Exploring the interactions of NH3 and H2O co-condensation: A study on the potential of supersonic separators for NH3–H2 separation

Abstract

The use of a supersonic separator presents a novel approach for separating ammonia (NH3) from hydrogen (H2). Even trace amounts of water (H2O) can significantly influence the condensation characteristics of NH3. This study presents mathematical models for homogeneous NH3 and H2O condensation and heterogeneous NH3–H2O condensation. Through computational analysis, we revealed that the droplet radius and liquid mass fraction of a single condensable gas condensation increased accordingly with increasing inlet condensable gas content. Interactions between the condensation processes of NH3 and H2O were also captured in the simulation. Notably, at 100 ppm H2O content, H2O spontaneously condensed before NH3, serving as a condensation nucleus for NH3, and the heterogeneous condensation of NH3 decreased the rate of its spontaneous condensation. At an inlet H2O content of 50 ppm, the onset of spontaneous NH3 condensation coincided with that of H2O, with H2O having a negligible effect on NH3 condensation. The impact of H2O on NH3 condensation transitioned from minimal to inhibitory and then to facilitative as the content of H2O increased from 25 ppm to 250 ppm. At the nozzle outlet, the liquid mass fraction of NH3 initially decreased from 0.0414 to 0.0352 and then increased to 0.0446.

Keywords

• Hydrogen-ammonia separation
• Laval nozzle
• Liquefaction efficiency
• Heterogeneous condensation