Design and fabrication of a system to capture ambient CO2

Abstract

Introduction:In the coming decades, addressing climate change necessitates substantial Carbon dioxide (CO2) emission reductions. Carbon capture and storage are vital for achieving these goals. Beyond industrial emissions, Direct Air Capture (DAC) extracts CO2 from the atmosphere, complementing point source capture and enabling the reduction of atmospheric CO2 concentrations. Our research confirms the thermodynamic feasibility of DAC with Potassium hydroxide (KOH) solution, taking into account energy and performance considerations. Materials and methods: To assess DAC's potential, we built a 1.2 m contactor prototype measuring CO2 absorption from the air. Operating at 100 pa with an air speed of 1.75 m/s in a cross-flow regime, we used KOH and NaOH solutions as capture mediums, implementing duty cycles for absorbent pumping and exhaust fan operation. Results: Our findings revealed that transitioning to intermittent operation can dramatically reduce overall energy costs by 70%. We explored various absorbent concentrations for both KOH and NaOH solutions, examining their impact. Operating temperatures ranged from 14°C to 33°C, providing insights into temperature's pivotal role in DAC performance. Conclusion: This study showcases the viability of DAC with a KOH solution, particularly highlighting the significant energy savings achieved through intermittent operation. These findings emphasise DAC's role as a vital tool in our collective efforts to combat climate change.

Keywords

• Direct air capture (DAC); Sorbent; Captures solution; The equilibrium solubility; Mean residence time