4 replies to this topic

[m42364236k]

Dears

in my project the produced water from plant after separating the oil sending to atmospheric tank

 

this  tank have nitrogen blanketing and also have connection to atmosphere  when the pressure increased

 

(split range control)

 

produced water with 2.5barg operation pressure with 300 ppm h2s content in water send to this tank

 

my question is

 

dose it need to change the split range line form atmosphere and connect it to flare network or we can vent it to atmosphere  but in safe location?

 

-as i know h2s content in hydrocarbon have lot of problem but what about the water does it have another problem or not?

 

 

thanks

 

 

[narendrasony]

Hello,
How safe will be storage tank vent to atm (to safe location) with 300 ppm H2S ? Where will it be routed to?
H2S being heavier than air, it's dispersion in the near by area will have to be considered with dispersion model.

In my view, atm vent to safe location should be considered for small venting requirements only. I would ultimately divert it to flare only.
H2S is H2S, whether from HC tank or water tank.

Regards
Narendra

[shahid780812]

Connecting storage tank vent to thermal oxidiser or incinerator is another option.
If flare network is not available.....

[Dacs]

Assumptions:

1. Produced water is 2.5 barG being sent to an atmospheric tank

2. 300 ppm H2S is in free water at 2.5 barG

 

That said, you need to do these:

1. Perform a flash calculation to bring down the pressure of water with H2S from 2.5 to atmospheric. This will liberate some H2S in your stream

2. Consider the flowrate of N2 blanket in your tank and calculate the corresponding concentration of H2S from degassing performed in #1

 

I am NOT comfortable releasing any gas to atmosphere with 300 ppm (see MSDS for the reason) of H2S. While you can rely on dispersion to thin out H2S, will you be comfortable working on top of tank with H2S lurking around you?

 

Hooking the vent to flare while an option, you need to also consider the backpressure produced by the flare system as well.

 

You may send this to a thermal oxidizer/incinerator as shahid780812 has pointed out, but IMHO a better option is to employ a adsorption system (such as carbon filters) to absorb the H2S from your vent. This has been done in a project I was involved with years back.

 

Good luck

Edited by Dacs, 02 June 2014 - 08:17 AM.

[Art Montemayor]

As Dacs has inferred, any exposure to hydrogen sulfide is not to be taken lightly.  I would not waste any time in totally eradicating its presence around my working personnel.  Flaring and/or incineration would be my immediate response.

 

Hydrogen sulfide is an extremely hazardous, toxic, and deadly compound.

 

Although H₂S has a very low odor threshold (with its smell being easily perceptible at concentrations well below 1 part per million (ppm) in air) nevertheless, at concentrations above 100 ppm, a person's ability to detect the gas is affected very rapidly with a temporary paralysis of the olfactory nerves in the nose - leading to a loss of the sense of smell.  This means that the gas can be present at dangerously high concentrations, with no perceivable odor.  Prolonged exposure to lower concentrations can also result in similar effects of olfactory fatigue.  This unusual property of H₂S makes it extremely dangerous to rely totally on the sense of smell to warn of the presence of the gas.

 

Human exposure to high concentrations of H₂S (50 - 200 ppm) can result in:

• Severe respiratory tract irritation;
• Eye irritation / acute conjunctivitis;
• Shock;
• Convulsions;
• Coma; and,
• Death in severe cases

Even exposures at lower levels can lead to bronchitis, pneumonia, migraine headaches, pulmonary edema, and loss of motor coordination.

 

I would never recommend any adsorption system to safely remove the H₂S.  Should the adsorbent become saturated or you suffer a breakthrough of H₂S, you could wind up with a worse situation than the initial release.   There is no way that I know of that can detect and monitor the effectiveness of adsorption while it is in operation.   Converting it to SO₃ is more secure and positive to get rid of this deadly poison.