3 replies to this topic

[vista]

we have a rich amine (MDEA) flash tank where rich amine from contactor enters the flash tank and due to pressure reduction, absorbed gases are flashed out. Two regulators are installed at this flash tank. The 1st one is used for make up of pressure in the flash tank upto 85 psig and the second one is used to release excess pressure to the LP flare....

my question is that what will be effect when flash tank pressure is reduced too much, say 20 to 30 psig?why the designers set the pressures for flash tank by installing pressure regulators for make up and/or for releasing the excess pressure?

[Dacs]

If I recall, you usually have a flash drum to remove as much HC as possible from your Rich Amine stream.

Thing is, the lower the pressure the better but at the expense of needing a pump (to send Rich Amine to Regenerator) should the flash drum pressure dips low enough.

So you'd normally set the flash drum pressure high enough to send the Rich Amine to the Regenerator although sometimes a pump is also used as well.

You seem to describe one line acting as inbreathing (makeup) and one acting as outbreathing (to flare). This is to ensure that you're maintaining the proper pressure in your flash drum by adding gas (I have to guess N2) when you're losing pressure and venting gas to flare when you experience increase in pressure. Just to add, sometimes the vapor produced from the flash drum is sometimes sent to offgas system in your refinery.

[vista]

Dacs'

thanks for your input...

I would like to ask one more thing...

we are not using Nitrogen for this make up purpose infact we are using the sweet gas from the utility skid...Is it good to use sweet gas instead of N2?

[Dacs]

It really doesn't matter. Sweet Gas would be more economical to be honest since you don't have to use N2.

Hope this helps

PS. Typing with your iPhone while on a commute to work is such a pain