Hot zone formation in combustion tests simulating solvent fires in reprocessing plants – concerns on boilover phenomenon

This paper reports the first case of hot zone formation in a combustion test simulating an organic solvent fire in a reprocessing plant. Our goal is to add a boilover component to a computational model for quantitatively predicting the accident progression of the fire. Although the scale of boilover combustion increases when hot zones are formed in the solvent, it has not been clarified whether a hot zone is formed in the combustion of a 30% tributyl phosphate (TBP)/dodecane solvent mixture. To clarify this point, we conducted beaker-scale combustion tests and measured the temperature distribution in the burning solvent with thermocouples to obtain the following results. (1) No hot zone was formed by the combustion of only dodecane. (2) In the combustion of 30% TBP/dodecane, hot zones were not formed as long as dodecane remained in the solvent. (3) A hot zone was formed when only TBP was burned. These results suggest that boilover combustion with hot zones may occur in the case of a fire caused by the leakage of organic solvents with nitric acid solution in a reprocessing plant.

本研究首次报道了模拟后处理厂有机溶剂火灾的燃烧试验中热区形成的案例。本研究旨在为用于定量预测火灾事故进程的计算模型添加沸溢（boilover）组分。尽管溶剂中形成热区时沸溢燃烧的规模会增大，但30%磷酸三丁酯（tributyl phosphate, TBP）/十二烷混合溶剂燃烧时是否会形成热区，目前尚未明确。为明确该问题，本研究开展了烧杯级燃烧试验，采用热电偶测量燃烧中溶剂的温度分布，得到如下结果：（1）仅十二烷燃烧时未形成热区；（2）在30% TBP/十二烷混合溶剂燃烧过程中，只要溶剂中仍存在十二烷，便不会形成热区；（3）仅TBP燃烧时会形成热区。上述结果表明，后处理厂中含硝酸溶液的有机溶剂泄漏引发火灾时，可能会发生伴随热区的沸溢燃烧。