched in smaller particles. 

 

Experiments were conducted with this mesofluidic pin configuration to evaluate the separation of large particles in non-Newtonian yield stress slurries.  Two array configurations were evaluated:  full array and tapered array.  In the full array when the array of pins spans the entire flow channel there is a finite pressure drop, flow split, and large particle separation between the permeate and the express lane.  In the tapered array the array of posts does not span the entire flow channel so the pressure drop, flow split and large particle separation are expected to differ from that obtained when using the full array.  The tapered array configuration could provide benefits of reduced pressure drop with minimal impact on separation performance.  Tests were conducted to evaluate the performance of full and tapered arrays for separating large particles from non-Newtonian slurries. Two configurations of arrays with 10-pin and 20-pin repeats were evaluated. 

 

In this paper, we describe the experiments and the experimental results. These tests were conducted to evaluate the separation and concentration of large particles in non-Newtonian slurries with a yield stress using full and tapered bump arrays, a novel unexplored experimental configuration. A Bentonite clay – kaolin clay mixture which included larger particles was selected for the test simulant. These results are applicable for many industrial processes including removal of larger particles from slurries of nuclear waste that could be processed at the Hanford site, where excessively large particulate in the flow stream is detrimental to processes.

Presenting Author: Judith Bamberger FEDSM2020 Chair and Senior Research Engineer, Pacific Northwest National Laboratory

Presenting Author Biography: Dr. Judith Bamberger specializes in slurry mixing and transport at Pacific Northwest National Laboratory in Richland, Washington.

Authors:

Judith Ann Bamberger FEDSM2020 Chair and Senior Research Engineer, Pacific Northwest National Laboratory
Leonard F. Pease Pacific Northwest National Laboratory
Jason E. Serkowski Pacific Northwest National Laboratory
Michael J. Minette Pacific Northwest National Laboratory
Carolyn A. Burns Pacific Northwest National Laboraotry