Experimental study on solid CO2 BLEVE based on the superheat limit theory

Abstract

In this work, a small-scale experiment of solid CO2 Boiling Liquid Expanding Vapor Explosion (BLEVE) has been conducted and comparisons between experimental results and theoretical results have been performed. The process of solid CO2 BELVE which can be divided into several phases has been observed clearly. It is verified that SLT can't be the absolute criterion of CO2 BLEVE, but it is still an important parameter for BLEVE. The possible relationship between the relative pressure rise and the relative pressure drop were found, but it needs more experiments to be verified. Conclusions: The process of CO2 explosion can be divided into pressure sudden dropping, superheated liquid boiling and extending, pressure recovering unstably then decreasing to ambient pressure. The comparison results of theoretical calculation with experimental data show that solid CO2 BLEVE may occur below the SLT and may not occur beyond the SLT, so, whether the initial temperature of the liquid reached the limit temperature of the liquid can't be a necessary condition to determine whether the BLEVE will occur. But it is confirmed that the blast effect may be much higher with a higher superheat degree and it is no doubt that SLT is still an important parameter for CO2 BLEVE. So in the CO2 injection process and for the large volumes of high pressure CO2 it is better to decrease the superheat degree under the SLT to avoid CO2 BLEVE accident. This can be an effective method for BLEVE risk management. It is also found that thermal stratification appears in the liquid zone, and from top to bottom are the gas phase, gas-liquid phase and liquid phase, respectively. This may be the reason why BLEVE may happen both below and beyond the SLT. Meanwhile, both the amount of depressurizations and the rate of depressurizations are found to be positively correlation with the amount of depressurization and the rate of depressurization. And there is a certain kind of fixed proportional relationship between relative pressure rise and relative pressure drop and further studies are still needed.