Abstract: A process is disclosed for the pretreatment of lignocellulosic fibrous materials prior to delingification. The process in one of its embodiments is comprised of the following steps:1. Contacting the pulp material with treated filtrate and alkali for a short reaction period of about 1 to 2 minutes at 40.degree. C.,2. Withdrawing part of the liquid phase by filtration,3. Displacing substantially all of the remaining liquid phase with treated filtrate, and4. Allowing the pulp to react under conditions normally used for alkaline extraction or oxygen delignification.The treated filtrate is obtained by subjecting the liquor removed from the pulp at steps 2 and 3 to temperature of 5.degree. to 60.degree. C. for periods of about 5 to 10 minutes. Alternatively, step 3 can be eleminated.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.