Evaluation of solids friction factor models for fluidised dense-phase pneumatic conveying
This paper presents results from an investigation into the modelling of solids friction factor for fluidised dense-phase pneumatic conveying of powders. A model generated by the authors (based on straight pipe data) and three other popular/applicable models (developed by other researchers) were initially evaluated to predict the total pipeline pressure drop for the conveying of power-station fly ash (median particle diameter 30 1/4m; particle density 2300 kg/m3; loose-poured bulk density 700 kg/m3) in a test rig pipeline having an internal diameter of 69 mm and total length of 168 m. A comparison between the predicted pneumatic conveying characteristics (PCC) and the experimental plots indicated that certain models seem to predict within some reasonable range of deviation from the experimental data, whereas the other models resulted in relatively large over-predictions. The models that showed promise in the initial assessment were then further examined under scale-up conditions (to check their stability andscale-up accuracy) by predicting the pressure drop for pipelines with larger diameter or length (viz. 105 mm I.D. x 168 m; 69 mm I.D. x 554 m). The resulting scale-up predictions were found to be inaccurate when compared with the corresponding experimental plots.