FEDERAL UNIVERSITY OF VIÇOSA DEPARTMENT OF FOREST ENGINEERING LABORATORY OF PULP AND PAPER Membrane treatment of alkaline bleaching effluent on a kraft pulp mill Rafael Quezada, Claudio Mudadu Silva, Leif Nilsson Christian Hoffstedt and Niklas Berling
Outline • Introduction • Objectives • Results – Membrane treatment of alkaline bleaching effluent – Effects of the (EPO) membrane filtration on the effluent treatment plant – Membrane permeate recycling to the bleaching plant – Membrane retentate send to black liquor evaporation • Conclusions
Effluent generation 1,3 – 6,0 4 – 10 15 – 30 4 – 7 DRYNG COOKING BLEACHING WOODYARD MACHINE 0,5 – 2,0 EVAPORATORS RECOVERY 1,0 – 2,0 BOILER Water consumption Bleaching area: 45.000 m 3 /d Total: 65.000 m 3 /d 2,0 – 4,0 CAUSTICIZING Volume (m 3 /adt)
Membrane treatment Module Retentate (EPO) filtrate Membrane Permeate
Bleaching sequence D (EPO) D D NaOH D Pre – O 2 Pulp (EPO) D D ClO 2 Acid effluent (EPO) filtrate Alkaline effluent
Objectives Evaluate the membrane treatment of (EPO) filtrates from a kraft pulp mill Specific objectives a) Compare three configurations of membrane to treat alkaline (EPO) filtrate of a kraft pulp mill using pilot plants and determine the best operation conditions; b) Study the effect of the (EPO) filtrate membrane treatment on the effluent treatment plant; c) Evaluate the feasibility of recycling of the UF permeate within the bleaching plant; d) Evaluate the feasibility to send the UF retentate to the black liquor evaporation sector
Membrane treatment of alkaline bleaching effluent
Membrane treatment – Experimental set-up Membrane configuration selection (UF, UF + NF, NF) Optimal condition determination Long-term operation
Membrane treatment – Pilot plants
Membrane treatment • The nanofiltration membranes require a pre- treatment to reduce temperature and neutralize pH; • In order to select the best option it was considered not only the selectivity but also the costs and operation simplicity; • The selected configuration was ultrafiltration ; • The best condition for higher permeate flux (over 200 L/m 2 h) was 3,0 m/s of cross-flow velocity and 7 bar of TMP, for a COD removal and color of 58% and 91% , respectively.
Effects of the (EPO) UF on the effluent treatment plant
Effects on the ETP Scenario 1 NaOH D Pre – O 2 Pulp (EPO) D D ClO 2 Acid effluent Permeate ETP Retentate
Effects on the ETP Scenario 2 NaOH D Pre – O 2 Pulp (EPO) D D ClO 2 Acid effluent Permeate Chemical recovery ETP process Retentate
Effects on the ETP – Lab. simulation Biological Tertiary treatment treatment Reference Scenario 1 Effluent with (EPO) UF permeate Scenario 2 Effluent without (EPO) filtrate. UF permeate is recycled
Effects on the ETP Effects of the UF on the Effluent Treatment Plant Scenario 1 Scenario 2 Parameter Softwood Hardwood Softwood Hardwood COD reduction efficiency +10,1% + 9,8 % + 6,0 % + 8,1 % Final color - 9,8 % - 8,0 % -8,3 % - 8,0 % Biological sludge production 0 % 0 % - 20,3 % - 17,1 % Energy consumption 0 % 0 % - 20,3 % -17,1 % Coagulant dosage - 30 % - 37 % - 40 % - 40 % Tertiary sludge production - 28 % - 35 % - 44 % - 46 % (+) Increase; (-) decrease
Membrane permeate recycling to the bleaching plant
Permeate recycling • Software simulation (WinGEMS); • Steady state model approach; • Hot water on the EOP-press is stepwise replaced with permeate from the membrane filtration unit all washing liquor on the press is permeate; • Same efficiency assumed at different filtrate concentrations although a different filtrate composition can be expected when recycling the permeate on the EOP-press. EPO permeate Hot water used on EPO- available (m 3 /adt) press (m 3 /adt) Softwood 8,4 5,8 Hardwood 6,2 5,4
Permeate recycling – CaCO 3 formation 200 150 CaCO 3 g/Adt Softwood (EPO) Stage campaign (EPO) Filtrate 100 Supersaturation limit 50 0 0 20 40 60 80 100 Hot water on EOP-press replaced with permeate (%) 300 250 CaCO 3 g/Adt 200 (EPO) Stage 150 (EPO) Filtrate Hardwood 100 Supersaturation limit campaign 50 0 0 20 40 60 80 100 Hot water on EOP-press replaced with permeate (%)
Permeate recycling – Mg(OH) 2 formation 250 200 Mg(OH) 2 g/Adt 150 Softwood 100 (EPO) Stage campaign (EPO) Filtrate 50 0 0 20 40 60 80 100 Hot water on EOP-press replaced with permeate (%) 80 60 Mg(OH) 2 g/Adt Hardwood 40 campaign (EPO) Stage 20 (EPO) Filtrate 0 0 20 40 60 80 100 Hot water on EOP-press replaced with permeate (%)
UF retentate send to black liquor evaporation
Retentate reuse Hardwood Softwood Parameter Weak black Retentate CI Weak black Retentate CI (%) liquor (kg/h) (kg/h) (%) liquor (kg/h) (kg/h) Na 26380 10,28 0,04 35596 11,74 0,03 Ca 65 0,43 0,66 33 0,37 1,13 K 361 0,28 0,08 3379 0,29 0,01 Mg 25,5 0,34 1,33 36,6 0,95 2,59 Mn 8,0 0,16 1,96 4,0 0,05 1,24 Ba 1,59 0,003 0,18 0,22 0,001 0,39 Al 12,7 0,22 1,72 8,8 0,23 2,63 Si 76,3 0,11 0,14 40,2 0,34 0,84 P 55,0 0,06 0,10 16,1 0,06 0,34 Cl 239 0,83 0,35 576 1,25 0,22 SO 4 7415 3,55 0,05 4147 1,79 0,04 CI= Concentration increment of the element on the weak black liquor after adding the (EPO) retentate
Conclusions • The treatment of the (EPO) filtrate by tight UF allows an increase on the COD removal efficiency by 10% in the biological treatment plant. It also decreased the color on the treated effluent by approximately 9% ; • The recycle of the resulting UF permeate in the bleaching area is the best option available for the reuse of this current; • It can increase the efficiency of COD reduction in 8% , and 20% reduction in the generation of biological sludge, 45% of tertiary sludge and 40% less coagulant. • Water economy: 200 L/s ( 17.280 m 3 /d )
Conclusions • In the hardwood and in the softwood case, 100% replacement of hot water on EPO-press is possible (5,4 m 3 /adt and 5,8 m 3 /adt) • Small CaCO 3 (s)-formation in EOP-filtrate above 50% replacement of hot water due to high carbonate content according to equilibrium calculations • Supersaturation calculations indicate that the precipitations will not start to form when replacing 100% of the hot water with permeate • It is expected that the relation of S/Na 2 remain unchanged after the addition of the retentate to the black liquor stream, therefore the recovery boiler chemical performance will not be affected
FEDERAL UNIVERSITY OF VIÇOSA DEPARTMENT OF FOREST ENGINEERING LABORATORY OF PULP AND PAPER Membrane treatment of alkaline bleaching effluent on a kraft pulp mill Rafael Quezada Reyes Rafael.Reyes@ufv.br
• Membrane configuration selectivity • PCI modules • Cost information • Industrial design • Membrane performance experiment • Characterization of filtrates, permeate and retentate
FEDERAL UNIVERSITY OF VIÇOSA DEPARTMENT OF FOREST ENGINEERING LABORATORY OF PULP AND PAPER Membrane treatment of alkaline bleaching effluent on a kraft pulp mill Rafael Quezada Reyes Rafael.Reyes@ufv.br
MICRO ULTRA NANO REVERSE FILTRATION FILTRATION FILTRATON OSMOSE 0,1 - 10 m 0,02 - 0,1 m 500 - 20.000 Da <500 Da Diâmetro Poros Pressão 170 - 850 KPa 500 - 1500 KPa 3500 - 5000 KPa 70 - 350 KPa Suspended Multivalent Monovalent Water Bacteria Virus Solids ions Ions Mudado, 2008
PCI – B1 Module lenght (m) 1,22 2,44 3,66 Area (m 2 ) 0,88 1,75 2,63
PCI – ESP04 Membrane 70 – 75 ° C Temperature Press Above 8 bar 11 – 11,5 pH 98 – 99% Permeate recuperation Permeate flux 90 l/m2.h Area 7.971,6 m2 Lines 3 Steps/Line 7 Modules/steps 146 Investment: $15.000.000 USD Energy: $1.200.000 USD/year (1.485 kW) Membrane: $920.000 USD/year Cleaning: $250.000 USD/year
P1 P2 P3 P4 P5 P6 Permeate 7 R1 R4 R2 R3 R5 R6 Retentate 7 (EPO) filtrate
Permeate flux, L/m 2 .h Volumetric concentration factor (VCF)
Parameter Na Ca K Mg Mn Ba Al Si P Cl SO 4 Raw material Units mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L Permeate (198 L/s) 666 0,95 12,7 0,09 0,01 0,2 4,8 163,7 Retentate (2 L/s) 1428 59,9 39,18 47 21,71 0,391 30,5 14,9 7,69 115 492,8 D0 filtrate 575 26 33 3,1 1 0,05 0,37 - - - - Eucalyptus (EPO) filtrate 625 2,6 7,3 0,6 0,15 0,02 0,26 - - - - D1 filtrate ND ND ND ND ND ND 0,004 - - - - D2 filtrate 381 5,25 4,5 1,1 0,08 0,04 0,31 - - - - Water 150 1,2 1,6 0,3 0,01 0,01 0,31 - - - - Permeate (198 L/s) 694,5 1,36 9,34 0,07 0,005 0,14 8,1 142,7 Retentate (2 L/s) 1630 51,4 40,56 131,8 6,94 0,119 32 46,6 7,6 173 248,3 D0 filtrate 95,2 31,9 31,1 10,5 0,51 0,33 0,45 7,2 - - 790 Pine (EPO) filtrate 603 8,51 11,8 2,2 0,1 0,07 0,2 8,2 - - 250 D1 filtrate 89,7 32,5 34,6 15,9 0,45 0,36 0,69 25,3 - - 370 D2 filtrate 105 15,1 5,1 4 0,09 0,06 0,21 9,3 - - 230 Water 162 3,22 0,6 0,5 0,03 0,01 0,22 4,3 - - -
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