Ozone application in the dissolving pulp bleaching


A detailed study of the ozone stage (Z) in different bleaching sequences is an alternative to the traditional use of hypochlorite in order to investigate different sequences of bleaching, OZ(EH)P, OZ(EH)D, OZ(EP)P, OZ(EP)D, OZ/D(EH)P, OZ/D(EH)D, OZ/D(EP)P, OZ/D(EP)D e OZP, for the production of dissolving pulp for viscose. It was used eucalyptus chips, prehydrolysis process, kraft pulping (PHK) and oxygen delignification were performed under standard conditions to generate a non-bleached pulp sample, with typical characteristics of dissolving pulp. The Z stage was investigated regarding its ozone charge (3 and 4 kg/t of O3), pH (3.0, 4.0 and 5.0) and temperature (55 °C and 70 °C). Subsequent stages were made in fixed conditions and the bleaching sequence OD(EH)DP was used as reference. The Z stage allows to viscosity pulp control in the range of 400-550 dm3/kg; high brightness gains were achieved using Z stage technology; the best bleaching sequences based on viscosity, brightness and brightness reversion (NCP) were OZ(EP)P and OZ(EP)D, where pH 3.0, 55 °C and 3 kg/tas the optimal condition of the Z stage; the quality parameters of the pulp, dissolving grade viscose has been reached, except for the contents of silica; the sequences OZ(EP)D and OZ(EP)P showed a lower chlorine dioxide consumption, with savings of 4.5 kg/t compared to the reference bleaching sequence, OD(EH)DPQ.


Fernanda Rosa Vieira;Jorge Luiz Colodette; Marcela Freitas Andrade1

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