US20070000628A1 - Method for removal of metals from a bleach plant filtrate stream - Google Patents

Method for removal of metals from a bleach plant filtrate stream Download PDF

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Publication number
US20070000628A1
US20070000628A1 US11/171,013 US17101305A US2007000628A1 US 20070000628 A1 US20070000628 A1 US 20070000628A1 US 17101305 A US17101305 A US 17101305A US 2007000628 A1 US2007000628 A1 US 2007000628A1
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United States
Prior art keywords
bleach plant
filtrate
pulp
stream
bleach
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US11/171,013
Inventor
James Sealey
Kaaren Haynes
Doug Lloyd
Roger Campbell
Kent Robarge
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Weyerhaeuser Co
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Individual
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Filing date
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Priority to US11/171,013 priority Critical patent/US20070000628A1/en
Assigned to WEYERHAEUSER COMPANY reassignment WEYERHAEUSER COMPANY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CAMPBELL, ROGER O., ROBARGE, KENT, HAYNES, KAAREN KATHLEEN, LLOYD, DOUG, SEALEY, JAMES E. II
Priority to CA002548970A priority patent/CA2548970A1/en
Priority to ARP060102280A priority patent/AR056374A1/en
Priority to BRPI0603081-5A priority patent/BRPI0603081A/en
Priority to ZA200605257A priority patent/ZA200605257B/en
Priority to EP06253347A priority patent/EP1739225A2/en
Publication of US20070000628A1 publication Critical patent/US20070000628A1/en
Abandoned legal-status Critical Current

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Classifications

    • 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

Definitions

  • This application relates to the removal of non process elements from a Kraft bleach plant producing lyocell pulp. More particularly it relates to the removal of the non process elements from the bleach plant filtrate stream.
  • Transition metals are undesirable in lyocell pulp because they accelerate the degradation of cellulose and NMMO in the lyocell process resulting in a lower degree of depolymerization than desired in cellulose and degradation of the NMMO.
  • transition metals commonly found in pulp derived from trees and other sources include iron, copper, nickel and manganese.
  • the total level of copper, manganese and iron is less than 10 ppm.
  • Silica and calcium are also deleterious in that they interfere with spinning the fiber causing spinneret restrictions and fiber breakage. Silica levels of less than 50 ppm are desirable for lyocell pulp.
  • the above process cannot be used due to environmental restrictions.
  • all of the extracted wash water from the final stage of bleaching in a OD 1 E p D 2 sequence is used to wash the pulp in the first stage of bleaching.
  • the pH of the extracted wash water from the final bleach stage is reduced to approximately 3.1.
  • a large portion of the metals are washed off the pulp and are dissolved or suspended in the extracted filtrate.
  • the D 2 filtrate is used to wash the D 1 stage pulp, none of the D 2 filtrate is removed.
  • a large caustic dose is added to the D 1 pulp that leaves the D 1 washer.
  • the metals and silica removed from the D 2 washed pulp form complexes or are substantive to the pulp during the alternating acidic and alkaline conditions. These particles have a higher density than pulp and need to be removed to reduce the metals and other elements in the pulp.
  • an acidic bleach plant filtrate from a lyocell pulp bleach sequence is processed through a centrifugal cleaner.
  • Each of the non process elements may be reduced by at least 20% of their original levels in the bleach plant filtrate.
  • non process elements include, but are not limited to manganese, iron, copper, calcium and silica. Typical levels of these elements in the bleach plant filtrate are 3 to 9 ppm manganese, 80 to 170 ppm iron, 6 to 13 ppm copper, 3200 to 5500 ppm calcium and 190 to 370 ppm silica.
  • the manganese is reduced by at least 50 percent of the original level in the bleach plant filtrate.
  • manganese is reduced by at least 70 percent of the original level in bleach plant filtrate.
  • the acidic filtrate stream works best since the metal particles are liberated from the pulp fiber.
  • Silica particles tend to contain a significant concentration of transition metals which are removed with the silica.
  • silica may be removed by at least 50% of the original level in the bleach plant filtrate.
  • silica may removed by at least 70% of the original level in the bleach plant filtrate. Metal ions that are fully dissolved are not removed in the process.
  • Centrifugal cleaners suitable for removal of non process elements include forward and reverse centrifugal cleaners. These are available from Krebs, Tuscon, Ariz.; GL&V Sweden AB, Sweden; Noss, Darmstadt, Germany; Andritz, Alpharetta, Ga.; Kadant Black Clawson, Mason, Ohio and Metso Paper Norcross, Ga. Forward centrifugal cleaners can be used alone or in a series while reverse cleaners can be used with a single pass through the centrifugal cleaner cone.
  • the units can be positioned after any stage in the lyocell pulp bleach plant sequence and can process a filtrate stream in a bleach plant up to 5% solids content. In one embodiment the centrifugal cleaner is positioned after the last bleaching stage.
  • centrifugal cleaner is positioned after first bleach stage. In yet another embodiment the centrifugal cleaner is positioned after the second stage. Depending on the number of bleach stages, a centrifugal cleaner can be positioned after each stage. It is understood that either a single centrifugal cleaner or a series of centrifugal cleaners can be positioned after any bleach stage or stages.
  • Solids were measured as follows. A Whatman 47 mm glass microfiber filter (934-AH) was washed with distilled water and dried for at least one hour at 103° C.-105° C., weighed and inserted into the filtering apparatus, wetted to seat the filter medium and suction applied. One hundred ml. of the process stream was poured into filter apparatus with suction and washed successively with three 10 ml. volumes of distilled water. The filter was then dried for at least one hour at 105° C., weighed and the solids content calculated. Manganese was determined by EPA Method 6010C (SW-846) using inductively coupled plasma spectrometry.
  • the accept filtrate stream can be used to wash the pulp from any previous stage.
  • Rejects resulting from the centrifugal cleaner or centrifugal cleaners can go to the sewer or could be used in other areas of the pulp mill outside of the fiberline such as the power boiler sand/solids hopper sluice water, the log wash area or to control woodyard dust.
  • Wash filtrate from the second chlorine dioxide stage (D 2 ) of a lyocell pulp bleach sequence was processed through a Noss Radiclone AM80C centrifugal cleaner (Noss, Darmstadt, Germany) to remove non process elements from the filtrate stream before it was used to wash pulp from the first chlorine dioxide stage (D 1 ) in a OD 1 E p D 2 sequence.
  • D 2 filtrate was pumped through the Noss Radiclone centrifugal cleaner under the following conditions:
  • Wash filtrate from the second chlorine dioxide stage (D 2 ) of a lyocell pulp bleach sequence is processed through a Noss Radiclone AM80C centrifugal cleaner to remove non process elements from the filtrate stream before it is used to wash pulp from the first chlorine dioxide stage (D 1 ) in a OD 1 E p D 2 sequence.
  • D 2 filtrate is pumped through the Noss Radiclone centrifugal cleaner under the following conditions:
  • silica and other non process elements may be reduced by at least 20% of their original levels in the bleach plant filtrate.
  • Silica can be determined by ASTM D4517-04, copper, iron and calcium by EPA Method 6010C (SW-846).

Abstract

A method is disclosed for removal of non process elements from a Kraft bleach plant producing lyocell pulp. In the method the bleach plant filtrate is passed through at least one centrifugal cleaner. The non process elements are reduced by at least 20 percent of their original levels in the bleach plant filtrate.

Description

    FIELD
  • This application relates to the removal of non process elements from a Kraft bleach plant producing lyocell pulp. More particularly it relates to the removal of the non process elements from the bleach plant filtrate stream.
    • BACKGROUND
  • Transition metals are undesirable in lyocell pulp because they accelerate the degradation of cellulose and NMMO in the lyocell process resulting in a lower degree of depolymerization than desired in cellulose and degradation of the NMMO. Examples of transition metals commonly found in pulp derived from trees and other sources include iron, copper, nickel and manganese. For lyocell pulp manufacture it is desirable that the total level of copper, manganese and iron is less than 10 ppm. Silica and calcium are also deleterious in that they interfere with spinning the fiber causing spinneret restrictions and fiber breakage. Silica levels of less than 50 ppm are desirable for lyocell pulp.
  • Typically low metal levels in pulp are achieved in lyocell pulp by washing the pulp in the final stages of bleaching with fresh water. Many dissolving mills use ion-exchange water treatment for a portion of the make-up to the final bleach washer and/or dilution water used in the wet-end of a paper machine.
  • In some mills the above process cannot be used due to environmental restrictions. In some cases, all of the extracted wash water from the final stage of bleaching in a OD1EpD2 sequence is used to wash the pulp in the first stage of bleaching. In lyocell production, the pH of the extracted wash water from the final bleach stage is reduced to approximately 3.1. A large portion of the metals are washed off the pulp and are dissolved or suspended in the extracted filtrate. When the D2 filtrate is used to wash the D1 stage pulp, none of the D2 filtrate is removed. A large caustic dose is added to the D1 pulp that leaves the D1 washer. The metals and silica removed from the D2 washed pulp form complexes or are substantive to the pulp during the alternating acidic and alkaline conditions. These particles have a higher density than pulp and need to be removed to reduce the metals and other elements in the pulp.
    • DESCRIPTION
  • In one embodiment of the invention, an acidic bleach plant filtrate from a lyocell pulp bleach sequence is processed through a centrifugal cleaner. Each of the non process elements may be reduced by at least 20% of their original levels in the bleach plant filtrate. As defined herein, non process elements include, but are not limited to manganese, iron, copper, calcium and silica. Typical levels of these elements in the bleach plant filtrate are 3 to 9 ppm manganese, 80 to 170 ppm iron, 6 to 13 ppm copper, 3200 to 5500 ppm calcium and 190 to 370 ppm silica. In another embodiment the manganese is reduced by at least 50 percent of the original level in the bleach plant filtrate. In yet another embodiment manganese is reduced by at least 70 percent of the original level in bleach plant filtrate. The acidic filtrate stream works best since the metal particles are liberated from the pulp fiber. Silica particles tend to contain a significant concentration of transition metals which are removed with the silica. In one embodiment silica may be removed by at least 50% of the original level in the bleach plant filtrate. In another embodiment silica may removed by at least 70% of the original level in the bleach plant filtrate. Metal ions that are fully dissolved are not removed in the process. It may be possible to remove these by addition of chelating agents in the bleach plant or addition of polymeric cationic flocculants such as polymers of polyacrylamide or with anionic flocculants such as polyacrylic acid or ethylenediaminetetraacetic acid to the bleach plant filtrate stream before processing through the centrifugal cleaners.
  • Centrifugal cleaners suitable for removal of non process elements include forward and reverse centrifugal cleaners. These are available from Krebs, Tuscon, Ariz.; GL&V Sweden AB, Stockholm, Sweden; Noss, Darmstadt, Germany; Andritz, Alpharetta, Ga.; Kadant Black Clawson, Mason, Ohio and Metso Paper Norcross, Ga. Forward centrifugal cleaners can be used alone or in a series while reverse cleaners can be used with a single pass through the centrifugal cleaner cone. The units can be positioned after any stage in the lyocell pulp bleach plant sequence and can process a filtrate stream in a bleach plant up to 5% solids content. In one embodiment the centrifugal cleaner is positioned after the last bleaching stage. In another embodiment the centrifugal cleaner is positioned after first bleach stage. In yet another embodiment the centrifugal cleaner is positioned after the second stage. Depending on the number of bleach stages, a centrifugal cleaner can be positioned after each stage. It is understood that either a single centrifugal cleaner or a series of centrifugal cleaners can be positioned after any bleach stage or stages.
  • Removal of the non process element manganese through a Noss Radiclone centrifugal cleaner, (a forward cleaner), is shown in Table 1 below; the process conditions are shown in the working example.
    TABLE 1
    Manganese Removal In Each Process Stream.
    Mn
    Concen- Total Mn Mass
    Total Solid tration Volumetric Flow
    Process Concentration (ppm on Removal Flow Split Split
    Stream (%) solids) (%) (%) (%)
    Feed 0.0027 6.5 — n/a n/a
    Accept 0.0009 5.0 74  88 21
    Reject 0.009 6.9 26* 12 79

    *amount remaining with rejects
  • Solids were measured as follows. A Whatman 47 mm glass microfiber filter (934-AH) was washed with distilled water and dried for at least one hour at 103° C.-105° C., weighed and inserted into the filtering apparatus, wetted to seat the filter medium and suction applied. One hundred ml. of the process stream was poured into filter apparatus with suction and washed successively with three 10 ml. volumes of distilled water. The filter was then dried for at least one hour at 105° C., weighed and the solids content calculated. Manganese was determined by EPA Method 6010C (SW-846) using inductively coupled plasma spectrometry. The accept filtrate stream, the stream that results from passing the last bleach stage washing over drum washers and then through the centrifugal cleaner in the example, can be used to wash the pulp from any previous stage. Alternatively, there can be a series of centrifugal cleaners in which the resulting accept stream from the centrifugal cleaners can be processed and ultimately used to wash the pulp from any stage in the bleach sequence. Rejects resulting from the centrifugal cleaner or centrifugal cleaners can go to the sewer or could be used in other areas of the pulp mill outside of the fiberline such as the power boiler sand/solids hopper sluice water, the log wash area or to control woodyard dust.
    • WORKING EXAMPLE
  • Wash filtrate from the second chlorine dioxide stage (D2) of a lyocell pulp bleach sequence was processed through a Noss Radiclone AM80C centrifugal cleaner (Noss, Darmstadt, Germany) to remove non process elements from the filtrate stream before it was used to wash pulp from the first chlorine dioxide stage (D1) in a OD1EpD2 sequence. D2 filtrate was pumped through the Noss Radiclone centrifugal cleaner under the following conditions:
  • Feed Flow rate 94.6 l/min. (25 gpm); 172.37 kPa (25 psig); Temperature, 68.3° C., (155° F.)
  • Reject Flow rate—11.36 l/min., 3 gpm; 48.26 kPa (7 psig)
  • Accept Flow rate—83.28 l/min. (22 gpm); 82.73 kPa (12 psig)
  • 18.93 liters (five gallon sample) of the feed, accept and rejects streams were collected under the above conditions. The results of manganese removal are shown in Table 1 above.
    • EXAMPLE 1
  • Wash filtrate from the second chlorine dioxide stage (D2) of a lyocell pulp bleach sequence is processed through a Noss Radiclone AM80C centrifugal cleaner to remove non process elements from the filtrate stream before it is used to wash pulp from the first chlorine dioxide stage (D1) in a OD1EpD2 sequence. D2 filtrate is pumped through the Noss Radiclone centrifugal cleaner under the following conditions:
  • Feed Flow rate—94.6 l/min. (25 gpm); 172.37 kPa (25 psig); Temperature, 68.3° C., 155° F.
  • Reject Flow rate—11.36 l/min., (3 gpm); 48.26 kPa (7 psig)
  • Accept Flow rate—83.28 l/min. (22 gpm); 82.73 kPa (12 psig)
  • 18.93 liters (five gallon sample) of the feed, accept and rejects streams are collected under the above conditions. It is believed that silica and other non process elements (calcium, copper, iron) may be reduced by at least 20% of their original levels in the bleach plant filtrate. Silica can be determined by ASTM D4517-04, copper, iron and calcium by EPA Method 6010C (SW-846).
  • The embodiments of this invention, including the examples, are exemplary of numerous embodiments that may be made of this invention. It is contemplated that numerous other configurations of the process may be used and the equipment used in the process may be selected from numerous sources other than those specifically disclosed. In short, it is the applicant's intention that the scope of the patent issuing herefrom will be limited only by the scope of the appended claims.

Claims (17)

1. A method comprising the steps of:
providing a centrifugal cleaner,
providing an acidified bleach plant filtrate comprising non process elements,
passing said filtrate through said cleaner,
whereby each of said non process elements are reduced in the accept stream by at least 20% of their original levels in the bleach plant filtrate.
2. The method of claim 1 wherein said filtrate is a lyocell pulp bleach plant filtrate.
3. The method of claim 1 wherein the non process elements are selected from the group consisting of manganese, iron, copper, calcium and silica and mixtures thereof.
4. The method of claim 3 wherein the element is manganese.
5. The method of claim 3 wherein the element is iron.
6. The method of claim 3 wherein the element is copper.
7. The method of claim 3 wherein the element is silica.
8. The method of claim 3 wherein the element is calcium.
9. The method of claim 3 wherein manganese is reduced by at least 50% of the original level in the bleach plant filtrate.
10. The method of claim 3 wherein manganese is reduced by at least 70% of the original level in the bleach plant filtrate.
11. The method of claim 7 wherein the silica is reduced by at least 50% of the original level in the bleach plant filtrate.
12. The method of claim 7 wherein the silica is reduced by at least 70% of the original level in the bleach plant filtrate.
13. The method of claim 1 wherein the centrifugal cleaner is at least one forward cleaner.
14. The method of claim 1 where the centrifugal cleaner is a reverse cleaner.
15. The accept stream of claim 1 wherein said stream is circulated to the first bleach plant stage to wash the pulp.
16. The accept stream of claim 1 wherein said stream is circulated to any previous bleach plant stage to wash the pulp.
17. The accept stream of claim 1 wherein said stream is circulated to the last bleach plant stage to wash the pulp.
US11/171,013 2005-06-30 2005-06-30 Method for removal of metals from a bleach plant filtrate stream Abandoned US20070000628A1 (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US11/171,013 US20070000628A1 (en) 2005-06-30 2005-06-30 Method for removal of metals from a bleach plant filtrate stream
CA002548970A CA2548970A1 (en) 2005-06-30 2006-05-30 Method for removal of metals from a bleach plant filtrate system
ARP060102280A AR056374A1 (en) 2005-06-30 2006-06-01 METHOD FOR REMOVING METALS FROM A FILTER CURRENT OF A WHITENING PLANT
BRPI0603081-5A BRPI0603081A (en) 2005-06-30 2006-06-21 method for removing foreign elements from the process of a kraft bleaching plant
ZA200605257A ZA200605257B (en) 2005-06-30 2006-06-26 Methods for removal of metals from a bleach plant filtrate stream
EP06253347A EP1739225A2 (en) 2005-06-30 2006-06-27 Method for removal of metals from a bleach plant filtrate system

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US11/171,013 US20070000628A1 (en) 2005-06-30 2005-06-30 Method for removal of metals from a bleach plant filtrate stream

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EP (1) EP1739225A2 (en)
AR (1) AR056374A1 (en)
BR (1) BRPI0603081A (en)
CA (1) CA2548970A1 (en)
ZA (1) ZA200605257B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102556121A (en) * 2012-03-12 2012-07-11 大连华锐重工集团股份有限公司 Special wrong vehicle hooking detection device for open wagon

Citations (13)

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Publication number Priority date Publication date Assignee Title
US4188260A (en) * 1977-05-05 1980-02-12 Erco Envirotech Ltd. Low effluent pulp mill, bleach plant operation
US5302246A (en) * 1992-07-30 1994-04-12 Kamyr, Inc. Method of managing liquid steams in a pulp mill
US5360514A (en) * 1992-02-21 1994-11-01 Kamyr, Inc. Treatment of bleach plant filtrations using a magnesium filter
US5401362A (en) * 1993-03-24 1995-03-28 Kamyr, Inc. Control of metals and dissolved organics in the bleach plant
US5468396A (en) * 1994-03-16 1995-11-21 Pulp And Paper Research Institute Of Canada Centrifugal cleaning of pulp and paper process liquids
US5509999A (en) * 1993-03-24 1996-04-23 Kamyr, Inc. Treatment of bleach plant effluents
US5547543A (en) * 1992-07-30 1996-08-20 Ahlstrom Machinery Inc. Apparatus for minimizing effluent discharges and recovering chemicals in a pulp mill
US5639347A (en) * 1993-03-24 1997-06-17 Ahlstrom Machinery Inc. Method of controlling of metals in a bleach plant, using oxidation
US5792315A (en) * 1995-02-27 1998-08-11 Eka Chemicals Ab Purifying aqueous effluent from a pulp mill using electro chemical membrane device
US6024833A (en) * 1994-11-04 2000-02-15 Kvaerner Pulping Ab Process for removing metals and recovering a chelating agent from a bleach plant waste liquor
US6315862B1 (en) * 1992-07-07 2001-11-13 Kvaerner Pulping Technologies Process for bleaching pulp with adsorption of metals
US20020064654A1 (en) * 1996-08-23 2002-05-30 Weyerhaeuser Company Lyocell fibers produced from kraft pulp having low average degree of polymerization values
US20050051287A1 (en) * 2003-09-08 2005-03-10 Wade Chute Chemimechanical desilication of nonwood plant materials

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4188260A (en) * 1977-05-05 1980-02-12 Erco Envirotech Ltd. Low effluent pulp mill, bleach plant operation
US5360514A (en) * 1992-02-21 1994-11-01 Kamyr, Inc. Treatment of bleach plant filtrations using a magnesium filter
US6315862B1 (en) * 1992-07-07 2001-11-13 Kvaerner Pulping Technologies Process for bleaching pulp with adsorption of metals
US5547543A (en) * 1992-07-30 1996-08-20 Ahlstrom Machinery Inc. Apparatus for minimizing effluent discharges and recovering chemicals in a pulp mill
US5302246A (en) * 1992-07-30 1994-04-12 Kamyr, Inc. Method of managing liquid steams in a pulp mill
US5401362A (en) * 1993-03-24 1995-03-28 Kamyr, Inc. Control of metals and dissolved organics in the bleach plant
US5509999A (en) * 1993-03-24 1996-04-23 Kamyr, Inc. Treatment of bleach plant effluents
US5639347A (en) * 1993-03-24 1997-06-17 Ahlstrom Machinery Inc. Method of controlling of metals in a bleach plant, using oxidation
US5468396A (en) * 1994-03-16 1995-11-21 Pulp And Paper Research Institute Of Canada Centrifugal cleaning of pulp and paper process liquids
US6024833A (en) * 1994-11-04 2000-02-15 Kvaerner Pulping Ab Process for removing metals and recovering a chelating agent from a bleach plant waste liquor
US5792315A (en) * 1995-02-27 1998-08-11 Eka Chemicals Ab Purifying aqueous effluent from a pulp mill using electro chemical membrane device
US20020064654A1 (en) * 1996-08-23 2002-05-30 Weyerhaeuser Company Lyocell fibers produced from kraft pulp having low average degree of polymerization values
US20050051287A1 (en) * 2003-09-08 2005-03-10 Wade Chute Chemimechanical desilication of nonwood plant materials

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102556121A (en) * 2012-03-12 2012-07-11 大连华锐重工集团股份有限公司 Special wrong vehicle hooking detection device for open wagon

Also Published As

Publication number Publication date
EP1739225A2 (en) 2007-01-03
BRPI0603081A (en) 2007-03-06
CA2548970A1 (en) 2006-12-30
ZA200605257B (en) 2007-04-25
AR056374A1 (en) 2007-10-10

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