Stream Drying

The term impinging stream dryer (ISD) refers to a class of flash dryers in which moisture evaporation from wet particles or liquid droplets occurs in the impingement zone that develops as a result of the collision of two oppositely directed high-velocity gas streams, at least one of which contains the dispersed material to be dried. At the outset a distinction should be made from the impingement dryers in which gas jets are directed onto the web, sheet-form, or slablike materials (Mujumdar and Huang, 1995) or the jet-zone dryer in which a layer of particulates is pseudo-fluidized by a multiplicity of high-velocity airstreams exiting a number of perpendicularly oriented air nozzles (Kudra and Mujumdar, 1995). 

The constraint of reduced residence time is practically eliminated in impinging streams with a mobile impingement zone (Elperin and Meltser, 

Rectilinear, where streamlines are parallel with either aligned axes of the gas jets (coaxial flow) or displaced axes of the gas jets (eccentric 

Rotating (swirling), in which streamlines do follow a helix Curvilinear, in which streamlines are represented by circular arcs Flow direction 

Countercurrent, in which gas (or solid suspension) streams flow in opposite directions 

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Figure 6.1 Impinging stream drying system for aluminum sulfate [86, 87].

Wu Yuan, Cheng, Rong and Sun, Qin (1996). Internal circulative impinging stream drying (I) An experimental study under cold condition. Proc. of 96 Chinese Forum on Drying, Beijing, 112-120 (in Chinese). 

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