Mechanism of the effect of sodium chloride impurities on flash evaporation after accidental rupture of a storage tank

Abstract

BLEVE is a serious industrial accident that often occurs in liquid storage tanks where flammable or pressurized liquids are stored. The presence of liquid in the tank enhances the intensity of the liquid's superheating and boiling, which greatly increases the danger of the storage tank. In this study, based on a small high-pressure storage tank rupture and release experimental platform, the boiling phenomenon of liquids containing NaCl impurities during rapid depressurization was investigated, and the mechanism of NaCl-enhanced superheated boiling of the medium was determined. NaCl impurities dissolved in water provide a vaporization core through which bubbles nucleate directly, resulting in a large number of bubbles and enhanced boiling. The degree of NaCl-enhanced superheated boiling does not increase linearly with concentration, and a transition occurs at a saturated boiling concentration of 1 mol/L. Furthermore, this turnaround concentration diminishes with increasing initial pressure under the coupled effect of two factors: increasing number of vaporized cores and increasing pressure. Gas-phase venting is not a necessary condition for the occurrence of superheated flash boiling. Significant superheated boiling can also occur when sodium chloride impurities are present, as liquid phase venting increases the degree of boiling.This paper provides some value for the safe handling and storage of superheated liquids containing NaCl impurities.