The addition of hydrogen into the natural gas network is being considered as a practical way to reduce GHG emissions from combustion equipment. This report has looked at potentially
serious changes to combustion properties and surveyed the scientific literature investigating the behaviour of hydrogen enriched natural gas in industrial combustion equipment.
There are three combustion properties that increase significantly
with the addition of hydrogen: flame speed, upper flammability limit, and flame temperature. This enhanced combustion has been used to improve the performance of gas turbines and internal combustion engines. Generally, addition of hydrogen increases
the emissions of NOx because the higher flame temperature increases the thermal NOx formation mechanism. Flashback is a safety concern for using unmodified equipment with hydrogen enriched natural gas.
Finally, one has to consider the actual
scenario for hydrogen addition to the natural gas network. The hydrogen content could vary, perhaps with the variation in solar and wind electicity output. This variation can be tracked and process controls adjusted to maintain efficient and safe
operation, and control emissions of regulated pollutants (NOx). However, an industrial facility may not have the necessary instrumentation to measure the composition of the fuel gas in real time, or a sophisticated control system to make the
necessary adjustments. Such users can experience degraded performance and increased emissions even with the maximum hydrogen threshold set at 10%-vol.
RECOMMENDATION: To realize the benefits of enriching natural gas with hydrogen, industrial
combustion facilities need to be properly instrumented, the control systems modified, and the operators trained to take full advantage of the new fuel. This is particularly important for Power-to-Gas scenarios that introduce significant fluctuations
in the fuel gas properties.