paper making process by nirjhar

WELCOME WELCOME

IN THE WORLD IN THE WORLD

OF OF

PAPERPAPER

22

Let us have an overall concept of paper making process with

Nirjhar Chakravorti

33

Nirjhar Chakravorti, a Mechanical Engineer by profession, has completed engineering in the year 2000, from Jalpaiguri Government Engineering College, India.

As an engineering professional Nirjhar has worked at different industries.

Nirjhar’s interest is to know different technology and process engineering.

During study about paper technology, Nirjhar has prepared this presentation, which can be helpful for those who wants to know the complete cycle of paper making process.

44

PaperPaperAn essential part of life…………An essential part of life………… CulturallyCulturally EconomicallyEconomically SociallySocially

55

Indian paper industry is growing todayIndian paper industry is growing today

Paper usage in India is very less, compared to global Paper usage in India is very less, compared to global scenarioscenario

(less than 5% of total world wide paper usage)(less than 5% of total world wide paper usage)

In 21st Century India is booming, and so Paper usage is also rising

Where from paper is made?Where from paper is made?

77

PULP

VIRGIN FIBER

WASTE PAPER

PAPERPAPER

RECENT DEVELOPMENT

TRADITIONALDe-inking Process

How paper is made?How paper is made?

99

Paper is processed broadly in 3-steps:Paper is processed broadly in 3-steps:

Stock PreparationStock Preparation Approach Flow SystemApproach Flow System Paper Making ProcessPaper Making Process

1010

Stock PreparationStock Preparation

1111


Stock Preparation means….Stock Preparation means….

Preparation of Pulp.Preparation of Pulp.

PulpPulp is processed, cleaned and bleached is processed, cleaned and bleached Cellulose FibersCellulose Fibers along with along with waterwater which is which is present in present in semi-solid state.semi-solid state.

1212

Percentage of solid materials or dry Percentage of solid materials or dry substance (i.e. Cellulose fiber) in the substance (i.e. Cellulose fiber) in the sample of stock is defined as Consistency.sample of stock is defined as Consistency.

Consistency is an important term in Paper Consistency is an important term in Paper Technology.Technology.

1313

Other important terms:Other important terms:

Moisture Ratio:Moisture Ratio:Ratio of weight of water and weight of dry Ratio of weight of water and weight of dry substance in a sample of stock or paper.substance in a sample of stock or paper.

Basis Weight:Basis Weight:Weight in grams of one square meter after Weight in grams of one square meter after paper has been conditioned in a paper has been conditioned in a standardised environment (usually at 20standardised environment (usually at 2000C C temperature and 50% relative humidity)temperature and 50% relative humidity)

1414

Preparation of Pulp from Waste Paper

Waste Paper Pulper

Belt Conveyor

Water Chemical

1515

PulperPulper

The waste paper is slushed in a The waste paper is slushed in a continuously running pulper in medium continuously running pulper in medium consistency (10-14%).consistency (10-14%).

Pulper is agitator of raw material, chemical Pulper is agitator of raw material, chemical and water.and water.

Chemicals added in the pulper are: Sodium Chemicals added in the pulper are: Sodium Hydroxide, Hydrogen Peroxide, Sodium Hydroxide, Hydrogen Peroxide, Sodium Silicate and Soap.Silicate and Soap.

1616


Waste PaperPulper

Belt Conveyor

Water Chemical

Fiberizer

1717

FiberizerFiberizer

The fiberizer is used for mixing dilution water into the suspension and for removing coarse contaminants.

The pressure produced by the fiberizer rotor conveys the contaminants and part of stock suspension to downstream screening unit.

1818


Waste PaperPulper

Belt Conveyor

Water Chemical

FiberizerDump Tower

Drum Screen

Reject

Accept

1919

Dump TowerDump Tower

Dump Tower is basically a storage tank.

In Dump Tower, pulp gets sufficient retention time for chemical reaction, along with the chemicals added.

From Pulper to Dump Tower, the production is Batch type.

2020


Waste PaperPulper

Belt Conveyor

Water Chemical

FiberizerDump Tower

Drum Screen

Reject

Accept

High Density Cleaner

2121

High Density CleanerHigh Density Cleaner

The High Density Cleaner cleans stock separation of sorted and unsorted waste paper.

Relatively coarser contaminants such as small bolts, stones, wires and knots are separated.

Cleaner protects machinery downstream against damage and rapid wear.

2222


Waste Paper PulperBelt Conveyor

Water Chemical

FiberizerDump Tower

Drum Screen

Reject

Accept

High Density Cleaner

Hole Screen

2323

Hole ScreenHole ScreenPulp is passed through multi-stage screen of Ø1.2 mm holes.

New developed machines, with special rotor geometry and Ø1 mm hole screen, can clean fibrous stock suspensions at consistencies up to 3.5%.

In Hole Screening, contaminants removed at the beginning stages of stock preparation.

2424



Water Chemical

Fiberizer Dump Tower

Drum ScreenReject

Accept

High Density CleanerHole ScreenStand tube

FloatationPrimary Cell

2525

Floatation CellFloatation Cell

After Hole Screening, stock goes to Primary Floatation Cell, through Stand Tube.

Additives are added in Stand Tube.

Purpose of Floatation:

• To enhance brightness to high degree.

•To reduce dirt and stickies efficiently

Floatation Cell Continues….

2626


Floatation Machine comprises of cells in series forming a horizontal tube with elliptical cross section.

A weir extending over the entire aggregate separates the suspension chamber from the foam collection channel.

Suspension is removed uniformly from the bottom of each cell and pumped via aeration element to the next cell.


2727


Function of aeration element is based on step diffuser design.

Acceleration in the aeration tube generates a vacuum, which sucks the necessary process air, which forms bubbles in the stock.

Bubbles remove particles from the stock suspension.


2828


Dirt laden bubbles rise to the top of the cell, forming a foam layer.

The foam layer carried over the wire into the foam collecting channel.

The cleaner stock suspension remain in the cell and pumped to the next level.

2929



Water Chemical


Drum ScreenReject

Accept

High Density CleanerHole ScreenStand tube

FloatationPrimary Cell

Venting Cyclone

Foam TankFloatation

Secondary Cell

Reject from foam chamber

3030

Combined Floatation SystemCombined Floatation System

Two stage floatation system is an important feature of modern de-inking plant.

The primary floatation stage ensures high stock purity, while the secondary stage optimises floatation yield without sacrifice of brightness and cleanliness.

Floatation foam from the primary stage is further deaerated in a cyclone before pumping to the secondary stage.


3131

Combined Floatation SystemCombined Floatation System

In Secondary Cell, usable fibers are recovered from the foam, and the rejects from the Primary Stage are selectively removed from the system.

The accept from the Secondary Stage is returned to the Primary Stage inlet.

3232



Water Chemical


Drum ScreenReject

Accept High Density Cleaner

Hole ScreenStand tubeFloatation

Primary Cell

Venting Cyclone

Foam TankFloatation

Secondary Cell

Accept

Reject

CL1

CL2CL3

CL4

Reject Accept

Reject

Accept Reject

Accept

stands for Heavy & Light Weight Cleaner

CL

3333

Heavy & Light Weight Cleaner

After Floatation, light and heavy weight contaminants are cleaned in multi-stage cleaner.

Multi-stage cleaner operates in the concept of cyclone cleaner.

3434



Water Chemical


Drum ScreenReject



Primary Cell

Venting Cyclone

Foam TankFloatation

Secondary Cell

Accept

Reject

CL1

CL2

CL3

CL4

Reject Accept

Reject

Accept Reject

Accept

Slot Screen

Acc

ep

t

3535

Slot ScreenSlot Screen

After Cleaning, stock passes through the multi-stage Slot Screen Arrangement.

Cleaned stock is pumped to the vertical screen.

Accept from first stage Slot Screen pumped to the Disc Filter.

Slot Screen Continues….

3636


Reject from the first stage Slot Screen pumped to the second stage Slot Screen, via storage tank.

From second stage Slot Screen, accept pumped to Disc Filter, and reject pumped to third stage Slot Screen via another storage tank.

Slot Screen Continues….

3737


From third stage Slot Screen, the accept goes to the tank placed in between first and second stage Slot Screen and reject goes to the sludge tank.

CLEANERSLOT SCREEN

SLOT SCREEN

SLOT SCREEN

TANK

TANK

SLUDGETANK

DISCFILTER

3838



Water Chemical


Drum ScreenReject



Primary Cell

Venting Cyclone

Foam TankFloatation

Secondary Cell

Accept

Reject

CL1

CL2

CL3

CL4

Reject Accept

Reject

Accept Reject

Accept

Slot Screen

Acc

ep

t

Disc Filter

3939

Disc FilterDisc Filter

After Slot Screen, pulp is dewatered in the Disc Filter.

The recovered water is re-used in various locations.

For pulp dewatering, feed consistencies as low as 0.6% are acceptable.

Discharge consistencies of 10-15% can be achieved.

Disc Filter Continues….

4040

Disc FilterDisc FilterThe filter consists of low volume discs mounted on a horizontal shaft with conical flow channel.

The filtrate valve at the outlet end of the shaft has a wear plate and bridges for separating the various filtrate zones.

The filtrate valve is connected to a barometric drop-leg that generates the required vacuum.

Disc Filter Continues….

4141

Disc FilterDisc Filter

The dewatered pulp is removed from the discs by jets of water and the filter cloth is continuously washed with an oscillating shower.

The shaft with the discs is built into a vat.

Each disc has separate inlet flow vane and weir for optimised pulp distribution.

4242



Water Chemical


Drum ScreenReject



Primary Cell

Venting Cyclone

Foam TankFloatation

Secondary Cell

Accept

Reject

CL1

CL2

CL3

CL4

Reject Accept

Reject

Accept Reject

Accept

Slot Screen

Acc

ep

t

Disc FilterScrew Press

Heater Disperger

The process in Screw Press, Heater and Disperger is called

Dispersion.

4343

DispersionDispersion

Purpose:Purpose: Shears off ink particles still adhering to the Shears off ink particles still adhering to the

fibersfibers Reduce size of ink and stickies and Reduce size of ink and stickies and

disperse them in the stock suspensiondisperse them in the stock suspension Technological treatment of fiberTechnological treatment of fiber Transport of stockTransport of stock Mix bleaching additivesMix bleaching additives

Dispersion Continues….

4444


Function:Function:Dispersion effectiveness depends on two Dispersion effectiveness depends on two operational parameters:operational parameters:

TemperatureTemperature Shear forceShear forceψψ Stock temperature up to 100Stock temperature up to 100°C are adequate for °C are adequate for

dispersion. A reduction in fiber strength, which is dispersion. A reduction in fiber strength, which is expected above 100°C, will not therefore occur.expected above 100°C, will not therefore occur.

ψψ Shear force of a certain integrity must be created Shear force of a certain integrity must be created during mechanical treatment.during mechanical treatment.


4545


Dispersion system generally includes Dispersion system generally includes three process stages:three process stages:

Dewatering, achieved by Screw PressDewatering, achieved by Screw Press Heating, achieved by HeaterHeating, achieved by Heater Dispersion, achieved by DispergerDispersion, achieved by Disperger


4646

DispersionDispersionFunction of each stage of dispersion:Function of each stage of dispersion:Dewatering: Increase consistency and viscosity for high shear forces,Increase consistency and viscosity for high shear forces, Remove dissolved contaminantsRemove dissolved contaminantsHeating: Soften stickies and inksSoften stickies and inks Reduce micro-organismReduce micro-organismDispersion: Make stickies and inks floatableMake stickies and inks floatable Disperge coating gritsDisperge coating grits Mix in bleaching chemicalsMix in bleaching chemicals


4747


Type of disperger:Type of disperger: Disc DispergerDisc Disperger Kneading DispergerKneading Disperger Disc Disperger:Disc Disperger:

In Disc Disperger, movement of stock is in radial In Disc Disperger, movement of stock is in radial direction.direction.

Kneading Disperger:Kneading Disperger:

In Kneading Disperger, movement of stock is in In Kneading Disperger, movement of stock is in axial direction.axial direction.

Disc Disperger

Kneading Disperger


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4949


Disc Disperger:Disc Disperger: Stock passed through the clearance between Stock passed through the clearance between

two plates along with projected fills. Shearing of two plates along with projected fills. Shearing of ink particles takes place due to the relative ink particles takes place due to the relative rotational movement of the plates.rotational movement of the plates.

Kneading Disperger:Kneading Disperger: Shaft with projected fills placed axially in a Shaft with projected fills placed axially in a

cylindrical housing. Fills projected in the internal cylindrical housing. Fills projected in the internal wall of the housing. Shaft rotates and stock wall of the housing. Shaft rotates and stock moves axially. Shearing of ink particles takes moves axially. Shearing of ink particles takes place due to relative motion of the shaft and the place due to relative motion of the shaft and the housing.housing.


5050


Possible influence of the Dispersion on Possible influence of the Dispersion on fiber quality:fiber quality:

CurlCurl Fibrillation/FlexibilisationFibrillation/Flexibilisation


5151


CurlCurlEffect of curl on fiber quality:Effect of curl on fiber quality:

Higher wet strength and shrinkageHigher wet strength and shrinkage Higher absorption capacity and porosityHigher absorption capacity and porosity Higher bulk and greater softnessHigher bulk and greater softness Lower static strength valueLower static strength value Lower dewatering resistanceLower dewatering resistance Lower apparent fiber lengthLower apparent fiber length


5252


CurlCurlorigin of curl:origin of curl:

In principal curl originates during all fiber In principal curl originates during all fiber treatment processes where sufficiently high treatment processes where sufficiently high forces act on fibers which can not escape these forces act on fibers which can not escape these forces.forces.

Curl originates in the high consistency stock Curl originates in the high consistency stock ((>20% consistency), as well as medium >20% consistency), as well as medium consistency stock and paper machine itself.consistency stock and paper machine itself.

With increasing temperature curl and the With increasing temperature curl and the porosity in the stock increases and tensile porosity in the stock increases and tensile strength decreases.strength decreases.


5353


CurlCurl

Reversible curl:Reversible curl: All the curls generated in stock All the curls generated in stock

preparation, do not present when it preparation, do not present when it reaches the paper machine.reaches the paper machine.

A certain percentage of curl is always A certain percentage of curl is always reversible during process, depending on reversible during process, depending on furnish and operating parameters. furnish and operating parameters.


5454


CurlCurl

influence of dispersion machine type on curlinfluence of dispersion machine type on curl :: Curl generated in both type of disperger.Curl generated in both type of disperger. The porosity increase after Disc Disperger The porosity increase after Disc Disperger

is much less and disappears during hot is much less and disappears during hot disintegration.disintegration.

The increase in porosity after Kneading The increase in porosity after Kneading Disperger is clearly measurable. Disperger is clearly measurable.


5555


CurlCurl

COMPARISON OF CURL GENERATIONDISINTEGRATION COLD HOT

KNEADING DISPERGER

DISC DISPERGER

SPECIFIC DISPERSION ENERGY

RE

LAT

IVE

CH

AN

GE

IN P

OR

OS

ITY

(%

)


5656


CurlCurlInfluence of furnish on curl:Influence of furnish on curl:

Wood containing stocks have a high proportion of Wood containing stocks have a high proportion of reversible curl and wood free stocks are largely reversible curl and wood free stocks are largely irreversible.irreversible.

The curl in wood containing stock behaves like elastic The curl in wood containing stock behaves like elastic fiber. when these fibers are bent they absorbs fiber. when these fibers are bent they absorbs distortion forces, and as soon as they get chance (e.g. distortion forces, and as soon as they get chance (e.g. by dilution or agitation), they straighten again.by dilution or agitation), they straighten again.

The curl of wood free kraft paper behaves like plastic The curl of wood free kraft paper behaves like plastic fiber. These fibers contain amorphous zones, which fiber. These fibers contain amorphous zones, which are in a state of plastic flow above their softening are in a state of plastic flow above their softening temperature and can not absorb any stress.temperature and can not absorb any stress.

ELASTIC FIBER


5757


Fibrillation/Flexibilisation:Fibrillation/Flexibilisation:while curl leads to loss to strength, some while curl leads to loss to strength, some dispersion processes have the effect of dispersion processes have the effect of enhancing strength. They can therefore be enhancing strength. They can therefore be compared with refining.compared with refining.

To achieve large increase in strength, the To achieve large increase in strength, the Disperger can be operated cold without prior Disperger can be operated cold without prior heating. heating.

EXTERNALFIBRILLATION

INTERNALFIBRILLATION

TEMPERATURE

RE

LAT

IVE

CH

AN

GE

IN T

EN

SIL

E S

TR

EN

GT

H

COMPARISON OF CHANGE OFTENSILE STRENGTH

KNEADING DISPERGER

DISC DISPERGER

5858



Water Chemical


Drum ScreenReject



Primary Cell

Venting Cyclone

Foam TankFloatation

Secondary Cell

Accept

Reject

CL1

CL2

CL3

CL4

Reject Accept

Reject

Accept Reject

Accept

Slot Screen

Acc

ep

t

Disc Filter Screw Press Heater Disperger

Floatation

Water

ThickenerReductive Bleaching

Storage Tower

Mixing Chest

China Clay+ soap stone Intermediate Chest

Machine Chest

5959

After Dispersion…..After Dispersion…..

After Dispersion, water is added to the After Dispersion, water is added to the stock and the stock again passed through stock and the stock again passed through flotation second cell and thickener for flotation second cell and thickener for further treatment. After reductive bleaching further treatment. After reductive bleaching it goes to the Storage Tower. From it goes to the Storage Tower. From Storage Tower stock goes to the Machine Storage Tower stock goes to the Machine Chest through Mixing Chest and Chest through Mixing Chest and Intermediate Chest.Intermediate Chest.

6060

Preparation of Pulp from Waste Paper: Complete Cycle


Water Chemical


Drum ScreenReject



Primary Cell

Venting Cyclone

Foam TankFloatation

Secondary Cell

Accept

Reject

CL1

CL2

CL3

CL4

Reject Accept

Reject

Accept Reject

Accept

Slot Screen

Acc

ep

t

Disc Filter Screw Press Heater Disperger

Floatation

Water

ThickenerReductive Bleaching

Storage Tower

Mixing Chest

China Clay+ Soap Stone

Intermediate Chest

Machine Chest

6161


The steps and the equipments described The steps and the equipments described here in the process flow is for general here in the process flow is for general idea. Sometimes steps and equipments idea. Sometimes steps and equipments vary depending on process requirement, vary depending on process requirement, quality of fiber, end product, etc. But as a quality of fiber, end product, etc. But as a whole the steps remain same.whole the steps remain same.

6262

Approach Flow SystemApproach Flow System

6363


Approach Flow System also known as Wet End Process.Approach Flow System also known as Wet End Process.Advantages of Approach Flow System:ЖЖ To reduce Stochastic Variations:To reduce Stochastic Variations: Perfect homogeneity of the stock in the headboxPerfect homogeneity of the stock in the headbox No uncontrolled fluctuations in the headbox consistencyNo uncontrolled fluctuations in the headbox consistency Low signal noise level at the headboxLow signal noise level at the headboxЖЖ To reduce Periodic Variations:To reduce Periodic Variations: Very low level of pulses created by rotating elementsVery low level of pulses created by rotating elements Fast, stable and accurate control loopsFast, stable and accurate control loopsЖЖ To satisfy other requirements:To satisfy other requirements: Low air content in the systemLow air content in the system Stable retention and chemical balanceStable retention and chemical balance

6464


Stock Preparation Macro & Micro Mix

6565

Macro & Micro MixMacro & Micro MixPurpose:Purpose: Complete mixing of all stock components, Complete mixing of all stock components,

including broke and stock coming back from including broke and stock coming back from save all.save all.(save all means collection tray of extracted and (save all means collection tray of extracted and recovered white water from initial stages of recovered white water from initial stages of paper making machine, and broke means paper making machine, and broke means rejected semi-made papers during process of rejected semi-made papers during process of paper making).paper making).

To eliminate consistency variations.To eliminate consistency variations. Attenuation of fluctuation.Attenuation of fluctuation.

preparation

Broke

Saveall

Macro Mix Micro Mixor

6666

Macro & Micro MixMacro & Micro Mix

Features:Features: Macro mix takes place in the mixing pipe.Macro mix takes place in the mixing pipe.

The feed pipes are tangentially placed to the The feed pipes are tangentially placed to the main pipe. In this pipe, the kinetic energy of the main pipe. In this pipe, the kinetic energy of the stock is used to provide a high degree of pre stock is used to provide a high degree of pre mixing.mixing.

Micro mix takes place in the static mixer.Micro mix takes place in the static mixer.preparation

Broke

Saveall

Macro Mix Micro Mixor

6767



Jet Mix

6868

Jet MixJet Mix

Features:Features: Consecutive mixing of componentsConsecutive mixing of components Most intensive mixing at thick stock additionMost intensive mixing at thick stock addition

The kinetic energy of backflows is used to The kinetic energy of backflows is used to premix the streams.premix the streams.Final mixing takes place at the thick stock Final mixing takes place at the thick stock injection point.injection point.

6969



Jet Mix

Cleaner

7070

CleanerCleaner

In cleaner, dilution water is added in the In cleaner, dilution water is added in the critical region of the cone, so that fiber critical region of the cone, so that fiber losses become less.losses become less.

In smaller systems, three cleaner stages In smaller systems, three cleaner stages plus an integrated fiber recovery cleaner plus an integrated fiber recovery cleaner are needed.are needed.

Cleaner

7171



Jet Mix

Cleaner

Break Tank

7272

Break TankBreak Tank

Purpose:Purpose: To keep pulsation away from headbox (Head box To keep pulsation away from headbox (Head box

is the first equipment of Paper Making Machines)is the first equipment of Paper Making Machines)

Break tank is basically a hydraulic de-coupling Break tank is basically a hydraulic de-coupling between Jet Mix and Head boxbetween Jet Mix and Head box

To deaerate the white water; because air in the To deaerate the white water; because air in the system can create problem during paper making, system can create problem during paper making, such as amplifying pulsation, pump speed such as amplifying pulsation, pump speed fluctuation and cleanliness related problemfluctuation and cleanliness related problem

Break Tank

7373



Jet Mix

Cleaner

Break TankSlot Screen

7474


Slot Screening machine is important, because it Slot Screening machine is important, because it is the last process stage before paper making is the last process stage before paper making machine.machine.

Purpose of Slot Screen:Purpose of Slot Screen: To efficiently remove residual impuritiesTo efficiently remove residual impurities Policing of fibersPolicing of fibers

Important feature of Slot ScreenImportant feature of Slot Screen:: No pulsation should occurNo pulsation should occur No stringing should generateNo stringing should generate

Slot Screen

7575



Jet Mix

Cleaner


Pulsation Damping Tank

7676

After Approach Flow System....After Approach Flow System....

Slot Screen is the last equipment of Approach Slot Screen is the last equipment of Approach Flow System.Flow System.

After Slot Screen, Stock goes to Pulsation After Slot Screen, Stock goes to Pulsation Damping Tank (PD Tank). Name implies that, Damping Tank (PD Tank). Name implies that, PD Tank dampen the pulsation to increase the PD Tank dampen the pulsation to increase the quality of paper. After PD Tank, stock goes to quality of paper. After PD Tank, stock goes to Headbox, the first equipment of paper making Headbox, the first equipment of paper making machine.machine.

The combination of equipments in the Approach The combination of equipments in the Approach Flow System varies, depending on Flow System varies, depending on requirements.requirements.

7777



Jet Mix

Cleaner


Pulsation Damping Tank

7878

Paper Making MachinePaper Making Machine

7979


Enroute to the Headbox, the stock (i.e. Enroute to the Headbox, the stock (i.e. pulp) is diluted to about or below 1% pulp) is diluted to about or below 1% consistency.consistency.

From the Headbox, the stock is distributed From the Headbox, the stock is distributed in a thin layer onto a endless running in a thin layer onto a endless running fabric, dewatered, pressed and dried to fabric, dewatered, pressed and dried to paper of a dryness of about 95%.paper of a dryness of about 95%.

8080


8181

Paper Making ProcessPaper Making Process

HeadboxApproach Flow System

PulpWire

Section

Press Section

Dryer Section

Calender Section

Pope Reel Section

8282

HeadboxHeadbox

The Headbox is an equipment which discharges an uniform The Headbox is an equipment which discharges an uniform jet of paper making stock onto the moving forming fabric.jet of paper making stock onto the moving forming fabric.

The functions of Headbox are :The functions of Headbox are : Spread stock evenly across the width of the machine.Spread stock evenly across the width of the machine. Level out cross currents and consistency variations.Level out cross currents and consistency variations. Level out machine direction velocity gradients.Level out machine direction velocity gradients. Create controlled turbulence to eliminate fiber floccing.Create controlled turbulence to eliminate fiber floccing. Discharge evenly from the slice opening; impinge on the Discharge evenly from the slice opening; impinge on the

forming fabric at the correct location and angle.forming fabric at the correct location and angle.

8383

HeadboxHeadbox

8484

HeadboxHeadbox

8585

Wire SectionWire Section

In Wire section, paper is formed on an In Wire section, paper is formed on an end-less fabric wire running in a loop end-less fabric wire running in a loop across foils and various dewatering across foils and various dewatering element. This concept is called Fourdrinier element. This concept is called Fourdrinier System.System.

For dewatering from both the side of the For dewatering from both the side of the paper web and minimum two sidedness of paper web and minimum two sidedness of the product, a equipment called Duo the product, a equipment called Duo Former is used.Former is used.

8686


HEADBOX

BREAST ROLL

SUCTIONKUTCH ROLL

FORWARD DRIVE ROLL STRETCH ROLL STRETCH ROLL

WIRE GUIDE ROLL

WIRE GUIDE ROLL

FOURDRINIER WIRE SECTION

DUO FORMER

STRETCH ROLL

LEAD IN ROLL

GUIDE ROLL

SEPARATION ROLL

DEWATERINGELEMENT

8787


Major influencing factor for fiber formation: Fiber type and preparation Filler content Consistency Type and arrangement of dewatering element Wire shaking Dandy roll Top wire unit (Duo former)

Wire Section has the maximum potential for formation improvement

8888


8989


9090


9191


9292


9393


The strength of fiber network being The strength of fiber network being dewatered on the forming fabric (i.e. wire) dewatered on the forming fabric (i.e. wire) depends on surface tension and depends on surface tension and mechanical friction between the fibers.mechanical friction between the fibers.The forces created by the surface tension The forces created by the surface tension increase in inverse proportion to the increase in inverse proportion to the distance between adjoining surfaces, distance between adjoining surfaces, which means wet strength of the paper which means wet strength of the paper web increases with dryness.web increases with dryness.

9494

Press SectionPress Section

After Wire Section, paper web is pressed After Wire Section, paper web is pressed by multiple rollers in the Press Section.by multiple rollers in the Press Section.

To ensuring good machine efficiency and To ensuring good machine efficiency and pressing, a compact bi-nip press followed pressing, a compact bi-nip press followed by a straight press is used.by a straight press is used.

In the Press Section, paper web is In the Press Section, paper web is conveyed by the felt; drive to the rolls also conveyed by the felt; drive to the rolls also transmit through these felts.transmit through these felts.

9595


9696


9797


Feature:Feature: Minimum two sidedness as both sides of Minimum two sidedness as both sides of

the sheet comes in contact with hard rollsthe sheet comes in contact with hard rolls Better sheet release and easy paper Better sheet release and easy paper

transfertransfer Minimum open drawMinimum open draw Better smoothness and hence, better Better smoothness and hence, better

printabilityprintability Faster and easier felt changeFaster and easier felt change

9898


In the press nips water is removed by three effects:In the press nips water is removed by three effects: One part is thrown out of the nip and collected in the One part is thrown out of the nip and collected in the

pans and channels.pans and channels. Another part is removed by the suction rollAnother part is removed by the suction roll Majority of the water is transported by the press felt.Majority of the water is transported by the press felt.

So after the nip, the press felt is contaminated with So after the nip, the press felt is contaminated with waste water. This felt is cleaned and water is taken out waste water. This felt is cleaned and water is taken out during one revolution to get the felt ready to pass the nip during one revolution to get the felt ready to pass the nip again. For this purpose suction tubes in each felt circuit again. For this purpose suction tubes in each felt circuit is used.is used.

9999

Press SectionPress Section During pressing a new phenomenon comes into During pressing a new phenomenon comes into

play at about 40% dryness, known as Hydrogen play at about 40% dryness, known as Hydrogen Bond.Bond.

Fiber surfaces are pressed close enough Fiber surfaces are pressed close enough together that the oxygen atoms of hydroxil together that the oxygen atoms of hydroxil groups protruding from adjoining surfaces come groups protruding from adjoining surfaces come within a distance of 2.5-3.5 within a distance of 2.5-3.5 Å to one another.Å to one another.In this situation two oxygen can share a proton In this situation two oxygen can share a proton of a hydrogen atom. In effect, the hydrogen atom of a hydrogen atom. In effect, the hydrogen atom can not choose between the two oxygen atoms, can not choose between the two oxygen atoms, thus producing a hydrogen bond.thus producing a hydrogen bond.

100100


The phenomenon of hydrogen bonding The phenomenon of hydrogen bonding occurs because of the singular geometry occurs because of the singular geometry of the glucose unit in a cellulose chain.of the glucose unit in a cellulose chain.

The strength of the hydrogen bond The strength of the hydrogen bond depends on the number of bond per depends on the number of bond per contact surface and on the size of this contact surface and on the size of this surface.surface.

101101

Press SectionPress Section Fiber Structure of Paper & Hydrogen BondFiber Structure of Paper & Hydrogen Bond

n nCellulose Starch Amylose

µm0.83

1.03

µm

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Dryer SectionDryer Section

After Press Section, paper web passes After Press Section, paper web passes through number of drying cylinders. The through number of drying cylinders. The cylinders are driven by fabric wires.cylinders are driven by fabric wires.

The classical drying section consists of The classical drying section consists of two tiers of drying cylinders. The cylinders two tiers of drying cylinders. The cylinders are cast in normal grey iron and coded for are cast in normal grey iron and coded for a steam pressure of 250-750 kPa a steam pressure of 250-750 kPa depending on the type of paper being depending on the type of paper being made. They are turned inside and outside.made. They are turned inside and outside.

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The cylinders are divided into steam groups The cylinders are divided into steam groups (usually four), where all the dryers within a group (usually four), where all the dryers within a group operate at the same steam pressure. operate at the same steam pressure.

The cylinders also divided into drive groups, The cylinders also divided into drive groups, each group having one directly driven cylinder; each group having one directly driven cylinder; the other cylinders in each group are driven by the other cylinders in each group are driven by gears or pulled by a dryer fabric.gears or pulled by a dryer fabric.

In modern issue machine drying is carried out on In modern issue machine drying is carried out on a yankee cylinder. Yankee is a cast cylinder a yankee cylinder. Yankee is a cast cylinder having a diameter of 4 to 6 m and coded for a having a diameter of 4 to 6 m and coded for a steam pressure of about 1MPa.steam pressure of about 1MPa.

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The Steam is supplied to and the condensate is The Steam is supplied to and the condensate is removed from the each cylinder.removed from the each cylinder.

The steam is introduced through a central pipe in The steam is introduced through a central pipe in the back-side journals. Condensate is entrained by the back-side journals. Condensate is entrained by steam through a syphon going to a pipe concentric steam through a syphon going to a pipe concentric to the steam pipe. On wide machines syphons may to the steam pipe. On wide machines syphons may be used at both sides of the cylinders.be used at both sides of the cylinders.

STEAM SUPPLY AND CONDENSATE REMOVAL ON A DRYING CYLINDERBASIC CONCEPT

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In Dryer Section, also hydrogen bonding In Dryer Section, also hydrogen bonding takes place. As water is evaporated from takes place. As water is evaporated from the wall, annular cracks in the wall makes the wall, annular cracks in the wall makes the wall thinner and stiffer. If the fiber are the wall thinner and stiffer. If the fiber are soft enough, surface tension during drying soft enough, surface tension during drying collapses the lumen and changes the collapses the lumen and changes the tubular fibers into bonds. These processes tubular fibers into bonds. These processes are not always desirable and depends are not always desirable and depends largely on temperature. The changes can largely on temperature. The changes can partly be reversed by refining.partly be reversed by refining.

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Calender SectionCalender Section

After Drying Section, paper is pressed in After Drying Section, paper is pressed in the Calender section, by calender rolls.the Calender section, by calender rolls.

Concept of pressing in the Calender Concept of pressing in the Calender Section, is different than pressing of paper Section, is different than pressing of paper webs in the Press Section.webs in the Press Section.

Pressing in the Calender Section provides Pressing in the Calender Section provides ironing effect in the paper. ironing effect in the paper.

The calender rolls may be heated or The calender rolls may be heated or unheated depending on design.unheated depending on design.

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Influencing parameters of calendering:Influencing parameters of calendering: Number of nipsNumber of nips Compressive stressCompressive stress Temperature or roll in the nipTemperature or roll in the nip Dwell time of the paper web in the nipDwell time of the paper web in the nip Hardness of soft coversHardness of soft covers Surface properties of the rollsSurface properties of the rolls

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Advantages of heated rolls over unheated rolls:Advantages of heated rolls over unheated rolls: Better paper smoothness achieved at lower line Better paper smoothness achieved at lower line

loadsloads Less loss in the bulk for a required smoothness.Less loss in the bulk for a required smoothness.

Less line load required for given paper finishLess line load required for given paper finish Less damage to the paper fibersLess damage to the paper fibers

Heat reduces the porosity of the sheet surfaceHeat reduces the porosity of the sheet surface Improved printabilityImproved printability

Less temperature variations across the sheetLess temperature variations across the sheet More uniform surface finishMore uniform surface finish

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Advantages of soft calendering 2x2 rolls:

• Minimisation of two sidedness of paper

• Wide load and temperature range

• Quality range from very rough to very smooth

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Pope Reel SectionPope Reel Section

After Calender Section, paper winding takes After Calender Section, paper winding takes place in the Pope Reel Section.place in the Pope Reel Section.

Pope reel shell is made of cast iron. Primary Pope reel shell is made of cast iron. Primary arms swivel empty reel spool over pope reel into arms swivel empty reel spool over pope reel into threading position for reel spool changes and threading position for reel spool changes and then into transfer position on reel spool track. then into transfer position on reel spool track. Secondary arms presses spool against pope Secondary arms presses spool against pope reel with controlled linear force and pushes the reel with controlled linear force and pushes the full reel spool into final position. Full reel spool full reel spool into final position. Full reel spool brakes in end position by means of levers and brakes in end position by means of levers and hydraulic shock absorbers.hydraulic shock absorbers.

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Pope Reel SectionPope Reel Section

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DoctorDoctor

One important part of paper making machine is One important part of paper making machine is Doctor.Doctor.

Doctor is basically a cleaner….Doctor is basically a cleaner….which cleans the different rolls.which cleans the different rolls.

For different rolls, doctors of different For different rolls, doctors of different construction and material are used.construction and material are used.

apart from doctors, other cleaning arrangements apart from doctors, other cleaning arrangements are also used at different sections of paper are also used at different sections of paper machines. machines.

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DoctorDoctor

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Apart from these equipments, some Apart from these equipments, some optional equipments are used, as per optional equipments are used, as per requirement:requirement:

Size Press/ Speed SizerSize Press/ Speed Sizer CoaterCoater After Dryer SectionAfter Dryer Section

After reeling in the Pope Reel Section, the After reeling in the Pope Reel Section, the paper is again re-wound and cut to suit paper is again re-wound and cut to suit customer’s requirements.customer’s requirements.

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PaperPaperToday different quality of papers are used in the market, e.g.:Today different quality of papers are used in the market, e.g.:** Graphic Paper:Graphic Paper: NewsprintNewsprint Super calendaredSuper calendared Light Weight CoatedLight Weight Coated Wood Free CoatedWood Free Coated Wood Free UncoatedWood Free Uncoated** Board & Packaging:Board & Packaging: Kraft LinerKraft Liner Corrugated MediumCorrugated Medium Folding Box Board, e.g. Cosmetic PackFolding Box Board, e.g. Cosmetic Pack Liquid Packaging, e.g. milk cartoonsLiquid Packaging, e.g. milk cartoons White Lined Chip BoardWhite Lined Chip Board Sack KraftSack Kraft** Special Paper:Special Paper: Cigarette PaperCigarette Paper Thermal PaperThermal Paper Photo Base PaperPhoto Base Paper Décor PaperDécor Paper

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PaperPaper

Today customer is very much quality Today customer is very much quality conscious.conscious.

So paper manufacturers and paper So paper manufacturers and paper machine designers are continuously machine designers are continuously developing new technologies to satisfy developing new technologies to satisfy customer’s requirement and to meet customer’s requirement and to meet changing global priorities.changing global priorities.

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PaperPaper

Paper represents the quality of human Paper represents the quality of human living and also, human civilisation….living and also, human civilisation….So Quality of paper and also Quality of So Quality of paper and also Quality of paper making process is very paper making process is very important……important……That’s why paper technology is evolving That’s why paper technology is evolving continually….continually….and journey through the world of paper and journey through the world of paper technology is a wonderful experience.technology is a wonderful experience.

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