EP1816259A1 - Verwendung von Kohlendioxid zur Optimierung des pH-Werts im nassen Teil der Papiermachine - Google Patents

Verwendung von Kohlendioxid zur Optimierung des pH-Werts im nassen Teil der Papiermachine Download PDF

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Publication number
EP1816259A1
EP1816259A1 EP06300114A EP06300114A EP1816259A1 EP 1816259 A1 EP1816259 A1 EP 1816259A1 EP 06300114 A EP06300114 A EP 06300114A EP 06300114 A EP06300114 A EP 06300114A EP 1816259 A1 EP1816259 A1 EP 1816259A1
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EP
European Patent Office
Prior art keywords
carbon dioxide
paper
index
water
saturation
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Withdrawn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
EP06300114A
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English (en)
French (fr)
Inventor
Vincent Boisdon
Michel Epiney
Meenakshi Sundaram
Arnaldo Araújo
Michel Muguet
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.)
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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 Air Liquide SA, LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Priority to EP06300114A priority Critical patent/EP1816259A1/de
Publication of EP1816259A1 publication Critical patent/EP1816259A1/de
Withdrawn legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/64—Alkaline compounds
    • 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
    • D21C9/001—Modification of pulp properties
    • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
    • D21C9/004—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives inorganic compounds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
    • D21H17/675—Oxides, hydroxides or carbonates
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/70—Inorganic compounds forming new compounds in situ, e.g. within the pulp or paper, by chemical reaction with other substances added separately

Definitions

  • the present invention relates to the use of carbon dioxide to control the calc-carbon properties of water during the formation of a paper sheet in the paper machine, it relates more particularly to a method of controlling the pH of the flow of cellulose pulp for the manufacture of a paper product entering the paper machine, in which method carbon dioxide is introduced into at least one aqueous vehicle circulating in the circuit of the machine head.
  • the papermaking process comprises two successive and separate parts.
  • the first part is the manufacture of the dough itself.
  • the paper pulp is made from various fibrous materials containing cellulose (wood and / or vegetable), using chemical agents and / or mechanical processes.
  • the second part of the papermaking process is the manufacture of the paper itself, from the pulp.
  • the term "paper” means a paper product, including, but not limited to, paper for printing and writing, wrapping paper, paper for sanitary and household purposes, various varieties of specialty paper, as well as cartons and other products. .
  • the starting material of papermaking (second part of the papermaking process) is paper pulp, i.e. a suspension of fibers in water.
  • the fibers are dispersed in water and then worked to obtain the desired properties for the final product.
  • the fibers will have to be refined, entangled and dried. During drying, the fibers have the property of adhering naturally to each other.
  • non-fibrous materials such as fillers, dyes, starches and other auxiliary products are added to the fibers.
  • Their incorporation is either by direct addition within the fiber suspension, or by deposition on the surface of the paper. The purpose of this incorporation is to give the final product particular properties that are specific to its use.
  • pulp When pulp is obtained from raw materials, such as wood and various plants - this paste is usually called "virgin pulp” - it can be of chemical, mechanical, chemical-mechanical, chemical-thermo-mechanical or other type ..., depending on the nature of the plants and the mechanical and / or chemical means used to obtain it.
  • the dough has the characteristics associated with the manufacturing processes (pH, presence of additives ).
  • the virgin pulp can be produced at the papermaking site (it is then referred to as an integrated plant), it is then in the form of a suspension consisting essentially of cellulosic fibers in water, at a concentration of the order from 1 to 45% by weight.
  • the paper mill does not manufacture the dough, or if it is stored intermediate, it may be in the form of bales with a dryness of about 90%.
  • the first step in papermaking will then be to suspend the cellulose fibers in the water.
  • This operation aims to obtain individual fibers, it is facilitated by the affinity of the fiber for water, affinity due to the numerous hydroxyl (OH) groups on the fiber.
  • the pulp used for making the paper may also be recycled pulp.
  • it can come from the recycling of waste paper, which may have undergone different types of treatment: pulper trituration, purification, de-inking, bleaching, as well as other complementary treatments that depend on the end use of the paper.
  • Paper pulp used in the paper industry is primarily derived from one of two types of pulp, or a mixture of both, which may include different types of virgin pulp and different types of recycled pulp.
  • the term paste used in the rest of the document means a pasta mixture comprising 0 to 100% virgin pulp and 0 to 100% recycled pulp.
  • the formation of the paper sheet takes place by depositing the fibers contained in the paste on a canvas or on the felts of the paper machine. Free water is removed from the dough suspension as it drips through the fabric or felts.
  • the processes for making paper in a neutral medium require a pH of between 6.5 and 8 to obtain effective removal (also called drainage) of the water contained in the sheet, effective, as well as to obtain a satisfactory whiteness of the paper and optimize the effectiveness of the reagents.
  • wet end waters means the aqueous streams that circulate in the wet end (wet end in English) of the paper machine.
  • the terms “wet end waters” and “wet end” will be used in the remainder of the description.
  • better drainage allows a reduction in steam consumption during subsequent drying of the dough in the drier and an energy gain in the machine press section.
  • improving the drainage ability of the paper sheet makes it possible to improve the formation of the sheet, to increase the speed and hence the productivity of the paper machine.
  • Mineral acids or mineral acid salts such as sulfuric acid or alumina sulfate are typically used in the production of certain types of paper, for example coated / uncoated paper, sanitary paper English), or thin papers, in order to compensate for the action of hydroxyl ions, or alkalis, resulting for example from the addition of sodium hydroxide, calcium carbonate, alkaline reagents, etc., which tend to increase the pH of the dough.
  • the acid product is generally added to the drain water recovered at the machine.
  • Sulfuric acid (H 2 SO 4 ) and / or sulphate of alumina are commonly used.
  • Phosphoric acid (H 3 PO 4 ) may be preferred in the manufacture of certain types of paper because of its weak acid properties which minimize the risks of dissolution of the charges present in the suspension of dough, in particular the carbonates of calcium.
  • the use of phosphoric acid has certain drawbacks, among which its high cost, delicate handling conditions, but also an increase in the phosphate content of the waste water.
  • pH control agent is carbon dioxide (CO 2 ). From a theoretical point of view, for every 1 m of proton released, each kg of phosphoric acid can be replaced by 1.14 kg of carbon dioxide, while the substitution ratio of sulfuric acid by carbon dioxide is in the range of 1 to 0.9.
  • carbon dioxide makes it possible to reduce the content of salts of said acid, for example with sulphates or phosphates.
  • the aggressive nature of the water is related to the presence of carbonic acid H 2 CO 3 in the water; the presence of sulphate and chloride anions contributes to the increase of the corrosive nature of the waters.
  • Phosphate ions precipitate almost instantly with calcium ions, in fact, the solubility products of calcium phosphate salts are very low, which means that they precipitate when there are traces of calcium and phosphate in the body. aqueous medium.
  • the increase of the TAC makes it possible to increase the buffer capacity of the waters and thus to improve the stability of the pH; the pH of these waters is then less sensitive to the introduction of other reagents.
  • the nuisances induced by pH shocks such as the appearance of various agglomerates including anionic contaminants (trash in English), glue or resin points (pitch in English) from wood, stickies (stickies in English language) from waste paper, as well as the formation of foam, are thus reduced.
  • the alkalinity and the hardness of the wet end waters result from the phenomena of increasing concentration related to the closing of the circuits, to the evaporation on the machine, but also to the dissolution of the added or present charges with the recycled fibers, to the production. or the destruction of bicarbonates related to the use of CO 2 and / or strong acids, as well as the use of sodium hydroxide or other alkaline agents.
  • Calcium carbonate is commonly used in the manufacture of paper as a filler or pigment because it is one of the whitest fillers in a moderate price range. Calcium carbonate can come from chalk or calcite, but it can also be produced synthetically as precipitated calcium carbonate (PCC).
  • PCC precipitated calcium carbonate
  • Calcium carbonate is solubilized by acidic substances such as sulfuric acid or sulphate of alumina; it is therefore not suitable for papermaking under acidic conditions.
  • the dissolution of the calcium carbonate fillers leads to an increase in the free calcium concentration, there is a risk of occurrence of foam. Due to the increasing closure of water circuits in papermaking processes, the dissolution of calcium carbonates leads to an increasing concentration of calcium and bicarbonate ions in the wet end waters.
  • the bicarbonate ions necessary to catalyze the neutral bonding reaction with alkylketenes dimer bonding agents can be generated by dissolving the carbon dioxide in the pulp suspension. If calcium carbonate is added as a mineral filler, the bicarbonate catalyst ions can be produced by reaction between carbon dioxide and calcium carbonates. However, the combination of carbon dioxide and calcium carbonate is only proposed for a pH below 8.6.
  • carbon dioxide can be used to adjust the pH of the alkaline pastes upstream of a fibrillation step.
  • carbon dioxide is used in conjunction with additives during papermaking to change the level of filler of the fibers and fines present in the dough.
  • the carbon dioxide is added in combination with alkaline reagents to increase the buffering capacity and stabilize the pH of a slurry.
  • carbon dioxide is used to stabilize the pH of a slurry to improve drainage or dehydration during sheet formation.
  • This saturation pH varies with temperature, conductivity, and hardness.
  • the calcium carbonates precipitate in the aqueous medium; if the pH is lower than the pHs, the aqueous medium is not saturated and calcium carbonate tends to solubilize in the aqueous medium.
  • the control of the alkalinity in the white water circuits is therefore done by one or more injection (s) of CO 2 as a function of the amount of alkaline ions (OH - ) present in the suspension of pasta.
  • OH- ions can come from alkaline treatments applied to one or more of the pulp slurry used; these treatments include, among others, alkaline hydrolysis of broken, alkaline bleaching, deinking.
  • the use of carbon dioxide is then advantageously added for the fine control of the pH of the waters coming from the headbox of the paper machine, the strong acid is advantageously used in the white waters to reduce the level of TAC and to limit the phenomena of accumulation of bicarbonate ions.
  • the acid used in addition to the CO 2 is preferably chosen from sulfuric acid, sulphate of alumina and phosphoric acid, alone or as a mixture, but any other strong acid may be used.
  • pH of saturation or equilibrium pH is a theoretical notion, its value corresponding to a perfect physicochemical balance of the calcium bicarbonates in solution, and therefore to the disappearance of any incrusting or aggressive tendency. ; this notion was introduced to predict the behavior of a given water.
  • said quantity of carbon dioxide to be introduced is determined according to the Ryznar index defined above.
  • the amount of carbon dioxide introduced is such that the Ryznar index is between 3 and 9, preferably between 4 and 7.
  • the amount of carbon dioxide introduced is determined according to the Langelier IL index defined above.
  • the amount of carbon dioxide introduced is such that the Langelier index is between 0 and 3, preferably between 0.5 and 2, so as to promote the retention of the charges.
  • This index is preferably used in addition to the Ryznar index.
  • the amount of carbon dioxide introduced is such that the saturation index is between 0.1 and 20.
  • this relates to a device for carrying out the process according to one of the preceding variants, in which all or part of the carbon dioxide is introduced into at least one of the following points: the circuit runs from the white waters, and / or in the long circuit of the white waters.
  • all or part of the carbon dioxide is introduced in two of the following at least, in the short circuit of the white water, and / or in the long circuit of the white water, and / or in the flow of pulp intended to feed the paper machine.
  • the device for introducing carbon dioxide is characterized in that it comprises at least one injection point in the short circuit of the white water and an injection point in the long circuit of the white water.
  • the pH profile varies depending on the added reagents, the alkalinity and / or acidity provided by the different aqueous streams entering the composition of the pulp flow entering the paper machine, and the driving conditions ( stripping in English language) free CO 2 at the level of the fabric of the machine and the deaerator.
  • the distribution of the CO 2 injection points also makes it possible to reach the optimum pH level in the wet part without being limited by the phenomena of saturation with dissolved gas in the white waters of the short circuit.
  • the introduction of carbon dioxide on the broken line is very important in increasing the pH stability of wet end waters.
  • the carbon dioxide is used in combination with alkaline reagents such as, non-exhaustively, sodium hydroxide, lime or mineral fillers based on calcium carbonate to increase the difference between the pH and the saturation pH. or increase the Langelier index, or reduce the Ryznar index.
  • alkaline reagents such as, non-exhaustively, sodium hydroxide, lime or mineral fillers based on calcium carbonate to increase the difference between the pH and the saturation pH. or increase the Langelier index, or reduce the Ryznar index.
  • the carbon dioxide can also be used in combination with strong acids such as sulfuric acid, alumina sulphate, phosphoric acid to reduce the difference between the pH and the saturation pH or to decrease the pH. Langelier index, or increase the Ryznar index.
  • strong acids such as sulfuric acid, alumina sulphate, phosphoric acid to reduce the difference between the pH and the saturation pH or to decrease the pH. Langelier index, or increase the Ryznar index.
  • FIG. 1 is a schematic illustration describing, by way of non-limiting examples, certain constituent elements of an installation for the manufacture of paper from the pulp.
  • one (or more) dough stream coming for example from processes for manufacturing thermomechanical, chemical or deinked pasta feeds via lines 12 and / or 13 a vat (or silo) mixture 14.
  • the mixing vat 14 also receives recycled pulp from broken via lines 16, 18 and 20, from 22 coated, and uncoated broken 24. Foreign particles can be removed from the broken pulp by filtering through the filter 19.
  • Fresh dough from 10 and / or 11, as well as broken from 22 and / or 24 are diluted in the vat 14 to a consistency of the order of 3.0 to 4.0% solids.
  • the diluted mixture is directed from the mixing tank 14 to the machine chest 26 via line 28. Loads are added via line 32 to the diluted mixture.
  • the amount of filler added is frequently from 0 to 20% by weight of the final sheet.
  • Calcium carbonate is a particularly useful filler in the manufacture of paper due in particular to its whiteness properties.
  • Other known fillers in the field of papermaking can also be added to the pasta mixture in the vat 26.
  • the pulp suspension is diluted to a consistency of the order of 0.5 to 1.2% and sent to the paper machine 36.
  • Retention aids such as polyacrylamides, polydialllydimethylammonidum chlorides, polyethyleneimine, acrylic acid / acrylamide copolymers in combination with starches may be added to the dough stream prior to the machine head 34 to facilitate retention of the charges on the sheet as it is formed on the paper machine 36.
  • the sheet of paper is formed by depositing fibers from the machine head 34 on a fabric 37. The free water from the suspension is removed through the fabric 37 essentially by gravity and optionally by means of pumps. empty. The water thus eliminated forms what is known as the white waters.
  • the sheet formed in the paper machine 36 undergoes other unrepresented operations, including drying in the section of the presses, then the section of the drying section (not shown) of the machine. paper 36 where the residual water is removed to a dryness of at least 90%, preferably 95% or more.
  • the roughness of the surface of the sheet may be corrected by smoothing or calendering.
  • smoothing or calendering For certain paper applications, for example for the manufacture of paper for writing or printing, and in order to improve the surface condition of the sheet, various elements will be deposited via a coating color. This operation can be performed on the paper machine itself, or outside the machine, after the smoothing operations.
  • the pulp When making the paper from the pulp, the pulp will first be processed in the circuit, the primary circuit in which the pulp from the mixing chamber is diluted and cleaned before entering the paper machine. The sheet is then formed, a step or succession of steps performed in the papermaking machine in which the pulp from the short circuit is injected into the paper machine at the machine head and then dried. surfaced.
  • the pulp 10, previously refined is introduced via line 12 into a mixing vat 14 into which various additional materials are also introduced, including the broken pieces 22 and / or 24 as well.
  • adjuvants used in the composition of the dough including in particular, starches, sizing agents and fillers. It is diluted to a consistency of about 3%.
  • the dough prepared in the mixing vat 14 is then introduced via the line 28 into the machine chest 26 where it is stored before passing into the short circuit or primary circuit for the preparation of the dough.
  • fillers can be added to the dough at the line 28 supplying the machine chest 26.
  • a pump 27 allows the transfer of the dough between the two vats 14 and 26, via the line 28.
  • aqueous dilution vehicles the essential elements of what is known as the "short circuit" for processing the dough, in which the dough previously prepared, and possibly stored in the cuvier of the machine 26 is both purified and suitably diluted before its introduction into the paper machine 36.
  • the aqueous vehicles are formed from recycled white water, from the paper machine, recovered during the production phase. drip of the paste, these waters represent at least 80% and preferably at least 90% of the total aqueous vehicle, the balance being process water and fresh water.
  • the dough from the vat 26 is sent via a pump 29 to the suction of the pump 40 of the supply of the headbox (fan pump), 40 via the line 42, then to the machine head 34, via lines 45 and 47.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
EP06300114A 2006-02-07 2006-02-07 Verwendung von Kohlendioxid zur Optimierung des pH-Werts im nassen Teil der Papiermachine Withdrawn EP1816259A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP06300114A EP1816259A1 (de) 2006-02-07 2006-02-07 Verwendung von Kohlendioxid zur Optimierung des pH-Werts im nassen Teil der Papiermachine

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP06300114A EP1816259A1 (de) 2006-02-07 2006-02-07 Verwendung von Kohlendioxid zur Optimierung des pH-Werts im nassen Teil der Papiermachine

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EP1816259A1 true EP1816259A1 (de) 2007-08-08

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998056988A1 (en) * 1997-06-13 1998-12-17 Aga Aktiebolag A PROCESS FOR STABILIZING THE pH OF A PULP SUSPENSION AND FOR PRODUCING PAPER FORM THE STABILIZED PULP
WO1999024661A1 (en) * 1997-11-05 1999-05-20 Aga Aktiebolag A process for improving the drainage of cellulosic pulps
CA2377695A1 (en) * 1999-07-09 2001-01-18 Anette Karlsson Method for eliminating detrimental substances in a process liquid
US6207062B1 (en) * 1998-03-09 2001-03-27 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Treatment of aqueous effluents by injection of carbon dioxide
WO2002097189A1 (en) * 2001-05-30 2002-12-05 Linde Ag A method for treating circulation waters
WO2003050356A1 (en) * 2001-12-12 2003-06-19 Linde Aktiengesellschaft An apparatus and a method for controlling the alkalinity and ph of an industrial process

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998056988A1 (en) * 1997-06-13 1998-12-17 Aga Aktiebolag A PROCESS FOR STABILIZING THE pH OF A PULP SUSPENSION AND FOR PRODUCING PAPER FORM THE STABILIZED PULP
WO1999024661A1 (en) * 1997-11-05 1999-05-20 Aga Aktiebolag A process for improving the drainage of cellulosic pulps
US6207062B1 (en) * 1998-03-09 2001-03-27 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Treatment of aqueous effluents by injection of carbon dioxide
CA2377695A1 (en) * 1999-07-09 2001-01-18 Anette Karlsson Method for eliminating detrimental substances in a process liquid
WO2002097189A1 (en) * 2001-05-30 2002-12-05 Linde Ag A method for treating circulation waters
WO2003050356A1 (en) * 2001-12-12 2003-06-19 Linde Aktiengesellschaft An apparatus and a method for controlling the alkalinity and ph of an industrial process

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