Direct Air Capture via Natural Draft Dry Cooling Tower

Abstract

Capturing carbon dioxide (CO2) from atmospheric air has a great potential to reduce the greenhouse effect, which is of significance to the global campaign against climate change. Due to the extremely low concentration of CO2 in the air, the current carbon absorption technology has the problems of high consumption of both electrical energy to lead the airflow and water evaporation. In this study, a novel direct air capture (DAC) system, which integrates the conventional natural draft dry cooling towers (NDDCTs) and the current DAC technology, is proposed to lower the operating cost during the CO2 capture process and enhance the cooling effects of NDDCTs in a thermal power plant as well. The results indicate that the water evaporation during the CO2 absorption process could create a considerable cooling capacity, which is expected to favor the NDDCTs to reject more heat. Under the design ambient conditions for the NDDCT (30 °C, RH=40%), the thermal performance of the cooling tower can be increased by about 16% with the integration of the DAC absorption process. For a 20 m short NDDCT, the annual CO2 capture capacity is about 846 tons. By using the cost-free natural draft effect provided by NDDCTs, a great amount of electrical energy can be saved. The mutual benefits could be achieved by integrating both systems.