RE: Liquid Natural Flatulence
R. A. Hettinga wrote:
A *cryogenic* liquid, mind you, meaning that you'd have to heat the stuff up a lot, and very quickly, in order to set it ablaze, much less blow it up. A liquid which is busily sublimating directly into the gas that it is at room temperature, and diluting, accordingly, with the vast amount of normal air around it in the process. More to the point, as a gas, it's about half the weight of air itself, so it *rises*, as it dissipates, straight up, again, very quickly. It doesn't hang around, flowing down hill, and pooling like, say, C02 might, with the potential to asphyxiate people in the process.
Bob: Get your facts straight: * Evaporating LPG (liquids do not 'sublimate') will burn at the interface where the proper mixture is obtains - and the heat from that will speed the evaporization of the rest. * LPGs (both butane and propane) are denser than air. Propane has about the same density as CO2. Butane is even denser. They will both travel downhill and pool in low spots. * LPGs can most definitely asphyxiate you. Check: http://www.lpga.co.uk/safe_handling.htm "LPG can form a flammable mixture when mixed with air. The flammable range at ambient temperature and pressure extends between approximately 2 % of the vapour in air at its lower limit and approximately 10 % of the vapour in air at its upper limit. Within this range there is a risk of ignition. Outside this range any mixture is either too weak or too rich to propagate flame. However, over-rich mixtures can become hazardous when diluted with air and will also burn at the interface with air." "LPG vapour is denser than air: butane is about twice as heavy as air and propane about one and a half times as heavy as air. Consequently, the vapour may flow along the ground and into drains, sinking to the lowest level of the surroundings and be ignited at a considerable distance from the source of leakage. In still air vapour will disperse slowly." "At very high concentrations in air, LPG vapour is anaesthetic and subsequently an asphyxiant by diluting or decreasing the available oxygen.." The 'rise to the sky and disperse' stuff you're talking about applies to hydrogen, not LPG. A massive LPG spill will spread out over the surface of the ground and water, and when a source of ignition is found, the whole mass will burn at the interface where it mixes with air. You might also want to take a look at www.respondersafety.com/downloads/standoff.doc "Improvised Explosive Device (IED) Safe Standoff Distance Cheat Sheet" which reccomends in the case of an 18 wheeler LPG truck to keep people at least 1996 feet away. I would not want to be nearby when a tanker - or a massive storage tank - gets hit. Peter Trei
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Peter, I'm not going to get into a fisking match with you, but I didn't just make this stuff up, and I resent you saying I did. At 10:26 AM -0500 3/31/04, Trei, Peter wrote:
* Evaporating LPG (liquids do not 'sublimate') will burn at the interface where the proper mixture is obtains - and the heat from that will speed the evaporization of the rest.
Right. And, uncontained, it doesn't explode, either, which was my main point. It'll burn like hell, but that wasn't what the sanctified idiots at the Bulletin of the Atomic "Scientists" were FUDding on about. As for "sublimate", when you toss a cup of boiling water into the air at extremely cold temperatures it converts straight into a gas, all at once. That's what I was talking about. A chemist I bumped into with that story called it sublimation, and when I said I thought "sublimate" was meant for solids only, he said no, that instantaneous conversion to a gas is sublimation whether origin state is a solid or liquid. Go figure. As for
* LPGs (both butane and propane) are denser than air. Propane has about the same density as CO2. Butane is even denser. They will both travel downhill and pool in low spots.
I did actually look this up when I wrote my rant. LNG floats on water, and, as a gas, it's lighter than air by about half the weight of same. Here's my source, from the US Department of Energy: <http://216.239.41.104/search?q=cache:iM5Hh-010ksJ:www.borderpowerplan ts.org/pdf_docs/DOE_LNG_accident_impact_2002.pdf+distrigas+lng+tank+ev erett+ma+size&hl=en&lr=lang_en&ie=UTF-8> See pages 12 and 13: LNG's density is 26.5 Lb/Cu.Ft. It's lighter than water, which is 65/lb/cuft The density of Natural gas is lighter than air, at .47, with air being 1. "Natural gas rises under normal atmospheric conditions"
* LPGs can most definitely asphyxiate you.
Duh? Did I say something about breathing the stuff? No. I said something about it pooling and causing asphyxiation that way. I got a better idea, Peter, read my source and tell me what you think. Maybe we can have an intelligent discussion without you pissing on my shoes about it.
"Improvised Explosive Device (IED) Safe Standoff Distance Cheat Sheet" which reccomends in the case of an 18 wheeler LPG truck to keep people at least 1996 feet away.
I would not want to be nearby when a tanker - or a massive storage tank - gets hit.
Right, and this is exactly the kind of thing I was talking about. In
order to lay in enough explosive make *all* of a multi-million-gallon
LNG tanker/storage-tank go up the same way you might be able to do
with C4 to an LNG truck, you would need either air superiority and a
bunker-buster nuke, or you would need a battalion of ground forces to
defend the demolition operation.
If you can't control your airspace or defend your turf against either
one of those, you have bigger problems than The End Of Boston As We
Know It, the apocryphal "blast radius from Boston to Billerica", or
whatever, as Mr. Clarke, The Boston Globe, and the Bulletin of the
Atomic "Scientists" would have us believe.
So, yes, if you could instantaneously convert *all* the LNG at the
Everett Distrigas terminal into an explosion, you'd get a big one.
And if every chinaman gave me a dollar, I'd be a billionaire, too.
Cheers,
RAH
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R. A. Hettinga
R. A. Hettinga (2004-03-31 16:41Z) wrote:
At 10:26 AM -0500 3/31/04, Trei, Peter wrote:
* Evaporating LPG (liquids do not 'sublimate')...
As for "sublimate", when you toss a cup of boiling water into the air at extremely cold temperatures it converts straight into a gas, all at once. That's what I was talking about. A chemist I bumped into with that story called it sublimation, and when I said I thought "sublimate" was meant for solids only, he said no, that instantaneous conversion to a gas is sublimation whether origin state is a solid or liquid.
I very seriously doubt that. That "chemist" sounds full of shit. Boiling, evaporation, condensation, sublimation, melting, and freezing have nothing to do with the speed at which the phase change occurs. They refer to the qualitative aspect of state changes, notably the beginning, (transition,) and ending states. Sublimation is solid->gas with no intervening liquid state, that state being impossible due to prevailing pressure/temperature conditions. Haven't you ever seen a phase diagram? Furthermore, can you please explain how boiling water could change phase into a gas "all at once"? It takes energy for a compound to change to gas state, genius. Where's it going to get that energy, particularly when the surrounding air is at "extremely cold temperatures"? No macro-level events happen "instantaneously" in any reasonable sense of the word. Increase in atomic motion can only happen due to applied forces, and acceleration takes time. Even if one of those damned 50MT Russian thermonuclear bombs went off 100m away, a glass of water wouldn't vaporize instantaneously. -- "If you don't do this thing, you won't be in any shape to walk out of here." "Would that be physically, or just a mental state?" -Caspar vs Tom, Miller's Crossing
On Wed, 31 Mar 2004, Justin wrote:
As for "sublimate", when you toss a cup of boiling water into the air at extremely cold temperatures it converts straight into a gas, all at once. That's what I was talking about. A chemist I bumped into with that story called it sublimation, and when I said I thought "sublimate" was meant for solids only, he said no, that instantaneous conversion to a gas is sublimation whether origin state is a solid or liquid.
-------------------------------------------------------------------------- http://en.wikipedia.org/wiki/Sublimation_(chemistry) "Sublimation of an element or substance is a conversion between the solid and the gaseous states with no liquid intermediate stage." -------------------------------------------------------------------------- http://www.britannica.com/search?query=sublimation&ct=&fuzzy=N "sublimation: "in physics, conversion of a substance from the solid to the vapour state without its becoming liquid. An example is the vaporization of frozen carbon dioxide (dry ice) at ordinary atmospheric ..." --------------------------------------------------------------------------
I very seriously doubt that.
That "chemist" sounds full of shit. Boiling, evaporation, condensation, sublimation, melting, and freezing have nothing to do with the speed at which the phase change occurs. They refer to the qualitative aspect of state changes, notably the beginning, (transition,) and ending states. Sublimation is solid->gas with no intervening liquid state, that state being impossible due to prevailing pressure/temperature conditions.
Yep. -- Jim Dixon jdd@dixons.org tel +44 117 982 0786 mobile +44 797 373 7881 http://jxcl.sourceforge.net Java unit test coverage http://xlattice.sourceforge.net p2p communications infrastructure
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 At 7:56 PM +0100 3/31/04, Jim Dixon wrote:
"Sublimation of an element or substance is a conversion between the solid and the gaseous states with no liquid intermediate stage."
Yes, I know the common definition.
But, like I said, I was told by someone who claimed to know better,
and, thinking about it, I think he's right.
Since some people, like Peter, hypothesize that it's an extreme
example of evaporation and not sublimation, :-), I'm going to go poke
my nephew the chemistry student and see if I can get a pointer to an
authoritative explanation.
How's that?
Cheers,
RAH
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R. A. Hettinga
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 At 6:16 PM +0000 3/31/04, Justin wrote:
Haven't you ever seen a phase diagram?
Sigh. Yes. Here's one, for water: http://wine1.sb.fsu.edu/chm1045/notes/Forces/Phase/Forces06.htm And your point is? Let's see, if we rapidly cool boiling water by dispersing it in supercold air... somewhere past the triple-point, it goes straight through the solid state, do not pass go, and *sublimates* directly into the air. Now, maybe, it freezes at the molecular level, or something, first. But to the observer, it never reaches a solid state, and it turns directly into a gas. It sublimates. My understanding is that it has something to do with the extreme temperature differential. Like you get with a bunch of boiling LNG floating on the Mystic River under the Tobin Bridge. Which is what that guy from the USDOE said.
Furthermore, can you please explain how boiling water could change phase into a gas "all at once"?
I don't have to "explain how". It, in fact, *happens*. This is a common school-science trick in Alaska when it's cold enough: <http://www.efieldtrips.org/Climbing/05d_ate_answer_detail.cfm?recordI D=1219> <http://kinder.cmsd.bc.ca/pipermail/kinder-l/1999-February/020295.html
I went to middle-school in Anchorage, but I didn't know about it
myself until my sister-in-law told me the story, when I'd moved back
to the Lower 48 years later.
She heard about it from an (astronomer?) friend from *Fairbanks* (the
"real" Alaska, you see, they don't call it "Los Anchorage" for
nothing :-)) who used to do it at -60+ below, or something. The first
example, above, is from Mt. McKinley, at 100 below.
Anchorage, being in the "banana-belt" and warmed by the Humbolt
current just like BC, usually only gets down to -40 or so. Hence the
second example, some water, as ice, hits the ground.
So, if you'll stop humping my leg, I'll finish my lunch now...
Cheers,
RAH
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R. A. Hettinga
participants (4)
-
Jim Dixon -
Justin -
R. A. Hettinga -
Trei, Peter