Gas Transmission System Operators (TSO) are considering injecting hydrogen gas into their networks. Blending hydrogen into the existing natural gas pipeline network appears to be a strategy for storing and delivering renewable energy to markets.

In the paper GT2019-90348, the authors have explored the efficiency of H~2~-blending in a natural gas pipeline network. The conclusion of the paper is: if the energy transmission capacity and the efficiency decrease with the introduction of H~2~, the authors conclude that it is not an obstacle, but the way of using transmission natural gas networks should be closely studied to find an economic optimum, based both on capital and operating expenses.  To establish the comparison, the paper did not take into account the limits of the equipment; all equipment was considered as compatible with any load of hydrogen blending.

In the current paper, the idea is to consider the hypothesis that the only factor which has impact on the infrastructure is the partial pressure of H~2~. The idea is not new, in 1802, Dalton published a law called Dalton's Law of Partial Pressures. Dalton established empirically that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual component gases. The partial pressure is the pressure that each gas would exert if it alone occupied the volume of the mixture at the same temperature.

Independent of the limits of the equipment, the authors explore the relationships between a network capacity and its associated pressures in regards to the H~2~ partial pressure. Within the partial pressure constraint, the goal is to find the maximum H~2~ flowrate.  This flowrate is then compared with a flowrate which is a function of % H~2~.

Nevertheless, steel is subjected to hydrogen invasion while being exposed to hydrogen containing environments during mechanical loading: resulting in hydrogen embrittlement (HE). HE also depends on the textured microstructure. In the final results, the measured fatigue data reveals that the fatigue life of steel pipeline is degraded by the added hydrogen. The H~2~ has an effect on the steel fatigue which is not simply due to the partial pressure.

The idea of the authors through the results of their 2 papers is to give the key points to help to find the optimum points for introducing H~2~ into a natural gas network, because, for them, the idea is that partial pressure is a factor in the equilibrium between H~2~ capacity and the remaining lifetime of the equipment.

In conclusion, to optimize the H~2~ capacity in their network, TSOs will need to adjust their dispatching methodology and their Pipeline Integrity Management (PIM).   


Managing the Pressure to Increase the H2 Capacity Through a Natural Gas Transmission Network

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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