March 28, 2024, 07:14:22 AM
Forum Rules: Read This Before Posting


Topic: Trying to understand Liquefied Gas at high pressure and properties  (Read 2631 times)

0 Members and 1 Guest are viewing this topic.

Offline pewpewlaser

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Hi,

I’m not sure if this is the right spot, please move if it isn’t.

I trying to determine how much molecules by weight will fit in a cylinder at a certain pressure.   My background is Mechanical Engineering with only chem 1 and 2. (10 years ago).

For instance, SF6.  I have a cylinder with a water volume of 16,786in^3 (275L ) and working pressure of 207bar (3000psi).  I want to determine how much SF6 (by weight) I can put into this cylinder at 2400psi.  I assume you can use liquid density*vol of liquefied SF6 and same with the gas?  Or would I use PV=nRT (but I assumed that was for gas only).  How would I determine how much has been liquefied @ certain pressure/temperature?

Looking to improve my knowledge on this, so please recommend a textbook or some resources too. Thanks!

SF6
Molecular mass 146g/mol
Boiling point -63.9C
Vapor pressure: 2100 kpa (304psi)

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2049
  • Mole Snacks: +296/-12
Re: Trying to understand Liquefied Gas at high pressure and properties
« Reply #1 on: March 27, 2015, 12:34:24 PM »
http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=34#VaporPressureGraph
This gives vp as a function of temperature. Critical temp is about 320K, so it won't liquefy above that.

Offline pewpewlaser

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Re: Trying to understand Liquefied Gas at high pressure and properties
« Reply #2 on: March 30, 2015, 10:34:23 AM »
http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=34#VaporPressureGraph
This gives vp as a function of temperature. Critical temp is about 320K, so it won't liquefy above that.

Ok, So lets say its @ 80F (~300K), vp = 25bar (~363 psi). I fill the tank up 2400psi, how wouldi determine how much (by wt) would be liquid and how much would be gas?

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2049
  • Mole Snacks: +296/-12
Re: Trying to understand Liquefied Gas at high pressure and properties
« Reply #3 on: March 30, 2015, 12:38:13 PM »
You can't fill it up to 2400 psi; it will condense at 363 psi. Then you will just be filling the cylinder with liquid.

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2049
  • Mole Snacks: +296/-12
Re: Trying to understand Liquefied Gas at high pressure and properties
« Reply #4 on: March 31, 2015, 09:56:58 AM »
I found this:
http://www.solvaychemicals.com/Chemicals%20Literature%20Documents/Fluor/F-Specs/SF6_Sulphur_Hexafluoride.pdf
See particularly the Internal Pressure table on p 26, also p38. I assume that this refers to a cylinder completely full of liquid, as these pressures are higher than the vp at the relevant temperature, and the blank area at top left is where there would be liquid and gas in equilibrium at the vp, in variable proportions, so a density (average) can't be defined.

Sponsored Links