ragauskas@hotmail.com Mini Oxygen Stages for SW Kraft Pulps Mini Oxygen Stages for SW Kraft Pulps More Delignification with Less Capital More Delignification with Less Capital Art J. Ragauskas ragauskas@hotmail.com Evolution of Oxygen Delignification Evolution of Oxygen Delignification ? 1960/70s ? Basic engineering ? General chemistry ? 1980/early 1990s ? Process variables, energy, environmental, pretreatments ? Fundamental chemistry & pulp properties ? Late 1990s/2000 ? Yield, selectivity, process parameters, ? Lignin/carbohydrate chemistry, catalysis ragauskas@hotmail.com Application in North American Application in North American Bleach Plants Bleach Plants 0 25 50 75 100 125 150 175 M i l l i o n T o n s 1 9 8 3 1 9 8 6 1 9 9 4 2 0 0 0 Chlorine Chlorine Dioxide Oxygen Delignification ragauskas@hotmail.com Increased Selectivity, Yield, and Increased Selectivity, Yield, and Environmental Performance Environmental Performance 38 39 40 41 42 43 44 45 46 47 48 49 50 0 10 20 30 40 50 60 Pulp Yield, % 30 ECF 30 (O) 40 (OO) 50 (OO) Kraft KAPPA DEopD DEopD Jameel, H. "High Kappa Pulping and Extended Oxygen Delignification to Increase Yield," 1998 TAPPI Proceedings: Breaking the Yield Barrier Symposium, pps. 165-182. ragauskas@hotmail.com Chemistry of Oxygen Chemistry of Oxygen Delignification Delignification ragauskas@hotmail.com Oxidative Agents Oxidative Agents Addition to ring, ketones, aldehydes Hydroperoxide (O2H-) Attack of rings and carbohydrates Oxoanion (O-) Severe oxidation and fragmentation Hydroxyl (OH.) Addition to ring Superoxide (O2 -.) Oxidative Result Species ragauskas@hotmail.com Oxidation of Lignin Oxidation of Lignin OCH3 OH OH Free Phenolic OCH3 O O2 OCH3 O -H2O -O2 Canonical Resonance Structure OCH3 O O-O OCH3 O O O Muconic Methyl Ester ragauskas@hotmail.com Research Attention Research Attention ? APPLIED ? Oxygen delignification addresses the top P&P research need for increased mill closure (TAPPI Workshop Paper Industry Research Needs, 1996) ? Mini oxygen systems have not been as thoroughly investigated as warranted by capital cost effectiveness and performance ? FUNDAMENTAL ? The number of citations has risen to over 100/year ? The chemical mechanisms are controversial ragauskas@hotmail.com Research Objective I Research Objective I Examine the chemical similarities and differences in typical SW kraft pulp after standard O and mini O stages ? % Delignification ? Viscosity ? Fundamental lignin structures ragauskas@hotmail.com Experimental Design Experimental Design Bleaching Conditions ?O Stage: 10% cn., 90°C, 60 min., 2.5% NaOH odw ?D Stage: 2 kappa factors used – 0.05 and 0.20 (D0) at 10% cn., 70°C, 30 min. ?(E+O): 10% cn., 90°C, 20 min., 1.25% NaOH odw ?(E+O)*: 10% cn., 90°C, 40 min., 2.5% NaOH odw ragauskas@hotmail.com Oxygen Delignification Results Oxygen Delignification Results ragauskas@hotmail.com SW Kraft Pulp Delignification SW Kraft Pulp Delignification ? (E+O) provides up to 25% delignification ? At low caustic, the mini-O, (E+O)D(E+O), performs within 5% as well as a standard O ? By splitting caustic charge in mini-O, the interstage D stage enhanced performance of subsequent (E+O) 8 10 12 14 16 18 20 22 24 26 28 Brownstock NaOH:1.5 NaOH:2.5 NaOH:3.5 Kappa # Conventional O (E+O) (E+O)Dkf:0.05(E+O) ragauskas@hotmail.com Delignification from Mini O Delignification from Mini O ? Splitting caustic charge is not as effective as one dose in (E+O)* ? Placement of low kappa factor charge impacts the final delignification level ? (E+O) strongly complements the D0 0 5 10 15 20 25 30 K a p p a # B r o w n s t o c k O D o ( E + O ) * ( E + O ) * ( E + O ) ( E + O ) D k f : 0 . 0 5 ( E + O ) ( E + O ) ( E + O ) D k f : 0 . 0 5 ( E + O ) ragauskas@hotmail.com Viscosity from Mini O Trials Viscosity from Mini O Trials 0 5 10 15 20 25 30 35 Viscosity/cP B r o w n s t o c k O D o ( E + O ) ( E + O ) * ( E + O ) ( E + O ) D k f : 0 . 0 5 ( E + O ) ( E + O ) ( E + O ) D k f : 0 . 0 5 ( E + O ) ragauskas@hotmail.com Kappa Viscosity Kappa Viscosity Comparison of Mini O Trials Comparison of Mini O Trials A mini O stage is less sensitive to base induced pulp degradation than a full O BS O (E+O) D(E+O)* (E+O)(E+O) D(E+O)(E+O) (E+O)D(E+O), 1.5% base (E+O)D(E+O), 2.5% base (E+O)D(E+O), 3.5% base Kappa Viscosity 0 5 10 15 20 25 30 35 ragauskas@hotmail.com Selectivity of Mini O Selectivity of Mini O 0 1 2 3 4 5 6 7 8 9 Selectivity O (E+O) D(E+O)* (E+O)(E+O) D(E+O)(E+O) (E+O)D(E+O), 1.5% base (E+O)D(E+O), 2.5% base (E+O)D(E+O), 3.5% base ? (E+O) stage provides more selectivity than a full O ? The D stage placement is critical to the overall performance of the mini O ragauskas@hotmail.com Influence of Washing and Influence of Washing and Carryover Carryover ragauskas@hotmail.com Effect of Washing on Selectivity Effect of Washing on Selectivity 0 2 4 6 8 Selectivity O ( E + O ) ( E + O ) D ( E + O ) ( E + O ) ( E + O ) D ( E + O ) W a s h e d U n w a s h e d ? (E+O) stage provides much more selectivity than a full O ? The D stage placement is important to the overall performance of the mini O ragauskas@hotmail.com Interstage Washing Effect on Kappa Interstage Washing Effect on Kappa ? Washing was done between the first and second stage ? Carryover appears to slightly enhance the delignification of the stage ? A slight increase in delignification obtained when D stage is after (E+O) in mini O 0 5 10 15 20 25 Kappa # O D(EO ) (E+O )(E+O ) D(E+O )(E+O ) (E+O )D(E+O ) Interstage Washing No Interstage Washing ragauskas@hotmail.com Interstage Washing Effect on Viscosity Interstage Washing Effect on Viscosity ? In this case, washing slightly improves the viscosity of the pulp ? Loss in selectivity is therefore compensated by increase in delignification 0 5 10 15 20 25 30 35 Viscosity/cP O D(E+O ) (E+O )(E+O ) D (E+O )(E+O ) (E+O )D (E+O ) Interstage Washing No Interstage Washing ragauskas@hotmail.com BL Carryover: 2kg/ton BL Carryover: 2kg/ton ? The level of carryover does not have a pronounced effect on the levels of delignification obtained in the trials ? A slight drop in delignification does not have a major impact on viscosity 0 5 10 15 20 25 30 35 Viscosity (cP) D k f = 0 . 0 5 ( E + O ) * D k f = 0 . 2 0 ( E + O ) * ( E + O ) ( E + O ) ( E + O ( E + O ) * D k f = 0 . 0 5 ( E + O ) ( E + O ) * D k f = 0 . 2 0 ( E + O ) ( E + O ) * ( E + O ) D k f = 0 . 0 5 ( E + O ) * ( E + O ) D k f = 0 . 2 0 ( E + O ) * 0 2 4 6 8 10 12 14 16 Kappa # D k f = 0 . 0 5 ( E + O ) * D k f = 0 . 2 0 ( E + O ) * ( E + O ) ( E + O ) ( E + O ( E + O ) * D k f = 0 . 0 5 ( E + O ) ( E + O ) * D k f = 0 . 2 0 ( E + O ) ( E + O ) * ( E + O ) D k f = 0 . 0 5 ( E + O ) * ( E + O ) D k f = 0 . 2 0 ( E + O ) * ragauskas@hotmail.com BL Carryover : 10kg/ton BL Carryover : 10kg/ton ? In this case, the higher levels of carryover appear to reduce the delignification levels slightly ? Viscosity changes are not as pronounced as expected 0 2 4 6 8 10 12 14 16 Kappa # D k f = 0 . 0 5 ( E + O ) * * D k f = 0 . 2 0 ( E + O ) * * ( E + O ) ( E + O ) ( E + O ) ( E + O ) * * D k f = 0 . 0 5 ( E + O ) ( E + O ) * * D k f = 0 . 2 0 ( E + O ) ( E + O ) * * ( E + O ) D k f = 0 . 0 5 ( E + O ) * * ( E + O ) D k f = 0 . 2 0 ( E + O ) * * 0 5 10 15 20 25 30 35 V is c os ity, c P D k f = 0 . 0 5 ( E + O ) * * D k f = 0 . 2 0 ( E + O ) * * ( E + O ) ( E + O ) ( E + O ) ( E + O ) * * D k f = 0 . 0 5 ( E + O ) ( E + O ) * * D k f = 0 . 2 0 ( E + O ) ( E + O ) * * ( E + O ) D k f = 0 . 0 5 ( E + O ) * * ( E + O ) D k f = 0 . 2 0 ( E + O ) * * ragauskas@hotmail.com Summary of Selectivity Changes Summary of Selectivity Changes ? Increasing the number of (E+O) stages may have an impact on the overall selectivity 0 2 4 6 8 10 Dkf=0.05(E+O) Dkf=0.20(E+O) (E+O)(E+O) (E+O)(E+O)* Dkf=0.05(E+O)(E+O) Dkf=0.20(E+O)(E+O) (E+O)Dkf=0.05(E+O) (E+O)Dkf=0.20(E+O) Selectivity 2 kg/ton 10 kg/ton ragauskas@hotmail.com 31 31 P NMR Structural Elucidation P NMR Structural Elucidation ragauskas@hotmail.com Oxygen Selectivity Trials Oxygen Selectivity Trials -0.1500 -0.1000 -0.0500 0.0000 0.0500 0.1000 0.1500 0.2000 0.2500 1 0 % c n , l o w s t i r 1 0 % c n , m e d . s t i r 1 0 % c n , h i g h s t i r 1 8 % c n , l o w s t i r 1 8 % c n , m e d . s t i r 1 8 % c n , h i g h s t i r Selectivity Difference ? All differences are based on a normalized selectivity (1) change ? Higher consistency pulps have lower selectivity trends as demonstrated from the literature ? Rates in stirring are based on a 5, 15, and 30 hz rate for 10 seconds every 5 minutes for one hour ? Basis of effect was investigated by NMR interrogation of effluents ragauskas@hotmail.com Typical Typical Phenolic Phenolic Structures Structures OH OH OCH3 H3CO R R OH OH OCH3 H3CO R R 5,5'-Condensed Phenolic Subunits of Lignin Non-condensed (free) Phenolic Subunits of Lignin OH H3CO R OH R ragauskas@hotmail.com Lignin Structural Differences Lignin Structural Differences Observed in O Effluent Observed in O Effluent 0% 5% 10% 15% 20% Change From BS 1 0 % c n , l o w s t i r r i n g 1 0 % c n , m e d s t i r r i n g 1 0 % c n , h i g h s t i r r i n g 1 8 % c n , l o w s t i r r i n g 1 8 % c n , m e d s t i r r i n g 1 8 % c n , h i g h s t i r r i n g Free Phenolics 5,5'-Condensed Phenolics ragauskas@hotmail.com Important Structural Differences Important Structural Differences B r o w n S t o c k O ( E + O ) D = 0 . 0 5 ( E + O ) Carboxylic Acids Condensed Phenolics Free Phenolics 0 0.2 0.4 0.6 0.8 1 mmol/g lignin ? 31P NMR was used to evaluate the chemical differences ? Acid concentration did not change between the O and mini O ? Changes in phenolics are not as pronounced in mini O as in O ragauskas@hotmail.com Conclusions Conclusions ? Mini O systems have some inherent pulp property benefits over full O ? Placement of D stage is important to the selectivity obtained ? The NMR studies from O and mini O systems suggest that the concentration of the condensed and non-condensed phenolics may not directly correlate with bleachability ragauskas@hotmail.com Institute of Paper Institute of Paper Science & Technology Science & Technology