for the proposed 800 MW Combined Cycle Power Plant ...

CO 2 Capture Study
For 800 MW Power Plant – Tjeldbergodden
3.3 Energy Integration
In a conventional Combined Cycle Gas Turbine power plant the steam circuit
is arranged to follow the decay in temperature of the exhaust gas as heat is
abstracted to give the most efficient thermal cycle as shown below:
HP Steam
Source
Reheat
Coils
IP Steam
Source
LP Steam
Source
Condenser
Conventional Steam Circuit for CCGT Power Plant
Where a plant is to be fitted with Carbon Dioxide capture, a considerable
amount of heat is required for the regeneration of the scrubbing liquor. We
have formulated a number of rules, which will give the best thermal efficiency
of the total unit and are:
1. Add “source heat at as high a temperature as possible so as to achieve
the highest possible Carnot efficiency (set by source and sink
temperatures). Add this heat to the highest efficiency combustion system
and do nt add auxiliary low efficiency combustion devices.
2. Reject heat to the “sink” at as low a temperature as possible
3. Extract as much work from the working fluids in the expansion turbines of
the power train and only extract LP steam for amine reboilers at the
lowest possible pressure and temperature.
4. Reject as little heat as possible to the “sink” and utilise as much waste
heat as possible without violating any pinch rules
5. Use the lowest possible energy in the amine stripper. This requires the
use of the best solvents plus intensive integration within the amine
capture plant.
In designing a plant where the CO 2 capture plant is commissioned with the
power plant, the steam turbine is sized so that it is working under optimum
conditions when steam is being extracted for the CO 2 capture plant.
If the CO 2 capture plant is to be commissioned some time after the power
plant, then one can either:
CB2005-0022_Final Report.Doc