ACKNOWLEDGEMENT

I would like to express my deepest gratitude to all the people who were a part of
my Summer Internship Program and helped me make it learning and a rewarding
experience. This would not have been possible without the help of Mr. S.K. Atri
(DGM, PRCE, BILT) my industry guide, who has given me this wonderful
opportunity to be able to study and observe the whole unit. He helped me in
coordinating and getting information from various departmental heads.

I also thank Mr. K.K. Sharma (Manager Recovery & chemical) who supported me
with his invaluable insights and suggestions. My project and the tremendous work
exposure I had in this Unit would have been incomplete if I had not had his co-
operation.

I also thankful to Mr. Amit Dhiman (H.R. Manager BILT) for his
kindness and co-operation to our project work.

I express my gratitude to my Faculty Guide D. Prof. P.K. Bajpayi

(TU, Patiala) and Dr. H.P. Bhunia (TU, Patiala) who were a source of constant
support and guidance. Their guidance, inputs, support, inspiration and motivation
were very important for the completion of this project.

I would also like to extend my gratitude and regards to the teams of

Unit BILT, Yamunanagar, who supported me and gave me their valuable time for
helping me in understanding the various activities being undertaken by them.

Surender Kumar
10601056

1
 ABSTRACT

The word paper derives from the Greek term for the ancient Egyptian writing
material called papyrus, which was formed from beaten strips of papyrus plants.
The immediate predecessor to modern paper is believed to have originated in
China in approximately the 2nd century CE, although there is some evidence for it
being used before this date. Papermaking is considered to be one of the Four Great
Inventions of Ancient China, since the first papermaking process was developed in
China during the early 2nd century CE by the Han court eunuch Cai Lun. China
used paper as an effective and cheap alternative to silk, letting them sell more silk,
leading to a Golden Age. The use of paper spread from China through the Islamic
world, where the first paper mills were built, and entered production in Europe in
the early 12th century. Mechanized production of paper in the early 19th century
caused significant cultural changes worldwide, allowing for relatively cheap
exchange of information in the form of letters, newspapers and books for the first
time. In 1844, both Canadian inventor Charles Fenerty and German inventor F.G.
Keller had invented the machine and process for pulping wood for the use in paper
making. This would end the nearly 2000-year use of pulped rags and start a new
era for the production of newsprint and eventually all paper out of pulped wood.

Paper remained expensive, at least in book-sized quantities, through

the centuries, until the advent of steam-driven paper making machines in the 19th
century, which could make paper with fibres from wood pulp. Although older
machines predated it, the Fourdrinier paper making machine became the basis for
most modern papermaking. Nicholas Louis Robert of Essonnes, France, was
granted a patent for a continuous paper making machine in 1799. At the time he
was working for Leger Didot with whom he quarrelled over the ownership of the
invention. Didot sent his brother-in-law, John Gamble, to meet Sealy and Henry
Fourdrinier, stationers of London, who agreed to finance the project. Gamble was

2
granted British patent 2487 on 20 October 1801. With the help particularly of
Bryan Donkin, a skilled and ingenious mechanic, an improved version of the
Robert original was installed at Frogmore, Hertfordshire, in 1803, followed by
another in 1804. A third machine was installed at the Fourdriniers' own mill at Two
Waters. The Fourdriniers also bought a mill at St Neots intending to install two
machines there and the process and machines continued to develop.However,
experiments with wood showed no real results in the late 18th-century and at the
start of the 19th-century. By 1800, Matthias Koops (in London, England) further
investigated the idea of using wood to make paper. And in 1801 he wrote and
published a book titled, "Historical account of the substances which have been
used to describe events, and to convey ideas, from the earliest date, to the invention
of paper." His book was printed on paper made from wood shavings (and adhered
together). No pages were fabricated using the pulping method (from either rags or
wood). He received financial support from the royal family to make his printing
machines and acquire the materials and infrastructure needs to start his printing
business. But his enterprise was short lived. Only a few years following his first
and only printed book (the one he wrote and printed), he went bankrupt. The book
was very well done (strong and had a fine appearance), but it was very costly.

Then in the 1830s and 1840s, two men on two different continents
took up the challenge, but from a totally new perspective. Both Charles Fenerty
and Friedrich Gottlob Keller began experiments with wood but using the same
technique used in paper making; instead of pulping rags, they thought about
pulping wood. And at about exactly the same time, by mid-1844, they announced
that their findings. They invented a machine which extracted the fibres from wood
(exactly as with rags) and made paper from it. Charles Fenerty also bleached the
pulp so that the paper was white. This started a new era for paper making. By the

3
end of the 19th-century almost all printers in the western world were using wood in
lieu of rags to make paper.

Together with the invention of the practical fountain pen and the mass
produced pencil of the same period, and in conjunction with the advent of the
steam driven rotary printing press, wood based paper caused a major
transformation of the 19th century economy and society in industrialized countries.
With the introduction of cheaper paper, schoolbooks, fiction, non-fiction, and
newspapers became gradually available by 1900. Cheap wood based paper also
meant that keeping personal diaries or writing letters became possible and so, by
1850, the clerk, or writer, ceased to be a high-status job.

The original wood-based paper was acidic due to the use of alum and
more prone to disintegrate over time, through processes known as slow fires.
Documents written on more expensive rag paper were more stable. Mass-market
paperback books still use these cheaper mechanical papers (see below), but book
publishers can now use acid-free paper for hardback and trade paperback books.

The purpose of a chemical pulping process is to break down the

chemical structure of lignin and render it soluble in the cooking liquor, so that it
may be washed from the cellulose fibers. Because lignin holds the plant cells
together, chemical pulping frees the fibres and makes pulp. The pulp can also be
bleached to produce white paper for printing, painting and writing. Chemical pulps
tend to cost more than mechanical pulps, largely due to the low yield, 40–50% of
the original wood. Since the process preserves fibre length, however, chemical
pulps tend to make stronger paper. Another advantage of chemical pulping is that
the majority of the heat and electricity needed to run the process is produced by
burning the lignin removed during pulping.

4
Papers made from chemical wood-based pulps are also known as woodfree papers.

The Kraft process is the most commonly practiced strategy for pulp
manufacturing and produces especially strong, unbleached papers that can be used
directly for bags and boxes but are often processed further, e.g. to make corrugated
cardboard.

The sizing system in Europe is based on common width to height

ratios for different paper sizes. The largest standard size paper is A0 (A zero). Two
sheets of A1 placed upright side by side fit exactly into one sheet of A0 laid on its
side. Similarly, two sheets of A2 fit into one sheet of A1 and so forth. Common
sizes used in the office and the home are A4 and A3 (A3 is the size of two A4
sheets).

The density of paper ranges from 250 kg/m3 (16 lb/ft3) for tissue paper
to 1500 kg/m3 (94 lb/ft3) for some specialty paper. Printing paper is about
800 kg/m3 (50 lb/ft3).

Some manufacturers have started using a new, significantly more

environmentally friendly alternative to expanded plastic packaging made out of
paper, known commercially as paper foam. The packaging has very similar
mechanical properties to some expanded plastic packaging, but is biodegradable
and can also be recycled with ordinary paper.

With increasing environmental concerns about synthetic coatings

(such as PFOA) and the higher prices of hydrocarbon based petrochemicals, there
is a focus on zein (corn protein) as a coating for paper in high grease applications
such as popcorn bags.

5
 Contents

Topics Page no.

Acknowledgement 1

Abstract 2

Chapter one 9

1.1 About the company 9

1.2 Vision of the company 11

1.3 Core values of company 11

1.4 Strategic intent 12

1.5 Various departments 13

1.6 Distribution network 14

1.7 Products and brands 15

Chapter two 17

2.1 Raw material 17

2.2 Types of papers and their uses 15

2.3 Properties of paper 26

Chapter three 34

3.1 Introduction 34

3.2 Industrial papermaking 34

3.3 The process model 35

Chapter four 41

4.1 Introduction 41

4.2 Types of chipper 41

4.3 Chipper knives 43

4.4 Chipper department 44

6
4.5 Procedure 45

4.6 Silo department 46

Chapter five 47

5.1 Introduction 47

5.2 Pulping mills 48

5.3 Process description 50

5.4 Environment issues 61

Chapter six 62

6.1 Introduction 62

6.2 Evaporator section 62

6.3 Recovery boilers 70

6.4 Recovery plant heat losses 72

6.5 Soda recovery plant 73

6.6 DORR recausticizing plant 73

Chapter seven 77

7.1 Introduction 77

7.2 Types of wastes 78

7.3 Waste water management 79

7.4 Evaluation of performance efficiency of ETP 80

7.5 Sampling & analysis 81

7.6 Effluent treatment practices 82

7.7 Other treatment options 82

7.8 Recycling of back water or waste water 83

7.9 Disposal of treated effluent 85

Project calculation 88

7
References 93

List of Tables and Figures 94

CHAPTER ONE INTRODUCTION

1.1 About the company

8
 Ballarpur Industries Ltd.(BILT) promoted by LM Thapar, is the leader
in Indian paper industry with five manufacturing facilities produces ordinary and
superior varieties of writing, printing and specialty papers etc. The company is also
backwardly integrated with its Caustic soda/Chlorine manufacturing facility, which
is a vital material consumed in the production process of paper.

BILT which is originally incorporated in 1945 as Ballarpur Straw

Board Mills has changed its name in March 1946 to Ballarpur Paper and Straw
Board Mills and again it was changed to the present name in Oct. 1975. Since then
the company has grown to be a leader in paper industry by continuous expansion
and modernization of its capacity, plant and strategic acquisitions. In 1969 the
company has merged Shree Gopal Paper Mills with itself and the company which
has acquired the Sinar Mas Pulp and Paper(India) Ltd.(now BILT Graphic Papers
Ltd[BGPL]) which has state of the art 115000 tpa paper plant and a market leader
in the high end coated art paper and art paper board segment in India. Further the
company has merged BGPL with itself during the year 2002-03.

Bilt Tree Tech Ltd and The Paperbase Company Ltd are subsidiaries
of the company.

The company which was one of the most diversified companies in the
pre-liberalization era of industrial licensing with interests in Paper, Chemicals
(Phosphoric Acid, STPP, Chlor Alkalies), Vanaspati & Edible oils and Glass has
decided to focus on its core competence that is in paper and exit from its non-core
businesses. First major step on these lines was initiated in the year 1994-95 with
hiving off the glass business. Thereafter the company sold its vanaspati and edible
oils business in 1996-97. And in 1998, the chemical division of the company with
its plant at Karwar, Karnataka and which has interests in Phosphates, Chlor Alkali
and Bromine and Bromine Chemicals was spun of into a separate company i.e.

9
Ballarpur Chemicals Ltd(now Solaris ChemTech Ltd). To further rationalize its
focus the company exited from Janpath Investments & Holdings Ltd and brought
APR Packaging Ltd partially under its control. It has also shut down the Unit
Choudwar (a paper plant in Orissa) in 2002-03 due to scarcity of Raw material.

To complement its restructuring and to enable it to emerge as a

stronger and more competitive organization, the company has implemented a
project involving modernization and expansion of capacity at its Units in Shree
gopal, Ballarpur and Sewa by 105000 TPA. The Project was implemented in two
phases. In the first phase, the capacity expansion of 35000 TPA and 28000 TPA
was planned over a two-year period from 2000-01 to 2002-03 for Units Sewa and
Shree Gopal. In the second phase 42000 TPA of capacity was expected to come on
stream at Unit Ballarpur by 2003-04. During the year 2001-02, the company has
completed the up gradation of pulp mill at unit Sewa resulting in increase in
capacity by 37 tonnes from the earlier 125 tonnes of unbleached pulp per day.
BILT entered into strategic alliance with Hansol of South Korea to
provide world-class blade coated paper to the Indian customer. It is the first
company in the world to commercially exploit the fractionation of bamboo and has
applied for the world patent for this process. It has also entered into direct retail
distribution with the launch of A4 size, 100-sheet pack of Royal Executive Bond.
The company has increased its installed capacity of paper including Wrapper and
Coated Paper by 20000 MT and with expansion the total installed capacity of paper
including wrapper and coated paper has increased to 406568 MT during 2004-05.

BILT has acquired the integrated pulp and paper facility of Sabah
Forest Industries-a Malaysian based firm- along with J P Morgan for 261 million
US dollars in June 2006.The two companies have acquired 97.8% equity stake in
the Malaysian firm, of which 20% will be taken by J P Morgan and the rest by
BILT.

10
1.2 Vision of the company

(a) To become a leading creator of Shareholder Value in the Paper Industry. To

achieve this, they will use the energy of their people, develop and implement
leading edge technologies and draw on both to deliver effective world-class
solutions to their customers

(b) To consistently outperform expectations and deliver superior value to both the
Customers and Stakeholders. To achieve this, they will Energize their people, with
a positive culture that rewards Innovation, breeds Initiatives and encourages
Intelligent risk taking.

1.3 Core values of company

(a) Honesty: To be principled, straight-forward and fair in all dealings.

(b) Integrity: Maintaining the highest standards of professionalism.

(c) Flexibility: Adapting ourselves to always stay a step ahead of change.

(d) Respect for Individual: Giving each person room to contribute and grow.
(e) Respect for Knowledge: To acquire and apply leading edge expertise in all
aspects of our business.
(f) Team Performance: The team comes first; none of us is as good as all of us!

1.4 Strategic Intent

BILT, in the recent years has evolved as a more dynamic, knowledge-

driven organization with a singular focus on creating stakeholder value. Aimed at
making the organization more market-oriented and customer-centric, the following
initiatives are to drive BILT forward in the rapidly changing business environment:

11
 (a) Consolidation: A Continuous streamlining of capacities and products in their
core business area.
(b) Brand Building: Increasing brand involvement for the products amongst
customers to reduce market fragmentation and attain “generic brand” status
via strategic building.
(c) De-Commodisation and Service Orientation: Redefining the paper industry
with customer at the center stage.
(d) Wider Product Range: Adding high value-added products to BILT's portfolio
expanding it to cover the widest range of basic to high-end usage paper
products.
(e) Product-mix Rationalization: Maintaining an intelligent product-mix based
on value and demand curves to maximize returns.
(f) Exploring Global Markets: Reaching out to international markets with
world-class products while maintaining leadership in India.
(g) Operational Improvements & Cost-competitiveness: To attain higher
efficiency levels and world-class quality in production processes.
(h) Increasing Capacities: Expansion of manufacturing and processing
capabilities across product range, in line with market dynamics.
(i) Sound Investments: Accelerate growth by way of investments into focused,
synergetic acquisitions.
(j) Captive Market Share: Sustaining and strengthening BILT's leadership
position in its market segments way ahead of competitors.
(k) Extending 'Touch-Points': Building a wider and 'intelligent' distribution
network that enables BILT to serve its markets in a customized and localized
manner and attain higher penetration, without losing the economies of scale.
1.5 Various Departments
1.5.1 Administrative Departments

12
(a) Personnel Department: This department is primarily concerned with the
training, selection, recruitment, promotion, demotion, labor, welfare, retirement,
work culture and work awareness.
(b) Account Department: The function of this department is to maintain every
details and record of all the transactions covered by different departments.
(c) Material Department: These people are concerned with procurement and
storage of process material.
(d) Sales Department: Sailing out of finished paper is their main activity.
(e) Raw Material: Department Each and every product required for paper
making is arranged/purchased by this department.
(f)Traffic Department: This department includes weighing section, raw material
section, transport section etc.
1.5.2 Process Departments
(a) Pulp Mill includes manufacturing of pulp and stock preparation.
(b) Machine House Controls the working of various paper machines and prepares
the paper of required quality.
(c) Coating Plant Primary function of this department is to coat the paer as per the
requirements.
(d) Soda Recovery Plant Function of this department is to look after the process of
recovery of useful chemicals from waste liquor.
1.5.3 Engineering Departments
(a) Electrical Engineering : This department attaches itself with the maintenance
of installations of electrical machines, distribution & generation of electrical
energy anr various other installations at the unit.
(b) Civil Engineering: All the construction work like building of roads, sanitory,
waste disposal, water supply etc. are under their control.
(c) Instrument Engineering: Maintenance of all the electrical controls of
machines is carried out their expert guidance.

13
(d) Power House: Having a total installed capacity of 25 MW and maintained by
two power houses, old and new, this department, backup’s the total demand of the
unit efficiently and effectively.
1.6 Distribution Network

With the customer at the center of the business activities, they have
pioneered the transition of the traditional 'transaction-based' model to a
'relationship-based model' in the Indian paper industry. This relationship is built by
constantly leveraging the physical proximity to the markets, further enhanced by
intelligent systems offering a strong emotional proximity to their customers even at
a micro-level.

Their distribution network and understanding of local requirements is

unmatched in the Indian paper industry. Over the decades, BILT has transitioned
from the 'metro' concept to cross country distribution. While their five
manufacturing facilities for paper and pulp are strategically spread across the
country, they have assiduously brought their products within physical proximity of
the customers. Their network of 126 dealers - the largest within the industry in
India - is present across the principal consuming centers of the country and is the
key fulcrum to this proximity.

Strategically implemented Enterprise Resource Planning (ERP)

System, real-time logistics and Just-in-Time (JIT) inventory solutions enable
highly effective and efficient distribution of localized BILT products across urban,
semi-urban and rural consumption centers nation-wide. A direct marketing
initiative by the company to establish a two-way interaction with customers is
another step forward in this direction.

BILT has five Paper & Pulp Manufacturing Units in the country
located at the following places –

14
 Ballarpur Unit, Distt. Chandrapur, Maharastra.

 Shree Gopal, Yamuna Nagar, Haryana.

 Ashti, Maharastra.

 Bhigwan, Maharashtra

 Sewa, Orissa

1.7 Products and Brands

Segments BILT Brands

BILT Emperor Art Paper C1S

Chromo BILT Royal Art Paper C1S

Sunshine Art Paper C1S

Easy Print

Creamwove Sunshine Maplitho NSS

BILT Copy Power

Copiers BILT Image Copier

Royal Executive Bond,

Bonds Sunlit Bond

Royal Executive Bond (Coloured Bonds in

Laid finish) Moonbeam, Aquas, Camelle

15
 BILT Emperor Art Board

Art Board BILT Royal Art Board

Sunshine Art Board Plus

Sunlit Coated Art Board

Sunshine Super Printing

Hi Bright TA Maplitho NSD premium

BILT Royal Print Plus

BILT Emperor Art Paper C2S

Art Paper BILT Royal Art Paper C2S

Sunshine Art Paper C2S

CHAPTER TWO ABOUT PAPER

2.1 Raw material

 Main sources of pulp raw material are wood, bamboo and waste from wood
products manufacturing companies.
 Waste from wood products manufacturing companies is the cheapest named
Veneer Waste and popular is most expensive wood.
 This department also gives suggestions to farmers so as to max their
efficiencies.

16
 Around 600-700 tonnes of wood is required by the pulper daily depending upon
the moisture conditions and the product mix.
 Out of which around 120 tonnes is bamboo.
 Min. inventory requirement is 40,000 tonnes.
 Approx. annual consumption is around 2, 74,000 tonnes. Out of which 50,000
tonnes is bamboo which has to be procured between the time periods of
November to March.
 Procurement is from states like Himachal Pradesh through Punjab, Eastern U.P,
Uttranchal, Bihar, Assam, Bengal, Orissa depending upon availability, price and
transportation cost.
 The department has to make seasonal procurement adjustments depending
upon weather like rain and fog.
 Materials come at an average cost from road at 1500 p/t and rail at 900 p/t.
 For Veneer Waste it’s necessary to do sorting due to presence of many foreign
particles.
 Inspection and approval is done by pulp mill this department may only just help
in this activity.
 If there are minor defects then just percentage cuts in weight or price maybe
made.
 Moisture can vary from 40 to 55 % depending upon weather conditions,
 More moisture less yield.
 Procurement depots are also there in the market which provides info about the
market conditions.
 Prices maybe adjusted according to the info provided by such depots if there is
shortage.
 This department uses Oracle for ERP services such as Order preparing, Order
approval, receipts, inventory and issues.

17
 Order approval comes from HO and the approval comes from the post
depending upon the sum involved.
 Production department tells the daily requirement.
 Traffic department may receive raw material at gate and send it directly to the
pulper instead of the stock yard is it’s required and can be consumed then only.
 Flow of action in this department is as follows –
1. Annual Requirement to be finalized in a meeting of various heads.
2. Kinds of Raw Material required and quality to be decided.
3. Market Survey done to check price and availability.
4. Annual Budget of the department made.
5. Various parties are contacted terms are finalized and even tenders are
asked to be submitted by the interested parties.
6. Getting the material delivered.
7. Raw Material Department’s work end when material reaches the factory
premises after which only negotiations for defects and payments are
coordinated by them with the help of various departments.

2.2 Types of papers and their uses

Following are the main types of paper and their uses. The differences
among various grades and types of paper are determined by: (i) The type of fibre or
pulp (ii) The degree of beating or refining of the stock (iii) The addition of various
materials to the stock (iv) Formation conditions of the sheet, including basis
weight, or substance per unit area (v) The physical or chemical treatment applied to
the paper after its formation

 Abrasive Kraft: Abrasive Kraft is used for making sand paper used in
roughening applications.

18
 Absorbent Kraft: Used for Laminates, tube making and defense
applications.

 Alkaline Paper: Paper having pH values greater than 7 made by an

alkaline manufacturing process.

 Anti Rust Paper: Paper which has the property of protecting the
surfaces of ferrous metals against rust.

 Antique Paper: Printing paper having good bulk and opacity with rough
or matt surface.

 Art Paper: Normally, china clay (kaolin) coated on both sides of the
paper. This finish of both the sides is same, be it glossy or matt. Used For
: Brochures, calendars, magazine covers, magazine text, where high
quality printing is required

 Azurelaid Paper: A laid paper usually bluish green in Colour having a

good writing surface.

 Barograph Paper: Red thin paper coated on one side with a white wax,
so that the needle of the barograph leaves a red line on a white ground,
sold in rolls and coils and to suit the type of barograph.

 Base Paper: This paper is generally used by a converter to either coat or

laminate. Different grades are available for different applications. Used
For : Mostly used for converting into a value added grade

 Battery Jacket: Used for Laminates, tube making and defence

applications.

19
 Beedi Wrap Paper: Used for decorative purposes in different colors.

 Bible paper: Thin white opaque heavily loaded, used for printing bibles.
Not suitable for pen and ink, because of its absorbency.

 Blade Wrapper (SS): Used for making of small packs for keeping razor
blades.

 Bond Paper: This paper has good strength properties, good stiffness and
good aesthetical look. The name "bond" was originally given to a paper
which was used for printing bonds, stock certificates, etc. Important
characteristics are finish, strength, and freeness. Used For : Mostly used
for letterheads and for image building stationery

 Book Paper: A general term used to define a class of papers used by the
book publishing industry; most commonly used for the book text paper
but also for book cover paper.

 Business Forms Paper: Paper made for the manufacture of business

forms. Used For: Business forms and data processing such as computer
printouts.

 Carbon Base: Carbon is normally manufactured in lower grammages

like 20 gsm or less. The most important property in this paper is porosity
which should be controlled at about 15-20 ml/min, so that absorption
leads to cost increase while less absorption makes poor quality of carbon
paper which is used many a time.

 Carbon Paper: This thin paper could be either coated on one side or
both sides with dry impressionable ink. The main function being to

20
 impart an identical copy of the original on the substrate. Used For:
Mostly used where more than one copy is required simultaneously.

 Carbonless Paper: The stock specially treated or coated to provide

copies without the use of interleaved carbon. The copy process requires
mechanical pressure such as from writing or typing and sometimes a
chemical reaction. Used For: Application forms, computer stationery,
time saving stationery. Also used in copying applications without carbon
paper.

 Cardboard: A range of various boards such as pulp board, paste board,

bristol board, ivory board, art board, chromo board in the form of a
coherent sheet or web used for printing, packaging, decorating etc.

 Cast Coated Paper: A coated paper with high gloss and absorptivity in
which the coating has been allowed to harden or set while in contact with
a mirror like polished chrome surface.

 Chromo Paper: China clay (kaolin) coated on one side. The coating on
one side could be glossy or matt as per requirement of the customer. Used
For: Mainly used for self adhesive stickers, calendars , posters, labels and
for applications where only one side has to be printed

 Cigarette Slide: Used for making of Cigarette Slides (180-200

gsm).Pulp board are multi layer boards can be used

 Cigarette Tissue: It is a product of fashion. Hence brightness and

whiteness of paper needs to be maintained. It is highly technical. Used
For: Used in bobbins of 25 mm width or so.

21
 Cinema Poster: For printing Cinema posters, Wall papers

 Clay Coating Base Paper: Used for coating with Clay for making
chromo and art paper

 Coated Paper: Paper could be coated on either or both sides. Coating

applied on the paper could be as per the requirement. For example, china
clay coating for glossy paper used for high quality printing or gum coated
paper for use of printing stamps. Used For: Could have different
applications for different coated papers

 Copier Paper: Mainly used for copying. Used extensively in

photocopiers, plain paper faxes, etc. and other office stationery.
Thickness could range from 70 GSM onwards. Used For: Copying,
typing, plain paper faxes, general stationery

 Creamwove Paper: Used for Computer Stationery purposes.

 Defence Kraft: Used for Laminates, tube making and defence

applications.

 Diary Paper: Used for making of diaries and sometimes for book
printing and other applications.

 Diazo Base Paper: The process involves coating of paper with Diazo
solutions and a coupler. This is exposed to ultra violet rays coming
through the image. The final print is developed by making the coating
alkaline. In some cases it is developed by ammonia vapor. Used For:
Used for making of ammonia paper for image recording.

 Electrical Insulating Papers: Used for Electrical insulation.

22
 Extensible Sack Kraft: This paper is characterized by very high stretch
and high capability to absorb tensile energy. Used For: Used for
packaging in sacks, the bulk commodities.

 Fax Base Paper: It is first coated with photo conductive zinc oxide on
which images exposed. Hence electrical conductivity / resistivity is to be
controlled to ensure that the image is not conducted through the paper to
the other side Used For : For making Fax images

 Flexible Carton Board: Used for making Flexible Cartons.

 Fluorescent Paper: Used for Labels, Posters and decorative

applications.

 Fluting Medium: Used for Corrugated Board manufacturing.

 Foil Base Poster, Board Paper is laminated with metal foil using a
suitable adhesive. Hence paper must have porosity to accept glue. Used
For: Used for lamination of paper with metal foil.

 General Writing Paper (Note book): Paper used for Note Books should
have excellent bulks because note book should appear bulky, as otherwise
it will be perceived as having less number of pages. Another important
factor is cobb, since writing ink must go into the paper instantly and dry.
Used For: Note books.

 Glassine paper: These papers are characterized by very low porosity (air
permeability less than 10 cubic cm min. Preservation of aroma and
perfection against attack of external environment to the packed contents

23
 are also important qualities of the subject papers. Used For: Used for
food packaging and other special wrapping applications.

 Greaseproof Paper: These papers are characterized by very low porosity

(air permeability less than 10 cubic cm min. This gives resistance to
grease and moisture. Preservation of aroma and perfection against attack
of external environment to the packed contents are also important
qualities of the subject papers. Used For: Used for food packaging and
other special wrapping applications.

 Gypsum Board: This is used for making panel boards for interior
partitions, false ceiling etc.

 Ice Cream Cup: Used for making Ice Cream Cups.

 Inter Leaving Kraft: Inter Leaving Kraft is used for separation of steel
sheets in a stack.

 Kite Poster: Used for decorative, purpose, Kites

 Label Paper: Labels are normally printed on offset machine. Hence

good wax pick is required. Wire side of the paper used for application of
gum should have adequate porosity. Good printability, compressibility,
absorbency and ink hold out give satisfactory printing. Used For: Used
for printing of labels in multi Colour.

 Laser Paper: Used for printing purposes where Laser beams are used.

 Liner Board: Used for Corrugated Board manufacturing.

24
 Metallization Base Paper: Used for vacuum metallization for packaging
applications.

 MICR Cheque Paper: MICR stands for Magnetic Ink Character

Recognition. Codes, figures and words are read by computer by magnetic
field created on them. By careful formulations the paper is designed to
react against a wide range of ink eradicators. It gives a characteristic
colored stain of "flare up" on contact with acid, alkali, bleach and organic
solvents like acetone, benzene, and ethanol. Used For: Used in making of
cheques which are processed by computer.

 Multi Part Stationery: Multi part stationery paper is used for computer
applications where number of copies is printed in one attempt.

 Newsprint paper: It has to be made with adequate strength properties

and surface characteristics; especially wax pick. Optical properties
brightness is required for better readability and appeal (with ink to paper
contrast which improves readability of print) and opacity. Used For: Used
for printing our daily news papers and associated issues. It is used under
very stringent shop-floor conditions by the news paper blouses for
printing our daily news papers and associated.

 One Time Carbon (OTC) Paper: A carbon paper intended to be used

once as opposed to many times or multiple use carbon papers. Used For:
Mostly used in multi-part continuous stationery.

 Poly Extrusin Base Paper Used For: Used for Poly Extrusin for
packaging.

25
 Sanitary Tissue: Sanitary Tissues are made with rag pulp content in
lower gram mages from 5 gsm onward. Normal gsm range is 15 to 30.
These papers are made in soft loosely felted conditions in order to obtain
max. Absorbency so that they can take water quickly and hold it after
absorption. Made with high content of Alpha Cellulose or Rag %, they
are treated with wetting agents to improve absorbency. Used For: Used as
Paper Towels, napkins, toilet tissues etc.

 Shell Boards Used For: Used for making of Cigarette Slides (180-200
gsm).Pulp board are multi layer boards can be used

 Soap Wrapper Poster (ARSR) Used For: Used for Wrapping of Soaps
and detergents.

 Soap Wrapper Poster (TDL) Used For: Used for Wrapping of Soaps
and detergents.

 Tea Bag Paper Used For: Used for retail packing of tea.

 Textile Tubes and Cones Used For: Used for Laminates, tube making
and defence applications.

 Twist Wrap tissue: It possesses properties of with standing breaking

stress when twisted during packing of toffees. High bursting strength
combined with excellent machine run ability makes it suitable for special
packing operations which require papers with high twisting properties.
Used For: It is used in packing of pharmaceutical products after poly
lamination or coating.

26
  Wall Paper: Coated with multiple colors or floral designs. Used For:
Used as an alternative to paint. To give better aesthetic appeal to the
walls.

 Yellow Pages Paper: used for this needs to have high bulk (1.1 to 1.2),
high tensile strength of about 2 kg/15 mm in MD and good opacity (90%)
so that the fine print made on thin paper like 40 gsm would be readable
on both side. Excellent reel build up is required for smooth feeding
during printing. This requires every uniform profile of bulk, gsm, caliper,
moisture etc. Used For : Used for printing classified addresses and
information in telephone directory.

2.3 Properties of paper

1) 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.

2) Brightness, Whiteness and Color - 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

27
 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.

3) 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.

4) 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 cellulose fibres swell in diameter from 15 to 20% in passing from the dry
condition to the fibre 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

28
 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.

5) 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.

6) 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.

7) Gloss - It is the secularly 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.

29
8) 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).

9) Moisture - Most physical properties of paper undergo change as a result of

variations in moisture content. Water has the effect of plasticizing the
cellulose fibre and of relaxing and weakening the inter fiber 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.

30
10) 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.

11) Porosity - Because paper is composed of a randomly felted layer of fibre, 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, Anti tarnish 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.

12) Sizing / Cobb - Because paper is composed of a randomly felted layer of

fibre, its 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.

31
13) 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.

14) 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.

15) 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.

32
16) 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. Fibre 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.

17) 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 buildup of static of the paper sheet subjected to pressure and to friction.
The tendency for paper to develop static becomes greater with increasing
dryness. Cellulose 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.

18) Thickness - Thickness or Caliper of paper is measured with a micrometer as

the perpendicular distance between two circular, planes, parallel surfaces
under a pressure of 1 kg./ CM 2. 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.

33
19) Wax Pick No. (Surface Strength) - This indicates the surface strength of
the paper. This test is important for all uncoated printing papers.

20) 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.

CHAPTER THREE PAPER MAKING PROCESS

34
3.1 Introduction

Papermaking is the process of making paper, a substance which is

used ubiquitously today for writing and packaging.

In papermaking a dilute suspension of fibers in water is drained

through a screen, so that a mat of randomly interwoven fibers is laid down. Water
is removed from this mat of fibers by pressing and drying to make paper. Most
paper is made from wood pulp, but other fiber sources such as cotton and textiles
may be used.

Modern papermaking began in the early 1800s in Europe with the

development of the Fourdrinier machine, which produces a continuous roll of
paper rather than individual sheets. These machines have become very large, up to
500 feet (~150 m) in length, producing a sheet 400 inches (~10 m) wide, and
operating at speeds of over 60 mph (100 km/h).

3.2 Industrial papermaking

A modern paper mill is divided into several sections, roughly

corresponding to the processes involved in making hand-made paper. Pulp is
refined and mixed in water with other additives to make a pulp slurry, the head box
of the paper machine (Fourdrinier machine) distributes the slurry onto a moving
continuous screen, water drains from the slurry (by gravity or under vacuum), the
wet paper sheet goes through presses and driers and is finally rolled into large rolls,
often weighing several tons.

Another type of paper machine makes use of a cylinder mold that

rotates while partially immersed in a vat of dilute pulp. The pulp is picked up by

35
the wire and covers the mold as it rises out of the vat. A couch roller is pressed
against the mold to smooth out the pulp, and picks the wet sheet off of the mold

Standardization ISO sizes - While opinions and speculation abound on

exact reasons for standardized paper sizes, the most revealing feature of popular
sizes (such as Letter and ISO 216 sizes) is that they conform not to some arbitrary
device dimension, but that the length of the paper is chosen to be the width of the
page times the square root of 2. This feature allowed for a large page to be cut in
half and the resulting 2 pages to have the same aspect ratio as the original piece
(just with half the size). Repeated cuts can be made to reduce the entire sheet to
one size of pages without wasted paper. This format was formalized by ISO 216
however such logic dictated efficient paper sizes long before the ISO was created.
For example, traditional 8.5"x11" Letter paper is within a few millimeters of A4
paper (ISO 216) dimensions. While paper sizes "may" have been chosen based on
the size of original frames, the frames themselves were chosen to make page
reduction efficient without distorting the aspect ratio of the pages regardless of
final size chosen. That said, there are paper sizes that do not conform to this idea
when specific applications are needed.

3.3 The Process Model

The following is the basic model of paper manufacturing process. Various

companies have their own methods which have some differences but follow this
method basically.

36
Fig 3.1 Process Model

37
Step 1: Forestry

Typically, trees used for papermaking are specifically grown and harvested like a
crop for that purpose. To meet tomorrow's demand, forest products companies and
private landowners plant millions of new seedlings every year.

Fig 3.2 forestry

Step 2: Debarking, Chipping and/or Recycling To begin the process, logs are
passed through a debarker, where the bark is removed, and through chippers, where
spinning blades cut the wood into smaller pieces. Those wood chips are then
pressure-cooked with a mixture of water and chemicals in a digester.

Fig 3.3 Debarking, Chipping and Recycling

38
Used paper is another important source of paper fiber. Thanks to curbside
recycling programs in many communities lot of paper is recoverable. The paper is
shredded and mixed with water.

Step 3: Pulp Preparation

The pulp is washed, refined, cleaned and sometimes bleached, then turned to slush
in the beater. Color dyes, coatings and other additives are mixed in, and the pulp
slush is pumped onto a moving wire screen.

Fig 3.4 Pulp Preparation

Computerized sensors and state-of-the-art control equipment monitor each stage of

the process.

39
Step 4: Paper Formation

As the pulp travels down the screen, water is drained away and recycled. The
resulting crude paper sheet, or web, is squeezed between large rollers to remove

Fig. 3.5 Paper Formation

Most of the remaining water and ensure smoothness and uniform thickness. The
semidry web is then run through heated dryer rollers to remove the remaining
water. Waste water is carefully cleaned and purified before its release or reuse.
Fiber particles and chemicals are filtered out and burned to provide additional
power for the mill.

Fig. 3.6 Paper Check

40
Papermakers carefully test for such things as uniformity of color and surface, water
resistance, and ink holding ability.

Step 5: Paper Finishing

The finished paper is then wound into large rolls, which can be 30 feet wide and
weigh close to 25 tons. A slitter cuts the paper into smaller, more manageable
rolls, and the paper is ready for use.

Fig 3.7 Paper Finishing

Papermaking is one of the most capital intensive industries in the nation, investing
over $100,000 in equipment for each employee. The largest papermaking
machines are over 32 feet wide, 550 feet long and can produce over 1,000 miles of
paper a day.

CHAPTER FOUR WOOD CHIPPER HOUSE

41
4.1 Introduction

A tree chipper or wood chipper is a machine used for reducing wood

(generally tree limbs or trunks) into smaller parts, such as wood chips or sawdust.

Tree chippers are typically made of a hopper with a collar, the chipper
mechanism itself, and an optional collection bin for the chips. A tree limb is
inserted into the hopper (the collar serving as a partial safety mechanism to keep
human body parts away from the chipping blades) and started into the chipping
mechanism. The chips exit through a chute and can be directed into a truck-
mounted container or onto the ground. Typical output is chips on the order of one
to two inches (3-5 cm) across in size. The resulting wood chips being fed into a
digester during.

Large wood chippers frequently are equipped with grooved rollers in

the throat of their feed funnels. Once a branch has been gripped by the rollers, the
rollers transport the branch to the chipping blades at a steady rate. These rollers are
a safety feature and are generally reversible for situations where a branch gets
caught on clothing.

4.2 Types of chipper

4.2.1. High-Torque Roller

Shredders that make use of high-torque low-speed grinding rollers are

growing in popularity for residential use. These shredders are driven with an
electric motor and are very quiet, dust free and self feeding. Some of these
machines are equipped with an anti-jamming feature.

4.2.2. Drum

42
 The first commercially marketed chippers were of a design that was
drum-based. They are still produced and sold today. The chipping mechanism in a
drum-style chipper is a large steel drum powered by the motor, usually by a belt. It
is mounted parallel to the hopper and spins towards the output chute. The drum
also serves as the feed mechanism, drawing the material through as it chips it. This
caused it to be colloquially known as a "chuck-and-duck" chipper, because
material would start moving through the chipper very quickly as soon as it made
contact with the drum.

These chippers have many downsides. The drum-style chipper is not

as safe as newer designs. If an operator becomes snagged on material being fed
into the machine, injury or death is very certain. These chippers are also very loud.
The chips produced can be very large, and if thin material is inserted, it may be cut
into slivers rather than chips. Finally, since the drum cannot be disengaged from
the engine, if too large or too long material is fed through the machine, it will stall,
usually with the material stuck firmly in the drum.

Newer models have overcome many of these disadvantages with

digitally-controlled reversible hydraulic feed wheels and muffling systems. The
reversible feed system allows the newer style drum chippers to handle larger
diameter materials. Modern drum-style chippers usually have a material capacity
of 6 to 20 inches (15-48 cm).

4.2.3. Disk

A newer chipper design employs a steel disk with knives mounted

upon it as the chipping mechanism. In this design, (usually) reversible
hydraulically powered wheels draw the material from the hopper towards the disk,
which is mounted perpendicularly to the incoming material. As the disk spins, the

43
knives cut the material into chips. These are thrown out the chute by flanges on the
drum. This design is not as energy-efficient as the drum-style design, but produces
chips of more uniform shape and size.

Consumer grade disk-style chippers usually have a material diameter

capacity of 6 to 18 inches (15-60 cm). Industrial grade chippers are available with
discs as large as 160 inches in diameter, requiring 4000-5000 horsepower.

Much larger machines for wood processing exist. "Whole tree

chippers" and "Recyclers," which can typically handle material diameters of two to
six feet (60-180 cm), may employ drums, disks, or a combination of both. The
largest machines used in wood processing, often called "Tub Grinders," may
handle a material diameter of eight feet (250 cm) or greater, and use carbide tipped
flail hammers to pulverize wood rather than cut it. These machines usually have
200 to 1,000 horsepower. Some are so heavy that they must be moved by a semi-
trailer truck. Smaller models can be pulled with a medium duty truck.

The cutting blades form a small electric chipper. The blades can be
removed, by loosening the bolt in the centre, to facilitate sharpening or for
replacement.

4.3 Chipper Knives

Although chippers vary greatly in size, style, and capacity, the knives
they use are similar. They are rectangular in shape and are usually four to six
inches (10-15 cm) across by six to twelve inches (15-30 cm) long. They vary in
thickness from about one-half to two inches (1-5 cm). Chipper knives are made
from high grade steel and usually contain a minimum of 8% chromium for
hardness.

44
4.4 Chipper department

 Working Hours 12 from 6 am to 6 pm.

 Mainly contracted labor.
 There are five knives on the cutter one bottom dead knife and four rotating
sharp knives. Dead knife is changed after every 4-5 days but sharp knives are
changed every day.
 The capacity of this chipper was 25 tonnes per hour but after modification it has
been converted to be able to chip 50 tonnes per hour.
 This department uses electricity from outside and uses own electricity in case of
a power breakdown only.
 Dimension of knife is 200 mm width and 1250 mm length, which is used only
up to 140 mm and after which it is used in small chipper.
 This department has only three permanent employees.
 The daily wood mix is fixed and does not depend upon the product mix but
availability, It is as follows :

1. Veneer Waste 40%

2. Bamboo 20%
3. Eucalyptus 16%
4. Veneer Chips 10%
5. Popular Tree 6%
6. Popular Rulla 4%
7. Eucalyptus Rulla 2%
8. Wood Chips 2%

 Amongst these Veneer Chips and Wood Chips are outsourced as it is.

45
 Checking of the quality and moisture in wood is this department’s responsibility
and after which it informs the raw material department.
 Sorting out of Veneer and chips is done in the stock yard to check for any
foreign particles like plastic wires.
 Water is first put on material while on conveyers to make the dust settle.
 Almost whole of the process is automatic except only for putting the material
on the conveyers.
 Almost 100 tonnes is outsourced.
 Daily around 600-700 tonnes is chipped depending upon the weather
conditions.
 There are automatic metal detectors attached before knives which shut the
machine if metal is present in the material.
 Machine shuts automatically if overweight.
 Ideal size of wood is 8 inch diameter and 7 to 10 feet length.

4.5 Procedure
The machine starts when the felt from the Silo starts after which the
labor starts putting material on the conveyers. Wood, Bamboo separately and
Veneer Waste. While on felt first the material is washed to reduce dust then it’s
checked for any metal such as nails then it is cut separately. After which its
screened separately, there are 3 screens one for Veneer which has only one
screening that is for dust of 5 mm after which it put on the felt and moved to the
Silo. As for the wood and Bamboo there are two screens and screening is done
twice once to check the oversize pieces using 50 mm screen if oversize then
material is moved back for re-cutting on a separate small cutter, but rest right size
pieces are screened for dust and moved to the Silo. Dust is collected in a dust
chamber. Wood comes to the screens again once its re cut. Oversize wood can’t be

46
cooked in the digester whereas the oversize veneer can easily be cooked in the
digester as it’s very thin. The outsourced chips are directly put on the veneer
screens.

4.6 Silo Department

 It’s the storage tank for the chipped wood and veneer. Its main function is to
store the unused chipped wood.
 It has 8 tanks of 50 tons capacity each so total capacity is 400 tons.
 It has automatic system at the top which itself selects the tank in which the
chipped wood is to be stored depending upon quantity already present.
 Then when the felt from the digester starts the felts on the bottom of this tank
also start and the material starts getting pored on the belt and starts moving
towards the digester.
 The residual wood which is not cooked by the digester for the first time is
added to the felt at the bottom so as to reuse it.
 Such residual wood is first checked for foreign particles before being put on the
felt again.

CHAPTER FIVE PULP MILL

47
5.1 Introduction

A pulp mill is a manufacturing facility that converts wood chips

or other plant fiber source into a thick fiber board which can be shipped to a paper
mill for further processing. Pulp can be manufactured using mechanical, semi-
chemical or fully chemical methods (kraft and sulfite processes). The finished
product may be either bleached or non-bleached, depending on the customer
requirements.

Wood and other plant materials used to make pulp contain three
main components (apart from water): cellulose fibres (desired for papermaking),
lignin (a three-dimensional polymer that binds the cellulose fibres together) and
hemicelluloses, (shorter branched carbohydrate polymers). The aim of pulping is to
break down the bulk structure of the fiber source, be it chips, stems or other plant
parts, into the constituent fibers.

Pulp is a dry fibrous material prepared by chemically or

mechanically separating fibers from wood, fiber crops or waste paper.

Pulp can be either fluffy or formed into thick sheets. The latter
form is used if the pulp must be transported from the pulp mill to a paper mill. Pulp
which is shipped and sold as pulp (not processed into paper in the same facility) is
referred to as market pulp. When suspended in water the fibers disperse and
become more pliable. This pulp suspension can be laid down on a screen to form a
sheet of paper, and this is the primary use for wood pulp. Wood pulp is the most
common material used to make paper. The timber resources used to make wood
pulp are referred to as pulpwood. Wood pulp comes from softwood trees such as
spruce, pine, fir, larch and hemlock, and hardwoods such as eucalyptus, aspen and
birch.

Using wood to make paper is a fairly recent innovation. In the

1800s, fiber crops such as linen fibres were the primary material source, and paper
was a relatively expensive commodity. The use of wood to make pulp for paper
began with the development of mechanical pulping in Germany by F.G. Keller in
the 1840s, and by the Canadian inventor Charles Fenerty in Nova Scotia.[2]
Chemical processes quickly followed, first with J. Roth's use of sulfurous acid to
treat wood, followed by B. Tilghman's US patent on the use of calcium bisulfite,
Ca(HSO3)2, to pulp wood in 1867.[3] Almost a decade later the first commercial
sulfite pulp mill was built in Sweden. It used magnesium as the counter ion and
was based on work by Carl Daniel Ekman. By 1900 sulfite pulping had become the
dominant means of producing wood pulp, surpassing mechanical pulping methods.
The competing chemical pulping process, the sulfate or Kraft process was

48
developed by Carl F. Dahl in 1879 and the first Kraft mill started (in Sweden) in
1890. The invention of the recovery boiler by G.H. Tomlinson in the early 1930s
allowed Kraft mills to recycle almost all of their pulping chemicals. This, along
with the ability of the Kraft process to accept a wider variety of types of wood and
produce stronger fibers made. The Kraft process the dominant pulping process
starting in the 1940s

Global production of wood pulp in 2006 was 160 million

tons(175 million tons) .In the previous year, 57 million tonnes (63 million tons) of
market pulp (not made into paper in the same facility) was sold, with Canada being
the largest source at 21% of the total, followed by the US at 16%. Chemical pulp
made up 93% of market pulp.

Prior to the use of wood pulp for making paper, the preferred
material was the hemp plant, which produces a longer-lasting paper than wood,
requires less processing, with the added benefit that it is easier to grow than trees,
requires no pesticides or insecticides, and is less resource-intensive with a higher
yield per hectare. Now that forests are endangered worldwide, hemp is once again
emerging as an ideal raw material for paper. The Gutenberg Bible, Thomas Paine's
pamphlets, and the novels of Mark Twain were all printed on hemp paper, as was
the US Declaration of Independence. Hemp currently makes up around .05% of the
world annual pulp production volume at around 120,000 tons/year.

5.2 Pulping mills

There are a number of different processes which can be used to

separate the wood fibers.

5.2.1 Mechanical pulp mill

Manufactured grindstones with embedded silicon carbide or

aluminum oxide can be used to grind small wood logs called "bolts" to make stone
ground wood pulp (SGW). If the wood is steamed prior to grinding it is known as
pressure ground wood pulp (PGW). Most modern mills use chips rather than logs
and ridged metal discs called refiner plates instead of grindstones. If the chips are
just ground up with the plates, the pulp is called refiner mechanical pulp (RMP)
and if the chips are steamed while being refined the pulp is called thermo
mechanical pulp (TMP). Steam treatment significantly reduces the total energy
needed to make the pulp and decreases the damage (cutting) to fibers. Mechanical
pulps are used for products that require less strength, such as newsprint and
paperboards.

49
5.2.2 Thermo mechanical pulp mill

Thermo mechanical pulp is pulp produced by processing wood

chips using heat (thus thermo) and a mechanical refining movement (thus
mechanical). It is a two stage process where the logs are first stripped of their bark
and converted into small chips. These chips have a moisture content of around 25-
30% and a mechanical force is applied to the wood chips in a crushing or grinding
action which generates heat and water vapor and softens the lignin thus separating
the individual fibers. The pulp is then screened and cleaned; any clumps of fiber
are reprocessed. This process gives a high yield of fiber from the timber (around
95%) and as the lignin has not been removed, the fibers are hard and rigid.

5.2.3 Chemithermomechanical pulp mill

Wood chips can be pretreated with sodium carbonate, sodium

hydroxide, sodium sulfite and other chemical prior to refining with equipment
similar to a mechanical mill. The conditions of the chemical treatment are much
less vigorous (lower temperature, shorter time, less extreme pH) than in a chemical
pulping process since the goal is to make the fibers easier to refine, not to remove
lignin as in a fully chemical process. Pulps made using these hybrid processes are
known as chemithermomechanical pulps (CTMP).

5.2.4 Chemical pulp mills

Chemical pulping processes such as the kraft (or sulfate)

process and the sulfite process remove much of the hemicelluloses and lignin. The
kraft process does less damage to the cellulose fibers than the sulphite process,
thereby producing stronger fibers, but the sulfite process makes pulp that is easier
to bleach. The chemical pulping processes use a combination of high temperature
and alkaline (kraft) or acidic (sulphite) chemicals to break the chemical bonds of
the lignin.

The material fed into the digester must be small enough to

allow the pulping liquor to penetrate the pieces completely. In the case of wood,
the logs are chipped and the chips screened so that what is fed to the digester is a
uniform size. The oversize chips are rechipped or used as fuel, sawdust is burned.
The screened chips or cut plant material (bamboo, kenaf, etc) goes to the digester
where it is mixed an aqueous solution of the pulping chemicals, then heated with
steam. In the Kraft process the pulping chemicals are sodium hydroxide and
sodium sulfide and the solution is known as white liquor. In the sulfite process the
pulping chemical is a mixture of metal (sodium, magnesium, potassium or
calcium) or ammonium sulfite or bisulfite.

50
 After several hours in the digester, the chips or cut plant
material breaks down into a thick porridge-like consistency and is "blown" or
squeezed from the outlet of the digester through an airlock. The sudden change in
pressure results in a rapid expansion of the fibers, separating the fibres even more.
The resulting fiber suspension in water solution is called "brown stock".

Brown stock washers, using countercurrent flow, remove the

spent cooking chemicals and degraded lignin and hemicellulose. The extracted
liquid, known as black liquor in the kraft process, and red or brown liquor in the
sulfite processes, is concentrated, burned and the sodium and sulfur compounds
recycled in the recovery process. Lignosulfonates are a useful byproduct recovered
from the spent liquor in the sulfite process. The clean pulp (stock) can be bleached
in the bleach plant or left unbleached, depending on the end use. The stock is
sprayed onto the pulp machine wire, water drains off, more water is removed by
pressing the sheet of fibers, and the sheet is then dried. At this point the sheets of
pulp are several millimeters thick and have a coarse surface: it is not yet paper. The
dried pulp is cut, stacked, bailed and shipped to another facility for whatever
further process is needed.

Bleached kraft pulp and bleached sulfite pulp are used to make
high quality, white printing paper. One of the most visible uses for unbleached
kraft pulp is to make brown paper shopping bags and wrapping paper where
strength is particularly important. A special grade of bleached sulfite pulp, known
as dissolving pulp, is used to make cellulose derivatives such as methylcellulose
which are used in a wide range of everyday products from laxatives to baked goods
to wallpaper paste.

5.3 Process description:

5.3.1 Overview

51
 SILO

Cooking

Screening & Washing

Bleaching

Centricleaning

Bleach HD Towers

Fig 5.1 main processes of pulp mill

The process starts when chipped wood stored in the SILO

comes to this department where it’s filled in the digesters for cooking then
screened and washed to remove unwanted particles, such particles are again
refined and reused so there is minimum wastage, after which the pulp is bleached
to improve brightness and in the end its finally centricleaned to remove minutest
possible foreign particles. Then it’s stored in tanks before being taken from there
for preparation. The whole procedure is almost automatic only manual loading is
done that to with help of machines and just few operators are there to keep a check
and make small adjustments. The software employed for this procedure is
developed by ABB. This pulp mill was established in 1997 and there is no specific
life just improvement and maintenance is done. The actual capacity is not more
than 120 tonnes but its producing almost 180 tonnes per day. There is a new
proposal in pipeline to dismantle this pulp mill and to start using imported pulp
seed which is just required to be dissolved in the water and its ready for use. The
costing of the whole procedure of pulp is Rs 15 per/kg. They try to run this mill
always not taking into consideration small wear and tear and deal with them only if
there is a plant shutdown. Capacity of the tanks in this process are Blow Tank 300
m3, Black Liquor 400 m3, Seal Tank of washer 1 & 2 are 400 m 3, Seal tank of

52
washer 3 & 4 are 242 m3, Un Build Tower 400 m3, Bleaching Seal Tanks 50 m3,
Build Tower 1 is 1000 m3 and Build Tower 2 is 500 m3.

5.3.2 Cooking process description

This procedure is carried out mainly to remove lignin in

the wood which is its stickiness which may harm the end product quality. The
wood is converted into slurry form. White Liquor is used for this process which
constitutes of Sodium Hydroxide, Sodium Sulphite, and Sodium Carbonate. Total
time taken in the procedure is around 4 hrs 15 – 20 min. Which can be divided in
the following manner 1 hour for loading of chipped wood and white liqueur some
times black liquor is added for make up composition, then the mixture is heated to
135o C which takes 1 more hour, then 135o C temperature is maintained for another
half n hour for impregnation, after which another 1 hour is taken to raise the temp
of the mixture to 160o C, then the mixture is left at this temp for half n hour for
final cooking and after which digester is completely emptied and mixture is put
into a blow tank. The procedure is done in batches taking 45-48 tons of wood in a
batch using 3 different digesters. The yield of this procedure is 42-44%. If for
example 682 tons of wood is used in a day then because of almost 40% moisture
effective quantity comes out to be 409 tons and 44% yield makes it 180 tons of
pulp produced. The black liquor used in this procedure is recoverable up to 96.5%
for reuse. ISPN no. is the degree of cooking. Reheating of white liquor is also done
by sucking it from the middle of the digester passing it through heat exchangers
and then put back into the digester from its top and bottom layer.

COOKING PROCESS

53
 Check Digester Status

Is Digester Empty Check

Low
Reblow Digester No Inform Soda Recovery

Add 10 M3 White
Chips from SILO Liqueur & Chips
for 1st Loading

Add More
1st Loading Complete Chips
No

Charge Remaining White

Liqueur & Chips for 2nd
Loading

Check Capping U/V & STM Scheduling Pressure

Low
Inform Power House

54
 Is Temp Achieved in 1 Hour

No Charge More
Steam

Give Time at Temp 45 Min

Start 2nd Steam to

Achieve Temp 165o C

Is Temp Achieved in 1 Hour

No
Expose More
Steam

Maintain Cooking
Time 20 – 30 Min

ISPN No.
Increase Cooking TimeMore 11.5 – 12.5 Decrease Cooking Time
Less

Check Blow Tank Level < 50 %

No Held Up At Digester

55
 Yes

Add 10 M3 Cold Black

Liqueur

Start the BHR

Pumps

Blow Digester to Blow Tank

Fig 5.2 Cooking process

5.3.3 Screening & Washing process description

After taking material from the blow tank it’s passed

through Junk Trap to remove waste then its screened to remove the uncooked
material which is again sent to SILO and after cleaning is reused. As there is
formation of foam in the slurry of pulp a deformer chemical is added to remove
foam. Then the slurry is washed by passing it through 4 washers that use water for
washing it and in the last washer the color gets changed from black to brown. The
hot water is added for washing in the 4th washer and it moves in the opposite
direction from washer No.4 to No.1 and becomes completely black in color which
is then send to recovery department to get sodium and caustic from it. The whole
procedure mainly helps in removing 4 kinds of impurities present in the pulp that
are black liquor, caustic soda, solid impurities and uncooked material called knots.
Water is recycled and used again and again. Talcum powder is added to the pulp in
the 4th washer after mixing it with water so as to improve quality and bulk of the
pulp. After as the pulp is very thick water is mixed in it to enable it to move into
the Un bleached HD towers where its stored before bleaching. VAT is a rotating
machine part in the washer which had to move in the washer at a certain level of

56
dilution in the water and any difference can harm the quality of the pulp. Mat is the
thickness of the pulp moving on the big rotator.

57
 Blow Tank

Screening

Check DP & Rejection

Decrease Reject More Less Increase Reject

Flow Flow

Brown Stock Washer No.1

Check VAT
Consistency Less
Increase Vat More Reduce Vat
Dilution Dilution

Brown Stock Washer No.2

Check VAT
More Consistency Less
Increase Vat Reduce Vat
Dilution Dilution

Brown Stock Washer No.3

Check VAT
More Consistency Less
Increase Vat Reduce Vat
Dilution Dilution

58
 Brown Stock Washer No.4

Check Condition of Seal Tank

More
Increase Less Reduce
MAT MAT
Dilution Dilution

Un Build HD Tower

Fig 5.3 screening and washing

Four different Seal tanks are attached at all the four washing stages where water
from these washers gets stored and this also helps in maintaining proper vacuum.

5.3.4 Bleaching process description

The Un Build Pulp is taken out from the Un Build Tank

and is checked whether the brightness is 30% or not then Chlorine and Chlorine
Dioxide is added to start the bleaching process which is undertaken to remove the
minutest possible impurities and increase the brightness of the pulp, then if the
brightness becomes 57% then its washed with hot water, Oxygen and Caustic are
added then acidity of the water is checked then its again washed after which
Chlorine Dioxide is added again to increase the brightness to 86 – 87% then the
pulp is checked for residual amount after which its again washed and chlorine
dioxide is added to achieve 89% brightness which is the final aim after which the
pulp is centricleaned to remove the minutest possible sand particles and then the
pulp is washed for the last time after which a chemical is added to remove pitch
blackness which maybe caused by the blackness of the machine. The seal tanks are

59
attached at all the 4 stages which are used to store water and to maintain vacuum.
Four Stage tanks are also attached to give the required time for the chemical to do
its work. The seal tanks are made of fiber because the water from this process
contains chemical that can cause corrosion. The first stage is called Cd stage where
Chlorine Dioxide is added, second stage is called Eop where extraction of oxygen
and hydrogen peroxide takes place then last two stages are D1 & D2 where again
chlorine dioxide is added. If the brightness in the end is below 89 % then its stored
in Build Tower 1 which supplies to machine 1, 2 & 4. But the material stored in the
Build Tower 2 has to be of 89% brightness because it supplies to machine 5, 6, & 7
where better quality of paper is made.

60
 Blow Tank

Screening

Check DP & Rejection

Decrease Reject More Less Increase Reject

Flow Flow

Brown Stock Washer

No.1

Check VAT
Consistency Less
Increase Vat More Reduce Vat
Dilution Dilution

Brown Stock Washer

No.2

Check VAT
More Consistency Less
Increase Vat Reduce Vat
Dilution Dilution

Brown Stock Washer

No.3

Check VAT
More Consistency Less
Increase Vat Reduce Vat
Dilution Dilution

61
 Brown Stock
Washer No.4

Check Condition of Seal Tank

More
Increase Less Reduce
MAT MAT
Dilution Dilution

Un Build HD Tower

Fig 5.4 bleaching process

5.4 Environmental issues

The United Nations Environmental Program (UNEP) has

approved only two processes for making the chemical bleach chlorine dioxide,
which produce 99.8% chlorine dioxide and contain only 0.2% elemental chlorine.
Contamination of the chlorine dioxide with elemental chlorine is considered
undesirable, and may lead to environmental pollution. While properly treated
effluent may be safe to discharge into water catchment areas, mills which discharge
untreated effluent pollute water ways with persistent organic pollutants (organ
chlorides and dioxins), and may breach the Stockholm Convention.

62
CHAPTER SIX RECOVERY SECTION
6.1 Introduction

Recovery of chemicals has always been considered as the

backbone of pulp and paper industry in the phase of increase of pulping chemicals.
Strict laws of pollution control and power crisis arising from mushrooming of
industries the recovery of pulping chemicals has become more important.

6.2 Evaporator section

In this section black liquor is concentrated to a required

condition and sent to the soda causticizing plant for making of green liquor to
white liquor which is further sent to pulp mill to make pulp.

The black liquor is concentrated with the help of evaporators. In

this section there are mainly two types of evaporators, one is falling film and other
is calandria type evaporators.

Black liquor is a byproduct of the Kraft process, one of the

processes used by pulp mills during the production of paper pulp. Wood is
decomposed into cellulose fibers (from which paper is made), lignin fragments and
hemicelluloses. Black liquor is an aqueous solution of lignin residues,
hemicelluloses, and the inorganic chemicals used in the process. The black liquor
contains more than half of the energy content of the wood fed into the digester.

Paper mills have used black liquor as an energy source since at

least the 1930s. Most Kraft pulp mills use recovery boilers to recover and burn
much of the black liquor they produce, generating steam and recovering the
"cooking chemicals" (sodium hydroxide and sodium sulfide used to separate lignin
from the cellulose fibers needed for papermaking). This has helped paper mills
reduce problems with water emissions, reduce their use of chemicals by recovery
and reuse, and become nearly energy self-sufficient by producing, on average, 66
percent of their own electricity needs on-site.

In the United States, paper companies have consumed nearly all

of the black liquor they produce since the 1990s. As a result, the forest products
industry has become one the United States' leading generators of carbon-neutral
renewable energy, producing approximately 28.5 million megawatt hours of

63
electricity annually--more than the solar, wind and geothermal industries
combined.

6.2.1 Types of evaporators

The chief types of steam heated tubular evaporator in use today are:

(1) Long tube vertical evaporators

a. Upward flow (climbing film type)

b .Downward flow (falling film type)

c. Forced circulation

2. Agitated film evaporator.

6.2.2 Once through and circulation evaporators:

Evaporators may be operated either as once-through or as circulation

units. In once-through operation the feed liquor passes through the tubes only once,
releases the vapour, and leaves the unit as thick liquor. All the evaporation is
accomplished in a single pass. The ratio of evaporation to feed is limited in single-
pass units; thus these evaporators are well adapted to multiple-effect operation,
where the total amount of concentration can be spread over several effects.
Agitated-film evaporators are always operated once through; falling film and
climbing-film evaporators can also be operated in this way.

Once-through evaporated are especially useful for heat-sensitive

materials. By operation under high vacuum, the temperature of the liquid can be
the evaporation temperature but a short time and be quickly cooled as soon as it
leaves the evaporator.

In circulation evaporators a pool of liquid is held within the

equipment. Incoming feed mixes with the liquid from the pool, and the mixture
passes through the tubes. Unevaporated liquid discharged from the tubes returns to
the pool, so that only part of the total evaporation occurs in one pass. All forced-
circulation evaporators are operated in this way; climbing-film evaporated is
usually circulation units.

64
 The thick liquor from a circulation evaporator is withdrawn from the
pool. All the liquor in the pool must therefore be at the maximum concentration.
Since the liquid entering the tubes may contain several parts of thick liquor for
each part of feed, its viscosity is high and the heat-transfer coefficient tends to be
low.

Circulation evaporators are not well suited to concentrating heat-

sensitive liquids. With a reasonable good vacuum the temperature of the bulk of
the liquid may be non-destructive, but the liquid is repeatedly exposed to contact
with hot tubes. Some of the liquid, therefore, may be heated to an excessively high
temperature. Although the average residence time of the liquid in the heating zone
may be short, part of the liquid is retained in the evaporator for a considerable
time. Prolonged heating of even a small part of a heat-sensitive material like a food
can ruin the entire product.

Circulation evaporators, however, can operate over a wide range of

concentration between feed and thick liquor in a single unit, and are well adapted
to single-effect evaporation. They operate either with natural circulation, with the
flow through the tubes induced by density differences, or with forced circulation,
with flow provided by a pump.

(a)Long-tube evaporators with upward flow: A typical long-tube vertical

evaporator with upward flow of the liquid is shown in the fig.6.1.The essential
parts are (1) a tubular exchanger with steam in the shell and liquid to be
concentrated in the tubes,(2) a separator or vapor space for removing entrained
liquid from the vapor, and(3) when operated as a circulation unit, a return leg for
the liquid from the separator to the bottom of the exchanger. Inlets are provided for
feed liquid and steam, and outlets are provided for vapor, thick liquor, steam
condensate, and non condensable gases from the steam.

The tubular heater operates in exactly the same way as the natural-circulation. The
tubes, however, are larger than in a calandria: they are typically 25 to 50 mm (1 to
2 in.) in diameter and 3 to 10m (10 to 32 ft.)Long. Dilute feed enters the system
and mixes with the liquid draining from the separator. Concentrated liquor is
withdrawn from the bottom of the heater; the remaining liquor is partially
vaporized as it rises through the tubes. The mixture of liquid and vapour from the
top of the tubes flow into the separator, where its velocity is greatly reduced. To aid
in eliminating liquid droplets the vapor impinges on and then passes around sets of

65
baffle plates before leaving the separator. The evaporator shown in the fig. 6.1 can
be operated only as a circulation unit.

Long-tube vertical evaporators are especially effective in concentrating liquids that

tend to foam. Foam is broken when the high-velocity mixture of liquid and vapor
impinges against the vapor-head baffle.

Fig 6.1 Climbing film long tube vertical evaporator

(b) Falling film evaporators:

Concentration of highly heat sensitive materials such as orange

juice requires a minimum time of exposure to a heated surface. This can be done in
once through falling film evaporator, in which the liquid enters at the top, flows
downstream inside the heated tubes as a film, and leaves from the bottom. The
tubes are large, 50 to 250mm, in diameter. Vapor evolved from the liquid is usually
carried downward with the liquid and leaves from the bottom of the unit. In
appearance these evaporators resemble long, vertical, tubular exchangers with a
liquid vapor separator at the bottom and a distributor for the liquid at the top.

The chief problem in the falling film evaporator is that of

distributing the liquid uniformly as a film inside the tubes. This is done by a set of
perforated metal plates above a carefully leveled tube sheet, by inserts in the tube

66
ends to cause the liquid to flow evenly into each tube or by “spider” distributors
with the radial arms from which the feed is sprayed at a steady rate on the inside
each tube.

When recirculation is allowable without damaging the liquid,

distribution of liquid to the tubes is facilitated by a moderate recycling of liquid to
the tops of the tubes. This provides a larger volume of flow through the tubes than
is possible in once through operation.

For good heat transfer the Reynolds number 4Γ/µ of the falling
film should be greater than 2000 at all points of tube. During evaporation the
amount of liquid is continuously reduced as it flows downward, and too great a
reduction can lead to dry spots near the bottom of the tube. Thus the amount of
concentration that can be done in a single pass is limited.

Falling film evaporator, with no recirculation and short

residence times, handle sensitive products that can be concentrated in no other way.
They are also well adapted to concentrating viscous liquids.

(c) Forced circulation evaporator

In a natural circulation evaporator the liquid enters the tubes at

0.3 to 1.2 m/s .The linear velocity increases greatly as vapor is formed in the tubes,
so that in general the rates of heat transfer are satisfactory. With viscous liquids,
however, the overall coefficient in a natural circulation unit may be
uneconomically low. Higher coefficients are obtained in forced circulation
evaporators. An example is shown in figure.6.2. Here a centrifugal pump forces
liquid through the tubes at an entering velocity of 2 to 5.5 m/s. The tubes are under
sufficient static head to ensure that there is no boiling in the tubes, the liquid
becomes superheated as the static head is reduced during flow from the heater to
the vapor space, and it flashes into a mixture of vapor and spray in the outlet line
from the exchanger just before entering the body of the evaporator. The mixture of
the liquid and vapor impinges on a deflector plate in the vapor space. Liquid return
to the pump inlet, where it meets incoming feed; vapor leaves the top of the
evaporator body to a condenser or to the next effect. Part of the liquid leaving the
separator is continuously withdrawn as concentrate.

In the design of the figure the exchanger has horizontal tubes

and is two pass on both tube and shell sides. In others vertical single pass

67
exchangers are used. In both types the heat transfer coefficient are high, especially
with thin liquids, but the greatest improvement over natural circulation evaporation
is with viscous liquids. With thin liquids the improvement with forced circulation
does not warrant the added pumping costs over natural circulation, but with
viscous material the added costs are justified, especially when expensive metals
must be used. An example is caustic soda concentration, which must be done in
nickel equipment.

In multiple effect evaporators producing a viscous final

concentrate the first effect may be natural circulation units and the later ones,
handling viscous liquid, forced circulation units. Because of high velocities in a
forced circulation evaporator, the residence time of the liquid in the tubes is short
about 1 to 3 seconds –so that moderately heat sensitive liquids can be concentrated
in them. They are also effective in evaporating salting liquors or those that tend to
foam.

Fig 6.2 Forced circulation evaporator

2. Agitated-film evaporator

The principle resistance to overall heat transfer from the steam to the
boiling liquid in an evaporator is on the liquid side. One way of reducing this
resistance, especially with viscous liquids, is by mechanical agitation of the liquid
film, as in the evaporator shown in figure. This is a modified falling film
evaporator with a single jacketed tube containing an internal agitator. Feed enters
at the top of the jacketed section and is spread out into a thin, highly turbulent film
by the vertical blades of the agitator. Concentrate leaves from the bottom of the

68
jacketed section; vapor rises from the vaporizing zone into an unjacketed separator,
which is somewhat larger in diameter than the evaporating tube. In the separator
the agitator blades throw entrained liquid outward against stationary vertical plates.
The droplets coalesce on these plates and return to the evaporating section. Liquid
free vapor escapes through outlets at the top of the unit.

The chief advantage of an agitated film evaporator is its ability to give

high rates of heat transfer with viscous liquids. The product may have a viscosity
as high as 1000 Poise at the evaporation temperature.

Condensate Fig 6.3 Agitated-film evaporator

6.2.3 Methods of feeding

The usual method of feeding a multiple-effect evaporator

is to pump the thin liquid into the first effect and send it in turn through the other
effect as shown in fig. (a) This is called forward feed.

69
 Another common method is backward feed, in which
dilute liquid is fed to the last effect and then pumped through the successive effects
to the first, as shown in the fig. (b).

Other patterns of feed are sometimes used. In mixed feed the dilute liquid enters an
intermediate effect, flow in forward feed to the end of the series, and is then
pumped back to the first effects for final concentration. This eliminates some of the
pumps needed in backward feed and yet permits the final evaporation to be done at
the highest temperature. In crystallizing evaporators, where slurry of crystals and
mother liquor is withdrawn, feed may be admitted directly to each effect to give
what is called parallel feed. In parallel feed there is no transfer of liquid from one
effect to another.

6.3 Recovery Boilers

There are two types of recovery boiler in the company-

a) ABL boiler

b) JMW boiler

70
 NEW PULP MILLL

18-19% Solids at 72-75*C

Screen

Feed tank

Evaporator

Recovery Boiler

Fig 6.4 Black liquor flow

6.3.1 Difference between ABL and JMW boiler

1. At ABL boiler wall firing is being employed while at JMW centre

base firing is securing the purpose. Wall firing gives more surface area
for burning of black liquor. The other advantage is that it spreads heat
more evenly in the furnace. The black liquor is sprayed on to walls
leaves the walls as it is dehydrated & fluffs then it goes to the base of
furnace where complete ingeneration takes place while in JMW
dehydration takes place in the time of filth from liquor gun to the
bottom of furnace only and a char bed is formed in the centre furnace.
2. In ABL smelt dissolving tank agitator is at the bottom while it is at the
top at JMW recovery boiler.
3. ED fan is before the ESP in JMW recovery boiler but is after the ESP
at ABL boiler. It gives fine gases to chimney a ABL while it is given
to the ESP by the ED fan at JMW recovery boiler.

71
 4. At ABL sump pump is used for mixture salt cake for better mixing of
two while same mixing tank is being used at JMW boiler for mixing
both ESP ash and salt cake.
5. All the soot blowers used at ABL are retractable type automatic sot
blowing is done while at the JMW only 5 soot blowers are retractable
type and rest of 17 are retractable type soot blowing is done manually
at JMW.
6. Soot blowing is being employed to economize at ABL recovery boiler
decamping against the bromen steel short being practiced at the JMW
for economizes tube cleaning.
7. Steam used for soot blowing is taken from the steam forced by itself
at ABL while JMW uses steam produced by other boiler for the same.
8. Two ESP are being used at ABL but one is being used at JMW. In case
of any trouble one of these other can be taken in line for soda recovery
from the boiler flue gases but these are to be by pass to chimney in
case of any problems in ESP at JMW.
9. There is one forced draft fan at ABL as compared to two forced draft
fans secondary and total air fans are being used.
10.At ABL there are four pumps being used two for recirculation and two
for transferring liquor to Dorr plant while there are two to serve both
the purposes at JMW recovery boiler.

6.3.2 Problems encountered in boiler section

1. Black liquor gun may jam due to a no of reasons like low

temperature of black liquor, more solids etc. Steam is fired for
cleaning the firing gun. If it is not get cleaned then mechanical
cleaning is done.
2. The other problems include jamming of airports which may occur
due to black liquor or stuff coming in front of airport. For opening
the airports compressed is used. If airport jam the may not remain
sufficient for of black liquor and may cause black mug of char bed
and a higher suction.
3. Sometimes due to some negligible are failing of some furnace stuff
etc. in front of smelt spout jamming of spout may take place which
if not opened early cause a lot of losses. This is opened by manual
lancing. If it is not opened the level of smelt may increases a lot

72
 and few may take place from airport smelt may carryover to boiler
zone etc.
4. ED or FD failure may cause shut of boiler because without air
supply burning not take place and with flue gases not going of
furnace pressure may be exerted.
5. Due to some reason like lower concern of black liquor or lesser air
supply black of char bed may take place which may load to in
sufficient heat in the furnace which can be increased by starting oil
burners to maintain the furnace temperature.
6. Water level becoming very less may cause a lot of loss to the tubes
so an indrgator for always is used for water level. Tube leakage is
the most dangerous thing to happen which may cause smelt water
explosions depending on the part of furnace in which it has taken
place. Emergency shut procedure is known to all in the plant
although these are very rare and dangerous and may cause serious
loss.

High tension trip in the ESP may cause a lot of problems

because soda will go with flow gases and may cause environment
problems ESP from ESP to mixing.

Except from these there are a no of other problems like

scaling, tubes due to hardness agitator failure in tanks etc. which
can be occur in the plant.

6.4 Recovery plant heat losses

1. Sensible heat in dry flue gases.

2. Moisture losses include evaporators and sensible heat losses.
3. Heat in molten smelt.
4. Reduction of salt cake makeup.
5. Heat of reaction correction.
6. Radiation.
7. Unaccounted for tolerance.
6.5 Soda Recovery Plant

The main objects of a Soda recovery plant includes:

73
 1. Recovery of pulping chemicals (inorganic matter) used in preparation of
white liquor which is further consumed for cooking of wood chips in
digester house.
2. Recovery of heat energy from organic matter used for generating steam for
power generation as well as use in other process in the mill.
3. Minimization of pollution which has become more important due to strict
law coming in practice.

If we are not recovering the chemicals from black liquor we are

losing chemicals in black liquor which may be high as 80-85% of the total
chemicals used in cooking as well as steam producing capacity because 1KG of
black liquor solid produces around 2.87 KG of steam an average basis depending
on black liquor quality of black liquor supplied. A part from this we are causing a
lot of pollution which may cause irreparable loss to our surrounding as well as to
ourselves.

6.6 DORR Recausticizing Plant

The plant is designed to produce 375m3white liquor per day of

22-23% sulphidity green liquor at 500-600*C from the smelt dissolving tank is
pumped to raw green liquor storage tank. Green liquor is prepared of 95-100 GPL
as Na2O for pumping is to the green liquor clarifier. The green liquor is screen over
the storage tank and floes are removed drags are passed on separated in the green
liquor is sent to clarified green liquor storage tank. The temperature is always kept
at 95-100*C so that slaking and caustisizing reaction takes place at desired rate.
Dregs are passed on line mud washer .Clarified green liquor from the storage is
supplied to splitting box. The capacity of green liquor clarifier is 300m 3. A device
suctioned pump has been given for removal of dregs the capacity of clarified green
liquor tank is 165m3.Lime is introduced in the slacker where the liquor come from
the splitter box in the slacker by two lines one in head and another in tale. Lime is
transferred from lime kiln. This is fed manually in lime conveyor and then it goes
to crusher for lime bin for lime storage .from lime bin storage lime is added in
rotary slacker on the top. In the slacker causticizing reaction completed around 80-
90%.

The slaking reaction is as follows:-

CaO+H2O Ca (OH) 2+Heat (486 Btu/lb)

74
Lime react first with water in the green liquor to the green liquor to from Ca (OH) 2
with the evaluation of heat.

The reacted slurry then passes through gift classifier to

three caustisizers. The grift are separated in grit classifier by spraying hot water
over it continuously. Grits are by the conveyor belt stored in trolley for thrown
away the caustisizing efficiency is 85%. The residence time in the caustisizers is
kept so that the causticizing reaction is completed .The temperature is kept 100-
110*C in the caustisizer the resultant Ca(OH)2 react with sodium carbonate to form
NaOH this reaction is called caustisizing reaction:

Ca (OH) 2+NaCO3 2NaOH+CaCO3

After caustisizing raw white liquor is ready

which should be clarified now. So far the purpose of clarifying it is supplied to
white liquor clarifier after three stage caustisizing. The sludge come out of the raw
white liquor during clarifying which is send to caustisizers, where steam is applied
for increasing temperature. The sludge send to lime mud washer through a dorrco
suction pump for washing while clarified. White liquor is sent to storage tank from
where it is sent to pulp mill according to the demand. The overflow of lime mud
washer no 1 is weak white liquor which is stored in weak white liquor storage tank.

The under flow of LMW 1 is pumped to LMW 2.

The under flow of LMW 2 is pumped to sludge tank and then to sludge filter where
mud is washed and filtered and filtrate is pumped to the 2nd compartment of LMW.

The overflow of LMW 2 is pumped to the

recaustisizier. Thus there is five stages washing of lime mud. Finally sludge
coming out of sludge filter is dispersed off by trolley as waste. This sludge can be
brunt in a rotary lime kiln to reproduce lime but it has not been installed here. The
weak wash coming from LMW 1 is firstly stored and then can be used for
dissolving smelt.

Apart from these problems in all the plants there

may be a no of other problems which may be mechanical, electrical or from
process point of view. There many steps are taken for removing each and every
problem as early as possible according to the plant conditions, sources and other
factors like stock of black liquor. If we have got enough stock for running boilers
for two or three days at their full capacity then we need not do anything in hurry

75
but the case is vice versa in other condition. Similarly if we have enough green
liquor to run Dorr plant then we can shut the boiler for general cleaning.

So the problems coming in the plant are

encountered according to the situation in which they have come, plant conditions
& sources for encountering the trouble.

6.6.1 Operating techniques

Start up

Before the unit is placed in operation equipment

lubrication should be checked. Cooling water should be supplied to the smelt
spouts bearings, B/L pump glands and access doors. The boiler should be
filled with suitable treated water to the proper level. The dissolving tank
should be field with either weak wash on water air dampers should be
properly set. Access doors should be closed and smelt holes should be free
of any abstractions. All personnel not involved in the startup should be
cleared from the area. After the unit has been inspected and prelimary start
up steps taken.

The following lighting ff procedure should be followed:

a) Start ED fan and adjust furnace.

b) Start FD fan and adjust the air flow fan proper auxiliary burner operation.
Purge the unit for the require period of time.

Start sufficient auxiliary burners to boil out pendant super heater and putting
unit on the line following pressure raising curve supplied by the
manufacturer. Maintain the proper boiler water level by proper feed waer
addition. When the level drops as the unit goes on the line as the unit
reaches operating pressure open the main steam valve to stop valve.

Start the green liquor circulating pumps and dissolving tank agitators.

When the liquor in the evaporators has reached the desired

concentration for using open the liquor valve to the mixing tank, filling the
tank to the operating level.

76
 Start the hopper system pump adjusts the liquor to the hoppers.
Open the steam valve to the black liquor heater in the mix tank. Install the
size liquor nozzle desired for boiler firing.

Start the black liquor fuel pump and start spraying liquor in the
furnace. The unit should be on the line, generating steam to firing black
liquor.

Adjust and put on automatic control ED fan and feed heater

control. Adjust the FD fan to compensate the liquor firing. As the liquor
firing becomes able to auxiliary bamers at a time until the liquor firing itself
sufficient. Start salt cake makeup feed. Make final adjustment of auxilator
sweep and distribution.

Shut down

 Shut off salt cake feed to mixing tank.

 Shut off black liquor feed to mixing tank as soon as the black liquor flow the
nozzle has stopped indicating that mixing tank is empty.

 Turn on to steam to spray to clean it out when spray gun assembly has been
cleaned out remove it from the furnace.

 Flush with water all black liquor line not in use.

 When steam flows starts to drop insert auxiliary fuel burners to burn down
bed as much as desired and to maintain steam flow of necessary. The bed must not
be burned down so fast that excessive flow of smelt is produced which will cause
trouble in the dissolving tank. A burner should be installed near each smelt spout
to keep smelt burning as long as possible to get appreciable flow. Be sure there is
sufficient steam pressure on slutter jets.

6.6.2 Emergency procedure

a) Sound an alarm to clear the recovery area of unnecessary process.

b) Immediately shut down the air supply by tripping E.D. & closing F.D. fan
damper.
c) Immediately stop firing all fuels secure the unit auxiliary fuel system at a remote
location.

77
d) Start smoothing the bed by sufficient black liquor (minimum concentration
should be 60% solids at all the times).

Except from all these problems given general closing of JMW

is done weakly and a complete shut after each six months as according to
requirement. At ABL boiler a complete shut is done whenever required for
removing shut which deposits on the tubes during working.

CHAPTER SEVEN ETP PLANT

7.1 Introduction

With increased environmental awareness, public pressures &

strictness of regulatory authorities, the environmental management has been the
major concern of pulp and paper industry and in last decade the industry has made
remarkable efforts in the area of resource conservation and environmental
management .As a result the volume of waste water discharge and magnitude of
pollution load has drastically reduced from the level prevailing before
1990’s.Today in spite of having all inherent limitations , improved product quality
coupled with resource conservation and cleaner environment are on the top
priority in the agenda of the every pulp and paper mill to make itself and the
industry on the whole, competitive and environmentally sustainable.
7.2 Types of wastes

78
7.2.1 Liquid Wastes
Pulp and paper industry requires huge amount of water and
major part of which (i.e. around 90%) is discharged as waste water. The waste
water discharge varies from mill to mill; depending upon the raw material used and
process employed. The waste water discharge varies from 150-175 m3/tpaper in
newsprint and rayon grade pulp mills while in writing and printing paper mills, the
waste water discharge varies generally from 100-175 m3/t paper.

7.2.2 Solid Wastes

The major proportion of solid wastes generated in large mills is inorganic in nature
such as lime sludge, cinder and fly ash .The estimated quantity of lime sludge,
cinder and fly ash generated per annum in paper industry is around 0.8,0.6, 0.105
million tonnes respectively. The general practice is to dispose of the lime sludge as
such on land. Some mills have lime kiln to reburn lime sludge to recover lime for
reuse in recausticisation.

7.2.3 Air Pollutants

The air pollutants can be classified into two major categories:
· Primary Pollutants
· Secondary Pollutants

A brief summary of major air pollutants are as under:

Major Sub class Constituents

Class

Inorganic Oxides of Nitrogen Nitric Oxide, Nitrogen dioxide

gases
Oxides of Sulfur Sulfur dioxide, Sulfur trioxide

Oxides of Carbon Carbon mono oxide, Carbon dioxide

79
 Organic Hydrocarbons C1 –C5
gases
Aldehydes or Ketones Formaldehyde, Acetone

Mercaptans H2S ,CH3SH, (CH3)2 SH etc

Particulates Solids Fume, dust, smoke, ash, carbon

,lead

Liquid Mist spray, oil, grease, acids

Table 7.1 Major Pollutants

7.3Waste water management
Indian Pulp & Paper Industry use huge amount of water
primarily because of use of mixed fibrous raw material and old / obsolete
technology & equipments with low efficiency. This result in generation of high
volume of waste water .The waste water generated contains both inorganic salts
& oxygen consuming organic matter which if discharged untreated to receiving
bodies / stream can cause adverse impact on flora & fauna. Treatment of the
waste water to acceptable norms/ quality is expensive in terms of energy and
chemical consumption and sometimes difficult which in turn influence the
overall economics of paper production. In recent times the mills have put up
sincere efforts in the direction of reducing their water consumption/ waste water
discharge and as a result the average waste water discharge figures have
reduced drastically from 250-300 m3 / tpaper to 100- 175m3 / tpaper.
7.3.1 Sources of Waste Water
The manufacture of paper consumes high proportion of water
and most of which (about 90%) is discharged as wastewater. The characteristics
of the influent (waste water entering the ETP) depend upon the process
employed, end products as well as at source control measures and house
-keeping.

Generally the major points of discharge of waste water in pulp & paper mills
are:

80
 Sources Discharge Intensity of pollution

Pulp washing The final wash often referred Small volume with moderate
as brown stock wash or level of pollutant
unbleached wash

Pulp bleachig Wastewater from chlorination Large volume with high level
stage having low pH and high of pollutants. A major source
chlorolignins, from caustic of pollution as it also contains
extraction stage with dark toxic chloral-organic
brown color & high pH as well compounds.
as chlorolignins from
hypochlorite stage

Chemical Spills of black liquor in the Small volumes, but high

Recovery evaporators, foul condensates pollutants.
and washings of the caustics

Table 7.2 Discharge of waste water

7.3.2 Flow Measurement

Mills are generally having on line flow meters to monitor the

consumption of fresh / raw water. For the waste water discharge, the mills are
adopting the usual open channel flow measurement techniques like V notch,
rectangular notch etc. Some mills are having online flow meters also. Flow
measurement studies were carried out during the period of composite sampling
of different effluent streams as well as combined influent & effluent .Flow
measurement were carried out as per standard procedure in accordance with the
type of notch available at the drains. In absence of any such facility, flow
measurements were carried out by float velocity method.
7.4 Evaluation of Performance Efficiency of ETP
The performance efficiency of various units of existing ETP
was evaluated for selected mills and is summarized under:

81
 a) Primary Clarifier
The major function of the primary clarifier is to remove the
suspended solids so as to reduce the pollution load going to secondary
treatment .The efficiency of the clarifier is influenced by the volume of effluent
generated & capacity of the clarifier as well as nature of suspended solids. A
sufficient retention time is required for good settling.
(b) Anaerobic Treatment
Anaerobic treatment involves biological treatment in absence of
oxygen. Among the selected mills three mills have been treating their effluent an
aerobically through biomethanation. In newsprint category, TNPL is using the
process for treating around 12,000 m3/day bagasse washings which have high COD
& BOD due to residual sugar and acids. The major advantage of the process along
with an appreciable reduction in COD & BOD is cogeneration of 18000-20,000 m3
biogas/day which is used in limekiln.
(c) Secondary Treatment System
The effluent after primary clarification is further subjected to
secondary treatment which involves biological treatment followed by secondary
clarification .The biological treatment adopted by the mills involve both aerobic &
anaerobic treatment :
(d) Aerobic Treatment
In aerobic treatment (ASP) exhaustive aeration is provided to
facilitate the degradation of pollutants by the biological biomass or mixed liquor
suspended solids (MLSS). The number of aerators required are governed by the
pollution load particularly BOD load to be fed to the aeration tank.

7.5 Sampling & Analysis

To have a true & representative sample, twenty four (24) hrs
composite sampling of the identified effluent streams were carried out in two
batches. The sampling was generally continued for forty eight (48) hours .The
sampling was also carried out at individual stages of ETP to determine the
performance efficiency of individual units as well as over all ETP. The samples
collected were preserved & analyzed for major pollution parameters as per
standard procedures already mentioned under methodology. Regular flow
measurements were also conducted during the period of sampling.

82
7.6 Effluent Treatment Practices
All the large mills are having conventional aerobic effluent treatment
system based on activated sludge process (ASP) involving basic unit i.e. primary
clarifier, aeration tank & secondary clarifier (Fig 4.1).As indicated in the figure the
general features of the ETP and their functions are as under:

Features Function

Bar Screen To remove big suspended particles debris wood

chips etc

Primary Clarifier To remove suspended material. The primary clarifier

sludge (underflow) is dewatered using sludge press
& usually sold to board mills

Aeration tank It contains microbial population, which degrade

organic matter. Oxygen is provided mechanically
through surface aerators or diffused aerators

Secondary Clarifier To remove the suspended matter including biological

sludge. A portion of biological sludge is recycled
back to aeration tank to maintain the desired level of
MLSS level & the rest purged out for ultimate
disposal.

Table 7.3 Functions of features

7.7 Other Treatment Options

83
(a)Tertiary Treatment
During biological treatment of waste water sometimes it is very
difficult to control the discharge of biological solids along with secondary clarifier
overflow. During the visits to the selected mills, it has been observed that some
mills i.e. Bilt-Yamunanagar & Mysore Paper Mills have the provision of tertiary
treatment by having tertiary clarifier and polishing pond respectively mainly for
arresting bio solids as well as for conditioning the effluent. Bilt - Yamunanagar has
installed one tertiary clarifier after secondary clarifier for arresting any biosolids
escaping along with secondary clarifier overflow. The mill also has provision for
adding chemicals like alum & lime for improving the performance of tertiary
clarifier and to meet the discharge norms.

(b) Reclaimation Plant

With increasing emphasis on water conservation & reduction in

volume of effluent discharge most of the mills are recycling paper machine
backwater into paper machine itself or pulp mill after primary treatment through
savealls or fiber recovery units based on sedimentation or floatation. Some of the
mills have segregated their paper machine back water from other effluent streams
and treat it separately in reclaimation plant/ primary clarifier to remove the
suspended solids and reuse it in the process.

7.8 Recycling of back water or waste water

With the ease of water availability at practically free of

cost the major trend in the mills till recent past was to use fresh water in its all
operations resulting in high water consumption and accordingly high volume
of waste water is discharged. Due to scarcity of water, high treatment cost,
stringent environmental norms. Industry has realized the need and taken
considerable efforts for efficient water usage through process optimization and
recycling of back water. In Indian paper industry, though the efforts have been
taken to bring down the water requirements, but the water consumption (with
few exceptions) is still high compared to international bench marks. The
overall scenario of recycling of backwater to various sections in general is
given below:

84
Section wise back water/ Recycled to % of
filtrate generation recyclin
g

Pulp Mill BSW & screening & 40-60

cleaning plant
Decker filtrate(Unbleached)

Bleach Plant effluent

- C/D Stage filtrate Vat dilution 20-40

- Eo/Ep stage filtrate Vat dilution 20-40

- H/D stage filtrate Vat dilution & at showers of 60-80

C/D stage

Vat dilution at H/D stage and

- Decker filtrate (Bleached) at showers of C/D, Eo/EP, 60-80
H/D stage

Paper Machine

- Excess back water Pulp mill, stock preparation, 60-80

raw material cleaning, ash
quenching 60-80
- Machine condensate Boiler house

Evaporator & recovery

- Primary (steam) Boiler house 50-70

condensate
Recausticization & un build. 60-80
Pulp washing at showers

85
 - Secondary (foul)
condensate

Table 7.4 Recycling of back water

The major limitations encountered during recycling of water are:
 Increases operating problems due to change in water quality because of the
accumulation of various inorganic and organic components.
 Corrosion problem due to increased levels of calcium, chlorides, sulphates
and suspended matter etc.
 Adverse impact on the product quality due to lower retention and drainage
of the additives.
 Increased levels of microbial population (slime) with rise in temperature
by water recycling which might affect the run ability of the paper
machines.
To overcome these limitations, options are available which
include both chemical treatments as well as physic-chemical treatment
methods like, Reverse Osmosis, Membrane filtration, Evaporation,
Crystallization, Adsorption etc however their adaptability & techno-
economics in Indian context needs to be explored.
7.9 Disposal of treated effluent

The major practices adopted for the disposal of treated effluent are:

1. Discharge into river or canal

2. on land discharge for irrigation / cultivation
In some cases the mills are discharging into a nearby or
specially constructed canal which eventually meets the river. In some cases
the mills are required to store their highly concentrated effluent streams for a
period of 5-6 months and are allowed to discharge only during rainy season.
The impact of the discharge of treated effluent on river water quality is
evaluated by analyzing the upstream & downstream river water samples and
comparing their characteristics. The factors influencing impact of treated
effluent on river water characteristics are:

86
 1. Distance of the final discharge point from the mill & river.
2. Availability of water in the river for dilution.
3. Human settlement in the downstream.
4. Location of other industries in upstream and downstream.

7.10 Some stills from ETP plant

Waste Water Discharge From Mill

87
 Bar Screening

Lime Tank

Primary Clarifier

Aeriation Tank

88
 Secondary Clarifier

Tertiary Clarifier

Project on evaporator (heat and mass balances)

For B2 evaporator:

Data:

Calendria pressure =0.05 kg/cm²

Calendria tempter =95º c

Vapor head pressure =0.25

89
Vapor tempter =93ºc

Liquid tempter inlet =72 ºc

Liquid tempter outlet 76ºc

Solid fraction in =0.181

Solid fraction out =0.188

Cp in= 4.187*(0.98-0.52*solid in)

=4.187*(0.98-0.52*0.181)

=3.709 MJ/ton

Cp out =4.187*(0.98-0.52*0.188)

= 3.694 MJ/ton

Project calculation

Overall mass balance:

Inlet black liquor = 62 m³/hr

Density of black liquor =1.07 g/cm³

= 1070 kg/m³

Inlet solid % =18.1%

Outlet solid percentage =63.3%

Inlet mass flow rate =1070*62

= 66.34 ton/hr

The feed contains = (81.9/18.1)

= 4.525 kg water per kg of solid.

The outlet contains = (36.7/63.3)

= 0.580 kg water per kg of solid

90
The quantity evaporated =4.525-0.580

= 3.945 kg of water per kg of solid.

Water evaporated:

= 3.945*66.34*0.181*1000

=47367.74 kg/hr

= 47.37 ton/hr

Energy balance:

Calandria latent heat =2269 kJ/kg

Vapor head enthalpy =2276 kJ/kg

Mass of steam = mass of vapor coming from finishers +mass of vapor coming
from B2A+condensate flash of B2

Condensate flash of B2=?

Condensate enthalpy out = 410.7 MJ/ton

Condensate enthalpy in = outlet condensate enthalpy=419.7 MJ/ton

Condensate flash of B2

= {(mass of steam of finishers) + (mass of steam from B1A) + (mass of steam of

B1)}*{(condensate enthalpy in – condensate enthalpy out)}/ (vapor head enthalpy
– condensate enthalpy out)

= {(12+5.17+5.06)*(419.1-410.7)}/ (2276-410.7)

= 0.101ton/hr

Mass of steam to B2

=1.766+2.8785+0.101

91
=4.74 ton/hr

Now energy balance to calculate mass rate of evaporated water:

(Mass of steam to B2)*(Latent heat)

= (mass of liquid out) *(average cp) *(liquid outlet temperature -liquid inlet
temperature) + (mass of evaporated water) *{vapor head enthalpy + (average
cp)*(vapor temperature –liquid temperature)}

(4.74)*(2269) = {63.87*3.702*(4)} +m {2276+3.702*(93-72)}

m = [4.74*2269-63.87*3.702*4/2276+3.702*21]

m = 4.171 ton/hr

= 4.171*10³ kg/hr

To calculate U-overall heat transfer coefficient.

Now heating area A=460 m2

∆T=calendria temperature –liquid out temperature =95-76

=19 ⁰C

Q=UA∆T = (mass of steam) (latent heat)

U*460*19=4.74*2269*1000

U=1230.5 kJ/m²hr⁰C

Total heat transfer from evaporator B2

Q= (mass of steam)*(latent heat of steam)

= 4.74*2269*1000

= 10755.06 kJ/hr

Economy of evaporator

92
 E= (water evaporated)/ (mass of total steam)

= (47.37)/12

= 3.9475

Results

Total water evaporated = 47.37ton/hr

Mass of steam to B2 = 4.74 ton/hr

Over all heat transfer coefficient of B2 = 1230.5 kJ/m²hr⁰C

Total heat transfer rate in B2=10755.06 kJ/hr

Economy of evaporator section = 3.9475

Similarly

We can calculate these values for other evaporators in the evaporator section.

Remar
Effect.No. Finishers B1A B1 B2 B3 B4 B5 B6 k
Calend
Pr.Kg/cm2 2.3 0.35 0.7 0.05 0.25 400 350 520
caln.temp C 128 110 100 95 86 85 79 74
vap. Head Pr. 0.8 0.15 0.05 0.25 390 520 510 630

vap.temp C 120 100 94 93 88 80 75 60

Liq Temp. inlet C 101 92 55 72 76 54 56 50

Liq. Temp.out C 110 101 92 76 58 56 50 55

solids in 0.425 0.400 0.3650 0.181 0.188 0.233 0.241 0.275

93
solids out 0.633 0.425 0.4000 0.188 0.233 0.241 0.275 0.365
Cp MJ/t C in 3.178 3.232 3.309 3.709 3.694 3.596 3.579 3.505
Cp MJ/t C out 2.725 3.178 3.232 3.694 3.596 3.579 3.505 3.309

Liq.Flow out TPH 18.969 28.253 30.02 63.87 51.53 49.82 43.66 32.90 m3/hr

Liq Flow in TPH 28.253 30.019 32.90 66.34 63.87 51.53 49.82 43.66 62
10.766
water evap.TPH 9.284 1.766 2.8785 2.4701 12.3354 1.7107 6.1600 4 47.37
calen.latent heat 2175 2228 2257 2269 2293 2296 2312 2324 MJ/ton
vap head
enthalpy 2199 2256.9 2273 2276 2288 2307 2320 2358 MJ/ton
Mass of
steam/vap 12 5.17 5.06 4.74 3.18 6.21 6.61 8.36 TPH
cond.flash 0.0 0.529 0.416 0.101 0.709 0.046 0.439 0.488
cond.enthalpy in 0.0 543.0 464.0 419.1 410.7 360.0 357.0 333.0 MJ/ton
cond enthal. Out 543.0 464.0 419.1 410.7 360.0 357.0 333.0 309.73 MJ/ton
evap. By
E.B.TPH 11.350 4.690 3.242 4.171 4.576 5.794 6.787 7.887 48.50
Area m2 456 460 460 460 460 460 460.0 657

dTC 18 9 8 19 28 29 29 19
2782.4 3101.8 1231.5 1556.2
U(KJ/m2hr c 3179.82 0 6 6 565.93 1069.30 1145.07 1
Total evap. TPH 47.371
ECONOMY 3.948
665.64 742.07 294.63 372.29
U (Kcal/m2 hr C) 760.724 7 1 1 135.389 255.813 273.941 9

Cp avg. 2.952 3.205 3.270 3.702 3.645 3.587 3.542 3.407

References-

1. Biermann, Christopher J. (1993). Handbook of Pulping and Papermaking.

San Diego: Academic Press. ISBN 0-12-097360-X.

2. Papermaking (2007). In: Encyclopedia Britannica. Retrieved April 9, 2007,

from Encyclopedia Britannica Online.

3. Needham, Volume 4, 122.

4. TAPPI,Pulp and paper manufacture, volume 5.

5. Meggs, Philip B. A History of Graphic Design. John Wiley & Sons, Inc.
1998. (pp 58) ISBN 0-471-291-98-6.

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 6. Mahdavi, Farid (2003), "Review: Paper before Print: The History and Impact
of Paper in the Islamic World by Jonathan M. Bloom", Journal of
Interdisciplinary History (MIT Press) 34 (1): 129-30.

7. Koops, Matthias. Historical account of the substances which have been used
to describe events, and to convey ideas, from the earliest date, to the
invention of paper. London: Printed by T. Burton, 1800.

8. Carruthers, George. Paper in the Making. Toronto: The Garden City Press
Co-Operative, 1947.

9. Matthew, H.C.G. and Brian Harrison. "Koops. Matthias." Oxford Dictionary

of National Biography: from the earliest times to the year 2000, Vol. 32.
London: Oxford University Press, 2004: 80.

10. Burger, Peter. Charles Fenerty and his Paper Invention. Toronto: Peter
Burger, 2007. ISBN 978-0-9783318-1-8 pp.30-32.

List of Tables and Figures

Figure number Title Page no.

3.1 Process model 36

3.2 Forestry 37

3.3 Debarking, chipping & recycling 37

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3.4 Pulp preparation 38

3.5 Paper formation 39

3.6 Paper check 39

3.7 Paper finishing 40

5.1 Main processes of pulp mill 51

5.2 Cooking process 55

5.3 Screening & washing 58

5.4 Bleaching process 60

6.1 Climbing film long tube vertical evaporator 65

6.2 Forced circulation evaporator 67

6.3 Agitated film evaporator 68

6.4 Black liquor flow 70

Table number Title Page no.

7.1 Major pollutants 79

7.2 Discharge of waste water 80

7.3 Functions of features 82

7.4 Recycling of back water 84

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