Sensitivity analysis of nucleation and droplet growth models in the prediction of natural gas non-equilibrium condensation in Laval nozzle

Abstract

Supersonic separation is a promising technology for purifying natural gas by removing impurities like H2O and heavy hydrocarbons. The condensation process of natural gas has obvious non-equilibrium characteristics, the accurate prediction of which is challenging and essential for efficient separators design. Euler-Euler two-fluid model was developed to investigate non-equilibrium condensation of four two-component gas mixtures: H2O, CO2, H2S and n-C9H20 in CH4. Various nucleation and droplet growth models were employed to analyze the sensitivity in predicted results. The obtained results show significant differences in condensation characteristics among four gas mixtures due to varying isentropic expansion coefficients. The choice of nucleation models had a pronounced impact on H2O and n-C9H20, especially using the internally consistent classical theory(ICCT). However, noticeable differences emerged for CO2 and H2S only when using ICCT compared to classical nucleation theory (CNT). Furthermore, results for H2O and n-C9H20 exhibits high sensitivity to calibration factors in the Gy and Yg droplet growth models. Conversely, due to the essentially continuous flow of initial droplet sizes for CO2 and H2S, the Nusselt number and results show minimal response to such calibrations. These results can provide a reference for determination or development of nucleation and droplet growth model for natural gas non-equilibrium condensation.