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694 33. MISCELLANEOUS TOPICS

than ring deflection as in the Conrad type) to

introduce the balls into the bearing. This permits

the use of the greatest possible number and size of

balls.

This type is capable of carrying very high

radial loads as well as some thrust loads.

Angular contact ball bearings

The most popular type are the single row

bearings; these can carry appreciable thrust load

in one direction combined with a radial load or

without a radial load.

Paired mounting of two or more single row

angular contact ball bearings is commonly used to

accommodate heavier or two—directional thrust

loads and/or radial loads in various combinations.

Tandem mounting is used for heavy unidirectional

thrust loads and duplex mounting (either face-

to—face or back—to—back) for two directional

thrust loading. Special flush ground bearings are

needed for paired mounting to assure either a

predetermined amount of axial internal clearance

or an even load sharing of bearings. Contact

angles of 40° are common except for large bear-

ings (above 110 nmi bore), which often use 37°.

Double row ball bearings

This design is similar to single row ball

bearings. Since they have two rows of balls (and

are wider) they can carry appreciably more radial

load. They are designed with one—piece inner

and outer rings. Most designs have contact angles

that converge outside the bearing to provide

overall application rigidity.

The use of larger and more balls allows for

increased load carrying capacity. Both Conrad

type,

with uninterrupted raceways, and Max type,

with a filling slot, bearings are used. Contact

angles of 0°, 25°, and 30° are available.

Self—aligning ball bearings

Self—aligning bearings

have

two

rows

of balls

and a common spherical raceway in the outer ring,

which provides then with the self—aligning fea-

ture.

Therefore, they are well suited for applica-

tions with misalignment from mounting errors or

shaft deflections. This bearing cannot exert a

bending influence on the shaft, which is important

for applications requiring extreme accuracy at high

speeds. It is recommended for radial loads com-

bined with moderate dual—direction thrust loads.

Bearings in

papermaking

machines (SKF, 1989)

Large paper machines may use as many as

3000 bearings, the majority of which are spherical

roller bearings. Spherical roller bearings are able

to support substantial axial and radial load combi-

nations of the rolls and cylinders used. They

tolerate misalignment of between the shaft and

housing. Bearings should have a rated life of at

least 200,000 hours in the dryer section and

120,000 hours (14 years) in the other sections.

Well—lubricated bearings will show little

signs of wear and corrosion and have lives as long

as new bearings. For sealing, a well greased mul-

ti-stage labyrinth gives good protection when the

housing is exposed to moisture. Bearings in the

wet section are often grease lubricated, and bear-

ings in the other sections are oil lubricated.

High—speed paper machines usually use oil lubri-

cation throughout with a circulating oil system.

33.13 ELECTRIC CIRCUIT SYMBOLS

Table 33-6 gives the meaning of electrical

power symbols.

33.14 ANNOTATED BIBLIOGRAPHY

Water treatment

Aono., BETZ Handbook of Industrial Water

Conditioning, 8th ed., BETZ®, Trevose,

Pennsylvania, 1980, 437 p. with numerous

color plates. This is a good source of infor-

mation on this topic and is often available to

mill personnel on a complimentary basis.

Boiler water treatment and control

A series of six articles on boiler water ap-

peared in Pulp and Paper starting in 1979.

They appeared in consecutive issues from

53(9) to 54(1). These articles were redone

starting in 1990 as follows: 64(7):97-100;

64(8):

130-135;

64(9):237-241; 64(10):138-

142;

64(11):

114-119;

and 65(1):87-91. This

is useful and concise.

Anon., Troubleshooting low or high pH in

boilers that use high purity water, Tappi J.

75(9):275-277(1992). This describes how to

maintain control of pH in boiler water.

Korbas, G. and J.K. Kasper, Water treatment

considerations for pulp and paper mill boil-

ANNOTATED BIBLIOGRAPHY 695

Table 33-6. Electric power symbols.

<it

alarm

(^ ammeter

antenna

ulur autotransformer

•H|I|—

battery

broken delta

t breaker combi-

-r nation starter

if^£&

broken delta with

protective relay

bus

H (- capacitor

/^^ chassis ground

contact set

^ current trans-

H former, single

phase

-=-

control ground

delta-delta

connection

delta winding

thermal overload

relay

instant, over-

current ground

sensor relay

-CCZD-

-mm.

overcurrent

protective relay

locking out

relay

differential

protective relay

diesel engine

diode

connection disk,

round

(crossover)

connection dot,

square

(crossover)

delta-wye

connection

fan

fused combi-

nation starter

fused disconnect

fuse

fused switch

generator

ground sensor

current

transformer

induction motor

inductor

lamp

low voltage

power circuit

breaker

/^ meter

I—I meter switch

molded case

breaker

moderate voltage

circuit breaker

moderate voltage

starter

normally closed

contact

switch,

normally closed

switch, normally

closed, momen-

tary contact

normally open

contactor

switch,

normally open

switch, normally

open momentary

contact

open delta

potential trans-

former, single

phase

potential trans-

former,

3-phase

"=r power ground

full wave rectifier

resistor

iTTT variable resistor

•-* box

rheostat

696 33. MISCELLANEOUS TOPICS

Table 33-6. Electric power symbols (continued).

-Wr

silicon controlled I OO" thermal

rectifier overload switch

speaker

disconnect I /^^/fl^

stabilizers | \JRy

/M^W^ substation ground

synchronous

function box

synchronous

motor

turbine

volts amps

reactive meter

variable resistor

@ surge arrester ( V ) ^^^^ meter

watt hour meter

watt meter

uuuu

wye winding

single winding

transformer

uuuu two winding

crrc\ transformer

u-LLUJjj three winding

nmn nnm transformer

wyw-wye

JL^

connection

•^

zig-zag

connection

zigzag winding

ers,

in TAPPI1989 Environmental Confer-

ence Proceedings, pp 231-237. Feedwater

for steam generation from power boilers must

be very pure so that much less than one ppm

dissolved solids will be found in the steam.

Tolerable levels of contaminants depend on

the nature of the system. Water treatment

methods and water conditioners must be used

so that corrosion can be minimized.

Corrosion

Garner, A., Pulp and Paper Industry, Alloy

Selection, in J.J. McKetta, Encyclopedia of

Chemical Processing and Design, Vol. 33,

Marcel Dekker, New York, 1990. "The

corrosion resistance of recently developed

stainless steels is reviewed with reference to

their performance in pulp mill bleach plants."

This is a listing of many stainless steels

available and their properties.

6. Proceedings of the 7th International Sympo-

sium on Corrosion in the Pulp & Paper

Industry, Orlando, Nov. 16-20, 1992, Tappi

Press.

This is a good resource on general

aspects of corrosion in pulp and paper pro-

cesses. Areas receiving high coverage in this

resource are corrosion aspects of kraft recov-

ery (especially the recovery boiler) and, to a

lesser extent, pulp bleaching. Some particu-

larly useful articles in this resource follow.

Crowe, D.C., Corrosion in acid cleaning

solutions for kraft digesters, pp. 33-39.

Kraft digester material was tested for corro-

sion with the four commonly used acids and

various corrosion inhibitors.

Magar, I.J., Protective coatings for paper

machine wet end service: an update, pp. 173-

180.

Of 42 systems from 14 manufacturers

evaluated in salt fog exposures, the best

system performance was obtained with an

organic zinc primer with an amine adduct—

cured, epoxy topcoat.

Sharp, W.B.A., Overview of recovery boiler

corrosion, pp.

23-31,

with 93 references.

The author divides the recovery boiler into

eight different zones and discusses each zone.

ANNOTATED BffiLIOGRAPHY 697

Reid, J.C. and D.C. Reid, Influence of non-

destructive test procedures on detection of

stress—corrosion cracks, Tappi J. 76(8):70-

85(1993).

Transportation

safety

8. Ainsworth, S.J., Chemical transportation &

distribution, Chem. & Eng. News, 71 (March

8):8-28(1993).

9. Anon., Railroads, chemical industry link up

for safety operations, Purchasing (Mar.

22):29(1990).

10.

Cooke, J.A., Taking safety seriously. Traffic

Management, 31(April):50, 51, 53(1992).

11.

Elmer-Dewitt, P., Death of a river. Time

Mag. 138(July29):24(1991).

12.

Gerhart, C, Heed new rules for hazardous

materials shipping, Alaska Business Monthly

8(June):42-47(1992).

13.

Gordon, J., In search of perfection. Distribu-

tion 89(Sept.):41-43(1990).

14.

Hamilton, D., Hazardous materials haulers

hail rejection of EDI plan. Journal of Com-

merce and

Commercial

(May

26):

11B(1993).

15.

McConville, D.J., Responsible care gains re-

spect. Distribution 91(1):52-55(1992).

16.

Morris, G.D.L. Getting it there, global

transportation

links the

chemical marketplace,

Chemicalweek 146(6, Feb. 14):26-48(1990).

17.

Rotman, D. and Gibson, W.D., The quicken-

ing pace of chemical distribution. Chemical

Week,

144(12, Mar. 22):22-36(1989).

28.

Stitt, W., Keeping highways safe, The Busi-

ness Journal 8(April

8):

12(1991).

Process

simulation

19.

Syberg, O., N.W. Wild, and H.A. Simons,

Ed.,

Introduction

to Process Simulation, 2nd

ed., Tappi Press, Atlanta, 1992. This is the

best available introduction to process simula-

tion in pulp and paper, although shallow.

Superabsorbency

20.

Masuda, P., Trends in the development of

suberabsorbent polymer for diapers, Polym.

Mat. Sci. Eng., 69:484(1993).

Bearings

21.

SKF, SKF Bearings in Papermaking Ma-

chines, SKF, King of Prussia, Pennsylvania,

1989,

44p. This very useful, detailed infor-

mation is published by a major bearing man-

ufacturing company and includes many for-

mulas and calculations.

22.

TIS 420-05, Design guide for the selection of

rolling contact bearings for paper mill ser-

vice,

5p.

23.

TIS 0420-08, Mounting, sealing, lubrication,

and troubleshooting guide for paper mill

rolling contact bearings, 13 p.

APPENDIX

Transportation

Acronyms

DOT U.S. Dept. of Transportation

RSPA Research and Special Programs Admin-

istration of the DOT

ANPRM Advance Notice of Proposed

Rulemaking

CMA Chemical Manufacturers Association

NPRM Notice of Proposed Rulemaking

RPI Railway Progress Institute

hazmat hazardous material

UPDATES AND BIBLIOGRAPHY

This bibliography is not intended to be

comprehensive. It includes selected articles such

as classic studies, comprehensive treatises on

specific topics, and additions and recent updates of

the first 20 chapters from the first edition (which

remain unaltered in the second edition). Articles,

though recent, which are not comprehensive and

do not add new knowledge are not listed. Specific

analytical techniques are listed in the last section.

In some areas where comprehensive sources

are not available, recent articles are listed to point

one in the right direction. Often literature cited

within these recent sources provides additional

useful information. Also, there are numerous

conference proceedings, monographs, bibliogra-

phies,

and other sources not included here. The

author simply cannot obtain all of these materials

for review. Some trends and predictions not

suited for other formal sections of this volimie are

presented here with references.

Additionally, this chapter provides a space

for recent advances in the industry, brief discus-

sions on topics that do not fit in other chapters,

and other housekeeping activities.

34.1 GENERAL PULP AND PAPER

Industry statistics

In 1989 U.S. exports reached a record

17,200,000 t. U.S. imports were 16,000,000 t,

much of which was newsprint from Canada.

McKeever, D.B., The United States Wood—pulp

Industry, Resour. Bull. FPL-RB-18, USDA For.

Ser. (1987) 29 p. This is a useful resource on the

U.S.

pulp and paper industry from 1961 to 1983.

In 1983, 315 woodpulp mills produced 174,000

ton/day (552 ton/day/mill). In 1961, 350 wood

pulp mills produced 90,000 ton/day (256

ton/day/mill). In 1983 the wood source was 38%

softwood roundwood, 22% hardwood roundwood,

and 40% plant by—products. Sulfate pulp ac-

counted for 70% of production. The south pro-

duced 66% of all U.S. pulp. Foreign trade in

woodpulp had never exceeded 10% of domestic

production through 1983. A breakdown of each

U.S.

mill is given.

Knocel, J.A., Am, Papermak,

55(4):

18-19(1992);

59(4):24-25(1996) and McReady, M. PaperAge

108 (3):27,34(March, 1992) list sales and earnings

for U.S. and Canadian pulp and paper companies.

The U.S. (1995) and Canadian (1991) sales are

presented in Table 34-1 for some of the larger

companies.

Table 34-1. Sales of major U.S. and Canadian

(1991) paper companies.

Company

Abitibi-Price

Boise Cascade

Bowater

Can. Pacific For. Prod.

Champion International Corp.

Domtar

Federal Paper Board

Fletcher Challenge Canada

Georgia—Pacific

International Paper

James River

Kimberly-Clark

Louisiana—Pacific

MacMillan Bloedel

Mead

Noranda Forest

Pentair

Potlatch Corp.

Repap Enterprises

Rayonier

Sonoco Products

Stone Container

Temple—Inland

Union Camp

Westvaco

Weyerhaeuser

Willamette Industries

1995 Sales

$Billions

(CAN$) 2.80

5.06

2.00

1.98

6.79

(CAN$) 1.80

1.91

(CAN$) 1.04

14.29

19.80

6.80

13.79

2.84

(CAN$) 2.73

5.18

(CAN$) 4.12

1.65

1.61

(CAN$) 1.07

1.60

2.71

7.35

3.46

4.21

3.27

11.79

3.87

698

GENERAL PULP AND PAPER 699

Pulp manufacturing costs

Fromson, D.A., One and only chance, Paper-

maker 57(11):39, 41, 42(1994). This article gives

a breakdown (fiber, chemicals, energy, labor,

materials) of costs for pulp manufacture in six

countries. Softwood pulp manufacturing costs

totaled $276 (USD) in Chile, $328 in the south-

eastern U.S., $361 in Canada, $422 in New

Zealand and Nordic, $444 in the western U.S.,

and $598 in Japan. Hardwood pulp manufacturing

costs ranged from $217—488; newsprint manufac-

turing ranged from $269—$577.

Chemical usage

Ferguson, K.H., Chemical markets remain stable

as industry activity levels off. Pulp & Paper

70(3):79, 80, 85(Mar., 1996). In 1996, the

annual U.S. consumption of chemicals in the paper

industry is estimated at 557,000 ton of alum at

$120 per ton, 1.2 million tons of calcium carbon-

ate at $100—$200 per ton, 3.5 to 3.8 million tons

of kaolin clay at $32—$65 per ton for filler grades

to more than $160 per ton for the premium coating

grades, 4 to 4.5 million pounds (seems very low)

of modified starch at $0.13—$0.29 per pound (up

to $0.50 per pound for some grades), 1.4 billion

pounds of styrene—butadiene latex for coating

binders at $0.60—$0.70 per pound, and 250,000

tons of titanium dioxide at $0.85—$1.00 per

pound. Other wet—end additives are discussed.

Piccone, J., Prices to increase as demand catches

up with supplies. Pulp Paper Can.

96(1):

18,

19,

22(1995). This is a good analysis of the availabil-

ity and use of chemical raw materials by the

Canadian pulp and paper industry. It shows some

trends: in 1993 this industry used 195,000 t of

CI2,

but in 1994 it was only 157,000 t.

34.2 WOOD

Wood procurement

Slinn, R.J., The impact of industry restructuring

on fiber procurement, J. Forestry (2)17-20(1989).

"The past and present roles of the pulp and paper

sector in wood procurement."

Wood handling

Piggott, H.R. and R.A. Thompson, Drum bark-

ing: key factors for design and performance, Tappi

J. 70(8):37-41(1987). No references.

Wood physics and transport properties

Woods like redwood that have a high level of

water—soluble extractives have a low apparent

value for the FSP; it is believed that these

extractives use some of the sites that water nor-

mally uses. Perhaps this effect is observed in

paper with certain water—soluble materials (like

polymers). On the other hand, hemicellulose has

a high FSP so starch might increase the FSP of

paper. Pulps generally have a slightly lower FSP

than the woods from which they were derived.

Cellulose molecules have an index of refrac-

tion of 1.599 in the axial direction and 1.532 in

the transverse direction. The dielectric constant is

5.7 and the breakdown voltage is 500 kV/cm.

Dunlop, F., U. S. Dept. Ag. Bull. 110 (1912).

The specific heat of wood as 0.266 at 0°C and

0.382 at 100°C for wood with 0% moisture.

A correction for specific heat at 0% mois-

ture,

c^, is calculated from the fractional moisture

content of wood, m, and the specific heat due to

wood—water bound energy, A, as follows:

Specific heat = A + (m + c^l{\ + m)

where at 0.10 water content A varies from 0.02 at

85°F to 0.04 at 140°F and at 0.30 water content

A varies from 0.04 to 0.09 for 85—140°F.

Huang, C—L., Revealing the fibril angle in wood

sections by ultrasonic treatment. Wood and Fiber

Sci. 27(1):49-54(1995).

James, W.L, Y.-H.Yen, and R.J. King, A

microwave method for measuring moisture con-

tent, density, and grain angle of wood, USDA,

For. Ser. Res. Note FPL-0250 (1985), 9 p. The

attenuation, phase shift, and depolarization of a

polarized 4.81 GHz wave transmitted through a

wood specimen can provide estimates of the

moisture content, density, and grain angle of the

specimen.

Jimenez, G, W.T. McKean, and R.R. Gustafson,

Using a kraft pulping model to improve pulp

uniformity, Tappi J. 73(7)173-176(1990). This

article covers diffusion of solutions at high pH

(12—14),

such as in kraft pulping, where swelling

of wood increases the diffusion in the radial and

tangential directions to that approaching the longi-

tudinal direction.

700 34. UPDATES AND BIBLIOGRAPHY

Siau, J.F., Transport Processes in

Wood,

Springer—Verlag, New York, 1984. 245 p. This

is not written for pulp and paper specifically, but

for those needing information on the wood—mois-

ture relationship, transport of fluids in wood (of

use in pulping), capillary and water potential,

thermal conductivity, and moisture movement

under steady—state or unsteady—state conditions,

this is a good starting point.

Stamm, A.J.,

Wood

and

Cellulose

Science,

Ronald

Press Co., New York, 1964. 549 p. This book

might be entitled "The Physical Chemistry of

Wood." It covers microscopy; X—ray structure;

solution properties of lignin, cellulose, and cellu-

lose derivatives; sorption behavior of wood with

water vapor and other gases; surface area and

accessibility; shrinking and swelling of wood and

cellulose in various liquids; mechanical, electrical,

and thermal properties of

wood;

diffusion through

wood; wood drying and preservation; adhesion;

and fiber bonding. Stamm pioneered many aspects

of the physical chemistry of wood.

Steinhagen, H.P., Thermal conductivity properties

of wood, green or dry, from —40° to +100°C: a

literature review, USDA For. Ser. Rep. general

tech. report FPL-9, (1977), 10 p. This work

investigating heat transfer in frozen logs and

includes information on the specific heat of wood

from 0—30% moisture. Values are given in the

USDA reference below.

Stone, J.E., The effective capillary

cross—sectional area of wood as a function of

pH,

Tappi, 40(7):539-541(1957). This classic work

shows (see page 88) that the diffusion of wood in

the radial and tangential direction, while normally

about 20% of that of the longitudinal direction,

begins to increase significantly above pH 12.5 and

increases to 80% of that of the longitudinal direc-

tion at pH above 13.5, typical of kraft pulping.

This is why kraft chips are screened by thickness,

and not size, as the thickness is the limiting factor.

USDA, Agriculture Handbook No. 72, Wood

Handbook, 1986 gives many properties of wood.

The thermal conductivity

{k)

of softwood for con-

struction is about 0.75 Btu-in./(ft^-hr-°F) com-

pared to aluminum at 1500, steel at 310, glass at

concrete at 6, plaster at 5, and glass wool at

0.25.

k in Btu-in./(ft2-hr' °F) perpendicular to the

grain (its about 2 to 2.8 times higher parallel to

the grain) as a

ftmction

of percent moisture content

ovendry basis, M, and specific gravity, S, is:

k « ^(1.39 + 0.028M) + 0.165 M <

2>Q7o

k « 5(1.39 + 0.038M) + 0.165 M > 30%

The coefficient of thermal expansion of

ovendry wood parallel to the grain (a^) is

0.0000017 to 0.0000025 per °F over the tempera-

ture range of —60 to 130°F. For ovendry wood

of specific gravity 0.1 to 0.8:

«r = [(sp. gr) X 18 + 5.5] X

10"^

per °F

«t = [(sp. gr) X 18 + 10.2] X

10-^

per °F

The electrical resistivity of wood varies from

10i4_io^6 ohm—meters when ovendry to 10^—10"^

at the fiber saturation point. Wood is about twice

as conductive in the longitudinal direction as in the

other two directions.

Wahren, D. (Bonano, E.J., Ed.), Paper Tech-

nology, Part 1:

Fundamentals,

Institute of Paper

Chemistry, Appleton, Wisconsin, 1980. pp. 60-96.

The wood—water relationship, especially in regard

to drying paper, capillary action and other forces

that hold paper together during pressing and

drying, and principles of drying are well covered

from the pulp and paper point of view.

Wenzl, H.F.J., The Chemical Technology of

Wood,

Academic Press, New York, 1970, pp.

410-416. The permeability of wood to gases and

liquids is discussed, especially in regard to sulfite

pulping.

34.3 ROUNDWOOD PROPERTIES

Sapwood thickness

Lassen, L.E. and E.A. Okkonen, Sapwood thick-

ness of Douglas—fir and five other western soft-

woods, USDA For. Ser. Res. Pap. FPL 124 (Oct.

1969).

The sapwood thickness was measured on

increment cores at breast height (4.5 ft above the

ground) on the title species. Sapwood thickness,

like any wood property, is highly variable and de-

pends on many factors. Generally, fast—growing

trees have a wider band of sapwood than slow—

ROUNDWOOD PROPERTIES 701

growing trees. Sapwood thickness decreases with

increasing trunk height in some species. Table 34-

2 summarizes the results of this work, but does

not indicate the high variability encountered.

Wood density

The U.S. Forest Products Laboratory has

numerous studies on wood density of trees. For

example, report FPL 176-177 (rev. 1975) is a

survey of wood density and structural properties of

the southern pines. At least several hundred

samples from each species were taken. From

these samples, regression equations have been

developed to predict the average specific gravity of

trees based on the results of increment cores.

34.4 WOOD CHEMISTRY

General wood chemistry

Browning, B.L., Ed., The Chemistry of

Wood,

R.E. Krieger Pub. Co., Huntington, New York,

1975,

689 p. While first published in 1963 by

Interscience, the addendums of each chapter of the

later edition add little. This volume is particularly

useful for detailed chemical compositions of

hemicellulose, lignin, bark, and extractives. The

chemical and physical properties of fibers, cellu-

lose,

and cellulose derivatives are well covered.

Browning, B.L., Methods of Wood Chemistry,

Interscience, New York, 1967. This is an excel-

lent resource for laboratory procedures of wood

chemistry. It is required reading for workers in

this area. Volume I, 384 p.; Volume II, 384 p.

Hon, D. N.—S. and N. Shiraishi, Ed., Wood and

Cellulosic Chemistry, Marcel Dekker, Inc., New

York, 1991, 1020 p. This is an extensive look at

many aspects of wood chemistry. The work is

divided into three sections of approximately equal

length: I. Structure and Chemistry, II. Degrada-

tion, and in. Modification and Utilization. The

areas of fiber chemistry and morphology and the

chemical structure of wood components are

particularly useful.

Wenzl, H.F.J., The

Chemical Technology

of Wood

(translated from the German by Brauns, F.E. and

Brauns, D.A.) Academic Press, New York, 1970,

692 p. This is a fairly practical volume on wood

chemistry including world distributions of forests,

anatomical and physical properties of wood, wood

chemistry, and chemical wood processing includ-

ing pulping, acid hydrolysis, and pyrolysis. There

are about 150 pages each on sulfite and alkaline

pulping chemistry. Each chapter contains 150—

500 references covering the time period of 1945—

1967 and many from the nineteenth century.

Lignin chemistry

Adler, E., Lignin chemistry—past, present and

future. Wood Sci. Technol. 11:169-218(1977).

The article summary is "some pertinent results and

views from the earlier history of lignin chemistry,

pointing to the importance of the arylpropane

skeleton, are outlined. Later development, begin-

ning with the dehydrogenation theory and experi-

mental studies on the dehydrogenation polymeriza-

tion of p—hydroxycinnamyl alcohols, is then re-

viewed. Finally, recent degradative work result-

ing in a detailed picture of lignin structure is dis-

cussed."

Table 34-2. Average sapwood thickness (in.) at 4.5 ft verses species and tree diameter.

Species

Coast Douglas—fir

Interior Douglas—fir

Ponderosa pine

Lodgepole pine

Englemann spruce

Western redcedar

Western larch

0.75

0.55

2.0

1.3

0.9

0.7

- Tree diameter inside bark (i

1.5

1.2

3.0

1.9

1.4

0.8

0.7

1.8

1.4

4.5

2.2

1.7

0.9

0.7

1.9

1.5

5.0

2.5

2.0

1.0

ildlCoy

2.0

1.6

5.0

3.0

2.0

1.1

2.1

1.7

5.0

3.5

2.1

1.1

702 34. UPDATES AND BffiLIOGRAPHY

Sarkanen, K.V. and C. H. Ludwig, Lignins:

Occurrence, Formation, Structure and Reactions,

Wiley—Interscience, New York, 1971, 916 p.

This is a useful work on lignin chemistry.

Carbohydrate

analysis

Bieraiann, CJ. and G.D. McGinnis, Eds., Analy-

sis of

Carbohydrates

GLC and

MS, CRC Press,

Boca Raton, Florida, 1988, 292 p. This book

covers hydrolysis of wood, pulp, and other poly-

saccharides and analysis of carbohydrates by gas-

liquid chromatography and mass spectrometry.

Mineral composition of

wood

and wood ash

The composition of wood ash is relevant to

impurities that might build up in pulping systems

with increasing closure (such as Al, Si, and Ca in

the kraft chemical recovery system) and as a

potential feedstock. Bark is considered to have a

10—fold amount of minerals such as Ca, Si, and

Al compared to wood.

Bailey, J.H.E. and D.W. Reeve, Spatial distribu-

tion of trace elements in black spruce by imaging

microprobe secondary ion mass spectrometry, /.

Pulp Paper

ScL

20(3):J83-J86(1994).

Campbell, A.G., Recycling and disposing of wood

ash,

TappiJ.

73(9):

141-146(1990). In preference

to being put in landfills, wood ash may be used as

a mineral source for agriculture or even as a

source of potash and calcium. The macro— and

microelemental analyses of six wood ashes are in-

cluded. The macro elements are Ca (7.4—

33.1%),

K (1.7-4.2%), Al (1.59-3.2%), Fe

(0.33-2.10), Mg (0.7-2.2%), P (0.3-1.4%),

Mn (0.3-1.3%), and Na (0.2-0.5%). The

composition in wood ash depends on the ashing

procedure as some elements are relatively volatile.

Guyette, R.P., Cutter, B.E., and G.S. Henderson,

Inorganic concentrations in the wood of western

redcedar grown on different sites.

Wood

and

Fiber

ScL

24(2):

133-140(1992).

This includes the

analysis of 30 elements in wood. The mean and

(standard deviation) in ppm for several elements in

sapwood are Ca, 1347 (167); Fe, 2.27 (1.19); K,

478 (135); Mg, 103 (27.6); Mn, 25.7 (28.6);

Na, 16 (13.2); P, 71 (19,5); Si, 23.9 (28.9).

These results with those of Campbell would

indicate that most iron in wood ash comes from

the processing equipment or additives.

Okada, N., et al.. Trace elements in the stem of

trees,

V, Mokuzai Gakkaishi 39(10):1111-

1118(1993); ibid VI

39(10):

1119-1127(1993).

These papers give radial distributions in Japanese

softwoods and hardwoods, respectively. In soft-

woods, alkali metal (group I) concentrations are

generally higher in heartwood than sapwood, but

the opposite is true for Mn and CI. Alkaline earth

(group II) concentrations did not change abruptly

except for Mg. In hardwoods, the elements were

generally of higher concentration in the sapwood

than the heartwood. Concentrations of metals are

typically Ca, 500-2000 ppm; K, 500—2000;

Mg, 50—400 ppm; CI, highly variable by species

from 10—1000 ppm; Mn, highly variable by

species, 0.5—500 ppm; Al, 10—100 ppm.

34.5 RECYCLING AND SECONDARY

FIBER

Progress in

Paper Recycling

Progress in

Paper

Recycling,

Doshi & Asso-

ciates,

Appleton, Wisconsin, published quarterly

since November, 1991, is an excellent resource in

this area. It is up—to—date and practical.

Flotation and washing for deinking

A comparison of flotation and washing

methods for deinking is presented in Table 34-3.

Paper containing water—based flexographic inks

often uses an acid bath for its removal; therefore,

the overall process may be an acid flotation—base

flotation method. In 1994, the global capacity for

flotation deinking was 20 million tons per year,

most of which is for newspapers and magazines.

Newsprint alone (which is essentially unfilled

in the U.S.) must be deinked by washing (and

water—based inks must be absent), but mixtures of

newsprint and magazines (or magazines alone) are

usually deinked by flotation.

Ferguson, L.D., Deinking chemistry (two parts),

TappiJ.

75(7):75-83 and75(8):49-58(1992). This

is a detailed look at deinking chemistry.

Agglomeration

deinking

Olson, C.R., Richmann, S.K., Sutman, F.J.,

Letscher, M.B., Deinking of laser—printed stock

using chemical densificationand forward cleaning,

TappiJ.

76(1):

136-144(1993).

RECYCLING

AND

SECONDARY FIBER 703

Table 34-3. Comparison of washing and flotation methods of deinking paper.

Washing

(like washing machine for clothes)

NaOH: fiber swelling, breaks up esters (e.g., soy

bean oil); coUoidally separates ink from fiber

sodium silicate: "buffer" and sequestering agent to

protect peroxide

hydrogen

peroxide:

prevents mechanical pulps from

yellowing above pH of 10; bleaching

dispersant: sodium salt of stearic acid (i.e., soap;

don't use calcium, just as one avoids hard

water to wash one's body or clothes) or

low—foaming (low number of C atoms in alkyl

chain),

nonionic alkylphenol ethoxylates or

linear alcohol ethoxylates

fillers and fines: largely removed in the process

general notes: emulsion particles of about

^m are

formed; hydrophilic particles more easily

removed; process from 1800s; only small

particles (less than 5 fim) removed; limited to

only a few types of paper; low consistency

with high reject volume using 10,000 or more

gallons of water per ton pulp; long pulping

times;

high brightness; low yield

Chemicals used in one or both processes:

Alkylphenol ethoxylate

CH3(CH2)„(C,H4)(OCH2CH2)„OH

Linear alcohol ethoxylate

CH3(CH2)„(OCH,CH2),OH

Fatty acid soap

CH3(CH2)„COO- Na+

Fatty acid ethoxylate

CH3(CH2)„(CO)(OCH2CH2)„OH

Flotation

NaOH: fiber swelling, breaks up esters (e.g., soy

bean oil); coUoidally separates ink fi:om fiber

sodium silicate: "buffer" and sequestering agent to

protect peroxide

hydrogen

peroxide:

prevents mechanical pulps from

yellowing above a pH of 10; bleaching

collector system: fatty acid

(0.5—5%,

usually 1%)

and calcium (200 ppm) to make fatty acid

water—insoluble, forming large

particles;

non-

polar surfactant, esp. C—9 alkyl phenol; or

large primary alcohol linked to 6—16 mono-

mers of ethylene oxide; the large nonpolar

particles 30—60 /xm adhere to air bubbles

fillers: 8—14% (clay) help process, but only

25—30%

is removed, so often OMG is added

when ONP is treated by flotation but this has

problems (heavy metals that are a disposal

concern, inks that are harder to remove, bale—

to—bale variability in ash composition)

general notes: new method (1960s) from metal ore

technology; required for modern polymeric

inks that do not disperse well; many choices

of paper grade; 1—2% consistency; 3000

gallons of water per ton pulp; low brightness;

high yield

Finely divided solids (fillers, alumina, fines,

and other colloids) contribute to foam problems by

surrounding air bubbles to decrease the surface

tension.

Miscellaneous

notes:

Postdeinking fiber treatment may use dispersion to break large particles into pieces the eye cannot detect

individually, but pulp brightness decreases. Carryover of calcium can cause scaling and corrosion problems,

carryover of surfactants can interfere with the wet end chemistry and surface sizing operations. Combined

flotation/washing systems provide some difficulties because washing requires a good dispersant that would

prevent large particles from forming during flotation. Dispersant collectors called

displectors

have been

developed. These are often ethoxylated derivatives of fatty acids. Mixtures of various surfactants are also

used commercially. If one uses paper machine Whitewater in the secondary fiber plant, alum may help the

ink bind to the fiber.

Effluent must be clarified of the ink so the water can be reused. Two chemical treatments may be used

including a primary flocculent which is a low molecular weight cationic polymer or alum and a secondary

flocculent of high molecular weight anionic polymer. Water soluble flexo inks have a large amount of

dispersant m their formulation and typically high levels of

flocculent

to clarify the water.