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

A bubbling jet in a cylindrical bath subject to centric bottom gas injection rotated around the vessel axis under a certain blowing condition. There exist two kinds of swirl motions: one is closely related to the so-called sloshing and the other is 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. However, 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 under swirl motions. This study was made to investigate the effects of the swirl motions on the above mentioned transport phenomena using a high-speed video camera, an electroresistivity probe, a laser Doppler velocimeter, an electrochemical sensor, and an electric conductivity probe. In order to stop the swirl motion, a cylindrical pipe was brought into contact with the bath surface. 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 motion. It should be kept in mind, however, that the errosion of vessel wall also is enhanced by swirl motion.