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Numerical and experimental study of vapor cloud explosions – mitigation by inhibitors

Friday, 30 September, 2011 - 17:00
Campus: Brussels Humanities, Sciences & Engineering campus
Leopold Hoorelbeke
phd defence

The oil industry operates installations and processes with important quantities of flammable substances
within a wide range of pressures and temperatures.

A particular hazard for this type of installations is an accidental release of a large quantity of flammable
material resulting in the formation of a flammable cloud within the installation. Historical evidence has
shown that the ignition of such a cloud can lead to a devastating explosion and a total destruction of the
installation. Such accidents are commonly named “Vapor Cloud Explosions” (VCE).

Five out of the 20 largest losses in the hydrocarbon industries were caused by a Vapour Cloud Explosion.

The total cost of these VCE’s was (3,57 Billion US$) which is about 26% of all 20 major losses.

Despite more than 40 years of experimental and numerical research there are still very few means to mitigate
the explosion effects once an accidental flammable cloud is ignited.

This research concerns a novel method: mitigation of the effects of a Vapour Cloud Explosion by inhibition
with solid particles. The idea was developed by the author. Literature search was performed and finally lab
test and medium scale tests were performed. An existing CFD code (FLACS) was adapted to incorporate the
mitigation method in numerical modelling of vapour cloud explosions. A patent is currently pending.

This research is innovator for science and society for the following reasons:

1. The use of solid particle inhibitors for vapour cloud explosions has never been studied in detail
2. The research explains the theoretical science behind the mechanism while the experimental work
shows conclusively that the inhibition mechanism works;
3. The inhibition mechanism is an additional active barrier against vapour cloud explosions.
Installations with a potential for a vapour cloud explosion will have an additional barrier to avoid
complete destruction of the plant in case of an accidental release of a flammable cloud. This will
enable to save lives and to limit property damage.
4. The novel technique could become a new safety standard in the oil industry.
5. The numerical code FLACS has been adapted to enable modelling of the influence of inhibitors on
the potential effects of vapour cloud explosions.

The thesis comprises 7 chapters:

1. Importance of the research for science and society
2. Theoretical part. Research on vapour cloud explosions involves multiple scientific fields such as
chemistry, physics, turbulences, combustions and numerical modelling.
3. Description of the experimental work
4. Description of the numerical modelling
5. Conclusions
6. Future work
7. References