Abstract: An apparatus for delignifying and bleaching a lignocellulosic pulp without the use of elemental chlorine. The bleaching reactor is a horizontal vessel having a central rotatable shaft which preferably contains paddles, cut and folded screw flights or a ribbon flight, to disperse and advance the pulp particles in a plug flow manner while contacting and mixing the pulp particles with a gaseous bleaching agent such as ozone for substantially uniform bleaching thereof.

Abstract: A method for delignifying and bleaching a lignocellulosic pulp with a gaseous bleaching agent in a reactor without the use of elemental chlorine. The bleaching reactor is a horizontal vessel having a central rotatable shaft which preferably contains paddles, cut and folded screw flights or a ribbon flight, to disperse and advance the pulp particles in a plug flow manner while contacting and mixing the pulp particles with a gaseous bleaching agent such as ozone for substantially uniform bleaching thereof.

Abstract: Unbleached pulp is combined with an aqueous alkaline solution while in a state of low consistency to distribute a first amount of alkaline material substantially uniformly throughout the pulp. The consistency of the pulp is then increased to above about 20%. Additional alkali is applied onto the high consistency pulp to provide a total amount of between 0.8 and 7% by weight of oven dry pulp. The high consistency alkali containing pulp is then treated with oxygen to effect delignification. High strength, low lignin pulps are formed which may be further bleached to high brightness with reduced amounts of chemicals by following the methods of the invention.

Abstract: A process for delignifying and bleaching a lignocellulosic pulp without the use of elemental chlorine by partially delignifying the pulp to a K No. of about 10 or less and a viscosity of greater than about 13 cps; and further delignifying the partially delignified pulp with an effective amount of ozone for a sufficient time to obtain a substantially delignified pulp having a K No. of about 5 or less, a viscosity of greater than about 10, and a GE brightness of at least about 50%. The substantially delignified pulp may be brightened by the addition of a bleaching agent such as chlorine dioxide or a peroxide to obtain a final product having a GE brightness of at least about 65%, preferably above 70% to as high as 90%. Because of the absence of elemental chlorine in this sequence, filtrate from all stages but the chlorine dioxide stage ( if used) can be recovered without sewering. Major environmental improvements are thus achieved.

Abstract: A process for delignifying and bleaching a lignocellulosic pulp without the use of elemental chlorine by partially delignifying the pulp to a K No. of about 10 or less and a viscosity of greater than about 13 cps; and further delignifying the partially delignified pulp with an effective amount of ozone for a sufficient time to obtain a substantially delignified pulp having a K No. of about 5 or less, a viscosity of greater than about 10, and a GE brightness of at least about 50%. The substantially delignified pulp may be brightened by the addition of a bleaching agent such as chlorine dioxide or a peroxide to obtain a final product having a GE brightness of at least about 65%, preferably above 70% to as high as 90%. Because of the absence of elemental chlorine in this sequence, filtrate from all stages but the chlorine dioxide stage (if used) can be recovered without sewering. Major environmental improvements are thus achieved.

Abstract: An apparatus for bleaching pulp particles comprising an inner tubular shaped shell member with lifter blades mounted on its internal wall surface. The shell member is rotatably mounted within an outer shell member with seals between the shell members providing an isolated space. This space is pressurized with a gas to prevent pulp particles and gases from escaping from the inner shell member by way of the seals.

Abstract: A method for the production of delignified wood pulp is provided which result in said pulp's having improved delignification ratios. In accordance with preferred embodiments, brownstocks are substantially uniformly treated with aqueous alkaline solution while in a state of low consistency. The consistency is then increased to values preferably in excess of about 20% and the brownstock treated with oxygen to effect delignification. The processes of the invention provide surprising improvements over prior methods in the high strength, low lignin containing pulps may be formed thereby. These pulps can be further bleached to high brightness with less subsequent bleach chemical.