Journal of the University ofC.Chemical
Technology I.
and
Metallurgy, 40, 3, 2005, 199-204
Atic, S. Immamoglu,
Valchev
DETERMINATION OF SPECIFIC BEATING ENERGY - APPLIED
ON CERTAIN PULPS IN A VALLEY BEATER
C. Atic1, S. Immamoglu2, I. Valchev3
1
Istanbul University, Faculty of Forestry,
Istanbul - Turkey
2
Kafkas University, Artvin Faculty of Forestry,
Artvin - Turkey
3
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
Received 14 June 2005
Accepted 21 July 2005
ABSTRACT
Beating performance of certain kraft pulps were accurately investigated in a laboratory valley beater device. To
determine beating response of the pulps, empirical specific edge load (SEL) or beating intensity, specific surface load
(SSL) and specific beating energy consumption (SBE) were experimentally found for each kraft pulp. Industrial application of refining or beating theory usually refers to the specification of three parameters: SEL, SSL and SBE, because of the
fact that, beating performance is controlled by these parameters. In order to simulate laboratory beating performance,
where beating is controlled by the time elapsed, and industrial beating performance, it is really necessary to investigate and
control the beating performance of the pulp using the aforementioned parameters. These laboratory results give us firstly,
significant information about the amount of energy and beating intensity necessary to put to the pulp samples to reach
required properties and secondly, information about comparable values for laboratory and industrial application.
Keywords: Beating performance, valley beater, kraft pulp, specific edge load, specific surface load, specific beating
energy.
INTRODUCTION
It would be desirable to make fundamental measurements to obtain basic information about the paper
that could then be used to predict the utility of the paper for any purpose [1]. With the development of industrial paper making during the last century, exigency
for fine determination of properties of utilized materials became unavoidable. Therefore, a number of analytical tests were developed and can be performed on
pulp samples for quality assessment.
Refining plays an important role in stock preparation as well as throughout the complete paper making
process. Next to the raw material selection, it has the
greatest influence on the final product quality [2]. Therefore, one of the important pulp tests tries to determine
the beating response of the pulps. ISO 5264 standard
method describes bench top beating devices used for
beating of small amount of pulp samples. The Valley
beater (ISO 5264-1), the PFI mill (ISO 5264-2) and
the Jokro mill (ISO 5264-3) are most widely used standard devices. These devices have different nature of fi-
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Journal of the University of Chemical Technology and Metallurgy, 40, 3, 2005
bre treatment compared to each other and to industrial
refining applications.
The valley beater is widely used in paper research
laboratories to investigate beating performance of pulp.
In terms of the beating process, this device seems to be
most similar to the industrial applications. In the paper
industry presently beating is controlled by the power
applied to the unit of pulp. Modern refiner control theory
is introduced with the specific refining energy as the
important measure of refining power put into the stock.
The average magnitude of fibre deformation is
directly related to the applied power divided by the product of rotating speed and edge length. This is the basis
of the Specific Edge Load Theory, which was first introduced back in the 1960’s. The calculated variable is
referred to as “refining intensity” or “specific edge load”
(SEL), and is typically expressed in units of watt-seconds per meter (Ws/m) or joule per meter (J m-1) [3, 4].
It is possible to determine refining response of
pulps with measuring of the refining power put in to
the stock in pilot scale refiners [2, 5]. But this is a labour
intensive way that needs expensive and sophisticated
equipments. On the other hand in laboratory cooking
and bleaching research activities, a relatively small
amount of pulp is used, therefore using of laboratory
beating devices is necessary for evaluation and comparison of the results.
The aim of this study is to determine the applicability of the Valley Beater, one of the most widespread
laboratory beating devices, for measuring the power
applied to the pulp. For this purposes beating responses
of some kraft pulp were used.
EXPERIMENTAL
Bleached and unbleached calabrian pine kraft
pulps and bleached eucalypt kraft pulp with air-dried
were suplied by Mopak Pulp and Paper Mill, Dalaman,
Turkey. The kraft pulps were reslushed by tearing the
lap pulp samples into thin pieces of less than 10 cm²
and soaking overnight in distilled water. All beating treatments of pulps were performed with a Valley beater
equipped and calibrated as described in the standard
ISO 5264/1. The initial pulp amount was 360 g of oven
dry pulp and the consistency of the stock in the beater
15.70 ±0.03 g/L. 18 L of water at 20 ±5°C was poured
200
into the Valley beater tube and the beater motor was
driven for approximately 10 min prior to the addition
of pulp. Over a period of 3 to 5 minutes all the pulp
and the water used for soaking were slowly added into
the tube. The total volume of water and pulp in the
beater was set to be 23 ± 0.21 L. Pulp was circulated in
the beater with the bedplate in its lowered (no load)
position until it was completely disintegrated. Beating
was initiated with the weight of 5500 ± 50 g by releasing the lever, and the timer was started when the bedplate bars move up against the bar roll.
As recommended in standard beating schedules,
bleached pine (softwood) and eucalypt kraft pulp (hardwood) samples were taken from the beater and tested at
5, 15, 30, 45 and 60 min intervals and unbleached pine
kraft pulp samples were taken from the beater at 5, 15,
30, 60 and 90 min intervals.
The total motor power (TMP) and no load power
(NLP) in Watts, were measured with an Emta GP22
model wattmeter and the rotational speed of the beater
(RPM) was 509-513 rpm measured with a Line Seiki
TM-4000 model tachometer.
In order to calculate the refining intensity or specific edge load, it is necessary to first determine the
true load or effective power applied (EPA) to the fibers. Because of that, measured no load power was subtracted from the total motor power. The cutting edge
length (CEL) of used the Valley beater is 34.16 m.r-1,
and the beating surface (BS) is 0.135 m² r-1. The specific edge load (SEL) or refining intensity was calculated by the effective power applied (TMP-NLP) divided by the rotating speed and cutting edge length.
SEL = [TMP − NLP] /[CEL × RPM]
(1)
SSL = [TMP − NLP] /[BS × RPM]
(2)
SEL - Specific edge load (J m-1) or (W s m-1)
SSL - Specific surface load (J m-2) or (W s m-2)
The net specific beating energy consumption of
a refiner or refining system determines the amount of
refining that is applied to a pulp in industry. In this
laboratory study, the specific beating energy for each
step was calculated by dividing the effective beating
power by the oven dry fiber mass. It has been indicated
above that, over a beating period, pulp samples were
C. Atic, S. Immamoglu, I. Valchev
Table 1. No load and total motor power applied to the certain pulps.
Beating Amount of
Stage oven dry pulp
Bleached
eucalypt
NLP
TMP
(W)
(W)
845
1005
Bleached
pine
NLP
TMP
(W)
(W)
870
1030
Unbleached
pine
NLP
TMP
(W)
(W)
860
1110
1
(g)
360.0
2
341.2
815
967
845
1007
845
1075
3
322.4
795
941
815
995
820
1040
4
303.6
777
925
790
979
780
1010
5
284.8
755
910
772
962
750
995
taken from the tube at scheduled five intervals and analyzed. Therefore at each step the 18.8 g oven-dry pulp
sample was decreased in the Valley beater tube. The
amount of decrease was taken into consideration when
the specific beating energy (SBE) was calculated for each
step. The total specific beating energy (TSBE) was beating energy that was applied from the beginning of the
beating to a particular beating step expressed as Wh kg-1.
Finally, the beating response (BRp) of a certain pulp was
calculated using Eq. 4
SBEn = [EPA n × BTn ] / FMn
[
]
BRp = SR o n − SR o n−1 / SBE n
(3)
(4)
SBEn - Specific beating energy in the step, Wh kg-1
EPA - Effective power applied (TMP-NLP), W
n - Sample removal step
BTn - Beating time in the step, h
FMn - Oven-dry fibres mass in the step, kg
BRp - Beating response, DSR°/Wh kg-1
Freeness was measured using a Schopper Riegler
devices according to ISO 5267-1 standard method and the
preparation of laboratory sheets for physical tests were
based on ISO 5269-2 standard method. Mass, tensile properties, tearing resistance (Elmendorf method) and burst
strength were measured according to ISO 536, ISO 1924,
ISO 1974 and ISO 2758 standard methods respectively.
This energy produces no measurable change in the properties of the pulp being beaten. No-load power is mostly
dependent on the diameter and rotational speed of the
rotor, stock consistency and amount of pulp being circulated. During the laboratory study all circumstances were
keep constant except pulp amount. As seen in Table 1,
no load and total motor power decreased throughout the
steps due to removal of sample from the tube. In addition, fiber length and bleaching operation notably affected
the no load and total motor power.
To better illustrate the influence of TSBE on
Schopper Riegler values, the results are plotted in
Fig. 1. This figure shows clearly that Schopper Riegler
values increas dramatically at higher TSBE levels. In
order to reach the same SR°, the unbleached pine needs
at least twice hiaher beating energy than that for the
bleached pine. The bleached eucalypt hardwood pulp,
having shorter fibre and fines, behavior is more sensible than that of the softwood pulp. Hence it is reached
50 SR° easily whenjust applying 500 Wh kg-1 SBE.
RESULTS AND DISCUSSION
In a valley beater application, a certain amount of
applied power is consumed for the circulation of the pulp.
Fig. 1. Increase of Schopper-Riegler values with increasing beating
energy.
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Journal of the University of Chemical Technology and Metallurgy, 40, 3, 2005
Fig. 2 illustrates beating responses of pulp with beating time. Delta SR° values, for applied Wh per kg pulp of
bleached and unbleached pine pulps, increase gradually up
to some point. Maximum level was attained at stage 3 then
dropped at final stage. Eucalypt pulp indicates the similar
trend throughout the stages with slight increases.
In industry, beating or refining is controlled by
the beating intensity and randomly by SSL. The nature
of the fiber treatment in a valley beater device for laboratory studies is very different compared to industrial
refining, and in admitted standard, beating is controlled
by the time elapsed. Hence, it is not possible to directly
compare the results of a laboratory test to the results of
on industrial one. In order to simulate a valley beater
to the industrial application, SEL or beating intensity
and SSL plotted against beating time is shown in figure 3. In industrial applications, the net specific en-
Fig. 2. Beating responses of pulps according beating time.
Fig. 3. Beating intensity changes during beating.
202
Fig. 4. Tensile strength conversions according to applied SBE.
ergy of kraft pulp for 1 pass is about 40-80 Wh kg -1
for hardwood and 60-600 Wh kg-1 for softwood, and SEL of kraft pulp is 0.4-1.5 J m-1
for hardwood and 2.0-6.0 J m-1 for softwood,
and SSL of kraft pulp is 200-500 J m-² for
hardwood and 500-1000 J m-² for softwood
[6].
With increasing beating time, the specific edge load of unbleached pine pulp decreases up to stage 3, then gradually increases
at the final stage. There is notably a distinction between unbleached and bleached pine
specific edge load. In the light of these results, control of beating in the valley beater
can be easily made by specific edge load or
specific surface load.
Fig. 4 shows the results of tensile index as a function of the total specific beating energy. The tensile strength development
of softwood fibres increases rapidly from the
first to stage 3 where the applied energy is
about 250-350 Wh.kg-1 and becomes steady
after that. The tensile strength properties of
the eucalypt pulp increases slowly in every
stage.
Fig. 5 exhibits burst strength versus total specific energy. Burst strength development is almost similar to tensile strength development. Tearing resistance (Fig. 6) of softwood pulps decreases with beating while eu-
C. Atic, S. Immamoglu, I. Valchev
Fig. 5. Burst index conversions according to applied SBE.
Fig. 5. Burst index conversions according to applied SBE.
Fig. 6. Tear index conversions according to applied SBE.
ratories, is based on the time used for beating of fibers.
On the contrary, industrial application of the beating
theory usually refers to the specification of three parameters: SEL, SSL and SBE. Because of the fact that
the laboratory studies should be simulated with industrial application.
Beating performance of three pulps (bleached and
unbleached calabrian pine kraft and bleached eucalypt kraft)
were investigated in a laboratory valley beater device.
Empirical SEL or beating intensity, SSL and SBE consumption were experimentally found for each kraft pulp.
Based on this laboratory study with certain kraft
pulps beaten in a valley beater instrument, it can be
concluded that:
• Beating intensity depends on the type of the
pulps and the amount of pulp which is decreased after
sample withdraw during treatment.
• Significant information about the amount of
energy and beating intensity must be necessary to put to
the certain pulp samples to reach required properties.
• Valley beater can be used for beating response
determination of pulp samples, and the influence of the
applied energy on development of strength properties
of pulps.
• Finally, these laboratory results will give significant information about pulp properties and information about that can be compared with other pulp and
industrial applications.
REFERENCES
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beating energy.
CONCLUSIONS
It has been agreed that simulation of industrial with
laboratory beating performance is really necessary to investigate and control beating performance of pulp and the laboratory beating method should be internationally acceptable, adoptable in industry, applicable for all fibre types and if possible
energy consumption during beating has to be measured.
The present version of the laboratory beating standard in a Valley beater which is widely used in labo-
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