NEW BROWN STOCK WASH AIDS FOR IMPROVED WASHING & FOAM CONTROL - PowerPoint PPT Presentation

NEW BROWN STOCK WASH AIDS FOR IMPROVED WASHING & FOAM CONTROL Dan Nicholson, Senior Staff Scientist Todd Bolton, Senior Team Leader Michael Evans , Research Scientist Lloyd Lobo, Pulp R&D Group Leader 28 May 2015

IMPORTANCE OF EFFICIENT WASHING Wash Water • Reduced water usage • Increase solids to recovery Washer Bleach • Less bleaching chemicals Tower • Increased production rate Washed Fiber Recovery Boiler Weak Black Liquor Strong Black Liquor Steam Bleaching Chemicals Evaporator 2 Confidential and proprietary.

WASH AID PRODUCT REQUIREMENTS Foam Control Drainage • Knock down existing foam • Rapid mat formation; separation of black liquor from fiber • Minimize foam in the vats, filtrate • Permeable mats tanks, etc. • Effectiveness persists through • Fast and uniform displacement multiple stages by wash fluid • Minimize bubble formation • Efficient removal of soluble material  Low carryover  Low water usage  More solids to recovery 3 Confidential and proprietary.

OUTLINE • Defoaming – designing the product to satisfy the needs of the system • Methods to measure product performance – defoaming and drainage • Mat formation and drainage- mechanism • Wash aids to improve washing efficiency 4 Confidential and proprietary.

EXPERIMENTAL - DEFOAMING Defoamer injection • Controlled Temperature Air supply Nozzle • Bubble size and air flow • Knockdown by Heating jacket defoamer injection • Persistence • Decay (air shut-off) Air sparge pump 5 Confidential and proprietary.

FOAM CONTROL - RESULTS Product A Product B Knockdown Test Persistence Test 350 350 Defoamer 300 300 Injection Foam Height (mm) Foam Height (mm) 250 250 Air Flow Air Flow Discontinued 200 200 Discontinued 150 150 100 100 50 50 0 0 0 1 2 3 4 5 6 0 1 2 3 4 5 6 Time (minutes) Time (minutes) • Defoamer is present at the start of the run • Foam bubbling and recirculation w/o defoamer • Air bubbling rate is controlled • Defoamer injected at foam height of 2.7mm • Bubbling stopped after 3 min and foam • Knockdown and persistence noted decay is observed • Bubbling and recirculation stopped after 3 min and foam decay observed 6 Confidential and proprietary.

FOAM CONTROL – EUCALYPTUS RESULTS • Eucalyptus black liquor can form very stable foam • High solids and high sulfidity are typical • The trends remain similar Persistence Test Knockdown Test 400 400 Defoamer Formulation A 350 350 Injection Air Flow Foam Height (mm) Foam Height (mm) 300 300 Discontinued Formulation B Air Flow Discontinued 250 250 200 200 150 150 100 100 50 50 0 0 0 1 2 3 4 5 6 0 1 2 3 4 5 6 Time (minutes) Time (minutes) 7 Confidential and proprietary.

FOAM CONTROL - SUMMARY • Species and pulping chemistry introduce variation • Importance of foam control varies with equipment • Defoaming is important, but the rest of the talk will focus on washing 8 Confidential and proprietary.

EXPERIMENTAL – DRAINAGE/ WASHING Entrained Air Sparged (by density) Air Displacement and Permeability (k) k A Δ P Shear Q = μ L μ A L Δ P Q Filtration Rate mass vs. time, conductivity, and color Filtration Rate vol vs. time 9 Confidential and proprietary.

DRAINAGE AND ENTRAINED AIR • Drainage rate decreases with increasing entrained air • Wash aid reduces amount of entrained air 14 mL/s 12 mL/s Shear Alone Average Drainage Rate 10 mL/s Shear + Sparged Air 8 mL/s 6 mL/s 4 mL/s 2 mL/s 0 mL/s 0% 5% 10% 15% 20% 25% 30% 35% Percent Entrained Air 10 Confidential and proprietary.

DRAINAGE – MAT FORMATION RATES • Drainage rate = slope of the curve under dynamic mat forming • Increase shear rate – slower drainage • Wash aid improves mat formation rate Treated Pulp Untreated Pulp 250 mL 250 mL 100% Power 200 mL 200 mL Filtrate Volume, mL Filtrate Volume, mL 40% Power 150 mL 150 mL 30% Power Increasing 100 mL 100 mL 20% Power shear 50 mL 50 mL 0 mL 0 mL 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 Time (s) Time (s) 11 Confidential and proprietary.

DRAINAGE- DISPLACEMENT • Displacement rate is much more linear • Method of addition of drainage aid is important 300 mL 250 mL Filtrate Volume 200 mL Blank 150 mL Q DA-1 in Wash Water 100 mL DA-1 in Pulp/Liquor Slurry 50 mL 0 mL 0 50 100 150 200 250 Time (s) 12 Confidential and proprietary.

DRAINAGE – PERMEABILITY DETERMINATION • Darcy equation used to calculate permeability  Experimental measured parameters used k A Δ P Q = μ L Experimental condition Mean, k·10 8 cm No Treatment 7.9 Treatment Added to Wash 13.5 Treatment Added to Pulp 16.8 13 Confidential and proprietary.

DRAINAGE- DISPLACEMENT EUCALYPTUS MILL • Faster than typical N. American hardwood species ! • Clearly improved by drainage aid • Removal of entrained air before/during mat formation is most effective 400 350 Filtrate Volume 300 250 Blank 200 Displacement DA-1 in Wash Water 150 DA-1 in Pulp/Liquor Slurry 100 Dynamic mat formation 50 0 0 25 50 Time (s) 14 Confidential and proprietary.

DRAINAGE- DISPLACEMENT WASHING APPLICATION • Method of addition of drainage aid is important • Different chemistries respond to addition point 15 Confidential and proprietary.

WASHING EFFICIENCY - MEASUREMENT Displacement Final Wash Ratio of 3.0 Saturated Mat Measurements 1. wet mass 2. filtrate conductivity 3. dry mass Filtration Rate 4 5 6 2 3 1 mass vs. time, conductivity, and color Effluent fill vials 16 Confidential and proprietary.

WASHING EFFICIENCY - RESULTS • Sodium level drops as wash ratio increases • Wash aids reach lower conductivity at a set wash ratio • Results in improved wash efficiency 17 Confidential and proprietary.

CONCLUSIONS • The proper design of brown stock washing aids may control foam in different ways, and improve drainage • Entrained air slows drainage rate, but can be controlled in different ways. We focus on chemical wash aids. • Wash aids reduce entrained air incorporated in the mat during formation, and during displacement washing • More permeable mat allows more efficient removal of dissolved solids Product Washing System Chemistry Requirements 18 Confidential and proprietary.

OBRIGADO • We are grateful for the assistance of Jorge Sepulveda, Jean-Michel Laurito, and Joao Eduardo Cassandre for mill trial experiments Dan Nicholson Senior Staff Scientist, Global Technology Hercules Pulp & Paper Division QUESTIONS? Solenis LLC 500 Hercules Road, Building 8100/ Lab 241 Wilmington, DE 19808 USA (302) 440-1242 DNicholson@Solenis.com 19 Confidential and proprietary.