Deinking of recycled fibers in a flotation flow loop

Conventional laboratory-scale flotation cells, used to study ink removal fr om pulp slurries, have various shortcomings. In most cells it is difficult to control physical parameters such as the volume of air intake and the bub ble size distribution. Moreover, the hydrodynamic conditions in such cells are different from those in industrial flotation cells. To overcome these d ifficulties we designed a new laboratory flotation cell, consisting of a fl ow loop and a flotation chamber. The hydrodynamic conditions at the air inl et point closely resemble those of an injection point in an industrial flot ation cell and the amount of air can be accurately measured. Moreover, a vi ewing window allows observation of bubble sizes to be made. Flotation deink ing efficiencies can be obtained either by analyzing the ink removed in the froth or by measuring the cleanliness of the pulp. Effects of fluid veloci ty and deinking chemicals on bubble size distributions and flotation effici ency are presented, as well as effects of air volume fraction. (C) 2001 Els evier Science B.V. All rights reserved.