CA2537033A1 - Methods of treating chemical cellulose pulp - Google Patents
Methods of treating chemical cellulose pulp Download PDFInfo
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- CA2537033A1 CA2537033A1 CA002537033A CA2537033A CA2537033A1 CA 2537033 A1 CA2537033 A1 CA 2537033A1 CA 002537033 A CA002537033 A CA 002537033A CA 2537033 A CA2537033 A CA 2537033A CA 2537033 A1 CA2537033 A1 CA 2537033A1
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- pulp
- treatment
- chlorine dioxide
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- bleaching
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
- D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
A single pulp bleaching stage comprises an acid treatment, A, a neutralization treatment, n, and a chlorine dioxide treatment, Do. The AnD o bleaching stage may optionally include washing between treatments, either between each treatment or only some treatments, represented by A-n-D o which indicates there is washing between the acid (A) and the neutralization (n) treatments and the neutralization (n) and the chlorine dioxide (D) treatments, or An-D o which indicates there is washing only between the neutralization (n) and the chlorine dioxide (D) treatments. The AnD o stage can be followed by washing and further bleaching stages. Preferably, the (AnD o) stage is followed by an extraction stage E op with caustic in the presence of oxygen and a peroxide.
Description
METHODS OF TREATING CHEMICAL CELLULOSE PULP
DOMESTIC PRIORITY CLAIM
The present invention is based on and claims domestic priority benefit under 35 USC ~119(e) from U.S. Provisional Patent Application Serial No.
60/659,077 filed on March 8, 2005, the entire content of which is expressly incorporated hereinto by reference.
FIELD OF THE INVENTION
The present invention relates to a method of treating chemical cellulose pulp from any chemical pulping process. In preferred embodiments, the present invention relates to treating chemical cellulose pulp in a stage with an acid treatment, a subsequent neutralization treatment and a chlorine dioxide treatment following the neutralization treatment.
BACKGROUND AND SUMMARY OF THE INVENTION
Pulp bleaching sequences using chlorine dioxide as the bleaching chemical are popular and environmentally feasible. Many practical and economic reasons exist for pulp bleaching sequences utilizing chlorine dioxide. For example, the price of chlorine dioxide is very competitive compared with that of other bleaching and delignifying chemicals. Also, the strength and brightness of the pulp obtained by chlorine dioxide bleaching are good, in fact at least approximately of the same order as those obtained by using peroxide at the same chemical consumption level (kg/admt).
Conventional chlorine dioxide bleaching is usually preformed at a temperature of 50-80°C, and with a chlorine dioxide dosage of about 10-30 kg per ton of pulp. Typical sequences used are, for example, DoED~ED2 and ODoED~ED2 and modifications thereof. The treatment time in a Do stage is usually shorter as compared to the treatment time in the other D stages, being for example, between about 30-90 minutes. The pH of the pulp decreases to the range of 1-3 towards the end of the Do stage. In the D, and D2 stages the treatment time is 2-3 hours and the pH is slightly higher than in the Do stage.
The chlorine dioxide stage (all types) is usually performed at a temperature of . about 70°C, while the treatment time in the Do stage is 0.5-2 hours and in the D~ and D2 stages 2-3 hours. Higher temperatures than about 70°C
have typically been avoided as the low final pH in the range of 1-3 in the D stage combined with a high temperature and long treatment time deteriorates the strength properties of the pulp fibers.
Although conventional chlorine dioxide sequences have achieved widespread acceptance in the industry, some improvements are still desired.
For example, improvements in the final brightness achieved by chlorine dioxide bleaching sequences are continually sought. It is towards fulfilling such improvements that the present is directed.
The present invention is especially embodied in a single bleaching stage which comprises an acid treatment, A, a neutralization treatment, n, and a chlorine dioxide treatment, D°. The AnDo bleaching stage of the present invention may optionally include washing between treatments, either between each treatment or only some treatments, represented by A-n-Do which indicates there is washing between the Acid (A) and the neutralization (n) treatments and the neutralization (n) and the chlorine dioxide (D) treatments, or An-D° which indicates there is washing only between the neutralization (n) and the chlorine dioxide (D) treatments. The AnDo stage can be followed by washing and further bleaching stages. Preferably, the (AnDo) stage is followed by an extraction stage Eop with caustic in the presence of oxygen and a peroxide.
When compared to a stage that is an acid treatment followed by a chlorine dioxide treatment without neutralization between the treatments (AD°), using this AnDo bleaching stage of the present invention gives the surprising results of higher brightness after the chlorine dioxide treatment and higher brightness and lower Kappa number after a subsequent Eop stage.
This AnDo bleaching stage also results in a higher final brightness at substantially identical bleaching conditions when bleaching does not include such an ADo or Do stage only.
Additionally, it has been found that reduced brightness reversion (that is, the measure of the loss of brightness of bleached pulp or paper over a period of time) occurs for pulp bleached in accordance with the present invention. In this regard, it is highly desirable for the bleached pulp to retain its white ("bleached") color over prolonged time periods and thus reduction of brightness reversion of bleached pulp is highly desirable. Thus, brightness reversion of bleached pulp from the AnDo bleaching stage when compared to a conventional ADo stage is lower. It has also been found that the AnDo bleaching stage at a given brightness level requires less bleaching chemicals, especially chlorine dioxide. All of the improvements are a result of the introduction of a neutralization treatment, n, between the A and Do treatments.
Further, it has been found when compared to a stage that is an AnDo, using an An-Do bleaching stage (acid treatment followed by neutralization followed by washing followed by chlorine dioxide) of the present invention gives even more surprising results of an even higher brightness after the chlorine dioxide treatment and higher brightness and lower Kappa number after a subsequent Eop stage. This An-Do bleaching stage also results in an even higher final brightness at substantially identical bleaching conditions when bleaching does not include such a stage.
As with the AnDo, it has been found that the An-Do results in a reduced brightness reversion (that is, the measure of the loss of brightness of bleached pulp or paper over a period of time) for pulps bleached in accordance with the present invention. In this regard, it is highly desirable for the bleached pulp to retain its white ("bleached") color over prolonged time periods and thus reduction of brightness reversion of bleached pulp is highly desirable. Thus, brightness reversion of bleached pulp from the An-Do bleaching stage when compared to a conventional ADo stage or even an AnDo is lower. It has also been found that the An-Do bleaching stage at a given brightness level requires less bleaching chemicals, especially chlorine dioxide. All of the improvements are a result of the introduction of a neutralization treatment, n, between the A and Do treatments with washing following the neutralization.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Reference will hereinafter be made to the accompanying drawings, wherein like reference numerals throughout the various FIGURES denote like structural elements, and wherein;
FIGURE 1 is a schematic view of the AnDo process;
FIGURE 2 is a schematic view of the An-Do process;
FIGURE 3 is a bar graph showing pulp brightness for chlorine dioxide bleaching sequences with and without a neutralization, n, stage and with and without a caustic extraction stage in the presence of oxygen and a peroxide (E°p).
FIGURE 4 is a bar graph showing the impact of a neutralization stage on E°p Kappa Number for chlorine dioxide bleaching stages;
FIGURE 5 is a graph of final brightness (% ISO) versus C102 charge in the D~ stage; and FIGURE 6 is a graph of final brightness (% ISO) versus Total C102 charge.
. CA 02537033 2006-02-21 DETAILED DESCRIPTION OF THE INVENTION
A schematic view of a system 10 according to the present invention is depicted in accompanying FIGURE 1. In this regard, the pulp slurry of the target consistency enters the treatment vessel 12 via supply line 14 so that the pulp can be subjected to an acid treatment, A. The acid treated pulp is discharged from the vessel 12 via line 16 and pumped by slurry pump 18 to a mixer 20. An appropriate amount of a neutralizing chemical (e.g., NaOH) is added to the pulp slurry at the mixer 20. The neutralized pulp slurry may then be introduced into treatment vessel 22 via supply line 24. The vessel 22 is sized to accommodate the desired residence time for the pulp slurry to be neutralized therein. The neutralized pulp slurry is then withdrawn from the vessel 22 via line 26 and directed to a mixer 28 wherein the bleaching charge of chlorine dioxide C102 is added. The pulp slurry is thus introduced into the bleaching vessel 30 via line 32. The bleaching vessel 30 is sized so as to allow the pulp slurry to reside for a time sufficient to bleach the pulp whereby the bleached pulp may then be discharged therefrom via line 34.
The present invention is especially embodied in a single bleaching stage which comprises an acid treatment, A, a neutralization treatment, n, and a chlorine dioxide treatment, Do. The (AnDo) bleaching stage of the present invention may optionally include washing between treatments represented by (A-n-Do), or between only the acid and neutralization treatments represented by (A-nDo) or between only the neutralization and chlorine dioxide treatments represented by (An-Do).
FIGURE 2 shows the schematic of the system 10 where washing occurs at a wash stage 40 between neutralization n (which occurs in vessel 22) and the addition of chlorine dioxide at mixer 28. This wash stage may involve a press (not shown). The wash stage 40 (which can occur with or without a press) includes the addition of wash liquid (preferably fresh water at about 20°C to about 100°C) via line 41 to the pulp after the neutralization stage such that the material leaving the wash stage 40 via line 26-1 is at a -s-consistency of between about 4 to about 35%, preferably at a consistency of between about 10 to about 14%. The wash liquid may be extracted from the wash stage 40 via line 42.
The preferred acid treatment will be conducted at a pH of between about 1 to about 5, and more preferably between about 2 to about 3.5. The acid used in such acid treatment may be any of those acids conventionally employed in the art, such as for example, sulfuric, hydrochloric acid and the like. Hydrofluoric acid may also be employed. The pulp retention time for the acid treatment will typically range between about 30 seconds to about 5 hours, and more preferably between about 2 to about 4 hours. The acid treatment will most preferably be conducted at an elevated temperature of between about 40 to about 100°C, and more preferably between about 80 to about 90°C (e.g., about 85°C). The consistency of the pulp slurry during acid treatment is preferably between about 0.1 to about 50%, more preferably about 4 to about 15%, and most preferably between about 10 to about 12%.
Particularly preferred acid treatments may be those described more fully in U.S. Patent No. 6,776,876 B1, the entire content of which is expressly incorporated hereinto by reference. Specifically, the preferred acid treatment stage (A) will include treating chemical cellulose pulp produced by alkaline delignification having a kappa number under 24 and a solids consistency of between 0.1-50% by treating the pulp at a temperature over 85°C and at a pH
between about 2-5 for sufficient time to remove at least 50% of the hexenuronic acid and to reduce the kappa number by at least 2 units.
The acid treatment of this invention is followed by a neutralization treatment stage (n) and optionally may include an intermediate washing stage. As will be discussed below, especially preferred embodiments subject the acid treated pulp to the neutralization treatment without an intermediate.
wash (i.e., so as to achieve reduced brightness reversion). The purpose of the neutralization treatment is to neutralize the pulp slurry to a pH of between about 7 to about 14 (preferably about 9.5 pH) using an alkaline chemical, such as sodium hydroxide. The preferred neutralization treatment is accomplished by adding the neutralizing chemical directly to the pulp slurry directly after the acid treatment without washing at a temperature of between about 40 to about 100°C, more preferably between about 60 to about 90°C, most preferably 80 to about 90°C. The pulp retention time for the neutralization treatment will typically range between about 30 seconds to about 2 hours, and more preferably between about 5 to about 20 minutes.
The consistency of the pulp slurry during the neutralization treatment is preferably between about 4 to about 15%, more preferably between about 10 to about 12%.
A chlorine dioxide treatment, Do, directly follows the neutralization treatment. As discussed previously, intermediate washing of the pulp slurry may or may not occur between the n and Do treatments. The chlorine dioxide treatment is conducted at a pH of between about 1 to about 7, preferably between about 2.5 to about 3.5. The target pH is achieved by adding chlorine dioxide and/or an acid such as sulfuric, hydrochloric, or hydrofluoric acids.
The temperature of the chlorine dioxide treatment will be between about 40 to about 100°C, more preferably between about 60 to about 90°C, most preferably 80 to about 90°C. Pulp retention times during the chlorine dioxide treatment will range between about 30 seconds to about 2 hours, preferably between about 15 to about 30 minutes. A chlorine dioxide charge of between about 0.05 to about 2.5% on oven dry pulp weight (odpt) or Kappa number 3 to 24 times the Kappa factor (Kappa factor of 0.05 to 1, preferably 0.15 to 0.25) will typically be employed at beginning of the Do treatment. Pulp slurry consistency during the Do treatment will be between about 4 to about 15%, preferably between about 10 to about 12%. The chlorine dioxide treatments that may be employed in the practice of this invention are described more fully in US Patent Application Publication 2002/0056533 A1 (the entire content of which is expressly incorporated hereinto by reference).
The AnDo or An-Do stage can be followed by washing and further bleaching stages. Preferably, the AnD° or An-Do stage is followed by an _ $ _ alkaline extraction, preferably by an E°p stage with caustic in the presence of oxygen and a peroxide. Preferably the E°p stage is as disclosed more fully in U.S. Patent No. 4,568,420 (the entire content of which is expressly incorporated hereinto by reference).
As noted previously, intermediate wash treatments may optionally be practiced between the neutralization treatment and each of the acid and chlorine dioxide bleaching treatments or between the acid and neutralization treatment or between the neutralization and chlorine dioxide treatment. Such a stage can be stated as A-n-Do or A-nDo or An-Do. Suitable wash liquids, typically at a temperature of 20-100°C for such intermediate wash treatments may be virtually any suitable water from the pulp mill, such as fresh water or filtrate from the last D (chlorine dioxide) stage or it can be condensate (either clean or dirty) from elsewhere in the mill, washer filtrate, waste water treatment plant effluent or combinations of any of these liquids, but preferably is fresh water.
Alternatively, an initial quantity of chlorine dioxide may be added to the acid treatment, A, resulting in a stage (AonDo). According to this embodiment of the invention, the total charge of chlorine dioxide would be split between the Ap and Do treatments so that chlorine dioxide is added in two treatments.
Specifically, chlorine dioxide would be added during or with the acid treatment as well as after the neutralization treatment.
Preferably, according to this embodiment, a treatment Ap is practiced to achieve an acid treatment with the addition of between 1 and 99% of the total chlorine dioxide to be used in the stage. For example, if 10% of the total chlorine dioxide to be added in this stage is added with the acid, A, treatment, then the remaining 90% of the chlorine dioxide is introduced in the subsequent chlorine dioxide, Do, treatment. The operating conditions of this Ao treatment are preferably substantially the same as those of the acid treatment described previously, that is a pH of 1 to 4 preferably 2 to 3.5; a retention time for the treatment of 30 seconds to 5 hours, preferably 2 to 4 hours; a temperature of treatment 40 to 100°C, preferably 80 to 90°C; and a pulp slurry consistency during treatment of 4 to 15%, preferably 10 to 12%.
Preferably, the acid used is sulfuric, hydrochloric or hydrofluoric.
The Ap treatment is followed directly by a neutralization treatment without intermediate washing. That is, there is no washing of the pulp slurry between the Ap and n treatments. The Do treatment follows directly the neutralization treatment without intermediate washing. That is, there is no washing of the pulp slurry between the n and the Do treatments. The operating conditions for the n and the'Do treatments are substantially the same as those described previously with the neutralization and Do treatments except of course that the balance of the chlorine dioxide charge is added in the Do treatment which depends on the amount of chlorine dioxide added in the Ap treatment.
Although no intermediate washings of the pulp are preferred, intermediate wash treatments may optionally be practiced between the neutralization treatment and each of the Ap and Do treatments. Such a sequence can be stated as (Ap-n-Do). Suitable wash liquids for such intermediate wash treatments may be virtually any suitable water from the pulp mill, such as washer filtrate, waste water treatment plant effluent and the like.
Another embodiment in accordance with the present invention involves having successive chlorine dioxide treatments whereby bleaching is accomplished first at a relatively high pH value and then at a relatively low pH
value. Such a sequence is identified as (AnDH,D~o). In this regard the acid and neutralization treatments are preferably practiced substantially the same as described previously. Preferably, no intermediate washing of the pulp slurry occurs either before or during the chlorine dioxide treatments DH,, Duo.
The total chlorine dioxide charge is split between the DH, and Duo treatments.
Thus, between about 1 to about 99% of the total chlorine dioxide charge will be added in the DHi treatment, whereas the balance (i.e., between 99% to 1 %) of the total chlorine charge is then added in the Duo treatment.
The DH, chlorine dioxide treatment is conducted at a relatively high pH
of between about 4 to about 7, preferably between about 5 to about 6. The target pH is achieved by adding sodium hydroxide or other alkaline chemicals with pH adjustment occurring after the addition of 1 to 99% of the chlorine dioxide charge. The DH, treatment is preferably practiced at a temperature 40 to 100°C, preferably 60 to 90°C; a retention time at high pH of 30 seconds to 2 hours, preferably 5 to 30 minutes; and a pulp slurry consistency of 4 to 15%, preferably 10-12%.
The Duo chlorine dioxide treatment is practiced at a relatively low pH, without intermediate washing of the pulp slurry after the DH, treatment, of between about 1 to about 4, preferably between about 2 to about 3. The pH
adjustment is achieved by adding a suitable acid, such as sulfuric acid, hydrochloric acid and/or hydrofluoric acid. The addition of acid for pH
adjustment can occur concurrently with or subsequent to the addition of the balance of the chlorine dioxide charge. Preferably, the Duo chlorine dioxide treatment is practiced at a temperature 40 to 100°C, preferably 60 to 90°C; a retention time at low pH of 30 seconds to 2 hours, preferably 5 to 30 minutes;
and at a pulp slurry consistency of 4 to 15%, preferably 10-12%.
Although no intermediate washings are preferred, it is possible to practice intermediate washings between each of the treatments, specifically between the neutralization treatment and each of the acid and high pH
chlorine dioxide treatments as well as between the high and low chlorine dioxide treatments. Such a stage can be stated as (A-n-DH,-Duo). Wash liquid could be any water from the mill, such as washer filtrate, waste water treatment plant effluent, and the like.
The present invention will be further understood from the following non-limiting Example.
Example 1 Hardwood pulp was treated in accordance with Table 1 below to compare the results of the AnDo treatment in accordance with the present invention, with and without a subsequent Eop stage, with a conventional ADo stage. The results appear in Table 1 below and are graphically presented as FIGURES 3-5.
As can be seen, improvements in the final brightness are achieved by chlorine dioxide bleaching stages according to the present invention.
Table 1 Furnish Mill Pulp Sample ID 2004-00 102403 Kappa Number 10.9 Vscosity, mPa.s 37.6 BS HexA, meq/kg 63.9 A Do Stage: 90C+85C, 180+15 min., 10h cons.
Sample ADo AnDo Kappa Factor 0.16 0.16 HzSO, % 1.32 1.32 NaOH, % --- 1.1 CIO z, % 0.37 0.37 Consumed CIO z 0.37 0.37 Final pH 2.3+ 2.3+
2.2 9.9+
4.1 Brightness, ISO 64.7 70.7 Kappa number --- ---HexA, meq/kg --- ---Eop Stage: 60 min.,85C, 40psi.,10% cons.
H20z, % 0.3 0.3 NaOH, % 0.8 0.8 Final pH 10.6 10.8 Consumed H zOz 0.3 0.27 Kappa Number 3.0 2.5 Brightness, % ISO 78.0 83.8 D Stage: 70C, 180 min.,10%
cons.
CIO z, % 0.2 0.4 0.6 0.20.4 0.6 NaOH, % --- --- 0.08------ 0.08 H zS0 a, % 0.110.03 --- 0.110.03 ---Final pH 4.2 3.8 3.9 4.24.1 3.4 CIO z Consumed, % 0.2 0.4 0.6 0.20.4 0.6 ISO Brightness, % 85.887.6 89.088.489.6 90.6 Reverted ISO units 2.3 2.3 2.5 2.52.1 2.3 1 O 4 Hrs @ 105C
Example 2 Pulp was treated in accordance with Table 2 below to compare the results of the AnDo and An-Do treatments in accordance with the present invention, with and without a subsequent EoP stage, with a conventional ADo stage. The results appear in Table 2 below and are graphically presented as FIGURES 6. Hardwood pulp was used in the study summarized in Table 2.
As can be seen, improvements in the final brightness are achieved by chlorine dioxide bleaching stages according to the present invention.
Specifically, as depicted in FIGURE 6, a comparison of three bleaching sequences (ADo), (AnDo) and (An-Do) reveals that the addition of the neutralization treatment between the acid and the chlorine dioxide treatments results in improved final brightness over the sequence with acid and chlorine dioxide treatments alone. It is also apparent the addition of washing between the neutralization and chlorine dioxide treatments results in an even higher final brightness than the case of neutralization between the acid and chlorine dioxide treatments without washing.
,CA 02537033 2006-02-21 Table 2 Furnish Hardwood Mill Oz Pulp Sample ID 2004-00 102640 Kappa Number 10.4 Viscosity, mPa.s 40.3 HexA, me 63.9 AD Staae: 90C+g5C.
180+15 min..
10% C011S.
AnDo Staae: 90Ct90C+85C.
120+5+15 min.. 10%
cons.
An-Do Staae: 90C+90C+85C.
120+5+15 min.. 10h cons.
Sample ADo AnDo An-Do Kappa Factor 0.18 0.18 0.18 HZSOs, % 1.42 1.96 1.25 NaOH, % - 1.1 0.9 CIOz, % 0.42 0.4 0.42 Consumed CIOz 0.42 0.4 0.42 2.5; 2.4;
9.4;
Final pH, each Stage 2.4 2.4; 10.8; 2.6 2.6 Brightness, ISO 65.9 66.0 72.8 E, Stake: 60 min..
85C. 40 nsi..
1~o C011S.
HzOz, % 0.5 0.5 0.5 NaOH, % 0.8 0.8 0.8 Final Ph 10.8 10.7 10.7 Consumed HzOz 0.5 0.5 0.5 Kappa Number 2.6 2.5 2.4 Brightness, % ISO 81.5 81.3 84.5 D Staae: 70C. 180 min.. 10% cons.
CIOz, % 0.2 0.4 0.6 0.20.4 0.6 0.2 0.4 0.6 NaOH, % --- --- 0.08 -- --- 0.08--- --- 0.08 HZSO,, % 0.110.03--- 0.110.03 --- 0.110.03 ---Final pH 4.5 4.0 3.9 4.23.9 3.8 4.2 4.0 3.9 Consumed CIOz 0.2 0.4 0.6 0.20.4 0.6 0.2 0.4 0.6 Brightness, % ISO 87.389.089.9 87.789.6 90.488.789.9 91.1 Reverted ISO units 2.7 2.5 2.8 2.32.5 2 1.7 1.5 1.9 4 Hrs 105C
DOMESTIC PRIORITY CLAIM
The present invention is based on and claims domestic priority benefit under 35 USC ~119(e) from U.S. Provisional Patent Application Serial No.
60/659,077 filed on March 8, 2005, the entire content of which is expressly incorporated hereinto by reference.
FIELD OF THE INVENTION
The present invention relates to a method of treating chemical cellulose pulp from any chemical pulping process. In preferred embodiments, the present invention relates to treating chemical cellulose pulp in a stage with an acid treatment, a subsequent neutralization treatment and a chlorine dioxide treatment following the neutralization treatment.
BACKGROUND AND SUMMARY OF THE INVENTION
Pulp bleaching sequences using chlorine dioxide as the bleaching chemical are popular and environmentally feasible. Many practical and economic reasons exist for pulp bleaching sequences utilizing chlorine dioxide. For example, the price of chlorine dioxide is very competitive compared with that of other bleaching and delignifying chemicals. Also, the strength and brightness of the pulp obtained by chlorine dioxide bleaching are good, in fact at least approximately of the same order as those obtained by using peroxide at the same chemical consumption level (kg/admt).
Conventional chlorine dioxide bleaching is usually preformed at a temperature of 50-80°C, and with a chlorine dioxide dosage of about 10-30 kg per ton of pulp. Typical sequences used are, for example, DoED~ED2 and ODoED~ED2 and modifications thereof. The treatment time in a Do stage is usually shorter as compared to the treatment time in the other D stages, being for example, between about 30-90 minutes. The pH of the pulp decreases to the range of 1-3 towards the end of the Do stage. In the D, and D2 stages the treatment time is 2-3 hours and the pH is slightly higher than in the Do stage.
The chlorine dioxide stage (all types) is usually performed at a temperature of . about 70°C, while the treatment time in the Do stage is 0.5-2 hours and in the D~ and D2 stages 2-3 hours. Higher temperatures than about 70°C
have typically been avoided as the low final pH in the range of 1-3 in the D stage combined with a high temperature and long treatment time deteriorates the strength properties of the pulp fibers.
Although conventional chlorine dioxide sequences have achieved widespread acceptance in the industry, some improvements are still desired.
For example, improvements in the final brightness achieved by chlorine dioxide bleaching sequences are continually sought. It is towards fulfilling such improvements that the present is directed.
The present invention is especially embodied in a single bleaching stage which comprises an acid treatment, A, a neutralization treatment, n, and a chlorine dioxide treatment, D°. The AnDo bleaching stage of the present invention may optionally include washing between treatments, either between each treatment or only some treatments, represented by A-n-Do which indicates there is washing between the Acid (A) and the neutralization (n) treatments and the neutralization (n) and the chlorine dioxide (D) treatments, or An-D° which indicates there is washing only between the neutralization (n) and the chlorine dioxide (D) treatments. The AnDo stage can be followed by washing and further bleaching stages. Preferably, the (AnDo) stage is followed by an extraction stage Eop with caustic in the presence of oxygen and a peroxide.
When compared to a stage that is an acid treatment followed by a chlorine dioxide treatment without neutralization between the treatments (AD°), using this AnDo bleaching stage of the present invention gives the surprising results of higher brightness after the chlorine dioxide treatment and higher brightness and lower Kappa number after a subsequent Eop stage.
This AnDo bleaching stage also results in a higher final brightness at substantially identical bleaching conditions when bleaching does not include such an ADo or Do stage only.
Additionally, it has been found that reduced brightness reversion (that is, the measure of the loss of brightness of bleached pulp or paper over a period of time) occurs for pulp bleached in accordance with the present invention. In this regard, it is highly desirable for the bleached pulp to retain its white ("bleached") color over prolonged time periods and thus reduction of brightness reversion of bleached pulp is highly desirable. Thus, brightness reversion of bleached pulp from the AnDo bleaching stage when compared to a conventional ADo stage is lower. It has also been found that the AnDo bleaching stage at a given brightness level requires less bleaching chemicals, especially chlorine dioxide. All of the improvements are a result of the introduction of a neutralization treatment, n, between the A and Do treatments.
Further, it has been found when compared to a stage that is an AnDo, using an An-Do bleaching stage (acid treatment followed by neutralization followed by washing followed by chlorine dioxide) of the present invention gives even more surprising results of an even higher brightness after the chlorine dioxide treatment and higher brightness and lower Kappa number after a subsequent Eop stage. This An-Do bleaching stage also results in an even higher final brightness at substantially identical bleaching conditions when bleaching does not include such a stage.
As with the AnDo, it has been found that the An-Do results in a reduced brightness reversion (that is, the measure of the loss of brightness of bleached pulp or paper over a period of time) for pulps bleached in accordance with the present invention. In this regard, it is highly desirable for the bleached pulp to retain its white ("bleached") color over prolonged time periods and thus reduction of brightness reversion of bleached pulp is highly desirable. Thus, brightness reversion of bleached pulp from the An-Do bleaching stage when compared to a conventional ADo stage or even an AnDo is lower. It has also been found that the An-Do bleaching stage at a given brightness level requires less bleaching chemicals, especially chlorine dioxide. All of the improvements are a result of the introduction of a neutralization treatment, n, between the A and Do treatments with washing following the neutralization.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Reference will hereinafter be made to the accompanying drawings, wherein like reference numerals throughout the various FIGURES denote like structural elements, and wherein;
FIGURE 1 is a schematic view of the AnDo process;
FIGURE 2 is a schematic view of the An-Do process;
FIGURE 3 is a bar graph showing pulp brightness for chlorine dioxide bleaching sequences with and without a neutralization, n, stage and with and without a caustic extraction stage in the presence of oxygen and a peroxide (E°p).
FIGURE 4 is a bar graph showing the impact of a neutralization stage on E°p Kappa Number for chlorine dioxide bleaching stages;
FIGURE 5 is a graph of final brightness (% ISO) versus C102 charge in the D~ stage; and FIGURE 6 is a graph of final brightness (% ISO) versus Total C102 charge.
. CA 02537033 2006-02-21 DETAILED DESCRIPTION OF THE INVENTION
A schematic view of a system 10 according to the present invention is depicted in accompanying FIGURE 1. In this regard, the pulp slurry of the target consistency enters the treatment vessel 12 via supply line 14 so that the pulp can be subjected to an acid treatment, A. The acid treated pulp is discharged from the vessel 12 via line 16 and pumped by slurry pump 18 to a mixer 20. An appropriate amount of a neutralizing chemical (e.g., NaOH) is added to the pulp slurry at the mixer 20. The neutralized pulp slurry may then be introduced into treatment vessel 22 via supply line 24. The vessel 22 is sized to accommodate the desired residence time for the pulp slurry to be neutralized therein. The neutralized pulp slurry is then withdrawn from the vessel 22 via line 26 and directed to a mixer 28 wherein the bleaching charge of chlorine dioxide C102 is added. The pulp slurry is thus introduced into the bleaching vessel 30 via line 32. The bleaching vessel 30 is sized so as to allow the pulp slurry to reside for a time sufficient to bleach the pulp whereby the bleached pulp may then be discharged therefrom via line 34.
The present invention is especially embodied in a single bleaching stage which comprises an acid treatment, A, a neutralization treatment, n, and a chlorine dioxide treatment, Do. The (AnDo) bleaching stage of the present invention may optionally include washing between treatments represented by (A-n-Do), or between only the acid and neutralization treatments represented by (A-nDo) or between only the neutralization and chlorine dioxide treatments represented by (An-Do).
FIGURE 2 shows the schematic of the system 10 where washing occurs at a wash stage 40 between neutralization n (which occurs in vessel 22) and the addition of chlorine dioxide at mixer 28. This wash stage may involve a press (not shown). The wash stage 40 (which can occur with or without a press) includes the addition of wash liquid (preferably fresh water at about 20°C to about 100°C) via line 41 to the pulp after the neutralization stage such that the material leaving the wash stage 40 via line 26-1 is at a -s-consistency of between about 4 to about 35%, preferably at a consistency of between about 10 to about 14%. The wash liquid may be extracted from the wash stage 40 via line 42.
The preferred acid treatment will be conducted at a pH of between about 1 to about 5, and more preferably between about 2 to about 3.5. The acid used in such acid treatment may be any of those acids conventionally employed in the art, such as for example, sulfuric, hydrochloric acid and the like. Hydrofluoric acid may also be employed. The pulp retention time for the acid treatment will typically range between about 30 seconds to about 5 hours, and more preferably between about 2 to about 4 hours. The acid treatment will most preferably be conducted at an elevated temperature of between about 40 to about 100°C, and more preferably between about 80 to about 90°C (e.g., about 85°C). The consistency of the pulp slurry during acid treatment is preferably between about 0.1 to about 50%, more preferably about 4 to about 15%, and most preferably between about 10 to about 12%.
Particularly preferred acid treatments may be those described more fully in U.S. Patent No. 6,776,876 B1, the entire content of which is expressly incorporated hereinto by reference. Specifically, the preferred acid treatment stage (A) will include treating chemical cellulose pulp produced by alkaline delignification having a kappa number under 24 and a solids consistency of between 0.1-50% by treating the pulp at a temperature over 85°C and at a pH
between about 2-5 for sufficient time to remove at least 50% of the hexenuronic acid and to reduce the kappa number by at least 2 units.
The acid treatment of this invention is followed by a neutralization treatment stage (n) and optionally may include an intermediate washing stage. As will be discussed below, especially preferred embodiments subject the acid treated pulp to the neutralization treatment without an intermediate.
wash (i.e., so as to achieve reduced brightness reversion). The purpose of the neutralization treatment is to neutralize the pulp slurry to a pH of between about 7 to about 14 (preferably about 9.5 pH) using an alkaline chemical, such as sodium hydroxide. The preferred neutralization treatment is accomplished by adding the neutralizing chemical directly to the pulp slurry directly after the acid treatment without washing at a temperature of between about 40 to about 100°C, more preferably between about 60 to about 90°C, most preferably 80 to about 90°C. The pulp retention time for the neutralization treatment will typically range between about 30 seconds to about 2 hours, and more preferably between about 5 to about 20 minutes.
The consistency of the pulp slurry during the neutralization treatment is preferably between about 4 to about 15%, more preferably between about 10 to about 12%.
A chlorine dioxide treatment, Do, directly follows the neutralization treatment. As discussed previously, intermediate washing of the pulp slurry may or may not occur between the n and Do treatments. The chlorine dioxide treatment is conducted at a pH of between about 1 to about 7, preferably between about 2.5 to about 3.5. The target pH is achieved by adding chlorine dioxide and/or an acid such as sulfuric, hydrochloric, or hydrofluoric acids.
The temperature of the chlorine dioxide treatment will be between about 40 to about 100°C, more preferably between about 60 to about 90°C, most preferably 80 to about 90°C. Pulp retention times during the chlorine dioxide treatment will range between about 30 seconds to about 2 hours, preferably between about 15 to about 30 minutes. A chlorine dioxide charge of between about 0.05 to about 2.5% on oven dry pulp weight (odpt) or Kappa number 3 to 24 times the Kappa factor (Kappa factor of 0.05 to 1, preferably 0.15 to 0.25) will typically be employed at beginning of the Do treatment. Pulp slurry consistency during the Do treatment will be between about 4 to about 15%, preferably between about 10 to about 12%. The chlorine dioxide treatments that may be employed in the practice of this invention are described more fully in US Patent Application Publication 2002/0056533 A1 (the entire content of which is expressly incorporated hereinto by reference).
The AnDo or An-Do stage can be followed by washing and further bleaching stages. Preferably, the AnD° or An-Do stage is followed by an _ $ _ alkaline extraction, preferably by an E°p stage with caustic in the presence of oxygen and a peroxide. Preferably the E°p stage is as disclosed more fully in U.S. Patent No. 4,568,420 (the entire content of which is expressly incorporated hereinto by reference).
As noted previously, intermediate wash treatments may optionally be practiced between the neutralization treatment and each of the acid and chlorine dioxide bleaching treatments or between the acid and neutralization treatment or between the neutralization and chlorine dioxide treatment. Such a stage can be stated as A-n-Do or A-nDo or An-Do. Suitable wash liquids, typically at a temperature of 20-100°C for such intermediate wash treatments may be virtually any suitable water from the pulp mill, such as fresh water or filtrate from the last D (chlorine dioxide) stage or it can be condensate (either clean or dirty) from elsewhere in the mill, washer filtrate, waste water treatment plant effluent or combinations of any of these liquids, but preferably is fresh water.
Alternatively, an initial quantity of chlorine dioxide may be added to the acid treatment, A, resulting in a stage (AonDo). According to this embodiment of the invention, the total charge of chlorine dioxide would be split between the Ap and Do treatments so that chlorine dioxide is added in two treatments.
Specifically, chlorine dioxide would be added during or with the acid treatment as well as after the neutralization treatment.
Preferably, according to this embodiment, a treatment Ap is practiced to achieve an acid treatment with the addition of between 1 and 99% of the total chlorine dioxide to be used in the stage. For example, if 10% of the total chlorine dioxide to be added in this stage is added with the acid, A, treatment, then the remaining 90% of the chlorine dioxide is introduced in the subsequent chlorine dioxide, Do, treatment. The operating conditions of this Ao treatment are preferably substantially the same as those of the acid treatment described previously, that is a pH of 1 to 4 preferably 2 to 3.5; a retention time for the treatment of 30 seconds to 5 hours, preferably 2 to 4 hours; a temperature of treatment 40 to 100°C, preferably 80 to 90°C; and a pulp slurry consistency during treatment of 4 to 15%, preferably 10 to 12%.
Preferably, the acid used is sulfuric, hydrochloric or hydrofluoric.
The Ap treatment is followed directly by a neutralization treatment without intermediate washing. That is, there is no washing of the pulp slurry between the Ap and n treatments. The Do treatment follows directly the neutralization treatment without intermediate washing. That is, there is no washing of the pulp slurry between the n and the Do treatments. The operating conditions for the n and the'Do treatments are substantially the same as those described previously with the neutralization and Do treatments except of course that the balance of the chlorine dioxide charge is added in the Do treatment which depends on the amount of chlorine dioxide added in the Ap treatment.
Although no intermediate washings of the pulp are preferred, intermediate wash treatments may optionally be practiced between the neutralization treatment and each of the Ap and Do treatments. Such a sequence can be stated as (Ap-n-Do). Suitable wash liquids for such intermediate wash treatments may be virtually any suitable water from the pulp mill, such as washer filtrate, waste water treatment plant effluent and the like.
Another embodiment in accordance with the present invention involves having successive chlorine dioxide treatments whereby bleaching is accomplished first at a relatively high pH value and then at a relatively low pH
value. Such a sequence is identified as (AnDH,D~o). In this regard the acid and neutralization treatments are preferably practiced substantially the same as described previously. Preferably, no intermediate washing of the pulp slurry occurs either before or during the chlorine dioxide treatments DH,, Duo.
The total chlorine dioxide charge is split between the DH, and Duo treatments.
Thus, between about 1 to about 99% of the total chlorine dioxide charge will be added in the DHi treatment, whereas the balance (i.e., between 99% to 1 %) of the total chlorine charge is then added in the Duo treatment.
The DH, chlorine dioxide treatment is conducted at a relatively high pH
of between about 4 to about 7, preferably between about 5 to about 6. The target pH is achieved by adding sodium hydroxide or other alkaline chemicals with pH adjustment occurring after the addition of 1 to 99% of the chlorine dioxide charge. The DH, treatment is preferably practiced at a temperature 40 to 100°C, preferably 60 to 90°C; a retention time at high pH of 30 seconds to 2 hours, preferably 5 to 30 minutes; and a pulp slurry consistency of 4 to 15%, preferably 10-12%.
The Duo chlorine dioxide treatment is practiced at a relatively low pH, without intermediate washing of the pulp slurry after the DH, treatment, of between about 1 to about 4, preferably between about 2 to about 3. The pH
adjustment is achieved by adding a suitable acid, such as sulfuric acid, hydrochloric acid and/or hydrofluoric acid. The addition of acid for pH
adjustment can occur concurrently with or subsequent to the addition of the balance of the chlorine dioxide charge. Preferably, the Duo chlorine dioxide treatment is practiced at a temperature 40 to 100°C, preferably 60 to 90°C; a retention time at low pH of 30 seconds to 2 hours, preferably 5 to 30 minutes;
and at a pulp slurry consistency of 4 to 15%, preferably 10-12%.
Although no intermediate washings are preferred, it is possible to practice intermediate washings between each of the treatments, specifically between the neutralization treatment and each of the acid and high pH
chlorine dioxide treatments as well as between the high and low chlorine dioxide treatments. Such a stage can be stated as (A-n-DH,-Duo). Wash liquid could be any water from the mill, such as washer filtrate, waste water treatment plant effluent, and the like.
The present invention will be further understood from the following non-limiting Example.
Example 1 Hardwood pulp was treated in accordance with Table 1 below to compare the results of the AnDo treatment in accordance with the present invention, with and without a subsequent Eop stage, with a conventional ADo stage. The results appear in Table 1 below and are graphically presented as FIGURES 3-5.
As can be seen, improvements in the final brightness are achieved by chlorine dioxide bleaching stages according to the present invention.
Table 1 Furnish Mill Pulp Sample ID 2004-00 102403 Kappa Number 10.9 Vscosity, mPa.s 37.6 BS HexA, meq/kg 63.9 A Do Stage: 90C+85C, 180+15 min., 10h cons.
Sample ADo AnDo Kappa Factor 0.16 0.16 HzSO, % 1.32 1.32 NaOH, % --- 1.1 CIO z, % 0.37 0.37 Consumed CIO z 0.37 0.37 Final pH 2.3+ 2.3+
2.2 9.9+
4.1 Brightness, ISO 64.7 70.7 Kappa number --- ---HexA, meq/kg --- ---Eop Stage: 60 min.,85C, 40psi.,10% cons.
H20z, % 0.3 0.3 NaOH, % 0.8 0.8 Final pH 10.6 10.8 Consumed H zOz 0.3 0.27 Kappa Number 3.0 2.5 Brightness, % ISO 78.0 83.8 D Stage: 70C, 180 min.,10%
cons.
CIO z, % 0.2 0.4 0.6 0.20.4 0.6 NaOH, % --- --- 0.08------ 0.08 H zS0 a, % 0.110.03 --- 0.110.03 ---Final pH 4.2 3.8 3.9 4.24.1 3.4 CIO z Consumed, % 0.2 0.4 0.6 0.20.4 0.6 ISO Brightness, % 85.887.6 89.088.489.6 90.6 Reverted ISO units 2.3 2.3 2.5 2.52.1 2.3 1 O 4 Hrs @ 105C
Example 2 Pulp was treated in accordance with Table 2 below to compare the results of the AnDo and An-Do treatments in accordance with the present invention, with and without a subsequent EoP stage, with a conventional ADo stage. The results appear in Table 2 below and are graphically presented as FIGURES 6. Hardwood pulp was used in the study summarized in Table 2.
As can be seen, improvements in the final brightness are achieved by chlorine dioxide bleaching stages according to the present invention.
Specifically, as depicted in FIGURE 6, a comparison of three bleaching sequences (ADo), (AnDo) and (An-Do) reveals that the addition of the neutralization treatment between the acid and the chlorine dioxide treatments results in improved final brightness over the sequence with acid and chlorine dioxide treatments alone. It is also apparent the addition of washing between the neutralization and chlorine dioxide treatments results in an even higher final brightness than the case of neutralization between the acid and chlorine dioxide treatments without washing.
,CA 02537033 2006-02-21 Table 2 Furnish Hardwood Mill Oz Pulp Sample ID 2004-00 102640 Kappa Number 10.4 Viscosity, mPa.s 40.3 HexA, me 63.9 AD Staae: 90C+g5C.
180+15 min..
10% C011S.
AnDo Staae: 90Ct90C+85C.
120+5+15 min.. 10%
cons.
An-Do Staae: 90C+90C+85C.
120+5+15 min.. 10h cons.
Sample ADo AnDo An-Do Kappa Factor 0.18 0.18 0.18 HZSOs, % 1.42 1.96 1.25 NaOH, % - 1.1 0.9 CIOz, % 0.42 0.4 0.42 Consumed CIOz 0.42 0.4 0.42 2.5; 2.4;
9.4;
Final pH, each Stage 2.4 2.4; 10.8; 2.6 2.6 Brightness, ISO 65.9 66.0 72.8 E, Stake: 60 min..
85C. 40 nsi..
1~o C011S.
HzOz, % 0.5 0.5 0.5 NaOH, % 0.8 0.8 0.8 Final Ph 10.8 10.7 10.7 Consumed HzOz 0.5 0.5 0.5 Kappa Number 2.6 2.5 2.4 Brightness, % ISO 81.5 81.3 84.5 D Staae: 70C. 180 min.. 10% cons.
CIOz, % 0.2 0.4 0.6 0.20.4 0.6 0.2 0.4 0.6 NaOH, % --- --- 0.08 -- --- 0.08--- --- 0.08 HZSO,, % 0.110.03--- 0.110.03 --- 0.110.03 ---Final pH 4.5 4.0 3.9 4.23.9 3.8 4.2 4.0 3.9 Consumed CIOz 0.2 0.4 0.6 0.20.4 0.6 0.2 0.4 0.6 Brightness, % ISO 87.389.089.9 87.789.6 90.488.789.9 91.1 Reverted ISO units 2.7 2.5 2.8 2.32.5 2 1.7 1.5 1.9 4 Hrs 105C
Claims (11)
1. A method of treating chemical cellulose pulp produced by alkaline delignification, comprising:
(a) acid treating the pulp at a pH of between about 1 to about 5 and at a temperature of between about 40 to about 100°C;
(b) neutralizing the acid treated pulp according to step (a) with an alkaline chemical to achieve a pH of between about 7 to about 14; and thereafter (c) bleaching the neutralized pulp.
(a) acid treating the pulp at a pH of between about 1 to about 5 and at a temperature of between about 40 to about 100°C;
(b) neutralizing the acid treated pulp according to step (a) with an alkaline chemical to achieve a pH of between about 7 to about 14; and thereafter (c) bleaching the neutralized pulp.
2. The method of claim 1, wherein step (c) is practiced by subjecting the neutralized pulp to at least one chlorine dioxide (D o) bleaching stage.
3. The method of claim 1, further comprising (d) washing the pulp after the acid treatment stage.
4. The method of claim 3, wherein the step of (d) washing the pulp is practiced between steps (a) and (b).
5. The method of claim 3, wherein the step of (d) washing the pulp is practiced between steps (b) and (c).
6. The method of claim 3, wherein the step of (d) washing the pulp is practiced between steps (a) and (b) and between steps (b) and (c).
7. The method of claim 1, wherein step (c) comprises bleaching the pulp with chlorine dioxide at a relatively high pH of between about 4 to about 7 (D HI), and thereafter bleaching the pulp with chlorine dioxide at a relatively low pH of between 1 to about 4 (D LO).
8. The method of claim 7, wherein D HI, and D LO are practiced without intermediate washing.
9. The method of claim 1, wherein the chemical cellulose pulp has a kappa number of less than 24, and a solids consistency of between about 0.1 to about 50%, and wherein step (a) is practiced for a time sufficient to remove at least 50% of the hexenuronic acid and to reduce the kappa number of the pulp by at least 2 units.
10. A method of treating chemical cellulose pulp produced by alkaline delignification, consisting essentially of:
(a) acid treating the chemical cellulose pulp at a pH of between about 1 to about 5 and at a temperature of between about 40 to about 100°C;
(b) neutralizing the pulp treated in step (a) with an alkaline chemical to achieve a pH of between about 7 to about 14;
(c) washing the neutralized pulp; and thereafter (d) bleaching the washed and neutralized pulp.
(a) acid treating the chemical cellulose pulp at a pH of between about 1 to about 5 and at a temperature of between about 40 to about 100°C;
(b) neutralizing the pulp treated in step (a) with an alkaline chemical to achieve a pH of between about 7 to about 14;
(c) washing the neutralized pulp; and thereafter (d) bleaching the washed and neutralized pulp.
11. The method of claim 10, further consisting essentially of (a1) washing the pulp between steps (a) and (b).
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65907705P | 2005-03-08 | 2005-03-08 | |
| US60/659,077 | 2005-03-08 | ||
| US11/339,853 US20060201642A1 (en) | 2005-03-08 | 2006-01-26 | Methods of treating chemical cellulose pulp |
| US11/339,853 | 2006-01-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2537033A1 true CA2537033A1 (en) | 2006-09-08 |
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ID=36968837
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|---|---|---|---|
| CA002537033A Abandoned CA2537033A1 (en) | 2005-03-08 | 2006-02-21 | Methods of treating chemical cellulose pulp |
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| US (1) | US20060201642A1 (en) |
| JP (1) | JP4976707B2 (en) |
| CN (1) | CN1896378B (en) |
| BR (1) | BRPI0600771A (en) |
| CA (1) | CA2537033A1 (en) |
| FI (1) | FI20060226A (en) |
| SE (1) | SE531227C2 (en) |
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| US10597820B2 (en) * | 2015-05-14 | 2020-03-24 | DuPont Nutrition USA, Inc. | Method of making bleached microcrystalline cellulose |
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| FI122626B (en) * | 2006-03-31 | 2012-04-30 | Laennen Tutkimus Western Res Inc Oy | Chemical pulp bleaching process |
| CA2665969C (en) * | 2006-10-11 | 2016-04-12 | Magnus Bjoerklund | Bleaching of pulp |
| US8920603B2 (en) * | 2006-10-11 | 2014-12-30 | Akzo Nobel N.V. | Bleaching of pulp |
| BR102014016692A2 (en) * | 2014-07-04 | 2016-03-29 | Univ Estadual Paulista Julio D | pulp bleaching process and pulp production |
| JP6411182B2 (en) * | 2014-11-13 | 2018-10-24 | 大王製紙株式会社 | Sludge dewatering aid and sludge dewatering method |
| HRP20190259A2 (en) | 2019-02-07 | 2020-08-21 | Marinko Mikulić | A continuous process for production of cellulose pulp from grassy raw materials |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US2166330A (en) * | 1938-09-12 | 1939-07-18 | Mathieson Alkali Works Inc | Method of bleaching |
| US4568420B1 (en) * | 1984-12-03 | 1999-03-02 | Int Paper Co | Multi-stage bleaching process including an enhanced oxidative extraction stage |
| US5268075A (en) * | 1989-10-19 | 1993-12-07 | North Carolina State University | High efficiency two-step, high-low pH chlorine dioxide pulp bleaching process |
| JPH06158573A (en) * | 1992-11-18 | 1994-06-07 | Mitsubishi Gas Chem Co Inc | Method for bleaching chemical pulp for paper manufacture |
| US6776876B1 (en) * | 1994-10-13 | 2004-08-17 | Andritz Oy | Method of treating cellulosic pulp to remove hexenuronic acid |
| FI102301B (en) * | 1994-10-13 | 1998-11-13 | Andritz Oy | Method for treating cellulosic pulps |
| PL332079A1 (en) * | 1996-09-11 | 1999-08-30 | Solvay Interox Sa | Paper pulp bleaching method |
| FI119383B (en) * | 1998-03-06 | 2008-10-31 | Andritz Oy | Procedure for treating pulp |
| SE0004438L (en) * | 1999-12-02 | 2001-06-03 | Andritz Ahlstrom Inc | Environmentally friendly fiber line for the production of bleached chemical pulp |
| CN1100177C (en) * | 2000-07-20 | 2003-01-29 | 华南理工大学 | High-temp ClO2 bleaching method of sulfated wood pulp |
| JP2003253582A (en) * | 2002-03-06 | 2003-09-10 | Nippon Paper Industries Co Ltd | Method for bleaching pulp |
| JP3915682B2 (en) * | 2002-12-04 | 2007-05-16 | 王子製紙株式会社 | Method for producing bleached pulp |
| JP2005226184A (en) * | 2004-02-12 | 2005-08-25 | Nippon Paper Industries Co Ltd | Method for bleaching treatment of pulp |
-
2006
- 2006-01-26 US US11/339,853 patent/US20060201642A1/en not_active Abandoned
- 2006-02-21 CA CA002537033A patent/CA2537033A1/en not_active Abandoned
- 2006-03-02 SE SE0600454A patent/SE531227C2/en not_active IP Right Cessation
- 2006-03-06 JP JP2006059870A patent/JP4976707B2/en not_active Expired - Fee Related
- 2006-03-07 CN CN2006100567830A patent/CN1896378B/en not_active Expired - Fee Related
- 2006-03-08 BR BRPI0600771-6A patent/BRPI0600771A/en not_active Application Discontinuation
- 2006-03-08 FI FI20060226A patent/FI20060226A/en unknown
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US10597820B2 (en) * | 2015-05-14 | 2020-03-24 | DuPont Nutrition USA, Inc. | Method of making bleached microcrystalline cellulose |
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| Publication number | Publication date |
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| US20060201642A1 (en) | 2006-09-14 |
| CN1896378A (en) | 2007-01-17 |
| CN1896378B (en) | 2011-07-20 |
| BRPI0600771A (en) | 2006-11-07 |
| JP4976707B2 (en) | 2012-07-18 |
| SE0600454L (en) | 2006-09-09 |
| SE531227C2 (en) | 2009-01-27 |
| JP2006249650A (en) | 2006-09-21 |
| FI20060226A (en) | 2006-09-09 |
| FI20060226A0 (en) | 2006-03-08 |
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