Challenges of blending hydrogen into natural gas

In our explanatory video, we describe the challenges of blending hydrogen into natural gas.

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With the Paris Agreement and EU legislation - such as the Fit for 55 package - becoming legally binding agreements on climate change, engineers faced an enormous challenge to resolve in the countdown of an hourglass.

In this context, blending hydrogen with natural gas is an important component that can accelerate current decarbonization plans to mitigate climate change.

However, there are two key challenges: To begin with, hydrogen has different chemical properties than natural gas, which means that the regulatory framework for natural gas loses its validity.

A second challenge is that the technical instructions for hydrogen that relate to valves have not yet been approved.

To help you understand the current state of blending, we have summarized the 5 most important points for you:
1. Legal limits for hydrogen
2. H2 tolerance of different components in the natural gas infrastructure
3. Temperature influences
4. Gas flow rate continuity in the network
5. And the storage proximity

Legal limits for hydrogen:
There are 4 main applications which should be kept in mind.
• Hydrogen Transportation
• Natural Gas Vehicles
• Gas Turbine
• And Underground Gas Storage Facilities

Hydrogen Transportation:
Hydrogen can be transported in the form of a gaseous energy carrier via the natural gas grid such as power-to-gas. In this context, the German DVGW regulation states that hydrogen from electrolysis and synthetic methane must comply with a legal limit of 1 to 10% in the natural gas grid.

Natural Gas Vehicles:
For natural gas vehicles, DIN 51624 stipulates a limit of 2% for hydrogen in the tank.

Gas Turbine:
Regarding gas turbines, manufacturers set a 1 to 5% hydrogen limit to avoid machine issues caused by a low-pollution premix in burners "sensitive" to the component.

Underground Gas Storage Facilities:
In any gas storage facilities, a hydrogen blending of 1% is allowed.
Beyond that, hydrogen's biogas content should not exceed 5% in underground pore storage areas. This limit avoids the growth of undesirable sulfate-reducing bacteria harmful to the site.

H2 tolerance of different components in the natural gas infrastructure
We have summarized the essential elements for you in a matrix.
The results of the compatibility analysis are divided into transportation, gas storage, M&C, distribution, and applications.

Thereby, the hydrogen concentration range goes from 0 percent to 70 percent.

The various compatibility areas are color coded. The blue section indicates the need for research and analysis. The yellow section illustrates where there is a need for regulation and control. And the turquoise section indicates the areas where hydrogen blending is safe.

Temperature influences:
This phenomenon happens in the high-temperature months of summer.
In the summer, the low energy consumption and throughput often come with a reduced flow rate. If this low flow rate is to feed hydrogen only, the mixture with (existing) natural gas won't be good. Hydrogen bubbles will form. Then, high hydrogen concentrations in the natural gas network appear. As turns out, watching over the temperature makes a difference in blending efficiency.

Gas flow rate continuity in the network:
The significance lies in the impact it can have on the compliance of legal limits. Since hydrogen's concentration in the natural gas network is about 10% and, for some applications, it can't be above 2%, monitoring gas flow rate is essential to decide when and where to feed H2 into the grid.

In addition, there is experience that a location with a continuously high gas flow in the network is helpful for electrolysers.

But on the other hand, even small hydrogen amounts in low natural gas flow rates can lead to local exceedance of the permissible limits.
This insight is crucial for operators. It allows them to choose the best location in the grid for H2 injection.

Storage proximity:
Especially when there is a large water electrolyzer with downstream methanation. This is a vital step that can enhance the process.

These were the key data you need to consider when blending hydrogen into natural gas.

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