5 Summary of flexibility characteristics of the basic plants

The overleaf table summarizes the expected flexibility characteristics of the basic plants with and without CCS, excluding solvent and oxygen storage, CO2 venting and other forms of energy storage, as assessed in the next sections of the report.

Flexibility features summary table

Turndown Cyling capablitiy Part load efficiency
Start-up to full load Ramp rates
NGCC Low Load Operation: 15-25% CC load(10-20% GT load) Hot start-up: 45-55 minWarm start-up: 120 minCold start-up: 180 min 35 - 50 MW/minute max Hot start-up load change rate:
  • 0-40% GT load: 3-5%/min
  • HRSG pressurisation: 1-2%/min
  • 40-85% GT load: 4-6%/min
  • 85-100% GT load: 2-3%/min
Approx. constant efficiency up to 85% GT load
Minimum Environmental Load: 40-50% CC NPO(30-40% GT load) 2-3 percentage points less @ 60% CC load
with CCS Post combustion unit minimum load: 30%CO2 compressor minimum efficient load: 70% Regenerator preheating:
  • hot start-up: 1-2 h
  • warm start-up: 3-4 h
Same as plant w/o CCS Same as plant w/o CCS
IGCC Minimum Environmental GT Load: 60% POProcess unit minimum load: 50%ASU cold box minimum load: 50%ASU compressor minimum efficient load: 70% Cold start-up: 80-90 hGasification hot start-up: 6-8 hASU hot start-up: 6 h Gasification ramp rate: 3-5%/minASU ramp rate: 3%/min Gross electrical efficiency: 2 percentage points less @ 70% CC load
with CCS CO2 compressor minimum efficient load: 70% Same as plant w/o CCS Same as plant w/o CCS Same as plant w/o CCS
USC PC Minimum boiler load: 25-30% Very hot start-up: < 1hHot start-up: 1.5-2.5 hWarm start-up: 3-5 hCold start-up: 6-7 h 30-50% load: 2-3%/min50-90% load: 4-8%/min90-100% load: 3-5%/min Subcritical boiler: 4 percentage point less &commat; 75% loadSupercritical boiler: 2 percentage point less &commat; 75% load
with CCS Post combustion unit minimum load: 30%CO2 compressor minimum efficient load: 70% Regenerator preheating:
  • hot start-up: 1-2 h
  • warm start-up: 3-4 h
Same as plant w/o CCS Same as plant w/o CCS
Oxy combustion
Air-firing mode Minimum boiler load: 25-30% Very hot start-up: < 1hHot start-up: 1.5-2.5 hWarm start-up: 3-5 hCold start-up: 6-7 h 30-50% load: 2-3%/min50-90% load: 4-8%/min90-100% load: 3-5%/min Subcritical boiler: 4 percentage point less &commat; 75% loadSupercritical boiler: 2 percentage point less &commat; 75% load
Oxy-firing mode ASU cold box minimum load: 40-50%ASU compressor minimum efficient load: 70%CO2 compressor minimum efficient load: 70% Start-up in air-firing mode,ASU start-up completed in approx. 36 h ASU ramp rate: 3%/min Same as plant in air-firing mode