摘要：

at the paper machine headbox increased to 13 800 mg/L. Appropriate reuse of screw press white water: The extremely rich white water (0.9%)extracted from the rejects screw press is mixed with the rich white water in the TMP rich white water chest.This mixing is a good example of a failure to respect the white water segre- gation rule. Instead of being mixed with the rest of the white water, the water extracted from the screw press should be used directly to dilute a high-consistency stream like the refined rejects.Figure 3 represents the flowsheet of this modification. This strategy reduces the consistency of the cloudy white water used for the dilution of the clean- ers' feed and reduces fibre loss to the sewer by 1 adt/d. This strategy has almost no effect on effluent flow or on dissolved solids levels. Increased use of white water on the paper machine showers: Increased white water use o n the paper machine is essential for substantial reduction of the mill's fresh water consumption. Fresh water used on the machine is in fact the largest addition of water in the mill. White water can be used instead if prop er precautions are taken to avoid plug- ging the shower heads and the felts.A system for the use of white water on the machine should include both self-cleaning showers and a very fine fil- ter to remove long and medium fibre from the white water. The white water used for this application should be the leanest available in the mill. It was decided to take the required 1350

展开