Dynamic characteristics of chlorine dispersion process and quantitative risk assessment of pollution hazard

The aim of this study was to analyze dispersion behavior characteristics and pollution hazard risk after a release of liquid chlorine. A full-scale model of liquid chlorine tanks in an area with a radius range of 3 km was established using FLACS (Flame Acceleration Simulator) code, and the chlorine dispersion characteristics of six leakage scenarios were calculated according to the POOL model, and the individual risk and social risk under different conditions as calculated quantitatively. The results show that leakage occurs in three stages: dynamic dispersion, gravity dispersion, and atmospheric dispersion. Variations in dispersion processes were expressed as "outward expansion" and "inward contraction." At the same time, dispersion was accompanied by the phenomenon of "cloud separation." In the six leakage scenarios, the total distance of chlorine dispersion was 84-1000 m for a concentration of 225 ppm, and 27.5-401.3 m for a concentration of 900 ppm. The corresponding times (duration) to the farthest dispersion distance were 235-1345 s and 185-680 s, respectively. Chlorine concentration and dispersion distance are consistent in trend; however, the farthest dispersion distance shows a "delay effect" in time. At 225 ppm and 900 ppm, the delay time was 125-1145 s and 75-480 s indifferent leakage scenarios. The installation of a safety instrument system (SIS) can effectively reduce the risk of chlorine dispersion.