High yield chemical pulping and bleaching process

Patent metadata

Field	Value
Publication number	US-12435469-B2
Application number	US-202318098490-A
Country	US
Kind code	B2
Filing date	Jan 18, 2023
Priority date	Feb 22, 2022
Publication date	Oct 7, 2025
Grant date	Oct 7, 2025

Abstract

A method of producing high yield chemical cellulosic pulp includes: (a) chemically pulping wood chips to separate lignin and liberate cellulosic fibers from the wood chips to generate a cellulosic pulp; (b) washing and screening the pulp of step (a); (c) pre-treating the washed pulp with oxygen; (d) optionally washing the treated pulp of step (c); (e) bleaching the pre-treated pulp in an extended duration oxidative bleaching stage; (f) optionally washing the bleached pulp of step (e); and (g) optionally further oxidatively or reductively bleaching the bleached pulp in a shorter duration bleaching stage, wherein the bleached pulp is produced at a yield of greater than 60% based on the weight of the pulped wood chips (dry basis).

First claim

The invention claimed is:

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).

2. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein the bleached pulp of step (d) is produced at a yield of from 65% to 80% based on the weight of the wood chips in step (a) (dry basis).

3. The method of producing high yield chemical cellulosic pulp according to claim 1 , further comprising:
(e) oxidatively or reductively bleaching the bleached pulp of step (d) in a shorter duration bleaching stage in a bleaching vessel for a residence time of from 5 minutes to 3.5 hours,

wherein the bleached pulp of step (e) is produced at a yield of from 60% to 75% based on the weight of the wood chips in step (a) (dry basis).

4. The method of producing high yield chemical cellulosic pulp according to claim 3 , wherein the step (c) of pre-treating the washed pulp with oxygen reduces the kappa number of the resulting pre-treated pulp by less than 50% compared to the washed pulp of step (b).

5. The method of producing high yield chemical cellulosic pulp according to claim 4 , wherein the step (d) of bleaching the pre-treated pulp in an extended duration oxidative bleaching stage is carried out in a bleaching vessel for a residence time of from 24 to 48 hours at a temperature of from 43° C. to 57° C.

6. The method of producing high yield chemical cellulosic pulp according to claim 5 , wherein the step (e) of bleaching the bleached pulp in a shorter duration bleaching stage is carried out in a bleaching vessel for a residence time of from 10 minutes to 2.5 hours at a temperature of from 65° C. to 125° C.

7. The method of producing high yield chemical cellulosic pulp according to claim 3 , wherein the step (d) of bleaching the pre-treated pulp in an extended duration oxidative bleaching stage is carried out in a bleaching vessel for a residence time of from 24 to 48 hours at a temperature of from 43° C. to 57° C.

8. The method of producing high yield chemical cellulosic pulp according to claim 7 , wherein the step (e) of bleaching the bleached pulp in a shorter duration bleaching stage is carried out in a bleaching vessel for a residence time of from 10 minutes to 2.5 hours at a temperature of from 65° C. to 125° C.

9. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein bleached pulp of step (d) has an ISO Brightness of 80 or more.

10. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein the step (c) of pre-treating the washed pulp with oxygen is carried out at an oxygen pressure of from 0.25-1 MPa.

11. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein the step (c) of pre-treating the washed pulp with oxygen is carried out in the presence of an alkaline agent.

12. The method of producing high yield chemical cellulosic pulp according to claim 11 , wherein the step (c) of pre-treating the washed pulp with oxygen is carried out for a residence time in a bleaching vessel of from 30 to 150 minutes at a temperature from 60° C. to 120° C.

13. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein the step (d) of bleaching the pre-treated pulp in an extended duration oxidative bleaching stage comprises: (i) providing the pre-treated pulp of step (c) in aqueous form to the extended duration bleaching stage at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5; (ii) bleaching the pulp in a bleaching vessel while maintaining an extended duration bleaching temperature of from 110° F. (43° C.) to 135° F. (57° C.) and a pH of the charge from 9.5 to 12.5 for a bleaching retention time in the extended duration bleaching stage for at least 6 hours.

14. The method of producing high yield chemical cellulosic pulp according to claim 13 , wherein the peroxy bleaching agent utilized in the extended duration bleaching stage of step (d) is hydrogen peroxide applied to the fiber in an amount of from 0.35% on dried pulp to 4% on dried pulp.

15. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein the method comprises one or more Q stages.

16. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein the step (c) of pre-treating the washed pulp with oxygen reduces the kappa number of the resulting pre-treated pulp by less than 50% compared to the washed pulp of step (b).

17. The method of producing high yield chemical cellulosic pulp according to claim 16 , wherein the step (d) of bleaching the pre-treated pulp in an extended duration oxidative bleaching stage is carried out in a bleaching vessel for a residence time of from 24 to 48 hours at a temperature of from 43° C. to 57° C.

18. The method of producing high yield chemical cellulosic pulp according to claim 1 , wherein the step (d) of bleaching the pre-treated pulp in an extended duration oxidative bleaching stage is carried out in a bleaching vessel for a residence time of from 24 to 48 hours at a temperature of from 43° C. to 57° C.

Assignees

• Gpcp Ip Holdings Llc

Inventors

• Lee Jeffrey A
• Holtman Kevin M

Classifications

• D21C9/1005

  Pretreatment of the pulp, e.g. degassing the pulp · CPC title

• D21C3/026 Primary

  in presence of O2, e.g. air · CPC title

• D21C9/163

  with peroxides · CPC title

• D21H11/02

  Chemical or chemomechanical {or chemothermomechanical} pulp · CPC title

• D21C9/1068

  with O2 (closed, see D21C9/147) · CPC title