Formation and Properties

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Feb 22, 2014 (3 years and 3 months ago)

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Combustion Aerosols:
Formation and Properties

Richard L. Axelbaum



Washington University in St. Louis

Dept. Energy, Environmental & Chemical Engineering




McDonnell International Scholars Academy

2
nd

International Symposium of Energy and Environment


December 8, 2008


Types of Combustion Particles

2.

soot

black (elemental) carbon

10 nm


1 µm

1.

organic carbon

1
-

100 nm



3.


residual fly ash

from combustion of solids

(coal, wood)


0.1 µm


100 µm


4.


secondary particles

formed by oxidation reactions of
combustion gases w/ atmosphere


examples

SO
x



SO
3
-

or SO
4
2
-


NO
x



NO
3
-



Carbonaceous Particles

devolatilization

400
o
C

condensation

nucleation

pyrolysis

(cracking)

fuel vapor

600
o
C

1000
o
C

soot
formation

temperature

time

high OC

content

high EC

content

EC


Elemental Carbon, OC


Organic Carbon

Elemental & Organic Carbon Content

source

EC / TC

cigarette smoke

0.01

meat smoke

0.00


0.04

candle (normal burning)

0.04

fireplace

0.1


0.2

gasoline vehicles

0.10


0.4

diesels

0.15


0.9

coal ash (stoker)

0.8


0.9

sooting candle

0.95

modified from

J. Schauer,
J. Exposure Analysis and Environ. Epidemiology
(2003)

EC


Elemental (black) Carbon, TC


Total Carbon

carbonization

Bockhorn, H. (1994)

Violi A, Sarofim AF, Voth GA (2004)

Soot Formation

Nanostructure of Soot

amorphous

graphitic

R. L. Vander Wal; A. J. Tomasek,
Combust. Flame
136:1
-
2 (2004)

Soot Formation in Nonpremixed Flames

Soot zone

Temperature

Peak Temperature

Location

Oxidizer

Fuel

High Temperature

Boundary, C/O = C/O
cr

Low Temperature

Boundary

P. Sunderland, D. Urban, D. Stocker, B.
-
H. Chao, R. Axelbaum,
Combust. Sci. Tech
. (2004)

D. Du, R. Axelbaum,
Combust. Flame
(1995)



C
2
H
4
/Air

T
ad

= 2370 K

C
2
H
4
+CO
2
/O
2


T
ad

= 2540 K


Soot
-
Free


High Temp.


Turbulent


Stable, unpiloted


Low
-
NO
x


High CO
2

exhaust
concentration for carbon
capture

Oxy
-
fuel combustion

B. Kumfer, S. Skeen, R. Axelbaum
Combust Flame
(2008)

B. Kumfer, S. Skeen, R. Chen, R.
Axelbaum
Combust Flame
(2006)


Fly ash particles

J. Lighty, J. Veranth, A. Sarofim
J. Air & Waste Manage. Assoc.
(2000)

Metals content in coal

more concentrated in
submicron fly ash

regulated under
Clean Air Act

Adapted from

W. Linak, J. Wendt
Prog. Energy Combust. Sci.
(1993)

legend: