EFFECTS OF THE SWIRL MOTION OF BUBBLING JET ON THE TRANSPORT PHENOMENA IN A BOTTOM BLOWN BATH

A bubbling jet in a cylindrical bath with centric bottom gas injection rotated around the vessel axis under certain blowing conditions. There existed two kinds of swirl motions: one was closely related to so-called rotary sloshing and the other was induced by hydrodynamic instability of a large scale ring vortex enclosing the bubbling jet. Conditions describing the occurrence and cessation of the swirl motions have been studied by many researchers. Meanwhile, the bubble characteristics, liquid flow characteristics, mass transfer from a solid body immersed in the bath, and mixing time of the bath have not been clarified in the presence of these swirl motions. This study was made to investigate the effects of the former swirl motion on the above-mentioned transport phenomena using a high-speed video camera, an electro-resistivity probe, a laser Doppler velocimeter, an electrochemical sensor, and an electric conductivity probe. In order to compare the results with those obtained in the absence of the swirl motion, a cylindrical pipe was used to stop the swirl motion. The swirl motion was found to enhance the mass transfer coefficient and reduce the mixing time significantly. This fact allows us to develop new metallurgical processes using swirl motions. It should be stressed, however, that the errosion of vessel walls also is enhanced by swirl motions.