From: ahk@chinet.com
dpeltier@my-deja.com wrote:
>"Adam H. Kerman" wrote:
>>dpeltier@my-deja.com wrote:
>>>"Adam H. Kerman" wrote:
>>>>dpeltier@my-deja.com wrote:
>>>>>"Adam H. Kerman" wrote:
>>>>>>dpeltier@my-deja.com wrote:
>>>>And how do we not assume that the more volatile fractions had simply
>>>>evaporated at that point?
>>>Because they were still there when they tested it. They showed up (in
>>>larger-than-expected quantities) in the chemical analysis, and their
>>>presence explains the low flash point found in their testing. That's why
>>>the TSB determined that the material had been classified into the wrong
>>>packing group, which might have affected the railroad's handling of the
>>>material but would not have had any effect on which tank car was allowed by
>>>federal regulation.
>>Aargh. The cars aren't pressurized. The gases don't remain dissolved.
>>They DON'T know how high the flash point was at ignition.
>The cars are not pressurized, but they are sealed. So yes, you quickly
>reach a point where the number of high-energy liquid molecules that escape
>the surface tension of the liquid (i.e. evaporate) is equal to the number
>of low-energy gas molecules get captured by the surface tension of the
>liquid (i.e. condense). Then you reach an equilibrium where some of the
>material is in gas form and some in liquid. And if the cars are loaded to
>near their volume capacity, it will mostly still be liquid.
They're not sealed against the evaporation of gases, nor from the atmosphere.
Rocking and rolling in transportation will keep dissolved gases from
evaportating.
>I think maybe you're missing the bigger point here. Liquids don't actually
>burn. So-called flammable liquids are by definition liquids that, at
>"normal" temperatures, give off enough gases to keep a fire going.
Ok. I think I remember enough chemistry to know that combustion takes place
at the surface of the pool of liquid, not in the center of the liquid
in the tank.
>The behavior of Bakken crude is not at all outside of the usual spectrum
>of behaviors one sees with flammable liquids. Until Lac Megantic people
>lots of people had assumed (either by failing to do the proper tests,
>or by ignoring the results) that it would behave more like the other
>kinds of crude commonly transported log distances. Turns out, it actually
>behaves more like ethanol.
. . . because of the dissolved propane, right?
>>>>That does NOT tell us what the characterists were when those cars were
>>>>loaded and whether the wellhead had deliberately adjusted pressure
>>>>settings so the separators weren't stripping out sufficient volatiles,
>>>>more quickly filling the tank cars.
>>>What do you mean "stripping out sufficient volatiles"? What would define
>>>"sufficient"?
>>The various newspaper articles have said there's cheating at the wellhead,
>>that they're trying to both fill the tank cars quicker and lower the
>>quality of the crude (while selling it at a price of higher quality crude),
>I'd be interested to see a cite from a reliable source to that effect, and
>I'm just about certain that the refineries will test the chemical
>composition of what they're receiving and reject anything that doesn't fall
>within their specs.
>Does having more dissolved light hydrocarbons really lower the value? I
>would think refineries can probably turn those into marketable products
>too.
Cheating by the producers means that they've sold more crude than has
actually been delivered. They've actually got a negative incentive to
correctly pressurize the separator to bleed off more dissolved gas.
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