On the off-design of a natural gas-fired combined cycle with CO2 capture

During the last 15 years cycles with CO2 capture have been in focus, due to the growing concern over our climate. Often, a natural gas fired combined cycle with a chemical absorption plant for CO2 capture from the flue gases have been used as a reference in comparisons between cycles. Neither the integration of the steam production for regeneration of amines in the combined cycle nor the off-design behaviour of such a plant has been extensively studied before.In this paper, the integration of steam production for regeneration of the amines is modelled at design load and studied in off-design conditions for a combined cycle. Different ambient conditions and part-load strategies and their influence on the cycle performance are also examined. Of particular interest is a novel strategy with the possibility of longer life of gas turbine blading, with marginal loss in efficiency.The off-design performance of the combined cycle is modelled in a rigorous way using a gas turbine performance deck, while the boiler is calculated using simplified correlations for off-design heat transfer and pressure drop. The steam turbine calculation is based on verified models for the flow–pressure–efficiency relations, whilst the steam condenser is based on the HEI method.