The Pipeline Of The Future Is Fuel Agnostic

Simply put, we have a long way to go until our pipeline system supports CO2 or hydrogen transport.

Or, perhaps we don’t.

Studies have shown that it may be safe to blend hydrogen with natural gas in our existing pipeline infrastructure, albeit, with some modifications required to infrastructure and protocol. It may also be possible to adapt existing natural gas pipelines to transport carbon dioxide – again, with modifications. To be truly “fuel-agnostic” there are various factors that need to be considered when transporting different fuels in existing pipeline infrastructure. But, there is also technology already in existence today that can help solve these challenges.

CO2 is transported in pipelines at pressures that are more than double the pressure of natural gas pipelines. This allows the CO2 to stay in a dense phase above its critical temperature. Hydrogen pipelines would also be higher pressure than natural gas pipelines but for a different reason. Hydrogen is much lighter than natural gas. By volume, hydrogen provides 1/3 the energy as natural gas. Therefore, to get the same amount of energy to end applications, pipeline operators would either need to increase the pressure of hydrogen or increase the volume of hydrogen transported.

Both equipment for compression and pressure letdown must be adapted to the requirements of different gases for a pipeline to be truly agnostic. However, there are technologies that exist today that have the potential to be flexible for these applications. For example, Baker Hughes’ turbo-compressor technology can now support up to 10% hydrogen blend and is being tested by leading European natural gas midstream operator Snam in Italy’s gas network.

However, the challenge of compressing hydrogen or CO2, can be costly. Energy recovery systems are particularly promising in terms of offsetting some of the higher costs of hydrogen and CO2 compression by creating green electricity from the byproducts of these very processes. For example, Sapphire Technologies’ FreeSpin® In-line Turboexpander (FIT), which is used to recover waste energy during pressure letdown processes in existing natural gas infrastructure, has various adaptations that make it a fuel-flexible decarbonization investment for pipeline operators.

Because the FIT has been successfully adapted for higher pressure fuels, it can be used for hydrogen liquefaction and pressure letdown processes. Liquefaction allows hydrogen to be stored in its densest state and transported with highest efficiency. Hydrogen liquefaction is achieved through a series of compression, cooling and expansion processes.

Using the Sapphire FreeSpin® turboexpander system, the energy lost in expansion processes can be recovered and used to offset energy consumed in other areas of the liquefaction process, such as powering the compressors. In pressure letdown processes, high pressure hydrogen would flow into the FreeSpin® turboexpander, which would expand the gas and generate electricity, once again creating energy that can be recycled into the operation or sold to generate additional revenue.

Hydrogen (H2), having an incredibly small mass, is prone to leak when stored and transported in pressurized equipment. The FIT eliminates potential leaks by providing a hermetically sealed environment with no dynamic seals.

To maintain the integrity of a pipeline carrying high pressure CO2 or hydrogen/hydrogen-blended natural gas, filtration systems to remove impurities must be adapted to meet the specifics on these fuels. For example, a dehydration system can help reduce risk of corrosion to pipelines carrying CO2, since wet CO2 can cause corrosion. Crack arrestors can also be installed to help a pipeline withstand CO2 or Hydrogen-induced cracking.

A new technology invented by researchers at the National Energy Technology Laboratory (NETL) may also provide a solution to meet the pipeline integrity challenges of adapting natural gas pipelines to other fuels. The invention is a self-healing cold spray coating that can be applied to existing pipelines to protect from internal corrosion. On the software side of technological developments, technology like digital twinning can allow pipeline operators to test and predict how a pipeline will operate under different pressure, flow, and stress conditions by creating a virtual model of the pipeline – all without impacting the physical pipeline.

Materials, hardware, and software innovations are all helping to make it more viable for natural gas pipeline operators to adapt their existing infrastructure to expedite emission-reducing endeavors like carbon capture and switching to cleaner fuels like hydrogen. Pipeline operators are already investing in important projects to create fuel-agnostic pipelines. For example, British midstream operator National Gas made news in March by testing various concentrations of hydrogen in a segment of their pipeline, including pure hydrogen – a world’s first. Leading US midstream provider Tallgrass Energy is converting its Trailblazer natural gas pipeline for carbon dioxide transport, which will ultimately result in a 400-mile CO2 pipeline that can transport over 10 million tons of CO2 per year.

One important way climate technology providers can help energy companies future-proof their assets is by envisioning and developing solutions that are fuel-flexible. By doing so, climate technology providers can close the gap between investing in decarbonization solutions for existing systems and investing in technology to support the energy transition for energy companies. “Fuel-flexible” should become table stakes especially when partnering with midstream operators – because the pipeline of the future is fuel-agnostic.

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