US 12,435,469 B2
High yield chemical pulping and bleaching process
Jeffrey A. Lee, Neenah, WI (US); and Kevin M. Holtman, Appleton, WI (US)
Assigned to GPCP IP Holdings LLC
Filed by GPCP IP Holdings LLC, Atlanta, GA (US)
Filed on Jan. 18, 2023, as Appl. No. 18/098,490.
Claims priority of provisional application 63/312,419, filed on Feb. 22, 2022.
Prior Publication US 2023/0265609 A1, Aug. 24, 2023
Int. Cl. D21C 9/10 (2006.01); D21B 1/02 (2006.01); D21C 3/02 (2006.01); D21C 9/16 (2006.01); D21H 11/02 (2006.01)
CPC D21B 1/026 (2013.01) [D21C 3/026 (2013.01); D21C 9/1005 (2013.01); D21C 9/1068 (2013.01); D21C 9/163 (2013.01); D21H 11/02 (2013.01)] 18 Claims
 
1. A method of producing high yield chemical cellulosic pulp comprising:
(a) chemically pulping wood chips in a Kraft Process to separate lignin and liberate cellulosic fibers from the wood chips to generate a cellulosic pulp;
(b) washing and screening the cellulosic pulp of step (a) to generate a washed pulp;
(c) pre-treating the washed pulp of step (b) with oxygen to generate a pre-treated pulp; and
(d) bleaching the pre-treated pulp of step (c) in an extended duration oxidative bleaching stage in a bleaching vessel for a residence time of from 6 to 200 hours to generate a bleached pulp;
wherein the bleached pulp of step (d) is produced at a yield of from 60% to 80% based on the weight of the wood chips in step (a) (dry basis).