Numerical simulation of condensation of supercritical water gasification products in a supersonic nozzle

Abstract

The clean and efficient separation of supercritical water gasification products (SCWGP) has emerged as a significant challenge in supercritical water gasification technology. This paper proposes the use of a supersonic nozzle for the condensation and separation of H2 and CO2 from SCWGP, leveraging the high-pressure characteristics of these products. By establishing a flow model and a condensation model for the supersonic nozzle, the effects of inlet pressure and inlet temperature on the condensation process are analyzed. The analysis reveals that the latent heat released during condensation causes an abnormal distribution of pressure and temperature within the nozzle. When the inlet pressure of the nozzle is increased from 7.0 to 9.0 MPa, the liquid phase mass fraction at the outlet rises from 5.3 × 10−3 to 0.056. Similarly, when the inlet temperature is lowered from 300.0 to 290.0 K, the liquid phase mass fraction at the outlet also rises from 5.3 × 10−3 to 0.058. The increase in inlet pressure leads to the condensation location shifting toward the throat by ∼8.5 × 10−3 m MPa−1, while the impact of inlet temperature is approximately −2.3 × 10−3 m K−1. The nucleation rate in the nozzle is always concentrated in a small region.