Latent Heat of Vaporization and Molecular Mass of Vapor for Asphalt/Bitumen and Used Motor Oil 1

[jimmyhutmacher]

I'm looking at designing emergency venting for two different tanks, one for asphalt/bitumen storage and one for used motor oil storage. In order to design the venting I need the Latent Heat of Vaporization and Molecular Mass of Vapor for both liquids.

I scoured the internet and haven't come up with anything definitive. I did come across the Vetere Model for the Latent Heat of Vaporization of Pure Hydrocarbons = 4.1868*T *(9.08+4.36*log(T)+0.0068*T/M+(0.0009*T^2)/M) T = Boiling Point in Kelvin M = Molecular Mass of Liquid Not sure if this is accurate since asphalt and used motor oil are composed of innumerous types of hydrocarbons with great variation in boiling points and molecular weights.

I don't need exact numbers, just need to be reasonably accurate and conservative. Is there some kind of database or equation?

P.S., I have no access to any software that would do this analysis.

Any help would be greatly appreciated. thank you

 

[Compositepro]

The data you are searching for seem to be trivial factors compared to others that will affect the vent sizing, such as rain cooling the tanks suddenly.

 

[don1980]

Since you're asking about the Hvap of this material, I assume you're performing calculations for a fire exposure case. Before proceeding with that design, consider the temperature at which this asphalt/bitumen boils and consider the likelihood of the tank will remaining intact, since the wall temperature will be even higher than the boiling T. There's obviously no point in sizing a relief device for a scenario which causes the tank to fail, with or without that relief device.

 

[jimmyhutmacher]

Compositepro,

I'm designing per API 2000 which specifies two types of venting, normal and emergency. Normal venting includes provisions for tank fill/discharge and thermal effects, the latter is what you're referencing with a rain event on a warm/hot tank.

Like don1980 assumed, I need the Latent Heat of Vaporization and Molecular Mass of Vapor for emergency venting due to external fire, which is generally significantly higher in terms of required relieving flow capacity.


don1980,

That's definitely something to consider. I believe the shell/roof above the liquid level would fail first before the shell below, which could be before the contents boil.

 

[don1980]

When exposed to fire, the liquid in the tank doesn't provide any significant cooling protection for the shell unless/until that liquid starts to boil. Once boiling starts (which occurs at the inner wetted surfaces of the shell, the Hvap helps limit the temperature of the shell metal (Hvap removes heat which is then expelled from the tank through the relief device).

In the case we're discussing, the shell below the liquid level isn't significantly protected because of the low rate of heat transfer between the shell and the liquid. The shell temperature (even in the wetted section) continues to rise unabated, because there's no boiling. And, because of the extremely high BP of this liquid, the tank is going to fail before boiling can start to occur.

Yes, the shell above the liquid level will be at a higher T, but the lack of boiling in the lower shell renders this difference insignificant.

Focus your attention on other layers of protection, those that can effectively provide some degree of protection (e.g. water spray, fire resistant insulation), rather than wasting time trying to size an emergency vent which doesn't provide any meaningful protection regardless of its size.

 

[pierreick]

Hi ,
You may find pointer in the excel sheet attached .
Pierre