Post on 04-Jan-2017
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.