Re-using LNG Terminals for Hydrogen

If you care about energy and decarbonization issues, you'd find it hard to avoid noticing the considerable hyperbolic messaging emitted by the fossil gas industry- producers and distributors- in relation to how their installed infrastructure can be re-used in future for hydrogen. As mentioned in my previous article,

...maintaining the illusion that their gas transmission and distribution infrastructure can be used to produce, transport and sell hydrogen, is existentially important to these people. Without that illusion, it becomes clear to the market that their assets are actually liabilities with an abandonment cost. You can therefore bet good money that they will do everything they can to maintain that illusion, even if what is required is a considerable stretching of the limits of credulity.

The disaster of the Russian invasion of Ukraine has been a double edged sword in this regard. While the vulnerability of European economies resulting from their reliance on Russian fossil fuels imports has been underlined, the gas industry definitely believes in the old adage that one must never let a good crisis go to waste!

The recent emphasis has been on the fast-tracking of new liquefied “natural” (fossil) gas (LNG) infrastructure, which is pitched as the only way Europe can be saved from freezing the dark when Russia closes the valves. Of course, the occasional bright spark wakes up and says, “Hey- aren't fossil fuels on the way out? Why are we building more fossil fuel infrastructure? Shouldn't we push harder on decarbonization and build things which are durable into a decarbonized future?”

The gas industry's answer in response is loud and clear, “Don't worry folks, we can use LNG facilities to transport liquid hydrogen (LH2) in future!

And the message has been inserted into the mouth of no less than Canada's Prime Minister Trudeau at the recent G7 meeting:

https://financialpost.com/commodities/energy/oil-gas/trudeau-says-canada-may-expand-energy-support-for-europe

The idea was so preposterous to me that when read Trudeau's comment in the newspaper, I literally laughed out loud. It would be a laughing matter, but for the fact that the fossil gas industry has managed to turn our prime minister into a #hopium addict and to cause him to display that addiction on a public stage as huge as that of the G7...that's horrifying to me.

Let's break the issue apart and see how much of this is myth, and how much is just nonsense.

Upstream Gas Transmission

Looking at the gas infrastructure in the previous article, we'd already concluded as follows:

• most fossil gas transmission infrastructure requires replacement to be used safely with pure hydrogen. That includes replacement of piping, compressors etc. These are the medium and high pressure pipes which carry fossil gas long distances
• Compressors of 3x the suction displacement and 3x the power would be required to deliver the same amount of energy
• the distribution network likely could be re-used with only modest energy capacity reduction, but leakage would be worrisome from both a safety and a global warming potential (GWP) perspective
• every end use device on the network would need replacement. Simply re-jetting existing burners is not an option

You can find endless articles and reports written by both the fossil gas industry and by “hydrogen economy” advocates which argue that the “re-use” of the existing fossil gas infrastructure is possible, or even imperative. But when you dig into those reports, you generally find that “re-use” is limited to a very small % of hydrogen being blended into existing natural gas. Generally this is a maximum of about 20% by volume, which is only 7% by energy content. And when they start talking about “repurposing” of gas infrastructure for hydrogen, what they really mean is re-use of existing rights of way for the installation of new pipe...

...which isn't re-purposing, it's REPLACEMENT! The two words have very, very different meanings!

You also find gems like this, from hydrogen advocates at the Transition Accelerator:

“Further research is needed to develop appropriate coatings, inhibitors and odorants for protecting hydrogen pipelines from corrosion.”

I'll translate that for you. This is what they meant:

“There are no coatings, inhibitors or odorants which will render the re-use of existing fossil gas pipelines safe with pure hydrogen (because if there were, we'd have mentioned them!) so we hope somebody will invent some...someday”

While hope is good, it should never be confused with a strategy! And in this case, the hope of rendering an existing pipe made of the wrong material, safely compatible with hydrogen, is a false one. When a gas has such high permeability that it's literally moving between the grains in intact metal, a coating you can apply to the interior of pipe in situ is not going to be a feasible strategy to prevent that permeation.

Why is this pertinent? Because in Canada at least, the hydrogen they're talking about liquefying isn't “green” hydrogen made from renewable electricity. No, it's blackish-blue, bruise-coloured hydrogen, to be made from fossil gas assets which would otherwise be stranded liabilities. And that gas, and the big holes in the ground the gas industry hopes to use to dispose of all that captured fossil CO2, are in Alberta. Alberta is landlocked- it's nowhere near a sea port capable of supporting an LNG terminal. So yeah, you've got to get the gas- and later the hydrogen- to that terminal...

But hey, we're not done yet!

We haven't even started to look at how stupid the idea of repurposing LNG terminals for LH2 is, itself! And yes, that idea is plenty stupid!

First, here's a little table comparing the properties of the two fuels:

Reference 1: Handbook of Liquefied Natural Gas, 2014, pp 229-257

Reference 2: K. Ohlig and L. Decker (Linde), “The latest developmetns and outlook for hydrogen liquefaction technology), AIP Conference proceedings 1573, 1311 (2014)

A few things should be easily apparent from this comparison:

1. Making LH2 is much more energy intensive than making LNG, taking about four times as much energy per joule of HHV in the feed. This should come as no surprise, since we've already established that just compressing hydrogen takes 3x as much energy per delivered joule than compressing methane does
2. Storing LH2 takes a lot more tank volume per joule- over twice as much per unit of HHV. The energy density of hydrogen per unit mass is excellent, but per unit volume- even as a 24 kelvin ultra-cryogenic liquid- is far from spectacular
3. Storing LH2 is harder, and more expensive, not just because of the colder temperature, but because for every joule of heat leaking into the tank, you lose over 3x as much fuel value as if it were leaking into a tank full of LNG. That means you'll have lots of motivation to think very, very carefully about insulation.

Fantasizing for the moment that the equipment was perfectly interchangeable between the two processes, and looking for a moment at just the raw power required here, we're talking about the LH2 terminal having a liquefaction capacity of 1/4 as much HHV as what it previously did for LNG- and it would have a storage capacity of less than half as much energy.

Liquefaction Equipment

Let's compare the flowsheets of a LNG plant to that of a LH2 plant to see how much equipment we could re-use.

(Air Products flowsheet- ref 1 fig 7.3)

The most widely used LNG flowsheet is that from Air Products, called C3MCR. After water, CO2, H2S and other junk is removed, it uses two refrigerant cycles to reduce energy consumption- one using primarily propane, and the other being a mixed N2/CH4/C2/C3/C4 refrigerant. Note that if we were to repurpose the LNG equipment for LH2, the gas purification equipment would just be abandoned, as all those steps would already have been carried out at the H2 plant as part of CO2 capture.

The Claude cycle H2 liquefaction flowsheet is considerably more complicated:

(Claude cycle flowsheet ref 2)

Details are given in my paper here:

https://www.dhirubhai.net/feed/update/urn:li:activity:6925207015648591872/

...but the quick summary version is that it involves liquid nitrogen cooling followed by a multistep hydrogen refrigeration cycle. Pumping heat out of anything within a few tens of degrees of absolute zero and dumping it at hundreds of degrees K is an absolutely energetically punishing task, and then you have the heat of ortho-para spin isomerization to deal with as well. These are all things not applicable to LNG.

What's the likelihood that the equipment optimized for the liquefaction of methane at -161 C can be re-used for the optimal liquefaction of hydrogen at -249 C? Pretty poor, to say the least! Sure, there are compressors and heat exchangers designed for cold operation- so what? The two gases are nowhere nearly the same density, so all the compressors sized for methane are going to be way, way too small for use with H2, in terms of both power and suction displacement. The flowsheets are totally different. The heat transfer conditions are not even close to similar.

But surely we can repurpose something? Sure- lots of stuff. The site, utilities, the loading terminal etc. etc. But repurposing is NOT the same thing as re-use!

Storage and Transport Equipment

When you're storing something so cold, you have limited choices:

1. Use vacuum insulation to minimize heat transfer: double wall construction with an evacuated space between them to minimize heat transfer. For large tanks such as “horton spheres”, the vacuum space can't be left unsupported, so it tends to be filled with an insulation material such as perlite
2. Use single wall tanks with the best insulation you can manage, and cope with boil off

For LNG, coping with boil-off is possible by either flaring it, using it as ship's fuel on an LNG tanker while at sea, or running compression equipment to liquefy the boil-off gas again. So you do have the choice, and in fact tanks without vacuum insulation are quite common for LNG- the capital cost savings pay for the extra energy. Note that the cover photo for this article shows flat-bottomed, simply insulated (not vacuum insulated) tanks under construction in a modern LNG terminal.

For LH2, the energy intensity is so high that you'd likely have no choice but to use vacuum insulated gas spheres for storage. The largest spherical tanks you can build- giant land-based tanks- have a boil-off rate of more than 0.2% per day due to the extremely low temperature. At the liquefaction terminal, you likely would feed the boil-off hydrogen back to the liquefaction train, reducing its capacity. But once onboard a ship, you won't be running a Claude cycle...you'll be coping with the boil-off by either feeding it to the ship's engines, or flaring it. And after a 20 day journey plus unloading at destination, the loss of what you've been trying to transport will be very significant indeed.

Conclusions

The notion that you could re-use LNG terminals later for liquid hydrogen transport and distribution is a further extension of the myth of LH2 as an energy transport medium. It's clearly much more of an excuse to make you feel better about fast-tracking the construction of new fossil fuel infrastructure, than something people would really take seriously as a design strategy.

1. Getting H2 to the terminal in future would require rebuilding the fossil gas transmission infrastructure
2. Even if re-purposing were possible, the plant would have a small fraction of the liquefaction and storage capacity that it had for LNG
3. Even if you did as much dual-purposing in design, massive amounts of equipment would be abandoned, not repurposed, because the gases and liquids are miles apart from one another in properties

But you know that if it's already coming out of the mouths of leaders of G7 nations, we can expect to hear more about this under the assumption that it must be true.??