Design-point and part-load considerations for natural gas combined cycle plants with post combustion capture

An investigation is made of two different integration options for a MEA post-combustion CO2 capture unit in a natural gas combined cycle (NGCC). Thereafter, a study is made of the part load operation of the NGCC with and without CO2 capture. The considered integration options were (1) steam extraction from LP superheater and at IP-LP crossover as heat source to the stripper reboiler and (2) partially integrating the reboiler directly into the HRSG while extracting steam at the IP-LP crossover for the remaining heat duty. The results show that both options exhibit similar operational performance at full and part-load. However, the process option with direct integration of 40% of the reboiler into the HRSG results in only one steam pressure level in the HRSG and the heat transfer area can be reduced with 38%. Additionally, the paper presents a qualitative discussion on the steam supply from the power plant to the CO2 capture unit under transient conditions. This is done with reference to the steady-state part-load results. An overall conclusion is that the NGCC will always be able to supply the capture unit with sufficient steam for solvent regeneration at full load, part load and during load changes. The ability to maintain a capture rate at 90% will depend on the operational performance of the capture plant. (c) 2012 Elsevier Ltd. All rights reserved.