Modelling Minimum Transport Boundary for Dense-Phase Pneumatic Conveying of Fine Powders

Abstract

This thesis present results of an ongoing investigation into modelling fluidized dense-phase pneumatic conveying of powders. For the reliable design of dense-phase pneumatic conveying systems, an accurate estimation of the minimum transport boundary condition or the minimum transport velocity requirement is of significant importance. The existing empirical models for fine powder conveying in fluidized dense-phase mode are either based on only a particular pipeline and product or have not been tested for their accuracy under a wide range of scale-up conditions. In this thesis, a validated test design procedure has been developed to accurately scale-up the minimum transport boundary with the help of a modelling format that employs solids loading ratio and Froude number at pipe inlet conditions using conveying data of two different samples of fly ash, ESP dust and cement (particle densities: 2197-3637 kg/m3; loose poured bulk densities: 634-1070 kg/m3; median size: 7-30 μm). The developed models (in power function format) have been used to predict the minimum transport boundary for larger diameter and longer pipelines (e.g. models based on 69 mm I.D.  168 m long pipe have been scaled up to 105 mm I.D. and 554 m length). The predicted minimum transport boundaries for the scale-up conditions were found to provide better accuracy compared to the existing models. A unified model was developed using data for a variety of powders and pipelines and the same has been evaluated under different scale up conditions.