outlet in a way that
Independently of the bleaching chemical used a medium consistency bleaching stage always
uses a medium consistency pump that feeds the pulp through the stage. In Figures 10.1 and 10.2
the pump is mounted on a stand-pipe which always has a certain level of pulp which is needed
for the pump to work properly. The pump pushes the pulp through the stage in an even manner
and it is important that air is not allowed to mix with the pulp as this can lead to a separation of
the pulp suspension into a liquor phase and a gas phase inside the reactor. This is called channelling
and it prevents a proper plug flow. Air in the pulp will also negatively influence the possibility
to transport and to wash the pulp properly after the stage. From the pump the pulp goes
to a mixer or a static distributor where the bleaching chemical is added to the pulp if the bleaching
chemical is chlorine dioxide, chlorine, oxygen, ozone (MC) or sometimes hydrogen peroxpulp