Measurements of Particle Residence Time Distributions in A Co-Current Spray Dryer

ABSTRACT

Measurements of particle residence time distributions by means of tracer analysis were done in a co-current pilot plant spray dryer operated with a pressure–nozzle. A system is described for injecting tracer into the feedstream just before the nozzle. Tracer concentrations were measured in two product streams: the tower product stream (mean particle size 134 microns) and the cyclone product stream (mean particle size 67 microns). The measurements show a very wide range of residence times: some particles have residence times shorter than 3 seconds, others have residence times longer than 10 minutes. The median of the distribution is 58·5 _s for the tower product stream and 42.2 _s for the cyclone product stream.