Alternative chemical solvent blends and spray mixing regimes for high-efficiency carbon capture

Abstract

There is an urgent need to develop sustainable and efficient carbon capture technologies in order to remain on track in achieving global climate goals such as net zero 2050 and the energy transition. Whilst existing capture systems already exhibit high CO_² absorption rates through the use of packed column infrastructure and highly reactive chemical solutions, the energy and cost to maintain these systems are unsustainable, and the safety risks posed through the usage of current industry standard gas scrubbing solvents are high. This research aims to address these issues by focusing on optimising CO_² absorption methods through the use of sprays, whilst simultaneously investigating the viability of alternative absorbents for next generation carbon capture technology. 

The effects of varying degrees of flash boiling on spray characteristics and subsequent impacts on carbon removal were experimentally studied. High-speed Diffuse Back Illumination imaging was implemented for temporal characterisation of the spray morphology foreach spray regime. A model based on the radiative heat transfer equation was created to quantify changes in CO_² density within the test chamber using infrared extinction recordings. Neat isopropylamine and a 20:80 (% w/w) blend of triethanolamine and methanol were evaluated under six temperature conditions to vary the amount of superheat. Novel results indicate up to a 34% increase in CO_² absorption capacities and a 3.3 to 4.5x boost in molar absorption rates at the higher temperature conditions where flash boiling was more intense. 

The CO₂ capture performance of two potassium glycinate based solvent blends were also investigated, the first being a novel deep eutectic solvent containing a 4.36M potassium glycinate concentration, and the other a non-deep eutectic blend with 5M potassium glycinate. Dual wavelength and path length infrared extinction imaging were employed simultaneously to detect changes in CO² concentration and overall carbon uptake. Molar absorption capacities and rates for both solvents were computed. The novel deep eutectic solvent blend achieved a CO₂ absorption capacity of 0.61 to 0.74 mol_CO2 / mol _solvent  which exceeded the theoretical capacity of traditional aqueous amine based solutions (0.5 mol_CO2 / mol _solvent), making it a promising alternative.

Phase rainbow refractometry was employed to investigate the mass transfer process of CO₂ into individual droplets of aqueous and non-aqueous monoethanolamine solutions. The effects of droplet size and distance relative to the nozzle post injection were experimentally studied. The molar flux results indicate that smaller droplet sizes yielded greater carbon absorption. Furthermore, the non-aqueous monoethanolamine solution was found to match the capture performance of the traditional aqueous blend, whereby the computed CO₂ molar flux was approximately 2.3-2.4 molm-² s-¹ for both solvents, suggesting it to be an effective and energy efficient alternative absorbent.

Date of Award	Jun 2026
Original language	English
Awarding Institution	University of Brighton
Supervisor	Guillaume De Sercey (Supervisor), Peter Cragg (Supervisor), Cyril Crua (Supervisor) & Konstantina Vogiatzaki (Supervisor)