Claims
- 1. A method for preparation of paper pulp from lignocellulosic material containing polysaccharides comprising precleaning said lignocellulosic material at a temperature of between about 40 and 150° C. under acidic conditions essentially without dissolution of said polysaccharides, said precleaning step having a final pH in the range of about 2.5 to 5, following said precleaning step, contacting said lignocellulosic material with a predetermined amount of an alkaline process liquor in order to effect the transition in said precleaning process condition to alkaline cooking process conditions, said predetermined amount of said alkaline process liquor being sufficient to neutralize said lignocellulosic material to a pH of at least about 7, subsequently removing the resulting neutralized liquor from said process and cooking said lignocellulosic material with alkaline cooking liquor thereby preparing a paper pulp high in hemicellulose content.
- 2. The method of claim 1 wherein said cooking comprises a batch cooking process.
- 3. The method of claim 2 wherein said cooking comprises a displacement batch cooking process.
- 4. The method of claim 1 wherein said cooking comprises a continuous cooking process.
- 5. The method of claim 1 wherein said precleaning step includes treating said lignocellulosic material with water or steam.
- 6. The method of claim 5 wherein said water or steam includes a predetermined amount of at least one acid.
- 7. The method of claim 1 wherein said method comprises an element of a kraft process.
- 8. The method of claim 1 wherein said transition step comprises a first alkaline stage following said precleaning step, and wherein said first alkaline stage has a final pH higher than about 10.
- 9. The method of claim 1 wherein said method comprises an element of a soda process.
- 10. A method for preparation of paper pulp from lignocellulosic material containing polysaccharides comprising precleaning said lignocellulosic material at a temperature of between about 40 and 150° C. under acidic conditions essentially without dissolution of said polysaccharides, said precleaning step having a final pH in the range of about 2.5 to 5, following said precleaning step, contacting said lignocellulosic material with a washing liquor in order to effect the transition in said precleaning process condition to alkaline cooking process conditions, subsequently removing the resulting liquor from said process and cooking said lignocellulosic material with alkaline cooking liquor, thereby preparing a paper pulp high in hemicellulose content.
- 11. The method of claim 10 wherein said adding of said washing liquor is carried out using water or evaporation condensate.
- 12. The method of claim 10 wherein said cooking comprises a batch cooking process.
- 13. The method of claim 12 wherein said cooking comprises a displacement batch cooking process.
- 14. The method of claim 10 wherein said cooking comprises a continuous cooking process.
- 15. The method of claim 10 wherein said precleaning step includes treating said lignocellulosic material with water or steam.
- 16. The method of claim 15 wherein said water or steam includes a predetermined amount of at least one acid.
- 17. The method of claim 10 wherein said method comprises an element of a kraft process.
- 18. The method of claim 10 wherein said method comprises an element of a soda process.
Priority Claims (1)
Number |
Date |
Country |
Kind |
974455 |
Dec 1997 |
FI |
|
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. Ser. No. 09/167,423 filed Oct. 6, 1998, now abandoned, which also claims the priority of Finland 974455 filed Dec. 8, 1997.
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
9612063 |
Apr 1996 |
WO |
Non-Patent Literature Citations (3)
Entry |
Sven A. Rydholm, “Pulping Processes,” Interscience Publishers, 1965, pp. 648-673. |
Sven A. Rydholm, “Pulping Processes,” Interscience Publishers, 1967, pp. 583 and 584. |
Vuorinen et al., “Selective Hydrolysis of Hexenuronic Acid Groups and its Applicatoin in ECF and TCF Bleaching of Kraft Pulps,” 1996 International Pulp Bleaching Conference, pp. 43-51. |
Continuations (1)
|
Number |
Date |
Country |
Parent |
09/167423 |
Oct 1998 |
US |
Child |
09/589706 |
|
US |