In view of the high H₂S content in biogas or high-sulfur natural gas, the wet oxidation process with chelated iron as catalyst is adopted for hydrogen sulfide removal. This process directly converts H₂S into elemental sulfur. The iron-based catalyst desulfurization technology is an innovative desulfurization process featuring simple workflow, high working sulfur capacity, environmental friendliness and non-toxicity. It overcomes the drawbacks of conventional desulfurization technologies such as low sulfur capacity, complicated process, high rate of by-product salt formation and severe environmental pollution. The sulfur recovery rate exceeds 99%, and the H₂S concentration in treated clean gas can be reduced to below 10 ppm.
Desulfurization principle:
Overall reaction equation for oxidation absorption
H2S(g) + 2Fe3+(L) → 2H+(L) + S↓+ 2Fe2+(L)
Overall reaction equation for regeneration and reduction
1/2O2(g) + H2O(L) + 2Fe2+(L) → 2OH-(L) + 2Fe3+(L)
The iron-based desulfurization catalyst leverages the redox property of chelated iron ions in aqueous solution to bring hydrogen sulfide-containing gas into gas-liquid contact reaction with the aqueous solution containing the iron-based catalyst.
In this gas-liquid contact reaction, hydrogen sulfide in the feed gas is first absorbed into the aqueous solution via acid-base chemical absorption at the slightly alkaline condition during gas-liquid contact. Within the solution, hydrogen sulfide is oxidized to elemental sulfur by the oxidizing property of ferric ions, while the chelated ferric ions are reduced to chelated ferrous ions.
Since chelated ferrous ions in the aqueous solution are readily oxidized by oxygen, the chelated ferrous ion solution is brought into direct gas-liquid contact with air. Oxygen in the air oxidizes the chelated ferrous ions back to chelated ferric ions in the aqueous solution.
