A Process for the Simultaneous Removal of SO2 and NOx Using Ce(IV) Redox Catalysis

Abstract

The paper presents a process for the treatment of SO 2 and NO x -containing waste gases involvingthe oxidation of the pollutantswith Ce(IV) in an acidic medium. This process was designed at the pilot scale with the aim of producing separate flows of nitric and sulphuric solutions and achieving the total recovery of the redox catalyst. The waste gas is continuously scrubbed in a counter-current column by the cerium-containing liquid which is recirculated in a loop: oxidant Ce(IV) is continuously regenerated at the anode of an electrochemical cell. The technical feasibility of the technique was investigated under industrial conditions for the treatment of 100Nm 3 h −1 waste gases produced by a glass-making furnace. Total abatement of sulphur dioxide was observed, whereas the removal efficiency of NO x was below 45%. In addition, a secondary process was studied for the treatment of the concentrated acid liquors produced in the absorption/electro-oxidation loop: nitric acid was separated by distillation, and two extraction procedures allowed the recovery of Ce-free sulphuric acid and the possible reuse of Ce(IV) species.