Strategies For Utilizing Ferrous*edta Chelate As An Additive In Combined SO/sub 2/No/sub x/ Aqueous Scrubbing Systems

Ferrous*EDTA chelate has been found to be an effective scrubbing agent for nitric oxide gas. A major problem encountered in its practical application is that the ferrous ion oxidizes in solution to the ferric species, thus decreasing the NO/sub X/ strategies under development in the United States for overcoming this problem. Dow Chemical has studied the use of an electrolytic cell to reduce ferric ions to the corresponding ferrous species [1]. Workers at the Pittsburgh Energy Technology Center have studied in situ bisuffite reduction of ferric ions to ferrous ions at elevated temperature (70//spl deg/C) [2]. We have studied NO/sub X/ removal from simulated flue gas mixtures under various oxidizing conditions and have found that addition of an organic, polyphenolic compound to an aqueous scrubbing solution containing Fe(ll)*F-DTA leads to a sustained NO/sub x/ removal significantly higher than was found without the secondary additive. The improved performance of Fe(II)*EDTA under these conditions is attributed to the known capabilities of these organic compounds to both inhibit oxidation by dissolved oxygen and to rapidly reduce any ferric ions back to the original ferrous species. Finally, advantages of a NO/sub x/-control process based upon an additive in an S02-control chemistry over serial processes are discussed.