High Temperature Peroxide Stage Optimization on Hardwood and Softwood Sulfite Pulps, 1997 Pulping Conference Proceedings

Over the past five years, the use of hydrogen peroxide for chemical pulp bleaching has increased significantly. As a part of this development, the conditions used for applying hydrogen peroxide have undergone continuous refinement in order to improve it’s applicability and efficiency for both ECF and TCF bleached pulps. One refinement has resulted in the High Temperature Peroxide stages, which are usually designated by (OP) or (PO).

This paper deals with the effects of retention time (30-120 minutes), temperature (85-110ºC), chelant type and alkali optimization on a (PO) stage when applied for Hardwood and Softwood Sulfite pulps with both low and high metals content, (Mn = 0.5 to 14 ppm). This allows a thorough understanding of the performance of High Temperature Peroxide so that the stage can be effectively designed and implemented in normal mill conditions.

The results show that high temperature and long retention times result in the best brightness gain, with a small decrease in viscosity of about 10%, when the pulp Manganese (Mn) content is low (Mn < 0.5ppm).="" as="" the="" mn="" content="" increases,="" the="" brightness="" gain="" will="" decrease="" by="" several="" points,="" but="" can="" be="" partly="" offset="" by="" the="" addition="" of="" a="" chelant="" to="" the="" (po)="">