Preparación de pasta. Pulper. Funcionamiento
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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.
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Preparación de pasta. Pulper. Funcionamiento
- 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 pulperPlato 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 alimen 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 ChangeinRepulpingTime(%)
- 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 DirtCount(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 ChangeinRepulpingTime(%) y = 0,0249x5 - 0,2967x4 - 2,0596x3 + 24,317x2 + 12,237x + 135,6 0 100 200 300 400 500 8.10 8.17 08:20 08:22 08:28 08:34 08:36 08:40 08:51 08:57 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 RejectsSewer 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 SCREENINGEFFICIENCY,% 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 SCREENINGEFFICIENCY,% 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.
- 36. Latin American Operations 10 mm 100 mm 500 mm 50 mm Burbuja de aire 1000 mm 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- 45oC • 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 2o 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
- 48. Latin American Operations • Introduction/History • Refining Theory • Effect on Sheet Properties • Refiner Plate Design • Process Control Stock Preparation Refining
- 50. Latin American Operations Modern Double Disk Refiner
- 52. Latin American Operations Double Disk Refiner with Double Inlet (Duo-Flow Configuration)
- 54. Latin American Operations • Introduction/History • Refining Theory • Fibers • Refining Mechanics • Effect on Sheet Properties • Refiner Plate Design • Process Control Stock Preparation Refining
- 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
- 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 RPMr s Lx 60 sec/min ELS = ELS = Number of edge length crossings per second (m/s) Lr = Total length of bars on a rotor (mm) Ls = Total length of bars on a stator (mm) Lx = 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 = PTot - PNL T
- 62. Latin American Operations Refining Intensity Where: ELS = Total edge lengths per second (mm 2 /sec) PTot = Total refiner power consumed (kW) PNL = Refiner no load power consumed (kW) RI = PTot - PNL 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 OperationsRefined & Unbleached Kraft Fibers
- 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 QalSoftness
- 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 SheetDensity
- 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 SteamDrying
- 73. Latin American Operations • Introduction/History • Refining Theory • Effect on Sheet Properties • Refiner Plate Design • Process Control Stock Preparation Refining
- 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) BarAngle Crossings perSeond (mmC/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. BreakingLength(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
- 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
- 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 H2O2 + -OH H2O + -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 53 42 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 x25oC 40oC 60oC 80oC 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: NaBH4, NaOH, SO2 Comb 2: NaBH4, H2SO4, NaHSO3 (borohydride) (bisulfite) Cs. 4-6 or 10-14% pH 8-10 Temp. 60-90oc 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 ISO85 80 75 70 65 0 30 60 90 120 Time (minutes) 90oC 70oC 50oC 40oC 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 ISO85 80 75 70 65 0 30 60 90 120 Time (minutes) 90oC 70oC 50oC 40oC 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. 55-90oc time 30-120 min FAS 0.4-0.8% FAS
- 100. Latin American OperationsTechnology 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