Investigations and modeling of the layer fraction in horizontal slug flow pneumatic conveying

The stationary layer of material between slugs in horizontal slug flow pneumatic conveying is an important reflection on the state and dynamics of a system. The gas-liquid analogy model of Konrad has been shown to accurately predict the layer fraction for a range of cases but the model breaks down near blockage conditions and does not consider material properties. A new model based on the rate of change of the layer fraction with respect to slug velocity was developed that addresses the shortcomings of the Konrad model. Results from tests on polypropylene pellets were compared to the new model and the model of Konrad with both models satisfactorily predicting the layer fraction in the range of slug velocities that were observed for the material. This paper further investigates the material dependent constant by applying the model to four different bulk materials