Flow Field Simulation of the Cyclonic Static Micro-bubble Column Flotation

摘要

Column flotation is being widely adopted for fine particle treatment by the mineral processing industry due to its simplicity of structure, high efficiency and good separation performance. Cyclonic static micro-bubble column flotation (FCSMC) is an innovative column separation technology that has been successfully applied in the coal preparation industry in China. Recently, the application of this equipment has been further expanded to the separation of several minerals such as fluorite, copper, iron, etc. The bottom of the FCSMC is a cone in which cyclonic field is generated when circulating pump is injected tangentially into the column. The unique cyclonic structure is believed to help enhance the column separation performance.Since the FCSMC is a new flotation device, little work has been done to understand the fundamentals of this technology. In this research, a computational fluid dynamics software, ANSYS/FLOTRAN, was employed to simulate the flow field of a lab FCSMC system (Φ0.2 m, Φ3.0 m by length.) The distribution patterns for velocity field and flow field were investigated under single phase condition.It has been found that axial velocity of the slurry decreases and becomes stable along the height of the column from bottom to top, and the slurry performs as a descending flow pattern. Another observation is the velocity fluctuates vigorously near the wall due to wall effect.Compared to axial velocity, the radial velocity distribution is smaller and more complicated.The basic pattern is that on a given cross section of the column radial velocity increases from the wall to the center and it the velocity changes greatly around the center. Under the condition of column height less than 0.8 m, the axial velocity is negative and it directs from the wall to the column axis. When column height is higher than 0.8 m a reverse pattern is obtained, i.e., axial velocity is positive while directing from column axis to the wall.Special efforts were directed to investigate the tangential velocity pattern. Results indicate that the tangential velocity patterns of different cross sections are similar and showed a symmetrical distribution. Tangential velocity distribution concluded two zones: outer whirlpool and inner whirlpool. And, interestingly, it has been found that on different cross sections the highest tangential velocity always occurs at the same position of the cross sections.