Hydrogen peroxide bleaching is a single-stage or two-stage process. This bleaching agent can be used in extraction stage of the bleaching sequence. However, it is also useful as a terminal stage. When it is used, it can be saved a great amount of ClO2 chemical in the subsequent stage. Some bleaching plant design the system as the first tower is at medium consistency whereas the second tower at high consistency. Ours bleaching plant is two stages and medium consistency system. We used it in extraction stage. At both stages we used 3-4 kg/ton whereas the magnesium sulfate is 1-1.5 kg/ton. At first extraction stage we also used oxygen with it. A two-stage process has an advantage in providing a cleaner pulp. The chemistry is very similar to that involved in oxygen delignification.
Hydrogen peroxide is a unique bleaching chemical with many applications in the bleach plant. Other bleaching chemicals have specific uses and requirements, but peroxide can be used for delignification or brightening and it doesn't require any special equipment. Peroxide is often used to reinforce extraction stages in elemental chlorine free (ECF) bleaching sequences. Peroxide use is essential to reaching the target brightness in total chlorine free (TCF) bleaching sequences. This course focuses on peroxide bleaching of chemical pulp, but peroxide is also used extensively for mechanical pulp bleaching