Experimental characterization of single droplets size and composition in liquid- liquid extraction systems with rainbow diffractometry

International audienceThis paper is focused on the analysis of the rainbow phenomenon produced by droplets with a low relative refractive index with the aim to characterize their size distribution and composition in liquid-liquid two-phase flows. The Lorenz-Mie theory, geometrical optics and physical approximations are used to bring insight on the specificities of the corresponding scattering patterns : near-forward location, reverse polarization and lower modulation compared to conventional rainbows. Material and methods to retrieve the parameters of the dispersed phase are reported when the rainbow diffractometry technique is operated as a single particle counting technique. Experimental results show that an accuracy better than 5% on the diameters and 4.10-4 on the refractive index (i.e. 0.8% in mass fraction of Marcol in hydrogenated tetrapropylene) can be achieved. These results open up perspectives for liquid-liquid extraction studies and more generally, mixing studies in two-phase flows