Using Hydrogen in natural gas pipelines

[synch]

TL;DR Summary

Are the usual natural gas pipe networks compatible with hydrogen?

Decades ago, our domestic gas supply was changed from coal gas to natural gas, and I watched on as our kitchen oven had different jets fitted. As coal gas had a large fraction of hydrogen, obviously the pipes etc in use at the time were ok with hydrogen. Now the times have changed and there is interest in the hydrogen economy and renewables. So I am wondering if using the existing distribution pipelines, which have been used for natural gas for a long time, to distribute hydrogen is realistic.
Hydrogen is quite different from methane of course.
A blend of hydrogen and ethane or ethylene would have the same calorific value per volume as methane, the viscosity would be different but maybe that could be compensated for. Both the hydrogen and ethane/ethylene could be sourced from bioethanol so would be renewable/green (at a cost of course) . That would allow the existing network to be used, instead of letting it become junk.

Is "hydrogen embrittlement" significant in this context ? I am hoping the pipeline standards already prevent that.

 

[.Scott]

Many of the long distance gas pipelines in the US are actually specially insulated Liquefied Natural Gas (LNG) pipelines. It is a more efficient way of transporting the natural gas.

 

[Baluncore]

TL;DR Summary: Are the usual natural gas pipe networks compatible with hydrogen?

Is "hydrogen embrittlement" significant in this context ?

Welding steel pipe with cellulose flux coated electrodes, generates hydrogen gas, that then dissolves in the hot steel. As the weld cools, the hydrogen gas comes out of solution in the melt, and is trapped between the forming crystals. The extreme pressure of the trapped hydrogen gas, makes the steel brittle.

MIG welding reduces hydrogen gas generation, so makes stronger, "low-hydrogen", welds.

Hydrogen will diffuse very slowly through some cold metals, but then it tends not to be at extreme pressure, so it does not make the material brittle.

 

[gmax137]

Hydrogen also has an easier time leaking compared to other gasses.

The power plants I worked at used H2 to cool the electrical generators (minimum windage losses). The piping was all welded fittings, not threaded black iron pipe like my home nat gas lines.

 

[synch]

I wonder what happens when a very thin gas is combined with a more usual gas like ethane, I guess the viscosity tends to default towards the more viscous gas ?

[small correction to my post - ethane or ethylene can be from bioethanol, hydrogen itself can be from the source sugar/biomass used for bioethanol ]

 

[256bits]

TL;DR Summary: Are the usual natural gas pipe networks compatible with hydrogen?

That would allow the existing network to be used, instead of letting it become junk.

Embrittlement is a result of H atoms diffusing into the metal structure, usually when the metal is hot from processes such as welding or forging, or from chemical means such as pickling, to say a few.
As the metal cools ( from a hot processing of the metal ) the atoms recombine into H2 molecules and thus can form pockets of stress points.
If your existing network is safe to flow the gas it now does under pressure showing no signs of embrittlement failure due to assembly processes, then it should be safe to flow H2 gas which does not diffuse into metal

 

[Tom.G]

Here is a research article on the hydrogen.energy.gov site titled

"Hydrogen Embrittlement of Pipeline Steels: Fundamentals,
Experiments, Modeling" iii_10_sofronis.pdf,

and if I am reading it correctly, indicates that Hydrogen embrittlement starts in surface tension micro-cracks.


a couple excerpts:

RESULTS
In the fracture of these materials, the
ductile fracture features such as microvoid nucleation,
growth, and coalescence process expected for low and
medium strength pipeline steels are not clearly identifiable.
.
.
.
CONCLUSIONS and FUTURE DIRECTIONS
...we discovered that the hydrogen-induced
failure mechanism in these steels is hydrogen
induced localized plasticity. In particular, we found
that the fracture process is governed by intense slip
activity despite the fact that the fracture surfaces
have the appearance of what is known to be quasicleavage
type of fracture. In fact, our research establishes
that quasi-cleavage is a mode of fracture fully
controlled by ductile processes.


(above found with:
http://www.google.com/search?hl=en&q=hydrogen+embrittlement+of+steel+pipelines+during+transients)

Cheers,
Tom

 

[BWV]

Begs the question of under what circumstances green H2 is a better energy source than electricity- I.e. just use electricity rather than using it to create H2

 

[Ken Fabian]

A lot of plastic gas piping around but most not rated for Hydrogen. Some newer ones are.

Blends with gas offer more use of existing infrastructure, appliances/engines with minimal upgrade but have limits to how much they can reduce the dependence on the gas and therefore the capability to get to very low/zero emissions. I've seen 5% - 20% H2 depending on existing piping and appliances, ie no one size fits all. https://docs.nrel.gov/docs/fy13osti/51995.pdf

Achieving some emissions reductions quicker or extending dependence on gas, making further emissions reductions slower? Given the pace of electrification, emergent heat pump technologies and RE growth it could become moot.

Worth keeping in mind that leaked H2, whilst not a ghg, has a global warming effect by slowing the breakdown of Methane.

I admit I am pessimistic about large scale use of Hydrogen outside industrial applications (iron smelting, chemical feedstocks) and expect those will work better making and storing the H2 on-site - using electricity grids to funnel the energy for that - than relying on Hydrogen being piped or trucked, because they are not relying on piping or trucking.

With a different kind of upgrading urban gas piping does appear to have potential for conversion to urban heating and cooling networks based in borehole ground source geothermal; the ground the piping is buried in becomes additional thermal heat storage. Trials of this approach have achieved COP's above 5 ie 5 times more energy out than electricity used.

 

[The Fez]

Many of the long distance gas pipelines in the US are actually specially insulated Liquefied Natural Gas (LNG) pipelines. It is a more efficient way of transporting the natural gas.

Actually that isn't true. LNG is used to transport natural gas overseas, but the vast majority within the country is transported in it's gaseous state. Per DOE website: "While the majority of natural gas is delivered in its gaseous form via pipeline in the United States, the growth in the international market for natural gas has given rise to the use of natural gas in a liquefied form, or LNG"

https://www.energy.gov/fecm/liquefied-natural-gas-lng

 

[The Fez]

Welding steel pipe with cellulose flux coated electrodes, generates hydrogen gas, that then dissolves in the hot steel. As the weld cools, the hydrogen gas comes out of solution in the melt, and is trapped between the forming crystals. The extreme pressure of the trapped hydrogen gas, makes the steel brittle.

MIG welding reduces hydrogen gas generation, so makes stronger, "low-hydrogen", welds.

Hydrogen will diffuse very slowly through some cold metals, but then it tends not to be at extreme pressure, so it does not make the material brittle.

You are correct that normal cellulose SMAW electrodes generate high hydrogen, but normal pipeline is still welded that way, since the majority of the hydrogen is diffused out when the weld cools. If you are welding on a pipeline such as hot tapping, where the pipeline is in service and the weld cools rapidly, you can still use low hydrogen SMAW electrodes (designated -H4R typically). MIG and TIG are good options too, although will take longer/cost more.

While there is some thought that the hydrogen can build up in voids and create high pressures to create hydrogen embrittlement, it is a complicated topic that many people are still studying today. It has been seen in room temperature steels, especially in the high pressures (100+ bar) that would be normally used for a transmission pipeline or storage. EPRI (among others) is currently studying the feasibility of converting the existing NG infrastructure to H2, and early findings seem to indicate hydrogen embrittlement is not as much of an issue with lower strength pipeline (i.e., API 5L X52 and lower).

 

[The Fez]

At the end of the day, I don't see much viability for the green hydrogen industry outside some niche applications. The round trip energy efficiency is horrid (about 30%) and storage is a problem. We did a study for one of our power plants, currently generates about 600 MW. I calculated it would take two tanks the size of the one at Kennedy Space Center, the largest liquid H2 tank in the world, to run the plant for a week. People are starting to blend hydrogen into existing NG systems, but the carbon reduction is very minimal. Because of the lower heating value of hydrogen, a 20% hydrogen blend in NG only reduces carbon emissions by something like 3%.

At the end of the day, pipeline operators will be too nervous to introduce hydrogen in their existing pipelines, especially in the face of all the current regulations from PHMSA and others, no one wants to take the risk. Add that to the fact that there won't be any significant supply of green H2 to transport anyway in the foreseeable future, it's pretty much a non starter.

Build more hydro pump storage.

 

[256bits]

The round trip energy efficiency is horrid (about 30%)

Assuming higher values of 85% electrolysis conversion, transportation 95%, and combustion 60%, one can achieve close to 50% utilization using H2 green as a fuel. Considering most H2 is made from fossil fuels, the carbon footprint from 'grey' H2 is one of not saving the planet in any way.

All energy extractions and conversions have losses.
I am not sure what it is for coal or natural gas, but for oil we have some figures.
For a new light crude oil well, extraction can be as high as 99%, transportation 95% (assume the same as H2 ), refined product 90% ( propane - as sulfur extraction and carbon chaining increases, the efficiency decreases ), and combustion 60%, for an overall conversion of 50%, which is similar to green H2.

For a well running dry, economics is the determining factor. Assuming a dry well is one where 90 units of energy have to be put in to get 10 units out, which I admit is a guess on my part, but depends upon the price of a barrel of crude, ( heavy crude has a Net Energy Ratio of approx 3 or 4 and is profitable), we then have extraction efficiency of 10%, yielding a conversion overall of 6%. A 1 to 1 NER has an energy conversion of 25%.

In comparison, green H2 energy conversion compares with fossil fuels as having an advantage, if that alone would be the criteria as H2 green being a sound and proper choice.

You have already mentioned H2 disadvantages of storage and transportation on existing pipeline networks.
Another is that if electrolysis is done on site, the assurance of H2 green becomes suspect.

 

[BWV]

Assuming higher values of 85% electrolysis conversion, transportation 95%, and combustion 60%, one can achieve close to 50% utilization using H2 green as a fuel. Considering most H2 is made from fossil fuels, the carbon footprint from 'grey' H2 is one of not saving the planet in any way.

All energy extractions and conversions have losses.
I am not sure what it is for coal or natural gas, but for oil we have some figures.
For a new light crude oil well, extraction can be as high as 99%, transportation 95% (assume the same as H2 ), refined product 90% ( propane - as sulfur extraction and carbon chaining increases, the efficiency decreases ), and combustion 60%, for an overall conversion of 50%, which is similar to green H2.

For a well running dry, economics is the determining factor. Assuming a dry well is one where 90 units of energy have to be put in to get 10 units out, which I admit is a guess on my part, but depends upon the price of a barrel of crude, ( heavy crude has a Net Energy Ratio of approx 3 or 4 and is profitable), we then have extraction efficiency of 10%, yielding a conversion overall of 6%. A 1 to 1 NER has an energy conversion of 25%.

In comparison, green H2 energy conversion compares with fossil fuels as having an advantage, if that alone would be the criteria as H2 green being a sound and proper choice.

You have already mentioned H2 disadvantages of storage and transportation on existing pipeline networks.
Another is that if electrolysis is done on site, the assurance of H2 green becomes suspect.

What is your source for the 99% energy loss on oil extraction? Its ridiculous to think that an entire industry could be profitable based on those economics. The numbers for oils sands mining, by far the least efficient form of oil extraction are as high as 6:1 see https://www.sciencedirect.com/science/article/abs/pii/S0360544213002776?via=ihub

 

[256bits]

What is your source for the 99% energy loss on oil extraction?

I said extraction, not energy loss.
One unit of energy to get 100 units out, so approx 99% extraction ratio.
How many new sweet wells are like that, less than in the past, as all low hanging fruit was picked early on in the industry. Now we have off-shore and fracking, which would be more energy intensive.

Oil sands, with carbon capture, becomes more energy intensive, and less profitable.
One of the reasons the industry does not like the caps on CO2 emissions placed on the industry by the Canadian govt under Trudeau, with Danial Smith's ranting and raving about it. One can agree or disagree on who is correct.

Its ridiculous to think that an entire industry could be profitable based on those economics.

One of the reasons that Trump's oil drilling boost is not panning out is the lowering of the world price. Some ventures are just not now profitable.
As I did admit, I am guessing when that happens for a well to become dry, Perhaps it is 1 to 1, but I used 1 to 10 (9 ) just as illustration when oil has a ( very ) high barrel price, giving the incentive to squeeze as much as possible from the field.

 

[Ken Fabian]

EROEI for oil has been declining, a lot - a quick look suggests now around 1/10th for production compared to the early days of oil. Yet it seems most of the energy inefficiency is still in the end uses, shedding vast amounts of wasted energy as heat.

But such calculations rarely include (and more often exclude) the climate considerations and consequences; in that respect oil burning delivers much more heat to the climate system (via enhanced greenhouse) than ever extracted from it (use + waste) - a very high and unhelpful kind of EROEI, giving a great abundance of unwanted and unusable and climate stability disrupting heat.

As for Hydrogen, I don't hold out great hopes for it as a large scale emissions solution and agree with analysts who expect overall use of Hydrogen to decline with diminished use in the oil production chain, mostly confined to industrial uses rather than as a replacement fuel for electricity and heat and transport fuel.

On-site production and storage will bypass the need for piped, shipped, trucked H2, by using electricity grids to aggregate energy from diverse and geographically scattered sources and stores, ie power lines will do the energy transporting, with greater efficiency.

 

[synch]

IIRC it is possible to burn using a oxygen-in-fuel system instead of the usual fuel-in-oxygen. I wonder if the oxygen resulting from water hydrolysis can be burned in the natural gas down a gas well ? The CO2 would then be left in-situ down the tube, the combustion could run the generator to create the electricity required, and the hydrogen could be piped out to consumers using the existing pipelines. But, hard to get a large generator down a bore hole I guess :)

 

[Ken Fabian]

IIRC it is possible to burn using a oxygen-in-fuel system instead of the usual fuel-in-oxygen. I wonder if the oxygen resulting from water hydrolysis can be burned in the natural gas down a gas well ? The CO2 would then be left in-situ down the tube, the combustion could run the generator to create the electricity required, and the hydrogen could be piped out to consumers using the existing pipelines. But, hard to get a large generator down a bore hole I guess :)

About 3 tons of CO2 is produced for each ton of gas burned, so there would not be room 'down the tube' to hold the CO2. Mixing exhaust gases underground with the natural gas being used seems to present problems too.

Ultimately displacing gas burning with non-fossil fuel energy appears necessary to achieve very low emissions.

 

[synch]

About 3 tons of CO2 is produced for each ton of gas

The volume is the significant factor, not the weight. The CH4 burns to CO2 or CO (same volume as the methane), and H20 (probably condenses at the pressures/temperatures underground).

 

[Ken Fabian]

@synch Good point. I had thought, incorrectly, the volumes would be a lot greater.

I still think the idea of underground natural gas burning using O2 from H2 production and relying in-situ CCS to make it low emssions is a non-starter. Permanent CO2 storage in gas fields that have numerous boreholes that have to be capped seems likely to present issues, just not necessarily within the life of the companies doing it. Lots of 'gas' fields are fracked shale and coal seams.
Relying on CCS to save fossil fuel as a primary energy seems problematic. Using any RE for H2 generally seems economically problematic and I think likely to be more limited than the optimistic proponents suggest. The extent that gas infrastructure can be converted to H2 seems likely to be limited.

Using the O2 generated plus CCS for extending the use of fossil fuels is something I think both inadvisable and unnecessary.