Slides from Fundamental Research Symposium, Oxford Presentation on Low Consistency Pulp Refining. We present a new method of representing low consistency pulp refining data so that refining operations and limits can be represented with straight lines on a single graph.

1. A new representation for low
consistency refining data
Co-Authors: Ali Elahimehr, Mark Martinez and James Olson
University of British Columbia
1
Dr. Warren Batchelor
Monash University

2. LC refining
Refiner: fibre mechanical treatment
• Strength up
• Porosity lower
• Drainage lower
Basic Principle:
• bar and groove pattern on rotating and
stationary elements
• Disc and conical types

3. Refiner production of MFC
• Refining is not just for papermaking
• Refining now critical as pre/main treatment
for MFC production
3

4. Refiner plates
4
Plate Geometry
4
θ
φ

5. Gap fluid dynamics are complicated
5Wide Gap Closely Spaced Gap

6. Trapping and forces are complicated
6
Illustration of a typical bar-passing event [1]
Pulp Properties
(i.e. Fibre length)
Bar Forces
(i.e. Normal (FN)
and shear (Fs)
forces
Refiner Control Variables
(i.e. rotational speed)
[1] A. Siadat, et al., Proc. Instn Mech. Engrs Vol. 217 Part E: J. Process Mech. Eng., (2003).

7. So we simplify…
• Primary control of refining
– Specific Energy, SEC, from total power, P , idling power, Po,
mass flow rate through refiner, M
– Idling power: - either by running refiner- water only, plates
together, or running refiner with pulp, plates apart
MPPSEC /)( 0−=
Pnet=P-Po

8. Usually with… Specific Edge Load
• Major method of characterising action of refiner
• SEL is usually expressed as Ws/m
• Another measure of intensity (I), use together with specific energy
barsstatorofnumbertheis
barsrotorofnumbertheis
(m)baroneoflength
projectedtheis
speedrefinertheis
);P-(PpowernettheisP
where
2
1
onet
21
n
n
L
nLn
P
SEL net
ω
ω
=

9. Refiner characterisation: C factor
• Refining characterised
by number of impacts
and intensity (energy)
absorbed in each
impact
• Considers most factors
of relevance to refining
outcome but
complicated
impactsimpose
refiner toofcapacity-factor-C
powerNet
refinerthroughrateflowMass
impactperEnergy
ssimpacts/maofNumber
(kWh/t)massEnergy/
C
P
F
P/CI
C/FN
SELI
N
ESEC
NISEC
=
=
∝
==
=
From Kerekes: 1990

10. Property as function of energy consumption for a given
refining intensity.
Issues: Predicting and interpolating between curves can be
tough.
• How do you meet multiple product specifications?
• How do you show refiner operations on this?
Usual method of representing refining data
0
10
20
30
40
50
60
70
80
0 50 100 150 200
Specific energy consumption (SEC ) (kWh/t)
Tensileindex(Nm/g)
SEL=0.5 J/m
SEL=1.5 J/m
SEL=3.0 J/m

11. • Refining should be characterised by force/energy per impact
AND number of impacts
• What if we plot our data with these as our X and Y axes?
• SEL standing in for force/energy..
Kerekes and others
0
0.5
1
1.5
2
2.5
3
3.5
0 50 100 150 200 250 300
(SEC/SEL)/3.6e6 (m/tonne)
SEL(J/m)
20
40
60
80
100
120
140
60 Nm/g

12. • Plot 1/SEL (1/intensity) and SEC/SEL which is
proportional to number of impact
• Lines of constant SRE now are straight
• Interpolating between points from previous graph now
gives correct result: energy required to reach 60 Nm/g is
100 kwh/t independent SEL
OK so turn this around
0
0.5
1
1.5
2
2.5
0 50 100 150 200 250 300
(SEC/SEL)/3.6e6 (m/tonne)
1/SEL(m/J)
60
80
100
120
140
60 Nm/g

13. What are the equations?
13
1
ornet
net
P CEL
SEL
CEL SEL P
ω
ω
=
[closed loop/batch refining]
[continuous flow refining]
F
F net
SEC t CEL
SEL C V
CEL
C Q
ω
ω
=
=

14. Common refining unit operations
• Close or open the plate gap: increase or
decreases, Pnet.
– 1/SEL changes but SEC/SEL is constant.
• Change batch refining time.
– SEC/SEL changes while 1/SEL is constant.
• Change flow rate for continuous refining.
– SEC/SEL changes while 1/SEL is constant.
• Refiner flow limit for continuous refining.
– Fixed value of SEC/SEL, independent of 1/SEL.
• Maximum available net refiner power.
– Fixed value of 1/SEL independent of SEC/SEL.
14

15. • Refiner unit operations plot OK
• Can represent control limits
Cool. How does this look?
0
0.5
1
1.5
2
2.5
0 50 100 150 200 250 300
SEC/SEL/3.6e6 (m/tonne)
1/SEL(J/m)
20
40
60
80
100
120
140
Plate gap increase
Power decrease
Plate gap decrease
Power increase
Power limit
Increase in time
(Batch)
Line of Constant Flow Rate
(Continuous)

16. Comparison with some data
• UBC data on their pilot plant. 3 plates, 3
speeds
Plate Inside/outside
diameter (mm)
Bar width
(mm)
Groove
width (mm)
Groove
depth (mm)
Bar edge
length
(km/rev)
Bar angle
(o)
1 229/406 1 2.4 4.8 5.59 15
2 229/406 1.6 3.2 4.8 2.74 15
3 229/406 3.2 4.8 4.8 0.99 15

17. 17Gap (mm)
0 0.5 1 1.5 2 2.5 3
SEL(J/m)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Plate 1
Plate 2
Plate 3

18. UBC Pilot system
• Flow loop with
– 2x4m3 tanks
– Centrifugal pump
– 16” disk refiner
• Experiments
– 3 plates
– Speeds 800, 1000, 1200 rpm
– 3% solids
– 250 lpm flow rate
18

19. Pulp
• Northern BC, Canada: CTMP
– 390 ml CSF
– Zero debris retained on a 0.15 mm flat screen
– Length weighted fibre length: 1.9 mm.
19

20. What does this look like with freeness?
0 10 20 30 40 50 60 70 80 90
150
200
250
300
350
400
450
SRE
Freeness(ml)

21. Expanding this out: Fibre length data
21
SEC (kWh/t)
0 10 20 30 40 50 60 70 80 90
Lengthweightedfibrelength(mm)
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
Plate 1
Plate 2
Plate 3
Fit 1
Fit 2
Fit 3

22. Freeness data
22
SEC (kWh/t)
0 10 20 30 40 50 60 70 80 90
CSF(ml)
0
50
100
150
200
250
300
350
400
450
Plate 1
Plate 2
Plate 3
Fit 1
Fit 2
Fit 3

23. And converted to ISO property lines
0 50 100 150 200 250 300
0
1
2
3
4
5
SRE/SEL
1/SEL
Freeness=300 ml
TI=39
TI=39 (fall)
Fibre length=1.75 mm

24. That was busy.. Better is..
24
SEC/SEL
0 50 100 150 200 250
1/SEL
0
1
2
3
4
5
6
7
330ml CSF
1.80mm Lw
CSF fit
Fibre length Fit

25. What do the fitting parameters mean?
•
1
𝑆𝑆𝑆𝑆𝑆𝑆
= 𝑝𝑝1
𝑆𝑆𝑆𝑆𝑆𝑆
𝑆𝑆𝑆𝑆𝑆𝑆
+ 𝑝𝑝2
• Reworks to
• 𝑆𝑆𝑆𝑆𝑆𝑆 =
1
𝑝𝑝1
−
𝑝𝑝2
𝑝𝑝1
𝑆𝑆𝑆𝑆𝑆𝑆
•
1
𝑝𝑝1
gives energy consumption in low SEL limit
•
𝑝𝑝2
𝑝𝑝1
gives sensitivity of property to SEL
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26. So what does this all mean?
• New idea: representation of refining space in
independent variables
• Straight lines
– SRE
– Refining operations
– ISO property data sets
• Easy visualisation of the refining space and
optimisation of multiple constraints.
26

27. Thank you
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