There are three bleaching lines (D, E and F-lines) in Niigata mill, Hokuetsu Kishu Paper Co., Ltd. The E-line started to be operated in 1998 at 1,200 T/D production capacity with a D
0-Eop-DnD bleaching sequence, which was the first operational ECF bleaching large-scale plant in Japan. In 2001, the productivity increased to 1,300 T/D by remodeling E-line, a bleaching sequence was changed to D
0-Ep-D
1. E-line has still been operated at 1,300 T/D productivity, which is about a half of a total production of three lines, because of remodeling digester, new construction of the F-line and others.
The bleaching agents consumption rate of E-line is the worth of the three. The D
0-stage washer has recently been changed an atmospheric diffusers with a wash press to improve bleaching agents consumption rate. In this paper, changes of operating conditions by changing D
0-stage washer were reported.
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