Amine based liquid capture technology for direct air capture of CO₂ – an overview on technology development

Abstract

The large-scale deployment of direct air capture (DAC) technologies is essential to meet the global target of limiting temperature increase to below 2°C. Amine-based liquid capture technology, as the leading method for point-source CO₂ capture, holds promise as a low-cost and scalable solution for DAC. We previously reported that the cost of this technology could approach US$100/tCO₂, using a non-volatile absorbent, inexpensive cooling towers as gas–liquid contactors, and scaling up to capture 1 million tonnes of CO₂ per year. To further reduce CO₂ capture costs, we developed a second-generation DAC system, named the mist contactor. This system atomises the absorption liquid into fine droplets, increasing the contact area between the liquid and air. The resulting lower liquid-to-gas ratio, reduced gas-side pressure drops, and potentially higher capture rates are expected to reduce CO₂ capture costs even further. We developed an optimised process design and model as a baseline for the design and construction of a pilot-scale system capable of capturing approximately 100 tonnes of CO₂ per year. For DAC to contribute to achieving net-zero emissions, the CO₂ captured must be either stored underground or utilised. Integrating DAC with downstream processes can further reduce costs by sharing infrastructure between capture, storage, and utilisation. A preliminary assessment of the integration between DAC and downstream processes, such as CO₂ compression and fuel production, has been conducted and will be presented.