Pulp and Paper making (2).pptx

paper making process

1. Pulp and Paper Making Process Presented by, C.Mathan Department of EIE

2. Overview of Indian paper industry The Indian paper industry accounts for about 3% of the world’s production of paper. The estimated turnover of the industry is INR 50,000 crore approximately . Total number of mills 750

3. STATISTICS

4. Different grades of paper

5. What does GSM mean? GSM  is an acronym standing for 'Grams per Square Meter‘ GSM of paper means the density of paper or weight of the paper. Effectively, this is the thickness of the paper Most printing paper has a gsm between 60 and 120. 80gsm is standard.

6. Introduction Paper is a dried, compressed mat of plant fibers . Paper plays a key role in our daily life and papers have been used for many years from now. Papers are made with the pulp of the woods, which is an Eco-friendly product . 90% of the raw material for papermaking comes from trees .

7. Raw Material The variety of raw material used wood, bamboo, recycled fibre, bagasse, wheat straw, rice husk , etc. Different kinds of trees produce a different texture of paper. Soft woods like pine have longer fibers and give paper more strength. Hardwood fibers are shorter but tend to work better in printing and writing papers. Most paper pulp is made from trees (mainly fast-growing, evergreen conifers ), though it can also be made from bamboo, cotton, hemp, jute , and a wide range of other plant materials. Smooth papers used for magazines or packaging often have materials such as china clay added so they print with a more colourful , glossy finish.

8. Primary Steps

9. Chemical Composition of wood

10. Lignin  is a class of complex organic polymers that form important structural materials in the support tissues of vascular plants. Cellulose is an insoluble substance which is the main constituent of plant cell walls and of vegetable fibres such as cotton.

11. Step 1:Pulp Production Pulp is a commercial fibrous material obtained from bamboo, wood, bagasse, etc . The primary goals of pulping are to free fibers in wood from the lignin that binds these fibers together and then to suspend the fibers in water into a slurry suitable for paper making. In the Pulp process which breaks the cellulose fibers  that are strong in tension and embedded in a matrix of  lignin(complex organic polymers) bonds.

12. There are several different methods of pulp production to make different strengths and grades of paper. The most common classifications are Chemical Pulping Mechanical Pulping Semi-chemical pulping techniques.

13. Chemical Pulping Chemical pulping uses various chemicals to separate lignin from the cellulose fibers. There are two main types of chemical pulping performed: Kraft ( sulphate ) pulping sulfite pulping

14. Kraft ( sulphate ) pulping

15. The sulphate or kraft process is the world's most common pulping process, since it yields higher pulp strengths and can be used with all types of wood . In the kraft pulp process the active cooking with hot mixture of water with chemicals ( white liquor) are sodium hydroxide ( NaOH ) and sodium sulphate ( Na 2 S ) that breaks the bonds that link lignin and cellulose.

16. Mechanical pulping

17. Mechanical pulping utilizes steam, pressure, and high temperatures instead of chemicals to tear the fibers. As the oldest form of pulping, mechanical pulping uses mechanical energy to weaken and separate fibers from wood via a grinding action . The advantage to mechanical pulping is that it produces much higher yields than chemical pulping processes. The fiber quality is greatly reduced because mechanical pulping creates short, weak fibers that still contain the lignin that bonds the fibers together.

18. Semi-Chemical Pulping Semi-chemical pulping techniques use weak chemical solutions composed of sodium sulfite (Na2SO3) and sodium carbonate (Na2CO3) to help digest the lignin in the pulp. In addition to the chemical solutions, mechanical refining is used to separate the fibers.

19. Step2:Pulp Processing and Chemical Recovery To further remove impurities of black liquor ( black liquor is the waste water from the  kraft process ). The removal of the black liquor takes place in washers and is necessary to reduce the chemical costs of the liquor. In addition, by recycling the cooking liquor back into the pulping process, environmental issues and costs are negated.

20. Step3:Pulp Bleaching Bleaching of wood pulp is the chemical processing carried out on various types of wood pulp to decrease the color of the pulp , so that it becomes whiter. chlorine dioxide, sodium hydroxide and hydrogen peroxide. Chlorine dioxide bleaching  is used in single or multi-stages process. Unlike chlorine, it does not react with water. It remains as a dissolved gas in water. It selectively attacks the phenolic groups of lignin without degrading cellulose fiber , allowing for increased yield and higher strength bleached pulp.

21. Step 4:Stock Preparation Cellulose fiber must be subjected to mechanical treatment before they can be made in to paper and board. Beating and refining is done to develop good fiber bonding and high paper strength.

22. Papermills do not always make their own pulp they are so called “ non integrated mills ” those who produce their own pulp are integrated mills

23. Step 5:Paper Making The pulp from stock preparation section after beating/ refing enters the to manifold and then to head box of Fourdrinier Machine and distribute it uniformly across the width of wire at constant head. .

24. PAPER MACHINE

25. Wet End Process When stock enters on the wire the consistency of stock remains 0.5-0.6percent , i.e., 99.5 gm water and 0.5 gm pulp in 100 gm of pulp stock Such a huge amount of water is removed on the wire part(97%), press section(1.5%) and dryer section(1%).

26. WIRE SECTION

27. Dry-End Operations Following the pressing of the wet-end operations, the continuous sheet is compressed by steam-heated rollers to allow the fibers to begin bonding together

28. Calendering After the sheet is dried, it is passed through a stack of heavy metal rolls , where it is calenderised under high pressure . The purpose of calendaring is to smooth down the felt and wire marks, to remove cockle and to level off lumpy formation and to make sheet of uniform caliper.

29. Thank You