S4FESUSTAINABLE FOSSIL FUELS FOR FUTURE ENERGY
ROMA, July 6-10, 2009
CO2 Capture and Storage in the Greek Electricity Generation Sector
A. Doukelis1, E. Kakaras1, D. Giannakopoulos2, N. Koukouzas2
1National Technical University of AthensLaboratory of Steam Boilers and Thermal Plants
2Centre of Research and Technology HellasInstitute of Solid Fuel Technology and Applications
2
Contents
! Lignite in the Greek electricity generation sector
! CO2 Capture and Storage
! Green-field Oxyfuel Greek Power Plant
! Retrofit Greek Power Plant with CCS
! Retrofit and new plant costs for Greek Power sector
! Conclusions
3
Lignite in the Greek electricity generation sector 1/2
" Lignite plays an important role in Greece’s energy sector as it currently satisfies ca. 60% of the country’s needs in electric power. The annual production of lignite is around 65 million tons and almost the entire production is consumed for electricity generation in the Greek coal-fired power plants, which are about 4800 MW and use conventional technology.
" It is estimated that in 2010, approximately 37.5 % of the existing lignite-fired power plants, which produce 49.2 % of electricity in Greece, will reach 30 years of their operational life.
" There is enough Greek low rank lignite to meet the demand of the electricity sector in terms of production and reserves. Certain -but very limited-amounts of local lignite (xylitic type with high heating value between 12-16 MJ/kg) and imported coal, are used as additional fuels.
" Therefore, taking into consideration the forecasts for increase in the electricity demand over the coming years, the old and low-efficiency units should be either renovated or replaced by new units.
4
Lignite in the Greek electricity generation sector 2/2
Share of Electricity production sources in Greece
-
10
20
30
40
50
60
70
2005 2006 2007 2008 2009
Year
(%)
LigniteOilNatural GasHydroWind + RESImports
The Electricity Production balance in Greece was 53.4 TWh in 2005
reaching 56.9 TWh in 2008 for the interconnected system
RES in HV grid
5
EC Directive proposals
European Commission and European Council proposals for post-Kyoto period
" Revision of Directive 2003/87/EC for the improvement and expansion of the Emission Trading System of Green House Gases (23.1.2008 COM(2008) 16 final 2008/0013 (COD))
" Regarding the CO2 storage in geological formations (23.1.2008, COM(2008) 18 final/ 2008/0015 (COD))
" Revision of Directive 2001/80/EC for CO2 capture ready units (> 300 MW)
6
CO2 Capture and Storage
! The development of novel electricity generation technologies aims at (near) zero CO2 emissions, through Carbon Capture and Storage (CCS).
! The current study has focused on a Greenfield application of Oxyfuel firing with advanced drying process and retrofit applications of both Oxyfuel and Amine Scrubbing technologies for typical power plants.
7
0
10
20
30
40
50
60
70
80
90
Hard coal Lignite Natural Gas
EUR
/MW
h
No capturePre-combustionPost-combustionOxyfuel
Note:Power generation cost without CO2 transport and storage cost
CO2 Capture and Storage in the European market 1/2
Estimated electricity generation cost from large coal, lignite and NG units in 2020, without
and with CO2 capture
European Technology Platform, Zero Emission Fossil Fuel Power Plants (ZEP), Working Group 1, Power Plant and Carbon Dioxide Capture
0
20
40
60
80
100
Hard coal Lignite Natural Gas
EUR
/t C
O2
Pre-combustionPost-combustionOxyfuel
Note:CO2 Avoidance cost without transport and storage cost
Power plant andCCS technologyimprovementpotential
Estimated CO2 capture cost from large electricity generation units in 2020 (coal, lignite and NG)
8
CO2 Capture and Storage in the European market 2/2
Pilot Projects CCS(Zero Emission Fossil Fuel Power Plants - ΖΕP)
6 of 43 projects on lignite All technological options are involved Most selected solution is post combustion
9
European Strategic framework for Energy
Carbon Capture and Storage (CCS) Projects
Proposal of Presidency to European Council (20/3/2009) related to European Economic Recovery Plan and call for proposals of
May 2009
Member State Station Capacity (ΜW) TechnologySaline
AquifersOil / Gas
fieldsEnvisaged EC
contribution Μ€Huerth 450 IGCC √
Jaenschwalde 500 OxyFuel √Eemshaven 1200 IGCC √Rotterdam 1080 PC √Rotterdam 800 PC √
Poland Belchatow 858 PC √ 180Spain Compostilla (Leon) 500 OxyFuel √ 180
Kingsnorth 800 PC √Longannet 3390 PC √
Tilbury 1600 PC √Hatfield (Yorkshire) 900 IGCC √
Italy Porto Tolle 660 PC √ 100
France Florange 50Application for transport of
CO2 from steel industry √ 50
Total 1050
United Kingdom
The Netherlands
Germany 180
180
180
Coa
l
105
Green-field Oxyfuel Greek Power Plant 1/6
" The reference power plant used for the assessment of the efficiency of a Greenfield oxyfuel power plant is a 360 MWel lignite-fired power plant with reheat and 7 water preheaters with steam extraction from the ST
" Since the raw lignite has high moisture content, a fuel pre-drying system has been integrated to both the reference and oxyfuel plant, in order to increase the plant efficiency. According to this pre-drying concept, the heat content of the moisture removed in the form of steam from the raw lignite, is used for the drying (WTA drying system).
Raw Lignite ultimate analysis C w% 18.5 H w% 1.5 S w% 0.4 O w% 8.7 N w% 0.6 Ash w% 15.0 H2O w% 55.3 LHV (kJ/kg) 5.418
Dried Lignite ultimate analysis C w% 36.5 H w% 2.9 S w% 0.8 O w% 17.2 N w% 1.1 Ash w% 29.5 H2O w% 12.0 LHV (kJ/kg) 13.025
116
Green-field Oxyfuel Greek Power Plant 2/6
360 MWel lignite-fired PP
S20
G3
G4
G5
G6
G7
G8
G9
G10
S3
S4
S5
S1
S7
S10S9
S6
S11S12
S17
S19
S21
S16
S29S30 S31
S32
S33 S34
S35 S36
S37S38
S40S39
ESP
LUVO
EVAP
SH1
SH2
SH3
RH1
RH2
ECO
HP
IP LP
S24
F1
F3
F21
D1D2
D3
D4 D5
D6
D7D8
D9
D10
D11
G1 G2
S2
S8
S13
S148 S15
S18
S23
S25
S22
S26
S27
S28
G11
127
Green-field Oxyfuel Greek Power Plant 3/6
! Combustion is achieved with high-purity O2 from an ASU. The oxygen purity is 95 % vol (the remaining 5 % vol is mainly Ar and N2).
! The main energy requirements for the O2/CO2 recycle combustion are:" ASU power consumption" Compression of final product for transportation/sequestration (110 bar)" Fans consumption for flue gas re-circulation" CW pumps consumption for flue gas cooling/air inter-cooling at the ASU
! When applying O2/CO2 recycle combustion, the air preheaters are not used, resulting in an increase of the flue gas exit temperature to ca. 310 ºC.
! The molecular sieves (removal of water vapour, CO2 and impurities from air before entering the distillation column) are regenerated utilising dry N2 from the ASU, heated by flue gas to 150ºC.
! The furnace stoichiometry applied is 1.05. ! Air infiltration rate in the boiler and ESP: 0.01 kg/ kg of flue gas (each)! CO2 compression occurs in 5 stages with intermediate cooling to 21 ºC.! Air compression for the ASU occurs in 2 stages with intermediate cooling
down to 21 ºC.
138
Green-field Oxyfuel Greek Power Plant 4/6
! Several process integration options were identified and an optimized scenario has been investigated, integrating these options.
! A hot ESP is used for particle removal at the boiler exit. The flue gas recycle is extracted downstream the hot ESP and mixed with the O2 stream from the ASU. The absence of an air preheater leads to the necessity of a second hot ESP, which increases air inleakage resulting into lower separation efficiency compared to a cold one. The O2 stream is heated from the remaining flue gas, which consequently follows a further particle removal process in a cold ESP.
! The flue gas that exits the boiler, before entering the flue gas treatment process line, is used to partly replace LPH4 water heater.
! Heat from the FGC is integrated in the water steam cycle by partly replacing low-pressure feedwater heaters 1 and 2.
! O2 is heated from the 1st CO2 compression step up to 110 ºC. Heat from the 2nd and 3rd compression steps is used for water preheating at the LPH1, LPH2 and LPH3 water heaters.
149
Green-field Oxyfuel Greek Power Plant 5/6
Feed
wat
er h
eatin
g LP
H1
to L
PH3
Feed
wat
er h
eatin
g LP
H1
to L
PH3
I1 I2
G7
G10
G11
G3
A7
G4
A8
A2
Air leakage
Ash
Air leakage
A5
A6
A9A10
I1 I3I2 I4
I5
G5
G6
G8G9
G1
G2
Lignite Dryer Waste water Dried lignite
F3
DC
AC
ASU
Wet ESP FGC Separation of non-
condensables
TEG
N2 t
o m
olec
ular
sh
ieve
s
ESP
A1 A3 A4
A11 A1
2
F1 F2
F3
Raw lignite
F3
D1
D2
D3
D4 D5 D6 D7 D8 D9 D10
D11
D12
D13
D14
D15
G12G13
G14
G15
G16
G17
G18
G19
S1
S2
S3
S4S5
S6
S7
S8S9
S10S11
S13
S12
S14
S15
S20
S16 S17
S21
S22
S18
S19
S23
S24
S25
I6 I7
I8
Oxygen Flow
I3 I4
G20 G21
G22
G23
1510
Green-field Oxyfuel Greek Power Plant 6/6
Ref. PP Greenfield oxyfuel PP
FW pump MWel 9.17 9.54
FD fan MWel 1.43 -
ID and gas fans MWel 2.77 3.55
Dryer MWel 25.21 25.21
Lignite mills MWel 9.05 9.05
ESP’s MWel 0.50 0.50
Fly ash transport MWel 0.85 0.85 Lignite feeding and handling system MWel 0.78 0.78
Condensate pumps MWel 0.54 0.56 Circulating and cooling water pumps MWel 3.74 3.93
Others MWel 1.14 1.20
ASU MWel - 52.39
CO2 compression MWel - 46.35
Raw Fuel flow kg/s 136.34 136.34
Gross power output MWel 356.78 392.45
Gross el. efficiency % 48.30 53.13
Net power output MWel 301.61 238.53
Net el. efficiency % 40.83 32.29
! In both reference and oxyfuel power plant, the fuel consumption remains the same.
! Despite the increase in gross power output by 10%, the high auxiliary power demand for CO2capture results in a significant penalty in power plant performance.
! The greenfield oxyfuel PP with waste heat integration has an efficiency penalty of ca. 8.5 percentage points.
16
Retrofit Greek Power Plant with CCS 1/5
Retrofit of brown coal Power Plant with CO2 sequestration
! The simulations of the power plant and the CO2 sequestration retrofit options were performed with the thermodynamic cycle calculation software ENBIPRO.
! The 330 Mwel (gross) power plant under examination has a supercritical boiler, a HP-MP-LP steam turbine and 8 preheating stages and represents a typical modern Greek low-quality coal fired power plant with flue gas desulphurisation.
! In the examined retrofit test cases, the following general assumptions have been made:- The fuel consumption remains the same- The water/steam cycle remains as much as possible unchanged- The final CO2-rich stream is compressed to 110 bar, in order to facilitate
transportation and sequestration- The final CO2 stream purity is 98%
17
Retrofit Greek Power Plant with CCS 2/5
" Combustion is achieved with high-purity O2 produced by a cryogenic air separation unit. The oxygen purity is 95%, the majority of the rest being Ar.
" When applying the oxyfuel concept in a coal-fired PP, air preheaters are not used, resulting in an increase of the flue gas exit temperature to ca. 310 ºC.
" Before air enters the distillation column, water vapour, CO2 and any other impurities are removed, utilising adsorption with molecular sieves, which are regenerated by dry N2 from the ASU at about 180ºC. The flue gases exiting the boiler provide the heat required for nitrogen heating.
" For 95% oxygen purity and 3% boiler air infiltration, the O2/CO2 recycle combustion process can capture 79% of the CO2 from coal combustion. In a greenfield application (improved sealing/lower air infiltration rate) the CO2recovery rate can be comparable to the amine scrubbing process.
" Excess oxygen is 1.5%, whereas the flue gas recirculation is chosen so as to maintain the flue gas flow and temperature inside the boiler at the same level as in the conventional power plant.
" The main energy requirements for the O2/CO2 recycle combustion are:# Air compression for the ASU (5.5 bar)# Flue gas compression for transportation and sequestration (110 bar)# CW pumps consumption for flue gas cooling and ASU air inter-cooling
18
Retrofit Greek Power Plant with CCS 3/5
ASU
FGTEG
H2O N2, NOx, O2, Ar Inert gases
N2
N2, to molecular sieves
O
Water
Water
ESP
Ash Coal
Slag Fly Ash
Flue gas from rezi-fans
HPST
IPST LPST
Unit 1200 & 1300
Unit 500
Uni
t 200
Unit 100
Unit 1100
Unit 700
Flue gas cooling/cleaning
Dehydration/ Flue gas compression
Air Separation Unit
Fuel Input/
Slag removal
Water/steam circuit
Retrofit : OxyFuel
Heat integration not implemented
19
Retrofit Greek Power Plant with CCS 4/5
Retrofit : Amine Scrubbing
" In the amine gas processing operation, CO2 is absorbed from flue gas by the liquid solvent in an absorption tower, where gas stream and liquid solvent are contacted in counter-current flow. In the stripper (regeneration) the charged amine solution is heated with steam, in order to strip off the CO2.
" Flue gases at the outlet of the boiler are cooled down to 40ºC to condense the water vapour and then compressed up to about 1.3 bar.
" CO2 recovery from the flue gases is assumed to be 90%. " The energy requirements of MEA scrubbing are:
# Heat consumption for regeneration of the reach solution, in the form of LP steam extraction at ~ 5 bars, which provides its latent heat and the condensate is compressed and returned to the feed-water tank. The thermal consumption (state of the art commercially available solutions) is ca. 3.25 MJ/kg of CO2 removed (or ca. 1.4 kg steam/kg CO2).
# Electricity consumption: the most energy-consuming process is the flue gas blower used to overcome the system pressure drop (~100-200mbar). This category also includes the energy required for the pumping of the amine solution and the pumping of the absorber wash water.
# Compression of the final product to 110 bar for transportation and sequestration.
20
Retrofit Greek Power Plant with CCS 5/5
ConventionalPower Plant
Oxyfuel Amine Scrubbing
Net Power Output MW 293.7 211.0 200.5
Net efficiency % 35.4 25.4 24.2 Power output decrease MW - 82.7 93.2
Efficiency decrease % - 10.0 11.2
Specific emissions
kg CO2/kWh
1.075 0.31 0.17
21
Retrofit and new plant costs for Greek Power sector 1/3
General assumptions
# Rate of return: 8%# Inflation rate: 3%# Lignite cost: 1.8 Euros/GJ# Natural gas cost: 5.5 Euros /GJ# Payback period for solid fuel-fired power plants: 25 years# Payback period for combined cycle power plants: 15 years# Operating and maintenance cost: 3% of the investment cost annually plus
0.01 Euros/kWh for lignite fired power plant or 0.005 Euros/kWh for NGCC# Operating hours per year: 7500h# The CO2 transportation and storage cost has not been included
22
Retrofit and new plant costs for Greek Power sector 2/3
0.760.370.8650.310.171.075kg/ kWh
CO2 specific emissions
13706001150157019001100€/kW
Investment cost
43.056.544.025.424.235.4%Net efficiency
766380300211200293.7MWel
Net power output
IGCCNGCCClean coalOxyfuelAmine scrubbing
Convent.lignite fired power plant
Specific assumptionsSpecific assumptionsSpecific assumptionsSpecific assumptions
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Retrofit and new plant costs for Greek Power sector 3/3
Cost of Electricity generation
Conventional Clean Coal Technology
Natural Gas Combined
Cycle
Fixed Cost
Variable cost
Risk due to NG price
Risk due to CO2 (as of CCGT)
Fixed Cost
Variable cost
Risk due to NG price
Risk due to CO2 (as of amine -oxyfuel)
Cost of Electricity generation
Clean Coal Technology
NGCC IGCCOxyfuelAmine
Total cost of electricity for different technological options
24
Thessaloniki BasinMesohellenic Trough
Source: GESTCO Project, 2003, European Potential for the Geological Storage of CO2
CCS potential in Greece 1/2
25
CCS potential in Greece 2/2
34onshoreAlexandria
2345Total
360onshoreMesohellenic basin
145onshoreW. Thessalonikisandstone
459onshoreW. Thessaloniki1343offshorePrinos
Storage Capacity (Mt CO2)
LocationAquifer
Source: GESTCO PROJECT
26
Conclusions
! Greek interconnected power system has a strong dependence on domestic fuel (lignite) for electricity generation
! CCS technologies reduce the efficiency of the power plants by 8.5 – 11% percentage points and capacity by 80 – 90 MW for a 300 MW unit, while the CO2 emissions are improved by up to 90%.
! Heat integration can reduce the efficiency penalty, especially in the Oxyfuel technological option by up to 1.5 – 2% percentage points.
! CCS plants can be economically viable compared to other low CO2emissions technological options for power generation