Separation processes for carbon dioxide capture with semi-clathrate hydrate slurry based on phase equilibria of CO2 + N2 + tetra-n-butylammonium bromide plus water systems

The objective of this work was to assess multi-stage separation processes for CO2 capture based on semi-clathrate hydrate (SCH) adsorption media. Phase equilibria were determined for CO2 + tetra-n-butyl ammonium bromide (TBAB), N-2 + TBAB and CO2 + N-2 + TBAB SCH and correlated with a modified van der Waals-Platteeuw model. Experimental CO2 separation factors ranged from 5 to 10, whereas calculated values were all around 18 implying inhomogeneous absorption in the slurries. For simulation conditions, hydrate mass fractions less than 0.09 were estimated to prevent aggregation of the hydrate solids. A two-stage batch separation process allowed enrichment of CO2 to more than 90 mol% from a 20 mol% CO2 feed. A three-stage continuous countercurrent separation process allowed a CO2 recovery of about 90%. Separation performance of semi-clathrate hydrates ranked favorably among the CO2 separation methods, showing that SCH adsorption media have excellent potential for carbon capture applications. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.