TEA of a Unique Two-Pathways Process for Post-Combustion CO2 Capture

Abstract

A unique two-Pathways process using aqueous sodium glycinate for CO2 capture from a split flue gas stream emitted from 600 MWe post-combustion coal power plant was developed in Aspen Plus v.10. The split gas flow rate used was 44.75 ton/h and contained 0.0023 mol% SO2 and 13.33 mol% CO2. The process includes a washing unit, a CO2 absorption unit, a reverse osmosis unit, and a solvent regeneration unit or an ultrafiltration unit. The washing unit uses deionized water to completely remove SO2 and the CO2 absorption unit uses SGS to capture at least 90 mol% of the CO2 in the split flue gas stream. Upon CO2 and SGS reactions, the resulting liquid products exhibit phase-separation into CO2-lean phase and CO2-rich phase, allow two distinct pathways. Pathway (i) is to regenerate mostly the CO2-rich phase, collect the released CO2, and compress it for sequestration purposes. Pathway (ii) is to send the liquid stream from the CO2 absorption unit to the ultrafiltration unit to separate the solid nanomaterials. The hydraulics and mass transfer characteristics in the washing and CO2 absorption units were obtained; and techno-economic analysis (TEA) for Pathways (i) and (ii), including Capital Expenditure (CAPEX), Operating Expenditure (OPEX), and Levelized Cost of CO2 Captured (LCOC), were calculated and compared. The simulation results revealed that the CAPEX, OPEX, and LCOC for Pathway (i) were ($12,039,251), (261 $/h), and (54.01 $/ton-CO2 captured), respectively, and those for Pathway (ii) were ($5,908,000), (237.2 $/h), and (39.90 $/ton-CO2 captured), respectively. Moreover, in Pathway (ii), 8.19 ton/h of CO2 were captured to produce 15.62 ton/h NaHCO3 nanomaterials, which were sold to offset the overall process cost. The LCOC values indicate that Pathway (ii) is more cost-effective than Pathway (i) because LCOC values for Pathway (ii) are much lower than those for Pathway (i).