PSE Core Concepts Flashcards
When and in what country was paper invented?
105 AD China
What is the technical definition of paper?
A web consisting of cellulose fibers deposited from water suspension and then dried to form inter-hydrogen bonds
How much paper and board does the US manufacture each year?
74 million tons/yr
What % does the US manufacture of the total world production?
19%
How much paper and board is made each year?
400 million tons
What is the per-capita consumption of paper in the US each year, in lbs? How does this compare to China?
US - 500 lb/year
China - 165 lb/yr
What are the three major broad grades of paper? What % does each represent of the total production in the US each year?
Printing/ Writing: 30%
Tissue: 10%
Board: 60%
What is the largest grade of paper produced in the US, by weight?
Uncoated free sheet
What is the largest grade of paperboard produced in the US, by weight?
Containerboard
What is “market pulp”?
Thick sheets of raw fiber sold to mills that have paper machines but not a pulp mill
What is “fluff pulp”?
Long, hammer milled fibers that are used in absorbent consumer products
What are the two types of paperboard that go into a corrugated box?
Linerboard and corrugating medium
Of all the paper and board produced in the US each year, what % comes from recyled paper and board?
37%
What % of all paper and board produced in the US is recovered each year, instead of being sent to the landfill?
67%
Major structures/ areas in wood, if shown a photo of drawing.
Outer bark, inner bark, cambium, sapwood, heartwood, phloem, ray parenchyma, xylem
What function does each section of the tree have?
Outer bark- protect tree
inner bark- conduct sap
cambium- grows to make new fibers
sapwood- conducts water and minerals, stores nutrients
heartwood- support,
phloem- carries and dissolves sugars
ray parenchyma- carry nutrients
What is it in wood that actually ends up in paper?
Fibers
How are hardwoods and softwoods different, physically?
Harwoods cotain vessel elements and have shorter fibers
Softwoods have longer fibers
What different properties do hardwoods and softwoods contribute to a sheet?
Hardwoods create for better smoothness
Softwood fibers are stronger
Why do many trees have light and dark rings?
They indicate different growing seasons, lightrings are spring wood and dark rings are summerwood
What are the three main compounds/ polymers found in wood? What do they look like? What is their funtion? In general, what % by weight of the wood is each?
Cellulose: linear polymer, 50%
Hemi-cellulose: branched polymer, 25%
Lignin: network polymer, 25%
What is paper, chemically?
A biopolymer, cellulose
How many layers does a wood fiber have?
- P, S1, S2, S3
What is the general goal of any pulping process?
Liberate fibers for papermaking
Name the four general/broad categories of pulping used in the paper industry.
Mechanical pulping: no lignin removal, higher yield, low cost, low quality
Semi chemical pulping: some lignin removal
Chemical pulping: total lignin removal, low yield, high cost, high quality
repulping: recycled fibers
What kinds of products is each type of pulping used for? What are the major steps involved in each?
Mechanical pulping: inexpensive printing grades
Semi-chemical: corrugating medium
Chemical: bleached grades
What do the following abbreviations stand for?
SGW, PGW, TMP, CTMP
Stone-ground wood mechanical pulping
Pressurized-ground wood mechanical pulping
Thermomechanical pulping
Chemi-thermomechanical pulping
What are the three main types of chemical pulping process? What major active chemicals are used in each process?
Kraft: NaOH + Na2S
Soda: NaOH
Sulfite: SO2
What one chemical distinguished the kraft process from the soda process?
Na2S
Where does the “kraft” process get its name?
Kraft is german for strong, and the kraft process makes for strong pulps
Why is the kraft process the most predominant chemical pulping process in the world?
Acceptable for all wood species, efficient chemical recovery system, high quality pulp, low cost, comparatively simple
What are the two main ways that a kraft pulping is carried out?
Batch digester or continuous digester
What is “H-Factor”? How is it calculated? How is it used to control a kraft cook?
Time + Temperature
What is “kappa number” what does it measure, and how is it used to control pulping?
Measures the lignin left in pulp after pulping.
What is AA? EA? Sulfidity?
AA: Active Alkali –> NaOH + Na2S
EA: Effective Alkali –> NaOH + 1/2 Na2S
Sulfidity: Ratio of Na2S to AA
What is “brownstock”?
unbleached and uncleaned pulp
What is “black liquor”? Where is it produced? Where is it separated from fibers?
Spent white liquor filled with chemicals and biomass. It is produced in brownstock washing, where the black liquor is separated from the fibers
What is the general goal of any bleaching process, for any pulp type?
Increase brightness
What does D-E-D-E-D bleaching sequence stand for?
Chlorine Dioxide, extraction, etc.
What is ECF bleaching? TCF?
ECF - elementally chlorine free, no ClO2
TCF - totally chlorine free, no chlorine at all
What are the three basic steps involved in the conversion of black liquor to white liquor?
Evaporation, incineration, and recausticizing
What is the job of the recovery boiler?
Combustion of black liquor to make white liquor in the kraft pulping process
Why is evaporation of black liquor done using multiple effects?
Save steam, energy
What is refining? Why is it carried out on papermaking stock? What effect does it have on fibers? On the paper sheet?
Refining improves sheet strength. Pulp fibers cannot deliver enough wet or dry strength to produce a successful sheet in their natural state
What is freeness? What does it measure? How is it used in the paper mill?
How freely water drains from a fiber slurry. This is an indication of the amount of refining via the generation of fines from P and S1 layers
What are the basic categories/types of additives used for papermaking? What is the role of each type?
Retention Aids
Sizing agents
Fillers
Strength Additives
Dyes and Pigments
pH Control Additives
Specialty Additives
Operation Improvement
What is the headbox? What are its roles on the paper machine?
Holds/ delivers stock onto the paper machine wet end
What are the three main forces used to remove water on the paper machine wet end?
Gravity, vacuum, and press
What are the three main types of paper machine wet ends?
Fourdrinier, top-wire former, and gap former
Identify the main features and components of the forming section, the vacuum section and the press section.
What is formation? What affects it?
How the fibers are oriented in the mat, microturbulence improves formation
