Design and validation of a capacitance-based sensor for slurry density measurement

Abstract

This work presents the design and the validation of a non-intrusive capacitance-based densimeter, for the on-line measurement of solid fraction in a slurry pipe flow. An asymmetrical type capacitance sensor was designed by means of numerical electric field analysis. The simulations conducted at different solid volume fractions revealed that the sensor is not sensitive to the distribution and the size of the solid particles. The simulations also provided a preliminary sensor calibration to link the capacitance values to the solid volume fraction (i.e., slurry density). The numerical calibration of the sensor was verified during slurry transport experiments with a mixture of HFE 7200 and sucrose crystals, while the reference density measurement was provided by a Coriolis flow meter. The validation proved that the capacitance sensor correctly measures the density of a downward slurry pipe flow with an accuracy of ±0.5% rdg, in the range of solid volume fraction between 0% and 29%.