Study on Process Layout of Paper Machine

STUDY ON PROCESS LAYOUT OF PAPER MACHINE

A Mini Project ReportSubmitted

By

A.Ramesh MD.Azeez G.Devendranath N.Ranjith kumar M.Kiran reddy

Under esteemed guidanceMr. G V PURUSHOTHAM, Deputy Manager

ITC Ltd -PSPD, BHADRACHALAM.

Department of Mechanical EngineeringDr. PAUL RAJ ENGINEERING COLLEGE

BHADRACHALAM - 507111.

ACKNOWLEDGEMENTS

We wish to our beloved Principal Prof G.Amarendar Rao, M.Tech, PhD for permitting

us to carry out this project work.

We also express our profound sense of gratitude to Prof P.Srinivasulu, M.Tech, (PhD)

Head of Department Mechanical Engineering and for his kind consent in doing the

course, project and incitement towards us.

We wish to express my deep sense of gratitude to my Internal Guide, Mr. S. Raja shekar,

M.Tech for his valuable guidance and useful suggestions, which helped us in completing

the project work, in time.

Our Pleasure to mention that Shri CH. VIJAYASARADTHI, General Manager ( Paper

M/c 6 ) of Indian Tobacco Company Limited who has been a source of inspiration and

for his timely guidance in the conduct of our project work. We would also like to thanks

Mr. G V PURUSHOTHAM, Deputy Manager (Paper M/c 6) of Indian Tobacco

Company Limited, for valuable guidance in this project work.

Words are inadequate in offering our special thanks to the Project GUIDE Mr.

PURUSHOTHAM, Deputy Manager for his encouragement and cooperation in carrying

out this project work.

Finally, yet importantly, we would like to express our heart full thanks to our beloved

parents for their blessings, and wishes for the successful completion of this project.

....Project associates

CONTENTS

Introduction

Properties of paper

Pulp preparation

Pulp Processing and Chemical Recovery

Pulp Bleaching

Stock Preparation

Paper manufacturing process

Applications

Environmental Concerns

Conclusion

Abstract

The process for making paper has in its fundamentals not changed, although

technological advancements of the highest degree in terms of mechanization and

atomization have been achieved in the last 150 years. In our study we focus on the how

the paper is manufacture in a paper making industry, finally at the end of our study we

concluded each paper machine has unique characteristics, and one process may suffer

different pitfalls than another.

Department of Mechanical Engineering

Dr. Paul Raj Engineering College

Bhadrachalam - 507111.

(Affiliated to JNTU-H)

CertificateThis is to certify that is a bonafied record of the project entitled “study on process layout of paper machine” carried out by bearing roll numbers A.Ramesh (07371A0324), in ITC Ltd-PSPD at Bhadrachalam, during The Academic year of 2010-2011 for the Partial fulfillment of degree in B.Tech from Jawaharlal Nehru Technological University Hyderabad.

Prof P. Srinivasulu, M.Tech, (PhD) Mr S. Raja shekar, M.Tech

Head of the Department Internal Guide

External Examiner





CertificateThis is to certify that is a bonafied record of the project entitled “study on process layout of paper machine” carried out by bearing roll number G.Devendranath (08375A0305), in ITC Ltd-PSPD at Bhadrachalam, during The Academic year of 2010-2011 for the Partial fulfillment of degree in B.Tech from Jawaharlal Nehru Technological University Hyderabad.



External Examiner





CertificateThis is to certify that is a bonafied record of the project entitled “study on process layout of paper machine” carried out by bearing roll number MD.Azeez (07371A0301), in ITC Ltd-PSPD at Bhadrachalam, during The Academic year of 2010-2011 for the Partial fulfillment of degree in B.Tech from Jawaharlal Nehru Technological University Hyderabad.



External Examiner





CertificateThis is to certify that is a bonafied record of the project entitled “study on process layout of paper machine” carried out by bearing roll number N.Ranjith kumar (07371A0325), in ITC Ltd-PSPD at Bhadrachalam, during The Academic year of 2010-2011 for the Partial fulfillment of degree in B.Tech from Jawaharlal Nehru Technological University Hyderabad.



External Examiner





CertificateThis is to certify that is a bonafied record of the project entitled “study on process layout of paper machine” carried out by bearing roll number M.Kiran reddy (07371A0313), in ITC Ltd-PSPD at Bhadrachalam, during The Academic year of 2010-2011 for the Partial fulfillment of degree in B.Tech from Jawaharlal Nehru Technological University Hyderabad.



External Examiner

INTRODUCTION

Though we may take it for granted, paper is always with us, documenting our

world and reminding us of the limitless possibilities of life. Invented by the Chinese

2,000 years ago, paper has been used ever since as a communication medium. Initially,

paper was made out of fibers from mulberry bark, papyrus, straw or cotton. Wood only

emerged as the chief raw material for paper mass production as recently as the mid 19th

century.

The printed page is immediate, its message cutting across cultures; a tactile

experience that demands attention and creates desire. It is a passport to knowledge, a

storage medium, a persuasive tool and an entertaining art form. Paper is a sustainable

resource and a permanent document. It is the universal medium on which we chronicle

our every-day history. Paper carries the past. It is the canvas on which we live the present

and the blueprint upon which we design our future.

Paper touches the lives of every individual on this planet, and at Sappi, we never

stop thinking about this fact. We are proud that Sappi is the largest and most successful

producer of coated fine papers in the world. At Sappi, we are relentlessly developing new

standards for the paper industry.

Drawing on centuries of experience, and the craftsmanship and expertise of its

own people supported by 21st century papermaking technology, Sappi will lead the

industry to ensure that this creative communication medium, paper, is the best it can be!

This brochure shows how we make this first class paper. Starting with the

production of the most important raw material, wood. The pulping process converts this

wood into the most appropriate type of pulp. The paper machine then converts the pulp

into a thin base paper, which, at the end of the production process, is coated to give it a

superb flat surface and bright shade.

The process for making paper has in its fundamentals not changed, although

technological advancements of the highest degree in terms of mechanization and

atomization have been achieved in the last 150 years. Essentially, paper is manufactured

using the following main operations.

PROPERTIES OF PAPER

Basis Weight (GSM) : - The weight or substance per unit area is obviously fundamental in

paper and paper board products. The Basis weight of paper is the weight per unit area.

This can be expressed as the weight in grams per square meter (GSM or g/M2), pounds

per 1000 sq. ft. or weight in kgs or pounds per ream (500 sheets) of a specific size.

REAM WEIGHT is a common term to signify the weight of a lot or batch of paper.

Control of basis weight is important as all other properties are affected. Variations in

moisture content in paper affect the gram mage.

Brightness, Whiteness and Colour:- Brightness is defined as the percentage reflectance

of blue light only at a wavelength of 457 nm. Whiteness refers to the extent that paper

diffusely reflects light of all wave lengths throughout the visible spectrum. Whiteness is

an appearance term. Colour is an aesthetic value. Colour may appear different when

viewed under a different light source. Brightness is an arbitrarily defined, but carefully

standardized, blue reflectance that is used throughout the pulp and paper industry for the

control of mill processes and in certain types of research and development programs.

Brightness is not whiteness. However, the brightness values of the pulps and pigments

going into the paper provide an excellent measure of the maximum whiteness that can be

achieved with proper tinting. The colour of paper, like of other materials, depends in a

complicated way on the characteristics of the observer and a number of physical factors

such as the spectral energy distribution of the illuminant, the geometry of illuminating

and viewing, the nature and extent of the surround and the optical characteristics of the

paper itself.

Bulk :- Bulk is a term used to indicate volume or thickness in relation to weight. It is the

reciprocal of density (weight per unit volume). It is calculated from caliper and basis

weight. Sheet bulk relates to all other sheet properties. Decrease the bulk or in other

words increase the density, and the sheet gets smoother, glossier, less opaque, darker,

lower in strength etc.

Dimensional Stability:- An important consequence of the absorption and de-absorption

of moisture by paper is the change in dimension that usually accompanies changes in

moisture content. Such changes in dimension may seriously affect register in printing

processes and interfere with the use of such items as tabulating cards. Uneven

dimensional changes cause undesirable cockling and curling. Dimensional changes in

paper originate in the swelling and contraction of the individual fibres. It has been

observed that cellulosic fibres swell in diameter from 15 to 20% in passing from the dry

condition to the fiber saturation point. It is impossible to be precise about the degree of

this swelling because paper-making fibres differ considerably in this property, and

because the irregular cross-section of fibres creates difficulty in defining diameter.

Change that occurs in the dimensions of paper with variation in the moisture content is an

important consideration in the use of paper. All papers expand with increased moisture

content and contract with decreased moisture content, but the rate and extent of changes

vary with different papers.

Folding Endurance (Double Folds) :- Folding endurance is the paper's capability of

withstanding multiple folds before it breaks. It is defined as the number of double folds

that a strip of 15 mm wide and 100 mm length can withstand under a specified load

before it breaks. It is important for printing grades where the paper is subjected to

multiple folds like in books, maps, or pamphlets. Fold test is also important for carton,

box boards, ammonia print paper, and cover paper etc. Folding endurance is a

requirement in Bond, Ledger, Currency, Map, Blue Print and Record Papers.

Formation :- Formation is an indicator of how the fibres and fillers are distributed in the

sheet. Formation plays an important role as most of the paper properties depend on it.

Paper that is poorly formed will have weak, thin spots and thick spots. These will affect

properties like caliper, opacity, strength etc. Paper formation also affects the coating

capabilities and printing characteristics of the paper.

Gloss :- It is the specularly and diffusely reflected light component measurement against

a known standard. Gloss is important for printing such things as magazine

advertisements. The level of gloss desired is very dependent on the end use of the paper.

Gloss and smoothness are different properties and are not dependent on each other.

Machine and Cross Direction :- Paper has a definite grain direction due to greater

orientation of fibres in the direction of travel of the paper machine. This grain direction is

known as machine direction. The cross direction is the direction of paper at right angles

to the machine direction. Some of the properties vary with the MD and CD and hence the

values are reported in both the directions. While sheeting the paper, machine and cross

direction are to be kept in mind and the sheet cutting to be done to suit the end use

requirements. Examples: 1. All printing papers are to be cut in long grain (The biggest

dimension in the grain direction). 2. Book papers fold better and the book stays open

better if the sheets are out so that the machine direction runs up and down the pages. 3.

Wrap around labels for metal cans and bottles are to be cut with the machine direction

vertical to obtain greater flexibility about the can. Long grain and Short grain : The sheet

is in long grain if the larger dimension is parallel to grain (MD) direction. The sheet is

said to be in short grain if the larger dimension is parallel to cross direction (CD).

Moisture :- Most physical properties of paper undergo change as a result of variations in

moisture content. Water has the effect of plasticizing the cellulose fiber and of relaxing

and weakening the interfibre bonding. The electrical resistance and the dielectric constant

of paper both vary with moisture content. The absorption and reflectance of certain bands

of infrared and microwave radiation by paper are affected by its moisture content. The

amount of water present in a sheet of paper is usually expressed as a percent. The amount

of water plays an important role in calendaring, printing and converting process. Moisture

control is also significant to the economic aspect of paper making. Poor moisture control

can adversely affect many paper properties.

Opacity :- Opacity is the measure of how much light is kept away from passing through a

sheet. A perfectly opaque paper is the one that is absolutely impervious to the passage of

all visible light. It is the ratio of diffused reflectance and the reflectance of single sheet

backed by a black body. Opacity is important in Printing Papers, Book Papers, etc.

Porosity :- Because paper is composed of a randomly felted layer of fiber, it follows that

the structure has a varying degree of porosity. Thus, the ability of fluids, both liquid and

gaseous, to penetrate the structure of paper becomes a property that is both highly

significant to the use of paper. Paper is a highly porous material and contains as such as

70% air. Porosity is a highly critical factor in Printing Papers Laminating Paper, Filter

Paper, and Cigarette Paper. Bag Paper, Antitarnish Paper and Label Paper. Porosity is the

measurement of the total connecting air voids, both vertical and horizontal, that exists in

a sheet. Porosity of sheet is an indication of absorptivity or the ability of the sheets to

accept ink or water. Porosity can also be a factor in a vacuum feeding operation on a

printing press.

Sizing / Cobb :- Because paper is composed of a randomly felted layer of fiber, it's

structure has a varying degree of porosity. Thus, the ability of fluids, both liquid and

gaseous, to penetrate the structure of paper becomes a property that is both highly

significant to the use of paper. The need to limit the spreading of ink resulted in "sizing"

the paper with gelatinous vegetable materials which had the effect of sealing or filling the

surface pores. Later, the term "sizing" was applied to the treatment of paper stock prior to

the formation of the sheet, with water-repellent materials such as rosin or wax. Resistance

towards the penetration of aqueous solution / water is measured by Sizing or Cobb

values.

Smoothness:- Smoothness is concerned with the surface contour of paper. It is the

flatness of the surface under testing conditions which considers roughness, liveliness, and

compressibility. In most of the uses of paper, the character of the surface is of great

importance. It is common to say that paper has a "smooth" or a "rough" texture. The

terms "finish" and "pattern" are frequently used in describing the contour or appearance

of paper surfaces. Smoothness in important for writing, where it affects the ease of travel

of the pen over the paper surface. Finish is important in bag paper as it is related to the

tendency of the bag to slide when stacked. Smoothness of the paper will often determine

whether or not it can be successfully printed. Smoothness also gives eye appeal as a

rough paper is unattractive.

Stiffness :- Stiffness is the measure of force required to bend a paper through a specified

angle. Stiffness is an important property for box boards, corrugating medium and to

certain extent for printing papers also. A limpy and flimsy paper can cause feeding and

delivery problems in larger sheet presses. A sheet that is too stiff will cause problems in

copier machines where it must traverse over, under, and around feed rollers. Bond papers

also require certain stiffness to be flat in typewriters etc.

Stretch (Elongation) :- Stretch is the amount of distortion which paper undergoes under

tensile stress. Stretch elongation is usually expressed, as percent stretch to rupture.

Stretch can be related to the paper's ability to conform and maintain conformance to a

particular contour, e.g. Copier paper, multicolor offset printing papers, liquids packing

cartons base papers etc. It is an important property in sack Kraft papers which are used

for cement bags etc. Stretch is higher in cross direction than machine direction.

Tearing Resistance :- Tearing resistance indicates the behavior of paper in various end

use situations; such as evaluating web run ability, controlling the quality of newsprint and

characterizing the toughness of packaging papers where the ability to absorb shocks is

essential. Fiber length and interfibre bonding are both important factors in tearing

strength. The fact that longer fibres improve tear strength is well recognized. The

explanation is straight forward; longer fibres tend to distribute the stress over a greater

area, over more fibres and more bonds, while short fibres allow the stress to be

concentrated in a smaller area.

Temperature and Humidity: Conditioning of Paper :- Conditioning of paper is also of

importance in many printing and converting operations. In addition to the effect of

moisture content on physical properties, it also determines the build up of static of the

paper sheet subjected to pressure and to friction. The tendency for paper to develop static

becomes greater with increasing dryness. Cellulosic fibres are hygroscopic i.e. they are

capable of absorbing water from the surrounding atmosphere. The amount of absorbed

water depends on the humidity and the temperature of the air in contact with the paper.

Hence, changes in temperature and humidity, even slight changes, can often affect the

test results. So, it is necessary to maintain standard conditions of humidity and

temperature for conditioning.

Thickness :- Thickness or Caliper of paper is measured with a micrometer as the

perpendicular distance between two circular, plane, parallel surfaces under a pressure of 1

kg./ CM2. Caliper is a critical measurement of uniformity. Variations in caliper can affect

several basic properties including strength, optical and roll quality. Thickness is

important in filling cards, printing papers, condenser paper, saturating papers etc.

Wax Pick No. (Surface Strength ) :- This indicates the surface strength of the paper. This

test is important for all uncoated printing papers.

Wire side and Felt side: - Also referred as wire side and top side. The side which is in contact

with the paper machine wire during paper manufacture is called the wire side. The other side is

top side. Certain properties differ between wire and felt side and it is customary to measure

these properties on both the sides. In case of paper to be printed on one side only, best results

are obtained by printing on felt side. Postage stamps are printed on wire side and then gummed

on felt side, where the smoothness is helpful for attaining an even application.

Cycle for paper processing

Flow diagram for paper making process

PULP PREPARATION

There are several different methods of pulp production

to make different strengths and grades of paper. The most common classifications are chemical,

mechanical, or semi-chemical pulping techniques.

Mechanical Pulping

Mechanical pulping utilizes steam, pressure, and high temperatures instead of

chemicals to tear the fibers. The fiber quality is greatly reduced because mechanical

pulping creates short, weak fibers that still contain the lignin that bonds the fibers

together. The presence of the lignin limits the amount that the pulp may be bleached

because the lignin binds with the bleaching chemicals. Newspaper and paperboards are

typical products of the mechanical pulping process. Mechanical pulping requires

materials such as 300 series stainless steel to prevent corrosion.

Semi-Chemical Pulping

Semi-chemical pulping techniques use weak chemical solutions composed of

sodium sulfite (Na2SO3) and sodium carbonate (Na2CO3) to help digest the lignin in the

pulp. In addition to the chemical solutions, mechanical refining is used to separate the

fibers.

Chemical Pulping

Chemical pulping uses various chemicals to produce long, strong, and stable

fibers and to remove the lignin that bonds the fibers together. The chemicals used will

vary depending on the type of chemical pulping used. In this there are two main types of

chemical pulping performed:

Kraft (sulphate) pulping

Sulfite pulping.

The corrosion rate in these processes can be significant depending on the amount and

kind of chemicals and the type of materials used.

PULP PROCESSING AND CHEMICAL RECOVERY

To further remove impurities and recycle the cooking liquor, also known at this

stage as black liquor, the pulp is processed through a series of washes. The removal of the

black liquor takes place in washers and is necessary to reduce the chemical costs of the

liquor, generate energy from pulp residue burned in the recovery boiler, and prevent the

cooking liquor from binding to the bleach chemicals. In addition, by recycling the

cooking liquor back into the pulping process, environmental issues and costs are negated

since there are no chemicals that must be discharged from the system.

Kraft Pulping Chemical Recovery:-

To recover chemicals from the black liquor, the slurry goes through a chemical

recovery process, such as the Kraft pulping chemical recovery. The liquor passes through

evaporators, recovery boilers, and causticizers to eventually produce white liquor.

The first step of chemical recovery is the evaporation process, which increases the

concentration of solids from approximately 15 percent to more than 60 percent. The

concentrated slurry contains approximately 50 percent organic solids and 6 percent total

sulfur in the form of sodium sulfate (Na2SO4) and sodium thiosulfate (Na2S2O3) and is

placed into a recovery boiler. The organic solids are burned for energy while the

inorganic process chemicals, also know as smelt, flow through the floor of the recovery

boiler to be recausticized. Mills with high levels of closure operate at high levels of

sodium chloride (NaCl). Typically, the NaCl concentration in black liquor is

approximately 12 percent in closed systems.

Recausticizing:-

Recausticizing is the process used to transform the inorganic smelt recovered

from the recovery boiler into white liquor so that the chemicals may be recycled. the

recycled inorganic chemicals are discharged as molten smelt from the recovery boiler and

then dissolved using water to form green liquor. Any unwanted substances are

precipitated out. Lime is then added to the clarified green liquor to produce sodium

hydroxide (NaOH) from the remaining sodium carbonate (Na2CO3). The resulting

solution (white liquor) contains sodium hydroxide, sodium sulfide (Na2S), and a solid

phase of calcium carbonate (lime mud). Before the white liquor is recycled back to the

digester, the white liquor is clarified further to remove the lime mud.

Sulfite Pulping Chemical Recovery:-

An alternative process is sulfite pulping chemical recovery. The chemical

recovery system of sulfite pulping differs from that for the Kraft process discussed

previously. The magnesium-based and calcium-based recovery systems are the most

corrosive recovery systems for sulfite pulping. Pitting and crevice corrosion under scale

deposits are the major corrosion concerns. The sulfite pulping process contains greater

amounts of sulfite (SO3), hydrogen sulfide (H2S), and hydrochloric acid (HCl) than those

used in the Kraft pulping process. Because of the presence of these corrosive species, the

internal portions of the recovery boilers and the evaporators are generally constructed of

reinforced plastics,

PULP BLEACHING

Pulp bleaching is performed on the pulp in order to increase its brightness. Bleaching is

an extremely corrosive process that is executed under acidic conditions with strong oxidants

such as chlorine, chlorine dioxide, sodium hydroxide, and hydrogen peroxide.

Traditional Bleaching Techniques:-

The bleaching process as normally having three to five stages in which the pH of

the pulp is alternated between acid and alkaline conditions. During the acid cycle,

chemical reactions between the bleach and the lignin bonds turn the pulp lighter in color.

During the alkaline cycle, the reaction products from the acid stage are removed.

Environmentally Friendly Techniques:-

In recent years, less chlorine and more sodium hydroxide have been used for

bleaching. Currently, chemical pulps and the de-inking of secondary fibers are the

primary users of chlorine bleaching techniques. The European paper and pulp industry

has demonstrated success in using a totally chlorine-free bleaching process for selected

pulp grades.

STOCK PREPARETION

After bleaching, the pulp is processed into (liquid) stock that can be transferred to

a paper mill. This processing is performed to get the required paper product and quality

specified. It can include blending various pulps together, beating and refining, dispersion

in water, and the addition of any wet additives such as resins, waxes, fillers, or dyes for

coloring.

Wood is a renewable resource that consists mainly of cellulous, lignin, and a

small portion of terpenes, resins, and fatty acids. The breakdown of wood is 45%

cellulose and 30% hemi-cellulose. It also contains 23% lignin, which is a resinous

material that binds the cellulose fibers together. It has less than 5% substances like

terpenes, resins and fatty oils and acids.

Many pulp mills have a paper mill adjacent to them; therefore, transferring the

products is not costly. The pulp mills, which produce market pulp, dry the pulp and

transfer it by truck, train, or ship. The equipment used to store and transport the pulp can

undergo crevice corrosion and pitting; therefore, they are usually completely or at least

partially clad with stainless steel.

PAPER MANUFACTURING PROCESS

Head box operation

Discharge a uniform flow of pulp stock on to the moving wire. The Paper stock at this

point in the process is 99% water and 1% fiber. The Fan Pump forces the Paper stock through

a set of nozzles in the head box onto the “wire” mesh . The fan pump speed is a major factor in

the basis weight and formation of the sheet of paper.

Forming Section

A typical flat former is a continuous rotating wire (today this is plastic) mesh that

removes water from the paper by sucking it out of suspension. Multi-layer paper

machines and paper board machines include additional forming sections (one forming

section for each layer of paper).

Wire

Once the suspension has left the headbox and comes into contact with the wire,

the paper fibres move to the wire as a result of their natural flow resistance, thus forming

a layer of fibres on the wire which accumulates towards the top of the stock. At the same

time, water drains away at the bottom, and this combination of processes leads to two

different forms of sheet formation, depending on the freedom of motion of the fibres in

the suspension: through filtration and by means of thickening. It also known as a four

driner a moving fabric that forms the fibers in to that mat as the drains out of the mat.

Presses

Pressing is done to remove water, compacts the web and improves strength. A press

section works by using felts and vacuum devices to remove water.. The press section can

comprise of two or more presses. The still wet web of paper is transferred from the wire of the

wet end onto the felt at the couch roll, and is then carried through the presses on the felts; the

texture and character of the felts may vary depending on the various surface structures which

can be applied here. Sometimes a linen pattern or other types of surface structure are

introduced to the paper depending on the grade of paper being made. The main function of the

press is to continue to remove water from the pulp fibers and to smooth the surface

characteristics of the felt and wire sides (top and bottom sides) of the paper web running the

length of the machine.

Dryers

The web of paper enters the drier section with water content of approximately 65%, The drier

section consists of a series of driers, These are used to remove residual water by evaporation

will paper sheet is moves over a rollers. It is done by two processes,

Wet-End Operations:-

Using a paper production machine the processed pulp is converted into a paper

product at the beginning of this stage, the water content of the paper is greater than 99

percent. The most common machine utilized is the Fourdriner paper machine. In the wet-

end operation, the slurry of pulp is deposited onto a continuously, moving belt that

suctions the water from the slurry using gravity, vacuum chambers, and vacuum rolls.

The continuous sheet then moves though additional rollers that compress the fibers and

remove the residual water.

Dry-End Operations:-

Following the pressing of the wet-end operations, the continuous sheet is

compressed by steam-heated rollers to allow the fibers to begin bonding together.

Coatings are then applied to add to the surface appearance before the sheet is spooled for

storage.

Size press

The simplest form of refinement is surface treatment in the size press which is

integrated in the paper machine. Here, starch is applied to strengthen the paper surface.

At the same time, this “closes” the surface of the paper, thus preventing problems like

dusting or picking from occurring in the later printing process. In many cases, treatment

in the size press is used to prepare the paper for the subsequent process of coating. The

size press consists of a pair of soft rolls, often coated with rubber, which press against

each other as the paper web is guided through the nip between the rolls. The size solution

is transferred to the paper through this nip, which also serves to control the dose of sizing

being applied. In the size press, the quantity of applied pigments is limited.

Calendaring & Reeling

The calendar section, the final section, consists of calendar stacks with a winding mechanism for gathering the paper web onto a roll as it leaves the end of the paper machine. The calendaring section of the paper machine gives the desired finish to the web.

Calendaring compacts the sheet and increases smoothness. A higher degree of smoothness

usually results in better printability. Calendar stacks consists of smooth rolls of varying

configurations. Items such as roll compositions, whether or not steam is used in the rolls, the

number of rolls and the types of control over these rolls all vary from paper machine to paper

machine. The paper leaving from the calendar stack is wound into a large roll of paper referred

to as the "parent roll". Parent rolls are wound to the specific diameter needed to produce

subsequent "sets" of smaller diameter reels to satisfy customer requirements. After that they sent to a converting station where the paper will be either slit into smaller rolls or where it may be sheeted for use in offset printing.

Winding

Winders convert parent rolls into customer requested reels of

specific width and diameter. They also make the removal of defective paper possible,

and are designed to control the amount of tension wound into rolls.

Applications

Paper of different QUALITY, different GSM and GRADE can be used for various purposes like:

For all Commercial Printing Business Communication, Publications, Diaries, Books and Stationary.

For Calendars, catalogues, Annual Reports, Advertising, Brochures & Pamphlets.

Environmental Concerns

The number of trees and other vegetation cut down in order to make paper is

enormous. Paper companies insist that they plant as many new trees as they cut down.

Environmentalists contend that the new growth trees, so much younger and smaller than what

was removed, cannot replace the value of older trees. Efforts to recycle used paper (especially

newspapers) have been effective in at least partially mitigating the need for destruction of

woodlands, and recycled paper is now an important ingredient in many types of paper

production.

The chemicals used in paper manufacture, including dyes, inks, bleach, and sizing, can

also be harmful to the environment when they are released into water supplies and nearby land

after use. The industry has, sometimes with government prompting, cleared up a large amount

of pollution, and federal requirements now demand pollution free paper production. The cost of

such clean-up efforts is passed on to the consumer.

Diagram that shows how the paper is made

http://www.forestprod.org/cdromdemo/pf/dona

















Conclusion

For papermakers who want to realize these flow sheets on existing machines, it is

important to implement the previously mentioned items one change at a time to reduce

machine downtime. Furthermore, gradual implementation permits operators to become

accustomed to each modification.

Finally, each paper machine has unique characteristics, and one process may

suffer different pitfalls than another. A progressive implementation and follow-up

procedure ensures the success of the project. TJ

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Study on Process Layout of Paper Machine

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