Process for de-inking paper pulp and flotation cell used for this process

摘要

The de-inking procedure consists of circulating the pulp in a flotation cell comprising a chamber (2) with a vertical axis in which the pulp can move downwards from top to bottom, passing through a series of stages (E1...En), in each of which bubbles (13) introduced in the lower part of the chamber pass through it. The bubbles reach the top of the chamber in the form of a foam (5) carrying particles of non-soluble materials, the foam being removed at the top while the de-inked pulp is drawn off at the bottom. In each of the aforementioned stages the rising bubbles follow the under-surface of a spiral guide (12) to reach the passages taking them to the higher levels. In addition, the speed of the pulp is accelerated at the passage entrances by a progressive reduction in the passages' cross-section to draw the bubbles through and mix them with the pulp.