As the mixing of hydrogen with traditional natural gas becomes one of the main topics in the industry, several cases of the pipeline system capacity studies are presented to show the impact, and to show and explain the phenomena experienced. The cases studied include long-distance transmission system with gas compression, high-pressure backbone system for gas distribution, and finally mid- and low-pressure grids.

The investigation assumes keeping the overall pressure drop over the dedicated pipeline constant i.e., to assume keeping the inlet and delivery (minimum) pressures, and to plot the final capacity of flow in energy basis against the hydrogen content from 0 to 100% mol.

The long-distance transmission faces dramatic increase of compression power and gas cooling requirements with secondary effects due to the temperature profile but the overall energy capacity faces a moderate drop following the trend of mixture’s Wobbe index. The high-pressure distribution systems are exhibiting a moderate capacity drop too, basically proportional to the mixture’s Wobbe index. Mid- and namely low-pressure systems are prone to dramatic drop of the energy flow transferred in proportion of the mixture’s heating value when the flow regime tends to transition to laminar flow, which leaves quite an open discussion whether the existing last-yard distribution pipes can be used for high % of hydrogen. For low-pressure system the vertical lift effect is increasing as the mixture gravity decreases dramatically.


The injection of hydrogen into traditional natural gas networks has become a vivid topic within the gas industry during the latest years. Potential sources of hydrogen injected to gas systems seem to be related with renewable electricity generation and use of gas system properties (line pack) and storage facilities for short-term and seasonal balancing. These ideas also shifted the requirements for gas infrastructure to handle time-varying hydrogen content. The hydrogen compatibility issues constitute quite a large area of several technical disciplines; here we stay related directly to the plain hydraulic analysis.

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