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Pentane Storage Peculiarities


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#1 Rajesh India

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Posted 21 April 2009 - 06:07 AM

Hi, I need to define pentane storage requirements. Pentane boiling point is about 37 degC, which is very close to ambient temperatures in India. While searching on internet, I came across some references of pressure relief valves on pentane storage. Wonder why relief valves would be required, when a vent condenser with chilled water can be provided. Or these could be coming out of nitrogen pressurized tank to minimize losses to atmosphere? The tank itself could be buried or one with solar insulation. Please throw some light in terms of normal provisions of pentane storage about 20 m3.

Moreover, for a buried pressurized vessel, how is heat gain estimated, say from external fire? API mentions of a very low environment factor for earth covered tanks, should entire tank area be considered for relief rate estimation along with environment factor?

#2 Qalander (Chem)

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Posted 21 April 2009 - 12:13 PM


Dear
Kindly further elaborate on your storage purpose and usage issues.

Also the extent of Covering Earth Pad;since this is instrumetal in deciding the solar or soil heat impact level therby determining the effect on the storage.

As regards pressure safety(relief) valve;since it is usually liquid under its own vapour pressure(As e.g. LPG) There are possibilities of sudden extreme pressure variation with simultaneous phase change that requires this(i.e.PSV) to safeguard storage itself.

Hope this helps in showing way forward!

#3 chemtan

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Posted 21 April 2009 - 10:04 PM

It is a pressure vessel !! As Qalandar pointed that C5 is liquid under its own vap pressure so you need a Pressure Relief Valve to save the vessel from rupture due to over pressure.

As for the Relief quantity, that is a separate discussion in all but would say you will have to consider many scenarios and choose the "worst" one.

Some scenarios worth looking at in your case could be:
External Fire.
Failure of control valve upstream\downstream (if any)



#4 Rajesh India

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Posted 22 April 2009 - 12:33 AM

QUOTE (Qalander (Chem) @ Apr 21 2009, 10:43 PM) <{POST_SNAPBACK}>
Dear
Kindly further elaborate on your storage purpose and usage issues.

Also the extent of Covering Earth Pad;since this is instrumetal in deciding the solar or soil heat impact level therby determining the effect on the storage.

As regards pressure safety(relief) valve;since it is usually liquid under its own vapour pressure(As e.g. LPG) There are possibilities of sudden extreme pressure variation with simultaneous phase change that requires this(i.e.PSV) to safeguard storage itself.

Hope this helps in showing way forward!


Thanks Qalander for your comment.
There are two storages of 20 m3 each. Road tanker is unloaded by its own pump. Pentane transfer takes place by another vertical submersible pump.
As mentioned, pentane boiling point is about 37 degC, so in this sense it is different from LPG which is under its own pressure. So if the tank is pressurized by nitrogen to reduce losses to atmosphere, it anyway needs to be depressured at the time of road tanker unloading, so saves only from normal diffusional losses.
How to account of the extent of earth pad in terms of actual design; i.e. the earth pad thickness should correspond to what environment factor F as in API to estimate heat gain from external fire?




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