DILUTE SUSPENSION FLOW: AN EXPERIMENTAL AND MODELING STUDY

1. DILUTE SUSPENSION FLOW: AN EXPERIMENTAL AND MODELING STUDY Jennifer Sinclair Curtis Chemical Engineering, University of Florida Center for Particulate & Surfactant Systems (CPaSS) IAB Meeting Columbia University, New York City August 20, 2009

2. Relevance and Impact • Slurry flows are prevalent across a diverse range of industrial and geophysical processes • Transport lines for chemicals, minerals and ores • Debris flows and sediment transport • Non-homogeneous slurries often have problems with settled, stationary particles which can cause pipeline blockage • Current approaches to pipeline operation and design are largely empirical • Pumping systems account for nearly 20% of the world's electrical energy demand and are typically responsible for 25-50% of the energy usage in industrial plant operation

3. Objectives • Via a combined effort of CFD simulations and non-intrusive experimentation, the project will develop a fundamental modeling tool which can be used for: • Prediction of the critical settling velocities in pipeline operation in dilute-phase flow leading to reduced shut down times • Improvement in design of new slurry lines • Increasing operating efficiency of existing lines, resulting in higher solids flow and lower energy costs • …….as a function of the particle properties of the material to be conveyed

4. Research Background Fluid-particle flows involve complex interactions between fluid and particles that influence solids distribution and motion For fluid-particle flows that are not treated as a homogeneous suspension, previous work (both experimental and modeling) has focused exclusively on extremes of viscous-dominated flow or inertia-dominated flow regime (e.g. gas-solid flows with larger particles) Work in this project emphasizes “transition flow regime” which characterizes non-homogeneous slurries Viscous Flow Inertial Flow

5. Research Methods/ Techniques • Experimentation • Pilot-scale slurry flow facility in the Particle S&T Building high bay area • Non-intrusive flow measurements via LDV/PDPA • Can accommodate a wide range of flowrates, particle sizes and solids concentrations (refractive index matching under dense-phase conditions)

6. Research Methods/ Techniques • CFD Modeling • Continuum-approach for the particle phase using kinetic theory concepts to describe particle-phase stress • Good success in many gas-solid flow applications • For liquid-solid flow, particle-phase stress is modified to include influence of a viscous liquid

7. Results – Completed Experiments Particles: Glass Beads, 1mm and 1.5mm Seed Particles to Trace Fluid: 1 micron hollow glass spheres Particle concentration: 0.7%, 1.7%, 3% Re: 200,000, 335,000, and 500,000 Bagnold Number range: 90 – 700 Measurements Pressure Drop Axial Mean Fluid and Solids Velocity Profiles Axial Fluctuating Fluid and Solid Velocity Profiles Solid Concentration Profiles

8. Results – Mean and Fluctuating Velocity Ba = 94 Ba = 701 With increasing Ba, Increase in mean slip velocity Increase in particle velocity fluctuations Increase in fluid turbulence enhancement

9. Results – Solids Distribution Ba = 94 Ba = 701 Increased solids concentration at the wall, similar to gas-solid systems

10. Future Plans Order and set-up of upgraded LDV/PDPA equipment Experiments with smaller particles and slightly higher solids concentrations Begin model testing (in-house code, MFIX, and Fluent) using experimental data Acknowledgements PhD students Mark Pepple & Akhil Rao NSF & CPaSS