Superheated flash-boiling atomisation effects on spray carbon capture performance using non-aqueous amines

Abstract

There is an urgent need to develop energy and space efficient carbon capture technologies for hard to decarbonise sectors. While spray-based carbon capture systems can offer high CO₂ absorption rates compared to packed columns, their optimisation requires fine control on spray homogeneity and droplet properties such as size and relative velocity. More specifically, denser mono-disperse sprays with micron scale droplets have been found to increase the rate of CO₂ absorption due to increased surface area for mass transfer. One approach that has not previously been investigated is to control the solvent spray properties through flash boiling atomisation to consistently produce fine and homogeneous droplets. To address this gap, we present optical measurements comparing the performance of solvents atomised with varying degrees of flash boiling. Diffuse-back illumination extinction imaging was used for temporal characterisation of spray morphology. We tested a 20:80 ($\text{\%}$ w/w) blend of triethanolamine and methanol, and neat isopropylamine under six temperature conditions to vary the amount of superheat. Absorption capacities, molar absorption rates, and CO₂ percentage removal are reported for each test condition, showing significant improvements at the higher temperature conditions where flash boiling was more intense. While flash boiling carbon capture carries a higher energy demand than conventional technologies, our results offer an innovative and promising avenue for high-efficiency CO₂ absorption in hard-to-abate sectors such as marine transportation, especially when coupled with a waste heat recovery strategy.