pulp and paper processing
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Pulp and Paper Processing
The paper and pulp industry is typicallylocated in areas with abundant rawmaterials. These facilities are spread out
over many acres and closely resemble thescope of large chemical plants.
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Pulp and Paper Processing
This industry is composed of two sections:mills and converting operations.
Pulp and paper mills produce chemical,mechanical, and thermomechanical pulpsto form paper. Pulp is made by chemically
or mechanically separating wood fibersfrom non-fibrous material. The typicalprocess uses NaOH and Na 2S to dissolvenonfibrous material.
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Paper and Pulp Manufacturing
Wood PreparationPulpwood is brought into the paper mill
from local forest. Raw wood is sent to adevice called a barker where bark isremoved.
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Paper and Pulp Manufacturing
After debarking, the logs are broken itnosmaller chunks or pieces in the chipper.
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Paper and Pulp Manufacturing
CookingA screen ensures that uniform wood chips
fed into the digester where chemicals areadded, recovered, and added again.
Here, the chips are mixed
with a solution called white liquor and disintegrated into fibres by blowing -suddendecrease of pressure.
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Paper and Pulp Manufacturing
Pulp ScreeningApart from fibres, the cooked pulp also
contains partially uncooked fibre bundlesand knots. Modern cooking processeshave good control over the delignificationand produce less "rejects". Knots andshives are removed by passing the pulpover pulp screens equipped with fine holesor slots.
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BleachingBleaching involves removing virtually all of
the lignin that still remains after cooking,as the lignin contains the chromophoricgroups which make the pulp dark.
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Paper and Pulp Manufacturing
Paper MakingThe mechanical treatment of the fibre
normally takes place by passing itbetween moving steel bars which areattached to revolving metal discs - the so-called refiners. This treatment has twoeffects: it shortens the fibre and itfibrillates the fibre.
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Jordan Refiner
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Paper and Pulp Manufacturing
After refining, the pulp is sent to a cleaner.The cleaner has two separate flow: a wetside and a dry side.
On the wet side, the water is removed from
the treated pulp. A device called, Fourdrinier machine prepares the pulpbefore it enters the presses.
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Paper and Pulp Manufacturing
On the dry side of the cleaners, the pulpgoes to a cylinder machine before goingto presses and dryers.
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Paper and Pulp Manufacturing
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Paper and Pulp Manufacturing