Deinking of recycled fibers in a flotation flow loop

Conventional laboratory-scale flotation cells, used to study ink removal from pulp slurries, have various shortcomings. In most cells it is difficult to control physical parameters such as the volume of air intake and the bubble size distribution. Moreover, the hydrodynamic conditions in such cells are different from those in industrial flotation cells. To overcome these difficulties we designed a new laboratory flotation cell, consisting of a flow loop and a flotation chamber. The hydrodynamic conditions at the air inlet point closely resemble those of an injection point in an industrial flotation cell and the amount of air can be accurately measured. Moreover, a viewing window allows observation of bubble sizes to be made. Flotation deinking efficiencies can be obtained either by analyzing the ink removed in the froth or by measuring the cleanliness of the pulp. Effects of fluid velocity and deinking chemicals on bubble size distributions and flotation efficiency are presented, as well as effects of air volume fraction.