A 10-DAY MILL TRIAL OF NEAR-NEUTRAL SULPHITE DEINKING. PART Ⅱ: RECYCLED PLANT

摘要

In this second part of a three-part series on a 10-day mill trial of near-neutral sulphite deinking, we report a detailed analysis of the data collected within the recycle plant. A flotation cell-by-cell analysis showed that: 1) in secondary flotation, brightness was 2 to 3 points higher in conventional than in near-neutral flotation, 2) with near-neutral deinking, more fragmented ink went into secondary flotation (870 vs. 730 ppm), but was equal at the secondary accepts, 3) for ink coverage, near-neutral flotation matched conventional and out performed the industry average in primary flotation; by the end of flotation, ink coverage was higher with near-neutral than with conventional deinking by 0.2-0.5 percent, 4) the ash contents for both conventional and near-neutral deinking were about the same, 5) the rejects consistency for sulphite-based neutral deinking was within normal mill operations, and 6) the difference in solids loss between conventional flotation (8.8%) and near-neutral flotation (9.6%) was within the normal variation seen in the flotation process. The microstickies measurement of the recycle plant using the IPST detection method showed a 40% reduction. It also appears that there is a relationship between the deposition rate index as measured by the Paprican method and the Effective Measurement of Microstickies Accumulation (EMMA) as measured by the IPST method. Finally, the amount of free ink in the process dilution water was similar during conventional and near-neutral deinking.