Application of in-line ultrasound Doppler-based UVP–PD rheometry method to concentrated model and industrial suspensions

The in-line ultrasound Doppler-based UVP–PD rheometry method was evaluated for non-invasive, real-time rheological characterization of complex model- and industrial suspensions. The method is based on the combination of ultrasound velocity profile (UVP) and pressure drop (PD) measurements. Experiments were carried out in pressure driven, steady shear flow at different volumetric flow rates in a flow loop, designed to mimic industrial conditions. Results showed that instantaneous velocity profiles and rheological properties could be monitored in real-time, in-line. A much wider range of model and industrial suspensions was covered compared to what has so far been reported in literature. Investigated suspensions differed in particle sizes, distributions, shapes and suspension characteristics. The agreement was good between shear viscosities measured in-line and off-line using conventional rheometers for particles smaller than the shear gap in the concentric cylinders. The UVP–PD method is applicable to suspensions for which conventional, off-line rheometers fail due to shear gap size restrictions. The UVP–PD method can be a valuable tool for process monitoring since rapid changes in rheology during processing can be monitored in real-time, in-line.