Direct Air Capture: Economy and Technical Cost of Low-Purity CO2 on Post-Capture Operating Cost

Abstract

Direct air capture has the potential to capture from innumerable random, mobile and immobile small-scale carbon-emission sources.    In this study, simulations result of Direct Air Capture (DAC) reveal the isentropic compression work increases as the mole fraction of CO2 decreases in the stream. At the same depth of sequestration, compression power requirement increases by 20% to sequestrate 10% CO2 stream compared to pure CO2.  Also, sequestration at deeper geological layer further raises the power cost of the compression by approximately 14% from 1000 to 1500m and by almost 32% from 1500m to 2500m depth, for pure CO2. This increases to around 34% for storage at 2500m with 50% CO2 mole fraction and 36% for 20% CO2 fraction at the same depth.  Similarly, the cost of cooling compressed CO2 increases in proportion to the reduction in CO2 mole fraction in the gas stream. It was shown that the solution density increase with impurities as a result of falling pH in the presence of N2 and O2.