On the explosion characteristics of natural gas with hydrogen and inert gas additions

In this work, the explosion limits of three different natural gas mixtures (with various proportions of methane (CH4), ethane (C2H6), and propane (C3H8)) have been investigated numerically based on detailed chemical kinetics. Furthermore, a comprehensive investigation of the effects of hydrogen (H2) and inert gas (N2, CO2) addition on the explosive properties of natural gas has been carried out. The results indicate that the C3H8 components have a dominant effect on the explosion limits of natural gas. The addition of high-hydrocarbons in natural gas can significantly reduce the auto-ignition temperature, shorten the ignition delay time, and enhance the explosion risk of the mixture. Furthermore, the negative temperature coefficient (NTC) response of natural gas in the second explosion limit gradually disappears, and changes to the Z-curve response with the addition of H2. However, the explosion tendency of the mixture is reduced with the addition of H2 under normal to high-pressure conditions. In addition, with the increase of inert gas (N2, CO2), the explosion limits of the mixtures shift upwards to a higher-pressure region, which significantly reduces the explosion tendency. Nevertheless, the explosion propensity of the mixture increases significantly under low-pressure conditions when the mixture contains hydrogen. To elucidate the critical control reactions and determine their synergistic effects, sensitivity analyses under different conditions are performed. Finally, the interaction of different fuels in natural gas mixtures is further summarized by analyzing the explosion limits of single-component, binary-component, and multi-component mixtures of hydrogen to propane. This paper provides an important guidance for the development of natural gas with high safety, low risk, and low pollution.