coagulants – operating by charge neutralisation – may be rendered inactive towards pitch particles if their charge is consumed by other anionic “trash” materials. Additionally, polyelectrolyte complexes (symplexes) formed from coagulant and soluble anionic materials are sticky, water- holding, and consequently very detrimental to machine runnability. Overcoming reduced activity of coagulants simply by increasing their dosage would be both costly and would affect machine performance. HYBRID polymers, with their lower cationic charge and bridging flocculation mechanism of performance, are less affected by anionic charge and represent a better choice in such systems. Native starch retention: Mills that operate with 100% OCC furnish can apply HYBRID polymer with the aim of reducing the colloidal load that causes deposits and interferes with retention, drainage, and strength additives. Despite natural variability in this kind of system, an increase in strength was established allowing for 3-5% basis weight reduction. Using proprietary starch assay based upon the reaction with I2/KI, it was established that at least part of this strength improvement originated from retaining granular native starch that had accumulated in the system. Measuring the increase in total starch content after the cooking of the filtered MC sample, showed a drop of the granular starch level in the filtrate from 55% to 13% when the HYBRID polymer was applied upstream in the system. Retention applications: Although deposit control applications are a focus of this paper, second- generation HYBRID polymers can also be applied to achieve a more mild and easier way to control the retention program components. As with the first-generation HYBRIDS, these products have been applied in many cases as a single polymer program, dual polymer programs with cationic and anionic flocculants, and co-mixed with cationic flocculants. As in the case of deposit control applications, proper mixing with the Pareto nozzle became best practice for the retention application. Typical advantages observed with HYBRID when used as part of retention programs included improved filler retention, improved formation, improved drainage, better basis weight, better moisture profiles and so on. MILL CASES 100% MODERN RECYCLED LINERBOARD MACHINE Application of HYBRID in the thick stock resulted in production increases of 5.5% (at 2lbs/t dosage) and 8.2% (at 4 lbs/t). This represents OEE changes from the pre-trial level of 76% to 82% and 88%, respectively. The mill also observed a reduction in effluent COD by 11%, mainly obtained through native starch retention – this was confirmed by I2/KI starch testing. This starch retention led to the increase in strength allowing for 83 tpd less fibre used to meet the compression strength target. TISSUE MACHINE A mill, using both virgin and recycled fibre, was interested in increasing a low FPR value (76%), reducing downtime and lowering the amount of solvent-based products used in cleaning applications. Retention was increased to 84%, downtime was reduced by 2600 min/year, and solvent usage was almost eliminated, saving the mill US$ 155,000 per year, whilst also improving operational safety. UNBLEACHED SWK BOARD WITH 15% RECYCLED FIBRE The application of HYBRID resulted in the turbidity reduction from 500 NTU to 300 NTU; this led to a productivity Figure 6. Impact of HYBRID and typical coagulant on system charge Second – generation HYRBRID polymers can also be applied to achieve a more mild and easier way to control the retention program components DEPOSIT CONTROL IN PAPERMAKING SYSTEMS WORLD PULP&PAPER 98