Comparison of Solvent Development Options for Capture of CO₂ from Flue Gases

Chemical absorption is widely regarded as the most commercially ready technology for postcombustion CO 2 capture from large industrial emission sources. The benchmark solvent is monoethanolamine (MEA). Alternate solvents to MEA have been developed with improved properties such as solvent loading, regeneration energy, and absorption rate. Improvements in solvent properties can be challenging because of possible adverse interactions between solvent properties. Ideally improving all solvent properties and process designs concurrently is desirable to reduce the total cost of CO 2 capture. The changes in cost of CO 2 capture for postcombustion CO 2 capture from a black-coal power plant using absorption are investigated using Monte Carlo simulations, where key solvent parameters are varied simultaneously. Different classes of solvents are considered covering aqueous and phase-change solvents in conventional and encapsulated solvent systems. The results show that it is not necessary for new solvents to have superior values for all properties. There are combinations of solvent properties where low total capture cost can be achieved because improvements in the more significant parameters offset smaller or negative improvement in other parameters. In particular, low total capture cost can be achieved when solvents have the following properties: good stability toward SO x and NO x, a low heat of reaction, a high absorption rate, a low water vaporization rate, and a low price per unit of the solvent. The results also show that regardless of the solvent type, different solvent systems can potentially achieve almost the same lowest capture cost of approximately U.S. $37–39 per tonne of CO 2 avoided.