Trycksatt klordioxidblekning med återvinning av klordioxid

摘要

The present invention relates to a multi-stage paper pulp bleaching process in which at least one of the bleaching stages is carried out in a reactor with chlorine dioxide at a pulp concentration of 8-40 %. The pulp is bleached with chlorine dioxide in a pressurized vessel at an overpressure of 0.1-10 bars and at a temperature of between 90-110 DEG C and for a reaction time of 1-90 minutes. The pressure of the pulp is lowered in a downstream tower in a manner such as to also lower the temperature of the pulp and enable residues of chlorine dioxide to be extracted in gas phase.