Many traditional laboratory-scale flotation cells lack the attribute of being hydrodynamically similar to the actual industrial flotation process. A device was built that simulated solely the air-injection section of an industrial flotation cell, in which industrial Reynolds numbers can be achieved. It was found that fluid velocity has a moderate effect on the bubble size distribution and surfactant concentration has a large effect. In addition, the presence of 0.2% consistency TMP fibres or fines was found to have a small effect on the bubble size distribution. The air-injection unit was then expanded into a functioning lab-scale flotation cell. The objective of these experiments was to investigate the effect of furnish type, air volume fraction and slurry velocity on the deinking efficiency. The 100% aged newsprint runs had considerably lower initial brightness, considerably higher initial ERIC, as well as a much lower Speck Removal after 30 minutes of flotation, compared to the runs using 70% fresh newsprint and 30% fresh magazine. Increasing the air volume fraction while keeping the suspension velocity constant, did slightly improve the deinking efficiency for the 100% aged NP case, however, did not result in any significant improvement for the 70% NP/30% MG case. It is believed that the increased shear forces associated with increasing the suspension velocity broke-up ink agglomerates that were in suspension into a larger number of smaller ink particles. Increasing the suspension velocity increased the rate of flotation.

van de Ven, Theo (Supervisor)

Garnier, Gil (Supervisor)