PAPERMAKING: FIBERS INTO PAPER

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PAPERMAKINGFIBERS INTO PAPER
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PaperThe Currency of Civilization

• Paper has proven to be invaluable in the
  establishment of an advanced, educated,
  comfortable society of human beings

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Paper and Productivity/Comfort
Gross Domestic Product (GDP) /year
Paper Consumption, lbs/year
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Paper Consumption per capita(pounds per year)
USA -- 700 lbs/year
Europe -- 300 lbs/year
China -- 20 lbs/year
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Significant Developmentsin the History of Paper

• lt 105 AD -- writing done using tablets (clay,
  stone, wood), parchment (animal hides), silk and
  other fabrics, papyrus
• 105 AD -- Tsai Lun, councilor to the Emperor of
  China, makes the first paper out of individual
  fibers produce by beating mulberry bark, rags,
  hemp, and fish nets

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Significant Developmentsin the History of Paper

• China keeps hold of this invention for 600 years
• 750 AD -- first paper made outside of China
• 900 AD -- first paper made in Egypt
• 1309 AD -- first use of paper in England
• At this point, all paper made by hand and all
  books printed by hand

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Significant Developmentsin the History of Paper

• 1450-55 AD -- Gutenburg invents the printing
  press and prints the Bible
• 1487 AD -- almost every country in Europe now
  printing large quantities of books and using more
  paper
• 1495 AD -- first paper mill in England

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Significant Developmentsin the History of Paper

• 1600s - 1700s AD -- increasing literacy and
  industrialization lead to surging demands for
  paper
• 1666 AD -- paper shortage leads to laws in
  England forbidding the burial of the dead in
  cotton and linen shrouds, so that these materials
  may be used for papermaking

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Significant Developmentsin the History of Paper

• 1799 AD -- Louis Robert of France invents the
  first machine capable of forming an endless web
  of paper
• 1803 AD -- first successful paper machine in
  England
• 1807 AD -- Henry and Sealy Fourdrinier purchase
  patent rights....thus the name!

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Significant Developmentsin the History of Paper

• 1810 AD -- Gamble and Donkin perfect machine
  design, including presses and dryers
• 1827 AD -- first paper machine in US (Saugerties,
  NY)
• 1850 AD -- wood discovered to be suitable for
  pulping

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So....How is Paper Made?
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Pulp

• A collection of cellulosic fibers liberated
  during the pulping process

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Paper

• A thin, flexible web consisting of cellulosic
  fibers deposited upon each other and then dried
  to form hydrogen bonding between them

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Papermaking
The process of going from
PULP
to
PAPER
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The Structure of Paper

• Paper is a three-dimensional matrix
• In a typical printing and writing grade, the
  sheet it 7-8 fibers thick
• These fibers are pressed onto each other and
  bonded together

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The Structure of Paper
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Basic Steps in Papermaking

• Step 1 -- suspend pulp fibers in a dilute slurry
  with water, to minimize chances of their running
  into each other and forming tangles (called
  flocs)
• Step 2 -- gently deposit the fibers in a filter
  mat by allowing the slurry to drain through a
  fine-mesh wire keep the slurry agitated to
  insure a random distribution of fibers

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Basic Steps inPapermaking

• Step 3 -- remove the bulk of the water from the
  wet web, taking care not to disturb the
  arrangement of the fibers
• Step 4 -- gently press the wet web to remove more
  water and also to bring the cellulose fibers
  within a few molecules distance from each other

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Basic Steps inPapermaking

• Step 5 -- permit the remaining tiny amount of
  water to evaporate or boil away the sheet has
  now been bonded together

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Cellulose Fibers

• Fibers from plants are made up of cellulose, a
  six-carbon sugar made during photosynthesis
• The surface of this molecule is covered with
  hydrogen (H) and hydroxy (OH) groups

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Structure of Glucose
O
Aldehyde End Group
C H
OH
C
H
H
C
OH
OH
C
H
OH
C
H
Alcohol End Group
CH2OH
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Celluose

• To make fibers, the plant converts the glucose
  molecules into six-membered rings, then
  polymerizes these rings together to form
  celllulose
• Even after this treatment, the cellulose molecule
  surface is still covered with H and OH groups

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Hydrogen Bonds

• Each OH group has a slightly negative charge
• By bonding with a slightly positive H group, each
  OH group becomes more stable
• It can be said that the OH groups are trying to
  be like water and are looking for H groups to do
  so

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Wet Pulp H-Bonds
In wet pulp, the OH groups on the cellulose
chain are associated with H groups on the water
molecules
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Dried Paper H-Bonds
When the final bit of water is removed from
the wet paper sheet, the bonds between cellulose
and water are traded for bonds between OH and H
groups on adjacent cellulose chains
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H-Bonds Are Strong!

• Without any additional glue or resins, the
  cellulosic sheet bonds itself together during
  drying
• A strip of typical printing and writing paper 1
  inch wide, suspended in air by one end, would
  have to more than 6 km long before it would break
  of its own weight!

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The Paper Machine

• Commercially, paper is made in a continuous web
  on the fourdrinier (FOR-DRUH-NEER) paper machine
• This machine converts a flow of dilute pulp
  slurry into a fully-dried web -- at speeds of up
  to 10,000 ft/min (114 miles/hour) !
• Commercial machines up to 400 inches wide

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The Fourdrinier
Headbox
Stock Slurry
Wire
Paper
Water drains through one side of a single wire
Most paper worldwide is made on this type of
machine
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The Paper Machine

• Is made up of sections, to accomplish the tasks
  described earlier
• forming section -- to gently deposit fibers onto
  the moving wire while removing water by gravity
• vacuum section -- to remove the bulk of water in
  the fragile wet web

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The Paper Machine

• press section -- to squeeze more water from the
  sheet and bring the fibers into intimate contact
• dryer section -- uses heat to boil out the
  remaining water in the sheet and cause formation
  of fiber-fiber hydrogen bonds

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Sheet consistency is 3
Sheet consistency is 20
Slurry consistency is 0.5
Headbox -- dilute slurry comes out here
Vacuum dewatering section
Forming section
Endless wire running in loop
Gravity Drainage (84 of water is removed here)
Vacuum suction boxes (14 of water is removed
here)
Press section
Dryer section
Fully-dried sheet
(1.5 of water is removed here)
Steam-heated cylinders
Sheet consistency is 50
Sheet consistency is 95
(0.5 of water is removed here)
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Tasks for thePaper Machine

• Distribute the fibers randomly into a uniform
  sheet
• Remove almost all the water from the sheet in the
  most economical way

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Refining
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Raw Papermaking Fibers

• As liberated during pulping, the fibers are still
  hollow conducting tubes
• This type of structure does not permit maximum
  surface contacting and bonding between fibers

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Tubes Have LimitedSurface Contact
Limited points of contact
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The Purpose of Refining

• If these hollow tubes could be collapsed into
  flat ribbons, the entire surface of the fibers
  would be available for contact and bonding
• Refining is an intense mechanical action which
  collapses the fibers
• It also shreds up (fibrillates) the outside of
  the fibers, exposing even more surface area

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Collapsed fibers
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The Need for Refining

• Strong paper CANNOT be made without refining
• Unrefined pulps make sheets that feel fluffy and
  felt-like -- no strength
• Refined pulps makes sheets with a smooth, strong
  feel and a snap to them

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How is Refining Done?

• In the industry, refining is done by passing the
  pulp slurry between rotating plates covered with
  bars
• The shearing action between the plates causes the
  fibers to flex and release -- after many cycles
  of this action, the fibers collapse

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Refined pulp
Stationary bar-covered plate
Rotating bar-covered plate
Slurry pumped into center of stationary plate
Powerful motor 3000-10,000 HP 1200-3600 rpm
Plate gap less than 1 mm
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How is the pulp made?

• Pulping operations correspond to smelting of
  metal from ores, or to fractionation of petroleum
  products from crude oil.  And downstream
  operations involving the forming of pulp into
  finished paper products are analogous to
  operations like metal forming and finishing. 

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How is the pulp made?
Pulp is made by mechanically or chemically
separating the fibers in wood or other cellulose
materials from nonfibrous material. In the kraft
pulping process, used to make most chemical pulp,
a solution of sodium hydroxide and sodium sulfide
dissolves the nonfibrous materials.
The pulp is then bleached if white paper is being
produced. Several chemicals can be used for
bleaching, including chlorine gas, sodium
hydroxide, calcium hypochlorite. chlorine
dioxide, hydrogen peroxide. and sodium peroxide.
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Environmental considerations
Large volume waste generated by the paper
industry are not often classified as hazardous
under RCRA
Several lower volume hazardous wastes are
generated, including Spent halogenated
solvents used in degreasingCorrosive waste
generated from the use of strong acids and
basesPaint waste containing solvents and paint
waste with heavy metalsInk waste, which can
include solvents, metals, or ignitable
materialsPetroleum distillates from cleanup
operations.
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Liquid effluents pulping liquors bleaching
effluents chlorinated dioxins and furans
chloroform other chlorinated compounds
bleaching alternatives totally chlorine free
(TCF) -- ozone, etc. elemental chlorine free
(ECF) -- chlorine dioxide nonylphenol
ethoxylates (NPE) used as nonionic surfactants
in some papermaking processes break down to
nonylphenol, (NP), a suspected endocrine
disrupter TMDL restrictions discharge color
Environmental considerations
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Environmental considerations

• Air quality
• Hazardous air pollutants (HAPs) and other toxic
  substances, including
• reduced sulfur compounds (hydrogen sulfide,
  mercaptans, and alkyl disulfides)
• VOCs (acetaldehyde, methanol, propionaldehyde,
  methyl ethyl ketone, phenols, terpenes,
  etc.)odor (including sulfides generated during
  chemical recovery of kraft process "black
  liquors")
• acid gases (sulfuric, hydrochloric, hydrofluoric)
  
• emissions from boilers and lime kilns (including
  particulates, and sulfur and nitrogen oxides)

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Solid waste Disposal of reject fiber
"captive" landfills, and associated leachate
Resource consumption Energy Water Forest
sustainability Recycling
Environmental considerations
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Environmental considerations

• Particulate Matter (PM2.5) tiny airborne
  particles - small but deadly in lungs, linked to
  asthma and heart disease.
• Dioxin going into air, land, and water - toxic
  in minute amounts linked to cancer, diabetes,
  learning disabilities, and other illnesses.
• Chlorine/Chlorine Dioxide Gas cause or worsen
  lung disease react to form organochlorines which
  are linked to cancer, hormone problems and
  reproductive ailments.
• Hydrogen Sulphide a gas linked to damage of
  immune systems, respiratory problems and chemical
  sensitivity.
• Formaldehyde and Acetaldehyde hundreds of tonnes
  of these cancer causing by-products are released
  into air and water yearly.

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Environmental considerationsOn the good side
Solid waste (non-hazardous) generation rate 
287 pounds per ton of product (excluding wood
waste burned for energy recovery) Water quality
Wastewater generation rate  12,600 gallons per
ton of production (a 44 reduction since 1975)
Biological oxygen demand (BOD)  2.9 pounds per
ton of production (an 84 decrease since 1975)
Total suspended solids (TSS)  4.2 pounds per
ton of production (a 68 decrease since 1975)
Adsorbable organic halides (AOX)  less than 0.4
kilograms per metric ton of chemically bleached
pulp (a 90 decrease since 1975) Air quality
Sulfur dioxide (SO2)  9 pounds per ton of
production (a 65 decrease since 1980) Nitrogen
oxides (NOx)  6 pounds per ton of production (a
23 decrease since 1980) Total reduced sulfur
(TRS)  0.9 pounds per ton of kraft pulp
production
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PAPERMAKINGFIBERS INTO PAPER
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