Controlling food powder deposition in spray dryers: Wall surface energy manipulation as an alternative

A recent recommendation to control deposition in spray drying is to manipulate the wall surface energy in order to reduce the formation of particle-wall liquid bridges. It was recently demonstrated that this is applicable for ‘rubbery’ particle-wall contacts at relatively low wall temperatures. In this work, experimental investigation was carried out at quasi-steady and relatively elevated wall temperatures to better represent industrial operation of such dryers. Deposition fluxes were collected using Teflon and stainless steel plates. Results indicated that lower wall surface energy does reduce the deposition of amorphous particles, further illustrating the applicability of this approach in industrial condition. This advantage is even more pronounced for deposition of droplets. Utilizing an air operated tester, it was found that wall surface energy only affects the tendency for deposits to detach within certain operation ‘window’ limits. Such analysis will be critical in evaluating the application of having a less ‘sticky’ wall.