New insight in Micro-hole screening for the separation of fines Saurabh Kumar EFPRO-CEPI Early Stage Researchers Workshop 2012 1/16 Paper for recycling Introduction Share of paper for recycling of the world's papermaking fibre furnish increased from 40 to 54% between 1995 and 2009 It represents 200 millions tons in the world In EU countries: Recycling rate: 47 69% from 1995 and 2010 Recycled fibres are a major source of furnish in European Paper Industry Threats to paper recycling: waste collection; import/export; energy generation potential Recycled fibres average utilisation rate extremely variable: newsprint grade ~92%; graphic/fine papers ~10% Opportunity to optimise recycling & recycled fibre utilisation rate with new manufacturing concept(s)? 2/16
Manufacturing concept Introduction Single unit operations on the whole pulp, i.e. on a very heterogeneous material (scale range nm mm) Cellulose fibres Cellulose fines Mineral fillers Pulping Screening & cleaning Deinking Thickening Dispersing Reject ~20% losses containing 98% fines Is this linear & full-stream process the best adapted? Towards a rationalization of deinking lines through the implementation of dedicated treatments to specific pulp fraction 3/16 Future manufacturing concept! Introduction Fines Towards a rationalization of deinking lines through the implementation of dedicated treatments to specific pulp fraction Pulping ex. B. McNett classifier Fines Passing (P) 200 mesh (76µm opening) Long fibres Specific treatment Fines Specific treatment ERIC (ppm) 4000 3000 2000 1000 Fines contain maximum ink 50% ONP 50% OMG 100% ONP 0 R 14 P14 R28 P28 R48 P48 R100 P100 R150 P150 R200 P200 McNett fractions 4/16
by pressure screening Inlet Fibrous suspension Accept Shorter length fibres Reject Longer length fibres Micro-hole: 250µm Ø Smooth surface screen cylinder 5/16 Passage ratio and fibre length Passage ratio The first published results (TMP) gave: ( l β λ ) (Olson et al. 2000) P( l ) = e Illustration of fibre passage ratio curves (Gooding et al. 2001) Size constant λ : level of Pf(l) related to slot/hole size, Vp, pulp, etc. Shape constant β : degree of fractionation β = 0.5 β = 1.0 β = 5.0 Slot screening (macro) Hole screening Ideal case/perfect fractionation 6/16
Analysis of Passage ratio Passage ratio Virgin fibre pulp Deinking pulp Passage ratio, P 1.00 0.80 0.60 0.40 0.20 Chem ical pulp SGW Passage ratio, P 1.00 0.80 0.60 0.40 0.20 1st 2nd 1st stage 2nd stage 0.00 0.0 1.0 2.0 3.0 4.0 Fibre length (mm) 0.00 0.0 1.0 2.0 3.0 4.0 Fibre length (mm) For new screening configuration, the Micro-hole screen plate has β = 1.0 High fractionation efficiency 7/16 Understanding of the screen plate degree of fractionation Passage ratio Passage ratio, P 1.00 0.80 0.60 0.40 0.20 Micro-holes Degree of fractionation β: 1.0 ONPOMG 1st stage Chemical pulp 5g/L 0.7m/s SGW 5g/L 0.7m/s ONPOMG 2nd stage 1.0 0.8 0.6 0.4 0.2 Slots Degree of fractionation β: 0.5-0.6 Fibre passage ratio / Fibre length (mm) 0.20mm 0.15mm 0.10mm 0.06mm 0.00 0.0 1.0 2.0 3.0 4.0 5.0 Fibre length (mm) 0.0 0 1 2 3 4 5 6 From Julien Saint Amand & Perrin 03 Smaller perforations are more selective towards fines (cellulosic + fillers + ink+ micro-stickies ) separation into accepts than micro-slots 60µm 8/16
Rotor pressure pulses Accept chamber Screen basket Positive pulse screening phase Rotor hydrodynamics Background Negative pulse reverse flow for cleaning/back flush the magnitude increases the capacity of the screen Magnitude is proportional to the square of rotor tip speed positive pulse Feed side Mid section Reject side 5.0 mm Foil rotor Julien Saint Amand, 1999 100,000 measurements 5000hz 310 rotations Average values, maximum values 9/16 Screening capacity Rotor hydrodynamics Accept chamber Screen basket Fibre grammage, g/m² 160 120 80 40 Ci 11 g/l reject side Ci 05 g/l reject side Ci 11 g/l feed side Ci 05 g/l feed side 0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Ve (m/s) Mat formation 10/16
Screening capacity Rotor hydrodynamics Accept chamber Screen basket Fibre grammage, g/m² 160 120 80 40 Ci 11 g/l reject side Ci 05 g/l reject side Ci 11 g/l feed side Ci 05 g/l feed side 0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Ve (m/s) Mat formation and non disruption Offers the perspectives to increase the process capacity 11/16 Production of pulp fractions for selective processing or papermaking Free Ink fraction Deinking operations rationalization Fractionator Ink on fibre 12/16
Micro-hole screen application Application Deinking Deinking pulp Flotation loss: 23.7% Ink removal efficiency: 83% 100g Pulp 900ppm ERIC 76.3g Pulp 200ppm ERIC Flotation loss: 39% Ink removal efficiency: 81.0% 100g Pulp 900ppm ERIC 1 st 77.4g Pulp 234ppm ERIC 42g Pulp 105ppm ERIC 2 nd 3 rd Possible energy savings on fibre fraction (dispersing) Potential flotation benefits 13/16 Fines valorisation Application Papermaking f1 Bulk (cm 3 /g) 2 1.95 1.9 1.85 f2 SGW 1.8 f1 SGW & f2 SGW f1 SGW LF f2 1.75 0% 10% 20% 30% 40% 50% % added SGW Property Fines fraction Bulk (cm 3 /g) Breaking length (m)/ young modulus (MPa) Tear (mn.m²/g) Opacity (%) Light scattering coefficient (m²/kg) Air permeance (cm 3 /m².pa.s) Scott bond (J/m²) f1 f2 No effect No effect Fibrillar fines (f1) increase mechanical strength properties Twice as effective as f2 fines 14/16
Perspectives Pressure screening with micro-holes Optimization of screen plate and rotor design Increasing screening system capacity and consistency Applications towards new concepts Optimised deinking line right treatment to the right fraction Stratified paper manufacturing right fibre & fines fractions in the right layer Towards increased utilization rate in graphic grades 15/16 Thank you for your attention! Saurabh.Kumar@webctp.com The present research has been performed in the framework of the European project BoostEff European Community's 7th Framework Programme under Grant Agreement n 246059 16/16