Techno-economic Evaluation of CO<sub>2</sub> Capture from Flue Gases Using Encapsulated Solvent

Encapsulated solvents are a solvent system for CO<sub>2</sub> capture, where the operating solvent fluid is enclosed in a thin membrane capsule with a diameter of 100–600 μm. The encapsulation provides a significantly higher surface area compared to conventional packings, which potentially reduces the absorber dimensions. In this paper, a high-level assessment of costs for postcombustion CO<sub>2</sub> capture using encapsulated solvent systems is carried out to identify key areas for future development. Two process configurations for an encapsulated solvent system are assessed. In the first process configuration, multiple fixed-bed columns are used as the absorber and regenerator. In the second process configuration, a circulating fluidized-bed absorber and a bubbling fluidized-bed regenerator are used. For each system, possible cost reductions through improvements in the capsule properties are investigated. Key design and operational challenges for these systems are also evaluated. The capture costs for using an encapsulated MEA 30% wt. solvent system are found to be 60% to 2 times higher than a conventional MEA solvent system. Higher capture cost is due to the extra membrane resistance in the encapsulated system which increases the regeneration energy required, coupled with higher equipment and capital cost. To reduce cost, future developments for an encapsulated solvent system should consider implementing a suitable heat recovery scheme within the process, using novel absorber and/or regenerator column designs and using solvents encased in very thin capsules. The performance of the encapsulated system could also be improved by using solvents other than MEA with more favorable properties.