US20040238140A1 - Method in a paper or pulp process to control the chemical state of the pulp and circulation water system - Google Patents

Method in a paper or pulp process to control the chemical state of the pulp and circulation water system Download PDF

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Publication number
US20040238140A1
US20040238140A1 US10/487,304 US48730404A US2004238140A1 US 20040238140 A1 US20040238140 A1 US 20040238140A1 US 48730404 A US48730404 A US 48730404A US 2004238140 A1 US2004238140 A1 US 2004238140A1
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Prior art keywords
pulp
raw
reject
tmp
process water
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Abandoned
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US10/487,304
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English (en)
Inventor
Sakari Laitinen-Vellonen
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Liqum Oy
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Liqum Oy
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Priority claimed from FI20015022A external-priority patent/FI20015022A0/fi
Application filed by Liqum Oy filed Critical Liqum Oy
Assigned to LIQUM OY reassignment LIQUM OY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LAITINEN-VELLONEN, SAKARI
Publication of US20040238140A1 publication Critical patent/US20040238140A1/en
Abandoned legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G9/00—Other accessories for paper-making machines
    • D21G9/0009—Paper-making control systems
    • D21G9/0018—Paper-making control systems controlling the stock preparation
    • 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
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1052—Controlling the process
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
    • 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
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/78—Controlling or regulating not limited to any particular process or apparatus
    • 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
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
    • D21H23/06—Controlling the addition
    • D21H23/08—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH

Definitions

  • the present invention relates to a method in a paper or pulp process to control the chemical state of the pulp and circulation water system, in which said process one or more raw-material components diluted in liquid, possible fillers, and one or more additives are mixed to form stock.
  • the said raw-material components can be, for example, mechanicals pulps, for instance mechanical pulps from chips and groundwood pulps (SGW, RMP, TMP, etc.) or chemical pulps, such as cellulose.
  • mechanicals pulps for instance mechanical pulps from chips and groundwood pulps (SGW, RMP, TMP, etc.
  • chemical pulps such as cellulose.
  • DIP pulp DeInked Pulp
  • the control of the chemical state of the pulp and circulation water system significantly affects the success of the papermaking process.
  • the chemical state can be used to affect such things as the runnability properties of the machine, the paper quality, the dirtying of the machine, the environmental load, and the operation of the waste-water treatment plant of the paper or pulp mill. Disequilibrium in the chemical state can lead to sedimentation, gas formation, and diminished retention in the stock, for example.
  • the pH value i.e. the acidity level
  • the pH value presently appears to be an important variable, for example, in controlling the chemical state of the raw material components of the paper process, as changes take place in the charge level and solubility of the wood material when the pH value changes.
  • Good pH-value control is an essential variable in achieving even retention, i.e. the percentage of solids remaining in the web in the wire section compared to that in the headbox feed.
  • the pH value affects not only the retention substances, but also the action of other additives, the control of the phase changes, the runnability and dirtying of the machine, and the quality of the paper.
  • the pH value is controlled with the aid of lye or sulphuric acid, which can be dosed, for example, into the wire pit, either automatically or manually. Careful control movements are essential, as sudden changes can cause pH shocks or other disturbances. A sudden change in the pH value will cause the sedimentation of a dissolved or dispersed substance. Control of the pH value is slow, because the regulating chemical must be allowed to enter the fibre and the pH measurement point must be located to provide the measurement result after a specific delay.
  • controlling the pH value with the said substances introduces additives, such as sodium and sulphur, which are detrimental to the process, and which for their part will cause problems, such as reduced retention, in the wire section.
  • the pH value is usually well controlled in the pulp and circulation water system of a paper machine.
  • attempts to control phase changes in the paper process have generally taken place through sensitive control of the pH value, thus affecting, for instance the general runnability of the machine, due to the varying charge level.
  • the present invention is intended to create an new type of method in a paper or pulp process to control the chemical state of the pulp and circulation water system.
  • the paper process can also be held to include board and pulp manufacture.
  • the characteristic features of the method according to the invention are listed in the accompanying claim 1 .
  • the method according to the invention is characterized by the regulation in the pulp and circulation water system of the electrochemical state of at least one raw-material component and/or the stock.
  • the regulation can be carried out on, for example, a raw-material component, on part of it, or on a mixture of two or more raw-material components, before the stock formation, or, for example, on the stock in the short circulation, or before it is fed from the headbox to the web-formation section.
  • a raw-material component and/or stock when a raw-material component and/or stock is in the reduction area, its electro-chemical state is regulated, for example, by equalizing it or increasing it in relation to the other pulp components, according to one preferred embodiment by using a suitable oxidizing or reducing compound or substance, while the electro-chemical state of a raw-material component in the oxidizing area is regulated by using a suitable reducing or oxidizing compound or substance.
  • the electrochemical state of a raw-material component or stock can be regulated by connecting it to a selected potential level by means of an external source of alternating or direct current.
  • an external source of alternating or direct current no additives are required.
  • the regulation by means of chemical can be used in conjunction with regulation using an external power source. In regulation carried out using an external power source, the polarity can also be reversed.
  • the electrochemical state of the process can be regulated through the order of mixing the raw-material components.
  • the order can be optimized to suit different running situations.
  • the method according to the invention substantially improves the control of the chemical state, the paper quality, and the runnability of the machine in general, besides reducing the environmental load. Further, corrosion in the machine structures and in the pulp and circulation water systems is significantly reduced and the formation of gas diminishes, leading to a substantial improvement in the reliability of consistency measurements, among other things.
  • the method according to the invention can also be used to advantageously affect the retention of the wire section, the amount of fines, and possible bacteria growths in the liquid. This further reduces the need for chemicals.
  • the method according to the invention brings further advantages in improved paper strength and formation and in the control of the paper-web edges, which significantly affects the effective production capacity.
  • FIG. 1 shows a schematic example of one embodiment of the method according to the invention
  • FIG. 2 a shows a schematic example of a second embodiment of the method according to the invention.
  • FIG. 2 b shows a schematic example of a third embodiment of the method according to the invention.
  • FIG. 1 shows a diagram of one preferred embodiment of the method according to the invention, which depicts very roughly on a schematic level the pulp and circulation water system 10 of a paper machine 35 .
  • the storage towers 15 , 14 , 13 for the raw-material components are shown.
  • Raw materials are brought to them along lines 15 a , 14 a , 13 a , for example, from a pulp mill, pulp pretreatment plants, such as disintegration (bale pulper) and grinding, or other similar places (not shown).
  • the PULP and TMP pulps are lead along lines 15 b , 14 b through possible cleaners, defibrators, or other operational devices (not shown) to their dosing tanks 18 , 19 .
  • the dispersed DIP pulp 13 can also be lead along a line 13 b direct to the mixing tank 12 .
  • the pulp is dosed to lines 18 b , 19 b , through possible beating stages (not shown), to the mixing tank 12 .
  • reject pulp may be coated or uncoated, i.e. so-called base reject.
  • reject pulp is dosed in a suitable ratio over line 24 b to the mixing tank 12 .
  • collection lines 20 a , 21 a for leading the reject pulp, for example, from machine pulpers (not shown) to the storage towers 20 , 21 for coated and uncoated reject.
  • the coated reject is led on from the storage tower 20 along line 20 b to the reject tank 22 and on along line 22 b to the reject pulp dosing tank 24 .
  • the uncoated reject is led along line 21 b , for example, through precipitation (not shown) to the reject tank 23 , and from there along line 23 b to the same dosing tank 24 as the coated reject. From there, the reject pulp is dosed in a suitable ratio over line 24 b to the mixing tank 12 .
  • the raw-material components are mixed together to form a so-called high consistency pulp, which is led along line 25 a to the machine tank 25 .
  • the high consistency pulp is dosed over the line 25 b to the wire pit 30 , in which it dilutes to form stock.
  • the stock is transferred over line 34 to the short circulation 26 of the paper machine 35 , which incorporates, for instance, hydro-cyclone cleaning and deaeration devices, as well as filters and pumps (not shown).
  • the stock is diluted, sorted, and transferred by a head feed pump (not shown) along line 27 a to the headbox 27 , which is used to spread the stock evenly to the subsequent wire section 28 .
  • the stock is wet-formed to create a paper web, when most of the water is removed from it.
  • a bypass circulation 31 is arranged, which is used to return excess stock that has been led there to the deaeration (not shown) of the short circulation 26 .
  • devices 29 are used to collect the so-called tail water, which contains both water and also material not retained in the web (0-water).
  • the tail water is led by lines 27 b , 29 a to the wire pit 30 , from which it is reused at various points in the pulp systems and the short circulation 26 .
  • chemically purified water and raw water are generally used in the processes, all of which together are referred to in the following as process water.
  • An overflow 33 is arranged in the wire pit 30 , the tail water from which is led by line 32 a to the circulation water tank 32 . Water is added from this, for example, over line 32 b to the connecting line 25 a between the mixing tank 12 and the machine tank 25 .
  • the method according to the invention can be advantageously applied not only to the pulp and circulation water systems 10 shown in the embodiment example, but also, for example, to a board machine and the pulp manufacturing process.
  • the electrochemical state of at least one raw-material component PROCESS WATER, TMP, PULP, REJECT, DIP, and/or the stock formed from them is controlled by regulation.
  • an attempt is made to equalize the electrochemical states of the raw-material components, before mixing them together.
  • the process waters and generally the substances (for example, fillers and additives) mixed into the liquids in the processes described can also be regarded as raw-material components.
  • the electrochemical state of a raw-material component PROCESS WATER, TMP, PULP, REJECT, DIP can be expressed, for example, as the level of its electrical potential.
  • the regulation of the electrochemical state of a raw-material component PROCESS WATER, TMP, PULP, REJECT, DIP involves according to a first embodiment either raising or lowering the level of its potential, in such a way that the electrochemical states of the raw-material components fed into the mixing tank 12 are essentially more equalized than before their regulation, without substantially altering the pH value of the components, due to a rise or drop in the level of their electrochemical potential.
  • the difference between the electrochemical states of the raw-material components can also be increased, to eliminate detrimental reactions and to increase advantageous reactions.
  • a reducing agent for example, sulphur dioxide, SO 2
  • SO 2 sulphur dioxide
  • an oxidizing agent for example, hydrogen peroxide H 2 O 2
  • the substance added to it is an oxidizing agent (for example, H 2 O 2 ), which raises the electrical potential to the chosen level. If it is desired to lower the potential, a reducing agent, for example SO 2 , is added. In the method, it is essential for the said reducing or oxidizing agents to be added not to affect the pH value of the raw-material components.
  • FIG. 1 shows an example, in which the bleaching of a mechanical pulp TMP 14 , carried out by using reducing dithionite (Na 2 S 2 O 4 ⁇ 2 ), significantly lowers the potential of the raw-material component, leading to unfavourable reactions in the process.
  • hydrogen peroxide H 2 O 2
  • the addition is made through the line 17 b to the dosing tank 19 , essentially before the mixing tank 12 , and thus before the formation of the stock.
  • the addition of the hydrogen peroxide 17 raises the electrochemical state of the TMP pulp in question to a level at which it does not react when mixed with the other raw-material components PULP, REJECT, thus preventing disturbances that diminish the runnability of the machine 35 , for example.
  • H 2 S extremely detrimental hydrogen sulphide
  • H 2 O 2 hydrogen peroxide
  • Oxidizing can also be carried out simply by using pure air.
  • the electrochemical state of the pulp component PULP will then rise to a favourable level, thus preventing detrimental reactions when it is mixed with the other components TMP, REJECT, DIP.
  • electrochemical states of the raw-material components may differ also very naturally, without any specific factor.
  • the differences in level in the electrochemical states of the raw-material components caused by the aforementioned dithionite and hydrogen sulphide are only individual factors and in no way restrict the scope of protection of the method according to the invention.
  • the electrical potentials of the raw-material components PROCESS WATER, TMP, PULP, REJECT, DIP are regulated before they are fed into the mixing tank 12 , or the electrochemical state of the stock formed from the raw-material components is regulated to an optimal level, thus preventing detrimental chemical reactions, which cause, for example, sedimentation or air bubbles in the stock. Differences in the electrochemical states of the raw-material components or mixtures formed from them are permitted, in order to find the optimal level, depending, for example, on the running situation/manner, or on the other properties of the raw-material components.
  • the electrochemical state of the stock formed from the raw-material components can be regulated after the formation of the stock, however, essentially before it is fed out of the headbox 27 of the paper machine 35 to the wire section 28 .
  • the minimum requirement for determining the electrochemical state is only a single measurement of the electrical potential, in which the electrical potential of the liquid is measured in relation to a chosen reference electrode. If the potential distribution is uneven, the number of measurement locations can be increased to determine the average potential level.
  • the said electrode are Fe, Pt, Rst, Cu, Au, Ag.
  • the raw-material components' potential levels can vary between, for example, ⁇ 800 mV, PULP and +350 mV, REJECT.
  • the correction of an electrochemical disequilibrium can be achieved in place of, or possibly along with the chemical additions described above, by means of an external alternating or direct current source 40 .
  • one or several electrodes 40 connected to an external power supply are arranged, for example, in the dosing tanks 18 , 19 , 22 , 23 , 24 , or before or after them.
  • This embodiment is most advantageous, for example, for implementing regulation that takes place in pulses and/or by reversing polarity.
  • the order of mixing the raw-material components PULP, TMP, DIP, REJECT can be used to equalize or increase their electrochemical states. For example, the two raw-material components with the lowest potential levels are mixed first, and then these are mixed with the component with the next lowest level, and so on.
  • FIGS. 2 a and 2 b show further additional application examples of preferred embodiments of the method according to the invention. In both, the differences between the electrochemical states of the raw-material components, or of the divided parts of individual raw-material components are increased.
  • the electrochemical state of a raw-material component TMP used in the manufacture of newsprint is regulated in such a way as to reduce, or even in certain cases to omit entirely, the most cost-intensive amount of pulp required in the manufacture of the paper grade in question.
  • the regulation of the electrochemical state takes place by leading at least part of the TMP pulp to the manipulation M 40 of the electrochemical state, after which both the manipulated raw-material component TMPM and the unmanipulated raw-material component TMP are mixed together.
  • the difference in potential created between the components creates advantageous reactions, thus allowing the amount of pulp to be reduced.
  • FIG. 2 b shows a second embodiment example, in which the difference in the electrochemical state of the TMP pulp relative to the REJECT pulp is increased M 40 prior to them being combined.
  • the increase in the difference between the electrochemical states of the raw-material components TMP, REJECT allows the PULP component to be reduced, and, in the best case, for it to be omitted.
  • the electrochemical state of the raw-material components can be measured using other forms of electrochemical measurement, such as the measurement of electrochemical noise, current measurement, measurement of the linear polarization resistance, and frequency measurement.
  • electrochemical noise E, Electrochemical Noise
  • the potential or current noise i.e. the fluctuation at a low frequency and amplitude
  • LPR linear polarization resistance
  • the speed of the oxidizing reactions taking place on the surface of a sensor is measured. The measurement reacts to such things as changes in the conductivity and temperature of an electrolyte, i.e. diluting liquid, and the concentrations of the oxidizing components.
  • the chemical state can also be controlled by means of electro-flocculation.
  • two or more electrodes of different models for example, plates, rods, spheres
  • the regulation parameters are affected by the electrode materials used.
  • the diluted raw-material component of the process water, or the stock is arranged to circulate through electrodes arranged in parallel in a bank of electrodes.
  • the elements in the raw-material components and/or in the stock can be charged electrically, so that the electrochemical conditions of the raw-material component and/or the stock can be regulated to be advantageous to the process.
  • disturbing substances can be collected from the raw-material components and/or the stock onto electrodes, to prevent them from disturbing the process.
  • the materials of the electrodes can be advantageously selected so that additives, which charge the fibres and/or particles in a raw-material component and/or the stock, thus advantageously affecting the electrochemical state of the process, can be released from them.
  • the method according to the invention can also be used to advantageously affect the retention in the wire section, because conditions favourable to retention can also be created by regulating the electrochemical state of the stock, thus reducing the need to use retention agents. Further, the formation and strength of the paper improve and the bacterial activity in the process water diminishes. The runnability and level of cleanliness of the machine 35 also improve.
  • Yet another application of the method according to the invention is the improvement of the properties of the edge parts of the paper web.
  • the strength of the edge parts of the paper web is weaker than that of the web on average. In part, this is due to the fact that the temperature distribution of the drying cylinders (not shown) of the dryer section of the paper machine 35 is uneven, so that the ends of the cylinders are hotter than the central part.
  • process water the electrochemical state of which has been regulated according to the method of the invention in an advantageously direction in terms of the desired effect, is added to the edge parts of the headbox 25 of the paper machine 35 .
  • This also improves the properties of the edge parts of the paper web, thus increasing the effective width of the web.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
US10/487,304 2001-08-21 2002-08-21 Method in a paper or pulp process to control the chemical state of the pulp and circulation water system Abandoned US20040238140A1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
FI20015022A FI20015022A0 (fi) 2001-08-21 2001-08-21 Menetelmä paperin- tai kartonginvalmistuksessa
FI20015022 2001-08-21
FI20025023A FI20025023A (fi) 2001-08-21 2002-05-17 Menetelmä paperi- tai selluprosessissa massa- ja kiertovesijärjestelmän kemiallisen tilan hallitsemiseksi
FI20025023 2002-05-17
PCT/FI2002/000684 WO2003018908A1 (fr) 2001-08-21 2002-08-21 Procede dans un traitement de papier ou de pate pour le controle de l'etat chimique de la pate et systeme d'eau de circulation

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US20040238140A1 true US20040238140A1 (en) 2004-12-02

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US10/487,304 Abandoned US20040238140A1 (en) 2001-08-21 2002-08-21 Method in a paper or pulp process to control the chemical state of the pulp and circulation water system

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US (1) US20040238140A1 (fr)
EP (1) EP1430178B1 (fr)
AT (1) ATE357556T1 (fr)
CA (1) CA2456538C (fr)
DE (1) DE60219046T2 (fr)
FI (1) FI20025023A (fr)
WO (1) WO2003018908A1 (fr)

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US20090114359A1 (en) * 2005-10-31 2009-05-07 Savcor Process Oy Method For Use In The Wet End Of A Paper Machine, Cardboard Machine Or An Equivalent Web Forming Machine
US20110011548A1 (en) * 2008-02-22 2011-01-20 Jouni Matula Method of and an arrangement for proportioning thick stock to a short circulation of fiber web machine
WO2011149797A1 (fr) * 2010-05-22 2011-12-01 Eltron Research & Development Inc. Déshydratation du papier
US20130213596A1 (en) * 2010-09-20 2013-08-22 Voith Patent Gmbh Method for regulating the formation of a fibrous web
US11193238B2 (en) * 2016-08-31 2021-12-07 Seiko Epson Corporation Sheet manufacturing apparatus and control method for sheet manufacturing apparatus
US11384482B2 (en) * 2018-11-07 2022-07-12 Seiko Epson Corporation Web manufacturing apparatus and sheet manufacturing apparatus

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DE102011083709A1 (de) * 2011-09-29 2013-04-04 Voith Patent Gmbh Betriebsverfahren für eine Stoffaufbereitung
US20220026343A1 (en) * 2018-11-27 2022-01-27 Kemira Oyj Method for estimating the vapor phase corrosion load

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US20090114359A1 (en) * 2005-10-31 2009-05-07 Savcor Process Oy Method For Use In The Wet End Of A Paper Machine, Cardboard Machine Or An Equivalent Web Forming Machine
US8133355B2 (en) * 2005-10-31 2012-03-13 Savcor Process Oy Method for use in the wet end of a paper machine, cardboard machine or an equivalent web forming machine
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DE60219046T2 (de) 2007-12-13
EP1430178B1 (fr) 2007-03-21
FI20025023A0 (fi) 2002-05-17
ATE357556T1 (de) 2007-04-15
WO2003018908A1 (fr) 2003-03-06
DE60219046D1 (de) 2007-05-03
FI20025023A (fi) 2003-02-22
EP1430178A1 (fr) 2004-06-23
CA2456538C (fr) 2010-04-27
CA2456538A1 (fr) 2003-03-06

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