(154g) Particle Flow, Mixing and Heat Transfer: Scaling and Scale-up

Heating and drying of particulates plays an important role in a wide variety of industries, including the pharmaceutical industry, the bulk chemical industry, and the food industry. The complexity of the drying process stems from the fact that heat transfer, mass transfer, and changes in physical and chemical properties can occur simultaneously throughout drying. Complications often plague the process, including lengthy drying times, over-drying, nonuniform drying, agglomeration and attrition. These circumstances make drying a complicated process to understand and control. When considering scale up, these challenges are coupled with the difficulties typically associated with transferring knowledge from the laboratory scale to the pilot or the manufacturing scale. As a result, it can be difficult to design an appropriate drying protocol that optimizes heat transfer and can be translated from scale to scale. In this work, we have decoupled the problem and focused on studying the heat transfer aspect of drying processes. More specifically, we investigate the influence of process and material parameters on heat transfer in beds of particles. Our approach consists of a combination of experiments and the discrete element method (DEM) to analyze how heat transfer scales with bed parameters. We have carried out a design of experiments and computed heating times as well as heat transfer coefficients and temperature distributions to address scale-up. We find that scaling influences the flow of the bed and therefore creates a balance between conduction and granular convection as the dominant mode of heat transfer. We will discuss how our results can be used to inform heating and drying protocols in industrial processes.