Effects of a multistage ozone bleaching process were compared with those of a conventional single-stage process. The multistage process is composed of alternate three times repetition of ozone bleaching and water-washing. The influence of temperature on bleaching effects was also examined.
The results obtained are as follows :
(1) In comparison with the conventional process, the amount of ozone consumption in the multistage process was distinctly less, e. g., the amount of ozone consumption in the multistage process was 2.6%, at 80% pulp brightness, although the corresponding value was 4.7% in the conventional one. Moreover, in the multistage process the decrease in viscosity of bleached pulp was somewhat prevented.
(2) In the range of bleaching temperature 030 C, the effects mentioned in the multistage process were more distinct with lowering temperature.
(3) The effects stated above are probably attributed to the removal of ozone oxidation products by water-washing.
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