enzyme applications in pulp and paper - nc state...

Endo-Beta 1,4 Xylanase

Enzyme Applications in Pulp and Paper: An Introduction to Applications

Dr. Richard VendittiAssociate Professor - Director of Graduate ProgramsDepartment of Wood and Paper Science Biltmore Hall Room 1204Raleigh NC 27695-8005Tel. (919) 515-6185 Fax. (919) 515-6302Email: [email protected]

Slides courtesy of Phil Hoekstra.


Enzymes

• Are proteins that catalyze chemical reactions

• Biological cells need enzymes to perform needed functions

• The starting molecules that enzymes process are called substrates and these are converted to products


Cellulase enzyme which acts on cellulose substrate to make product of glucose.


Enzymes

• Are extremely selective for specific substrates

• Activity affected by inhibitors, pH, temperature, concentration of substrate

• Commercial enzyme products are typically mixtures of different enzymes, the enzymes often complement the activity of one another


Types of Enzymes in Pulp and Paper and Respective Substrates

• Amylase --- starch• Cellulase --- cellulose fibers• Protease --- proteins• Hemicellulases(Xylanase) ---hemicellulose• Lipase --- glycerol backbone, pitch• Esterase --- esters, stickies• Pectinase --- pectins


Enzyme Applicationsin Pulp and Paper

• Treat starches for paper applications• Enhanced bleaching• Treatment for pitch• Enhanced deinking • Treatment for stickies in paper recycling• Removal of fines• Reduce refining energy• Cleans white water systems• Improve softness in tissue• Clean outs


Starch Conversion for Surface Coatings

• Amylases are used to cleave starch molecules to reduce the viscosity

• Used for surface sizing and for starch in coatings

• Not used for dry strength agent additive


Bleaching

• Hemicellulases (xylanases) are used to cleave hemicelluloses in fiber, making the bleaching process more effective

• May be able to reduce bleaching chemicals by up to 30%

• Can improve brightness


Pitch treatment

• Lipases used to control pitch in pulping processes

• Converts tri-glycerides to fatty acids which are more stable in water, won’t deposit as much


CH2 –--------- CH –---------CH2 Triglycerides

Ester-Bonds

│OH OH

│C=O│(CH2)15 CH3

glycerolFatty acids

OH OH

O OO

C=O

(CH2)15 CH3

C=OC=O

(CH2)15 CH3 (CH2)15 CH3

CH2 –--------- CH –---------CH2


Deinking

• Paper recycling inks and stickies attach to fibers at the surface of the fibers, stuck to microfibrils

• Cellulase and hemicellulase enzymes hydrolyze these microfibrils, releasing the adhesives

• Esterases help breakdown ink particles • Enzyme assisted DI reported to remove 30-60%

more toners• Enzyme assisted DI reported to improve

brightness by 4-5 points


Control and Removal Methods for Stickies

– Use of environmentally benign adhesive (recyclable adhesive)

– Avoidance: Control of recovered paper quality– Mechanical removal: screening and water clarification– Chemical control: polymers surfactants, others– Passivation with inorganics– Enzyme hydrolysis– Physical adsorption to paper fibers: retention– Dispersion– Protection: treatment of equipment to limit deposits– Mill shut down for clean-up


CLASSIFICATION OF STICKIES

PRIMARY SECONDARY(Formed in

pulper)(Change in environment, pH, temp., etc.)


MACRO VS MICRO STICKIES

Macrostickies

Microstickies

Retained on 6-cut (0.15 mm) slotted screen*

Accepted by 6-cut (0.15 mm) slotted screen*

* Trend is towards 0.10 mm or 0.075 mm slotted screen


Stickies Control

• Microstickies in dilution water recirculateback into the systems

• Microstickies agglomerate under shear and pH changes and contribute to macrostickies, secondary stickies

• Reducing microstickies will make a significant impact on macrostickies

• Ability to measure both micro and macro is important


Without Proper Water Clarification (<20% reduction):“ re-introduction of stickies”


Enzymes as stickies treatment

• Esterases used to break ester bonds in polymers used in toners and adhesives

• Improved paper cleanliness• Less deposits, less clean up on PM• Can be used as substitute for talc or

solvent based dispersants


- (CH2 – CH - CH2 – CH - CH2 – CH )n -

PVAcEster-Bonds

- (CH2 – CH )- CH2 – CH - CH2 – CH )n -│OH OH

│C=O│CH3

PVAlcoholAcetic acid

OH OH

O OO

C=O

CH3

C=OC=O

CH3 CH3


polyvinyl acetate -(-CH2CH-)n-

OCOCH3

HydrophobicSurface

without Esterase

Agglomerates of PVAc

Polyvinyl alcohol

OH

OHHO

OHOH

OH

OHHO

OHOH

OH

OHHO

OHOH

OH

OHHO

OHOH

OH

OHHO

OHOH

OH

OHHO

OHOH

OH

OHHO

OHOH

OH

OHHO

OHOH

OH

OHHO

OHOH

with Esterase

OH

Hydrophilic

OH

OHOH

OH

OH

OH

OHOH

OHOH

OH

OH

polyvinyl alcohol + acetic acid-(-CH2CH-)n-

OH + CH3COOH


Impact on stickies chemistry

• Optimyze has two impacts on stickies– Cleaves ester bonds to reduce size of stickies– Surfaces on smaller stickies are converted to

alcohol groups• Alcohol groups are less tacky• Alcohol groups are polar, which allow DAF

polymers to grab onto them for removal


Electron micrographsUntreated Treated


Optimyze Plus 735 trial data

stickies transfer on reel samplesduring Optimyze Plus 735 evaluation

0

20

40

60

80

100

120

140

160

2/12 3/4 3/24 4/13 5/3 5/23

stic

kies

0

0.2

0.4

0.6

0.8

1

1.2

BLX

130

64 d

osag

e (lb

/t)

count

PPM

BLX dosage


Caustic replacement: neutral deinking for newsprint deinking

• Caustic is used in pulping recycled fibers to swell fibers, improving paper making potential

• Cellulase enzymes can be used in conjunction with or as a substitute for the caustic to swell fibers

• Neutral deinking has some advantages including less COD in the white water, lower costs


Decrease energy in refining

• Cellulase enzymes cause partial depolymerization of cellulose and swelling of fibers, more flexible fibers

• Reduction of fines• Improves efficiency of refining, can

decrease energy consumption or obtain improved strength at higher freeness

• Often better runnability or less dryer energy required

Endo-Beta 1,4 Xylanase3/3/2010

Fibrillation


Fiber Modification

• Enzymes can assist this de-lamination process

• Conditions fiber for refining• Reduces refining energy• Changes the refining curve• Old rules do not apply• Laboratory Testing


Case History

• MILL: Quebec• FIBER: Recycled/Softwood Kraft• GRADE: Napkin• GOAL: Increase tensile strength to

middle of specification, reduce kraft fiber usage

• METHODS: Treated MOW stock at the pulperwith 0.5 to 1.0 kg/tonne BZM 2545, about 3 hours of contact time


Machine Trial of Buzyme 2545in Napkin grade

0

5

10

15

20

25

30

35

40

45

Pre-trial Trial

Kraf

t Usa

ge (%

)

245

250

255

260

265

270

275

Tens

ile S

tren

gth

SWK UsageTensile


Machine Trial of Buzyme 2545in Napkin grade

0

5

10

15

20

25

Pre-trial Trial

Kraf

t Usa

ge (%

)

0

50

100

150

200

250

300

Tens

ile S

tren

gth

SWK UsageTensile

Refining energy reduced


Results: Machine Trial of Buzyme 2545in Napkin grade

• Reduced kraft from 40% to 0% of furnish• Increased tensile to a “comfortable” range• Refining energy reduced 14% • Drainage is better, but cannot take

advantage of it, due to drive limitations


Hydrolysis of fines

• Fines build up in water loop in PM and cause drainage, formation and paper properties problems

• Cellulase enzymes hydrolyze these fines, making them soluble, improving PM ops

• Can run PM faster (up to 10% faster in some cases?)


Softness in tissue

• Cellulase enzymes improve softness by hydrolyzing cellulose in fibers, creating weak spots in fibers, making fibers flexible

• Softness increases of up to 25%• P&G has several patents, some donated

to NCSU


Case History

• MILL: Quebec• FIBER: 95% SWD/5% Recycled Fiber• GRADE: Premium Bath• GOAL: Reduce refining energy, increase

softness and bulk, maintain tensile

• METHODS: Treated stock at the pulper with0.5 to 1.0 kg/tonne BZM 2545, about 3 hours of contact time


Bulk vs. TensileBuzyme 2535 vs. Glyoxylated Polyacrylamide

7

8

9

10

11

12 14 16 18 20 22GMT/BW

B/B

W

Buzyme 2535 Gloxylated PAM

Linear (Buzyme 2535) Linear (Gloxylated PAM)

Average Bulk to Tensile Increase of 3.5%


Results

• Shut down refiners• Maintained tensile• Bulk/basis weight increased by avg. of 3.5%• Able to reduce BWT due to increase in tensile• Machine speed increase of 100 FPM, due to

better drainage


ROI for Fiber Modification• Reduction in refiner energy• Less fines generation

– Better drainage– Softer feel– Less dusting– Cleaner white water

• Reduction in starch or CMC• Fiber substitution

– Could use more MOW, less virgin


Improved biodegradability of pulp mill waste water

• Cellulases and Hemicellulases used to degrade cellulose and other high molecular weight polymers

• COD/BOD ratio of domestic sewage 2:1• COD/BOD ratio of paper mill waste water

up to 5:1• Hydrolysis of cellulose fines by enzymes

to lower molecular weight sugars that are more biodegradable


Clean Ups / Boil Outs

• Amylase to treat starch deposits in clean ups of starch preparation/application equipment

• Protease used as biodispersants or enzyme boil-outs, cleave protein molecules in deposits and solubilize deposits


Summary• Enzymes are green chemicals that can

improve operations in pulp and paper• Wide variety of enzymes, must be

applied with understanding of how they work

• Several widely accepted applications, starch, bleaching, clean ups

• Future: high valued functionalized fibers, improved pulping, specialized paper properties, conversion of wastes to fermentable sugars.

enzyme applications in pulp and paper - nc state...

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