Abstract: A process for bleaching wood pulp is provided comprising subjecting the wood pulp, after brown stock washing, to an oxygen delignification stage, a washing sequence, a first chlorine dioxide bleaching stage, an oxidative extraction stage, optionally at least one final chlorine dioxide bleaching stage and then recycling the filtrate from the oxidative extraction stage counter-currently through the bleaching plant and brown stock washing. Additionally, and quite beneficially, the filtrate from the first chlorine dioxide bleaching stage is also recycled counter-currently through the brown stock washing thereby significantly reducing the environmental impact associated with the manufacture of bleach wood pulp.

Abstract: The flow patterns of the wood/paper pulp in a paper pulp treatment tower are controlled to provide for even flow through and discharge of the pulp from the upper end of the tower. Flow-altering fluids are injected into the pulp stock in the tower via appropriately positioned nozzles which create flow-altering fluid streams in the pulp stock. The streams are operable to produce either an inwardly directed pulp flow, or an outwardly directed pulp flow, whichever is desired. The system results in smooth, relatively even movement of the pulp stock from the bottom of the tower to the top, so that each fraction of the pulp mass will spend substantially the same dwell time in the tower, whereby the pulp mass is evenly processed and reacted in the tower. The resultant treated stock is superior to pulp stock treated in a tower without such flow controls.

Abstract: Apparatus for feeding wood chips and the like into a treatment bin includes a feed tube assembly adapted to lead into the bin at a non-zero angle relative to the horizon. A plate is supported underneath the lower end of the feed tube assembly to collect in a mound wood chips fed through the feed tube. The height of the lower end of the feed tube assembly is adjusted so that the lower end of the feed tube assembly engages the mound of wood chips and thereby forms a seal with the mound. A plow is supported between the plate and the lower end of the feed tube assembly. Either the plate is stationary and the plow rotates or the plow is stationary and the plate rotates to knock wood whips from the mound off the plate. The apparatus optionally includes a feed screw mounted within and longitudinally of the feed tube assembly to compress the wood chips into the mound.

Abstract: A design of a distribution unit allowing a gas or other material to be uniformly supplied to a mixing device close to the point of mixing. The distribution unit can be used for mixing chemicals into pulp at a refiner inlet.