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Boiling liquid, expanding vapor explosions.

You might want to bone up on these things before assuming LNG ships are safe because you need some energy to vaporize the liquid.

Try Flixborough as a Google search if you want some idea of how bad one of these unconfined vapor cloud explosions can be.  I worked around refineries some.  People were very aware of how careful you had to be around propane/butane facilities.

If you had a shipping accident that split open an LNG ship you could put a lot of explosive material out pretty quickly.    Plenty of heat in the ocean to vaporize it too.

LNG is heavier than air and will form a low lying cloud near the surface.  Find an ignition source and away you go.

Do I think LNG terminals are too risky?  No.  But this assesment plays down the risks too much IMHO.

by HiD on Sat Jun 25th, 2005 at 07:43:45 PM EST
[ Parent ]
I didn't say I thought it was 100% safe - nothing is. But the hype you read is that LNG are the equivalent to 'floating nuclear bombs'... ready to take out a city like Long Beach or LA. Reality is they are probably safer than tankers full of gasoline - something we will need to think about should we start importing a lot more 'finished distillates' and less crude.

And I worked in the chem business too... ran distillation columns in alcohol processing plants 'splitting the azeotrope'... we had alcohol, benzene, gasoline and natural gas (boilers)... all of them like potential bombs about to go off all the time. LNG is a risk but not worse than others - probably less so due to the nature of the liquid gas and the way they transport it.

As long as the LNG is liquid - it is fairly safe. Once it goes gaseous then it isn't... and it needs a lot of heat to do that. But 'ya' if a whole tanker split open in a harbor and the liquid boiled out over the rapidly freezing ocean ... ya that would be bad. Eventually it would evaporate and disperse & dilute to a concentration able to support an explosion...  somewhere if not immediately at the accident site. On the other hand it is possible it might disperse too quickly to explode. The concentrations need to be right... enough gas, enough air... and of course the ignition source... It is far more likely to happen in a confined space like a building or city block then out on the ocean, in the open, wind rain and all.

But it would be just as bad if a tanker of distillate spilled open in the same heavily populated harbor... and spread out over the surface of the water, evaporating then if conditions get right BOOM...

The whole point is it isn't easy to make these things happen... make all the factors work in concert. Nd these LNG tankers aren't one big open cargo ship... they are a little more complex then the Exxon Valdez. They have many smaller high pressure tanks hooked up together but isolated from each other. They all aren't going to just 'split open'...  

I think there is plenty to worry about - but this isn't even close to the top of my list.

"On the Internet, nobody knows you're a dog." - Peter Steiner

by dryfly (jjwhodat at hotmail dot com) on Sat Jun 25th, 2005 at 09:05:12 PM EST
[ Parent ]
nuclear bomb, no.  Seriously worse than gasoline, yes.  Mogas just isn't as volatile as LNG.  You don't get the big vapor cloud forming.  Typically mogas has a boiling range of 100F to 430 F.  You can get it to boil off, but over time rather than a rapid, BLEVEE situation. Otherwise we'd have pressurized mogas tanks in our cars.    Mogas tends to burn, LNG to go BANG.

Distillate -- no worries at all.  It vaporizes, but slowly.  Great for avoiding killing aquatic life, but little risk of an explosion.

I agree with you.  It's pretty hard to actually fuck up enough to cause the worst case scenario.  Unfortunatly, we humans seem to always find a way to do just that.  I wouldn't want to live 1000 yards from an LNG facility and wouldn't want to ask anyone else to do so either.  Whereever we put them, and we do need them, we need to maximize the distance to people.  Fear no, caution yes.

The Exxon Valdez also had many compartments.  All oil tankers do.  But like the Titanic, when a tanker hits a rock or another ship rams you at an angle, you tend to slide along it rupturing a number of tanks.  The product tankers I used to charter would hold 250 MB of liquid in usually 15-25 individual tanks.  Crude tankers not all that different in design.  You need a bunch of tanks for stability and to prevent the liquid from sloshing around in heavy seas.

by HiD on Sun Jun 26th, 2005 at 01:28:34 AM EST
[ Parent ]
The 1000 yds idea is a good one... but I wouldn't want to be 1000 yds from any facility including the plant I used to run... we had to 'evacuate' a couple thousand residents at least twice while I worked there... people in a large mobile home park down the street and a neighborhood just north. No incident but hairy.

Irony is many of the workers lived in those communities because of the convenience & low cost... saved money than bought nicer homes in a better part of the city much farther away.

And you remind me of another point - I do not believe the 'big release' will be the problem though that is what everyone is hyping ... my guess is it is going to be the same as it is with all natural gas processing - the maintenance of seals & valves. It will be the little leaks that will kill. And it will probably happen long after the product has been unloaded & revaporized.

And while maybe I underestimated the risk of LNG... I think maybe you underestimate the risk of the lighter distillates & gasoline... again depending on where it happens and how much. Out in open water - not a big deal... disperse & not explode even if lit up.

But in a harbor or river with dockage and confined pockets & jetties - very big deal. I've read of accidents on the Illinois River where relatively small amounts of gasoline spilled (1000s of gallons not whole tankers) and that still had the response teams paranoid as hell and evacuating as the spill worked down stream until it dispersed...

Even though the cloud isn't as large as LNG... the distillate liquid flows out over the surface, evaporating slowly... under bridges & culverts it traps and if the mixture is right... it blows as badly as any combustible gas. The thing that is especially dangerous is the fact the ignition source can be hundreds of yards away and ignite a small quantity of the liquid... run along the surface of the water like a fuse and then only  'blow' the trapped pockets under bridges, docks, etc. like isolated bombs.

When I heard the Saudis were planning on a massive increase in refining capacity and plan to sell us 'finished' product as opposed to crude... my first thought was... I wonder where they plan to unload it.  It better be well offshore.

"On the Internet, nobody knows you're a dog." - Peter Steiner

by dryfly (jjwhodat at hotmail dot com) on Sun Jun 26th, 2005 at 08:51:22 AM EST
[ Parent ]
for the enlightening discussion.

It does seem to make sense to put big plants that manipulate vast volumes of flammable or explosive materials away from inhabited areas...

In the long run, we're all dead. John Maynard Keynes

by Jerome a Paris (etg@eurotrib.com) on Sun Jun 26th, 2005 at 10:10:41 AM EST
[ Parent ]
can we have a quick discussion by Those Who Know, of the relationship between LNG, LPG, propane, and other petro gas nomenclature?  how many gaseous byproducts of petro distillation or extraction are compressed and used in liquid form?  the "flows like a liquid and can go Bang" risks being discussed here sound a lot like propane.

also, has anyone a reading on the amount of energy used to compress these gases into their liquid state for storage and transport?  how many BTU does it take to compress 1000 BTU of any of these liquid gases into their commercially usable form?  just curious about the EROEI as usual...

The difference between theory and practise in practise ...

by DeAnander (de_at_daclarke_dot_org) on Sun Jun 26th, 2005 at 12:59:48 PM EST
[ Parent ]


as to the EROEI, I'd say from rough memory that you get on the other side (i.e. after liquifeaction, transport and regasification) 90%+ of the natural gas you put in, so it's not too bad as a transport chain.

In the long run, we're all dead. John Maynard Keynes

by Jerome a Paris (etg@eurotrib.com) on Sun Jun 26th, 2005 at 03:06:38 PM EST
[ Parent ]
the US East coast already has enormous mogas imports via tanker.  Mogas has been moving into NY on 60-80 KT ships (500K+ bbls) from Mobil Yanbu (red sea side of Saudi) for 10 yrs+.  Not to mention Venz, brazil, Norway, and the rest of Europe.  

You might want to check out how large mogas imports already are.  And I'd guess 90% of it goes to the USAC from Virginia north.  Rest to USWC in summer.

by HiD on Mon Jun 27th, 2005 at 02:26:21 PM EST
[ Parent ]


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