Modern Bleaching with Powerful Ozone Bleaching, 2005 Engineering, Pulping & Environmental Conference

The aim of this laboratory study was to investigate the impact of installing high consistency ozone bleaching or oxygen delignification as a first stage after cooking in an already existing bleach plant, D(EOP)D or D(EOP)DD.

The bleaching results showed that the chlorine dioxide consumption was considerably reduced and brightness ceiling was increased both by using oxygen delignification and ozone bleaching. The bleaching chemical cost can be reduced both by installing oxygen delignification and ozone bleaching.

Testing of mechanical properties showed that both the ozone-bleached pulp and the oxygen delignified pulp required less beating energy compared with the reference. There was no difference in bulk, tensile stiffness and light scattering, neither by using ozone bleaching nor oxygen delignification, but tear index decreased in both cases.

The environmental load can be decreased by using both ozone bleaching and oxygen delignification, as the filtrates are alkaline and can be recycled. As a consequence of that, the COD discharge can be reduced. Furthermore, the AOX discharge and organic halogens OX present in the pulp after bleaching will be lower as the chlorine dioxide consumption is reduced.