6 replies to this topic

[dungnt]

Dear all

I have some questions when studying SCOT process. In the process, why the gas after scot reactor is contained CO₂, and why we have to selectively absorb H₂S, it's OK if the alkanolamine also absorb CO₂ ?

 

Thank in advanced !

[RockDock]

There is a lot more to this question.

 

The "scot" reactor is a hydrogenation reactor, meant to convert and remaining Sulfur compounds back to H2S. However, the stream will still be ~90% N2, H2O and CO2. You want to get rid of as much of the inerts (including CO2) as possible, but recycle your H2S back to the beginning of the SRU. The purpose is to have a greater total sulfur recovery (~99.98%).

[dungnt]

Thanks RockDock

Is your point: CO₂ has to be removed to the SRU has effective recovery (Sorry! English's not my native, so cannot totally understand your reply)?. But I think if the fed contains CO₂, the SRU is still fine ? 

[RockDock]

No problem. I think I had a typo or two in there, too.

 

CO2 does not hurt the process, per se. In fact, you will be producing CO2 through the combustion chamber, anyways. The trouble is that the higher the concentration of H2S in the inlet to the SRU, the easier it will be to operate the SRU. Since there is no reason to have the CO2 being recycled back to the SRU, it just makes sense to use MDEA to selectively recycle the H2S and let the CO2 slip to the incinerator. The more CO2 in the acid gas, the lower the concentration of H2S.

 

CO2 is more or less inert. Ideally, you want the feed to the SRU to be about 40-60% H2S. Below that and you will need to modify the design and probably spend additional money for various enrichment technology.

[dungnt]

Thank sir

It very useful and helpful. Now, it's very clearly to me 

[Bobby Strain]

Rock,

      I think that a SCOT, (Shell Claus Offgas Treater), unit is nothing more than an amine absorber and stripper to remove H2S from the Claus unit offgas and return it to the Claus unit feed. This allows sulfur recovery to approach 100%. I didn't know that a hydrogenation reactor is also included. But now I know about the hydrogenation step. Thanks.

 

Bobby

Edited by Bobby Strain, 17 June 2014 - 04:44 PM.

[RockDock]

Glad I can help!