Förfarande och anordning för syrgasdelignifiering med förbättrad kappareduktion

摘要

The present invention relates to a process and a device for the oxygen delignification of cellulose pulp suspensions giving improved kappa reduction. According to the process in accordance to the invention, the return liquor (40) which is recovered from a displacement or washing device (20) after an oxygen stage (/17) is subjected to wet oxidation under pressure (30). The wet oxidation process is accelerated by the liquor being pressurized in an oxygen-containing media and preferably at an elevated temperature. The wet-oxidized return liquor is supplied to the cellulose pulp such that the wet-oxidized return liquor constitutes the bulk of the liquid part of the cellulose pulp suspension before the latter is conducted to an oxygen delignification stage. Sodium hydroxide is also supplied (35) in a quantity which is such that the oxygen delignification can take place in a buffered medium such that the pH is kept essentially constant during the whole of the oxygen delignification. The invention provides an optimum kappa reduction at minimum cost.