Optimization and economic analysis of amine-based acid gas capture unit using monoethanolamine/methyl diethanolamine

Abstract

In this work, process optimization and economic analysis of amine-based acid gas capture unit using monoethanolamine (MEA) and methyl diethanolamine (MDEA) blends have been carried out using Aspen Plus (version 8.8). Amine-based CO2 absorption technology is proposed in this study to be retrofitted into the power plant due to its high selectivity and high absorption capacity. However, the associated energy penalty to such technology is relatively high and energy intensive and exhibits process dynamic which necessitates more research to ensure a significant reduction in carbon capture costs achievable. The present work tackles these limitations by analysing the steady-state simulation via Aspen Plus (version 8.8) in determining the technical and economic parameters that make CO2 capture system more efficient, economic and less energy intensive. Optimization of the process was aimed towards minimal reboiler heat duty and maximum CO2 removal efficiency in having the least economic impact of the process. The optimal operating conditions resulted from this study were found to be at 30 °C (1 atm.) for the absorber and at 120 °C (2 atm.) for stripper. The methyl diethanolamine (MDEA) to monoethanolamine (MEA) ratio is fixed at 3:7 with 40 wt% of amine in the solvent. The results showed an increase of 5.5% in acid gas removal rate which resulted in 91.27% of CO2 removal rate as compared to the optimized parameters obtained by Tenaga Nasional Berhad Research’s (TNBR) pilot plant case study situated in Kajang, Selangor. A 300% reduction in energy penalty and heat duty cost is achieved when MEA/MDEA mixture is used instead of MEA alone, resulting in a more economic acid gas removal process with optimum operation. The results showed that this optimization successfully achieved significant energy saving whilst minimizing greenhouse gas emission bringing a significant beneficial environmental and economic impact.