Water Circuit System for Graphic Papers

1 Water Circuit System in a DIP-based Newsprint Mill 

The system consists of three water loops, two in stock preparation (because of the combination of flotation - dispersion - flotation) and one in the paper machine. The water circuit design follows the previously mentioned principles of counter current flow and thereby allows the fresh water to be used to the maximum effect. In addition the save-all is followed by an additional DAF unit DAF 1 is used as a kidney for removal of detrimental substances, treating the make-up water from the paper machine (clear filtrate) together with part of the clear filtrate from the disc filter in loop II. DAF 2 treats the filtrates from reject and sludge dewatering. The clarified water is partly recycled back into loop I, the rest being sent to the effluent treatment 

the fresh water is added only at the paper machine. White water 11 is used for redilution after thickening in the stock preparation plant. The save-all clear filtrate is used for make-up in the fiber preparation system. Filtrate from the thickening stage in the fiber preparation system is the main source of water for slushing and dilution. Waste water is sent as filtrate from reject handling to the end-of-pipe effluent treatment. 

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