Relief Valve (Fire Case) for amine - LPG tower

[hianbotech]

Where could I find guidelines to design a relief valve (fire case) for a amine-lpg tower (liquid-liquid contactor tower).

I know that the relief valve will open in fire case when there will be vapor in the top. However the relief valve will handle liquid-vapor mix. How can i estimated the relationship between the two phase in the relief valve???. This relationship will change in the time. How can i be conservative to estimate the load?

I will apreciate your comments
Hianbo

 

[Lblopez]

Hello hianbo,

The API 520 and 521 appear the equation to make a calculation for fire case in any vessel for two phase flow.

In my work I have the equation, may be I can send to you, but I dont go to my office until tuesday.

Good look,

LbLópez.

 

[Montemayor]

hianbo:

Could you be specific in describing your Unit Operation? Are you saying that you are treating a flow of Liquefied Petroleum Gas (LPG) with a liquid flow of an Amine (i.e., Monoethanolamine -MEA, or DEA, MDEA, etc.)?

If so, what are you treating for? Amines are normally used to remove acid gases - but out of gaseous streams, not liquid streams. Additionally, Amines are usually employed in an aqueous solution in strengths that may vary between 15 to 40% by weight.

Also, are you in the recommended blocked-in scenario when the pool fire occurs? If so, then you have a complex case where the tower is 100% liquid-full and subject to thermal expansion relief prior to considering over-pressure due to liquid vaporization. Is this your situation?

Await your more detailed and specific reply.

 

[hianbotech]

Montemayor:

The tower operates with MDEA (55% water) and LPG, liquid - Liquid contactor, at 420 psig and temperatures between 125 and 148°F. The amine is used to remove the H2S in the LPG

In the first estimated when I calculated the possible relief load for pool fire scenario. I get that the tower "blocked outlet case" requires 9 hours to get the first vapor bubble with heat-rate caused by a pool fire scenario (using the calculations procedure in API 521; Q=21000FA^0.82, where A Is wetted area,.....).

For this reason we were not considering that fire case applied. Then the main relief load for design relief valve will be due to thermal liquid expansion, considering only liquid phase.

I really apreciated your comments regarding this proposal

Regards, Hianbo