Hydrocyclone deinking of paper during recycling

Abstract

Deinking of paper having print during the production of recycled paper is accomplished by a froth flotation process using a hydrocyclone. A finely comminuted liquid solids used paper suspension having a consistency of about 1 to 4% is introduced into a generally vertical axis vortex provided in a hydrocyclone. Air is sparged into the suspension in the vortex, by passing through a porous inner wall of the hydrocyclone, to cause ink particles to attach to the air bubbles and to rise in a foam while cellulosic pulp moves downwardly in the vortex. The foam--containing the ink particles--and the pulp are removed from the vortex in separate streams. The pulp is deaerated and the air component of the foam is removed in the cyclone. About 5-15% of the total flow of the suspension is removed with the foam in each stage, and about 95-85% with the pulp. In practicing the froth flotation a plurality of vertical axis hydrocyclones are connected together in-series, with a plurality of the series connected in parallel with a paper comminuting device (pulper) and a common outflow conduit.

Dependencies are inferred from the claim text.