Descreve os principais conceitos da lavagem da polpa no processo de fabricação de celulose.

1. Pulp and Paper Industry
Brown Stock Washing

2. Is a mill’s Soda Loss equal to its
Soda Make-up ?
YES !!
Focus on Soda Loss, not Soda Make-up !

3. Anatomy of Soda Loss
100 #Na2SO4/ADT (total mill loss/make-up)
80 #/ADT (BSW loss) 20 #/ADT (spills/purges)
Washable Bound Pulp and Power sewers
50#/ADT 30#/ADT
- Paper sewer - paper sewer 10#/ADT – World Class
- Paper sheet - paper sheet 15#/ADT – Best Practice
20#/ADT – Go find the low hanging fruit

5. Pulp and Power Sewer Losses
Good sewer flow and conductivity system
w/Alarms on PI or DCS (awareness/training)
Food for thought:
Establish conductivity round in smaller sewers to find sources
Dregs filter (<= 2#/ADT)
Slaker grit leachate (<=2#/ADT)
Digester sand separator trap
Weak wash balance
Salt cake purging
Use of sumps in recaust and evaps

6. Monthly Saltcake Reconciliation
• Properly establishes true loss/make-up with
inventory changes taken into account
• Matches make-up to measured total mill
sewer loss to insure good measurement
• Prattville Example

7. Daily Focus Big Picture
• BSW Carryover Soda Loss
• Pulp/Power Sewer Soda Loss
• Total Mill Sewer Soda Loss

8. BSW Optimization & Economics
• Visual audit
• Evaluate washing efficiencies
• Audit equipment condition during outage
• Audit controls
• Determine benefit of washing versus cost of
evaporation
• Employ dilution factor control to minimize
over washing and under washing
April 2005 Pulp Washing Training 8 of 152

9. BSW Assessment
• Separate digester washing from external
washing
• Assess washers against OEM DF/DR curves
• Assess digester against OEM DF/DR curves
• Water/Dissolved solids balance

10. Dilution Factor
1st Stage BSW
0.86
0.84
Displacement Ratio
0.82
0.80
0.78
0.76
0.74
1 2 3 4
Dilution Factor
Dilution Factor
April 2005 Pulp Washing Training 10 of 152

11. Dilution Factor
• Shower Liquor In Excess Of The Liquor In
The Discharging Pulp Mat
• DF = (lb liq/lb pulp)shower - (lb liq/lb pulp)mat
• May Be Positive Or Negative

12. Displacement Ratio
• The Ratio of DS Removed to the Maximum
Possible DS Removable
• DR = (DS vat – DS mat) / (DS vat – DS shower)
• 0.0 < DR < 1.0

13. Washer Stage Data Collection
- Inlet vat DS
- Outlet mat filtrate DS
- Outlet mat consistency* (high sensitivity/biggest chance for error)
- Shower DS
- Production rate
- Shower flow
- Inlet vat consistency** ( needed for DS and water balance)
- Washer filtrate DS** ( needed for DS and water balance)

14. DR Formula
DR = (Sv - Sm) / (Sv - Ss)

15. DF Formula
DF = Shower flow(gpm) x 6 - 100-mat const
Production (odt/d) mat const

16. Example Problem
Is this first stage drum washer performing to
OEM standards ?
Production rate : 1154 ODT/day
Drum specific loading: 0.80 ODT/ft2
Shower flow: 1440 gpm
Discharge consistency: 14%
Vat DS: 6.41%
Mat DS: 2.88%
Shower DS: 1.76%

17. Results
DF = 1.35
OEM DR = 0.802
Tested DR = 0.759
No ! Washer is not performing to OEM standards.
Result of getting this one drum to OEM standards:
96#/ton -> 90 #/ton
Net savings is over $500M/yr

18. Drum Washer Operation
CYLINDER ROTATION
WASHING
PULP MAT
 Key issues
SHOWERS
1. Uniform shower distribution TAKE-OFF
DOCTOR
INLET
2. Maximize Vat dilution BOX INLET WEIR
8-12”
3. Proper Vat level CASCADE
DISPLACEMENT
TO VAT ATMOSPHERIC
ZONE
4. Minimize air entrainment LEVEL TAKE-OFF ZONE
5. Operator training EXTRACTION
GRAVITY
ZONES
6. Keep equipment in good condition FORMATION
ZONE
7. Uniform sheet formation VACUUM
FORMATION
8. Mat thickness 1 to 2” ZONE
9. Proper vacuum
10. Good sheet take-off REPULPER
11. Temperature
12. Run Automated Controls PULP DISTRIBUTION
13. Apply defoamer at the point of the BAFFLES
problem
DILUTION
CD0024-002

19. Washing Basics to Audit
• Showering – Maximize displacement washing
• Vat consistency – Maximize dilution washing
• Vat level control – Reduce air entrainment
• Inspect Vacuum Valves - Reliability
• Vacuum leaks - Reliability
• Face wire – Reliability
• Drum Integrity – Reliability

20. Purpose of Wash Showers
Gently & uniformly apply wash water to the
pulp mat for optimal displacement washing.
Distribute the washer water flow
appropriately over the washing arc.

21. Washer Showers Basics
Uniform distribution
– Keep showers clean and washed off
– Keep nozzles unplugged
– Soda losses can vary 30% or better across a
washing stage due to poor shower distribution
– Consider feeding water to both sides of the
shower headers on washer larger than 18’.
– Shower pipes should be free to rotate for finite
adjustment

22. Washer Showers Basics
Low turbulence
– Apply gently / tangentially to mat, do not disturb
the mat
– Blasting the sheet with shower water tends to
aerate the stock
– Minimize roll-back, balance the shower flows to
each shower. Run back grooves the pulp mat,
causing uneven mat formation. Uneven mat
means an uneven wash.

23. Washer Showers Basics
– Shower type / arrangement
 High volume / low velocity on top
 Low volume / high velocity on bottom
 Bottom shower as low as possible to avoid air
entrainment into sheet
 Top shower in position such that filtrate is pulled
into mat before vacuum cut-off
 The velocity of the shower water should be close
to the speed of the drum. Shower water should
lay on the mat gently and evenly

25. Operations
Maximize Inlet Vat Dilution
• Vacuum increases with increased dilution. More flow
down the drop leg produces more vacuum.
• Typically as mills increase production, the vat dilution
pump is a constraint – Consider upgrading pump
• Mills should consider a separate shower pump which will
improve washing by reducing variability
• Maximize blow tank dilution – dilution washing starts here

26. Operations
Maximize Inlet Vat Dilution
• Ideal consistency as a result of adding dilution is 1% to 1 ½%. The
surface area of the inlet vat will appear “velvety” with little or no
flocculation
– More vat dilution will reduce entrained air, improve mat formation, induce
good vat turbulence, no dead zones, good deflocculation
– Thinner sheet for better displacement, minimizes “fingering” in mat, ideal
mat thickness is 1” – 2”
– Dilution should be as much as the washer can hydraulically handle, while
keeping the washer drum speed at an average of 2 to 2½ RPM
– If drum speed is too high, then rewetting of sheet discharge mat could
reduce washing effectiveness

27. Operations
• Vat level control – Reduce air entrainment
 4-8” cascade over weir
 Need some drop over weir to shear/deflock the pulp
 Higher levels allow more vat dilution – it increases the
drainage area in the vat
 Ensures gravity fill of drum – looser sheet, better formation,
liquor can move through sheet easier
 Higher levels reduce air entry into mat
 Good level indication and control tuning required

28. Consequences of Low Vat Level Operation
Total surface area = 3.14 x 11.5’=36.11’
Total Surface area lost = 11%
Submergence zone = 16’
BUT actually 25% of the
submergence zone is lost.
24”
This allows air to enter the
pulp mat which affects
April 2005 Pulp Washing Training efficiency by 5 to 10%.
28 of 152

29. Air is the Enemy
• Air bubbles interfere with wash water drainage
• Use defoamers to control air at the point of the problem
• Do not overuse defoamers – carryover will harm paper machine
runnability – it reduces surface tension which cause an increase
in machine breaks
– Measure defoamer carryover - carryover should be:
• Less than 30 PPM out of the brownstock wash system
• Less than 10 PPM out of the bleach plant
• Recommend using low molecular weight silicon defoamer
• Check to make sure defoamer is effective in the temperature
range that the washers operate
• If use increases, operators should check places where air can
enter system

30. Operations
Potential Sources of Air
• Low level in blow tank
• Low level in filtrate tanks
• Dilution injection points
 Make sure dilution points are submerged. Free falling
dilution will cause foaming
• Soap build-up in first stage service tank
• Vortexing in dilution and stock pump suctions
• Poor air removal from filtrate tanks
• Improper drum washer operation
 Low vat levels
 Poor shower distribution
April 2005 Pulp Washing Training 30 of 152

31. Brownstock Seal Tank Design
Air is released
DROP LEG
VERTICAL
BAFFLES
Filtrate
DROP LEG ENTRY Overflows
Air & Filtrate
Separate
DROP LEG INSIDE OUTSIDE VERTICAL
SIZE DIAMETER DIAMETER OPENINGS BAFFLES
Up to 12” dia. 36” 60” 6” x 12”
300 900 1500 150 x 300
14” & 16” dia. 48” 72” 6” x 18” SIX OPENINGS
350 - 400 1200 1800 150 x 450
18” dia. 60” 84” 8” x 24”
450 1500 2150 200 x 600
20” & 22” dia. 72” 102” 10” x 24”
500 - 550 1800 2600 250 x 600
24” & 26” dia. 84” 120” 10” x 30”
600 - 700 2150 3050 250 x 750
April 2005 Pulp Washing Training 31 of 152

32. Washer Seal Tank/Dropleg Design
Dropleg Design:
• Sized for > 12 to 16 fps Drum
superficial velocity Washer
• Straight, vertical, drop
no jogs
Dropleg
Pulp
Recommended Vent Feed
ht. > 30 ft. Filtrate
Tank
Seal
Baffle Chamber
Vat
To Shower
Dilution
or Effluent EKA of 152
32 CHEMICALS
Courtesy April 2005
of Beloit Pulping Pulp Washing Training
CONFIDENTIAL & TRADE SECRET Technical Marketing & Mill Services

33. Diffuser Efficiency Keys
• Screen and backflush cycle
• Pulp and wash water distribution (orifice sizing)
• Pulp consistency and bed integrity (>10% inlet,
<14% outlet)
• Washing temperature (>160 F)
• Production Load (5-6 ADMT/d m2)

34. Screen and Backflush Cycle
*Only washing when your extracting
• Upstroke 10% faster than pulp (proportional valve)
• Quick closing time of extraction valve and wash valve
to minimum position (2-3 sec) (mech stops for wash)
• Short backflush (<= 1sec)
• Proper pressure and volume of backflush

35. Atmospheric Diffuser

36. Pressure Diffuser

38. April 2005 Pulp Washing Training 38 of 152

39. Cost of Brown Stock Washing
Typical Mill Economic Relationship
4500.00
ClO2 $M/year
4000.00
NaOH $M/year
Steam $M/year
Total $M/year
3500.00
3000.00
Net Cost ($1000/year)
2500.00
2000.00
1500.00
$$ Sweet Spot $$
1000.00
500.00
0.00
April 2005
Decreasing Washing DF
Pulp Washing Training 39 of 152
Soda Loss lbs/ton (% Weak Liquor Solids)

40. Drum Wash Line Controls
Control Objectives
- Reduce soda carryover variability
- Optimize use of DF
- Wash line operating stability
- Reduce mundane low valve activities of
operator

41. Drum Wash Line Controls
Minimum Control Expectations
- Vat level control with drum speed
- Seal take levels w/cascade shower flows &
digester bypass
- Dilution factor, open loop
- On-line measurement of conductivity

42. Pulp
Wash Water In
Dirty Pulp Washer
Decker
In
Knotter Washed Pulp
Screens
Out
Filtrate Tanks
Liquor
Liquor out to
April Evaps
2005 Pulp Washing Training 42 of 152

43. BSW Improve Projects
• New high performance showers to replace old whistles, spoons,
and weirs
 LaValley, Comarco Uniflows, Oramac
• Split Washing - Hot water to last washer top showers to replace
high COD condensate
• Dilution factor controls – Course control of showers
• Shower control using conductivity – Fine control of showers
• Closing decker filtrate systems – Reduced soda loss, energy
• Anti-rewet drum decks
• Training operators on the principles of drum washers
April 2005 Pulp Washing Training 43 of 152

44. Digester Washing Assessment
Compare to OEM DF/DR curve:
- Vat DS are calculated end of cook DS or upper
extraction DS
- Shower flow and DS are cold blow flow and DS
- Mat consistency and DS are blow consistency
and DS
- Filtrate flow and DS are total extraction flow
and DS