The application of laser granulometer on carbon
powder characterization for quality control and
optimization of nuclear graphite products
Qian Zheng1, Jing Zhang1, Yuzhen Mao1, Junguo Zhao1, Dai Huang1, Houzheng Wu1,2*
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Outline
Background
Laser granolumeter
Test conditions
Application
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Background
Graphite power
Nuclear fuel pellets
Coke powder
Ultrafine powder
Mixing powder
high temperature gas-cooled reactors
Graphite
A strict control of particle size and size distribution of powders of carbon power is required
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Why laser grnulometer
 Grain size measuring means
Laser granulometer
Vibrating screening
Airflow screening
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Vibrating screening
Advantage:
easy to operate and achieve
Disadvantage:
a）Measurement of size distribution is discrete
b) Agglomerated particles can’t go through the sieve –
suitable for large particulates, rather than fine ones.
transmittance(%)
size distrubution on vibrating screen
45
40
35
30
25
20
15
10
5
0
32
43
75
patticle size(μm)
100
150
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Airflow screening
Advantage:
The scope, efficiency, precision and repeatability of
airflow screening are better than vibration
Disadvantage:
a) Only one sieving can be used for separation each
time, leading to a complex operation required.
b)The detailed size distribution is hard to be provided.
Airflow screening
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Laser granulometer
 Grain size measuring means
Advantage:
A small amount of power is enough to
have details on size distribution
quick and convenience,
good repeatability,
Cover wide range of particle sizes.
transmittance(%)
size distribution with laser
granolumeter
14.00
12.00
10.00
8.00
6.00
4.00
2.00
.00
particle size(μm)
Disadvantage:
Risk of error for
representativeness
a
lack
of
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Test conditions
Instrument: laser granulometer (S3500), US Microtrac corp.
Samples:
graphite powder,
coke powder,
mixed powder of coke and binder,
ultrafine powder, i.e. D50<5µm)
Surfactant used:
Triton X-100(octyl phenoxy poly ethoxy -US Fisher Scientific)
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Results
 Suspension concentration
The affect of suspension
concentration on different
material
√
√
excessive
appropriate
small
√
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Results (cont.)
 Repeatability test with different suspension concentration of mixing power
√
√
Repeatability is poor
for a sample lack of
representativeness
Best choice
Risk on instrument
maintenance
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Results (cont.)
 using surfactant
Before
√
After
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Results (cont.)
 The affect of surfactant on different materials
√
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Results (cont.)
The affect of ultrasonication on different material
√
√
√
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Results (cont.)
 Repeatability test results of different materials under optimum disperse conditions
D50:CV-2.03%
D50:CV-3.21%
D50:CV-0.87%
D50:CV-4.04%
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Application
 model
Laser granolometer measurements are used as the fundamental inputs of modelling,
for achieving the best possible particle sizes and size distribution through a
combination of powders with different ones, with models developed via theoretical
prediction.
New particle population =A+B+  C+…
WE chose A,B,C three types of powder having different size distribution, and had
the : :  in different ratios, such as 3:1:3，2:1:2，3:1:2
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Application (cont.)
 The comparison between theoretical prediction and experimental measurement
Test
result
Test
result
Theoretical
result
Theoretical
result
Test
result
Theoretical
result
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Application (cont.)
 Relation between CS and SSA
CS: Specific surface area that was calculated by size distribution data
with a hypothesis that particles are all spherical solid.
SSA: Specific surface area measured with BET based on the N2
adsorption
We chose different raw materials, 1 and 2, which is milled with same
equipment but different conditions to get five powders with different
size distribution.
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Application
 Relation between CS and SSA
CS
0.323
0.3
I 0.331
0.338
0.563
0.262
0.273
II 0.279
0.346
0.356
SSA
SSA/
CS
4.7
4.7
4.67
5.08
7.7
1.23
1.3
1.3
1.68
1.68
14.6
15.7
14.1
15.0
13.7
4.7
4.8
4.7
4.9
4.7
SSA=k*CS
R
0.97
0.99
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Application
 Relation between CS and SSA
Need more experiments
to build the model
CS
5min
k
SSA
4h
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Summary
 To achieve better dispersion suitable for laser ganulometer,
appropriate suspension concentration, surfactant, and ultrasonication
are necessary
 It is approved possible and controllable to achieve a powder with
expected particle population through combining powders with
different particle population, based on a theoretical model.
 If the powder production technology is relatively stable and
consistent, it is possible to establish relationship between normalized
specific surface area measured with laser granulometer and that with
BET based on the N2 adsorption. It will offer foundation on estimating
the SSA by laser granulometer.
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Thank you for your attention!
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