Vapor Pressure of Natural Gas

This might help.

http://www.jmcampbell.com/tip-of-the-month/2010/01/variation-of-properties-in-the-dense-phase-region-part-2-%E2%80%93-natural-gas/

http://encyclopedia.airliquide.com/images_encyclopedie/VaporPressureGraph/Methane_Vapor_Pressure.GIF

The container isn't the problem. The infrastructure needed to distribute it is what hinders it. Would be very costly.

GA

If it's good enough for PW, it's good enough for me.

What happens to the LNG when the temperature in the container gets above -117deg F ? If the container is 90% filled with LNG (leave a little void space) and the temperature goes to 100 degrees F, what happens? The amount of energy in the tank isn't going to change. So, if it's filled with LNG and it heats up to ambient. What would happen?

If the internal temperature goes to 100°F, the energy will change a lot, as will the pressure. If only the ambient goes to 100°F, the internal energy may change a bit from thermal leakage. LNG tanks are insulated and refrigerated (possibly self-refrigerated by bleed-off).

At -117ºF, you'd already be at around 650 psi. (The normal boiling point is around -255ºF.) If you heated it to 100ºF, you'd be around 3500 psi. Don't even think about filling it at -255 and letting it heat up to 100ºF in a closed container.

Answer: it is no longer LNG; It's SNG [Supercritical Natural Gas].

In a road vehicle, volume is a constraint. So it makes more sense to use propane, which will have a liquid phase at ambient temperatures and more moderate pressures; the fuel tank volume contains more energy-of-combustion that way, and the concept vehicle would have a far greater range and weigh rather less than if methane/natural gas were the fuel.

Unless the container is cooled or extremely well insulated.

TT3

How does the Freightliner LNG fuel tank work?

http://www.freightlinertrucks.com/Trucks/Alternative-Power-Trucks/Natural-Gas/Natural-Gas-FAQ

There are plenty of alternatives to fossil fuels. Very few want to use them.

Given the generalized specs for pure NG at the temps you stated its going to be in a physical state classified as a super fluid or dense gas. Ether way that will give it a static pressure of around 2000 - 2500 PSI in the 70 - 120 F temp range.

As far as containers go that the typical working range of standard high pressure gas cylinders used fore industrial gasses which are already mass produced and can be found in countless sizes and volumes.

Relating to filling such a cylinder with high pressure DNG (Dense state Natural Gas) its probably going to follow the similar filling rules of 80 - 90% NG volume measured by weight or specially designed and calibrated flow meters Vs the internal tank volume like how propane tanks are filled.

Personally as someone who has worked with propane and with high pressure cylinders plus the pressure regulators and related fuel systems for running vapor based fuels I don't really see an big problems with using DNG as a vehicle fuel.

Provided the enviro nutters don get their fingers in the design specs for the systems. If they do I would expect the safety protocols and requirements along with the systems themselves to be unnecessarily over designed 'for safety' of course and priced unrealistically high to the point of making the concept cost prohibitive to most anyone in the industrialized world.

More like nitrogen, argon, etc. in a pressure bottle. One cylinder of methane at 3000 psi and 70 degF isn't going to get you very far. Not like propane - in a barbecue tank there is a distinct gas phase taking up ˜10% (when tank is 'full') over a distinct liquid phase taking up the balance. That's why when you shake the tank, you can feel the liquid swishing around. With supercritical fluids, there is no distinction between liquid and gas phases.

Read Kramarats link if you want to know more about what I am referring to.

Gases being held in their supercritical and dense phase while contained in tanks are not the same as just highly pressurized gases.

They get a little weird at certain temps and pressure points which can be greatly affected by the ratio of supercritical fluid to fixed tank volume due to not having specific phase change curve like propane which is why a specific filled mass to tank volume ratio needs to be followed for a specific peak tank temp.

I went back and read it - that's interesting stuff for the blend that natural gas is, somemost of the components do have critical temperatures higher than ambient and the mixture behaves in a complex fashion. I was quoting properties of pure methane from a P-h diagram I had handy. And, actually, nitrogen, argon, etc. in cylinders are supercritical, just as pure methane would be.

They are classified as permanent gasses due to their natural tendencies to behave more like supercritical gases than supercritical fluids regardless of how much they are compressed even though they are past their critical point .

They are most often defined as super dense gases, permanent gases, or super critical gases being they still lack the necessary properties to be fully classified as being in a supercritical fluid state.

Mostly at this point how they are defined is more semantics than anything.

This is how they do it in China. Gas at atmospheric pressure. Economical container too.

there are already hd trucks on the road using LNG:

www.freightlinertrucks.com/trucks/alternative...trucks/natural-gas

Not LNG, CNG.

About the only type of conveyance using cryogenic fuels (and oxidizers) fly into space.

LNG=Liquified Natural gas

CNG=Compressed Natural gas

We currently have a few LNG Plow trucks as well as a fleet of CNG vehicles.

I'm good with the CNG but I am surprised to learn that trucks are using LNG due to the difficulty handling and storing cryogenic fuels. If you are constantly using the fuel, you of course can self cool it, but what happens when you shut down the engine?

CNG ≠ LNG ≠ LPG

Following various comments about low critical temp of natural gas, use propane instead. That will liquefy by pressure alone at room temp.

http://www.energy.ca.gov/lng/faq.html

this might be helpful