BTU Value in Crude Oil Vapors

[sid9999]

Need help in determining the BTU value per cubic foot of crude oil vapors being removed from storage tanks. Any input?

Thanks

 

[Jdin]

There is no simple answer to this question. It's same as asking how much BTU is in VOC? You'll need to know much more about this vapour before we can theoretically estimate the "potential energy content".

 

[Flareman]

It seems to me that vapor over any oil has to be a function of the temperature and pressure just as it would be in any other hydrocarbon calculation. The light stuff comes off first and in the greatest quantites.
If you are controlling and sweeping the tanks with an inert purge then it's anybody's guess but, if it's just hydrocarbon, and you know the temperature and pressure in the vapor space, you can make a good guess by assuming it's a single component and checking which component would have that as a BP condition. Then look it up in tables. Failing that, you already know that it's primarily paraffinic so it will have a CV between 19,000 and 20,000 Btu/lb. (except if it's "live" crude when most of the gas will be Methane 21,000 Btu/lb)
You clearly don't have a lab at your disposal otherwise they could analyse the stuff, but if you are in the field you might be able to do a simple experiment to find the SG. Weigh an empy container with air inside, fill it with gas and weigh it again, (takes a bit of doing but it's possible). Even a 1 cubic foot container will give you a weight difference (maybe 1 or 2 oz / 30 - 50 gm). If you can determine the volume you have the density and Mol wt.


David