Refiner Bleaching With Magnesium Hydroxide and Hydrogen Peroxide, 2007 International Mechanical Pulping Conference

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Conventional bleaching of mechanical pulp with magnesium hydroxide and hydrogen peroxide has shown significant economic benefits for pulp mills over bleaching with caustic soda and sodium silicate. Magnesium hydroxide (Mg(OH)₂) bleaching generates lower effluent BOD/COD, higher pulp yield, lower anionic trash in the paper machines, reduced oxalate scaling and in some cases, higher bulk.

NORPAC has taken this bleaching process one step further through their patented refiner bleaching technology, which provides an enhanced and more efficient peroxide bleaching process. The excellent mixing, high temperature and high consistency of the refining environment solubilize the magnesium hydroxide and provide an excellent bleach reactor with the addition of hydrogen peroxide. By adding magnesium hydroxide into the refining system, refiner energy demand is reduced by 100-200 KW-hr/odmt and pulp strength is improved by 5-10%. This paper describes NORPAC's development of refiner bleaching with magnesium hydroxide and hydrogen peroxide, University of Maine lab refiner studies that support NORPAC’s work and the additional benefits this technology provides to the mill.