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

Abstract

A unique two-Pathways process using aqueous sodium glycinate for CO<sub>2</sub> 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% SO<sub>2</sub> and 13.33 mol% CO<sub>2</sub>. The process includes a washing unit, a CO<sub>2</sub> absorption unit, a reverse osmosis unit, and a solvent regeneration unit or an ultrafiltration unit. The washing unit uses deionized water to completely remove SO<sub>2</sub> and the CO<sub>2</sub> absorption unit uses SGS to capture at least 90 mol% of the CO<sub>2</sub> in the split flue gas stream. Upon CO<sub>2</sub> and SGS reactions, the resulting liquid products exhibit phase-separation into CO<sub>2</sub>-lean phase and CO<sub>2</sub>-rich phase, allow two distinct pathways. Pathway (i) is to regenerate mostly the CO<sub>2</sub>-rich phase, collect the released CO<sub>2</sub>, and compress it for sequestration purposes. Pathway (ii) is to send the liquid stream from the CO<sub>2</sub> absorption unit to the ultrafiltration unit to separate the solid nanomaterials. The hydraulics and mass transfer characteristics in the washing and CO<sub>2</sub> 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 CO<sub>2</sub> 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-CO<sub>2</sub> captured), respectively, and those for Pathway (ii) were ($5,908,000), (237.2 $/h), and (39.90 $/ton-CO<sub>2</sub> captured), respectively. Moreover, in Pathway (ii), 8.19 ton/h of CO<sub>2</sub> were captured to produce 15.62 ton/h NaHCO<sub>3</sub> 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).