Paper Manufacturing process

THE FULL DETAILS OF THE MANUFACTURE OF PAPER FROM WOOD(PULP) IS EXPLAINED .
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1. PAPER AND PULP INDUSTRY BY GEET KH SINGH

2. CONTENTS Introduction Manufacturing steps Treatment process

3. INTRODUCTION   The Paper Industry plays a very prominent role in the world economy.  The pulp and paper industry converts wood or recycled fibre into pulp and primary forms of paper. In the 1800s, there was a shift away from using cotton rags for paper production . But later Wood became the most important source of fiber . F irst mechanical and then chemical methods have been developed to produce pulp from wood .

4. PULP AND PAPER MILLS Pulp mills separate the fibres of wood or from other materials, such as rags, wastepaper or straw in order to create pulp . Paper mills primarily are engaged in manufacturing paper from wood pulp and other fibre pulp

5. MANUFACTURING STEPS TIMBER DE –BARKING CHIPPING PROCESS CHEMICAL PULPING PROCESS MECHANICAL PULPING PROCESS HYDRAPULPING BLEND CHEST WASTE PAPER DE- INKING REFINING SCREENING & CLEANING PAPERMAKING MACHINE CONVERSION & PRINTING

6. Timber Timber used for papermaking comes from well managed forests where more trees are planted than harvested to ensure sustainable growth.

7. De-Barker Bark is stripped from the logs by knife, drum, abrasion, or hydraulic barker. The stripped bark is then used for fuel or as soil enrichment. MAN U A L L Y ME CHAN I CA L

8. CHIPPING Stripped logs or timber are chipped into small pieces by knives mounted in massive chipping machine . chips are then stored in huge bins ready for the next process. CHIPPING MACHINE

9. CHEMICAL PULPING PROCESS Chips from the storage bins are fed into a digester. The woodchips are then 'cooked' to remove lignin. Lignin is the binding material which holds the cellulose fibres together. The chemical process is energy self-sufficient as nearly all by-products can be used to fire the pulp mill power plant.

10. MECHANICAL PULPING PROCESS Mechanical pulp yields over 90% of the wood as fiber is produced by forcing debarked logs, about two meters long, and hot water between enormous rotating steel discs with teeth that literally tear the wood apart

11. HYDRAPULPER The wood fibres are brought into a circular tank containing water . This has a very powerful agitator at the bottom which breaks up the bales (wooden fibres ) into small pieces.

12. BLEND CHEST CHEMICALS CAN BE ADDED TO OBTAIN THE REQUIRED CHARACTERISTICS TO THE FINISHED PAPER. DYES ARE ALSO ADDED , aS NECESSARY , tO COLOR THE PAPER

13. WASTE PAPER Waste paper is collected from Waste Paper Banks and Commercial dumps. Waste paper currently represents 67% of the raw material in paper industry. Paper not suitable for recycling is removed .

14. DE-INKING Before printed paper can be recycled the ink needs to be removed, otherwise it will be dispersed into the pulp. There are two main processes for de-inking waste paper – washing flotation .

15. SCREENING AND CLEANING Pulps contain undesirable fibrous and non-fibrous materials, which should be removed before the pulp is made into paper . Cleaning involves removing small particles of dirt and grit using rotating screens and centrifugal cleaners.   REFINING This is where the cellulose fibers pass through a refining process which is vital in the art of papermaking. Before refining, the fibers are stiff, inflexible and form few bonds.

16. PAPERMAKING MACHINE a slurry of fibre (usually wood or other vegetable fibres ) is drained to create a continuous paper web. After the forming section the wet web passes through a press section to squeeze out excess water, then the pressed web passes through a heated drying section .

17. TREATMENT OF WASTE FROM PULP INDUSTRY

18. PULP AND PAPER INDUSTRY Use wood ad raw material to produce paper, pulp, board and other cellulose based products. Bagase , hemp, straw are also used Composition of the pollutants in the effluent depends on the raw material used.

19. EFFLUENTS Waste water- 60 m³/ tonne of paper produced Contain solids and dissolved matter . Potentially very polluting COD as high as 11000mg/l

20. SOURCE EFFLUENT CHARACTERISTICS Water used in wood handling/ debarking Solids, BOD, color Chip digester and liquid evaporator concentrate Concentrated BOD, can contain reduced sulphur “white waters” from pulp screening, thickening and cleaning Suspended solids, can have significant BOD Bleach plant washer filtrates BOD, color, chlorinated organic compounds Paper machine water flows Solids, often precipitated for reuse Fiber and liquor spills Solids, BOD, color

21. CHARACTERISTICS OF COMBINED EFFLUENT OF P & P MILLS ITEM SMALL MILL LARGE MILL 20 TONS of paper per day 2000 TONS of paper per day Flow per day 330 m3/ tonnes 222m3/ tonnes Colour 7800 units pH 8.2-8.5 8.5-9.5 Total solids mg/l ---------- 4410 Suspended solid 900-2000 3300 COD 3400-5780 716 BOD 680-1250 155 COD/BOD 3.9-5 4.6

22. EFFLUENT TREATMENT SCEHME

23. SCREENING Screens- to remove course, bulky and fibrous components from effluents Grid chambers and settling tanks are used Efficiency of screening depends on the spacing between screen bars - fine screening, spacing < 10mm - mediun screening, spacing 10-40mm - coarse screening, spacing > 40mm

24. SEDIMENTATION Using gravity to remove suspended solids from water. Removal of suspended particles by sedimentation depends on size and specific gravity of the particles. Sedimentation tanks are used Settled sludge is removed High efficiency is achieved in the subsequent treatment processes.

25. BIOLOGICAL TREATMENT Degrade pollutants dissolved in effluents by the action of microorganisms. Pollutants are used as nutrients Microorganisms use these pollutants to live and reproduce.

26. ANAEROBIC TENCHNOLOGY Effluents originating from recycle paper mills Effluents from mechanical pulping (peroxide bleached), semi-chemical pulping, sulphite and kraft evaporator concentrates Bacterial hydrolysis of input materials to break down insoluble organic polymers