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

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

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

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 FlowInertial Flow

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)

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

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

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

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

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