Reducing the Cost of CO2 Capture from Flue Gases Using Aqueous Chemical Absorption

Chemical absorption is widely regarded as the most promising technology for CO2 capture from large industrial sources in the short term. The cost of CO2 capture from postcombustion power plants using monoethanolamine (MEA), the benchmark for chemical absorption, is currently over US$70 per metric ton of CO2 avoided. This high cost is considered as the major obstacle to current large-scale implementation of carbon capture and storage (CCS). Thus, there has been significant focus on the development of new solvents with the aim to reduce costs. This paper provides insights into the impact of solvent properties on the cost of capture to assist in the development of new solvents based on a 500 MW supercritical black coal power plant as the emission source. The effect of solvent properties, specifically solvent loading, heat of reaction, solvent loss, and solvent concentration is examined. The effect of improvements in process design, specifically high pressure stripper operation, advanced structured packing, use of concrete for the process vessels, and advanced heat exchangers, is also evaluated. Sensitivity analysis and Monte Carlo simulation are performed to provide an estimate of the capture cost variability. The results show that the development of aqueous chemical absorption technology for CO2 capture should focus on new solvents with good stability toward SOx and NONx, high solvent concentration (above 50 wt %), and high working capacity (above 0.35 mol of CO2/mol of solvent). These three parameters have the most significant impact on the capture cost. Based on Monte Carlo simulation, within a 95% confidence level, the capture cost with improved solvent properties and process design is estimated at US$62-80 per metric ton of CO2, with the most likely cost of US$71 per metric ton of CO2 avoided. This number reduces to US$44-59 per metric ton of CO2, with the most likely cost of US$52 per metric ton of CO2 avoided, if the flue gas desulfurization (FGD) and selective catalytic reduction (SCR) units can be eliminated.