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Fundamentals of CCGT Power Technology and the application of CCS
Tom Snow Design Development Engineer
Agenda
• Overview of SSE• Fundamentals of CCGT Technology• Application of CCS to new build CCGT plant• Peterhead CCS Project
• Overview of Peterhead Power Station• Overview of Peterhead Carbon Capture Process• Interfaces between Peterhead Power station and the carbon capture process
• Conclusions
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Overview of SSE
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Wholesale – Generation• 11,500MW of electricity generation capacity in total (UK and Ireland)
• Most diversity in fuel sources among UK generators
• 3,326MW of capacity for generating electricity from renewable sources
– Greater Gabbard Offshore Wind ‐ 500MW
– Clyde Onshore Wind – 350 MW
– Hydro – 1500 MW
• 3,009MW of coal‐fired capacity with biomass ‘co‐firing’ capability
• 4,262MW of gas‐ and oil‐fired capacity, including share of Marchwood, one of the UK’s most efficient gas‐fired power stations
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Fundamentals of CCGT Technology
Overall Process
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Thermodynamic Advantages of CCGT
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Gas Turbine
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• Air intake and compression
• Combustion• Gas Turbine
Gas Turbine air intake and compression
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• Air intake• Filtration• Silencer• Minimise pressure drop
• Compression• A number of stages of blading consisting of ‘rotating’ and ‘fixed’ sets
• Air compressed to circa 17bara and 410oC
Gas Turbine Combustion
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• Gas pre‐heated to circa 100‐200oC• Excess air ~ 200% leading to a flue
gas with a 14% O2 level• High excess air required to
achieve flue gas temperatures of circa 1250oC at GT inlet
• NOx emissions below 50mg/Nm3
with low NOx burner technology• CO emissions typically negligible
at base load and below 100mg/Nm3 at part load
Gas Turbine
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• Converts energy in hot combustion gases to mechanical work
• Single shaft driving compressor and converts mechanical work to power by means of the power shaft
• Similar blade pairing to the compressor but this time expanding the gases rather than compressing them
• Turbine stages heavily stressed due to high temperatures. Careful blade material selection and cooling required
Heat Recovery Steam Generator (HRSG)
• Boiler which generates steam from gas turbine exhaust gases
• Three pressure stage HRSG with reheat optimal design solution
• Vertical or horizontal orientations available
• Natural or forced circulation
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Heat Recovery Steam Generator (HRSG)
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HRSG/Steam Turbine Triple Pressure Process
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Steam Turbine
• Three staged to meet optimal HRSG configuration – HP‐IP, LP• Steam bypasses used on start up and trip scenarios
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Gas Turbine and Steam Turbine Configurations
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Condenser
Site conditions dictate Condenser cooling options:
• Once through cooling• Closed cooling with cooling towers (Hybrid ‘Wet‐Dry’)
• Air cooled condensers
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Benefits of CCGT plant compared to Supercritical coal
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CCGT Supercritical coal
Thermal efficiency (% LHV basis)
55‐60 40‐45
CO2 emissions (g/kwhr)
370 760
Emissions (IED)
NOx (mg/Nm3)
SOx (mg/Nm3)
Particulate (mg/Nm3)
CO2 (Vol flow %)
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N/A
N/A
4
200
200
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Capital cost (£/KW) 700 2000
Future power generation operational scenarios: Slow progression
21Source: 2013 National Grid UK Future energy scenarios
Future power generation operational scenarios: Gone Green
22Source: 2013 National Grid UK Future energy scenarios
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Application of CCS to new build CCGT
New CCGT plant permit applications must demonstrate CCS readiness
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High level concept report typically prepared considering:
• Choice of capture technology – Post combustion scrubbing with amine
• Indicative CCS plant layout• Pipeline route and storage site• Economic assessment
CCS readiness
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• Exhaust duct take off• Adaptability of steam extraction from steam turbine to supply CCS re‐boilers
• Sufficient space in turbine building to allow for steam extraction and installation of additional equipment
• Provision for additional electrical auxiliary load• Provision for additional cooling duty• Raw water supply and waste water treatment
CCS readiness
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For more information see The ‘Carbon Capture Readiness’ DECC guidance note
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Peterhead CCS Project
• July 2012 – Shell & SSE initial Bid to DECC
• October 2012 – DECC down select 4 Bidders to take through the Bid Improvement Process (BIP)
• January 2013 – Shell submitted Improved Bid on behalf of Shell & SSE
• March 2013 – Peterhead CCS and White Rose Projects selected by DECC to take forward
• February 2014 – Negotiations finalised with DECC and FEED contract signed
• March 2014 – FEED contract commences
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History of project
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Project Execution
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Overview of Peterhead Power Station
Peterhead Power Station CCGT Capacity 1180 MW 31
Peterhead History
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1973 1980 1985 1991 1998 2010 NOW
Peterhead Power Station
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Peterhead Power Station ‘Block 1’ CCGT
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Overview of Peterhead Carbon Capture Process
Why CCS at Peterhead, Why in Scotland?
Capture at Peterhead
•Existing Grid Connection, Utility capacity and fuel supply
• Existing available land
• Workforce
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Why CCS at Peterhead, Why in Scotland?
Transport and Store •Existing Pipeline Infrastructure• Existing Platform
(Goldeneye), Wells and Reservoir• Goldeneye reservoir well
studied – Good candidate for storage of CO2
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Overview of the Peterhead CCs project• CO2 capture from one gas
turbine flue gas stream (GT13) at Peterhead power station.
• ~400MW post combustion retrofit
• Capture rate of 1m tonnes p.a. for anticipated 10‐year period
• Capacity for at least 20m tonnes CO2 in the Goldeneye reservoir with significant expansion potential in the aquifer
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Overview of Full CCS Chain
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Capture Plant Location
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Capture Plant
Location
Dense Phase Compression
GT13
Interfaces between Peterhead and CCP Plant
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CCS steam requirements and options of supply
• CCS steam requirements ~50% Low pressure steam (3.5bar/150oC)• Utilise block 1 in current configuration with minimal changes to
the steam turbine• Block 1 steam turbine re‐sizing• New steam turbine• Positioned on the existing unit 2 plinth• A standalone new steam turbine house
• A boiler
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Steam Cycle Simplified – ‘Block 1’ CC2/3
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HRSG LP steam
Unit 1 Steam Turbine• U1 is a 660 MW GEC machine. Two main process/mechanical
constraints – HP and LP stages• HP swallowing capacity too large for low ‘CC1’ steam flow rates• Risk of windage heating, HP exhaust trip level 420oC, P.R < 1.4• CS cold reheat pipework creep damage risk
• LP cylinder (2x double‐flow, LD66 7.8 m2 annuli), 20% recommended minimum exhaust flowrate:• Last stage blade vibration leading to fatigue cracking• Casing and blade overheating due to windage
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Unit 1 Steam Turbine Resizing and CCS• HP constraint will be addressed by HP/IP resizing (Contract signed)
• CC1 will be possible, GT min load LP exhaust flowrate (just) > 20%
• But, if CCP steam extraction taken, LP flowrates < 20%
• Sensitivity of low flows on LD66 37” blades has recently increased with issues elsewhere in the fleet
• Conclusion: CC1+CCP not recommended on U1
• LP resizing considered but ruled out due to wide operating rangerequired: CC1+CCP to CC3 no CCP
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Unit 1 Steam Turbine Resizing and CCS• CC2/CC3+CCP operation possible, but which steam source?
• IP/LP crossover pipe not practical, size and location
• IP (HRH) steam 15 bar minimum
• Not very efficient way to supply LP steam to CCP
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New Steam Turbine ‘ST13’ options
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Steam turbine operational regime post CCS• New Steam Turbine ST13
• Operating in ‘CC1’ mode with GT/HRSG 13
• Steam extraction from IP/LP crossover
• Remainder of Block 1 to operate in CC1 or CC2 modes
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Gas Turbine Exhaust Gas• GT exhaust gas • Quite Important for the process with its CO2
• Tapping downstream of HRSG with booster fan• GT13 flue left open with Fan pressure control, some leakage ‘up or down’ inevitable, but lower risk for HRSG ductwork integrity
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Selective Catalytic Reduction
• Shell wish to minimise NO2 to reduce amine solvent degradation and production of by‐products• HRSG is ‘SCR ready’ with
space• ST design pressure
influencing factor on flue gas temperature
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Cooling Water• Current abstraction licence based on 2x 660MW Rankine Units gives
flexibility• Block 13 and Block 1• CCP and Compression & Conditioning Plant
• Various options still under investigation, all involve new pipework to CCP• Upgrade CW pump(s) for higher head, including extensive modifications
in ‘pit’• Unmodified CW pumps, retain condenser philosophy of syphonic
system, more complicated CCP cooling circuits • Unmodified CW pumps with CCP booster pump station
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Cooling Water
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Conclusions
• CCGT Technology has an important part to play to help meet the UK’s electricity demand in a ‘low carbon’ future
• CCS on CCGT technology must be demonstrated to prove technology at an industrial scale
• If demonstration successful there is potential for further roll out• New build coal dependent on CCS demonstration• Work undertaken to date by SSE/Shell confirms the suitability of
Peterhead PS to provide necessary materials and interfaces for a CCGT CCS demonstration project
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Thank you
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