THE USE OF HYDROGEN PEROXIDE IN THE BLEACHING OF CHEMICAL PULP

THE USE OF HYDROGEN PEROXIDE IN THE USE OF HYDROGEN PEROXIDE IN THE BLEACHING OF CHEMICAL PULPTHE BLEACHING OF CHEMICAL PULP

Ross Anderson

Kemira Chemicals

Southeastern TAPPI and TAPPI Bleaching Committee

Joint Meeting

St. Augustine, FL - June 13, 2002

AgendaAgenda

• Introduction• Safety and Handling• Chemistry• Process Control• Bleaching Applications• New Developments

AgendaAgenda


Overcoming Bleach Plant LimitationsOvercoming Bleach Plant Limitations

• short sequences• eliminate hypochlorite• prevent dioxin formation• extend ClO2 capacity to more pulp prod’n• ECF

• decrease cost• increase brightness• increase pulp production

• TCF

Evolution in Hydrogen Peroxide UseEvolution in Hydrogen Peroxide Use

Add to existing bleaching stages

Intensify process conditions to get more effect

Add pretreatment to get more focused effect

Add specialized process stages and equipment

Modify chemistry to get different effect

Hydrogen Peroxide ManufactureHydrogen Peroxide ManufactureAnthraquinone Anthraquinone ProcessProcess

OC2H5

O

OHC2H5

OH

H2 O2

H2O2

circulatingworksolution

Hydrogen Peroxide ManufactureHydrogen Peroxide Manufacture

Purification

HydrogenPlant

Hydrogenation

Stabilization

Storage

Oxidation &Extraction

Concentration

PropertiesProperties

• clear, colorless liquid• low vapor pressure• sp.gr. (50% solution) = 1.19 at 4°C• freezes at -52°C (50% solution)• boils at 114°C (50% solution)• pH 0.5 - 3.5

-60

-50

-40

-30

-20

-10

0

0 10 20 30 40 45 50 60 80 90 100

Freezing Point of Hydrogen PeroxideFreezing Point of Hydrogen Peroxide

H2O2 concentration, wt%

Tem

pera

ture

, oC

POINT A

H20 COOLINGWATER

H20 DILUTION

UNLOADINGSTATION

INDOOR

P1

P3

P2

H2O2 TODILUTION

REMOTE SETPOINTFROM PROCESS

LIALIA

TIATIA

H

HL

H

H

LIRSA

LLL

HHH

TIA

H

A A

FIC

DOSINGTANK2-4 M3

H2O2-STORAGE TANKMIN 60 M3

Storage System for Hydrogen PeroxideStorage System for Hydrogen Peroxide


HazardsHazards

• Oxidizer

• Corrosive

• Dangerously Reactive

Personal Protective EquipmentPersonal Protective Equipment

• Splash-proof goggles (and face shield)

• Rubber gloves and boots

• Acid suit

Hazard of CombustionHazard of Combustion

• Peroxide, itself, does not burn• Decomposition reaction is exothermic

• produces heat and oxygen• Remove combustible materials• Water removes heat and decreases

reactivity

Hazard of PressurizationHazard of Pressurization

• Decomposition in pump

• Decomposition in storage tank

• Non-pulp & paper: Submarine Kursk

Hazard of PressurizationHazard of Pressurization

• Decomposes continuously at slow rate• Pressure increase in “closed” systems

• storage tank vents• piping PRVs• ball valves drilled on upstream side

• Design systems to limit potential for contamination

• Use approved materials only• Passivate process contact surfaces

Volume of Oxygen Released atVolume of Oxygen Released atDecomposition of HDecomposition of H22OO22

050

100150200250300350400450500

0 10 20 30 40 50 60 70 80 90 100

H2O2 concentration, wt%

liter

O2

/ lit

erH

2O

2

HYDROGEN PEROXIDE H2O2

Stainless Steel Ball ValvesStainless Steel Ball Valves

SMALLOPENING

FLOW

TO TANK

Vent hole is required to prevent entrapment in the cavity of the valve body

Pumps for Hydrogen PeroxidePumps for Hydrogen Peroxide

CENTRIFUGAL

SS 316 or 304 wetted parts

• Process flush single mechanical seals: only seals of silicon carbide with Kal-Rez “O” Rings.• Ease of operation and maintenance• Requires recirculation line for assured minimum flow• Greater range of control of flow with flow meter and flow control valve (most common in industry)• Allows multiple application from one header

METERING OR POSITIVE DISPLACEMENT

SS 316 or 304 Teflon® wetted components.

• Can provide very small flow control.

• Requires pulsation damper for uniform flow and pressure regulating device for proper operation.

• Can achieve high pressure discharge.

• Has a tendency to vapor lock if shut down..

• Built in check valve can be a problem.

Most Common Materials Compatible with Most Common Materials Compatible with Hydrogen Peroxide in Concentrations of Hydrogen Peroxide in Concentrations of

70%, 50% and 5%70%, 50% and 5%

Compatible Incompatible

Storage Tanks - wetted parts only Exterior StructuralAluminum 5254 Aluminum 6061TStainless Steel 316L, 304L High carbon content SS

Piping Stainless Steel 316L, 304L Carbon SteelWetted Parts Pumps All other Metals

Valves ASTM A- 312 and Hoses Stainless Steel 316, 304, 321, Carbon Steel, Brass andand Teflon® most other materials

Pump Seals Carbon and most other materials- Silicon Carbide, Glass filledTeflon® on 316SS Asbestos Graphite and most Kal-Rez “O” Rings, Viton ® other materials

Gaskets Teflon®, Gylon ®, Tygon®, Teflon® envelope BrassPressure Gauges 316 Stainless Steel Silicone, mineral oil and most other fluids

Liquid pressure gauges316 Stainless Steel filled with ABS, Brass, Flurolube® or Krytox ® Copper, Lead, Mercury

Lab SuppliesGlass, Stainless Steel 316, 304, Tygon®, Polyethylene, PVC, Teflon®

Materials of ConstructionMaterials of Construction

Acceptable:

• 316L (304,304L) stainless steel • 5254 aluminum

• carbon steel• brass• copper• zinc

Not Acceptable:

Materials of ConstructionMaterials of ConstructionTitaniumTitanium

• high “Handbook” corrosion rate• significant corrosion potential at:

• > 0.2% H2O2 in solution ( 2% on pulp @10% Cs)

• > pH 11• > 90°C

• corrosion inhibited by Ca and Mg• corrosion has not been an issue in refit

TCF sequences


ChemistryChemistryPerhydroxyl Perhydroxyl AnionAnion

H2O2 + HO- ⌦ HOO- + H2O

pKa = 11.6 at 25°C

ChemistryChemistryRadicalsRadicals

H2O2 + Mn+ ⌫ •OH + M(n+1)+ + OH-

M(n+1)+ + OOH- ⌫ Mn+ + •O2- +

H+

Assay MethodsAssay Methods

• Density

• KI-Thio titration

• 2° titration with Ceric Sulphate• peroxide-specific Ti4+ indicator• Peroxidase analytical sticks

Pure solution

Process residual

Differentiation from ClO2


Process ControlProcess ControlpHpH

Process ControlProcess ControlTemperature and TimeTemperature and Time

Process ControlProcess ControlConsistencyConsistency

Process ControlProcess ControlPeroxide ChargePeroxide Charge

Process ControlProcess ControlMetals RemovalMetals Removal

Process ControlProcess ControlMetals RemovalMetals Removal

Process ControlProcess ControlMagnesiumMagnesium


Effectiveness of ApplicationsEffectiveness of Applications

• Consumption in non-bleaching reactions• chemical carryover• organic carryover• metals

• Optimized process conditions

• Mixing

PeroxidePeroxide--Reinforced Oxygen Reinforced Oxygen DelignificationDelignification

PeroxidePeroxide--Reinforced Reinforced Oxygen Oxygen DelignificationDelignification

PeroxidePeroxide--Reinforced Reinforced Brownstock EopBrownstock Eop

PeroxidePeroxide--Reinforced E1Reinforced E1--StageStage

• Decrease colour• eliminate dioxin in CD Eop D E D• decrease AOX in DC Eop D E D• decrease cost and increase

brightness in D Eop D E D





• higher ClO2 replacement ratio (>2:1)

• limited H2O2 consumption (<2 kg/tp)

• lower pH target than for Eop-stage

Peroxide in Bleached Pulp StoragePeroxide in Bleached Pulp Storage

• improved brightness stability

• complicated process control

• decreased bleach plant operating flexibility

Peroxide in Bleached Pulp StoragePeroxide in Bleached Pulp Storage

Final Peroxide Brightening StageFinal Peroxide Brightening Stage


• high pressure, high temperature

• low metals content

• Mg/Mn > 100



PO Stage in a TCF Bleach PlantPO Stage in a TCF Bleach Plant

TCF BleachingTCF BleachingHardwood

H2O2 5 kg/tNaOH 10 kg/tMgSO4 1 kg/t

Final pH: 5 Final pH: 9.8H2O2 residual: 1 kg/t

PAA 4-5 kg/t H2O2 19 kg/tNaOH 11 kg/t

Final pH: 5.8 Final pH: 9.6H2O2 residual: 5.2 kg/t

Op POPAAQ2Q1

EDTA 0.8 - 1.3 kg/t EDTA 1.3 kg/t

TCF TCF BleachingBleachingHardwood

O2 Stage

Brightness: 88.7 %ISOKappa: 4.8Viscosity: 818 dm3/kg

Op PO

Brightness: 59.3 %ISOKappa: 9Viscosity: 1025 dm3/kg



PAAQ2Q1

Modify Peroxide ChemistryModify Peroxide Chemistry

• Peroxide Bleaching Enhancers

• Peracids• in situ formation• distilled Peracetic Acid, PAA

• Metal Catalysis, mP

Oxidation Potentials of Oxidation Potentials of Bleaching ChemicalsBleaching Chemicals

Oxidation Reaction Oxidation Potential, eV

O3 + 2H+ + 2e- ⌫ O2 + H2O 2.07

HClO2 + 3H+ + 4e- ⌫ Cl- + 2H2O 1.56

HOCl + H+ + 2e- ⌫ Cl- + H2O 1.49

Cl2 + 2e- ⌫ 2Cl- 1.36

ClO2 + H+ + e- ⌫ HClO2 1.15

CH3CO3H + 2H+ + 2e- ⌫ CH3CO2H + H2O 1.06

ClO- + H2O + 2e- ⌫ Cl- + 2OH- 0.90

HOO- + H2O + 2e- ⌫ 3OH- 0.87

ClO2- + 2H2O + 4e- ⌫ Cl- + 4OH- 0.78

O2 + 2H2O + 4e- ⌫ 4OH- 0.40

Production of Production of Peracetic Peracetic AcidAcid

CO

OHCH3 + H2O2 C

O

OCH3

OH+ H2O

catalyst

hydrogenperoxide

peraceticacid

acetic acid water

Production of Distilled Production of Distilled Peracetic Peracetic AcidAcid

Aceticacid

Hydrogenperoxide

Productstorage

dPAA

Water

Productstorage

ePAA

Catalyst

Stabilizator

Generation of Generation of Caro’s Caro’s AcidAcid

Effect of Molar Ratio and Concentration of Feed Chemicals

0

10

20

30

40

50

60

70

80

90

100

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00

98% H2SO4/H2O2 Molar Ratio

Pero

xide

Con

vers

ion,

%

65% Oleum 70% H2O2

50% H2O2

Chemical Impact of Chemical Impact of Peracid Peracid AdditionAddition

Need of neutralisation & side products

dPAA ePAA PFA Caro's acidPeracid, kg/tp * 10 10 7.9 15NaOH Demand, kg/tp ** 1 4 26 20By-Product acetic acid CH3COONa HCOONa Na2SO4

Na, kg/tp negligible 4.6 29.9 23S, kg/tp n/a n/a n/a 9.9

* amount needed for delignification of 3 kappa units** amount of NaOH needed for adjusting the pH to 5

PAA in Final DPAA in Final D--StageStageSoftwoodSoftwood

0 2 4 6 8 10858687888990919293

Brig

htne

ss, %

ISO

ClO2 + 2 kg Paa/tp

ClO2 alone

ClO2, kg/tp (act. Cl)

Effect of ClO2 Dosage

PAA PostPAA Post--BleachingBleachingProcess ConditionsProcess Conditions

• Temperature: 40 - 70°C• pH: 4 - 7• PAA charge: < 3 kg/tp

• Fast reaction…even at low consistency

PAA PostPAA Post--BleachingBleachingBenefits at Pulp MillBenefits at Pulp Mill

• Decreased usage of ClO2

• decreased AOX• extra pulp production if ClO2 capacity is a bottleneck

• Improved pulp quality• higher and less variable brightness• improved brightness stability (less yellowing)• less variable pH

• No brightness reversion

• Easy to install and use

PAA in Bleached Pulp Storage TowerPAA in Bleached Pulp Storage Tower

1 1 -- 2 kg/2 kg/ tptp PAA PAA ≈ ≈ + 2 %ISO+ 2 %ISO

pH 5-6

StoragetowerD2-washer

White waterWhite waterWhite water

PAAPAA

pulp outpulp out

Pulp toPulp topapermachinepapermachineT: 55 °C

Effluenttank

Bleached pulpBleached pulpBleached pulp

Pulp fromPulp frompulp plantpulp plant


Effect of PAA Charge on Brightness

0 1 2 3 4 5PAA, kg/tp

8989,5

9090,5

9191,5

92

Brig

htne

ss, %

ISO

softwood kraft pulp, initial Br. 89.8%ISO, kappa 0.4, viscosity 834 dm3/kg


Effect of Time and Consistency on Brightness

0 20 40 60 80 100 120Time, min

89

89,5

90

90,5

91

91,5

92

Brig

htne

ss, %

ISO

10% Cs

4% Cs

Softwood kraft pulp, initial Br. 89.8%ISO, PAA @ 1.5 kg/tp


0123456

Yellowness b* delta E*

swsw-PAAhwhw-PAA

Effect on Yellowness

PAA @ 2 kg/tp, final pH 5, 50°C, 60 min, Cs 10%

b* - yellow/blue axisE* - calculated difference in L,a*,b* space…corresponds to a visually perceived colour difference

PAA in Bleached Pulp Storage TowerPAA in Bleached Pulp Storage TowerMill TrialMill Trial

Stora Enso - Veitsiluoto Pulp Mill, Kemi

SoftwoodPAA @ 2.5 kg/tp avg. Br gain = 1.9 pts, std.dev. decreased by 30%

Brightening with Brightening with Peracetic Peracetic AcidAcidVeitsiluoto Veitsiluoto Pulp Mill TrialPulp Mill Trial

Reference PAA

Tensile index, Nm/g SR 20 SR 30

82.494.6

82.595.1

Tear index, mNm2/g SR 20 SR 30

9.17.9

10.08.6

Viscosity, dm3/kg 718 748

PAA: Effect on Microbial GrowthPAA: Effect on Microbial GrowthPAA added to ECF kraft bleached pulp storage chest

0

5

10

15

20

25

30

0 5 10 15 20 25 30 35 40Time, days

tota

l mic

robe

s, 1

0000

00/m

l

BrokeHeadboxBackwater

Reference period

Test period:PAA in storage chest

After PAA trial

PAA: Effect on Optical BrightenersPAA: Effect on Optical BrightenersImproved light emission at 457 nm

85

90

95

100

105

110

0 1 2 3 4 5 6OB A , k g/ tp (c om m erc ia l product )

R45

7 U

V on

PA A 0 k gPA A 1 k g

pine:birch:euca=20:60:20 8% consistency, 30 min., 40°C, pH 7-7.5Pulp dewatered prior to OBA addition

PAA PostPAA Post--BleachingBleachingBenefits at Fine Paper MachineBenefits at Fine Paper Machine

• Decreased demand for optical brighteners

• Stabilized surface charge on fibres

• Improved AKD/ASA size retention• size retention from 60-70% to 90-95%• decreased AKD content in white water• cleaner press section (fewer breaks, holes, and dirty spots)• decreased hydrolysis of AKD

• decreased formation of ketones• copy machines run more cleanly

• Biocide-free paper production

Documents

THE USE OF HYDROGEN PEROXIDE IN THE BLEACHING OF CHEMICAL PULP