Effect of liquid addition on the bulk and flow properties of cohesive powders

In this work, the effect of water on the packing and flow properties of cohesive powders was experimentally investigated. Two cohesive powders with small particle sizes were studied with weight percentages of added water of 0, 10, 25, 40, and 50%. Particle properties including conditioned bulk density, porosity, compressibility, flow function coefficient, cohesion, etc., were tested using the Freeman FT4 Powder Rheometer and examined as a function of water content. Results show that water content has a significant effect on the packing and flow of the powders. With small amounts of water added, the particle beds became more cohesive, due to the formation of liquid bridges, and the bed volume increased roughly in proportion to the mass of water added leading to a fairly constant conditioned bulk density. When greater amounts of water were added to the particle beds, there was a substantial increase in conditioned bulk density. The bulk densities of both powders increased from around 0.3–0.55 g/ml when the added water was increased from 40% to 50%. As the water weight fraction increased, there was generally an increase in basic flow energy and cohesion, while the porosity and pressure drop generally decreased.