Packing of Granular and Granular Fluid Systems

Session Chair:

• Michael Sigman, BASF

Schedule:

Assessing the Impact of Particle Breakage on Bed Packing Behavior

Benjamin Tiemens, UOP, a Honeywell Company

Many commercial processes in the refining and petrochemical industry utilize packed beds of catalyst or adsorbent particles.  When these particles break, the nature in which they pack together can change and negatively impact the performance of the packed bed.  Predicting these effects using standard quality control methods for particle mechanical strength is difficult given the complex nature of packed assemblies of irregularly shaped particles.  This talk will present several examples of how advanced characterization tools in conjunction with controlled bed packing studies have been used to study the impact of particle breakage in packed beds.  High speed video imaging of rapid breakage events reveal different fracture mechanisms of UOP catalysts and how these effects cause differences in quality control tests.  Additionally, 3D x-ray tomography (XRT) has been successfully used to non-destructively characterize both individual catalyst particles and sub-scale packed catalyst beds both before and after particle breakage has occurred.  Findings from these studies can be used to develop a fundamental understanding of the impact of catalyst breakage on commercial operations.

Multiphysics Simulations of Rigid and Deformable Discrete Bodies

Matthew Purvance, Itasca Consulting Group, Inc.

The newest version of the Particle Flow Code, PFC 5.0, is used to explore self-assembly of complex shaped, rigid particles with embedded magnets and the mechanical properties of large assemblies of carbon nanotubes. PFC 5.0 is a computational platform that allows for rapid simulations of particulate systems via the Distinct Element Method. For the self-assembly investigation, complex-shaped particles described as triangulated surfaces are approximated by rigidly connected spheres. An algorithm approximating the particle mid-surface is used to determine the sphere distribution. Custom interactions laws are created either with a scripting language or with compiled dll's. In this case, a custom dll is described that simulates both the mechanical and magnetic interactions between particles. Simulations using this linear-dipole interaction law produce realistic responses for simplified geometries and when applied to the complex geometry of the self-assembly problem. PFC aptly handles both intimate and long-range interactions effectively. For the carbon nanotube investigation, strings of particles are bonded with a custom interaction law to simulate elastic beams. A unique van der Waals interaction law has been developed to alleviate the commonly used corrugated potential. The results demonstrate a strong agreement between laboratory experiments and simulations of macro-sized samples of carbon nanotube assemblies.

Granular Materials near Jamming

Robert Behringer, Duke University

This talk focuses on materials near the jamming transition. A key aspect of jamming is the system density. If the density is low, then the granular material will flow; if it is high, then the system will be mechanically stable, and hence unable to flow. This suggests a transitional density, below which flow will always occur, and above which no flow will occur, until the system is sheared strongly enough. For frictional grains, reality is more complex and more interesting. There exists a range of densities for which either flowing or jammed states are possible, depending on the shear stress. For instance, if a system is prepared in this 'shear jamming' density range in a stress-free state, the application of shear strain leads to a jammed (shear jammed) state. This talk will explore the shear jamming process, the dynamics that can occur near shear jamming, and how this kind of state is manifested in flows of particle interest.