浮盘和气窗位置对内浮顶罐正己烷蒸发损耗的影响

Influence of floating roof and vent locations on n-hexane evaporative losses of internal floating-roof tanks

在环境保护日趋严格和受到重视的大环境下,内浮顶罐的蒸发损耗机理和减排降耗规律尚有进一步研究的空间。使用自制的1 000 m3内浮顶罐缩比模型,研究了不同气窗和浮盘位置对罐内气体空间气流分布、罐内风速、储液蒸气浓度以及损耗速率的影响。结果表明:罐壁通气孔储罐和罐顶边缘通气孔储罐的气孔流向均呈现两进两出的特点;壁面通气孔储罐内风速大于顶盖边缘通气孔储罐,而浓度小于后者;浮盘位置越高,蒸发损耗速率越大,顶孔罐相比于壁孔罐的减排效果就越明显,其原因是贯穿整个壁孔罐内气体空间的大旋涡对边圈密封处的影响造成的。通过分析,建议将罐壁通气孔改造成罐顶边缘通气孔,建议在API内浮顶罐损耗公式的修订中考虑气窗和浮盘位置的影响。

With the increasingly strict environmental protection and attention to the environment,it deserves further investigation into mechanisms for evaporative loss and emission reduction in internal floating-roof tanks.A scaled-model of 1 000 m^3 internal floating-roof tank was made to investigate the influence of vent and floating-roof locations on the distribution of airflow,wind speed,mass concentration and evaporative loss rate in tanks.The results show that both tanks with shell vents and fixed-roof vents have two in-flowing vents and two out-flowing vents through which wind flows.The wind speed in shell-vent tanks is higher than that in fixed-roof-vent tanks,but mass concentration lower than that in the latter.The higher the floating-roof is,the higher the evaporative loss rate is and clearer the emission reduction,and the reason is that the circular movement of wind through the whole vapor space in shell-vent tanks has great influence on rim seal.It is recommended that vents should be transformed from tank shell to fixed-roof of tanks,and that the influence of vent and floating-roof locations should be considered in API loss formula.