Small-scale experimental study of microevolutionary processes and dynamics of CO₂-N₂ mixtures before BLEVE

CCS technology involves carbon capture, where the captured CO₂ contains N₂ impurities and there is a risk of Boiling Liquid Expanding Vapor Explosion (BLEVE) in the high-pressure CO₂-N₂ mixtures vessel. Therefore, in this paper, we experimentally investigated the jet structure and boiling nucleation microevolution process after the sudden release of high-pressure CO₂-N₂ mixtures in a pressure vessel and discussed the effects of rupture disc diameter, and N₂ molar ratio on the dynamic pressure before the startup of BLEVE. The results show that under-expanded jets are experimentally observed due to the Joule-Thompson effect. The boiling and nucleation microevolution is divided into six main stages, in the second of which the boiling expansion of the liquid and the “backfilling” of the gas leads to a dynamic pressure peak greater than the initial pressure, and BLEVE starts to occur. In the experiments, the dynamic pressure peaks were larger at 8 mm rupture disc diameter and 8 mol% N₂, BLEVE did not occur at 15 mm, and N₂ content below 5 mol% had less effect on the dynamic pressure behavior. This study provides a preliminary investigation of the pre-BLEVE behavior of CO₂-N₂ mixtures and provides theoretical support for risk prevention.