Stora Enso Kabel (Hagen, Germany) is one of the leading suppliers of single and double-coated wood-containing printing papers. The production program on 3 paper machines covers paper for rotogravure and offset printing, sheets and reels, in a range of 35 - 170 g/m~2. The pulp furnish for the paper machines consists primarily of market pulp and bleached SGW, which is produced in 2 lines with a total capacity of 540 t/day. Until November 1997, the SGW was bleached in a simple hydrosulfite bleach plant (rotogravure) and a single-stage, high-consistency peroxide bleach plant with subsequent hydrosulfite bleaching (offset). Due to an ever increasing demand for paper qualities with higher brightness and also because of increasing production quantities, existing bleach plants could not longer meet the requirements. Thus, in November 1997, an additional new 2-stage peroxide bleach plant (delivered by Andritz AG) with a subsequent, existing hydrosulfite stage was started up. With this new 3-stage bleach plant (capacity 315 t/day) the target brightness of 84.5% ISO was reached shortly after start-up. The concept of the plant with medium and high-consistency bleaching stages and the key machines are presented, followed by a presentation of typical operating conditions and plant data. Operating results from the first 6 months in 1998 demonstrate that the new 2-stage bleach plant can achieve approx. 1.5% ISO higher final brightness than the older, single-stage peroxide bleach plant, starting from the same unbleached brightness and with the same chemical charges. Further important goals when building the new bleach plant were achieving a low additional COD load for the effluent treatment plant and leaving pulp properties unchanged. A COD-balance for the groundwood and bleach plants together is presented and typical waste water data are shown. Pulp measurements demonstrate that the freeness and strength properties of the SGW pulp remain practically unchanged in the bleach plant.
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