Co-condensation and interaction mechanism of acidic gases in supersonic separator: A method for simultaneous removal of carbon dioxide and hydrogen sulfide from natural gas

Abstract

Supersonic separator offers a new research field for the simultaneous purification of acidic gases (such as carbon dioxide (CO2) and hydrogen sulfide (H2S)). However, the condensation characteristics and interaction mechanism of various acidic components in the methane (CH4) are not clear, resulting in low liquefaction efficiency. In this paper, mathematical models of homogeneous nucleation of the CH4-CO2/CH4-H2S binary mixture and heterogeneous condensation of the CH4-CO2-H2S ternary mixture were established. Numerical calculations and a detailed description of the condensation process were carried out. The results demonstrate that the liquefaction efficiency of CO2 can reach a high of 67.47 % by the homogeneous nucleation in the CH4-CO2, whereas the liquefaction efficiency of H2S is only 16.91 % in the CH4-H2S when the condensable inflow mole fraction is 10 %. The heterogeneous condensation of H2S will be promoted by the condensation nuclei of CO2 in the CH4-CO2-H2S. Although the nucleation rate of H2S is significantly reduced from 4.88 × 1021 to 0.369 m−3·s−1 compared with the CH4-H2S, the liquefaction efficiency of H2S is greatly increased from 16.91 % to 39.5 %. In actual gas processing, the condensation nuclei of CO2 will promote the heterogeneous condensation of the component H2S and increase the condensation efficiency of the H2S droplets.