Relief line design / vapor condensation or freezing during relieve?

[rojans]

I am looking at a project to relocate the relief of a destillation column to safe location. Set pressure of RD = 0.5 bar. To reach safe location significant length of piping is required; about 60m (200 ft) of which 20m to go to higher altitude. the vapor relief is at boiling point (about 200 degC). The relief rate is 4000 kg/h with a molar weight of 100 kg/kmol. residence time is about 6 seconds.
Freezing temperature is 45 degC.
What will happen to the temperature during venting? What would happen to the temperature of the ventpipe (this is critical as at 190 degC stress calculation is required)?
I expect some condensation; but can I also expect freezing?
? What would roughly be the percentage of condensation?
Is it necessary to use tracing?
I would like to a liquid drain to safe location to remove condensated vapors and rain.

Do u consider this a good solution of have a better one? I

 

[JoeWong88]

There are few issue required clarification...

i) Set pressure of RD = 0.5 bar. Does this mean 0.5 bar abs or 0.5 barg ?

ii) Vapor relief is at boiling point (200degC). I guess when the fluid is contacted with discharge piping (normally at ambient temperature) would quickly experience condensation. Please check if the condensation temperature at ATM is above maximum ambient temperature. If so, very likely to see condensation.

iii) If condensation is expected, huh...2 (or 3 or 4...) phases flow is rather complicated. Backpressure is changing, pipe vibration, etc. Multiphase flow in upward piping make condition even worst. Please consider a proper disposal system e.g. RD outlet is free draining towards a KO drum for multiphase separation and only vapor discharge to "safe location"...

iv) ...relocate the relief of a distillation column to safe location...Please check the composition and environment regulation requirement if direct discharge direct relieving to ATM is meeting regulation requirement...

v)Assuming 0.5 barg, i think the temperature drop is not that significant with 0.5 bar of JT effect. But the discharge pipe cooling could bring temperature drop quickly.
Nevertheless, freezing may occur at the discharge pipe surface.

BTW, is 2 phase (vapor-liquid) in the column ? Normally yes. Is the fluid reactive or foaming ? If so, please kindly consider to conduct detail safety analysis (or engage specialist study) on this relieving system. It is far more complicated than i can imagine...