5 replies to this topic

[Chacarita]

Hi,

I need to validate the size of a flare KOD for some flare scenarios, one of them (not the governing) is a pool fire of liquid propane @ Pset 20 barg and T 60 deg C. My question is, can I assume 100% vaporization due to the fire entering the flare KOD, and what about the conditions inside the drum, the KOD is operating @ 0.1 barg. What temperature can I expect there and how can I determine liquid droplets size? Basically I need to clarify operating conditions in the flare KOD to determine physical properties. Any advice?

Edited by Chacarita, 24 October 2018 - 11:08 AM.

[Bobby Strain]

Your query is not at all clear. Want to try again?

 

Bobby

[Chacarita]

Thanks for your reply.

I need to clarify a what temperature is the propane inside the flare KOD which operates at 0.1 barg. The relief temperature is 60 deg C at set pressure 20 barg. But its not clear at what conditions is the propane inside the flare KOD. Sorry but I don't have a process simulator available to do it and it's almost pure propane. I can not assume all vaporized inside the KOD. Maybe I have two question at the same time but basically I need to know if I can get two phase flow in the flare KOD. 

[flarenuf]

hi

sorry but your query still isnt clear as to what you asking here.

you say you have a pool fire of propane entering the flare KO drum?

Firstly a pool fire exists in the plant either on the floor or on a supporting structure, not inside a drum. So i dont think we are clear here.

Are you saying that you have a vessel V1 , say, which is subject to a fire scenario where you have a propane pool fire around it. The PSV on V1 is set at 20barg and the relief temp is 60C , if so that seems low for a fire scenario.

As to the 2nd part, the pressure, and hence the temperature  in the KO drum will depend on the back pressure in the drum, which in turn is  dependent on the sum of the flow of this relief and any other co reliefs  for the fire scenario.

The operating T & P in the drum will depend on several factors as above so  whether you get 2 phase flow depends on the T&P as well as the composition of the fluid entering the drum.  The drum should be sized to handle a certain droplet size , say 400mic for its design case.   so if, as you say the pool fire scenario is not the governing case then the drum should be able to settle better than this.
You seem to be confused here a little and so i suggest you ask your supervisor for some guidance as with the information provided i surmise that  non of us can really assist with your problem.

Flarenuf

[Chacarita]

Hi flarenuf, thanks for your reply, it seems that my question is not very clear, sorry for that. I'm trying to say that I have a relief scenario for a PSV for a fire case (that involves a pool fire), the relief valve is a safety measure I guess to avoid a catastrophic event... now is it more clear?

At that temperature, not more than 70 deg C the safety valve will open, set pressure 20 barg, the fluid is liquid propane. The relief load will be sent to a flare KOD. I need to validate the size of this vessel for that relief load but I'm not sure about the temperature that can reach the propane at 0.1 barg, that is the operating pressure for the flare KOD and if i can have two phase flow in the vessel? Can I assume isothermal flow?

Hope that this can clarify my query, sorry Im new in the forums

[shan]

If C3 is letdown from 60 C, 20 barg to 0.1 barg through a valve, the outlet stream is 100% vapor at 27.7 C.