Dynamic phase-splitting behaviour of biphasic solvent for carbon capture in a novel annular phase separator

Abstract

Compared with biphasic solvents with blend amines, the mixture of physical solvent, amines and water (ternary solvent) was a promising preparation strategy. Chemical CO2 absorption with amine-based solvents is a promising route for industrial CO2 capture, but suffering from intensive heat duty for solvent regeneration. Developing high-performance biphasic solvent and efficient dynamic phase separator is an effective solution. In this study, poly(ethylene glycol) dimethyl ether (NHD) was selected as the separating agent to prepare a biphasic solvent based on a blended amine (Diethylenetriamine (DETA) and N,N-dimethylcyclohexylamine (DMCA) solvent with a screened proportion of DETA: DMCA: NHD: H2O of 1:3:4:2. The CO2 loading of the saturated solvent was 4.6 mol·L−1, with over 96% of the CO2 species concentrated in the rich phase, and with low viscosity of 48.60 mPa·s. The maximum desorption rate of CO2-saturated solvent was up to 1.68 mmol·min−1, and it increased by 243% compared to the MEA solvent (30 wt% MEA and 70 wt% water). The intermediates in various phases were identified using NMR to monitor the species changes during phase splitting. The dynamic phase-splitting capacity was first determined using a quasi-two-dimensional separator, and the results revealed that the liquid velocity of the mixed phase had a dominant effect on the separation efficiency. Furthermore, a novel annular phase separator was proposed to achieve efficient phase separation (the relatively rich separation efficiency increased by 13.40% compared to that with the benchmark.) by decreasing the tangential turbulence from the inlet velocity. The time–space distribution of the CO2 loading was obtained at different operational parameters. In particular, the effect of water content on separation efficiency was investigated to verify the adaptability of biphasic solvents for practical application.