EP0920552A1 - Method for lowering the level of oxalic acid - Google Patents

Method for lowering the level of oxalic acid

Info

Publication number
EP0920552A1
EP0920552A1 EP97935959A EP97935959A EP0920552A1 EP 0920552 A1 EP0920552 A1 EP 0920552A1 EP 97935959 A EP97935959 A EP 97935959A EP 97935959 A EP97935959 A EP 97935959A EP 0920552 A1 EP0920552 A1 EP 0920552A1
Authority
EP
European Patent Office
Prior art keywords
oxalic acid
oxalate
enzyme
liquids
enzymes
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Withdrawn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
EP97935959A
Other languages
German (de)
English (en)
French (fr)
Inventor
Nils-Olov Nilvebrant
Anders Reimann
Filipe De Sousa
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.)
Svenska Traforskningsinstitutet
STFI Skogsindustrins Tekniska Forskningsinstitut AB
Original Assignee
Svenska Traforskningsinstitutet
STFI Skogsindustrins Tekniska Forskningsinstitut 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 Svenska Traforskningsinstitutet, STFI Skogsindustrins Tekniska Forskningsinstitut AB filed Critical Svenska Traforskningsinstitutet
Publication of EP0920552A1 publication Critical patent/EP0920552A1/en
Withdrawn legal-status Critical Current

Links

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
    • D21C9/008—Prevention of corrosion or formation of deposits on pulp-treating equipment
    • 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
    • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
    • D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes

Definitions

  • the present invention pertains to the lowering of the concentration of oxalic acid in process liquids in the production of pulp and paper.
  • the present invention concerns the lowering of the concentration of oxalic acid and in particular the prevention of the formation of calcium oxalate incrust and/or the degrading of precipitated calcium oxalate in the production of pulp and paper.
  • Oxalic acid is the smallest among the dicarboxylic acids, as it contains only two acid moieties, linked together. Oxalic acid dissociates in water according to the following:
  • the dissociation coefficient is temperature dependent. It decreases with increasing temperatures. Oxalic acid occurs abundantly in various plants, the most well known examples being rhubarb and spinach. Nevertheless it also occurs in significant amounts in wood, in concentrations in the range of about 0.1 to 0.4 kg/ton.
  • the bark may contain up to 10-fold higher concentrations and hardwood bark can contain even up to about 15 kg oxalic acid per ton. This underlines the importance of using thoroughly debarked wood for the production of pulp.
  • the main portion of the problem caused by oxalic acid is however related to its formation in the process, namely during pulping and bleaching. Examples of the underlying reactions will be given further in the description.
  • the calcium involved in the forming of calcium oxalate enters the process mainly as a component of the wood raw material. In trees most of the calcium is contained in the bark, but it is found also in the wood and in the foliage. Pine can contain about 0.3 to 0.5 kg/ton and contents of about 0.3 to 0.6 kg/ton are found for hardwood. The concentrations in the bark are, as for oxalic acid, again considerably higher.
  • Oxalic acid is shown to form in all bleaching steps that involve oxidative bleaching.
  • the source is thought to be aromatic ring structures with free phenolic hydroxy moieties, split in the decomposition of the lignin. This reaction seems to be most pronounced in bleaching with oxygen, hydrogen peroxide and ozone. In particular ozone bleaching seems to cause the formation of considerable amounts of oxalic acid. Oxalic acid formation is also observed in bleaching with chlorine dioxide and peracetic acid.
  • Another source of oxalic acid is though to be carbohydrates.
  • the decomposition of carbohydrates is, however, an unwanted effect.
  • xylane one of the polysaccharides joining the lignin and the cellulose in the wood, is though to be a major source of oxalic acid.
  • One intermediate compound formed in the decomposition of xylane is hexenuronic acid, which in turn is sensitive for bleach chemicals. degrades such structures to equimolar amounts of oxalic acid.
  • Calcium oxalate is a solid with very low solubility product in water (2.57 x 10-9 at 25°C and 1.78 x 10-9 at 18°C). Oxalic acid also forms salts with other metal ions than calcium, e. g. sodium, potassium and ammonium. These are, however, more soluble in water and do not cause problems to any greater extent in comparison with calcium oxalate, while other counter ions like barium and manganese yield salts with low solubility.
  • the solubility of calcium oxalate is temperature and pH dependent and accordingly precipitates are formed in places where the pH or temperature changes rapidly. Locations liable for precipitation are thus e g washing filters after acid bleaching, white water tanks and on filters and heat exchangers. Calcium oxalate scaling can naturally also form in other places, sometimes very locally, provided that the surrounding conditions favour precipitation. Also precipitation directly on the pulp occur.
  • changing the conditions governing the formation of incrusts includes the adjustment of pH, temperature and the addition of chemicals.
  • Said chemicals either form a complex with one of the ions involved or inhibit the crystal -growth of calcium oxalate.
  • the possibilities of manipulating the process parameters such as pH and temperature are restricted by process requirements and economical considerations.
  • COD chemical oxygen demand
  • oxalic acid decomposing enzymes The use of oxalic acid decomposing enzymes is known from medical applications, mainly for the determination of oxalate in urine samples. Problems caused by the presence
  • US 4 652 452 deals with this problem. According to US 4 652 452, the level of oxalic acid must be lowered to less than about 15 pp in finished beer to prevent "gushing", whereby beer gushes from the bottle when opened. The precipitate of calcium oxalate, formed when calcium is added to stabilize and activate amyiases during mashing, is also unwanted as the precipitating "beerstone” harbours contaminating microorganisms. US 4 652 452 consequently describes the introduction of oxalate decarboxylase (EC 4.1.1.2) during mashing and/or fermentation to avoid the production of beerstone.
  • oxalate decarboxylase EC 4.1.1.2
  • Figure 1 illustrates the enzymatic degradation of oxalic acid using different doses of oxalate decarboxylase and oxalate oxidase, respectively.
  • the present inventors have surprisingly shown, that the influence of an effective amount of an oxalic acid decomposing enzyme or mixture of such enzymes on at least one process fluid or flow of such fluid, solves the above problems.
  • the term "effective amount” refers to an amount that, under the given conditions, leads to a reduction of the amount of oxalic acid present in a liquid to a level below the level where oxalates can precipitate in any partial volume of said liquid under the given conditions.
  • condition refers to the conditions influencing both the activity of the oxalic acid decomposing enzyme and the formation of oxalate precipitates, i e temperature, pH, concentration of enzyme inhibitors, concentration of ions capable of forming sparingly soluble oxalate salts, other components reacting with the oxalic acid or oxalate, components influencing the crystal growth of the oxalates and the like.
  • process liquid refers to any stream or volume of process liquids in a plant for the production of pulp and/or paper where oxalate precipitation occurs.
  • process liquid naturally also includes any stream or volume, diverted or separated from the process, e.g. for complete or partial recirculation to the process.
  • the oxalic acid decomposing enzyme is preferably an enzyme or a mixture of enzymes which exhibits optimal activity under the conditions present in the process liquid, or at conditions to which the process liquid can be adjusted without undue cost or complication.
  • Said enzyme or mixture of enzymes can be extracted from natural sources or synthesized, for example using existing or genetically modified microorganisms expressing said enzyme or enzymes.
  • the microorganisms are modified, by selection or genetical engineering or a combination of both, to express an enzyme with suitable pH and temperature tolerance, in amounts making the production economically feasible.
  • Non-limiting examples of oxalic acid decomposing enzymes suitable for use in a method according to the present invention, are oxalate decarboxylase (EC 4.1.1.2) and oxalate oxidase (EC 1.2.3.4). A combination of the above enzymes can also be used.
  • the oxalic acid is efficiently decomposed to either carbon dioxide or formic acid or a combination of both. Any excess of CO 2 is then released in a gaseous form. However, if the process conditions are such, that the CO is trapped as carbonates and the risk of CaCO formation arises, the-choice of oxalate oxidase is preferred. Formic acid, being highly soluble in water, poses no problem.
  • Non-limiting examples of natural sources of oxalic acid decomposing enzymes are for example beet shots, beet roots, barley roots and/or seedlings, grain sorghum and
  • Microorganisms presently known to express suitable enzymes include fungi, such as Aspergillus, Myrothecium and Collybia, e g Collybia velutipes and selected bacteria, such as Pseudomonas sp OX-53.
  • Singular species known to produce suitable enzymes further include Postia placenta and Cariolus versicolor.
  • the fungi and bacteria listed above are only given as examples.
  • Presently microorganisms of the species Aspergillus are considered practically suitable for the production of the present enzymes but the scope of the present invention is not limited to the use of the named microorganisms. It is very possible that other enzyme producing microorganisms suitable for the present invention already exist or will be developed using mutation and selection or methods of genetical engineering. It is also likely, that the enzyme producing capabilities of an existing microorganism can be further enhanced through genetical engineering.
  • the oxalic acid decomposing enzyme is added in an effective amount under the given conditions, preferably in an amount in the interval of 1 to 10 000 U/l, wherein 1 U is a measure of enzyme activity, correspondning to the activity needed to decompose 1 mmol oxalic acid / min.
  • the enzyme is present in the process liquid in a stabilized form.
  • the enzyme can be stabilized according to conventional methods, known to a practitioner, skilled in the field of enzyme technol- ogy. Examples of methods of stabilization are, but not limited to, the following: chemical modification, cross-linkage (polymerization) of enzyme molecules, enzyme bonding to inert carriers, incorporation of enzymes within semi-permeable membranes, microencapsulation and the like.
  • the oxalic acid decompos- ing enzyme is added- to the process liquid in a stabilized but soluble form.
  • the enzyme is preferably combined with suitable additives or chemically modified to better tolerate the chemical and physical conditions in the process liquid.
  • the oxalic acid decomposing enzyme is encapsulated in microspheres and the process liquid or a diverted stream of process liquid is brought to pass in intimate contact with said microencapsulated enzyme.
  • the microencapsulated enzyme is preferably contained in a reactor or other suitable vessel, through which the process liquid or diverted stream thereof is brought to pass. Preferably the conditions in said vessel is adjusted to the
  • the environmental conditions during the enzymatic treatment are not critical for the scope of invention, but can of course be used to control the enzymatic reaction.
  • the environmental conditions of the enzymatic treatment are to a certain extent governed by the normal process parameters of the pulping and paper making processes. Simultaneously, the requirements of the enzyme or enzyme mixture have to be considered. A pH in the interval of 2 to 13 is possible, while an interval of 2.5 to 8 is preferable, depending on the enzymes used.
  • the temperature of the reaction mixture is of considerable importance as it affects the reaction rate of the enzymes. The reaction rate directly influences the time needed for the desired reaction to take place and thus the necessary storage volumes.
  • the temperature can be in an interval from about 5 - 95 °C, theoretically even higher e.g. about 100 °C, but preferably about 30 - 60 °C and most preferably about 30 - 45 °C.
  • highly thermotolerant enzymes which would enable the enzymatic treatment to be performed at considerably higher temperatures. It is possible that this would give rise to unexpected synergistic effects.
  • a skilled worker can, given the requirements of the enzymes in question, determine more exactly the optimum environmental conditions for application of the enzyme or enzyme mixture. The presence of heavy metals can also influence the en- zymatic activities and should therefore be avoided. A skilled worker with knowledge of both the manufacturing of paper and the usage of enzymes is able to adapt the process to accommodate the enzymatic treatment according to the present invention.
  • Example 1 Degradation of oxalic acid using oxalate oxidase
  • Oxalate oxidase from barley seedling was added to an aqueous solution containing 40 ppm oxalic acid, at pH 4 and 37 °C.
  • the amount oxalate oxidase added was 0.14 units per ⁇ tnol oxalic acid. Samples were taken after 5, 9 and 33 minutes, respectively. The results are presented in table 1.
  • oxalic acid present in an aqueous solution at pH 4 and 37 °C, was precipitated with calcium. Subsequently oxalate oxidase from barley seedlings was added, in an amount corresponding to 0.18 U per ⁇ mol oxalic acid. Samples were taken after 40, 90 and 140 minutes, respectively. The remaining calcium oxalate was determined as oxalic acid after dissolution of the salt with a strong cation exchanger (Amberlite IR-120 in proton-form). The results are presented in table 2.
  • oxalic decarboxylase from Aspergillus
  • 0.14, 0.45 and 0.21 U per ⁇ mol oxalic acid at pH 5 and 37 °C The results are presented in tables 3, 4 and 5.
  • the acids were separated by ion chromatography and oxalic acid was quantified using standard solutions, while the quantification of formic acid was relative.
  • the applicability of the enzymatic oxalic acid degradation according to the present invention was confirmed by a test on an authentic sample taken from a kraft pulp bleachery; the process water after an ozone stage (Z).
  • the sample initially contained 41 ppm oxalic acid. After less than 15 minutes at room temperature in the presence of 2 U oxalate decarboxylase, no oxalic acid remained.
EP97935959A 1996-08-20 1997-08-20 Method for lowering the level of oxalic acid Withdrawn EP0920552A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9603029A SE9603029D0 (sv) 1996-08-20 1996-08-20 Method for lowering the level of oxalic acid
SE9603029 1996-08-20
PCT/SE1997/001365 WO1998007922A1 (en) 1996-08-20 1997-08-20 Method for lowering the level of oxalic acid

Publications (1)

Publication Number Publication Date
EP0920552A1 true EP0920552A1 (en) 1999-06-09

Family

ID=20403605

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97935959A Withdrawn EP0920552A1 (en) 1996-08-20 1997-08-20 Method for lowering the level of oxalic acid

Country Status (3)

Country Link
EP (1) EP0920552A1 (sv)
SE (1) SE9603029D0 (sv)
WO (1) WO1998007922A1 (sv)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8486389B2 (en) 1997-05-23 2013-07-16 Oxthera, Inc. Compositions and methods for treating or preventing oxalate-related disease
SE518075C2 (sv) * 2000-12-07 2002-08-20 Stora Kopparbergs Bergslags Ab Sätt att avlägsna svårlösliga beläggningar
JP2005537037A (ja) * 2001-10-05 2005-12-08 イクシオン・バイオテクノロジー・インコーポレーテッド 流体の蓚酸塩濃度を減少させる物質および方法
AU2005339139A1 (en) 2005-12-14 2007-06-21 Oxthera, Inc. Pharmaceutical compositions and methods for treating or preventing oxalate-related disease
DE602006020347D1 (de) 2005-12-16 2011-04-07 Oxthera Inc Zusammensetzungen und verfahren zur oxalatreduktion

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE417114B (sv) * 1977-07-25 1981-02-23 Mo Och Domsjoe Ab Forfarande for forebyggande av inkrustbildning i cellulosafabriker
US5320757A (en) * 1993-04-05 1994-06-14 Betz Laboratories, Inc. Method of inhibiting calcium oxalate scale deposition
DE69428230T2 (de) * 1993-06-14 2002-06-27 Solutia Europ Nv Sa Verfahren zur Verhinderung von Oxalatablagerungen
US5554259A (en) * 1993-10-01 1996-09-10 Union Camp Patent Holdings, Inc. Reduction of salt scale precipitation by control of process stream Ph and salt concentration
SE504424C2 (sv) * 1994-11-04 1997-02-10 Kvaerner Pulping Tech Sätt att fälla ut övergångsmetaller och alkaliska jordartsmetaller ur blekeriavlutar genom att tillsätta alkalisk vätska

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9807922A1 *

Also Published As

Publication number Publication date
WO1998007922A1 (en) 1998-02-26
SE9603029D0 (sv) 1996-08-20

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