クラフトパルプのオゾン漂白における針葉樹パルプと広葉樹パルプの漂白性
1976 年 30 巻 7 号 p. 381-391
詳細
1976 年 30 巻 7 号 p. 381-391
From environmental point of view, the use of ozone as a bleaching agent seems to be favorable. In this paper, unbleached pine and beech kraft pulps with almost the same brightness were bleached to assess the bleachability of softwood and hardwood pulps in ozone bleaching. The results obtained were as follows.
1. The optimum moisture content was about 50% for both pine and beech pulps.
2. Beating time of ozone bleached pulps was reduced by about one half in comparison with unbleached pulps. Maximum strength of pulp sheets was established at less CSF 300 ml.
3. Increased brightness per consumed ozone of beech pulps was superior to that of pine, especially in the early stage to middle stage of bleaching time Rates of delignification of beech pulps were almost the same as those of pine. Therefore it was presumed that factors, other than quantity of lignin and rate of delignification, also took part in the difference of increasing the brightness between pine and beech. Reduction of viscosity of bleached pulps was remarkably in both species.
4. Strength properties of pulp sheets of ozone bleached pulps decreased compared with unbleached pulps, and the degree of reduction of pine was larger than that of beech.
5. COD (Mn) pollution of ozone bleaching waste water from pulps over brightness 72% was 3050 g/kg-pulp, and BOD/COD (Mn) ratio was 0.60.8, and those of beech were a little higher than those of pine. Reduction of. COD (Mn) by activated sludge treatment of Ozone bleaching waste water was higher than that of alkaline extraction waste water of chlorine containing bleaching system, and that of beech was higher than that of pine.
