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Wood and pulp
 

Wood and pulp

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Wood types and pulp production

Wood types and pulp production

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    Wood and pulp Wood and pulp Presentation Transcript

    • Wood and pulp1 | Wood and Pulp | Sappi Fine Paper Europe
    • Contents 1. Wood types 3 1.1. Wood structure 6 1.2. Wood growth 7 1.3. Cellulose formation 8 1.4. Chemical composition 9 2. Pulp production 10 2.1. Woodyard 11 2.2. Debarking 12 2.3. Chipping 13 2.4. Defibring 14 2.4.1. Mechanical vs. chemical pulp 15 2.4.2. Mechanical pulp 16 2.4.3. Chemical pulp 19 2.5. Measurement data 24 2.6. Bleaching 25 2.6.1. Bleaching methods 27 3. Overview pulp mill Sappi Gratkorn 282 | Wood and Pulp | Sappi Fine Paper Europe
    • 1. Wood types Typed Wood types Deciduous Coniferous (Hardwood) (Softwood) Beech Spruce Birch Pine Poplar Fir3 | Wood and Pulp | Sappi Fine Paper Europe
    • 1. Wood types • Structure Hardwood Softwood Short fibres Long fibres4 | Wood and Pulp | Sappi Fine Paper Europe
    • 1. Wood types Characteristics for paper mixture (pulp) Deciduous woord Nconiferous woodz Short fibre Long fibre Firmness Medium High Flexibility Medium High Bulk/Volume High Medium Opacity High Medium Suited for High g/m² Low g/m² Fibre length 1 mm 2-3 mm Fibre width 15-25 µm 35-45 µm Basics: The magic is in the mixture5 | Wood and Pulp | Sappi Fine Paper Europe
    • 1.1. Wood structure • Bark: – Outer layer consisting of dead cork cells – Protection against damage, loss of water, weather, bacteria – Bark cells do not grow, they burst • Cork cambium: – Builds cork cells and thus, the bark – Closes tears in the bark coat • Phloem (Inner bark) – Storage and transport of substances for the process of assimilation Assimilation = Conversion of substance and energy • Cambium: – The living, growing part of the tree • Sapwood: – Transport of water and nutrients, strengthening and assimilation substance storage – One new ring is formed every year (in seasonally affected phases) – Storage of lignin (gum) • Heartwood: – Supporting column, which usually starts to grow at a tree age of 20-40 years • Pith: – Dead fibre tissue, the core of the tree trunk6 | Wood and Pulp | Sappi Fine Paper Europe
    • 1.2. Wood growth Cambium splits Spring off thin-walled cells: spring Broad growth rings wood Cambium splits Summer off thick-walled cells: summer Narrow growth rings wood Winter No growth No ring formation • Growth periods depending on climate and location7 | Wood and Pulp | Sappi Fine Paper Europe
    • 1.3. Cellulose formation – Grape sugar (glucose) is converted to starch by shedding water – As it multiplies, cellulose is formed8 | Wood and Pulp | Sappi Fine Paper Europe
    • 1.4. Chemical composition • Cellulose: – Primary cell wall substance – Long, fibrous polysaccharide chain of glucose molecules – Hydrogen bonding builds a crystalline structure • Hemicellulose: – Sealants and flexibilisators – Short polysaccharide chain consisting of various sugars • Lignin: – Wood glue – Filling substance in the cellulose frame – Wood formation initiator – Absorbs pressure, protects agains attacks9 | Wood and Pulp | Sappi Fine Paper Europe
    • 2. Pulp production Process10 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.1. Wood yard Step 111 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.2. Debarking Step 2: Debarking drum12 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.3. Chipping Step 313 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4. Defibring Step 414 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.1. Mechanical vs. chemical pulp Mechanical pulp Chemical pulp Cost Low High Yield High: approx. 90% Low: approx. 50% Chemicals Few Many (re-usable >99%) Energy Intensive Energy generation Brightness Low High Yellowing High Low Opacity High Low Stiffness Low High15 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.2. Mechanical pulp Wood containing • Stone groundwood (SGW) – Developed1843 by F. G. Keller – No pre-processing – Processing under atmospheric pressure and temperature – Yield: 90-95%  All wood components are fully maintained • Brown groundwood – Vaporization before grinding – Fibres have brownish colour – Yield: <90%  But better stiffness • Pressurized groundwood (PGW) – Processing under pressure (2 to 4.5 bar) and high temperature (110-135°C) • Chemical groundwood (CGW) – Chemical pre-processing – Lignin is partially removed  Low yield16 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.2. Mechanical pulp (Chemi) Thermo Mechanical Pulp • TMP – Wood chips are vaporized – Chips are ground down to single fibres in refiners, under vapour pressure • CTMP – Wood chips are impregnated (mixed with a chemical substance) – Cooked – Ground – Bleached17 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.2. Mechanical pulp (Chemi) Thermo Mechanical Pulp T: light cooking of C: chemical woodchips impregnation of woodchips P: pulp ready for bleaching M: mechanical refining18 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.3. Chemical pulp • Purpose: – Stripping and dissolving lignin  Lignin is what holds the individual fibres together – Maintaining the cellulose fibre structure • In practice: – Only residual lignin remains – Hemicelullose and cellulose are also partially removed – Yield is approx. 50% (mechanical pulp approx. 90%) • Main types: – Sulphate pulp – Sulphite pulp19 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.3. Chemical pulp Sulphate pulp Sulphite pulp (kraft pulp) Cooking time 1-2 hours 3-8 hours Temperature 170-180°C 130-140°C pH-value 13+ (alkaline) 1-2 (acidic) Yield 45-50% 50-55% Stiffness High Low Fibres assailed from outside Fibres assailed from within Raw materials Flexible Limited Cost High Low Odour Heavy Neutral20 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.3. Chemical pulp Sulphate pulp • Developed 1879 – 80 – 85 % of all pulp production worldwide • Basic materials: – Roundwood and wood chips • Alkaline cooking process: pH value 11 • Special features: – Suitable for all wood types, including annuals – Obligatory recycling of used chemicals – Energy generation from burnt waste21 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.3. Chemical pulp Sulphite pulp • Developed 1876 - 1878 – 15 – 20 % of all pulp production worldwide • Basic materials: – Roundwood and wood chips • Acidic cooking process: pH value 4 – Cooking time 3-8 hours in sulphurous acids (magnesium bisulphite) – Lignin is washed out in acidic environment – Defibring under pressure at 130-145°C – Requires high quality wood – Yield approx. 55% • Special features: – Not suitable for resinous wood types (pine) – Recent regulations make recycling of used chemicals obligatory22 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.4.3. Chemical pulp Sulphite pulp Advantages Disadvantages Cost-effective use of small units from Limited raw material base  Sulphite: 100,000 tons per year  Sulphate: 500,000 tons per year Good yield Bark sensitive Good bleaching characteristics Low stiffness High basic whiteness High burden on waste water  Sulphite: greyish white / Sulphate: brown23 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.5. Measurement data Pulp hardness Kappa Residual lignin Very soft 0.5 – 1 1.5% Soft 11 – 15 1.5 – 2.5% Normal 23 – 31 3.0 – 4.0% Hard 46 – 54 6.0 – 7.0% Very hard 54 – 69 7.0 – 9.0%24 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.6. Bleaching • Modification of coloured substances in the pulp – Coloured substances lose the ability to fully absorb light – Residual lignin and other undesired substances are removed Cooking O₂ Bleaching25 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.6. Bleaching • Intermediate washing phases during chemical treatment First washing phase Last washing phase26 | Wood and Pulp | Sappi Fine Paper Europe
    • 2.6.1. Bleaching methods • Pulp can be bleached with: – Elemental chlorine and chlorine dioxide  In the past  Highly negative effects on the environment  Modern ECF/TCF pulp  Elemental Chlorine Free/Totally Chlorine Free – Ozone (O3) and oxygen (O₂) in various forms  Resulting paper is virtually odour free  Sappi was the first paper producer to use the „Sapoxal oxygen bleach process“ – Hydrogen peroxide (H₂O₂)  Components: caustic soda, water glass, sulphuric acid  Oxidative process: metal + oxygen is converted to metal oxide – Natriumdithionit (NaS₂O4)  Reductive process: metal oxide is dissolved into metal + oxygen27 | Wood and Pulp | Sappi Fine Paper Europe
    • 3. Overview pulp factory Sappi Gratkorn28 | Wood and Pulp | Sappi Fine Paper Europe
    • Thank you for your attention Jörg Abelmann29 | Wood and Pulp | Sappi Fine Paper Europe