Preparación de pasta. Pulper. Funcionamiento

Para tener una idea clara se podría hablar de cierta similitud a la cocina, sobretodo en la primera parte del proceso. Por esta razón los italianos lo saben trabajar tan bien, la producción de una hoja de papel es muy parecida al proceso de creación de la pasta. ¡Oído cocina!

El pulper es un recipiente con una hélice en su parte inferior en el que se mezclan todos los ingredientes básicos para la creación de la pasta de papel. Por lo tanto se añade la pasta que se presenta en hojas gruesas y se debe deshacer y mezclar con el agua adecuadamente para conseguir una mezcla estable. Aunque no lo parezca este primer proceso de producción debe realizarse de manera precisa y controlar por lo tanto la velocidad del rotor, el caudal de salida y el nivel de agua para que el resultado final sea una pasta homogénea y perfecta evitando problemas posteriormente.

1. Latin
American
Operations
Introduccion
•Teoria de operacion
•Variables que afectan el pulpeo.
Pulpeo preparacion de pasta

2. Latin
American
Operations
Funcion del pulper
•Desfibrar
•Mezclar
•Tamizar gruesos
•Controlar la consistencia
del proceso.
•Almacenar pasta.

3. Latin
American
Operations Tipos de Pulper
•Baja consistencia (3-6%)
•Alta consistencia (15-20%)
•Pulper de tambor (15-20%)

4. Latin
American
Operations
Pulper de bajo %C tipico
Rotor
Bafles fijos
Cuerpo del Pulper
Accionamiento del pulper Plato de extraccion

5. Latin
American
Operations
Pulper de alta consistencia
Rotor
Salida
Cuerpo
Accionamiento
Detrasher
o pera

6. Latin
American
Operations High Density Pulper
Theory of High Density Pulping
1. Water and waste paper mixed
2. Rotor tears
paper apart
3. Majority of defibering caused by fiber to fiber rubbing
4. Defibering/Rubbing causes ink to breakdown
5. Thicker mix (high consistency) causes more rubbing
6. Target 18% consistency to achieve best results
7. Optimum pulping
time 20-50 minutes

7. Latin
American
Operations
Hi-Con Pulper- Internal View
Pulp circula lentamente debe
girar completamente.
La pulpa se ve
Espesa como concreto.
Son visibles los
contaminantes grandes
El papel se desintegra
En 10 minutos.
El rotor es relativamente grande
Con respecto al cuerpo.

8. Latin
American
Operations
Impactos en calidad
•La consistencia afecta lafriccion fibra a
fibra. La consistencia debe ser tan alta
como sea posible permitiendo la circulacion
en el pulper. 15%-22% C
•Mas tiempo de pulpeo da como resultado
tintas de tamano mas pequeño. Las tintas
pequenas son mas faciles de remover que
las grandes. 20 a 40 minutos
•No se recomienda usualmente la adicion de
quimicos.

9. Latin
American
Operations Impactos en calidad
•La temperatura debe ser lo mas baja
posible para permitir que las particulas
de tinta laser se fracturen.
•Bajas Temperaturas mejoraran el
desempeno en la remocion de stickies
en los fine screen.
•La consistencia de descarga debe ser
controlada para permitir que los equipos
posteriores trabajen eficientemente.

10. Pulper de Tambor
Papel reciclado se alimenta
En esta tolva.
Contaminantes
Grandes salen por
este lado al recipiente
de basuras
Los aceptados se lavan
Fuera del tambor por los agujeros
De la superficie del tambor y se
Bombean al tanque de pasta.
Todo el
tambor
rota

11. Accion de pulpeo - 3 Etapas
Circulacion Impact Defibering
Traer las fibras a la zona
De desfibracion
Reducir la pulpa
a masas de fibras
Separar las masas
en fibras individuales.

12. Latin
American
Operations Pulping Consistency vs. Repulping Time
Pulping Consistency (%)
3 4 5 6 7 8
-40
-30
-20
-10
0
10
20
30
Change in Repulping Time (%)

13. Latin
American
Operations
Effect of Pulping Consistency
on Defiberization
91
92
93
94
95
96
97
98
99
100
0 5 10 15 20 25 30 35 40 45 50
Pulping Time (min.)
% Defiberization

6%
12%
15%

14. Latin
American
Operations
Effect of Pulping Consistency on Dirt Count
(20 minutes pulping)
4395
1580
6961
1403
0
1000
2000
3000
4000
5000
6000
7000
6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 16%
Pulping Consistency
Dirt Count (ppm)

15. Latin
American
Operations
Specific Energy
SE =
T x kW
B x 60
min
hr
Where: SE
T
kW
B
=
=
=
=
Specific Energy (kW-hr/mton)
Pulping Time (min)
Installed motor capacity (kW)
Pulper capacity (mtons)

16. Latin
American
Operations Power Input vs. Repulping Time
Change in Power Input (%)
0 25 50 75 100
-60
-50
-40
-30
-20
-10
0
10
Change in Repulping Time (%)

y = 0,0249x
5
- 0,2967x
4
- 2,0596x
3
+ 24,317x
2
+ 12,237x + 135,6
0
100
200
300
400
500
8.10 8.1708:2008:2208:2808:3408:3608:4008:5108:57
Kwatt

Hora
Kwatt pulpeo vs tiempo bache #5

17. Latin
American
Operations
Typical Specific Energy Applied
(kW-hr/mTon)
White Ledger

(non wet strength)
Towel
(wet strength)
Bleached Kraft Pulp
Bleached Sulfite Pulp
Slush-Maker
90
89-108
54
46
Brute
72
-----
43
36

18. Latin
American
Operations
¿Donde estaría el ahorro aquí?

19. Latin
American
Operations
Aditivos quimicos al pulper
•Blanqueadores (hipoclorito de Sodio)
•Sulfito de sodio /Bisulfito
•Control de slime
•Dispersantes
•Talco
•Ayudantes de pulpeo
•Acidos y causticos
•Colorantes

20. Latin
American
Operations
FINE SCREENING
Proposito:
El objetivo de toda criba fina es eliminar
contaminantes pequenos de la pasta forzada a
travez de su criba (mayores que su ancho de
ranura pero menores que los agujeros de una
criba gruesa) .
•Algunas masas de fibra y otros pequenos
contaminantes son tambien removidos.
• Un minimo de tintas seran eliminadas.
•No se espera ganar puntos de blancura.
•Muchos de los contaminantes rechazados son
stickies.

21. Latin
American
Operations 0.050” Hole
1.27 mm
1270 Microns
Fine
Hardwood Fiber
1.15 mm X 30 microns
Softwood Fiber
3.6 mm X 37 microns
INK PARTICLES
100 Microns
50 Microns
10 Microns
2 Microns
0.008”
0.20 mm
slot
200 Microns
Sticky
Particle
Comparison of Particle Size,
Ink Sizes and Screen Openings

22. Latin
American
Operations Inlet Line
•Contains output
from previous
system.
•Fed between
basket and rotor
Accepts Line
•Contains fibers and inks
that mde it through
basket
Rejects Line
•Contains material that
does not make it through
basket (stickies)
Basket
•Slot perforated
barrier between
Accepts and Rejects
•Accepts make it
through the basket
Rotor
•Helps fibers cross through basket
•Helps keeps basket from plugging
Vent Pipe
•Vents entrained air
from screen body
Fine Screen
Vetical and Centrifugal

23. Latin
American
Operations Fine Screens in Cascade
Primary
Secondary
Next
System
Feed
Prior
System
Feed
Accepts
Rejects
Sewer
Tertiary
Arreglo en cascada de tres etapas

24. Latin
American
Operations
Fine screen con arreglo hacia
adelante en tres etapas Fine Screens in Feed Forward
Primary
Secondary
Next
System
Feed
Feed
Accepts
Rejects
Sewer
Tertiary
Primary
Prior
System

25. Latin
American
Operations
Comportamiento del flujo en la
superficie de la cesta Basket
Rotor
•Stock flow ing between
the basket and the rotor
1
Foil
High
Pressure
Vacuum
Accepts
2
•Stock forced through basket
slots due to inlet pressure
•Stock gets extra boost from
centrifugal force created by
rotor foil
+
++
-
- -
3
•Slot velocity is very
important to control
Fine Screen
Vetical and Centrifugal

26. Latin
American
Operations
Fine Screen Variables a
considerar
Aunque poseen ranuras de poca abertura
se deben tener en cuenta otras variables
en la remocion de contaminantes:
1. Presion de entrada y presion diferencial.
2. Consistencia de entrada,
3.Velocidad de paso por ranura.
4. Rata de rechazo
5. Diseno de la criba, perfil
6. Diseno del rotor y velocidad (intensidad
de pulso).

27. Latin
American
Operations
Velocidad de paso por ranura 100
80
60
40
20
0
SCREENING EFFICIENCY, %
SLOT VELOCITY, m/s
0.5 1.0 1.5 2.0 2.5 3.0
Compressible
Conformable
Comp./Conformable
Noncompressible
Slotted Basket
0.25 mm (1.010 in)
Slot velocity and Screening Efficiencies
for various types of contaminants

28. Latin
American
Operations
Area abierta de canastilla
•Entre 6% y 9% de O.A. PL
W
L
DS
W = WIDTH OF SLOT
L = LENGTH OF SLOT
DS = DISTANCE BETWEEN SLOTS
PL = LONGITUDINAL PITCH
% OPEN AREA =
W X L X 100
DS X PL
OPEN AREA IN A SLOT PERFORATED BASKET

29. Latin
American
Operations
Influencia de la rata de rechazo
•Entre 25% a 30% en peso en primarios
•Entre 5% a 15% en peso en los trerciarios. 100
80
60
40
22
0 10 20 30 40
REJECT RATE, % OF WEIGHT
EFFICIENCY, %
0.5 mm (0.020 in.) smooth
0.23 mm (0.010 in.) coanda
0.25 mm (0.010 in.) bar
Reject Rates and Screening Efficiencies
for various types of basket styles

30. Latin
American
Operations
Velocidad del rotor - foils
•La velocidad del TIP va generalmente de 16
m/sef a 22 m/seg en criba centrifuga. 22 m/s
13.5 m/s
18 m/s
100
80
60
40
20
0 10 20 30 40
REJECT RATE, % OF WEIGHT
SCREENING EFFICIENCY, %
Reject Rates and Screening Efficiencies
for various Rotor Speeds

31. Latin
American
Operations
Tipos de rotores
•Su uso depende de la naturaleza de la pasta
a tratar.

32. Latin
American
Operations
Tipos de cribas
•Los disenos modernos se asemejan mas a la
tecnologia de C- bar de Voith o Cobra de
Kadant, HSW WAVES LEHMAN
PROFILE
TM
Fine Screens Basket Surface Profiles
C-BAR
TM
Flow

33. Latin
American
Operations
Sistema fine screen de tres
etapas
•Centrifugo Black Clawson – Diabolo Lamort

34. Latin
American
Operations
Principales factores del proceso
de flotacion.
•Particulas a remover
•Tamano
•Forma
•Distribucion
•Burbujas de aire
•Numero
•Distribucion de tamano
•Mezclado
•Combinacion de la pasta gris con las
burbujas de aire.
•Quimica.

35. Latin
American
Operations

36. Latin
American
Operations
10 m
m
100 m
m
500 m
m
50 m
m
Burbuja de aire
1000 m
m
Particula de tinta

37. Latin
American
Operations
Quimica
•Surfactante -”agente activo de superficie”
–Contiene cola hidrofobica y cabeza
hidrofilica.
–Genera hidrofobicidad a las particulas
de tinta y genera espuma.
–Se adiciona en niveles de 0.01% a
0.2%
•Los jabones no se usan porque insolubiliza
el calcio que forma depositos y afecta los
productos de recubrimiento del secador.

38. Latin
American
Operations
Cabeza Hidrofilica
Cabeza hidrofilica
(e.j. oxido de etileno
Cola Hidrofobica

(e.j.oxido de propileno)
Cola hidrofobica
SURFACTANTES DE LAVADO
SURFACTANTE DE FLOTACION
Surfactantes no ionicos.

39. Latin
American
Operations
Factores que afectan el desempeno de
la flotacion
•Consistencia de alimentacion: 0.7-1.1%
•Recirculacion: tipicamente de 3-5 pasos
(recirculacion redistribuye las burbujas de aire,
como estrategia para no incrementar el tiempo
de retencion)
•PH: neutro para surfactantes sinteticos.
•Temperatura: Ningun control especial se
requiere. Tipica temperatura de proceso 40-
45
o
C
•Contenido de cenizas: ~7% a 10% ayuda.

40. Latin
American
Operations
Consistencia de alimentacion
•Ensayos en KC con – Celda Escher-Wyss
CF3C
•1.0% consistencia
alimentacion…..71% eficiencia en
tamanos de 40 a 165 micron
•1.5% consistencia
alimentacion…..43% eficiencia en
tamanos de 40 to 165 micron
•1.0% consistencia
alimentacion……53% eficiencia en
tamanos >160 micron
•1.5% consistencia
alimentacion……14% eficiencia en
tamanos >160 micron

41. Latin
American
Operations Weir
Internal
Side Wall
Froth
Knock-Down
Shower
Rejects
Trough
Flotation
Main Components
Voith-Sulzer celda “E”
Aceptados : 3-6 pasos. Rechazos van a una 2
o

celda en algunos modelos.

42. Latin
American
Operations Flotation Cell
Main Components
Rejects
Accepts
Aerated
Pulp
Froth
containing ink
Weir
Rejects
Trough
Interior de la celda “E” de Voith-Sulzer
(With or without
flotation aid)

43. Latin
American
Operations Feed Inlet
Accepts
Rejects
Orifice Plate
Pulp
Air Holes
Flow
Helper
Air in
Air-Pulp
Mixture
Celda “E” Voith-Sulzer & Difusor
Algunos modelos
requieren aire
comprimido . Otros
inducen aire
atmosferico.

44. Latin
American
Operations AIr
Grey stock
Mixture
of suspension and air
Difusor de aire Escher -Wyss
•Un difusor de aire debe generar burbujas en un rango deseable de
tamano de ~0.3mm.
•Un difusor de aire debe inyectar una cantidad de aire del 30-60% del
flujo de alimentacion.

45. Latin
American
Operations
Celda MAC de Lamort

46. Latin
American
Operations
Celda Mac de Lamort

47. Latin
American
Operations

48. Latin
American
Operations
• Introduction/History
• Refining Theory
• Effect on Sheet Properties
• Refiner Plate Design
• Process Control
Stock Preparation
Refining

49. Latin
American
Operations Hollander Beater

50. Latin
American
Operations Modern Double Disk Refiner

51. Latin
American
Operations Jordan Conical Beater
(updated version)

52. Latin
American
Operations
Double Disk Refiner with Double Inlet
(Duo-Flow Configuration)

53. Latin
American
Operations Duo-Flo
Stator

Stator

Stator

Stator

Plate

Plate

Plate

Plate

Rotor

54. Latin
American
Operations
• Introduction/History
• Refining Theory
• Fibers
• Refining Mechanics
• Effect on Sheet
Properties
• Refiner Plate Design
• Process Control
Stock Preparation
Refining

55. Latin
American
Operations Softwood Fiber Cross-Section

56. Latin
American
Operations
Layer Thickness Cellulose Hemicellulose Lignin
microns

Primary 0.03-0.10 10% 20% 70%

S1 0.10-0.20 35% 25% 40%

S2 0.50-0.20 55% 30% 15%

S3 0.07-0.10 55% 30% 15%

M Lamella 1.00-2.00 0% 10% 90%

57. Latin
American
Operations
Moving
Refining Mechanical Action
Stationary
1 Preliminary Dewatering
2 Removal of S1 Wall
3 Wall Extraction, Delamination
4 Fibril Stimulation
5 Dispersion & Hydration
1 2 3 4 5

58. Latin
American
Operations
Fiber
Fibrils
Network
CELLOBIOSE
Lignin
Hemicellulose
Fibril
Paper
250
OH
OH
OH
OH

59. Latin
American
Operations
Number of Bars Crossings
Net Specific Energy
Refining Intensity
Intensity Factor
Refining Variables

60. Latin
American
Operations
Specific Edge Load Theory
(Edge Lengths per Second)
L x L x RPM r s
L
x 60 sec/min
ELS =
ELS = Number of edge length crossings
per second (m/s)
L r = Total length of bars on a rotor
(mm)
L s = Total length of bars on a stator
(mm)
L
x = Average length of the bar
RPM =

Rotor speed (revs/min)
Where:
or
# bars
rotator
X
# bars
stator
X
bar
length
X RPM

61. Latin
American
Operations
Net Specific Energy
Where: NSE = Net specific energy (kW-hr/mton)
P
Tot
= Total refiner power consumed (kW)
P
NL
= Refiner no load power consumed (kW)
T = Refiner throughput (mtons/hr)
NSE =
P
Tot
- P
NL
T

62. Latin
American
Operations Refining Intensity
Where: ELS = Total edge lengths per second (mm
2
/sec)
P
Tot
= Total refiner power consumed (kW)
P
NL
= Refiner no load power consumed (kW)
RI =
P
Tot
- P
NL
ELS

63. Latin
American
Operations
• Introduction/History
• Refining Theory
• Effect on Sheet
Properties
• Refiner Plate Design
• Process Control
Stock Preparation
Refining

64. Latin
American
Operations
Unrefined & Unbleached Kraft Fiber

65. Latin
American
Operations Refined & Unbleached Kraft Fibers

66. Refining Effects
Fiber
Shortening
Surface
Increase
Crill
Production
Lumen
Reduction
Axial
Compression
Form
Change
Structure
Change
Unravelling

67. Latin
American
Operations
Strength - Softness Curve
Facial Tissue
Invariant Tensile Strength (g/ 3" sheet)
0
2
4
6
8
10
12
0 200 400 600 800 1,000 1,200 1,400
Qal Softness

68. Latin
American
Operations
HI
LO
0 160
Strength vs Refining
KWH/T
Brush
Cut
Mullen/Tensile

69. Latin
American
Operations
HI
LO
0 160
Bulk vs Refining
KWH/T
Brush
Cut
Bulk (Caliper)

70. Latin
American
Operations
HI
LO
0 160
Density vs Refining
KWH/T
Brush
Cut
Sheet Density

71. Latin
American
Operations
GOOD
BAD
0 160
Formation vs Refining
KWH/T
Brush
Cut
Formation

72. Latin
American
Operations
HI
LO
0 160
Drying vs Refining
KWH/T
Brush
Cut
Steam Drying

73. Latin
American
Operations
• Introduction/History
• Refining Theory
• Effect on Sheet
Properties
• Refiner Plate Design
• Process Control
Stock Preparation
Refining

74. Latin
American
Operations
Bars
Plate
Dams
Refiner Plate Design - Dams

75. Latin
American
Operations Refining Action
Refining Action
Plate Clearance
Groove Width
Bar Width
Bar Angle
Increasing

76. Latin
American
Operations
Hydraulic Capacity of Refiner
Plate Clearance
Groove Width
Bar Width
Bar Angle
Hydraulic Capacity
Increasing

77. Latin
American
Operations
Coarse
Refining
Mild
Refining
Cutting
Brushing
Groundwood
High
contaminant
secondary
Hardwood
Softwood
Clean
Secondary
Ni-hard
Ni-hard
or
Stainless
steel
Bar
4.75
Groove -
4.75
Bar -
3.18
Groove -
3.18
7.9
6.4
5
10
1000x10
3000x10
Refiner Plate Design
Recommendations
o
o 6
6
Refining

Action

Fiber

Types

Plate

Material

Bar/Groove

Width (mm)

Groove

Depth (mm)

Bar Angle

Crossings

per Seond

(mm C/s)

78. Latin
American
Operations
Brushing Plates
Effect of Consistency
Applied Energy (HPD/ADT))
0 1 2 3 4 5 6 7 8 9 10
3400
3800
4200
4600
5000
5400
5800
6200
4.5% Cons.
3.5% Cons.
Breaking Length (m)

79. Latin
American
Operations
Typical Refiner Curve
Burst vs Power
Power Input (kW-hr/mton)
0 20 40 60 80 100
100
120
140
160
180
200
Burst (kPa)

80. Latin
American
Operations
Recommendations
•Maximize inch crossings per second
•Increase refiner consistency above 4%
•Maintain even pressure through the
refinerthrough the use of recirculation
•Monitor differential pressure
•Routinely develop refiner curves

81. Latin
American
Operations
• Introduction/History
• Refining Theory
• Effect on Sheet
Properties
• Refiner Plate Design
• Process Control
Stock Preparation
Refining

82. Latin
American
Operations Electro-Mechancial Actuator

83. Latin
American
Operations Typical Refiner Controls
FIC
FT
FSL
PSH
M
JIC
Sel. Sw.
Target KW
(By Operator)
From
Chest
JT
I
To
Chest
Seal
Water
Net Specific Energy Target
(By Operator)
NSE
Calculation
KT
KIC PSL
Cons.
Dilution
Water
FINE SCREENING
Purpose:
The objective of all Fine Screens is to eliminate small size contaminants (bigger than its slot width but smaller than the coarse screen’s holes) from the stock. Many of the rejected contaminants are stickies. Few fiber bundles and other small contraries are also removed. Minimal ink removal and no brightness gains are expected.

84. Latin
American
Operations OBJETIVO:
Blanqueamiento tiene tres funciones:
• Blanquear las fibras
• Despojar los colorantes.
•Remover lignina en algunos casos.
Todo esto es para mejorar la apariencia de la fibra
reciclada.
Overview:
Una variedad de quimicos se usan para abrillantar o
blanquear la pulpa reciclada. Cada uno tiene sus
ventajas y desventajas. Algunos quimicos son
compuestos oxidantes y otros reductores. Las reacciones
oxidacion – reduccion son las responsables de
decolorizar y deslignificar la pasta.
La lignina es la causa del amarillamiento de la fibra
cuando se expone a la luz o a un alto PH.
Blanqueo

85. Latin
American
Operations
ELEMENTOS DE COLOR EN
PAPEL RECICLADO
•Son tres fuentes de color presentes en el
papel reciclado.
–Lignina presente en la pasta mecanica.
–Colorantes
–Pigmentos

•Aqui nos ocuparemos de tratar
quimicamente las dos primeras.

86. Latin
American
Operations
Agentes quimicos de blanqueo
•Blanqueadores Oxidantes :
–Peroxido de Hidrogeno
–Oxigeno
–Ozono
–Hipoclorito de Sodio
•Blanqueadores Reductivos:
–Acido Formamidina sulfinico (FAS)
–Sodium hydrosulfite

87. Latin
American
Operations
•Most used bleach in waste paper recycling
•Bajio, Ecatepec, Ramos Arizpe, Guiacaipuro, Peru,
Owensboro, Aranguren, Malaysia, Philippines,
Thailand, South Africa, PDC, Israel, Argentina, Brazil (3
mills)
•Bleaches by breaking down color
structures attached to lignin
•Best results are seen after washing
•These reactions are irreversible
Hydrogen peroxide

88. Latin
American
Operations
H
2O
2 +
-
OH H
2O +
-
OOH
•Perhydroxy anion is responsible for brightening action
•Some dyes and pigments are not sensitive to oxidative
degradation
•Multi valent metal ions and enzymes (Catalase) decompose
peroxide
% Decomposed Peroxide
0 10 20 30 40 50 60
Time (minutes)
20
40
60
80
100
0
Boiled filtrate
Untreated filtrate
Hydrogen peroxide

89. Latin
American
Operations
•High pulp consistency benefits bleaching
•Stabilizers (Sodium silicate) and chelating
agents (DTPA,EDTA) optimize Peroxide
bleaching
0 5 10 15 20 25 30
62
56
58
60
Brightness ISO
% Consistency
60
% Silicate applied
Brightness ISO
1 5 3 4 2
57
58
59
61
62
63
2 % Perox.
1 % Perox.
0.5 % Perox.
Hydrogen peroxide

90. Latin
American
Operations
Cs.
pH
Temp.
Time
Equip.
15-30
9-11
90-130ºC
1-3 hrs
pressurized tower
Typical conditions
•Used with Peroxide
•Very little or no brightening on its own
•Color structures are exposed for
peroxide to bleach
•KC South Africa tried to use oxygen
Oxygen

91. Latin
American
Operations
Cs.
pH
Temp.
Time
Equip.
~15
7-8
35-45ºC
~20 min
sealed tower
Typical condition in RF
•Very strong oxidizing agent with very
little selectivity
•In RF the target is fluorescence instead of
lignin or colorant
•Very expensive
•Commercial installations have not been
successful
Ozone

92. Latin
American
Operations
Cs.
pH
Temp.
Time
Equip.
15-25
9-11
20-80ºC
20-180 min
tank or tower
Typical conditions
•Used for wood free waste papers because it
generates yellowing over lignin containing
fibers.
•It is cheap to use
•After bleaching Sodium bisulfite can
be used to kill residuals
•Environmentally unfavorable/corrosive
Sodium hypochlorite

93. Latin
American
Operations
Brightness increase
9
7
5
3
0
0 5 7 9
pH value
x
x
x
x
25
o
C
40
o
C
60
o
C
80
o
C
x
•High temperature improves efficiency
•Retention time typically is 30-60 min but some
uses as little as 15min.
•High consistency improves chemical efficiency
but de-gasing is required or entrained air
will consume
hydrosulfite
•Direct coupling of
reductive to oxidative
bleaching is
discouraged
Sodium Hydrosulfite

94. Latin
American
Operations 60
65
70
75
80
85
90
Brightness ISO
Yellow Red Green Black
1% Hydro, 70ºC,4%Cs,1 hr
pH 5.5 pH 9.5
•Used for color-stripping of dyes in RF
•Brightens brown fiber in wood containing pulp
(modifies chromophore groups in lignin)
•For color-stripping: pH above neutral
•For lignin bleaching: pH below neutral
•Used by K-C mills:
Bajio, Ramos, Coleshill,
Guaicaipuro, Reisolz
Aranguren, Mainz
South Africa
Sodium Hydrosulfite

95. Latin
American
Operations
Typical RF conditions
•Requires special storage and handling
(self combustible)
•Hydro is less expensive than comparable
reductive bleach FAS
•On site generation is economical and safer if usage is >1
ton/day
•Chemicals used in onsite generation:
comb 1: NaBH
4, NaOH, SO
2
Comb 2: NaBH
4, H
2SO
4, NaHSO
3
(borohydride) (bisulfite)
Cs. 4-6 or 10-14%
pH 8-10
Temp. 60-90
o
c
time 30-60 min
Hydro 0.8-1.6%
Sodium Hydrosulfite

96. Latin
American
Operations •Used for color-stripping of dyes
•More efficient than Hydro, particularly on
yellow dyes
•Either high pH (9-11) or high temperature
activates FAS
•High temperatures
improve bleaching
•Used by:
Barrow, Hadera
Villanoveta,
Korea,
80
75
70
65
60
Temperature ºC
50 60 70 80
0.2 % FAS
0.4 % FAS
0.6 % FAS
0.8 % FAS
Brightness ISO
FAS

97. Latin
American
Operations
•Requires a retention time of 40-120 min
•High consistency improves efficiency
but watch out for entrained air.
•Air decomposes FAS although
less susceptible
than Hydro. Brightness ISO
85
80
75
70
65
0 30 60 90 120
Time (minutes)
90
o
C
70
o
C
50
o
C
40
o
C
0.4 % FAS
0.2 % NaOH
4 % Cs
FAS

98. Latin
American
Operations
•Requires a retention time of 40-120 min
•High consistency improves efficiency
but watch out for entrained air.
•Air decomposes FAS although
less susceptible
than Hydro. Brightness ISO
85
80
75
70
65
0 30 60 90 120
Time (minutes)
90
o
C
70
o
C
50
o
C
40
o
C
0.4 % FAS
0.2 % NaOH
4 % Cs
FAS

99. Latin
American
Operations
Typical conditions
•FAS is more expensive than comparable
reductive bleach Hydro
•Moisture impedes FAS powder make down
Cs. 4-6 or 10-
14%
pH 9-11
Temp. 55-90
o
c
time 30-120 min
FAS 0.4-0.8%
NaOH 1 NaOH : 1
FAS
FAS

100. Latin
American
Operations Technology comparison:
Bleach Comparison Table
Oxidative
Bleaches
Peroxide Oxygen Ozone Hypochlorite
Reductive
Bleaches
Hydrosulfite FAS DBI
Bleachables
Lignin and
some dyes
Removes
Lignin aids
bleaching
Most dyes
and
Fluorescence
Most dyes
Lignin and
many dyes
many dyes many dyes
Disadvantage
s
Poor color
stripper
High capital
cost, high
BOD, poor
color stripper experimental
Darkens
lignin,
environmental
restrictions
Limited
capability:
combustible
More
expensive
than
hydrosulfite
pH 9-11 9-11 7-8 9-11 8-10 8.5-11 7-8
Consistency 15-30 15-30 15-30 15-25 4-6 &10-14 4-6 &10-14 30
Time 1-2 hrs 2-3 hrs 5-45 min 40-180 min 30-60 min 30-120 min <5 min
Temperature 70-90 90-130 23-45 20-80 60-90 55-90 60-90