• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    lö ABSTRACT A continuous process for producing a chemical grade pulp,the process comprising the steps of: (a) steaminglignocellulosic material for a first period of time betweenl and 60 minutes; (b) after steaming, impregnating thesteamed lignocellulosic material in an impregnation vesselwith green liquor for a second period of time up to 5minutes and at a temperature between llO°C and l50°C; and(c) after impregnation, continuously cooking thelignocellulosic material in a digester to produce a chemical grade pulp.
    公开号:SE535028C2
    申请号:SE1050387
    申请日:2010-04-20
    公开日:2012-03-20
    发明作者:Namhee Shin
    申请人:Andritz Inc；
    IPC主号:
    专利说明:

    This invention generally relates to impregnatinglignocellulosic material and cooking the impregnatedlignocellulosic material in a continuous kraft pulping process.
    BACKGROUND OF THE INVENTION Previous proposals have been made to use black,green, and/or white liquor as an impregnation liquor duringthe treatment of lignocellulosic material, including, forexample, softwood and hardwood chips. See, e.g., U.S.Patent No. 5,674,359; U.S. Patent No. 3,520,773; U.S.Patent No. 1,691,511; EP 0 810 321 Bl; Svedman et al., TheUse of Green Liquor And Its Derivatives in Improving KraftPulping, Tappi Journal Vol. 81, No. 10, pp. 151-158 (Oct.1998); Ban et al., Low Capital, High Return Modificationsto Kraft Pulping Operations, Tappi 2001 Pulping Conference;Ban et al., The Relationship of Pretreatment PulpingParameters With Respect to Selectivity: Optimization ofGreen Liquor Pretreatment Conditions for Improved Kraft Pulping, Paperia ja Puu - Paper and Timber, Vol. 86, No. 2, pp. 102-108 (2004); Ban et al., Eundamental CorrelationsBetween Green Liquor (GL) Pretreatment and Pulp Qualities,2002 Tappi Fall Conference & Trade Fair; Ban et al., KraftGreen Liquor Pretreatment of Softwood Chips. Part II:Chemical Effect of Pulp Carbohydrates, Journal of Pulp andPaper Science, Vol. 29, No. 4, pp. ll4-ll9 (April 2003);Mao et al., Technical Evaluation of a Hardwood BiorefineryUsing the “Near-Neutral” Hemicellulose Pre-ExtractionProcess, 2007 AIChE Annual Meeting; Lucia et al., GreenLiquor Pretreatment of Chips Could Boost Kraft PulpingEfficiency, PaperAge, Nov/Dec 2002, pp. 24-26.
    Black liquor impregnation processes, for example,are described in U.S. Patent No. 5,l92,396 and U.S. PatentNo. 5,346,59l. Additionally, the importance of highsulfidity present in the black liquor and its use inimpregnation is described in U.S. Patent No. 5,660,686.
    While black liquor is known to be useful, its usemay involve some complications. One such complication maybe the change in pH that occurs resulting in theundesirable precipitation of lignin. Another is the merepresence of material in the black liquor that can bedetrimental to pulp quality and chemical consumption. It is known that the ratio of sodium sulfide to sodium hydroxide can be important to achieve a high sulfidityliquor.
    Previous proposals have also included the use ofgreen liquor as an impregnation medium. But theseproposals involve batch processes or require the use oflong impregnation times (e.g., much longer than 30minutes), which requires large and/or multiple vessels tomaintain a constant throughput in a commercial continuousprocess for making chemical grade pulp. These priorapproaches have drawbacks, e.g., relating to increased capital costs and maintenance costs.
    SUUMARY OF THE INVENTION It is an object of the present invention toimprove the overall cooking process.
    It is also an object of the present invention to improve the properties of the pulp produced by the process.
    It is an object of the present invention toimprove the kappa number of the pulp produced by theprocess.
    It is also an object of the present invention to decrease the number of side reactions in the process.
    It is a further object of the present inventionto reduce the number and/or amount of chemicals that areadded to the process.
    It has now surprisingly been found that the useof green liquor for a short period of time as animpregnation liquor is advantageous. Green liquor has theadvantages of containing the beneficial sulfur compoundspresent in the black liquor without the presence of other,not desirable solid compounds. Furthermore, the ratio ofsodium sulfide to sodium hydroxide may be high. Withoutbeing limited to any specific mechanism, it is alsocontemplated that the short contact time may allow for astable pH condition to exist during impregnation andthereby decrease the possibility of lignin precipitationfrom acid soluble lignin.
    For these and other objects that are evident fromthe specification, there is according to one aspectprovided a continuous process for producing a chemicalgrade pulp, the process comprising the steps of: (a)steaming lignocellulosic material for a first period oftime between l and 60 minutes; (b) after steaming,impregnating the steamed lignocellulosic material in an impregnation vessel with green liquor for a second period of time up to 5 minutes and at a temperature between llO°Cand l50°C; and (c) after impregnation, continuously cookingthe lignocellulosic material in a digester to produce achemical grade pulp.
    In a preferred embodiment, the lignocellulosicmaterial comprises wood chips.
    In one preferred embodiment, step (a) occurs inthe presence of water vapor and in the absence of whiteliquor, green liquor, and black liquor.
    In a preferred embodiment, the first period oftime lasts approximately 15 minutes.
    In one preferred embodiment, step (a) occurs at apressure up to lO bar, such as at atmospheric pressure.
    In a preferred embodiment, step (b) occurs for aperiod of time of up to 2 minutes, such as up to l minute.
    In one preferred embodiment, step (b) occurs at apressure up to lO bar, such as up to 6 bar.
    In a preferred embodiment, the process is furthercomprising the step of removing free green liquor between step (b) and step (c).
    BRIEF DESCRIPTION OF THE DRAWING Figure l is a schematic representation of a two vessel digester system with impregnation.
    DETAILED DESCRIPTION OF THE INVENTION The terms “black liquor,” “white liquor,” and“green liquor” as used in accordance with their commonlyunderstood meanings in the pulping and papermaking art.For example, black liquor may generally refer to the liquorextracted during or the post-cooking, residual liquor;white liquor may generally refer to a mixture of sodiumhydroxide and sodium hydrosulfide; and green liquor maygenerally refer to the dissolved inorganic smelt from therecovery boiler. Green liquor may include, for example,sodium sulfide, sodium carbonate, and sodium hydroxide.
    Lignocellulosic material used in this process maygenerally be wood chips of either softwood or hardwoodvarieties or mixtures thereof. It is also possible to useother cellulosic materials such as straw, begasse, etc.
    Figure l schematically illustrates a continuousprocess involving a two vessel system with green liquorimpregnation in an impregnation vessel and cooking in a digester. As exemplified, the system may include a high pressure feeder 10 or other pressurizing device such as apump (or hydrostatic pressure) to raise the pressure of theslurry of lignocellulosic material that feeds animpregnation vessel 11, a high pressure inlet line 12leading to the top 13 of the impregnation vessel 11, and areturn line 17 passing from behind screens at the top ofthe impregnation vessel 11 to the high pressure feeder 10or other location in the feed system.
    Pre-steamed lignocellulosic material (e.g.,lignocellulosic material steamed at atmospheric pressure)may be fed to high pressure feeder 10 or other pressurizingdevice. Alternatively, lignocellulosic material may besteamed at high pressure after transfer from the highpressure feeder 10 or other pressurizing device beforeentering impregnation vessel 11 (or even in an initialstage of impregnation vessel 11). The steaming may occurat any pressure as well as possibly at super-heatedconditions.
    Green, white, and/or black liquor may be added tothe line 17 to cause impregnation, as well as to variousrecirculation lines and systems associated with thedigester 30, which may be any digester suitable for cooking lignocellulosic material with liquor. The slurry (lignocellulosic material and liquor) is fed via line 29 tothe top of the digester 30, and from in back of the screensat the top of the digester 30 liquid is removed in line 3l,being heated by heaters 32.
    The digester 30 may be any type of conventionalor unconventional digester, regardless of whether hydraulicor vapor phase. The impregnation vessel ll, furthermore,may comprise one or more impregnation zones, e.g., twodifferent zones with first a lower temperature zone andthen a higher temperature zone, and possibly with adifferent level of effective alkali in each of the zones.Furthermore, each of the two or more impregnation zones mayinvolve differing concentrations of green liquor, whiteliquor, and/or black liquor.
    In the impregnation process, alkali diffuses intothe fiberwall. This opens up the wood structure andperhaps partially dissolves a portion of the wood duringpretreatment. This impregnation may last for a shortperiod (e.g., l minute) or a long period (e.g., up toseveral hours). The impregnation temperature is aboutllO°C-l50°C, more preferably at about l20°C.
    In the impregnation vessel ll, the impregnation zone(s) can be co-current and/or countercurrent (in any combination or permutation). Although illustrated as aseparate impregnation vessel, understood that under somecircumstances impregnation may be on top of the digester30. Again the digester 30 may be any suitable type used inthe pulp and paper industry.
    In an embodiment, there is a continuous process using green liquor to produce a pulp. This process mayrequire fewer chemicals compared to extant processes. Theprocess may generally include these steps: (a) steaming lignocellulosic material; (b) after steaming, impregnatingthe steamed lignocellulosic material with green liquor inan impregnation vessel; and (c) after impregnation,continuously cooking the lignocellulosic material underconventional conditions, possibly with the addition ofwhite liquor, to produce a chemical grade pulp.
    In some embodiments, it may be possible to havetwo or more further impregnation steps involving greenliquor, white liquor, and/or black liquor prior tocontinuously cooking the lignocellulosic material.Preferably, the green liquor is drained and the impregnatedlignocellulosic material is sent immediately to thedigester for cooking with liquor (e.g., white liquor) without further impregnation step(s). lO In step (a), the lignocellulosic material - suchas, for example, softwood or hardwood chips - are steamed(e.g., at a temperature of lOO°C at l bar) for a period ofl-60 minutes (and preferable about l5 minutes) with watervapor in the absence of any added chemicals (e.g., in theabsence of white liquor, black liquor, or green liquor).Other temperatures and pressures (e.g., 6 bar or lO bar)may be suitable for the steaming step.
    In step (b), the impregnation occurs for a periodof time up to 5 minutes (e.g., l minute, 2 minutes, 5minutes, l-5 minutes, l-2 minutes or 2-5 minutes) at highpressures (e.g., 6 bar or lO bar). The impregnation mayoccur at a temperature of about llO°C-l50°C, morepreferably at about l20°C. After the desired contact time,the free green liquor may be removed prior to step (c).
    Using the process described above, applicantbelieves that a good transfer of sulfidity into thelignocellulosic material from the green liquor might beachieved at the very early stage of treatment, and thiscould manifest itself in great benefits to the overallcooking process. It is known that sulfidity transfer at anearly stage of the process contributes to improve properties of the pulp produced compared to sulfidity ll transfer at later stages of the process. See, e.g., U.S.Patent No. 5,660,686 to Henricson et al.
    From tests using the described process (as wellas a comparative example conducted at 90-lOO°C) it wasfound that at an impregnation temperature of about l20°Cand between 2 and 5 minutes of contact time, the kappanumber may be positively impacted by 2 Kappa units. It isbelieved that pressure was not a significant factor,meaning when impregnation with green liquor occurred at thesame temperature, but different pressures, there may be noadvantage achieved through varying the pressure.
    While at the impregnation temperature, the effectof contact time was explored. Green liquor was allowed tocontact the lignocellulosic material for three specificperiods of time: l minute, 2 minutes and 5 minutes. Whilethere was a difference in the Kappa number when contactoccurred for l minute versus 2 minutes (2 minutes beginbeing more favorable), there was no significant differencein the Kappa number when contact occurred for 5 minutesversus 2 minutes. These contact time tests may indicatethe green liquor rapidly penetrates the wall of thelignocellulosic material to fill the void space in the lignocellulosic material wall. 12 This short contact time can be significant,because it may allow for a stable pH condition to existduring impregnation. The short green liquor contact timeresults in a minimum change in the pH of thelignocellulosic material and green liquor mix before thegreen liquor may be withdrawn and replaced with whiteliquor. The relatively stable pH environment may result ina decreased possibility of lignin precipitation from acidsoluble lignin. Decreased lignin precipitation may causefewer side reactions, such as condensation of lignin.
    The benefit of the short duration green liquorimpregnation as described above may also include areduction (e.g., of up 40%) in the consumption of EffectiveAlkali (EA) charge to the cooking process. For example, toachieve a Kappa number 16 in the process without greencharge may require an 18% (EA). Using the described greenliquor impregnation process a Kappa number of 16 mayrequire a 10% EA change. This significant reduction in thequantity of EA can reduce the size of the causticizingplant as well as reduce the size of the lime kilnfacilities. Reduction in these facilities (as well as theobvious reduction in impregnation vessel size) may cause a reduction in the overall energy consumed in the mill as l3 well as a reduction in the pollutants such as carbondioxide.
    While the invention has been described inconnection with what is presently considered to be the mostpractical and preferred embodiment, it is to be understoodthat the invention is not to be limited to the disclosedembodiment, but on the contrary, is intended to covervarious modifications and equivalent arrangements included within the spirit and scope of the appended claims.
    权利要求:
    Claims (11)
    [1] 1. l. A continuous process for producing a chemical gradepulp, the process comprising the steps of: (a) steaming lignocellulosic material for a firstperiod of time between l and 60 minutes; (b) after steaming, impregnating the steamedlignocellulosic material in an impregnation vessel withgreen liquor for a second period of time up to 5 minutesand at a temperature between llO°C and l50°C; and (c) after impregnation, continuously cooking thelignocellulosic material in a digester to produce a chemical grade pulp.
    [2] 2. The continuous process of claim l, wherein the lignocellulosic material comprises wood chips.
    [3] 3. The continuous process of any preceding claim, whereinstep (a) occurs in the presence of water vapor and in the absence of white liquor, green liquor, and black liquor.
    [4] 4. The continuous process of any preceding claim, wherein the first period of time lasts approximately 15 minutes.
    [5] 5. The continuous process of any preceding claim, wherein step (a) occurs at a pressure up to 10 bar.
    [6] 6. The continuous process of c1aim 5, wherein step (a) occurs at atmospheric pressure.
    [7] 7. The continuous process of any preceding claim, wherein step (b) occurs for a period of time of up to 2 minutes.
    [8] 8. The continuous process of c1aim 7, wherein step (b) occurs for a period of time of up to 1 minute.
    [9] 9. The continuous process of any preceding claim, wherein step (b) occurs at a pressure up to 10 bar.
    [10] 10. The continuous process of c1aim 9, wherein step (b) occurs at a pressure up to 6 bar.
    [11] 11. The continuous process of any preceding claim, furthercomprising the step of removing free green liquor between step (b) and step (c).
    类似技术:
    公开号 | 公开日 | 专利标题
    US5676795A|1997-10-14|Process for the production of viscose pulp
    US5779856A|1998-07-14|Cooking cellulose material using high alkali concentrations and/or high pH near the end of the cook
    US6245196B1|2001-06-12|Method and apparatus for pulp yield enhancement
    CA1043515A|1978-12-05|Method for controlling batch alkaline pulp digestion in combination with continuous alkaline oxygen delignification
    US20070256801A1|2007-11-08|Alkaline Process and System for Producing Pulp
    FI127582B|2018-09-14|Method for extracting lignin
    WO2012158075A1|2012-11-22|Compact process for producing prehydrolyzed pulp
    EP2286022A1|2011-02-23|Prehydrolysis sulfate cooking process
    Brännvall2009|Pulping technology
    SE535028C2|2012-03-20|Pre-treatment of lignocellulosic material with green liquor
    US20040089431A1|2004-05-13|Method for alkaline batch cooking of fiber material
    JP2900091B2|1999-06-02|Kraft pulp manufacturing method
    US20210040688A1|2021-02-11|Method of producing dissolving pulp
    US3738908A|1973-06-12|Prehydrolysis and digestion of bagasse fibers
    US3832278A|1974-08-27|Prehydrolysis and digestion of bagasse fibers
    CN100406646C|2008-07-30|Prepared high hardness pulp using grass kind plant as raw material and preparation method thereof
    US1977879A|1934-10-23|Process of manufacturing sulphite pulp
    CA2189899C|2002-07-16|Cooking cellulose material using high alkali concentrations and/or high ph near the end of the cook
    US1801782A|1931-04-21|Process for the manufacture of high-alpha-cellulose fiber
    JP3064607B2|2000-07-12|Modified Kraft Pulp Production Method
    Elhelece2018|10596 Rice Straw as a Raw Material for Pulp and Paper Production
    US20040089430A1|2004-05-13|Method for alkaline cooking of fiber material
    SU1131943A1|1984-12-30|Method of producing sulfate pulp for making packaging paper and board
    SU1587094A1|1990-08-23|Pulp manufacturing method
    SU779471A1|1980-11-15|Pulp production method
    同族专利:
    公开号 | 公开日
    CN101871176A|2010-10-27|
    SE1050387A1|2010-10-22|
    CA2698163A1|2010-10-21|
    US20100263813A1|2010-10-21|
    JP2010255171A|2010-11-11|
    CL2010000390A1|2011-04-08|
    RU2010115741A|2011-10-27|
    BRPI1001050A2|2011-03-22|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US1631511A|1927-06-07|Baymond c |
    US3520773A|1968-05-17|1970-07-14|Mac Millan Bloedel Ltd|Alkaline pulping processes with chemical pretreatment|
    US5192369A|1986-11-20|1993-03-09|British Technology Group Ltd.|Apparatus for spraying harvested crops|
    US5213662A|1991-08-14|1993-05-25|Kamyr, Inc.|Treatment of chips with high temperature black liquor to reduce black liquor viscosity|
    JPH05321181A|1992-05-25|1993-12-07|New Oji Paper Co Ltd|Production of pulp from dismounted material|
    SE9301161L|1993-04-07|1994-10-08|Sunds Defibrator Ind Ab|Process for treating process water|
    US5660686A|1994-09-02|1997-08-26|Ahlstrom Machinery Inc.|Cooking with spent liquor pretreatment of cellulose material|
    US5674359A|1995-02-08|1997-10-07|Ahlstrom Machinery Inc.|Continuous cooking of cellulosic fibrous material with cold alkali impregnation|
    US5736006A|1996-10-10|1998-04-07|Ahlstrom Machinery Inc.|Method and apparatus for pulping with controlled heating to improve delignification and pulp strength|
    JPH11286883A|1998-03-31|1999-10-19|Mitsubishi Paper Mills Ltd|Production of kraft pulp|
    SE525065C2|2003-04-17|2004-11-23|Kvaerner Pulping Tech|Pre-treatment of chips with acidic liquid during steaming|
    FI120547B|2004-10-04|2009-11-30|Metso Paper Inc|Alkaline cooking process and pulp making plant|
    FI126694B|2005-12-02|2017-04-13|Metsä Board Oyj|Chemical-mechanical pulp and process for producing chemical-mechanical pulp|
    AU2007253774C1|2006-05-19|2012-03-22|The Research Foundation Of State University Of New York|Methods for carbonate pretreatment and pulping of cellulosic material|
    US20090038767A1|2007-08-07|2009-02-12|Andritz Inc.|Method and System for Semi-Chemical Pulping|CN110305683A|2019-05-14|2019-10-08|潘广国|A kind of sawdust deep processing production new cleaning fuel and preparation method|
    法律状态:
    2015-12-15| NUG| Patent has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    US17110909P| true| 2009-04-21|2009-04-21|
    US12/720,967|US20100263813A1|2009-04-21|2010-03-10|Green liquor pretreatment of lignocellulosic material|
    [返回顶部]