Hardwood alkaline pulping processes and systems

a technology of alkaline pulping and hardwoods, applied in the field of chemical treatments, can solve the problems of decreasing the percentage of pulp rejects at a given kappa number, and conventionally not being able to practice, and achieve the effect of reducing the percentage of pulp rejects

Inactive Publication Date: 2012-12-06
ANDRITZ INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005]It has now been discovered that rejects from cooking hardwoods at a given Kappa number can be reduced by subjecting the hardwoods to specific cooking conditions at the end of cooking. According to the present invention, therefore, alkaline cooking processes and apparatus, especially those useful for hardwoods, are provided which aim to increase the Kappa number of the hardwood pulp at the end of cook to levels above 17, but with much lower rejects levels. The present invention may be combined with an effective oxygen delignification stage to reduce the kappa number below 17. The present invention therefore contributes to benefits in respect to overall pulping yield and pulp strength.

Problems solved by technology

In order to increase pulp yield it would be desirable to cook hardwoods to a higher Kappa number but such a practice is conventionally not possible since the amount of rejects would increase to a point that would not be commercially feasible.
Thus, when cooking hardwoods, relatively harsher cooking conditions (e.g., higher cooking temperatures) at the end of the cooking have been discovered to decrease the percentage of pulp rejects at a given Kappa number as a result of g-lignin breakdown.

Method used

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  • Hardwood alkaline pulping processes and systems
  • Hardwood alkaline pulping processes and systems
  • Hardwood alkaline pulping processes and systems

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0031]A hardwood cooking cycle was performed using a total EA (effective alkaline as NaOH) charge of 18% introduced during the impregnation, first cook and second cook stages. The following conditions were used during each of the stages:

[0032]Impregnation:

[0033]60% of the total EA or 10.8% EA charged

[0034]Impregnation temperature of 110° C.

[0035]Time to impregnation temperature=15 minutes

[0036]Time at impregnation temperature=30 minutes

[0037]1st Cook Stage:

[0038]25% of the total EA or 4.5% EA added at beginning of cook

[0039]Cook temperature=140° C.

[0040]Time to heat to cook temperature=15 minutes

[0041]Time at cook temperature=60 minutes

[0042]2nd Cook Stage:

[0043]15% of total EA or 2.7% EA added at beginning of cook

[0044]Cook temperature=158° C.

[0045]Time at cook temperature=76 minutes

[0046]From this set of cooking conditions, the high temperature in the second stage of the cook gave lower Kappa number and at least 30% lower reject rate than the set of cooking conditions using 140° C...

example 2

[0047]A hardwood cooking cycle was performed using a total EA (effective alkaline as NaOH) charge of 17.5% introduced during the impregnation, first (or upper) cook and second (or lower) cook sequences. The following conditions were used during each of the cook sequences:

[0048]Impregnation:

[0049]50% of the total EA or 8.75% EA charged

[0050]Impregnation temperature of 110° C.

[0051]Time to impregnation temperature=15 minutes

[0052]Time at impregnation temperature=30 minutes

[0053]1st (Upper) Cook:

[0054]30% of the total EA or 5.25% EA added at beginning of cook

[0055]Cook temperature=155° C.

[0056]Time to heat to cook temperature=15 minutes

[0057]Time at cook temperature=60 minutes

[0058]2nd (Lower) Cook:

[0059]20% of total EA or 3.5% EA added at beginning of cook

[0060]Cook temperature=156° C.

[0061]Time at cook temperature=120 minutes

[0062]A sample of the cellulosic material (wood chips) was taken after impregnation was complete and tested for s-lignin and g-lignin in the laboratory using the...

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Abstract

Systems are provided for continuously producing chemical cellulose pulp from a slurry of comminuted hardwood material by subjecting the slurry of comminuted hardwood material to a first cooking stage under conditions sufficient to reduce syringyl lignin (s-lignin) content in the hardwood material as compared to guaiacyl lignin (g-lignin) content therein, and thereafter subjecting the slurry of comminuted hardwood material to a second cooking stage under conditions sufficient to reduce the g-lignin content remaining therein after the first cooking stage.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of commonly owned co-pending U.S. application Ser. No. 11 / 709,278, filed Feb. 22, 2007, which is based on and claims domestic priority benefits under 35 USC §119(e) from U.S. Provisional Application Ser. No. 60 / 791,431 filed on Apr. 13, 2006, the entire content of which is expressly incorporated hereinto by reference.FIELD OF THE INVENTION[0002]The present invention relates generally to the field of chemical treatments of comminuted cellulosic fibrous material. In especially preferred embodiments, the present invention relates to processes and apparatus for the alkaline pulping of comminuted hardwoods.BACKGROUND AND SUMMARY OF THE INVENTION[0003]Chemical cooking of hardwoods can typically result in greater pulp rejects as compared to pulp obtained from the chemical cooking of softwoods at Kappa numbers of 17 and greater. In this regard, the present applicants have discovered that the middle lamella in hard...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): D21C7/00
CPCD21C1/06D21C3/26D21C3/222D21C3/02D21C3/022D21C3/24D21C3/266
Inventor SHIN, NAM HEESTROMBERG, C. BERTIL
Owner ANDRITZ INC
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