Leak detection and SOx emissions tradeoffs with odorized hydrogen natural gas fuel blends in gas turbines

Abstract

The scalable, dispatchable operation mode leveraged by modern gas turbine power generators exploits pipeline distribution of gaseous fuels with no natural color or odor such as natural gas (NG) and potentially hydrogen (H2). To reduce fire and explosion hazards in the event of leakage, regulations in many countries require that such fuels be doped with pungent malodorants to enable early leak detection by human smell. These compounds typically rely on fragrant sulfur groups that ultimately generate sulfur oxide (SOx) emissions when the odorized fuel is burned. To mitigate negative air quality and environmental impacts associated with SOx pollution, many countries also restrict SOx emissions from gas turbines, inducing a fundamental tradeoff between upstream leak safety and end-use SOx emissions. Historically, this tradeoff has not been a significant issue, as odorant concentrations used in current NG distribution networks do not generate sufficient SOx emissions to warrant regulatory concern. However, this paper shows that SOx emissions issues may become relevant for proposed future H2 distribution networks and H2 turbines, where the tradeoff between leak safety and SOx emissions is over four times stronger. This disparity arises from the lower molar heating value and broader flammability limits of H2 relative to NG, which are both shown to elevate SOx emissions in the case of H2. Among several other important considerations, the paper also discusses how the extreme diffusivity of H2 and the increased pressures expected in H2 networks may require greater odorization levels to ensure effective leak detection, inducing even steeper SOx emissions tradeoffs.