Biological Sulfur Reduction To Generate H₂S As a Reducing Agent To Achieve Simultaneous Catalytic Removal of SO₂ and NO and Sulfur Recovery from Flue Gas

Abstract

The conventional flue gas treatment technologies require high capital investments and chemical costs, which limit their application in industrial sectors. This study developed a sulfur-cycling technology to integrate sulfide production by biological sulfur reduction and simultaneous catalytic desulfurization and denitrification with H₂S (H₂S-SCDD) for flue gas treatment and sulfur recovery. In a packed bed reactor, high-rate sulfide production (1.63 ± 0.16 kg S/m³-d) from biological sulfur reduction was achieved using organics in wastewater as electron donors at pH around 5.8. 93% of sulfide in wastewater was stripped out as H₂S_g, which can be a low-cost reducing agent in the H₂S-SCDD process. Over 90% of both SO₂ and NO were removed by the H₂S-SCDD process under the test conditions, resulting in the formation of sulfur. 88% of the input S (H₂S_g and SO₂) were recovered as octasulfur with high purity. Besides partial recycling to produce biogenic sulfide, excessive sulfur can be obtained as a sellable product. The integrated sulfur-cycling technology is a chemical-saving and even profitable solution to the flue gas treatment in industrial sectors with wastewater available.