Transcript No Slide Title

SAFIR interim seminar 20. - 21.1.2005
Behaviour of Ruthenium
in
high temperature oxidising conditions
Ulrika Backman & Ari Auvinen & Jorma Jokiniemi &
Maija Lipponen & Riitta Zilliacus
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Objective
Quantify the effect of
–
–
–
Oxygen partial pressure
Oxidation temperature
Tube material
on ruthenium release, transport and speciation
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Experimental facility
110 cm
ID 1''
alumina
SS
5.5 cm
ID 1''
SS
10 cm
ID 1''
SS
69 cm
ID 1 ''
MFC
P
Air
20 cm
5 lpm
MFC
Tubular reactor
25 cm
I.D. 22 mm
Length 110 cm
Heated length 2 x 40 cm
1 M NaOH
Air
0.3 lpm
ESP
CO - critical orifice
MFC - mass flow controller
ESP - electrostatic precipitator
DMA - differential mobility analyzer
CNC - condensation nucleus counter
DMA
0.3 lpm
CO
Vac.
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CNC
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Methods
Solid RuO2 particles were collected on plane filters.
 Gaseous RuO4 was trapped in 1M NaOH-water solution.
 Filters and precipitates were analysed with INAA
(detection limit 2g/sample).
 NaOH solution was analysed using ICP-MS
(detection limit 0.05g/l).
 Deposition profile was measured using radiotracer
technique (Ru103 -isotope)
 RuO2 particle morphology was determined with TEM.
 RuO2 particle crystallinity determined with SAD.
 RuO2 deposit morphology was studied with SEM.

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Experimental matrix
EXP
#
1
2
3
4
5
6
T RELEASE
[C]
1227
1227
1227
1427
1227
1227
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GAS
TUBE MATERIAL
Air, 5 l/min
Air, 5 l/min
Air, 5 l/min
Air, 5 l/min
N2 + 10 % O2, 5 l/min
Air, 5 l/min
Stainless steel
Alumina
Stainless steel
Stainless steel
Stainless steel
Stainless steel
NOTE
Tracer used
Seed particles added
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Equilibrium of Ru species in air
1.00E+01
1.00E+00
Mass (g)
1.00E-01
g-Ru(g)
1.00E-02
g-RuO(g)
1.00E-03
g-RuO2(g)
g-RuO3(g)
1.00E-04
g-RuO4(g)
g-Ru(s)
1.00E-05
1.00E-06
1000
g-RuO2(s)
g-RuO4(s)
1200
1400
1600
Temperature (K)
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1800
2000
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RuO2 - deposition profile and gas temperature
500
15
450
12
350
300
9
250
200
6
150
100
3
50
0
-40
-20
0
20
40
Distance [cm]
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60
80
0
100
% of Ru released
Temperature [C]
400
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SEM images of ceramic tube wall
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TEM image and SAD pattern of RuO2 particle
-110
01-1
10-1
11-2
R uO
240303
50 nm
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{101}
<112>
[111]
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Conclusions (1/2)

Ruthenium release
–
–
–
–

Released mainly as RuO3, 5% released as RuO4.
Approximately constant 9-11 mg/min in air flow at 1500 K.
Release rate decreases as O2 partial pressure decreases.
Release rate increases with oxidation temperature.
Ruthenium deposition
–
–
–
–
–
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Very significant (65-88%).
Deposition by RuO3 to RuO2 reaction at 800°C.
Deposition by thermophoresis at furnace outlet.
Deposition by decomposition of RuO4 on steel at 150-200°C.
Deposition decreased by increased furnace temperature
(faster quench), by seed particles and by decreased O2 and
RuO3 partial pressures.
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Conclusions (2/2)

Transport of gaseous ruthenium
–
–
–
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In dry experiments with stainless steel tube: 0.1 - 0.2 %
– Fraction was independent of release temperature, oxygen partial
pressure and concentration of ruthenium
– Probably due to the catalytic effect of the stainless steel tube
surface on the decomposition of RuO4 to RuO2
Using alumina tube: 5%
– Comparable to the fraction given by thermodynamic equilibrium
– RuO2 seems not have a strong catalysing effect on the
decomposition of RuO4.
When atmosphere contained some water: 5 %
– Most likely the water vapour passivated the stainless steel tube
surface
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Further experiments

The effect of water vapour on Ru release and speciation
–
–

The effect of seed particles on Ru transport
–
–

In dry conditions.
Variable particle number concentration.
Time dependence of Ru release rate and speciation
–

With and wo. seed particles.
Variable steam partial pressure.
Online experiments with radioactive ruthenium.
Catalytic decomposition of RuO4 by RuO2
–
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Experiments with and wo. filters doped with RuO2.
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T
[K]
Flow rate
[l/min]
Gas
composition
Tube
material
Particle
consentration
Radiotracer
Autocatalytic
1500
1700
1500
1500
5
5
2
8
Air sat. H2O
Air sat. H2O
Air sat. H2O
Air sat. H2O
Steel
Steel
Steel
Steel
-
Online
-
-
1500
1700
1500
1700
1900
1500
1700
5
5
5
5
5
5
5
10% H2O
10% H2O
50% H2O
50% H2O
50% H2O
70% H2O
70% H2O
Steel
Steel
Steel
Steel
Steel
Steel
Steel
-
Online
Online
-
-
1500
1500
1500
1500
1500
1500
5
5
5
5
5
5
Air
Air
Air
50% H2O
Air sat. H2O
Air
Steel
Steel
Steel
Steel
Steel
AlO2
Low
High
High
-
Online
Online
Online
Online
-
Yes
Yes
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