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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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Background

Laser granolumeter

Test conditions

Outline

Application

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Background

A strict control of particle size and size distribution of powders of carbon power is required

Graphite power Nuclear fuel pellets

high temperature gas-cooled reactorsGraphite

Coke powder

Mixing powder

Ultrafine powder

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Why laser grnulometer

Vibrating screening Airflow screening

Laser granulometer

Grain size measuring means

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Vibrating screening

Advantage: easy to operate and achieve

Disadvantage: a ） Measurement of size distribution is discreteb) Agglomerated particles can’t go through the sieve – suitable for large particulates, rather than fine ones.

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Airflow screening

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.

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Laser granulometer

Grain size measuring means

Advantage: A small amount of power is enough to have details on size distributionquick and convenience, good repeatability, Cover wide range of particle sizes.

Disadvantage: Risk of error for a lack of representativeness

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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-0.87%

D50:CV-3.21%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

Theoretical result

Test result

Test 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 SSASSA/CS

R

I

0.323 4.7 14.6

0.97

0.3 4.7 15.7

0.331 4.67 14.1

0.338 5.08 15.0

0.563 7.7 13.7

II

0.262 1.23 4.7

0.99

0.273 1.3 4.8

0.279 1.3 4.7

0.346 1.68 4.9

0.356 1.68 4.7

SSA=k*CS

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Application

Relation between CS and SSA

CS SSA

5min 4h

k

Need more experiments to build the model

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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!