Caro's Acid Activation of Sulfite Pulps, 2001 Pulping Conference Proceedings
R. P. Sundara, J. D. Kronis--Magnesium based sulfite mills (Magnefite mills) use a two or three stage totally chlorine free bleaching sequence to
produce 86 - 91% ISO pulp. Whether it is two or three stage bleaching the most common sequences include an
oxygen-containing delignification stage (Op or Eop) followed by medium or high consistency peroxide bleaching
with or without an interstage such a chelation stage.
This study investigates the use of Caro’s acid and Peracetic acid as an activating agent placed between the Eop and
P stages using caustic as alkali source and compares with a standard chelation stage. It has been found that Caro’s
activation not only achieves higher pulp brightness and viscosity and lower filtrate COD compared to Peracetic acid
and chelation treatment, but also reduces the total bleaching cost.