Process and apparatus for flotation, in particular for waste water purification

摘要

Process and apparatus for flotation, in particular for waste water (effluent) purification, in which a frother is introduced into the pulp to be treated and the flotation pulp thus produced is forced into an essentially vertically running stream within a flotation cell. In the lower region of the flotation cell, finely dispersed small gas bubbles are generated by compressed air feed into this stream, to which gas bubbles some of the solid constituents of the flotation pulp to be floated adhere and are carried by the stream to the surface of the pulp. The froth can be removed there. The pulp to be treated is divided in this case into two flow paths, of which only a part-stream is provided with the frother and is exposed to the gas bubble formation, while the second part-stream is only fed to the first part-stream when a uniform gas bubble distribution and a uniform flow profile are achieved therein. This process and the corresponding apparatus make it possible, because of the high concentration of the frother in the flotation pulp, to achieve very small gas bubbles which also remain stable over a significant flow section. Despite this, only an environmentally acceptable frother concentration is present in the subequent purified water, without the purifying action of the flotation being impaired.