Efficient silicate-free hydrogen peroxide bleaching of mechanical pulps

摘要

Mechanical pulps are bleached with alkaline hydrogen peroxide in presence of sodium silicate,which may cause some scaling problems in mill operation.It is therefore interesting to find silicate substitutes.Different polymers were evaluated on different softwood or hardwood high-yield pulps(TMP,PGW and CTMP).Among the different tested products,a polyhydroxyacrylate polymer showed a great potential to increase the bleachability of mechanical pulps.The dosage to be used on the different pulps was studied.Comparison was done with conventional sodium silicate in terms of pulp brightness,hydrogen peroxide consumption and chemistry modification.Results showed that it was possible to replace totally sodium silicate in hydrogen peroxide bleaching of mechanical pulps with positive effects on pulp quality and bleaching costs.