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Good Day!
Kindly help me how to get the minimum temperature during depressurization of Propane and Butane service vessel
Calculation results using simulation programs shows, temperature increases as pressure decreases. Would that be correct?.. why is it so?
Im verying the requirement for LTCS materials fo the said vessels thats why I neet to know, the lowest temperature the vessel can attain during depressurization
Thank you very much in advance for the help
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Minimum Depressuring Temperature
Started by millany, Dec 18 2003 04:42 AM
4 replies to this topic
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#2
Diederik Zwart
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Posted 18 December 2003 - 07:55 AM
Millany,
It is possible to get a temperature increase when depressurizing. That depends on where your starting piont and ending point are in the Mollier diagram. If you've got the Mollier diagrams of propane and butane you can check this by determining your starting point (operating conditions) and then graphically going to your ending point (depressurized conditions) following the isenthalpic route. It is possible that along the way you'll see a temperature increase (reversed Joule-Thompson effect).
As for the design temperature of the vessels. Atmospheric boiling point of propane is -42.4°C and that of butane is -0.83°C according to my physical property data source. If you design for that you'll be OK.
Regards,
Diederik Zwart
It is possible to get a temperature increase when depressurizing. That depends on where your starting piont and ending point are in the Mollier diagram. If you've got the Mollier diagrams of propane and butane you can check this by determining your starting point (operating conditions) and then graphically going to your ending point (depressurized conditions) following the isenthalpic route. It is possible that along the way you'll see a temperature increase (reversed Joule-Thompson effect).
As for the design temperature of the vessels. Atmospheric boiling point of propane is -42.4°C and that of butane is -0.83°C according to my physical property data source. If you design for that you'll be OK.
Regards,
Diederik Zwart
#3
gvdlans
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Posted 18 December 2003 - 10:31 AM
For selection of material it is important to know whether simultaneous occurance of low temperature and high pressure is possible or not. For example, for butane, -42.4 °C only occurs at atmospheric pressure, provided the vessel will not be immediately repressurized after a blowdown.
Could you tell us what the initial pressure is of the vessel?
Could you tell us what the initial pressure is of the vessel?
#4
Guest_Ben Thayer_*
Guest_Ben Thayer_*
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Posted 18 December 2003 - 05:53 PM
First of all, you might want to keep it simple and use the Mollier diagrams instead of a modeling program when you can. Or at least refer to the simpler methods to make sure your model is working properly.
Also, Isobutane and N-butane can make a difference.
Can you also relate what you mean by LTCS? A quick google yielded Lower Thermosphere Coupling Study & Landfill tax credit Scheme. Perhaps you are concerned with Low Temperature Carbon Steel? I apologize, but I am unfamiliar with that term.
That being said, if you are concerned with low temperatures as you cool down, review this with a knowledgeable Mechanical engineer. For chemicals like chlorine and ammonia that go below -20°F at atmospheric pressure, there is basically no pressure on the equipment at that point and the code allows for temperatures below -20°F based on several parameters such as pressure/stress/metal thickness, etc. Because of this, you can have piping, etc. constructed of standard grades such as A-106 without going to A333 for -50°F service.
regards, ben
Also, Isobutane and N-butane can make a difference.
Can you also relate what you mean by LTCS? A quick google yielded Lower Thermosphere Coupling Study & Landfill tax credit Scheme. Perhaps you are concerned with Low Temperature Carbon Steel? I apologize, but I am unfamiliar with that term.
That being said, if you are concerned with low temperatures as you cool down, review this with a knowledgeable Mechanical engineer. For chemicals like chlorine and ammonia that go below -20°F at atmospheric pressure, there is basically no pressure on the equipment at that point and the code allows for temperatures below -20°F based on several parameters such as pressure/stress/metal thickness, etc. Because of this, you can have piping, etc. constructed of standard grades such as A-106 without going to A333 for -50°F service.
regards, ben
#5
millany
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Posted 21 December 2003 - 12:33 AM
Thank you very much everyone for the help
the information you've mentioned would be a big help
thanks again
Take care and God Bless everyone!
the information you've mentioned would be a big help
thanks again
Take care and God Bless everyone!
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