Integrated Tests for Removal of Nitric Oxide with Iron Thiochelate in Wet Flue Gas Desulfurization Systems

Wet flue gas desulfurization scrubbers can be retrofitted for combined removal of SO2 and NO x from flue gas by adding a newly developed iron(II) thiochelate to limestone slurries. This additive enhances the solubility of NO in limestone slurries by binding NO to form iron nitrosyl thiochelates. The bound NO is then converted to an ammonium ion by iron metal, regenerating the active iron(II) catalyst for continued NO capture. The conditions of the chemical regeneration of iron(II) thiochelate have been studied. This chemical reduction method is efficient, simple, and cost-effective. Integrated tests of this new iron additive on a bench-scale system have been conducted. A turbulent contact absorber was employed to test simultaneous removal of NO and SO2 with iron(II) thiochelate in a limestone slurry. The steady-state NO removal efficiency depends on the operating conditions of an absorber, the iron chelate concentration, the fraction of the flow diverted for regeneration, and the conditions used in the regeneration reactor. The bench-scale test results were used to develop a prediction of the performance of a full-scale spray absorber.