#04 –EPISODE 4

A new chemistry for fibres bleaching!

To produce paper pulps” whiter than white” but also cleaner, less consuming water and electricity...


The Principle is simple !! To produce paper pulps” whiter than white” but also cleaner, less consuming water and electricity; therefore more environmentally friendly.

In fact, the chemical pulps are generally bleached with sequences based on serveral bleaching stages. While, during the last decades, the chemistry of bleaching stages has been revisited to reduce the environmental impact, the kraft pulp mills use mainly chlorine dioxide (ClO2) as bleaching agent, generating some organochlorinated compounds (AOX) in the effluents. Nevertheless, it is still possible to enhance this environmental impact. This is the reason why a new bleaching stage, called Dalkmod been developed and patented by CTP and LGP2.

This new stage is based on the use of chlorine dioxide in alkaline medium in presence of other bleaching chemicals conventionally used in the bleaching lines of the paper pulp mills.
Diverse studies were carried out on unbleached and semi-bleached kraft pulps of different wood species (hardwoods, softwoods, eucalyptus) (kappa number: 22 to 3).

They allowed to:

  • Reduce the environmental impact (COD up to 50%, AOX up to 70%)
  • Decrease the water and energy consumption by the removal of one bleaching tower and on washing stage
  • Increase the production by reducing the time: - 60 to 180 minutes
  • Reduce the ClO2 consumption up to 50%
  • Decrease the production costs up to 5 €/t (without process optimisation)
  • Maintain the paper pulp quality. The pulp viscosity, its brightness and optical and mechanical properties before and after refining are equivalent to the reference pulp.

It is a win-win project between CTP and the industrialist.

Do you want to find out more? Contact-us!

Project leaders = Auphélia BURNET & Michel PETIT-CONIL