Effect of stripper pressure and low lean loadings on the performance of a PCC plant for 99% CO2 capture level

Abstract

Process modelling based on an open-access design for an MEA post-combustion capture plant that treats CCGT flue gas, has been used to examine the effect of stripper pressure on the energetic performance at low lean loadings as well as potential improvements that can be achieved, such as reducing packing height in the absorber (typically the most expensive unit in a PCC plant) by operating at high stripper pressures. In principle, operating at low lean loadings (that can facilitate high capture levels in the absorber) requires high pressure operation in the stripper in order to avoid excessive heat inputs. The associated higher temperatures might be expected to lead to increased thermal degradation of the solvent but this is likely to be mitigated by the lower lean loadings and also by effective solvent management strategies, which can recover both solvent and energy. Based on Aspen Plus/CCSI thermodynamics, we identified lean loading inflexion points (beyond which excessive energy is required) for each investigated stripper pressure. Finally, in some cases, it appears that, by using lower lean loadings the absorber packing height can be reduced by 25% for the same capture fraction while still requiring reasonable specific reboiler duty values.

Keywords: post combution capture, high capture levels, process modelling, Aspen Plus CCSI