Using Math To Blend Hydrogen Into Natural Gas Pipelines

Los Alamos National Laboratory researchers are reporting that mathematical modeling can show how to safely blend hydrogen with natural gas for transport in existing pipeline systems. A secure and reliable transition to hydrogen is one of the proposed solutions for the shift to a net-zero-carbon economy.

Anatoly Zlotnik, a co-author of a new paper on the modeling in the journal PRX Energy. Zlotnik, a mathematician at Los Alamos National Laboratory, has expertise in modeling, designing and controlling energy-transmission systems briefly explained, “Mixing hydrogen into a natural gas pipeline changes how the gases flow, which will create new conditions for operators. Our modeling shows that injecting hydrogen gradually into a natural gas pipeline network allows safe, predictable operations.”

According to the paper, Zlotnik and his Los Alamos colleagues used nonlinear partial differential equations to develop the model for transporting heterogeneous mixtures of natural gas and hydrogen through pipeline systems. The infrastructure modeling includes compressor and regulator units, supply stations that inject gas into the network at defined pressure and hydrogen blends, and flow stations that withdraw the mixture from the network.

Solving challenges to pipeline operation

 Transporting hydrogen in existing natural gas pipeline networks would enable operators to maximize the utility of these extensive and expensive facilities as part of a strategy to reduce carbon-emitting fossil fuels. Hydrogen is much lighter than natural gas, which is mostly methane, so blending them challenges pipeline operation in new ways.

The Los Alamos team’s mathematical modeling determined that limiting the rate of change of hydrogen injection into a natural gas pipeline will prevent large, rapid changes in pressures. The team’s methods for simulating a pipeline network could allow operators to develop standards on injection rates.

Hydrogen offers several advantages as a clean fuel that doesn’t emit carbon dioxide. In a fuel cell, hydrogen plus oxygen create electricity to power cars, trucks and facilities. Hydrogen can also be blended with natural gas for use in appliances such as household furnaces and dryers, or it can be burned to power manufacturing facilities or generate electricity.

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Getting a method in hand to handle the pressure variances that occur when pumping the very light hydrogen into a heavier gas is a critical improvement. A mixed gas system seems to be a very good idea.

There remains the hydrogen embrittlement of steel problem. Its no small problem, either. Hydrogen under pressure in a simple steel vessel just soaks into the steel, like hydrogen seems to soak into about everything when contained under pressure. To get appreciable volumes the pressure needs to be quite high. Over time the hydrogen simply makes the steel a brittle hydrogen alloy and could become easily fragmented. High pressures in a fragmentable vessel offers a quite unpleasant possibility.

It would really be better to alloy the hydrogen to some carbon and cut or eliminate the pressure and the destruction of the storage vessels with the possible consequences.

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