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Old 2022-10-10, 00:34   #1
ewmayer
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Default CH4+H2O Ice Clathrates as alternative to LNG transport?

For good or ill, it looks like US-produced liquefied natural gas will be a huge part of Europe's energy future for the next few decades. That piqued my interest with respect to the economics of substituting US LNG for Russian pipeline gas to Europe. The number I've heard most often is that the former costs roughly 3x as much per-molecule than the latter, due to the added expense of chilling to -162C (by way of comparison, N2 liquefies at -196C at standard atmospheric pressure), transporting across the Atlantic in an LNG tanker, and regasifying at the other end. 3x the cost, needless to say, has huge economic implications for European industry and consumers.

That got me wondering - we often hear about the greenhouse-warming potential of methane sequestered in deep ocean sediments in the form of CH4+H2O ice clathrates. The problem from a production and transport perspective is that such clathrates contain only ~13% CH4 by mass, the rest being the water-molecule lattice. Nonetheless, the relatively modest temperatures needed to produce clathrates and the relative ease of transporting the resulting solid product struck me as perhaps still being viable economically. A little more online searching turned up this:
Quote:
A significant portion of the volume of hydrate comprises the methane molecules. As a result, 1 L of hydrate has approximately 169 L of methane. Some consideration has been given to using methane hydrates as a mode of gas transportation, an alternative to liquefied natural gas (LNG). British Gas and Aker Engineering, among others, investigated the idea, but no commercial system exists. Aker published a complete design of a system and demonstrated that hydrate transport was feasible up to 3500 nautical miles at ordinary freezer temperatures for a capital cost 25% below that of LNG.[8]
There would likely be further efficiencies to be found from commercial-scaling of the needed technologies. If the chemists could find some way of packing even more CH4 into the crystal lattice that would of course be another win, as would discovery of a means to safely "mine" clathrates from existing deep sediments.

Insights from the chemistry-trained/interested appreciated!

Last fiddled with by ewmayer on 2022-10-10 at 00:35
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Old 2022-10-10, 02:05   #2
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I did a lot of "web research" (for many years) about natural gas and its relatives. This means that I read everything I could put my hands or eyes on, pro and contra, I could say I am an "expert" I also did a couple of posts here about my "belief" that the car of the future is a CNG-electric hybrid. Not electric-only, and not hydrogen or other stuff. There are a million reasons to be so. And we will live to see it.

I am driving a CNG car for the last ~12 years or so.

So, trust me when I say, the CNG/LNG is tricky to transport and store. And the only thing that hinder the "explosion" (excuse the pun, I mean in an economic/social/commercial way) of it is the fact that it is freaking tricky to store and transport. I could dive into the "why" if anybody is interested. I still hope to live to see a reliable method to store it in such a way to be safe when you transport it, and to be easy/cheap to recover it (assuming you pack it somehow, into some material, etc, during storage/transport).

Edit: don't know if the "$" in the thread title is intentional or typo (as $ and 4 are on the same key). I like it, so I will not edit it, but non computer-literate people may not understand the charade...

Last fiddled with by ewmayer on 2022-10-10 at 20:53 Reason: @LaurV: Yes, '$' was accidental, but kinda fits the theme. :)
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Old 2022-10-10, 02:35   #3
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You'd be better off co-shipping gasoline or other longish-chain hydrocarbons also of value, as solvent for the methane. At 30 atmospheres pressure vessel working pressure, instead of ~12% by mass useful fuel, it would be 100% useful fuel content. And not require refrigeration. At 30 atmospheres, 25C, vapor drawn off is essentially 100% methane from methane-octane blend. https://docecity.com/multiphase-and-...63ea0b2af.html
Methane allows high compression ratio in both spark ignition and compression ignition engines, so high thermal efficiency, making it a good fuel for ship propulsion also on the trip over.
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Old 2022-10-10, 22:43   #4
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Quote:
Originally Posted by kriesel View Post
You'd be better off co-shipping gasoline or other longish-chain hydrocarbons also of value, as solvent for the methane. At 30 atmospheres pressure vessel working pressure, instead of ~12% by mass useful fuel, it would be 100% useful fuel content. And not require refrigeration. At 30 atmospheres, 25C, vapor drawn off is essentially 100% methane from methane-octane blend. https://docecity.com/multiphase-and-...63ea0b2af.html
Methane allows high compression ratio in both spark ignition and compression ignition engines, so high thermal efficiency, making it a good fuel for ship propulsion also on the trip over.
I considered this sort of thing, but the numbers seem to make it impractical. Let's use Germany as an example. Someone please check my math:

I considered similar, b4t the numbers seem to make it impractical. Let's use Germany as an example. Someone please check my math:

Per this site, Germany natgas imports ~155 billion cubic meters / yr

OTOH Statista cites a figure of ~90 bcm / yr. I'll use this lower figure below.

CH4 density at STP = 0.657 kg/m^3
A mole of CH4 has mass 16g, so ~65 moles/m^3 at STP, thus 90 bcm/yr ~= 5850 billion mole / yr

Per here, annual gasoline+diesel consumption ~50 million tons/yr; assume that is ~100% imported (or locally refined from imported oil)

Octane has mole ~= 0.114 kg, thus annual German gasoline+diesel consumption ~= 440 billion mole / yr

Thus CH4 imports are over 10x gasoline imports mole-for-mole. I expect CH4 imports similarly dwarf those of total longer-chain hydrocarbons. But again, someone please check my math.

The other issue here: for LNG transport I've seen numbers citing quite-modest pressurization, under 1 atm overpressure. For both LNG and gasoline, unpressurized transport is dangerous enough; I doubt high-pressure bulk-transport means exist for that very reason.

Last fiddled with by ewmayer on 2022-10-10 at 23:53 Reason: Yep, I fubared my 1st attempt - updated numbers above
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Old 2022-10-11, 00:57   #5
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Ok, German natural gas use far exceeds the liquid fuels, and half of the natural gas used is from Russian sources which would be good to have a replacement for. Germany's domestic production is in single digits percentage of use. https://newsingermany.com/what-natur...or-in-germany/
657gm/m^3 / (16.043 grams/gm-mole) = 40.95 gm-mole/m^3 methane at STP (density & molecular mass from https://en.wikipedia.org/wiki/Methane)
Assume domestic usage 100E9 m^3/year in 2022-2023, as in 2021 per https://www.reuters.com/world/europe...as-2022-01-20/, of which half is to be replaced as CNG, LNG, NG in solution, etc, so ~5E10 m^3 imported from Russia to be replaced.
40.95 gm-mole/m^3 x 5E10 m^3 ~ 2.05E12 gm-mole CH4 to replace as import.
That's lower but within a factor of 3 of Ernst's figures for the whole usage.

Taking Ernst's revised gasoline+diesel figures as given, and supposing it was all imported from the US or other replacer of Russian CH4, at ~13 mole% CH4, 87% gasoline, and 1/3 gasoline, 2/3 diesel,
5/3 E13 gm / ( 114gm/gm-mole) ~1.5E11 gm-mole gasoline as octane,
13/87*1.5E11 ~ 2.2E10 gm-mole CH4 in solution ~ 0.0107 times the CH4 import need. So, only ~1.% of the needed scale.
Some of the gasoline is heptane, butane, MTBE, methyltoluene, etc but octane gives a ballpark figure, probably well within 2:1 either way.

The heavier components of diesel fuel (~dodecane) have poor solubility for methane, so the two thirds that is diesel is ignored as potential methane solvent.

LPG tends to be expensive compared to natural gas.

Half the use of natural gas is for comfort heating & water heating. Over time this could be reduced by a combination of small scale cogeneration and heat pumps. Japan does this already; natural gas engines drive the heat pumps and the exhaust heat is captured, providing the equivalent of ~200% thermal efficiency furnace, at higher capital cost.

Most people don't realize how energy intensive our way of living is. One thing that can forcefully make that clear is cutting enough firewood to heat a well insulated 3 BR home for a year in the upper midwest US. It's about 5 cords ~ 10 tons of good firewood. That is a lot of work and involves gallons of gasoline for chain saws, and more gallons for hauling from source to point of use.

As a youth, I had an experience with leaked gasoline igniting under a lawnmower's exposed fuel tank. The flame from the vent hole of the tank cap was a 2 foot torch, quite impressive, before I pulled the mower out of the garage and then set to work getting the fire out before the cap departed or the tank or line to the carb ruptured. A larger tank subjected to uncontrolled external heating could be spectacularly unpleasant. Pressure control and fire suppression would need to be well addressed.

Last fiddled with by kriesel on 2022-10-11 at 01:22
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Old 2022-10-11, 02:00   #6
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Quote:
Originally Posted by kriesel View Post
LPG tends to be expensive compared to natural gas.
Nope, this is either a typo, and you mean LNG, or you confuse the two things. LPG is mostly propane, the stuff you put in your cigarettes lighter, it liquefies at room temperature if you compress it just a little bit, or at normal pressure if you cool it just a little bit, that is why it is called "LPG" (liquefied petroleum gases) and it is cheaper than CNG in the most parts of the world. It is easier to store in liquid state at low pressure (no need tough containers, your lighter is made of thin plastic), and easier to transport too, but its caloric power is also lower than CNG. (ex: my car digests ~7-8 liters of gasoline for 100 km, while it will take only 5-6 kg of CNG; in the same time, my former car, which was a LPG car, used to digest about 8-9 liters of gasohol - a local mixture of gasoline and about 10% ethanol - but it sucked 10-12 liters of LPG for the same 100 km).

For the rest, we kind of agree...

About Ernst' calculus, albeit correct, the units "smell" wrong, i.e. they are kinda viceversa. You sell gasoline and LPG and LNG by volume, because the liquids are not compressible (well...), and they have a fix volume. You can sell them by kilogram too, if you like, but in general, everywhere in the world you buy gasoline at the pump in liters (or, on the other side of the pool, in gallons), and not in kilograms. While the CNG, and other (compressed or not) gasses, you buy them in kilograms (or tons, if you drive some old dodge, ). Because they are compressible, and specifying how many cubic meters of gas you buy has absolutely no meaning, unless you specify its temperature and pressure. However, those sites are not wrong, there is a standard for international sales of CNG, which specifies that a cubic meter of gas is "the quantity which fills a cubic meter, at ~15°C and sea-level pressure" (official formulation, albeit this "sounds so wrong", you fart in a room and the fart fills all the room, regardless of pressure and temperature )
.

Last fiddled with by LaurV on 2022-10-11 at 02:35
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Old 2022-10-11, 02:57   #7
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Quote:
Originally Posted by LaurV View Post
Nope, this is either a typo, and you mean LNG, or you confuse the two things. LPG is mostly propane, the stuff you put in your cigarettes lighter
Nope and nope. First:
Liquified propane for residential use, typ 2021 fall price $2.70 US/gallon
https://www.eia.gov/dnav/pet/hist/Le...RS_NUS_DPG&f=M
so ~$2.7/3.784= $.714/liter
0.498kg/liter, 50.4 MJ/kg; $.0284/MJ, which is nearly triple the cost of natural gas:

natural gas $11/1000cf https://www.eia.gov/energyexplained/...gas/prices.php
.022kg/cf 52.2 MJ/kg; $0.0096/MJ

Second: Round here, cigarette lighters are butane or liquid fueled. Fireplace lighters might initially ship propane filled, but the refill cans are butane, with perhaps a bit of propellant included.

Quote:
About Ernst' calculus, albeit correct, the units "smell" wrong
Units were appropriate to the computations, which included getting to mole ratios because that's what the solubility data was expressed in, in the references.

Last fiddled with by kriesel on 2022-10-11 at 03:07
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Old 2022-10-11, 04:10   #8
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Quote:
Originally Posted by kriesel View Post
Nope and nope.
Ken-
Why cite US prices when the conversation is about importing items to Europe, and LaurV pointed out "in most of the world...."? US prices are the least relevant rebuttal to either possible location of interest- Europe or LaurV's southeast Asia personal experience.

America isn't the only location forumites live in, after all. It would do you good to absorb how things work elsewhere, rather than deny what folks tell you. LaurV may well be mistaken, but it's gonna take data from somewhere other than USA to reach that conclusion.
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Old 2022-10-11, 05:41   #9
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The discussion Laurv was commenting on was between Ernst and me, about methods and exporting US sourced fuel to Germany. Asian fuel costs were a non sequitur in that context, not US costs. And LaurV offered no independent documentation / references to support his counterclaims.
Note the first sentence of the thread: "For good or ill, it looks like US-produced liquefied natural gas will be a huge part of Europe's energy future for the next few decades." (emphasis mine)

There is indeed drastic variation worldwide in energy pricing. https://www.globalpetrolprices.com/G...al_gas_prices/ Germany has nearly the highest listed price, and Russia nearly the lowest. The US natural gas price there appears near the log mean of Germany and Russia prices.

Getting back to the clathrate idea, what keeps the clathrates at depth and so at enough pressure to be stable is that the methane clathrate is ballasted by mineral material it's bonded to, so it doesn't float upward (0.9 g/cc vs ~1.03 for seawater) and discharge its methane as it encounters lower pressure. Harvesting it in a way that drastically limits methane outgassing as it's brought up is a challenge. Separating it from the minerals so as to avoid shipping multiple tons of mineral material per ton of clathrate is another.

Last fiddled with by kriesel on 2022-10-11 at 06:13
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Old 2022-10-11, 05:46   #10
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Quote:
Originally Posted by VBCurtis View Post
America isn't the only location forumites live in
+1. Problem with the LPG in US is that they have none. They take almost all of it (over 90%) from a minuscule country like Trinidad, or so, don't remember exactly. In other countries (Romania and Thailand included, but possible, not alone) the LPG market is private (i.e. any guy can dig a hole in the garden, fill it with LPG, and start buying/selling it, which keep the prices down) and even sponsored by the government, which contribute with a part of the price, like 10%, to stimulate the economy (Thai price for LPG at the pump varies between 11 and 15 baht per liter, depends on the region), while the CNG market is mostly state-owned, and getting the approvals to put a bucket of it in your yard to buy/sell it, is freaking difficult, mostly due to the technical difficulties that such enterprise requires (dealing with high pressure, steel/concrete walls, releasing valves for LNG, because it continuously evaporates when you don't cool it, increasing the pressure to tremendous values which no container can hold, that is why you sometimes see an open flame on top of reservoirs or even on top of trucks that transport LNG - in fact, the evaporation is encouraged, because that is how the rest of the liquid cools down and maintains its liquid state, but that is another story), and as the business is mostly state-owned and there is no competition, or only few potentate people can play with it, the prices are artificially higher. I pay ~22 baht for a kilogram, but I live quite "remote", the prices near Bangkok are a bit lower.

Moreover, driving on CNG in a country like Thailand requires about 10% more cost just because you drive on CNG. No joke, the surplus is due half to the fact that you can not take so much gas with you - you can only compress about 10-12 kg in a 75 liters tank in your car, which lasts for about 200 km, so you have to visit the station more often - and the other half to the fact that the stations, being state-owned only, are "rare", for example, a city like Chiang Mai, with half a million people, has only 5 such stations (by contrast, there are over 200 LPG stations). So, as I commute over 60km daily (return way) I have to drive "way out of my way" every 3-4 days (sometimes 2 days, if the pump doesn't have enough pressure, and only fills 7-8 kilograms into the tank, which is also common, they reduce the pressure to increase the safety, avoid possible accidents, etc) to refill, therefore driving about 10% more.

And yes, I understand that me driving my car in Thailand may have nothing to do with a German guy heating his house in Germany , but couldn't miss the opportunity to argue...
.

Last fiddled with by LaurV on 2022-10-11 at 05:50
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Old 2022-10-11, 05:51   #11
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Quote:
Originally Posted by kriesel View Post
The discussion Laurv was commenting on was between Ernst and me, about methods and exporting US sourced fuel to Germany. Asian fuel costs were a non sequitur in that context, not US costs.
Note the first sentence of the thread: "For good or ill, it looks like US-produced liquefied natural gas will be a huge part of Europe's energy future for the next few decades." (emphasis mine)
The discussion was not about LPG, you just brought it in from the thin air, and I wanted to make sure is not a typo.
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