6 replies to this topic

[dungnt]

Hi all,

I am doing a project about reducing carbon dioxide content in the feed gas of Sulfur Recovery Unit. Problem is I want to separate CO₂ from H₂S. I have two idea: using membrane and using chemical solution, but using membrane seems to be impossible because they have the same size. Please, anyone has ideas about it.

Thanks for your response.

 

[Zubair Exclaim]

do you have  a upstream gas sweetening unit from where you recieve you sour gas? you can play there by using sterically hindered  amines, for selective absorption.

[Erwin APRIANDI]

Hi dungnt,

 

Both solution that you say

- Membrane and

- Chemical solution

Both are possible, but for the membrane there is a membrane that is selective to H2S it will separate the CO2 but it will not completely separate it.

 

Based on my experience with the membrane vendor they can only get about 50% reduction of CO2 and the reject stream will still have some rejected H2S therefore need to recycle and need a sour gas compressor (but this is for my condition at that time 2008) you can try to ask this to the membrane vendor or lisencor.

 

By using chemical solution you can use tertiary amine like MDEA which more H2S compare to the CO2 (2 step of absorption, first to sweetened the gas and the second one to enrich the H2S), but still there will be some CO2 in the regen gas. But based on what has been proposed to me by the lisencor at that time, the regen gas feed to SRU is meeting the required CO2 level.

Edited by Erwin APRIANDI, 29 May 2014 - 03:47 AM.

[Zubair Exclaim]

Dungt,

 

As erwin said you can have the membrane set up there ... for the chemical route ... it may be more economical for you to see if the upstream sweeteining unit can be modified to selectively remove H2S .. .. this will dump a bit of CO2 in your sweet gas ... but you dont have gas BTU spec on the border it should be OK

 

installing a new CO2 chemical absorption unit upstream for sru may be a little cost ineffecient .. but do investigate and let us know

[Technical Bard]

You could use a physical solvent system like Rectisol (refrigerated methanol) to absorb both and then release them separately.  This is commonly done in gasification facilities.

[dungnt]

Thanks you all

The information is very useful for me. I will think about all ways that're possibly and ask some questions when i need help later  .

[RockDock]

Selexol, Rectisol, Fluor Solvent can all be used as physical solvents. I don't think a membrane will be very economical.

 

However, MDEA is the most commonly used solvent for this process. When I attended the ProMax training course, we were able to model all the options and compare them. I would recommend you do that for this project. Or you can attend their training course. It's free to attend.