AO_Pulp und Paper

Pulp & Paper

Versatile bleaching and anti-slime agents 

Evonik supplies Hydrogen Peroxide and Peracetic Grades specifically designed for the different needs in the pulp & paper industry. 


In the pulp & paper industry hydrogen peroxide is applied as a versatile bleaching agent in cheical pulp bleaching sequences, in mechanical pulp bleaching (as the only or as the dominant bleaching chemical) as well as in paper recycling with printing ink removal (de-inking). The bleaching conditions can be adjusted within a wide range to suit equipment limitations or a given temperature level.

CHEMICAL PULP

In the bleaching of kraft pulp, the internationally most important pulp type, hydrogen peroxide is one of the chemicals applied in multi-stage processes. Alkaline conditions are required to generate the active bleaching species from hydrogen peroxide, the perhydroxyl anion. Consequently, extraction stages can be used for peroxide addition to boost the effects on extraction and brightness. The application of hydrogen peroxide allows top brightness levels with improved brightness stability, optimized economy through savings in the total chemicals required, low residue of halogenated compounds both in pulp (OX) and in effluent (AOX) and low effluent color. Hydrogen peroxide is applied as the exclusive bleaching agent in sulfite pulp brightening. In single or two-stage processes it allows bleaching to full brightness.

MECHANICAL PULP 

Mechanical pulp, generated by the conventional ground-wood process or modern refining technology (TMP or CTMP, and APMP processes), is bleached with hydrogen peroxide to very high brightness levels. Yield and fiber properties are kept on a very high level. The conventional approach is the application of hydrogen peroxide together with caustic soda as alkali source, sodium silicate for stabilization and buffering and a chelant for the sequestering of heavy metal traces in the wood pulp.
Hydrogen peroxide gives high brightness and high brightness stability against aging and yellowing, moderate effluent load and good biodegradability.

RECOVERED PAPER

In paper recycling the removal of printing ink is the most important objective when the fibers are reused in the manufacture of printing papers or tissue grades. Brightness and color removal are secondary targets. Fiber brightening is achieved mainly with hydrogen peroxide. The alkaline conditions of the repulping of wastepaper are ideally suited for a simultaneous application of hydrogen peroxide. Small amounts of hydrogen peroxide are sufficient to improve brightness and prevent alkaline yellowing. In post bleaching steps, e.g. in a disperser, the brightness is further improved.

For Pulp & Paper applications Evonik recommends the use of our standard hydrogen peroxide grade

HYPROX®.

 

Slime formation in paper machines causes high costs. This requires the implementation of anti-slime agents. Typical anti-slime agents are bromium-, organic sulfur- and quaternary ammonium compounds, as well as aldehydes. The application of PERACLEAN® represents an environmentally benign alternative to the currently implemented organic biocides.

After the disinfection, it decomposes into harmless residues like water, oxygen and acetic acid.

In highly organic loaded water circuits of paper mills bacteria can produce unwanted smell which negatively impacts the final paper quality or the environment. In such cases PERACLEAN® as a biocide and strong oxidizer can be used for smell control.

High brightness in TCF and ECF pulps can be achieved by using PERACLEAN® in a post-bleaching stage. Advantages of post-bleaching with PERACLEAN® are:

  • higher brightness

  • good brightness stability and no yellowing

  • cleaner pulp 

  • lower consumption of other biocides 

  • stand-by solution with limited investment costs

 

In many mills there is a need to disinfect  the water system to prevent microbial  contamination of fibrous material in the circulation water. Polysaccharides, which  are leached from the pulp, act as nutrients for microbial growth and result into formations of microbial or semi-chemical  slimes. These cause critical failures in papermaking and reduction in the quality of paper, resulting in overall losses. 

The uncontrolled growth of slimes can  ultimately cause the breakages of paper and, as a consequence, a stoppage of the production line.

Solutions of PERACLEAN® peracetic acid have been  proved to be an effective bio-film remover in the water systems and are used as an environmentally benign oxidizing biocide in the pulp & paper industry. 

The addition of HYPROX® into the  effluent is a useful tool to prevent odors  and anaerobic conditions.

Further information about water treatment can be found here.

 

Please contact us directly for further information about our hydrogen peroxide grades or formulations.

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