1 reply to this topic

[azeotrope]

Hello all,

I have a storage tank of a flammable solvent with a BP of 10C. We keep a N2 blanket on the tank of 60psig and use that pressure to move the solvent from the tank to reactors.

When we load the tank, it must be vented to atm pressure. The tank wagon is pressureized with N2 and the tank is refilled.

What is the best way to handle the venting of the the solvent/N2 mixture during depresurizing and filling? It is not much of an issue on cold days but we get temperatures over 35 C in the summer. We do not have a flare.

Is there an API RP or some other guide to get regs?

Thanks,
T.J.

[Art Montemayor]

T.J.:

Since your solvent’s boiling point is so low, you have to have a nitrogen blanket on it while it resides in the storage tank – regardless of whether you need it to hydraulically “push” it into the reactor downstream.

Therefore, if you need to eradicate your venting problems because you cannot pressurize the loading “tank wagon” to 60 psig, then you have little choice but to install two pumps:

• One to transfer solvent from the tank wagon into the storage tank;
• Another to pump solvent into the reactor.

I have to assume (because you fail to identify) that you cannot equalize the tank wagon with the 60 psig in the storage tank. Therefore, you have to pump from the tank wagon into the storage tank while both tanks are equalized at the same nitrogen pressure that the tank wagon is at (assuming this is the MAWP of the tank wagon and below 60 psig).
Then you are forced to maintain your storage vessel at that same tank wagon pressure during storage and use a second pump as a feed pump to your reactor.

There should be no venting or waste of solvent vapors in this operation.