Hydrocarbons on top of water in sour water storage tank

[bailey1]

We are planning to put 2 feet of hydrocarbons (say, diesel)on top of water in the very large sour water storage tank to minimize H2S vent. The tank will also be nitrogen blanketed. If I know the saturated H2S concentration in the hydrocarbons and the H2S concentration in sour water, then how often do I need to replace the hydrocarbons in the tank?
Please advise method of calculation.

 

[mbeychok]

baily1:

A better idea is to route the tank vent gas through a small amine absorber that uses lean amine from your main amine unit and returns rich amine to your main amine unit.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[Jason5000]

I've heard of gravity being used as a monitoring point for systems such as you're proposing. Say you put in a 32 API diesel to start with. As it sponges light ends the API gravity will slowly increase over time. Provided you have skim points to grab an oil sample from you can measure gravity, watch the API gravity increase as the oil saturates, and change out as required. Sorry I don't remember exactly how much gravity increase to look for, but the facility I know of that operated this way changed out the sponge oil about every 3 - 6 months.