Compressed natural gas (methane) tanks require pressures of more than 200 atmospheres. The energy stored in the compressed gas is in itself a bomb, but when a tank ruptures and the methane very quickly expands and mixes with oxygen in the air- the potential is created for a massive fiery inferno.
Gasoline is also very flammable, but has a vapour pressure much less than one atmosphere. A ruptured gasoline tank can make a substantial fire, but actual gasoline explosions require extraordinary circumstances.
And spilling a bag of coal out of your pickup truck onto the highway will only briefly make a bumpy ride for the cars behind you. That would be a very safe fuel to power transportation, if someone could figure that one out.
Buy a Stanley Steamer, Jay Leno has two of them.
All taxi cabs in Oz run on LPG and they don’t blow up routinely. Let the free merit decide if they want to use LPG. The government forcing it down people’s throat is almost always a bad idea.
LPG is not CNG, and your remark is idiotic,
Not entirely idiotic. Just use similar system as for acetylene, which uses some acetone in each cylinder. For example this one. Achieves same energy density (of CH4) at 50 atm for solvent system as CNG at 200 atm.
Probably the most interesting option is to use LNG, ie propane/butane as a self liquifying solvent for the methane, and supply a set CH4:C3H8 mix.
Sorry meant to write ‘LPG’ as the methane solvent, not LNG.
The pressure of LPG is 2 atmospheres, compared to 200 atmospheres for CNG.
CNG is much more dangerous.
CNG tanks are built stronger so that is supposed to compensate for the increased pressure. It only ignites at a limited range of temperatures, plus it is lighter than air so doesn’t pool. LPG and CNG vehicles are extensively deployed around the world and I have not noted any on going safety concerns about these vehicles, excluding Steve’s paranoia of course.
The danger of a gas explosion only exists when the volatile gas has time to mix with oxygen before igniting. Otherwise it will just burn off through the ruptured part of the tank. The high pressure actually aids in preventing explosions by carrying away the fuel from the vehicle. Until 2007 it was not allowed to park a cng powered vehicle in underground parking spaces in Europe, that rule has actually been revoked since due to improved safety.
I’ll have to chide you on the use of the Hindenburg picture though, that’s about as misleading as showing water vapor over a power plant to cry about CO2 emissions. The Hindenburg was filled with hydrogen, not methane.
And it was the Diesel fuel that killed the passengers.
The principle for hydrogen and methane is identical. They are both lighter than air combustive gases with a low boiling point.
I think Al Qaeda would really like a hydrogen economy. A free car bomb with every car on the road. H2 has a wide explosion/ignition range with air.
No need for hydrogen – we have methane.
http://www.youtube.com/watch?feature=player_embedded&v=IpYIvyCXv9w
Stevem your whole argument was that it’s the high pressure containment of natural gas that is dangerous. Then you try to justify your Hindenburg example. Piss poor weak, as far as logic goes.
Nonsense Will. High pressure methane mixes with oxygen rapidly upon rupture, and creates a massive fireball like the Hindenburg. I’m sorry that you can’t follow the logic, but don’t blame it on me.
Wow. Fossil fuels can ignite under the right circumstances. You might even get a “fire ball” if the circumstances are just right. Any actual evidence that CNG’s is more dangerous than LPG or propane? (Other than some hand waving about “pressure”.) Or is this just one of your brain bubbles? 😉
CNG is a bad idea.
LPG is much safer as Steve says due to lower pressure.
The Hindenberg fire deaths were predominantly due to diesel. The hydrogen fire explosion burnt upward.
Of course the diesel would never have ignited without the temendous heat from the massive compressed hydrogen explosion – diesel is very difficult to combust without significant pressure.
And of course gasoline or diesel do not explode in the absence of significant pressure – its why engines have carburettors or injectors.
Again, there is a big difference between LPG and CNG.
The risk of rupturing a highly compressed gas tank is extremely high in vehicles – there is no part of a vehicle safe from serious impact except in your garage.
Highly compressed gas by itself won’t explode or even ignite. It would have to, for example, feed an existing fire.
RE: Will Nitschke – “Highly compressed gas by itself won’t explode or even ignite. It would have to, for example, feed an existing fire.”
Will, There are many exceptions. There are tens of thousands of substances that have sufficient propensity to propagate a deflagration. You are stepping into my area of expertise.
1. Any compressed gas with a negative Joule-Thomson coefficient can ignite just by leaking. No fire required (hydrogen)
2. Any compressed gas with a low ignition energy can explode outside the presence of a fire. The energy in a static spark, or even the energy from a two way radio in close proximity is enough. Many gases have ignition coefficients much less than gasoline
In case you can’t join the dots here… CNG is heavily compressed in the first place because it is not as powerful as LPG, propane, etc. And LPG and CNG are both capable of feeding a fire anyway, given the right circumstances. So I think the argument as presented is bullshit.
Nonsense. CNG is at high pressure because its boiling point is very low. In order to liquefy it you have to put it under 200 atmospheres. The boiling point of propane is much higher and does not require near as much pressure to liquefy.
So what? How does that disagree with anything I just wrote?
What part of rapidly expanding fireball being forced outward at 200 atmospheres pressure isn’t clear? Have you ever worked with very high pressure gasses?
There is no comparison between an LPG rupture and a CNG rupture, and the very high pressure inside the CNG tank makes it much more likely to rupture.
Steve you have the annoying habit of attacking some straw man claim I didn’t make when you can’t back-up your own assertions. Wow, pressurised natural gas could potentially cause a bigger fireball than unpressurised gas. Who would have thought?
Do CNG vehicles blow up more than other types of vehicles? Have you got data? If you don’t, you’re just speculating and making shit up aren’t you? Hey, maybe you’re right, but you need to show me evidence. That’s why I’m a sceptic. A personal theory that sounds good to you, doesn’t cut it for me.
http://www.youtube.com/watch?feature=player_embedded&v=IpYIvyCXv9w
“Highly compressed gas by itself won’t explode or even ignite.”
I think this is another example of people making foolish statements without really examining what they are claiming.
Diesel engines run without any spark at all. The “glow plug” merely gets the engine to working temperature – after that compression of the diesel injected into the cylinder )which evaporates to gaseous form) causes ignition and keeps the engine running.
And remember that diesel is quite difficult to burn as a liquid – the flash point of gasoline is much lower than diesel.
I do not know of any CNG vehicles in Australia nor any filling stations – I personally do not think there are any at all.
I have, however, inspected the installation of numerous gasoline and LPG service stations during my work time for compliance with Australian Standards and Government Regulation.