The use of inert gas for mitigating fires and gas explosions

Abstract

Hydrogen has been proposed as an alternative carbon-zero energy source for power generation fuel cells, transportation, and other industries. Furthermore, Li-ion batteries are gaining popularity as a better storage storage for converted green energy because they have higher energy density and low maintenance costs. However, both hydrogen and Li-ion batteries pose a significant fire hazard. Hydrogen is regarded as a very flammable substance with its properties, and Li-ion batteries, known as thermal runaway, can vent out flammable gas mixtures in case of failure. A significant number of incidents have been reported and will increase with the increasing demand for hydrogen and Li-ion batteries. Therefore, understanding this behaviour and implementing safety barriers for hydrogen and lithium-ion battery-vented gas is essential. Adding an inert gas to a flammable mixture is one of the steps that can be taken to avoid an undesirable consequence like a fire or an explosion.

This work studied combustion characteristics of hydrogen and li-ion battery-vented gases with air and inergen mixtures in a 20-litre explosion sphere vessel at 300 K and 1 atm absolute pressure. Maximum explosion pressure, maximum rate of explosion pressure rise, and deflagration index were measured for different mixture compositions. A simple flammability limit analysis was done on hydrogen-air-inergen mixtures to identify how inergen affects the flammability of hydrogen. A comparison was done to validate the experimental results with numerical calculations based on Cantera and experimental data with other published research results.

Hydrogen and air mixtures agreed well with the computational results and the published data. Hydrogen showed better combustion characteristics than battery gases used in the experiments. However, with the inclusion of inergen, deviations were observed between the actual and the computational results. The results showed that adding inergen to a flammable mixture significantly reduces its flammable properties.