Non-equilibrium condensation of carbon dioxide in flue gas with the coexistence of swirl flows and supersonic flows

Abstract

To achieve clean use of fossil energy and reduce carbon dioxide emissions, this work studies a potential clean technology for capturing carbon dioxide. Because the capturing process involves supersonic flows, swirl flows and heat and mass transfer, the flow structure and non-equilibrium condensation process in supersonic nozzles are not well understood. Taking the separation of carbon dioxide from flue gas as the research background, this work develops and validates a two-component steam (CO2-N2) condensation model to study the non-equilibrium condensation of carbon dioxide in flue gas with the coexistence of supersonic flows and swirl flows. The results show that the supersonic nozzle has the potential to liquefy carbon dioxide in flue gas considering swirl flows. Swirl flow move the starting point of nucleation towards the nozzle throat, greatly increases the peak nucleation rate, and weakens the mass and heat transfer process of non-equilibrium condensation. When the swirl intensity increases from 0 to 0.42, the liquid fraction in decreases from 0.101 to 0.081, with a decrease range of 19.8%. When using single-phase assumption without considering condensation, the calculation results misestimates the temperature drop characteristics and the expansion characteristics of steam, and the maximum error can reach 13.6%.