Evaluation of refractive index gradients in droplets by rainbow technique: application to CO _2 capture by monoethanolamine aqueous spray

Reactive sprays can be found in numerous industries such as combustion, spray drying, and purification of exhaust gases. The characterization of transient state for such droplets in these sprays is a challenge, asking for the measurement of the temperature and/or composition gradients inside the droplets. In this work, rainbow technique is extended to characterize internal gradients. After the numerically study of the characteristics of rainbow scattered by droplet with radial refractive index gradients, an experimental study was carried out for the case of CO _2 capture by Monoethanolamine (MEA) droplets. The investigation demonstrates that the gradients can be quantified during the first moments of injection. Graphical Abstract