Educational Wealth: paper industry

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<span style="font-size: large;"><span style="color: #274e13;">How to make paper </span></span></h2>
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<span style="font-size: large;">Definition of paper </span></h3>
<span style="font-size: large;">Paper is a semisynthetic sheet material which is a chemically processed product of naturally occurring fiber called cellulose.

Paper is a product of network of interlocking cellulose fibers.</span><br />
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<span style="font-size: large;"> Early History of paper </span></h3>
<span style="font-size: large;">The word paper is derived from Greek and Latin word ‘papyrus. Papyrus was a name of a plant which was used by the ancients for writing. Thin strips were cut from the stem, soaked in water and pressed together after drying to make rolls. Papyrus grew in abundance along marshy delta of the <a href="http://educational-wealth.blogspot.com/2014/02/worlds-rivers.html" target="_blank">River</a> Nile in Egypt around 3000 B.C. </span><br />
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<span style="font-size: large;">Making of paper </span></h3>
<span style="font-size: large;">The actual manufacturing of the paper started in China about 105 A.D. The name of the inventor is Ts’ai Lun in the history. This man prepared a sheet of paper using bark of mulberry tree that was treated with lime, bamboo and other fibres. </span><br />
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<span style="font-size: large;">Raw material for paper manufacturing: </span></h3>
<span style="font-size: large;"> There are two types of raw material. </span><br />
<span style="font-size: large;">These are: </span><br />
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<span style="font-size: large;">Non-woody raw materials for paper making</span></h3>
<span style="font-size: large;">Corn straw,wheat straw,rice straw,sugarcane crushed waste,Rag,Bamboo,Cotton stalk,Cotton linter(Removal of waste from seeds after processing </span><br />
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<span style="font-size: large;">Woody raw material  for paper making</span></h3>
<span style="font-size: large;">Poplar(A woody stem,grow fast,)

(Euclyptus ,a tree called safaida)

Fur
Essential steps in processing raw material:

Cutting of raw materials:

The non-woody raw materials come in the precut state and are processed as such. But in the case of wood based raw materials, big logs are cut into small chips before further processing.</span><br />
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<span style="font-size: large;"> Dry cleaning: </span></h3>
<span style="font-size: large;">Wheat straw is collected from the stock and is then sent for dry cleaning. For this purpose air is blown into the raw material, which removes unwanted particles.
Wet cleaning:

Dry wheat straw is then subjected to wet cleaning, which not only removes the remaining dust particles, but the soluble materials also get dissolved in water. </span><br />
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<span style="font-size: large;">Screening of papers</span></h3>
<span style="font-size: large;">In most pulp and paper processes, some type of stock screening operation is required to remove the over sized troublesome and unwanted particles. Magnetic

Pieces are removed by centri-cleaners. The major types of stock screens arc vibratory, gravity, and centrifugal.</span><br />
<span style="font-size: large;"> The material is then sent to wet silo (vessel).
Methods of Pulping

There are three chemical methods of pulping of obtain paper making pulps:

Kraft process (alkaline)

Sulphite process (acidic)

Neutral sulphite semi chemical process (NSSC) </span><br />
<span style="font-size: large;"> The details are given below: </span><br />
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<span style="font-size: large;">Kraft process for paper making </span></h3>
<span style="font-size: large;">The pulp is obtained by the digestion of wood chips by caustic soda (NaOH) containing sodium sulfate. </span><br />
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<span style="font-size: large;">Sulphite process for paper making </span></h3>
<span style="font-size: large;"> The wood chips are digested with magnesium, ammonium or calcium disulfite containing, free SO2. </span><br />
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<span style="font-size: large;">NSSC process for paper making </span></h3>
<span style="font-size: large;">Natural sulphite semi chemical process is dominant over the other two as described above.

In this process sodium sulphite cooking liquor (aqueous solution) is buffered with NaOH or Na2C03 to neutralize organic acids of raw materials. </span><br />
<span style="font-size: large;">Then the raw material is passed from the process of digestion either by batch or continuous methods. In Pakistan batch method is chiefly used.

Steam is given to the digester from bottom. Sodium sulphite liquor is injected at the same time to the digester containing raw materials. Liquor covers all the material. Buffer in it, maintains pH between 7-9. Digester is closed and put it into revolution at 2.5 revolution per minute (RPM). </span><br />
<span style="font-size: large;">The <a href="http://educational-wealth.blogspot.com/2014/02/temprature-of-earth.html" target="_blank">temperature</a> provided is 160 to 180°C. Digester attains this temperature within 45 minutes and then automatically it gets switched off and pressure is released.
Blow tank

This cooked material of the digester is now blown into a tank called ‘blow tank’. From this section it is pumped to centrifugal screen so that the cooked and uncooked materials and separated from each other.
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 . It is then thickened and finally stored in high-density storage tower.

Lignin is chemically phenylpropane polymer and contains 17-30% of wood. It acts as plastic binder is cellulose fibers in wood and also give brittleness (roughness) when present in paper
Colour of the pulp obtained:

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

Bleaching of the pulp:

In Pakistan, bleaching is done with chlorine or sodium hypochloride. Chlorine reacts very rapidly with pulp and most of it is consumed within a few minutes. The correct dosage is very important and enough chlorine is needed to achieve the required brightness. After chlorination, pulp is washed with hot water at 60°C and is then sent to the storage.
Stock preparation plant:

Prior to deliver the pulp to paper making machine, it is passed further through following three stages of treatment.
Formation of slurry:

The pulp is mixed with water to form a thin watery suspension called slurry.
Mechanical refining:

The slurry is beaten physically, so that its fibres develop good physical and mechanical properties.
Addition of chemical additives:

Certain chemical additives are added in it. Recycled fibres from waste paper plant are also added at this stage.
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 spreader takes the pulp and distributes it evenly across the machine from back to front.
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 Table:

The paper endless, moving fourdrinier fabric forms the fibre into a continuous matted web while the fourdrinier table drains the water by suction forces.
Press Section:

The paper sheet is conveyed through a series of roll presses where additional water is removed and the web structure is consolidated.
Dryer Section:

Wet sheet of paper so formed is dried in the dryer section of the machine with the help of rotary d"iim. Water is separated from the fibre either by gravity, by suction or by pressing.
Calender Stack:

The sheet is calendered through a series of roll nips to reduce thickness and smooth the surface.

Fourdrinier Paper Making Machine

Reel:

The dried paper is wound in the form of a reel having final moisture of about

6-8%.

Fourdrimer machine:

The name of this machine is on its inventors belongs to England. It was introduced in mid-19th century. It can manufacture paper of all varieties ranging from heavy board to light tissues.

The machine is consisted of a traveling wire belt having small pores (mesh, sieve) in it. Slurry runs on this unique belt from its starting point the ‘head box’. The wire belt is made up of bronze and brass. Water is drained off through the pores.

After leaving the wire the sheet (called the web) passes through press section of the machine. Here number of rollers remove enough of the remaining water and make the sheet. From press section, the sheet then goes to drying section. After drying the moisture contents in the sheet remain to 6-8%.

At the last is reel section that rolls the sheet.
Paper Industry in Pakistan

There was no pulp and paper industry in Pakistan at the time of independence in 1947. The country consumed about 25000 tons of pulp and paper products per year and all of these were imported from abroad at a cost of 25 million rupees. The start o the paper industry in our country was very slow because of various reasons. Amongst the major ones being the non-availability of suitable fibrous raw material.

Due to high prices of paper in Pakistan its per head consumption is among the lowest in the world. Paper consumption in Pakistan is around 5 Kg per person per year. To make our country self-sufficient in this important commodity, we mus utilize everv source of raw material like non-woody and woody. Fortunately, Pakistan

of our pulp and paper industry. The efforts are being made to install more pulp and paper industries in the country.

At present there are more than 30 pulp and paper industries in private as well as in public sectors, which are manufacturing pulp and paperboard.

Agriculture has been one of the oldest industry known to man. Since 5000 B.C Chinese have been using animal manure in their fields.

Fertilizer is the natural of artificial substance containing the chemical elements that improve growth and productiveness of plants.

Natural fertilizers are materials derived from plants and animals whereas artificial fertilizers consists of manufactured material like urea, calcium phosphate and ammonium nitrate, etc.

Synthetic fertilizers are mainly used for making up the immediate deficiency of essential nutrient elements needed in relatively large amount.

The nutrients required in a very small amount for growth of plants are called micro-nutrients and the nutrients which are required in a very large amount are called macro-nutrients.

Urea and ammonium nitrate are the major nitrogenous fertilizers whereas super phosphate and triple phosphate are important phosphatic fertilizers.

Cement is a very important building material which was first of all introduced in 1824 by an English Mason Joseph Aspdin.

Cement is the material obtained by burning an intimate mixture of calcarious and argillaceous materials at sufficiently high temperature to produce clinkers which are subsequently ground to a fine powder. Wet process is generally used in the production of cement.

The use of cement for construction purposes is based on its property of setting to a hard mass when mixed with water

Paper is a sheet material made up of a network of natural cellulosic fibres.

The neutral sulphite semi-chemical process is often used for the manufacturing of paper because of the advantages in the chemical recovery and pulp strength.

The prime objective of all pulp making steps is to separate fibres present in the straw from cementing material called lignin, which is a natural binder.</span></div>

Paper Industry

How to make paper Definition of paper Paper is a semisynthetic sheet material which is a chemically processed product of naturally occu...

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