# Modelling the solids transport phenomena within flighted rotary dryers

Lee, Andrew (2008) Modelling the solids transport phenomena within flighted rotary dryers. PhD thesis, James Cook University.

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## Abstract

This thesis presents the development and testing of a solids transport model for flighted rotary dryers based on the physical and geometric properties of the system. Particular emphasis was placed on understanding the internal flows and phenomena. An introduction to flighted rotary dryers is given in Chapter 1, where the context and relevance of this research is outlines. Chapter 2 gives a review of literature pertaining to the modelling and analysis of solids transport in flighted rotary dryers.

Chapter 3 discusses the development of the solids transport model based on the physical behaviour of a flighted rotary dryer. The solids transport model was developed based on numerical methods, dividing the dryer into a number of discrete slices, and each slice was further separated into two discrete phases. One phase selected to represent the material contain in the flights and in the bottom of the drum, whilst the other phase was selected to represent the solids falling through the moving gas stream. The flow of solids between phases was based on the physical movement of solids that occurs within an actual dryer. The magnitude of these flows was described using solid residence times and partitioning coefficients.

The solids transport phenomena occurring in the two phases were described using the geometry of the dryer and the physical properties of the solids. Chapter 4 presents a model for the unloading profile of a generic unserrated, straight, two-section flight, which was developed based on geometric analysis of the holdup within a flight. This unloading profile was then used to calculate the average fall path of a solid particle within a dryer, and thus the time spent within each phase of the dryer. Using measurements from CSR Invicta Mill’s raw sugar dryer number 2, the average fall time of a particle was found to be in the order of 0.9 seconds, and the average time a particle spent in the flights to be in the order of 9 seconds. These residence times were then used to govern the flow of solids within the overall solids transport model, and the methodology describes a generic approach to modelling flighted rotary dryers.