PSE Core Concepts

Question 1

When and in what country was paper invented?

Answer 1

105 AD China

Question 2

What is the technical definition of paper?

Answer 2

A web consisting of cellulose fibers deposited from water suspension and then dried to form inter-hydrogen bonds

Question 3

How much paper and board does the US manufacture each year?

Answer 3

74 million tons/yr

Question 4

What % does the US manufacture of the total world production?

Answer 4

19%

Question 5

How much paper and board is made each year?

Answer 5

400 million tons

Question 6

What is the per-capita consumption of paper in the US each year, in lbs? How does this compare to China?

Answer 6

US - 500 lb/year
China - 165 lb/yr

Question 7

What are the three major broad grades of paper? What % does each represent of the total production in the US each year?

Answer 7

Printing/ Writing: 30%
Tissue: 10%
Board: 60%

Question 8

What is the largest grade of paper produced in the US, by weight?

Answer 8

Uncoated free sheet

Question 9

What is the largest grade of paperboard produced in the US, by weight?

Answer 9

Containerboard

Question 10

What is “market pulp”?

Answer 10

Thick sheets of raw fiber sold to mills that have paper machines but not a pulp mill

Question 11

What is “fluff pulp”?

Answer 11

Long, hammer milled fibers that are used in absorbent consumer products

Question 12

What are the two types of paperboard that go into a corrugated box?

Answer 12

Linerboard and corrugating medium

Question 13

Of all the paper and board produced in the US each year, what % comes from recyled paper and board?

Answer 13

37%

Question 14

What % of all paper and board produced in the US is recovered each year, instead of being sent to the landfill?

Answer 14

67%

Question 15

Major structures/ areas in wood, if shown a photo of drawing.

Answer 15

Outer bark, inner bark, cambium, sapwood, heartwood, phloem, ray parenchyma, xylem

Question 16

What function does each section of the tree have?

Answer 16

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

Question 17

What is it in wood that actually ends up in paper?

Answer 17

Fibers

Question 18

How are hardwoods and softwoods different, physically?

Answer 18

Harwoods cotain vessel elements and have shorter fibers
Softwoods have longer fibers

Question 19

What different properties do hardwoods and softwoods contribute to a sheet?

Answer 19

Hardwoods create for better smoothness
Softwood fibers are stronger

Question 20

Why do many trees have light and dark rings?

Answer 20

They indicate different growing seasons, lightrings are spring wood and dark rings are summerwood

Question 21

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?

Answer 21

Cellulose: linear polymer, 50%
Hemi-cellulose: branched polymer, 25%
Lignin: network polymer, 25%

Question 22

What is paper, chemically?

Answer 22

A biopolymer, cellulose

Question 23

How many layers does a wood fiber have?

Answer 23

4. P, S1, S2, S3

Question 24

What is the general goal of any pulping process?

Answer 24

Liberate fibers for papermaking

Question 25

Name the four general/broad categories of pulping used in the paper industry.

Answer 25

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

Question 26

What kinds of products is each type of pulping used for? What are the major steps involved in each?

Answer 26

Mechanical pulping: inexpensive printing grades Semi-chemical: corrugating medium Chemical: bleached grades

Question 27

What do the following abbreviations stand for? SGW, PGW, TMP, CTMP

Answer 27

Stone-ground wood mechanical pulping Pressurized-ground wood mechanical pulping Thermomechanical pulping Chemi-thermomechanical pulping

Question 28

What are the three main types of chemical pulping process? What major active chemicals are used in each process?

Answer 28

Kraft: NaOH + Na2S Soda: NaOH Sulfite: SO2

Question 29

What one chemical distinguished the kraft process from the soda process?

Answer 29

Na2S

Question 30

Where does the "kraft" process get its name?

Answer 30

Kraft is german for strong, and the kraft process makes for strong pulps

Question 31

Why is the kraft process the most predominant chemical pulping process in the world?

Answer 31

Acceptable for all wood species, efficient chemical recovery system, high quality pulp, low cost, comparatively simple

Question 32

What are the two main ways that a kraft pulping is carried out?

Answer 32

Batch digester or continuous digester

Question 33

What is "H-Factor"? How is it calculated? How is it used to control a kraft cook?

Answer 33

Time + Temperature

Question 34

What is "kappa number" what does it measure, and how is it used to control pulping?

Answer 34

Measures the lignin left in pulp after pulping.

Question 35

What is AA? EA? Sulfidity?

Answer 35

AA: Active Alkali --> NaOH + Na2S EA: Effective Alkali --> NaOH + 1/2 Na2S Sulfidity: Ratio of Na2S to AA

Question 36

What is "brownstock"?

Answer 36

unbleached and uncleaned pulp

Question 37

What is "black liquor"? Where is it produced? Where is it separated from fibers?

Answer 37

Spent white liquor filled with chemicals and biomass. It is produced in brownstock washing, where the black liquor is separated from the fibers

Question 38

What is the general goal of any bleaching process, for any pulp type?

Answer 38

Increase brightness

Question 39

What does D-E-D-E-D bleaching sequence stand for?

Answer 39

Chlorine Dioxide, extraction, etc.

Question 40

What is ECF bleaching? TCF?

Answer 40

ECF - elementally chlorine free, no ClO2 TCF - totally chlorine free, no chlorine at all

Question 41

What are the three basic steps involved in the conversion of black liquor to white liquor?

Answer 41

Evaporation, incineration, and recausticizing

Question 42

What is the job of the recovery boiler?

Answer 42

Combustion of black liquor to make white liquor in the kraft pulping process

Question 43

Why is evaporation of black liquor done using multiple effects?

Answer 43

Save steam, energy

Question 44

What is refining? Why is it carried out on papermaking stock? What effect does it have on fibers? On the paper sheet?

Answer 44

Refining improves sheet strength. Pulp fibers cannot deliver enough wet or dry strength to produce a successful sheet in their natural state

Question 45

What is freeness? What does it measure? How is it used in the paper mill?

Answer 45

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

Question 46

What are the basic categories/types of additives used for papermaking? What is the role of each type?

Answer 46

Retention Aids Sizing agents Fillers Strength Additives Dyes and Pigments pH Control Additives Specialty Additives Operation Improvement

Question 47

What is the headbox? What are its roles on the paper machine?

Answer 47

Holds/ delivers stock onto the paper machine wet end

Question 48

What are the three main forces used to remove water on the paper machine wet end?

Answer 48

Gravity, vacuum, and press

Question 49

What are the three main types of paper machine wet ends?

Answer 49

Fourdrinier, top-wire former, and gap former

Question 50

Identify the main features and components of the forming section, the vacuum section and the press section.

Question 51

What is formation? What affects it?

Answer 51

How the fibers are oriented in the mat, microturbulence improves formation