CHLORINE-FREE BLEACHING METHOD FOR DISSOLVING-GRADE PULPS

摘要

A three-stage bleaching process for dissolving grade pulp utilizes the sequence EOP-Z-P and the off gas from the Z stage is delivered to the EOP stage whose parameters are controlled to fully react all of the oxygen of the off gas. The filtrate or waste water from the Z stage, at a pH below 3, serves to dilute the EOP pulp before Z stage bleaching and/or for de-ashing of the P pulp follow- ing the P stage.