EP0876196A1 - Procede d'epuration d'un liquide pollue par des molecules filiformes - Google Patents

Procede d'epuration d'un liquide pollue par des molecules filiformes

Info

Publication number
EP0876196A1
EP0876196A1 EP96942225A EP96942225A EP0876196A1 EP 0876196 A1 EP0876196 A1 EP 0876196A1 EP 96942225 A EP96942225 A EP 96942225A EP 96942225 A EP96942225 A EP 96942225A EP 0876196 A1 EP0876196 A1 EP 0876196A1
Authority
EP
European Patent Office
Prior art keywords
nanofiltration
liquid
daltons
molecules
hemicellulose
Prior art date
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.)
Withdrawn
Application number
EP96942225A
Other languages
German (de)
English (en)
Inventor
René S. DANZIGER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CM CELFA AG
Original Assignee
Krebs and Co AG
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 Krebs and Co AG filed Critical Krebs and Co AG
Publication of EP0876196A1 publication Critical patent/EP0876196A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
    • C01D1/04—Hydroxides
    • C01D1/28—Purification; Separation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration

Definitions

  • the present invention relates to a method for cleaning a liquid contaminated with thread molecules according to the preamble of patent claim 1 and a device for carrying out the method according to the preamble of patent claim 7.
  • liquids for example sodium hydroxide solution
  • production steps are known in which liquids, for example sodium hydroxide solution, are used to carry out a reaction and which, after the reaction has taken place, are contaminated with dissolved substances. The contaminated liquids are then cleaned and returned to the production process for the reaction to be carried out again.
  • Such production plants are used, for example, by breweries, manufacturers of non-alcoholic beverages such as fruit juices, dairies, aluminum producers, manufacturers of various catalysts, but also by manufacturers and processors of cellulose and viscose.
  • Thread molecules are understood to mean those molecules whose geometric extension in one direction is at least a power of ten greater than the extension in the directions transverse to this main direction.
  • the term "technical hemicellulose” is understood according to K. Götze, "man-made fibers according to the viscose process", 3rd edition, page 120, generally those polysaccharides of the pulp which are soluble in sodium hydroxide solution, primarily in the dipping or mashing solution , and which are thus theoretically removed in the viscose process. From a chemical point of view, these are both degraded cellulose and degradation products of the native hemicelluloses, which arose during pulping in wood pulp production.
  • the first step is generally the mercerization, i.e. a lye treatment of the cellulose material with strong alkali solutions which generally contain more than 17% sodium hydroxide.
  • strong alkali solutions which generally contain more than 17% sodium hydroxide.
  • the majority of the hemicellulose and the breakdown products of the pulp are dissolved in the lye treatment.
  • a practiced solution for the recovery of the sodium hydroxide solution is the cleaning of the immersion solutions by dialysis. This process leads to high investment and maintenance costs.
  • the large amount of purified, highly diluted NaOH solution formed still has to be concentrated for its recycling, which is mainly done by evaporating water.
  • the hemicellulose is precipitated from the alkali liquor obtained in the preparation of the viscose, likewise using aliphatic alcohols.
  • the alkalizing liquor is first concentrated to a hemicellulose content of 90 to 140 g / l by ultrafiltration.
  • the liquid to be cleaned is passed through an anisotropic membrane, the working pressure being selected in a first step so that the hemicellulose forms a gel on the membrane surface.
  • the working pressure is then increased in order to compress the gel until the flow through the membrane has stabilized.
  • the working pressure is reduced to the value of the first step.
  • the working pressures used correspond to classic values of ultrafiltration.
  • the advantage of separation by means of membrane filtration is that no precipitants and no additional energy, such as is necessary for evaporation, for example, have to be added.
  • the membranes used in ultrafiltration have a sufficiently small separation limit for the macromolecules which occur in the manufacture of pulp and viscose, there has been a lack in practice that the membranes clog relatively quickly and also by means of backflushing, ie with a liquid flow in the opposite direction Direction of permeate flow, can hardly be cleaned. It is therefore an object of the invention to provide a method for removing dissolved hemicellulose from sodium hydroxide solution which prevents the membrane from clogging.
  • the process according to the invention is not only suitable for cleaning a stream of sodium hydroxide solution from hemicellulose dissolved therein, but can also be used for any liquids which are contaminated with substances in the form of thread molecules and with molecular weights of at least 10,000 Daltons.
  • nanofiltration for cleaning contaminated liquids, in particular lyes
  • Typical reverse osmosis membranes completely separate ingredients with a molecular weight above 100 daltons, while ultrafiltration membranes only retain molecules with a molecular weight above 100,000 daltons, typically above 10,000 daltons.
  • the retention capacity of the nanofiltration membranes lies between these values.
  • Nanofiltration is used primarily for solutions containing ions, whereas in nanofiltration, unlike reverse osmosis, monovalent anions can pass through the membrane.
  • Nanofiltration has proven itself in those areas in which substances have to be filtered which, owing to their molecular weight, cannot be separated from the liquid by means of ultrafiltration or microfiltration, but where reverse osmosis is not suitable due to its separation behavior due to the high osmotic pressure would. If possible, however, membranes and thus filtration processes with the greatest possible separation limit are always used in order to keep the excess pressure to be applied as low as possible on the feed side and to keep the permeate flow as large as possible.
  • EP-A-0'551'245 discloses a process for the filtration of soiled alkalis, which are obtained in food processing, by means of nanofiltration. In order to remove coarse impurities, a microfiltration is carried out beforehand. Nanofiltration per se serves to remove the particles remaining in the lye as well as the organic or polyphenolic compounds.
  • WO 95/27681 describes a process for cleaning an alkali by means of nanofiltration in order to recover hydroxides.
  • the substances retained on the feed side are organic compounds with a small molar mass of at least 150 daltons, in particular complexing agents such as EDTA (ethylenediaminetetraacetic acid ⁇ ) or NTA (nitrilotriacetic acid) with typical molecular weights of 200 to 400 Dalton.
  • complexing agents such as EDTA (ethylenediaminetetraacetic acid ⁇ ) or NTA (nitrilotriacetic acid) with typical molecular weights of 200 to 400 Dalton.
  • CHEMICAL ENGINEERING PROGRESS Vol. 90, No. 3, March 1994, New York, pages 68-74, lists various areas of application of nanofiltration, such as the demineralization of water, cleaning of groundwater and the removal of dyes in paper manufacture.
  • test liquids were cleaned by means of nanofiltration.
  • the test liquids consisted of water with sodium chloride, ammonium chloride, magnesium chloride, iron chloride, sucrose, vanillin, lignin sulfonate, dextran sulfate, potato starch and / or corn starch. Tests with thread molecules were not carried out.
  • the first result of the experiments is purely phenomenological. It was found that membranes, which are more permeable to a certain substance, of of this substance become clogged more quickly than impermeable membranes. Neither the molecular weight nor the structure of the molecules was taken into account. The second result was that polar substances do not clog the membranes, since the dissolved ions have the same electrical charge as the membrane and are therefore repelled.
  • the special geometry of the thread molecules means that in the case of membranes with large pores, such as, for example, an ultrafiltration membrane with a separation limit of 10,000 daltons, pore clogging takes place.
  • the molecules can penetrate the pores and, since these pores consist of angled channels, the molecules get stuck and clog the individual pores.
  • Such clogged pores cannot be cleaned with a backwash, since the pressure drop in these pores is greater than in the case of the still open pores.
  • the cleaning fluid will take the open pores as the preferred flow path.
  • the thread molecules cannot clog the pores of the membrane due to the much smaller separation limit.
  • nanofiltration processes which have a separation limit of less than 100,000 daltons, preferably less than or equal to 300 daltons.
  • the membranes used are preferably produced from alkali-resistant materials.
  • nanofiltration membranes are used in which the Donnan effect occurs.
  • This effect occurs according to the previously cited publication, University course membrane processes, Prof. Dr.-Ing. R. Rautenbach et al., Aachen 25-27. May 1994, when desalination of solutions containing mono- and polyvalent anions.
  • ion-containing solution in particular when removing hemicellulose from sodium hydroxide solution, and thus the Donnan effect does not occur, it has been shown that such membranes unexpectedly achieve better results than other nanofiltration membranes when removing thread molecules, in particular hemicellulose.
  • the method according to the invention essentially consists of the same method steps as US Pat. No. 4,270,914, the disclosure content of which is part of this description. Instead of ultrafiltration, however, nanofiltration is used.
  • a resulting contaminated alkali with 200 g NaOH / 1 contains 30 g hemicellulose / 1. This is in a filter with a
  • the hemicellulose content is reduced by a factor of 20 to approximately 1.5 g hemicellulose / 1 in the permeate.
  • the operating conditions are: pressure of 30 bar absolute on the feed side at a temperature between 40 and 50 ° C.
  • the permeate flow achieved is approximately 30 l / (m 2 -h).
  • the sodium hydroxide concentration in the permeate was 10% lower than in the feed. This phenomenon can be explained by the fact that the hemicellulose content in the retentate (concentrate) increases and the hemicellulose dissolves a certain proportion of the sodium hydroxide. These values were measured in a winding module.
  • the polymer membrane used has a "cut off "of 300 Daltons. When using this membrane for cleaning an aqueous solution which contains both mono- and polyvalent ions, the Donnan effect would occur.
  • the module was used a 5% sucrose solution tested sucrose has a molecular weight of 342 daltons.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Nanotechnology (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)

Abstract

Des liquides qui ont été pollués dans une installation de production par des molécules filiformes ayant des masses molaires d'au moins 10 000 daltons sont épurés par séparation par membrane, avant d'être renvoyés dans l'installation de production. Ces liquides peuvent par exemple être de la soude caustique polluée par de l'hémicellulose, comme il s'en produit dans le cadre de la préparation de cellulose et de viscose. Ce précédé de séparation par membrane se caractérise en ce qu'une nanofiltration est effectuée avec une limite de séparation inférieure à 1000 daltons.
EP96942225A 1995-12-23 1996-12-20 Procede d'epuration d'un liquide pollue par des molecules filiformes Withdrawn EP0876196A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
CH365595 1995-12-23
CH3655/95 1995-12-23
PCT/CH1996/000454 WO1997023279A1 (fr) 1995-12-23 1996-12-20 Procede d'epuration d'un liquide pollue par des molecules filiformes

Publications (1)

Publication Number Publication Date
EP0876196A1 true EP0876196A1 (fr) 1998-11-11

Family

ID=4260685

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96942225A Withdrawn EP0876196A1 (fr) 1995-12-23 1996-12-20 Procede d'epuration d'un liquide pollue par des molecules filiformes

Country Status (5)

Country Link
EP (1) EP0876196A1 (fr)
AU (1) AU1136697A (fr)
CA (1) CA2241193A1 (fr)
DE (1) DE19681150D2 (fr)
WO (1) WO1997023279A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000354742A (ja) * 1999-04-13 2000-12-26 Nitto Denko Corp スパイラル型分離膜エレメント
US6896810B2 (en) * 2002-08-02 2005-05-24 Rayonier Products And Financial Services Company Process for producing alkaline treated cellulosic fibers
AT413708B (de) * 2003-12-18 2006-05-15 Chemiefaser Lenzing Ag Verfahren zur reinigung von mit makromolekularen kohlehydraten und/oder deren abbauprodukten verunreinigten aggregaten
AT413548B (de) * 2004-06-02 2006-03-15 Chemiefaser Lenzing Ag Verfahren zur herstellung eines chemiezellstoffes und seine verwendung
US20070167618A1 (en) * 2006-01-13 2007-07-19 Celanese Acetate, Llc Manufacture of cellulose esters: recycle of caustic and/or acid from pre-treatment of pulp

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0251691A2 (fr) * 1986-06-24 1988-01-07 The Water Research Commission Traitement d'effluent

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3556992A (en) * 1969-07-22 1971-01-19 Amicon Corp Anisotropic ultrafiltration membrane having adhering coating and methods of forming and using this membrane
US4270914A (en) * 1979-10-26 1981-06-02 Borregaard Industries Limited Process for controlling hemicellulose concentration during the mercerization of cellulose
SE453840B (sv) * 1984-12-21 1988-03-07 Mo Och Domsjoe Ab Forfarande vid framstellning av cellulosamassa
EP0551245B1 (fr) * 1992-03-06 1996-09-11 Filtrox-Werk AG Procédé de filtration de lessives polluées et installation pour mettre en oeuvre ce procédé
IL109249A0 (en) * 1994-04-07 1994-07-31 Weizmann Kiryat Membrane Prod Process and system for purifying a contaminated caustic feed solution

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0251691A2 (fr) * 1986-06-24 1988-01-07 The Water Research Commission Traitement d'effluent

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
GART: "Römpp Chemie Lexicon, Band 4", 1991, THIEME VERLAG, STUTTGART *
GART: "Römpp Chemie Lexicon, Band 5", 1992, THIEME VERLAG, STUTTGART *
MULDER M.: "Basic Principles of Membrane Technology", 1990, KLUWER, DORDRECHT, NL *
See also references of WO9723279A1 *
ZAIDI A. ET AL: "Ultra- and Nano-Filtration in Advanced Effluent Treatment Schemes for Pollution Control in the Pulp and Paper Industry", WATER SCIENCE AND TECHNOLOGY, vol. 25, no. 10, 1992, pages 263 - 276, XP000600511 *

Also Published As

Publication number Publication date
WO1997023279A1 (fr) 1997-07-03
DE19681150D2 (de) 1999-08-12
AU1136697A (en) 1997-07-17
CA2241193A1 (fr) 1997-07-03

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