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Aerosol & Air Quality Research Lab (AAQRL) Aerosol & Air Quality Research Lab (AAQRL)

Nanoparticle Formation, Measurement and Capture in Coal Combustion

Systems

Pratim Biswas The Lucy and Stanley Lopata Professor He Jing, Sameer Patel, Zhichao Li

Dept. of Energy, Environ. & Chemical Engineering Washington University in St., Louis

19th ETH Conference Combustion Generated Nanoparticles Zurich, Switzerland

June 29, 2015

Aerosol & Air Quality Research Lab (AAQRL)

NSF, NIH, DOE Consortium for Clean Coal Utilization MAGEEP (McDonnell Academy Global Energy & Env. Partnership)

MAGEEP

Acknowledgements

Results of work by Graduate Students in AAQRL, Washington University in St. Louis

NNIN – A NSF NANOTECHNOLOGY NETWORK


NP PARTICLE & PRECURSOR

SOURCES

PRIMARY NP

CONTROL TECHNOLOGY

Life Cycle of Inadvertently Produced Nanoparticles

CLIMATE &

HEALTH EFFECTS nucleation in atmosphere

molecules

SECONDARY NP

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://www.easy-drawings-and-sketches.com/draw-a-tree.html&ei=vMDXVPL2DMOjyASmpIDABw&bvm=bv.85464276,d.aWw&psig=AFQjCNH91upfGjjnezMdIiXiIkB0vwC-2A&ust=1423512084433940


Outline of Presentation

COAL COMBUSTION - Formation of NP & Role of

Precursors - Size Distributions of NP - Inorganic and Organic Species - Charging of Coal Combustion NP

CONTROL TECHNOLOGY (ESPs) - Penetration through ESPs - Improvement of Collection Eff by Photoionizer - Role of Pressure on Charging and Capture

ULTRA FINE PARTICLES &

MOLECULAR PRECURSORS

NPs &

PRECURSORS

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://holbert.faculty.asu.edu/wise/electrostaticprecip.html&ei=lsHXVODuMZKTyAS5-YDoDw&bvm=bv.85464276,d.aWw&psig=AFQjCNE7YB_rfDISucgc7NsXoF7cdzBQLQ&ust=1423512335575201

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://www.clipartpanda.com/categories/clouds-clip-art&ei=csXXVNffCdGeyASEh4KICQ&psig=AFQjCNGoRbIEEYPioKBaRc2tvnJNxy8Nqg&ust=1423513322881333


Combustion in O2-CO2 Environment • Affects Flame Temperature • Affects Volatilization Rates (Formation of Suboxides)

Oxy-Coal Combustion System

Adapted from Jordal, Anheden, Yan, Stromber,( Sweden)

PRESSURIZED


DROP TUBE FURNACE REACTOR EARLY STAGE COMBUSTION / PYROLYSIS

• SIZE DISTRIBUTION EVOLUTION • AEROSOL MASS SPECTROMETRY

Detailed Understanding of Particle Formation


• Workhorse Electrical Mobility Measurement (SMPS, NanoDMA: ~ 10 nm)

• Low size resolution CPCs (can count ~ 1 nm) • Fast DMAs (down to sub 1 nm) [Anal. Chem., 86:

7523-7529 (2014); J. of Aerosol Sci., 71(1): 52-64 (2014)] • Portable Size Distribution Measurement: Nanoscan,

PAMS, DISCmini • Time of Flight Mass Spectrometers [Atmos. Chem. &

Phys., 13(2): 3345-3377 (2013) ]

• Tandem DMA – Mass Spectrometers • LIBS, LII – Composition Analysis • Bring to bear Nanomaterials Characterization Tools

(BET, AFM, HRTEM, SEM, XRD, Raman, etc)

INSTRUMENTATION ENABLES NP STUDIES


Fine Particles(Submicrometer Aerosol)

Coarse ParticlesChar burning

Coalesce and Fragmentation

Vol

atile

Met

al

Vap

oriz

atio

n

De-volatilization

coal

Vap

oriz

atio

n

Scav

engi

ng

Fragmentation

and Attrition

Vap

oriz

atio

n vi

a re

duct

ion-

oxid

atio

n re

actio

n.e.

g. S

iO2+

CO

SiO

+CO

2

Gas Phase Chemical ReactionNucleation

Condensation

Molecules

Coagulation

Vaporization rateof mineral matters strong function of

particle temperature

e.g. Na, Hg, Pb

e.g. Ca, Se.g. SiO2

CO2 Environment Affects Flame Temperature

CO2 Environment Affects Vaporization Rates (Formation of Sub Oxide)

MECHANISTIC PATHWAY OF PARTICLE FORMATION DURING OXY-COAL COMBUSTION

Energy and Fuels, 20 (6), 2357-2363, 2006


When AIR is replaced by 20%O2+80%CO2: Geometric mean particle size decreases from 40 nm to 29 nm Total number concentration decreases from 6.4 x104 to 3.9 x104

No effects on particle shape

Oxy-Coal vs Air Combustion: Air vs. 21%O2+79%CO2

Fine / Coarse = 0.97

Fine / Coarse = 0.4

AIR

O2+CO2

40 nm 29 nm

)()(25.0)()1( sMOgMOOgnMO →↔+−

)(2)()1()()( gCOgnMOgCOsnMO +−↔+

O2

CO

CO2

Coal

O2

CO

CO2

Coal

•High CO2 conc. delays vaporization via reduction of metal oxide

Dp (nm)10 100 1000

dN/ d

log

Dp

(#/c

m3 )

103

104

105

106

Air 20% O2-80%CO2

•High CO2 conc. delays devolatilization process due to thermophysical properties of N2 and CO2 •Flame temperature higher in Air (2311 K) vs CO2/O2 (1722 K) - Cp: N2=20.78 kJ/kmol-ºC, CO2 = 58.84 kJ/kmol-ºC - DO2/N2= 1.7x10-4 m2/s; DO2/CO2 = 1.3x10-4 m2/s

22

5.2COOAIR AshCoarse

AshterSubmicromeAshCoarse

AshterSubmicrome

−

=

Energy and Fuels, 20 (6), 2357-2363, 2006

Fine Particles(Submicrometer Aerosol)

Coarse ParticlesChar burning

Coalesce and Fragmentation

Vol

atile

Met

al

Vap

oriz

atio

n

De-volatilization

coal

Vap

oriz

atio

n

Scav

engi

ng

Fragmentation

and Attrition

Vap

oriz

atio

n vi

a re

duct

ion-

oxid

atio

n re

actio

n.e.

g. S

iO2+

CO

SiO

+CO

2

Gas Phase Chemical ReactionNucleation

Condensation

Molecules

Coagulation

Vaporization rateof mineral matters strong function of

particle temperature

e.g. Na, Hg, Pb

e.g. Ca, Se.g. SiO2

CO2 Environment Affects Vaporization Rates (Formation of Sub Oxide)

CO2 Environment Affects Flame Temperature

Pathway of Particle Formation: Organic & Inorganic

Wang, Biswas et al. Atmospheric Chemistry & Physics, 13(2): 3345-3377 (2013)

* Volatiles (organics) are released * Small fraction is associated with Inorganic ash constituents * Prevents from complete oxidation & released into atmosphere


0 100 200 300 400 500 6000.00

0.04

0.08

0.12

0.16

0.20

0.24

Mas

s Co

ncen

tratio

n (µ

g/m

3 )

Oxygen/Coal Ratio (Gas Composition): 10.0 (Air) 9.0 (10% N2 + 90% Air) 8.0 (20% N2 + 80% Air) 6.0 (40% N2 + 60% Air)

m/z

Adding More N2, lowering O2 concentration

Wang, Biswas et al. Atmospheric Chemistry & Physics, 13(2): 3345-3377 (2013)

ORGANIC CONSTITUENTS IN NP FROM COAL

Contrary trend (consistent with Hypothesis) Oxygen increase results in more Organic Aerosol Constituents

OXYGEN / COAL RATIO

9

10

8

6


0 50 100 1500.00

0.05

0.10

0.15

69

Mas

s C

once

ntra

tion

(µg/

m3 )

Pyrolysis: PRB Coal

41

43

55

5751 67

1158183 91

107

2729

0 50 100 1500.0

0.1

0.2

0.3

0.4(b)

Mass-to-charge Ratio (m/z)

Combustion: PRB Coal

41

43

5557

69

67 818391 115107

28

(a)

20 25 30 35 40 45

20 25 30 35 40 45

2

Sig

nal I

nten

sity

(A. U

.)

PRB Combustion

1 34 5

6

7

89

10

(b)

PRB Pyrolysis

12

34

5

67

8 9 10

Retention Time (min)

(a)

AMS and TAG-GC ANALYSIS AMS TAG-MS

Both cases: non-aromatic hydrocarbons carboxylic acids and aromatics

Wang, Biswas: Proc.Combustion Institute , 35, 2347-2354 2 (2015).

Oxygenated

Aromatics


Chemical Composition of Particles: Coal Combustion

Air firing (Test 3) Oxy (40% O2, Test 4) Oxy (50% O2, Test 5)

0

20

40

60

80

100

120

140

BC: 0

270 KW

Mas

s Co

ncen

tratio

n in

Flu

e G

as (µ

g/m

3 )

Combustion Condition

Organic Carbon (OC) Black Carbon (BC)

400 KW

270 KWBCBC: 0 BC

Carbon in Fine Particles

Fe S Si Ca Zn Ba Cu P Ti K0

1000

2000

3000

4000

5000

Mas

s Co

ncen

tratio

n (µ

g/m

3 )

Element

Air firing (Test 3) 40% O2 (Test 4) 50% O2 (Test 5)

Elemental Analysis Inorganic Constituents of Ash Dominate NPs

Organic Carbon & Brown Carbon Exceeds Black Carbon in NPs


ESPS: How good are they to remove NPs ?

CONTROL TECHNOLOGY (ESPs) - Penetration through ESPs - Improvement of Collection Eff - Co-Pollutant Removal

NPs &

PRECURSORS

Image from: Powerspan Corpn.

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://holbert.faculty.asu.edu/wise/electrostaticprecip.html&ei=lsHXVODuMZKTyAS5-YDoDw&bvm=bv.85464276,d.aWw&psig=AFQjCNE7YB_rfDISucgc7NsXoF7cdzBQLQ&ust=1423512335575201




Kr-85 Radioactive Source

Air

CO2

N2

O2

Condensation Particle Counter

Differential Mobility Analyzer

Collison Nebulizer

Mass Flow Controllers

Po-210 Radioactive Source

Diffusion Dryer

Charged Particle Remover

High Voltage Sources

Ammeter

Electrostatic Precipitator

Air

N2

O2

Ammeter

CO2 Differential Mobility Analyzer



Coal Combustor

Po-210 Radioactive Source

Electrostatic Precipitator

Coal Feeder

Mass Flow Controllers

High Voltage Sources

Sets II & IV

Sets I & III

Figure 1

CAPTURE CHARACTERISTICS IN THE ESP


Particle Diameter [nm]10 100

Char

ge F

ract

ion

0.0

0.1

0.2

0.3

0.4

0.5

Figure 2

CHARGED FRACTION OF COAL COMBUSTION PARTICLES

Fraction of +1 and -1 charged particles Legend: Air (-1), Air (+1), 20%O2-80%CO2 (-1), 20%O2-80%CO2 (+1), 50%O2-50%CO2 (-1), 50%O2-50%CO2 (+1). Equilibrium lines: Weidensohler, 1988. Solid Line (-1), Dashed Line (+1).

AIR 20%O2-80%CO2 50%O2-50%CO2

PARTICLE SIZE (nm)

Aerosol & Air Quality Research Lab (AAQRL) Applied Voltage [kV]

7.0 7.5 8.0 8.5 9.0 9.5 10.0

Cur

rent

[ µA

]

5

10

15

20

25

30

Figure 3a

AIR

50 O2-50 N2

N2

CO2

20 O2-80 CO2

50 O2 50 CO2

30 O2 70 CO2

CORONA INITIATION VOLTAGE (POSITIVE VOLTAGES) (LARGER WHEN CO2 CONCENTRATIONS ARE HIGHER

Suriyawong et al. / Fuel 87 (2008) 673–682


( ( , , , )) ( , 1) ( , 1, , ) ( , ) ( , , , )

( , 1) ( , 1, , ) ( , ) ( , , , )

( , 1) ( , 1, , ) ( , ) ( , , , )

ion ion

ion ion

n v q x t v q N n v q x t v q N n v q x tt

v q N n v q x t v q N n v q x t

v q n v q x t v q n v q x t

β β

β β

α α

γ

+ + + +

− − − −

+ +

∂= − − −

∂+ + + −

+ − − −

+

2

,

0

( , 1) ( , 1, , ) ( , ) ( , , , ) ( , , , )

( , , , ) ( , ) ( , , , ) ( )( ) ( ) ( , , , )

1 ( ', ') ( ', , ,2

ext p

v s q s

s

v q n v q x t v q n v q x t n v q x t u

n v q x t u v q n v q x t v u u D v n v q x t

v v v n v s x t

γ

τ

β

+ +

∞−

=−∞

− − − − ∇ ⋅

− ∇ ⋅ + ∇ ⋅ ∇ ⋅ + ∇

+ −∑ ∫

,

0

) ( ', , , ) '

( , , , ) ( , ') ( ', , , ) 'q s

s

n v v q s x t dv

n v q x t v v n v s x t dvβ∞ ∞

=−∞

− −

− ∑ ∫

Comprehensive Charging Model: Apply to ESP 2

2 /

0

exp( ( ) / )( , )1 exp( ( ) / ) exp( ( / ) / )d

4

ion B

aion

B Bion

c U k Tv qcU k T U a y k T yD a

δ

πθ δ δβθ δδ

±±

±

±

−=

+ − ∫2

( , ) ( ( , ))mc

I av q K h v qhπα υυ

+ = − Φ

22 ( , ) 4( , ) exp( )

B

v q av q BTk T e

πγ + Φ= −

Attachment coefficient

Photoelectric yield coefficient

Thermionic yield coefficient

Spatio-temporal number concentration of particles with size (volume) v and q elementary charges at location and time t x

Jiang, Lee, Biswas: J. of Electrostatics,65, 209-220, 2007.


Particle Diameter [nm]6 7 8 9 20 30 40 50 60 70 80 90 20010 100

Pene

trat

ion

20

30

40

50

60708090

10

100

Figure 8

Condition 1 Condition 2

Condition 4

Condition 3

AIR

O2-CO2 (high ion concentration)

O2-CO2 (low ion concentration)

O2-CO2 (intermediate ion concentration)

PENETRATION AS A FUNCTION OF SIZE

Suriyawong, et al. Fuel, 673-682, 2008 Zhuang, Biswas:J. Electrostatics, 245-260,2000

UFPs are not Captured Efficiently in ESPs. Difficult to charge large fraction


SOFT X-RAY ENHANCED CORONA SYSTEM ENHANCES NANOMETER SIZE PARTICLE CAPTURE

Biswas P., Namiki N. & Kulkarni P. US Patent 6,861,036

Zhuang Y., Kim Y.J., Lee T.G., Biswas P.: "Experimental and Theoretical Studies of Ultra-Fine Particle Behavior in Electrostatic Precipitators", J. of Electrostatics, 48, 245-260, 2000.

Soft X-ray emitter

hν Photoemission of electrode surface

Discharge Electrode (DE) Collecting electrode of ESP

e hν

Unipolar ion atmosphere due to corona around DE

Diffusion charging

Particle

Free ion Bipolar ion atmosphere created by photoionization of gas molecules

hν

e Photoionization of particle

hν Particle

e

e

e e

SXC – ESP: ENHANCES NP CAPTURE


Time (min)

0 3 6 9 12 15 18 21 24 27 30

Parti

cle

num

ber c

once

ntra

tion

(#/c

m3 )

105

106

107 Average charge per particle (unit electron charge)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Vol

tage

,V=0

kV

X-r

ay O

FF

V=0

kV

X-r

ay O

NV=0 kVX-ray OFF

V=1

0 kV

X-r

ay O

FF

V=10 kVX-ray ON

V=0 kVX-ray OFF

V=10 kVX-ray OFF

SXC-ESP COLLECTION EFFICIENCY

Kulkarni P., Namiki N., Otani Y. and Biswas P.: "Charging of particles in unipolar coronas irradiated in-situ soft X-rays: Enhancement of Capture Efficiency of Ultrafine Particles", J. Aerosol Sci., 33 (9), 1279-1298, 2002.

Aerosol & Air Quality Research Lab (AAQRL) 22

Capture efficiency at different particle diameters from 10 –225nm (Q=10 lpm).

Particle Diameter [nm]20 30 40 50 60 70 80 90 20010 100

Cap

ture

Eff

icie

ncy

[-]

0.0

0.2

0.4

0.6

0.8

1.0

3kV, X-ray off 3kV, X-ray on 6kV, X-ray off 6 kV, X-ray on 8 kV, X-ray off 8 kV, X-ray on

Uncharged fraction

Corona + soft x-ray On

SXC OFF

SXC ON


Capture in ESP at Various Pressures

-H.V. -H.V. - - - -

- - - - - -

38

A

vx

vTE dx dy

H

L

• Deutsch-Anderson equation

𝜼𝜼 = 𝟏𝟏 − 𝐞𝐞𝐞𝐞𝐞𝐞 −𝑨𝑨𝒄𝒄𝒗𝒗𝑻𝑻𝑻𝑻𝑸𝑸

Capture efficiency Volumetric flow rate

Particle migration velocity ESP collection surface area

𝐶𝐶𝑐𝑐 = 1 +𝜆𝜆𝑑𝑑𝑝𝑝

2.34 + 1.05 𝑒𝑒𝑒𝑒𝑒𝑒 −0.39𝑑𝑑𝑝𝑝𝜆𝜆

𝑛𝑛 = 𝑛𝑛𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 + 𝑛𝑛𝑑𝑑𝑑𝑑𝑓𝑓𝑓𝑓𝑑𝑑(𝜆𝜆)

λ =𝑅𝑅𝑅𝑅

2𝜋𝜋𝑑𝑑𝑚𝑚2𝑃𝑃𝑁𝑁𝐴𝐴

Dependent on gas pressure

=𝟏𝟏 − 𝒆𝒆𝒆𝒆𝒆𝒆(−𝑨𝑨𝒄𝒄

𝒏𝒏𝒆𝒆𝑻𝑻𝑪𝑪𝒄𝒄𝟑𝟑𝟑𝟑𝟑𝟑𝒅𝒅𝒆𝒆𝑸𝑸 )

Robinson. Air pollution control. 1970


Fine Particle Capture in a Pressurized ESP

V-I Characteristics

1 atm

2 atm

3 atm

Application of pressurized ESP

Gas cleaning for • Pressurized combustion • Coal/biomass gasification

Benchtop pressurized ESP


Fine Particle Capture in a Pressurized ESP

Current controlled

Voltage controlled

Challenging aerosols: NaCl Particles

Higher pressure Higher collection efficiency Due to combined effect of Slower particle migration and Higher filed intensity

Positive Voltage

Positive Voltage Negative Voltage

Negative Voltage

Higher pressure Lower collection efficiency Due to Lower ion concentration

1 atm

1 atm

1 atm

1 atm

2 atm 2 atm

2 atm 2 atm

3 atm 3 atm

3 atm

3 atm


3 10 1000.980

0.985

0.990

0.995

1.000

1 atm (20mA, -8.9kV) 1 atm (500mA, -12.9kV) 2 atm (20mA, -12.9kV) 2 atm (200mA, -16.7kV) 3 atm (20mA, -16.7kV) Theoretical curve

Re

mov

al e

fficie

ncy

(exp

erim

enta

l dat

a)

AcvTE/Q (calculated value)

1 atm 2 atm

3 atm

39

𝜼𝜼 = 𝟏𝟏 − 𝐞𝐞𝐞𝐞𝐞𝐞 −𝑨𝑨𝒄𝒄𝒗𝒗𝑻𝑻𝑻𝑻𝑸𝑸

Capture Efficiency at Different Pressures


3 10 1000.980

0.985

0.990

0.995

1.000

1 atm (20mA, -8.9kV) 1 atm (500mA, -12.9kV) 2 atm (20mA, -12.9kV) 2 atm (200mA, -16.7kV) 3 atm (20mA, -16.7kV) Theoretical curveRe

mov

al e

fficie

ncy

(exp

erim

enta

l dat

a)

(AcvTE/Q)modi (calculated values)40

Modified Capture Efficiency Equation

𝜼𝜼 = 𝟏𝟏 − 𝐞𝐞𝐞𝐞𝐞𝐞 −𝑨𝑨𝒄𝒄𝒗𝒗𝑻𝑻𝑻𝑻𝑸𝑸 × 𝒇𝒇 𝑷𝑷


SUMMARY • Detailed source and control technology studies for NP

are essential • New instrumentation enables detailed studies which will

help tackle potential NP problem (design new systems) • Timing for NP study due to changing energy source mix is

now • Coal combustion aerosols complex: cannot ignore organic

constituents (related to inorganic constituents) • Performance of ESP can be improved by using photo-

ionizer charging systems • Effect of pressure on charging NPs and capture efficiency

elucidated

nanoparticle formation, measurement and capture in … · nanoparticle formation, measurement and...

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