Numerical simulation of carbon separation with shock waves and phase change in supersonic separators

Abstract

The current study evaluated a potential carbon separation method. Based on engineering thermodynamics, heat transfer and phase transition dynamics, a mathematical model is proposed to predict the phase change in high pressure supersonic flow, and a flue gas model after dehydration, desulfurization and denitration is established. The flow features with shock waves and spontaneous condensation in the supersonic separator are clarified, the influence of flow model on shock waves and flow features is quantified, and the energy recovery process with phase change is studied. The results show that flue gas enters the supercooled state near the throat, reaches Wilson point at x = 0.077 m, and the nucleation rate surges from 0 to 4.46 × 1020 m−3 s−1. When vapor molecules reach the surface of droplets, droplets grow, and latent heat is transferred from droplets to the vapor phase, resulting in condensation wave. A shock wave is generated at the diffuser inlet, and the flow and liquid phase parameters change abruptly after the shock wave. The single-phase model incorrectly predicted the separator refrigeration capacity, flue gas expansion capacity, location and intensity of the shock wave, and the maximum deviation is up to 65.5%. Excessive improvement of pressure recovery efficiency results in reducing the liquefaction capacity of the separator.