Paper Industry 2013

HITEC UNIVERSITY TAXILADepartment of Mechanical Engineering

Assignment No. 3

Submitted To: Mam. Munaza_haq

Name: Registration No. Adnan Aslam 13-ME-008 Muhammad Majid 13-ME-109 Muhammad Maaz Akhtar 13-ME-108

Section: Mechanical (B) Date of submission: 22-11-2013

Max. Marks: ______________ Obtained Marks: _____________

Checked By: _____________

1

Paper Industry 2013

What is Paper: It is the material manufactured in thin sheets from the pulp of wood or other fibrous substances, used for writing, drawing, or printing on, or as wrapping material.

Invention & History:

The word paper is derived from the name of a reedy plant papyrus, which grew mostly along the River Nile in Egypt around 3000B.C.

The invention of modern paper is credit to Ts’ai Lun of china, who officially attached to the Imperial Court of China. He prepared a sheet of paper using the bark of mulberry tree that was treated with lime (CaCo3) and mixed with bamboo and other fibers to get the paper of desired properties.

Raw materials for paper Industry:

The raw material used in production of paper and pulp in Pakistan of two types

1. Nonwoody raw material:

1) Wheat straw 2) Rice straw 3) Bagasse Bamboo4) Rag 5) Cotton stalk 6) Cotton linter7) Kahi grass 8) Grasses

2. Woody raw material:

1) Poplar (hard wood) 2) Eucalyptus (hard wood)

2) Douglas fir (soft wood)

Pulp:

A mixture of cellulose material, such as wood, paper, and rags, ground up and moistened to make paper

Pulping Processes (Manufacturing Methods):

Three principal methods used for manufacturing of Paper are:

2

Kraft process (Alkaline)

Sulphite (Acidic)

NSSC

Paper Industry 2013

Kraft process (Alkaline) Sulphite (Acidic) Neutral sulphite semi-chemical process (NSSC)

In Pakistan we used NSSC process for pulping

Flow sheet diagram for NSSC process:

Process description:

This process utilizes sodium sulphite cooking liquor which is buffered with sodium carbonate or NaOH to neutralize the organic acid liberated from the raw materials.

The non-woody raw materials which are used in the process are wheat straw, rice straw, bagasse, cotton linter and rags. Wheat straw may be used alone or combined with other materials in different proportions. The essential steps for this process are:

1. Cutting of raw material:

The non-woody raw materials come in the precut state and are preprocessed as such. But in both case of wood based raw materials, big loge are cut into small chips before the further processing.

2. Dry cleaning:

Wheat straw is collected from the storage and is then sent for the dry cleaning. For this purpose air is blown into the raw material, which removes unwanted particles.

3. Wet cleaning:

3

Cutting of Raw

material

Dry section

WET CLEANING

BLOW TANK

DIGESTING UNIT

SCREENING CENTRIFUGAL SCREENS

PLUP WASHER

WASHING THICKNING

MATERIAL UNIT

READY FOR BLEACHING

Paper Industry 2013

Dry wheat straw is then subjected to wet cleaning, which removes the remaining dust particles and soluble materials get dissolved in water.

4. Screening:

In most paper processes some type of screening operation is required to remove oversized and unwanted particles. Magnetic separator removes iron pieces like nails and bolts etc. Stones and other oversized pieces are removed by centricleaners. The major type of screens are vibratory, gravity and centrifugal. The material is then sent to wet silo.

5. Digestion:

From wet silo, the material is sent to digester. The digester is usually 10 meters in height and 2 meters in diameter .It is made of steel and wrought iron.This is the main unit of the pulping process . The digestion process can be either batch or continuous. In our country batch process is mostly used.

As the raw material enters into the digester, steamIs introduced at the bottom and liquor containing sodium

sulphite is injected simultaneously to cover the raw material. Sodium sulphite used is buffered with sodium carbonate or Sodium hydroxide to maintain its pH 7-9. The digester is closed carefully.

It is revolved at 2.5 R.P.M and a temperature of 160-180oC is maintained .The digester takes 45 minutes to attain the desired temperature after which it gets switchedoff automatically and pressure is released.

6. Blow tank:

4

Paper Industry 2013

The cooked material from the digester is blown into a blow tank and then pumped to a centrifugal screen for the separation of cooked from uncooked materials.

7. Pulp washing:

The cooked material from the blow tank is washed thoroughly with water using 80 mesh sieve to remove the black liquor that would contaminate the pulp during subsequent processing steps. The pulp is washed with required amount of water to remove soluble lignin and coloured compounds. Lignin is an aromatics polymer and causes paper to become brittle. It is then thickened and finally stored in high-density storage tower.

8. Bleaching:

The pulps obtained from chemical pulping are brown in color and are unsuitable for printing and writing papers which require a bright white pulp. The color of these pulps is mainly due to residual lignin. These pulps are then sent to bleaching unit.

In Pakistan, bleaching is done with chlorine or hydrogen peroxide. After washing, the unbleached pulp is sent to the chlorinator where chlorine at 4-5 bar pressure is injected from chlorine tank. The residual chlorine is neutralized with water which acts as antichlor. The correct dosage is important and calculated amount of chlorine is needed to achieve the required brightness. After chlorination pulp is washed with hot water at 60o C and then sent to the storage tank. Pulp is dried with hot air supply. After drying the pulp is ready for manufacturing of paper.

9. Stock preparation plant:

5

Paper Industry 2013

There are three important stages in the treatment of the pulp prior to its delivery to the paper making machine. The first is the dispersion of the pulp as slurry in water, the second is the mechanical refining or beating of the fibers to develop appropriate physical and mechanical properties for the product being made and the third is the addition of the chemical additives and recycled fibers from the waste paper plant.

10. Paper making machine:

A basic fourdrinier type machine is used for paper making and a brief description of its major components is given below:

Flow spreader: The flow of spreader takes the pulp and distributes it evenly across the

machine from back to front. Consistency of the stock is below 1%.

Head box: The pressurized head box discharges a uniform jet of pulp suspension on a fabric

where special suction devices work for the removal of water.

Fourdrinier: The endless, moving fourdrinier fabric forms the fibre into a continuous matted web

while the fourdrinier table drains the water by suction forces.

Press suction: The paper sheet is conveyed through a series of roll presses where additional water is

removed and the web structure is consolidated (i.e. the fiber are forced into intimate contact).

Dryer section: Wet sheet of paper is so formed is dried in the dryer section of the machine with the

help of rotary drum. Water is separated from the fiber either by gravity, by suction or by pressing and by heating.

Calendar stock: The sheet is calendared through a series of roll nips to reduce thickness and smooth

the surface.

Reel: The dried paper is wound in the form of a reel having final moisture of about 6-8%.

6

Paper Industry 2013

Recycling of paper:

Some industry sources estimate that an ordinarySheet of paper made from cellulose fibers derivedFrom wood can survive only four to six trips throughthe recycling process.

The paper is shredded and chopped, then

subjected to a mixture of chemicals and water and

heated as it is repulped.It is centrifuged and screened

to remove impurities, de-inked with more chemicals,

then sprayed onto a wire screen, drained, dried and

squeezed through heated rollers.

With each step, the fibers become shorter, coarser and stiffer, so that eventually,

recycled fiber needs to be mixed with virgin fiber to make paper of the desired quality.

An ordinary newspaper can be recycled five (5) times.

Sizes of paper:

According to the International Organization for Standardization ( I.S.O ) 216 system use in most other countries is based on the surface area of a sheet of paper, not on a sheet's width and length.

Some internationally accepted paper sizes are:

Legal Letter Tabloid A0 A1 A2 A3 A4 B1

Annual usage of paper in Pakistan:

7

Paper Industry 2013

Usage of paper (million matric tone) in Pakistan is given in the following table:

S.N.

Particular Time of Informatio

n01 Country Pakistan02 Population (Million) 180.0 201203 Total

Pulp/Paper/Paperboard Production

1.079 2010

03.1 Writing & printing 0.258 201003.2 Others 0.821 201004 Import 0.409 201005 Export 0.008 201006 Net Consumption 1.480 201007 Per Capita

Consumption (Kg./year/person)

8.22 2010

08 No. of Pulp/Paper Mills

App. 10 2010

List of paper mills in Pakistan:

Some major paper mills (Private & public sector) names are given below:

Bulleh Shah Paper Mill,

Misk paper mills

century paper mills

Empire Paper & Board Mills

jasmine paper mills

Sana paper mills

Fiaz Paper and Board mills

Ali Murtaza Paper Mills

Usama Paper mills

Al Aziz Paper mills

8