Improved Brownstock Quality FY2007 Yunqiao Pu, Arthur J. Ragauskas Dongho Kim Institute of Paper Science and Technology, School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta, GA 30332 TIP3 Year-end Project Review Meeting, Atlanta, GA August 8, 2007
Project Objectives and Key Questions To evaluate the use of carbon dioxide acidification to improve pulp washing, reduce bleaching costs, and improve products performance for Georgia s southern softwood resources. Main Objectives: Effect of carbon dioxide acidification washing for GA SW bleachable grade: COD, carryover sodium, extractives, physical properties Effect of carbon dioxide acidification washing for GA SW kraft liner board: COD, carryover sodium, extractives, physical properties Effect of carbon dioxide acidification in combination with alcohol ethoxylates. Effect of carbon dioxide acidification on subsequent bleaching stage
Project Status - proposed vs. achieved Kraft SW brownstock to assess CO 2 injection for improved washing Done Kraft SW linerboard to assess CO 2 injection for improved washing Done Kraft SW brownstock to assess CO 2 injection/ alcohol ethoxylates for improved washing Done Kraft SW liner board to assess CO 2 injection/ alcohol ethoxylates for improved washing -Done Evaluating improved D 0 (EO) bleaching Done Evaluating physical properties of pulp and linerboard - Done Final report on FY 2007 project
Key Findings to-date Depending on the different brownstock, carbon dioxide acidification washing can reduce the carryover COD by 21% Carbon dioxide acidification washing can reduce the carryover sodium by 23% CO2 acidification washing can reduce extractives content by up to ~50%. The use of CO2 washing can improve drainage property After D(EO) bleaching, the CO2 washed pulp demonstrated slight improved physical/strength properties. After D(EO) bleaching, the CO2 washed pulp had lower AOX content by ~ 6.8% in the bleaching effluent.
Washing experimental Laboratory Displacement Washer Employ 5 od gram sample ph3.7 CO2 solution (amount adjusted to obtain final ph 8.5), 2%CSC, DF- 2, 60 o C, vacuum-7in.hg retention time 5~10 (1st displacement)-5~10 min (2nd displacement) -10min(3rd displacement) Analyzed: Extractives, strength properties, COD, Na
ph value after washing Linerboard pulp Filtrate ph Squeeze ph Run #1 9.4 8.9 Run #2 9.3 8.7 Run #3 9.4 8.9 Run #1 8.6 8.4 Run #2 8.7 8.4 Run #3 8.7 8.4 Brownstock Run #1 8.6 8.4 Run #2 8.7 8.4 Run #3 8.8 8.5 Run #1 8.4 8.2 Run #2 8.4 8.1 Run #3 8.4 8.1 Post-O2 Run #1 8.8 8.5 Run #2 8.7 8.4 Run #3 8.7 8.5 Run #1 8.6 8.3 Run #2 8.5 8.2 Run #3 8.6 8.3
COD carryover in the washed pulp Carryover COD(mg/g OD Pulp) 12.0 10.0 8.0 6.0 4.0 2.0 0.0 w ithout CO2 w ith CO2 Carryover COD(mg/g OD Pulp) 12.0 10.0 8.0 6.0 4.0 2.0 0.0 w ithout CO2 w ith CO2 Linerboard pulp Bleachable pulp 12.0 Carryover COD(mg/g OD Pulp) 10.0 8.0 6.0 4.0 2.0 0.0 w ithout CO2 w ith CO2 Post-O2 pulp Laboratory Displacement Washer STDEV: 0.2~0.4
Metal ion content in washed pulp samples (mg/kg) Na K Mg Ca Bleachable pulp 2320 506 198 930 2830 568 202 1000 Linerboard pulp 4475 550 312 853 4765 573 303 795 Post-O2 pulp 1560 320 282 1220 2035 358 276 1205
COD Linerboard pulp (Inland) Bleachable pulp (Cortland) Post O2 pulp (Courtland) 6.6 3.6 5.0 4.8 2.5 4.5 washing conditions: 5g pulp, ph3.7 CO2 solution (amount adjusted to obtain final ph 8.5), 2%CSC, DF- 2, 60oC, vacuum-7in.hg, retention time 5min- 5min(1st displacement)-5min (2nd displacement) -10min(3rd displacement) Linerboard pulp Bleachable pulp Post O2 pulp Before wash 20.3 12.7 21.3
Effect of CO2 washing on TMP extractives content and strength properties. Extractives, % Tensile Index, Nm/g Burst Index kpa.m 2 /g Original 2.4 18.8 0.8 Control Washing 1.5 20.0 0.9 CO2 Washing 1.3 20.1 0.9 Effect of CO2 washing on linerboard pulp extractives and strength properties. Extractives % Density (g/cm3) Tensile index Nm/g Tear index (mn.m2/g) STFI index (Nm/g) Control washing 0.041 0.417 48.1 24.6 18.3 CO2 washing 0.021 0.422 48.9 25.3 19.1 Initial extractive 4.45% Drainage properties for linerboard pulp. ph11.5 pulp slurry - Control ph 11.5 pulp slurry + 0.25% Alcohol ethoxylates ph 8.5 pulp slurry adjusted by CO2 ph 8.5 pulp slurry adjusted by CO2 + 0.25% Alcohol ethoxylates Time to 700ml, sec 10.87 10.94 8.86 9.12 CSF Freeness, ml 714 707 726 718
D(EO) bleaching Initial Kappa number of SW pulp (from Internation Paper, Augusta): - 27.3, -27.5 Bleaching conditions- - D: kf:0.2, 50oC, 3.5%CSC, 45min, Terminal ph-with CO2-2.07, -2.13, 10kg BLS/T pulp was added to the pulp slurry - EO: 90 o C, 10% CSC, 60min, 3.6% NaOH, 35psi O2 for 15min-atmospheric for 45min, Terminal ph -11.9-11.9; 10% of D stage filtrate was added to the pulp slurry
Extractives content for bleachable pulp Bleachable Original Alcohol ethoxylate only CO2 only Alcohol ethoxylate + CO2 Extractives content (%) 0.154 0.011 0.010 0.011
Effect of CO2 washing on D(EO) bleaching Pulp properties after D(EO) bleaching sequence. without alcohol ethoxylates Without CO2 With CO2 with alcohol ethoxylates Without CO2 With CO2 Kappa number 3.1 2.9 3.0 2.9 Tappi Brightness 50.2 51.1 49.9 50.5 Initial kappa #: 27.3; 27.5. Viscosity (mpa.s) 26.2 26.4 25.4 25.7 AOX (µg/l) 23600 22000 - - Density (g/cm3) Tensile index (Nm/g) Tear index (mn.m2/g) Taber stiffness (mn m) without alcohol ethoxylates 0.539 36.4 24.2 0.27 0.540 36.7 24.9 0.29 with alcohol ethoxylates 0.538 36.4 24.1 0.26 0.543 37.1 24.7 0.28
Relevance to Industry Needs Potential Economic benefits The performance of many brownstock washers has been challenged as pulping capacity has been increased and mill closure technologies have been implemented. Improved brownstock washing is one of key processes which can reduce costs and improve final pulp properties. Important to know effects of CO2 acidification washing on Georgia s southern SW pulp COD carryover, sodium carryover, extractives and drainage properties, as well as on the subsequent bleaching stage. The results of CO2 acidification washing provided mills with lower cost washing technology, lower bleaching cost and improved products performance. The improved brownstock quality washing can be accomplished without additional modification to bleach plant equipment
Acknowledgement