Apparatus for the removal of impurities from fiber suspensions

Claim 1

Apparatus for mixing gas bubbles into a fiber suspension containing impurities in order to remove said impurities by means of flotation, said apparatus comprising an inlet for said fiber suspension, an outlet for said fiber suspension including said gas bubbles therein, said outlet including diverging upper and lower wall portions, an intermediate mixing section between said inlet and said outlet, said intermediate mixing section including an upper wall surface, a lower wall surface, and a wing member immovably disposed between said upper and lower wall surfaces thereby creating upper and lower wall passages between said wing member and said upper and lower wall surfaces of said intermediate mixing section, said wing member including an imperforate, continuous external surface, a diverging portion facing said inlet, a converging portion facing said outlet, and a central portion having a maximum thickness therebetween, whereby said upper and lower passages have a minimum transverse dimension at a location corresponding to the central portion of said wing member, said converging portion of said wing member corresponding with said diverging upper and lower wall portions of said outlet, whereby said upper and lower passages diverge substantially symmetrically in the direction of flow of said fiber suspension containing said gas bubbles therein, gas injection means including a transversely extending slot in both said upper and lower wall surfaces of said intermediate mixing section at locations corresponding to said central portion of said wing member, said gas injection means comprising adjustable gas injection means, including upper and lower pairs of axially movable nozzle portions adjustably carried in corresponding recesses formed in said upper and lower wall surfaces of said mixing section, for adjusting the dimensions of said transversely extending slot, and gas supply means communicating with said gas injection means for supplying said gas to said fiber suspension flowing through said upper and lower passages of said intermediate mixing section.