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Retention-Drainage-Formation
By: Saurabh Mittal
Ravi S Joshi
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This presentation will cover
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RETENTION
DRAINAGE
FORMATION
THEORY
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POLYMER CHEMISTRY
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CHARACTERISTICS THAT DEFINE A POLYMER:
• Monomers in the Polymer
• Charge of the Polymer
• Molecular Weight
• Configuration
• Natural or Synthetic
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GENERAL CLASSIFICATIONS OF MOLECULAR
WEIGHT
Classification
Low
Medium
High
Molecular Weight Range
< 100,000
100,000 x <1,000,000
1,000,000
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RETENTION-DRAINAGE MECHANISMS
•Three steps of retention and drainage
– Coagulation
– Flocculation
– Filtration
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COAGULATION
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Coagulation reduces the repellant forces between fillers and fines by
development of charged patches (charge neutralization)
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Discrete Fillers
And Fines
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Coagulant
Agglomerated
Fillers And Fines
Through
Patching
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Anionic Trash & Neutralization
• Anionic polymeric substances able to interact with cationic polymers
• Poorly washed pulps, coated broke or hydrogen peroxide bleaching are the
main sources
• Highly closed systems accumulate anionic substances with time
Two Types:
• Inorganic
 Alum
 PAC
• Synthetic - low molecular weight, high-charged cationic polymers
 Polyamines
 PolyDADMAC’s
• Generates small, compact floc structures
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FLOCCULATION
• Combining or forming a bridge between particles with
a polymer to produce discrete agglomerates
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Flocculation by
Particle Bridging
Attachment of HMW Polymer
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FLOCCULATION DUE TO BRIDGING
• High level of hydrodynamic volume favors bridging - long loops and
tails
• Bridging influenced strongly by molecular weight of the polymer
• Bridging also influenced (to lesser extent) by the amount of polymer
charge
• Generates large diffuse floc structure (macro flocs)
• Shear sensitive; higher the charge, the stronger the bond
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IMPACT OF SHEAR ON FLOC FORMATION
Polymer Bridging
Charged Patches
Disruptive
Force
Redispersion
Bonds Re-formed
Reduced Bridging
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RETENTION/DRAINAGE
• The papermaker’s goal is to produce:
– The most uniform product (formation)
– At the highest speed (drainage)
– At the lowest cost (retention)
• These factors are interrelated and must be balanced to
meet the paper maker’s needs
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FOUR STAGES OF WATER REMOVAL
•Gravity drainage
•Vacuum assisted water removal
•Mechanical pressure (table and press)
•Drying (heat energy)
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FACTORS AFFECTING DRAINAGE
• Large flocs - high retention of fines
– Stage 1: Fast gravity drainage due to large void areas between flocs.
– Stage 2: Slow drainage over vacuum units due to thin spots caused by heavy
floccing. This increases the openness of the sheet and allows vacuum to be lost
through the sheet.
– Stage 3: Large, high fines content flocs are dense, making it difficult to remove
water by pressing and drying.
• Dispersed, unflocculated system, low retention of fines
– Stage 1: Slow gravity drainage due to high fines level of system; sheet twosidedness.
– Stage 2: Good drainage over vacuum units due to uniform sheet providing high
vacuum.
– Stage 3 & 4: Good drainage in the press and dryers unless a high level of fines
causes severe two-sidedness
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FACTORS AFFECTING DRAINAGE
• Uniform microflocs, good fines retention
– Stage 1: Small flocs provide for paths of water drainage.
Fines controlled at low equilibrium level.
– Stage 2: Uniform flocs and sheet gives good vacuum
drainage.
– Stage 3: Uniform floc size and well-distributed fines give
good pressing and drying.
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Benefits of RDF Program
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High FPR% & FPAR%
High Chemical Retention
Lowers Back-Water Turbidity
Less Load on ETP
Better Formation at High Retention
Fast Drainage
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Example: Volume of Water Removal
Given: 25.00 ton/hr @ 7% reel moisture & Calculation - 23.25
ton/hr Bone-Dry Fiber
@40% Press Section Solids
60% water
Ratio 1.5:1
34.9 ton/hr water
@42% Press Section Solids
58% water
Ratio 1.38:1
32.1 ton/hr water
 2.7 m3/hr less water to be evaporated in the dryers
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Drainage – Rule of Thumb
 1% increase in press solids correlates to: –11-13%
increase in wet-web strength
 4-5% machine speed increase (directly related to
production increase) on drying-limited grades
 4-5% reduction in steam consumption
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Application Technology
• Flocculants
– Feedpoint Selection - Based on desired results
• Post screen will achieve the most efficient and
maximum retention
• Post screen will also typically provide the best gravity
drainage
• Prescreen will result in less negative impact on
formation
• Prescreen will result in less efficient retention but may
not reduce drainage
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Application Technology
• Flocculants
– Feed Scheme
• Feed ring
 Before or after screen
• Injection quill
 Often before screen
• Post dilution
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At least 10 to 1
More is better
Fresh water if possible (can dilute at feed system)
Clean white water only at feedpoint
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Filler pre-treatment
• Treating filler stream with additive maximizing interactions with retention program
• Non – flocculative pre-treatment
– Reduction of zeta potential – coagulant additon
– Sensitizing filler particle for flocculant addition (Phenol formaldehyde resin additon)
• Flocculative pre-treatment
– Increasing filtration component of filler retention:
Wet-end Process Variables
Effecting RDF
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Chemistry – water and additives – already discussed
Headbox Set-up and Headbox Type
Former Set-up and Former Type
Furnish Components and Ratios
Refining
Forming Fabric
Temperature, pH, consistency, mill closure
Entrained air
Basis Weight
Distribution of fines and fillers
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Case Study
Mill Information:
 Mill is having one machine of 200 TPD along with integrated
pulp of 170 TPD.
 They are producing pulp of 70 kappa no.
 Mill is producing Kraft Liner Board of 120 – 250 GSM.
 Mill is using bagasse as basic raw material.
 Mill follows Cobb 120 in place of Cobb 60 and maintaining
Cobb 120 @ 50 - 60.
 Mill is using solid rosin along with solid non ferric alum.
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Case Study
Lab Trial Report:
1. Set 1:- Pulp + Alum (20 Kg) + Rosin (1.5 Kg) + Defoamer (0.8 Kg) = pH @ 4.1, Cobb 120 @
131 & Drainage @ 340 ml/30 sec.
2. Set 2:- Pulp + Alum (20Kg) + Rosin (1.5Kg) + WSR (10Kg) + Defoamer(0.8 Kg) = pH @ 4.2,
Cobb 120 @ 160 & Drainage @ 345 ml/30 sec.
3. Set 3:- Pulp + AKD (4Kg) + WSR (10Kg) + Defoamer (0.3 Kg)
& Drainage @ 335 ml/30 sec.
4. Set 3 A:- Pulp + AKD (4 Kg) + Defoamer (0.3 Kg)
@ 330 ml/30 sec.
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pH @ 6.95, Cobb 120 @ 38
pH @ 7.1, Cobb 120 @ 63 & Drainage
5. Set 3 B:- Pulp + WSR (10Kg) + AKD (4Kg) + DCPAM (0.15 Kg) + Defoamer (0.3Kg) = pH 7.4,
Cobb 120 @ 41 & Drainage @ 398 ml/10 sec.
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Case Study
6. Set 4:- Pulp + WSR (10Kg) + AKD (4 Kg) + DCPAM (0.15 Kg) + LAPAM (0.15 Kg) + Defoamer
(0.3 Kg) = pH @ 7.49, Cobb 120 @ 37 & Drainage @ 400 ml/30 sec.
7. Set 5:- Pulp + WSR (10 Kg) + AKD (4 Kg) + DCPAM (0.15 Kg) + LAPAM (0.15 Kg) + Bentonite
(2 Kg) + AF 270 (0.3 Kg) = pH 7.35, Cobb 120 @ 30 & Drainage @ 445 ml/30 sec.
8. Set 6:- Pulp + WSR (10 Kg) + AKD (4 Kg) + DCPAM (0.15 Kg) + Bentonite (2 Kg/T) + Defoamer
(0.3 Kg/T) = pH @ 7.41, Cobb 120 @ 34 & Drainage @ 430 ml/30 sec.
9. Set 7:- Pulp + WSR (10 Kg) + AKD (4 Kg) + DCPAM (0.3 Kg) + LPAM L (0.15 Kg) + Defoamer
(0.3 Kg) = pH @ 7.5, Cobb 120 @ 28 & Drainage @ 472 ml/30 sec.
10.Set 8:- Pulp + WSR (10Kg) + AKD (4 Kg) + LCCP (0.3 Kg) + LCCP (1 Kg) + Defoamer
(0.3 kg) =
pH @ 7.5, Cobb 120 @ 38 & Drainage @ 560 ml/30 sec.
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RDF
Thanks