1
Prof. Dr. techn. G. Scheffknecht
Institute of Combustion and Power Plant Technology
Pilot scalePilot scale combustion testing
Installation and Operation of R&D test facilities under oxy-fuel
conditions
4th APP OFWG Capacity Building Course, Tokyo, Japan 2012
Joerg [email protected]
University Stuttgart
Prof. Dr. techn. G. Scheffknecht
Institute of Combustion and Power Plant Technology
Institute of Combustion and PowerInstitute of Combustion and Power Plant Technology - IFK (former IVD)
Universität Stuttgart
2
Outline
• 0.5 MWth Unit Retrofit
• Oxy-fuel Burner DevelopmentOxy fuel Burner Development
• Test Results and Experiences• NO formation and reduction• S behaviour• Corrosion, slagging and foulinggg g g• Modelling
• Ongoing/Future R&D topics
3
Example of Emission Reduction (Reunion of Germany)
1982 - 1999: old federal states1990 - 1999: new federal statesDust
in millon tons0.25
Sulphur dioxidein millon tons2.0
Nitrogen oxidein millon tons0.8
4
1982 84 86 88 90 92 94 96 1999
3
IFK 0.5 MWth Unit Retrofit for Oxy-Fuel operation
under the requirement to keep availability for air firingunder the requirement to keep availability for air firing
0.5MWth Unit Modifications for Oxyfuel Combustion Conditions
Coal feeding
FD fan
Oxygen supply
Flue gas recycle duct
Condensers
6
Bottomash
APH
g
ID fan
ESPSCR stack
Bypass
4
Pf-fired 0.5 MWth Test Facility(15 years operation)
additional fuel +conveyor air
coal + primary air
secondary air, flue gas recirculation
ti l
burner
to stack
verticalfurnace
SP 1 SP 2 SP 3 SP 4 SP 5
7
ESP
fabricfilter
slag and ash
Φ > 100 µm
SCR Catalyst
fly ash(1 fraction)
fly ash(3 fraction)
fly ash(1 fraction)
SP 6
O2/ CO2 Supply Infrastructure
Preparation:
Oxy-fuel Mode IntegrationInfrastructure
• Negotiations with providers:commissioning of tanks, lines, product prices, installations, maintenance, …
• Permission procedures:City of Stuttgart and
8
City of Stuttgart and University authorities
• Engineering:work safety aspects, construction and ground works,climatic constraints, …
5
O2/ CO2 Supply Infrastructure
Consumption (planned):
Infrastructure
• Oxygen: 72,000 m3N
• Carbon dioxide: 48 tons
Tank capacities:
• Oxygen: 6,000 m3N
• Carbon dioxide: 5 tons
Modifications for Oxyfuel Combustion
CO2O2
gas distribution
storage tanks consumers20kWth
0.5MWth
others
6
level no.
123
Concerned area of the major changes for the adaptation for the new burner design
COCO
Infrastructure
Air-Oxyfuel Test Facility (500kWth)
345
6789
10
1112131415
1617181920
21
22
StoragetanksFD/ RG fan
O2
CO2
AiO2 CO2
Gasdistribution
Coal feeding
Burnerwindbox
Air
StoragetanksFD/ RG fan
O2
CO2
AiO2 CO2
Gasdistribution
Coal feeding
Burnerwindbox
Air
Inflame Measurements•Gas emissions•Gas temperature•Heat Flux•Radiation etc.
Air/Flue gas
11
23
24
25
26
27
28
29
30
31
Continuous gas emission measurements
Bottomash
ID fanESPSCR
Stack
Air
APH
By-passes
Bottomash
ID fanESPSCR
Stack
Air
APH
By-passes
Sampling•Ash, HCL, SO3
re-circulationventilator
O2/recyled flue gas 0.5MWth Unit Modifications for Oxyfuel Combustion Conditions
duct for re-cycled flue-gas
O2 injection system(MFC, injector)
12
Venturi orifice to furnace
7
Topics of first Oxyfuel-Tests
• Start-up/shut-down procedure
• Identification of air inleakage• Identification of air-inleakage
• Max. CO2 concentration
• Switch from air to oxyfuel operation
• Parameter optimisation (variation of O2-injection,
13
Parameter optimisation (variation of O2 injection,
recycle rate, …)
• Definition reference flame definition (air/oxyfuel)
• Start of test programmes
Switch from once-through to re-circulation mode (I)Lausitz lignite
80
100
80
100O2 in vol.-%dry
CO2 in vol.-%dry
flap open
air combustion
start of O2 injection and
CO2 as carrier gas
flap for flue-gas re-circulation (FGR) opened
40
60
40
60FGR flapposition in %
14
air combustion
0
20
18:09 18:29 18:49 19:09Time
0
20
LA_OXY_1_20980-21450
flap closed
8
Shift from Air to Oxyfuel of the 30MW Pilot Plant
Approx. 60 min
Behaviour of flue gas concentrations
15
Source: Vattenfall, Alstom Cottbus 2009
• Switching from air to oxy-fuel combustion, achievable in short time interval (~30 minutes).
• High CO2 concentration achievable (~95% dry).
Conclusions from 0.5 MW Retrofit Test Facility
High CO2 concentration achievable ( 95% dry).• Operation under oxy-coal combustion with different
ranks of coals achieved successfully.• Burner adjustments required and successful
implemented• O2-concentrations at the burner inlet ducts up to 100%
16
• High flexibility of recycle rate (40-90%)• Additional safety measures required
More than 1500h successful Oxyfuel operation
9
Burner adjustments and further burner developments
17
Development of Low NOx Oxyfuel burner
Performed Investigations at the electrically heated 20 kW test facility:
•Determination of optimum oxygen injection method (pure or premixed
•Determination of optimum burner operation mode; swirl,
O2 concentrations in the different gas streams
Total combustion gas
Carrier stream Primary stream Secondary stream
21% 21% / 5% / 5% 21% / 23% / 100% 21% / 23% / 5%
27% 27% / 5% / 5% 27% / 30% / 100% 27% / 30% / 5%
39% 39% / 5% / 5% 39% / 43% / 100% 39% / 43% / 5%
momentum, velocity•Determination of optimum parameters for oxy-fuel operation using high volatile Brown Coals (Stoichiometric ratio, oxygen excess, oxygen content in combustion gas)•Staging at the oxyfuel combustion
10
Development of Low NOx Oxyfuel burner
Investigations at the 500 kW semi-technical test facility:
Comparison of two different burner designs• Flame characterisation and ignition optimisation under recycled
diti
Inflame Measurements•Gas emssions
•Gas temperature
conditions• Optimum O2 injection method• Impact of recycle rate on flue gas momentum,
flame stabilisation, internal recirculation• Staging at the oxyfuel combustion• Emission behavior
New burner designActual burner
19
secondary gas stream(optionally swirled)
primary gas streamand fuel
gas probe with nine drillings
secondary gas stream(optionally swirled)
primary gas streamand fuel
gas probe with nine drillings
Continuous gas emssion
measurements
Integration of the new burner design
20
Implementation of:• new primary line for the new burner• 4 new secondary lines for the new burner
• oxy-fuel staging• Second source of oxygen injektion
11
Integration of the new burner design
Previous burner installation (previous burner) with one primary and one secondary lines.
Current burner installation (new burner) with:• one primary • four different measured and controlled secondary lines • one oxygen line
21
Example of O2-Injection Modes
22
Pre-mixing (total) Individual Pre-mixing Direct injection
Source: Alstom Cottbus 2009
12
Test Results and ExperiencesTest Results and Experiences
• NO formation and reduction• S behaviour• Slagging and fouling
23
• Corrosion• Modelling
Electrically heated test reactor (20kW)
Experiment Conditions Air & 27% O2/73% CO2
Coals Klein Kopje, Lausitz
Oxidant flow through burner
Constant for all cases [6.7 m³/h]
24
λoverall 1.15λ1 (burner stoichiometry) 0.75, 0.85, 0.95
T1 1, 2 and 3 seconds
13
NOx reduction potential during staged combustion
300
350
400Air_3 sec
Air_2 sec
Klein Kopje Coal
0
50
100
150
200
250
0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2
Burner Stoichiometry
NO
x [m
g/M
J] 27% Oxy_3 sec
27% Oxy_2 sec
Un-staged
Com
bustion
25
Parameters Optimum EffectBurner Stoichiometry 0.75-0.85 Oxygen deficiency, encouraging
formation of N2
Residence time in reduction zone 2-3 seconds Longer time available for conversion of NOx precursors to N2
Temperature Shift of coal-N towards gas phase
Fate of recycled NO - Summary
99
8596
8895
81
9810091
72
92
798391
80
100
120
led
NO
[%]
Air_KK 27% O2_KK Air_LA 27% O2_LA Air_NG Oxy_NG
595049
3847
13
5339
0
20
40
60
80
0.75 0.85 0.95 Unstaged
Stoichiometric Ratio
Red
uctio
n of
recy
cl
26
• Reduction dependent on combustion mode (burner stoichiometry and residence time in reduction zone).
• Generally higher reduction for oxy-coal combustion.
• For the coals investigated: for a particular combustion condition, percentage reduction during oxy-coal combustion is almost similar.
• Combustion modification can take care of recycled NOx accumulation.
14
Conclusions from 20 kW furnaceNOx emission rate is lower during oxy-coal combustion with oxygen partial pressure between 21-27% (un-staged combustion). Oxidant staging is applicable for oxy-coal combustion.Recycled NOx can be reduced by combustion modification, with ~60% reduction during un-staged combustion and ~100% during staged combustion (λ1=0.75 and T1=3 sec) for all coals tested.CO in the near burner region is higher during oxy-coal
27
CO in the near burner region is higher during oxy coal combustion indicating enhancement of water-shift and CO2shift reactions.
Test Results and ExperiencesTest Results and Experiences
• NO formation and reduction• S behaviour• Slagging and fouling
28
• Corrosion• Modelling
15
Set-up and description of 20 kW once through furnace
• SO2 Injection: up to 6000 ppm via the secondary stream of the burnerof the burner
• In-flame measurements H2S/SO2, staged/unstaged
• SO2 measurements outlet rediative section T=1150°C
29
• SO2/SO3 measurements outlet of convective section T= 350°C
SO2 and H2S formation concentrations in an Air and Oxyfuel environment
6000
24
30SO2 H2S SO2+H2S O2
6000
24
30SO2 H2S SO2+H2S O2
SO2+H2S]max
SO2+H2S]-mass balance
0
2000
4000
0 0.5 1 1.5 2 2.5
SO
2 , H
2 S [p
pm]
0
6
12
18
O2
[vol
%]
SO2+H2S]max
0
2000
4000
0 0 5 1 1 5 2 2 5
SO
2 , H
2 S [p
pm]
0
6
12
18
24
O2 [
vol%
]
30
Distance from Burner [m]0 0.5 1 1.5 2 2.5
Distance from Burner [m]
Air- Blown Combustion, λ1=0.75
OF27 Combustion, λ1=0.75
16
Measuring SO3 - Methods
• Controlled condensation method (CCM): discontinuous sampling; selective
condensation of H2SO4 in a tempered (85-95°C) glass coil
in out
H2SO4 condenser
31
• Continuous SO3 monitor working on a wet-chemical principle1: The analyser should be further tested under oxy-fuel conditions (tested by EOn in the UK2)
1 Jackson, P. J.; Hilton, D. A.; Buddery, J. H. Continuous measurement of sulphuric acid vapour in combustion gases using a portable automatic monitor. J. Inst. Energy 1981, 54, 124–135. 2 Couling, D. Impact of Oxyfuel Operation on Emissions and Ash Properties based on E.ON’s 1MW CTF. Presented at the IEAGHG Special Workshop on Oxyfuel Combustion, London, January 2526, 2011.
Correlation of SO3-Moisture and Acid dew point
• Considerable increase of acid dewpoint due to high SO3 and H2O concentrations• Increase by 20-40°C will influence operation of low temperature units
)
air
wpo
int
tem
pera
ture
(°C
)
32(Scheffknecht et al 2009)
Moisture content of flue gas (%Vol)
Acid
dew
17
Correlation of SO3-Moisture and Acid dew point
Similar increase of SO3 concentration at a SCR catalyst, but much less effect on dew point temperature under oxy-fuel conditions.
)w
poin
ttem
pera
ture
(°C
)
33
SO3 content (mg/Nm3)
Acid
dew
(Spörl et al 2011)
Measuring SO3
• Measuring SO3 is difficult, due to high reactivity
• SO3/H2SO4 can be absorbed by3 2 4 y
• filter materials
• fly ash on sample filter
• Carefull choice of construction materials for sampling system
• Sampling system must be carefully heated above sulfuric
acid dewpoint
34
18
Test Results and ExperiencesTest Results and Experiences
• NO formation and reduction• S behaviour• Corrosion, slagging and
35
fouling• Modelling
Corrosion under oxy-fuel
• Corrosion risk• Tests at IFK• Results
36
19
Identification of corrosion risk
37
Source: Takashi Kiga, Experimental study Results on corrosion issues in oxy-fuel combustion process, Special Workshop on Oxyfuel Combustion, Addressing SO2/SO3/Hg and Corrosion Issues, London, Jan. 25th – 26th, 2011
Tests at IFK
CO2
GC lAir
CO2
GC lAir
short-term testsup to 100 h
long-term tests
StoragetanksFD/ RG fan
O2
Stack
AirO2 CO2
Gasdistribution
Coal feeding
Burnerwindbox
By-passes
StoragetanksFD/ RG fan
O2
Stack
AirO2 CO2
Gasdistribution
Coal feeding
Burnerwindbox
By-passes
Bottomash
ID fanESPSCRAPHBottom
ash
ID fanESPSCRAPH
Real fly ashGas composition: SO2,
CO2, H2O, O2, NOx
source: Stein-Brzozowska et al, [GSB6]
20
Lignite fly ash deposit, end of radiative zone
air oxy-fuel
conc
entra
tion
S S
39
In both cases Fe-rich molten phasesMore S in oxyfuel and bigger fraction of smaller particles noticedEnrichment at the particles surface
SEM-MAP – Ca + S + O / Ca + C + O
Ca+S+O Ca+C+O
40
- Close relation between sulfates and carbon on the particle surface- Carbon content increased by exposure time
21
Alloy N1 after 350h at 750°C
0C_7
50h_
3
case
BSE MAE and O S
conc
entra
tion
N1-
A_3
550
C_7
50h_
1
air-c
y-fu
el
BSE MAE and O S
41
N1-
O_3
5
oxy
• higher growth of oxide-scale under oxy-fuel conditions;• internal oxidation was noticed already in the pre-exposed state;• no sulphur-front recognized
Results of the 500kW facility- SO3 and Deposits
• Clear tendencies that under Oxyfuel conditions the SO3concentration are higher
• Impact of Oxyfuel conditions on SO2/SO3 conversion rateneeds further clarification
• Verification of data according to pilot scale measurements (30MW plant Schwarze Pumpe)
• Indications that beside sulfatization carbonization on the particle
42
• Indications that beside sulfatization carbonization on the particle surface of deposits occurs under Oxyfuel conditions
• Carbonatisation of sulfates can enhance the release of SulphurComponents which promotes sulphur corrosion mechanism
22
Test Results and ExperiencesTest Results and Experiences
• NO formation and reduction• S behaviour• Corrosion, slagging and
43
fouling• Modelling
Numerical Modeling and Simulation, combined Simulation (Furnace and Steam Side)
Program Code AIOLOS
Burner level 3
Burnout air
PulverizedCoal
Combustion
HomogeneReaktionen
Radiation
TurbulenceTwo Phase
Flow
Homo-geneous
Reactions
44
Burner level 1
Burner level 2ChemicalReactions
HeatTransfer
HeterogeneReaktionen
OpticalProperties
Hetero-geneous
Reactions
23
Detailed Coupled Simulation
Measurement data 3D geometry Heat3D geometry
AIOLOS DYNAMIK
Measurement dataProcess data
Tubewall
Heat fluxesTemperatures
3D geometry Heat exchanger
Water/SteamProcess
Simulation
Iterations
g yboiler
Furnace Simulation
Iterations
45
Results forthe whole system
with high spatial resolution
Temperaturepressure
material stressTemperature velocity
concentrations
Current Model Developments for Oxy-Fuel
• Model developments for Oxy-fuel combustion• Development of mathematical models for heterogeneous char
conversion under Oxy-Fuel conditions including enhanced gasificationconversion under Oxy Fuel conditions, including enhanced gasification reactions
• Mathematical models for turbulent gas phase reactions:
• gas phase combustion, NOx formation and destruction
• Development of mathematical models for radiative heat transfer in CO2-enriched atmospheres
46
• Validation of new modelling approaches with experimental results
• Combined coupled approach to furnace and steam generation simulation
• Simulation and optimization of oxyfuel-combustion (0.5MWth, 30MWth,….
24
Extended chemical reaction models
» Gas phase reactions:
(1) CnHm + n/2 O2 → n CO + m/2 H2n m 2 2
(2) CnHm + n H2O → n CO + (m/2 +n) H2
(3) H2 + ½ O2 ↔ H2O(4) CO + H2O ↔ CO2 + H2
» implementation of additional reactions and considering equilibrium reactions enables accounting for chemical effects of specifically high O2and CO levels in the oxidizing atmosphere during oxy fuel combustionand CO2 levels in the oxidizing atmosphere during oxy-fuel combustion
» including reverse reaction of (3) is particularly required for correct prediction of local flame temperatures since equilibrium is shifted towards educts in high temperature flames
47
Extended chemical reaction models
» Char burnout reactions:
(1) C + ½ O2 → CO (char oxidation)2
(2) C + CO2 → 2 CO (Boudouard reaction)(3) C + H2O → CO + H2 (water-gas-shift reaction)
» gasification reactions (2) and (3) may have major impact in O2-lean regions due to higher partial pressures of CO2 and H2O compared to conventional air-firing
» at ambient pressure and typical combustion temperatures the reactions (2) and (3) may be considered irreversible since the equilibrium is shifted towards the product side
48
25
Simulation results / Validation
» Test case: 500 kWth reactor, Lausitz lignite, O2 direct injection @ burner, total [O2] = 21%
Axial plots showing:Axial plots showing:
• very good agreement after ~ 0.5 m
• improved CO prediction
• deviations at near burner region
49
regiondelayed ignition late O2 consumption
• overall good accuracy
Ongoing/Future R&D Topics at IFK
• Experimental Oxy-fuel combustion topics: • Rank of coal (bituminous, lignite, hard coals…)• Slagging, Fouling, (impact of higher SO2, H2S, CO2, HCl etc.)Slagging, Fouling, (impact of higher SO2, H2S, CO2, HCl etc.)• Corrosion high-low temperature (Deposits, HCl, SO2, SO3, H2O…)• Fly ash quality and utilisation (EN 450 …)• Component development and test (burner, …)• Emissions (Hg, fine dust, etc)• Flue gas cleaning (SCR, Additives…)• Particle removal and impact to particle removal systems ( ESP and Bag
50
• Particle removal and impact to particle removal systems ( ESP and Bag-filter performance)
• Biomass (co-)combustion• Oxy-fuel: CFB • Improvement and validation of CFD models
26
Biomass (co)-firing under oxy-fuel Bio-CCS
In order to keep• Global temperature rise• Safe CO2 levels Below 450 ppm
Below 2°C
2
Given • Growing population• Increasing energy demand• Energy mix
Atmosphericcarbon
51
measures beyond CCSneed to be considered
Organiccarbon
Geological Storage
Bio-CCS
Bio-CCS (or BECCS)
52
(Koornneef, ECOFYS, 2010 in Dixon et al, IEA, 2012)
27
Bio-CCS technologies
• Biochemical production of biofuels• Biomethane• Bioethanol
• Thermochemical production of biofuels• Hydrogen• SNG• BtL
• Biomass combustion for electricity and/or heat production• Biomass co-firing (direct/indirect)g ( / )• 100% Biomass combustion (CHP plants and CFB boilers)• Biomethane/Bio-SNG• Biomass-based IGCC (BIGCC)
• Industrial applications (Fuel substitution, pulp and paper, etc.)
53
(EBTP/ZEP, 2012)
Vattenfall Oxy-fuel Pilot Plant
54