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Universität StuttgartProf. Dr. techn. G. Scheffknecht
Institut für Verfahrenstechnik und DampfkesselwesenInstitute of
Process Engineering and Power Plant Technology
3rd WorkshopIEAGHG International Oxy-Combustion Network
Yokohama, Japan5th and 6th March 2008
Impact of Combustion Conditions
on Emission Formation (SO2, NOX)
and fly ash
Patrick Mönckert, Bhupesh Dhungel, René KullJörg Maier
[email protected]
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Universität StuttgartTopics of Presentation, R&D Topics at
IVD
• Fuel characterization (electrical heated pf reactors)•
Combustion
• Rank of coal (bituminous, lignite…)• Emission formation,
ricirculation (NOX, SO2, H2S, CO…• Char burnout and fly ash
formation
• Pyrolysis under CO2 and N2 atmosphere• Volatile release and
char formation/reactivity
• Technical scale combustion tests (0.5MWth)• Combustion and
emission behavior, slagging, fouling, corrosion, SO3,,
acid dew point• Component development and test (burner…)• Plant
handling and operation, safty requirements
• Model development and combustion simulation (AIOLOS)
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Universität Stuttgart
Parameter Study on Emission Formation (SO2, H2S)
electrically heated reactor (20kW)
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Universität StuttgartAnalysis of the Coals Used
Coals LHV [%,ar]Moist. [%,ar]
Ash [%, wf]
Vol. [%, waf]
Cfix [%, waf]
C [%, waf]
H [%, waf]
N [%, waf]
S [%, waf]
O [by diff]
Ca in ash [%]
Ca/S [mol. Ratio]
Klein Kopje 24932 3.60 19.29 27.76 72.24 83.93 4.50 1.67 0.72
9.18 5.8 2.98
Lausitz 21412 10.20 5.46 57.36 42.64 66.78 5.26 0.65 0.85 (0.36)
26.5 17.0 3.17
Rhenish 20965 11.50 4.07 54.18 45.82 67.96 7.68 0.73
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Universität StuttgartUniversität StuttgartSet-up and description
of 20 kW once through furnace
SO2 Injection: up to 3000 ppm via the secondary stream of the
burner
In-flame measurements H2S/SO2, staged/unstaged
SO2 measurements outlet rediative section T=1150°C
SO2 measurements outlet of convective section T= 450°C
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Universität Stuttgart
Test Results:
• SO2 emission at the outlet of the rediative section(1150°C) by
SO2 injection up to 3000ppm
• SO2 captured along the convective section(1150°C down to
450°C) by SO2 injection up to 3000ppm
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Universität Stuttgart
Impact of SO2 injection at the outlet of the radiative section
(1150°C), OF27
Negligible reduction of recycled SO2 in the high temperature,
radiative section of the furnace.
646
0
1000
2000
3000
4000
SO
2 [pp
m]
SO2-injection SO2-measured
936
0
1000
2000
3000
4000
SO
2 [pp
m]
315
0
1000
2000
3000
4000
SO
2 [pp
m]
788
0
1000
2000
3000
4000
SO2 [
ppm
]
D. Ensdorf Coal
A. Klein Kopje Coal B. Lausitz Coal
C. Rhenish Coal
646936
320
788
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Universität Stuttgart
SO2 captured along the convective part(down to 450°C) by
different inlet concentrations
Oxy-fuel 27 % O2
0
100
200
300
400
500
0 1000 2000 3000 4000
SO2 measured at the end of radiative section [ppm]
SO
2 ca
ptur
ed @
flue
-gas
pa
th [p
pm]
KK_Captured RH_Captured LA_Captured EN_Captured
SO2 injection increased
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Universität Stuttgart
In-flame measurements of staged flames withfocus on SO2 and H2S
with and without
injection of 3000ppm SO2
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Universität Stuttgart
H2S formation: Impact of SO2 accumulation (λ1=0.75)
0
200
400
600
800
1000
1200
1400
0 0.5 1 1.5 2 2.5
Distance from Burner [m]
H2S
[ppm
]
KK_0
KK_3000
LA_0
LA_3000
0
200
400
600
800
1000
1200
1400
0 0.5 1 1.5 2 2.5
Distance from Burner [m]
H2S
[ppm
]
KK_0
KK_3000
LA_0
LA_3000
Air-BlownOF27
Higher SO2 concentrations (3000ppm) in the furnace results in at
least 2 times more H2S formation in the sub-stoichiometric region
H2S induced corrosion.
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Universität Stuttgart
Impact of coal property on H2S formation (λ1=0.75, T1~3 Sec)
OF27
0
25
50
75
100
KK_0 KK_3000 EN_0 LA_0 LA_3000
SO
2 an
d H
2S V
olum
etric
Fra
ctio
n
H2S
SO2
Volumetric percentage of H2S and SO2 in the sub-stoichmetric
furnace section, Oxyfuel 27 % O2
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Universität StuttgartResults of Parameter Study (SO2/H2S)
H2S concentrations in the furnace can significant increased
under oxyfuel conditions,
Volumetric percentage of H2S in the furnace decreases by higher
SO2 input concentrations
H2S formation seems to be influenced by volatile content of the
coal and may other parameters: mineral composition etc.
conversion of Sulphur to SO2 close to 100% at the outlet of the
rediative section for the investigated coals and atmospheres
calcium rich coals show a clear tendency to capture additional
Sulphur with increasing SO2 concentration (Oxyfuel conditions),
this correlates with increasing SO3 concentrations of the fly
ash
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Universität Stuttgart
SO3 measurements and acid dew point calculations
in the flue gas duct of a 500kW facility
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Universität Stuttgart
Oxyfuel facility (0.5 MWth) – SO3 sampling
Bottomash
ID fanESPSCR
StoragetanksFD/ RG fan
O2
CO2
Stack
AirO2 CO2
Gasdistribution
HX
Coal feeding
Burnerwindbox
Air
By-passes
SO3 sampling position
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Universität Stuttgart
Measured SO3 concentrations for Lausitz coalat AIR and OXYFUEL
combustion conditions
0
20
40
60
80
100
120
140
0 500 1000 1500 2000 2500SO2 at measurment position, ppm
SO3 measured,ppm
AIR
OXYFUELSO2measured
SO3measured
ppm
733
1758
ppm
AIR 8 (6 – 11)*
OXYFUEL 85 (36 – 121)*
* ... min. / max. value measured
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Universität Stuttgart
Acid dew point T correlated with conversion rate of SO2 SO3
1.0%
2.0%3.0%
4.0%
5.0%
60
70
80
90
100
110
120
130
140
150
0 10 20 30moisture content (of flue-gas), vol.-%
acid dew point T, °C
acid dew point for AIR with 733 ppm
1.0%
2.0%
3.0%
4.0%
5.0%
60
70
80
90
100
110
120
130
140
150
0 10 20 30
moisture content (of flue-gas), vol.-%
acid dew point T, °C
acid dew point for OXYFUEL with 1758 ppmAcid dew point T for AIR
with 733 ppm SO2
Acid dew point T for OXYFUELwith 1758 ppm SO2
129°C
98°C
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Universität Stuttgart
Desposits under oxyfuel conditions
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Universität StuttgartDeposit-Sampling Probes (air/oxyfuel)
Un-cooled ceramic
ESP2
APH
Tsample = T flue gas = 750-850 °C,
Texposed: 10 h
temperature controlled
(alloys 400-750°C)
AK
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Universität StuttgartSEM-BSE and SEM-MAP Ca-C
Ca,C
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Universität StuttgartSEM-WDS/EDS-MAP: Al, Si, O and Ca, S,
Fe
OSiAl
Ca FeS
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Universität StuttgartSEM-MAP: Ca,S / Ca,C
Ca,S Ca,C
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Universität StuttgartResults of the 500kW facility- SO3 and
Deposits
• Clear tendencies that under Oxyfuel conditions the
SO3concentration is increasing and also the acid dew point
temperature
• Impact of Oxyfuel conditions on SO2/SO3 conversion rate needs
further clarification
• Further measurements of SO3 and acid dew point temperatures
are required to minimize uncertainties (measurement device,
measurement procedure, operational issues of plant etc.
• Indications that beside sulfatization carbonization on the
particle surface of deposits occurs under Oxyfuel conditions
• Impact of carbonization on fouling and corrosion in the
convective section of the boiler needs further testing
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Universität StuttgartOngoing/Future R&D Topics at IVD
• Experimental Oxyfuel combustion topics: • Rank of coal
(bituminous, lignite…)• Slagging, Fouling, (impact of higher SO2,
H2S, CO2, HCl etc.• Corrosion high-low temperature (Deposits, HCl,
SO2, SO3, H2O…• Fly ash quality (EN 450 …)• Component development
and test (burner, …)• Emissions (Hg, fine dust etc)• Flue gas
cleaning (SCR, Additives…)
• Oxy-fuel: PF/CFB, • Post combustion capture: Carbonate Looping
(connected
CFB/FB starts operation April 2008)• Lime Enhanced Gasification:
Hydrogen rich Syngas
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Universität Stuttgart
SO2/ SO3 sampling and analysis procedureaccording to VDI (draft)
guideline
flue gas
SO3 Condenser
Sampling equipment
1 Sampling probe2 Particle filter3 Heating4 SO3 condenser
and
thermostat5-6 SO2 absorption vessels7-9 Sampling pump
Topics of Presentation, R&D Topics at IVDAnalysis of the
Coals UsedImpact of SO2 injection at the outlet of the radiative
section (1150°C), OF27SO2 captured along the convective part(down
to 450°C) by different inlet concentrationsH2S formation: Impact of
SO2 accumulation (λ1=0.75)Impact of coal property on H2S formation
(λ1=0.75, T1~3 Sec)Results of Parameter Study
(SO2/H2S)Deposit-Sampling Probes (air/oxyfuel)SEM-BSE and SEM-MAP
Ca-CSEM-WDS/EDS-MAP: Al, Si, O and Ca, S, FeSEM-MAP: Ca,S /
Ca,CResults of the 500kW facility- SO3 and DepositsOngoing/Future
R&D Topics at IVD
