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

2

Confidential and proprietary.

IMPORTANCE OF EFFICIENT WASHING

• Increase solids to recovery
• Reduced water usage
• Less bleaching chemicals
• Increased production rate

Bleach Tower Steam Weak Black Liquor Strong Black Liquor

Wash Water

Washed Fiber

Bleaching Chemicals

Washer Evaporator Recovery Boiler

3

Confidential and proprietary.

WASH AID PRODUCT REQUIREMENTS

Foam Control Drainage

• Knock down existing foam
• Minimize foam in the vats, filtrate

tanks, etc.

• Effectiveness persists through

multiple stages

• Minimize bubble formation
• Rapid mat formation; separation
• f black liquor from fiber
• Permeable mats
• Fast and uniform displacement

by wash fluid

• Efficient removal of soluble

material

• Low carryover
• Low water usage
• More solids to recovery

4

Confidential and proprietary.

• 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

OUTLINE

5

Confidential and proprietary.

EXPERIMENTAL - DEFOAMING

Air supply pump Air sparge Heating jacket

Defoamer injection

Nozzle

• Controlled Temperature
• Bubble size and air flow
• Knockdown by

defoamer injection

• Persistence
• Decay (air shut-off)

6

Confidential and proprietary.

FOAM CONTROL - RESULTS

• Defoamer is present at the start of the run
• Air bubbling rate is controlled
• Bubbling stopped after 3 min and foam

decay is observed

• Foam bubbling and recirculation w/o defoamer
• Defoamer injected at foam height of 2.7mm
• Knockdown and persistence noted
• Bubbling and recirculation stopped after 3 min

and foam decay observed

Product A Product B

50 100 150 200 250 300 350 1 2 3 4 5 6

Foam Height (mm) Time (minutes)

Persistence Test

Air Flow Discontinued

50 100 150 200 250 300 350 1 2 3 4 5 6

Foam Height (mm) Time (minutes)

Knockdown Test

Defoamer Injection Air Flow Discontinued

7

Confidential and proprietary.

FOAM CONTROL – EUCALYPTUS RESULTS

Formulation A Formulation B 50 100 150 200 250 300 350 400 1 2 3 4 5 6 Foam Height (mm) Time (minutes)

Knockdown Test

Defoamer Injection Air Flow Discontinued

50 100 150 200 250 300 350 400 1 2 3 4 5 6 Foam Height (mm) Time (minutes)

Persistence Test

Air Flow Discontinued

• Eucalyptus black liquor can form very stable foam
• High solids and high sulfidity are typical
• The trends remain similar

8

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
• n washing

9

Confidential and proprietary.

EXPERIMENTAL – DRAINAGE/ WASHING

Sparged Air Shear Entrained Air (by density) Filtration Rate vol vs. time Displacement and Permeability (k)

Q = kAΔP μL Q A μ L ΔP

Filtration Rate mass vs. time, conductivity, and color

10

Confidential and proprietary.

DRAINAGE AND ENTRAINED AIR

• Drainage rate decreases with increasing entrained air
• Wash aid reduces amount of entrained air

0 mL/s 2 mL/s 4 mL/s 6 mL/s 8 mL/s 10 mL/s 12 mL/s 14 mL/s 0% 5% 10% 15% 20% 25% 30% 35% Average Drainage Rate Percent Entrained Air Shear Alone Shear + Sparged Air

11

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

0 mL 50 mL 100 mL 150 mL 200 mL 250 mL 20 40 60 80 100 120 140 Filtrate Volume, mL Time (s)

Untreated Pulp

0 mL 50 mL 100 mL 150 mL 200 mL 250 mL 20 40 60 80 100 120 140 Filtrate Volume, mL Time (s)

Treated Pulp 100% Power 40% Power 30% Power 20% Power

Increasing shear

12

Confidential and proprietary.

DRAINAGE- DISPLACEMENT

• Displacement rate is much more linear
• Method of addition of drainage aid is important

0 mL 50 mL 100 mL 150 mL 200 mL 250 mL 300 mL 50 100 150 200 250 Filtrate Volume Time (s) Blank DA-1 in Wash Water DA-1 in Pulp/Liquor Slurry

Q

13

Confidential and proprietary.

DRAINAGE – PERMEABILITY DETERMINATION

• Darcy equation used to calculate permeability
• Experimental measured parameters used

Experimental condition Mean, k·108 cm No Treatment 7.9 Treatment Added to Wash 13.5 Treatment Added to Pulp 16.8

Q = kAΔP μL

14

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

50 100 150 200 250 300 350 400 25 50 Filtrate Volume Time (s) Blank DA-1 in Wash Water DA-1 in Pulp/Liquor Slurry

Dynamic mat formation Displacement

15

Confidential and proprietary.

DRAINAGE- DISPLACEMENT WASHING APPLICATION

• Method of addition of drainage aid is important
• Different chemistries respond to addition point

16

Confidential and proprietary.

WASHING EFFICIENCY - MEASUREMENT

Displacement Filtration Rate mass vs. time, conductivity, and color 4 3 2 1 5 6

Final Wash Ratio of 3.0

• 1. wet mass
• 2. filtrate conductivity
• 3. dry mass

Saturated Mat Measurements Effluent fill vials

17

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

18

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 Chemistry Washing System Requirements

19

Confidential and proprietary.

QUESTIONS?

• We are grateful for the assistance of Jorge Sepulveda,

Jean-Michel Laurito, and Joao Eduardo Cassandre for mill trial experiments OBRIGADO

Dan Nicholson Senior Staff Scientist, Global Technology Hercules Pulp & Paper Division Solenis LLC 500 Hercules Road, Building 8100/ Lab 241 Wilmington, DE 19808 USA (302) 440-1242 DNicholson@Solenis.com