Abstract: Unbleached pulp is washed with an aqueous alkaline solution in a wash press to substantially uniformly distribute a first amount of alkaline material throughout the pulp. The consistency of the pulp exiting the wash press is above about 18%, preferably between 25 to 35 percent by weight, and the high consistency alkali containing pulp is then treated with oxygen to effect delignification. The use of a wash press reduces the overall amounts of alkaline material utilized in the process compared to processes which add alkaline material to the pulp at low consistency. Additional alkali may be applied, if desired, onto the high consistency pulp prior to oxygen delignification to provide a total amount of between 0.8 and 7 percent by weight of oven dry pulp. High strength, low lignin pulps are formed after oxygen delignification which may be further bleached to high brightness with reduced amounts of bleaching chemicals.

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 or chlorine-containing compounds by oxygen delignifying the pulp to a K No. of about 14 or less and a viscosity of greater than about 10 cps and thereafter further delignifying the partially delignified pulp by lifting, displacing and tossing the pulp in a radial direction while advancing it in an axial direction in a plug flow-like manner with an effective amount of ozone for a sufficient time to obtain a substantially delignified pulp having a K No. of about 6 or less, a viscosity of at least about 7 cps and a GE brightness of at least about 35. The substantially delignified pulp may then be brightened to a final product having a GE brightness of at least about 75, or alternately up to about 83 or more by contacting the ozonated pulp with chlorine dioxide or a peroxide compound.

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: 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 18%, and the high consistency alkali containing pulp is then treated with oxygen to effect delignification. The total amount of alkaline material applied to the pulp is between 0.8 and 7% by weight of oven dry pulp. High strength, low lignin pulps are subsequently formed which may be further bleached to high brightness with reduced amounts of chemicals.

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: 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: 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.