Tracking hydrogen in pipelines

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Dr Dale Erickson
Technical Expert

As we work towards decarbonising energy, gaseous fuels have a fundamental role to play in this transition where the production of low carbon-impact fuels is necessary. Household carbon emissions in the UK from heating alone need to drop from almost three tonnes a year today, to just 135kg by 2050. Blending up to 20% hydrogen into the gas grid with existing natural gas could save around six million tonnes of carbon dioxide emissions every year. This is the equivalent of taking 2.5 million cars off the road[1]. Some of the most advanced efforts are underway where utilities, including National Grid and Scottish Gas Network, are blending hydrogen into pipelines not only to fuel power plants or industrial processes, but to also serve homes and businesses alike.

There is much discussion around moving hydrogen through existing gas networks. We have previously talked about the design aspect where subject matter expert Callum Peace, highlights the innovative R&D that is helping to repurpose infrastructure to transport hydrogen. But once we have hydrogen in the gas network, how can we monitor and ensure that it can be not only used safely buat also is cost effectively within the pipelines? These crucial questions are what tracking hydrogen is all about as we look to move it to the end user.

The hydrogen challenge

Hydrogen is an extremely useful future fuel because it can be generated via water electrolysis which can be powered by electricity and stored for later use. The majority of hydrogen is currently produced via steam reforming of fossil origin feedstock. The key problem with using hydrogen in pipelines is that it has a lower energy density than natural gas and a different Wobbe index (WI), so sometimes pure hydrogen cannot be used in existing systems since it carries less energy and is harder to move. The WI or Wobbe number is an indicator of the interchangeability of gases when they are used as a fuel and their ability to deliver energy. i.e. natural gas, liquefied petroleum gas and town gas.

The opportunity to mix hydrogen into existing natural gas networks is useful because when blended with hydrogen at these lower concentrations, anywhere from 2% to 20%, you can use the existing infrastructure to move it to end users. This saves a lot of money on capital costs as newer installations are not required. There also can be reduced operating costs as we do not need to monitor newer pipeline assets.

This sounds promising, but the major problem with hydrogen is that small molecules can sometimes disperse through the steel wall of pipework and cause damage. Lots of R&D is going into this for future solutions, but for now there is currently a limit on how much hydrogen can be used for different pipeline materials.

Natural gas networks are complex as gas can be routed in many different directions; the pipeline branches are potentially constructed of many different materials and different branches will have different specifications. The scale is considerable, in the United States alone, there are around three million miles of mainline and other pipelines that link natural gas production areas and storage facilities[2]. Some branches may have a tolerance of 6% and some may have a tolerance all the way up to 20%. The differences in tolerances mean that the same volume cannot be the single solution for all networks as this will lead to pipeline failures and potentially serious safety breaches.

Solutions to monitor

In light of these complexities, there is a need to focus on the thermodynamics of hydrogen. In other words, to get it accurately modelled. But more importantly, being able to track the concentration of hydrogen in any given segment is key. Another key area in blending hydrogen and the routing of hydrogen is the need to route hydrogen into the branches where it can be most readily handled and prevent high hydrogen spikes from going into hydrogen pipeline branches that cannot handle that.

Pipeline failure is often thought of as an external agent, corrosion attacking structures and pipework from the outside. But this targets internal systems as well. Internal integrity presents a separate set of challenges since access becomes much more of an issue, involving shutdowns, suspended production and complex survey techniques.

Monitoring and predicting failures are very important disciplines relevant to the entire lifecycle of a pipeline network or its branch. Pipes are simple enough in principle, but when your pipelines are complex or extend for thousands of miles things quickly become complicated. Flow rates can be different in different areas of the pipe; hotspots focus on the effects of weakness in certain areas or allow it to develop elsewhere, and corrosion inhibitors might not reach the right areas.

Consequentially innovative digital technology can be used to help monitor these complexities without having to interfere with the pipeline. Our Virtuoso® software is used to model and predict flows in pipeline networks. It can operate both on and offline, allowing predictions to be made based on historical data and confirmed in real-time with live data to build increasingly accurate refinements. Recently, we have been working with HyNet where we will identify the optimum system sizing and also perform testing of the complex network to ensure flexibility under the full range of operational scenarios by considering the future demand and project expansion. Design of the system will take place with the use of our H2 modelling technology, Virtuoso® conducts the assessment for a full hydrogen network. The use of Virtuoso®, will be key in modelling the complex hydrogen network and for success of the project.

Electronic Corrosion Engineer (ECE) is our specialist software that predicts corrosion rates based on temperature, pressure and flowrate conditions. There are thousands of potential combinations of conditions that lead to various levels of corrosion making it difficult to predict accurately.

By plugging the flow modelling data from Virtuoso® into the corrosion calculations of ECE we have been able to create a powerful tool for assessing the impact of flowrates on corrosion. In addition, when we look at mitigating corrosion with inhibitors we can model and predict how effective an application will be.

Tracking hydrogen animation

Move it

Operating midstream gas infrastructure is becoming increasingly complex. The addition of hydrogen in natural gas is going to further accelerate needs for solutions in this space and a more detailed dynamic real-time operational model will be required to address transportation and processing issues.

While the idea of using hydrogen in existing pipelines is an attainable approach, it is not something that can happen without expert solutions to monitor the impact of this gas flowing though the network. Real-time and offline digital tools are required for the efficient management of operations. By addressing this we can ensure that the most complex pipeline systems can be used to move hydrogen and help industry and people alike in their day-to-day energy needs.

[1] Britain’s gas grid to be ready to deliver hydrogen across the country from 2023, energy networks announce – Energy Networks Association (ENA)

[2] Natural gas pipelines - U.S. Energy Information Administration (EIA)

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