Specifications of the LPG spherical tank.

Liquefied Petroleum Gas (LPG) is typically stored in pressurized spherical tanks, where accidental leaks can create dense, flammable vapor clouds. This study used PHAST to simulate LPG dispersion from a refinery-scale spherical tank, considering various leak diameters (5–805 mm), leak locations, seasonal meteorological conditions, and three propane–butane mixtures (15/85, 30/70, and 50/50 by volume). Dispersion distances were evaluated at both the Lower Flammability Limit (LFL) and 50% LFL thresholds. The findings indicate that leak diameter is the primary factor influencing dispersion extent, showing strong correlations for both LFL (ρ = 0.89) and 50% LFL (ρ = 0.91). Predicted dispersion distances downwind ranged from approximately 20–60 m for small leaks to around 400–800 m for larger releases, depending on the concentration threshold and release conditions. Distances at the 50% LFL were consistently greater than those at the LFL. Power-law regression revealed nearly linear scaling between dispersion distance and leak diameter (b = 0.94 for LFL and b = 0.96 for 50% LFL), explaining over 80% of the observed variance. Butane-rich mixtures resulted in longer dispersion distances at the LFL, while compositional effects were not significant at the 50% LFL. Meteorological and temporal factors had limited influence under typical site conditions. Overall, the results emphasize comparative scaling behavior rather than pointwise concentration prediction and demonstrate deviations from ideal D² scaling due to turbulence, buoyancy, and atmospheric entrainment. Using both LFL and 50% LFL thresholds provides a conservative and practically relevant basis for hazard zoning, quantitative risk assessment, and emergency planning at LPG storage facilities.液化石油气（Liquefied Petroleum Gas, LPG）通常储存于加压球形储罐中，若发生意外泄漏，将形成浓密的可燃蒸气云。本研究借助PHAST软件模拟炼厂级球形储罐的LPG泄漏扩散过程，纳入的变量包括：泄漏孔径范围为5~805 mm、泄漏位置、季节气象条件，以及三种体积比分别为15/85、30/70与50/50的丙烷-丁烷混合组分。研究分别以燃烧下限（Lower Flammability Limit, LFL）和50% LFL作为浓度阈值，对扩散距离开展评估。结果显示，泄漏孔径是影响扩散范围的核心影响因素，在LFL阈值下（相关系数ρ=0.89）与50% LFL阈值下（ρ=0.91）均呈现极强的相关性。顺风方向的预测扩散距离随泄漏规模差异显著：小泄漏的扩散距离约为20~60 m，大规模泄漏则可达400~800 m，具体数值取决于浓度阈值与泄漏工况。50% LFL阈值下的扩散距离始终大于LFL阈值下的结果。幂律回归分析表明，扩散距离与泄漏孔径近乎呈线性缩放关系（LFL阈值下缩放系数b=0.94，50% LFL阈值下b=0.96），该关系可解释超过80%的观测方差。富丁烷混合组分在LFL阈值下会带来更长的扩散距离，但在50% LFL阈值下，组分影响并不显著。在典型场地工况下，气象与时间因素对扩散结果的影响有限。总体而言，本研究结果更侧重于扩散行为的相对缩放规律，而非单点浓度预测，同时证实了由于湍流、浮力与大气卷吸效应，实际扩散结果偏离理想的D²缩放模型。同时采用LFL与50% LFL阈值作为依据，可为LPG储存设施的危险分区、定量风险评估与应急规划提供保守且贴合实际需求的参考标准。