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Cooling A Liquid-Filled Lpg Vessel

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#1 Butterfly


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Posted 16 November 2017 - 02:36 PM



Let's say I have a vessel full of propylene (70% propylene/30% propane) at 25 kg/cm2g and ambient temperature, so that it is in liquid phase. If temperature drops, liquid density will go down. So, will we have a vacuum condition at the vessel? What I think is that, if the vessel cools down to, let's say to 0ºC, liquid propylene will vaporize to some extent and the pressure of the vapor phase will be propylene vapor pressure at 0ºC. Is this correct? Or will the vessel collapse?


Thanks for your help

#2 Bobby Strain

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Posted 16 November 2017 - 04:08 PM

You should read your query carefully. Your statement as fact in the second sentence needs attention. The correct answer is no to one question, yes to another. And the remaining question has no answer, necessarily. Of course, one should never fill a container completely with liquid. Unless it is properly protected.



Edited by Bobby Strain, 16 November 2017 - 04:18 PM.

#3 Butterfly


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Posted 17 November 2017 - 09:37 AM

Thanks. I have a propylene purification system where a liquid stream flows through a vessel which has with an adsorption bed. This is why my system is filled with liquid. And when I have to change the adsorption bed, because it is saturated with contaminants, I will block the vessel and flow my stream through another adsorber. If the operator let's the system with an adsorption vessel blocked, and temperature drops, I was afraid of having the vacuum condition I mentioned

#4 MrShorty


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Posted 17 November 2017 - 10:52 AM

Considering that both propylene and propane are above their normal boiling points at 0 C, I doubt you would get a vacuum at that temperature. I would not expect to be able to get a vacuum until you get below the boiling point of one of the compounds.


It should be fairly easy to quantify the pressure for a system like this. Even if you assume Raoult's law (https://en.wikipedia...ki/Raoult's_law ), you should be able to calculate the bubble point pressure of any propane/propylene mix and determine whether it is reasonable to expect a vacuum or not.

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