Pulp and paper applications in Europe
Currently, the two major bleaching agents used in the pulp and paper industry are hydrogen peroxide and sodium chlorate. Hydrogen peroxide is used across a wide range of pulp productions including chemical (both hardwood and softwood), mechanical and recovered fibers, in addition to the bleaching of annual plants, like bagasse and rice straws. Sodium chlorate on the other hand, is used only in the production of chemical pulp.
In the process of manufacturing mechanical pulps, i.e., SWG pulp (Stone Wood Ground), TMP pulp (Thermo Mechanical Pulp), CTMP pulp (Chemi Thermo Mechanical Pulp) and APMP pulp (Alkaline Peroxide Mechanical Pulp), hydrogen peroxide plays a key role in the development of the optical properties. Hydrogen peroxide remains the principal bleaching agent of mechanical pulps. Applied alone or in combination with other bleaching agents, it ensures optimal whitening performance.
Sodium chlorate is the principal bleaching agent on ECF (Elemental Chlorine Free) sequences, whereas hydrogen peroxide is the leading chemical in TCF (Total Chlorine Free). In both these bleaching processes, these products are the key agents to ensure a high degree of brightness while minimizing the impact of effluents.
Sodium chlorate is an on-site generator for chlorine dioxide. Chlorine dioxide is an efficient delignification and bleaching agent in ECF (Elemental Chlorine Free) bleaching sequences for all types of chemical pulp, kraft or sulfite. It enables ECF pulps, with high and stable brightness together with excellent mechanical properties, to be obtained with minimum cost and high yield.
Moreover, waste water from ECF pulps giving a level of aquatic toxicity much lower than that of conventional processes based on chlorine, ECF process has become a best available technology (BAT) and has obtained an enviable position of the most widespread in the world of chemical pulp bleaching.
Hydrogen peroxide is used as a bleaching agent, alone or in combination with others oxidizing or reducing agents, in the pulping stage of recovered papers, ensuring therefore a very high degree of brightening effect.