Abstract
The influence of process variables in oxygen-bleaching on the pulp properties were studied and it was found that the variations of alkali-charge, oxygen pressure and reaction temperature cause considerable changes in viscosity, permanganate number and brightness of the bleached pulp, whereas reaction time is of less importance within two hours. The characteristics of bleached pulp and effluent load were also compared between oxygen-bleaching and conventional bleaching process. In the case of hardwood, the viscosity of oxygen-bleached pulp is slightly lower than that of conventionally bleached pulp of approximately the same brightness, however the permanganate number of the former is significantly high. On the contrary softwood and tropical wood pulps bleached with oxygen-alkali have the relatively poor properties under the conditions applied. It should also be mentioned that improvement of sequence subsequent to oxygen stage must be of importance. One of the significant advantages is that the effluent from oxygen stage does not include chloride ion at all, Oxygen bleaching seems to be advantageous for avoiding the pitch trouble which can be occured during bleaching of sulfate pulp of tropical wood, because the oxygen bleaching system does not form chlorinated resin that may be the origin of the pitch precipitated in various stages of bleaching process.
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