WO1996014465A1 - Evaporation du filtrat de blanchiment dans le systeme de refroidissement de gaz d'une installation de gazeification de liqueur noire - Google Patents

Evaporation du filtrat de blanchiment dans le systeme de refroidissement de gaz d'une installation de gazeification de liqueur noire Download PDF

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Publication number
WO1996014465A1
WO1996014465A1 PCT/SE1995/001105 SE9501105W WO9614465A1 WO 1996014465 A1 WO1996014465 A1 WO 1996014465A1 SE 9501105 W SE9501105 W SE 9501105W WO 9614465 A1 WO9614465 A1 WO 9614465A1
Authority
WO
WIPO (PCT)
Prior art keywords
bleaching
filtrate
plant
combustion
gas
Prior art date
Application number
PCT/SE1995/001105
Other languages
English (en)
Inventor
Lars Stigsson
Original Assignee
Kvaerner Pulping Ab
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Kvaerner Pulping Ab filed Critical Kvaerner Pulping Ab
Priority to AU38607/95A priority Critical patent/AU3860795A/en
Priority to BR9509567A priority patent/BR9509567A/pt
Priority to JP8515229A priority patent/JPH10513226A/ja
Priority to CA 2202494 priority patent/CA2202494A1/fr
Publication of WO1996014465A1 publication Critical patent/WO1996014465A1/fr
Priority to FI971866A priority patent/FI971866A/fi

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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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/10—Concentrating spent liquor by evaporation
    • D21C11/103—Evaporation by direct contact with gases, e.g. hot flue gases
    • 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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0021—Introduction of various effluents, e.g. waste waters, into the pulping, recovery and regeneration cycle (closed-cycle)
    • D21C11/0028—Effluents derived from the washing or bleaching plants
    • 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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/10—Concentrating spent liquor by evaporation
    • 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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/12—Combustion of pulp liquors

Definitions

  • the present invention relates to a method for evaporating bleaching effluents in association with the partial or complete combustion of cellulose spent liquors in a reactor.
  • bleaching pulp without using chlorine-containing chemicals permits process solutions which are of great interest.
  • the discharges of pollutants in bleaching effluents can be greatly reduced, especially by returning the bleaching filtrates in countercurrent to the recovery stage.
  • Bleaching without chlorine- containing chemicals is preferably carried out using various combinations of oxygen, hydrogen peroxide, peracetic acid and ozone. Developments within this field are currently taking place very rapidly, and pulp brightnesses close to, and above, 90% ISO have been reported for softwood kraft pulps .
  • Swedish Patent SE 469 387 describes various processes for carrying out TCF bleaching.
  • bleaching with peroxides is sensitive to the content of transition metals and alkaline earth metals in the pulp and the bleaching liquors.
  • an acidic ozone stage can wash out magnesium which it is important to retain for selective peroxide bleaching.
  • an ozone stage can mobilise transition metals, which metals can catalyse peroxide decomposition and carbohydrate breakdown in a subsequent peroxide bleaching stage. It is common practice to add complexing agents of the EDTA or DTPA type in association with the peroxide bleaching of chemical pulp.
  • the content of metals in the pulp can be decreased by means of an acidic wash, with or without complexing agents. Addition of the alkaline earth metals which are important for the bleaching result can be effected directly downstream of the acidic washing stage.
  • a commonly occurring alternative is to adjust the pH with an acid and add complexing agents in a washing stage prior to the peroxide stages.
  • EDTA and a pH of 6
  • most of the transition metals are chelated while the magnesium content is not affected.
  • Precipitating metals by means of adjusting the pH and filtering.
  • the pH adjustment can be carried out using alkali which is normally present in the pulp mill such as sodium hydroxide, green liquor, white liquor and/or calcium compounds.
  • alkali which is normally present in the pulp mill
  • the disadvantages of this method are the need to invest in a special filter and the difficulty in achieving a good filtration result.
  • the filtration of filtrates containing complexing agents may require new developments to take place in the filtration field. It is also doubtful whether the filtered liquid achieves the desired degree of purity.
  • the present invention relates to a novel method for converting bleaching filtrates into a pure liquid which can be reused, preferably in the bleaching plant.
  • the bleaching filtrate is supplied to the cooling system in a plant for gasifying and/or partially or completely combusting cellulose spent liquors, with the water content of the filtrate converting wholly or partially into steam.
  • the formed steam is subsequently cooled, after which thereby formed condensate is drawn off for direct or indirect return to the process water system of the pulp mill.
  • the principle of such a combustion plant, in which the method can be applied, is well known to the person skilled in the art and is described in more detail, for example, in US 4.808.264 and SE-C- 464 921.
  • the hot combustion gas which develops during the combustion is cooled rapidly by direct contact with an aqueous cooling liquid.
  • the cooling liquid can consist of water, condensate, green liquor or weak liquor, or combinations of these.
  • the cooling liquid could consist of filtrates from bleaching plants, something which has shown to be advantageous, inter alia with regard to the water balance and evaporation requirements of the modern mill.
  • the plant to which the bleaching filtrate or Q filtrate is supplied will be designated as a gasification plant, even though the invention also can be applied in conjunction with complete or overstoichiometric combustion of cellulose spent liquors, that is with a greater oxygen supply than that which is needed stoichiometrically for the combustion.
  • Figure 1 which shows a preferred embodiment of a gasification plant for applying the method according to the invention
  • FIG 2 which shows the integration of a gasification plant according to Figure 1 into a pulp mill.
  • Black liquor (17) is supplied to a pressure vessel containing a ceramically lined gasification reactor (1) .
  • the reactor is also provided with an inlet (not shown) for oxygen or oxygen-containing gas, and a burner.
  • the reactor includes a liquid bath or quench (2) for collecting green liquor which is formed when the mixture of gas and smelt, resulting from the gasification, from the respective reactor is cooled by direct contact with the aqueous " cooling liquid.
  • the cooling system of the gasification plant also consist of a venturi scrubber (3) with appurtenant liquid separator (4) and a gas treatment tower (5) .
  • bleaching filtrate (6) preferably from a chelating stage, is supplied to the cooling system, in this preferred case the quench (2) .
  • the cooling system in this preferred case the quench (2) .
  • water evaporates to generate steam, which steam is drawn off from the reactor and the quench together with the partially cooled combustion gas (7) .
  • the inorganic content in the remaining part of the filtrate liquid is mixed with the green liquor in the cooling system and is drawn off in the form of a liquid (16) .
  • Any organic compounds which are present in the filtrate liquid are likewise separated off together with drawn-off liquid (16) in the form of green liquor. In this way, a purification of the bleaching filtrate takes place, as a result of which undesirable compounds which have been separated off end up in the green liquor. The latter is then purified in a green-liquor filter.
  • the temperature of the combustion gas (7) which is drawn off from the reactor and the quench corresponds in the main to the boiling point of the drawn-off liquid (16) at the pressure prevailing in the system.
  • the combustion gas (7) is subjected to further washing in a venturi scrubber (3) and liquid (8) is then separated off in a liquid separator (4) .
  • This liquid which has been separated off is returned to the venturi scrubber. Due to the fact that a certain quantity of the liquid (9) is bled off from this recirculation and a corresponding quantity of purer liquid (10) is supplied, undesirable compounds do not become concentrated in the liquid.
  • the quantity of bleaching effluent filtrate which can be supplied to the cooling system of a gasification plant in this manner varies with the capacity of the plant, the gas flow, the gas composition, the gas pressure and the gas temperature at the outlet of the reactor prior to cooling, and also with the desired strength and composition of the drawn- off liquid.
  • the invention is elucidated in the following examples.
  • a plant for gasifying black liquor described in more detail in US 4.808.264, is supplied with 500 tons of black liquor, calculated as dry substance, per 24 h.
  • the smelt which is generated in the reactor has the following principal composition
  • the hot combustion gas is contacted by Q-stage filtrate from a TCF bleaching plant in a cooling device and dissolver, for example of the type which is described in more detail in SE-A-9001957.
  • the quantity of filtrate which is supplied to the system corresponds to 74 m 3 /hour.
  • the filtrate contains 1.6% dry substance in the form, inter alia, of undissolved organic substance, sodium compounds and transition metals such as manganese.
  • the pH of the filtrate can be adjusted to 6-8.
  • a green liquor flow of 48 m 3 /hour, having a concentration of 160 grams/litre (calculated as NaOH) is drawn off from the quench.
  • the temperature of the combustion gas drawn off from the reactor and the cooling system essentially corresponds to the boiling point of the drawn-off liquid at the pressure prevailing in the system, i.e. approximately 80-90°C in this example.
  • the gas is cooled down to about 40°C,
  • FIG. 2 shows how a gasification plant (22) which operates in accordance with the present method can be integrated with a fibre line, including bleaching plant (20) , and recovery boiler (21) together with dissolving tank (23), in a pulp mill.
  • black liquor (17) is apportioned between the recovery boiler and the gasification plant, both of which produce green liquor (16) .
  • Bleaching effluent (6) is also supplied to the gasification plant, which effluent, according to the invention, undergoes an evaporation. Condensate (12) from this evaporation is preferably returned to the bleaching plant (20) for use as washing liquid in the latter.
  • the partial oxidation, or alternatively the combustion, of the cellulose spent liquor can be carried out at temperatures of between 700-1200°C and at pressures of from 0.1 MPa to 10 MPa.
  • the Q filtrate can be added to any point in the cooling system.
  • the invention can be put into practice in conjunction with several variants of gasification and combustion of cellulose spent liquors.
  • the cellulose spent liquor per se can be a sulphite spent liquor, soda spent liquor or bleaching effluent liquor.
  • the stoichiometry during the oxidation in the reactor can vary from 0.3 to overstoichiometric combustion.
  • the steam partial pressure and energy content of the combustion gas can be utilized for evaporating a further quantity of filtrate, thereby achieving multi-stage economy in the evaporation. If a more dilute green liquor is acceptable (for example 75 g/1, calculated as NaOH) , a correspondingly larger quantity of Q filtrate can be supplied to the combustion plant.
  • the Q filtrate specified in the description is not limited to filtrate from chelating stages, and any bleaching filtrate whatsoever, or any other water- containing process stream, can be purified and evaporated by means of the present invention.
  • the present invention can be applied in mill systems using either TCF or ECF bleaching, but is especially applicable in conjunction with TCF bleaching - for example in association with bleaching plants having the following bleaching sequences: Q (OP) (ZQ) (PO) Q (OP) Pa (PO) Q (PO) Q Z P

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  • Paper (AREA)

Abstract

Procédé de récupération/purification d'effluents de blanchiment produits par une installation de blanchiment (20) de fibre de cellulose, selon lequel un filtrat de blanchiment (6) est acheminé vers un système de refroidissement de gaz associé à une installation (22) en vue de la combustion partielle ou surstoechiométrique de liqueurs de cellulose épuisées, la teneur en eau du filtrat étant intégralement ou partialement convertie en vapeur, ladite vapeur étant ensuite refroidie, après quoi le condensat (12) ainsi formé est évacué en vue de son retour direct ou indirect dans le système d'eau de traitement de la fabrique de pâte à papier.
PCT/SE1995/001105 1994-11-04 1995-09-29 Evaporation du filtrat de blanchiment dans le systeme de refroidissement de gaz d'une installation de gazeification de liqueur noire WO1996014465A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
AU38607/95A AU3860795A (en) 1994-11-04 1995-09-29 Evaporation of bleach filtrate in the gas cooling system of a plant for gasifying black liquor
BR9509567A BR9509567A (pt) 1994-11-04 1995-09-29 Processo para recuperação/purificação de efluentes do banqueamento procedente de uma planta de branqueamento para fibra de celulose
JP8515229A JPH10513226A (ja) 1994-11-04 1995-09-29 黒液ガス化プラントのガス冷却装置における漂白濾液の蒸発法
CA 2202494 CA2202494A1 (fr) 1994-11-04 1995-09-29 Evaporation du filtrat de blanchiment dans le systeme de refroidissement de gaz d'une installation de gazeification de liqueur noire
FI971866A FI971866A (fi) 1994-11-04 1997-04-30 Valkaisusuodatteen haihdutus mustalipeän kaasuuntamislaitoksen kaasujääähdytysjärjestelmässä

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9403780-1 1994-11-04
SE9403780A SE505249C2 (sv) 1994-11-04 1994-11-04 Återvinning av blekerifiltrat genom att filtratet används i ett gaskylsystem i en förgasningsanläggning

Publications (1)

Publication Number Publication Date
WO1996014465A1 true WO1996014465A1 (fr) 1996-05-17

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1995/001105 WO1996014465A1 (fr) 1994-11-04 1995-09-29 Evaporation du filtrat de blanchiment dans le systeme de refroidissement de gaz d'une installation de gazeification de liqueur noire

Country Status (6)

Country Link
JP (1) JPH10513226A (fr)
AU (1) AU3860795A (fr)
BR (1) BR9509567A (fr)
FI (1) FI971866A (fr)
SE (1) SE505249C2 (fr)
WO (1) WO1996014465A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018046482A1 (fr) * 2016-09-08 2018-03-15 Suncarbon Ab Procédé et système de traitement d'effluent de papeterie usagé

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3453174A (en) * 1965-01-25 1969-07-01 Hooker Chemical Corp Pulping and bleaching process wherein effluent liquor from alkaline extraction of bleached pulp is used to dissolve smelt
WO1991019042A1 (fr) * 1990-05-31 1991-12-12 Chemrec Aktiebolag Procede de preparation d'une solution aqueuse de composes de sodium
WO1993002249A1 (fr) * 1991-07-16 1993-02-04 Chemrec Aktiebolag Procede de recuperation de produits chimiques et d'energie a partir de bains epuises
EP0564443A1 (fr) * 1992-03-15 1993-10-06 Kamyr, Inc. Traitement d'éffluents de blanchiment

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3453174A (en) * 1965-01-25 1969-07-01 Hooker Chemical Corp Pulping and bleaching process wherein effluent liquor from alkaline extraction of bleached pulp is used to dissolve smelt
WO1991019042A1 (fr) * 1990-05-31 1991-12-12 Chemrec Aktiebolag Procede de preparation d'une solution aqueuse de composes de sodium
WO1993002249A1 (fr) * 1991-07-16 1993-02-04 Chemrec Aktiebolag Procede de recuperation de produits chimiques et d'energie a partir de bains epuises
EP0564443A1 (fr) * 1992-03-15 1993-10-06 Kamyr, Inc. Traitement d'éffluents de blanchiment

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018046482A1 (fr) * 2016-09-08 2018-03-15 Suncarbon Ab Procédé et système de traitement d'effluent de papeterie usagé

Also Published As

Publication number Publication date
FI971866A0 (fi) 1997-04-30
SE9403780D0 (sv) 1994-11-04
SE505249C2 (sv) 1997-07-21
AU3860795A (en) 1996-05-31
BR9509567A (pt) 1997-09-16
SE9403780L (sv) 1996-05-05
FI971866A (fi) 1997-04-30
JPH10513226A (ja) 1998-12-15

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