It's not enough to just aerosolize the LNG, it needs to mix with air in a rather narrow fuel-air ratio of 5-15% to burn. Further the flame front speed of methane in open air is only 4 mph - it won't explode, though as the flame front spreads it might kind of look like an explosion (think about what it looks like when you light a gas stove or grill). Such a fireball can potentially ignite things in close proximity, but there won't be a pressure wave that damages structures, so you can't have a situation where one tank 'exploding' causes other tanks to explode, though in a crash it's easily possible multiple tanks are damaged.

Natural gas is an explosion hazard in enclosed spaces. If you walk into your house and smell gas, that's very dangerous. Note also that even if there is no explosion hazard, fire is still dangerous.

If you are uncomfortable with rail transport of crude, that's a perfectly legitimate stance to take. Honestly, transporting any flammable substance (and many non-flammable ones as well) does pose risks. If you know the risks and benefits and think the former outweigh the latter, let people and especially your representatives in government know. However, society generally seems to accept rail transport of oil and similar chemicals, so outrage over the transport of a less dangerous substance seems like it would be more likely to come from a place of ignorance than rational analysis.

Your statements do not seem to be consistent with those in the article.

> Ray Mentzer, a chemical engineer at Purdue University, spent his career working on LNG projects for Exxon Mobil. He says the specially designed containers that transport hydrocarbons have a good safety record. But he says transporting the gas through densely populated areas increases the risk if there's a leak.

> "It's not flammable until it's vaporized, but it's going to be vaporized pretty darn quickly and then it's going to seek an ignition source," he says. "Believe me, it will find an ignition source pretty darn readily."

I will also note that those train tracks in the town in the photos had a derailment only a few years back. I am familiar with the area and know people who live there.

https://response.restoration.noaa.gov/about/media/train-dera...

There is no inconsistency. Natural gas is most certainly flammable once it's vaporized (it would be a very poor fuel if it wasn't), but there's a big difference between something being flammable and something being explosive. If you have a big leaking tank, it is very likely that it will catch fire, and no one really wants a big raging fire in a residential area, but that fire will only burn at the leak where fuel and air are mixing. It's very difficult out in the open to form cloud of natural gas and air with a uniform mixture such that it can all burn at the same time, and even then the flame front is too slow to cause a damaging explosion.

I would also note that the engineer's use of informal language here is clearly alarmist.

>Would a crash be sufficient to cause a sudden aerosolization of the lng?

Well yes, but actually no.

You can't get a freight train up to the kind of speed you need to create an "instantly dump the contents of the pressure vessel" type crash without creating a "slowly vent the contents out" type crash first.

You would need to use a bomb to rupture a pressure vessel to get the kind of fuel/air mix you need for an explosion or fireball. Fuel-air explosives operate in this manner. But they are devices with countless engineering man-hours spent making them actually work and fairly precise manufacturing. Parking ye ol' Winnebago (or Penske, if you're a history buff) beside the tracks and waiting for the train to go by is not going to be a very productive approach. Look at people blowing up propane tanks on YouTube. At best they get a fireball.

I'd much rather have nat-gas wafting up and away rather than crude oil, propane, or some other volatile that sits at ground level.

You get real differences of scale which makes smaller models inconsistent with what happens in a train derailment. Lac-Mégantic rail disaster for example had some serious explosions from oil.

According to the Wikipedia article there was much destruction, but... that happened when the oil flowed where it shouldn't and then burned in places where one really doesn't want it to burn.

Lighter-than-air gas is crucially different. If you let that leak out it won't flow downhill through the city, it'll go straight up. Of course you can argue that gas is dangerous, but not by example of an accident where most of the flammable material flowed away (and caused harm elsewhere) instead of either burning or exploding at the site.

LNG isn’t a gas, it’s a cryogenic liquid like liquid nitrogen except flammable. If we are talking say 100+ DOT-111 tank car‘s that’s 3,450,000+ gallons which isn’t going to simply fly into the air instantly. The phase change from liquid to has takes significant energy at the scale which takes time.

Again it’s a question of scale, you don’t think of say molasses as fast moving liquid but increase the scale to 2.3 million gallons and you can be talking about a 25 foot tall 35 mph wave. https://en.wikipedia.org/wiki/Great_Molasses_Flood

AIUI it's not flammable. It is flammable when mixed with air in the right proportion, but if it's mixed with air it is a gas and rises straight up, rather than flow as a wave across the landscape.

You can't have your cake and eat it.

Again small scale vs large scale. If your talking a square foot of the stuff then it’s going to rise like your suggesting. Cover a few acres in LNG you get complex boundary layer interactions and giant swirls of natural gas mixed with air.

Read up on how you can get temperature inversion layers in the atmosphere. In your model that kind of effect shouldn’t happen, but actual fluid dynamics gets complicated.

Explain how you get spontaneous combustion in the spots where the mixture is right.

Or were you thinking about transporting LNG together with something that that would help start a fire?

Train crashes have plentiful ignition sources as metal scrapes across metal. Oddly enough it’s surprisingly common for train crashes to result in fires ex: https://youtu.be/vww5V-xmtzs or https://baltimore.cbslocal.com/2016/07/06/recent-derailments... or the original disaster I mentioned.

At which point those secondary fires can easily ignite the literal pools on LNG being described.

I've thought about this a few times now.

Would you describe this as a noticeable risk compared to driving around in a car, in urban traffic, with gasoline? Or are you comparing it rather to an alternative that more or less avoids transport of LNG?

It could. But so could a crash of a truck or a train carrying any type of liquid/gaseous fuel (e.g. truck carrying the gas to your local gas station). The article talk about LNG requiring thicker tanks than ethylene and ethane, both of which could also 100% explode if in a wreck.

I think the worry is that the volume of shipments for LNG would be much higher, and hence the probability of something happening is higher. A singular shipment of LNG would be no worse than a single shipment of car gas.

Natural gas is lighter than air.

Any such aerosolization would rapidly go up into the sky.

It would make a fire, but not a disaster.