2 replies to this topic

[deltaChe]

I have a problem how to define a LPG.

Take for example, propane is LPG, but
it seems contradict with the defination that
any liquid at 1 atm with the normal boiling point is less than
40 degree C is not LPG.

And the other question is how to define that gas
is high pressure gas or not. Take for example,
liqufied ammonia storage tank 's nomral operating temperature -10 degree C and
its saturation vapor pressure is 1.93 kg/cm2 G. Is it belong the high pressure gas?

Thank you very much.

[luuquocdai]

I don't agree with you.
Propane is not LPG. It's a component of LPG. Anyway, LPG is a mixture of gas (Propane + Butane and very little is Mercaptane)

[Propacket]

I have a problem how to define a LPG.

Take for example, propane is LPG, but
it seems contradict with the defination that
any liquid at 1 atm with the normal boiling point is less than
40 degree C is not LPG.

And the other question is how to define that gas
is high pressure gas or not. Take for example,
liqufied ammonia storage tank 's nomral operating temperature -10 degree C and
its saturation vapor pressure is 1.93 kg/cm2 G. Is it belong the high pressure gas?

Thank you very much.

hswang2,

Perhaps you are trying to define LPG in terms of overhead temperature of distillation column. Fractions obtained from distillation column are usually characterized by their boiling points. C3 & C4 fractions have very low boiling point (even less than that you defined) and they are carried as overhead vapors. Instead they are carried to condenser as vapors and then condensed by removing energy. LPG obtained from the condenser is at its boiling point at the applied pressure. Therefore, boiling point of LPG is governed by the temperature of condenser not overhead temperature of column. Also, it is not customary to define LPG in terms of boiling point. Rather, LPG is defined in terms of C3 and C4 content and RVP. Depending upon the composition, LPG has RVP 100-150 psia. However this is a very rough figure and correct RVP will be governed by the composition of LPG. Whatever the composition of LPG is, it is a mixture of C3 and C4. I agree with luuquocdai that pure propane is not LPG but a component of LPG. Presence of C4 is necessary.

Whether Ammonia is HP gas or not will be governed by the phase diagram of Ammonia. I am not familiar with the phase diagram of Ammonia. But if ammonia it is outside the dew point curve then it will be a single phase gas. And you can call it as a HP gas otherwise if it is on the dew point curve,it will be vapour not gas.

Edited by P.Engr, 08 June 2010 - 02:55 AM.