Computational investigation of particle flow characteristics in pressurised dense phase pneumatic conveying systems

Abstract

A new model for predicting particle flow characteristics in dense phase pneumatic conveying systems is presented. The domain of the solid phase is evenly divided by discrete grids, based upon which particle collision forces are solved. Specifically, the collision forces inside a grid are described based on the Lagrangian framework as a function of particle flow dynamics and the local solid concentration, whilst collision forces driving particles to flow amongst grids are calculated based on the Eulerian framework as the shear stress forces induced by the solid concentration gradient. The model was applied to solve the particle flow through a dense phase pneumatic conveying pipe with a 90° horizontal-to-vertical bend. Good agreements on the pressure drop through the horizontal and the bend sections were achieved between the prediction results and the experimental data. Effects of key parameters including superficial gas velocity, bend radius and particle size on the particle flow characteristics in terms of solid flow pattern, solid concentration distribution and fluctuation, and particle velocity distribution have been investigated. The results showed that the typical particle flow patterns, i.e. stratified flow, dune flow and slug flow, were sequentially observed when decreasing the superficial gas velocity or the bend radius, or increasing the particle size. The fluctuation intensity of solid concentration that is often seen as an indication of particle flow stability was substantially higher in the bend compared to those in straight sections. The model is simple yet proves efficient and capable of accurately predicting the particle flow characteristics in the dense phase pneumatic flow systems.