EP0110683B1 - Determining the degree of cooking in a sulphite digester delignification - Google Patents

Determining the degree of cooking in a sulphite digester delignification Download PDF

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Publication number
EP0110683B1
EP0110683B1 EP83307188A EP83307188A EP0110683B1 EP 0110683 B1 EP0110683 B1 EP 0110683B1 EP 83307188 A EP83307188 A EP 83307188A EP 83307188 A EP83307188 A EP 83307188A EP 0110683 B1 EP0110683 B1 EP 0110683B1
Authority
EP
European Patent Office
Prior art keywords
digester
delignification
pressure
value
controller module
Prior art date
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Expired
Application number
EP83307188A
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German (de)
English (en)
French (fr)
Other versions
EP0110683A1 (en
Inventor
Ralph K. Johnson
Marion A. Keyes Iv
Azmi Kaya
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.)
Babcock and Wilcox Co
Original Assignee
Babcock and Wilcox Co
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 Babcock and Wilcox Co filed Critical Babcock and Wilcox Co
Publication of EP0110683A1 publication Critical patent/EP0110683A1/en
Application granted granted Critical
Publication of EP0110683B1 publication Critical patent/EP0110683B1/en
Expired legal-status Critical Current

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    • 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
    • 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
    • D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
    • D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites

Definitions

  • This invention relates to methods of and apparatus for determining the degree of cooking in a sulphite digester for delignification.
  • the invention can be used, for example, in the pulp industry.
  • Lignin is the major noncarbohydrate constituent of wood. It functions as a natural plastic binder for the cellulose fibres. Its exact formula is unknown. Lignin is removed from wood by both the sulphite and sulphate pulp processes.
  • the rate of delignification is a function of cooking liquor composition and cooking temperature, and that this rate increases rapidly with temperature and is affected by acid concentration. It is further known that the rate of deliginification for acid pulping varies with temperature in accordance with the known Arrhenius equation.
  • the velocity factor reaction rate (k) can be determined from this equation and subsequently substituted in the standard rate of delignification equation to determine this latter rate.
  • US Patent No. US-A-3 941 649 (Wallin) describes a method of obtaining a predetermined Kappa number (a measure of the degree of cooking) in a sulphate pulping process by taking a sample of the pulping liquor at a stage when the preliminary alkali-consuming reactions are substantially complete but before any substantial delignification has taken place, and analysing the sample to establish the alkali content.
  • the alkali content is then adjusted by addition of alkali until a predetermined alkali content per unit mass of wood is achieved. This additional alkali content can then be used to calculate the pulping conditions necessary to obtain the required Kappa number.
  • the pulping time and temperature are then controlled on the basis of this information during delignification.
  • the invention also provides apparatus for accomplishing the foregoing method including individual function blocks which are connected together to achieve the various calculations.
  • apparatus for determining the degree of cooking in a sulphite batch digester for delignification the apparatus being characterised by:
  • a preferred embodiment of the present invention described hereineblow provides a method and apparatus for calculating sulphite digester rate of delignification and determining the completion of cooking, utilising function blocks to continuously solve the so-called Arrhenius equation for the velocity factor reaction.
  • This calculation takes place in the first controller module with the second controller module being provided with function blocks to obtain a value corresponding to the rate of delignification.
  • the delignification rate is continuously computed and monitored, and when the cook has been brought up to a desired set point, an indication, such as an alarm, is provided to an operator to terminate the cooking process.
  • the preferred apparatus for and methods of determining the degree of cooking in a sulphite digester are simple in design, rugged in construction, and economical to manufacture.
  • the drawings show apparatus embodying the invention for determining the degree of cooking in a delignification sulphite digester.
  • the rate of delignification is primarily a function of the cooking liquor composition and cooking temperature. Since there are established mathematical expressions for the rate of delignification, it is possible to determine how much cooking time is required based upon the cooking temperature for a particular pulp quality. See Pulp and Paper Manufacture, 2nd Ed., Volume I, The Pulping of Wood, pp 282 to 285.
  • the rate of reaction is a little more than doubled by an increase of 10°C in temperature. Cooking is extremely slow at temperatures below 100°C.
  • Figure 1 illustrates how calculation of the digester rate of delignification and Kappa (K) Number can be implemented in a Bailey Network 90 (Trade Mark) system. The entire delignification rate and K-number calculation can be accomplished using two Network 90 controller modules 10, 30 for a particular digester. Information concerning the Network 90 can be found in Bailey Controls Company Application Guide 260-2 and Bailey Controls Company Product Specification E93-906.
  • the Arrhenius equation can be continuously solved for the velocity factor reaction rate (k), by means of a calculator unit or module 23 shown in greater detail in Figure 2.
  • the calculation is based upon digester temperature measurement as determined by a digester temperature transmitter 12 which provides one of a plurality of inputs to the unit 23.
  • the partial pressure of sulphur dioxide in the digester is approximated by measuring the difference between steam pressure at the digester temperature and the actual digester pressure. This partial pressure is linearised and corrected for the assumption that the digester pressure is that of only steam and sulphur dioxide in equilibrium with the digester acid. Steam pressure is calculated as a function of temperature in a unit 14 and the actual pressure is supplied by a digester pressure transmitter 15. The difference between the steam pressure and digester pressure is taken in a comparator unit 16. The n power factor in Equation (2) is provided by a function generator 17 and provides a means for compensating for the foregoing assumption.
  • the constants A, E, 2.303 and R of Equation (1) are provided to the unit 23 by units 18,19,20 and 21, respectively.
  • An output (log k) from the unit 23 is integrated to provide k and multiplied by the partial pressure output value from the function generator 17 to provide an output from the controller module 10 which represents the rate of delignification at any instant for the sulphite digester, in accordance with Equation (2), and is directed to the second controller module 30.
  • the digester cook operator manually enters total S0 2 and free S0 2 acid strength chemical tests as inputs to the controller module 30 over units 32 and 33, respectively.
  • the controller automatically subtracts the difference, which become the combined S0 2 content, in a comparator unit 34.
  • the delignification rate can then have acid strength S0 2 correction applied over a function generator 35 and multipliers 36, 37.
  • the delignification rate will be integrated for each cook, in a unit 38, with respect to time, for totalising the area under the reaction curve of Figure 3.
  • This area totalisation is related to a degree of cooking (Kappa Number) set point for the particular grade.
  • Kappa Number degree of cooking
  • the degree of cooking (CD) is derived as follows:

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  • Paper (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
  • Investigating Or Analysing Materials By The Use Of Chemical Reactions (AREA)
EP83307188A 1982-11-24 1983-11-24 Determining the degree of cooking in a sulphite digester delignification Expired EP0110683B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US44427282A 1982-11-24 1982-11-24
US444272 1982-11-24

Publications (2)

Publication Number Publication Date
EP0110683A1 EP0110683A1 (en) 1984-06-13
EP0110683B1 true EP0110683B1 (en) 1987-04-08

Family

ID=23764204

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83307188A Expired EP0110683B1 (en) 1982-11-24 1983-11-24 Determining the degree of cooking in a sulphite digester delignification

Country Status (11)

Country Link
EP (1) EP0110683B1 (OSRAM)
JP (1) JPS59137584A (OSRAM)
KR (1) KR880000744B1 (OSRAM)
AU (1) AU2149983A (OSRAM)
BR (1) BR8306460A (OSRAM)
CA (1) CA1198858A (OSRAM)
DE (1) DE3370840D1 (OSRAM)
ES (1) ES8505479A1 (OSRAM)
HK (1) HK95287A (OSRAM)
IN (1) IN159330B (OSRAM)
SG (1) SG60987G (OSRAM)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4990219A (en) * 1989-06-13 1991-02-05 Elsag International B.V. Apparatus for controlling the degree of cooking in a digester
US4978425A (en) * 1989-06-13 1990-12-18 Elsag International B.V. Method for controlling the degree of cooking in a digester
EP0445321B1 (de) * 1990-03-05 1994-06-01 Siemens Aktiengesellschaft Verfahren zur Herstellung von Zellstoff in einem kontinuierlichen Kocher
CN1064096C (zh) * 1994-04-28 2001-04-04 东芝株式会社 蒸煮锅温度分布控制系统
ATE189715T1 (de) * 1995-10-09 2000-02-15 Siemens Ag Verfahren zur bestimmung des endpunktes der zellstoffkochung und anordnung zum steuern der kochzeit bei der zellstoffkochung in einem reaktor

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3941649A (en) * 1972-07-14 1976-03-02 Mo Och Domsjo Aktiebolag Process for obtaining a predetermined Kappa number in sulfate pulping

Also Published As

Publication number Publication date
ES527326A0 (es) 1985-05-16
EP0110683A1 (en) 1984-06-13
IN159330B (OSRAM) 1987-05-02
KR840006688A (ko) 1984-12-01
SG60987G (en) 1987-10-23
BR8306460A (pt) 1984-06-26
JPS59137584A (ja) 1984-08-07
HK95287A (en) 1987-12-24
DE3370840D1 (en) 1987-05-14
CA1198858A (en) 1986-01-07
ES8505479A1 (es) 1985-05-16
KR880000744B1 (ko) 1988-05-04
AU2149983A (en) 1984-05-31

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