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WO1997010384A2 - Procede et dispositif permettant de surveiller la cuisson de cellulose - Google Patents

Procede et dispositif permettant de surveiller la cuisson de cellulose Download PDF

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Publication number
WO1997010384A2
WO1997010384A2 PCT/DE1996/001720 DE9601720W WO9710384A2 WO 1997010384 A2 WO1997010384 A2 WO 1997010384A2 DE 9601720 W DE9601720 W DE 9601720W WO 9710384 A2 WO9710384 A2 WO 9710384A2
Authority
WO
WIPO (PCT)
Prior art keywords
cooking
value
measured
cooker
measurement
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.)
Ceased
Application number
PCT/DE1996/001720
Other languages
German (de)
English (en)
Other versions
WO1997010384A3 (fr
Inventor
Klaus Fischer
Herbert Furumoto
Uwe Lampe
Ingeborg Schmidt
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.)
Siemens AG
Siemens Corp
Original Assignee
Siemens AG
Siemens Corp
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 Siemens AG, Siemens Corp filed Critical Siemens AG
Priority to EP96939808A priority Critical patent/EP0850333A2/fr
Priority to CA002232171A priority patent/CA2232171A1/fr
Publication of WO1997010384A2 publication Critical patent/WO1997010384A2/fr
Publication of WO1997010384A3 publication Critical patent/WO1997010384A3/fr
Anticipated expiration legal-status Critical
Priority to NO981172A priority patent/NO981172L/no
Ceased 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
    • D21C7/00—Digesters
    • D21C7/12—Devices for regulating or controlling
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/228—Automation of the pulping processes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/34—Paper
    • G01N33/343—Paper pulp

Definitions

  • the invention relates to a method for monitoring the pulp boiling, in particular for determining the end point of the boiling time, and for controlling the carbohydrate breakdown with measurement of physical and / or chemical parameters on the digestion medium, such as color value, conductivity, pH value, bre- index, IR spectrum, UV absorption, fluorescence and / or concentrations of digestion chemicals used in the cooking.
  • a method for monitoring the pulp boiling, in particular for determining the end point of the boiling time, and for controlling the carbohydrate breakdown with measurement of physical and / or chemical parameters on the digestion medium, such as color value, conductivity, pH value, bre- index, IR spectrum, UV absorption, fluorescence and / or concentrations of digestion chemicals used in the cooking.
  • Such a method is used particularly advantageously in the production of chemical pulp, but also of paper pulp.
  • the invention also relates to the associated arrangement for carrying out the method, with sensors for online measurement of individual characteristic variables and related evaluation.
  • the wood in the form of debarked wood chips is digested by boiling for several hours in a solution called "cooking acid". This process usually takes place at a temperature between 130 and 140 ° C under a pressure of about 8 bar over a period of 4 to 6 hours.
  • the cooking acid used has an initial pH of between 2 and 3 and usually consists of an aqueous solution of SO2 and calcium bisulfite (Ca (HSC> 3) 2) or magnesium bisulfite ( Mg ( HS0 3 ) 2 ) •
  • DD 293 215 A5 describes a method for determining the digestion time for determining the termination of digestion at
  • Paper pulp production by the acid bisulfite pulping process is known, in which the pulping time required for the production of paper pulp with a specific predetermined residual lignin content L in the unbleached pulp from concrete primary data of the process after the relationship
  • the SO2 concentrations are measured in short successive time intervals.
  • the SO2 concentration for the termination time is shown according to the relationship
  • the individual L mean the lignin content, t the time, ⁇ an exponential factor, T the temperature in K, FV the liquor ratio, S the number of splits in the cellulose chain, kj ⁇ the rate constants, Ej_ the activation energies, C sc , the concentration of SO2 in the
  • the object of the invention is to provide a method and an arrangement with which the pulp boiling can be better monitored. With an associated evaluation method, the optimal end point of the cooking time should be kept as accurate as possible.
  • the object is achieved according to the invention by an inline measurement of the pH and, if appropriate, the color of the cooking acid during the cooking.
  • the pH of the cooking acid is preferably determined "in situ" to an accuracy of 0.1 pH and recorded at least in the final phase of the cooking at a time interval of 30 s.
  • So-called enamel electrodes are used as sensors for the pH value.
  • the absorbance of the cooking acid inline is measured under operating conditions in the range of visible light.
  • Immersion probes are preferably used for "in situ" extinction measurement. With a spectrometer, spectra in the range between 400 and 800 nm can advantageously be recorded at least every 30 s simultaneously with the pH value.
  • the invention results in an improvement in productivity in cellulose cooking compared to the prior art.
  • the sensors for so-called inline measurement, i.e. at approx. 140 ° C and approx. 8 bar. Specifically, this means that neither bypasses, sampling or dilutions are required, but the measured values are available "in situ". No more SO2 can escape, which led to incorrect measurements during conventional sampling. Rather, the measured values are now unadulterated and can thus be used in an optimal manner to monitor the pulp boiling.
  • the process according to the invention can be used both in the discontinuous and in the continuous pulp cooker realize.
  • the sensors for the pH value can be used at a suitable point.
  • the advantage of the enamel sensors for measuring the pH is, in particular, the long service life with virtually undetectable wear, which means that an entire cooking process can now be followed.
  • the H + concentration is measured, which is actually present on the cellulose molecule and which catalyzes the depolymerization of the carbohydrates.
  • no more SO2 can escape, so that in particular no errors can occur due to reaction with the waste liquor.
  • a control device is provided a computer available, the computer the connection between the measured variables or their temporal course and the product quality and / or product yield determined and fed back to the control device.
  • a correlation can be derived by a multi-component correlation analysis, which describes the results between product quality and / or product yield and the measured variables.
  • controlled variables can win advertising% to with which the properties of the produced Zellu ⁇ loose, such as viscosity, kappa number tenacity u. Like., are specifically adjustable. This allows the yield in production to be maximized.
  • FIG 1 shows the relationship between the pH of the cooking acid
  • FIG. 3 shows a basic illustration of a batch-operated cooker
  • FIG. 3 the principle of a continuously operating cooker
  • FIG. 6 the evaluation of the measured variables in a cooker according to FIG. 5 and
  • FIG. 7 an associated evaluation device.
  • the lignin is a macromolecule with an aromatic basic structure, in which the individual benzene rings are linked as basic elements via side chains.
  • the side chains are particularly reactive and are split in the cooking acid with the aid of catalytically active hydrogen ions and substituted by sulfone groups.
  • the water solubility of the lignin is caused by the introduction of the strong hydrophilic sulfone groups.
  • the existing bonds between the lignin and the cellulose also have to be hydrolytically split in order to achieve complete removal. It follows that the delignification -d [L] / dt is proportional to both the bisulfite concentration and the hydrogen ion concentration. For that applies
  • Glucose + bisulfite gluconic acid + thiosulfate
  • the thiosulfate can decompose the bisulfite accordingly
  • the pH value is on the one hand directly in the cooker, i.e. Inline, and on the other hand with a sufficient repetition rate, i.e. continuously or with small time intervals, must be measured. Interference due to cooling, outgassing of SO2 or other reactions are avoided by the inline measurement.
  • the diagram according to FIG. 2 shows the results of optical measurements obtained from a simultaneous spectrometer with a diode array. It is essential that the dilute cooking acid / ie "in situ" was measured, for which temperature-resistant immersion probes are used, which can be placed anywhere in the cooker. The same location as that of the pH probes is advantageously chosen as the measuring location. By means of multiplexing, different measuring probes can be queried in succession with a single spectrometer.
  • spectrometers With known spectrometers, a complete spectrum is acquired at the time of measurement, i.e. the extinction as a function of the wavelength. Appropriate processing of such spectra allows time-dependent graphs 21 to 23 to be derived, the abscissa in FIG. 2 representing the time in hours corresponding to FIG. 1 and the ordinate representing the associated absorbance value in relative units.
  • the wavelengths of the spectral light for example between 400 and 800 nm, are given as parameters.
  • the finished pulp can be characterized by the so-called kappa number. From Figure 2 it follows that up to
  • FIG. 3 shows a cellulose cooker 30 which works discontinuously.
  • Essential for the operation of such a cellulose cooker 30 in the present context are a filler neck 31 for the wood on the one hand and a feed line 32 for acid on the other hand and the outlet nozzle 33 for emptying.
  • a circuit 35 with a circulation pump 36 is essential, with which a circulation via a heat exchanger 37 is realized.
  • the pH value according to FIG. 1 rises to a maximum during heating.
  • the pH value can be influenced by various measures independently of the actual cooking process: on the one hand, the cooking liquid can be diluted with wood water, on the other hand, SO2 diffuses into the wood.
  • the pH is further influenced by the so-called peezen, i.e. Pressure drop before the addition of SO2, or by the addition of liquid S ⁇ 2 according to Figure 4a).
  • the aim is to either keep the pH constant over time after the maximum or to drive graph 41, 43 or 44 according to a predetermined profile.
  • a predetermined profile For example, an MgO addition according to FIG. 4b) or a pressure reduction according to FIG. 4c) can be used.
  • the significant evaluation variables ⁇ 1, ⁇ 2, the maximum and the time of the maximum come into question.
  • the first derivative according to time (d (pH) / dt) and the total integral over time (JpHdt) can be used as further significant evaluation variables.
  • the carbohydrate breakdown can be controlled in the desired sense.
  • the following sizes can be changed, for example, in accordance with sub-figures 4a) to d): - During the cooking, MgO is added, which increases the pH;
  • the viscosity of the pulp can be specifically adjusted, in particular in the production of viscose pulp.
  • the tear length can be specified accordingly.
  • a maximum yield in the cooking process can be achieved by the appropriate control and regulation of the above sizes.
  • FIG. 5 shows a continuously operating cooker 50 with inlet 51 for the wood and feed line 52 for the cooking acid and outlet 53 for pulp. Because of the continuous operation, such a cooker is considerably more complex than a discontinuous cooker. Certain points which are essential for the operation of the cooker are picked out in the hydraulic lines. On the one hand, these are the so-called impregnation zone, the cooking zone and the washing zone. Corresponding points are designated in Figure 5 with C2, C3, C5, C6, C15, C16 and C8.
  • C2 denotes the entry of the wood and the cooking acid
  • C2 to C5 the so-called impregnation zone
  • C6 to C15 the cooking zone
  • C16 to C8 the so-called washing zone
  • C8 the discharge of the pulp
  • graph 61 in FIG. 6 shows the pH to be controlled above the height of the cooker, while graph 62 shows the MgO concentration and graph 63 the SO2 concentration as control variables. It can be seen that there are coordinated concentration profiles in the continuous cooker. This gives the following options for influencing the pH:
  • C5, C6 preferably with the C5 circulation, optionally also in the middle of the cooking zone, specification of the setpoints for the pH value, the temperature T and the circulation quantity in the C5 and C6 circulation via the stove model.
  • C5, C6 preferred for the C5 circulation, optionally also in the middle of the cooking zone, specification of the setpoints for the pH value, the temperature and the circulation quantity in the C5 and C6 circulation via the cooker model;
  • the complexity of the stove model and the laundry model depend on the task, in particular on the quality of the pulp and the required accuracy with which the quality is to be adjusted and the yield is to be increased.
  • color measurements in the C5 and C6 circulation can increase the model accuracy and thus the uniformity of the pulp.
  • a computer 70 is provided with an associated evaluation device, which uses the measured values to determine associated function values for determining the cooking time in accordance with a predetermined algorithm. For example, a function ⁇ (t) can be calculated that has a significant progression for the cooking time.
  • the structure of the associated algorithm is:
  • ⁇ (t) ⁇ 0 + 0 ⁇ x / (pH) dt + ⁇ 2 / (pH) dt / er dt + ⁇ 3 / (S0 2 ) dt
  • Corresponding process functions with "measured in situ" measured time profiles and in particular pH measured inline are input to computer 70 via separate inputs.
  • the start values of the process variables at t 0 and the measured values via individual switches 81 to 84
  • Certain simulation values can also be entered in assigned modeling units 91 to 94 via the switches 81 to 84.
  • the output of the computer 70 supplies the function ⁇ (t) corresponding to a modeling unit 95, which can in particular represent the viscosity In addition to the cooking time, this can also be used to make statements about the
  • Product quality and / or product yield can be derived.
  • the process functions can also be fed to a regulating device and specifically regulated in order to optimize the cooking time by means of appropriate means for feedback.
  • the method described and the associated device can be used particularly advantageously in the acid sulfite method for cellulose cooking.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Medicinal Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Paper (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)

Abstract

Dans la cuisson de cellulose, la détermination du point final du temps de cuisson est fondamental pour la qualité du produit et/ou les rendements que l'on peut obtenir. Selon l'invention, pendant la cuisson, on mesure in situ le pH et éventuellement la teinte de l'acide de cuisson. Ce procédé s'applique aussi bien aux cuiseurs fonctionnant en continu qu'à ceux qui fonctionnent en discontinu. Un dispositif de mise en ÷uvre dudit procédé, avec des détecteurs appropriés permettant de mesurer le pH en ligne, comprend une unité d'évaluation comportant un ordinateur (70) qui détermine le temps de cuisson d'après les valeurs mesurées et leur variation dans le temps.
PCT/DE1996/001720 1995-09-15 1996-09-12 Procede et dispositif permettant de surveiller la cuisson de cellulose Ceased WO1997010384A2 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP96939808A EP0850333A2 (fr) 1995-09-15 1996-09-12 Procede et dispositif permettant de surveiller la cuisson de cellulose
CA002232171A CA2232171A1 (fr) 1995-09-15 1996-09-12 Procede et dispositif permettant de surveiller la cuisson de cellulose
NO981172A NO981172L (no) 1995-09-15 1998-03-16 FremgangsmÕte og anordning til overvÕking av cellulosekoking

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19534377.8 1995-09-15
DE19534377 1995-09-15

Publications (2)

Publication Number Publication Date
WO1997010384A2 true WO1997010384A2 (fr) 1997-03-20
WO1997010384A3 WO1997010384A3 (fr) 1997-05-09

Family

ID=7772349

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE1996/001720 Ceased WO1997010384A2 (fr) 1995-09-15 1996-09-12 Procede et dispositif permettant de surveiller la cuisson de cellulose

Country Status (5)

Country Link
EP (1) EP0850333A2 (fr)
CA (1) CA2232171A1 (fr)
NO (1) NO981172L (fr)
WO (1) WO1997010384A2 (fr)
ZA (1) ZA967695B (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999057551A1 (fr) * 1998-05-04 1999-11-11 Honeywell-Measurex Corporation Systeme de nettoyage chimique d'electrodes utilisees dans un environnement liquide
WO2002016690A1 (fr) * 2000-08-22 2002-02-28 Siemens Aktiengesellschaft Procede de controle de processus lors de la production de pate de cellulose
EP1528148A3 (fr) * 2003-10-27 2011-06-08 Siemens Aktiengesellschaft Méthode et appareil pour conduire le procédé de cuisson de pâte cellulosique

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3630832A (en) * 1969-11-10 1971-12-28 Int Paper Canada Controlled alkaline sulfite pulping
DE3437619A1 (de) * 1984-10-13 1986-04-17 Pfaudler-Werke Ag, 6830 Schwetzingen Messsonde
CA1277110C (fr) * 1986-05-07 1990-12-04 Rudolf Patt Methode de contro le de la cuisson des lignocelluloses par spectroscopie aux irtf
DE9017325U1 (de) * 1990-12-21 1992-01-02 Siemens AG, 8000 München Prozeßleitsystem zur Steuerung der Herstellung von Zellstoff
DE4118507A1 (de) * 1991-06-06 1992-12-10 Thale Eisen Huettenwerk Messeinrichtung
US5420682A (en) * 1993-07-02 1995-05-30 Honeywell Inc. Method and apparatus for compensating spectral data with a color sensor

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999057551A1 (fr) * 1998-05-04 1999-11-11 Honeywell-Measurex Corporation Systeme de nettoyage chimique d'electrodes utilisees dans un environnement liquide
US6235123B1 (en) 1998-05-04 2001-05-22 Honeywell-Measorek Corporation Chemical cleaning system for electrodes used in a liquid environment
WO2002016690A1 (fr) * 2000-08-22 2002-02-28 Siemens Aktiengesellschaft Procede de controle de processus lors de la production de pate de cellulose
EP1528148A3 (fr) * 2003-10-27 2011-06-08 Siemens Aktiengesellschaft Méthode et appareil pour conduire le procédé de cuisson de pâte cellulosique

Also Published As

Publication number Publication date
NO981172D0 (no) 1998-03-16
ZA967695B (en) 1997-03-17
NO981172L (no) 1998-05-14
WO1997010384A3 (fr) 1997-05-09
CA2232171A1 (fr) 1997-03-20
EP0850333A2 (fr) 1998-07-01

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