Figure 2. Retention of nonionic starch from recycled fibre using PAC, silica and polymer. DDA tests with different retention systems were conducted and starch retention was measured by iodine staining from the DDA filtrate. Figures 3a & 3b. Dryness after DDA (a) and after laboratory press (b). WORLD PULP&PAPER 65 The resuls show that FennoSil 55D polymer sheet dryness was better than with conventional CPAM at both measuring points. Effect of polymer system on drainage. Drainage was studied by measuring sheet dryness after the DDA experiment and after the laboratory press (Figure 3). The results show that FennoSil 55D polymer sheet dryness was better than with conventional CPAM at both measuring points. This shows that FennoSil 55D improves drainage and dewatering. Dryness after the press section is important for speed increase, suggesting that with FennoSil 55D production speed can be increased. Polymer dosage, kg/t 0 0,2 0,4 0,6 0,8 25 20 15 10 5 0 Starch reduction in DDA filtrate, % Drainage system:PAC + Silica + Polymer Pulp:OCC 100 % PAC Silica Amphoteric polymer Total polymer dosage, kg/t 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 18,0 17,5 17,0 16,5 DDA dryness after wire, % Drainage system: Alum + Polymer + Betonite Pulp: OCC 50 % + Kraft 50 % CPAM Amphoteric polymer Total polymer dosage, kg/t 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 45,5 45,0 44,5 44,0 43,5 43,0 42,5 DDA dryness after laboratory press, % Drainage system: Alum + Polymer + Betonite Pulp: OCC 50 % + Kraft 50 % Constant pressing: 1 min 4 bar CPAM Amphoteric polymer