Influence of Air Flow Rate, Time and Total Air Volume on Efficiency of Toner Removal in Mixed Office Waste Flotation, 1995 Recycling Symposium Proceedings

Hatice Kocer

Donna A. Johnson

Edward V. Thompson

University of Maine

Results are presented of two series of flotation trials of repulped, laser printed paper, the first at two and the second at three air flow rates. Air flow rate greatly influences flotation efficiency, which in turn may be highly dependent on toner particle size. A third series of flotation experiments considered the interactive effects of air flow rate, flotation cell rotor speed, and time. These results indicate that total air volume (air flow rate x time) may be a decisive parameter in predicting flotation efficiency. A fourth series of experiments considered six sets of trials at three values of total air volume and two rotor speeds. It was found that in all cases flotation efficiencies were higher for lower air flow rate/longer time combinations compared to higher air flow rate/shorter time combinations. This observation was found to be inconclusive, however, as measurements of air bubble size distribution indicated that lower air flow rate yielded many more smaller bubbles and fewer larger bubbles, compared to a high air flow rate. It is hypothesized that a greater number of smaller bubbles provide greater surface area for bubble/particle interaction and attachment, and therefore leads to a higher flotation efficiency.