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.

本论文首次报道了模拟后处理厂有机溶剂火灾的燃烧试验中出现燃烧热区（hot zone）的案例。本研究旨在为计算模型添加沸溢（boilover）子模块，以定量预测火灾的事故发展进程。尽管溶剂中形成热区时，沸溢燃烧的规模会随之增大，但针对30%磷酸三丁酯（TBP）/十二烷混合溶剂的燃烧是否会形成热区，目前仍未明确。为厘清这一问题，我们开展了烧杯级燃烧试验，利用热电偶测量燃烧溶剂的温度分布，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，只要溶剂中仍残留十二烷，便不会形成热区；（3）仅TBP燃烧时则会形成热区。上述结果表明，若后处理厂发生夹带硝酸溶液的有机溶剂泄漏引发的火灾，则可能出现伴随热区的沸溢燃烧现象。