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 50 ppmv, 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.

► Water and oxygen removal technologies were techno-economically evaluated.
► Full CO2 purification process design, sizing and costing were developed.
► The CO2 compression system is responsible for the major CAPEX and OPEX costs.
► The CO2 purification step will add around 23% to the CO2 compression cost.
► The CO2 purification step is found to be only 3–4% and 5–7% of the total CO2 capture and compression costs for coal-fired and NGCC case, respectively.