Claims
- 1. A method of treating a slurry of comminuted cellulosic fibrous material to produce a bleached chemical pulp, comprising:
(a) treating the material in a first stage with a gas containing ozone; (b) treating the material in a second stage with a liquid containing chlorine dioxide; (c) between (a) and (b) treating the material with an alkaline liquid to raise the pH of the material prior to (b) and so that no washing is performed between (a) and (b).
- 2. A method as in claim 1 wherein (c) is practiced to raise the pH of the material to at least about 6.0.
- 3. A method as in claim 1 further comprising (d), prior to (a), treating the material in an alkaline chemical pulping process, to produce chemical pulp.
- 4. A method as in claim 3 wherein (d) is practiced using an essentially sulfur-free pulping process.
- 5. A method as in claim 4 wherein (d) is practiced using an alkaline chemical pulping process that includes treatment with a strength or yield enhancing additive.
- 6. A method as in claim 5, wherein (d) is further practiced using an alkaline chemical pulping process includes a bulk delignification stage, and at least one stage prior to or during bulk delignification stage in which a liquid containing a first level of dissolved organic material is removed from the material and replaced with a second liquid having an at least about 50% lower level of dissolved organic material.
- 7. A method as in claim 1 wherein (a) is preceded by (a1) treating the material with a liquid containing chlorine dioxide, followed by (a2) treating the material with an alkaline liquid.
- 8. A method as in claim 7 wherein (a2) includes a treatment with oxygen, a peroxide, or both.
- 9. A method as recited in claim 4 wherein (d) is practiced using a soda pulping process.
- 10. A method as recited in claim 4 wherein (d) is practiced using a soda/AQ pulping process.
- 11. A method as recited in claim 10 wherein (c) is practiced to raise the pH of the material to at least about 7.0
- 12. A method as recited in claim 2 further comprising (d), prior to (a), treating the material in an alkaline chemical pulping process that includes anthraquinone, polysulfide, or their equivalents or derivatives.
- 13. A method as in claim 2 wherein (a) is preceded by (a1) treating the material with a liquid containing chlorine dioxide, followed by (a2) treating the material with an alkaline liquid.
- 14. A method as in claim 13 further comprising (d), prior to (a), treating the material in an alkaline chemical pulping process, to produce chemical pulp.
- 15. A method as recited in claim 14 wherein (d) is practiced using a soda/AQ pulping process.
- 16. A method as in claim 15, wherein (d) is further practiced using an alkaline chemical pulping process includes a bulk delignification stage, and at least one stage prior to or during bulk delignification stage in which a liquid containing a first level of dissolved organic material is removed from the material and replaced with a second liquid having an at least 50% lower level of dissolved organic material.
- 17. A method for producing bleached chemical pulp from comminuted cellulosic fibrous material comprising:
(a) treating the material in a chemical pulping process in the presence of chemical additive to produce a chemical pulp containing at least some of the additive; (b) treating the chemical pulp with at least one elemental-chlorine-free bleaching agent to produce a bleached chemical pulp having at least some discoloration due to the presence of the chemical additive; and (c) treating the bleached pulp with at least one oxidizing agent to remove the discoloration produced by the presence of the chemical additive.
- 18. A method as in claim 17 wherein (a) is practiced using anthraquinone or its equivalents or derivatives as the chemical additive used in the pulping process.
- 19. A method as in claim 17 wherein (b) is practiced using as the at least one bleaching agent one or more of the following bleaching agents: oxygen, chlorine dioxide, sodium hydroxide, ozone, and hydrogen peroxide.
- 20. A method as in claim 17 wherein (b) is practiced so that the discoloration is characterized by a yellow or orange tinge to the pulp.
- 21. A method as in claim 17 wherein (c) is practiced using as the oxidizing agent at least one of air, oxygen, peroxide, or ozone.
- 22. A method as in claim 18 wherein (c) is practiced using as the oxidizing agent a gas containing ozone; and wherein (a) is a soda/AQ pulping process; and wherein (b) is practiced using as the at least one bleaching agent one or more of the following bleaching agents: oxygen, chlorine dioxide, sodium hydroxide, ozone, and hydrogen peroxide.
- 23. A method of ECF treatment of comminuted cellulosic fibrous material comprising the sequence soda/AQ cooking, and then one of D-Ep-(ZEND), or D-Eo-(ZEND), or D-Eop-(ZEND).
- 24. A method as in claim 23 wherein the treatment is practiced to produce pulp with a brightness over 89% ISO.
- 25. Pulp produced according to claim 24, having a viscosity of over 21 cP.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon provisional application Ser. No. 60/167,537 filed Dec. 2, 1999, the disclosure of which is hereby incorporated by reference herein.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60167537 |
Dec 1999 |
US |
Divisions (1)
|
Number |
Date |
Country |
Parent |
09722420 |
Nov 2000 |
US |
Child |
10633536 |
Aug 2003 |
US |