(514a) An Adsorbent Screening Tool with Integrated Process Economics for Carbon Capture By PVSA

There is significant interest in the development of step-change technologies for CO₂ capture, with adsorption processes in general and MOF-based systems in particular attracting a lot of attention. Although there are several screening models available, none attempt to quantify the process economics^1-4. In order to prioritise research efforts in this important area, the development of screening tools which link fundamental scientific insights with engineering considerations is key.

In this work, we use a reduced order pressure/vacuum swing adsorption model⁵ which models a one bed, three step cycle made up of feed, desorption and feed re-pressurisation steps. This allows for the non-isothermal nature of adsorption to be accounted for, yielding more reliable results than simple isotherm analysis, while still allowing a rapid solution.

The cycle performance results based on one kilogram of adsorbent are then taken as the input to the process design tool. The number and size of the process equipment is then determined for a user specified amount of feed gas, and the capital and operating costs are estimated to obtain the cost of capture per tonne of carbon dioxide.

Having the cost of capture as a screening metric is beneficial on several fronts. It allows an adsorbent to be selected based on overall process cost in addition to traditional parameters such as purity, recovery, working capacity and specific work. The relationship between adsorbent characteristics, separation performance, and capture cost can also be uncovered which allows additional insights. For example, in the case of a 150 kPa_a feed of 4 %_mol CO₂, reducing the desorption pressure to 1 kPa_a from 15 kPa_a for ZIF-8 results in a 44 % and 57 % increase in CO₂ purity and recovery respectively, however the capture cost increases by 3.8 times. In the case of Ni-MOF-74 which displays good isothermal performance, the cyclic performance is poor which results in CO₂ purities and recoveries 5.7 and 3.0 times lower than 13X and a capture cost 3.9 times higher at a desorption pressure of 3 kPa_a.

[1] G.D. Pirngruber et al., ChemSusChem, 5, 762-776, 2012

[2] L. Joss et al., Ind. Eng. Chem. Res., 54, 3027-3038, 2015

[3] M. Khurana, S. Farooq, Ind. Eng. Chem. Res., 55, 2447-2460, 2016

[4] V.S. Balashankar et al., Ind. Eng. Chem. Res., 58, 3314-3328, 2019

[5] B.J. Maring, P.A. Webley, Int. J. Greenh. Gas. Con., 15, 16-31, 2013