An efficient method for removing hydrogen sulfide from natural gas using supersonic Laval nozzle

A new method was proposed for hydrogen sulfide removal from natural gas through the utilization of supersonic flow in a Laval nozzle. For this purpose, a mathematical model was established for the supersonic non-equilibrium condensation flow of the binary methane-hydrogen sulfide mixture. The condensation parameters were numerically calculated and described in detail, and a sensitivity analysis was carried out to investigate the influence of the inlet parameters on the supersonic condensation flow. The results show that when the inlet temperature and pressure were 290 K and 5 MPa respectively, and the mole fraction of hydrogen sulfide was 15%, the removal efficiency of hydrogen sulfide was 64.83%, which indicates that the use of supersonic separation technology for this application is indeed feasible. It was also found that with the decrease of inlet temperature or the increase of inlet pressure, the nucleation site moved forward (i.e. closer to the throat), and the maximum droplet radius and liquid mass fraction of hydrogen sulfide increased. When the mole fraction of hydrogen sulfide was less than 5%, however, the liquid mass fraction of hydrogen sulfide was almost zero. Therefore, it appears that using a reasonable hydrogen sulfide fraction, a lower inlet temperature, and a higher inlet pressure can promote the supersonic condensation of hydrogen sulfide in the Laval nozzle and improve the efficiency of the removal process. These results suggest that supersonic separation technology can provide an efficient and environment-friendly way to remove hydrogen sulfide from natural gas, thereby reducing emissions. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.