Air Products and Chemicals, Inc.

The Black Clawson Company

Edward F Elton

Vincent L Magnotta

Larry D Markham

Joseph G Santangelo

Scott A Wallick

Andrew C Martin

Andrew J Patrylak

Rejects such as knots, shives, slivers, chops, and uncooked and partially cooked wood chips are separated from a pulp slurry and treated to produce a bleachable grade pulp. The rejects are dewatered to a 10-15% consistency, mechanically fiberized, and then delignified at the same 10-15% consistency in the presence of oxygen and alkaline pulping chemicals. The delignification is carried out at 80.degree.-140.degree. C. for 5-120 minutes. The process has low external power requirements, requires no expensive dewatering machinery, and proceeds at a rapid rate to yield a bleachable grade pulp which can be used alone or mixed with other pulp.

Process for the oxygen delignification of pulp mill rejects

A process is set forth for the recovery of fiber from paper waste and paper broke which paper has been treated with wet-strength resins. The process involves shredding the paper to be recovered and then subjecting the shredded paper to an alkaline solution and an oxygen containing atmosphere to liberate the paper fiber from the resin with retention of the paper fiber brightness. The liberated fiber can then be recycled through the paper web forming process. The process is particularly appropriate to the removal of thermoplastic resins from paper.

Process for recovering fiber from wet-strength resin coated paper

An apparatus and process for the oxygen delignification of pulp is provided in which the pulp is transported by means of timing screws in essentially plug flow through one or more substantially horizontal reactor tubes. Oxygen gas is injected into the system at a point adjacent to the pulp inlet and travels concurrently in substantially plug flow with the pulp through the system. In this manner, the pulp is initially exposed to gas of a high oxygen partial pressure while gas vented from the system adjacent the pulp outlet is of low oxygen partial pressure and has a high content of diluent gases. The process and apparatus avoid the formation of gas pockets and hot spots which may adversely affect the pulp. In an alternate embodiment, a countercurrent gas flow process is disclosed. Also provided is a catalytic treatment and recirculation system for the vented gas which permits efficient use of oxygen within the system.

Method and apparatus for oxygen delignification

High recovery of useful energy from the heat of reaction in the oxidation of black liquor is obtained by integrating the oxidation into the multiple effect evaporation system of the pulp mill recovery sequence. The heat of reaction is thereby recovered as flash steam, which when combined with the vapors from an appropriate evaporator body enables recovery of its energy through further evaporation. The oxidation reaction may be carried out on the liquor leaving the second effect of the evaporation sequence for maximum energy recovery, or in accordance with an alternative embodiment, the reaction is carried out between the first effect and the flash tank with preferable addition of a second flash tank in series with the first.

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Bethlehem, PA, United States of America

Edward F Elton