CO₂ purification. Part II: Techno-economic evaluation of oxygen and water deep removal processes

According to the findings of the first part of this work, the two impurities in the CO₂ stream, from post-combustion capture, which require deep removal, are oxygen and water, down to 10 and 50ppmv, respectively. In addition, a review and preliminary evaluation of the possible technologies which can be used for oxygen and water deep removal were conducted. The results showed that the promising technologies are: catalytic oxidation of hydrogen for oxygen removal and refrigeration and condensation for water removal. In this paper, detailed process modeling, design and a techno-economic evaluation are performed on these two technologies. Both selected technologies were designed and proved their potential by reducing the impurities to the required levels with a total cost of treating and compressing one ton of CO₂ of $13.09 for the coal-fired power plant full purification case and $17.23 for the NGCC full purification process. The cost of CO₂ compression without the purification step was found to be approximately $10.12/ton of CO₂ for the coal-fired case and $11.98/ton CO₂ for the NGCC case. This means that adding the purification technologies will increase the cost of CO₂ compression by around 29.3% for the coal-fired case and 43.8% for the NGCC case. Assuming a total CO₂ capture and compression cost of $73-94/ton of CO₂ shows that the total CO₂ purification cost is roughly 3-4% of the overall capture cost for the coal-fired case and 5.5-7% for the NGCC case.