Process for obtaining a predetermined Kappa number in sulfate pulping

Abstract

A fully controllable process is provided for the manufacture of sulfate pulp having a predetermined degree of delignification and therefore a predetermined Kappa number. A sample of the pulping liquor is taken at a stage at which the preliminary alkali-consuming physical and chemical reactions and processes have substantially been completed, the sample is analysed to give the content of alkali in the liquor, and the alkali content adjusted to at least 20 g calculated as NaOH per kilogram of wood initially added, by addition of alkali. From this alkali content the pulping intensity expressed as "H" factor for obtaining the desired Kappa number is determined, and the pulping time and pulping temperature during delignification are controlled according to this H factor. It is also possible to adjust the alkali content in a controllable manner by injecting white liquor, black liquor or water into the digester. The process is applicable to continuous digesters as well as batch digesters.

Dependencies are inferred from the claim text.