Abstract: The operation of a centrifugal pump which pumps a liquid or suspension (e.g. 8-12 percent consistency) containing gas is controlled to minimize pump power consumption, or to vary the pump flow rate. The suspension is rotated within the pump so that a gas bubble is created at a central part of the pump, and gas is discharged from the gas bubble, at a gas discharge pressure. The differential pressure between the suspension inlet and the gas discharge is determined, and the head and/or discharge flow rate of the pump are controlled by controlling the differential pressure so determined. The discharge flow rate may be maintained constant utilizing a control valve and flow meter in the pump discharge line, in which case controlling the discharge of gas from the gas bubble controls the head, and minimizes power consumption for a given flow rate. Alternatively the flow rate is controlled by controlling the gas discharge, with no control valve in the pump discharge line being provided.

Abstract: Pulp degassification is effected by a structure that may be mounted on a pulp treatment vessel, such as an oxygen reactor blow tank. The degassifier includes a housing that is substantially circular in cross-section and tapers from a first end to a second end along a central axis. A pulp inlet is adjacent the first end and introduces pulp tangentially and an outlet is adjacent the second end extending concentrically with the central axis. A blade assembly is mounted for rotation about an axis generally coincident with the housing central axis, and the blade assembly is rotated to impart a high speed rotational velocity component to the pulp as it enters the housing. A gas outlet is adjacent the housing first end, vertically above the housing second end, and adjacent the central axis. A conically shaped baffle or the like is provided surrounding the gas outlet to prevent short-circuiting of pulp from the inlet to the gas outlet.

Abstract: A first portion of bleaching liquid is passed through cellulosic pulp in a bleaching zone at a first level with respect to the pulp feed direction and withdrawn through transversely spaced strainer means located at about said first level so that the passage of the first portion of bleaching liquid through the pulp is in a direction transverse to the feed direction of the pulp and a second portion of bleaching liquid is passed through said cellulosic pulp at a second level with respect to the pulp feed direction and withdrawn through transversely spaced strainer means located at about the second level so that the passage of the second portion of bleaching liquid through the pulp is in a direction transverse to the feed direction of the pulp and opposite from the transverse direction through said first level.