A PROCESS FOR THE SIMULTANEOUS REMOVAL OF SO2 AND NOX USING CE(IV) REDOX CATALYSIS

The paper presents a process for the treatment of SO2 and NOx-containi ng waste gases involving the oxidation of the pollutants with Ce(N) in an acidic medium. This process was designed at the pilot scale with t he aim of producing separate flows of nitric and sulphuric solutions a nd achieving the total recovery of the redox catalyst. The waste gas i s continuously scrubbed in a counter-current column by the cerium-cont aining liquid which is recirculated in a loop: oxidant Ce(IV) is conti nuously regenerated at the anode of an electrochemical cell. The techn ical feasibility of the technique was investigated under industrial co nditions for the treatment of 100 Nm(3) h(-1) waste gases produced by a glass-making furnace. Total abatement of sulphur dioxide was observe d, whereas the removal efficiency of NOx was below 45%. In addition, a secondary process was studied for the treatment of the concentrated a cid liquors produced in the absorption/electro-oxidation loop: nitric acid was separated by distillation, and two extraction procedures allo wed the recovery of Ce-free sulphuric acid and the possible reuse of C e(IV) species.