Experimental investigation on vertical plug formation of coarse particles by a non-mechanical feeder

Plug flow receives attention due to its advantages of low particle attrition, low pipeline wear and low energy consumption. A novel non-mechanical draft tube type feeder (DTF) for plug formation has been proposed in our previous study for vertical plug conveying of coarse particles. We further investigate the influence of key geometry parameter of the DTF on plug formation for different particle diameter. Furthermore, we attempt to extend the application of PIV technique to evaluate plug velocity in pneumatic plug conveying. Experiments for vertical plug formation are conducted with glass beads of three kinds of particle diameter (i.e. 6 mm, 4 mm and 2 mm). Plug formation characteristics are examined in terms of flow pattern in riser pipe, solids mass flowrate and pressure fluctuation. The experimental results show that four main features of plug flow pattern in the riser pipe are observed. Solids mass flowrate displays good linear relation to superficial gas velocity forthe same particle diameter in the plug flow regime, even with different relative entrainment height. Some interesting phenomena are observed for the pressure fluctuation. Plug velocity is successfully obtained by PIV technique with high temporal resolution. The present study provides a further understanding of the flow pattern and dynamic behavior of coarse particles in vertical plug formation with the draft tube type feeder.