Technical Paper (in Japanese)
Ryosuke AOYAMA1, Yutaka KITAMURA1,† and Yamazaki KAZUHIKO2
1Graduate School of Life and Environmental Sciences, University of Tsukuba
2 TANABE ENGINEERING CORPORATION
Abstract
Vacuum Spray Drying (VSD) produce powders at lower temperature (40-60℃)
due to vacuuming of the drying chamber to low atmospheric pressures (10-20
kPa). In this study the spraying and drying characteristics in the vacuumed
drying chamber was investigated experimentally to have fundamental data
on the design and operation of VSD. Condensed milk and yogurt slurry as
feeding materials were sprayed in the vacuumed or non-vacuumed drying chamber
and the sprayed droplet diameters were determined. Analysis of the relationships
between droplet diameter and volumetric flow rate of spray air or spray
pressure revealed that the droplets sprayed into the vacuumed chamber became
smaller and these fine droplets were produced even at lower flow rate of
spray air. However the drying in VSD was insufficient when the spray was
conducted at the lower flow rate of spray air. On the contrary higher flow
rate resulted in the discharge of fine powders out of the drying chamber
so that some methods to collect those fine powders easily should be devised
to improve the drying performance of VSD.
Keywords: vacuum spray dry, droplet, spray pressure, flow rate of spray air