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PSE 476: Lecture #1 1
Pulping and BleachingPSE 476
Lecture #1Introduction
Lecture #1Introduction
PSE 476: Lecture #1 2
Introduction to Pulping:History of Papermaking
• 3000 BC: Papyrus» Exterior of reed is laminated and pressed to
form sheet» Developed by Egyptians» Word paper derived from papyrus
• Making of papyrus
• 3000 BC: Papyrus» Exterior of reed is laminated and pressed to
form sheet» Developed by Egyptians» Word paper derived from papyrus
• Making of papyrus http://www.lib.umich.edu/pap/exhibits/papyrus_making/slides.html
PSE 476: Lecture #1 3
Papyrus Making-Harvesting
PSE 476: Lecture #1 4
Papyrus Making-Peeling
PSE 476: Lecture #1 5
Papyrus Making-Cutting
PSE 476: Lecture #1 6
Papyrus Making-Soaking
PSE 476: Lecture #1 7
Papyrus Making-Rolling
PSE 476: Lecture #1 8
Papyrus Making-Pressing, Drying
PSE 476: Lecture #1 9
Papyrus Making-Final Product
PSE 476: Lecture #1 10
Introduction to Pulping:History of Papermaking
• 200 BC: Parchment» Tanned skin of animals» Today parchment refers to high quality paper from
vegetable fibers
• 105 AD: Paper from plant (mulberry) fibers» Developed by Chinese Emperor by Ts'ai Lun» National secret stolen by Arabs in ~700 AD
• 1796: First continuous paper machine developed near Paris. Fiber source - rags (cotton)
• 200 BC: Parchment» Tanned skin of animals» Today parchment refers to high quality paper from
vegetable fibers
• 105 AD: Paper from plant (mulberry) fibers» Developed by Chinese Emperor by Ts'ai Lun» National secret stolen by Arabs in ~700 AD
• 1796: First continuous paper machine developed near Paris. Fiber source - rags (cotton)
PSE 476: Lecture #1 11
Introduction to Pulping:History of Papermaking
• 1854: Soda pulping process developed in England
• 1840: Groundwood pulping developed in Germany
• 1867: Sulfite (acid) pulping process developed in US
• 1884: Kraft pulping process developed in Germany
• 1854: Soda pulping process developed in England
• 1840: Groundwood pulping developed in Germany
• 1867: Sulfite (acid) pulping process developed in US
• 1884: Kraft pulping process developed in Germany
PSE 476: Lecture #1 12
Introduction to Pulping:Two Ways to Generate Fibers
• Mechanically: “Grind up” raw material (most of the lignin retained).» Newsprint
• Chemically: Dissolve away the lignin» Kraft pulping: NaOH/NaSH (dominant process)» Sulfite: (Sulfur Dioxide/bisulfite/sulfite) (limited number of
mills)» Other: Organosolv, steam explosion, etc (very minor)
• In this class, we are going to discuss the methods and chemistry used in the processes which convert fibrous materials to bleached fibers.
• Mechanically: “Grind up” raw material (most of the lignin retained).» Newsprint
• Chemically: Dissolve away the lignin» Kraft pulping: NaOH/NaSH (dominant process)» Sulfite: (Sulfur Dioxide/bisulfite/sulfite) (limited number of
mills)» Other: Organosolv, steam explosion, etc (very minor)
• In this class, we are going to discuss the methods and chemistry used in the processes which convert fibrous materials to bleached fibers.
PSE 476: Lecture #1 13
Raw Material
• Fibrous material can come in the form of:» Wood (main form in the United States)» Other plant material (straw, reeds, etc)
• Wood» Softwoods & hardwoods» Logs (chipped directly from logs for pulp
production)» Chips (residuals from saw mill operations)
• Fibrous material can come in the form of:» Wood (main form in the United States)» Other plant material (straw, reeds, etc)
• Wood» Softwoods & hardwoods» Logs (chipped directly from logs for pulp
production)» Chips (residuals from saw mill operations)
PSE 476: Lecture #1 14
Regional Affects on Raw Material
For this lecture,we will be lookingat raw material useby these regions.
PSE 476: Lecture #1 15
Raw Material Log/Chip Makeup
Region Roundwood(%)
Residual(%)
Softwood(%)
Hardwood(%)
Totalcords*103
W. 38 62 92.5 7.5 10,420
N.C. 86.5 13.5 28 72 6,715
S. C. 71 29 63 37 39,137
N. E. 78 22 40 60 6,902
S. E. 74 26 73 27 29,387
Region Roundwood(%)
Residual(%)
Softwood(%)
Hardwood(%)
Totalcords*103
W. 38 62 92.5 7.5 10,420
N.C. 86.5 13.5 28 72 6,715
S. C. 71 29 63 37 39,137
N. E. 78 22 40 60 6,902
S. E. 74 26 73 27 29,387
PSE 476: Lecture #1 16
Raw Material Log/Chip Makeup
Roundwoodmaterials * 103M3
(%) Residualmaterials * 103M3
(%)
1953 60,661 92 4,937 8
1996 145,170 71 60,341 29
Softwoodmaterials * 103M3
(%) Hardwoodmaterials * 103M3
(%)
1953 54,006 82 11,592 18
1996 136,072 65 72,439 35
Roundwoodmaterials * 103M3
(%) Residualmaterials * 103M3
(%)
1953 60,661 92 4,937 8
1996 145,170 71 60,341 29
Softwoodmaterials * 103M3
(%) Hardwoodmaterials * 103M3
(%)
1953 54,006 82 11,592 18
1996 136,072 65 72,439 35
PSE 476: Lecture #1 17
Raw Material HandlingPhysical Measurements
• Physical measurements important for:» Determining how much wood is coming into the
mill.» How much wood is being charged into the
digesters.» How much actual wood mass (dry) is being
charged so to get the correct liquor to wood ratio.
• Mills use scales and other devices » Moisture content meters» Laboratory chip screening» Wood species determination
• Physical measurements important for:» Determining how much wood is coming into the
mill.» How much wood is being charged into the
digesters.» How much actual wood mass (dry) is being
charged so to get the correct liquor to wood ratio.
• Mills use scales and other devices » Moisture content meters» Laboratory chip screening» Wood species determination
PSE 476: Lecture #1 18
Raw Material HandlingPhysical Measurements
• Moisture Content - Green (paper industry)» Wet basis, amount of water in wood as a fraction of
wet weight of wood
» Typical MCgr of freshly cut wood = 50% (30-60%)
• Moisture Content - Green (paper industry)» Wet basis, amount of water in wood as a fraction of
wet weight of wood
» Typical MCgr of freshly cut wood = 50% (30-60%)
MC gr =Mass of water in wood
Wet wood mass
• Moisture Content - Oven Dry (wood scientists/foresters)» Oven dry basis
» Typical MCOD of freshly cut wood = 100% (45-150%)
• Moisture Content - Oven Dry (wood scientists/foresters)» Oven dry basis
» Typical MCOD of freshly cut wood = 100% (45-150%)
Mass of water in woodOven dry wood mass
MC OD =
x 100%
x 100%
PSE 476: Lecture #1 19
Raw Material HandlingPhysical Measurements
• Solid Wood Density• Solid Wood Density
» Wood contracts 8-15% on volume basis when it dries below 30% moisture. This needs to be taken into account when determining density.
» Typical units lb/ft3 or kg/m3
» Wood contracts 8-15% on volume basis when it dries below 30% moisture. This needs to be taken into account when determining density.
» Typical units lb/ft3 or kg/m3
Dry weight of woodDensity =
Unit volume of green wood
PSE 476: Lecture #1 20
Raw Material HandlingDebarking and Chipping
• There are many different mechanical systems used to debark and chip wood. We will not cover these in this class. There are plenty of references available for you to read. Important points:» Get all of the bark of the log.» Bark typically used as fuel source.» Chip to a very consistent size.
• There are many different mechanical systems used to debark and chip wood. We will not cover these in this class. There are plenty of references available for you to read. Important points:» Get all of the bark of the log.» Bark typically used as fuel source.» Chip to a very consistent size.
PSE 476: Lecture #1 21
Raw Material HandlingChip Dimensions
• Uniform Chip Size is very important!» Large chips undercook
leaving shives (rejects).» Small chips clog liquor
circulation, use large amount of chemicals, and give a low yield of weak pulp.
» Chip thickness the primary concern.
• Uniform Chip Size is very important!» Large chips undercook
leaving shives (rejects).» Small chips clog liquor
circulation, use large amount of chemicals, and give a low yield of weak pulp.
» Chip thickness the primary concern.
TOP
1/2 to 1” long
Var
iabl
e W
idth
Side
1/8 to 1/4” thick
PSE 476: Lecture #1 22
Raw Material HandlingWood Deterioration
• Wood decay requires moisture and oxygen.» Moisture content > 20% MCOD.
» Remove either and slow/stop degradation.» Sprinkle solid wood (logs) with water to keep
the wood saturated and therefore limit oxygen content.
» Drying wood to <20% MCOD would slow degradation.
- Economically unsound.- Would slow liquor penetration and therefore
pulping.
• Wood decay requires moisture and oxygen.» Moisture content > 20% MCOD.
» Remove either and slow/stop degradation.» Sprinkle solid wood (logs) with water to keep
the wood saturated and therefore limit oxygen content.
» Drying wood to <20% MCOD would slow degradation.
- Economically unsound.- Would slow liquor penetration and therefore
pulping.
PSE 476: Lecture #1 23
Raw Material HandlingChip Pile Degradation
• Conditions that accelerate degradation.
» Tall chip piles » Chip pile compaction» Whole tree chips» Storage of hardwoods (high starch
contents).
• Method to reduce degradation.» FIFO (first in first out)
• Conditions that accelerate degradation.
» Tall chip piles » Chip pile compaction» Whole tree chips» Storage of hardwoods (high starch
contents).
• Method to reduce degradation.» FIFO (first in first out)
PSE 476: Lecture #1 24
Raw Material HandlingDeterioration in Wood Chip Piles
• General rule of thumb:» 1% loss to decay/month.
• Respiration of parechyma cells responsible for heat generation.
• Above 45-55°C, fungal and bacterial degradation stop.
• Chemical autoxidation takes over above 55°C. This results in severe losses during pulping.
• Loss of extractives high during storage.
• General rule of thumb:» 1% loss to decay/month.
• Respiration of parechyma cells responsible for heat generation.
• Above 45-55°C, fungal and bacterial degradation stop.
• Chemical autoxidation takes over above 55°C. This results in severe losses during pulping.
• Loss of extractives high during storage.
PSE 476: Lecture #1 25
Raw Material HandlingDebris
• Debris is not a good thing!• Sources
» Bark, foliage, plastic, metals, dirt, decayed wood
• Problems» Dirt specks, loss of strength, structural
imperfections, wear on equipment.
• Debris is not a good thing!• Sources
» Bark, foliage, plastic, metals, dirt, decayed wood
• Problems» Dirt specks, loss of strength, structural
imperfections, wear on equipment.
PSE 476: Lecture #1 26
Raw Material HandlingScreening
• Most mills use a screening system to achieve relative consistency in chip size.» Overs: Chips which are oversized
or over thick.» Accepts: Chips that are in the
correct size distribution.» Fines: Chips that are too small
(includes sawdust).
• Most mills use a screening system to achieve relative consistency in chip size.» Overs: Chips which are oversized
or over thick.» Accepts: Chips that are in the
correct size distribution.» Fines: Chips that are too small
(includes sawdust).