New Concept in Alkaline Peroxide Refiner Mechanical Pulping, 1999 International Mechanical Pulping Conference Proceedings

Eric C. Xu

Andritz Inc. Pilot Plant/R&D Laboratory

A new process concept for alkaline peroxide refiner mechanical pulping has been developed and investigated in large-scale pilot trial studies. The new process is based on peroxide bleaching chemistry, lignocellulose chemistry and refiner mechanism. It emphasizes preconditioning (P), refiner chemical treatment (RC), and proper distribution of bleaching reactions between the two after the chips being chemically impregnated. To reach an optimum bleaching efficiency, the new process, P-RC, requires a mild preconditioning and completes the majority of the bleaching reactions in the refiner chemical treatment. Because of the very short residence time in the refiner, a certain amount of high consistency retention after refining is required and is a necessary part of the refiner chemical treatment. Pilot trial results were in general consistent with the new concept, and demonstrated: 1) a mild preconditioning gave a higher bleaching efficiency and optical properties compared to a more aggressive thermo treatment; 2) there was a considerable brightness development, 2-3 points gain, during an interstage high consistency retention; and 3) a mild preconditioning was better than no precondition at all, as in a refiner bleaching process.