Pulp bleaching

In the paper industry, bleaching pulp is of great importance to produce good quality paper. However, optimally and cost effectively setting up the process is a continuous challenge. Corrosive chemical are often used for this purpose. Nedmag focuses on modernising existing bleaching formulas. Magnesium hydroxide is an innovative product which allows for environmentally friendly pulp bleaching.

Nedmag produces a stable magnesium hydroxide suspension. Depending on the bleaching process, it can replace various chemicals such as lye, silica, and/or magnesium sulfate. It is an environmentally friendly and cost effective alternative. In addition, magnesium hydroxide can significantly improve the productivity of paper machines and pulp production lines by reducing the time needed to clean equipment. Magnesium hydroxide is not harmful, is non-corrosive, and safe to use.

“Magnesium hydroxide can be used to bleach pulp in an environmentally friendly manner”

Collaboration

The business department continuously works on improving bleaching formulas, which results in innovative bleaching technology. Nedmag offers an experienced team, specialised in magnesium hydroxide pulp bleaching, that fully supports the transition to magnesium hydroxide. Nedmag and Imerys' research facilities are fully at the customers' disposal.

 

magnesiumhydroxide pulp

 

Magnesium hydroxide

Bleaching pulp with magnesium hydroxide offers the following benefits:

  • Higher whiteness ratings.
  • Lower chemical and biochemical oxygen consumption (typical reduction is approximately 40%).
  • Better pulp dewatering, allowing for a higher yield and cleaner water pipes.
  • Lower maintenance costs for paper machines and pulp production lines.
  • Magnesium hydroxide is not harmful, is non-corrosive, and safe to use.

Because producers use a variety of processes, different benefits can be distinguished for mechanical pulp bleaching and chemical pulp bleaching.

Mechanical and chemical pulp bleaching

In  mechanical pulp bleaching,  wood fibres are separated from each other using mechanical energy. When bleaching mechanical pulp, magnesium hydroxide offers the following benefits:

  • Lower costs at the same or higher whiteness ratings, by reducing or substituting lye and silicate.
  • Higher whiteness ratings. The colour of the pulp can be influenced by different alkali and peroxide ratios.
  • Increased productivity for paper machines and the pulp production line due to improved pulp dewatering.

In chemical pulp bleaching, especially during the kraft process, wood fibres are separated by dissolving them in chemicals. Magnesium hydroxide can be used in the lignin oxidation phase, the alkaline extraction phase, and for bleaching with peroxide. Magnesium hydroxide offers the following benefits for these processes: 

  • Lower costs per tonnes of pulp, due to the (partial) substitution of magnesium sulphate and lye.
  • Higher whiteness ratings. thanks to an optimum pH-profile.
  • Further cost savings by reducing the use of chemicals such as hydrogen peroxide.