Pulp bleaching technology

Pulp bleaching technology


The purpose of pulp bleaching is to increase the brightness and clarity of the pulp with a given quality standards when it comes to strengths of fibers. One of the most technologically effective and ecologically safe methods of bleaching is through use of chlorine dioxide. The bleaching technology that utilizes chlorine dioxide and does not take advantage of elemental chlorine, on one or multiple stages of bleaching process is called ECF (Elemental Chlorine Free). The stage that uses ozone as a bleaching agent is what is called a Z-stage. The use of ozone in combination with chlorine dioxide is possible due to ozone's high reactivity. Substitution at one of the bleaching stages allows producing pulp of the required quality standards at the areas of brightness and strength as well as decrease the overall chemical consumption in the production process and reduce the amount of sewage disposal. Real world tests have shown that ECF technology with follow up effluent treatment causes minimal impact to the ecology.

Specialties and advantages



  • Ozone - bleaching reagent for softwood and hardwood pulp with high reactivity;

  • Ozone is injected directly into the pulp and provides a high degree of brightness (90%);

  • Filtrates produced can be reused in the bleaching process;

  • Economic viability comes from the fact that ozone is more economical effective and provides higher yield compared to chlorine dioxide;

  • Smaller ecological footprint is achieved through reduced water and chemical consumption and reduced chemical indicators in waste water. АОХ – в 2-3 times, COD – by 20-40 %, BOD – by 25-30 %, color – up to 60-70 %.



Why ozone?



Use of ozone as a bleaching agent:

  • Complies with BAT (Best Available Technologies) and market realities of the industry;

  • The only realistic alternative to chlorine based reagents to lower the lignin content in pulp;

  • Increases productivity and effectiveness of the production process through lowering of production and operating costs;

  • Improves characteristics of effluent and future proofs production process to the upcoming environmental regulation changes  



Effects on the product mix



Ozone bleaching technology finding its place in contemporary pulp mills in part due to increasing the product offerings to include items like: 

  • Dissolving pulp;

  • Acetate pulp

  • Cord pulp;

  • Pulp for nitration.