(338g) Extending and Filling the Gaps in Solids Flow Theory

In the early 1960’s Andrew Jenike initiated a systematic study of the behavior of bulk materials in silos, bins and hoppers.  Later in the 1970’s Jerry Johanson added some rudimentary two-phase effects to these studies.  The resulting theories have helped us understand the basics of bin and silo design and the behaviors of fine powders in typical silos and hoppers.    However, these theories were limited by simplifying assumptions and did not extend to complex geometries, situations were external forces govern flow, or conditions where gas-solid interaction dominate behavior.   This paper examines the relationship between limiting behaviors and theory explained by early solids flow practitioners and behavior due to two or three phase systems, as well as behavior in complex geometries.  Specifically, the existing theories will be extended to include the effect of gas pressure gradients on mass flow, cohesive hang-ups, and rate limitations.  This will help bridge the gap between fluidization and cohesive behavior and extend limit analysis to conditions where bulk solids interact with gas, providing a means of using creative gas injection systems to mitigate flow problems in cohesive materials.  It will point a direction forward to extending existing fluid-solid systems to handle a wide range of materials.   The paper will extend the limiting theories to geometries other than simple conical hoppers and silos.  The limiting theory approach is general, but has only been widely applied to very simple geometries.  This paper discusses how to relate this theoretical approach to complex hopper geometries, feed devices, and devices with mechanical interaction.  It is hoped that extending this solid flow theory will allow the development of design equations for more complex geometries and extend the flow theories to two and three phase systems where engineers struggle with applying typical fluid laws only to discover that the cohesive nature of the system is not well suited to simple fluid behavior.   Such an extension to theory will help produce the next generation of process flow vessels that are designed to handle the new cohesive materials currently being created.