Chapter 1
Introduction
1.1 General
Refining refers to the mechanical treatment of chemical pulp in preparation for papermaking.
It is an important process for improving pulp properties. In the process of refining, fibers are
trapped in the gaps between bars during bar crossings where they are subjected to cyclic
compression and shear forces which modify the fiber properties. [Heymer, 2002]. The main
target of refining is to modify surface characteristics as well as fiber flexibility in order to
develop stronger and smoother paper with good printing properties,. In addition, sometimes
the purpose is to develop other pulp properties such as absorbency, porosity, or visual
appearance. [Yan Li, 2005].
Low Consistency (LC) refining at 3-5% has many benefits because the pulp suspension acts
as an incompressible fluid and therefore may be pumped through the refiner using an external
pump. This mixture is more homogeneous than pulp at high consistency (30%) and
consequently the refining treatment more uniform. This is evident in the smaller, more
uniform gap between the plates, and more stable refiner power consumption. Another benefit
of LC refining, related to the above, is that the intensity of treatment and pulp throughput are
decoupled, allowing them to be independently controlled and optimized. [Luukkonen, 2011]
The possibility of having an optimum condition for refining intensity arises from the fact that
low intensity refining imposes gentle refining effect, thus flexibilizing fibers through internal
fibrillation without further disrupting the fiber structure, while on the other hand, high
intensity disrupts the fiber structure harshly and creates fibre shortening. However, the
literature on an optimum intensity is inconclusive and occasionally contradictory. .Nazhad et
al (2001) studied the effect of refining of chemical pulp on paper formation. The authors
concluded that fiber shortening caused by refining had strong effect on reducing fiber
flocculation, thus improving formation. The author also discussed the fact that the optimum
refining intensity should vary depending on raw material properties.
The refining process is usually described by two factors, refining intensity and refining
amount. The amount of refining is represented by specific energy. The intensity is
represented in different ways. One approach is by a “machine intensity” (Kerekes 2010). The
most used parameters for this is Specific Edge Load (SEL) (Baker 1995). Modifications of
the specific edge load have been suggested, for example the Modified Edge Load (MEL) by
(Melzer 1995), Specific Surface Load (Lumiainen 1995). Even more complex expressions
1
were developed by (Joris 1995) (Radoslava, Roux et al. 1997)]. Another approach to
characterizing intensity is by a “fibre intensity ”. This is based on energy expended on fibre
rather than by bar crossings as is the case for machine intensities. An example is the C-factor
(Kerekes 1990) which takes into account the properties of the fiber suspension. However,
apart from the SEL, none of the other methods have gained wide acceptance.
Of the simpler models, Lumiainen (1994) studied the refining intensity on the hardwood
pulp. He concluded that the lower the intensity is better for fiber development and gives
lower the energy consumption. Kerekes (2010) compared tensile strength increase for
hardwoods and softwoods using both the SEL and the Specific Intensity from the C-Factor.
He showed that the that SEL had limitations, but for Specific Intensity the data for both
hardwood and softwood fell on one line, and that the optimum SEL’s for each occurred at the
same Specific Intensity. Eileen Joy and Desaeada (2010) concluded the ultra-low intensity
refining plate would have benefits for hardwood chemical pulps because gentle refining
action increased the specific surface area of the fibers by internal fibrillation, leading to
greater strength development. On the other hand, Soupajarviel at, (2009) reported higher
refining intensity results fiber fibrillation (external) while fiber length remained unchanged
by using high intensity dispergator with LC refining.
Koskenhely et al, 2005 compared the fillings in refining of softwood and hardwood pulp
fibers. Their results showed a better dewatering-tensile strength combination when SW was
refined with conical fillings. Also, the reduction in fiber length was inversely proportional to
gap size because fibers are squeezed and crushed between the bars.
Some work suggested that the refiner gap would be better indication of the ‘effective refining
intensity’ than the conventional Specific Edge Load (SEL) and that the power – gap
relationship governs the refining result [Luukkonen, 2011]. Moreover, changes in fiber length
and fiber curl were also controlled by plate gap and can be related to water retention value
(WRV) better than energy and power in refining of chemical pulp. [Mohlin, 2002].
1.2 Objectives of the research
The overall objective of this research is to determine optimum conditions for refining
Northern Bleached Softwood Kraft (NBSK) pulp ensure that Canadian pulp customers are
optimally refining their pulp. The objective is divided into three parts, which are:
1. To compare gap size and SEL for characterizing the refining intensity.
2. To study the effect of refining intensity on internal fibrillation (tensile, tear, water
retention value) and fibre cutting.
2
3. To determine the optimal refining conditions for chemical pulps in terms of maximum
tensile strength at a given specific energy.
1.3 Scope of Study
The scope of this experiment is limited to the pilot scale refiner to achieve the above
objectives. These studies focused on chemical pulp (bleached Softwood Kraft pulp).
3
Chapter 2
Literature Review
2.1 Refining mechanism
The refining mechanism is based on the following picture. It is assumed that the fibers are
captured in the form of fiber flocs and that the effective refining action starts when the fiber
bundle is pressed between the leading edges—the edge-to-edge phase in Figure 2.1. This
phase is followed by and edge-to-edge surface phase, which continues until the leading edges
reach the tailing edges of the opposite bars. The length and the strength of the fiber flocs
depend on the physical dimensions and the bonding ability of various fibers in the mixture.
Figure 2.1: Refining mechanism (Paulapuro et al., 2000)
4
2.2 Refining theories
The utilization of new theories, since 1967, has enabled a better understanding of what
happens inside the refiner, and allowed better means for optimization. Fundamental to all the
theories is the understanding that the refining result is a function of two major factors, among
others:


The amount of applied energy
How is the energy applied
More rigorously, the refining process is a cyclic application of energy to pulp, and therefore it
can be described in terms of number and intensity of impacts on fibres. The product of these
equals specific energy. Only two of these parameters are independent. It is common to only
use specific energy and intensity.
The most commonly used intensity is the Specific Edge Load (SEL).This machine intensity
has provided a significant contribution in the search for an index representing the intensity of
the beating performance, describing the beating absorption by a pulp, at least with respect to
its nature. Although developed empirically, it has been shown by Kerekes & Senger (2006)
to have a rigorous scientific meaning: its is the energy expended per bar crossing per bar
length. This concept has been developed into other refining theories, all involving the
character of the beating action as described by the type (or intensity) of refining, and the
extent of action, which is related to the amount of refining imposed on the fiber flocs.
The goal of refining theory is to predict changes in pulp properties from known refining
conditions and to allow for the comparison of different refining plates, or fillings, under
various operating conditions. There are currently seven main refining theories as shown
below:
2.2.1 Specific Edge Load Theory
The specific edge load theory is the most commonly used and simple theory in practice today.
The characterization of the refining process is given by the specific energy, E (kW*hr/ton),
and the refining intensity parameter, specific edge load (SEL). The SEL is a measure of the
energy expended per bar crossing per bar length, having unit of J/m. Its is obtained form
equation 2.1.
5
SEL 
PNET
P
 NET 
CEL
K p
PNET
Z ri Z si Li 


Eq. 2.1
i
PNET is the net input power (W). The cutting edge length, CEL (m/s), is the product of the
plate factor, Kp (m/rev) and the angular velocity,  (rev/s). Kp is the sum of the product of the
number of bars on the rotor, Zr, the number of the bars on the stator, Zs, and the length of a
bar, L(m), over increments, i, in the refining zone.
2.2.2 Modified Edge Load Theory
The modified edge load theory is an extension of the specific edge load theory that takes into
account additional filling parameters. The characterization of the refining process is given by
E and the refining intensity parameter, modified edge load (MEL), see Equation 2.2:

1
MEL  SEL
 2 tan 

 B  G 

 B 


Eq. 2.2
 is the average bar angle (the angle between the bar and a radial line drawn through the
center of the bar section in degrees), B is the bar width (m) and G is the groove width (m).
Note that the modified edge load theory is an empirically derived theory which accounts for
both operating conditions and filling parameters.
It should be noted that the benefit of the MEL theory is that it allows refining results to be
forecast as a function of freeness at a constant refining intensity is not considered in this
project. The trend of strength development as a function of refining intensity will be the focus
of this analysis.
2.2.3 Specific Surface Load Theory
The specific surface load theory is another extension of the SEL theory that accounts for
additional filling parameters. The refining process is characterized by E and the refining
intensity parameter, specific surface load (SSL). The SSL may be thought of as a measure of
the energy expended per area of bar crossing as its units is J/m2, see Equation 2.3:

W W
r
s
SSL  SEL
 2 cos 

2







Eq. 2.3
6
Wr is the width of the rotor bars (m), Ws is the width of the stator bars (m) and α is the cutting
angle (degrees), defined as twice  . As with the previous two theories, the specific surface
load theory is an empirically derived theory which accounts for both operating conditions and
filling parameters.
2.2.4 C-Factor Theory
The C-Factor theory characterizes the refining process by the refining intensity parameter, I,
and the number of impacts N. These parameters are related to E, PNET, the C-Factor (C), and
the fiber mass flow rate (F) as indicated in Equations 2.4 through 2.6:
E  NI
N
I 

Eq. 2.4
C
F
Eq. 2.5
PNET
C
Eq. 2.6
The C-Factor represents the capacity of refiner to inflict impacts on fibers passing through it
(impacts/s). Note that the C-Factor theory, unlike the other theories considered so far, is
derived from fundamental principles. It accounts for the operating conditions and the filling
parameters, as well as the fiber properties. Equation 2.7 gives C for a disc refiner with a small
gap and the same bar pattern on the rotor and stator.

8 2 GDC F ln 3  1  2 tan   R2  R1
C
3wl  D 
3
3

Eq. 2.7
D is the groove depth (m),  is the density of the pulp suspension (kg/m2), CF is the
consistency of the pulp suspension (fraction), l is the length-weighted average fiber length
(m), n is the bar density or bars per unit arc length (m-1), R2 is the outer radius of the refining
zone (m), R1 is the inner radius of the refining zone (m), and w is the fiber coarseness (kg/m).
Senger (1990) observed that the bar density is not constant across the entire length of the
refining zone due to changes in the bar pattern or large values of bar angle. To alleviate this
impact on the C-Factor, C may be derived in terms of the plate factor, see Equation 2.8:

2 C F   l

C
w
1 l

D


 1

 1  B

G



 cos 2   2 sin  K P





Eq. 2.8
7
Equation 2.9 may be used for either disc refiners. The refining process will be characterized
by the C –Factor theory using E and I.
2.3 Refining chemical pulp
Refining increases ability of fibre to hold water by causing swelling as a result of
delaminating the cell wall. This increases flexibility. Swelling is an indicator of the amount of
delamination. However, swelling and fines retard the drainage of water from the pulp thus
lowering the drainage rate on the former and making it harder to press and dry the wet-web.
The effect of refining on paper properties will depend upon the severity of the mechanical
treatment. Two terms that are used are “cutting” and “brushing”. Cutting refers to shortening
the fiber length of the stock by mechanical action, while brushing refers to internal and
external fibrillation and opening up the secondary wall of the fiber by stock hydration and
increasing the surface area of the pulp. If cutting predominates, the paper will be soft, bulky,
flexible, and dimensionally stable. By contrast, if brushing predominates, the paper will be
strong and stiff. (Genco J.M, 1999)
2.4 Effect of Refining on Fiber Morphology
Wood fibers are the structure material of paper. In order to understand the effects of refining
on paper properties the effects of refining on fiber must be clarified. Wood fiber is made up
of four parts: (W) tubercular core (lumen), (S1,2,3) secondary wall, (P) primary wall and (M)
intermediate lamella (Figure 2.2). (Marko Loijas, 2010)
Figure 2.2 Structure of Nordic softwood tracheids (Marko Loijas, 2010)
The chemical composition of these layers is primary cellulose, hemicelluloses and lignin. The
cellulose and the hemicelluloses molecules are able to form hydrogen bonds with the adjacent
molecules. The fibers of paper are bonded to each other by hydrogen bonds, thus giving the
8
fiber network its strength. Removal of the primary wall and S1 layer can be improves strength
properties of paper. (Marko Loijas, 2010)
The main effects of refining on pulp are internal fibrillation, external fibrillation, creation of
fines and shortening of fibers. The details of these effects are described below.
2.4.1 Internal Fibrillation
The refining chemical pulp increases fiber flexibility because of internal fibrillation. This
occurs from delaminating in the cell wall. Water is drawn into the fiber walls by capillary
forces, causing swelling which is often used as an indicator of degree of refining. The
weakened cell wall is more flexible and collapsible, thereby giving a larger relative bonded
area in paper. This in turn increases bonding and thereby paper strength.
2.4.2 External Fibrillation
External fibrillation is the delamination of fiber surfaces. This can be defined as a peeling off
of fibrils from the fiber surface, while leaving them attached to the fiber surface. It is
emphasized that the fiber surface can be fibrillated even in the early beating stage, and that
the external fibrils serve as bonding agents for inter-fiber bonding. The amount of such
fibrillation (parts of fiber wall still attached to fiber) can be quantified by measuring the
increase in the specific surface of the long fiber fraction
2.4.3 Creation of fines
Fines are produced in refining as a result of fiber shortening or removal of fibrils from fiber
walls. Generated fines consist mostly of fragments of P1 and S1 layers of the fiber wall due
to the abrasion of fibers against each other or against refiner bars. Fines, meaning loose
fibrous material of size less than 0.3 mm, are produced in refining
2.4.4 Shortening of fibers
Refining causes fiber shortening which is generally undesirable in refining. Fiber cutting
which reduce average fiber length and affect paper properties that are related to fiber length,
formation and strength. [Nazhad el at, 2001] In some rare applications it is a desired effect to
improve formation by decreasing the crowding number. (Kerekes, 1995, Nazhad el at. 2001)
2.5 Effect of Refining on Sheet Properties
Refining affects virtually all important sheet properties. Some properties are improved while
others are diminished , so the papermaker is always making judgments as to how much
refining to do. Properties such as paper formation, tensile, burst, fold, smoothness, density,
air resistance, and stiffness are improved, while the pulp drainage rate, porosity, tear (mainly
9
for softwoods), bulk, caliper, and dimensional stability are decreased. The sheet will have a
greater tendency to curl and have a cockled appearance with increased refining. Also, coating
holdout will increase. Thus, the degree of refining is an important wet end operation that the
papermaker must control.
The effect of refining on the properties of the final sheet can be classified into three groups:
(i) strength properties, (ii) sheet formation, and (iii) density-related properties.
2.5.1 Strength properties.
The properties of tensile, burst, and fold strength are improved by refining up to a maximum.
These improvements may be attributed to the increase in the Relative Bonded Area (RBA)
among fibres in paper, due to fibre flexibility and external fibrillation. The increase of these
two fiber properties promotes inter-fiber bonding, which promotes additional hydrogen
bonding between the hydroxyl groups on the cellulose molecules making up the fibrils.
Beyond the maximum, there is no change or a reduction in tensile, burst and folding
strengths. Using burst strength as an example eastern, western, and southern softwood kraft
pulps will all respond to refining differently because of intrinsic morphological differences
and small changes in the chemical composition of the pulp. General classification is difficult
due to the many types of pulp available. Thus, each pulp needs to be tested individually.
Additionally, there is considerable variation in the pulp due to the day-to-day operation of the
pulp mill.
An exception to the aforementioned behavior is the tear strength. The primary effect of
refining on softwood pulps is an initial increase in tear strength, followed by a continuous
reduction of tearing strength with an increasing degree of refining. For hardwood pulps, there
is a small increase and then little change in tear with refining. The tear strength of pulps is
strongly dependent upon the fiber length of the pulp. (Genco J.M, 1999)
2.5.2 Sheet Formation.
The uniformity of fiber distribution in a formed sheet can be improved by refining. This is
because sheet formation is controlled primarily by fiber length; long fibers make it more
difficult to achieve good formation. It should be noted that the maximum strength of a sheet
is attainable only when the sheet has good formation.
2.5.3 Density related properties.
The sheet density increases with refining since it is controlled by fiber flexibility and stock
hydration; more flexible fibers can form a denser sheet. It has been used as a measure of the
extent of refining. Density-related properties such as the bulk (bulk=1/density), porosity,
opacity and dimensional stability are all reduced by refining.
10
Chapter 3
Methodology
3.1 Materials
3.1.1 Pulp
A market softwood bleached kraft pulp from Canfor pulp mill was used in the study. This
softwood is a blend of white spruce (Piceaglauca), lodgepole pine (Pinuscontorta) and alpine
fir (Abieslasiocarpa). This raw material was produced by using kraft pulping process and
modern bleaching and screening systems. Bleaching is done with chlorine dioxide, oxygen
and hydrogen peroxide resulting in environmentally superior enhanced ECF pulps. Length of
average fiber is 2.4 – 2.6 mm.
3.1.3 Equipment
The Low Consistency (LC) refining facility consists of a 16 inch LC refiner, 150HP variable
speed motor, gap sensor and with a wide range of FineBar refiner plate patterns. The refiner
is fed by 2, 4 m3 tanks and a 40kW variable speed pump. It is instrumented with flow,
pressure and temperature and has actuated valves which are computer controlled. The 150
HP, 1800 RPM motor allows a wide range of refining power at different speeds.
Figure 3.1 The UBC – PPC Low consistency refiner and refining facility
11
3.2 Experimental Procedure
This experiment focused on studying the effect of refining intensity on fiber properties. The
properties of the pulp were measured before refining. Properties measured were freeness,
fiber length, paper strength (tensile, tear, density) and water retention value (WRV). The pulp
was refined in the pilot LC refiner at 3.5% consistency and constant flow rate. The refining
temperature was 20-25 ºC. The refining parameters studied were refining plate geometries,
refining speed and bar gap. These measurements were done in order to quantify the refining
intensity.
Plate patterns studied were various bar width, groove width and groove depth as well as bar
angle. The refining speed was 1000, 1200 and 1400 rpm, respectively. Refining conditions
are given in table 3.1 and 3.2. Specific energy and intensity were calculated using measured
data in each condition.
Table 3.1 Summary of the parameters studied in this experiment.
Parameters
Consistency
Plate geometrics
Refiner speed
Flow rates
Gap
Condition
3.5%
Two
1000, 1200, 1400 rpm
200 l/min
Fives
Table 3.2 Refining plate geometries.
No.
1
2
# BarWidth
[mm]
1.6
2.0
GrooveWidth
[mm]
3.2
3.6
GrooveDepth
[mm]
4.8
4.8
Angle
[°]
15
15
BEL
[km/rev]
2.74
2.01
Pilot low consistency (LC) refiner is a part of UBC flow loop system in figure 3.1. The flow
loop consists of two tanks, a centrifugal pump, and a single 16” disc LC refiner. Pulp injected
to LC refiner from a tank and the output ended up in the second tank. This refiner equipped
with magnetic flow meters, pressure sensors, temperature sensors, power meters, plate
position and it is controlled by actuated valves, plate actuation and variable speed drives on
the pump as well as refiner. The refiner is operated and data collected using a LABVIEW™
interface. The procedure to operate LC refiner are as follows:
1. The procedure was started by changing the refiner plate, then pulps were prepared
at 3.5% consistency in tank A and mixed for 4 h.
12
2. To adjust flow rate, the circulation loop of the LC refiner was started. The refiner
speed was adjusted as well, then the refiner gap was changed from 9.0 to 2.5 mm to measure
no-load power.
3. After system recirculation and recording of no- load power, refining process was
started by feeding pulp from tank A to the LC refiner, then collecting it at tank B after
refining. Refiner gap was changed in the process, and the samples were also collected for
further analysis.
4. Refiner speed and refiner plate were changed when the new condition applied.
TankA
TankB
Sample
valve
LabView
LC
refiner
Pump
Figure 3.2 Illustration of the UBC pilot LC refiner loop system used for these trials.
Refined fibers from each condition were characterized in terms of freeness and fiber length.
For fiber strength development, handsheets from refined pulp were formed and tensile
strength, tear strength and density were measured.
Canadian Standard Freeness (CSF) [ml] is a measure of the volume of water collected from a
pulp suspension drained from one exit-nozzle in a specialized dewatering cell. The standard
procedure of measuring pulp drainage is laid out in standard TAPPI T227.
13
The tensile index [Nm/g] is the ratio of the tensile strength per unit width [N/m] of a paper
sheet to its basis weight [g/m2]. The tensile index is a measure of the ultimate strength of
paper. It is normalized to its areal density, opposed to its thickness, as the thickness of the
paper is highly variable. In this case, the roughness elements of paper are the same order of
magnitude as its average thickness. The standard method for this measurement is explained in
TAPPI T494.
Tear index [mNm2/g] is calculated similarly to the tensile index by dividing the measured tear
strength [mN] of the paper sheet normalized by its basis weight [g/m2], TAPPI standard
T414. Higher paper tear strength indicates greater resistant to the propagation of a tear.
Density [g/cm3] calculated from caliper, i.e. thickness [mm], and basis weight [g/m2], TAPPI
standard T500. Paper density is related to the resulting paper quality, and higher bulk is
desired for absorbent papers.
Fiber length is determined by measuring the length of a large number of individual fiber and
then averaging the values either as the arithmetic average fiber length. These measurements
use a Fiber Quality Analyzer (FQA).
Water retention value (WRV) test is water into lumens of fibre that provides the ability of
fibre to take up water and swell. The WRV value equals the ratio of the water mass to the dry
mass. The test is carried out by placing a pad of moist fibers in a centrifuge tube that has a
fritted glass filter at its base. The centrifuge is accelerated at 900g to remove water from the
outside surfaces and lumens of the fiber (a higher force is used according to some European
standards). The remaining water is believed to be associated with submicroscopic pores
within the cell wall. The centrifuged fiber pad is weighed, dried at 105 degrees Centigrade,
and then reweighed.
14
Raw material preparation
(Measure the initial properties: Freeness, Fiber length, tensile
index, tear index and density)
Refining
(Constant: consistency, temperature, flow rate, plate)
(Variable: refiner speed and Gap)
Characterizing
Pulp properties:
(Freeness (CSF), fiber length)
(Make handseets from refined pulp: tensile index, tear index and
density)
Refining energy:
Specific refining energy (SRE), refining intensity
Analyzing
(Gap-power, critical gap on fibre cutting and strength
properties)
Figure 3.3 Experiment chats
15
Figure 3.4 Design of experiment
16
Chapter 4
Result and Discussions
4.1 Refiner performance (Power-Gap relationship)
Refiner performance is commonly characterized by the specific energy and intensity. Both
are affected by the power input to the refiner. This power is controlled by actuating the
plate position to change the gap between the plates. Power increases when the plate gap is
decreased as show in the figure 4.1. The power increases due to fiber trapping on the bar
edge when we close the gap and it requires more power to compress and shear the fiber
network (Bachelor et al, 2006).The interaction of fiber and rapidly rotating bars create a
complex relationship between the operating conditions, design variables of the refiner and
the resulting pulp quality (Olson el, 2012).
Figure 4.1 shows the relationship between power and gap clearance. The trends of the
curves suggest that high refining speed requires high power consumption..
120.00
2.74 km/rev, 1000 rpm
2.74 km/rev, 1200 rpm
2.74 km/rev, 1400 rpm
2.01 km/rev, 1000 rpm
2.01 km/rev, 1200 rpm
2.01 km/rev, 1400 rpm
Total power, kW
100.00
80.00
60.00
40.00
20.00
0.00
0.00
0.50
1.00
1.50
Gap, mm
2.00
2.50
3.00
Figure 4.1 Relationship between total power and gap clearance at low consistency refining
for bleached softwood kraft pulp
17
As the above figure shows the no-load power at gap clearance of 2.5 mm is quite different
from plate to plate, but the dominating factor is the refiner speed. The no-load power of
plates 2.74 and 2.01 are approximately 16.33 and 15.90 kW at1000 rpm, but it increases to
26.64 and 25.11 kW or 42.18 and 34.72 with incremental increase of 200 rpm in refining
speed. The no-load power of high refiner speed is higher because the refiner uses the
motor to drive rotor plate of refiner, so the high rotation speed of refiner needs more power
to operate the motor.
90.00
80.00
y = 58.077e-3.727x
1000 rpm, 2.74 km/rev
y = 76.366e-3.782x
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/revy = 138.27e-3.616x
1000 rpm, 2.01 km/revy = 61.266e-3.654x
1200 rpm, 2.01 km/revy = 68.418e-3.329x
1400 rpm, 2.01 km/revy = 78.701e-3.158x
Power (net), Kw
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
0.00
0.10
0.20
0.30
0.40
Gap, mm
0.50
0.60
0.70
0.80
Figure 4.2 Relationship between net power and gap clearance at low consistency refining
for bleached softwood kraft pulp
Although some works have suggested a possible relationship between power and gap
clearance, yet there is no theory to define the relationship between power and gap
clearance, even though it is very important for understanding the refining function, Gap
clearance controls power, energy as well as intensity in refining. Batchelor and Lundin
(2006) used exponential function to explain the relationship between power and gap
clearance. Our observation (Figure 4.2) supports finding of Batchelor and Lundin (2006)
where the refiner net power was consumed as a function of the refining gap between the
rotor and stator bars, however, the relation could not be used for estimating the refining
intensity.
18
60.00
Power (net), kW
50.00
40.00
30.00
20.00
10.00
0.00
-10.00 0.00
1.00
2.00
3.00
4.00
5.00
6.00
1/Gap, mm-1
1000 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.74 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.74 km/rev
1400 rpm, 2.01 km/rev
Figure 4.3 Relationship between net power and inverse of gap clearance for low
consistency refining of bleached softwood kraft pulp
Figure 4.3 well demonstrates the relationship between plate gap power. Decrease in plate
gap suggests increase in power. Work of Mohlin (2007) and Luukkonen (2010) have also
shown that power is inversely proportional to the gap, G, between the refiners plates, that
is,
. Figure 4.3 also shows the relationship between the net power and inverse of gap
clearance is linear. According to the figure, gap was decreased as the power was increased.
The relationship is strongly affected by refiner speed. The figure also highlights that at a
given gap size, larger power is attained at larger velocities. Similar findings were reported
by Luukkonen (2010). Also, at 1400 rpm of plate 2.74 has more effect on power than 2.01
plate.
.
19
4.50E-05
3.50E-05
Pnet /3
2.50E-05
1.50E-05
5.00E-06
-5.00E-06 0.00
1.00
2.00
3.00
4.00
5.00
6.00
1/Gap, mm-1
1000 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.74 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.74 km/rev
1400 rpm, 2.01 km/rev
Figure 4.4 Relationship between net power/refiner speed^3 and inverse of gap clearance
for low consistency refining of bleached softwood kraft pulp
Luukkonen (2010) have tried to link the intensity to the gap clearance for low consistency
refining (LCR), using the following relation:
SEL, J/m
Figure 4.4 is plotted using Luukkonen (2010) equation for the gap clearances used in
Figure 4.3. As the figure (Fig. 4.4) shows the curves overlapped indicating that
normalizing to refiner speed cubed eliminates power distinctions due to refining speed.
Power normalized to refining speed might be used for estimating refiner gap.
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.00
1.00
2.00
3.00
1/Gap, mm-1
4.00
5.00
6.00
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
Figure 4.5 Relationship between SEL and inverse of gap clearance for low consistency
refining of bleached softwood kraft pulp
20
Figure 4.5 shows the relationship between SEL and 1/Gap. According to the figure, SEL
versus 1/Gap is influenced by refiner speed. SEL increased as the refiner gap was reduced.
SEL increase due to changes in refiner speed is marginal, indicating that the SEL is not a
good predictor of intensity than gap clearance.
4.2 Comparison with a Preliminary Theoretical Model
From a fundamental standpoint, power is linked to gap size through shear on pulp, which
in turn depends on the amount of fibre captured and the nature of compression and shear
imposed during bar crossings. Based on a mechanistic model of this process, Kerekes
(2012) has suggested an approximate form for power, expressed through SEL, as follows:
SEL 
P
 A exp( BG ) (1)
BEL.
We may compare this form to our data examine this by plotting SEL against gap size, G.
This may be done conveniently by a semi-logarithmic plot. To bring the value of the
variables into a convenient range, we multiply both sides of (1) by 100. This gives
ln(100SEL)  ln(100. A)  B.T (2)
6.00
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
5.00
ln(100SEL)
4.00
3.00
2.00
1.00
0.00
0.00
0.50
1.00
1.50
2.00
2.50
3.00
Gap, mm
Figure 4.6 Plot of ln(100SEL) against gap size.
In Fig 4.6, the very large gap size of 2.5 mm is surely in the no-load range.. It gives a
value ln(100SEL)=0, suggesting that SEL=0.01 corresponds to no-load. Extrapolating the
21
data from the smaller gap sizes to ln(100SEL) =0 suggests that a gap size of 1.5 mm and
larger corresponds to no-load.
It is apparent that fit of the form of the theoretical equation to the data is good. This
suggests that an approach based on fundamentals is promising and worthy of further
investigation.
4.3 Critical gap and fiber cutting
Fiber shortening is due to fiber cutting by refiner, so it is important to understand this
results because it is a limitation of LC refiner (Olson, 2003). Figure 4.7 and 4.8 show
fiber length as a function of gap clearance. According to the figure, when the refining gap
was too narrow, then fiber shortening became more severe. At the critical refining gap
(namely at about 0.25-0.45 mm), the fiber length dropped, but the drop was more
significant when refining speed was 1400 rpm. The fibers were fibrillated by refiner when
the refiner gap was wider than critical gap but when the gap size was less than the critical
refining gap, then the fibers were cut by refiner. (Mohlin, 2003)
Figure 4.7 shows that refining speed influences the cutting role of the refiner, specifically
if the gap clearance is less than the critical refining gap. This observation was confirmed
by two different plates having different patterns. For detailed information the reader is
referred to Appendix B.
2.70
Fiber length, mm
2.65
2.60
2.55
1000 rpm, 2.74 km/rev
2.50
1200 rpm, 2.74 km/rev
2.45
1400 rpm, 2.74 km/rev
2.40
0.00
0.25
0.50
0.75
1.00
1.25 1.50
Gap, mm
1.75
2.00
2.25
2.50
2.75
Figure 4.7 Length weighted average fiber length of bleached softwood kraft pulp for
various plate gaps of plate 2.74 BEL using different refiner speed
22
2.70
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
Fiber length (Lw), mm
2.65
2.60
2.55
2.50
2.45
2.40
0.00
2.50
5.00
7.50
10.00
12.50
1/Gap, mm-1
15.00
17.50
20.00
Figure 4.8 Mean length weighted fiber length of bleached softwood kraft pulp for various
inverse of gaps of plate 2.74 BEL using different refiner speed.
4.00E-05
3.50E-05
Power (net)/3
3.00E-05
2.50E-05
2.00E-05
1.50E-05
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1.00E-05
5.00E-06
0.00E+00
0.00
5.00
10.00
1/Gap, 1/mm
15.00
20.00
Figure 4.9 Relationship between net power/refiner speed^3 and inverse of gap clearance at
low consistency refining of bleached softwood kraft pulp
23
Figure 4.9 shows relationship between the power normalized to refiner speed versus the
gaps of two plate patterns. According to the figure, the relationship of the power and
refiner gap clearance was linear prior to critical refining gap, but the trend was changed as
the gap clearance was higher than the critical refining gap. The relationship between the
power (power normalized to the refiner speed) and gap seems to be linear for the gap sizes
of less than the critical refining gap, but it is non-linear when the gap size remains higher
than the critical gap. Beyond the refining critical gap, the power is independent of the gap
clearance, but it depends on the refiner speed. These observations were valid for all the
plates. Olson (2012) hypothesized that the sudden change in slope of the relationship
between power and gap indicates a mechanistic change in energy transfer to the fibres and
may correspond to a reduction of the number of fibres between the bars.
700
600
Freeness, CSF
500
1000 rpm, 2.74 km/rev
400
1200 rpm, 2.74 km/rev
300
1400 rpm, 2.74 km/rev
200
100
0
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
Gap, mm
Figure 4.10 Relationship between freeness and gap clearance at low consistency refining
of bleached softwood kraft pulp
Freeness is one of the refining indicators that estimates drainage ability of fiber after
refining and it is a useful tool for controlling the wet end performance. Figure 4.10 shows
that freeness is dramatically dropped for the gap sizes near or lower than the critical
refining gap. This is due to the fact that the fibers at the smaller gap sizes shortened,
fibrillated and mostly converted into fines, thus reducing the freeness sharply.
24
120.00
Tensile index, kNm/kg
110.00
100.00
90.00
80.00
70.00
1000 rpm, 2.74 km/rev
60.00
1200 rpm, 2.74 km/rev
50.00
1400 rpm, 2.74 km/rev
40.00
0.00
5.00
10.00
1/Gap, mm-1
15.00
20.00
Figure 4.11 Relationship between tensile index and inverse gap clearance at low
consistency refining of bleached softwood kraft pulp
23.00
21.00
1000 rpm, 2.74 km/rev
Tear Index, mNm2/g
19.00
1200 rpm, 2.74 km/rev
17.00
1400 rpm, 2.74 km/rev
15.00
13.00
11.00
9.00
7.00
5.00
0.00
2.50
5.00
7.50
10.00
12.50
1/Gap, mm-1
15.00
17.50
20.00
Figure 4.12 Relationship between tear index and inverse gap clearance at low consistency
refining of bleached softwood kraft pulp
As Figures 4.11 and 4.12 suggests, the paper properties were strongly influenced by
refining gap. The increase in tensile was sharp as well as the changes in tear strength, but
in reverse direction for the gap sizes smaller than the critical refining gap, indicating higher
bonding and lower fiber strength or probably fiber shortening. It should be cautioned that
25
the reduction in tear in the process of refining is barely related to fiber cutting. Therefore,
tear index depend very much on fibre length that it is strongly influenced by cutting. So,
with tear results per se, it could not be concluded that the fiber cutting takes place. In both
cases the changes were minimal for either the tensile strength or tear strength when the gap
size was higher than the critical refining gap. Mohlin (2006) also reported similar results.
These observations suggest that the refining gap is a good indicator of refining intensity.
These conclusions were also supported by Mohlin and Lukkonneen.
4.3 Effect of refining on fiber properties
To understanding of the refining process it is important to evaluate the refining result in
terms of changes in fiber as well as paper properties.
In addition to fiber properties, Mohlin (2002) suggests measure of water retention value
(WRV). WRV is the measure of water holding capacity of fibers, which relates to swelling
capacity of fibers due to fibers internal and external fibrillation. Figure 4.13 shows the
relationship between refining energy and water retention value. It seems refining increases
water holding capacity of fibers, thus bringing about fiber swelling or fiber flexibility.
Increase in WRV also suggests increase in tensile strength (see Figure 4.14). It should be
cautioned that WRV emphasize water holding capacity, which is indirectly proportional to
swelling, or as a consequence fiber flexibility. Water holding capacity suggests water
deposition in fibrillated fibers including both external and internal fibrillation, but swelling
mainly addresses internal fibrillation.
However, tensile strength depends not only to fiber flexibility but also specific bond
strength. Specific bond strength does not originate from swelling or flexibility. Refining
not only strengthens water holding capacity of the fibers but also increases specific
bonding strength of the fibers. Most literature holds that RBA is the main factor and that
specific bond strength change is relatively unimportant. However, some recent work
suggests specific bond strength may be more important than thought, but some of this work
was based on refining recycled paper. Water retention values are also quite different for
different plates indicating the plate pattern effect on fiber properties. WRV of plate 2.74
was very different from the WRV of 2.01 (Figure 4.13).
26
0.80
Water rentention Value, g/g
0.70
0.60
0.50
0.40
1000 rpm, 2.74 km/rev
0.30
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
0.20
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
0.10
1400 rpm,2.01 km/rev
0.00
0
50
100
150
200
SRE, kWh/ton
Figure 4.13 Relationship between water retention value and specific energy at varying
refining speed and plate pattern
0.80
Water rentention Value, g/g
0.70
0.60
0.50
0.40
1000 rpm, 2.74 km/rev
0.30
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
0.20
1000 rpm, 2.01 km/rev
0.10
0.00
40.00
1200 rpm, 2.01 km/rev
1400 rpm,2.01 km/rev
50.00
60.00
70.00
80.00
90.00
100.00
110.00
120.00
Tensile index, mN/g
Figure 4.14 Relationship between water retention value and tensile index at varying
refining speed and plates
27
120.00
Tensile Index, kNm/kg
110.00
100.00
90.00
80.00
70.00
1000 rpm, 2.74 km/rev
60.00
1200 rpm, 2.74 km/rev
50.00
1400 rpm, 2.74 km/rev
40.00
0.00
50.00
100.00
SRE, kwhr/T
150.00
200.00
Figure 4.15 Relationship between tensile index and specific energy at varying refining
speed and plates
120.00
Tensile Index, kNm/kg
100.00
80.00
60.00
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
40.00
20.00
0.00
0.00
50.00
100.00
150.00
200.00
SRE, kwhr/T
Figure 4.16 Relationship between tensile index and specific energy at varying refining
speed and plates
28
Tensile strength development in refining is a good indicator of refining effect. Tensile
strength is sensitive to fiber-to-fiber bonding. Figure 4.15 and 4.16 shows relationship
between tensile strength and specific energy. According to the figures, increase in specific
energy increases tensile strength. Figure 4.15 also suggests that the tensile is higher for
refiner speed of 1000 rpm when compared to the higher refiner speeds for the same
refining plate. Figure 4.17 shows the tensile strength of plate 2.74 BEL is higher than the
tensile strength of plate 2.01 BEL at the same refiner speed. It seems 1000 rpm is an
optimum refining speed for higher tensile strength regardless to plate types.
110.00
Tensile Index, kNm/kg
100.00
90.00
80.00
70.00
60.00
1200 rpm, 2.74 km/rev
50.00
1200 rpm, 2.01 km/rev
40.00
0.00
20.00
40.00
60.00
80.00
SRE, kwhr/T
100.00
120.00
140.00
Figure 4.17 Relationship between tensile index and specific energy at refiner speed of
1200 rpm and varying plates
Figure 4.18 shows relationship between tear index and specific energy at the different
refiner speed and plate. Tear index decreased when specific energy increased due to change
in fiber length, but most probably due to increase in fiber to fiber bonding and weakening
of fiber strength. Fiber length is the more important. It is a common knowledge that to pull
a fiber from the network requires more energy than to break the fiber. Refining weakens
the fibers due to fibrillation, and at the same time increases the bonding potential of the
fibers, thus causing the fibers to break instead of being pulled out from the network. More
likely, even modest fiber shortening is more important. In fact, even after a lot of beating,
fiber strength stays remarkably constant. No correlation was observed between the refining
speed and the tear strength and the tear was higher for 2.01 plate as compared with plate
2.74 (Figure 4.18).
29
25.00
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
Tear Index, mNm2/g
20.00
15.00
10.00
5.00
0.00
0.00
50.00
100.00
SRE, kWhr/T
150.00
200.00
Figure 4.18 Relationship tear index and specific energy at varying refining speed and
plates
0.700
deltaTensile/deltaSRE
0.600
0.7
deltaTensile/deltaSRE
0.6
0.5
0.4
0.500
0.400
deltaTensile/deltaSRE vs Gap
0.300
0.200
0.100
0.000
0.00
0.20
0.40
0.60
0.80
1.00
SEL, J/m
1.20
1.40
1.60
1.80
0.3
0.2
0.1
2.74, 1000 rpm
2.01, 1000 rpm
2.74, 1200 rpm
2.01, 1200 rpm
2.74, 1400 rpm
2.01, 1400 rpm
0 4.19 Slope of tensile index and specific energy for different intensities calculated
Figure
using0.00
the specific0.10
Edge Load
theory 0.30
0.20
0.40
0.50
0.60
0.70
Gap, mm
30
Figure 4.19 is a plot of change in tensile strength increase from unrefined condition
normalized to specific refining energy versus specific edge load (SEL). As the figure
suggests, there is no change in tensile due to increase in SEL. Therefore, at a given
refining energy, the tensile strength remains independent of the SEL. This may suggest
that tensile strength increase in this range is not influenced by SEL.
Tensile index, Nm/g (@100 kWh/ton)
An alternative approach for analyzing these data is to plot increases in tensile strength for
differing intensities at a common specific energy in Fig 4.20. This avoids ambiguities
introduced by the non-linear dependence of tensile strength on energy. It permits direct
comparison of tensile strength to SEL. Such a plot is shown below for a common specific
energy of 100 kWh/ton. This too shows the SEL has no clear influence on tensile strength
increase.
120
100
80
60
40
20
0
0
0.2
0.4
0.6
0.8
S.E.L, J/m
1
1.2
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
1.4
Figure 4.20 Relationship between Tensile index and S.E.L of softwood kraft pulp by using
low consistency refiner compare at 100 kWh/ton
31
0.700
deltaTensile/deltaSRE
0.600
0.500
0.400
deltaTensile/deltaSRE vs Gap
0.7 0.300
deltaTensile/deltaSRE
0.6 0.200
0.5 0.100
0.4
0.3
0.000
0.00
0.10
0.20
0.30
0.40
Gap, mm
0.50
0.60
0.70
0.2
0.1
2.74, 1000 rpm
2.01, 1000 rpm
2.74, 1200 rpm
2.01, 1200 rpm
2.74, 1400 rpm
2.01, 1400 rpm
0
Figure
4.21 Slope
of tensile0.20
index and0.30
specific energy
0.00
0.10
0.40 at different
0.50 intensities
0.60 calculated
0.70
using the Specific Edge Load theory
Gap, mm
Figure 4.21 shows the data for delta tensile/delta energy plotted for different gap sizes.
Here too the data is scattered. However, the graph might be indicates that at gap sizes
between 0.25-0.35 mm the delta tensile/delta SRE at 1000 rpm for plate BEL 2.74 is
maximum. To the left of the critical gap sizes namely gap sizes less than 0.25-0.35, see
also Figure 4.19, the intensity is high, thus fiber cutting takes place, but for the right hand
side of the critical refining gap the refining intensity is insufficient to create permanent
deformations in the fibre cell wall, thus energy is consumed by the elastic deformations
instead. (Luukkonen, 2010)
32
Tensile index, Nm/g (@100 kWh/ton)
-0.05
120
100
80
60
40
20
0
0
0.05
0.1
1000 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1200 rpm, 2.01 km/rev
0.15
Gap, mm
0.2
0.25
0.3
0.35
1200 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
Figure 4.22 Relationship between tensile index and gap size of softwood kraft pulp by
using low consistency refiner compare at 100 kWh/ton
As in the case of SEL, these data may be examined for a constant specific energy of 100
kWh/ton. This is shown in Figure 4.22. This graph shows no apparent influence of gap size
on tensile strength and consequently no optimum. Thus, comparison at a common energy
differs from comparison based on tensile/energy ratio. This suggests that some clarification
is needed on how the influence of gap size should be assessed.
33
Chapter 5
Conclusion
The objective of this study was to investigate the role of low consistency refining on fiber
cutting as well as finding a better method of controlling refining intensity at low
consistency refining. The raw material used for this project was bleached softwood kraft
pulp.
The observations suggested that fiber shortening takes place in low consistency refining
where the raw material for refining is bleached softwood kraft pulp. Fiber cutting occurred
where refining was conducted prior to the region referred as critical gap size. Also, it was
observed in power, tensile index and tear index. The critical gap size for the pulp was in
the range of 0.25 mm to 045 mm for the refining speeds practiced here.
It was observed that where the gap size was smaller than the critical gap size, cutting took
place. The refining speed also accelerated the cutting. If the gap size was higher than the
critical gap size, then no fiber shortening was observed.
It was also speculated that the lower gap sizes (namely lower than the critical gap size)
correspond to higher refining intensity. Most importantly, when the tensile strength of the
refined pulp was judged in relation to specific edge load (SEL) compare with gap size, it
was observed that the SEL is insensitive to tensile variation more than gap size. It was
concluded that the gap size is a better tool for papermakers to control the refining action
than the SEL.
34
Reference
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37
Appendix A
Summarize data
38
Table A1 Summarize refining data from Low consistency refiner of Softwood kraft pulp
using plate 2.74 km/rev
Run
no.
PP-1000-2.5
PP-1000-G1
PP-1000-G2
PP-1000-G3
PP-1000-G4
PP-1200-2.5
PP-1200-G1
PP-1200-G2
PP-1200-G3
PP-1200-G4
PP-1200-G5
PP-1400-2.5
PP-1400-G1
PP-1400-G2
PP-1400-G3
PP-1400-G4
PP-1400-G5
PP-1400-G6
39
Gap
mm
2.49
0.44
0.26
0.20
0.10
2.45
0.48
0.35
0.27
0.18
0.06
2.52
0.76
0.65
0.46
0.42
0.28
0.16
P nolaod
kW
16.33
26.64
42.18
P
total
kW
16.33
28.01
36.19
46.46
56.03
26.64
36.75
49.03
61.71
67.84
77.23
42.18
49.94
54.31
71.88
84.57
94.51
103.39
P net
kw
0.00
11.68
19.86
30.13
39.69
0.00
10.12
22.39
35.08
41.21
50.59
0.00
7.76
12.13
29.71
42.39
52.33
61.21
Refiner
speed
Flow Consist
S.R.E
S.E.L
rpm
ml/min
%
kWh/odt J/m
1016
194
3.57
0.00
0.00
1016
190
3.51
29.13
0.25
1016
188
3.52
49.84
0.43
1017
189
3.43
77.27
0.65
1016
221
3.43
87.21
0.86
1217
191
3.54
0.00
0.00
1216
203
3.36
24.66
0.18
1217
172
3.57
60.80
0.40
1216
209
3.54
79.00
0.63
1216
216
3.59
88.61
0.74
1216
206
3.29
124.42
0.91
1406
208
3.15
0.00
0.00
1406
204
3.36
18.91
0.12
1405
214
3.53
26.84
0.19
1405
187
3.35
78.91
0.46
1406
223
3.51
90.08
0.66
1405
225
3.48
111.39
0.82
1405
177
3.28
175.46
0.95
Table A2 Summarize refining data from Low consistency refiner of Softwood kraft pulp
using plate 2.01 km/rev
Run
no.
2PP-1000-2.5
2PP-1000-G1
2PP-1000-G2
2PP-1000-G3
2PP-1000-G4
2PP-1000-G5
2PP-1000-G6
2PP-1200-2.5
2PP-1200-G1
2PP-1200-G2
2PP-1200-G3
2PP-1200-G4
2PP-1200-G5
2PP-1200-G6
2PP-1400-2.5
2PP-1400-G1
2PP-1400-G2
2PP-1400-G3
2PP-1400-G4
2PP-1400-G5
2PP-1400-G6
2PP-1400-G7
40
Gap
mm
2.48
0.45
0.35
0.24
0.09
0.05
0.03
2.49
0.48
0.34
0.24
0.15
0.09
0.05
2.44
0.58
0.44
0.34
0.20
0.12
0.09
0.07
P noP
laod total
kW
kW
15.90 15.90
25.86
35.29
45.50
57.05
65.54
68.74
25.11 25.11
37.86
48.92
59.00
63.99
73.33
82.84
34.72 34.76
45.78
56.41
65.39
75.24
83.34
94.58
98.79
P net
kw
0.00
9.96
19.39
29.60
41.15
49.64
52.84
0.00
12.75
23.80
33.88
38.88
48.22
57.73
0.00
11.06
21.69
30.67
40.52
48.62
59.86
64.07
Refiner
speed
Flow Consist
S.R.E
rpm
ml/min
%
kWh/odt
1016
216
3.18
0.00
1017
233
3.14
22.61
1016
203
3.35
47.57
1017
199
3.28
75.76
1018
225
3.12
97.74
1017
207
2.99
133.37
1017
231
2.98
128.21
1222
220
3.35
0.00
1222
225
3.25
29.03
1222
235
3.29
51.34
1222
235
3.27
73.45
1223
232
3.16
88.47
1222
222
3.24
111.89
1222
229
3.20
131.70
1412
240
3.26
0.00
1411
235
3.23
24.34
1411
231
3.27
47.80
1411
240
3.23
65.84
1411
246
3.13
87.70
1411
211
3.17
120.80
1412
215
3.06
152.03
1411
231
3.23
143.25
S.E.L
J/m
0.00
0.29
0.57
0.87
1.21
1.46
1.55
0.00
0.31
0.58
0.83
0.95
1.18
1.41
0.00
0.23
0.46
0.65
0.86
1.03
1.27
1.36
Table A3 Summarize fiber properties from Low consistency refiner of Softwood kraft pulp
using plate 2.74 km/rev
Run
Freeness
Fiber length, Lw
Fine
Kink
Curl
WRV
no.
PP-1000-2.5
PP-1000-G1
PP-1000-G2
PP-1000-G3
PP-1000-G4
PP-1200-2.5
PP-1200-G1
PP-1200-G2
PP-1200-G3
PP-1200-G4
PP-1200-G5
PP-1400-2.5
PP-1400-G1
PP-1400-G2
PP-1400-G3
PP-1400-G4
PP-1400-G5
PP-1400-G6
ml csf
656
630
588
527
427
658
620
534
530
454
341
658
634
617
534
442
297
176
mm
2.64
2.65
2.65
2.63
2.62
2.64
2.65
2.65
2.63
2.62
2.60
2.65
2.65
2.65
2.65
2.64
2.60
2.47
%
29.98
31.12
31.82
31.76
32.55
29.88
31.75
32.04
32.02
31.92
32.90
29.97
29.99
29.99
30.99
30.95
33.05
34.65
index
1.47
1.29
1.20
1.17
1.14
1.41
1.23
1.13
1.15
1.18
1.15
1.21
1.07
1.24
1.14
1.16
1.15
1.19
index
0.12
0.11
0.11
0.10
0.10
0.12
0.11
0.44
0.11
0.11
0.10
0.10
0.09
0.11
0.45
0.11
0.11
0.11
g/g
0.43
0.53
0.59
0.67
0.68
0.46
0.52
0.64
0.69
0.71
0.71
0.41
0.47
0.53
0.55
0.57
0.62
0.69
41
Table A4 Summarize fiber properties from Low consistency refiner of Softwood kraft pulp
using plate 2.01 km/rev
Run
no.
2PP-1000-2.5
2PP-1000-G1
2PP-1000-G2
2PP-1000-G3
2PP-1000-G4
2PP-1000-G5
2PP-1000-G6
2PP-1200-2.5
2PP-1200-G1
2PP-1200-G2
2PP-1200-G3
2PP-1200-G4
2PP-1200-G5
2PP-1200-G6
2PP-1400-2.5
2PP-1400-G1
2PP-1400-G2
2PP-1400-G3
2PP-1400-G4
2PP-1400-G5
2PP-1400-G6
2PP-1400-G7
42
Freeness
ml csf
661
643
592
521
420.1
328.9
271.8
662.5
620.4
580.6
525.3
454.3
337.8
258.0
649.9
623.5
592.3
519.0
422.8
323.8
240.6
184.1
Fiber length, Lw
mm
2.64
2.65
2.65
2.62
2.61
2.57
2.50
2.64
2.64
2.64
2.62
2.61
2.57
2.54
2.64
2.67
2.67
2.63
2.63
2.59
2.50
2.44
Fine
%
35.11
33.93
33.17
33.71
33.06
34.88
35.20
34.59
32.58
32.93
33.33
34.18
33.52
34.44
34.85
35.69
35.45
36.05
36.88
37.21
38.27
38.93
Kink
index
1.39
1.31
1.18
1.19
1.16
1.16
1.18
1.45
1.28
1.21
1.19
1.20
1.21
1.22
1.42
1.23
1.16
1.10
1.09
1.14
1.17
1.21
Curl
index
0.12
0.11
0.11
0.11
0.11
0.11
0.11
0.13
0.12
0.12
0.11
0.12
0.12
0.11
0.13
0.12
0.11
0.11
0.11
0.10
0.10
0.11
WRV
g/g
0.38
0.42
0.46
0.51
0.54
0.64
0.68
0.39
0.43
0.46
0.47
0.52
0.53
0.57
0.40
0.44
0.47
0.47
0.55
0.58
0.61
0.64
Table A5 Summarize handsheet properties from Low consistency refiner of Softwood
kraft pulp using plate 2.74 km/rev
43
Run
Tensile
Tear
Density
no.
PP-1000-2.5
PP-1000-G1
PP-1000-G2
PP-1000-G3
PP-1000-G4
PP-1200-2.5
PP-1200-G1
PP-1200-G2
PP-1200-G3
PP-1200-G4
PP-1200-G5
PP-1400-2.5
PP-1400-G1
PP-1400-G2
PP-1400-G3
PP-1400-G4
PP-1400-G5
PP-1400-G6
Nm/g
50.81
66.80
79.65
88.69
96.96
53.16
61.09
81.37
84.31
84.51
98.48
51.21
61.03
65.81
78.84
96.06
100.10
107.80
mNm2/g
19.37
13.86
12.68
11.24
9.56
17.12
13.65
11.63
10.94
10.88
9.67
21.04
17.40
13.86
12.55
10.27
9.57
9.81
g/cm3
0.560
0.595
0.611
0.624
0.643
0.576
0.584
0.549
0.565
0.617
0.593
0.511
0.533
0.511
0.553
0.645
0.648
0.638
Table A6 Summarize handsheet properties from Low consistency refiner of Softwood
kraft pulp using plate 2.01 km/rev
44
Run
Tensile
Tear
Density
no.
2PP-1000-2.5
2PP-1000-G1
2PP-1000-G2
2PP-1000-G3
2PP-1000-G4
2PP-1000-G5
2PP-1000-G6
2PP-1200-2.5
2PP-1200-G1
2PP-1200-G2
2PP-1200-G3
2PP-1200-G4
2PP-1200-G5
2PP-1200-G6
2PP-1400-2.5
2PP-1400-G1
2PP-1400-G2
2PP-1400-G3
2PP-1400-G4
2PP-1400-G5
2PP-1400-G6
2PP-1400-G7
Nm/g
50.80
61.61
77.41
87.81
91.40
99.25
101.87
50.44
57.37
72.03
80.46
86.69
92.98
98.68
50.11
58.81
68.42
78.08
90.18
97.13
100.50
106.10
mNm2/g
20.66
17.60
13.44
12.77
12.11
11.69
10.41
21.51
18.63
16.65
15.44
13.82
12.17
10.66
21.03
18.19
16.31
13.96
12.55
11.48
10.30
10.09
g/cm3
0.56
0.58
0.61
0.62
0.59
0.61
0.61
0.50
0.51
0.54
0.56
0.57
0.59
0.61
0.50
0.51
0.54
0.56
0.58
0.60
0.63
0.62
Appendix B
Fiber cutting and Refiner gap size
45
2.70
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
Fiber length, mm
2.65
2.60
2.55
2.50
2.45
2.40
0.00
5.00
10.00
15.00
20.00
1/G, mm-1
25.00
30.00
35.00
Figure B1 Relationship between Fiber length (lw) and Gap clearance of softwood kraft
pulp by using low consistency refiner
2.70
1000 rpm, 2.01 km/rev
2.65
Fiber length, mm
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
2.60
2.55
2.50
2.45
2.40
0.00
5.00
10.00
15.00
20.00
1/G, mm-1
25.00
30.00
35.00
Figure B2 Relationship between Fiber length (lw) and Gap clearance of softwood kraft
pulp by using low consistency refiner compare at plate 2.01 km/rev
46
2.70
Fiber length, mm
2.65
2.60
2.55
1000 rpm, 2.74 km/rev
2.50
1000 rpm, 2.01 km/rev
2.45
2.40
0.00
0.25
0.50
0.75
1.00
1.25 1.50
Gap, mm
1.75
2.00
2.25
2.50
2.75
Figure B3 Relationship between Fiber length (lw) and Gap clearance of softwood kraft
pulp by using low consistency refiner compare at refiner speed 1000 rpm
2.70
Fiber length, mm
2.65
2.60
2.55
1200 rpm, 2.74 km/rev
2.50
1200 rpm, 2.01 km/rev
2.45
2.40
0.00
0.25
0.50
0.75
1.00
1.25 1.50
Gap, mm
1.75
2.00
2.25
2.50
Figure B4 Relationship between Fiber length (lw) and Gap clearance of softwood kraft
pulp by using low consistency refiner compare at refiner speed 1200 rpm
47
2.75
2.70
Fiber length, mm
2.65
2.60
2.55
1400 rpm, 2.74 km/rev
2.50
1400 rpm, 2.01 km/rev
2.45
2.40
0.00
0.25
0.50
0.75
1.00
1.25 1.50
Gap, mm
1.75
2.00
2.25
2.50
Figure B5 Relationship between Fiber length (lw) and Gap clearance of softwood kraft
pulp by using low consistency refiner compare at refiner speed 1400 rpm
48
2.75
Appendix C
Tensile index and Refiner gap size
49
120.00
Tensile index, kNm/kg
110.00
100.00
90.00
80.00
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
70.00
60.00
50.00
40.00
0.00
5.00
10.00
15.00
20.00
1/Gap, mm-1
25.00
30.00
35.00
Figure C1 Relationship between Tensile index and Gap clearance of softwood kraft pulp
by using low consistency refiner
110.00
Tensile index, kNm/kg
100.00
90.00
80.00
70.00
1000 rpm, 2.74 km/rev
60.00
50.00
1000 rpm, 2.01 km/rev
40.00
0.00
5.00
10.00
15.00
20.00
1/Gap, mm-1
25.00
30.00
35.00
Figure C2 Relationship between Tensile index and Gap clearance of softwood kraft pulp
by using low consistency refiner compare at refiner speed 1000 rpm
50
110.00
Tensile index, kNm/kg
100.00
90.00
80.00
70.00
1200 rpm, 2.74 km/rev
60.00
50.00
1200 rpm, 2.01 km/rev
40.00
0.00
5.00
10.00
15.00
1/Gap, mm-1
20.00
25.00
Figure C3 Relationship between Tensile index and Gap clearance of softwood kraft pulp
by using low consistency refiner compare at refiner speed 1200 rpm
120.00
Tensile index, kNm/kg
110.00
100.00
90.00
80.00
70.00
1400 rpm, 2.74 km/rev
60.00
1400 rpm, 2.01 km/rev
50.00
40.00
0.00
2.00
4.00
6.00
8.00
10.00
-1
1/Gap, mm
12.00
14.00
16.00
Figure C4 Relationship between Tensile index and Gap clearance of softwood kraft pulp
by using low consistency refiner compare at refiner speed 1400 rpm
51
Appendix D
Pulp properties at 100 kWhr/odt
52
Tear index, mNm2/g (@100 kWh/ton)
14
12
10
8
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
6
1400 rpm, 2.74 km/rev
4
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
2
1400 rpm, 2.01 km/rev
0
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Gap, mm
Tear index, mNm2/g (@100 kWh/ton)
Figure D1 Relationship between Tear index and Gap clearance of softwood kraft pulp by
using low consistency refiner compare at 100 kWh/odt
14
12
10
8
6
4
2
0
0
0.2
0.4
0.6
0.8
S.E.L, J/m
1
1.2
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
1.4
Figure D2 Relationship between Tear index and S.E.L of softwood kraft pulp by using low
consistency refiner compare at 100 kWh/odt
53
Fiber length (Lw), mm (@100 kWh/ton)
2.62
2.615
2.61
2.605
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
2.6
1400 rpm, 2.74 km/rev
2.595
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
2.59
1400 rpm, 2.01 km/rev
2.585
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Gap, mm
Fiber length (Lw), mm (@100 kWh/ton)
Figure D3 Relationship between Fiber length and Gap clearance of softwood kraft pulp by
using low consistency refiner compare at 100 kWh/odt
2.62
2.615
2.61
2.605
2.6
2.595
2.59
2.585
0
0.2
0.4
0.6
0.8
S.E.L, J/m
1
1.2
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
1.4
Figure D4 Relationship between Fiber length and SEL of softwood kraft pulp by using
low consistency refiner compare at 100 kWh/odt
54
Freeness, ml CSF (@100 kWh/ton)
450
400
350
300
250
200
150
100
50
0
-0.05
0
0.05
0.1
0.15
0.2
Gap, mm
0.25
0.3
0.35
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
0.4
Figure D5 Relationship between Freeness and Gap clearance of softwood kraft pulp by
using low consistency refiner compare at 100 kWh/odt
Freeness, ml CSF (@100 kWh/ton)
450
400
350
300
250
200
150
100
50
0
0
0.2
0.4
0.6
0.8
S.E.L, J/m
1
1.2
1000 rpm, 2.74 km/rev
1200 rpm, 2.74 km/rev
1400 rpm, 2.74 km/rev
1000 rpm, 2.01 km/rev
1200 rpm, 2.01 km/rev
1400 rpm, 2.01 km/rev
1.4
Figure D6 Relationship between Freeness and SEL of softwood kraft pulp by using low
consistency refiner compare at 100 kWh/odt
55