Enhancing the efficiency of an amine-based CO2 capture plant using an interheated stripper modification

Although chemical absorption is an effective technique for capturing CO2 from a natural-gas combined-cycle plant (NGCC), it results in a loss of about 8 % points in thermal efficiency. To address this concern, this paper investigates different NGCC configurations incorporating either selective exhaust gas recirculation (77%SEGR) or exhaust gas recirculation (30%EGR), with the amine-based CO2 capture plant modified using an interheated stripper (IHS). With 77%SEGR, the flue gas stream directed to the absorber can be reduced from 1083.6 kg/s (baseline) to 238.0 kg/s (SEGR), and the CO2 level in the flue gas can be increased from 4.2 mol% (baseline) to 19.3 mol% (SEGR). Therefore, SEGR provides 6.0 % energy savings in specific reboiler duty (SRD) and 52.9 % savings in total packing volume for the absorber and stripper compared to baseline. Introducing IHS to the SEGR configuration increases the stripper middle-stage temperature by up to 3.2 °C, meaning SEGR+IHS reduces SRD by 11.7 % compared to the baseline. Moreover, the IHS alone boosts thermal efficiency by 0.30 percentage points at NGCC plant loads of 100% and 42% for all assessed configurations. Although the IHS has significant potential, it has rarely been discussed in the literature for NGCC plants, and this investigation considers it the paper’s main contribution. However, the main limitation of IHS is that it performs poorly at lean loadings of 0.17 mol CO2/mol MEA or below and at stripper pressures of 130 kPa or below.