Jaco-Pierre van der Merwe

MSc. Project

2013

Supervisors

Prof. Dr. Reino E. Pulkki Lakehead University (Canada)

Mr. Pierre Ackerman Stellenbosch University

Dr. Dirk Längin Mondi (Forest Re-Engineering Manager)

The impact of mechanical log surface damage on fibre loss and chip

quality when processing Eucalyptus pulpwood using a single-grip

harvester

1

Contents

Objectives, Research Problem and Question

Background

Experimental design and Methodology

Results

Discussion and Conclusion

2

Research problem & Question

Influence of mechanized debarking, log dryness class and log

size on:

Wood chip size distribution

Wood chip bark content values

Fibre loss

How does mechanised debarking of eucalyptus roundwood logs

influence wood chip quality and fibre loss in pulp and paper

manufacturing?

3

Mill value chain

4

?

?

?

Log surface damage

5

Typical wood chip size specifications

Sawdust

< 1/8 " rh

Fines

< 1/4 " rh

Pins

< 1/2 " rh

Accepts

<8mm slot

> 1/2 " rh

Overs

>11/4" rh >8mm slot

6

Fines Pins Accepts Over-

thick Oversize

Relative pulp yield values 0.25 0.50 1.00 0.94 0.92

Pulp Yield % for E. grandis × urophylla (9 years) 12.85 25.70 51.40 48.32 47.29

(True, 2006; McEwan, 2004)

Site information

7

Experimental design 180 Trees harvested (540 logs)

Harvesting treatments (18 with 30 logs per treatment)

Three debarking treatments Mech 1 (3 processor head passes) Mech 2 (5 processor head passes) Motor-manual (control)

Two drying periods One week Two weeks

Three log section classes Base section Middle section Top section

3 × 2 × 3 Factorial design

Degree of confidence 95%

8

Harvesting

9

Marking & Fibre collection– log level

Logs marked after felling (5.5m logs)

Use of timber tags

Numerically sequenced

Complementary data

Tree –DBH, height

Log position – Base, middle, top

Debarking treatment

10

Fibre collection

11

Secondary transport

12

Chipping

13

Wood chip sampling Wood chip samples

Non bias (12 litres) per log – thoroughly mixed wood chips Chip screening and classification

Oversize chips

Over-thick chips

Accept chips

Pins

Fines

Wood chip moisture content calculated

Wood chip purity Bark and knots removed

Expressed as a weight fraction of sampled chips

14

Harvesting residues: Micro CT scanning

15

Physical log properties

16

Wood chip moisture Content %

17

Base Middle Top

Log section:

28

30

32

34

36

38

40

42

44

46

48

50

52

Mois

ture

conte

nt %

(gre

en b

ase)

b

a

c

d

a

e

Drying period: 1 week

Drying period: 2 weeks

• Log drying rates higher with decreasing log size • No significant difference in log MC across debarking treatments

Base Middle Top

Log section:

34

36

38

40

42

44

46

48

50

Mois

ture

conte

nt %

(gre

en b

ase)

a

a a

bc

b b

d

cd

d

Debarking: Manual Debarking: Mechanical (3 pass) Debarking: Mechanical (5 pass)

Wood Chip Purity

18

Bark content %: Treatment

19

Manual Mech. (3 pass) Mech. (5 pass)

Debarking treatment:

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11B

ark

conte

nt

%

a

b

a

• Manually and Five pass mechanically debarked logs produced wood chips with a significantly lower

bark content.

• Wood chip bark contents of 0.3% - 0.5 % allowed (Biermann, 1996)

Wood Chip Uniformity

20

Accepted chips %

21

Manual Mech. (3 pass) Mech. (5 pass)

Debarking treatment:

76.0

76.5

77.0

77.5

78.0

78.5

79.0

79.5

80.0

80.5A

ccepte

d c

hip

s %

2.06 %

0.59 %

Accepted chips %

22

Base Middle Top

Log section:

68

70

72

74

76

78

80

82

84

86A

cce

pte

d c

hip

s %

a

a

b

c

d

e

Drying period: 1 week

Drying period: 2 weeks

• Logs dried for a one week period produced significantly less accept chips

• Accept chip content decreased with decreasing log size

Over-thick chips:

Treatment × Drying period

23

Manual Mech. (3 pass) Mech. (5 pass)

Debarking treatment:

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2O

ve

r-th

ick c

hip

s %

a

b

a

b

a

b

Drying period: 1 week

Drying period: 2 weeks

• Logs dried for a one week period produced significantly less over-thick wood chips

Over-thick chips:

Treatment × Log section

24

Base Middle Top

Log section:

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2O

ver-

thic

k c

hip

s %

ab

a

ac

bc

acd

ab

bd

b

b

Debarking: Manual

Debarking: Mech. (3 pass)

Debarking: Mech. (5 pass)

• Feed roller induced log surface damage had a significant effect on over-thick chip production

Pins:

Treatment×Drying period×Log section

25

Drying period: 1 week

Drying period: 2 weeksManual

Log s

ection:

Base

Mid

dle

Top

6

8

10

12

14

16

18

20

22

24

26

28

Pin

s %

Mech. (3 pass)

Log s

ection:

Base

Mid

dle

Top

Mech. (5 pass)

Log s

ection:

Base

Mid

dle

Top

b

ab

d

b

ab

ac

c

cd

b

ab

a

ac

d

e

f

aca

e

• Logs dried for a one week period produced wood chips with significantly more pins

• Wood chip pin content increased with decreasing log size

• Log surface damage caused greater increases in pin chip production after a one week

drying period

Fines: Treatment × Log section

26

Base Middle Top

Log section:

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0F

ines %

e

a

ab

a

bc

bd

ac

d

f

Debarking: Manual

Debarking: Mech. (3 pass)

Debarking: Mech. (5 pass)

• Manually debarked logs produced wood chips with significantly less fines

• Wood chip fines content increased with decreasing log size

Fines: Drying period × Log section

27

Base Middle Top

Log section:

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0F

ines %

a

b

c

d

e

a

Drying period: one week

Drying period: two weeks

• Logs dried for a one week period produced significantly more wood chip fines

• Wood chip fines content increased with decreasing log size

Feed roller induced fibre loss

28

Wood fibre loss volume:

Per setting (10 trees)

29

Mech. (2 pass) Mech. (4 pass)

Debarking treatment:

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040W

ood v

olu

me loss (

m3)

a

b

Treatment % Treatment % Diff.

Mech. debarked (two pass) 0.83 Mech. debarked (four pass) 1.58 0.75

Wood fibre loss volume: Per ha

30

Mech. (2 pass) Mech. (4 pass)

Debarking treatment:

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

Wood v

olu

me loss p

er

hecta

re (

m3)

a

b

Treatment m3 Treatment m3 Diff.

Mech. debarked (two pass) 2.64 Mech. debarked (four pass) 5.09 2.45

Economic Evaluation

31

Value of recoverable pulp: Debarking

Treatment

32

Manual Mech. (3 pass) Mech. (5 pass)

Debarking treatment:

3610

3620

3630

3640

3650

3660

3670

3680

3690

3700

3710

3720

Valu

e o

f re

cove

rable

pulp

yie

ld (

R/tonne)

R 50.90

R 9.64

Product Pulp price (August 2013)

US Dollar/tonne Rand/tonne

Bleached Eucalyptus Kraft pulp (BEKP) $ 792.00 R 7 989.21

(KSH Consulting, 2013)

Value of recoverable pulp: Drying

Period

33

one week two weeks

Drying period:

3560

3580

3600

3620

3640

3660

3680

3700

3720

3740

3760

Valu

e o

f re

cove

rable

pulp

yie

ld (

R/tonne)

R 137.90

Product Pulp price (August 2013)

US Dollar/tonne Rand/tonne

Bleached Eucalyptus Kraft pulp (BEKP) $ 792.00 R 7 989.21

(KSH Consulting, 2013)

Value of wood fibre lost: Debarking

Treatment (10 trees)

34

Mech. (two pass) Mech. (four pass)

Debarking treatment:

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5V

alu

e o

f harv

esting r

esid

ue

fib

re lost (R

an

d/ten tre

es)

R 3.32

Product Rand/tonne Reference

Eucalyptus pulpwood (green state) R 299.28 FES, 2012

Value of wood fibre lost: Debarking

treatment (1600 trees)

35

Mech. (2 pass) Mech. (4 pass)

Debarking treatment:

200

300

400

500

600

700

800

900

1000

1100

1200V

alu

e o

f harv

esting r

esid

ue

fib

re lost (R

/ha)

R 137.90

Product Rand/tonne Reference

Eucalyptus pulpwood (green state) R 299.28 FES, 2012

Results summary

36

Wood chip uniformity and fibre loss is related to feed roller

induced log surface damage

Log drying period influence wood chip uniformity and pulp

recovery

Wood chip uniformity and pulp recovery decreases with

decreasing log/tree size

Discussion and Conclusion

37

Fewer feed roller passes

Residual bark

Harvesting head calibration

Research into optimum log moisture content

Optimum debarking break point

References

38

Biermann, C.J. 1996. Handbook of pulping and papermaking, 2nd edition. Oxford: Academic Press.

FES, 2012. Detailed Analysis and Cost Benchmark Report for KwaZulu – Natal,2011/2012

KSH Consulting, 2013. Forest Industry News Report.

McEwan, L. 2004. News & Views. Report No.54. NCT Forestry Co-operative Limited, Pietermaritzburg.

True, G.R., 2006. Pins And Fines: a Small Cause of Big Losses, TAPPI Frontline Report.