Effect of Fire Walls on Explosion Risk in Hydrogen Storage Facilities

One mitigation measure that is frequently encountered in hydrogen installations is the use of fire walls to protect equipment, buildings, roads and other public places from potential jet fires. However, the use of fire walls can also increase the accumulation of hydrogen due to the reduction in ventilation caused by the walls. The accumulation of a large flammable cloud of hydrogen can result in large explosion overpressures in case of ignition. In particular, hydrogen clouds at concentrations above 10% can undergo a deflagration to detonation transition (DDT), which would result in severe overpressures and potentially catastrophic damage.

This contribution will present a study of several accidental release scenarios in a typical hydrogen storage facility. CFD modelling was used to understand the effect of the presence and geometry of fire walls and storage tank configurations on the air flow patterns to check whether there are areas of low ventilation where hydrogen could accumulate. The dispersion behaviour of different leaks was then simulated, allowing us to understand how the fire walls and tank geometry influence both the size and concentration of the flammable clouds. Finally, selected flammable clouds were ignited to obtain the potential explosion overpressures.

The objective of this presentation is to highlight the potential disadvantages to using fire walls as a mitigation measure against thermal criteria and the factors that influence the severity of potential explosions in hydrogen storage facilities.