Multi-objective optimisation of a Rectisol™ process for carbon capture

•Multi-objective optimisation of a non-selective Rectisol™ unit for carbon capture.•Heat integration opportunities are explored.•Multi-stage refrigeration system optimisation within an Excel based MOO framework.•Pocket exploitation based on the grand composite curve.•CO2 condensation and pumping performs better than straightforward CO2 compression.

In the present work, a standalone Rectisol™ unit for carbon capture has been optimised with a Multi-Objective Optimisation (MOO) perspective. The energy penalty and carbon dioxide capture rate have been simultaneously optimised to get the best operating conditions for various carbon dioxide capture rates. The Rectisol™ process typically has high refrigeration demand. Hence, any optimisation of Rectisol™ is incomplete without simultaneous optimisation of the refrigeration system. Hence, in this work, the refrigeration system has also been optimised with the help of a separate algorithm. Two options for pressurising the captured carbon dioxide, i.e. by condensation and pumping the carbon dioxide (Case-I) and by compression (Case-II), have also been compared. The results show that Case-I performs better for low capture rates compared to Case-II. However, the relative difference between the two diminishes with increasing capture rates.