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
  • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
• • 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
  • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
• • 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
  • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
  • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone

Definitions

• the present invention relates to a process for chlorine-free bleaching of cellulose for the production of synthetic fibers with ozone according to a three-stage process, consisting of an oxygen bleach combined with a hydrogen peroxide bleach (EOP stage), an ozone bleach (Z stage) and a peroxide bleach ( P level).
• EOP stage hydrogen peroxide bleach
• Z stage ozone bleach
• P level peroxide bleach
• Example 24 which relates to Examples 10, 2 and 1), US Pat. No. 4,216,054.
• Douglas fir pulp is bleached with a relatively poor result (whiteness 74.6).
• CA-A 11 03 409 describes a bleaching process which uses three ozone stages in series and introduces the ozone-containing residual gas from the 3rd ozone bleaching stage into the 1st ozone bleaching stage in order to utilize the remaining ozone content.
• the residual gas generated in the 1st ozone bleaching stage is no longer used.
• This object is achieved according to the invention in a process of the type mentioned at the outset in that the residual oxygen content of the exhaust air from the Z stage is completely reacted in the EOP stage and that the waste water from the Z stage, the pH of which is preferably below 3 , is used for dilution between the EOP and Z stages and / or for ash removal from the pulp after bleaching.
• the kappa number of the pulp has to be reduced to such an extent that one single ozone stage is sufficient in the following. Do not bleach too much per ozone level, otherwise the quality of the pulp will suffer.
• the ozone requirement in the O stage (Z stage) is regulated by the temperature setting in the EOP stage so that the total amount of residual gas can be used in the EOP stage. Because of the low use of ozone, the temperature in the Z stage can be selected to be relatively high, so that the energy expenditure for cooling and reheating the pulp between the stages can be kept low.
• the activation via the temperature and the amount of NaOH in the EOP stage is chosen so that the total amount of residual gas from the O3 stage is reacted here.
• the EOP and the Z stage can be regarded as one unit from the chemical balance.
• the Z level can be an LC (low consistency) level, i.e. below 4 mass% ATS, or as MC (medium consistency) level, i.e. in a range of 5-20% by mass ATS, preferably 7-15% ATS, according to A 2494/89.
• the second option is of course particularly advantageous if the EOP stage and the P stage are also used as the MC stage, because then of course there is no need for dilution before the Z stage and sealing before the P stage to a much lesser extent.
• the temperature, the NaOH use and the O2 / H2O2 ratio in the EOP stage are controlled so that the oxygen consumption with constant conversion to the residual oxygen content of the exhaust air of the Z- Level is matched.
• the temperature of the EOP stage is 70-100.degree. C., preferably 75.degree. C.
• the NaOH concentration of the EOP stage is between 2.5-5% by mass, based on pulp, bleached dry and if there is at most as much H2O2 as O2, based on the mass, in the mixture O2 - H2O2 of the EOP stage
• the Z stage is operated with an O2 / O3 mixture with a maximum of 10% by mass O3 and the temperature of the Z stage is 40-70 ° C, preferably 50-60 ° C.
• the bleaching sequence EOP - Z - P begins with the introduction of the exhaust gas from the Z stage into a mixture of cellulose for the production of synthetic fibers NaOH and H2O2.
• the kappa value of the pulp for the production of synthetic fibers should be a maximum of 2.0, preferably 1.8-2.5.
• the P stage which follows the Z stage, is also adapted to the temperature of the preliminary stage, it runs between 60 - 70 ° C and requires less H2O2 than usual.
• the raw pulp with a consistency of 15% and a temperature of 75 ° C was mixed with sodium hydroxide in an amount of 33 kg / t cellulose bleached dry (corresponding to 366 l NaOH solution with 90 g / l) and 10.8 l of 50% H2O2 added and led to an MC pump (center consistency pump).
• MC pump center consistency pump
• On the pressure side of the MC pump 5.5 Nm3 of exhaust gas per ton of cellulose were bleached atroot the O3 stage, which were compressed to 7 bar, via a frit. With a share of approx. 95% O2 in the gas, this corresponds to an O2 addition of 7.5 kg O2 per t cellulose.
• the stock suspension was then treated in a "high-shear" MC mixer. Another 5.5 Nm3 of exhaust gas from the Z stage were fed into this mixer.
• This mixture was passed through a pre-reaction tube with a residence time of 3 min into an upward bleaching tower which allowed a reaction time of 2 h 45 min.
• the pulp was freed from the adhering liquor on two vacuum drum filters and a screw press.
• the filtrate of the screw press (3.3 m3 / t cellulose) was used in countercurrent with other 3.3 m3 fresh water via washing pipes on the filters for washing.
• the organic accompanying freight could thus be reduced to 3 kg OTS per t cellulose.
• the whiteness was 75.4%; the kappa number 1.89; the viscosity 24.0 mPas.
• the pulp was diluted to a consistency of 2% with return water from the vacuum drum filter after the Z stage and a pH of 3 was established with sulfuric acid.
• OZON bleaching plant of known design (Waagner-Biro)
• the oxygen suspension of 2% consistency was conveyed in a circuit via an injector.
• Step by step 1.45 g of OZONE per kg of pulp were introduced via this injector.
• the residence time in the reactor was 20 min, the temperature 51 ° C.
• the pulp was then washed again.
• the acidic filtrate was used to ash the pulp before the last filter.
• the pulp analysis values were: Whiteness 78.3; Kappa number 0.97; Viscosity 22.0.
• the 3rd stage is carried out with the addition of 4 kg NaOH / t pulp and 7 kg H2O2 (50%) at 65 ° C and 13% consistency with a residence time of 4 h.
• a continuous experimental apparatus for bleaching O3 was operated in the laboratory, O3-containing oxygen being introduced into a 2% pulp suspension via an injector.
• the exhaust gas was collected in a pressure vessel, compressed by pressing in water and used for the batch tests of the 1st bleaching stage (EOP) in a stirred laboratory autoclave.
• EOP 1st bleaching stage
• the 3rd bleaching stage (P) was also carried out batchwise.
• Pulp after the 1st bleaching stage of Example 1 was removed and further processed in the laboratory. (White content 75.4%, kappa number 1.89, viscosity 24.0 mPas) This was pressed to 20% consistency and diluted to 11% consistency with dilute sulfuric acid, so that the pH was 2.9.
• this pulp suspension was fluidized and compressed O3-containing oxygen gas was pressed.
• the mixing time was 15 s, the reaction time 180 s, the O3 pressure 5.1 bar, the temperature 50 ° C.
• the specific O3 use was 1.50 g O3 / kg cellulose bleached, the O3 consumption at 1.40 g.

Landscapes

• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Paper (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Artificial Filaments (AREA)
• Detergent Compositions (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Jellies, Jams, And Syrups (AREA)
• General Preparation And Processing Of Foods (AREA)
• Processing Of Solid Wastes (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=3485841

Family Applications (1)

Country Status (22)

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• 1990
  • 1990-02-07 AT AT0026190A patent/AT395028B/de not_active IP Right Cessation
  • 1990-12-20 EP EP90890348A patent/EP0441113B1/de not_active Expired - Lifetime
  • 1990-12-20 DE DE59007341T patent/DE59007341D1/de not_active Expired - Fee Related
  • 1990-12-20 DK DK90890348.7T patent/DK0441113T3/da not_active Application Discontinuation
  • 1990-12-20 AT AT90890348T patent/ATE112338T1/de not_active IP Right Cessation
  • 1990-12-20 ES ES90890348T patent/ES2061008T3/es not_active Expired - Lifetime
• 1991
  • 1991-01-28 IN IN85CA1991D patent/IN174833B/en unknown
  • 1991-02-05 CA CA002035698A patent/CA2035698C/en not_active Expired - Fee Related
  • 1991-02-05 ZA ZA91840A patent/ZA91840B/xx unknown
  • 1991-02-06 CZ CS91280A patent/CZ280077B6/cs unknown
  • 1991-02-06 RU SU914894510A patent/RU2040616C1/ru active
  • 1991-02-06 SK SK280-91A patent/SK278326B6/sk unknown
  • 1991-02-06 YU YU20691A patent/YU47388B/sh unknown
  • 1991-02-06 PL PL91288978A patent/PL169421B1/pl unknown
  • 1991-02-06 SI SI9110206A patent/SI9110206B/sl unknown
  • 1991-02-06 NO NO910455A patent/NO178079C/no unknown
  • 1991-02-07 JP JP3016575A patent/JPH04300380A/ja active Pending
  • 1991-02-07 BR BR919100516A patent/BR9100516A/pt not_active Application Discontinuation
  • 1991-02-07 US US07/652,027 patent/US5145557A/en not_active Expired - Lifetime
  • 1991-02-07 FI FI910601A patent/FI98077C/fi active IP Right Grant
• 1993
  • 1993-01-12 LV LVP-93-21A patent/LV10514B/lv unknown
  • 1993-03-23 HR HR930456A patent/HRP930456A2/hr not_active Application Discontinuation
  • 1993-07-02 LT LTIP753A patent/LT3392B/lt unknown

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