Direct Bubble Size Measurement in a Mechanical Flotation Cell by Image Analysis and Laser Diffraction Technique - A Comparative Study

In this study, a comparative measurement of bubble sizes in a two-phased medium (water and air) was performed in a mechanical flotation cell by Image Analysis (IA) and Laser Diffraction (LD) methods. The bubbles were generated in a mechanical cell with dimensions of ۲۵*۱۵*۱۷ cm۳. To determine the bubbles' size by the LD method, the bubbles were transferred from the cell to the Laser Particle Size Analyzer (LPSA) device through a hole in the cell, and Db(۵۰) of bubbles were also calculated from their scattering pattern data. A bubble viewer, made of Plexiglass with certain dimensions, including two main parts (sampling tube and viewing chamber) was employed for the IA method. Comparative experiments were conducted in the different conditions affecting the bubble sizes, which are the impeller speed, solution temperature, pH value, and frother types. Results indicated that the two measurement methods were in good agreement while bubbles' sizes were in a range of +۴۰۰-۸۰۰ microns. The difference between LD and IA results was less than ۷% in the range of +۴۰۰-۸۰۰. In the size range of -۲۰۰ microns, LD and IA results difference increased to ۳۶%. Moreover, in all experiments with the same conditions, the size of the bubbles by the LD method was recorded smaller than that by the IA method. Considering the fact that bubbles in the mechanical flotation cell are usually in the size range of +۶۰۰ -۲۰۰۰ microns, and in this range, LD and IA results had a negligible disagreement, LD can be successfully employed for the bubble size measurement in mechanical flotation cells.

کلیدواژه ها:

Bubble size distribution ، Mechanical flotation ، Laser Diffraction Technique (LDT) ، Image Analysis Technique (IAT) ، Bubble size measurment