The impact of hydrogen addition to natural gas on flame stability

Injecting hydrogen into existing natural gas networks is a promising step to mitigate global warming. However there is little evidence showing that how much degree of hydrogen admixture can be accepted. Experiments on populations of gas appliances are not available at present, thus a unified estimation method is required. First, a single-port burner was experimentally evaluated using methane-hydrogen mixtures (hydrogen percentage: 0–50%vol, unburned mixture temperature:373–573K, equivalence ratio:0.8–2). Mathematical formulae of the critical boundary velocity gradient, which quantitatively depict the relationships between flashback, lifting and hydrogen percentage, temperature were provided. A multi-ports burner was subsequently assessed, and the results of the two burners showed good agreement. An analysis method for changes in the flame stability region and gas source replacement decision was proposed based on curves of the flashback and lifting limits. This work provides an important basis for introducing hydrogen into gas networks and the design and adjustment of gas appliances.