3 replies to this topic

[kaisar]

I am working my final report (plant design) right now as a chemical engineering student and I am getting confused with one of my process, i.e LO-CAT system. This system uses liquid redox mechanism for removing H2S from a gas stream. There is one absorber and one oxidizer. In absorber, H2S is absorbed from the gas stream by diluted Fe-EDTA solution (EDTA as a chelating agent). H2S then transformed into elemental sulfur according to reaction :
H2S (v) + H2O(l) ----> H2S(l)
H2S(l) ----> H+ + HS-
HS- + 2Fe+3 ----> 2Fe+2 + S + H+
The liquid out from absorber is sent to oxidizer to oxidize the Fe+2 back into Fe+3 (regenerating) according to reaction :
1/2 O2 (air) + H2O(l) ---> 1/2 O2(l)
2Fe+2 + 1/2O2(l) + H2O ---> 2Fe+3 + 2OH-
The overall reaction :
H2S(v) + 1/2 O2 ---> S + H2O (with Fe as catalyst)
In oxidizer, sulfur is discarded and the solvent is recycled to the absorber.
(I attache the file from http://www.gtp-meric...quid_redox.php)
My problem is :
The reactions above are ionic reactions. I am confused how to calculate mass and heat balances in both absorber and oxidizer.
So, somebody PLEASE GIVE ME ASSISTANCE

[rxnarang]

For starters, can you deal in moles first? Moles In= In the absorber count the moles of H2S and EDTA ( Fe3+ compound; find out the complete molecular specie of this compound first). Looks like no water is consumed in this reaction.

Moles out = moles of S + moles of EDTA ( FE2+) + H2(?)

Do the same for the oxidizer.

Let me know if you are able to work this out further. Or write to me @

Regards
rxnarang@gmail.com

[kaisar]

Thanks first for your reply and suggestion. Now I know what actually the formulae for FeII-EDTA and FeIII-EDTA are. Therefore, I also know what the reactions occur both in absorber and oxidizer are. Here are they :
In absorber : H2S + C10H12FeN2O8 (this is FeIII-EDTA) -----> C10H14FeN2O8 (this is FeII-EDTA) + S
And in oxidizer FeII-EDTA is oxidized back to FeIII-EDTA according to reaction :
C10H14FeN2O8 + 0.5 O2 ----> C10H12FeN2O8 + H2O
But, I dont find neither from any literature nor from internet, the physical and chemical properties for both the iron-compunds above like density, Cp, etc. So what can you suggest to me?

[rxnarang]

This could be a patented chemical. Try looking for a material safety data sheet ( MSDS), which generally lists such properties.

Regards