Measurement and modelling of the apparent shear resistance for aerated fine powders

Fine powders (Formula presented.) behave analogously to liquids when aerated by air. Hence, methods (e.g. Couette method) used to determine the flow performance of liquids can be adopted to investigate the similar flow properties (e.g. apparent shear resistance) of aerated powders. By this means, the understanding and handling techniques for aerated fine powders can be significantly enhanced. This research aims to investigate the apparent shear resistance of aerated fine powders through a specialised viscometer. Such a viscometer is combined with a fluidisation system and a common rotary viscometer. Three types of fine powders (alumina, cement and flyash) were selected as testing materials. Experimental results indicated that aerated fine powders behave similarly to Herschel–Bulkley non-Newtonian fluids. Subsequently, the apparent shear resistance for three fine powders were modelled by modifying the original Herschel–Bulkley rheology model. Consequently, the apparent shear resistance of a specific aerated powder can be measured and modelled using the bench scale system developed in this study, thus can be utilised to predict the flow performance of fine powders in pneumatic conveyors.