Heinz Fissan AFS May 6-9, 2013 Fissan H.1,2, Kaminski H.1

Heinz Fissan AFS May 6-9, 2013 Fissan H.1,2, Kaminski H.1

“Measurement Techniques and Data Evaluation Procedures for Filter Testing
with Polydisperse Agglomerates and Aggregates”
Fissan H.1,2, Kaminski H.1, Asbach C.1, Buha J.3, Wang J3,4.
1 Institute of Energy and Environmental Technology (IUTA) e. V., Duisburg, Germany
2 Center for Nanointegration Duisburg-Essen (CENIDE), Duisburg, Germany
3 ETH Zürich, Zürich, Switzerland
4 Empa, Duebendorf, Switzerland
Nanoparticles synthesized in the gas phase occur mainly as agglomerates or partly sintered aggregates.
The geometric parameters like surface area or primary particle size and number per agglomerate
and the corresponding distributions are important for the properties of nanostructured materials.
Along with the pressure drop, the collection efficiency as function of a particle size measure is the most
important information about the performance of filter media. In the submicron size range the SMPS,
which allows the determination of the number distribution as function of the equivalent mobility diameter,
is widely used. In case of spheres the mobility diameter is equal to the geometric diameter.
Earlier we have shown that the collection efficiency curve as function of mobility diameter determined
by challenging the filter with polydisperse agglomerates/aggregates is not changing with
agglomerate/aggregate structure. This changes, if we plot concentration distributions as function of
other geometric size parameters. The needed relationship between mobility diameter of
agglomerates/aggregates and the volume diameter of the sphere with equal volume can be measured
or can be derived using a recently developed model for sintering. The model allows also a discussion abou
the differences or errors caused by the sphere assumption in case of agglomerates and aggregates.
Collection efficiency curves have been determined for loose silver agglomerates and are compared with
those of the sintered spheres with constant volume. They show that the collection efficiency
mainly in the range of interception is increased in case of loose agglomerates.
Key words:
SMPS, Volume per agglomerate/aggregate, collection efficiency curves of agglomerates/aggregates
Heinz Fissan
AFS May 6-9, 2013
1
Institut für Energieund Umwelttechnik e. V.
HEINZ FISSAN
H. Kaminski, C. Asbach, D. Pui, J. Wang
“Measurement Techniques and Data
Evaluation Procedures for
Filter Testing with Polydisperse
Agglomerates and Aggregates”
AFS 2013
May 6-9, 2013
Minneapolis, MN
Heinz Fissan
AFS May 6-9, 2013
2
Content
 Determination of filter efficiency as
function of mobility diameter
 Volume (mass) per aggl./aggr. determination:
• Aerosol Centrifuge (APM)
• Electrical Sensor (ES)
 Loose agglomerate and aggregate model
for structural parameters
Heinz Fissan
AFS May 6-9, 2013
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Determination of Filter Efficiency
C: Number,
Surface area,
Mass
concentrations
Filter
C1
c2
Penetration:
monodisperse P(dp) = c2 /c1
polydisperse
P(dp)= c2(dp) /c1(dp)
Filtration efficiency:
E(dp) = 1 – P(dp)
SMPS: Number concentration as f (mobility diameter)
Heinz Fissan
AFS May 6-9, 2013
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Size Distributions for Spheres, Agglomerates, Aggregates
Concentration measures:
- Number
- Surface area
- Volume (mass)
Aggregates:
Equivalent primary particle size
and equivalent number
Penetration or efficiency
Fissan et al., subm. to AAQR
Heinz Fissan
Sizes:
- Mobility diameter
- Volume (mass) per particle
- Primary particle size and number
- Surface area per particle
AFS May 6-9, 2013
5
NP-Agglomerate Synthesis and Characterization Set-up System
Buha et al., subm. To JNR
Heinz Fissan
AFS May 6-9, 2013
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Number – Size (mobility diameter) Distributions
Silver agglomerates
produced by
the coagulation process
upstream
downstream of filter
Heinz Fissan
AFS May 6-9, 2013
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Comparison of Penetration Curves
Penetration (-)
1
Ag agglomerates
Ag spheres
NaCl
0.1
10
100
1000
Mobility particle diameter (nm)
Calculation of penetration independant of structure;
valid for number, surface area and volume (mass) concentrations
Heinz Fissan
AFS May 6-9, 2013
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Silver Spheres and Agglomerates
a1,E+07
b
1,E+07
0,5
Particles: 188
AVG: 16.8 nm
Fraction (F)
dN/dlogDp (#/cm3 )
0,4
8,E+06
6,E+06
4,E+06
0,3
0,2
0,1
2,E+06
0
0,E+00
10
Mobility Diameter Dp (nm)100
Primary silver particles
Heinz Fissan
0
10
20
30
Particle diameter d (nm)
40
Silver agglomerates
produced by
the coagulation process
AFS May 6-9, 2013
Silver sphere
produced by
sintering process
9
Electrical Sensor (ES)
2.5 l/min
Charger and
ion trap
Filter
Pump
EAD
NSAM
AEROTRAC
ES
P
2.5 l/min
Filter
Digital
and Analog
Output
Faraday Cage
1.0 l/min
Ion Jet Flow
1.5 l/min Aerosol Flow
Electrometer
Filter
Trap to remove
excess ions/
small particles
Positively
Charged
Particles
Mixing
Chamber
Diffusion
Charging
+
+
+ + +
+
2.5 l/min
+ +
+
+ +
Positive
+
+
+ Ions
+
+
+
Corona
Needle
Small and portable (battery
operated; personal sampler)
Carbon
Filter
No radioactive source
HEPA
Filter
No liquid supply
On-line; real time
P
Electrical signal (current)
Structure sensitive
2.5 kV (positive)
Fissan et al., JNR, 2007; Patent: US 7,812,306 B2
Heinz Fissan
AFS May 6-9, 2013
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UNPA Technology
 Modified (bipolar charge
distribution) SMPS-measuring
technique for number
distribution
DMA
 SMPS + ES + New model for ES
relates charge per aggl. to
primary particle size
L-model
for loose agglomerates
ES
CPC
Bipolar
charger
Bypass
 ES for particle mass
determination of spheres,
aggl./aggr.
E-model for all
size distributions of aggl./aggr.
 Offline-Sampler for SEM/TEM
analysis
Pump Mass flow
controller
Bipolar
charger
Nanoparticle
Aerosol sampler
Patent: PCTIEP2009/05/234; Dixkens et al., JAS 1999;
Lall et al., JAS 2006; Wang et al., AST 2010; Fissan et al., submitted to AAQR
Heinz Fissan
AFS May 6-9, 2013
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Proof of Model for Loose Agglomerate Filtration
Wang et al., JAS 2008; Wang et al., AST 2011
Heinz Fissan
AFS May 6-9, 2013
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Volume (Mass) per Aggl./Aggr. Determination
Volume per particle
as function of mobility diameter:
Sphere: mobility diameter
Agglomerates: mobility diameter and
primary particle size
agglomerate models
Agglomerates/Aggregates:
(Sampling, counting and weighing)
(Sampling, counting and chemical analysis)
(Sintering to spheres (dm = dv))
Aerosol Centrifuge (APM) measurement
Electrical Sensor
Loose agglomerate and aggregate model
Fissan et al., subm. to AAQR
Heinz Fissan
AFS May 6-9, 2013
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Aerosol Particle Mass Analyzer (APM)
Source: KANOMAX Specification sheet APM 3600
Heinz Fissan
AFS May 6-9, 2013
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Measurement of dm and v of Aggl./Aggr.
SMPS: Bipolar charger – DMA – CPC
Number concentration as function of mobility diameter
with charge correction
Extension: Bipolar charger – DMA(dm):
- APM(m) – CPC
- CPC
- ES
Heinz Fissan
AFS May 6-9, 2013
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Particle Mass
1.0E+03
Silver NP agglomerate
Carrier gas: N2 (1.5 lpm)
Room temperature
Particle mass [fg]
1.0E+02
Df=3.0
Sphere
200°C
2.95
y = 5.56E-06x
600°C
y = 7.35E-05x
2.25
1.0E+01
2.08
y = 7.64E-05x
1.0E+00
1.0E-01
10
100
1,000
Mobility diameter dm [nm]
Kim et al. (2009): Aerosol Sci. Tech, 43, 344-355
Heinz Fissan
AFS May 6-9, 2013
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ES – Sensitivity ( C/Cn)
Loose chainlike agglomerates – aggregates - spheres
0.06
Room temperature
Sintering temperature 200°C
Sintering temperature 600°C
Silver
3
Sensitivity [fA*cm ]
0.05
0.04
0.03
0.02
Soot
0.01
0
60
80
100
120
140
160
180
200
Mobility diameter dm [nm]
Wang et al., AST 2010
Heinz Fissan
AFS May 6-9, 2013
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ES - Particle Mass Calibration Curve
1.0E-01
mobility diameter
50 nm
100 nm
150 nm
200 nm
250 nm
Sensitivity [fA*cm³]
8.0E-02
loose agglomerates
(room temperature)
aggregates
(200°C)
6.0E-02
4.0E-02
spheres
(600°C)
2.0E-02
0.0E+00
0.1
1
10
100
Particle mass [fg]
Heinz Fissan
AFS May 6-9, 2013
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Snapshots of Aggregates – E-model
Lall(L) model applicable
E-model
Measured quantities: dm and vp
Derived: number and diameter of equivalent primary particles
surface area per particle
E – model: Eggersdorfer et al., JAS 2012; Eggersdorfer et al., AST 2012
Heinz Fissan
AFS May 6-9, 2013
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Volume per Aggl./Aggr. from E-Model
1.0E+09
Spheres
aggl./aggr., primary particle d= 20 nm
1.0E+08
aggl./aggr., primary particle d= 40 nm
1.0E+07
3
Volume [nm ]
aggl./aggr., primary particle d= 60 nm
1.0E+06
1.0E+05
Model
Eqivalent primary particle
size
and number
1.0E+04
1.0E+03
10
100
1,000
Mobility diameter dm [nm]
Heinz Fissan
AFS May 6-9, 2013
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Penetration Curves as Function of Volume per Particle (E-model)
0.7
Penetration
0.6
0.5
0.4
0.3
0.2
0.1
Ag exp. analyzed with aggregate assumption
Ag exp. analyzed with sphere assumption
Sphere experiment
0
1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08
Volume per particle [nm³]
primary particle size: 17 nm
Heinz Fissan
AFS May 6-9, 2013
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Summary
 Simpler filter testing with polydisperse particles
 The calculation of the penetration as function of mobility diameter
is not structure dependent
 For the penetration as function of volume per particle,
the volume (mass) per aggl./aggr. can be measured with APM
or the much simpler, but structure limited ES after calibration
 The often used assumption of spherical particles
for the determination of penetration curves causes
structure dependent minor errors in number, surface area
 The largest errors occur for volume distributions
of loose agglomerates
 They can be estimated and avoided making use of
available models for agglomerates and aggregates
Heinz Fissan
AFS May 6-9, 2013
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Thanks for financial
support
Heinz Fissan
AFS May 6-9, 2013
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Thank you for
your attention
Heinz Fissan
AFS May 6-9, 2013
24