oxy-fuel process for hard coal with co capture · ¨denox and fgd prior to co 2 capture ¨denox and...
TRANSCRIPT
2nd Workshop
International Oxy-Combustion Research Network Hilton Garden Inn Windsor, CT, USA
25th and 26th January 2007
Hosted by:
Alstom Power Inc.
PRESENTATION - 16
Oxy-Fuel Process for Hard Coal with CO2 Capture A Part of the ADECOS Project
by: Prof. Alfons Kather Technical University of Hamburg-Harburg, Germany
2nd Int'l Oxy-Combusiton Workshop Page 1
Hamburg University of Technology
Oxyfuel Process for Hard Coal with CO2 Capture
A Part of the ADECOS Project
Presented by Alfons Kather
Funded by the German Federal Ministry of Economic Affairs within the COORETEC program
Partners:Vattenfall, ALSTOM, E.ON, RWE, SIEMENS, Hitachi, TU
Dresden, TU Hamburg-Harburg
Prof A KatherC Hermsdorf
M KlostermannK Mieske
Institute of Energy Systems
Institute of Thermal and Separation Processes
Prof R EggersD Köpke
IEAGHG International Oxy-Combustion Network, 2nd Workshop26th and 27th January 2007, Windsor (CT) USA
2
98 % CO22 % N2, Ar, O2,
NOx, SO2
Oxy-Fuel Process – Simplified Process Scheme
Air
Air SeparationUnit
N2
O2
Flue Gas Recycle
H2O
89 % CO211 % Ar, N2,
O2, …
2/3
1/3
Flue GasDrying
CO2 SeparationUnit
18 %
82 %
47 % CO253 % Ar, N2,
O2, …
all percentages asmolar percentage
Coalexhaust gas
► Introduction
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3
Objective
Identification of key factorsthat are decisive for the
▸ feasibility
▸ economic efficiency
particularly with regard to realistic design boundaries
IV
I
III
Current Research Projects at the TUHH
► Introduction
II
CO2
Ar,N2,O2, …
Air
exhaust gas
Air SeparationUnit
N2
O2
Coal
Flue Gas Recycle
H2O
Flue GasDrying
CO2 SeparationUnit
almost pureCO2
Ash
4
III
CO2
Ar,N2,O2, …
Air
exhaust gas
Air SeparationUnit
N2
O2
Coal
Flue Gas Recycle
H2O
Flue GasDrying
CO2 SeparationUnit
almost pureCO2
Ash
Flue Gas Recycle
► Flue Gas Recycle
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5
up to 26 g dust per m³ (@STP)
Flue Gas Recycle Design Considerations
Low-dust recycle
+ using high-efficiency axial-flow fan
− temperature limited to 190 °C,270 °C with fixed blades
mill-internal coal drying (300 °C)?
today’s feed water temperature at 300 °C heat sink for cooling?
− sensitive to load fluctuations (fixed blades)
− very large dust precipitatorand long recycle ducts
High-dust recycle
− requires low-efficiency radial-flow fan
+ more robust than axial-flow fans
+ very stable with respect to load fluctuations
+ small dust precipitator andshort recycle ducts
• no increased wear of boiler expected
+ temperature up to 350 °C possiblemill-internal coal drying
max. dust load:< 0.3 g/m³ @STP
► Flue Gas Recycle
AshCoal
up to 76 g dust per m³ (@STP)
max. dust load:76 g/m³ @STP
AshCoal
6
Factors influencing the Recycle Requirement
• Condition:tadiabatic, Air = tadiabatic, O2+Recycle
• Underlying assumptions:tAir = 320 °CtO2
= 25 °CtCoal = 40 °CO2-excess: 15 %O2-purity: 98 %
tRecycle
Q&
tO2
tCoal
tadiabatic
► Flue Gas Recycle
2008
2126
°C
tad,Air
22.69
25.40
MJ/kg
NCV
21.05.001.051.008.824.4358.70
7.4013.601.580.617.253.6365.93
H2OAshNSOHC
Composition (in % by mass)
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Oxygen Concentration in the Combustion Atmosphere
First approach: Oxygen and recycled flue gas are mixed completely prior to the combustion
The oxygen concentration
▸ rises by reducing the recycle,
▸ is always above 21 %vol(in the range of interest),
▸ is a function of both recycle rate and oxygen excess
► Flue Gas Recycle
λ = 1.15
8
Combustion
CO2
Ar,N2,O2, …
AirII
exhaust gas
Air SeparationUnit
N2
O2
Coal
Flue Gas Recycle
H2O
Flue GasDrying
CO2 SeparationUnit
almost pureCO2
Ash
► Combustion
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9► Combustion
Coal: Bituminous CoalO2-purity from ASU = 99.5 %tadiabatic = 2126 °C
λ = 1.15λ = 1.10
λ = 1.20
λ = 1.15
λ = 1.10
λ = 1.20
First combustionexperiments ( )
Oxygen Concentration in the Combustion Atmosphere of the first Combustion Experiments
10
Flue Gas Treatment and CO2 Separation
► Flue Gas Treatment and CO2 Separation
I
CO2
Ar,N2,O2, …
Air
exhaust gas
Air SeparationUnit
N2
O2
Coal
Flue Gas Recycle
H2O
Flue GasDrying
CO2 SeparationUnit
almost pureCO2
Ash
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Impurities in the Flue Gas
• O2, NOX, SO2
▸ They may influence negatively the geological storage of the injected CO2by changing transport properties or by causing geochemical reactions
The maximum permissible concentrations for these impuritiesare still to be defined
• N2, Ar▸ They are inert components which have no significant impact
underground▸ They increase auxiliary power demand during liquefaction of the CO2
(other impurities cause the same, too)
▸ Removing them during air separation (to achieve purer O2)increases the auxiliary power demand of the air separation unit
Need for optimization between air separationand CO2-liquefaction (considering also air leakage)
► Flue Gas Treatment and CO2 Separation
12
70
80
90
100
0 1 2 3 4 5 6
Air leakage as % of flue gas (wet basis)
CO
2 con
cent
ratio
n in
dry
flue
gas
(v
ol%
)
O2-purity 95.0 %mol, O2-excess 15 % O2-purity 98.0 %mol, O2-excess 15 % O2-purity 99.5 %mol, O2-excess 15 % O2-purity 99.5 %mol, O2-excess 10 %
3
Impact of Impurities on the CO2-Concentration
▸ Fuel’s nitrogen and sulfur
▸Oxygen excess3 – 3.5% / 4.5 – 5% O2-residue
▸ Air separation unit98% O2-purity: 2% Ar
95% O2-purity: 3.8% Ar + 1.2% N2
▸ Air leakageapprox. 3 % of flue gas flow fora new conventional power plantup to 10 % over the years forpower plants in use
Air leakage is a major source for impurities and needs to be reduced by appropriate design
► CO2 Separation
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Phase Equilibrium of Argon – CO2
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
102030405060708090
100110120130140
T1 T2 T3 T4
p
molar fraction in mol/mol
► CO2 Liquefaction
14
Phase Equilibrium of SO2 – CO2
20,00
30,00
40,00
50,00
60,00
70,00
80,00
90,00
100,00
10 30 50 70 90 110 130 150
Temperature in °C
Pres
sure
in b
ar
12
3 4 5 6
87
SO2CO2
► CO2 Liquefaction
Caubet 1901
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Phase Equilibrium of O2 – CO2
0
20
40
60
80
100
120
140
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
molar fraction O2 in mol/mol
p in
bar
► CO2 Liquefaction
16
Multi-Component Phase Equilibrium O2 – N2 – CO2
► CO2 Liquefaction
D. Köpke, TUHH, 2006
N2 (mol/mol)
O2 (m
ol/mol)
CO2
(mol
/mol
)
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Flue Gas Treatment for Low Purity Requirements
<1 ppm34 ppm24.62.925.247.3Stack Gas
439 ppm0.40.4450 ppm0.398.8CO2
597 ppm0.35.00.65.089.1Flue Gas, dry
NOxSO2O2ArN2CO2
1
31
2
3
2
All valuesas molar-%
• For low purity requirements of the liquefied CO2
DeNOx and FGD treat only 3 – 4 % of the total flue gas volume (referred to the total flue gas before the recycle branching)
► Flue Gas Treatment
18
Flue Gas Treatment for Higher Purity Requirements
• For higher purity requirements of the liquefied CO2
DeNOx and FGD prior to CO2 capture
DeNOx and FGD treat now 30 % of the total flue gas volume (referredto the total flue gas before the recycle branching)
<1 ppm<1 ppm24.62.825.247.3Stack Gas
43 ppm57 ppm0.4449 ppm0.399.2CO2
60 ppm47 ppm5.00.65.089.4Flue Gas, dry
NOxSO2O2ArN2CO2
1
3
2
All valuesas molar-%
► Flue Gas Treatment
31
2
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Flue Gas Treatment for Highest Purity Requirements
<1 ppm<1 ppm24.72.825.247.3Stack Gas
20 ppm57 ppm0.4449 ppm0.399.2CO2
29 ppm47 ppm5.00.65.089.4Flue Gas, dry
NOxSO2O2ArN2CO2
• For highest purity requirements of the liquefied CO2
DeNOx is now needed before recycle branching
Even higher purity requirements would result in processes like adistillation plant with still higher power demands
1
3
2
All valuesas molar-%
► Flue Gas Treatment
3
2
1
20
Test CO2 Separation Plantat the Institute of Energy Systems
compressor
condenser
water
condenser
phase separator
water
adsorption
CO2-condenser
coolingunit
collecting vesselgas
withdrawalprobe
collecting vesselliquid
entrained flow
reactor
phase separator
► CO2 Separation
Up to now: Phase Equilibria - This test plant: Kinetic Behavior
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Overall Process
► Overall Process
IV
CO2
Ar,N2,O2, …
Air
exhaust gas
Air SeparationUnit
N2
O2
Coal
Flue Gas Recycle
H2O
Flue GasDrying
CO2 SeparationUnit
almost pureCO2
Ash
22
• Simulation of the overall process
▸Definition of the global parameters supported by subprojects andindustry
▸Commercial software: Ebsilon®, Aspen®
▸Continuous integration of the results of the subprojects
▸Use of state of the art technology
• Objectives
▸Feasibility
▸Process optimization (overall energetic efficiency)
▸Clarification of important details (e.g. CO2 purity, part-load behavior)
▸Economic efficiency
Overall Process
► Overall Process
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-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
p-T-diagram for Single-StageCryogenic CO2 Liquefaction
► CO2 Separation
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
90% CO2
Purity
95% CO2
98% CO2
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
90% CO2
Purity
95% CO2
98% CO2
90%
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
90% CO2
Purity
95% CO2
98% CO2
90%
95%
Conditions:Air leakage: 2.0 %O2-purity: 99.5 %
Range of interest
24
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
p-T-diagram for Single-StageCryogenic CO2 Liquefaction
► CO2 Separation
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
90% CO2
Purity
95% CO2
98% CO2
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
90% CO2
Purity
95% CO2
98% CO2
90%
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate80%
90% CO2
Purity
95% CO2
98% CO2
90%
95%
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
Capture Rate
90%
90% CO2
Purity
95% CO2
98% CO2
-60 -50 -40 -30 -20 -10 0 100
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Pres
sure
(bar
)
90% CO2
Purity
95% CO2
98% CO2
Capture Rate
90%
Conditions:Air leakage: 2.0 %O2-purity: 99.5 %
Range of interest
133.5 kWh/tCO2↓
133.7 kWh/tCO2↓136.6 kWh/tCO2↓
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Overall Energy Demand
Requirements: 90 % capture rate and CO2-purity > 95%
► CO2 Separation
26
Comparison of Different Processes(1% Leakage, Capture Rate 90%, Purity > 98,5%)
► Overall Process
36.6%
45.7%
38.1%36.9%
Reference Plant Simple Heat Recovery Optimised Process Optimised Processwith 3-Column-ASU
Net Efficiency
Spezifische Em Emissions in gCO2/kWhNetto
748
93 92 89
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Thank you for your attention!