Accueil > Séminaires > Précédents séminaires > Dispersing a powder in a liquid : jets, islands and lumps.

Dispersing a powder in a liquid : jets, islands and lumps.

Marco Ramaioli Chemical and Process Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, UK

Product engineering is a growing engineering discipline at the crossroads of process engineering, material science and product-consumer interaction. Few recent food and FMCG examples are presented, to highlight some interesting challenges, relevant to the physics of granular media, interfacial science and rheology.
After this introduction, the talk will focus on the wetting and on the dispersion of a powder in a liquid, a process conditioning strongly the rehydration and dissolution of dehydrated powders, critical to many industrial sectors (food, pharmaceuticals, detergents, etc.). A stack of grains - a powder island - can be formed upon pouring grains onto a liquid interface and this provides a way to identify the conditions leading to a successful impregnation of the powder pores [1]. A continuous flow of grains onto the interface can induce these islands to grow and sink, forming a partially dry structure that is undesired in application : “a lump” [2]. Pouring grains can also lead to the formation of a jet, entraining air into the liquid. The conditions leading to these different structures will be discussed, presenting also preliminary results on the effect of liquid convection. These results will be linked to previous studies on the wettability of powders [3] and of soluble thin coatings [4].

References :

1. P.S. Raux et al., Wicking in a powder, (2013) Langmuir, 29 (11), pp. 3636-3644.
2. X.Y. Ong et al, (2017), in prep.
3. J. Dupas et al., Powder wettability at a static air-water interface, (2015) Journal of Colloid and Interface Science, 448, pp. 51-56.
4. J. Dupas et al., Glass transition accelerates the spreading of polar solvents on a soluble polymer, (2014) Physical Review Letters, 112 (18), art. no. 188302.