(120c) Relating Gas Pressure Gradient to Flow Profiles in Process Equipment

The influence of gas pressure gradients on the behavior of fine powders in process equipment is critical to proper process operation.  Sometimes these gas pressure gradients induce preferential flow channels in process equipment.  Sometimes these gradients induce a more uniform flow in the bulk material.  Gas injection is often required to overcome slow or limiting flow rates.  However, injecting too much gas can result in temporary arch formation and hang-ups.  Clearly, the gas within a bulk material has a significant influence on the flow of the mass.  This paper looks at the governing equations that relate gas flow profiles to solids velocity profiles in process equipment.  The relationship between flow along process vessel walls and the gas pressure gradient is presented.  This analysis allows the prediction of preferred flow channels in process equipment.  The new methodology also predicts new mass flow criteria based on the influence of gas pressures in the process vessel.  Finally, the analysis suggests that the controlled injection of gas into a bulk material could be the means of controlling the blending or anti-segregation behavior of the unit operation.