Abstract: The apparatus comprises a centrifugal pump (1) fed by a screw feeder (8). The screw feeder comprises a screw (9) with a partially open thread (11). The screw (9) is driven separately in opposed direction to and with a lower speed than the impeller (3) of the pump (1). By this arrangement pulp of high concentration can be pumped.

Abstract: A method is disclosed for delignification of ligno-cellulose containing fiber material comprising mixing an oxygen-containing gas with the cellulose fiber material so as to atomize the gas and form a foam of the gas and the cellulose fiber material, and without an intervening oxidation step, subjecting the foam to upwardly flowing, substantially non-pressurized, alkali extraction. The alkali extraction step is conducted at a temperature of from about 40.degree. to about 80.degree. C. and at a pH, ligno cellulose containing fiber concentration and oxygen containing gas concentration sufficient to provide a bleached, delignified cellulose fiber without bleaching the lignin substance extracted from the material and to suppress lignin condensation reaction during the extraction.

Abstract: Methods and apparatus for continuously mixing fluid processing media with pulp suspensions are disclosed. The method includes supplying pulp suspensions to the central portion of the substantially planar radial face of a cylindrical rotor, feeding a fluid processing medium to the pulp suspension as it approaches the rotor face, forming an annular gap at the axial outer surface of the rotor, so that the rapid rotation of the rotor causes the pulp suspension and fluid processing medium to flow radially outward along the planar face and to pass axially through the annular gap, and effecting turbulence between the pulp suspension and the fluid processing medium at the entrance to that gap.