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The role of wall deposition and re‐entrainment in swirl spray dryers
Author(s) -
Francia Víctor,
Martín Luis,
Bayly Andrew E.,
Simmons Mark J. H.
Publication year - 2015
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.14767
Subject(s) - fouling , entrainment (biomusicology) , agglomerate , air entrainment , mechanics , countercurrent exchange , deposition (geology) , work (physics) , residence time (fluid dynamics) , process engineering , spray drying , economies of agglomeration , materials science , chemical engineering , environmental science , mechanical engineering , engineering , chemistry , thermodynamics , geology , geotechnical engineering , physics , paleontology , biochemistry , membrane , sediment , rhythm , acoustics
A new experimental method is outlined to study fouling in spray dryers and similar devices. In essence, it makes the deposits traceable so that one can quantify the material that comes off the walls, how long it remains there and how the deposits agglomerate with particles in the air. This paper investigates a countercurrent swirl spray dryer of detergent and provides sound evidence that fouling is a dynamic process: clusters form and break at the walls renewing an active layer of deposits. Remarkably, the wall generates >20% of the product and most of the large granules, and increases drastically the residence time of the powder. The assumptions of current numerical models are clearly invalid (i.e. particles rebound at the wall or deposit indefinitely). Several re‐entrainment mechanisms and their times scales are identified in this work, and accordingly, a new general framework to describe fouling in spray dryers is proposed. © 2015 American Institute of Chemical Engineers AIChE J , 61: 1804–1821, 2015