Determining the degree of cooking in a sulphite digester delignification

Claim 3

A method according to claim 1, including calculating the digester reaction rate (k) according to the equation: where A is constant.

Claim 4

A method according to claim 1 or claim 2, wherein steam pressure (P ) in the digester is calculated (14) as a function of digester temperature (T) and a difference is taken (16) between the steam pressure (P ) and the digester pressure (Pd), which difference is proportional to the partial pressure of sulphur dioxide.

Claim 5

A method according to claim 1, -claim 2 or claim 3, including selecting a desired Kappa Number for a desired degree of cooking in the sulphite digester, comparing the desired Kappa number with the obtained Kappa number, and, when the desired Kappa number corresponds to the obtained Kappa number, generating a signal.

Claim 6

Apparatus for determining the degree of cooking in a sulphite digester for delignification, the apparatus being characterised by: a first sensor (12) for sensing a digester temperature (T); a second sensor (15) for sensing a digester pressure (P d ); a first controller module (10) connected to the first and second sensors (12, 15) and having means (18 to 20) for providing a plurality of constants including an energy of activity constant (E) for the digester reaction and the gas constant (R); means in the first controller module (10) for continuously calculating a digester reaction rate (k) of the digester as a function of digester temperature (T), pressure (P d ), and the plurality of constants to obtain values therefor over time; means in the first controller module (10) for obtaining a value corresponding to the partial pressure of sulphur dioxide in the digester as a function of the digester temperature (T) and pressure (P d ); at least one multiplier in the first controller module . (10) for multiplying the partial pressure value by the digester reaction rate value to obtain a delignification rate value; and a second controller module (30) connected to the first controller module (10) for receiving the delignification rate value and integrating the delignification rate value over time to obtain a Kappa value of cooking in the digester.

Claim 7

Apparatus for determining the degree of cooking in a sulphite digester for delignification, the apparatus being characterised by: a first sensor (12) for sensing a digester temperature (T); a second sensor (15) for sensing a digester pressure (P d ); a first controller module (10) connected to the first and second sensors (12, 15) and having means (18 to 20) for providing a plurality of constants including an energy of activity constant (E) for the digester reaction and the gas constant (R); means in the first controller module (10) for continuously calculating a digester reaction rate (k) of the digester as a function of digester temperature (T), pressure (P d ), and the plurality of constants to obtain values therefor over time; means in the first controller module (10) for obtaining a value corresponding to the partial pressure of sulphur dioxide in the digester as a function of the digester temperature (T) and pressure (P d ); at least one multiplier in the first controller module . (10) for multiplying the partial pressure value by the digester reaction rate value to obtain a delignification rate value; and a second controller module (30) connected to the first controller module (10) for receiving the delignification rate value and integrating the delignification rate value over time to obtain a Kappa value of cooking in the digester.

Claim 8

Apparatus according to claim 5, wherein the first and second controller modules (10, 30) include a plurality of function blocks each for conducting one of a comparison function, an arithmetic function, and a plurality of arithmetic functions.

Claim 9

Apparatus according to claim 5 or claim 6, wherein the first controller module (10) includes a first function generator (14) for receiving a signal from the first sensor (12) and generating a value corresponding to a steam pressure (P ) of the digester, a comparator (16) connected to the first function generator (14) and the second sensor (15) for obtaining a difference between the steam pressure (P ) and digester pressure (P d ), a second function generator (17) connected to the comparator (16) for generating a value corresponding to the partial pressure of sulphur dioxide in the digester, the second function generator (17) being connected to said at least one multiplier of the first controller module (10), and an Arrhenius equation unit (23) connected to the first sensor (12) and connected to the means (18 to 20) for providing the plurality of constants for generating the digester reaction rate value.

Claim 10

Apparatus according to claim 5, claim 6 or claim 7, wherein the second controller module (30) includes means (32, 33) for manually setting a percent total sulphur dioxide value and a percent-free sulphur dioxide value and a comparator (34) connected to the total and free sulphur dioxide setting means (32, 33) for obtaining a difference therebetween, the comparator (34) being connected in the second controller module (30) through a multiplier (37) for multiplying said difference with the delignification rate.