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world pulppaper 35 Bleaching of DIP is costly so efforts should be made to measure and control the effectiveness of deinking operations before the bleach plant the flotation cells. The objective is to provide a fibre feedstock with low and constant residual ink levels to the following hydrosulphite bleaching stage thus ensuring the paper machines receive a uniform brightness furnish. This residual ink regulation avoids any slowing of mill production if final brightness targets are not met. SavIng BleachIng chemIcalS Bleaching of DIP is costly so efforts should be made to measure and control the effectiveness of deinking operations before the bleach plant. A deinking plant providing furnish to a 110000 ty tissue and printing paper mill installed two BT-5400 brightness transmitters with UV fluorescence and ERIC measurements after the first flotation stage and then after the second flotation stage. Both stages operated at 3.5 consistency. In the first stage operators manage brightness levels by adjusting the mix of the recycled fibre quality to achieve stable target brightness. With this strategy brightness variations were reduced. In the second stage operators managed the residual ink ERIC levels by process adjustments. By reducing ERIC the need for bleaching chemicals was reduced without sacrificing brightness. Access to accurate and real time data about brightness has enabled the mill to maintain its stringent quality control standards while simplifying its process and cutting unnecessary chemical costs. This chemical saving plus the more common use of lower cost recycled fibre has provided a payback of less than one year. managIng PulPer BrIghtneSS for loweSt fIBre coSt An inline brightness transmitter can be used at the beginning of a batch re-pulping operation to achieve the right brightness for subsequent stages of ink removal and bleach with minimum furnish cost. For example a tissue mill that recycles waste paper installed a BT-5500 brightness transmitter on the wall of a batch pulper about 1 metre from the maximum fill level. The brightness measurement was on a large display above the pulper to emphasise its importance to the operators. To achieve their target brightness the mill used several qualities of baled waste paper with significantly different price levels. The highest priced bales contained no ink since it is paper mill trim waste. The mill reasoned that with the inline measurement the operators would get an indication about 8 minutes before the end of a 20-minute batch sequence if the brightness was on above or below target. This would allow them to decide if more high priced premium baled paper should be used to achieve their target or if lower cost bales could be substituted and still achieve the target brightness. This operator-managed strategy with the brightness measurement made at just the right time has saved this particular mill about 250000 in fibre costs. The strategy used by the operators is shown in figure 3. The operators aimed for a range of 63 to 78 ISO brightness in the batch pulper. figure 2. Flotation cell monitoring with BT brightness transmitters figure 3. ISO brightness measured in the batch pulper BT results versus laboratory