Simultaneous removal of NO and SO from flue gas in an integrated FGD-CABR system by sulfur cycling-mediated Fe(II)EDTA regeneration.

Chemical absorption-biological reduction (CABR) process is an attractive method for NO removal and Fe(II)EDTA regeneration is important to sustain high NO removal. In this study a sustainable and eco-friendly sulfur cycling-mediated Fe(II)EDTA regeneration method was incorporated in the integrated biological flue gas desulfurization (FGD)-CABR system. Here, we investigated the NO and SO removal efficiency of the system under three different flue gas flows (100 mL/min, 500 mL/min, and 1000 mL/min) and evaluated the feasibility of chemical Fe(III)EDTA reduction by sulfide in series of batch tests. Our results showed that complete SO removal was achieved at all the tested scenarios with sulfide, thiosulfate and S accumulation in the solution. Meanwhile, the total removal efficiency of NO achieved ∼100% in the system, of which 3.2%-23.3% was removed in spray scrubber and 76.7%-96.5% in EGSB reactor along with no NO emission. The optimal pH and S/Fe(III)EDTA for Fe(II)EDTA regeneration and S recovery was 8.0 and 1:2. The microbial community analysis results showed that the cooperation of heterotrophic denitrifier (Saprospiraceae_uncultured and Dechloromonas) and iron-reducing bacteria (Klebsiella and Petrimonas) in EGSB reactor and sulfide-oxidizing, nitrate-reducing bacteria (Azoarcus and Pseudarcobacter) in spray scrubber contributed to the efficient removal of NO in flue gas.