DETERMINING THE DEGREE OF COOKING IN A SULPHITE DIGESTER DELIGNIFICATION

摘要

To determine the degree of cooking in a sulphite digester used for delignification, the digester temperature (T) and pressure (Pd) are sensed (12, 15) and utilised in a unit comprising a plurality of function blocks to calculate the digester reaction rate (k) according to the Arrhenius equation. This output is multiplied by a value proportional to the partial pressure (p SO2) of sulphur dioxide in the digester to obtain a delignification rate value. The delignification rate value is integrated over time to determine the degree of cooking or Kappa Number. This number is compared to a desired set point value for the Kappa Number. When the actual Kappa number reaches the desired set point, a signal is produced which is provided to an operator. Function blocks spread over two controller modules are utilised to achieve the needed calculations in a simple manner without the use of an analog or digital computer.