Experimental study on boilover fire characteristics and uncertainty of high water-content crude oil

Abstract

Water is a necessary condition for a boilover to occur, crude oil storage tanks are extremely hazardous in the event of a boilover fire. In order to investigate the effect of water contained in the crude oil itself on the boilover phenomenon, 20 sets of replicate experiments were conducted using crude oil without deep water removal, with a water content reaching 3.45 %. As a whole, the combustion process is divided into 5 typical stages: ignition stage, stable combustion stage, pre-boilover stage, boilover stage and flame extinguishing stage, this paper focuses on analyzing the characteristics of the boilover stage. The results show that high water-content crude oil can still boilover without water layer and with a high degree of uncertainty, with a total of 6 scenarios occurring: no boilover occurred, boilover like a running pot of porridge, spray in one of the directions, the strongest boilover, continued stable combustion at the end of the boiliover, and flame extinguishing at the end of the boilover. Water contained in the crude oil will make the hot zone temperature lower, ranged between 145 °C and 165 °C. A higher oil water content can accelerate convection within the oil, which in turn weakens the process of temperature rise in the hot zone. Boilover intensity is generally weak, in most experiments maximum heat flux does not exceed 10 times the steady combustion period. Quantile-Quantile plot and Kolmogorov-Smirnov test were used to analyses the normality of boilover onset time and total burning time. Boilover onset time obeys a normal distribution, whereas total burning time excludes normality. This paper is the first to investigate the uncertainty of boilover phenomenon, to deepen the understanding of oil tank boilover fires, and to propose a research idea to analyses the boilover phenomenon from a probability perspective.