Effect of Carbon Dioxide Addition and Mesh Coverage on Reduction of Hydrogen Fire Risk

<p>Hydrogen is a promising clean energy carrier to build a zero carbon society in future. The hydorgen reletaed technologies such as production, storage/transportation, and conversion to electricity have been rapidly progressed especially in recent years. However, hydrogen is known to be excellent combustible owing to wide flammable range, low minimum ignition energy, and significantly high laminar burning and propagation velocities, and also their flames are difficult to be observed by naked eyes, which carry a high risk of serious accidents. Given the hazardous characteristics, efficient combustion management techniques are required for safe operation of hydrogen. Hereby, we present the effect of carbon dioxide addition and mesh coverage on reduction of hydrogen fire risk. The results of experiments with a small slit burner emulating a crack such on hydrogen transportaion pipes clarified follows: （1） hydrogen diffusion flames can be visualized by carbon dixoide addition to hydrogen gas; （2） carbon dioxide addition to hydrogen gas causes flame instability, resulting in the change in flame shape and the reduction of flame size, eventually quenching with increase in the carbon dioxide proportion ; （3） coverrage of gas ejection port by fine metal meshes is effective for quenching. The combination of carbon dioxide addition and mesh coverage with optimal specification can become a better safety operation technique for hydrogen related technologies.</p>