(398j) Process Modeling and Experimental Studies of a Novel Micro-Encapsulated Solvent System for CO2 Capture

To screen new CO₂ capture technologies and to expedite commercialization of potential technologies, process systems engineering tools can be highly useful. The U.S Department of Energy’s Carbon Capture Simulation Initiative (CCSI) has developed a number of innovative models and tools that can be instrumental in achieving this goal^[1]. Process level evaluation of a novel micro-encapsulated solvent (MECS) system is undertaken in this work by leveraging the tools developed by the CCSI.

A number of excellent solvents such as ionic liquids and phase-changing solvents have strong potential for reducing operating cost, but face significant transport issues due to their high viscosity and/or because of solids precipitation. Quite often, loadings of these solvents are kept low or their operating temperature is kept high to aid in the transport of these materials between the absorbers and desorbers. Microencapsulation of such solvents to minimize viscosity effects in transport can be instrumental in realizing the full potential of these technologies. The high-viscosity or phase-changing solvents can be encapsulated in an inert polymer shell through which mass transfer from/to the bulk still takes place. While the microencapsulation technology is more developed and prevalent in pharmaceutical and food industries, encapsulation of CO₂ capture solvents has not been investigated much. A number of studies have been recently conducted by Vericella et al.^[2] and Stolaroff et al.^[3] on microencapsulation of solvents for CO₂ capture. Vericella et al.(2015) have proposed polymer microcapsules with silicone as the shell material and liquid carbonate as the solvent. Stolaroff et al. (2016) reported the capability of encapsulating viscous ionic liquids for carbon capture. However, for commercial application of the MECS for CO₂ capture, selection of a suitable contactor technology and its optimal design by due consideration of mass transfer, heat transfer, and hydrodynamics is necessary.

In this work, first a detailed model of the MECS experimental setup at the Lawrence Livermore National Laboratory is developed. Experimental data under varying temperature and pressure conditions are used to obtain maximum likelihood estimate of the parameters for the mass transfer models. Heat transfer properties and hydrodynamic characteristics of the MECS system are also studied. Finally, a rigorous process model of a fluidized bed contactor is developed. An optimal design of the contactor is developed by exploiting the CCSI models and tools.

References

1. Miller, D. C., Syamlal, M., Mebane, D. S., Storlie, C., Bhattacharyya, D., Sahinidis, N. V., Sun, X. Carbon capture simulation initiative: a case study in multiscale modeling and new challenges. Annual review of chemical and biomolecular engineering 2014, 5, 301-323,.
2. Vericella, J. J. et al. Encapsulated liquid sorbents for carbon dioxide capture. Nature Communications, 6:6124, 1-7 (2015).
3. Stolaroff et al. Microencapsulation of advanced solvents for carbon capture. Faraday Discussions. DOI: 10.1039/c6fd00049e (2016).